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Catalysts, Volume 12, Issue 8 (August 2022) – 125 articles

Cover Story (view full-size image): Zeolites, aluminosilicate microporous eco-friendly solids, are characterized with a tremendous adsorption capability, which makes them desirable substrates in environmental protection, based primarily on the adsorption capacity of substances potentially harmful to the environment, such as pharmaceuticals. On the other hand, zeolites are recognized as drug delivery carriers. The enhanced bioactive ability of drug delivery systems with zeolite as a drug-carrying nanoplatform makes them more specific and efficient compared to the drug itself. These two applications of zeolite illustrate the importance of reversibility of the adsorption process. Knowing the balance and dynamics established during that process, i.e., the interaction between zeolites and pharmaceuticals, helps scientists to expand the knowledge necessary for more effective application of the adsorption phenomenon of zeolites. View this paper
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Review
Ionic Liquid/Deep Eutectic Solvent-Mediated Ni-Based Catalysts and Their Application in Water Splitting Electrocatalysis
Catalysts 2022, 12(8), 928; https://doi.org/10.3390/catal12080928 - 22 Aug 2022
Viewed by 351
Abstract
Nickel-based electrocatalysts have been widely used to catalyze electrocatalytic water splitting. In order to obtain high-performance nickel-based electrocatalysts, using ionic liquids and deep eutectic solvents mediated their preparation has received increasing attention. Firstly, ionic liquids and deep eutectic solvents can act as media [...] Read more.
Nickel-based electrocatalysts have been widely used to catalyze electrocatalytic water splitting. In order to obtain high-performance nickel-based electrocatalysts, using ionic liquids and deep eutectic solvents mediated their preparation has received increasing attention. Firstly, ionic liquids and deep eutectic solvents can act as media and templates for the preparation of Ni-based nanomaterials with novel structures and excellent catalytic activity. Secondly, ionic liquids and deep eutectic solvents can be employed as reactants to participate the synthesis of catalysts. Their participation not only increase the catalytic performance, but also simplify the reaction system, improve reproducibility, reduce emissions, and achieve atomic economy. On the basis of the work of our group, this review gives a detailed description of the impressive progress made concerning ionic liquids and deep eutectic solvents in the preparation of nickel-based electrocatalysts according to their roles. We also point out the challenges and opportunities in the field. Full article
(This article belongs to the Special Issue Advances in Transition Metal Catalysis)
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Article
The Effect of Arsenic on the Photocatalytic Removal of Methyl Tet Butyl Ether (MTBE) Using Fe2O3/MgO Catalyst, Modeling, and Process Optimization
Catalysts 2022, 12(8), 927; https://doi.org/10.3390/catal12080927 - 22 Aug 2022
Viewed by 360
Abstract
MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it [...] Read more.
MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it is expected that its interference in the photocatalytic removal of organic matter includes MTBE. Nevertheless, there is a lack of observation of this effect. In this study, the effect of arsenic on the photocatalytic removal of MTBE using an Fe2O3/MgO catalyst under UV radiation was investigated. Using an experimental design, modeling, and optimizing operational parameters, such as the arsenic and MTBE concentrations, catalyst dosage, pH, and reaction time, were studied. The synthesized nanocatalyst had a uniform and spherical morphological structure and contained 33.06% Fe2O3 and 45.06% MgO. The results indicate that the best model is related to the quadratic (p-value < 0.0001, R2 = 0.97) and that the effect of the MTBE concentration is greater than the others. The highest removal efficiency was taken in an initial concentration of 37.5 mg/L MTBE, 1.58 mg/L Fe2O3/MgO, pH 5, and a reaction time of 21.41 min without any As. The removal efficiency was negatively correlated with the initial MTBE concentration and pH, but it was positively associated with the Fe2O3/MgO dosage and reaction time. Finally, the presence of arsenic decreased the removal efficiency remarkably (90.90% As = 0.25 μg/L and 61% As = 500 μg/L). Consequently, MTBE was removed by the photocatalytic process caused by Fe2O3/MgO, but the presence of arsenic was introduced as a limiting factor. Therefore, pretreatment for the removal of arsenic and more details of this interference effect are suggested. Full article
(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)
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Article
High-Temperature Reaction Mechanism of Molybdenum Metal in Direct Coal Liquefaction Residue
Catalysts 2022, 12(8), 926; https://doi.org/10.3390/catal12080926 - 21 Aug 2022
Viewed by 377
Abstract
In this paper, the extraction residue of direct coal liquefaction residue-DCLR(ER) was used as raw material. The high-temperature reaction mechanism of Mo compound in DCLR(ER) was investigated using a synchronous thermal analyzer and the Factsage database. The high temperature reaction of [...] Read more.
In this paper, the extraction residue of direct coal liquefaction residue-DCLR(ER) was used as raw material. The high-temperature reaction mechanism of Mo compound in DCLR(ER) was investigated using a synchronous thermal analyzer and the Factsage database. The high temperature reaction of DCLR(ER)-MoO3 in an oxygen atmosphere consists of pyrolysis of organic components at 400–600 °C, molybdenum trioxide sublimation at 747–1200 °C, and a stable stage at 600–747 °C. The thermal reaction process of the DCLR(ER)-MoS2 system in the oxygen atmosphere involves the pyrolysis of unreacted coal and asphaltene, the oxidation of molybdenum sulfide at 349–606/666 °C, the diffusion of MoO3 at 606/666–85 °C, and the sublimation reaction process of MoO3 at 854–1200 °C. The results show that the lower heating rate can promote the oxidation of the Mo compound and the sublimation of molybdenum trioxide. On the other hand, the oxides of aluminum, calcium, and iron in DCLR(ER) can inhibit the oxidative pyrolysis efficiency of the DCLR(ER)-MoS2 system. Full article
(This article belongs to the Section Catalytic Reaction Engineering)
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Article
Integrated CO2 Capture and Hydrogenation to Produce Formate in Aqueous Amine Solutions Using Pd-Based Catalyst
Catalysts 2022, 12(8), 925; https://doi.org/10.3390/catal12080925 - 21 Aug 2022
Viewed by 456
Abstract
Integrated CO2 capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine [...] Read more.
