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Catalysts, Volume 10, Issue 6 (June 2020) – 126 articles

Cover Story (view full-size image): By using an ME-DRIFTS-PSD approach, in which the catalytic system was exposed to alternating CO2/CO2+H2 gas flow, active species in the rhodium/ceria catalyst are distinguished from spectator species by their infrared signatures. The strongly responding CO ad-species suggest a carbide reaction path for the CO2 methanation. View this paper.
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Article
Highly Active Catalysts for the Dehydration of Isopropanol
Catalysts 2020, 10(6), 719; https://doi.org/10.3390/catal10060719 - 26 Jun 2020
Cited by 1 | Viewed by 740
Abstract
Due to the high costs and low selectivity associated with the production of propylene, new routes for its synthesis are being sought. Dehydration has been widely investigated in this field, but, thus far, no study has produced efficient results for isopropanol. Vanadium-zirconia catalysts [...] Read more.
Due to the high costs and low selectivity associated with the production of propylene, new routes for its synthesis are being sought. Dehydration has been widely investigated in this field, but, thus far, no study has produced efficient results for isopropanol. Vanadium-zirconia catalysts have been shown to be effective for the dehydration of ethanol. Therefore, we investigated the activity of such catalysts in the dehydration of isopropanol. The catalysts were synthetized on a SBA-15 base, supplemented with zirconia or combined zirconia and vanadium. Tests were conducted in a continuous flow reactor at 150–300 °C. Samples were analyzed using a gas chromatograph. The most active catalyst showed 96% conversion with 100% selectivity to propylene. XRD, SEM and Raman spectroscopy analyses revealed that as the vanadium content increases, the pore size of the catalyst decreases and both isopropanol conversion and propylene selectivity are reduced. Thus, without the addition of vanadium, the Zr-SBA-15 catalyst appears to be suitable for the dehydration of isopropanol to propylene. Full article
(This article belongs to the Section Environmental Catalysis)
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Article
Asymmetry in Charge Transfer Pathways Caused by Pigment–Protein Interactions in the Photosystem II Reaction Center Complex
Catalysts 2020, 10(6), 718; https://doi.org/10.3390/catal10060718 - 26 Jun 2020
Viewed by 661
Abstract
This article discusses the photoinduced charge transfer (CT) kinetics within the reaction center complex of photosystem II (PSII RC). The PSII RC exhibits a structural symmetry in its arrangement of pigments forming two prominent branches, D1 and D2. Despite this symmetry, the CT [...] Read more.
This article discusses the photoinduced charge transfer (CT) kinetics within the reaction center complex of photosystem II (PSII RC). The PSII RC exhibits a structural symmetry in its arrangement of pigments forming two prominent branches, D1 and D2. Despite this symmetry, the CT has been observed to occur exclusively in the D1 branch. The mechanism to realize such functional asymmetry is yet to be understood. To approach this matter, we applied the theoretical tight-binding model of pigment excitations and simulated CT dynamics based upon the framework of an open quantum system. This simulation used a recently developed method of computation based on the quasi-adiabatic propagator path integral. A quantum CT state is found to be dynamically active when its site energy is resonant with the exciton energies of the PSII RC, regardless of the excitonic landscape we utilized. Through our investigation, it was found that the relative displacement between the local molecular energy levels of pigments can play a crucial role in realizing this resonance and therefore greatly affects the CT asymmetry in the PSII RC. Using this mechanism phenomenologically, we demonstrate that a near 100-to-1 ratio of reduction between the pheophytins in the D1 and D2 branches can be realized at both 77 K and 300 K. Our results indicate that the chlorophyll Chl D 1 is the most active precursor of the primary charge separation in the D1 branch and that the reduction of the pheophytins can occur within pico-seconds. Additionally, a broad resonance of the active CT state implies that a large static disorder observed in the CT state originates in the fluctuations of the relative displacements between the local molecular energy levels of the pigments in the PSII RC. Full article
(This article belongs to the Special Issue Photo-Induced Electron Transfer Kinetics in Catalysis)
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Article
Multi-Leg TiO2 Nanotube Photoelectrodes Modified by Platinized Cyanographene with Enhanced Photoelectrochemical Performance
Catalysts 2020, 10(6), 717; https://doi.org/10.3390/catal10060717 - 26 Jun 2020
Cited by 3 | Viewed by 1003
Abstract
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, [...] Read more.
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance. Full article
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Article
CFD Simulations of Radiative Heat Transport in Open-Cell Foam Catalytic Reactors
Catalysts 2020, 10(6), 716; https://doi.org/10.3390/catal10060716 - 26 Jun 2020
Cited by 6 | Viewed by 1034
Abstract
The heat transport management in catalytic reactors is crucial for the overall reactor performance. For small-scale dynamically-operated reactors, open-cell foams have shown advantageous heat transport characteristics over conventional pellet catalyst carriers. To design efficient and safe foam reactors as well as to deploy [...] Read more.
The heat transport management in catalytic reactors is crucial for the overall reactor performance. For small-scale dynamically-operated reactors, open-cell foams have shown advantageous heat transport characteristics over conventional pellet catalyst carriers. To design efficient and safe foam reactors as well as to deploy reliable engineering models, a thorough understanding of the three heat transport mechanisms, i.e., conduction, convection, and thermal radiation, is needed. Whereas conduction and convection have been studied extensively, the contribution of thermal radiation to the overall heat transport in open-cell foam reactors requires further investigation. In this study, we simulated a conjugate heat transfer case of a µCT based foam reactor using OpenFOAM and verified the model against a commercial computational fluid dynamics (CFD) code (STAR-CCM+). We further explicitly quantified the deviation made when radiation is not considered. We studied the effect of the solid thermal conductivity, the superficial velocity and surface emissivities in ranges that are relevant for heterogeneous catalysis applications (solid thermal conductivities 1–200 W m−1 K−1; superficial velocities 0.1–0.5 m s−1; surface emissivities 0.1–1). Moreover, the temperature levels correspond to a range of exo- and endothermal reactions, such as CO2 methanation, dry reforming of methane, and methane steam reforming. We found a significant influence of radiation on heat flows (deviations up to 24%) and temperature increases (deviations up to 400 K) for elevated temperature levels, low superficial velocities, low solid thermal conductivities and high surface emissivities. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
Kinetics and Mechanisms of Metal Chlorides Catalysis for Coal Char Gasification with CO2
Catalysts 2020, 10(6), 715; https://doi.org/10.3390/catal10060715 - 26 Jun 2020
Viewed by 567
Abstract
The gasification experiments of coal chars with CO2 were carried out isothermally, with K, Ca, Ni, and Zn chloride catalysts, adopting a thermal gravimetric analyzer (TGA) from 800 to 1100 °C. The kinetic characteristic of the samples were described using the volumetric [...] Read more.
