Next Issue
Previous Issue

Table of Contents

Catalysts, Volume 8, Issue 3 (March 2018)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story (view full-size image) Sabine Berteina-Raboin’s team has developed an efficient total synthesis of abscisic acid (ABA) and [...] Read more.
View options order results:
result details:
Displaying articles 1-30
Export citation of selected articles as:

Research

Jump to: Review

Open AccessFeature PaperArticle Tungsten-Based Mesoporous Silicates W-MMM-E as Heterogeneous Catalysts for Liquid-Phase Oxidations with Aqueous H2O2
Catalysts 2018, 8(3), 95; doi:10.3390/catal8030095
Received: 10 January 2018 / Revised: 15 February 2018 / Accepted: 18 February 2018 / Published: 27 February 2018
PDF Full-text (4458 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Mesoporous tungsten-silicates, W-MMM-E, have been prepared following evaporation-induced self-assembly methodology and characterized by elemental analysis, XRD, N2 adsorption, STEM-HAADF (high angle annular dark field in scanning-TEM mode), DRS UV-vis, and Raman techniques. DRS UV-vis showed the presence of two types of tungsten
[...] Read more.
Mesoporous tungsten-silicates, W-MMM-E, have been prepared following evaporation-induced self-assembly methodology and characterized by elemental analysis, XRD, N2 adsorption, STEM-HAADF (high angle annular dark field in scanning-TEM mode), DRS UV-vis, and Raman techniques. DRS UV-vis showed the presence of two types of tungsten oxo-species in W-MMM-E samples: isolated tetrahedrally and oligomeric octahedrally coordinated ones, with the ratio depending on the content of tungsten in the catalyst. Materials with lower W loading have a higher contribution from isolated species, regardless of the preparation method. W-MMM-E catalyzes selectively oxidize of a range of alkenes and organic sulfides, including bulky terpene or thianthrene molecules, using green aqueous H2O2. The selectivity of corresponding epoxides reached 85–99% in up to 80% alkene conversions, while sulfoxides formed with 84–90% selectivity in almost complete sulfide conversions and a 90–100% H2O2 utilization efficiency. The true heterogeneity of catalysis over W-MMM-E was proved by hot filtration tests. Leaching of inactive W species depended on the reaction conditions and initial W loading in the catalyst. After optimization of the catalyst system, it did not exceed 20 ppm and 3 ppm for epoxidation and sulfoxidation reactions, respectively. Elaborated catalysts could be easily retrieved by filtration and reused several times with maintenance of the catalytic behavior. Full article
Figures

Open AccessArticle X-Shaped ZIF-8 for Immobilization Rhizomucor miehei Lipase via Encapsulation and Its Application toward Biodiesel Production
Catalysts 2018, 8(3), 96; doi:10.3390/catal8030096
Received: 25 January 2018 / Revised: 21 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
PDF Full-text (7247 KB) | HTML Full-text | XML Full-text
Abstract
This study presents a one-step encapsulation method for synthesizing X-shaped zeolitic imidazolate frameworks (ZIF-8) and immobilizing Rhizomucor miehei lipase (RML). We proved that the morphological structure of ZIF-8 had changed after immobilization with enhanced characterization using a field-emission scanning electron microscope, an energy-dispersive
[...] Read more.
This study presents a one-step encapsulation method for synthesizing X-shaped zeolitic imidazolate frameworks (ZIF-8) and immobilizing Rhizomucor miehei lipase (RML). We proved that the morphological structure of ZIF-8 had changed after immobilization with enhanced characterization using a field-emission scanning electron microscope, an energy-dispersive spectrometer, a transmission electron microscope, a Fourier transform infrared spectrometer, and powder X-ray diffraction. The surface area and pore size of the carrier were investigated before and after immobilization using Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods, respectively. RML@ZIF-8 exhibited high recovery activity of up to 2632%, representing a 26-fold increase in its free lipase. Encapsulated RML was used for biodiesel production from soybean oil in an isooctane system with a conversion yield of 95.6% under optimum conditions. The resulting reusability of the immobilized enzyme indicated no substantial decline in the conversion yield, which remained at 84.7% of the initial activity after 10 cycles. The stability and high performance of the immobilized enzyme are attributed to the harmony between RML and ZIF-8 based on the easy synthesis of ZIF-8 and the short time required to immobilize RML. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessArticle Kinetics of CO Oxidation over Unloaded and Pd-Loaded α-Fe2O3 Spherical Submicron Powder Catalysts: Photoacoustic Investigations at Low Pressure
Catalysts 2018, 8(3), 98; doi:10.3390/catal8030098
Received: 29 January 2018 / Revised: 23 February 2018 / Accepted: 24 February 2018 / Published: 28 February 2018
PDF Full-text (7730 KB) | HTML Full-text | XML Full-text
Abstract
In this study, α-Fe2O3 spherical particles with an average diameter of approximately 200 nm were synthesized by a solvothermal method for use as both a catalyst and medium for a Pd catalyst. The kinetics of CO oxidation over powders of
[...] Read more.
In this study, α-Fe2O3 spherical particles with an average diameter of approximately 200 nm were synthesized by a solvothermal method for use as both a catalyst and medium for a Pd catalyst. The kinetics of CO oxidation over powders of α-Fe2O3 spherical particles and 14 wt % Pd/α-Fe2O3 spherical particles were measured in a static reactor by using a CO2 laser-based photoacoustic technique. The total pressure was fixed at 40 Torr for the CO/O2/N2 mixture for temperatures in the range of 225–350 °C. The variation in the CO2 photoacoustic signal with the CO2 concentration during CO oxidation was recorded as a function of time, and the CO2 photoacoustic data at the early reaction stage was used to estimate the rates of CO2 formation. Based on plots of ln(rate) vs. 1/T, apparent activation energies were calculated as 13.4 kcal/mol for the α-Fe2O3 submicron powder and 13.2 kcal/mol for the 14 wt % Pd/α-Fe2O3 submicron powder. Reaction orders with respect to CO and O2 were determined from the rates measured at various partial pressures of CO and O2 at 350 °C. The zero-order of the reaction with respect to Po2 was observed for CO oxidation over α-Fe2O3 submicron powder, while 0.48 order to Po2 was observed for CO oxidation over Pd/α-Fe2O3 submicron powder. The partial orders with respect to PCO were determined as 0.58 and 0.54 for the α-Fe2O3, and the Pd/α-Fe2O3 submicron powders, respectively. The kinetic results obtained from both catalysts were compared with those for the α-Fe2O3 fine powder catalysts and were used to understand the reaction mechanism. Full article
(This article belongs to the Special Issue Conversion of CO2 into CO Using Heterogeneous Catalysis)
Figures