Integrated CO2 capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were investigated as CO2-capturing and hydrogenation agents in the presence of a Pd/NAC catalyst. The effect of amine structures on the CO2 absorption products and formate yield was investigated thoroughly. It was found that the formate product was successfully produced in the presence of all three aqueous amine solutions, with tertiary amine TEA accounting for the highest formate yield under the same CO2 loadings. This is due to the fact that primary and secondary amine moieties in MEA and DEA are responsible for the formation of CO2 adducts of carbamate and bicarbonate, whereas the tertiary amine moiety in TEA is responsible for the formation of hydrogenation-favorable bicarbonate as the solo CO2 absorption product. A high yield of formate of 82.6% was achieved when hydrogenating 3 M TEA with 0.3 mol CO2/mol amine solution in the presence of a Pd/NAC catalyst. In addition, the physio-chemical properties of the Pd/NAC catalyst analyzed using TEM, XRD and XPS characterization were applied to rationalize the superior catalytic performance of the catalyst. The reaction mechanism of integrated CO2 capture and hydrogenation to produce formate in aqueous amine solutions over Pd/NAC catalyst was proposed as well. Full article
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Article
A Reusable FeCl3∙6H2O/Cationic 2,2′-Bipyridyl Catalytic System for Reduction of Nitroarenes in Water
Catalysts 2022, 12(8), 924; https://doi.org/10.3390/catal12080924 - 21 Aug 2022
Viewed by 343
Abstract
The association of a commercially-available iron (III) chloride hexahydrate (FeCl3∙6H2O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under [...] Read more.
The association of a commercially-available iron (III) chloride hexahydrate (FeCl3∙6H2O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under air using 1–2 mol% of catalyst in the presence of nitroarenes and 4 equiv of hydrazine monohydrate (H2NNH2∙H2O) in neat water at 100 °C for 12 h, and provided high to excellent yields of aniline derivatives. After separation of the aqueous catalytic system from the organic product, the residual aqueous solution could be applied for subsequent reuse, without any catalyst retreatment or regeneration, for several runs with only a slight decrease in activity, proving this process eco-friendly. Full article
(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)
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Review
Olive Mill Wastewater Remediation: From Conventional Approaches to Photocatalytic Processes by Easily Recoverable Materials
Catalysts 2022, 12(8), 923; https://doi.org/10.3390/catal12080923 - 21 Aug 2022
Viewed by 398
Abstract
Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can [...] Read more.
Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can be divided into solid waste and olive mill wastewaters (OMWW). These latter are characterized by high levels of organic compounds (i.e., polyphenols) that have been efficiently removed because of their hazardous environmental effects. Over the years, in this regard, several strategies have been primarily investigated, but all of them are characterized by advantages and weaknesses, which need to be overcome. Moreover, in recent years, each country has developed national legislation to regulate this type of waste, in line with the EU legislation. In this scenario, the present review provides an insight into the different methods used for treating olive mill wastewaters paying particular attention to the recent advances related to the development of more efficient photocatalytic approaches. In this regard, the most advanced photocatalysts should also be easily recoverable and considered valid alternatives to the currently used conventional systems. In this context, the optimization of innovative systems is today’s object of hard work by the research community due to the profound potential they can offer in real applications. This review provides an overview of OMWW treatment methods, highlighting advantages and disadvantages and discussing the still unresolved critical issues. Full article
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Review
Chemocatalytic Conversion of Lignocellulosic Biomass to Ethanol: A Mini-Review
Catalysts 2022, 12(8), 922; https://doi.org/10.3390/catal12080922 - 21 Aug 2022
Viewed by 401
Abstract
Ethanol has been widely used as a clean fuel, solvent, and hydrogen carrier. Currently, ethanol is generally produced through fermentation of starch- and sugarcane-derived sugars (e.g., glucose and sucrose) or ethylene hydration. Its production from abundant and inexpensive lignocellulosic biomass would facilitate the [...] Read more.
Ethanol has been widely used as a clean fuel, solvent, and hydrogen carrier. Currently, ethanol is generally produced through fermentation of starch- and sugarcane-derived sugars (e.g., glucose and sucrose) or ethylene hydration. Its production from abundant and inexpensive lignocellulosic biomass would facilitate the development of green and sustainable society. Biomass-derived carbohydrates and syngas can serve as important feedstocks for ethanol synthesis via biological and chemical pathways. Nevertheless, the biological pathway for producing ethanol through biomass-derived glucose fermentation has the disadvantages of long production period and carbon loss. These issues can be effectively mitigated by chemocatalytic methods, which can readily convert biomass to ethanol in high yields and high atomic efficiency. In this article, we review the recent advances in chemocatalytic conversion of lignocellulosic biomass to ethanol, with a focus on analyzing the mechanism of chemocatalytic pathways and discussing the issues related to these methods. We hope this mini-review can provide new insights into the development of direct ethanol synthesis from renewable lignocellulosic biomass. Full article
(This article belongs to the Special Issue Catalytic Conversion of Cellulose and Lignin)
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Article
Development of New Amphiphilic Catalytic Steam Additives for Hydrothermal Enhanced Oil Recovery Techniques
Catalysts 2022, 12(8), 921; https://doi.org/10.3390/catal12080921 - 20 Aug 2022
Viewed by 402
Abstract
In this paper, we propose the synthesis of green amphiphilic catalysts based on two metals: Ni and Al. The amphiphilic characteristics of the obtained catalyst were provided by alkylbenzenesulfonic acid (ABSA). The end product was thoroughly characterized by the FTIR analysis method. The [...] Read more.
