Catalysts

12 pages, 428 KiB

Open AccessEditor’s ChoiceArticle

One-Pot Synthesis of Fatty Amines: Rh-Catalyzed Hydroaminomethylation of 1-Decene in an Aqueous Microemulsion System—Influence of Reaction Conditions on the Reaction Performance

by Ariane Weber, Linus Porthun and Reinhard Schomäcker

Catalysts 2022, 12(7), 773; https://doi.org/10.3390/catal12070773 - 12 Jul 2022

Cited by 9 | Viewed by 2399

Abstract

The hydroaminomethylation of the long-chain olefin 1-decene and diethylamine with a homogeneous Rh(acac)(cod)/SulfoXantphos catalyst complex as a one-pot synthesis was investigated. The influence of reaction conditions such as temperature and synthesis gas pressure was determined, as well as the effects of the initial [...] Read more.

The hydroaminomethylation of the long-chain olefin 1-decene and diethylamine with a homogeneous Rh(acac)(cod)/SulfoXantphos catalyst complex as a one-pot synthesis was investigated. The influence of reaction conditions such as temperature and synthesis gas pressure was determined, as well as the effects of the initial concentrations of catalyst precursor, ligand, and reactants on the yield of fatty amine. Hydroaminomethylation was successfully carried out in an aqueous microemulsion system using a non-ionic surfactant with a reaction time of 2 h. A maximum yield of 34%, high regioselectivities >97%, and chemoselectivities >85% were achieved. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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20 pages, 3137 KiB

Open AccessEditor’s ChoiceReview

Single-Particle Measurements of Nanocatalysis with Dark-Field Microscopy

by Jing Shang, Jinsong Fan, Weiwei Qin and Kun Li

Catalysts 2022, 12(7), 764; https://doi.org/10.3390/catal12070764 - 10 Jul 2022

Cited by 8 | Viewed by 4223

Abstract

Due to the complexity of heterogeneous reactions and heterogeneities of individual catalyst particles in size, morphology, and the surrounding medium, it is very important to characterize the structure of nanocatalysts and measure the reaction process of nanocatalysis at the single-particle level. Traditional ensemble [...] Read more.

Due to the complexity of heterogeneous reactions and heterogeneities of individual catalyst particles in size, morphology, and the surrounding medium, it is very important to characterize the structure of nanocatalysts and measure the reaction process of nanocatalysis at the single-particle level. Traditional ensemble measurements, however, only provide averaged results of billions of nanoparticles (NPs), which do not help reveal structure–activity relationships and may overlook a few NPs with high activity. The advent of dark-field microscopy (DFM) combined with plasmonic resonance Rayleigh scattering (PRRS) spectroscopy provides a powerful means for directly recording the localized surface plasmon resonance (LSPR) spectrum of single plasmonic nanoparticles (PNPs), which also enables quantitative measurements. In recent years, DFM has developed rapidly for a series of single-particle catalytic reactions such as redox reactions, electrocatalytic reactions, and DNAzyme catalysis, with the ability to monitor the catalytic reaction process in real time and reveal the catalytic mechanism. This review provides a comprehensive overview of the fundamental principles and practical applications of DFM in measuring various kinds of catalysis (including chemocatalysis, electrocatalysis, photocatalysis, and biocatalysis) at the single-particle level. Perspectives on the remaining challenges and future trends in this field are also proposed. Full article

(This article belongs to the Special Issue Synthesis, Applications, and Chemical Measurements of Nanomaterials in Catalysis)

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12 pages, 1742 KiB

Open AccessEditor’s ChoiceArticle

Sonophotocatalysis—Limits and Possibilities for Synergistic Effects

by Dirk Paustian, Marcus Franke, Michael Stelter and Patrick Braeutigam

Catalysts 2022, 12(7), 754; https://doi.org/10.3390/catal12070754 - 8 Jul 2022

Cited by 16 | Viewed by 2635

Abstract

Advanced oxidation processes are promising techniques for water remediation and degradation of micropollutants in aqueous systems. Since single processes such as sonolysis and photocatalysis exhibit limitations, combined AOP systems can enhance degradation efficiency. The present work addresses the synergistic intensification potential of an [...] Read more.

Advanced oxidation processes are promising techniques for water remediation and degradation of micropollutants in aqueous systems. Since single processes such as sonolysis and photocatalysis exhibit limitations, combined AOP systems can enhance degradation efficiency. The present work addresses the synergistic intensification potential of an ultrasound-assisted photocatalysis (sonophotocatalysis) for bisphenol A degradation with a low-frequency sonotrode (f = 20 kHz) in a batch-system. The effects of energy input and suspended photocatalyst dosage (TiO₂-nanoparticle, m = 0–0.5 g/L) were investigated. To understand the synergistic effects, the sonication characteristics were investigated by bubble-field analysis, hydrophone measurements, and chemiluminescence of luminol to identify cavitation areas due to the generation of hydroxyl radicals. Comparing the sonophotocatalysis with sonolysis and photocatalysis (incl. mechanical stirring), synergies up to 295% and degradation rates of up to 1.35 min⁻¹ were achieved. Besides the proof of synergistic intensification, the investigation of energy efficiency for a degradation degree of 80% shows that a process optimization can be realized. Thus, it could be demonstrated that there is an effective limit of energy input depending on the TiO₂ dosage. Full article

(This article belongs to the Special Issue Photocatalysis and Sonocatalysis for Environmental Applications: Synergy or Competition?)

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15 pages, 2607 KiB

Open AccessEditor’s ChoiceArticle

In Situ H₂ Reduction of Al₂O₃-Supported Ni- and Mo-Based Catalysts

by Sabrina Maria Gericke, Jenny Rissler, Marie Bermeo, Harald Wallander, Hanna Karlsson, Linnéa Kollberg, Mattia Scardamaglia, Robert Temperton, Suyun Zhu, Kajsa G. V. Sigfridsson Clauss, Christian Hulteberg, Andrey Shavorskiy, Lindsay Richard Merte, Maria Elise Messing, Johan Zetterberg and Sara Blomberg

Catalysts 2022, 12(7), 755; https://doi.org/10.3390/catal12070755 - 8 Jul 2022

Cited by 14 | Viewed by 4255

Abstract

Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H₂ at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. [...] Read more.

Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H₂ at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. Here, we report on the first in situ study on the reduction of alumina supported Ni- and Mo-based catalysts in 1 mbar H₂ using ambient-pressure X-ray photoelectron spectroscopy (APXPS). The study confirms that mixing Ni and Mo lowers the reduction temperature of both Ni- and Mo-oxide as compared to the monometallic catalysts and shows that the MoO₃ reduction starts at a lower temperature than the reduction of NiO in NiMo/Al₂O₃ catalysts. Additionally, the reduction of Ni and Mo foil was directly compared to the reduction of the Al₂O₃-supported catalysts and it was observed that the reduction of the supported catalysts is more gradual than the reduction of the foils, indicating a strong interaction between the Ni/Mo and the alumina support. Full article

(This article belongs to the Special Issue In Situ/Operando Characterization of Complex Materials Employing Advanced Synchrotron-Based Techniques)

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16 pages, 5913 KiB

Open AccessEditor’s ChoiceArticle

An Advanced Approach for MgZnAl-LDH Catalysts Synthesis Used in Claisen-Schmidt Condensation

by Rodica Zăvoianu, Silvana-Denisa Mihăilă, Bogdan Cojocaru, Mădălina Tudorache, Vasile I. Pârvulescu, Octavian Dumitru Pavel, Solon Oikonomopoulos and Elisabeth Egholm Jacobsen

Catalysts 2022, 12(7), 759; https://doi.org/10.3390/catal12070759 - 8 Jul 2022

Cited by 7 | Viewed by 3293

Abstract

Using organic-base tetramethylammonium hydroxide (TMAH) is a viable, cheap, and fast option for the synthesis of MgZnAl-LDH-type materials by both co-precipitation and mechano-chemical methods. TMAH presents several advantages, such as the smaller quantity of water required in the washing step compared to the [...] Read more.

Using organic-base tetramethylammonium hydroxide (TMAH) is a viable, cheap, and fast option for the synthesis of MgZnAl-LDH-type materials by both co-precipitation and mechano-chemical methods. TMAH presents several advantages, such as the smaller quantity of water required in the washing step compared to the use of inorganic alkalis, the prevention of LDH contamination with alkali cations, and its action as a template molecule in texture tailoring. It also has disadvantages, such as its presence in small quantities in the resulting layered materials. Regardless of the use of organic/inorganic bases and co-precipitation/mechano-chemical methods, zincite stable phase was found in all the synthesized solids. The basicity of catalysts followed the trend: mixed oxides > reconstructed > parent LDH. The memory effect of LDH was supported only by the presence of Mg and Al cations, while Zn remained as a zincite stable phase. The catalytic activities for Claisen-Schmidt condensation of benzaldehyde with cyclohexanone provided values higher than 90% after 2 h, with a total selectivity toward 2,6-dibenzylidenecyclohexanone, while self-condensation of cyclohexanone yielded no more than 7.29% after 5 h. These behaviors depended on catalyst basicity as well as on the planar rigidity of the compound. Full article

(This article belongs to the Special Issue Layered Double Hydroxide-Based Catalytic Materials for Sustainable Processes)

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18 pages, 1213 KiB

Open AccessEditor’s ChoiceReview

Photoactive Materials for Decomposition of Organic Matter Prior to Water Analysis—A Review Containing Original Research

by Krzysztof Drwal, Krzysztof Miecznikowski and Beata Krasnodębska-Ostręga

Catalysts 2022, 12(6), 616; https://doi.org/10.3390/catal12060616 - 3 Jun 2022

Cited by 4 | Viewed by 2580

Abstract

Water plays a fundamental role in meeting the basic needs of society. Surface waters contain numerous organic pollutants, such as pesticides, drugs, and surfactants. The use of photolysis processes in organic matter degradation not only has practical applications in wastewater treatment but is [...] Read more.

Water plays a fundamental role in meeting the basic needs of society. Surface waters contain numerous organic pollutants, such as pesticides, drugs, and surfactants. The use of photolysis processes in organic matter degradation not only has practical applications in wastewater treatment but is also of major importance in the pretreatment of samples prior to the trace analysis of numerous analytes. The heterogeneous degradation is simple to implement prior to ultra-traces determination and is the only one allowed before the speciation analysis. Speciation analysis is currently the most important environmental challenge. The analysis of water, including tests associated with wastewater pretreatment and the monitoring of aqueous ecosystems, is the largest segment of environmental analysis. In the trace analysis of water, organic compounds are the principal interfering compounds reducing the quality of the obtained results or even preventing the determination of the examined analytes altogether. Some analytical techniques do not perform well in the presence, for example, of surfactants, so mineralization is sometimes required. Advanced oxidation processes are used to remove interfering organic compounds. The oxidation can be performed using homogenous photolysis (UV mineralization with hydrogen peroxide addition), while heterogenous photolysis using semiconductors helps to increase the removal efficiency of interferents dissolved in water. Utilizing semiconductor nanostructured materials as photocatalysts has been shown to be effective for the adequate removal of a wide spectrum of pollutants in water. Several semiconductor systems are used in the degradation of organic compounds, e.g., TiO₂, Fe₃O₄, WO₃, Fe₂O₃, ZnO, and mixtures of these oxides enriched with various precious metals, such as silver or gold. It is very challenging to manage the selectivity and reduction power so that organic compounds can be degraded but without disturbing the speciation of As, Cr, or Tl. Chemical modification of samples and the selection of semiconductor layers, light wavelength, and pH allow for the targeted degradation of specific compounds but may also indirectly affect the analysis of water samples. This review is a presentation of the state of the art of photocatalysis as a simple and effective technique for sample pretreatment in ultra-trace and speciation analysis and its critical as well as unpublished data related to this topic. Full article

(This article belongs to the Special Issue Photoactive Materials for the Catalytic Decomposition of Water Pollutants)

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17 pages, 4431 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Dimethyl Ether Oxidation over Copper Ferrite Catalysts

by Maria Smyrnioti and Theophilos Ioannides

Catalysts 2022, 12(6), 604; https://doi.org/10.3390/catal12060604 - 2 Jun 2022

Cited by 5 | Viewed by 2640

Abstract

The depletion of fossil energy sources and the legislation regarding emission control demand the use of alternative fuels and rapid progression of aftertreatment technologies. The study of dimethyl ether (DME) catalytic oxidation is important in this respect, as DME is a promising clean [...] Read more.

