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Catalysts, Volume 12, Issue 10 (October 2022) – 219 articles

Cover Story (view full-size image): Acetone, one of the most common VOCs (which are crucial precursors of PM2.5 and ozone) and widely used as an organic solvent, has a pernicious impact on the environment and humans. For catalytic oxidation on acetone removal, inappropriate temperature ranges, more macromolecular byproducts, carbon deposition and SO2/H2O poisoning problems were not resolved. A new type of transition metals (Cr/Fe/Mn/Co)-derived catalysts supported on γ-Al2O3 were prepared and compared for catalytic ozonation of acetone in this study. Results found that CrOx catalysts, bearing abundant Cr6+ and more chemically adsorbed oxygen species Oβ, were originally implied to acetone efficient degradation by catalytic ozonation in low-temperature, SO2/H2O-containing flue gas conditions. Additionally, the acetone catalytic ozonation pathways and sulfur/water poisoning mechanisms were proposed. View this paper
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Article
Synthesis of Novel Key Chromophoric Intermediates via C-C Coupling Reactions
Catalysts 2022, 12(10), 1292; https://doi.org/10.3390/catal12101292 - 21 Oct 2022
Viewed by 716
Abstract
The fundamentals of Pd-catalyzed Csp2−Csp2 Miyaura borylation, Suzuki cross-coupling, and Stille cross-coupling reactions for a variety of borylated precursors based on phenothiazine (PTZ), phenoxazine (POZ), carbazole (Cz), and quinoxaline (QX) units have been explored. Three palladium-based catalysts were chosen for [...] Read more.
The fundamentals of Pd-catalyzed Csp2−Csp2 Miyaura borylation, Suzuki cross-coupling, and Stille cross-coupling reactions for a variety of borylated precursors based on phenothiazine (PTZ), phenoxazine (POZ), carbazole (Cz), and quinoxaline (QX) units have been explored. Three palladium-based catalysts were chosen for this study: Pd(PPh3)4, Pd(PPh3)2Cl2, and Pd(dppf)Cl2, applying different reaction conditions. Around 16 desired chromophores were successfully designed and synthesized using C-C cross-coupling reactions in moderate to excellent yields, including PTZ, POZ, and Cz units coupled with QX, indolinium iodide, thienyl, phenyl, or triphenylamine moieties. Additionally, PTZ, POZ, and Cz have been employed in synthesizing various pinacol boronate ester derivatives in good to moderate yields. Interestingly, Pd(dppf)Cl2 was found to be the best catalyst for borylation, and C-C cross-coupling reactions occurred in as little as 30 min, with an excellent yield exceeding 98%. Pd(PPh3)4 and Pd(PPh3)2Cl2 catalyzed the reaction to obtain the desired products in moderate to good yields after a long time (20–24 h). On the other hand, the Suzuki-Miyaura cross-coupling between N-(2-methyl)hexyl carbazole pinacol boronate ester derivative 10c and three halogenated quinoxaline derivatives—4-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)benzaldehyde (27), 4-(5-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)thiophen-2-yl)benzaldehyde (30), and 4-(3-chloroquinoxalin-2-yl)benzaldehyde (25) catalyzed by Pd(PPh3)4—afforded three carbazole-quinoxaline chromophores (28, 30, and 31, respectively) in 2–3 h, with good to excellent yields reaching 86%. The electron-deficient QX couplers proved to be coupled efficiently using the Stille coupling reaction, which involves the coupling between electron-rich orgaostannane and electron-deficient halide. The synthesized precursors and desired chromophores were characterized by FTIR, 1H-NMR, 13C-NMR, and HRMS. 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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Article
Abundant Oxygen Vacancies Induced by the Mechanochemical Process Boost the Low-Temperature Catalytic Performance of MnO2 in NH3-SCR
Catalysts 2022, 12(10), 1291; https://doi.org/10.3390/catal12101291 - 21 Oct 2022
Viewed by 392
Abstract
Manganese oxides (MnOx) have attracted particular attention in the selective catalytic reduction of NOx with NH3 (NH3-SCR) because of their excellent low-temperature activity. Herein, we prepared a highly efficient MnO2 (MnO2-M) catalyst through a [...] Read more.
Manganese oxides (MnOx) have attracted particular attention in the selective catalytic reduction of NOx with NH3 (NH3-SCR) because of their excellent low-temperature activity. Herein, we prepared a highly efficient MnO2 (MnO2-M) catalyst through a facile ball milling-assisted redox strategy. MnO2-M shows a 90% NOx conversion in a wide operating temperature window of 75–200 °C under a gas hourly space velocity of 40,000 h−1, which is much more active than the MnO2 catalyst prepared by the redox method without the ball-milling process. Moreover, MnO2-M exhibits better H2O and SO2 resistance. The enhanced catalytic properties of MnO2-M originated from the high surface area, abundant oxygen vacancies, more acid sites, and higher Mn4+ content induced by the ball-milling process. In situ DRIFTS studies probed the reaction intermediates, and the SCR reaction was deduced to proceed via the typical Eley–Rideal mechanism. This work provides a facile method to enhance the catalytic performance of Mn-based catalysts for low-temperature denitrification and deep insights into the NH3-SCR reaction process. Full article
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Article
Photocatalytic Degradation of Eriochrome Black-T Using BaWO4/MoS2 Composite
Catalysts 2022, 12(10), 1290; https://doi.org/10.3390/catal12101290 - 21 Oct 2022
Viewed by 378
Abstract
Photocatalytic degradation of organic compounds using semiconductor oxide materials has attracted increased attention in the recent decades. Both the catalysts and light play an important role in the photocatalytic degradation process. This research work focuses on the synthesis of BaWO4/MoS2 [...] Read more.
Photocatalytic degradation of organic compounds using semiconductor oxide materials has attracted increased attention in the recent decades. Both the catalysts and light play an important role in the photocatalytic degradation process. This research work focuses on the synthesis of BaWO4/MoS2 composite using green chemical method and its use in the degradation of Eriochrome black-T dye. Synthesized BaWO4, and BaWO4/MoS2 composites were characterized by XRD, XPS, Raman, SEM, TEM, BET and UV-Vis characterizations techniques. BaWO4/MoS2 composite exhibits superior photocatalytic performance towards Eriochrome black-T degradation than BaWO4. Superior photocatalytic activity of BaWO4/MoS2 composite corresponds to enhanced light absorption, effective charge generation, separation, and minimum recombination of photogenerated charge carriers. Full article
(This article belongs to the Special Issue UV/Vis/NIR Photocatalysis and Optical Properties)
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Review
Asymmetric Hydroarylation Reactions Catalyzed by Transition Metals: Last 10 Years in a Mini Review
Catalysts 2022, 12(10), 1289; https://doi.org/10.3390/catal12101289 - 21 Oct 2022
Viewed by 434
Abstract
Hydroarylation reactions play a pivotal role in organic chemistry due to their versatility and efficiency. In the last 10 years, the scientific production around this reaction has been very high, but in its asymmetric version, the results are less. In this mini review, [...] Read more.
