Catalysts

12 pages, 5056 KiB

Open AccessArticle

N-Doped K₃Ti₅NbO₁₄@TiO₂ Core-Shell Structure for Enhanced Visible-Light-Driven Photocatalytic Activity in Environmental Remediation

by Xin Gao, Chen Wang, Qixiang Xu, Hongjie Lv, Ting Chen, Chao Liu and Xinguo Xi

Catalysts 2019, 9(1), 106; https://doi.org/10.3390/catal9010106 - 21 Jan 2019

Cited by 1 | Viewed by 5017

Abstract

A novel N-doped K₃Ti₅NbO₁₄@TiO₂ (NTNT) core-shell heterojunction photocatalyst was synthesized by firstly mixing titanium isopropoxide and K₃Ti₅NbO₁₄ nanobelt, and then calcinating at 500 °C in air using urea as the nitrogen [...] Read more.

A novel N-doped K₃Ti₅NbO₁₄@TiO₂ (NTNT) core-shell heterojunction photocatalyst was synthesized by firstly mixing titanium isopropoxide and K₃Ti₅NbO₁₄ nanobelt, and then calcinating at 500 °C in air using urea as the nitrogen source. The samples were analyzed by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy and X-ray photoelectron spectroscopic (XPS) spectra. Anatase TiO₂ nanoparticles were closely deposited on the surface of K₃Ti₅NbO₁₄ nanobelt to form a nanoscale heterojunction structure favorable for the separation of photogenerated charge carriers. Meanwhile, the nitrogen atoms were mainly doped in the crystal lattices of TiO₂, resulting in the increased light harvesting ability to visible light region. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic activity of NTNT was ascribed to the combined effects of morphology engineering, N doping and the formation of heterojunction. A possible photocatalytic mechanism was proposed based on the experimental results. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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8 pages, 9055 KiB

Open AccessArticle

Direct Sulfoxidation of Aromatic Methyl Thioethers with Aryl Halides by Copper-Catalyzed C(sp³)–H Bond Activation

by Runsheng Xu, Yueer Zhu, Feixiang Xiong and Suli Tong

Catalysts 2019, 9(1), 105; https://doi.org/10.3390/catal9010105 - 21 Jan 2019

Cited by 4 | Viewed by 4738

Abstract

A copper-catalyzed direct sulfoxidation reaction by C(sp³)–H bond activation has been developed. Starting from sample aromatic methyl thioethers with aryl halides, versatile biologically-active arylbenzylsulfoxide derivatives were efficiently synthesized in good to high yields under mild conditions. This new methodology provides an [...] Read more.

A copper-catalyzed direct sulfoxidation reaction by C(sp³)–H bond activation has been developed. Starting from sample aromatic methyl thioethers with aryl halides, versatile biologically-active arylbenzylsulfoxide derivatives were efficiently synthesized in good to high yields under mild conditions. This new methodology provides an economical approach toward C(sp³)–C(sp²) bond formation. Full article

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19 pages, 3715 KiB

Open AccessArticle

Transient Kinetic Experiments within the High Conversion Domain: The Case of Ammonia Decomposition

by Yixiao Wang, M. Ross Kunz, Skyler Siebers, Harry Rollins, John Gleaves, Gregory Yablonsky and Rebecca Fushimi

Catalysts 2019, 9(1), 104; https://doi.org/10.3390/catal9010104 - 19 Jan 2019

Cited by 17 | Viewed by 7849

Abstract

In the development of catalytic materials, a set of standard conditions is needed where the kinetic performance of many samples can be compared. This can be challenging when a sample set covers a broad range of activity. Precise kinetic characterization requires uniformity in [...] Read more.

In the development of catalytic materials, a set of standard conditions is needed where the kinetic performance of many samples can be compared. This can be challenging when a sample set covers a broad range of activity. Precise kinetic characterization requires uniformity in the gas and catalyst bed composition. This limits the range of convecting devices to low conversion (generally <20%). While steady-state kinetics offer a snapshot of conversion, yield and apparent rates of the slow reaction steps, transient techniques offer much greater detail of rate processes and hence more information as to why certain catalyst compositions offer better performance. In this work, transient experiments in two transport regimes are compared: an advecting differential plug flow reactor (PFR) and a pure-diffusion temporal analysis of products (TAP) reactor. The decomposition of ammonia was used as a model reaction to test three simple materials: polycrystalline iron, cobalt and a bimetallic preparation of the two. These materials presented a wide range of activity and it was not possible to capture transient information in the advecting device for all samples at the same conditions while ensuring uniformity. We push the boundary for the theoretical estimates of uniformity in the TAP device and find reliable kinetic measurement up to 90% conversion. However, what is more advantageous from this technique is the ability to observe the time-dependence of the reaction rate rather than just singular points of conversion and yield. For example, on the iron sample we observed reversible adsorption of ammonia and on cobalt materials we identify two routes for hydrogen production. From the time-dependence of reactants and product, the dynamic accumulation was calculated. This was used to understand the atomic distribution of H and N species regulated by the surface of different materials. When ammonia was pulsed at 550 °C, the surface hydrogen/nitrogen, (H/N), ratios that evolved for Fe, CoFe and Co were 2.4, 0.25 and 0.3 respectively. This indicates that iron will store a mixture of hydrogenated species while materials with cobalt will predominantly store NH and N. While much is already known about iron, cobalt and ammonia decomposition, the goal of this work was to demonstrate new tools for comparing materials over a wider window of conversion and with much greater kinetic detail. As such, this provides an approach for detailed kinetic discrimination of more complex industrial samples beyond conversion and yield. Full article

(This article belongs to the Special Issue Multiscale and Innovative Kinetic Approaches in Heterogeneous Catalysis)

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22 pages, 11296 KiB

Open AccessArticle

High-Efficiency Catalytic Conversion of NO_x by the Synergy of Nanocatalyst and Plasma: Effect of Mn-Based Bimetallic Active Species

by Yan Gao, Wenchao Jiang, Tao Luan, Hui Li, Wenke Zhang, Wenchen Feng and Haolin Jiang

Catalysts 2019, 9(1), 103; https://doi.org/10.3390/catal9010103 - 18 Jan 2019

Cited by 20 | Viewed by 5414

Abstract

Three typical Mn-based bimetallic nanocatalysts of Mn−Fe/TiO₂, Mn−Co/TiO₂, Mn−Ce/TiO₂ were synthesized via the hydrothermal method to reveal the synergistic effects of dielectric barrier discharge (DBD) plasma and bimetallic nanocatalysts on NO_x catalytic conversion. The plasma-catalyst hybrid catalysis [...] Read more.

