Using MAS NMR method to determine the geometry of the Bronsted acid, the distribution of aluminium atoms in ZSM-5 and ZSM-5/MCM-41.

Abstract

Z5M-5/MCM-41 composite was prepared by using a dual-template synthetic get svstern Tetrapropylamoniumhydroxit TPAOH and cetyltritmetylamoniumbromide CTMAB. The structure of that material was investigated by IR, XRD, TEM, and TPD-NH₃, and nitrogen adsorption/desorption [1]. The results of IR, XRD, NMR showed that the most of aluminum atoms distributed in the framework. In this paper, ²⁷Al, ¹H MAS NMR are used to determine the geometry of the Bronsted acid and the distribution of aluminum atoms in ZSM-5/MCM-41. Acidic(-bridging-) OH groups in ZSM-5/MCM-41 are responsible for the catalytic activity. They can exist ill materials infourfonns: SiOHAl (δ= 4,1 ppm), AlOH (δ = 2.7ppm), SiOH1 (δ = 1,8 ppm), and SiOH2 (δ = 2.2 ppm). Here, we call see the differences of acidities between ZSM-5 and ZSM5-/MCM-41 base on the signals of the formation of bridging OH groups (SiOHAl)