The gasification experiments of coal chars with CO2 were carried out isothermally, with K, Ca, Ni, and Zn chloride catalysts, adopting a thermal gravimetric analyzer (TGA) from 800 to 1100 °C. The kinetic characteristic of the samples were described using the volumetric model (VM), the grain model (GM), and the random pore model (PRM). The morphology patterns of the samples were tested applying X-ray diffraction (XRD) and the catalytic mechanisms concerning the phase changes were proposed. The results confirm that the gasification rate and char reactivities are enhanced by K, Ca and Ni chlorides, while ZnCl2 inhibited the process. The catalysis ability shows the following cation order: Ca > K > Ni > Zn. Among the models described above, PRM was proven to give the best fitting value and hence adopted to kinetics parameters calculation. The activation energies in promoting conditions were lower than that of the uncatalyzed cases. In view of the catalytic mechanism, the K metals tend to form intermediate complexes and repeatedly connect with coal char, while the Ca species may follow the oxidation-reduction mechanism and the Ni metals catalyze the gasification process. Full article
(This article belongs to the Special Issue CO2 Capture, Utilization and Storage: Catalysts Design)
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Article
Continuous Production of 2-Phenylethyl Acetate in a Solvent-Free System Using a Packed-Bed Reactor with Novozym® 435
Catalysts 2020, 10(6), 714; https://doi.org/10.3390/catal10060714 - 26 Jun 2020
Cited by 3 | Viewed by 688
Abstract
2-Phenylethyl acetate (2-PEAc), a highly valued natural volatile ester, with a rose-like odor, is widely added in cosmetics, soaps, foods, and drinks to strengthen scent or flavour. Nowadays, 2-PEAc are commonly produced by chemical synthesis or extraction. Alternatively, biocatalysis is a potential method [...] Read more.
2-Phenylethyl acetate (2-PEAc), a highly valued natural volatile ester, with a rose-like odor, is widely added in cosmetics, soaps, foods, and drinks to strengthen scent or flavour. Nowadays, 2-PEAc are commonly produced by chemical synthesis or extraction. Alternatively, biocatalysis is a potential method to replace chemical synthesis or extraction for the production of natural flavour. Continuous synthesis of 2-PEAc in a solvent-free system using a packed bed bioreactor through immobilized lipase-catalyzed transesterification of ethyl acetate (EA) with 2-phenethyl alcohol was studied. A Box–Behnken experimental design with three-level-three-factor, including 2-phenethyl alcohol (2-PE) concentration (100–500 mM), flow rate (1–5 mL min−1) and reaction temperature (45–65 °C), was selected to investigate their influence on the molar conversion of 2-PEAc. Then, response surface methodology and ridge max analysis were used to discuss in detail the optimal reaction conditions for the synthesis of 2-PEAc. The results indicated both 2-PE concentration and flow rate are significant factors in the molar conversion of 2-PEAc. Based on the ridge max analysis, the maximum molar conversion was 99.01 ± 0.09% under optimal conditions at a 2-PE concentration of 62.07 mM, a flow rate of 2.75 mL min−1, and a temperature of 54.03 °C, respectively. The continuous packed bed bioreactor showed good stability for 2-PEAc production, enabling operation for at least 72 h without a significant decrease of conversion. Full article
(This article belongs to the Special Issue Biocatalytic Process Optimization)
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Review
Fundamentals of Gas Diffusion Electrodes and Electrolysers for Carbon Dioxide Utilisation: Challenges and Opportunities
Catalysts 2020, 10(6), 713; https://doi.org/10.3390/catal10060713 - 26 Jun 2020
Cited by 12 | Viewed by 3438
Abstract
Electrocatalysis plays a prominent role in the development of carbon dioxide utilisation technologies. Many new and improved CO2 conversion catalysts have been developed in recent years, progressively achieving better performance. However, within this flourishing field, a disconnect in catalyst performance evaluation has [...] Read more.
Electrocatalysis plays a prominent role in the development of carbon dioxide utilisation technologies. Many new and improved CO2 conversion catalysts have been developed in recent years, progressively achieving better performance. However, within this flourishing field, a disconnect in catalyst performance evaluation has emerged as the Achilles heel of CO2 electrolysis. Too often, catalysts are assessed in electrochemical settings that are far removed from industrially relevant operational conditions, where CO2 mass transport limitations should be minimised. To overcome this issue, gas diffusion electrodes and gas-fed electrolysers need to be developed and applied, presenting new challenges and opportunities to the CO2 electrolysis community. In this review, we introduce the reader to the fundamentals of gas diffusion electrodes and gas-fed electrolysers, highlighting their advantages and disadvantages. We discuss in detail the design of gas diffusion electrodes and their operation within gas-fed electrolysers in both flow-through and flow-by configurations. Then, we correlate the structure and composition of gas diffusion electrodes to the operational performance of electrolysers, indicating options and prospects for improvement. Overall, this study will equip the reader with the fundamental understanding required to enhance and optimise CO2 catalysis beyond the laboratory scale. Full article
(This article belongs to the Section Electrocatalysis)
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Article
A Highly Efficient Bifunctional Catalyst CoOx/tri-g-C3N4 for One-Pot Aerobic Oxidation–Knoevenagel Condensation Reaction
Catalysts 2020, 10(6), 712; https://doi.org/10.3390/catal10060712 - 25 Jun 2020
Cited by 1 | Viewed by 703
Abstract
A highly efficient bifunctional catalyst of an s-triazine-based carbon-nitride-supported cobalt oxide is developed for the aerobic oxidation–Knoevenagel condensation tandem reaction of benzyl alcohol and malononitrile, whereby 96.4% benzyl alcohol conversion with nearly 100% selectivity towards benzylmalononitrile can be obtained in 6 h at [...] Read more.