Hydroarylation reactions play a pivotal role in organic chemistry due to their versatility and efficiency. In the last 10 years, the scientific production around this reaction has been very high, but in its asymmetric version, the results are less. In this mini review, selected literature examples are considered to draw attention to directions of the asymmetric hydroarylation reaction mediated by transition metal catalysts. The selected works were grouped in two main sections. In the first, we reported examples relating the narrower definition of hydroarylation, namely the metal-catalyzed processes where inactivated aryl moiety undergoes a direct functionalization via insertion of an unsaturated compound. In the second part, hydroarylation reactions take place with the use of pre-activated aryl substrates, usually aryl-iodides or aryl-boronated. Full article
(This article belongs to the Special Issue Advances in Transition Metal Catalysis)
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Article
3D-Printed Raney-Cu POCS as Promising New Catalysts for Methanol Synthesis
Catalysts 2022, 12(10), 1288; https://doi.org/10.3390/catal12101288 - 21 Oct 2022
Viewed by 522
Abstract
Simultaneous generation and activation of Raney-type periodic open cellular structures (POCS) is a highly promising approach for generating novel structured methanol synthesis catalysts. In detail, we produced stable and highly active POCS from a Cu50Al50 alloy by additive manufacturing via Powder Bed Fusion [...] Read more.
Simultaneous generation and activation of Raney-type periodic open cellular structures (POCS) is a highly promising approach for generating novel structured methanol synthesis catalysts. In detail, we produced stable and highly active POCS from a Cu50Al50 alloy by additive manufacturing via Powder Bed Fusion by Electron Beam (PBF-EB) and activated them via selective leaching of aluminum in a sodium hydroxide/sodium zincate solution. The Raney-type Cu structures possessed catalytic methanol productivities of up to 2.2 gMeOHgnp-Cu h−1 (PBF-EB sticks) and 1.9 gMeOHgnp-Cu h−1 (PBF-EB POCS), respectively. Moreover, it was found that besides the nanoporous layer thickness, an optimum Zn/Cu ratio of 0.3–0.4 can also by adjusted by the leaching conditions. Full article
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Article
Computational Insights into Ru, Pd and Pt fcc Nano-Catalysts from Density Functional Theory Calculations: The Influence of Long-Range Dispersion Corrections
Catalysts 2022, 12(10), 1287; https://doi.org/10.3390/catal12101287 - 21 Oct 2022
Viewed by 409
Abstract
Ruthenium, palladium and platinum fall within the group of noble metals that are widely used in catalysis, especially for the electrocatalytic production of hydrogen. The dominant phase of the bulk Ru metal is hexagonal close-packed (hcp), which has been studied extensively. [...] Read more.
Ruthenium, palladium and platinum fall within the group of noble metals that are widely used in catalysis, especially for the electrocatalytic production of hydrogen. The dominant phase of the bulk Ru metal is hexagonal close-packed (hcp), which has been studied extensively. However, significantly less attention has been paid to the face-centred cubic (fcc) phases, which have been observed in nanoparticles. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D2, DFT-D3 and DFT-D3-(BJ)] to investigate the lattice parameters, surface energies and work functions of the (001), (011) and (111) surfaces of Ru, Pd and Pt in the fcc phase. When investigating the surface properties of the three metals, we observed that the DFT-D2 method generally underestimated the lattice parameters by up to 2.2% for Pt and 2.8% for Ru. The surface energies followed the observed trend (111) < (001) < (011) for both Ru and Pd with all three methods, which is comparable to experimental data. For Pt the same trend was observed with DFT-D2 and DFT-D3(BJ), but it deviated to Pt (111) < Pt (011) < Pt (001) for the DFT-D3 method. DFT-D2 overestimated the surface energies for all three Miller Indexes by 82%, 73%, and 60%, when compared to experimental values. The best correlation for the surface energies was obtained with the DFT-D3 and DFT-D3(BJ) methods, both of which have deviate by less than 15% deviation for all surfaces with respect to experiment. The work function followed the trend of Φ (111) < Φ (001) < Φ (011) for all three metals and calculated by all three methods. Five different types of Ru, Pd and Pt nanoparticles were considered, including icosahedral, decahedral, cuboctahedral, cubic and spherical particles of different sizes. The bulk, surface and nanoparticle calculations showed that the DFT-D2 method for Pt overestimated the exchange-correlation, leading to higher energy values that can be contributed erroneously to a more stable structure. The calculations showed that as soon as the surface-to-bulk ratio > 1, the energy per atom resembles bulk energy values. Full article
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Article
Spillover Hydrogen on Electron-Rich Ni/m-TiO2 for Hydrogenation of Furfural to Tetrahydrofurfuryl Alcohol
Catalysts 2022, 12(10), 1286; https://doi.org/10.3390/catal12101286 - 21 Oct 2022
Viewed by 476
Abstract
Conversion of biomass-derived furfural (FFA) platform molecule to value-added tetrahydrofurfuryl alcohol (THFA) molecule is a sustainable route using an efficient non-noble metallic catalyst in water solvent. In this work, Ni in various loadings on mesoporous titanium dioxide (m-TiO2) was synthesized in [...] Read more.
Conversion of biomass-derived furfural (FFA) platform molecule to value-added tetrahydrofurfuryl alcohol (THFA) molecule is a sustainable route using an efficient non-noble metallic catalyst in water solvent. In this work, Ni in various loadings on mesoporous titanium dioxide (m-TiO2) was synthesized in one pot by Evaporation-Induced Self-Assembly (EISA). The synthesised catalysts were evaluated for the hydrogenation of furfural to tetrahydrofurfuryl alcohol. The catalysts were characterised using a combination of spectroscopic techniques such as XRD, H2-TPR, H2-TPD, XPS, SEM-EDX, TEM, and HR-TEM. The characterization results show that the Ni/m-TiO2 materials exhibit enhanced electron-rich active sites, facilitated hydrogen spillover, uniform dispersion of small Ni particles (~5 nm), and strong metal support interaction between Ni and TiO2. Among the various Ni dopings, 7.5 wt.% Ni/m-TiO2 catalyst exhibited the best performance and achieved 99.9% FFA conversion and 93.2% THFA selectivity in water solvent at 100 °C and under 2 MPa H2. Additionally, detailed kinetic studies, process parameters, the stability and reusability of the catalyst were also studied. The results demonstrated that the 7.5 wt.% Ni/m-TiO2 catalyst is highly active and stable. Full article
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Article
Structure Sensitivity of Ammonia Synthesis on Cobalt: Effect of the Cobalt Particle Size on the Activity of Promoted Cobalt Catalysts Supported on Carbon
Catalysts 2022, 12(10), 1285; https://doi.org/10.3390/catal12101285 - 21 Oct 2022
Viewed by 447
Abstract
This work presents a size effect, i.e., catalyst surface activity, as a function of active phase particle size in a cobalt catalyst for ammonia synthesis. A series of cobalt catalysts supported on carbon and doped with barium was prepared, characterized (TEM, XRPD, and [...] Read more.
