Catalysis Surveys from Asia最新文献

At this moment the major challenge for the human beings is to address uninterrupted raise in CO₂ emissions and their consequences. The demands of globalization don’t permit to minimize the CO₂ emissions. The possible options to address issues related CO₂ emissions are (a) Use of renewable energy sources (b) CO₂ capture and storage (CCS) (c) CO₂ capture and utilization (CCU). However, the utilization of CO₂ in the production of chemicals is eco-economically advantageous. The utilization of CO₂ involves the conversion of CO₂ or use of CO₂ as co-feed in the reaction streams. The research community is progressive to develop CO₂ conversion technologies at various levels. The present review focuses on the recent trends in emission and utilization of CO₂ as feed stock for catalytic production of organic carbonates which possess ample industrial applications and use of CO₂ as soft oxidant in catalytic oxidative dehydrogenation reactions of hydrocarbons. Various catalytic systems for both the conversions are discussed.

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The approach towards CO₂ emissions is changing from CO₂ Capture and Storage (CCS) to CO₂ Capture and Utilization (CCU). The present review focused on the utilization of CO₂ as feed stock in dehydrogenation reactions and synthesis of organic carbonates using variety of catalysts.

Co₃O₄ catalyst derived from Co-MOFs demonstrated rich active sites in the catalytic reaction. In this paper, we prepared the rod-like Co₃O₄ catalysts by calcining Co-MOFs, which were synthesized by the solvothermal reaction of cobalt nitrate and diverse spatial structure linkers (L3, L4, and L5). Typically, the linkers with different spatial structures (L3, L4, and L5) were synthesized from p-aminobenzoic acid and tetracarboxylic anhydride with different structures (naphthalene-1,4,5,8-tetracarboxylic anhydride, benzene-1,2,4,5-tetracarboxylic anhydride, and perylene-3,4,9,10-tetracarboxylic anhydride). According to the BET analysis, the average pore size of Co₃O₄ increased with the increase of the linker spatial structure. However, the specific surface area of three Co₃O₄ increased at first, and then decreased with the increase spatial structure of the linker. Among three Co₃O₄ catalysts, the Co₃O₄-L3 exhibited the highest specific surface area. The Co₃O₄-L3 emerged with superior performance and stability for the catalytic combustion reaction of toluene due to large specific surface area, high redox capacity, plentiful surface active sites, and rich active adsorbed oxygen.

The adsorption properties for some gas molecules (H₂, N₂, CO, NO and CO₂) on pristine and transition metal-doped h-BN monolayer are investigated by using density functional theory (DFT) calculations. In contrast with N vacancy (V_N) substrates, those with B vacancy (V_B) are more easily doped with metal atoms, among which Ti atom doping shows the lowest binding energy. For the adsorption of these gas molecules, NO is most easily adsorbed on h-BN monolayer with metal dopants, especially Pt doped system yields the lowest adsorption energy of NO. Since a NO molecule on Pt doped h-BN monolayer could not be directly decomposed into O_ads and N_ads due to the high reaction energy barrier (≈ 2.00 eV), the (NO)₂ dimmer can interact with Pt to form a five-membered ring or a four-membered ring through two different Langmuir–Hinshelwood (LH) mechanisms for NO reduction catalytic reaction, respectively. The LH1 reaction process needs to overcome relatively lower energy barriers, while the product of the LH2 mechanism has a more stable structure. For the catalytic process of CO oxidation, the remained O_ads can bind with CO and form CO₂, by overcoming a much lower energy barrier of only 0.14 eV. It seems that Pt doping can enhance the adsorb capacity of h-BN monolayer for the gas molecules and the potential catalytic activity for electrochemical reduction of NO.

As a set of photocatalyst and its co-catalyst with exceptional photo-degradation performance, rGO exhibits a conspicuous board-spectrum sensitization effect to TiO₂. It has been widely recognized by studies in the field of water treatment that, their synergistic can also markedly complement short carrier lifetime and other shortcomings of TiO₂. Over the years, research conducted on TiO₂-rGO binary composite material manifests its wide modifiable space for seeking a better degradation performance and a higher solar availability. We presents an overview study on the latest modification methods of the TiO₂-rGO binary composite material and divide them into categories. This article focuses on the four of them as follows: morphology and crystalline engineering, doping modification, semiconductor ternary combination, noble-metal decoration. Furthermore, the in-depth degradation mechanism and novel structure design of the modified TiO₂-rGO binary composite materials are reviewed. Ongoing difficulties and promising opportunities have been summarized and expected in this article, aiming to guide the design and study of the future photo-degradation nanomaterial.