Three typical Mn-based bimetallic nanocatalysts of Mn−Fe/TiO₂, Mn−Co/TiO₂, Mn−Ce/TiO₂ were synthesized via the hydrothermal method to reveal the synergistic effects of dielectric barrier discharge (DBD) plasma and bimetallic nanocatalysts on NO_x catalytic conversion. The plasma-catalyst hybrid catalysis was investigated compared with the catalytic effects of plasma alone and nanocatalyst alone. During the catalytic process of catalyst alone, the catalytic activities of all tested catalysts were lower than 20% at ambient temperature. While in the plasma-catalyst hybrid catalytic process, NO_x conversion significantly improved with discharge energy enlarging. The maximum NO_x conversion of about 99.5% achieved over Mn−Ce/TiO₂ under discharge energy of 15 W·h/m³ at ambient temperature. The reaction temperature had an inhibiting effect on plasma-catalyst hybrid catalysis. Among these three Mn-based bimetallic nanocatalysts, Mn−Ce/TiO₂ displayed the optimal catalytic property with higher catalytic activity and superior selectivity in the plasma-catalyst hybrid catalytic process. Furthermore, the physicochemical properties of these three typical Mn-based bimetallic nanocatalysts were analyzed by N₂ adsorption, Transmission Electron Microscope (TEM), X-ray diffraction (XRD), H₂-temperature-programmed reduction (TPR), NH₃-temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The multiple characterizations demonstrated that the plasma-catalyst hybrid catalytic performance was highly dependent on the phase compositions. Mn−Ce/TiO₂ nanocatalyst presented the optimal structure characteristic among all tested samples, with the largest surface area, the minished particle sizes, the reduced crystallinity, and the increased active components distributions. In the meantime, the ratios of Mn⁴⁺/(Mn²⁺ + Mn³⁺ + Mn⁴⁺) in the Mn−Ce/TiO₂ sample was the highest, which was beneficial to plasma-catalyst hybrid catalysis. Generally, it was verified that the plasma-catalyst hybrid catalytic process with the Mn-based bimetallic nanocatalysts was an effective approach for high-efficiency catalytic conversion of NO_x, especially at ambient temperature. Full article

(This article belongs to the Special Issue Plasma Catalysis)

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12 pages, 3846 KiB

Open AccessArticle

Metallosupramolecular Polymer Precursor Design for Multi-Element Co-Doped Carbon Shells with Improved Oxygen Reduction Reaction Catalytic Activity

by Yuzhe Wu, Yuntong Li, Jie Mao, Haiyang Wu, Tong Wu, Yaying Li, Birong Zeng, Yiting Xu, Conghui Yuan and Lizong Dai

Catalysts 2019, 9(1), 102; https://doi.org/10.3390/catal9010102 - 18 Jan 2019

Cited by 7 | Viewed by 4931

Abstract

Heteroatom-doped carbon materials have been extensively studied in the field of electrochemical catalysis to solve the challenges of energy shortage. In particular, there is vigorous research activity in the design of multi-element co-doped carbon materials for the improvement of electrochemical performance. Herein, we [...] Read more.

Heteroatom-doped carbon materials have been extensively studied in the field of electrochemical catalysis to solve the challenges of energy shortage. In particular, there is vigorous research activity in the design of multi-element co-doped carbon materials for the improvement of electrochemical performance. Herein, we developed a supramolecular approach to construct metallosupramolecular polymer hollow spheres, which could be used as precursors for the generation of carbon shells co-doped with B, N, F and Fe elements. The metallosupramolecular polymer hollow spheres were fabricated through a simple route based on the Kirkendall effect. The in situ reaction between the boronate polymer spheres and Fe³⁺ could easily control the component and shell thickness of the precursors. The as-prepared multi-element co-doped carbon shells showed excellent catalytic activity in an oxygen reduction reaction, with onset potential (E_onset) 0.91 V and half-wave (E_half-wave) 0.82 V vs reversible hydrogen electrode (RHE). The fluorine element in the carbon matrix was important for the improvement of oxygen reduction reaction (ORR) activity performance through designing the control experiment. This supramolecular approach may afford a new route to explore good activity and a low-cost catalyst for ORR. Full article

(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)

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9 pages, 1750 KiB

Open AccessArticle

Computational Design of SCS Nickel Pincer Complexes for the Asymmetric Transfer Hydrogenation of 1-Acetonaphthone

by Bing Qiu, Wan Wang and Xinzheng Yang

Catalysts 2019, 9(1), 101; https://doi.org/10.3390/catal9010101 - 18 Jan 2019

Cited by 8 | Viewed by 4602

Abstract

Inspired by the active site structures of lactate racemase and recently reported sulphur–carbon–sulphur (SCS) nickel pincer complexes, a series of scorpion-like SCS nickel pincer complexes with an imidazole tail and asymmetric claws was proposed and examined computationally as potential catalysts for the asymmetric [...] Read more.

Inspired by the active site structures of lactate racemase and recently reported sulphur–carbon–sulphur (SCS) nickel pincer complexes, a series of scorpion-like SCS nickel pincer complexes with an imidazole tail and asymmetric claws was proposed and examined computationally as potential catalysts for the asymmetric transfer hydrogenation of 1-acetonaphthone. Density functional theory calculations reveal a proton-coupled hydride transfer mechanism for the dehydrogenation of (R)-(+)-1-phenyl-ethanol and the hydrogenation of 1-acetonaphthone to produce (R)-(+)-1-(2-naphthyl)ethanol and (S)-(−)-1-(2-naphthyl)ethanol. Among all proposed Ni complexes, 1_Ph is the most active one with a rather low free energy barrier of 24 kcal/mol and high enantioselectivity of near 99% enantiomeric excess (ee) for the hydrogenation of prochiral ketones to chiral alcohols. Full article

(This article belongs to the Section Computational Catalysis)

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13 pages, 2459 KiB

Open AccessArticle

Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

by G. Muthuraman, K. Chandrasekara Pillai and Il-Shik Moon

Catalysts 2019, 9(1), 99; https://doi.org/10.3390/catal9010099 - 17 Jan 2019

Cited by 6 | Viewed by 5511

Abstract

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)₃]⁺ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)₃]²⁺ (Co(II)) cyclic [...] Read more.

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)₃]⁺ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)₃]²⁺ (Co(II)) cyclic voltammetry in the presence of BKC demonstrates Co(II)/Co(III) redox couple for physicochemical analysis of BKC and Co(II)/Co(I) redox couple for catalytic application. Cyclic voltammetry over a range of scan rates and BKC concentrations revealed the BKC-bound Co(II)/Co(III) micelles showed that the identification of cmc and association of the probe Co(II) species, associated more in the hydrophobic region. In addition, change in diffusion coefficient value of Co(II)/Co(III) with BKC concentration demonstrates the association of Co(II) in micellar hydrophobic region. The beneficial effects of BKC could be accounted for by considering the benzyl headgroup-Co (II) precatalyst-volatile organic compounds (VOCs) (allyl chloride here) substrate interaction. Chromatography/mass spectroscopy (GC/MS) revealed 100% complete de-chlorination of allyl chloride accompanied by three non-chloro products. This is the first report of benzyl headgroup-induced micellar enhancement by an electrochemical method, showing that it is possible to use hydrophobic benzyl headgroup-substitution to tune the properties of micelles for various applications. Full article

(This article belongs to the Special Issue State-of-the-Art Catalytical Technology in South Korea)

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40 pages, 8134 KiB

Open AccessEditor’s ChoiceReview

The Use of Zeolites for VOCs Abatement by Combining Non-Thermal Plasma, Adsorption, and/or Catalysis: A Review

by Savita K. P. Veerapandian, Nathalie De Geyter, Jean-Marc Giraudon, Jean-François Lamonier and Rino Morent

Catalysts 2019, 9(1), 98; https://doi.org/10.3390/catal9010098 - 17 Jan 2019

Cited by 121 | Viewed by 16384

Abstract

Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite [...] Read more.

Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite as adsorbent and catalyst in combination with non-thermal plasma for VOC abatement in flue gas. The superior surface properties of zeolites in combination with its excellent catalytic properties obtained by metal loading make it an ideal packing material for adsorption plasma catalytic removal of VOCs. This work highlights the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolites via plasma. Full article

(This article belongs to the Special Issue Plasma Catalysis)

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25 pages, 8140 KiB

Open AccessReview

Synthesis of 1,3-Butadiene and Its 2-Substituted Monomers for Synthetic Rubbers

by Yanlong Qi, Zaizhi Liu, Shijun Liu, Long Cui, Quanquan Dai, Jianyun He, Wei Dong and Chenxi Bai

Catalysts 2019, 9(1), 97; https://doi.org/10.3390/catal9010097 - 17 Jan 2019

Cited by 48 | Viewed by 19308

Abstract

Synthetic rubbers fabricated from 1,3-butadiene (BD) and its substituted monomers have been extensively used in tires, toughened plastics, and many other products owing to the easy polymerization/copolymerization of these monomers and the high stability of the resulting material in manufacturing operations and large-scale [...] Read more.

Synthetic rubbers fabricated from 1,3-butadiene (BD) and its substituted monomers have been extensively used in tires, toughened plastics, and many other products owing to the easy polymerization/copolymerization of these monomers and the high stability of the resulting material in manufacturing operations and large-scale productions. The need for synthetic rubbers with increased environmental friendliness or endurance in harsh environments has motivated remarkable progress in the synthesis of BD and its substituted monomers in recent years. We review these developments with an emphasis on the reactive routes, the products, and the synthetic strategies with a scaling potential. We present reagents that are primarily from bio-derivatives, including ethanol, C4 alcohols, unsaturated alcohols, and tetrahydrofuran; the major products of BD and isoprene; and the by-products, activities, and selectivity of the reaction. Different catalyst systems are also compared. Further, substituted monomers with rigid, polar, or sterically repulsive groups, the purpose of which is to enhance thermal, mechanical, and interface properties, are also exhaustively reviewed. The synthetic strategies using BD and its substituted monomers have great potential to satisfy the increasing demand for better-performing synthetic rubbers at the laboratory scale; the laboratory-scale results are promising, but a big gap still exists between current progress and large scalability. Full article

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11 pages, 4257 KiB

Open AccessArticle

Effect of Mono-, Di-, and Triethylene Glycol on the Activity of Phosphate-Doped NiMo/Al₂O₃ Hydrotreating Catalysts

by Alexey L. Nuzhdin, Galina A. Bukhtiyarova, Aleksander A. Porsin, Igor P. Prosvirin, Irina V. Deliy, Vladimir A. Volodin, Evgeny Yu. Gerasimov, Evgeniya N. Vlasova and Valerii I. Bukhtiyarov

Catalysts 2019, 9(1), 96; https://doi.org/10.3390/catal9010096 - 17 Jan 2019

Cited by 11 | Viewed by 5816

Abstract

The effect of glycols on the catalytic properties of phosphate-doped NiMo/Al₂O₃ catalysts in the hydrotreating of straight-run gas oil (SRGO) was studied. The NiMo(P)/Al₂O₃ catalysts were prepared using ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol [...] Read more.

The effect of glycols on the catalytic properties of phosphate-doped NiMo/Al₂O₃ catalysts in the hydrotreating of straight-run gas oil (SRGO) was studied. The NiMo(P)/Al₂O₃ catalysts were prepared using ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) as additives. The organic agent was introduced into the aqueous impregnation solution obtained by the dissolving of MoO₃ in H₃PO₄ solution, followed by Ni(OH)₂ addition. The Raman and UV–Vis studies show that the impregnation solution contains diphosphopentamolybdate H_xP₂Mo₅O₂₃^(6−x)− and Ni(H₂O)₆²⁺, and that these ions are not affected by the presence of glycols. When the impregnation solution comes in contact with the γ-Al₂O₃ surface, H_xP₂Mo₅O₂₃^(6−x)− is decomposed completely. The catalysts were characterized by Raman spectroscopy, low-temperature N₂ adsorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is shown that the sulfide catalysts prepared with glycols display higher activity in the hydrotreating of straight-run gas oil than the NiMoP/Al₂O₃ catalyst prepared without the additive. The hydrodesulfurization and hydrodenitrogenation activities depend on the glycol type and are decreased in the following order: NiMoP-DEG/Al₂O₃ > NiMoP-EG/Al₂O₃ > NiMoP-TEG/Al₂O₃ > NiMoP/Al₂O₃. The higher activity of NiMoP-DEG/Al₂O₃ can be explained with the higher dispersion of molybdenum on the surface of the catalyst in the sulfide state. Full article

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9 pages, 912 KiB

Open AccessArticle

Improving Productivity of Multiphase Flow Aerobic Oxidation Using a Tube-in-Tube Membrane Contactor

by Michael Burkholder, Stanley E. Gilliland III, Adam Luxon, Christina Tang and B. Frank Gupton

Catalysts 2019, 9(1), 95; https://doi.org/10.3390/catal9010095 - 17 Jan 2019

Cited by 10 | Viewed by 5811

Abstract

The application of flow reactors in multiphase catalytic reactions represents a promising approach for enhancing the efficiency of this important class of chemical reactions. We developed a simple approach to improve the reactor productivity of multiphase catalytic reactions performed using a flow chemistry [...] Read more.

The application of flow reactors in multiphase catalytic reactions represents a promising approach for enhancing the efficiency of this important class of chemical reactions. We developed a simple approach to improve the reactor productivity of multiphase catalytic reactions performed using a flow chemistry unit with a packed bed reactor. Specifically, a tube-in-tube membrane contactor (sparger) integrated in-line with the flow reactor has been successfully applied to the aerobic oxidation of benzyl alcohol to benzaldehyde utilizing a heterogeneous palladium catalyst in the packed bed. We examined the effect of sparger hydrodynamics on reactor productivity quantified by space time yield (STY). Implementation of the sparger, versus segmented flow achieved with the built in gas dosing module (1) increased reactor productivity 4-fold quantified by space time yield while maintaining high selectivity and (2) improved process safety as demonstrated by lower effective operating pressures. Full article

(This article belongs to the Special Issue Catalytic Methods in Flow Chemistry)

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15 pages, 5384 KiB

Open AccessArticle

Zn-Co@N-Doped Carbon Derived from ZIFs for High-Efficiency Synthesis of Ethyl Methyl Carbonate: The Formation of ZnO and the Interaction between Co and Zn

by Ya-Nan Miao, Yuan Wang, Dong-Hui Pan, Xiang-Hai Song, Si-Quan Xu, Li-Jing Gao and Guo-Min Xiao

Catalysts 2019, 9(1), 94; https://doi.org/10.3390/catal9010094 - 17 Jan 2019

Cited by 14 | Viewed by 5325

Abstract

In this work, a series of Zn-Co@N-doped carbon materials were prepared by pyrolysis of Co/Zn-ZIF precursors under a N₂ atmosphere and used for high-efficiency synthesis of ethyl methyl carbonate (EMC) from dimethyl carbonate (DMC) and diethyl carbonate (DEC). The Co to Zn [...] Read more.