This work presents a size effect, i.e., catalyst surface activity, as a function of active phase particle size in a cobalt catalyst for ammonia synthesis. A series of cobalt catalysts supported on carbon and doped with barium was prepared, characterized (TEM, XRPD, and H2 chemisorption), and tested in ammonia synthesis (9.0 MPa, 400 °C, H2/N2 = 3, 8.5 mol% of NH3). The active phase particle size was varied from 3 to 45 nm by changing the metal loading in the range of 4.9–67.7 wt%. The dependence of the reaction rate expressed as TOF on the active phase particle size revealed an optimal size of cobalt particles (20–30 nm), ensuring the highest activity of the cobalt catalyst in the ammonia synthesis reaction. This indicated that the ammonia synthesis reaction on cobalt is a structure-sensitive reaction. The observed effect may be attributed to changes in the crystalline structure, i.e., the appearance of the hcp Co phase for the particles with a diameter of 20–30 nm. Full article
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Article
Production and Characterization of Durvillaea antarctica Enzyme Extract for Antioxidant and Anti-Metabolic Syndrome Effects
Catalysts 2022, 12(10), 1284; https://doi.org/10.3390/catal12101284 - 21 Oct 2022
Viewed by 435
Abstract
In this study, three enzyme hydrolysate termed Dur-A, Dur-B, and Dur-C, were produced from Durvillaea antarctica biomass using viscozyme, cellulase, and α-amylase, respectively. Dur-A, Dur-B, and Dur-C, exhibited fucose-containing sulfated polysaccharide from chemical composition determination and characterization by FTIR analyses. In addition, Dur-A, [...] Read more.
In this study, three enzyme hydrolysate termed Dur-A, Dur-B, and Dur-C, were produced from Durvillaea antarctica biomass using viscozyme, cellulase, and α-amylase, respectively. Dur-A, Dur-B, and Dur-C, exhibited fucose-containing sulfated polysaccharide from chemical composition determination and characterization by FTIR analyses. In addition, Dur-A, Dur-B, and Dur-C, had high extraction yields and low molecular weights. All extracts determined to have antioxidant activities by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), and ferrous ion-chelating methods. All extracts were also able to positively suppress the activities of key enzymes involved in metabolic syndrome: angiotensin I-converting enzyme (ACE), α-amylase, α-glucosidase, and pancreatic lipase. In general, Dur-B exhibited higher antioxidant and higher anti-metabolic syndrome effects as compared to the other two extracts. Based on the above health promoting properties, these extracts (especially Dur-B) can be used as potential natural antioxidants and natural anti-metabolic syndrome agents in a variety of food, cosmetic, and nutraceutical products for health applications. Full article
(This article belongs to the Special Issue Enzymes in Biomedical, Cosmetic and Food Application)
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Article
Integral Characteristic of Complex Catalytic Reaction Accompanied by Deactivation
Catalysts 2022, 12(10), 1283; https://doi.org/10.3390/catal12101283 - 20 Oct 2022
Viewed by 423
Abstract
New theoretical relationships for a complex catalytic reaction accompanied by deactivation are obtained, using as an example the two-step catalytic mechanism (Temkin–Boudart mechanism) with irreversible reactions and irreversible deactivation. In the domain of small concentrations, [...] Read more.
New theoretical relationships for a complex catalytic reaction accompanied by deactivation are obtained, using as an example the two-step catalytic mechanism (Temkin–Boudart mechanism) with irreversible reactions and irreversible deactivation. In the domain of small concentrations, Alim=NSk1CAkd, where Alim is the limit of the integral consumption of the gas substance, NS is the number of active sites per unit of catalyst surface; k1 and kd, are kinetic coefficients which relate to two reactions which compete for the free active site Z. CA is the gas concentration. One reaction belongs to the catalytic cycle. The other reaction with kinetic coefficient kd is irreversible deactivation. The catalyst lifetime, τcat=1CZ1kd, where CZ is the dimensionless steady-state concentration of free active sites. The main conclusion was formulated as follows: the catalyst lifetime can be enhanced by decreasing the steady-state (quasi-steady-state) concentration of free active sites. In some domains of parameters, it can also be achieved by increasing the steady-state (quasi-steady-state) reaction rate of the fresh catalyst. We can express this conclusion as follows: under some conditions, an elevated fresh catalyst activity protects the catalyst from deactivation. These theoretical results are illustrated with the use of computer simulations. Full article
(This article belongs to the Section Catalytic Materials)
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Article
Electrophoretic Deposition of Graphene Oxide and Reduced Graphene Oxide on the Rutile Phase of TiO2 Nanowires for Rapid Reduction of Cr (VI) under Simulated Sunlight Irradiation
Catalysts 2022, 12(10), 1282; https://doi.org/10.3390/catal12101282 - 20 Oct 2022
Viewed by 453
Abstract
Hexavalent chromium is very carcinogenic, and it is, therefore, important to remove it from wastewater prior to disposal. This study reports the photoreduction of Cr(VI) under simulated sunlight using graphene-derived TiO2 nanowire (TNW) composites. Electrophoretic deposition (EPD) of graphene oxide (GO) and [...] Read more.