The depletion of fossil energy sources and the legislation regarding emission control demand the use of alternative fuels and rapid progression of aftertreatment technologies. The study of dimethyl ether (DME) catalytic oxidation is important in this respect, as DME is a promising clean fuel and at the same time a VOC pollutant present in the tail gases of industrial processes. In the present work, copper ferrite catalysts synthesized via the citrate complexation method have been evaluated in DME oxidation. N₂-physisorption, XRD, H₂-TPR, and XPS were employed for the characterization of the mixed oxide catalysts. The copper ferrite spinel phase was detected in all samples accompanied by a gradual decrease in the bulk CuO phase upon increase in iron content, with the latter never vanishing completely. The Fe_0.67Cu_0.33 catalyst exhibited the highest catalytic activity in DME oxidation, attaining approximately a 4-fold higher oxidation rate compared to the respective pure copper and iron oxides. The enhanced catalytic performance was attributed to the higher specific surface area of the catalyst and its enhanced redox properties. Highly dispersed copper species were developed owing to the formation of the spinel phase. DME-TPD/TPSR experiments showed that the surface lattice oxygen of the Fe_0.67Cu_0.33 catalyst can oxidize preadsorbed DME at a lower temperature than all other catalysts which is in agreement with the H₂-TPR findings. Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Hydrocarbons and Volatile Organic Compounds (VOCs))

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11 pages, 3163 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Boosting Oxygen Electrocatalysis by Combining Iron Nanoparticles with Single Atoms

by Bowen Liu, Sihong Wang, Fang Song and Qinglei Liu

Catalysts 2022, 12(6), 585; https://doi.org/10.3390/catal12060585 - 27 May 2022

Cited by 6 | Viewed by 2577

Abstract

The development of high-performance non-noble metal-based oxygen electrocatalysts is crucial for the practical application of zinc–air batteries. Most of them suffer from low intrinsic activity and poor stability, failing to meet the needs of practical applications. Here, we report an efficient and durable [...] Read more.

The development of high-performance non-noble metal-based oxygen electrocatalysts is crucial for the practical application of zinc–air batteries. Most of them suffer from low intrinsic activity and poor stability, failing to meet the needs of practical applications. Here, we report an efficient and durable bifunctional oxygen electrocatalyst of Fe@Fe-SAC composite (SAC stands for single atoms on carbon). A facile and ease-to-scale-up process synthesizes it. Fe single-atom and Fe nanoparticles are anchored on nitrogen-doped porous carbon, with the latter encapsulated by the graphitic shell. It exhibits appealing activity and durability in a basic electrolyte, requiring a half-wave potential of 0.805 V for oxygen reduction reaction (ORR) and an overpotential of only 348 mV to deliver a current density of 10 mA cm⁻² for oxygen evolution reaction (OER). Both activities are comparable to the corresponding benchmarking electrocatalyst of Pt/C for ORR and IrO₂ for OER. The superior activities are attributed to the strong electronic interaction between metal single-atom and nanoparticles. The favorable stability is ascribed to the physical encapsulation of carbon coatings on nanoparticles. This work presents a feasible scheme for designing and large-scale preparation of high-performance non-noble metal-based bifunctional oxygen electrocatalysts. Full article

(This article belongs to the Special Issue Advanced Earth-Abundant Catalysts for Energy Related Electrochemistry)

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13 pages, 3384 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Role of Steps on Silver Nanoparticles in Electrocatalytic Oxygen Reduction

by Jack Jon Hinsch, Junxian Liu, Jessica Jein White and Yun Wang

Catalysts 2022, 12(6), 576; https://doi.org/10.3390/catal12060576 - 24 May 2022

Cited by 11 | Viewed by 3234

Abstract

Hydrogen fuel cell technology is an essential component of a green economy. However, it is limited in practicality and affordability by the oxygen reduction reaction (ORR). Nanoscale silver particles have been proposed as a cost-effective solution to this problem. However, previous computational studies [...] Read more.

Hydrogen fuel cell technology is an essential component of a green economy. However, it is limited in practicality and affordability by the oxygen reduction reaction (ORR). Nanoscale silver particles have been proposed as a cost-effective solution to this problem. However, previous computational studies focused on clean and flat surfaces. High-index surfaces can be used to model active steps presented in nanoparticles. Here, we used the stable stepped Ag(322) surface as a model to understand the ORR performance of steps on Ag nanoparticles. Our density functional theory (DFT) results demonstrate a small dissociation energy barrier for O₂ molecules on the Ag(322) surface, which can be ascribed to the existence of low-coordination number surface atoms. Consequently, the adsorption of OOH* led to the associative pathway becoming ineffective. Alternatively, the unusual dissociative mechanism is energetically favored on Ag(322) for ORR. Our findings reveal the importance of the coordination numbers of active sites for catalytic performance, which can further guide electrocatalysts’ design. Full article

(This article belongs to the Special Issue Heterogeneous Electrocatalysis: Fundamentals and Applications)

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12 pages, 2184 KiB

Open AccessEditor’s ChoiceArticle

Stability of Pt-Adsorbed CO on Catalysts for Room Temperature-Oxidation of CO

by Frédéric C. Meunier, Taha Elgayyar, Kassiogé Dembélé and Helena Kaper

Catalysts 2022, 12(5), 532; https://doi.org/10.3390/catal12050532 - 11 May 2022

Cited by 16 | Viewed by 3415

Abstract

A large signal of gas-phase CO overlapping with those of adsorbates is often present when investigating catalysts by operando diffuse reflectance FT-IR spectroscopy. Physically removing CO(g) from the IR cell may lead to a fast decay of adsorbate signals. Our work shows that [...] Read more.

A large signal of gas-phase CO overlapping with those of adsorbates is often present when investigating catalysts by operando diffuse reflectance FT-IR spectroscopy. Physically removing CO(g) from the IR cell may lead to a fast decay of adsorbate signals. Our work shows that carbonyls adsorbed on metallic Pt sites fully vanished in less than 10 min at 30 °C upon removing CO(g) when redox supports were used. In contrast, a broad band assigned to CO adsorbed on oxidized Pt sites was stable. It was concluded that physically removing CO(g) at room temperature during IR analyses will most likely lead to changes in the distribution of CO(ads) and a misrepresentation of the Pt site speciation, misguiding the development of efficient low-temperature CO oxidation catalysts. A tentative representation of the nature of the Pt phases present depending on the feed composition is also proposed. Full article

(This article belongs to the Topic Synthesis, Characterization and Performance of Materials for a Sustainable Future)

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16 pages, 4094 KiB

Open AccessEditor’s ChoiceArticle

Flower-like Co₃O₄ Catalysts for Efficient Catalytic Oxidation of Multi-Pollutants from Diesel Exhaust

by Zihao Li, Xianhuai Chen, Jinghuan Chen, Huazhen Chang, Lei Ma and Naiqiang Yan

Catalysts 2022, 12(5), 527; https://doi.org/10.3390/catal12050527 - 7 May 2022

Cited by 6 | Viewed by 2791

Abstract

Nowadays, the oxidation activity at the low-temperature regime for Co₃O₄ catalysts needs to be improved to meet the stringent regulation of multi-pollutant diesel exhaust. Herein, nanoflower-like Co₃O₄ diesel oxide catalysts (DOCs) were fabricated with the addition of [...] Read more.

Nowadays, the oxidation activity at the low-temperature regime for Co₃O₄ catalysts needs to be improved to meet the stringent regulation of multi-pollutant diesel exhaust. Herein, nanoflower-like Co₃O₄ diesel oxide catalysts (DOCs) were fabricated with the addition of a low-content Pt to trigger better catalytic activities for oxidizing multi-pollutants (CO, C₃H₆, and NO) emissions by taking advantage of the strong-metal supporting interaction. Compared to the conventional DOCs based on Pt/Al₂O₃, the as-synthesized Pt/Co₃O₄ catalysts not only exhibited better multi-pollutants oxidation activities at the low temperature but also obtained better resistance toward NO inhibition. Moreover, Pt/Co₃O₄ catalysts showed exceptional hydrothermal durability throughout long-term tests in the presence of water vapor. According to the XPS and H₂-TPR results, Pt promoted low-temperature catalytic activity by increasing the active surface oxygen species and reducibility due to the robust synergistic interaction between metallic Pt and supporting Co₃O₄. Meanwhile, TGA curves confirmed the Pt atoms that facilitated the desorption of surface-active oxygen and hydroxyl radicals in a low-temperature regime. Furthermore, instead of probing the intermediates during CO and C₃H₆ oxidation for Pt/Co₃O₄ catalysts, which included carbonates, formate, and acetate species, in situ DRIFTs experiments also revealed C₃H₆ oxidation mainly took place over metallic Pt sites. Full article

(This article belongs to the Special Issue Catalytic Materials: Elimination of Environmental Pollutants)

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24 pages, 5810 KiB

Open AccessEditor’s ChoiceArticle

Electrodeposition of a Li-Al Layered Double Hydroxide (LDH) on a Ball-like Aluminum Lathe Waste Strips in Structured Catalytic Applications: Preparation and Characterization of Ni-Based LDH Catalysts for Hydrogen Evolution

by Song-Hui Huang, Yu-Jia Chen, Wen-Fu Huang and Jun-Yen Uan

Catalysts 2022, 12(5), 520; https://doi.org/10.3390/catal12050520 - 5 May 2022

Cited by 9 | Viewed by 3665

Abstract

A functionally structured catalyst was explored for ethanol steam reforming (ESR) to generate H₂. Aluminum lathe waste strips were employed as the structured catalytic framework. The mixed metal oxide (Li-Al-O) was formed on the surface of Al lathe waste strips through [...] Read more.