In this work, a series of Zn-Co@N-doped carbon materials were prepared by pyrolysis of Co/Zn-ZIF precursors under a N₂ atmosphere and used for high-efficiency synthesis of ethyl methyl carbonate (EMC) from dimethyl carbonate (DMC) and diethyl carbonate (DEC). The Co to Zn molar ratio and calcination temperature were varied to study the physical and chemical properties of Zn-Co@N-doped carbon materials identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), inductively coupled plasma (ICP), thermogravimetric analysis (TG) and temperature programmed desorption (TPD) analysis. It was deduced that the formation of a ZnO crystalline structure and the interaction between zinc and cobalt providing weak basic sites and strong basic sites, respectively, in different samples significantly affected their catalytic performance. The catalyst activated the reaction most effectively when the Co to Zn molar ratio was 1.0 and calcination temperature was 600 °C. With the DMC to DEC molar ratio controlled at 1:1, a superior yield of around 51.50% of product EMC can be gained over catalyst ZnCo/NC-600 at 100 °C with 1 wt% catalyst loading in 7 h. Full article

(This article belongs to the Special Issue Microporous Zeolites and Related Nanoporous Materials: Synthesis, Characterization and Applications in Catalysis)

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15 pages, 6143 KiB

Open AccessArticle

Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5 Zeolite Supported Zinc Catalysts

by Long Lin, Xiaotong Zhang, Ning He, Jiaxu Liu, Qin Xin and Hongchen Guo

Catalysts 2019, 9(1), 100; https://doi.org/10.3390/catal9010100 - 17 Jan 2019

Cited by 33 | Viewed by 7294

Abstract

A series of defective ZSM-5 zeolites (~300 nm, SiO₂/Al₂O₃ ratio of 55, 100, 480 and 950) were systematically studied by XRD, SEM, ²⁹Si MAS NMR, argon physisorption, NH₃-TPD and FT-IR technologies. The nature, the amount [...] Read more.

A series of defective ZSM-5 zeolites (~300 nm, SiO₂/Al₂O₃ ratio of 55, 100, 480 and 950) were systematically studied by XRD, SEM, ²⁹Si MAS NMR, argon physisorption, NH₃-TPD and FT-IR technologies. The nature, the amount and the accessibility of the acid sites of defective ZSM-5 zeolites are greatly different from reported ZSM-5 zeolites with a perfect crystal structure. The Brønsted acid sites (Si(OH)Al) with strong acid strength and the Brønsted acid sites (hydroxyl nests) with weak acid strength co-existed over defective ZSM-5 zeolites, which leads to a unique catalytic function. Zn(C₂H₅)₂ was grafted onto defective ZSM-5 zeolites through the chemical liquid deposition (CLD) method. Interestingly, FT-IR spectroscopic studies found that Zn(C₂H₅)₂ was preferentially grafted on the hydroxyl nests with weak acid strength rather than the Si(OH)Al groups with strong acid strength over different defective ZSM-5 zeolites. In particular, home-built operando dual beam FTIR-MS was applied to study the catalytic performance of Zn species located in different sites of defective ZSM-5 zeolites under real n-hexane transformation conditions. Results show that Zn species grafted over hydroxyl nests obtain better dehydrogenative aromatization performance than Zn species over Si(OH)Al groups. This study provides guidance for the rational design of highly efficient alkane dehydrogenative aromatization catalysts. Full article

(This article belongs to the Special Issue Spectroscopy in Catalysis)

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13 pages, 2052 KiB

Open AccessArticle

Efficient Catalytic Dehydration of High-Concentration 1-Butanol with Zn-Mn-Co Modified γ-Al₂O₃ in Jet Fuel Production

by Jing Wu, Hong-Juan Liu, Xiang Yan, Yu-Jie Zhou, Zhang-Nan Lin, Shuo Mi, Ke-Ke Cheng and Jian-An Zhang

Catalysts 2019, 9(1), 93; https://doi.org/10.3390/catal9010093 - 16 Jan 2019

Cited by 14 | Viewed by 4863

Abstract

It is important to develop full-performance bio-jet fuel based on alternative feedstocks. The compound 1-butanol can be transformed into jet fuel through dehydration, oligomerization, and hydrogenation. In this study, a new catalyst consisting of Zn-Mn-Co modified γ-Al₂O₃ was used for [...] Read more.

It is important to develop full-performance bio-jet fuel based on alternative feedstocks. The compound 1-butanol can be transformed into jet fuel through dehydration, oligomerization, and hydrogenation. In this study, a new catalyst consisting of Zn-Mn-Co modified γ-Al₂O₃ was used for the dehydration of high-concentration 1-butanol to butenes. The interactive effects of reaction temperature and butanol weight-hourly space velocity (WHSV) on butene yield were investigated with response surface methodology (RSM). Butene yield was enhanced when the temperature increased from 350 °C to 450 °C but it was reduced as WHSV increased from 1 h⁻¹ to 4 h⁻¹. Under the optimized conditions of 1.67 h⁻¹ WHSV and 375 °C reaction temperature, the selectivity of butenes achieved 90%, and the conversion rate of 1-butanol reached 100%, which were 10% and 6% higher, respectively, than when using unmodified γ-Al₂O₃. The Zn-Mn-Co modified γ-Al₂O₃ exhibited high stability and a long lifetime of 180 h, while the unmodified γ-Al₂O₃ began to deactivate after 60 h. Characterization with X-ray diffraction (XRD), nitrogen adsorption-desorption, pyridine temperature-programmed desorption (Py-TPD), pyridine adsorption IR spectra, and inductively coupled plasma atomic emission spectrometry (ICP-AES), showed that the crystallinity and acid content of γ-Al₂O₃ were obviously enhanced by the modification with Zn-Mn-Co, and the loading amounts of zinc, manganese, and cobalt were 0.54%, 0.44%, and 0.23%, respectively. This study provides a new catalyst, and the results will be helpful for the further optimization of bio-jet fuel production with a high concentration of 1-butanol. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

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16 pages, 4645 KiB

Open AccessArticle

One-Pot Catalytic Conversion of Cellobiose to Sorbitol over Nickel Phosphides Supported on MCM-41 and Al-MCM-41

by Wipark Anutrasakda, Kanyanok Eiamsantipaisarn, Duangkamon Jiraroj, Apakorn Phasuk, Thawatchai Tuntulani, Haichao Liu and Duangamol Nuntasri Tungasmita

Catalysts 2019, 9(1), 92; https://doi.org/10.3390/catal9010092 - 16 Jan 2019

Cited by 12 | Viewed by 4750

Abstract

MCM-41- and Al-MCM-41-supported nickel phosphide nanomaterials were synthesized at two different initial molar ratios of Ni/P: 10:2 and 10:3 and were tested as heterogeneous catalysts for the one-pot conversion of cellobiose to sorbitol. The catalysts were characterized by X-ray diffractometer (XRD), N2 adsorption-desorption, [...] Read more.

