Promotive effect of hydrogen in n-hexane isomerization over Ni/PtHY catalyst

Abstract

Bifunctional catalyst containing 0.1 wt% Ni and 0.1 wt% Pt supported on HY were prepared by incipient wetness impregnation method. The properties of the catalyst were determined by XRD analysis and pyridine adsorbed FTIR spectroscopy. The catalytic activities were tested on n-hexane isomerization by pulse method in a microcatalytic reactor under atmospheric pressure in the presence of hydrogen or nitrogen carrier gas. XRD result showed the decrease of the crystallinity of PtHY after introduction of 0.1 wt% of Ni. While, the ratio of Lewis to Brønsted acid sites increased after the introduction of Ni on PtHY as evidenced by pyridine adsorbed FTIR spectroscopy. In the presence of hydrogen gas, 0.1 wt% Ni increased the yield of isohexane by about 24 % and decreased the activation energy from 124.1 to 111.2 kJ/mol at the temperature range of 403-423 K. In addition, the activation energy decreased to 48.3 kJ/mol for Ni/PtHY at high temperature range of 478-498 K. The presence of hydrogen as a carrier gas gave a promotive effect on the reaction which led to increase the formation of isohexane and suppress the cracking process. While, the presence of nitrogen as a carrier gas promoted dimerization of nhexane which formed the cracking products.