Open AccessArticle Methyl Chloride Synthesis over Metal Chlorides-Modified Mesoporous Alumina Catalyst
Catalysts 2018, 8(3), 99; doi:10.3390/catal8030099
Received: 30 January 2018 / Revised: 15 February 2018 / Accepted: 24 February 2018 / Published: 28 February 2018
PDF Full-text (2662 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Mesoporous alumina has been successfully prepared using sucrose as templates. Mesoporous alumina-based catalysts, neat and impregnated with metal chlorides, were tested for gas phase methyl chloride synthesis from methanol and HCl. The catalysts were characterized with Transmission electron microscope (TEM), N2-physisorption,
[...] Read more.
Mesoporous alumina has been successfully prepared using sucrose as templates. Mesoporous alumina-based catalysts, neat and impregnated with metal chlorides, were tested for gas phase methyl chloride synthesis from methanol and HCl. The catalysts were characterized with Transmission electron microscope (TEM), N2-physisorption, X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to identify the relationship between the catalyst characteristics and their activity and selectivity. Experimental studies revealed that the alumina acidity decreases with increasing calcination temperature, and the catalytic activity is strongly related to the acidity. The catalytic activity of mesoporous alumina (named as Al2O3-500 °C) is higher than that of the commercial alumina under the same experimental conditions. The metal chlorides-modified alumina has more Lewis acid sites than the neat alumina. Impregnation by alcohol is more effective for increasing the amount of Lewis acid sites than impregnation by water. The total Lewis acid concentration of the modified alumina decreases in the following order: ZnCl2/Al2O3-E > ZnCl2/Al2O3-W > FeCl3/Al2O3-E > FeCl3/Al2O3-W, Where E and W respectively indicate that the catalyst impregnation solution is ethanol and water, which agrees well with the catalytic performance order. The effect of ethanol as a solvent in the impregnation could be due to the inhibition of the hydrolysis of metal chloride. The catalyst delivered a stable performance during a 100 h test that was significantly higher than that of commercial alumina. Full article
Figures

Figure 1

Open AccessArticle Enhanced Low Temperature NO Reduction Performance via MnOx-Fe2O3/Vermiculite Monolithic Honeycomb Catalysts
Catalysts 2018, 8(3), 100; doi:10.3390/catal8030100
Received: 31 January 2018 / Revised: 22 February 2018 / Accepted: 27 February 2018 / Published: 28 February 2018
Cited by 1 | PDF Full-text (4497 KB) | HTML Full-text | XML Full-text
Abstract
Selective catalytic reduction of NOx by ammonia (NH3-SCR) was the most efficient and economic technology for De-NOx applications. Therefore, a series of MnOx/vermiculite (VMT) and MnOx-Fe2O3/VMT catalysts were prepared by an
[...] Read more.
Selective catalytic reduction of NOx by ammonia (NH3-SCR) was the most efficient and economic technology for De-NOx applications. Therefore, a series of MnOx/vermiculite (VMT) and MnOx-Fe2O3/VMT catalysts were prepared by an impregnation method for the selective catalytic reduction (SCR) of nitrogen oxides (NOx). The MnOx-Fe2O3/VMT catalysts provided an excellent NO conversion of 96.5% at 200 °C with a gas hourly space velocity (GHSV) of 30,000 h−1 and an NO concentration of 500 ppm. X-ray photoelectron spectroscopy results indicated that the Mn and Fe oxides of the MnOx-Fe2O3/VMT catalyst were mainly composed of MnO2 and Fe2O3. However, the MnO2 and Fe2O3 components were well dispersed because no discernible MnO2 and Fe2O3 phases were observed in X-ray powder diffraction spectra. Corresponding MnOx-Fe2O3/VMT monolithic honeycomb catalysts (MHCs) were prepared by an extrusion method, and the MHCs achieved excellent SCR activity at low temperature, with an NO conversion greater than 98.6% at 150 °C and a GHSV of 4000 h−1. In particular, the MnOx-Fe2O3/VMT MHCs provided a good SCR activity at room temperature (20 °C), with an NO conversion of 62.2% (GHSV = 1000 h−1). In addition, the NO reduction performance of the MnOx-Fe2O3/VMT MHCs also demonstrated an excellent SO2 resistance. Full article
(This article belongs to the Special Issue Selective Catalytic Reduction of NOx)
Figures

Open AccessArticle Cost-Effective and Facile Preparation of Fe2O3 Nanoparticles Decorated N-Doped Mesoporous Carbon Materials: Transforming Mulberry Leaf into a Highly Active Electrocatalyst for Oxygen Reduction Reactions
Catalysts 2018, 8(3), 101; doi:10.3390/catal8030101
Received: 6 January 2018 / Revised: 8 February 2018 / Accepted: 9 February 2018 / Published: 28 February 2018
PDF Full-text (3954 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Herein, a promising method to prepare efficient N-doped porous carbon-supported Fe2O3 nanoparticles (Fe2O3/N-PCs) ORR electrocatalysts is presented. The porous carbon was derived from a biomass i.e., mulberry leaf through a cost-effective approach. The existence of diverse
[...] Read more.
Herein, a promising method to prepare efficient N-doped porous carbon-supported Fe2O3 nanoparticles (Fe2O3/N-PCs) ORR electrocatalysts is presented. The porous carbon was derived from a biomass i.e., mulberry leaf through a cost-effective approach. The existence of diverse compounds containing carbon, oxygen, nitrogen and sulfur in mulberry leaf benefit the formation and uniform dispersion of Fe2O3 nanoparticles (NPs) in the porous carbon. In evaluating the effects of the carbon support on the Fe2O3 NPs towards the ORR, we found that the sample of Fe2O3/N-PCs-850 (Fe2O3/N-PCs obtained at 850 °C) with high surface area of 313.8 m2·g−1 exhibits remarkably superior ORR activity than that of materials acquired under other temperatures. To be specific, the onset potential and reduction peak potential of Fe2O3/N-PCs-850 towards ORR are 0.936 V and 0.776 V (vs. RHE), respectively. The calculated number of electron transfer n for the ORR is 3.9, demonstrating a near four-electron-transfer process. Furthermore, it demonstrates excellent longtime stability and resistance to methanol deactivation compared with Pt/C catalyst. This study provides a novel design of highly active ORR electrocatalysts from low-cost abundant plant products. Full article
(This article belongs to the Special Issue Catalysts for Oxygen Reduction Reaction)
Figures