A functionally structured catalyst was explored for ethanol steam reforming (ESR) to generate H₂. Aluminum lathe waste strips were employed as the structured catalytic framework. The mixed metal oxide (Li-Al-O) was formed on the surface of Al lathe waste strips through calcination of the Li-Al-CO₃ layered double hydroxide (LDH), working as the support for the formation of Ni catalyst nanoparticles. NaOH and NaHCO₃ titration solutions were, respectively, used for adjusting the pH of the NiCl₂ aqueous solutions at 50 °C when developing the precursors of the Ni-based catalysts forming in-situ on the Li-Al-O oxide support. The Ni precursor on the Al structured framework was reduced in a H₂ atmosphere at 500 °C for 3 h, changing the hydroxide precursor into Ni nanoparticles. The titration agent (NaOH or NaHCO₃) effectively affected the physical and chemical characterizations of the catalyst obtained by the different titrations. The ESR reaction catalyzed by the structured catalysts at a relatively low temperature of 500 °C was studied. The catalyst using NaHCO₃ titration presented good stability for generating H₂ during ESR, achieving a high rate of H₂ volume of about 122.9 L/(g_cat·h). It also had a relatively low acidity on the surface of the Li-Al-O oxide support, leading to low activity for the dehydration of ethanol and high activity to H₂ yield. The interactions of catalysts between the Ni precursors and the Li-Al-O oxide supports were discussed in the processes of the H₂ reduction and the ESR reaction. Mechanisms of carbon formation during the ESR were proposed by the catalysts using NaOH and NaHCO₃ titration agents. Full article

(This article belongs to the Special Issue Layered Double Hydroxide-Based Catalytic Materials for Sustainable Processes)

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14 pages, 4061 KiB

Open AccessEditor’s ChoiceArticle

Towards the Efficient Catalytic Valorization of Chitin to N-Acylethanolamine over Ni/CeO₂ Catalyst: Exploring the Shape-Selective Reactivity

by Yifan Zheng, Lijun Lu, Wei Chen, Anmin Zheng, Aiwen Lei and Abhishek Dutta Chowdhury

Catalysts 2022, 12(5), 460; https://doi.org/10.3390/catal12050460 - 20 Apr 2022

Cited by 6 | Viewed by 2991

Abstract

Global warming and rising waste content collectively accelerate the development of renewable-derived ‘low-carbon’ chemical technologies. Among all abundant renewables, marine-/food-waste-derived chitin, the only nitrogen-containing sustainable biomass, contains the unique N-acetylglucosamine units, which could be synthetically manipulated to a plethora of organonitrogen chemicals. [...] Read more.

Global warming and rising waste content collectively accelerate the development of renewable-derived ‘low-carbon’ chemical technologies. Among all abundant renewables, marine-/food-waste-derived chitin, the only nitrogen-containing sustainable biomass, contains the unique N-acetylglucosamine units, which could be synthetically manipulated to a plethora of organonitrogen chemicals. Herein, we report the efficient one-step catalytic valorization of chitin to N-acylethanolamine over cost-effective Ni/CeO₂-based materials, which interestingly demonstrate shape-based reactivity based on CeO₂ supports. In general, all three catalysts (Ni on cubic-, rod-, and polyhedral-shaped CeO₂ supports) were active for this reaction, but they differed in their catalytic efficiency and time-monitored reaction profiles. Herein, Ni on cubic-shaped CeO₂ delivered relatively better and stable catalytic performance, along with its rod-shaped counterpart, while the polyhedral CeO₂-based material also delivered decent performance. Such interesting catalytic behavior has been corroborated by their physicochemical properties, as revealed by their characterization studies. Herein, to establish an appropriate structure-property-reactivity relationship, multimodal characterization techniques and control mechanistic experiments have been performed. This work demonstrates a concept to reduce the consumption of primary carbon resources and increase the utilization of secondary waste materials to facilitate a smooth transition from a linear economy (cf. cradle-to-grave model) to a circular economy (cf. cradle-to-cradle model). Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds)

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21 pages, 4449 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Catalytic Routes to Produce Polyphenolic Esters (PEs) from Biomass Feedstocks

by Antonio Faggiano, Maria Ricciardi and Antonio Proto

Catalysts 2022, 12(4), 447; https://doi.org/10.3390/catal12040447 - 18 Apr 2022

Cited by 11 | Viewed by 4665

Abstract

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding [...] Read more.

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding the catalytic production of PEs from biomass feedstocks, namely, naturally occurred polyphenolic compounds. Several synthetic approaches are reported in the literature, mainly bio-catalysis and to a lesser extent acid catalysis. Immobilized lipases (e.g., Novozym 435) are the preferred enzymes thanks to their high reactivity, selectivity and reusability. Acid catalysis is principally investigated for the esterification of polyphenolic acids with fatty alcohols and/or glycerol, using both homogeneous (p-toluensulfonic acid, sulfonic acid and ionic liquids) and heterogeneous (strongly acidic cation exchange resins) catalysts. Based on the reviewed publications, we propose some suggestions to improve the synthesis of PEs with the aim of increasing the greenness of the overall production process. In fact, much more attention should be paid to the use of new and efficient acid catalysts and their reuse for multiple reaction cycles. Full article

(This article belongs to the Special Issue Recent Advances in Catalytic Biomass Conversion to Value-Added Chemicals)

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34 pages, 2860 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Catalysis for Methanation of CO₂ from Biogas

by Selina Nieß, Udo Armbruster, Sebastian Dietrich and Marco Klemm

Catalysts 2022, 12(4), 374; https://doi.org/10.3390/catal12040374 - 25 Mar 2022

Cited by 22 | Viewed by 5880

Abstract

Biogas, with its high carbon dioxide content (30–50 vol%), is an attractive feed for catalytic methanation with green hydrogen, and is suitable for establishing a closed carbon cycle with methane as energy carrier. The most important questions for direct biogas methanation are how [...] Read more.

Biogas, with its high carbon dioxide content (30–50 vol%), is an attractive feed for catalytic methanation with green hydrogen, and is suitable for establishing a closed carbon cycle with methane as energy carrier. The most important questions for direct biogas methanation are how the high methane content influences the methanation reaction and overall efficiency on one hand, and to what extent the methanation catalysts can be made more resistant to various sulfur-containing compounds in biogas on the other hand. Ni-based catalysts are the most favored for economic reasons. The interplay of active compounds, supports, and promoters is discussed regarding the potential for improving sulfur resistance. Several strategies are addressed and experimental studies are evaluated, to identify catalysts which might be suitable for these challenges. As several catalyst functionalities must be combined, materials with two active metals and binary oxide support seem to be the best approach to technically applicable solutions. The high methane content in biogas appears to have a measurable impact on equilibrium and therefore CO₂ conversion. Depending on the initial CH₄/CO₂ ratio, this might lead to a product with higher methane content, and, after work-up, to a drop in-option for existing natural gas grids. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis in Green Chemistry)

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30 pages, 31819 KiB

Open AccessEditor’s ChoiceReview

Prospects and Technical Challenges in Hydrogen Production through Dry Reforming of Methane

by Fábio Gonçalves Macêdo de Medeiros, Francisco Wendell Bezerra Lopes and Bruna Rego de Vasconcelos

Catalysts 2022, 12(4), 363; https://doi.org/10.3390/catal12040363 - 23 Mar 2022

Cited by 36 | Viewed by 10652

Abstract

Environmental issues related to greenhouse gases (GHG) emissions have pushed the development of new technologies that will allow the economic production of low-carbon energy vectors, such as hydrogen (H₂), methane (CH₄) and liquid fuels. Dry reforming of methane (DRM) [...] Read more.

Environmental issues related to greenhouse gases (GHG) emissions have pushed the development of new technologies that will allow the economic production of low-carbon energy vectors, such as hydrogen (H₂), methane (CH₄) and liquid fuels. Dry reforming of methane (DRM) has gained increased attention since it uses CH₄ and carbon dioxide (CO₂), which are two main greenhouse gases (GHG), as feedstock for the production of syngas, which is a mixture of H₂ and carbon monoxide (CO) and can be used as a building block for the production of fuels. Since H₂ has been identified as a key enabler of the energy transition, a lot of studies have aimed to benefit from the environmental advantages of DRM and to use it as a pathway for a sustainable H₂ production. However, there are several challenges related to this process and to its use for H₂ production, such as catalyst deactivation and the low H₂/CO ratio of the syngas produced, which is usually below 1.0. This paper presents the recent advances in the catalyst development for H₂ production via DRM, the processes that could be combined with DRM to overcome these challenges and the current industrial processes using DRM. The objective is to assess in which conditions DRM could be used for H₂ production and the gaps in literature data preventing better evaluation of the environmental and economic potential of this process. Full article

(This article belongs to the Special Issue Current Trends in Dry (CO₂) Reforming Catalysis)

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18 pages, 2562 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Stereochemical and Photophysical Properties of Functionalized Thiahelicenes

by Valentina Pelliccioli, Francesca Cardano, Giacomo Renno, Francesca Vasile, Claudia Graiff, Giuseppe Mazzeo, Andrea Fin, Giovanna Longhi, Sergio Abbate, Alessia Rosetti, Claudio Villani, Guido Viscardi, Emanuela Licandro and Silvia Cauteruccio

Catalysts 2022, 12(4), 366; https://doi.org/10.3390/catal12040366 - 23 Mar 2022

Cited by 7 | Viewed by 3698

Abstract

We report on the synthesis of a novel class of functionalized thia[6]helicenes and a thia[5]helicene, containing a benzothiophene unit and a second heteroatom embedded in the helix (i.e., nitrogen and oxygen) or a pyrene or a spirobifluorene moiety. These systems are obtained through [...] Read more.

We report on the synthesis of a novel class of functionalized thia[6]helicenes and a thia[5]helicene, containing a benzothiophene unit and a second heteroatom embedded in the helix (i.e., nitrogen and oxygen) or a pyrene or a spirobifluorene moiety. These systems are obtained through straightforward and general procedures that involve: (i) palladium-catalyzed annulation of iodo-atropoisomers with internal alkynes and (ii) Suzuki coupling of iodo-atropoisomers with phenyl boronic acid followed by a Mallory-type reaction. Both experimental and theoretical studies on the configurational stability of some selected thia[6]helicenes confirmed their stability toward racemization at room temperature, while the pyrene-based thia[5]helicene was found to be unstable. Moreover, the configuration assignment for one representative thiahelicene was established through the comparison between experimental and theoretical circular dichroism (CD) spectra. A systematic study of the photophysical properties of both thiahelicenes and the corresponding atropoisomers has been carried out to provide a complete overview on the new molecules proposed in this work. The obtained data showed regular trends in all the thiahelicene series with spectroscopic traits in line with those previously observed for similar heterohelicenes. Full article

(This article belongs to the Special Issue Catalysts for the Synthesis of Heterocyclic Compounds)

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23 pages, 7938 KiB

Open AccessEditor’s ChoiceArticle

Cerium-Copper Oxides Synthesized in a Multi-Inlet Vortex Reactor as Effective Nanocatalysts for CO and Ethene Oxidation Reactions

by Melodj Dosa, Miguel Jose Marin-Figueredo, Enrico Sartoretti, Chiara Novara, Fabrizio Giorgis, Samir Bensaid, Debora Fino, Nunzio Russo and Marco Piumetti

Catalysts 2022, 12(4), 364; https://doi.org/10.3390/catal12040364 - 23 Mar 2022

Cited by 15 | Viewed by 3481

Abstract

In this study, a set of CuCeO_x catalysts was prepared via the coprecipitation method using a Multi-Inlet Vortex Reactor: the Cu wt.% content is 5, 10, 20, 30 and 60. Moreover, pure CeO₂ and CuO were synthesized for comparison purposes. The [...] Read more.