A highly efficient bifunctional catalyst of an s-triazine-based carbon-nitride-supported cobalt oxide is developed for the aerobic oxidation–Knoevenagel condensation tandem reaction of benzyl alcohol and malononitrile, whereby 96.4% benzyl alcohol conversion with nearly 100% selectivity towards benzylmalononitrile can be obtained in 6 h at 80 °C. The excellent catalytic performance derives from the high basicity of carbon nitride and strong redox ability of Co species induced by carbon nitride. The catalyst is also quite stable and can be reused without any regeneration treatment, whose product yield is only an 11.5% reduction after four runs. Full article
(This article belongs to the Special Issue Multifunctional Heterogeneous Catalysis)
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Article
Photocatalytic Nanofiltration Membrane Using Zr-MOF/GO Nanocomposite with High-Flux and Anti-Fouling Properties
Catalysts 2020, 10(6), 711; https://doi.org/10.3390/catal10060711 - 25 Jun 2020
Cited by 3 | Viewed by 1135
Abstract
Photocatalytic nanofiltration (NF) membranes with enhanced flux and anti-fouling properties were prepared from a layered in situ nanocomposite of metal organic framework (i.e., UiO-66) and graphene oxide (UiO-66_GO) on a polyamide NF membrane using a pressure-assisted self-assembly method. For filtering pure water and [...] Read more.
Photocatalytic nanofiltration (NF) membranes with enhanced flux and anti-fouling properties were prepared from a layered in situ nanocomposite of metal organic framework (i.e., UiO-66) and graphene oxide (UiO-66_GO) on a polyamide NF membrane using a pressure-assisted self-assembly method. For filtering pure water and humic acid, the composite membrane with a 10% UiO-66_GO loading (UiO-66_GO/NF-10%) showed a higher water flux (up to 63 kg/m2 h bar), flux recovery (80%), and total fouling resistance (33%) than the pristine NF membrane. Physical and chemical characterization revealed that this performance was attributed to improvements in hydrophilicity, porosity, surface smoothness, and charge repulsion. The UiO-66_GO/NF-10% composite membrane exhibited better physical stability with a relatively low mass loss (8.64%) after five washes than the membranes with mass loadings of 5 and 15 wt%. Furthermore, the UiO-66_GO/NF-10% composite membrane exhibited considerable photocatalytic activity under ultraviolet (UV) irradiation (bandgap: 3.45 eV), which reduced irreversible fouling from 20.7% to 2.4% and increased flux recovery to 98%. This study demonstrated that surface modification with the UiO-66_GO nanocomposite produced a high-flux anti-fouling photocatalytic NF membrane, which is promising for water purification. Full article
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Article
Reduced Graphene Oxide/ZnIn2S4 Nanocomposite Photocatalyst with Enhanced Photocatalytic Performance for the Degradation of Naproxen under Visible Light Irradiation
Catalysts 2020, 10(6), 710; https://doi.org/10.3390/catal10060710 - 24 Jun 2020
Cited by 3 | Viewed by 735
Abstract
The development of photocatalysts with visible light response is of great significance to cope with energy crisis and environmental remediation. In this study, a visible light-driven photocatalyst reduced graphene oxide/ZnIn2S4 (rGO/ZIS) was prepared by a facile one-pot hydrothermal method. The [...] Read more.
The development of photocatalysts with visible light response is of great significance to cope with energy crisis and environmental remediation. In this study, a visible light-driven photocatalyst reduced graphene oxide/ZnIn2S4 (rGO/ZIS) was prepared by a facile one-pot hydrothermal method. The photocatalyst was used for the degradation of naproxen under visible light illumination and it exhibited remarkably degradation efficiency (nearly 99% within 60 min). The improved photocatalytic degradation performance can be attributed to the enhancement of light adsorption capacity and effective separation of photoinduced electron–hole pairs. The reactive species quenching experiments and EPR measurements demonstrated that superoxide radical (–O2) and hole (h+) play a dominant role in the photocatalytic degradation reactions. In addition, the degradation intermediates were identified and the degradation pathway was suggested. Full article
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Review
Recent Progresses on Metal Halide Perovskite-Based Material as Potential Photocatalyst
Catalysts 2020, 10(6), 709; https://doi.org/10.3390/catal10060709 - 24 Jun 2020
Cited by 13 | Viewed by 1613
Abstract
Recent years have witnessed an incredibly high interest in perovskite-based materials. Among this class, metal halide perovskites (MHPs) have attracted a lot of attention due to their easy preparation and excellent opto-electronic properties, showing a remarkably fast development in a few decades, particularly [...] Read more.
Recent years have witnessed an incredibly high interest in perovskite-based materials. Among this class, metal halide perovskites (MHPs) have attracted a lot of attention due to their easy preparation and excellent opto-electronic properties, showing a remarkably fast development in a few decades, particularly in solar light-driven applications. The high extinction coefficients, the optimal band gaps, the high photoluminescence quantum yields and the long electron–hole diffusion lengths make MHPs promising candidates in several technologies. Currently, the researchers have been focusing their attention on MHPs-based solar cells, light-emitting diodes, photodetectors, lasers, X-ray detectors and luminescent solar concentrators. In our review, we firstly present a brief introduction on the recent discoveries and on the remarkable properties of metal halide perovskites, followed by a summary of some of their more traditional and representative applications. In particular, the core of this work was to examine the recent progresses of MHPs-based materials in photocatalytic applications. We summarize some recent developments of hybrid organic–inorganic and all-inorganic MHPs, recently used as photocatalysts for hydrogen evolution, carbon dioxide reduction, organic contaminant degradation and organic synthesis. Finally, the main limitations and the future potential of this new generation of materials have been discussed. Full article
(This article belongs to the Special Issue Progression in Photocatalytic Materials for Efficient Performance)
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Article
Pt-Amorphous Barium Aluminum Oxide/Carbon Catalysts for an Enhanced Methanol Electrooxidation Reaction
Catalysts 2020, 10(6), 708; https://doi.org/10.3390/catal10060708 - 24 Jun 2020
Cited by 1 | Viewed by 694
Abstract
A new type of amorphous barium aluminum oxide was synthesized using a polyol thermal method involving a mixture with Vulcan XC-72 carbon and supported with 20%Pt catalysts to enhance the activity of a methanol electrooxidation reaction (MOR). The maximum current density, electrochemically active [...] Read more.