Hexavalent chromium is very carcinogenic, and it is, therefore, important to remove it from wastewater prior to disposal. This study reports the photoreduction of Cr(VI) under simulated sunlight using graphene-derived TiO2 nanowire (TNW) composites. Electrophoretic deposition (EPD) of graphene oxide (GO) and reduced graphene oxide (rGO) was carried out on rutile phase TNWs. The TNWs were fabricated by thermal oxidation of titanium foil in the presence of 1M potassium hydroxide mist at 750 °C. The TNWs uniformly covered the surface of the titanium foil. EPD of GO or rGO was done as a function of time to produce deposits of different thicknesses. The photocatalytic performances of the GO/TNWs or rGO/TNWs were tested to reduce Cr(VI) under visible light. The performance of rGO/TNWs in reducing Cr(VI) was better than GO/TNWs. A 10-second-deposited rGO on TNW samples can reduce 10 mg/L Cr(VI) within 30 min under visible light, likely as a result of the high electron transfer from rGO to TNWs accelerating the Cr(VI) reduction. Full article
(This article belongs to the Section Nanostructured Catalysts)
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Article
Self-Doped Carbon Dots Decorated TiO2 Nanorods: A Novel Synthesis Route for Enhanced Photoelectrochemical Water Splitting
Catalysts 2022, 12(10), 1281; https://doi.org/10.3390/catal12101281 - 20 Oct 2022
Viewed by 482
Abstract
Herein, we have successfully prepared self-doped carbon dots with nitrogen elements (NCD) in a simple one-pot hydrothermal carbonization method, using L-histidine as a new precursor. The effect of as-prepared carbon dots was studied for photoelectrochemical (PEC) water splitting by decorating NCDs upon TiO [...] Read more.
Herein, we have successfully prepared self-doped carbon dots with nitrogen elements (NCD) in a simple one-pot hydrothermal carbonization method, using L-histidine as a new precursor. The effect of as-prepared carbon dots was studied for photoelectrochemical (PEC) water splitting by decorating NCDs upon TiO2 nanorods systematically by changing the loading time from 2 h to 8 h (TiO2@NCD2h, TiO2@NCD4h, TiO2@NCD6h, and TiO2@NCD8h). The successful decorating of NCDs on TiO2 was confirmed by FE-TEM and Raman spectroscopy. The TiO2@NCD4h has shown a photocurrent density of 2.51 mA.cm−2, 3.4 times higher than the pristine TiO2. Moreover, TiO2@NCD4h exhibited 12% higher applied bias photon-to-current efficiency (ABPE) than the pristine TiO2. The detailed IPCE, Mott–Schottky, and impedance (EIS) analyses have revealed the enhanced light harvesting property, free carrier concentration, charge separation, and transportation upon introduction of the NCDs on TiO2. The obtained results clearly portray the key role of NCDs in improving the PEC performance, providing a new insight into the development of highly competent TiO2 and NCDs based photoanodes for PEC water splitting. Full article
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Article
DFT Investigations on the Ring-Opening Polymerization of Trimethylene Carbonate Catalysed by Heterocyclic Nitrogen Bases
Catalysts 2022, 12(10), 1280; https://doi.org/10.3390/catal12101280 - 20 Oct 2022
Viewed by 438
Abstract
Organocatalysts for polymerization have known a huge interest over the last two decades. Among them, heterocyclic nitrogen bases are widely used to catalyse the ring-opening polymerization (ROP) of heterocycles such as cyclic carbonates. We have investigated the ring-opening polymerization of trimethylene carbonate (TMC) [...] Read more.
Organocatalysts for polymerization have known a huge interest over the last two decades. Among them, heterocyclic nitrogen bases are widely used to catalyse the ring-opening polymerization (ROP) of heterocycles such as cyclic carbonates. We have investigated the ring-opening polymerization of trimethylene carbonate (TMC) catalysed by DMAP (4-dimethylaminopyridine) and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) as case studies in the presence of methanol as co-initiator by Density Functional Theory (DFT). A dual mechanism based on H-bond activation of the carbonyl moieties of the monomer and a basic activation of the alcohol co-initiator has been shown to occur more preferentially than a direct nucleophilic attack of the carbonate monomer by the heterocyclic nitrogen catalyst. The rate-determining step of the mechanism is the ring opening of the TMC molecule, which is slightly higher than the nucleophilic attack of the TMC carbonyl by the activated alcohol. The calculations also indicate TBD as a more efficient catalyst than DMAP. The higher energy barrier found for DMAP vs. TBD, 23.7 vs. 11.3 kcal·mol−1, is corroborated experimentally showing a higher reactivity for the latter. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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Article
Efficient Cross-Coupling of Acetone with Linear Aliphatic Alcohols over Supported Copper on a Fluorite-Type Pr2Zr2O7
Catalysts 2022, 12(10), 1279; https://doi.org/10.3390/catal12101279 - 20 Oct 2022
Viewed by 444
Abstract
In cross-coupling of biomass-derived acetone and alcohols contributing to the production of carbon-elongated chemicals and fuels, the essential catalyst components are metal dispersion for alcohol dehydrogenation and, more importantly, basicity for carbon–carbon coupling. Herein, we report the potential of co-precipitated praseodymia–zirconia solid solution [...] Read more.
In cross-coupling of biomass-derived acetone and alcohols contributing to the production of carbon-elongated chemicals and fuels, the essential catalyst components are metal dispersion for alcohol dehydrogenation and, more importantly, basicity for carbon–carbon coupling. Herein, we report the potential of co-precipitated praseodymia–zirconia solid solution (Pr2Zr2O7) as a support of Cu catalyst for the conversion of acetone and butanol into C7 and C11 products. Cu/Pr2Zr2O7 exhibits a high yield of C7 and C11 (ca. 84%) compared to Cu/ZrO2 and Cu/PrO1.83. Moreover, it is robust under the employed solvent-free conditions owing to a solid solution of Pr2Zr2O7 compared to PrO1.83 showing phase transition to PrOHCO3. It is also tolerant to up to 5 wt % water of the reactant mixture, recyclable once adequate post-treatment is employed after the reaction, and can convert the acetone–butanol–ethanol mixture into C5–C11 products at the nearly equivalent yield (82%) to the acetone–butanol mixture. Therefore, the Cu/Pr2Zr2O7 reported herein is an efficient catalyst for the coupling of acetone with linear aliphatic alcohols into biofuel precursors. Full article
(This article belongs to the Special Issue Catalysis for Environmentally Benign Production of Alternative Fuels)
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Article
Selective C-O Coupling Reaction of N-Methoxy Arylamides and Arylboronic Acids Catalyzed by Copper Salt
Catalysts 2022, 12(10), 1278; https://doi.org/10.3390/catal12101278 - 19 Oct 2022
Viewed by 411
Abstract
Herein, we report a copper-catalyzed C-O cross-coupling of N-methoxy amides and arylboronic acids for the synthesis of aryl-N-methoxy arylimides. The fully selective O-arylation of the N-methoxy amides is found to be greatly prompted by the inexpensive and commercially available CuI. The reaction conditions [...] Read more.
