Post-synthesis alumination of MCM-41 by Al(NO{sub}3){sub}3 (I): improvement in acidity for purely siliceous MCM-41

摘要

The effects of post-synthesis alumination on purely siliceous MCM-41 material with Al(NO{sub}3){sub}3 on acidity have been studied by FTIR, NH{sub}3-TPD, and IPA decomposition reaction. The FTIR results of pyridine absorption show that both Lewis and Bronsted acid sites are increased by the post-modification. The amount of NH{sub}3 adsorbed on the alumina-modified MCM-41 samples increases with the loading of Al onto the surface of MCM-41. Due to the improved acidity, the alumina-modified MCM-41 materials show considerably higher catalytic activity for dehydration of isopropanol than purely siliceous MCM-41. In addition, XPD and N{sub}2 adsorption results show that all MCM-41 samples maintained their uniform hexagonal mesoporous structure well after they have been subjected to post-synthesis alumination with the loading of Al species on Si-MCM-41 varied from 0.1 wt. % up to 10 wt. % (calculated based on Al{sub}2O{sub}3).