A new type of amorphous barium aluminum oxide was synthesized using a polyol thermal method involving a mixture with Vulcan XC-72 carbon and supported with 20%Pt catalysts to enhance the activity of a methanol electrooxidation reaction (MOR). The maximum current density, electrochemically active surface area (ECSA), and electrochemical impedance spectra (EIS) of the obtained catalysts for MOR were determined. The MORs of barium aluminum oxide with different calcination temperatures and Ba and Al contact ratios were studied. The MOR of the uncalcined amorphous Ba0.5AlOx catalysts prepared with a mole ratio of 2/1 Ba/Al mixed with Vulcan XC-72 carbon and supported with 20%Pt catalyst (Pt-Ba0.5AlOx/C) was enhanced compared with that of 20%Pt-Al2O3/C and 20%Pt/C catalysts due to its obtained largest maximum current density of 3.89 mA/cm2 and the largest ECSA of 49.83 m2/g. Therefore, Pt-Ba0.5AlOx/C could provide a new pathway to achieve a sufficient electrical conductivity, and possible synergistic effects with other active components improved the catalytic activity and stability of the prepared catalyst in MOR. Full article
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Article
Understanding Surface Basic Sites of Catalysts: Kinetics and Mechanism of Dehydrochlorination of 1,2-Dichloroethane over N-Doped Carbon Catalysts
Catalysts 2020, 10(6), 707; https://doi.org/10.3390/catal10060707 - 24 Jun 2020
Cited by 3 | Viewed by 788
Abstract
The production of vinyl chloride (VCM) by pyrolysis of 1,2-dichloroethane (DCE) is an important process in the ethylene-based poly(vinyl chloride) industry. The pyrolysis is performed at temperatures above 500 °C, gives low conversions, and has high energy consumption. We have shown that N-doped [...] Read more.
The production of vinyl chloride (VCM) by pyrolysis of 1,2-dichloroethane (DCE) is an important process in the ethylene-based poly(vinyl chloride) industry. The pyrolysis is performed at temperatures above 500 °C, gives low conversions, and has high energy consumption. We have shown that N-doped carbon catalysts give excellent performances in DCE dehydrochlorination at 280 °C. The current understanding of the active sites, mechanism, and kinetics of DCE dehydrochlorination over N-doped carbon catalysts is limited. Here, we showed that pyridinic-N on a N-doped carbon catalyst is the active site for catalytic production of vinyl chloride monomer from DCE. The results of CO2 and DCE temperature-programmed desorption experiments showed that the pyridinic-N catalytic sites are basic, and the mechanism of dehydrochlorination on a N-doped carbon catalyst involves a carbanion. A kinetic study of dehydrochlorination showed that the surface reaction rate on the N-doped carbon catalyst was the limiting step in the catalytic dehydrochlorination of DCE. This result enabled clarification of the dehydrochlorination mechanism and optimization of the reaction process. These findings will stimulate further studies to increase our understanding of the relationship between the base strength and catalytic performance. The results of this study provide a method for catalyst optimization, namely modification of the amount of pyridinic-N and the base strength of the catalyst, to increase the surface reaction rate of DCE dehydrochlorination on N-doped carbon catalysts. Full article
(This article belongs to the Special Issue Progress in Catalytic Hydrodechlorination)
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Review
Immobilization of Cellulolytic Enzymes in Mesostructured Silica Materials
Catalysts 2020, 10(6), 706; https://doi.org/10.3390/catal10060706 - 23 Jun 2020
Cited by 4 | Viewed by 874
Abstract
Mesostructured silica nanoparticles offer a unique opportunity in the field of biocatalysis thanks to their outstanding properties. The tunable pore size in the range of mesopores allows for immobilizing bulky enzyme molecules. The large surface area improves the catalytic efficiency by increasing enzyme [...] Read more.
Mesostructured silica nanoparticles offer a unique opportunity in the field of biocatalysis thanks to their outstanding properties. The tunable pore size in the range of mesopores allows for immobilizing bulky enzyme molecules. The large surface area improves the catalytic efficiency by increasing enzyme loading and finely dispersing the biocatalyst molecules. The easily tunable pore morphology allows for creating a proper environment to host an enzyme. The confining effect of mesopores can improve the enzyme stability and its resistance to extreme pH and temperatures. Benefits also arise from other peculiarities of nanoparticles such as Brownian motion and easy dispersion. Fossil fuel depletion and environmental pollution have led to the need for alternative sustainable and renewable energy sources such as biofuels. In this context, lignocellulosic biomass has been considered as a strategic fuel source. Cellulases are a class of hydrolytic enzymes that convert cellulose into fermentable sugars. This review is intended to survey the immobilization of cellulolytic enzymes (cellulases and β-glucosidase) onto mesoporous silica nanoparticles and their catalytic performance, with the aim to give a contribution to the urgent action required against climate change and its impacts, by biorefineries’ development. Full article
(This article belongs to the Special Issue Porous Materials and Catalysts)
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Review
Asymmetric Ring-Opening of Epoxides Catalyzed by Metal–Salen Complexes
Catalysts 2020, 10(6), 705; https://doi.org/10.3390/catal10060705 - 23 Jun 2020
Cited by 3 | Viewed by 1319
Abstract
The asymmetric ring-opening of epoxides is an important reaction in organic synthesis, since it allows for the enantioselective installation of two vicinal functional groups with specific stereochemistry within one step from a highly available starting material. An effective class of catalysts for the [...] Read more.
The asymmetric ring-opening of epoxides is an important reaction in organic synthesis, since it allows for the enantioselective installation of two vicinal functional groups with specific stereochemistry within one step from a highly available starting material. An effective class of catalysts for the asymmetric ring-opening of epoxides is metal–salen complexes. This review summarizes the development of metal–salen catalyzed enantioselective desymmetrization of meso-epoxides and kinetic resolution of epoxides with various nucleophiles, including the design and application of both homogeneous- and heterogeneous epoxide-opening catalysts as well as multi-metallic covalent and supramolecular catalytic systems. Full article
(This article belongs to the Special Issue New Trends in Asymmetric Catalysis)
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Article
Methanation of CO2 over Cobalt-Lanthanide Aerogels: Effect of Calcination Temperature
Catalysts 2020, 10(6), 704; https://doi.org/10.3390/catal10060704 - 23 Jun 2020
Cited by 4 | Viewed by 747
Abstract
High surface area cobalt-lanthanide bimetallic aerogels were successfully synthesized by the epoxide addition method. The bimetallic aerogels were calcined at two different temperatures and either bimetallic oxides containing oxychlorides, Co3O4.3LnOCl (Ln = La, Sm, Gd, Dy and Yb) or [...] Read more.