Open AccessFeature PaperArticle A New Approach to Deep Desulfurization of Light Cycle Oil over Ni2P Catalysts: Combined Selective Oxidation and Hydrotreating
Catalysts 2018, 8(3), 102; doi:10.3390/catal8030102
Received: 15 January 2018 / Revised: 21 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
PDF Full-text (1901 KB) | HTML Full-text | XML Full-text
Abstract
Amphiphilic phosphotungstic acid (A-PTA) and Ni2P/SBA-15 catalysts were prepared to apply for selective oxidation of refractory sulfur compounds in light cycle oils and hydrotreating of the oxidized S compounds, respectively. Physical properties of the catalyst samples were analyzed by BET, CO
[...] Read more.
Amphiphilic phosphotungstic acid (A-PTA) and Ni2P/SBA-15 catalysts were prepared to apply for selective oxidation of refractory sulfur compounds in light cycle oils and hydrotreating of the oxidized S compounds, respectively. Physical properties of the catalyst samples were analyzed by BET, CO uptake chemisorption, and TEM. Structural properties for the supported Ni2P catalysts were analyzed by X-ray diffraction (XRD) and extended X-ray absorption fine structure (XAFS) spectroscopy. The selective oxidation of S compounds in the LCO feed was conducted in a batch reactor at H2O2/S ratio of 10, atmospheric pressure and 353 K and then the products were fed to a continuous flow fixed-bed reactor for hydrotreating at 623 K, 3.0 MPa, and LHSV’s of 0.5–2.0 h−1. A-PTA catalyst showed a high oxidation conversion of 95% for a real LCO feed. The following hydrotreating led to a hydrodesulfurization (HDS) conversion of 99.6% and a hydrodenitrogenation (HDN) conversion of 94.7% over Ni2P/SBA-15, which were much higher than those of direct hydrotreating results which gave an HDS conversion of 63.5% and an HDN conversion of 17.5% based on the same LHSV of 2.0 h−1. It was revealed that the reduction in refractory nitrogen compounds after oxidative treatment contributed to the increase of the following HDS activity. Full article
Figures

Figure 1

Open AccessArticle Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalysts: Mechanism Investigation on NaOH as a Reaction Additive
Catalysts 2018, 8(3), 104; doi:10.3390/catal8030104
Received: 16 January 2018 / Revised: 23 February 2018 / Accepted: 28 February 2018 / Published: 2 March 2018
PDF Full-text (4396 KB) | HTML Full-text | XML Full-text
Abstract
Ru-Zn catalysts were synthesized via a precipitation method, and the mechanism of NaOH modifying Ru-Zn catalysts on the selective hydrogenation of benzene to cyclohexene was thoroughly investigated. Fresh as well as used catalysts were characterized via X-ray diffraction (XRD), X-ray Fluorescence (XRF), transmission
[...] Read more.
Ru-Zn catalysts were synthesized via a precipitation method, and the mechanism of NaOH modifying Ru-Zn catalysts on the selective hydrogenation of benzene to cyclohexene was thoroughly investigated. Fresh as well as used catalysts were characterized via X-ray diffraction (XRD), X-ray Fluorescence (XRF), transmission electron microscope (TEM), scanning electron microscope (SEM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT), respectively. Before catalytic experiments, metallic Ru and rodlike ZnO were detected from fresh Ru-Zn catalysts. Notably, with the increasing concentration of NaOH added into the reaction medium (e.g., from 0 to 0.6 mol·L−1), the dispersion of ZnO on the Ru surface significantly improved, resulting in the enhancement Ruδ+ species of electron deficiency. The catalytic activity towards benzene conversion was therefore retarded and the selectivity towards cyclohexene was improved. When the added NaOH concentration reached 0.6 mol·L−1, the atomic ratio of Zn/Ru decreased from 0.27 (when no NaOH was added) to 0.16, benzene conversion of 45.3%, and cyclohexene selectivity of 89.3% was achieved using a batch reactor after 25 min of reaction time. However, with continually increasing the NaOH concentration, i.e., to 1.2 mol·L−1, parts of ZnO could react with the over-added NaOH, leading to the unfavorable consumption of uniformly dispersed ZnO. This causes the increasing of catalytic activity towards benzene conversion, as well as the decreasing of the selectivity towards cyclohexene. Moreover, no loss of catalytic activity and selectivity towards cyclohexene formation from selective hydrogenation of benzene was observed after 10 times of catalytic experiments without any regeneration. Full article
Figures

Figure 1

Open AccessArticle Synthesis of Tetrahydropyran from Tetrahydrofurfuryl Alcohol over Cu–Zno/Al2O3 under a Gaseous-Phase Condition
Catalysts 2018, 8(3), 105; doi:10.3390/catal8030105
Received: 24 January 2018 / Revised: 7 February 2018 / Accepted: 7 February 2018 / Published: 6 March 2018
PDF Full-text (1574 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Tetrahydropyran (THP) represents an O-containing hetero-cyclic compound that can be used as a promising solvent or monomer for polymer synthesis. In this work, Cu–ZnO/Al2O3 catalysts have been prepared by a facile precipitation–extrusion method and used for the synthesis of THP
[...] Read more.
Tetrahydropyran (THP) represents an O-containing hetero-cyclic compound that can be used as a promising solvent or monomer for polymer synthesis. In this work, Cu–ZnO/Al2O3 catalysts have been prepared by a facile precipitation–extrusion method and used for the synthesis of THP through gaseous-phase hydrogenolysis of tetrahydrofurfuryl alcohol (THFA). The effect of the molar ratio of Cu/Zn/Al, reaction temperature, and hydrogen pressure was investigated. An 89.4% selectivity of THP was achieved at 270 °C and 1.0 MPa H2. Meanwhile, the optimum molar ratio of Cu/Zn/Al was determined to be 4:1:10. The Cu–ZnO/Al2O3 catalyst exhibited high catalytic activity and stability for 205 h on-stream. A possible reaction mechanism involving several consecutive reactions was proposed: THFA was firstly rearranged to 2-hydroxytetrahydropyran (2-HTHP), followed by the dehydration of 2-HTHP to 3,4-2H-dihydropyran (DHP) over acid sites; finally, the DHP was hydrogenated to THP. The synergy of acid sites and metal sites of Cu–ZnO/Al2O3 played an important role during the production of THP. Full article
Figures

Figure 1

Open AccessArticle Effects of Mesopore Internal Surfaces on the Structure of Immobilized Pd-Bisphosphine Complexes Analyzed by Variable-Temperature XAFS and Their Catalytic Performances
Catalysts 2018, 8(3), 106; doi:10.3390/catal8030106
Received: 29 January 2018 / Revised: 2 March 2018 / Accepted: 5 March 2018 / Published: 9 March 2018
PDF Full-text (1477 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, mesoporous and nonporous silica-supported Pd complexes were synthesized and characterized. Variable-temperature XAFS measurements and a curve-fitting analysis showed a slightly larger contribution of σ2static when the Pd complexes were on a nonporous support in comparison to a mesoporous
[...] Read more.
In this study, mesoporous and nonporous silica-supported Pd complexes were synthesized and characterized. Variable-temperature XAFS measurements and a curve-fitting analysis showed a slightly larger contribution of σ2static when the Pd complexes were on a nonporous support in comparison to a mesoporous support. In contrast, the catalytic performance of the attached Pd complex in the Suzuki-Miyaura cross-coupling reaction was not affected by such small differences in the static disorder of the Pd complex. Full article
(This article belongs to the Special Issue Porous Materials in Catalysis)
Figures

