Dynamic modification of H+ active sites from molecular hydrogen on Zn loaded HZSM-5 was studied by IR spectroscopy of adsorbed pyridine. By heating in the presence of molecular hydrogen, H+ active sites were formed with a concomitant decline of Lewis acid sites. The Lewis acid sites began to convert into H+ active sites at 348 K and the number of H+ active sites increased by increasing the heating temperature. The activity of HZSM-5 catalyst was tested on the hydroisomerization of pentane