Herein, we report a copper-catalyzed C-O cross-coupling of N-methoxy amides and arylboronic acids for the synthesis of aryl-N-methoxy arylimides. The fully selective O-arylation of the N-methoxy amides is found to be greatly prompted by the inexpensive and commercially available CuI. The reaction conditions tolerate a variety of functional groups and promote different reactivities depending on the electronic and steric properties of the distorted substrates. Full article
(This article belongs to the Special Issue Catalyzed Carbon-Heteroatom Bond Formation)
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Article
Catalytic Oxidative Decomposition of Dimethyl Methyl Phosphonate over CuO/CeO2 Catalysts Prepared Using a Secondary Alkaline Hydrothermal Method
Catalysts 2022, 12(10), 1277; https://doi.org/10.3390/catal12101277 - 19 Oct 2022
Viewed by 435
Abstract
Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 [...] Read more.
Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 lattice. The physical and chemical properties of CeO2, CuO/CeO2, and CuO were investigated. H2 temperature-programmed reduction characterization showed that the oxidation activity of CuO/CeO2 was significantly improved. X-ray photoelectron spectroscopy results showed that electron transfer occurred between Ce and Cu in the CuO/CeO2 catalyst. Additionally, Raman characterization confirmed the strong interaction between Cu and Ce. After CuO was loaded, the thermal catalytic decomposition performance of the catalyst was significantly improved with respect to the sarin simulant dimethyl methyl phosphonate (DMMP); with an increase in the Cu/Ce ratio, the performance first strengthened and then weakened. Additionally, the reaction tail gas and catalyst surface products were analyzed using mass spectrometry and ion chromatography, and the changes in the surface products during the thermal catalytic decomposition of DMMP were characterized at different temperatures using in situ diffuse reflectance infrared Fourier transform spectroscopy. Finally, the catalytic reaction pathways of DMMP on CeO2, CuO/CeO2, and CuO were inferred. The study results not only demonstrate an effective catalyst for the removal of nerve agent but also a feasible preparation method for lattice-doped bimetallic catalysts in the field of environmental protection. Full article
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Article
Two-Dimensional Fe-N-C Nanosheets for Efficient Oxygen Reduction Reaction
Catalysts 2022, 12(10), 1276; https://doi.org/10.3390/catal12101276 - 19 Oct 2022
Viewed by 482
Abstract
Fe-N-doped carbon (Fe-N-C)-based electrocatalysts are considered to be promising alternatives to replace Pt-based catalysts for oxygen reduction reactions (ORR). Here, we reported a simple and effective approach to prepare Fe-N-C-based electrocatalysts with the shape of two-dimensional nanosheets (termed Fe/NCNSs) to enhance the ORR [...] Read more.
Fe-N-doped carbon (Fe-N-C)-based electrocatalysts are considered to be promising alternatives to replace Pt-based catalysts for oxygen reduction reactions (ORR). Here, we reported a simple and effective approach to prepare Fe-N-C-based electrocatalysts with the shape of two-dimensional nanosheets (termed Fe/NCNSs) to enhance the ORR performance. Fe/NCNSs were prepared by the calcination of Fe/Zn dual-metal ZIFs nanosheets as precursors. Benefiting from its higher specific surface area, electrochemically active surface area, and proportion of pyridinic N and Fe-N, the optimized Fe/NCNS showed excellent ORR performance both in acidic (E1/2 = 0.725 V vs. RHE) and alkaline (E1/2 = 0.865 vs. RHE) media, being 23 mV more negative and 24 mV more positive than that of a commercial Pt/C. The optimized Fe/NCNS also exhibited long durability. In addition, the Zn-air battery with Fe/NCNS-1 and RuO2 as the air catalyst exhibited high power density (1590 mW cm−2 at a current density of 2250 mA cm−2) and superior charging/discharging durability. Full article
(This article belongs to the Special Issue Heterogeneous Electrocatalysis: Fundamentals and Applications II)
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Article
Thermodynamic and Kinetic Study of Carbon Dioxide Hydrogenation on the Metal-Terminated Tantalum-Carbide (111) Surface: A DFT Calculation
Catalysts 2022, 12(10), 1275; https://doi.org/10.3390/catal12101275 - 19 Oct 2022
Viewed by 410
Abstract
The need to reduce our reliance on fossil fuels and lessen the environmentally harmful effects of CO2 have encouraged investigations into CO2 hydrogenation to produce useful products. Transition metal carbides exhibit a high propensity towards CO2 activation, which makes them [...] Read more.
The need to reduce our reliance on fossil fuels and lessen the environmentally harmful effects of CO2 have encouraged investigations into CO2 hydrogenation to produce useful products. Transition metal carbides exhibit a high propensity towards CO2 activation, which makes them promising candidates as suitable catalysts for CO2 hydrogenation. Here, we have employed calculations based on the density-functional theory to investigate the reaction network for CO2 hydrogenation to product molecules on the tantalum-terminated TaC (111) surface, including two routes from either HCOOH* or HOCOH* intermediates. Detailed calculations of the reaction energies and energy barriers along multiple potential catalytic pathways, along with the exploration of all intermediates, have shown that CH4 is the predominant product yielded through a mechanism involving HCOOH, with a total exothermic reaction energy of −4.24 eV, and energy barriers between intermediates ranging from 0.126 eV to 2.224 eV. Other favorable products are CO and CH3OH, which are also produced via the HCOOH pathway, with total overall reaction energies of −2.55 and −2.10 eV, respectively. Our calculated thermodynamic and kinetic mechanisms that have identified these three predominant products of the CO2 hydrogenation catalyzed by the TaC (111) surface explain our experimental findings, in which methane, carbon monoxide, and methanol have been observed as the major reaction products. Full article
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Article
Solvent-Free Synthesis of Nickel Nanoparticles as Catalysts for CO2 Hydrogenation to Methane
Catalysts 2022, 12(10), 1274; https://doi.org/10.3390/catal12101274 - 19 Oct 2022
Viewed by 471
Abstract
The solid-state combustion method was used to prepare nickel-based catalysts for CO2 hydrogenation from [Ni(C3H4N2)6](NO3)2 and [Ni(C3H4N2)6](ClO4)2. These complexes [...] Read more.