High surface area cobalt-lanthanide bimetallic aerogels were successfully synthesized by the epoxide addition method. The bimetallic aerogels were calcined at two different temperatures and either bimetallic oxides containing oxychlorides, Co3O4.3LnOCl (Ln = La, Sm, Gd, Dy and Yb) or perovskites, LnCoO3 (Ln = La, Sm, Gd and Dy) were obtained at 500 or 900 °C, respectively. The exceptions are the aerogels of cerium and ytterbium, which after oxidation at 500 and 900 °C, stabilize as sesquioxides: Co3O4.3CeO2 and 2Co3O4.3Yb2O3, the first at both temperatures and the second only at the highest temperature. The bimetallic cobalt-lanthanide oxychlorides or perovskites were tested as catalysts for the methanation of CO2. The cobalt catalytic activity is determined by the type and acid-base properties of the lanthanide oxide phase and by its pre-reduction under hydrogen. The best results were those obtained over the calcined aerogels pre-reduced under hydrogen. In particular, the highest values were those obtained over the Co-Ce aerogel calcined at 900 °C that in the same conditions present an activity comparable to that measured over a 5 wt.% Rh catalyst supported on alumina, one of the literature references. The activity and the selectivity increase with the catalysts’ basicity, showing an inverse dependence of the reduction temperature that decreases along the lanthanide series either for the aerogels calcined at 500 or 900 °C. In general, the basicity of the aerogels calcined at 900 °C (perovskites) is higher and they are more active but less selective than those calcined at 500 °C (oxychlorides), which to our knowledge is for the first time reported for the methanation of CO2. Full article
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Article
Utilization of Waste Grooved Razor Shell (GRS) as a Catalyst in Biodiesel Production from Refined and Waste Cooking Oils
Catalysts 2020, 10(6), 703; https://doi.org/10.3390/catal10060703 - 22 Jun 2020
Cited by 6 | Viewed by 763
Abstract
Biodiesel is a potential alternative for fossil fuel. However, its large-scale application is held up by the disadvantage of a homogenous process, the scarce availability of raw materials and the production cost, which is higher than for fossil diesel. In this work, biodiesel [...] Read more.
Biodiesel is a potential alternative for fossil fuel. However, its large-scale application is held up by the disadvantage of a homogenous process, the scarce availability of raw materials and the production cost, which is higher than for fossil diesel. In this work, biodiesel production was carried out using both refined and used cooking oils. The process was investigated in a batch reactor, in the presence of CaO as a heterogeneous catalyst prepared by the calcination of the natural Waste Grooved Razor Shell (GRS). Characterizations by X-Ray Diffraction (XRD) and Thermal Gravimetric (TG)/Differential Thermal Analysis (DTA) showed that the as-received GRS consists of aragonite, (i.e., CaCO3) as the main component and of water and organic matter in a lower amount. After calcination at 900 °C, CaO was formed as the only crystalline phase. The effects of several experimental parameters in the transesterification reactions were studied, and their impact on the produced biodiesel properties was investigated. The studied variables were the methanol/oil molar ratio, the catalyst weight percentage (with respect to the oil mass), the calcination temperature of the parent GRS and the recycling and regeneration of the catalyst. The physico-chemical and fuel properties, i.e., viscosity, density and acid value of used oils and of the produced biodiesel, were determined by conventional methods (American Society for Testing and Materials (ASTM) methods) and compared with the European standards of biodiesel. The optimal identified conditions were the following: the use of a 15:1 methanol/oil molar ratio and 5 wt% of CaO with respect to the oil mass. After 3 h of reaction at 65 °C, the biodiesel yield was equal to 94% and 99% starting from waste and refined oils, respectively. Full article
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Article
Activity in the Photodegradation of 4-Nitrophenol of a Zn,Al Hydrotalcite-Like Solid and the Derived Alumina-Supported ZnO
Catalysts 2020, 10(6), 702; https://doi.org/10.3390/catal10060702 - 22 Jun 2020
Cited by 1 | Viewed by 1016
Abstract
A Zn,Al layered double hydroxide (LDH), with the hydrotalcite structure and the mixed oxide obtained upon its calcination at 650 °C, was tested in the adsorption and photocatalytic degradation of 4-Nitrophenol in aqueous solution. The Zn,Al LDH was fast and easily obtained by [...] Read more.
A Zn,Al layered double hydroxide (LDH), with the hydrotalcite structure and the mixed oxide obtained upon its calcination at 650 °C, was tested in the adsorption and photocatalytic degradation of 4-Nitrophenol in aqueous solution. The Zn,Al LDH was fast and easily obtained by the coprecipitation method. Hydrothermal treatment under microwave irradiation was applied to compare the effect of the ageing treatment on the photocatalytic behavior. The efficiency of the synthetized solids was compared to that of a commercial ZnO. The ageing treatment did not improve the performance of the original samples in the degradation of 4-nitrophenol. The activity of the synthetized solids tested exceeded that observed for the reaction with commercial ZnO. The photocatalytic performance of the original non-calcined hydrotalcite is similar to that of commercial ZnO. The calcined hydrotalcite showed a better performance in the adsorption-degradation of the contaminant than ZnO, and its reusability would be possible as it recovered the hydrotalcite-like structure during the reaction. Full article
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Article
Facile Fabrication of a Novel Au/Phosphorus-Doped g-C3N4 Photocatalyst with Excellent Visible Light Photocatalytic Activity
Catalysts 2020, 10(6), 701; https://doi.org/10.3390/catal10060701 - 22 Jun 2020
Cited by 8 | Viewed by 881
Abstract
The intrinsic disadvantages of pristine graphitic carbon nitride (g-C3N4) significantly restrict its applications in photocatalysis field. Hence, we have demonstrated facile thermal copolymerization and in situ photodeposition methods to fabricate a novel Au/phosphorus-doped g-C3N4 (Au/P-g-C3 [...] Read more.
The intrinsic disadvantages of pristine graphitic carbon nitride (g-C3N4) significantly restrict its applications in photocatalysis field. Hence, we have demonstrated facile thermal copolymerization and in situ photodeposition methods to fabricate a novel Au/phosphorus-doped g-C3N4 (Au/P-g-C3N4) photocatalyst. The results showed that phosphorus was doped into the structure of g-C3N4 and that the surface deposition of gold was successfully accomplished. The H2 generation rate of the optimal Au/P-g-C3N4 is 8.4 times compared with the pristine g-C3N4 under visible light irradiation. The enhancement of photocatalytic activity is due to the synergic effect between gold induced surface plasmon resonance and the modified structural and electronic properties of the g-C3N4 induced by the phosphorus dopant. Full article
(This article belongs to the Special Issue Photocatalysis: Activity of Nanomaterials)
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Review
Catalytic Foldamers: When the Structure Guides the Function
Catalysts 2020, 10(6), 700; https://doi.org/10.3390/catal10060700 - 22 Jun 2020
Cited by 5 | Viewed by 1059
Abstract
Enzymes are predominantly proteins able to effectively and selectively catalyze highly complex biochemical reactions in mild reaction conditions. Nevertheless, they are limited to the arsenal of reactions that have emerged during natural evolution in compliance with their intrinsic nature, three-dimensional structures and dynamics. [...] Read more.