MCM-41- and Al-MCM-41-supported nickel phosphide nanomaterials were synthesized at two different initial molar ratios of Ni/P: 10:2 and 10:3 and were tested as heterogeneous catalysts for the one-pot conversion of cellobiose to sorbitol. The catalysts were characterized by X-ray diffractometer (XRD), N2 adsorption-desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), ²⁷Al-magnetic angle spinning-nuclear magnetic resonance spectrometer (²⁷Al MAS-NMR), temperature programmed desorption of ammonia (NH₃-TPD), temperature-programmed reduction (H₂-TPR), and inductively coupled plasma optical emission spectrophotometer (ICP-OES). The characterization indicated that nickel phosphide nanoparticles were successfully incorporated into both supports without destroying their hexagonal framework structures, that the catalysts contained some or all of the following Ni-containing phases: Ni⁰, Ni₃P, and Ni₁₂P₅, and that the types and relative amounts of Ni-containing phases present in each catalyst were largely determined by the initial molar ratio of Ni/P as well as the type of support used. For cellobiose conversion at 150 °C for 3 h under 4 MPa of H₂, all catalysts showed similarly high conversion of cellobiose (89.5–95.0%). Nevertheless, sorbitol yield was highly correlated to the relative amount of phases with higher content of phosphorus present in the catalysts, giving the following order of catalytic performance of the Ni-containing phases: Ni₁₂P₅ > Ni₃P > Ni. Increasing the reaction temperature from 150 °C to 180 °C also led to an improvement in sorbitol yield (from 43.5% to 87.8%). Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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27 pages, 7168 KiB

Open AccessEditor’s ChoiceReview

Titanium Dioxide (TiO₂) Mesocrystals: Synthesis, Growth Mechanisms and Photocatalytic Properties

by Boxue Zhang, Shengxin Cao, Meiqi Du, Xiaozhou Ye, Yun Wang and Jianfeng Ye

Catalysts 2019, 9(1), 91; https://doi.org/10.3390/catal9010091 - 16 Jan 2019

Cited by 56 | Viewed by 8538

Abstract

Hierarchical TiO₂ superstructures with desired architectures and intriguing physico-chemical properties are considered to be one of the most promising candidates for solving the serious issues related to global energy exhaustion as well as environmental deterioration via the well-known photocatalytic process. In particular, [...] Read more.

Hierarchical TiO₂ superstructures with desired architectures and intriguing physico-chemical properties are considered to be one of the most promising candidates for solving the serious issues related to global energy exhaustion as well as environmental deterioration via the well-known photocatalytic process. In particular, TiO₂ mesocrystals, which are built from TiO₂ nanocrystal building blocks in the same crystallographical orientation, have attracted intensive research interest in the area of photocatalysis owing to their distinctive structural properties such as high crystallinity, high specific surface area, and single-crystal-like nature. The deeper understanding of TiO₂ mesocrystals-based photocatalysis is beneficial for developing new types of photocatalytic materials with multiple functionalities. In this paper, a comprehensive review of the recent advances toward fabricating and modifying TiO₂ mesocrystals is provided, with special focus on the underlying mesocrystallization mechanism and controlling rules. The potential applications of as-synthesized TiO₂ mesocrystals in photocatalysis are then discussed to shed light on the structure–performance relationships, thus guiding the development of highly efficient TiO₂ mesocrystal-based photocatalysts for certain applications. Finally, the prospects of future research on TiO₂ mesocrystals in photocatalysis are briefly highlighted. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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13 pages, 4124 KiB

Open AccessArticle

Mechanism and Performance of the SCR of NO with NH₃ over Sulfated Sintered Ore Catalyst

by Wangsheng Chen, Fali Hu, Linbo Qin, Jun Han, Bo Zhao, Yangzhe Tu and Fei Yu

Catalysts 2019, 9(1), 90; https://doi.org/10.3390/catal9010090 - 16 Jan 2019

Cited by 15 | Viewed by 3575

Abstract

A sulfated sintered ore catalyst (SSOC) was prepared to improve the denitration performance of the sintered ore catalyst (SOC). The catalysts were characterized by X-ray Fluorescence Spectrometry (XRF), Brunauer–Emmett–Teller (BET) analyzer, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared spectroscopy [...] Read more.

A sulfated sintered ore catalyst (SSOC) was prepared to improve the denitration performance of the sintered ore catalyst (SOC). The catalysts were characterized by X-ray Fluorescence Spectrometry (XRF), Brunauer–Emmett–Teller (BET) analyzer, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared spectroscopy (DRIFTS) to understand the NH₃-selective catalytic reduction (SCR) reaction mechanism. Moreover, the denitration performance and stability of SSOC were also investigated. The experimental results indicated that there were more Brønsted acid sites at the surface of SSOC after the treatment by sulfuric acid, which lead to the enhancement of the adsorption capacity of NH₃ and NO. Meanwhile, Lewis acid sites were also observed at the SSOC surface. The reaction between −NH₂,

{NH}_{4}^{+}

and NO (E-R mechanism) and the reaction of the coordinated ammonia with the adsorbed NO₂ (L-H mechanism) were attributed to NO_x reduction. The maximum denitration efficiency over the SSOC, which was about 92%, occurred at 300 °C, with a 1.0 NH₃/NO ratio, and 5000 h⁻¹ gas hourly space velocity (GHSV). Full article

(This article belongs to the Special Issue Emissions Control Catalysis)

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9 pages, 1625 KiB

Open AccessCommunication

Exfoliated Molybdenum Disulfide Encapsulated in a Metal Organic Framework for Enhanced Photocatalytic Hydrogen Evolution

by Ren Ren, Huilei Zhao, Xiaoyu Sui, Xiaoru Guo, Xingkang Huang, Yale Wang, Qianqian Dong and Junhong Chen

Catalysts 2019, 9(1), 89; https://doi.org/10.3390/catal9010089 - 16 Jan 2019

Cited by 17 | Viewed by 5457

Abstract

An exfoliated MoS₂ encapsulated into metal-organic frameworks (MOFs) was fabricated as a promising noble-metal-free photocatalyst for hydrogen production under visible light irradiation. The as-synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron [...] Read more.