Open AccessArticle Synthesis of Rectorite/Fe3O4/ZnO Composites and Their Application for the Removal of Methylene Blue Dye
Catalysts 2018, 8(3), 107; doi:10.3390/catal8030107
Received: 10 February 2018 / Revised: 2 March 2018 / Accepted: 6 March 2018 / Published: 9 March 2018
PDF Full-text (9762 KB) | HTML Full-text | XML Full-text
Abstract
A novel series of rectorite-based magnetic zinc oxide (ZnO) photocatalysts (REC/Fe3O4/ZnO) was synthesized and characterized in the present work. The fabricated REC/Fe3O4/ZnO composite possessed a high specific surface area and high capacity of adsorption and
[...] Read more.
A novel series of rectorite-based magnetic zinc oxide (ZnO) photocatalysts (REC/Fe3O4/ZnO) was synthesized and characterized in the present work. The fabricated REC/Fe3O4/ZnO composite possessed a high specific surface area and high capacity of adsorption and photocatalysis toward methylene blue (MB) dye. The adsorption isotherm of the dye on the composite fitted well to the Langmuir model, with a maximum adsorption of 35.1 mg/g. The high adsorption capacity increased the interactions between the dye and the REC/Fe3O4/ZnO, which enabled efficient decomposition of the dye under simulated solar radiation using REC/Fe3O4/ZnO as the photocatalyst. The degradation kinetics of MB dye followed the Langmuir–Hinshelwood model. More importantly, the degradation of MB dye and the mass loss of REC/Fe3O4/ZnO after three repetitive experiments were quite small. This suggests that the magnetic composite has great potential as an effective, stable, and easily recovered catalyst. Four major intermediates were detected during the degradation of MB dye and the degradation pathway was proposed. Full article
(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)
Figures

Open AccessArticle High Performance of Manganese Porphyrin Sensitized p-Type CuFe2O4 Photocathode for Solar Water Splitting to Produce Hydrogen in a Tandem Photoelectrochemical Cell
Catalysts 2018, 8(3), 108; doi:10.3390/catal8030108
Received: 22 January 2018 / Revised: 3 March 2018 / Accepted: 6 March 2018 / Published: 9 March 2018
PDF Full-text (1976 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel composite composed of (5, 10, 15, 20-tetraphenyl) porphinato manganese sensitized p-type CuFe2O4 was developed for constructing the photocathode of a tandem photoelectrochemical (PEC) cell. The prepared material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray
[...] Read more.
A novel composite composed of (5, 10, 15, 20-tetraphenyl) porphinato manganese sensitized p-type CuFe2O4 was developed for constructing the photocathode of a tandem photoelectrochemical (PEC) cell. The prepared material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (DRS). Light-driven water splitting to produce hydrogen can be achieved through the PEC cell, and the results show that H2 and O2 can be collected separately at low applied bias. This work demonstrates that manganese porphyrin sensitized CuFe2O4 is an effective hybrid material for building the photocathode of a PEC cell for solar water splitting to produce H2. Full article
(This article belongs to the Special Issue Photocatalytic Water Splitting)
Figures

Figure 1

Open AccessFeature PaperArticle Use of Lactobacillus rhamnosus (ATCC 53103) as Whole-Cell Biocatalyst for the Regio- and Stereoselective Hydration of Oleic, Linoleic, and Linolenic Acid
Catalysts 2018, 8(3), 109; doi:10.3390/catal8030109
Received: 22 February 2018 / Revised: 7 March 2018 / Accepted: 8 March 2018 / Published: 9 March 2018
PDF Full-text (2207 KB) | HTML Full-text | XML Full-text
Abstract
Natural hydroxy fatty acids are relevant starting materials for the production of a number of industrial fine chemicals, such as different high-value flavour ingredients. Only a few of the latter hydroxy acid derivatives are available on a large scale. Therefore, their preparation by
[...] Read more.
Natural hydroxy fatty acids are relevant starting materials for the production of a number of industrial fine chemicals, such as different high-value flavour ingredients. Only a few of the latter hydroxy acid derivatives are available on a large scale. Therefore, their preparation by microbial hydration of unsaturated fatty acids, affordable from vegetable oils, is a new biotechnological challenge. In this study, we describe the use of the probiotic bacterium Lactobacillus rhamnosus (ATCC 53103) as whole-cell biocatalyst for the hydration of the most common unsaturated octadecanoic acids, namely oleic acid, linoleic acid, and linolenic acid. We discovered that the addition of the latter fatty acids to an anaerobic colture of the latter strain, during the early stage of its exponential growth, allows the production of the corresponding mono-hydroxy derivatives. In these experimental conditions, the hydration reaction proceeds with high regio- and stereoselectivity. Only 10-hydroxy derivatives were formed and the resulting (R)-10-hydroxystearic acid, (S)-(12Z)-10-hydroxy-octadecenoic acid, and (S)-(12Z,15Z)-10-hydroxy-octadecadienoic acid were obtained in very high enantiomeric purity (ee > 95%). Although overall conversions usually do not exceed 50% yield, our biotransformation protocol is stereoselective, scalable, and holds preparative significance. Full article
(This article belongs to the Special Issue Enzyme-Mediated Stereoselective Synthesis)
Figures

Open AccessArticle A Comparative Study of Mn/Co Binary Metal Catalysts Supported on Two Commercial Diatomaceous Earths for Oxidation of Benzene
Catalysts 2018, 8(3), 111; doi:10.3390/catal8030111
Received: 27 January 2018 / Revised: 8 March 2018 / Accepted: 9 March 2018 / Published: 12 March 2018
PDF Full-text (4592 KB) | HTML Full-text | XML Full-text
Abstract
Two commercial diatomaceous earths were used as supports for the preparation of Mn/Co binary metal catalysts at different metal loads (5 to 10 wt % Mn and 5 to 15 wt % Co) by incipient wetness deposition. The activity of the prepared catalysts
[...] Read more.
Two commercial diatomaceous earths were used as supports for the preparation of Mn/Co binary metal catalysts at different metal loads (5 to 10 wt % Mn and 5 to 15 wt % Co) by incipient wetness deposition. The activity of the prepared catalysts towards the complete oxidation of benzene to CO2 and water was investigated between 100 and 400 °C. Raw supports and synthesized catalysts were characterized by XRD, N2 physisorption, SEM-EDS, H2-TPR, and TPD. The purification treatment of food-grade diatomite significantly affected the crystallinity of this support while reducing its specific surface area (SSA). A loss of SSA, associated with the increase in the metal load, was observed on samples prepared on natural diatomite, while the opposite trend occurred with food-grade diatomite-supported catalysts. Metal nanoparticles of around 50 nm diameter were observed on the catalysts’ surface by SEM analysis. EDS analysis confirmed the uniform deposition of the active phases on the support’s surface. A larger H2 consumption was found by TPR analysis of natural diatomite-based samples in comparison to those prepared at the same metal load on food-grade diatomite. During the catalytic oxidation experiment, over 90% conversion of benzene were achieved at a reaction temperature of 225 °C by all of the prepared samples. In addition, the formation of coke during the oxidation tests was demonstrated by TGA analysis and the soluble fraction of the produced coke was characterized by GC-MS. Full article
Figures