In this paper, we propose the synthesis of green amphiphilic catalysts based on two metals: Ni and Al. The amphiphilic characteristics of the obtained catalyst were provided by alkylbenzenesulfonic acid (ABSA). The end product was thoroughly characterized by the FTIR analysis method. The efficiency of both catalysts was tested by modeling the catalytic hydrothermal upgrading of heavy-oil samples from Ashal’cha field (Russia) in a high-pressure/high-temperature (HP/HT) reactor with a stirrer at a temperature of 250 °C. The physical and chemical properties of the heavy oils and their fractions were studied before and after the catalytic hydrothermal upgrading by analytical procedures such as SARA analysis, FTIR spectroscopy, GC–MS, elemental analysis, gas chromatography, etc. The results showed that both catalysts had a different influence on the viscosity-reduction degree. It was revealed that the contribution of Al ABSA to the viscosity reduction was the highest: more than 80% in contrast to the initial crude oil sample. The Al-based catalyst showed the best activity in hydrogenation and decarbonization, and hence the H/C ratio of the upgraded oil was at a maximum in the presence of Al ABSA. Full article
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Article
Pd-Supported Co3O4/C Catalysts as Promising Electrocatalytic Materials for Oxygen Reduction Reaction
Catalysts 2022, 12(8), 920; https://doi.org/10.3390/catal12080920 - 20 Aug 2022
Viewed by 305
Abstract
This paper describes the activity of PdCo3O4/C obtained by wet impregnation towards the oxygen reduction reaction (ORR). For this purpose, the Co3O4/C substrate was synthesized using the microwave irradiation heating method with further annealing of [...] Read more.
This paper describes the activity of PdCo3O4/C obtained by wet impregnation towards the oxygen reduction reaction (ORR). For this purpose, the Co3O4/C substrate was synthesized using the microwave irradiation heating method with further annealing of the substrate at 400 °C for 3 h (Co3O4/C-T). Then, the initial Co3O4/C substrate was impregnated with palladium chloride (Pd-Cl2-Co3O4/C), and then part of the obtained Pd-Cl2-Co3O4/C catalyst was annealed at 400 °C for 3 h (PdOCo3O4/C). The electrocatalytic activity of the prepared catalysts was investigated for the oxygen reduction reaction in alkaline media and compared with the commercial Pt/C (Tanaka wt. 46.6% Pt) catalyst. It was found that the annealed PdOCo3O4/C catalyst showed the largest ORR current density value of −11.27 mA cm−2 compared with Pd-Cl2-Co3O4/C (−7.39 mA cm−2) and commercial Pt/C (−5.25 mA cm−2). Full article
(This article belongs to the Special Issue Catalytical Processes in Presence of 2D Nanomaterials)
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Review
Recent Advances in Metal-Based Molecular Photosensitizers for Artificial Photosynthesis
Catalysts 2022, 12(8), 919; https://doi.org/10.3390/catal12080919 - 19 Aug 2022
Viewed by 462
Abstract
Artificial photosynthesis (AP) has been extensively applied in energy conversion and environment pollutants treatment. Considering the urgent demand for clean energy for human society, many researchers have endeavored to develop materials for AP. Among the materials for AP, photosensitizers play a critical role [...] Read more.
Artificial photosynthesis (AP) has been extensively applied in energy conversion and environment pollutants treatment. Considering the urgent demand for clean energy for human society, many researchers have endeavored to develop materials for AP. Among the materials for AP, photosensitizers play a critical role in light absorption and charge separation. Due to the fact of their excellent tunability and performance, metal-based complexes stand out from many photocatalysis photosensitizers. In this review, the evaluation parameters for photosensitizers are first summarized and then the recent developments in molecular photosensitizers based on transition metal complexes are presented. The photosensitizers in this review are divided into two categories: noble-metal-based and noble-metal-free complexes. The subcategories for each type of photosensitizer in this review are organized by element, focusing first on ruthenium, iridium, and rhenium and then on manganese, iron, and copper. Various examples of recently developed photosensitizers are also presented. Full article
(This article belongs to the Special Issue Chiral Nanomaterials and Their Photo(Electro)catalytic Applications)
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Article
Catalytic Activity of Carbon Materials in the Oxidation of Minerals
Catalysts 2022, 12(8), 918; https://doi.org/10.3390/catal12080918 - 19 Aug 2022
Viewed by 347
Abstract
This study aims to advance the knowledge of using carbon materials as catalysts in the oxidation of chalcopyrite. For this, two different materials (a commercial activated carbon (CC) and commercial biochar (BC)) were added to chalcopyrite ore (CPY) at three weight ratios (1:1, [...] Read more.