An exfoliated MoS₂ encapsulated into metal-organic frameworks (MOFs) was fabricated as a promising noble-metal-free photocatalyst for hydrogen production under visible light irradiation. The as-synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) surface analysis. It is well known that bulk MoS₂ is unsuitable for photocatalysis due to its inadequate reduction and oxidation capabilities. However, exfoliated MoS₂ exhibits a direct band gap of 2.8 eV due to quantum confinement, which enables it to possess suitable band positions and retain a good visible-light absorption ability. As a result, it is considered to be an encouraging candidate for photocatalytic applications. Encapsulating exfoliated MoS₂ into MOF demonstrates an improved visible light absorption ability compared to pure MOF, and the highest hydrogen production rate that the encapsulated exfoliated MoS₂ could reach was 68.4 μmol h^-1g^-1, which was much higher than that of pure MOF. With a suitable band structure and improved light-harvesting ability, exfoliated MoS₂@MOF could be a potential photocatalyst for hydrogen production. Full article

(This article belongs to the Special Issue Platinum-Free Electrocatalysts)

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2 pages, 159 KiB

Open AccessEditorial

Solid Catalysts for the Upgrading of Renewable Sources

by Federica Zaccheria and Nicoletta Ravasio

Catalysts 2019, 9(1), 88; https://doi.org/10.3390/catal9010088 - 15 Jan 2019

Cited by 4 | Viewed by 2879

Abstract

The use of renewable resources as raw materials for the chemical industry is mandatory in the transition roadmap toward the Bioeconomy [...] Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

26 pages, 2868 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Insights in Transition Metal Sulfide Hydrodesulfurization Catalysts for the Production of Ultra Low Sulfur Diesel: A Short Review

by Jorge Noé Díaz de León, Chowdari Ramesh Kumar, Joel Antúnez-García and Sergio Fuentes-Moyado

Catalysts 2019, 9(1), 87; https://doi.org/10.3390/catal9010087 - 15 Jan 2019

Cited by 81 | Viewed by 12256

Abstract

The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal [...] Read more.

The literature from the past few years dealing with hydrodesulfurization catalysts to deeply remove the sulfur-containing compounds in fuels is reviewed in this communication. We focus on the typical transition metal sulfides (TMS) Ni/Co-promoted Mo, W-based bi- and tri-metallic catalysts for selective removal of sulfur from typical refractory compounds. This review is separated into three very specific topics of the catalysts to produce ultra-low sulfur diesel. The first issue is the supported catalysts; the second, the self-supported or unsupported catalysts and finally, a brief discussion about the theoretical studies. We also inspect some details about the effect of support, the use of organic and inorganic additives and aspects related to the preparation of unsupported catalysts. We discuss some hot topics and details of the unsupported catalyst preparation that could influence the sulfur removal capacity of specific systems. Parameters such as surface acidity, dispersion, morphological changes of the active phases, and the promotion effect are the common factors discussed in the vast majority of present-day research. We conclude from this review that hydrodesulfurization performance of TMS catalysts supported or unsupported may be improved by using new methodologies, both experimental and theoretical, to fulfill the societal needs of ultra-low sulfur fuels, which more stringent future regulations will require. Full article

(This article belongs to the Special Issue Structure–Activity Relationships in Catalysis)

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6 pages, 2846 KiB

Open AccessCommunication

Pd(CH₃CN)₂Cl₂/Pipecolinic Acid as a Highly Efficient Catalytic System for Suzuki-Miyaura Cross-coupling Reaction of Bromoaryl Carboxylic Acids in Water

by Xiaogang Li, Wenbin Zhang, Leiqing Fu and Mengping Guo

Catalysts 2019, 9(1), 86; https://doi.org/10.3390/catal9010086 - 15 Jan 2019

Cited by 3 | Viewed by 4973

Abstract

In this study, a convenient and highly efficient catalytic system for the Suzuki-Miyaura coupling reaction was investigated under mild conditions. A combination of Pd(CH₃CN)₂Cl₂ and pipecolinic acid showed excellent catalytic performance and afforded high turnover numbers; turnover numbers [...] Read more.

In this study, a convenient and highly efficient catalytic system for the Suzuki-Miyaura coupling reaction was investigated under mild conditions. A combination of Pd(CH₃CN)₂Cl₂ and pipecolinic acid showed excellent catalytic performance and afforded high turnover numbers; turnover numbers were up to 4.9 × 10⁵ for the coupling reaction of 4-bromobenzoic acid and tetraphenylboron sodium. The catalytic system was also effective for the indexes of 4-bromobenzoic acid, and high turnover numbers were obtained. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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11 pages, 2935 KiB

Open AccessArticle

Effect of Fe₂O₃–ZrO₂ Catalyst Morphology on Sulfamethazine Degradation in the Fenton-Like Reaction

by Pan Gao, Mengjie Hao, Yue He, Yuan Song and Shaoxia Yang

Catalysts 2019, 9(1), 85; https://doi.org/10.3390/catal9010085 - 14 Jan 2019

Cited by 7 | Viewed by 4255

Abstract

Fe₂O₃–ZrO₂ catalysts with different morphologies (nanoplates (HZNPs), nanorods (HZNRs), nanocubes (HZNCs), and nanotubes (HZNTs)) were prepared by a hydrothermal method to investigate the effect of the morphology on the catalytic performance in the Fenton-like reaction for sulfamethazine (SMT) [...] Read more.

Fe₂O₃–ZrO₂ catalysts with different morphologies (nanoplates (HZNPs), nanorods (HZNRs), nanocubes (HZNCs), and nanotubes (HZNTs)) were prepared by a hydrothermal method to investigate the effect of the morphology on the catalytic performance in the Fenton-like reaction for sulfamethazine (SMT) degradation. The Fe₂O₃–ZrO₂ catalysts were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis. The H₂O₂ adsorption and the Fe²⁺ density sites on the Fe₂O₃–ZrO₂ catalysts had a close relationship with the morphologies and exhibited an important effect on the ·OH formation in the Fenton-like reaction. Free ·OH radicals were the main oxidative species in the reaction, and the normalized ·OH concentration per surface area of the catalysts was 4.52, 2.24, 2.20, and 0.37 μmol/m² for HZNPs, HZNRs, HZNCs, and HZNTs, respectively. The Fe₂O₃–ZrO₂ catalysts with different morphologies showed good catalytic performance, and the order of SMT degradation was HZNPs > HZNRs > HZNCs > HZNTs. Total SMT removal was achieved in the Fenton-like reaction over HZNPs at pH 3.0 and 45 °C after 240 min. Full article

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8 pages, 601 KiB

Open AccessBrief Report

Non-Monotonic Trends of Hydrogen Adsorption on Single Atom Doped g-C₃N₄

by Hao Li, Zhien Zhang and Zhijian Liu

Catalysts 2019, 9(1), 84; https://doi.org/10.3390/catal9010084 - 14 Jan 2019

Cited by 22 | Viewed by 4969

Abstract

To estimate the reaction free energies of the hydrogen evolution reaction (HER) on under-coordinated metallic sites, density function theory (DFT) calculations are usually employed to calculate the hydrogen adsorption energy with an “only-one-hydrogen-adsorption” model, assuming that adsorption with one hydrogen is the most [...] Read more.