Open AccessArticle Fabrication of a Z-Scheme g-C3N4/Fe-TiO2 Photocatalytic Composite with Enhanced Photocatalytic Activity under Visible Light Irradiation
Catalysts 2018, 8(3), 112; doi:10.3390/catal8030112
Received: 30 January 2018 / Revised: 7 March 2018 / Accepted: 8 March 2018 / Published: 13 March 2018
Cited by 1 | PDF Full-text (9094 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, a nanocomposite material g-C3N4/Fe-TiO2 has been prepared successfully by a simple one-step hydrothermal process and its structural properties were thoroughly studied by various characterization techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR)
[...] Read more.
In the present study, a nanocomposite material g-C3N4/Fe-TiO2 has been prepared successfully by a simple one-step hydrothermal process and its structural properties were thoroughly studied by various characterization techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectrometry (UV-vis DRS). The performance of the fabricated composite material towards the removal of phenol from aqueous phase was systematically evaluated by a photocatalytic approach and found to be highly dependent on the content of Fe3+. The optimum concentration of Fe3+ doping that showed a dramatic enhancement in the photocatalytic activity of the composite under visible light irradiation was observed to be 0.05% by weight. The separation mechanism of photogenerated electrons and holes of the g-C3N4/Fe-TiO2 photocatalysts was established by a photoluminescence technique in which the reactive species generated during the photocatalytic treatment process was quantified. The enhanced photocatalytic performance observed for g-C3N4-Fe/TiO2 was ascribed to a cumulative impact of both g-C3N4 and Fe that extended its spectrum-absorptive nature into the visible region. The heterojunction formation in the fabricated photocatalysts not only facilitated the separation of the photogenerated charge carriers but also retained its strong oxidation and reduction ability. Full article
(This article belongs to the Special Issue Photocatalysts for Organics Degradation)
Figures

Figure 1

Open AccessArticle Highly Active and Selective Supported Rhenium Catalysts for Aerobic Oxidation of n-Hexane and n-Heptane
Catalysts 2018, 8(3), 114; doi:10.3390/catal8030114
Received: 23 December 2017 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 15 March 2018
PDF Full-text (3938 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of derivative C-scorpionate rhenium complexes, i.e., [ReCl2{NNC(O)C6H5}(Hpz)(PPh3)2] (A) (where Hpz is pyrazole), [ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] (B), [ReClF{NNC(O)C6H
[...] Read more.
A series of derivative C-scorpionate rhenium complexes, i.e., [ReCl2{NNC(O)C6H5}(Hpz)(PPh3)2] (A) (where Hpz is pyrazole), [ReCl2{NNC(O)C6H5}(Hpz)2(PPh3)] (B), [ReClF{NNC(O)C6H5}(Hpz)2(PPh3)] (C), and their precursor [ReOCl3(PPh3)2] (D), immobilized on 3-aminopropyl-functionalized silica have been prepared and used for neat O2 oxidation of n-hexane and n-heptane mainly to the corresponding alcohols and, in lower amounts, ketones. The supported catalyst C, with fluoro- and diazenido-ligands, exhibits the highest activity for both alkanes (overall turnover numbers (TONs) up to 3.8 × 103 and 2.5 × 103, for n-hexane and n-heptane, respectively) and can be reused in consecutive catalytic cycles. Improved conversion was observed after addition of hetero-carboxylate co-catalysts. A free-radical-based mechanism is proposed to explain the product formation. Full article
(This article belongs to the Special Issue New Trends in Scorpionate Catalysts)
Figures

Open AccessFeature PaperArticle Solvent-Free Mizoroki-Heck Reaction Applied to the Synthesis of Abscisic Acid and Some Derivatives
Catalysts 2018, 8(3), 115; doi:10.3390/catal8030115
Received: 28 February 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 15 March 2018
PDF Full-text (1191 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Abscisic acid (ABA) is a natural product, which is a well-known phytohormone. However, this molecule has recently exhibited interesting biological activities, emphasizing the need for a simple and direct access to new analogues based on the ABA framework. Our strategy relies on a
[...] Read more.
Abscisic acid (ABA) is a natural product, which is a well-known phytohormone. However, this molecule has recently exhibited interesting biological activities, emphasizing the need for a simple and direct access to new analogues based on the ABA framework. Our strategy relies on a pallado-catalyzed Mizoroki-Heck cross-coupling as key reaction performed in solvent and ligand free conditions. After a careful optimization, we succeeded in accessing various (E/Z)-dienes and (E/E/Z)-trienes in moderate to good yields without isomerization and applied the same approach to the synthesis of ABA in an environmentally sound manner. Full article
(This article belongs to the Special Issue Catalyzed Mizoroki–Heck Reaction or C–H activation)
Figures

Open AccessArticle Catalytic Oxidation of Chlorobenzene over Ruthenium-Ceria Bimetallic Catalysts
Catalysts 2018, 8(3), 116; doi:10.3390/catal8030116
Received: 28 February 2018 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 16 March 2018
PDF Full-text (9243 KB) | HTML Full-text | XML Full-text
Abstract
A series of Ru-based mono and bimetallic materials were prepared and evaluated in the catalytic oxidation of chlorobenzene. Among the different Ru-based catalysts, 1Ru/TiO2(P25) was the most active catalyst and contributed the lowest complete oxidation temperature, suggesting that commercial P25 TiO
[...] Read more.
A series of Ru-based mono and bimetallic materials were prepared and evaluated in the catalytic oxidation of chlorobenzene. Among the different Ru-based catalysts, 1Ru/TiO2(P25) was the most active catalyst and contributed the lowest complete oxidation temperature, suggesting that commercial P25 TiO2 was the best support for Ru catalysts. After ceria oxides were introduced into the Ru catalytic system, the catalytic activity of 1Ru-5Ce/TiO2(Rutile) dramatically improved and that of P25 supported catalysts was decreased. Comparing the chlorobenzene consumption rates for 1Ru/TiO2 and 1Ru-5Ce/TiO2 at 280 °C, it could be concluded that monometallic Ru catalytic system was appropriate for P25 support, and the Ru-Ce bimetallic catalytic system was suitable for the rutile TiO2 support. At 280 °C, for 1Ru-5Ce/TiO2(Rutile) and 1Ru-5Ce/TiO2(P25), the chlorobenzene conversion was stabilized at approximately 91% and 86%, respectively. According to the physicochemical properties of the catalysts as characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and Hydrogen temperature programmed reduction (H2-TPR), it can be concluded that (a) electrophilic Oads species play an important role in VOCs oxidation; (b) abundant RuO2 nanoparticles on the surface of 1Ru-5Ce/TiO2(Rutile) result in higher catalytic activity and stability; and (c) dispersion is not the major factor for the catalytic activity, rather the unique structure greatly facilitated the catalytic activity and stability. Full article
Figures

