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排序方式: 共有189条查询结果,搜索用时 203 毫秒
181.
采用沉积沉淀和浸渍法制备了Au-Zn组合改性HZSM-5催化剂.并且对比研究了HZSM-5,Au/HZSM-5,Zn/HZSM-5和Au-Zn/HZSM-5催化剂的性质和催化性能.采用UV-Vis和XPS表征揭示出Au-Zn/HZSM-5催化剂中Au物种与Zn物种的相互作用.正丁烷探针反应结果表明,在Zn/HZSM-5催化剂中引入Au有效地提高了正丁烷的脱氢芳构化性能,同时抑制了正丁烷在Zn活性中心上的氢解副反应.在相同条件下,与Zn/HZSM-5催化剂相比,正丁烷转化率由49.1%增加到70.8%,烯烃和芳烃产物总选择性由57%增加到61.98%,干气的选择性由31%降低至28.4%.上述结果表明,Au-Zn/HZSM-5催化剂在轻烃芳构化反应中具有良好的催化性能. 相似文献
182.
183.
Adsorption and dehydrogenation of ethylene on Cu(410) surface are investigated with firstprinciples calculations and micro-kinetics analysis. Ethylene dehydrogenation is found to start from the most stable π-bonded state instead of the previously proposed di-σ-bonded state. Our vibrational frequencies calculations verify the π-bonded adsorption at step sites at low coverage and low surface temperature and di-σ-bonded ethylene on C-C dimer (C2H4-CC) is proposed to be the species contributing to the vibrational peaks experimentally observed at high coverage at 193 K. The presence of C2H4-CC indicates that the dehydrogenation of ethylene on Cu(410) can proceed at temperature as low as 193 K. 相似文献
184.
185.
有关醇类水溶液光催化贮能脱氢反应研究大多集中在提高半导体TiO2和CdS表面修饰组分的光催化活性[1~3]及考察TiO2半导体晶体结构与光催化性能的关系上[4,5],CdS半导体晶体结构形态对光催化性能的影响尚未见报道.本文在这方面进行了一些有益的研究. 相似文献
186.
本文通过密度泛函理论(DFT),计算研究了金属原子Ga和非金属原子N共同掺杂磷化钴(Co P)作为催化剂催化氨硼烷(NH3BH3)的脱氢过程.在这里,我们设计了四条可行的反应路径,并且计算了每条路径中间体过渡态的能量.通过研究结果得出结论,路径Ⅱ为最优反应路径.这将为金属和非金属共同掺杂Co P催化NH3BH3脱氢反应提供一定的理论基础. 相似文献
187.
Jianshuo Zhang Yuki Nakaya Prof. Dr. Ken-ichi Shimizu Prof. Dr. Shinya Furukawa 《Angewandte Chemie (International ed. in English)》2023,62(18):e202300744
Electric field catalysis using surface proton conduction, in which proton hopping and collision on the reactant are promoted by external electricity, is a promising approach to break the thermodynamic equilibrium limitation in endothermic propane dehydrogenation (PDH). This study proposes a catalyst design concept for more efficient electroassisted PDH at low temperature. Sm was doped into the anatase TiO2 surface to increase surface proton density by charge compensation. Pt−In alloy was deposited on the Sm-doped TiO2 for more favorable proton collision and selective propylene formation. The catalytic activity in electroassisted PDH drastically increased by doping an appropriate amount of Sm (1 mol % to Ti) where the highest propylene yield of 19.3 % was obtained at 300 °C where the thermodynamic equilibrium yield was only 0.5 %. Results show that surface proton enrichment boosts alkane dehydrogenation at low temperature. 相似文献
188.
Dr. Guo-Qing Yang Dr. Yiming Niu Dr. Vita A. Kondratenko Dr. Xianfeng Yi Dr. Chang Liu Prof. Dr. Bingsen Zhang Prof. Dr. Evgenii V. Kondratenko Prof. Zhong-Wen Liu 《Angewandte Chemie (International ed. in English)》2023,62(49):e202310062
Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx−Al2O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V−O−Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2−ZrO2−Al2O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non-oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution. 相似文献
189.
Mikalai A. Artsiusheuski René Verel Jeroen A. van Bokhoven Vitaly L. Sushkevich 《Angewandte Chemie (International ed. in English)》2023,62(44):e202309180
Copper(II)-containing mordenite (CuMOR) is capable of activation of C−H bonds in C1-C3 alkanes, albeit there are remarkable differences between the functionalization of ethane and propane compared to methane. The reaction of ethane and propane with CuMOR results in the formation of ethylene and propylene, while the reaction of methane predominantly yields methanol and dimethyl ether. By combining in situ FTIR and MAS NMR spectroscopies as well as time-resolved Cu K-edge X-ray absorption spectroscopy, the reaction mechanism was derived, which differs significantly for each alkane. The formation of ethylene and propylene proceeds via oxidative dehydrogenation of the corresponding alkanes with selectivity above 95 % for ethane and above 85 % for propane. The formation of stable π-complexes of olefins with CuI sites, formed upon reduction of CuII-oxo species, protects olefins from further oxidation and/or oligomerization. This is different from methane, the activation of which proceeds via oxidative hydroxylation leading to the formation of surface methoxy species bonded to the zeolite framework. Our findings constitute one of the major steps in the direct conversion of alkanes to important commodities and open a novel research direction aiming at the selective synthesis of olefins. 相似文献