The solid-state combustion method was used to prepare nickel-based catalysts for CO2 hydrogenation from [Ni(C3H4N2)6](NO3)2 and [Ni(C3H4N2)6](ClO4)2. These complexes were synthesized by adding nickel nitrate and perchlorate to melted imidazole. The composition and structure of the obtained complexes was confirmed by ATR FTIR, powder XRD, and elemental analysis. The stages of thermal decomposition of the complexes and their kinetic parameters were established. It was found that incomplete gasification of more thermostable Ni(C3H4N2)6](ClO4)2 led to the formation of carbon, nitrogen, and chlorine impurities. According to powder XRD and XPS, the solid products of gasification of both complexes consist of NiO and Ni0 covered with nickel hydroxide and/or a carbonate layer. In the case of the sample prepared from [Ni(C3H4N2)6](ClO4)2, this layer was pronounced. Therefore, it limits the nickel reduction in the reaction medium of CO2 hydrogenation, even at 450 °C. The surface of the sample prepared from [Ni(C3H4N2)6](NO3)2 contains nickel oxide, which is easily reduced. So, the catalyst active phase is already formed at 250 °C in the presence of CO2 and efficiently catalyzes CO2 hydrogenation as the temperature increases. Therefore, [Ni(C3H4N2)6](NO3)2 is a promising precursor for the CO2 hydrogenation catalyst, and its solvent-free synthesis follows Green Chemistry principles. Full article
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Article
Clean Syngas and Hydrogen Co-Production by Gasification and Chemical Looping Hydrogen Process Using MgO-Doped Fe2O3 as Redox Material
Catalysts 2022, 12(10), 1273; https://doi.org/10.3390/catal12101273 - 19 Oct 2022
Viewed by 466
Abstract
Gasification converts biomass into syngas; however, severe cleaning processes are necessary due to the presence of tars, particulates and contaminants. The aim of this work is to propose a cleaning method system based on tar physical adsorption coupled with the production of pure [...] Read more.
Gasification converts biomass into syngas; however, severe cleaning processes are necessary due to the presence of tars, particulates and contaminants. The aim of this work is to propose a cleaning method system based on tar physical adsorption coupled with the production of pure H2 via a chemical looping process. Three fixed-bed reactors with a double-layer bed (NiO/Al2O3 and Fe-based particles) working in three different steps were used. First, NiO/Al2O3 is used to adsorb tar from syngas (300 °C); then, the adsorbed tar undergoes partial oxidization by NiO/Al2O3 to produce CO and H2 used for iron oxide reduction. In the third step, the reduced iron is oxidized with steam to produce pure H2 and to restore iron oxides. A double-layer fixed-bed reactor was fed alternatively by guaiacol and as tar model compounds, air and water were used. High-thermal-stability particles 60 wt% Fe2O3/40 wt% MgO synthetized by the coprecipitation method were used as Fe-based particles in six cycle tests. The adsorption efficiency of the NiO/Al2O3 bed is 98% and the gas phase formed is able to partially reduce iron, favoring the reduction kinetics. The efficiency of the process related to the H2 production after the first cycle is 35% and the amount of CO is less than 10 ppm. Full article
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Review
3D Printing/Vat Photopolymerization of Photopolymers Activated by Novel Organic Dyes as Photoinitiators
Catalysts 2022, 12(10), 1272; https://doi.org/10.3390/catal12101272 - 19 Oct 2022
Viewed by 438
Abstract
Even though numerous organic dyes which are used as photoinitiators/photocatalysts during photopolymerization have been systematically investigated and collected in previous reviews, further designs of these chromophores and the developments in high-performance photoinitiating systems have emerged in recent years, which play the crucial role [...] Read more.
Even though numerous organic dyes which are used as photoinitiators/photocatalysts during photopolymerization have been systematically investigated and collected in previous reviews, further designs of these chromophores and the developments in high-performance photoinitiating systems have emerged in recent years, which play the crucial role in 3D printing/Vat polymerization. Here, in this mini-review, various families of organic dyes that are used as newly synthesized photoinitiators/photocatalysts which were reported in literature during 2021–2022 are specified by their photoinitiation mechanisms, which dominate their performance during photopolymerization, especially in 3D printing. Markedly, visible light-induced polymerization could be employed in circumstances not only upon the irradiation of artificial light sources, e.g., in LEDs, but also in sunlight irradiation. Furthermore, a short overview of the achievements of newly developed mechanisms, e.g., RAFT, photoinitiator-RAFT, and aqueous RAFT using organic chromophores as light-harvesting compounds to induce photopolymerization upon visible light irradiation are also thoroughly discussed. Finally, the reports on the semiconducting nanomaterials that have been used as photoinitiators/photocatalysts during photopolymerization are also introduced as perspectives that are able to expand the scope of 3D printing and materials science due to their various advantages such as high extinction coefficients, broad absorption spectra, and having multiple molecular binding points. Full article
(This article belongs to the Section Photocatalysis)
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Article
Ex Situ Upgrading of Extra Heavy Oil: The Effect of Pore Shape of Co-Mo/γ-Al2O3 Catalysts
Catalysts 2022, 12(10), 1271; https://doi.org/10.3390/catal12101271 - 18 Oct 2022
Viewed by 524
Abstract
Co-Mo/γ-Al2O3 catalysts with different pore shapes were synthesized for the ex situ upgrading of extra heavy oils by hydrodesulfurization (HDS), hydrodemetallization (HDM), and hydrodeasphaltization (HDA). The catalysts were synthesized using aluminum oxides that were prepared by various methods. It was [...] Read more.
Co-Mo/γ-Al2O3 catalysts with different pore shapes were synthesized for the ex situ upgrading of extra heavy oils by hydrodesulfurization (HDS), hydrodemetallization (HDM), and hydrodeasphaltization (HDA). The catalysts were synthesized using aluminum oxides that were prepared by various methods. It was found that using the product obtained by the thermochemical activation of gibbsite leads to the formation of slit-shaped pores in aluminum oxide, while the application of the hydroxide deposition method by the precipitation of sodium aluminate and nitric acid gives cylindrical pores in aluminum oxide. Co-Mo catalysts synthesized using these two types of pores exhibit different catalytic activities. The catalyst synthesized on a carrier with cylindrical pores exhibited a higher catalytic activity in sulfur, heavy metals, and asphaltenes removal reactions that are synthesized on a carrier with slit-like pores. This is because the presence of cylindrical pores leads to a decrease in diffusion restrictions when removing large molecules of asphaltenes and sulfur-containing and metal-containing compounds. Full article
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Article
Ni-Al Self-Propagating High-Temperature Synthesis Catalysts in Dry Reforming of Methane to Hydrogen-Enriched Fuel Mixtures
Catalysts 2022, 12(10), 1270; https://doi.org/10.3390/catal12101270 - 18 Oct 2022
Cited by 1 | Viewed by 439
Abstract
The worldwide increase in demand for environmentally friendly energy has led to the intensification of work on the synthesis of H2-containing fuel. The dry reforming of methane has become one of the most important avenues of research since the consumption of [...] Read more.
