distributionofmoinmozsm5catalystpreparedbyimpregnationmethod

Abstract

The Mo/ZSM-5 catalyst sample with 6 % Mo loading prepared by impregnation method has been proved to be the best catalyst for methane non-oxidative aromatization. In this paper, the distribution of Mo species in 6 % Mo/ZSM-5 was focused on. The crystalline structure of Mo/ZSM-5 was determined by XRD and refined by Rietveld method. The results revealed that the Mo species had three states in the Mo/ZSM-5 catalyst. One kind of Mo species, Mo5O12(6+), situated at the channel of ZSM-5 zeolite. There was about 0.4 of Mo5O12(6+) unit per cell of ZSM-5 zeolite on the average. These units neutralized a number of B acid sites. As a result, the B acid sites of the Mo/ZSM-5 catalyst decreased obviously compared with the parent HZSM-5 zeolite By contraries, the amount of L acid sites increased slightly in the Mo/ZSM-5 catalyst. The Mo in Mo5O12(6+) units was about 3.03 % of Mo/ZSM-5 crystals in mass fraction. The other two kinds of Mo species, alpha-MoO3 and amorphous Mo oxides, distributed on the external surface of the Mo/ZSM-5 crystal and modified it