Open AccessCommunication Functional Analysis of Methylomonas sp. DH-1 Genome as a Promising Biocatalyst for Bioconversion of Methane to Valuable Chemicals
Catalysts 2018, 8(3), 117; doi:10.3390/catal8030117
Received: 27 January 2018 / Revised: 7 March 2018 / Accepted: 15 March 2018 / Published: 16 March 2018
PDF Full-text (1671 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Methylomonas sp. DH-1, newly isolated from the activated sludge of a brewery plant, has been used as a promising biocatalytic platform for the conversion of methane to value-added chemicals. Methylomonas sp. DH-1 can efficiently convert methane and propane into methanol and acetone with
[...] Read more.
Methylomonas sp. DH-1, newly isolated from the activated sludge of a brewery plant, has been used as a promising biocatalytic platform for the conversion of methane to value-added chemicals. Methylomonas sp. DH-1 can efficiently convert methane and propane into methanol and acetone with a specific productivity of 4.31 and 0.14 mmol/g cell/h, the highest values ever reported, respectively. Here, we present the complete genome sequence of Methylomonas sp. DH-1 which consists of a 4.86 Mb chromosome and a 278 kb plasmid. The existence of a set of genes related to one-carbon metabolism and various secondary metabolite biosynthetic pathways including carotenoid pathways were identified. Interestingly, Methylomonas sp. DH-1 possesses not only the genes of the ribulose monophosphate cycle for type I methanotrophs but also the genes of the serine cycle for type II. Methylomonas sp. DH-1 accumulated 80 mM succinate from methane under aerobic conditions, because DH-1 has 2-oxoglutarate dehydrogenase activity and the ability to operate the full TCA cycle. Availability of the complete genome sequence of Methylomonas sp. DH-1 enables further investigations on the metabolic engineering of this strain for the production of value-added chemicals from methane. Full article
(This article belongs to the Special Issue Biocatalysis and Biotransformations)
Figures

Figure 1

Open AccessArticle Photocatalytic Performance and Degradation Mechanism of Aspirin by TiO2 through Response Surface Methodology
Catalysts 2018, 8(3), 118; doi:10.3390/catal8030118
Received: 16 January 2018 / Revised: 11 March 2018 / Accepted: 13 March 2018 / Published: 16 March 2018
PDF Full-text (4401 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the present work, the photocatalytic performance of P25TiO2 was investigated by means of the degradation of aspirin, while the reaction system was systematically optimized by central composite design (CCD) based on the response surface methodology (RSM). In addition, three variables of
[...] Read more.
In the present work, the photocatalytic performance of P25TiO2 was investigated by means of the degradation of aspirin, while the reaction system was systematically optimized by central composite design (CCD) based on the response surface methodology (RSM). In addition, three variables of initial pH value, initial aspirin concentration and P25 concentration were selected to assess the dependence of degradation efficiencies of aspirin. Meanwhile, a predicted model of degradation efficiency was estimated and checked using analysis of variance (ANOVA). The results indicated that the PC removal of aspirin by P25 was significantly influenced by all these variables in descending order as follows: P25 concentration > initial aspirin concentration > initial pH value. Moreover, the parameters were optimized by the CCD method. Under the conditions of an initial pH value of 5, initial aspirin concentration of 10 mg/L and P25 concentration of 50 mg/L, the degradation efficiency of aspirin was 98.9%with 60 min of Xenon lamp irradiation. Besides, based on the liquid chromatography-mass spectrometry measurements, two main PC degradation pathways of aspirin by TiO2 were deduced and the tentative degradation mechanism was also proposed. Full article
Figures

Figure 1

Open AccessArticle Catalytic Conversion of Model Tars over Carbon-Supported Ni and Fe
Catalysts 2018, 8(3), 119; doi:10.3390/catal8030119
Received: 9 February 2018 / Revised: 5 March 2018 / Accepted: 15 March 2018 / Published: 17 March 2018
PDF Full-text (1717 KB) | HTML Full-text | XML Full-text
Abstract
Tar removal from gasification gases is a determinant step to guarantee the operational feasibility of gasification-to-chemicals/energy systems. This study aimed to develop novel carbon-supported catalysts for the elimination of tarry aromatics (toluene, naphthalene and benzene) from gasification gases. Effects of reaction temperature (700
[...] Read more.
Tar removal from gasification gases is a determinant step to guarantee the operational feasibility of gasification-to-chemicals/energy systems. This study aimed to develop novel carbon-supported catalysts for the elimination of tarry aromatics (toluene, naphthalene and benzene) from gasification gases. Effects of reaction temperature (700 < T < 900 °C) and catalyst nature (Fe0 and Ni0) on the activity were assessed by considering thermo-catalytic conversion and steam reforming, under a simulated gasification gas. The catalysts (Ni and Fe) and support (AC) were characterized by X-ray diffraction (XRD), N2 physisorption, thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and compositional analyses. Both catalysts and support, presented a mesoporous-like texture with a considerable high surface area (690 < SBET < 743 m2/g). Furthermore, dispersion of the metal nanoparticles (active phase) was uniform as confirmed by TEM images. Results from activity tests suggest that Ni/AC has higher effectivity for converting tars than Fe/AC, as confirmed by the low apparent activation energies (34 < Eapp < 98 kJ/mol) for naphthalene and benzene conversion between 700 and 900 °C. The conversion was 100% above 850 °C; nevertheless; below 750 °C, a sharp reduction in benzene conversion was observed, which was attributed to reversible carbon deposition. Full article
Figures

Figure 1

Open AccessArticle Single-Atom Mn Active Site in a Triol-Stabilized β-Anderson Manganohexamolybdate for Enhanced Catalytic Activity towards Adipic Acid Production
Catalysts 2018, 8(3), 121; doi:10.3390/catal8030121
Received: 5 February 2018 / Revised: 10 March 2018 / Accepted: 14 March 2018 / Published: 19 March 2018
PDF Full-text (2306 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Adipic acid is an important raw chemical for the commercial production of polyamides and polyesters. The traditional industrial adipic acid production utilizes nitric acid to oxidize KA oil (mixtures of cyclohexanone and cyclohexanol), leading to the emission of N2O and thus
[...] Read more.
Adipic acid is an important raw chemical for the commercial production of polyamides and polyesters. The traditional industrial adipic acid production utilizes nitric acid to oxidize KA oil (mixtures of cyclohexanone and cyclohexanol), leading to the emission of N2O and thus causing ozone depletion, global warming, and acid rain. Herein, we reported an organically functionalized β-isomer of Anderson polyoxometalates (POMs) nanocluster with single-atom Mn, β-{[H3NC(CH2O)3]2MnMo6O18} (1), as a highly active catalyst to selectively catalyze the oxidation of cyclohexanone, cyclohexanol, or KA oil with atom economy use of 30% H2O2 for the eco-friendly synthesis of adipic acid. The catalyst has been characterized by single crystal and powder XRD, XPS, ESI-MS, FT-IR, and NMR. A cyclohexanone (cyclohexanol) conversion of >99.9% with an adipic acid selectivity of ~97.1% (~85.3%) could be achieved over catalyst 1 with high turnover frequency of 2427.5 h−1 (2132.5 h−1). It has been demonstrated that the existence of Mn3+ atom active site in catalyst 1 and the special butterfly-shaped topology of POMs both play vital roles in the enhancement of catalytic activity. Full article
(This article belongs to the Special Issue Active Sites in Catalytic Reaction)
Figures