This study aims to advance the knowledge of using carbon materials as catalysts in the oxidation of chalcopyrite. For this, two different materials (a commercial activated carbon (CC) and commercial biochar (BC)) were added to chalcopyrite ore (CPY) at three weight ratios (1:1, 1:0.5, and 1:0.25). Mixtures were treated with sulfuric/ferric solution for 96 h at 90 °C. Experimental results showed that extraction of copper from CPY was around 36%, increasing to higher than 90% with the addition of CC or BC at the proper ratio. The best result (99.1% Cu extraction) was obtained using a 1:1 ratio of CPY:CC. Analysis of solid residues shows that CC, with a high surface area, adsorbs sulfur onto its surface, limiting elemental sulfur formation. Additionally, the treatment of CPY in the CC’s presence transforms the chalcopyrite into CuS. Sulfur adsorption or CuS formation was not observed after the leaching of chalcopyrite with BC. However, the addition of BC to CPY at a ratio of 1:0.25 also increased the extraction of copper to 91.1%. Two carbon materials were oxidized after treatment with a sulfuric/ferric solution, and BC probably displayed catalytic properties in the leaching medium. Full article
(This article belongs to the Special Issue Catalysis and Carbon-Based Materials)
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Article
Determination of Chemical Kinetic Parameters for Adsorption and Desorption of NH3 in Cu-Zeolite Used as a DeNOx SCR Catalyst of Diesel Engines
Catalysts 2022, 12(8), 917; https://doi.org/10.3390/catal12080917 - 19 Aug 2022
Viewed by 273
Abstract
Ammonia-based selective catalytic reduction is one of the most effective NOx reduction technologies for diesel engines, but its low NOx reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH3 adsorption and desorption [...] Read more.
Ammonia-based selective catalytic reduction is one of the most effective NOx reduction technologies for diesel engines, but its low NOx reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH3 adsorption and desorption that occurs in an SCR catalyst of Cu ion-exchanged zeolite. However, many studies conducted to data on the control of the NH3 adsorption and desorption in SCR catalysts have considered a simple chemical reaction related to a single acid site. This study demonstrates a detailed process for determining the chemical kinetic parameters of the adsorption and desorption of NH3 for different types of acid sites of a zeolite catalyst. The determined chemical kinetics parameters will be used for more effective control of the SCR system in future studies. Full article
(This article belongs to the Special Issue Catalytic Methods for Nitrogen Pollutants Conversion in Flue Gases)
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Article
Effects of Potassium Loading over Iron–Silica Interaction, Phase Evolution and Catalytic Behavior of Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis
Catalysts 2022, 12(8), 916; https://doi.org/10.3390/catal12080916 - 19 Aug 2022
Viewed by 417
Abstract
Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO2 catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With the increase in K content from 2.3% (100 g Fe based) up to 7% in [...] Read more.
Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO2 catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With the increase in K content from 2.3% (100 g Fe based) up to 7% in the calcined precursors, Fe–O–Si interaction was weakened, as reflected by ATR/FTIR, H2-TPR and XPS investigations. XRD results confirmed that the diffraction peak intensity from (510) facet of χ-Fe5C2 phase strengthened with increasing K loading, which indicates the crystallite size of χ-Fe5C2 increased with the increase in K contents either during the syngas reduction/carburization procedure or after FTS reaction. H2-TPH results indicated that more reactive surface carbon (alpha-carbon) was obtained over the higher K samples pre-carburized by syngas. Raman spectra illustrated that a greater proportion of graphitic carbon was accumulated over the surface of spent samples with higher K loading. At the same time, ATR-FTIR, XRD and Mössbauer spectra (MES) characterization results showed that a relatively higher level of bulk phase Fayalite (Fe2SiO4) species was observed discernibly in the lowest K loading sample (2.3 K%) in this work. The catalytic evaluation results showed that the CO conversion, CO2 selectivity and O/P (C2–C4) ratio increased progressively with the increasing K loading, whereas a monotonic decline in both CO conversion and O/P (C2–C4) ratio was observed on the highest K loading sample during c.a. 280 h of TOS. Full article
(This article belongs to the Special Issue Development of Novel Catalysts for Fischer–Tropsch Synthesis)
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Article
Formation and Intramolecular Capture of α-Imino Gold Carbenoids in the Au(I)-Catalyzed [3 + 2] Reaction of Anthranils, 1,2,4-Oxadiazoles, and 4,5-Dihydro-1,2,4-Oxadiazoles with Ynamides
Catalysts 2022, 12(8), 915; https://doi.org/10.3390/catal12080915 - 19 Aug 2022
Viewed by 354
Abstract
α-Imino gold carbenoid species have been recognized as key intermediates in a plethora of processes involving gold-activated alkynes. Here, we explored the pathways of the Au(I)-catalyzed [3 + 2] reaction between the mild nucleophiles: anthranil, 1,2,4-oxadiazole, or 4,5-dihydro-1,2,4-oxadiazole, and an ynamide, PhC≡C-N(Ts)Me, proceeding [...] Read more.