Enzymes are predominantly proteins able to effectively and selectively catalyze highly complex biochemical reactions in mild reaction conditions. Nevertheless, they are limited to the arsenal of reactions that have emerged during natural evolution in compliance with their intrinsic nature, three-dimensional structures and dynamics. They optimally work in physiological conditions for a limited range of reactions, and thus exhibit a low tolerance for solvent and temperature conditions. The de novo design of synthetic highly stable enzymes able to catalyze a broad range of chemical reactions in variable conditions is a great challenge, which requires the development of programmable and finely tunable artificial tools. Interestingly, over the last two decades, chemists developed protein secondary structure mimics to achieve some desirable features of proteins, which are able to interfere with the biological processes. Such non-natural oligomers, so called foldamers, can adopt highly stable and predictable architectures and have extensively demonstrated their attractiveness for widespread applications in fields from biomedical to material science. Foldamer science was more recently considered to provide original solutions to the de novo design of artificial enzymes. This review covers recent developments related to peptidomimetic foldamers with catalytic properties and the principles that have guided their design. Full article
(This article belongs to the Special Issue Organocatalysis: Advances, Opportunity, and Challenges)
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Article
Photocatalytic Degradation of Chlorpyrifos with Mn-WO3/SnS2 Heterostructure
Catalysts 2020, 10(6), 699; https://doi.org/10.3390/catal10060699 - 21 Jun 2020
Cited by 3 | Viewed by 1070
Abstract
Tungsten trioxide (WO3) is a photocatalyst that has gained interest amongst researchers because of its non-toxicity, narrow band gap and superior charge transport. Due to its fast charge recombination, modification is vital to counteract this limitation. In this paper, we report [...] Read more.
Tungsten trioxide (WO3) is a photocatalyst that has gained interest amongst researchers because of its non-toxicity, narrow band gap and superior charge transport. Due to its fast charge recombination, modification is vital to counteract this limitation. In this paper, we report on the fabrication of Mn-doped WO3/SnS2 nanoparticles, which were synthesised with the aim of minimising the recombination rates of the photogenerated species. The nanomaterials were characterised using spectroscopic techniques (UV-Vis-diffuse reflectance spectroscopy (DRS), Raman, XRD, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS)) together with microscopic techniques (FESEM-EDS and high resolution transmission electron microscopy selected area electron diffraction (HRTEM-SAED)) to confirm the successful formation of Mn-WO3/SnS2 nanoparticles. The Mn-doped WO3/SnS2 composite was a mixture of monoclinic and hexagonal phases, confirmed by XRD and Raman analysis. The Mn-WO3/SnS2 heterojunction showed enhanced optical properties compared to those of the un-doped WO3/SnS2 nanoparticles, which confirms the successful charge separation. The Brunauer–Emmett–Teller (BET) analysis indicated that the nanoparticles were mesoporous as they exhibited a Type IV isotherm. These nanomaterials appeared as a mixture of rectangular rods and sheet-like shapes with an increased surface area (77.14 m2/g) and pore volume (0.0641 cm3/g). The electrochemical measurements indicated a high current density (0.030 mA/cm2) and low charge transfer resistance (157.16 Ω) of the Mn-WO3/SnS2 heterojunction, which infers a high charge separation, also complemented by photoluminescence with low emission peak intensity. The Mott–Schottky (M-S) plot indicated a positive slope characteristic of an nn heterojunction semiconductor, indicating that electrons are the major charge carriers. Thus, the efficiency of Mn-WO3/SnS2 heterojunction photocatalyst was monitored for the degradation of chlorpyrifos. The effects of pH (3–9), catalyst loading (0.1–2 g) and initial chlorpyrifos concentration (100 ppb–20 ppm) were studied. It was observed that the degradation was purely due to photocatalysis, as no loss of chlorpyrifos was observed within 30 min in the dark. Chlorpyrifos removal using Mn-WO3/SnS2 was performed at the optimum conditions of pH = 7, catalyst loading = 1 g and chlorpyrifos concentration = 1000 ppb in 90 min. The complete degradation of chlorpyrifos and its major degradation by-product 3,5,6-trichloropyridin-2-ol (TCP) was achieved. Kinetic studies deduced a second order reaction at 209 × 10−3 M−1s−1. Full article
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Article
A Comparative Study on Oxidation of Acidic Red 18 by Persulfate with Ferrous and Ferric Ions
Catalysts 2020, 10(6), 698; https://doi.org/10.3390/catal10060698 - 21 Jun 2020
Cited by 2 | Viewed by 592
Abstract
Ferrous and ferric salts were tested for the persulfate activation (PS/Fe2+ and PS/Fe3+) and the oxidation of Acid Red 18 (AR18). A complete removal was attained after 90 min in both PS/Fe2+ and PS/Fe3+ processes with the persulfate [...] Read more.
Ferrous and ferric salts were tested for the persulfate activation (PS/Fe2+ and PS/Fe3+) and the oxidation of Acid Red 18 (AR18). A complete removal was attained after 90 min in both PS/Fe2+ and PS/Fe3+ processes with the persulfate concentration of 6 mM. High concentrations of PS, Fe2+, and Fe3+ promoted the AR18 degradation in both processes and the optimized pH were 3 and 3.3 for PS/Fe2+ and PS/Fe3+ processes, respectively. The mechanism of PS activation by Fe3+ was also investigated. It was found that hydroxyl radical (HO•) and sulfate radical (SO4•) were formed and acted as dominating radicals in both processes. It is also deduced that Fe recycle offers Fe2+ for PS activation in PS/Fe3+ process to produce HO• and SO4•. The less radical side reactions lead to a higher contribution of HO• and SO4• on AR18 degradation in PS/Fe3+ process. Full article
(This article belongs to the Section Environmental Catalysis)
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Review
Recent Trends in Biomaterials for Immobilization of Lipases for Application in Non-Conventional Media
Catalysts 2020, 10(6), 697; https://doi.org/10.3390/catal10060697 - 20 Jun 2020
Cited by 7 | Viewed by 1106
Abstract
The utilization of biomaterials as novel carrier materials for lipase immobilization has been investigated by many research groups over recent years. Biomaterials such as agarose, starch, chitin, chitosan, cellulose, and their derivatives have been extensively studied since they are non-toxic materials, can be [...] Read more.