Open AccessArticle The PT/S-Box of Modular Cellulase AcCel12B Plays a Key Role in the Hydrolysis of Insoluble Cellulose
Catalysts 2018, 8(3), 123; doi:10.3390/catal8030123
Received: 24 February 2018 / Revised: 10 March 2018 / Accepted: 11 March 2018 / Published: 20 March 2018
PDF Full-text (1767 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Cellulases play key roles in the degradation of lignocellulosic materials. The function and mechanism of the catalytic domain (CD) and carbohydrate-binding module (CBM) of cellulases were earlier revealed by analysis and characterization of protein structure. However, understanding of the catalytic mechanism of the
[...] Read more.
Cellulases play key roles in the degradation of lignocellulosic materials. The function and mechanism of the catalytic domain (CD) and carbohydrate-binding module (CBM) of cellulases were earlier revealed by analysis and characterization of protein structure. However, understanding of the catalytic mechanism of the entire enzyme, and the analysis of the catalytic model, were inadequate. Therefore, the linker chain between CD and CBM has been extensively studied to bridge this gap. Cellulase AcCel12B and three mutants with different linker lengths (with no or 1–3 PT/S-box units) were successfully constructed and purified. Results showed that the activity of cellulases on Avicel and regenerated amorphous cellulose (RAC) increased with the number of PT/S-box units. Furthermore, the desorption of AcCel12B and its mutants from RAC and Avicel were significantly different. The energy of desorption of wild-type and mutant AcCel12B from cellulose decreased with the number of PT/S-box units. Thus, AcCel12B containing more PT/S-box units was more easily desorbed and had more opportunity to hydrolyze cellulose than other samples. The number of PT/S-box units in endocellulase affected the desorption of the enzyme, which is possibly responsible for the differences in the activity of wild-type and mutant AcCel12B on Avicel and RAC. Full article
Figures

Figure 1

Review

Jump to: Research

Open AccessReview The Role of Yeast-Surface-Display Techniques in Creating Biocatalysts for Consolidated BioProcessing
Catalysts 2018, 8(3), 94; doi:10.3390/catal8030094
Received: 31 January 2018 / Revised: 19 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
PDF Full-text (4326 KB) | HTML Full-text | XML Full-text
Abstract
Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient
[...] Read more.
Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient bioconversion of lignocellulosic biomass (an ideal feedstock) to a platform chemical, such as bioethanol, can be achieved via the consolidated bioprocessing technology, termed yeast surface engineering, to produce yeasts that are capable of this feat. This approach has various strategies that involve the display of enzymes on the surface of yeast to degrade the lignocellulosic biomass, then metabolically convert the degraded sugars directly into ethanol, thus elevating the status of yeast from an immobilization material to a whole-cell biocatalyst. The performance of the engineered strains developed from these strategies are presented, visualized, and compared in this article to highlight the role of this technology in moving forward to our quest against climate change. Furthermore, the qualitative assessment synthesized in this work can serve as a reference material on addressing the areas of improvement of the field and on assessing the capability and potential of the different yeast surface display strategies on the efficient degradation, utilization, and ethanol production from lignocellulosic biomass. Full article
(This article belongs to the Special Issue Immobilized Biocatalysts)
Figures

Figure 1

Open AccessReview A SET Approach to the Interplay of Catalysts and Reactants
Catalysts 2018, 8(3), 97; doi:10.3390/catal8030097
Received: 29 October 2017 / Revised: 25 January 2018 / Accepted: 31 January 2018 / Published: 28 February 2018
PDF Full-text (1367 KB) | HTML Full-text | XML Full-text
Abstract
Research within the area of selective energy transfer (SET) on how resonance develops between a specific vibration within a catalyst system and a corresponding vibration within a reacting system that resonates with it is discussed here. The catalyst system is assumed to donate
[...] Read more.
Research within the area of selective energy transfer (SET) on how resonance develops between a specific vibration within a catalyst system and a corresponding vibration within a reacting system that resonates with it is discussed here. The catalyst system is assumed to donate one or more vibrational quanta to the reacting system. The term ‘specific vibration’ refers to vibration of a type involving bending or stretching that, when transferred resonantly to the reacting system, serves to drive the reactant molecules involved to assume the basic structure of the molecules of the catalyst system. Regardless of whether the catalyst is a pure metal surface or a complex polymolecular system (an enzyme), its role is seen to be that of transferring energy to corresponding vibrations of the reactant system. Examples are here presented of vibrators of various types that can act as catalysts. Full article
Figures

Figure 1

Open AccessReview Designing Multifunctionality into Single Phase and Multiphase Metal-Oxide-Selective Propylene Ammoxidation Catalysts
Catalysts 2018, 8(3), 103; doi:10.3390/catal8030103
Received: 5 February 2018 / Revised: 25 February 2018 / Accepted: 26 February 2018 / Published: 2 March 2018
PDF Full-text (2224 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Multifunctionality is the hallmark of most modern commercial heterogeneous catalyst systems in use today, including those used for the selective ammoxidation of propylene to acrylonitrile. It is the quintessential principle underlying commercial catalyst design efforts since petrochemical process development is invariably driven by
[...] Read more.
Multifunctionality is the hallmark of most modern commercial heterogeneous catalyst systems in use today, including those used for the selective ammoxidation of propylene to acrylonitrile. It is the quintessential principle underlying commercial catalyst design efforts since petrochemical process development is invariably driven by the need to reduce manufacturing costs. This is in large part achieved through new and improved catalysts that increase selectivity and productivity. In addition, the future feedstocks for chemical processes will be invariably more refractory than those currently in use (e.g., replacing alkenes with alkanes or using CO2), thus requiring a disparate combination of chemical functions in order to effect multiple chemical transformations with the fewest separate process steps. This review summarizes the key chemical phenomena behind achieving the successful integration of multiple functions into a mixed-metal-oxide-selective ammoxidation catalyst. An experiential and functional catalyst design model is presented that consists of one or both of the following components: (1) a mixed-metal-oxide–solid solution where the individual metal components serve separate and necessary functions in the reaction mechanism through their atomic level interaction in the context of a single crystallographic structure; (2) the required elemental components and their catalytic function existing in separate phases, where these phases are able to interact for the purposes of electron and lattice oxygen transfer through the formation of a structurally coherent interface (i.e., epitaxy) between the separate crystal structures. Examples are provided from the literature and explained in the context of this catalyst design model. The extension of the model concepts to the design of heterogeneous catalysts in general is also discussed. Full article
Figures

