Overgrowth of mesoporous MCM-41 on zeolite Y
The deep hydrodearomatization and desulfurization of diesel fuel is a very challenging task by conventional hydrotreating processes using conventional catalyst support. Based on the molecular dimensions for typical aromatics and sulfur-containing compounds in diesel fuel, a pore structure design was proposed for sulfur-tolerant catalysts used in the second stage for aromatics reduction. A novel molecular sieve composite Y overgrown with a thin layer of mesoporous MCM-41 was prepared. The as-synthesized samples were characterized with various techniques. The results indicated that this composite was different from the mechanical mixture of MCM-41 and NaY. The composite possessed a mesopore system as well as a microporous structure of zeolite Y. Moreover, the mesopore wall of the composite was built of a lot of secondary building units characteristic of zeolite Y, which was quite different from the amorphous nature of MCM-41 in the mechanical mixture. The hydrothermal stability was improved.