Improving bifunctional zeolite catalysts for alkane hydroisomerization via gas phase sulfation

Pt-containing H-BEA zeolites were functionalized with sulfate anions via H2S chemisorption followed by oxidation. This treatment generates sulfate groups and Brønsted acidic sites, modifies the supported metal particles, and leads to higher activity and selectivity for pentane hydroisomerization. The strength and the accessibility of the acid sites present in the parent material were not affected by this procedure. The concentration of Brønsted acidic sites and the catalytic activity for light alkane isomerization varied sympathetically. The parallel increase in isomerization selectivity indicates that either the residence time of the alkoxy intermediates decreases for the modified samples (suppressing undesired cracking reactions on the acid sites) or the selective decoration of the Pt particles with sulfur reduces hydrogenolysis on the metal particles.