The worldwide increase in demand for environmentally friendly energy has led to the intensification of work on the synthesis of H2-containing fuel. The dry reforming of methane has become one of the most important avenues of research since the consumption of two greenhouse gases reduces the rate of global warming. A study of NiAl composite materials as catalysts for methane reforming has been carried out. Self-propagating high-temperature synthesis (SHS) has been used to produce NiAl catalysts. Comparative studies were carried out regarding the dry reforming and partial oxidation of methane, as well as catalysts prepared using the impregnation (IM) and SHS methods. A catalyst with 29% Ni and 51% Al after SHS contains the phases of NiAl and NiAl2O4, which are active phases in the dry reforming of methane. The optimal crystal lattice parameter (for the maximum possible conversion of CO2 and CH4) is 3.48–3.485 Å for Al2O3, which plays the role of a catalyst carrier, and 1.42 Å, for NiAl2O4, which plays the role of a catalyst. The aim of the work is to develop a new and efficient catalyst for the dry reforming of methane into a synthesis gas, which will further promote the organization of a new era of environmentally friendly energy-saving production methods. Full article
(This article belongs to the Special Issue Catalytic Conversion of Low Carbon Alkane)
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Article
Solar Light-Induced Photocatalytic Degradation of Ciprofloxacin Antibiotic Using Biochar Supported Nano Bismuth Ferrite Composite
Catalysts 2022, 12(10), 1269; https://doi.org/10.3390/catal12101269 - 18 Oct 2022
Cited by 1 | Viewed by 439
Abstract
Research on advanced materials for environmental remediation and pollutant degradation is rapidly progressing because of their numerous applications. Biochar is an excellent material support for the catalytic activity of bismuth ferrite (BiFeO3), which is one of the best perovskite-based photocatalysts in [...] Read more.
Research on advanced materials for environmental remediation and pollutant degradation is rapidly progressing because of their numerous applications. Biochar is an excellent material support for the catalytic activity of bismuth ferrite (BiFeO3), which is one of the best perovskite-based photocatalysts in this work for diverse pollutant degradation when exposed to direct sunlight. Biochar was produced by pyrolyzing oil palm empty fruit bunches (OPEFBs) and then integrate with BiFeO3 in the presence of cross-linked chitosan to create a BFO/biochar coupled magnetic photocatalyst (CBB). This research was conducted to examine the performance of the photocatalytic activity of CBB towards the degradation of ciprofloxacin antibiotics. To determine the optimal condition, two operational parameters that are photocatalyst dosage and initial pollutant concentrations, were evaluated. The results of the powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope-energy dispersive X-ray (SEM-EDX) analyses confirmed the high purity of the rhombohedral BiFeO3 with a high surface area, as well as the successful coupling of BiFeO3 and biochar at a ratio of 1:1. The most effective conditions for the various variables are 1.5 g/L CBB dosage at 10 ppm with 77.08% photodegradation under direct sunlight for 2 h. Further, a pseudo-first-order kinetic reaction was followed and observed with decreasing k values as the initial concentration increased. This shows that the system performs best at low concentrations. This finding confirms that the catalytic parameters improved the efficiency of photocatalysts with biochar assistance in removing antibiotic pollutants. Full article
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Article
Study of the Hydrothermal-Catalytic Influence on the Oil-Bearing Rocks of the Usinskoye Oil Field
Catalysts 2022, 12(10), 1268; https://doi.org/10.3390/catal12101268 - 18 Oct 2022
Viewed by 443
Abstract
In this work, a synthesis of an oil-soluble iron-based catalyst precursor was carried out and its efficiency was tested in a laboratory simulation of the aquathermolysis process at different temperatures. The rocks of the Usinskoe field from the Permian deposits of the Komi [...] Read more.
In this work, a synthesis of an oil-soluble iron-based catalyst precursor was carried out and its efficiency was tested in a laboratory simulation of the aquathermolysis process at different temperatures. The rocks of the Usinskoe field from the Permian deposits of the Komi Republic, obtained by steam-gravity drainage, and the iron-based catalyst precursor, as well as the products of non-catalytic and catalytic aquathermolysis, were selected as the object of study. As a result, it was found that the content of alkanes in the samples after thermal steam treatment (TST) at 300 °C increased 8-fold compared to the original oil, and the content of cycloalkanes in the sample with the catalyst increased 2-fold compared to the control experience. This may indicate that not only the carbon-heteroatom bonds (C-S, N, O) but also the C-C bonds were broken. It also shows that increasing the iron tallate concentration at TST 300 °C leads to a decrease in the molecular mass of the oil compared to the control experiment. According to SEM, the catalyst is nanodisperse particles with a size of ≈60–80 nm, which are adsorbed on the rock surface, catalyst removal occurs at a small scale. Full article
(This article belongs to the Special Issue Catalysis for Bitumen/Heavy Oil Upgrading and Petroleum Refining)
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Article
Surface Modification of GdMn2O5 for Catalytic Oxidation of Benzene via a Mild A-Site Sacrificial Strategy
Catalysts 2022, 12(10), 1267; https://doi.org/10.3390/catal12101267 - 18 Oct 2022
Viewed by 458
Abstract
Thermal catalytic oxidation technology is an effective way to eliminate refractory volatile organic pollutants, such as Benzene. Nevertheless, a high reaction temperature is usually an obstacle to practical application. Here, GdMn2O5 mullite (GMO-H) catalyst with disordered surface Gd-deficient and oxygen-vacancy-rich [...] Read more.
Thermal catalytic oxidation technology is an effective way to eliminate refractory volatile organic pollutants, such as Benzene. Nevertheless, a high reaction temperature is usually an obstacle to practical application. Here, GdMn2O5 mullite (GMO-H) catalyst with disordered surface Gd-deficient and oxygen-vacancy-rich concentrations was synthesized via a controllable low-temperature acid-etching route. Results show that the preferentially broken Gd-O bond is conducive to exposing more Mn-Mn active sites, which Gd species covered. The affluent surface oxygen vacancies supply sufficient adsorption sites for oxygen molecules, facilitating the oxygen cycles during Benzene catalytic oxidation. Furthermore, surface exposed Mn3+ species were oxidized to Mn4+, which is beneficial to increase catalytic activity at a lower temperature. Compared with the conventional GdMn2O5, the reaction temperature for removing 90% Benzene over GMO-H was dropped from 405 to 310 °C with WHSV of 30,000 mL g−1 h−1. Significantly, during a 72 h catalytic test, the catalytic activity remains constant at 90% of the Benzene removal at 300 °C, indicating excellent activity stability. This work reported an efficient approach to preparing manganese-base mullite thermal catalyst, providing insight into the catalytic oxidation of Benzene. Full article
(This article belongs to the Section Environmental Catalysis)
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Article
Environmentally Safe Magnetic Nanocatalyst for the Production of Biodiesel from Pongamia pinnata Oil
Catalysts 2022, 12(10), 1266; https://doi.org/10.3390/catal12101266 - 18 Oct 2022
Viewed by 472
Abstract
Biodiesel is an alternative fuel in many developing and developed countries worldwide. Biodiesel has significant and numerous economic, environmental, and social benefits. However, the problem with conventional biodiesel production is the high industrial production cost, mainly contributed by the raw materials. Therefore, catalysts [...] Read more.