To estimate the reaction free energies of the hydrogen evolution reaction (HER) on under-coordinated metallic sites, density function theory (DFT) calculations are usually employed to calculate the hydrogen adsorption energy with an “only-one-hydrogen-adsorption” model, assuming that adsorption with one hydrogen is the most thermodynamically favorable situation during catalysis. In this brief report, we show that on many single atom sites, adsorption of more than one hydrogen is sometimes even more thermodynamically favorable, with the presence of two or three hydrogens resulting in lower adsorption energies. These interesting non-monotonic trends indicate that modeling HER and other hydrogen-related reactions on under-coordinated sites should also consider the numbers of hydrogen being adsorbed at the same site, otherwise the results could deviate from real experimental situations. Full article

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45 pages, 8697 KiB

Open AccessReview

Copper Containing Molecular Systems in Electrocatalytic Water Oxidation—Trends and Perspectives

by Dávid Lukács, Łukasz Szyrwiel and József S. Pap

Catalysts 2019, 9(1), 83; https://doi.org/10.3390/catal9010083 - 14 Jan 2019

Cited by 27 | Viewed by 7545

Abstract

Molecular design represents an exciting platform to refine mechanistic details of electrocatalytic water oxidation and explore new perspectives. In the growing number of publications some general trends seem to be outlined concerning the operation mechanisms, with the help of experimental and theoretical approaches [...] Read more.

Molecular design represents an exciting platform to refine mechanistic details of electrocatalytic water oxidation and explore new perspectives. In the growing number of publications some general trends seem to be outlined concerning the operation mechanisms, with the help of experimental and theoretical approaches that have been broadly applied in the case of bioinorganic systems. In this review we focus on bio-inspired Cu-containing complexes that are classified according to the proposed mechanistic pathways and the related experimental evidence, strongly linked to the applied ligand architecture. In addition, we devote special attention to features of molecular compounds, which have been exploited in the efficient fabrication of catalytically active thin films. Full article

(This article belongs to the Section Electrocatalysis)

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16 pages, 3739 KiB

Open AccessArticle

Adsorption and Photocatalytic Decomposition of Gaseous 2-Propanol Using TiO₂-Coated Porous Glass Fiber Cloth

by Sayaka Yanagida, Kentaro Hirayama, Kenichiro Iwasaki and Atsuo Yasumori

Catalysts 2019, 9(1), 82; https://doi.org/10.3390/catal9010082 - 14 Jan 2019

Cited by 10 | Viewed by 4432

Abstract

Combinations of TiO₂ photocatalysts and various adsorbents have been extensively investigated for eliminating volatile organic compounds (VOCs) at low concentrations. Herein, TiO₂ and porous glass cloth composites were prepared by acid leaching and subsequent TiO₂ dip-coating of the electrically applied [...] Read more.

Combinations of TiO₂ photocatalysts and various adsorbents have been extensively investigated for eliminating volatile organic compounds (VOCs) at low concentrations. Herein, TiO₂ and porous glass cloth composites were prepared by acid leaching and subsequent TiO₂ dip-coating of the electrically applied glass (E-glass) cloth, and its adsorption and photocatalytic ability were investigated. Acid leaching increased the specific surface area of the E-glass cloth from 1 to 430 m²/g while maintaining sufficient mechanical strength for supporting TiO₂. Further, the specific surface area remained large (290 m²/g) after TiO₂ coating. In the photocatalytic decomposition of gaseous 2-propanol, the TiO₂-coated porous glass cloth exhibited higher adsorption and photocatalytic decomposition ability than those exhibited by the TiO₂-coated, non-porous glass cloth. The porous composite limited desorption of acetone, which is a decomposition intermediate of 2-propanol, until 2-propanol was completely decomposed to CO₂. The CO₂ generation rate was affected by the temperature condition (15 or 35 °C) and the water content (2 or 18 mg/L); the latter also influenced 2-propanol adsorption in photocatalytic decomposition. Both the conditions may change the diffusion and adsorption behavior of 2-propanol in the porous composite. As demonstrated by its high adsorption and photocatalytic ability, the composite (TiO₂ and porous glass cloth) effectively eliminates VOCs, while decreasing the emission of harmful intermediates. Full article

(This article belongs to the Special Issue Emerging Trends in TiO₂ Photocatalysis and Applications)

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22 pages, 2844 KiB

Open AccessReview

The Catalytic Mechanism of Steroidogenic Cytochromes P450 from All-Atom Simulations: Entwinement with Membrane Environment, Redox Partners, and Post-Transcriptional Regulation

by Angelo Spinello, Ida Ritacco and Alessandra Magistrato

Catalysts 2019, 9(1), 81; https://doi.org/10.3390/catal9010081 - 14 Jan 2019

Cited by 26 | Viewed by 8359

Abstract

Cytochromes P450 (CYP450s) promote the biosynthesis of steroid hormones with major impact on the onset of diseases such as breast and prostate cancers. By merging distinct functions into the same catalytic scaffold, steroidogenic CYP450s enhance complex chemical transformations with extreme efficiency and selectivity. [...] Read more.

Cytochromes P450 (CYP450s) promote the biosynthesis of steroid hormones with major impact on the onset of diseases such as breast and prostate cancers. By merging distinct functions into the same catalytic scaffold, steroidogenic CYP450s enhance complex chemical transformations with extreme efficiency and selectivity. Mammalian CYP450s and their redox partners are membrane-anchored proteins, dynamically associating to form functional machineries. Mounting evidence signifies that environmental factors are strictly intertwined with CYP450s catalysis. Atomic-level simulations have the potential to provide insights into the catalytic mechanism of steroidogenic CYP450s and on its regulation by environmental factors, furnishing information often inaccessible to experimental means. In this review, after an introduction of computational methods commonly employed to tackle these systems, we report the current knowledge on three steroidogenic CYP450s—CYP11A1, CYP17A1, and CYP19A1—endowed with multiple catalytic functions and critically involved in cancer onset. In particular, besides discussing their catalytic mechanisms, we highlight how the membrane environment contributes to (i) regulate ligand channeling through these enzymes, (ii) modulate their interactions with specific protein partners, (iii) mediate post-transcriptional regulation induced by phosphorylation. The results presented set the basis for developing novel therapeutic strategies aimed at fighting diseases originating from steroid metabolism dysfunction. Full article

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15 pages, 2245 KiB

Open AccessArticle

Catalytic Decomposition of an Energetic Ionic Liquid Solution over Hexaaluminate Catalysts

by Sunghoon Hong, Sujeong Heo, Wooram Kim, Young Min Jo, Young-Kwon Park and Jong-Ki Jeon

Catalysts 2019, 9(1), 80; https://doi.org/10.3390/catal9010080 - 14 Jan 2019

Cited by 12 | Viewed by 4223

Abstract

The objective of this study was to determine the effect of a synthesis procedure of Sr hexaaluminate on catalytic performance during the decomposition of ionic liquid monopropellants based on ammonium dinitramide (ADN) and hydroxyl ammonium nitrate (HAN). Sr hexaaluminates were prepared via both [...] Read more.