α-Imino gold carbenoid species have been recognized as key intermediates in a plethora of processes involving gold-activated alkynes. Here, we explored the pathways of the Au(I)-catalyzed [3 + 2] reaction between the mild nucleophiles: anthranil, 1,2,4-oxadiazole, or 4,5-dihydro-1,2,4-oxadiazole, and an ynamide, PhC≡C-N(Ts)Me, proceeding via the formation of the aforementioned α-imino gold carbene intermediate which, after intramolecular capture, regioselectively produces 2-amino-3-phenyl-7-acyl indoles, N-acyl-5-aminoimidazoles, or N-alkyl-4-aminoimidazoles, respectively. In all cases, the regioselectivity of the substituents at 2, 3 in the 7-acyl-indole ring and 4, 5 in the substituted imidazole ring is decided at the first transition state, involving the attack of nitrogen on the C1 or C2 carbon of the activated ynamide. A subsequent and steep energy drop furnishes the key α-imino gold carbene. These features are more pronounced for anthranil and 4,5-dihydro-1,2,4-oxadiazole reactions. Strikingly, in the 4,5-dihydro-1,2,4-oxadiazole reaction the significant drop of energy is due to the formation of an unstable α-imino gold carbene, which after a spontaneous benzaldehyde elimination is converted to a stabilized one. Compared to anthranil, the reaction pathways for 1,2,4-oxadiazoles or 4,5-dihydro-1,2,4-oxadiazoles are found to be significantly more complex than anticipated in the original research. For instance, compared to the formation of a five-member ring from the α-imino gold carbene, one competitive route involves the formation of intermediates consisting of a four-member ring condensed with a three-member ring, which after a metathesis and ring expansion led to the imidazole ring. Full article
(This article belongs to the Section Computational Catalysis)
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Article
Controllable Construction of IrCo Nanoclusters and the Performance for Water Electrolysis
Catalysts 2022, 12(8), 914; https://doi.org/10.3390/catal12080914 - 19 Aug 2022
Viewed by 315
Abstract
Finding a suitable catalyst is an important research direction in hydrogen (H2) production from water electrolysis. We report a synthetic method to obtain IrxCo/C clusters by polyol reduction. The catalyst is small in size and can be evenly distributed. [...] Read more.
Finding a suitable catalyst is an important research direction in hydrogen (H2) production from water electrolysis. We report a synthetic method to obtain IrxCo/C clusters by polyol reduction. The catalyst is small in size and can be evenly distributed. The Ir3Co/C cluster catalyst had very good activity under acidic conditions. The overpotential of the best-performing Ir3Co/C cluster for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is only 290 mV and 91 mV when 10 mA cm−2 and 100 mA cm−2. The catalyst performance may be improved because of the synergistic effect and the small size of the prepared catalyst, which accelerates proton transfer. This approach offers a strategy to reduce costs while improving catalytic activity. Full article
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Article
Monolayer CoMoS Catalysts on Hierarchically Porous Alumina Spheres as Bifunctional Nanomaterials for Hydrodesulfurization and Energy Storage Applications
Catalysts 2022, 12(8), 913; https://doi.org/10.3390/catal12080913 - 19 Aug 2022
Viewed by 472
Abstract
In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization [...] Read more.
In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization reactor using two model sulfur molecules, dibenzothiophene and 4,6-dimethyl dibenzothiophene, as well as feeding a heavy oil fraction. The results indicated that the spheres obtained by Pluronic P-123 allowed a greater dispersion degree of MoS2 slabs than US, indicating that the size and hierarchically porous structure of alumina spheres played a principal role as a booster of the HDS catalytic efficiency of DBT, 4,6 DMDBT and diesel fuel. Then, these catalysts were used for the electrocatalysis of the oxygen reduction and oxygen evolution reactions (ORR/OER), which take place in rechargeable Zn-air batteries. For the ORR, the CoMoS catalyst on PS in the presence of a conductive support (N-doped carbon nanotubes + graphene) displayed an overpotential of only 90 mV in comparison with Pt/C. Importantly, the chalcogenide enabled an increase in the stability, maintaining almost two times higher current retention than Pt/C for the ORR and IrO2/C for the OER. These results suggest that expended chalcogenides from the hydrodesulfurization industry can have a second life as co-catalysts for renewable energy storage systems, enabling a circular economy. Full article
(This article belongs to the Section Catalytic Reaction Engineering)
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Perspective
Asymmetric Organocatalysis—A Powerful Technology Platform for Academia and Industry: Pregabalin as a Case Study
Catalysts 2022, 12(8), 912; https://doi.org/10.3390/catal12080912 - 18 Aug 2022
Viewed by 694
Abstract
Enantioselective organocatalysis has quickly established itself as the third pillar of asymmetric catalysis. It is a powerful technology platform, and it has a tremendous impact in both academic and industrial settings. By focusing on pregabalin, as a case study, this Perspective aims to [...] Read more.
Enantioselective organocatalysis has quickly established itself as the third pillar of asymmetric catalysis. It is a powerful technology platform, and it has a tremendous impact in both academic and industrial settings. By focusing on pregabalin, as a case study, this Perspective aims to show how a process amenable to industry of a simple chiral molecule can be tackled in several different ways using organocatalysis. Full article
(This article belongs to the Special Issue Organocatalysis: Advances, Opportunity, and Challenges)
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Review
Copper-Catalyzed Reactions of Aryl Halides with N-Nucleophiles and Their Possible Application for Degradation of Halogenated Aromatic Contaminants
Catalysts 2022, 12(8), 911; https://doi.org/10.3390/catal12080911 - 18 Aug 2022
Viewed by 349
Abstract
This review summarizes recent applications of copper or copper-based compounds as a nonprecious metal catalyst in N-nucleophiles-based dehalogenation (DH) reactions of halogenated aromatic compounds (Ar-Xs). Cu-catalyzed DH enables the production of corresponding nonhalogenated aromatic products (Ar-Nu), which are much more biodegradable and can [...] Read more.
This review summarizes recent applications of copper or copper-based compounds as a nonprecious metal catalyst in N-nucleophiles-based dehalogenation (DH) reactions of halogenated aromatic compounds (Ar-Xs). Cu-catalyzed DH enables the production of corresponding nonhalogenated aromatic products (Ar-Nu), which are much more biodegradable and can be mineralized during aerobic wastewater treatment or which are principally further applicable. Based on available knowledge, the developed Cu-based DH methods enable the utilization of amines for effective cleavage of aryl-halogen bonds in organic solvents or even in an aqueous solution. Full article
(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)
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Article
Hollow CuFe2O4/MgFe2O4 Heterojunction Boost Photocatalytic Oxidation Activity for Organic Pollutants
Catalysts 2022, 12(8), 910; https://doi.org/10.3390/catal12080910 - 18 Aug 2022
Viewed by 381
Abstract
P-n heterojunction-structured CuFe2O4/MgFe2O4 hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe2O4 [...] Read more.
