Catalysis Surveys from Asia最新文献

A facile and efficient electrocatalyst for hydrogen evolution reaction (HER) to produce hydrogen is very important for future energy. In this paper, amorphous manganese–cobalt nanosheets are successfully prepared by electrospinning on a foamed nickel substrate. It is found that the manganese (Mn) introduction in manganese–cobalt composites can simultaneously enhance their electrocatalytic performances. As a result, benefitting from the 3D structure, the self-supported Mn–Co hydroxides exhibits unprecedented HER activity with a relatively low overpotential of 100 mV at 10 mA cm⁻² and has a possibility for the large-scale production of hydrogen.

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Amorphous PVP/Mn₄Co nanofibers formed by electrospinning on Ni foam (NF) has remarkable catalytic activity and stability for HER after operation for 6 h in 1 M KOH, with a low overpotential of 0.1 V at 100 mA cm⁻², a low Tafel slope of 65.4 mV dec⁻¹.

With the target to fabricate more feasible catalysts for SRM to produce hydrogen, the interaction between Ni and LaBO₃ (B = Al, Cr and Fe) perovskite supports with different B-sites has been explored. To avoid the formation of big Ni grains, the Ni loading is intentionally set as low as 2 wt%. XRD and Raman results revealed that the three LaBO₃ supports are composed of pure perovskite phase, but have differed fine crystal structures. While LaFeO₃ and LaCrO₃ can be indexed to the orthorhombic perovskite phase, LaAlO₃ can be indexed to the hexagonal phase. H₂-TPR and XPS results have validated that NiO has varied interfacial interactions with the LaBO₃ supports through partial electron transfer from the supports to Ni. As a consequence, the active metallic Ni surface areas are in the order of 2%Ni/LaAlO₃ > 2%Ni/LaCrO₃ > 2%Ni/LaFeO₃, well consistent with the reaction performance. Furthermore, by varying the B-site element, the abundance of the active surface oxygen species (mainly O₂²⁻) is varied, obeying the sequence of 2%Ni/LaCrO₃ > 2%Ni/LaAlO₃ > 2%Ni/LaFeO₃, well consistent with the anti-coking ability of the catalysts. It is discovered that the change of the fine crystal structure of LaBO₃ supports can influence the SRM performance of the 2%Ni/LaBO₃ catalysts evidently. The reaction performance of the catalysts is mainly determined by the active Ni surface area, but the anti-coking ability is majorly decided by the amount of active oxygen species.

Sulfur poisoning of catalyst is a well-known phenomenon observed during the production of syngas (CO + H₂). The presence of traces of sulfur content in the feedstock can drastically reduce the catalyst activity and life. Several measures have been developed over the years to mitigate the catalyst deactivation process due to sulfur poisoning. In this paper, we review literature from 1996-present related to all the developments made for sulfur-resistant systems. The basis of poisoning being the sulfur content in the feedstock, potential fuel-containing feedstocks for syngas production were briefly discussed. The basics of sulfur poisoning mechanisms are also summarized. Then, a framework consisting of sulfur tolerance methodologies were discussed. In particular, we have discussed: (i) catalyst development by altering catalyst composition and support systems, (ii) influence of using catalyst structures, (iii) process modifications and optimization, (iv) desulfurization techniques for removal of sulfur from feed and/or product streams, and (v) effective catalyst regeneration techniques to extend the catalyst life. This review emphasizes the integration of the best set of methods to develop sulfur tolerance strategies.

New catalysts prepared by simple mixing of molecular iodine and inexpensive monodonor amines can efficiently catalyze the coupling of CO₂ with different epoxides at moderate temperatures (60–90 °C), pressures (10–56 atm) and low (0.25–0.5 mol %) catalytic loading. The molecular systems can be considered as the simplest and most inexpensive catalyst for the reactions.

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Propane dehydrogenation to propene is an endothermic reaction and CO₂ hydrogenation to light olefins is an exothermic reaction. Using the CO₂ hydrogenation reaction to consume the hydrogen from the propane dehydrogenation reaction, which is more favorable to propylene formation. A new method for coupling propane and CO₂ to propylene is presented. The V–Fe modified KIT-6 was prepared by the ultrasonic-assisted impregnation method and used for coupling reaction of propane with CO₂ to propylene. Exploring the relationship between catalytic properties and physicochemical characteristics through several characterization methods. As the appropriate amounts of V and Fe species were introduced into the framework of KIT-6, V–Fe modified KIT-6 performed large specific surface area, a highly ordered mesoporous structure and highly dispersed V and Fe active sites. The catalysis performance of V–Fe modified KIT-6 zeolites for production of propylene by propane dehydrogenation, CO₂ hydrogenation and coupling reaction of C₃H₈ with CO₂ was compared. Under the conditions of C₃H₈/CO₂/N₂ = 1:4:5, total flow rate = 20 mL/min, the temperature at 580 °C, the reaction pressure at 0.1 MPa, V/Fe molar ratio = 2 and the catalyst mass of 0.2 g, the propane conversion, propylene selectivity and yield are 37.8%, 87.0% and 32.9%, respectively.