In this study, a set of CuCeO_x catalysts was prepared via the coprecipitation method using a Multi-Inlet Vortex Reactor: the Cu wt.% content is 5, 10, 20, 30 and 60. Moreover, pure CeO₂ and CuO were synthesized for comparison purposes. The physico-chemical properties of this set of samples were investigated by complementary techniques, e.g., XRD, N₂ physisorption at −196 °C, Scanning Electron Microscopy, XPS, FT-IR, Raman spectroscopy and H₂-TPR. Then, the CuCeO_x catalysts were tested for the CO and ethene oxidation reactions. As a whole, all the prepared samples presented good catalytic performances towards the CO oxidation reaction (1000 ppm CO, 10 vol.% O₂/N₂): the most promising catalyst was the 20%CuCeO_x (complete CO conversion at 125 °C), which exhibited a long-term thermal stability. Similarly, the oxidative activity of the catalysts were evaluated using a gaseous mixture containing 500 ppm C₂H₄, 10 vol.% O₂/N₂. Accordingly, for the ethene oxidation reaction, the 20%CuCeO_x catalyst evidenced the best catalytic properties. The elevated catalytic activity towards CO and ethene oxidation was mainly ascribed to synergistic interactions between CeO₂ and CuO phases, as well as to the high amount of surface-chemisorbed oxygen species and structural defects. Full article

(This article belongs to the Section Nanostructured Catalysts)

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19 pages, 5510 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Temperature-Dependent Activity of Gold Nanocatalysts Supported on Activated Carbon in Redox Catalytic Reactions: 5-Hydroxymethylfurfural Oxidation and 4-Nitrophenol Reduction Comparison

by Stefano Scurti, Alessandro Allegri, Francesca Liuzzi, Elena Rodríguez-Aguado, Juan Antonio Cecilia, Stefania Albonetti, Daniele Caretti and Nikolaos Dimitratos

Catalysts 2022, 12(3), 323; https://doi.org/10.3390/catal12030323 - 11 Mar 2022

Cited by 7 | Viewed by 3873

Abstract

In this study, the temperature-dependent activity of Au/AC nanocatalysts in redox catalytic reactions was investigated. To this end, a series of colloidal gold catalysts supported on activated carbon and titania were prepared by the sol immobilization method employing polyvinyl alcohol as a polymeric [...] Read more.

In this study, the temperature-dependent activity of Au/AC nanocatalysts in redox catalytic reactions was investigated. To this end, a series of colloidal gold catalysts supported on activated carbon and titania were prepared by the sol immobilization method employing polyvinyl alcohol as a polymeric stabilizer at different hydrolysis degrees. The as-synthesized materials were widely characterized by spectroscopic analysis (XPS, XRD, and ATR-IR) as well as TEM microscopy and DLS/ELS measurements. Furthermore, 5-hydroxymethylfurfural (HMF) oxidation and 4-nitrophenol (4-NP) reduction were chosen to investigate the catalytic activity as a model reaction for biomass valorization and wastewater remediation. In particular, by fitting the hydrolysis degree with the kinetic data, volcano plots were obtained for both reactions, in which the maximum of the curves was represented relative to hydrolysis intermediate values. However, a comparison of the catalytic performance of the sample Au/AC_PVA-99 (hydrolysis degree of the polymer is 99%) in the two reactions showed a different catalytic behavior, probably due to the detachment of polymer derived from the different reaction temperature chosen between the two reactions. For this reason, several tests were carried out to investigate deeper the observed catalytic trend, focusing on studying the effect of the reaction temperature as well as the effect of support (metal–support interaction) by immobilizing Au colloidal nanoparticles on commercial titania. The kinetic data, combined with the characterization carried out on the catalysts, confirmed that changing the reaction conditions, the PVA behavior on the surface of the catalysts, and, therefore, the reaction outcome, is modified. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, etc.)—Series II)

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18 pages, 963 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthesis of Propylene Carbonate by Urea Alcoholysis—Recent Advances

by Łukasz Kotyrba, Anna Chrobok and Agnieszka Siewniak

Catalysts 2022, 12(3), 309; https://doi.org/10.3390/catal12030309 - 9 Mar 2022

Cited by 10 | Viewed by 7177

Abstract

Organic carbonates are considered the chemicals of the future. In particular, propylene carbonate is widely used as a non-reactive solvent, plasticizer, fuel additive, and reagent, especially in the production of environmentally friendly polymers that are not harmful to human health. This paper reviews [...] Read more.

Organic carbonates are considered the chemicals of the future. In particular, propylene carbonate is widely used as a non-reactive solvent, plasticizer, fuel additive, and reagent, especially in the production of environmentally friendly polymers that are not harmful to human health. This paper reviews recent literature findings regarding the development of propylene carbonate synthetic methods starting from propane-1,2-diol and urea. The ammonia formed during the synthesis is recycled to obtain urea from carbon dioxide. Full article

(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)

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11 pages, 1337 KiB

Open AccessEditor’s ChoiceArticle

Comparing the Performance of Supported Ru Nanocatalysts Prepared by Chemical Reduction of RuCl₃ and Thermal Decomposition of Ru₃(CO)₁₂ in the Sunlight-Powered Sabatier Reaction

by Daria Burova, Jelle Rohlfs, Francesc Sastre, Pau Martínez Molina, Nicole Meulendijks, Marcel A. Verheijen, An-Sofie Kelchtermans, Ken Elen, An Hardy, Marlies K. Van Bael and Pascal Buskens

Catalysts 2022, 12(3), 284; https://doi.org/10.3390/catal12030284 - 2 Mar 2022

Cited by 6 | Viewed by 4130

Abstract

The preparation of Ru nanoparticles supported on γ-Al₂O₃ followed by chemical reduction using RuCl₃ as a precursor is demonstrated, and their properties are compared to Ru nanoparticles supported on γ-Al₂O₃ prepared by impregnation of γ-Al₂ [...] Read more.

The preparation of Ru nanoparticles supported on γ-Al₂O₃ followed by chemical reduction using RuCl₃ as a precursor is demonstrated, and their properties are compared to Ru nanoparticles supported on γ-Al₂O₃ prepared by impregnation of γ-Al₂O₃ with Ru₃(CO)₁₂ and subsequent thermal decomposition. The Ru nanoparticles resulting from chemical reduction of RuCl₃ are slightly larger (1.2 vs. 0.8 nm). In addition, Ru nanoparticles were deposited on Stöber SiO₂ using both deposition techniques. These particles were larger than the ones deposited on γ-Al₂O₃ (2.5 and 3.4 nm for chemical reduction and thermal decomposition, respectively). Taking into account the size differences between the Ru nanoparticles, all catalysts display similar activity (0.14–0.63 mol·g_Ru⁻¹·h⁻¹) and selectivity (≥99%) in the sunlight-powered Sabatier reaction. Ergo, the use of toxic and volatile Ru₃(CO)₁₂ can be avoided, since catalysts prepared by chemical reduction of RuCl₃ display similar catalytic performance. Full article

(This article belongs to the Special Issue Catalytic CO₂ Methanation Reactors and Processes)

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66 pages, 6105 KiB

Open AccessEditor’s ChoiceReview

Metal-Supported Biochar Catalysts for Sustainable Biorefinery, Electrocatalysis, and Energy Storage Applications: A Review

by Rubén Ramos, Víctor K. Abdelkader-Fernández, Renata Matos, Andreia F. Peixoto and Diana M. Fernandes

Catalysts 2022, 12(2), 207; https://doi.org/10.3390/catal12020207 - 9 Feb 2022

Cited by 62 | Viewed by 9416

Abstract

Biochar (BCH) is a carbon-based bio-material produced from thermochemical conversion of biomass. Several activation or functionalization methods are usually used to improve physicochemical and functional properties of BCHs. In the context of green and sustainable future development, activated and functionalized biochars with abundant [...] Read more.

Biochar (BCH) is a carbon-based bio-material produced from thermochemical conversion of biomass. Several activation or functionalization methods are usually used to improve physicochemical and functional properties of BCHs. In the context of green and sustainable future development, activated and functionalized biochars with abundant surface functional groups and large surface area can act as effective catalysts or catalyst supports for chemical transformation of a range of bioproducts in biorefineries. Above the well-known BCH applications, their use as adsorbents to remove pollutants are the mostly discussed, although their potential as catalysts or catalyst supports for advanced (electro)catalytic processes has not been comprehensively explored. In this review, the production/activation/functionalization of metal-supported biochar (M-BCH) are scrutinized, giving special emphasis to the metal-functionalized biochar-based (electro)catalysts as promising catalysts for bioenergy and bioproducts production. Their performance in the fields of biorefinery processes, and energy storage and conversion as electrode materials for oxygen and hydrogen evolutions, oxygen reduction, and supercapacitors, are also reviewed and discussed. Full article

(This article belongs to the Special Issue Catalytic Sustainable Processes Using Carbonaceous Materials)

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24 pages, 5093 KiB

Open AccessEditor’s ChoiceArticle

Lignin Depolymerization in the Presence of Base, Hydrogenation Catalysts, and Ethanol

by Iuliia Romanenko, Felix Kurz, Robert Baumgarten, Ivana Jevtovikj, Jean-Pierre Lindner, Arunabha Kundu, Alois Kindler and Stephan Andreas Schunk

Catalysts 2022, 12(2), 158; https://doi.org/10.3390/catal12020158 - 27 Jan 2022

Cited by 17 | Viewed by 5092

Abstract

Being the major renewable source of bio-aromatics, lignin possesses considerable potential for the chemical industry as raw material. Kraft lignin is a couple product of paper industry with an annual production of 55,000,000 ton/y and is considered the largest share of available lignin. [...] Read more.

Being the major renewable source of bio-aromatics, lignin possesses considerable potential for the chemical industry as raw material. Kraft lignin is a couple product of paper industry with an annual production of 55,000,000 ton/y and is considered the largest share of available lignin. Here we report a facile approach of Kraft lignin depolymerization to defined oligomeric units with yields of up to 70 wt.%. The process implies utilization of an aqueous base in combination with a metal containing catalyst and an alcohol under non-oxidative atmosphere at 300 °C. An advantage of the developed approach is the facile separation of the oligomer product that precipitates from the reaction mixture. In addition, the process proceeds without char formation; both factors make it attractive for industrialization. The suppression of the repolymerization processes that lead to char formation is possible when the combination of metal containing catalyst in the presence of an alcohol is used. It was found that the oligomer units have structural features found in phenol-acetaldehyde resins. These features result from the base catalyzed condensation of lignin fragments with in situ formed aldehydes. Catalytic dehydrogenation of the alcohol provides the latter. This reaction pathway is confirmed by the presence condensation products of Guerbet type reactions. Full article

(This article belongs to the Special Issue 10th Anniversary of Catalysts: Contributions in Biomass Catalytic Conversion for a Sustainable Future)

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17 pages, 11545 KiB

Open AccessEditor’s ChoiceArticle

Highly Efficient and Sustainable ZnO/CuO/g-C₃N₄ Photocatalyst for Wastewater Treatment under Visible Light through Heterojunction Development

by Md. Abu Hanif, Jeasmin Akter, Young Soon Kim, Hong Gun Kim, Jae Ryang Hahn and Lee Ku Kwac

Catalysts 2022, 12(2), 151; https://doi.org/10.3390/catal12020151 - 25 Jan 2022

Cited by 29 | Viewed by 4943

Abstract

Dye-containing pollutants are currently a threat to the environment, and it is highly challenging to eliminate these dyes photocatalytically under visible light. Herein, we designed and prepared a ZnO/CuO/g-C₃N₄ (ZCG) heterostructure nanocomposite by a co-crystallization procedure and applied it to [...] Read more.

