Heteropolyacid catalysts for hydroisomerization of n-hexane: Effects of alkali salt modification

12-Tungstophosphoric acid, H3PW12O40, and a series of its acid alkali salts associated with silica-supported platinum have been used as catalysts in t he hydroisomerization of n-hexane and compared with platinum-supported, app ropriately dealuminated mordenite. High selectivity toward isomerization wa s observed with both the heteropolyacid (HPA)-type catalysts and the morden ite at elevated conversions. The acid sites of the heteropolyacids/salts ex hibited an efficiency higher than that of mordenite, in line with the highe r acid strength of the former sites. Yet, despite their higher acid strengt h, heteropolyacids/salts showed a lower selectivity toward dimethylbutanes than mordenite. In addition, heteropolyacids, though more active than morde nite at low temperature, appeared to be only poor monofunctional isomerizat ion catalysts. (C) 2001 Academic Press.