Paraffin isomerization catalyzed by polymer-supported superacids

Abstract

Solid superacids were prepared by the reaction of metal-halide Lewis acids with macroporous sulfonated poly(styrene-divinylbenzene), and a supported trifluoromethanesulfonic acid was prepared on the unsulfonated support. These polymers were used to catalyze the isomerization and dehydrogenation of n-butane in a flow reactor at 60–120 °C and 0.54 bar butane partial pressure. The catalysts were active in the presence of small amounts of HCl co-catalyst (the reaction rates being about 2 × 10 −9 mol/g · s for the most active catalysts), but rapid deactivation resulted from loss of hydrogen halide. Catalysts prepared from SnCl 4 and TiCl 4 were relatively inactive in comparison with those prepared from SbF 5 and BF 3; the catalysts prepared from AlCl 3 were as active as those containing fluorine and more stable. The activities of the catalysts are compared to the acid strengths of unsupported conjugate Lewis-acid analogs indicated by the Hammett acidity function.