Dye-containing pollutants are currently a threat to the environment, and it is highly challenging to eliminate these dyes photocatalytically under visible light. Herein, we designed and prepared a ZnO/CuO/g-C₃N₄ (ZCG) heterostructure nanocomposite by a co-crystallization procedure and applied it to eliminate pollutants from wastewater via a photocatalytic scheme. The structural and morphological features of the composite confirmed the formation of a ZCG nanocomposite. The photocatalytic capability of the ZCG photocatalyst was investigated via the decomposition of methylene blue dye. The outstanding activity level of 97.46% was reached within 50 min. In addition, the proficiency of the ZCG composite was 753%, 392%, 156%, and 130% higher than photolysis, g-C₃N₄, CuO, and ZnO, respectively. Furthermore, the photodeterioration activity on Congo red was also evaluated and found to be excellent. The enhanced catalytic achievement is attributed to the construction of heterojunctions among the constituent compounds. These properties boost the charge transfer and decrease the recombination rate. Moreover, the reusability of the ZCG product was explored and a negligible photoactivity decline was detected after six successful runs. The outcomes suggest the as-prepared nanocomposite can be applied to remove pollutants, which opens a new door to practical implementation. Full article

(This article belongs to the Special Issue Effect of the Modification of Catalysts on the Catalytic Performance)

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11 pages, 2296 KiB

Open AccessEditor’s ChoiceArticle

Continuous-Flow Sunlight-Powered CO₂ Methanation Catalyzed by γ-Al₂O₃-Supported Plasmonic Ru Nanorods

by Jelle Rohlfs, Koen W. Bossers, Nicole Meulendijks, Fidel Valega Mackenzie, Man Xu, Marcel A. Verheijen, Pascal Buskens and Francesc Sastre

Catalysts 2022, 12(2), 126; https://doi.org/10.3390/catal12020126 - 21 Jan 2022

Cited by 14 | Viewed by 4050

Abstract

Plasmonic CO₂ methanation using γ-Al₂O₃-supported Ru nanorods was carried out under continuous-flow conditions without conventional heating, using mildly concentrated sunlight as the sole and sustainable energy source (AM 1.5, irradiance 5.5–14.4 kW·m⁻² = 5.5–14.4 suns). Under 12.5 [...] Read more.

Plasmonic CO₂ methanation using γ-Al₂O₃-supported Ru nanorods was carried out under continuous-flow conditions without conventional heating, using mildly concentrated sunlight as the sole and sustainable energy source (AM 1.5, irradiance 5.5–14.4 kW·m⁻² = 5.5–14.4 suns). Under 12.5 suns, a CO₂ conversion exceeding 97% was achieved with complete selectivity towards CH₄ and a stable production rate (261.9

mmol \cdot g_{Ru}^{- 1} \cdot h^{- 1}

) for at least 12 h. The CH₄ production rate showed an exponential increase with increasing light intensity, suggesting that the process was mainly promoted by photothermal heating. This was confirmed by the apparent activation energy of 64.3 kJ·mol⁻¹, which is very similar to the activation energy obtained for reference experiments in dark (67.3 kJ·mol⁻¹). The flow rate influence was studied under 14.4 suns, achieving a CH₄ production plateau of 264 µmol min⁻¹ (792

mmol \cdot g_{Ru}^{- 1} \cdot h^{- 1}

) with a constant catalyst bed temperature of approximately 204 °C. Full article

(This article belongs to the Special Issue Catalytic CO₂ Methanation Reactors and Processes)

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16 pages, 6339 KiB

Open AccessEditor’s ChoiceArticle

Mixed Metal Oxides of M1 MoVNbTeO_x and TiO₂ as Composite Catalyst for Oxidative Dehydrogenation of Ethane

by Yuxin Chen, Dan Dang, Binhang Yan and Yi Cheng

Catalysts 2022, 12(1), 71; https://doi.org/10.3390/catal12010071 - 9 Jan 2022

Cited by 9 | Viewed by 3202

Abstract

Composite catalysts of mixed metal oxides were prepared by mixing a phase-pure M1 MoVNbTeO_x with anatase-phase TiO₂. Two methods were used to prepare the composite catalysts (the simple physically mixed or sol-gel method) for the improvement of the catalytic performance [...] Read more.

Composite catalysts of mixed metal oxides were prepared by mixing a phase-pure M1 MoVNbTeO_x with anatase-phase TiO₂. Two methods were used to prepare the composite catalysts (the simple physically mixed or sol-gel method) for the improvement of the catalytic performance in the oxidative dehydrogenation of ethane (ODHE) process. The results showed that TiO₂ particles with a smaller particle size were well dispersed on the M1 surface for the sol-gel method, which presented an excellent activity for ODHE. At the same operating condition (i.e., the contact time of 7.55 g_cat·h/mol_C2H6 and the reaction temperature of 400 °C), the M1-TiO₂-SM and M1-TiO₂-PM achieved the space time yields of 0.67 and 0.52 kg_C2H4/kg_cat/h, respectively, which were about ~76% and ~35% more than that of M1 catalyst (0.38 kg_C2H4/kg_cat/h), respectively. The BET, ICP, XRD, TEM, SEM, H₂-TPR, C₂H₆-TPSR, and XPS techniques were applied to characterize the catalysts. It was noted that the introduction of TiO₂ raised the V⁵⁺ abundance on the catalyst surface as well as the reactivity of active oxygen species, which made contribution to the promotion of the catalytic performance. The surface morphology and crystal structure of used catalysts of either M1-TiO₂-SM or M1-TiO₂-PM remained stable as each fresh catalyst after 24 h time-on-stream tests. Full article

(This article belongs to the Special Issue 10th Anniversary of Catalysts: Feature Papers in Catalytic Reaction Engineering)

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20 pages, 4331 KiB

Open AccessEditor’s ChoiceReview

Dielectric Barrier Discharge Plasma-Assisted Catalytic CO₂ Hydrogenation: Synergy of Catalyst and Plasma

by Xingyuan Gao, Jinglong Liang, Liqing Wu, Lixia Wu and Sibudjing Kawi

Catalysts 2022, 12(1), 66; https://doi.org/10.3390/catal12010066 - 8 Jan 2022

Cited by 30 | Viewed by 6614

Abstract

CO₂ hydrogenation is an effective way to convert CO₂ to value-added chemicals (e.g., CH₄ and CH₃OH). As a thermal catalytic process, it suffers from dissatisfactory catalytic performances (low conversion/selectivity and poor stability) and high energy input. By utilizing [...] Read more.

CO₂ hydrogenation is an effective way to convert CO₂ to value-added chemicals (e.g., CH₄ and CH₃OH). As a thermal catalytic process, it suffers from dissatisfactory catalytic performances (low conversion/selectivity and poor stability) and high energy input. By utilizing the dielectric barrier discharge (DBD) technology, the catalyst and plasma could generate a synergy, activating the whole process in a mild condition, and enhancing the conversion efficiency of CO₂ and selectivity of targeted product. In this review, a comprehensive summary of the applications of DBD plasma in catalytic CO₂ hydrogenation is provided in detail. Moreover, the state-of-the-art design of the reactor and optimization of reaction parameters are discussed. Furthermore, several mechanisms based on simulations and experiments are provided. In the end, the existing challenges of this hybrid system and corresponding solutions are proposed. Full article

(This article belongs to the Special Issue Advancements in Non-Thermal Plasma Catalysis Processes)

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16 pages, 10684 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Heterogeneous Gold Nanoparticle-Based Catalysts for the Synthesis of Click-Derived Triazoles via the Azide-Alkyne Cycloaddition Reaction

by Ivy L. Librando, Abdallah G. Mahmoud, Sónia A. C. Carabineiro, M. Fátima C. Guedes da Silva, Francisco J. Maldonado-Hódar, Carlos F. G. C. Geraldes and Armando J. L. Pombeiro

Catalysts 2022, 12(1), 45; https://doi.org/10.3390/catal12010045 - 31 Dec 2021

Cited by 16 | Viewed by 3376

Abstract

A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC [...] Read more.

A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC reaction, additional robust catalytic systems complementary to the copper catalyzed AAC remain in high demand. Herein, Au nanoparticles supported on Al₂O₃, Fe₂O₃, TiO₂ and ZnO, along with gold reference catalysts (gold on carbon and gold on titania supplied by the World Gold Council) were used as catalysts for the AAC reaction. The supported Au nanoparticles with metal loadings of 0.7–1.6% (w/w relative to support) were able to selectively obtain 1,4-disubstituted-1,2,3-triazoles in moderate yields up to 79% after 15 min, under microwave irradiation at 150 °C using a 0.5–1.0 mol% catalyst loading through a one-pot three-component (terminal alkyne, organohalide and sodium azide) procedure according to the “click” rules. Among the supported Au catalysts, Au/TiO₂ gave the best results. Full article

(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)

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32 pages, 3987 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Fundamentals and Principles of Solid-State Electrochemical Sensors for High Temperature Gas Detection

by Elena Gorbova, Fotini Tzorbatzoglou, Costas Molochas, Dimitris Chloros, Anatoly Demin and Panagiotis Tsiakaras

Catalysts 2022, 12(1), 1; https://doi.org/10.3390/catal12010001 - 21 Dec 2021

Cited by 50 | Viewed by 8197

Abstract

The rapid development of science, technology, and engineering in the 21st century has offered a remarkable rise in our living standards. However, at the same time, serious environmental issues have emerged, such as acid rain and the greenhouse effect, which are associated with [...] Read more.

The rapid development of science, technology, and engineering in the 21st century has offered a remarkable rise in our living standards. However, at the same time, serious environmental issues have emerged, such as acid rain and the greenhouse effect, which are associated with the ever-increasing need for energy consumption, 85% of which comes from fossil fuels combustion. From this combustion process, except for energy, the main greenhouse gases-carbon dioxide and steam-are produced. Moreover, during industrial processes, many hazardous gases are emitted. For this reason, gas-detecting devices, such as electrochemical gas sensors able to analyze the composition of a target atmosphere in real time, are important for further improving our living quality. Such devices can help address environmental issues and inform us about the presence of dangerous gases. Furthermore, as non-renewable energy sources run out, there is a need for energy saving. By analyzing the composition of combustion emissions of automobiles or industries, combustion processes can be optimized. This review deals with electrochemical gas sensors based on solid oxide electrolytes, which are employed for the detection of hazardous gasses at high temperatures and aggressive environments. The fundamentals, the principle of operation, and the configuration of potentiometric, amperometric, combined (amperometric-potentiometric), and mixed-potential gas sensors are presented. Moreover, the results of previous studies on carbon oxides (CO_x), nitrogen oxides (NO_x), hydrogen (H₂), oxygen (O₂), ammonia (NH₃), and humidity (steam) electrochemical sensors are reported and discussed. Emphasis is given to sensors based on oxygen ion and proton-conducting electrolytes. Full article

(This article belongs to the Special Issue Catalysis in an Electrochemical Cell: Solid Oxide Fuel Cells, Electrolyzers and Electrochemical Sensors)

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24 pages, 4980 KiB

Open AccessEditor’s ChoiceReview

Applicability of Nickel-Based Catalytic Systems for Hydrodehalogenation of Recalcitrant Halogenated Aromatic Compounds

by Tomáš Weidlich

Catalysts 2021, 11(12), 1465; https://doi.org/10.3390/catal11121465 - 30 Nov 2021

Cited by 5 | Viewed by 4322

Abstract

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with [...] Read more.

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with Ar–Xs. Ni-catalyzed HDH enables the production of corresponding nonhalogenated aromatic products (Ar–Hs), which are principally further applicable/recyclable and/or Ar–Hs, which are much more biodegradable and can be mineralized during aerobic wastewater treatment. Developed HDH methods enable the utilization of both gaseous hydrogen via the direct HDH process or other chemical reductants as a source of hydrogen utilized in the transfer of the hydrodehalogenation process. This review highlights recent and major developments in Ni-catalyzed hydrodehalogenation topic since 1990. Full article

(This article belongs to the Special Issue Recent Advances in Nickel-Based Catalysts)

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20 pages, 4557 KiB

Open AccessEditor’s ChoiceArticle

Shape-Dependent Catalytic Activity of Gold and Bimetallic Nanoparticles in the Reduction of Methylene Blue by Sodium Borohydride

by Heike Lisa Kerstin Stephanie Stolle, Jonas Jakobus Kluitmann, Andrea Csáki, Johann Michael Köhler and Wolfgang Fritzsche

Catalysts 2021, 11(12), 1442; https://doi.org/10.3390/catal11121442 - 26 Nov 2021

Cited by 22 | Viewed by 4024

Abstract

In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as [...] Read more.

