Abstract:

The ZSM-11 zeolites with micro-meso porous were modified by Ag species, followed by incipient impregnation to prepare catalysts. The modified zeolites and catalysts were characterized by XRD, FT-IR, NH3-TPD, UV-Vis and N2 adsorption-desorption. The results indicated that small amounts of Ag had little influence on the structure of ZSM-11. Ag+, Agn+ and Agm were the main states of Ag on modified ZSM-11 zeolites. Besides, Ag species affect the acidity of the samples and increase the strong Lewis acidity. The heavy oil catalytic cracking performance of the catalysts was investigated in a fixed micro-reactor. The results indicated that the addition of small amount of Ag can enhance greatly the hydrothermal stability and the catalytic activity. However, larger Ag loadings favore the formation of dry gas and coke due to more strong Lewis acidity formed, resulting in the decrease of selectivity to light olefins.

Key words: ZSM-11, silver modification, catalytic cracking, hydrothermal stability