The comparison of two classes of bifunctional SBA-15 supported platinum-heteropolyacid catalysts for the isomerization of n-hexane

Mono- and bifunctional catalysts composed of silicotungstic acid (H4SiW12O40) and/or platinum nanoparticles supported on SBA-15 mesostructured silica were comparatively tested for the isomerization of n-hexane. Monofunctional catalysts were produced by impregnating the SBA-15 support with either H4SiW12O40 or the platinum particle precursor, H2PtCl6. In the bifunctional catalysts, both metallic and acidic functions were combined either by mechanically mixing the monofunctional solids yielding a multiphase bifunctional material (HSiW/SBA-15 + Pt/SBA-15), or by dual impregnation of H4SiW12O40 and Pt within a single material leading to the monophasic bifunctional catalyst, HSiW/Pt/SBA-15. These hybrid materials, with the exception of the monofunctional platinum catalyst, were all active for the gas-phase isomerization of n-hexane. The two bifunctional catalyst systems showed high activity and selectivity for branched isomers with no catalyst degradation over 3 days of reaction.