P-n heterojunction-structured CuFe2O4/MgFe2O4 hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe2O4/MgFe2O4 with a molar ratio of 1:2 (Cu:Mg) had the highest degradation efficiency with the model organic dye Acid Orange 7, with a degradation rate of 91.96% over 60 min. The synthesized CuFe2O4/MgFe2O4 nanocomposites were characterized by XRD, TEM, HRTEM, UV-vis spectroscopy, Mott–Schottky, and EIS. Due to the synthesis of the p-n heterojunction, CuFe2O4/MgFe2O4 has efficient photogenerated carriers, and the hollow structure has a higher specific surface area and stronger adsorption capacity, which is significantly better than that of CuFe2O4 and MgFe2O4 in terms of photocatalytic performance. The outstanding performance shows that the p-n heterostructure of CuFe2O4/MgFe2O4 has potential for application in wastewater degradation. Full article
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Review
Levulinic Acid Is a Key Strategic Chemical from Biomass
Catalysts 2022, 12(8), 909; https://doi.org/10.3390/catal12080909 - 18 Aug 2022
Viewed by 381
Abstract
Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are [...] Read more.
Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are currently produced in fossil based refineries. LA is a key strategic chemical, as fuel grade chemicals and plastic substitutes can be produced by its catalytic conversion. LA derivatisation to various product streams, such as alkyl levulinates via esterification, γ-valerolactone via hydrogenation and N-substituted pyrrolidones via reductive amination and many other transformations of commercial utility are possible owing to the two oxygen functionalities, namely, carbonyl and carboxyl groups, present within the same substrate. Various biomass feedstock, such as agricultural wastes, marine macroalgae, and fresh water microalgae were successfully converted to LA in high yields. Finding a substitute to mineral acid catalysts for the conversion of biomass to LA is a challenge. The use of an ultrasound technique facilitated the production of promising nano-solid acid catalysts including Ga salt of molybophosphoric acid and Ga deposited mordenite zeolite, with optimum amounts of Lewis and Bronsted acidities needed for the conversion of glucose to LA in high yields, being 56 and 59.9 wt.% respectively. Microwave irradiation technology was successfully utilized for the accelerated production of LA (53 wt.%) from glucose in a short duration of 6 min, making use of the unique synergistic catalytic activity of ZnBr2 and HCl. Full article
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Article
Crystalline Violet Wastewater Treatment by Low-Temperature Plasma Combined with Industrial Solid Waste Red Mud
Catalysts 2022, 12(8), 908; https://doi.org/10.3390/catal12080908 - 17 Aug 2022
Viewed by 334
Abstract
Low-temperature plasma (LTP) technology has been successfully used to treat persistent organic pollutants in water. Efforts have been devoted to combine catalysts and LTP to improve the degradation efficiency of pollutants and energy utilization efficiency. Herein, industrial solid waste red mud as a [...] Read more.
Low-temperature plasma (LTP) technology has been successfully used to treat persistent organic pollutants in water. Efforts have been devoted to combine catalysts and LTP to improve the degradation efficiency of pollutants and energy utilization efficiency. Herein, industrial solid waste red mud as a novel catalyst was added to an LTP system to treat crystalline violet (CV) wastewater. The energy yield at 50% CV decomposition and TOC after a 30 min reaction by the plasma treatment, red mud adsorption, and red mud/plasma treatment were compared. The effects of the main operating parameters, such as red mud dosing amount, initial pH, discharge voltage, and initial concentration of CV, on the removal efficiency of CV were investigated. The best degradation of CV was achieved with a red mud dosage of 2 g, a neutral environment, and a discharge voltage of 22 kV. When the red mud was recycled three times, the removal efficiency decreased a little in the red mud/plasma system. Hydroxyl radical plays an important role in the treatment of CV. The red mud was characterized by BET, SEM, XRD, and FT-IR, and the structure of the red mud was not greatly affected after being used in the red mud/plasma system. Full article
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Communication
The Shell Matters: Self-Organized CdS-ZnS/MnS-Core-Shell—Porphyrin-Polymer Nano-Assemblies for Photocatalysis
Catalysts 2022, 12(8), 907; https://doi.org/10.3390/catal12080907 - 17 Aug 2022
Viewed by 323
Abstract
A facile synthesis of catalytically tunable core-shell CdS-ZnxMn1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties [...] Read more.
A facile synthesis of catalytically tunable core-shell CdS-ZnxMn1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties and to optimize the catalytic activity. Further, the tetravalent cationic 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TAPP) fulfills a triple functionality in the catalyst: as a photosensitizer, as an electrostatic linker connecting the nanoparticles and as a probe to investigate the surface composition of the II-VI semiconducting nanoparticles. Different nanoparticles with varying zinc sulfide/manganese sulfide shell ratios are tested with regard to their photocatalytic behavior by crocin bleaching. The results reveal that the shell composition can be a crucial key to optimize the catalytic activity, which can further be important in tuning the reactivity of related systems. Fundamentally, the stepwise multi-component self-assembly in an aqueous solution has been demonstrated to allow the tuning of optic and catalytic properties of core-shell nanoparticles, a general concept that may be widely applicable. Full article
(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)
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Article
Modified Mn/ZSM-5 for Non-Thermal Plasma Mineralization of VOCs and DFT Simulation Using a Novel Y-Type ZSM-5 Model
Catalysts 2022, 12(8), 906; https://doi.org/10.3390/catal12080906 - 17 Aug 2022
Viewed by 328
Abstract
Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) [...] Read more.
Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) were used to introduce possible oxygen defects into the Mn/ZSM-5 to prepare modified catalysts, which were evaluated in VOCs degradation activity using a Double Dielectric Barrier Discharge (DDBD) plasma device. Additionally, a novel Y-type ZSM-5 model was employed in the DFT simulation. The new Y-type ZSM-5 model used in this paper is a more realistic aperiodic model. It showed that introducing possible oxygen defects can substantially enhance degradation efficiency. Taking the catalyst with oxygen defects introduced by plasma as an example, the conversion (CO2 selectivity) of the methanol, acetone, and toluene could reach 100% (100%), 97.7% (99.1%), 91.2% (93.9%), respectively, at an initial concentration of 2000 ppm and specific input energy of 9 kJ/L. The results demonstrated that modification could significantly enhance the activity of the catalyst in decomposing VOCs at room temperature using non-thermal plasma catalysis. Theoretical simulation of density functional theory (DFT) revealed that the adsorption of adsorbate on the catalyst becomes easier after possible oxygen defects are introduced. Full article
(This article belongs to the Special Issue Recent Progress of Catalysis in “Dual Carbon Targets”)
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Review
Single-Atom-Based Catalysts for Photocatalytic Water Splitting on TiO2 Nanostructures
Catalysts 2022, 12(8), 905; https://doi.org/10.3390/catal12080905 - 17 Aug 2022
Viewed by 403
Abstract
H2 generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO2 is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO2 as a photocatalyst [...] Read more.
H2 generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO2 is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO2 as a photocatalyst is the sluggish charge transfer on the surface of TiO2 that can be tackled to a great extent by the use of platinum group materials (PGM) as co-catalysts. However, the scarcity and high cost of the PGMs is one of the issues that prevent the widespread use of TiO2/PGM systems for photocatalytic H2 generation. Single-atom catalysts which are currently the frontline in the catalysis field can be a favorable path to overcome the scarcity and further advance the use of noble metals. More importantly, single-atom (SA) catalysts simultaneously have the advantage of homogenous and heterogeneous catalysts. This mini-review specifically focuses on the single atom decoration of TiO2 nanostructures for photocatalytic water splitting. The latest progress in fabrication, characterization, and application of single-atoms in photocatalytic H2 generation on TiO2 is reviewed. Full article
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Article
Chitin and Silk Fibroin Biopolymers Modified by Oxone: Efficient Heterogeneous Catalysts for Knoevenagel Reaction
Catalysts 2022, 12(8), 904; https://doi.org/10.3390/catal12080904 - 17 Aug 2022
Viewed by 370
Abstract
New materials from silk fibroin (FS-Ox) and chitin (CT-Ox) functionalized with Oxone® salt were developed for application in the synthesis of Knoevenagel adducts. The experiments were performed using benzaldehyde derivatives, malononitrile, and a mixture of water and ethanol as green solvents. The [...] Read more.
New materials from silk fibroin (FS-Ox) and chitin (CT-Ox) functionalized with Oxone® salt were developed for application in the synthesis of Knoevenagel adducts. The experiments were performed using benzaldehyde derivatives, malononitrile, and a mixture of water and ethanol as green solvents. The efficiency of conventional and microwave irradiation as heating sources for this reaction was also investigated. When the reactions were performed for 60 min under optimized conditions with conventional heating, twelve Knoevenagel adducts 2al were obtained, with good yields for both catalysts (CT-Ox 60–98% and FS-Ox 71–98%). When microwave irradiation was used, the reaction periods were reduced twelvefold, with the same Knoevenagel adducts with good CT-Ox (39–99%) and FS-Ox (35–99%) yields obtained in most cases. The reuse of these materials as catalysts in successive reactions was also evaluated, and CT-Ox FS-Ox were successfully used for 4 and 2 cycles, respectively. The results presented prove the efficiency of the CT-OxFS-Ox catalyst as a promising low-cost and reusable material with suitable catalytic properties to be applied in the aldol condensation reaction in a sustainable way. Full article
(This article belongs to the Topic Green and Sustainable Chemistry)
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Communication
Revealing the Synergetic Effects between Reactants in Oxidative Coupling of Methane on Stepped MgO(100) Catalyst
Catalysts 2022, 12(8), 903; https://doi.org/10.3390/catal12080903 - 17 Aug 2022
Viewed by 297
Abstract
The oxidative coupling of methane (OCM) on MgO is often computationally explored via Mars-Krevelen (MvK) mechanism. However, the difficult desorption of CH3 radical at stepped MgO surface shadow the feasibility of mechanism. In this work, density functional theory calculations are performed to [...] Read more.
The oxidative coupling of methane (OCM) on MgO is often computationally explored via Mars-Krevelen (MvK) mechanism. However, the difficult desorption of CH3 radical at stepped MgO surface shadow the feasibility of mechanism. In this work, density functional theory calculations are performed to unravel the syngenetic effects between reactants which lead to a new Langmuir-Hinshelwood (L-H)-like mechanism. It was found that co-adsorption of reactants pave ways for CH3 radical formation with negligible desorption energy. The role of oxygen molecule is not only to oxidize reduced surface but also decrease the reactivity of Mg-O site which facile CH3 desorption. Electronic structure analysis indicated the distinct feature along pathway between MvK and L-H. The current work clearly indicated the importance of effective interactions between reactants and provided new insights on the reaction mechanism of OCM. Full article
(This article belongs to the Special Issue Computational Insights into Small Molecule Activation)
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Article
Site and Structural Requirements for the Dehydra-Decyclization of Cyclic Ethers on ZrO2
Catalysts 2022, 12(8), 902; https://doi.org/10.3390/catal12080902 - 17 Aug 2022
Viewed by 358
Abstract
In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO2-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as [...] Read more.