The utilization of biomaterials as novel carrier materials for lipase immobilization has been investigated by many research groups over recent years. Biomaterials such as agarose, starch, chitin, chitosan, cellulose, and their derivatives have been extensively studied since they are non-toxic materials, can be obtained from a wide range of sources and are easy to modify, due to the high variety of functional groups on their surfaces. However, although many lipases have been immobilized on biomaterials and have shown potential for application in biocatalysis, special features are required when the biocatalyst is used in non-conventional media, for example, in organic solvents, which are required for most reactions in organic synthesis. In this article, we discuss the use of biomaterials for lipase immobilization, highlighting recent developments in the synthesis and functionalization of biomaterials using different methods. Examples of effective strategies designed to result in improved activity and stability and drawbacks of the different immobilization protocols are discussed. Furthermore, the versatility of different biocatalysts for the production of compounds of interest in organic synthesis is also described. Full article
(This article belongs to the Special Issue Enzymes in Sustainable Chemistry)
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Article
Fuel Pretreatment Systems in Modern CI Engines
Catalysts 2020, 10(6), 696; https://doi.org/10.3390/catal10060696 - 20 Jun 2020
Viewed by 570
Abstract
The article concerns the possibility of using a fuel pretreatment system in modern compression ignition CI engines, the main task of which is the reduction of toxic emissions in the form of exhaust gases. This fuel pretreatment system consists of a catalytic reactor [...] Read more.
The article concerns the possibility of using a fuel pretreatment system in modern compression ignition CI engines, the main task of which is the reduction of toxic emissions in the form of exhaust gases. This fuel pretreatment system consists of a catalytic reactor used in common rail (CR), and a modified fuel atomizer into spiral‒elliptical channels covered with catalytic material. In the system presented here, platinum was the catalyst. The catalyst’s task is to cause the dehydrogenation reaction of paraffin hydrocarbons contained in the fuel to create an olefin form, with the release of a free hydrogen molecule. In the literature, the methods of using catalysts in the exhaust systems of engines, or in combustion chambers, injection pumps, or fuel injectors, are known. However, the use of a catalytic reactor in the CR system in a high-pressure fuel atomizer rail is an innovative project proposed by the authors. Conditions in the high-pressure CR system are favorable for the catalyst’s operation. In addition, the spiral‒elliptical channels made on the inoperative part of the fuel atomizer needle increase the flow turbulence and contact surface for the catalyst. Full article
(This article belongs to the Special Issue Novel Structured Catalytic Reactors)
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Communication
Facile Formation of Anatase Nanoparticles on H-Titanate Nanotubes at Low Temperature for Efficient Visible Light-Driven Degradation of Organic Pollutants
Catalysts 2020, 10(6), 695; https://doi.org/10.3390/catal10060695 - 19 Jun 2020
Cited by 1 | Viewed by 647
Abstract
Anatase nanoparticles (5–10 nm) generated on H-titanate nanotube surface (H-titanate/anatase) were prepared by an ingenious and simple method. H-titanate tubes were prepared by a hydrothermal reaction of Ti powder in concentrated NaOH solution and an ion exchange process with HNO3 solution. After [...] Read more.
Anatase nanoparticles (5–10 nm) generated on H-titanate nanotube surface (H-titanate/anatase) were prepared by an ingenious and simple method. H-titanate tubes were prepared by a hydrothermal reaction of Ti powder in concentrated NaOH solution and an ion exchange process with HNO3 solution. After that, at a relatively low drying temperature (100 °C), a small quantity of anatase nanoparticles were in-situ formed on the H-titanate tubes surface by a surface dehydration reaction. In-situ transformation can form a strong interface coupling between H-titanate and anatase, which is conducive to accelerating charge transfer and improving its photocatalytic activity. In addition, the smaller average crystal size, the large specific surface areas (BET), the nanotubed and layered structure and the synergistic effect of dual phases would be beneficial to improving the photocatalytic efficiency. Full article
(This article belongs to the Special Issue Emerging Trends in TiO2 Photocatalysis and Applications)
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Article
Palm Oil Conversion to Bio-Jet and Green Diesel Fuels over Cobalt Phosphide on Porous Carbons Derived from Palm Male Flowers
Catalysts 2020, 10(6), 694; https://doi.org/10.3390/catal10060694 - 19 Jun 2020
Cited by 2 | Viewed by 780
Abstract
Porous carbon was successfully synthesized from palm male flowers (PMFs), using microwave-assisted potassium hydroxide (KOH) activation and was used as a catalyst support for the conversion of palm oil into bio-hydrocarbons, in fractions of green diesel and bio-jet fuel. Palm male flower-derived porous [...] Read more.
Porous carbon was successfully synthesized from palm male flowers (PMFs), using microwave-assisted potassium hydroxide (KOH) activation and was used as a catalyst support for the conversion of palm oil into bio-hydrocarbons, in fractions of green diesel and bio-jet fuel. Palm male flower-derived porous carbon (PC), consolidated with well dispersed cobalt phosphide (CoP) nanoparticles, was synthesized by simple wet-impregnation with subsequent thermal treatment. The physicochemical properties of the synthesized CoP/PC catalysts were evaluated by various techniques including proximate and ultimate elemental analysis, FTIR, XRD, N2 sorption, SEM, TEM–EDS, and NH3-temperature programmed desorption (TPD). The effects of the pyrolysis temperatures (600−900 °C), used for the impregnated samples before the reduction process, on catalyst properties and catalytic performance were investigated. Moreover, the effect of a liquid hourly space velocity of 0.5–1.5 h−1 and reaction temperatures of 340–420 °C was studied in the palm oil conversion. The catalyst pyrolyzed at 600 °C possessed the greatest particle dispersion and surface area, and showed the highest yield of liquid hydrocarbon product (C9–C18). We also found that the high pyrolysis temperature above 800 °C partially transformed the Co2P phase into CoP one which significantly exhibited higher cracking activity and bio-jet selectivity, due to the improved acidity of the catalyst. Full article
(This article belongs to the Section Biomass Catalysis)
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Article
Synthesis of Hierarchical Porous Ti-ZSM-5: A High Active Catalyst for Benzene Alkylation with Methanol
Catalysts 2020, 10(6), 693; https://doi.org/10.3390/catal10060693 - 19 Jun 2020
Cited by 1 | Viewed by 640
Abstract
The major challenge in the production of xylene from benzene alkylation with methanol is to avoid the side reaction of methanol with olefins, and this leads to the low utilization efficiency of methanol and the generation of byproduct ethylbenzene. Hierarchical porous Ti-ZSM-5 with [...] Read more.
