Recently, the team of Xiao Jianping, a researcher of the Research Group of Theoretical Catalytic Innovation Special State of the State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, teamed up with Professor Xiao Fengshou of Zhejiang University and Wang Liang, a team of researchers, to make new progress in the study of one-step synthesis of ethanol from syngas .
Ethanol is an important chemical and fuel. Efficient and highly selective direct production of ethanol via synthesis gas is currently a hotspot in the field of energy research. If the catalyst is too reactive or too weak, the selectivity of by-products will be too high, so it is also difficult to directly produce ethanol from syngas. A thorough understanding of the reaction mechanism of synthesis gas conversion is of great significance for the subsequent improvement of catalyst activity and the search for non-noble metal catalysts. There are dozens of intermediates and transition states and thousands of reaction paths in the synthesis gas conversion process, and the traditional theoretical methods cannot well understand this process. Based on this, the team of Xiao Jianping has developed a new method of reaction path research and product selectivity analysis, which can simplify the adsorption energy of dozens of intermediates and transition states to two dimensions-the adsorption energy of CO and OH, and to This is to describe the selectivity of different catalysts to products (such as the two-dimensional reaction phase diagram above), and to understand and guide the design of the catalyst. This method can also integrate thermodynamic and kinetic effects to automatically search for the optimal reaction path for ethanol production.
In the synthesis gas conversion process, if the CO molecule and the catalyst (such as pure Rh, Co catalyst, etc.) are too strongly combined, the carbon-oxygen bond is basically broken, and then methane is selectively obtained; if the CO and the catalyst (such as the Cu catalyst) are combined Too weak, the carbon-oxygen bond cannot be broken at all, so only methanol can be obtained. Only when there is a very small energy window between CO and catalyst, the intermediate (CHx *) after CO dissociation and undissociated CO * / CHO * can coexist to have better ethanol selectivity. Theoretical calculations show that the coupling of CH2 * and CO / CHO * intermediates is the most critical step. The MnOx structure and the restricted environment provided by the molecular sieve affect the electronic structure of the Rh atom at the interface (near MnOx), making RhMn @ S The -1 catalyst happens to fall in this range, and ultimately allows CH2 * and CO * / CHO * intermediate substances to coexist in large quantities, resulting in higher ethanol selectivity. This work provides new ideas for the design of catalysts for the preparation of ethanol with highly selective synthesis gas.
Related results were published in Chem. This work was supported by the National Major R & D Program, the National Natural Science Foundation of China, the key deployment project of the Chinese Academy of Sciences, and the "Xingliao Talent Program" in Liaoning Province.
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