In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as bimetallic gold–palladium and gold–platinum core-shell nanorods, we evaluate the effect of the catalyst surface area as available gold surface area, the shape of the nanoparticles and the impact of added secondary metals in case of bimetallic nanorods. We track the reaction by UV/Vis measurements in the range of 190–850 nm every 60 s. It is assumed that the gold nanoparticles do not only act as a unit transferring electrons from sodium borohydride towards methylene blue but can promote the electron transfer upon plasmonic excitation. By testing different particle shapes, we could indeed demonstrate an effect of the particle shape by excluding the impact of surface area and/or surface ligands. All nanoparticle solutions showed a higher methylene blue turnover than their reference, whereby gold nanoprisms exhibited 100% turnover as no further methylene blue absorption peak was detected. The reaction rate constant k was also determined and revealed overall quicker reactions when gold or bimetallic nanoparticles were added as a catalyst, and again these were highest for nanoprisms. Furthermore, when comparing gold and bimetallic nanorods, it could be shown that through the addition of the catalytically active second metal platinum or palladium, the dye turnover was accelerated and degradation rate constants were higher compared to those of pure gold nanorods. The results explore the catalytic activity of nanoparticles, and assist in exploring further catalytic applications. Full article

(This article belongs to the Special Issue Innovative Functional Materials in Photocatalysis)

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16 pages, 1702 KiB

Open AccessEditor’s ChoiceArticle

Application Potential of Cyanide Hydratase from Exidia glandulosa: Free Cyanide Removal from Simulated Industrial Effluents

by Anastasia Sedova, Lenka Rucká, Pavla Bojarová, Michaela Glozlová, Petr Novotný, Barbora Křístková, Miroslav Pátek and Ludmila Martínková

Catalysts 2021, 11(11), 1410; https://doi.org/10.3390/catal11111410 - 21 Nov 2021

Cited by 8 | Viewed by 3325

Abstract

Industries such as mining, cokemaking, (petro)chemical and electroplating produce effluents that contain free cyanide (fCN = HCN + CN⁻). Currently, fCN is mainly removed by (physico)chemical methods or by biotreatment with activated sludge. Cyanide hydratases (CynHs) (EC 4.2.1.66), which convert fCN [...] Read more.

Industries such as mining, cokemaking, (petro)chemical and electroplating produce effluents that contain free cyanide (fCN = HCN + CN⁻). Currently, fCN is mainly removed by (physico)chemical methods or by biotreatment with activated sludge. Cyanide hydratases (CynHs) (EC 4.2.1.66), which convert fCN to the much less toxic formamide, have been considered for a mild approach to wastewater decyanation. However, few data are available to evaluate the application potential of CynHs. In this study, we used a new CynH from Exidia glandulosa (protein KZV92691.1 designated NitEg by us), which was overproduced in Escherichia coli. The purified NitEg was highly active for fCN with 784 U/mg protein, k_cat 927/s and k_cat/K_M 42/s/mM. It exhibited optimal activities at pH approximately 6–9 and 40–45 °C. It was quite stable in this pH range, and retained approximately 40% activity at 37 °C after 1 day. Silver and copper ions (1 mM) decreased its activity by 30–40%. The removal of 98–100% fCN was achieved for 0.6–100 mM fCN. Moreover, thiocyanate, sulfide, ammonia or phenol added in amounts typical of industrial effluents did not significantly reduce the fCN conversion, while electroplating effluents may need to be diluted due to high fCN and metal content. The ease of preparation of NitEg, its high specific activity, robustness and long shelf life make it a promising biocatalyst for the detoxification of fCN. Full article

(This article belongs to the Special Issue Enzymes and Biocatalysis)

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11 pages, 7629 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups

by Yang Li, Xiaoling Lai, Xiaowei Xu, Yat-Ming So, Yijing Du, Zhengze Zhang and Yu Pan

Catalysts 2021, 11(11), 1392; https://doi.org/10.3390/catal11111392 - 18 Nov 2021

Cited by 7 | Viewed by 3128

Abstract

Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by three half-metallocenes, [...] Read more.

Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by three half-metallocenes, (η⁵-C₅Me₅)TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1), (η⁵-C₅Me₅)TiCl₂(N=C^tBu₂) (2) and [Me₂Si(η⁵-C₅Me₄)(N^tBu)]TiCl₂ (3), have been investigated by density functional theory (DFT) method. At the initiation stage, a higher free energy barrier was determined for complex 1, probably due to the presence of electronegative O atom in phenoxy ligand. At the propagation stage, front-side insertion of the second ethylene is kinetically more favorable than back-side insertion for complexes 1 and 2, while both side insertion orientations are comparable for complex 3. The energy decomposition showed that the bridged cyclopentadienyl amide ligand could enhance the rigidity of the active species as suggested by the lowest deformation energy derived from 3. At the chain termination stage, β-H transfer was calculated to be a dominant chain termination route over β-H elimination, presumably owing to the thermodynamic perspective. Full article

(This article belongs to the Special Issue Advances in Ziegler-Natta Type Catalysts for Olefin Polymerization)

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17 pages, 4960 KiB

Open AccessEditor’s ChoiceArticle

Mapping the Effects of Potassium on Fuel Conversion in Industrial-Scale Fluidized Bed Gasifiers and Combustors

by Teresa Berdugo Vilches, Jelena Maric, Henrik Thunman and Martin Seemann

Catalysts 2021, 11(11), 1380; https://doi.org/10.3390/catal11111380 - 16 Nov 2021

Cited by 3 | Viewed by 2437

Abstract

Potassium (K) is a notorious villain among the ash components found in the biomass, being the cause of bed agglomeration and contributing to fouling and corrosion. At the same time, K is known to have catalytic properties towards fuel conversion in combustion and [...] Read more.

Potassium (K) is a notorious villain among the ash components found in the biomass, being the cause of bed agglomeration and contributing to fouling and corrosion. At the same time, K is known to have catalytic properties towards fuel conversion in combustion and gasification environments. Olivine (MgFe silicate) used as gasifier bed material has a higher propensity to form catalytically active K species than traditional silica sand beds, which tend to react with K to form stable and inactive silicates. In a dual fluidized bed (DFB) gasifier, many of those catalytic effects are expected to be relevant, given that the bed material becomes naturally enriched with ash elements from the fuel. However, a comprehensive overview of how enrichment of the bed with alkali affects fuel conversion in both parts of the DFB system is lacking. In this work, the effects of ash-enriched olivine on fuel conversion in the gasification and combustion parts of the process are mapped. The work is based on a dedicated experimental campaign in a Chalmers DFB gasifier, wherein enrichment of the bed material with K is promoted by the addition of a reaction partner, i.e., sulfur, which ensures K retention in the bed in forms other than inactive silicates. The choice of sulfur is based on its affinity for K under combustion conditions. The addition of sulfur proved to be an efficient strategy for capturing catalytic K in olivine particles. In the gasification part, K-loaded olivine enhanced the char gasification rate, decreased the tar concentration, and promoted the WGS equilibrium. In the combustion part, K prevented full oxidation of CO, which could be mitigated by the addition of sulfur to the cyclone outlet. Full article

(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)

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70 pages, 18281 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review and Experimental Revisit of Alternative Catalysts for Selective Oxidation of Methanol to Formaldehyde

by Joachim Thrane, Uffe V. Mentzel, Max Thorhauge, Martin Høj and Anker D. Jensen

Catalysts 2021, 11(11), 1329; https://doi.org/10.3390/catal11111329 - 31 Oct 2021

Cited by 31 | Viewed by 11358

Abstract

The selective oxidation of methanol to formaldehyde is a growing million-dollar industry, and has been commercial for close to a century. The Formox process, which is the largest production process today, utilizes an iron molybdate catalyst, which is highly selective, but has a [...] Read more.

The selective oxidation of methanol to formaldehyde is a growing million-dollar industry, and has been commercial for close to a century. The Formox process, which is the largest production process today, utilizes an iron molybdate catalyst, which is highly selective, but has a short lifetime of 6 months due to volatilization of the active molybdenum oxide. Improvements of the process’s lifetime is, thus, desirable. This paper provides an overview of the efforts reported in the scientific literature to find alternative catalysts for the Formox process and critically assess these alternatives for their industrial potential. The catalysts can be grouped into three main categories: Mo containing, V containing, and those not containing Mo or V. Furthermore, selected interesting catalysts were synthesized, tested for their performance in the title reaction, and the results critically compared with previously published results. Lastly, an outlook on the progress for finding new catalytic materials is provided as well as suggestions for the future focus of Formox catalyst research. Full article

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26 pages, 645 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Cutaneotrichosporon oleaginosus: A Versatile Whole-Cell Biocatalyst for the Production of Single-Cell Oil from Agro-Industrial Wastes

by Nicola Di Fidio, Filippo Minonne, Claudia Antonetti and Anna Maria Raspolli Galletti

Catalysts 2021, 11(11), 1291; https://doi.org/10.3390/catal11111291 - 27 Oct 2021

Cited by 29 | Viewed by 7851

Abstract

Cutaneotrichosporon oleaginosus is an oleaginous yeast with several favourable qualities: It is fast growing, accumulates high amounts of lipids and has a very broad substrate spectrum. Its resistance to hydrolysis by-products makes it a promising biocatalyst for custom tailored microbial oils. C. oleaginosus [...] Read more.

Cutaneotrichosporon oleaginosus is an oleaginous yeast with several favourable qualities: It is fast growing, accumulates high amounts of lipids and has a very broad substrate spectrum. Its resistance to hydrolysis by-products makes it a promising biocatalyst for custom tailored microbial oils. C. oleaginosus can accumulate up to 60 wt.% of its biomass as lipids. This species is able to grow by using several compounds as a substrate, such as acetic acid, biodiesel-derived glycerol, N-acetylglucosamine, lignocellulosic hydrolysates, wastepaper and other agro-industrial wastes. This review is focused on state-of-the-art innovative and sustainable biorefinery schemes involving this promising yeast and second- and third-generation biomasses. Moreover, this review offers a comprehensive and updated summary of process strategies, biomass pretreatments and fermentation conditions for enhancing lipid production by C. oleaginosus as a whole-cell biocatalyst. Finally, an overview of the main industrial applications of single-cell oil is reported together with future perspectives. Full article

(This article belongs to the Special Issue Biocatalysis and Bioconversion Utilizing Sustainable Feedstock)

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16 pages, 2929 KiB

Open AccessEditor’s ChoiceArticle

Thickness-Dependent Photocatalysis of Ultra-Thin MoS₂ Film for Visible-Light-Driven CO₂ Reduction

by Yi-Fan Huang, Kuan-Wei Liao, Fariz Rifqi Zul Fahmi, Varad A. Modak, Shang-Hsuan Tsai, Shang-Wei Ke, Chen-Hao Wang, Li-Chyong Chen and Kuei-Hsien Chen

Catalysts 2021, 11(11), 1295; https://doi.org/10.3390/catal11111295 - 27 Oct 2021

Cited by 12 | Viewed by 3924

Abstract

The thickness of transition metal dichalcogenides (TMDs) plays a key role in enhancing their photocatalytic CO₂ reduction activity. However, the optimum thickness of the layered TMDs that is required to achieve sufficient light absorption and excellent crystallinity has still not been definitively [...] Read more.