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Benzene methylation over zeolite offers an alternative route to produce high-value toluene or para-xylene directly from benzene and C₁ chemical sources, especially for countries with a shortage of crude oil but abundant coal, natural gas, or biomass. It also serves as a green “molecular engineering” to reduce costs of energy intensive separation for C₈ isomers by selective catalysis. Since numerous zeolite-based catalysts have been synthesized, characterized and evaluated in alkylation process, this review aims to present the roles of the zeolite topology and acidity in selective catalysis based on the reaction network and mechanisms for benzene methylation system during the recent years. It covers concise details in the shape-selective catalysis of zeolite topology and acidity to provide a theoretical basis of the chemical modification under reaction conditions, which give directions to or identify the catalyst design for benzene methylation, and also will provide the mechanistic insights and technical reference as an integral part of other aromatics production.

In this work, we developed a simple and effective one-pot method to synthesize the Pd-based bimetallic nanoparticles (NPs) in the presence of polyvinylpyrrolidone (PVP). By using high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometry (EDS) mapping and X-ray diffraction (XRD), the morphologies and compositions of the as-prepared bimetallic NPs were investigated in detail. Furthermore, this approach was also used to achieve the highly dispersive Pd-based bimetallic NPs directly on the carbon black. Significantly, the as-obtained carbon-supported Pd-based bimetallic NPs showed excellent electrocatalytic activity for the methanol oxidation. Among the Pd-based bimetallic NPs and the commercial Pd–C, the PdPt–C displayed the best electrocatalytic activity and stability, which may be mainly attributed to the specific nanostructure and the synergetic effect between Pt and Pd atoms.

The preparation of atomically dispersed catalysts with high metal loading remains a formidable challenge due to the high surface energy of single atoms. Here we prepared PtPd/TiO₂ catalysts possessing metal loading as high as 8.17 wt% by a new versatile method which based on metal oxide carriers with abundant oxygen defects. PtPd/TiO₂ catalysts consist of PtPd nanoparticles and atomically dispersed Pt and Pd atoms, and the content of PtPd nanoparticles is little. Pt₃Pd₁/TiO₂-400 catalyst exhibited the highest catalytic activity in toluene oxidation, and with a 94.7% conversion at 110 °C. Kinetic investigation reveals that the toluene oxidation follows a typical Langmuir-Hinshelwood mechanism. Experimental research indicates that the superior catalytic activity could be attributed to a large number of metal atoms atomically dispersed on the surface of the catalyst. Pt and Pd atoms are close to each other, which produces the synergetic effect and thereby promotes toluene oxidation. This work provides a promising pathway to fabricate single atom catalysts with high loading.

Exploring the morphology-property relationship is an important role in addressing the mechanism of hydrogen production. In this work, WO₃ photocatalysts with different morphology were prepared via a solvothermal method. Our first prepared porous WO₃ with the exposed (100) crystal plane, the WO₃ porous nano disk demonstrates a better photocatalytic activity, which is higher than the WO₃ nanorod, WO₃ nanoflower and WO₃ nano block. Further characterizations indicate the WO₃ porous nano disk exhibits high absorption capacity and active lattice structure. Meanwhile, with the introduction of non-noble metal Ni as the co-catalyst, the photocatalytic H₂ evolution was enhanced. This work reveals the importance of regulating surface atomic configuration and catalytic active sites, opens a new avenue for the development of solar-driven water splitting.

Water, as a byproduct in esterification, tends to adsorb on solid acid catalysts, causing loss of active components or decomposition of framework and thereby decreasing their reactivity and durability, while the development of water-tolerant solid acids is expected to solve these problems. In this review, the recent developments of major kinds of water-tolerant solid acids including zeolite, mesoporous silica, metal organic framework-based catalyst, magnetic nanoparticles, and polymeric catalyst are discussed in detail. Special attention has been paid to understand the role of hydrophobicity, acid strength, and structure of water-tolerant solid acids in catalytic performance and their stability. From the literature survey, it is found that despite the modified zeolites have a water contact angle as large as 160°, but their acid strength need to be improved and their small micropore sizes restrict their use in catalyzing the esterification of bulky molecules. In contrast, solid acids with abundant acid sites, suitable hydrophobicity, and abundant mesopores or macropores usually exhibit high activity and reusability. Among all the known solid acids, polystyrene-supported acidic ionic liquid catalysts (PS-CH₂-[SO₃H-pIM] [HSO₄]) show a high yield of n-butyl acetate with 99.1% and high reusability of 13 times, which is a breakthrough over the traditional. This review aims to offer a comprehensive understanding for the water-tolerant solid acid catalysts in esterification.

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