Promotion of catalytic performance by adding chromium into HZSM-5 zeolite catalyst for methyl mercaptan catalytic conversion

Abstract

The modified HZSM-5 zeolite by Cr with different loadings were prepared by incipient-wetness impregnation method and were used to catalytic conversion of CH3SH. The results suggested that the presence of Cr improved activity and stability for CH3SH catalytic conversion, the improved catalytic activity of the Cr-modified HZSM-5 catalysts could be closely associated with their increased reducibility, high adsorption capacity and easily activated of CH3SH. Furthermore, the introduction of Cr enhanced the stability of the Cr-HZSM-5 catalyst because these added Cr could offer an oxidizing character to reduce the carbonaceous deposits species. The added Cr species were highly dispersed on the HZSM-5 support when the loaded Cr content was lower than 2 wt%. A small amount of Cr species were located into the microporous at the 2 wt% Cr loading, which did not show significantly influence on the reducibility of the catalysts, and the activity of 2%Cr-HZSM-5 catalyst was slightly higher than those of other Cr-modified catalysts. However, it was found that at high Cr loding (5 wt%), the formation of Cr2O3 crystalline phase and the blocking pores by Cr species lead to the decrease of the reducibility of the catalysts, which caused the Cr-supported HZSM-5 catalyst exhibited no improvement in the activity.