The major challenge in the production of xylene from benzene alkylation with methanol is to avoid the side reaction of methanol with olefins, and this leads to the low utilization efficiency of methanol and the generation of byproduct ethylbenzene. Hierarchical porous Ti-ZSM-5 with appropriate acidity was achieved by substituting part of Al by Ti in the synthesis process, which exhibited the high utilization efficiency of methanol and high suppression of the ethylbenzene formation by the efficient suppression of methanol to olefins. Full article
(This article belongs to the Section Nanostructured Catalysts)
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Article
Synthesis of Valeric Acid by Selective Electrocatalytic Hydrogenation of Biomass-Derived Levulinic Acid
Catalysts 2020, 10(6), 692; https://doi.org/10.3390/catal10060692 - 19 Jun 2020
Cited by 3 | Viewed by 922
Abstract
The electrocatalytic hydrogenation (ECH) of biomass-derived levulinic acid (LA) is a promising strategy to synthetize fine chemicals under ambient conditions by replacing the thermocatalytic hydrogenation at high temperature and high pressure. Herein, various metallic electrodes were investigated in the ECH of LA in [...] Read more.
The electrocatalytic hydrogenation (ECH) of biomass-derived levulinic acid (LA) is a promising strategy to synthetize fine chemicals under ambient conditions by replacing the thermocatalytic hydrogenation at high temperature and high pressure. Herein, various metallic electrodes were investigated in the ECH of LA in a H-type divided cell. The effects of potential, electrolyte concentration, reactant concentration, and temperature on catalytic performance and Faradaic efficiency were systematically explored. The high conversion of LA (93%) and excellent “apparent” selectivity to valeric acid (VA) (94%) with a Faradaic efficiency of 46% can be achieved over a metallic lead electrode in 0.5 M H2SO4 electrolyte containing 0.2 M LA at an applied voltage of −1.8 V (vs. Ag/AgCl) for 4 h. The combination of adsorbed LA and adsorbed hydrogen (Hads) on the surface of the metallic lead electrode is key to the formation of VA. Interestingly, the reaction performance did not change significantly after eight cycles, while the surface of the metallic lead cathode became rough, which may expose more active sites for the ECH of LA to VA. However, there was some degree of corrosion for the metallic lead cathode in this strong acid environment. Therefore, it is necessary to improve the leaching-resistance of the cathode for the ECH of LA in future research. Full article
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Article
Exploring the Mechanism of Catalysis with the Unified Reaction Valley Approach (URVA)—A Review
Catalysts 2020, 10(6), 691; https://doi.org/10.3390/catal10060691 - 19 Jun 2020
Cited by 4 | Viewed by 902
Abstract
The unified reaction valley approach (URVA) differs from mainstream mechanistic studies, as it describes a chemical reaction via the reaction path and the surrounding reaction valley on the potential energy surface from the van der Waals region to the transition state and far [...] Read more.
The unified reaction valley approach (URVA) differs from mainstream mechanistic studies, as it describes a chemical reaction via the reaction path and the surrounding reaction valley on the potential energy surface from the van der Waals region to the transition state and far out into the exit channel, where the products are located. The key feature of URVA is the focus on the curving of the reaction path. Moving along the reaction path, any electronic structure change of the reacting molecules is registered by a change in their normal vibrational modes and their coupling with the path, which recovers the curvature of the reaction path. This leads to a unique curvature profile for each chemical reaction with curvature minima reflecting minimal change and curvature maxima, the location of important chemical events such as bond breaking/forming, charge polarization and transfer, rehybridization, etc. A unique decomposition of the path curvature into internal coordinate components provides comprehensive insights into the origins of the chemical changes taking place. After presenting the theoretical background of URVA, we discuss its application to four diverse catalytic processes: (i) the Rh catalyzed methanol carbonylation—the Monsanto process; (ii) the Sharpless epoxidation of allylic alcohols—transition to heterogenous catalysis; (iii) Au(I) assisted [3,3]-sigmatropic rearrangement of allyl acetate; and (iv) the Bacillus subtilis chorismate mutase catalyzed Claisen rearrangement—and show how URVA leads to a new protocol for fine-tuning of existing catalysts and the design of new efficient and eco-friendly catalysts. At the end of this article the pURVA software is introduced. The overall goal of this article is to introduce to the chemical community a new protocol for fine-tuning existing catalytic reactions while aiding in the design of modern and environmentally friendly catalysts. Full article
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Review
Constructing Strategies and Applications of Nitrogen-Rich Energetic Metal–Organic Framework Materials
Catalysts 2020, 10(6), 690; https://doi.org/10.3390/catal10060690 - 19 Jun 2020
Cited by 3 | Viewed by 721
Abstract
The synthesis of energetic metal–organic frameworks (EMOFs) with one-dimensional, two-dimensional and three-dimensional structures is an effective strategy for developing new-generation high-energy-density and insensitive materials. The basic properties, models, synthetic strategies and applications of EMOF materials with nitrogen-rich energetic groups as ligands are reviewed. [...] Read more.
The synthesis of energetic metal–organic frameworks (EMOFs) with one-dimensional, two-dimensional and three-dimensional structures is an effective strategy for developing new-generation high-energy-density and insensitive materials. The basic properties, models, synthetic strategies and applications of EMOF materials with nitrogen-rich energetic groups as ligands are reviewed. In contrast with traditional energetic materials, EMOFs exhibit some interesting characteristics, like tunable structure, diverse pores, high-density, high-detonation heat and so on. The traditional strategies to design EMOF materials with ideal properties are just to change the types and the size of energetic ligands and to select different metal ions. Recently, some new design concepts have come forth to produce more EMOFs materials with excellent properties, by modifying the energetic groups on the ligands and introducing highly energetic anion into skeleton, encapsulating metastable anions, introducing templates and so on. The paper points out that appropriate constructing strategy should be adopted according to the inherent characteristics of different EMOFs, by combining with functional requirements and considering the difficulties and the cost of production. To promote the development and application of EMOF materials, the more accurate and comprehensive synthesis, systematic performance measurement methods, theoretical calculation and structure simulation should be reinforced. Full article
(This article belongs to the Section Catalytic Materials)
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