The thickness of transition metal dichalcogenides (TMDs) plays a key role in enhancing their photocatalytic CO₂ reduction activity. However, the optimum thickness of the layered TMDs that is required to achieve sufficient light absorption and excellent crystallinity has still not been definitively determined. In this work, ultra-thin molybdenum disulfide films (MoS₂TF) with 25 nm thickness presented remarkable photocatalytic activity, and the product yield increased by about 2.3 times. The photocatalytic mechanism corresponding to the TMDs’ thickness was also proposed. This work demonstrates that the thickness optimization of TMDs provides a cogent direction for the design of high-performance photocatalysts. Full article

(This article belongs to the Special Issue Photocatalysis in 2D Materials Science)

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20 pages, 4663 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Expeditious Asymmetric Synthesis of Polypropionates Relying on Sulfur Dioxide-Induced C–C Bond Forming Reactions

by Pierre Vogel and José Angel Sordo Gonzalo

Catalysts 2021, 11(11), 1267; https://doi.org/10.3390/catal11111267 - 21 Oct 2021

Viewed by 3196

Abstract

For a long time, the organic chemistry of sulfur dioxide (SO₂) consisted of sulfinates that react with carbon electrophiles to generate sulfones. With alkenes and other unsaturated compounds, SO₂ generates polymeric materials such as polysulfones. More recently, H-ene, sila-ene and [...] Read more.

For a long time, the organic chemistry of sulfur dioxide (SO₂) consisted of sulfinates that react with carbon electrophiles to generate sulfones. With alkenes and other unsaturated compounds, SO₂ generates polymeric materials such as polysulfones. More recently, H-ene, sila-ene and hetero-Diels–Alder reactions of SO₂ have been realized under conditions that avoid polymer formation. Sultines resulting from the hetero-Diels–Alder reactions of conjugated dienes and SO₂ are formed more rapidly than the corresponding more stable sulfolenes resulting from the cheletropic additions. In the presence of a protic or Lewis acid catalyst, the sultines derived from 1-alkoxydienes are ionized into zwitterionic intermediates bearing 1-alkoxyallylic cation moieties which react with electro-rich alkenes such as enol silyl ethers and allylsilanes with high stereoselectivity. (C–C-bond formation through Umpolung induced by SO₂). This produces silyl sulfinates that react with carbon electrophiles to give sulfones (one-pot four component asymmetric synthesis of sulfones), or with Cl₂, generating the corresponding sulfonamides that can be reacted in situ with primary and secondary amines (one-pot four component asymmetric synthesis of sulfonamides). Alternatively, Pd-catalyzed desulfinylation generates enantiomerically pure polypropionate stereotriads in one-pot operations. The chirons so obtained are flanked by an ethyl ketone moiety on one side and by a prop-1-en-1-yl carboxylate group on the other. They are ready for two-directional chain elongations, realizing expeditious synthesis of long-chain polypropionates and polyketides. The stereotriads have also been converted into simpler polypropionates such as the cyclohexanone moiety of baconipyrone A and B, Kishi’s stereoheptad unit of rifamycin S, Nicolaou’s C₁–C₁₁-fragment and Koert’s C₁₆–C_I fragment of apoptolidin A. This has also permitted the first total synthesis of (-)-dolabriferol. Full article

(This article belongs to the Special Issue Catalysts in Carbon-Carbon Coupling Reactions)

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12 pages, 2271 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Facile Surfactant-Assisted Synthesis of BiVO₄ Nanoparticulate Films for Solar Water Splitting

by Laura Montañés, Camilo A. Mesa, Ana Gutiérrez-Blanco, Christian Robles, Beatriz Julián-López and Sixto Giménez

Catalysts 2021, 11(10), 1244; https://doi.org/10.3390/catal11101244 - 15 Oct 2021

Cited by 5 | Viewed by 3621

Abstract

Bismuth vanadate (BiVO₄), which has attractive applicability as a photoactive material, presents applications that range from catalysis to water treatment upon visible light irradiation. In this study, we develop a simple synthesis of < 200 nm monoclinic BiVO₄ nanoparticles, which [...] Read more.

Bismuth vanadate (BiVO₄), which has attractive applicability as a photoactive material, presents applications that range from catalysis to water treatment upon visible light irradiation. In this study, we develop a simple synthesis of < 200 nm monoclinic BiVO₄ nanoparticles, which were further deposited on transparent conductive substrates by spin coating and calcination, obtaining nanostructured films. The obtained nanostructured BiVO₄ photoanodes were tested for water oxidation, leading to promising photocurrents exhibiting competitive onset potentials (~0.3 V vs. RHE). These nanoparticulate BiVO₄ photoanodes represent a novel class of highly potential materials for the design of efficient photoelectrochemical devices. Full article

(This article belongs to the Special Issue Photoelectrochemical and Photocatalytic Materials for Fuel Production)

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22 pages, 3267 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Multifunctional Electrocatalysis on Single-Site Metal Catalysts: A Computational Perspective

by Ritums Cepitis, Nadezda Kongi, Vitali Grozovski, Vladislav Ivaništšev and Enn Lust

Catalysts 2021, 11(10), 1165; https://doi.org/10.3390/catal11101165 - 27 Sep 2021

Cited by 17 | Viewed by 5130

Abstract

Multifunctional electrocatalysts are vastly sought for their applications in water splitting electrolyzers, metal-air batteries, and regenerative fuel cells because of their ability to catalyze multiple reactions such as hydrogen evolution, oxygen evolution, and oxygen reduction reactions. More specifically, the application of single-atom electrocatalyst [...] Read more.

Multifunctional electrocatalysts are vastly sought for their applications in water splitting electrolyzers, metal-air batteries, and regenerative fuel cells because of their ability to catalyze multiple reactions such as hydrogen evolution, oxygen evolution, and oxygen reduction reactions. More specifically, the application of single-atom electrocatalyst in multifunctional catalysis is a promising approach to ensure good atomic efficiency, tunability and additionally benefits simple theoretical treatment. In this review, we provide insights into the variety of single-site metal catalysts and their identification. We also summarize the recent advancements in computational modeling of multifunctional electrocatalysis on single-site catalysts. Furthermore, we explain each modeling step with open-source-based working examples of a standard computational approach. Full article

(This article belongs to the Special Issue Recent Advancements in M-N-C Catalysts for Electrochemical Energy Conversion Devices)

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16 pages, 2136 KiB

Open AccessEditor’s ChoiceArticle

Insights into the Nature of the Active Sites of Pt-WO_x/Al₂O₃ Catalysts for Glycerol Hydrogenolysis into 1,3-Propanediol

by Clara Jarauta-Córdoba, Mikel Oregui Bengoechea, Iker Agirrezabal-Telleria, Pedro-Luis Arias and Iñaki Gandarias

Catalysts 2021, 11(10), 1171; https://doi.org/10.3390/catal11101171 - 27 Sep 2021

Cited by 11 | Viewed by 3086

Abstract

The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WO_x materials are effective catalysts for this transformation, and their activity is often related to the [...] Read more.

The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WO_x materials are effective catalysts for this transformation, and their activity is often related to the tungsten surface density and Brönsted acidity, although there are discrepancies in this regard. In this work, a series of Pt-WO_x/γ-Al₂O₃ catalysts were prepared by modifying the pH of the solutions used in the active metal impregnation step. The activity–structure relationships, together with the results from the addition of in situ titrants, i.e., 2,6-di-tert-butyl-pyridine or pyridine, helped in elucidating the nature of the bifunctional active sites for the selective production of 1,3-propanediol. Full article

(This article belongs to the Special Issue Emergent Materials and Strategies for Catalytic Glycerol Transformation with Low Energy Input)

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20 pages, 3215 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Sustainable One-Pot Immobilization of Enzymes in/on Metal-Organic Framework Materials

by M. Asunción Molina, Victoria Gascón-Pérez, Manuel Sánchez-Sánchez and Rosa M. Blanco

Catalysts 2021, 11(8), 1002; https://doi.org/10.3390/catal11081002 - 20 Aug 2021

Cited by 27 | Viewed by 5960

Abstract

The industrial use of enzymes generally necessitates their immobilization onto solid supports. The well-known high affinity of enzymes for metal-organic framework (MOF) materials, together with the great versatility of MOFs in terms of structure, composition, functionalization and synthetic approaches, has led the scientific [...] Read more.

The industrial use of enzymes generally necessitates their immobilization onto solid supports. The well-known high affinity of enzymes for metal-organic framework (MOF) materials, together with the great versatility of MOFs in terms of structure, composition, functionalization and synthetic approaches, has led the scientific community to develop very different strategies for the immobilization of enzymes in/on MOFs. This review focuses on one of these strategies, namely, the one-pot enzyme immobilization within sustainable MOFs, which is particularly enticing as the resultant biocomposite Enzyme@MOFs have the potential to be: (i) prepared in situ, that is, in just one step; (ii) may be synthesized under sustainable conditions: with water as the sole solvent at room temperature with moderate pHs, etc.; (iii) are able to retain high enzyme loading; (iv) have negligible protein leaching; and (v) give enzymatic activities approaching that given by the corresponding free enzymes. Moreover, this methodology seems to be near-universal, as success has been achieved with different MOFs, with different enzymes and for different applications. So far, the metal ions forming the MOF materials have been chosen according to their low price, low toxicity and, of course, their possibility for generating MOFs at room temperature in water, in order to close the cycle of economic, environmental and energy sustainability in the synthesis, application and disposal life cycle. Full article

(This article belongs to the Special Issue Recent Advances in Biocatalysis and Metabolic Engineering)

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20 pages, 2239 KiB

Open AccessEditor’s ChoiceReview

Contemporary Enzyme-Based Methods for Recombinant Proteins In Vitro Phosphorylation

by Marcela Slovakova and Zuzana Bilkova

Catalysts 2021, 11(8), 1007; https://doi.org/10.3390/catal11081007 - 20 Aug 2021

Cited by 10 | Viewed by 4661

Abstract

Phosphorylation is a reversible, enzyme-controlled posttranslational process affecting approximately one-third of all proteins in eukaryotic cells at any given time. Any deviation in the degree and/or site of phosphorylation leads to an abnormal conformation of proteins, resulting in a decline or loss of [...] Read more.

Phosphorylation is a reversible, enzyme-controlled posttranslational process affecting approximately one-third of all proteins in eukaryotic cells at any given time. Any deviation in the degree and/or site of phosphorylation leads to an abnormal conformation of proteins, resulting in a decline or loss of their function. Knowledge of phosphorylation-related pathways is essential for understanding the understanding of the disease pathogenesis and for the design of new therapeutic strategies. Recent availability of various kinases at an affordable price differs in activity, specificity, and stability and provides the opportunity of studying and modulating this reaction in vitro. We can exploit this knowledge for other applications. There is an enormous potential to produce fully decorated and active recombinant proteins, either for biomedical or cosmetic applications. Closely related is the possibility to exploit current achievements and develop new safe and efficacious vaccines, drugs, and immunomodulators. In this review, we outlined the current enzyme-based possibilities for in vitro phosphorylation of peptides and recombinant proteins and the added value that immobilized kinases provide. Full article

(This article belongs to the Special Issue Recent Advances in Biocatalysis and Metabolic Engineering)

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16 pages, 3397 KiB

Open AccessEditor’s ChoiceArticle

The Activity Enhancement Effect of Ionic Liquids on Oxygen Reduction Reaction Catalysts: From Rotating Disk Electrode to Membrane Electrode Assembly

by Kan Huang, Oscar Morales-Collazo, Zhichao Chen, Tangqiumei Song, Liang Wang, Honghong Lin, Joan F. Brennecke and Hongfei Jia

Catalysts 2021, 11(8), 989; https://doi.org/10.3390/catal11080989 - 18 Aug 2021

Cited by 11 | Viewed by 3887

Abstract

Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation [...] Read more.

Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation of ILs on the catalytic reaction, two cations ([MTBD]⁺ and [bmim]⁺) were paired with three anions ([TFSI]⁻, [beti]⁻, and [C₄F₉SO₃]⁻) to form various IL structures. By systematically varying the IL combinations and studying their effects on the electrochemical behaviors, such as electrochemical surface area and specific ORR activities, it was found that cation structure had a higher influence than anion, and the impact of the [MTBD]⁺ series was stronger than the [bmim]⁺ series. In addition to the investigation in the half-cell, studies were also extended to the membrane electrode assembly (MEA). Considerable performance enhancements were demonstrated in both the kinetic region and high current density region with the aid of IL. This work suggests that IL modification can provide a complementary approach to improve the performance of proton exchange membrane fuel cells. Full article

(This article belongs to the Special Issue Novel Developments in Fuel-Cell Oxygen Reduction Electrocatalysts)

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17 pages, 3102 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

LuxAB-Based Microbial Cell Factories for the Sensing, Manufacturing and Transformation of Industrial Aldehydes

by Thomas Bayer, Aileen Becker, Henrik Terholsen, In Jung Kim, Ina Menyes, Saskia Buchwald, Kathleen Balke, Suvi Santala, Steven C. Almo and Uwe T. Bornscheuer

Catalysts 2021, 11(8), 953; https://doi.org/10.3390/catal11080953 - 10 Aug 2021

Cited by 14 | Viewed by 6178

Abstract

The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was [...] Read more.

The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was implemented in Escherichia coli to monitor the enzymatic production of aldehydes from primary alcohols and carboxylic acid substrates. A simple high-throughput assay utilized the bacterial luciferase—previously reported to only accept aliphatic long-chain aldehydes—to detect structurally diverse aldehydes, including aromatic and monoterpene aldehydes. LuxAB was used to screen the substrate scopes of three prokaryotic oxidoreductases: an alcohol dehydrogenase (Pseudomonas putida), a choline oxidase variant (Arthrobacter chlorophenolicus) and a carboxylic acid reductase (Mycobacterium marinum). Consequently, high-value aldehydes such as cinnamaldehyde, citral and citronellal could be produced in vivo in up to 80% yield. Furthermore, the dual role of LuxAB as sensor and monooxygenase, emitting bioluminescence through the oxidation of aldehydes to the corresponding carboxylates, promises implementation in artificial enzyme cascades for the synthesis of carboxylic acids. These findings advance the bio-based detection, preparation and transformation of industrially important aldehydes in living cells. Full article

(This article belongs to the Special Issue Biocatalytic Cascade Reactions (in vivo and in vitro))

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14 pages, 33866 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Performance of Pt Nanoparticles on Ni-N Co-Doped Graphitized Carbon for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells

by Won Suk Jung

Catalysts 2021, 11(8), 909; https://doi.org/10.3390/catal11080909 - 28 Jul 2021

Cited by 4 | Viewed by 2968

Abstract

Since the reaction rate and cost for cathodic catalyst in polymer electrolyte membrane fuel cells are obstacles for commercialization, the high-performance catalyst for oxygen reduction reaction is necessary. The Ni encapsulated with N-doped graphitic carbon (Ni@NGC) prepared with ethylenediamine and carbon black is [...] Read more.

Since the reaction rate and cost for cathodic catalyst in polymer electrolyte membrane fuel cells are obstacles for commercialization, the high-performance catalyst for oxygen reduction reaction is necessary. The Ni encapsulated with N-doped graphitic carbon (Ni@NGC) prepared with ethylenediamine and carbon black is employed as an efficient support for the oxygen reduction reaction. Characterizations show that the Ni@NGC has a large surface area and mesoporous structure that is suitable to the support for the Pt catalyst. The catalyst structure is identified and the size of Pt nanoparticles distributed in the narrow range of 2–3 nm. Four different nitrogen species are doped properly into graphitic carbon structure. The Pt/Ni@NGC shows higher performance than the commercial Pt/C catalyst in an acidic electrolyte. The mass activity of the Pt/Ni@NGC in fuel cell tests exhibits over 1.5 times higher than that of commercial Pt/C catalyst. The Pt/Ni@NGC catalyst at low Pt loading exhibits 47% higher maximum power density than the Pt/C catalyst under H2-air atmosphere. These results indicate that the Ni@NGC as a support is significantly beneficial to improving activity. Full article

(This article belongs to the Special Issue Novel Catalyst Materials for Low-Temperature Fuel Cells and Electrolyzers)

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35 pages, 3632 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Green Synthesis of Metallic Nanoparticles: Applications and Limitations

by Pritam Kumar Dikshit, Jatin Kumar, Amit K. Das, Soumi Sadhu, Sunita Sharma, Swati Singh, Piyush Kumar Gupta and Beom Soo Kim

Catalysts 2021, 11(8), 902; https://doi.org/10.3390/catal11080902 - 26 Jul 2021

Cited by 527 | Viewed by 43950

Abstract

The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of [...] Read more.

The past decade has witnessed a phenomenal rise in nanotechnology research due to its broad range of applications in diverse fields including food safety, transportation, sustainable energy, environmental science, catalysis, and medicine. The distinctive properties of nanomaterials (nano-sized particles in the range of 1 to 100 nm) make them uniquely suitable for such wide range of functions. The nanoparticles when manufactured using green synthesis methods are especially desirable being devoid of harsh operating conditions (high temperature and pressure), hazardous chemicals, or addition of external stabilizing or capping agents. Numerous plants and microorganisms are being experimented upon for an eco–friendly, cost–effective, and biologically safe process optimization. This review provides a comprehensive overview on the green synthesis of metallic NPs using plants and microorganisms, factors affecting the synthesis, and characterization of synthesized NPs. The potential applications of metal NPs in various sectors have also been highlighted along with the major challenges involved with respect to toxicity and translational research. Full article

(This article belongs to the Special Issue Recent Advances on Nano-Catalysts for Biological Processes)

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17 pages, 3384 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Shape Effects of Ceria Nanoparticles on the Water‒Gas Shift Performance of CuO_x/CeO₂ Catalysts

by Maria Lykaki, Sofia Stefa, Sónia A. C. Carabineiro, Miguel A. Soria, Luís M. Madeira and Michalis Konsolakis

Catalysts 2021, 11(6), 753; https://doi.org/10.3390/catal11060753 - 21 Jun 2021

Cited by 17 | Viewed by 3496

Abstract

The copper–ceria (CuO_x/CeO₂) system has been extensively investigated in several catalytic processes, given its distinctive properties and considerable low cost compared to noble metal-based catalysts. The fine-tuning of key parameters, e.g., the particle size and shape of individual counterparts, [...] Read more.

The copper–ceria (CuO_x/CeO₂) system has been extensively investigated in several catalytic processes, given its distinctive properties and considerable low cost compared to noble metal-based catalysts. The fine-tuning of key parameters, e.g., the particle size and shape of individual counterparts, can significantly affect the physicochemical properties and subsequently the catalytic performance of the binary oxide. To this end, the present work focuses on the morphology effects of ceria nanoparticles, i.e., nanopolyhedra (P), nanocubes (C), and nanorods (R), on the water–gas shift (WGS) performance of CuO_x/CeO₂ catalysts. Various characterization techniques were employed to unveil the effect of shape on the structural, redox and surface properties. According to the acquired results, the support morphology affects to a different extent the reducibility and mobility of oxygen species, following the trend: R > P > C. This consequently influences copper–ceria interactions and the stabilization of partially reduced copper species (Cu⁺) through the Cu²⁺/Cu⁺ and Ce⁴⁺/Ce³⁺ redox cycles. Regarding the WGS performance, bare ceria supports exhibit no activity, while the addition of copper to the different ceria nanostructures alters significantly this behaviour. The CuO_x/CeO₂ sample of rod-like morphology demonstrates the best catalytic activity and stability, approaching the thermodynamic equilibrium conversion at 350 °C. The greater abundance in loosely bound oxygen species, oxygen vacancies and highly dispersed Cu⁺ species can be mainly accounted for its superior catalytic performance. Full article

(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)

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16 pages, 2662 KiB

Open AccessEditor’s ChoiceArticle

Passivation of Co/Al₂O₃ Catalyst by Atomic Layer Deposition to Reduce Deactivation in the Fischer–Tropsch Synthesis

by José Antonio Díaz-López, Jordi Guilera, Martí Biset-Peiró, Dan Enache, Gordon Kelly and Teresa Andreu

Catalysts 2021, 11(6), 732; https://doi.org/10.3390/catal11060732 - 14 Jun 2021

Cited by 5 | Viewed by 3821

Abstract

The present work explores the technical feasibility of passivating a Co/γ-Al₂O₃ catalyst by atomic layer deposition (ALD) to reduce deactivation rate during Fischer–Tropsch synthesis (FTS). Three samples of the reference catalyst were passivated using different numbers of ALD cycles (3, [...] Read more.

The present work explores the technical feasibility of passivating a Co/γ-Al₂O₃ catalyst by atomic layer deposition (ALD) to reduce deactivation rate during Fischer–Tropsch synthesis (FTS). Three samples of the reference catalyst were passivated using different numbers of ALD cycles (3, 6 and 10). Characterization results revealed that a shell of the passivating agent (Al₂O₃) grew around catalyst particles. This shell did not affect the properties of passivated samples below 10 cycles, in which catalyst reduction was hindered. Catalytic tests at 50% CO conversion evidenced that 3 and 6 ALD cycles increased catalyst stability without significantly affecting the catalytic performance, whereas 10 cycles caused blockage of the active phase that led to a strong decrease of catalytic activity. Catalyst deactivation modelling and tests at 60% CO conversion served to conclude that 3 to 6 ALD cycles reduced Co/γ-Al₂O₃ deactivation, so that the technical feasibility of this technique was proven in FTS. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts Optimization: From Material Design to Properties)

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44 pages, 4493 KiB

Open AccessEditor’s ChoiceReview

Application of TiO₂-Based Photocatalysts to Antibiotics Degradation: Cases of Sulfamethoxazole, Trimethoprim and Ciprofloxacin

by Anastasiya Kutuzova, Tetiana Dontsova and Witold Kwapinski

Catalysts 2021, 11(6), 728; https://doi.org/10.3390/catal11060728 - 12 Jun 2021

Cited by 120 | Viewed by 10274

Abstract

The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more [...] Read more.

The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more than once. Sulfamethoxazole, trimethoprim and ciprofloxacin are the most commonly detected antibiotics in water systems worldwide. The persistent and toxic nature of these antibiotics makes their elimination by conventional treatment methods at wastewater treatment plants almost impossible. The application of advanced oxidation processes and heterogeneous photocatalysis over TiO₂-based materials is a promising solution. This highly efficient technology has the potential to be sustainable, cost-efficient and energy-efficient. A comprehensive review on the application of various TiO₂-based photocatalysts for the degradation of sulfamethoxazole, trimethoprim and ciprofloxacin is focused on highlighting their photocatalytic performance under various reaction conditions (different amounts of pollutant and photocatalyst, pH, light source, reaction media, presence of inorganic ions, natural organic matter, oxidants). Mineralization efficiency and ecotoxicity of final products have been also considered. Further research needs have been presented based on the literature findings. Among them, design and development of highly efficient under sunlight, stable, recyclable and cost-effective TiO₂-based materials; usage of real wastewaters for photocatalytic tests; and compulsory assessment of products ecotoxicity are the most important research tasks in order to meet requirements for industrial application. Full article

(This article belongs to the Special Issue Environmental Remediation via Metal-Oxides-Mediated Heterogeneous Photocatalysis)

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