Open AccessReview Recent Scientific Progress on Developing Supported Ni Catalysts for Dry (CO2) Reforming of Methane
Catalysts 2018, 8(3), 110; doi:10.3390/catal8030110
Received: 20 February 2018 / Revised: 8 March 2018 / Accepted: 9 March 2018 / Published: 11 March 2018
PDF Full-text (3442 KB) | HTML Full-text | XML Full-text
Abstract
Two major green house gases (CO2 and CH4) can be converted into useful synthetic gas (H2 and CO) during dry reforming of methane (DRM) reaction, and a lot of scientific efforts has been made to develop efficient catalysts for
[...] Read more.
Two major green house gases (CO2 and CH4) can be converted into useful synthetic gas (H2 and CO) during dry reforming of methane (DRM) reaction, and a lot of scientific efforts has been made to develop efficient catalysts for dry reforming of methane (DRM). Noble metal-based catalysts can effectively assist DRM reaction, however they are not economically viable. Alternatively, non-noble based catalysts have been studied so far, and supported Ni catalysts have been considered as a promising candidate for DRM catalyst. Main drawback of Ni catalysts is its catalytic instability under operating conditions of DRM (>700 °C). Recently, it has been demonstrated that the appropriate choice of metal-oxide supports can address this issue since the chemical and physical of metal-oxide supports can prevent coke formation and stabilize the small Ni nanoparticles under harsh conditions of DRM operation. This mini-review covers the recent scientific findings on the development of supported Ni catalysts for DRM reaction, including the synthetic methods of supported Ni nanoparticles with high sintering resistance. Full article
(This article belongs to the Special Issue Conversion of CO2 into CO Using Heterogeneous Catalysis)
Figures

Figure 1

Open AccessReview Waste into Fuel—Catalyst and Process Development for MSW Valorisation
Catalysts 2018, 8(3), 113; doi:10.3390/catal8030113
Received: 28 December 2017 / Revised: 8 March 2018 / Accepted: 12 March 2018 / Published: 14 March 2018
PDF Full-text (4183 KB) | HTML Full-text | XML Full-text
Abstract
The present review paper highlights recent progress in the processing of potential municipal solid waste (MSW) derived fuels. These wastes come from the sieved fraction ( < 40 mm), which, after sorting, can differ in biodegradable fraction content ranging from 5–60%. The
[...] Read more.
The present review paper highlights recent progress in the processing of potential municipal solid waste (MSW) derived fuels. These wastes come from the sieved fraction ( < 40 mm), which, after sorting, can differ in biodegradable fraction content ranging from 5–60%. The fuels obtained from these wastes possess volumetric energy densities in the range of 15.6–26.8 MJL−1 and are composed mainly of methanol, ethanol, butanol, and carboxylic acids. Although these waste streams are a cheap and abundant source (and decrease the fraction going to landfills), syngas produced from MSW contains various impurities such as organic compounds, nitrogen oxides, sulfur, and chlorine components. These limit its use for advanced electricity generation especially for heat and power generation units based on high temperature fuel cells such as solid oxide fuel cells (SOFC) or molten carbonate fuel cells (MCFC). In this paper, we review recent research developments in the continuous MSW processing for syngas production specifically concentrating on dry reforming and the catalytic sorbent effects on effluent and process efficiency. A particular emphasis is placed on waste derived biofuels, which are currently a primary candidate for a sustainable biofuel of tomorrow, catalysts/catalytic sorbents with decreased amounts of noble metals, their long term activity, and poison resistance, and novel nano-sorbent materials. In this review, future prospects for waste to fuels or chemicals and the needed research to further process technologies are discussed. Full article
(This article belongs to the Special Issue Novel Enzyme and Whole-Cell Biocatalysis)
Figures

Open AccessReview Recent Progress in Asymmetric Catalysis and Chromatographic Separation by Chiral Metal–Organic Frameworks
Catalysts 2018, 8(3), 120; doi:10.3390/catal8030120
Received: 7 February 2018 / Revised: 14 March 2018 / Accepted: 15 March 2018 / Published: 19 March 2018
PDF Full-text (8384 KB) | HTML Full-text | XML Full-text
Abstract
Metal–organic frameworks (MOFs), as a new class of porous solid materials, have emerged and their study has established itself very quickly into a productive research field. This short review recaps the recent advancement of chiral MOFs. Here, we present simple, well-ordered instances to
[...] Read more.
Metal–organic frameworks (MOFs), as a new class of porous solid materials, have emerged and their study has established itself very quickly into a productive research field. This short review recaps the recent advancement of chiral MOFs. Here, we present simple, well-ordered instances to classify the mode of synthesis of chiral MOFs, and later demonstrate the potential applications of chiral MOFs in heterogeneous asymmetric catalysis and enantioselective separation. The asymmetric catalysis sections are subdivided based on the types of reactions that have been successfully carried out recently by chiral MOFs. In the part on enantioselective separation, we present the potentiality of chiral MOFs as a stationary phase for high-performance liquid chromatography (HPLC) and high-resolution gas chromatography (GC) by considering fruitful examples from current research work. We anticipate that this review will provide interest to researchers to design new homochiral MOFs with even greater complexity and effort to execute their potential functions in several fields, such as asymmetric catalysis, enantiomer separation, and chiral recognition. Full article
(This article belongs to the Special Issue Catalysis by Metal-Organic Frameworks)
Figures

Figure 1

Open AccessReview Platinum Group Metal Phosphides as Efficient Catalysts in Hydroprocessing and Syngas-Related Catalysis
Catalysts 2018, 8(3), 122; doi:10.3390/catal8030122
Received: 23 February 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 20 March 2018
PDF Full-text (3647 KB) | HTML Full-text | XML Full-text
Abstract
Platinum group metal phosphides are reviewed as catalytic materials for hydroprocessing and syngas-related catalysis. Starting from synthetic procedures leading to highly disperse nano-particular compounds, their properties in the applications are discussed and compared with relevant benchmarks, if available. Regarding their mode of action,
[...] Read more.
Platinum group metal phosphides are reviewed as catalytic materials for hydroprocessing and syngas-related catalysis. Starting from synthetic procedures leading to highly disperse nano-particular compounds, their properties in the applications are discussed and compared with relevant benchmarks, if available. Regarding their mode of action, two confronting mechanistic scenarios are presented: (i) a cooperative scenario in which catalytic sites of different functionalities are active in hydroprocessing and (ii) single site catalysis, which appears to be the relevant mode of action in syngas-related catalysis and which occurs over “frustrated” active sites. Full article
Figures

Figure 1

Back to Top