In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO2-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as a starting material to produce monomers for the plastics industry. To help identify the active sites for this reaction, studies were conducted in which ZrO2 surfaces were decorated with Na. These studies showed that Na was effective at poisoning the activity for the ring opening of cyclic ethers, but much less so for the dehydration of the resulting adsorbed alkoxides. The studies of the activity of different types of ZrO2 for the dehydra-decyclization reaction, including single crystals and ultra-thin films supported on MgAl2O4 and silica, also showed that the reaction was dependent on the local structure of the ZrO2 surface. The insights these results provide for identifying the active sites on the ZrO2 surface are discussed. Full article
(This article belongs to the Section Biomass Catalysis)
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Communication
An Efficient Zr-ZSM-5-st Solid Acid Catalyst for the Polyol Esterification Reaction
Catalysts 2022, 12(8), 901; https://doi.org/10.3390/catal12080901 - 16 Aug 2022
Viewed by 381
Abstract
In this study, Zr active species were implanted into a ZSM-5 zeolite framework to form a solid acid catalyst through steam treatment and the liquid-solid isomorphous substitution process. The as-synthesized Zr-ZSM-5-st catalyst ensured excellent esterification of trimethylolpropane and fatty acids (FAs) to achieve [...] Read more.
In this study, Zr active species were implanted into a ZSM-5 zeolite framework to form a solid acid catalyst through steam treatment and the liquid-solid isomorphous substitution process. The as-synthesized Zr-ZSM-5-st catalyst ensured excellent esterification of trimethylolpropane and fatty acids (FAs) to achieve a polyol ester production yield of 94.41%. Combined with N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, transmission electron microscopy mapping, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption, and inductively coupled mass plasma spectroscopy were conducted. The results revealed that the excellent performance of Zr-ZSM-5-st catalyst could be attributed to the enhanced acidity and the developed surface area and pore structure. Full article
(This article belongs to the Topic Green and Sustainable Chemistry)
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Article
Bifunctional Co3O4/ZSM-5 Mesoporous Catalysts for Biodiesel Production via Esterification of Unsaturated Omega-9 Oleic Acid
Catalysts 2022, 12(8), 900; https://doi.org/10.3390/catal12080900 - 16 Aug 2022
Viewed by 362
Abstract
In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) [...] Read more.
In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) analysis showed that the Co3O4 phase was formed in the surface of catalysts and the reducibility of Co3O4 nanoparticles on the ZSM-5-B was greater in comparison with that on the ZSM-5-A solid. In situ FTIR of pyridine adsorption characterization confirmed that all of the Co/ZSM-5 catalysts contained both Lewis (L) and Brønsted (B) acid sites, with a relatively balanced B/L ratio ranging from 0.61 to 1.94. Therefore, the Si/Al molar ratio in ZSM-5 affected both the surface acidity and the cobalt oxide reducibility. In the esterification of unsaturated omega-9 oleic acid with methanol, under the optimal reaction conditions (temperature 160 °C, catalyst concentration 2 g/L, methanol/oleic acid molar ratio 30, and reaction time 180 min), the biodiesel selectivity reached 95.1% over the most active 10 wt% Co/ZSM-5-B catalyst. The higher esterification activity of the Co/ZSM-5-B catalysts can be correlated with the greater amount of B and L acid sites, the balanced B/L ratio, and the higher reducibility of Co3O4 nanoparticles. The oleic acid esterification reaction followed the bifunctional mechanism of combining metal function (dispersed Co3O4 with a greater reducibility) with the acidity function (both B and L acid sites with a relative balanced B/L ratio) on the catalysts, which may help in providing a deep understanding of the esterification pathways and benefiting the design of novel bifunctional catalysts for biofuel production. Full article
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Article
Sorbent and Photocatalytic Potentials of Local Clays for the Removal of Organic Xenobiotic: Case of Crystal Violet
Catalysts 2022, 12(8), 899; https://doi.org/10.3390/catal12080899 - 16 Aug 2022
Viewed by 390
Abstract
Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two [...] Read more.
Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two irrigated rice field waters in the degradation of crystal violet. The structural, textural and compositional properties of the local clay were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analysis. The analysis results showed that these materials were composed mainly of quartz and kaolinite. The efficiency of these adsorbents (Y. Clay and L. Clay) to eliminate crystal violet dye from aqueous medium was examined at different initial concentrations, pH, contact time, adsorbent dose and the possible interference of inorganic salts from fertilizers. Kinetic studies showed that the adsorption process was well described by the pseudo-second order model and the equilibrium modelling results fitted adequately to the Freundlich model. The maximum amount of uptake capacity achieved at pH 2.0 was 18.40 (mg·g−1) and 20.40 (mg·g−1), respectively, for Y. Clay and L. Clay. The evaluation of the photocatalytic potential showed that the raw clay samples do not show photocatalytic activities during the 30 min of exposure to UV light. On the other hand, their photocatalytic potential is manifested when loaded with titanium dioxide (TiO2). Clays coupled with TiO2 under UV light showed an improvement in the degradation of the crystal violet dye by 15%. The synergistic effects between the high photocatalytic activity of TiO2 and the strong adsorption capacity of clays can be one promising technique for in situ remediation of contaminated soaked rice field. Full article
(This article belongs to the Special Issue Nanomaterials for Photocatalysis)
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