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Theoretical study of propylene epoxidation heterogeneous-homogeneous mechanism over MoOx/SiO2 catalyst |
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| Authors: | Zhehong Wan Zenan Lin Jiahui Peng Wei Chen Xiaohan Li Xiaohui Chen |
| Affiliation: | 1. College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian, China National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou, Fujian, China Contribution: Writing - original draft;2. College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian, China Contribution: Writing - review & editing;3. College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian, China Contribution: Investigation;4. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China;5. College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian, China National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou, Fujian, China Contribution: Formal analysis;6. College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian, China |
| Abstract: | The green direct propylene (C3H6) epoxidation on MoOx is well studied by experimental methods, but detailed molecular reaction mechanism studies using in-silico experiments method are few. Here, the different oxidation heterogeneous-homogeneous pathways for MoOx/SiO2 catalyst are calculated, mainly involving Mo=O on di-oxo tetracoordinate MoOx, allyl peroxy (C3H5OO•), and allyloxy (C3H5O•) radicals. The results show that, for surface reaction mechanism with Mo=O, the barriers of propylene oxide (PO) and acetone generation are too high; in comparison, the byproduct acrolein is more beneficial product with a lower barrier. In heterogeneous-homogeneous pathways, the desorbed allyl (C3H5•) from the surface can easily combine with O2 to synthesize C3H5OO• radical, and in the partial oxidation of propylene with C3H5OO• as an oxidant, PO is more beneficial with a low barrier compared to byproducts such as propanal, acetone, acetaldehyde, etc. These indicate that (a) gas-phase free radical reactions have important effects on PO generation, in which C3H5OO• is the main active species; (b) on MoOx surface, Mo=O is difficult to be used as the active O species for PO production. Further research is needed on other active sites such as Mo-O-Mo or defective sites. |
| Keywords: | Propylene Oxide (PO) heterogeneous-homogeneous reaction mechanism MoOx/SiO2 propylene epoxidation |