Temperature-Programmed Desorption and Infrared Spectroscopic Studies of Benzene Adsorption in Zeolite ZSM-5

The adsorption and desorption of benzene over the zeolite H-ZSM-5 has been investigated using simultaneous Fourier transform infrared (FTIR)−temperature-programmed desorption (TPD) measurements. The adsorption was studied as a function of benzene loading and the Si/Al ratio of the zeolite. FTIR and TPD confirm the existence of two types of sites for the adsorption of benzene in H-ZSM-5: Brønsted and non-Brønsted sites, with the latter located at the center of the intersection voids. The Brønsted sites are the favored sites for adsorption, and adsorption on the non-Brønsted sites occurs only after these sites are filled. There is no evidence for clustering or interaction between benzene molecules adsorbed on either the Brønsted or non-Brønsted sites.