The objective of this study was to determine the effect of a synthesis procedure of Sr hexaaluminate on catalytic performance during the decomposition of ionic liquid monopropellants based on ammonium dinitramide (ADN) and hydroxyl ammonium nitrate (HAN). Sr hexaaluminates were prepared via both coprecipitation and a sol–gel process. The surface area of hexaaluminate synthesized via the coprecipitation method was higher than that of hexaaluminate synthesized by the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is because of the sintering of α-Al₂O₃ on the hexaaluminate synthesized via the sol–gel process, which could not be observed on the catalysts synthesized via the coprecipitation method. The hexaaluminate synthesized via coprecipitation showed a lower decomposition onset temperature during the decomposition of ADN- and HAN-based liquid monopropellants in comparison with the catalysts synthesized via the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is attributed to the differences in the Mn³⁺ concentration and the surface area between the two hexaaluminates. Consequently, the hexaaluminate synthesized via coprecipitation which calcined above 1200 °C showed high activity during the decomposition of energetic ionic liquid monopropellants compared with the hexaaluminate synthesized via the sol–gel process. Full article

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12 pages, 3154 KiB

Open AccessArticle

The Role of NiO in Reactive Adsorption Desulfurization Over NiO/ZnO-Al₂O₃-SiO₂ Adsorbent

by Feng Ju, Miao Wang, Tian Wu and Hao Ling

Catalysts 2019, 9(1), 79; https://doi.org/10.3390/catal9010079 - 14 Jan 2019

Cited by 18 | Viewed by 4601

Abstract

The reactive adsorption desulfurization (RADS) of a model gasoline n-hexane containing thiophene was carried out with a NiO/ZnO-Al₂O₃-SiO₂ adsorbent in N₂ and H₂, respectively. A declining RADS trend has been observed in N₂ [...] Read more.

The reactive adsorption desulfurization (RADS) of a model gasoline n-hexane containing thiophene was carried out with a NiO/ZnO-Al₂O₃-SiO₂ adsorbent in N₂ and H₂, respectively. A declining RADS trend has been observed in N₂, without the presence of H₂, indicating that NiO is sulfurized and exhibits activity for RADS. TPR and XPS results presented NiO in the adsorbent is hard to be reduced because of the powerful interaction between NiO and the support. The sulfurization of NiO into NiSx is a primary condition for the RADS process, the same as the presulfurization of hydrotreating catalyst, while metallic Ni is an intermediate reduction product of NiSx. Results of a low RADS temperature at 300 °C, much lower than the reduction temperature of NiO, suggest that NiO plays an important role. Based on assumption of NiO as the main active component, the RADS could reduce the reaction temperature and energy consumption significantly. The participation of hydrogen and n-hexane in pretreatment conducted at 420 °C contributes to the activation of adsorbent. Also, these methods of pretreatment improved the desulfurization performance under the reaction temperature of 300 °C. Full article

(This article belongs to the Special Issue Ni-Containing Catalysts)

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12 pages, 2687 KiB

Open AccessArticle

Enzyme-Loaded Mesoporous Silica Particles with Tuning Wettability as a Pickering Catalyst for Enhancing Biocatalysis

by Tao Meng, Ruixue Bai, Weihao Wang, Xin Yang, Ting Guo and Yaolei Wang

Catalysts 2019, 9(1), 78; https://doi.org/10.3390/catal9010078 - 14 Jan 2019

Cited by 16 | Viewed by 5342

Abstract

Pickering emulsion systems have created new opportunities for two-phase biocatalysis, however their catalytic performance is often hindered by biphasic mass transfer process relying on the interfacial area. In this study, lipase-immobilized mesoporous silica particles (LMSPs) are employed as both Pickering stabilizers and biocatalysts. [...] Read more.

Pickering emulsion systems have created new opportunities for two-phase biocatalysis, however their catalytic performance is often hindered by biphasic mass transfer process relying on the interfacial area. In this study, lipase-immobilized mesoporous silica particles (LMSPs) are employed as both Pickering stabilizers and biocatalysts. A series of alkyl silanes with the different carbon length are used to modify LMSPs to obtain suitable wettability and enlarge the interfacial area of Pickering emulsion. The results show the water/paraffin oil Pickering emulsions stabilized by 8 carbon atoms silane grafted LMSPs (LMSPs_C8) with a three-phase contact angles of 95° get the relatively large interfacial area. Moreover, the conversion of enzymatic reaction catalyzed by LMSPs_C8 Pickering emulsion system is 3.4 times higher than that unmodified LMSPs with the reaction time of 10 min. Additionally, the effective recycling of LMSPs is achieved by simple low-speed centrifugation. As evidenced by a 6-cycles reaction of remaining 75% of relative enzymatic activity, the protection of 350–450 nm mesoporous silica particles can alleviate the inactivation of enzyme from the shear stress and make a benefit to form stabile Pickering emulsion. Therefore, the biphasic reactions in the Pickering emulsion system can be effectively enhanced through changing interfacial area only by the means of adjusting the wettability of biocatalysts. Full article

(This article belongs to the Special Issue Biocatalysts: Design and Application)

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11 pages, 3558 KiB

Open AccessArticle

Catalytic Hydrodechlorination of Chlorophenols in a Continuous Flow Pd/CNT-Ni Foam Micro Reactor Using Formic Acid as a Hydrogen Source

by Jun Xiong and Ying Ma

Catalysts 2019, 9(1), 77; https://doi.org/10.3390/catal9010077 - 12 Jan 2019

Cited by 22 | Viewed by 4776

Abstract

Catalytic hydrodechlorination (HDC) has been considered as a promising method for the treatment of wastewater containing chlorinated organic pollutants. A continuous flow Pd/carbon nanotube (CNT)-Ni foam micro reactor system was first developed for the rapid and highly efficient HDC with formic acid (FA) [...] Read more.

Catalytic hydrodechlorination (HDC) has been considered as a promising method for the treatment of wastewater containing chlorinated organic pollutants. A continuous flow Pd/carbon nanotube (CNT)-Ni foam micro reactor system was first developed for the rapid and highly efficient HDC with formic acid (FA) as a hydrogen source. This micro reactor system, exhibiting a higher catalytic activity of HDC than the conventional packed bed reactor, reduced the residence time and formic acid consumption significantly. The desired outcomes (dichlorination >99.9%, 4-chlorophenol outlet concentration <0.1 mg/L) can be obtained under a very low FA/substrate molar ratio (5:1) and short reaction cycle (3 min). Field emission scanning electron microcopy (FESEM) and deactivation experiment results indicated that the accumulation of phenol (the main product during the HDC of chlorophenols) on the Pd catalyst surface can be the main factor for the long-term deactivation of the Pd/CNT-Ni foam micro reactor. The catalytic activity deactivation of the micro reactor could be almost completely regenerated by the efficient removal of the absorbed phenol from the Pd catalyst surface. Full article

(This article belongs to the Special Issue Catalytic Methods in Flow Chemistry)

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