A series of hierarchical H-MOR zeolites with different pore structure were designed and synthesized by alkaline and alkaline-acid post-synthesis methods. The catalytic performance of hierarchical H-MOR zeolite-supported vanadium oxide was investigated for dimethyl ether (DME) direct oxidation. Different pore structures apparently affect the distribution of oxidation product distribution, especially the selectivity of DMMx and CO. The formation of mesopores for 10%V2O5/deAlmm-H-MOR markedly improved the DMMx selectivity up to 78.2% from 60.0%, and more notably, CO selectivity dropped to zero compared to that of 10%V2O5/H-MOR. The hierarchical H-MOR zeolites were confirmed to be successfully prepared by the post-synthesis method. Due to the presence of mesoporous structure, the dispersion of vanadium oxide species was enhanced, which could improve the reducibility of vanadium oxide species and also make better contact with the acid sites of zeolite to exert the synergistic effect of the bifunctional active sites. More importantly, the creation of mesopores was proved to be favorable to the mass transfer of intermediate and products to avoid the occurrence of secondary reaction, which could effectively suppress the formation of by-products. This work is helpful for us to provide a novel insight to design the catalyst with suitable pore structure to effectively synthesize diesel fuel additives from DME direct oxidation.
Impact of Synthesis Method on Phase Transformations of Layered Lithium Vanadium Oxide upon Electrochemical (De)lithiation