Over the past couple of years, fossil fuel consumption has been increased significantly. Today the consumption of coal, natural gas, and oil is rising continuously worldwide. In contrast to fossil fuels, biofuels can be advantageous because of their eco-friendly behavior with the environment. Ethanol is the “green” substitute for gasoline, as it can be blended with gasoline or can be used for the production of lighter olefins (ethylene and propylene). Ethanol can be produced either by fermentation or by catalytic route from various sources such as sugar/starchy material, carbon dioxide, carbon monoxide, and dimethylether. The catalytic route has emerged as the better route compared to fermentation due to the requirement of a large number of crops which is generally not suitable for every country. The study of ethanol synthesis and the catalytic transformation of ethanol to lighter olefins such as ethylene and propylene is presented in this review. The effect of catalysts such as zirconia, alumina, and zeolites in the ethanol transformation to olefins has been discussed in detail.

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Cr, Fe, Ce and W doped MoVTeNbO M2 phase catalysts were synthesized and used in the selective oxidation of propylene to acrylic acid (AA). Results show that the introduction of Cr, Fe, Ce and W substantially affects the physicochemical properties and catalytic performance of MoVTeNbO-based catalysts. Un-doped catalyst consists of M2 phase and TeO₂, while Cr, Fe, Ce and W-doped catalysts are mainly composed of M2 and MoO₃. It is indicated that doping of Cr, Fe, Ce and W can restrain the formation of TeO₂, but favour the formation of MoO₃. Un-doped, Cr and W-doped catalysts display irregular-shaped particles morphology, while Fe and Ce-doped catalysts display nanosheets morphology. In addition, the valence of superficial elements of catalysts changed greatly with the doping elements. For catalytic performance, in addition to Cr, the propylene conversion of the catalyst decreases obviously with doping of other elements, probably due to the drastically reduced specific surface area with doping of Fe, Ce and W. The existence of Cr and Ce can increase the selectivity to AA at all test temperatures (360–440 ℃), while Fe and W-doped catalysts only show higher selectivity than the un-doped one at high temperature of 420 and 440 ℃. It is illustrated that the catalysts with redox ability at relatively low temperature is more favorable for the selectivity to AA. Among them, Cr-doped catalyst shows the highest selectivity (85.3%) and yield (63.5%) of AA at test temperature of 380 ℃, which are 15.3 and 7.5% higher than that of un-doped catalyst, respectively.

Graphic Abstract

The M2 phase MoVTeNbO catalysts doped with Cr, Fe, Ce and W have been synthesized. It is demonstrated that the addition of Cr improves the stability of Te⁴⁺, and Cr-doped M2 phase shows excellent catalytic performance in the selective oxidation of propylene to acrylic acid.

An acid gas stream was utilized instead of pure H₂S as feedstock in the methanol thiolation reaction with Alkali/W/γ-Al₂O₃ catalysts. The catalysts were synthesized through incipient wetness impregnation and characterized by XRD, BET, and NH₃-TPD methods. The catalytic tests were performed in a fixed-bed flow reactor for an acid gas with 12.2%mol. H₂S at atmospheric pressure, 360 °C, H₂S to methanol molar ratio of 2, and LHSV of 0.5 h⁻¹. The results were then compared with the case in which pure H₂S was used as feedstock. H₂S conversion was lower in the acid gas feed than in pure H₂S feed due to participation of catalysts in hydrocarbon reforming reactions. Cesium-promoted catalysts gave the best results. H₂S in acid gas was converted about 92.8%. The yields were reported about 87.3% and 5.5% for dimethyl sulfide and methanethiol as organosulfur products respectively. The amount of hydrogen increased by about 110% in the reactor outlet.

NiMoS supported on ZSM-5 with different Si/Al ratio, crystallite size and pore structure was prepared by incipient impregnation method and applied in 1, 3, 5-trimethylbenzene (1, 3, 5-TMB) hydrodealkylation (HDAK). The physicochemical properties of samples were characterized by XRD, FTIR, SEM, N₂ adsorption–desorption, NH₃-TPD, Py-FTIR, H₂-TPR, HRTEM and TGA. It is demonstrated that for microporous NiMoS/ZSM-5, acid amount and crystallite size of HZSM-5 are key factors affecting HDAK performance. The larger acid amount and smaller crystallite size can promote the conversion of 1, 3, 5-TMB, especially the dealkylation reaction, resulting in higher BTX yield. Compared to NiMoZ-3, mesopores in micro-mesoporous NiMoAKZ-3 are beneficial to accessibility of 1, 3, 5-TMB to NiMoS and acid sites in close proximity, and the diffusion of reactant and product molecules inside pores, thus resulting in superior HDAK performance of NiMoAKZ-3. Moreover, the reaction network of 1, 3, 5-TMB HDAK was revealed according to product distribution.

Graphic Abstract

NiMoS supported on ZSM-5 was developed for heavy aromatic hydrodealkylation (HDAK). Acid amount and crystallite size of microporous ZSM-5 are key factors affecting 1,3,5-trimethylbenzene (1,3,5-TMB) HDAK. Mesopores inside ZSM-5 facilitate accessibility of 1,3,5-TMB to NiMoS and acid sites in close proximity and improve HDAK performance.