Biodiesel is an alternative fuel in many developing and developed countries worldwide. Biodiesel has significant and numerous economic, environmental, and social benefits. However, the problem with conventional biodiesel production is the high industrial production cost, mainly contributed by the raw materials. Therefore, catalysts and feedstock are essential in increasing total biodiesel production rates and minimizing production costs. Magnetic nano-catalysts play a crucial role in heterogeneous catalysis due to their easy recovery, recyclability, excellent selectivity, and fast reaction rates, owing to their larger surface area. This research activity used heterogeneous magnetic nano-catalysts of ICdO, ISnO, and their modified form, to produce biodiesel. The synthesized nano-catalysts were made through co-precipitation and found quite efficient for transesterifying Pongamia pinnata oil. The effect of various parameters on biodiesel yield in the presence of prepared magnetic nano-catalysts has been studied. In the transesterification supported by ISnO, high yield, i.e., 99%, was achieved after 2 h of reaction time at 60 °C. The nano-catalysts were magnetically recovered and reused 4–5 times without any change in their activity. All the synthesized magnetic nano-catalysts performed SEM analysis. Each fraction of the produced biodiesel was assessed for different quality parameters, and the results were per ASTM standards. The components present in biodiesel produced from Pongamia pinnata oil were determined by GCMS. Full article
(This article belongs to the Section Biomass Catalysis)
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Communication
Highly Efficient Synthesis of Cinnamamides from Methyl Cinnamates and Phenylethylamines Catalyzed by Lipozyme® TL IM under Continuous-Flow Microreactors
Catalysts 2022, 12(10), 1265; https://doi.org/10.3390/catal12101265 - 18 Oct 2022
Viewed by 490
Abstract
While a few derivatives of cinnamamides exhibited anti-inflammatory and/ or analgesic activity, in this study, we developed a highly efficient method for the synthesis of cinnamamides from methyl cinnamates and phenylethylamines catalyzed by Lipozyme® TL IM in continuous-flow microreactors. The reaction parameters [...] Read more.
While a few derivatives of cinnamamides exhibited anti-inflammatory and/ or analgesic activity, in this study, we developed a highly efficient method for the synthesis of cinnamamides from methyl cinnamates and phenylethylamines catalyzed by Lipozyme® TL IM in continuous-flow microreactors. The reaction parameters and broad substrate range of the new method was studied. Maximum conversion (91.3%) was obtained under the optimal condition of substrate molar ratio of 1:2 (methyl 4-chlorocinnamate: phenylethylamine) at 45 °C for about 40 min. The remarkable features of this work include short residence time, mild reaction conditions, easy control of the reaction process, and that the catalyst can be recycled or reused, which provide a rapid and economical strategy for the synthesis and design of cinnamamide derivatives for further research on drug activity. Full article
(This article belongs to the Topic Bioreactors: Control, Optimization and Applications)
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Article
In Situ X-ray Absorption Spectroscopy Cells for High Pressure Homogeneous Catalysis
Catalysts 2022, 12(10), 1264; https://doi.org/10.3390/catal12101264 - 17 Oct 2022
Viewed by 541
Abstract
We have designed, built, and tested two cells for in situ and, potentially, operando X-ray absorption spectroscopy experiments in transmission and fluorescence modes. The cells were developed for high-pressure and high-temperature conditions to study the catalytic processes under relevant industrial conditions. Operation of [...] Read more.
We have designed, built, and tested two cells for in situ and, potentially, operando X-ray absorption spectroscopy experiments in transmission and fluorescence modes. The cells were developed for high-pressure and high-temperature conditions to study the catalytic processes under relevant industrial conditions. Operation of the cells was tested for Ru and Rh-based homogeneous and heterogeneous catalytic systems. Using synchrotron-based in situ X-ray absorption spectroscopy we tracked the evolution of active metal species during catalytic reactions. Our setup proved that it was capable to investigate liquid-state homogeneous and heterogenous systems under elevated temperatures, high pressures of reactive gasses, and in the presence of corrosive reagents. Full article
(This article belongs to the Topic Catalysis: Homogeneous and Heterogeneous)
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Review
Preparation and Photocatalytic Activities of TiO2-Based Composite Catalysts
Catalysts 2022, 12(10), 1263; https://doi.org/10.3390/catal12101263 - 17 Oct 2022
Viewed by 512
Abstract
While modern industry has contributed to the prosperity of an increasingly urbanized society, it has also led to serious pollution problems, with discharged wastewater and exhaust gases causing significant environmental harm. Titanium dioxide (TiO2), which is an excellent photocatalyst, has received [...] Read more.
While modern industry has contributed to the prosperity of an increasingly urbanized society, it has also led to serious pollution problems, with discharged wastewater and exhaust gases causing significant environmental harm. Titanium dioxide (TiO2), which is an excellent photocatalyst, has received extensive attention because it is inexpensive and able to photocatalytically degrade pollutants in an environmentally friendly manner. TiO2 has many advantages, including high chemical stability, low toxicity, low operating costs, and environmental friendliness. TiO2 is an N-order semiconductor material with a bandgap of 3.2 eV. Only when the wavelength of ultraviolet light is less than or equal to 387.5 nm, the valence band electrons can obtain the energy of the photon and pass through the conduction band to form photoelectrons, meanwhile the valence band forms a photogenerated hole. And light in other wavelength regions does not excite this photogenerated electrons. The most common methods used to improve the photocatalytic efficiency of TiO2 involve increasing its photoresponse range and reducing photogenerated-carrier coupling. The morphology, size, and structure of a heterojunction can be altered through element doping, leading to improved photocatalytic efficiency. Mainstream methods for preparing TiO2 are reviewed in this paper, with several excellent preparation schemes for improving the photocatalytic efficiency of TiO2 introduced. TiO2 is mainly prepared using sol-gel, solvothermal, hydrothermal, anodic oxidation, microwave-assisted, CVD and PVD methods, and TiO2 nanoparticles with excellent photocatalytic properties can also be prepared. Ti-containing materials are widely used to purify harmful gases, as well as contaminants from building materials, coatings, and daily necessities. Therefore, the preparation and applications of titanium materials have become globally popular research topics. Full article
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