Transformation of n-hexane over EUROPT-1: fragments and C6 products on fresh and partially deactivated catalyst

Abstract

The reactions of n-hexane have been studied on 6.3% Pt/SiO₂(EUROPT-1) at different hydrogen and n-hexane pressures, and at 543–633 K, over fresh catalyst and over catalysts deactivated by long runs. Turnover numbers are compared with literature data: the differences are attributed to hydrogen pressure effects. Deactivation influences first of all, selectivity. In addition, the ‘depth’ and ‘pattern’ of hydrogenolysis have been determined. At low temperature multiple splitting seems to be favoured. Isomerization gives predominantly 3-methylpentane. At medium temperatures, isomerization, C₅-cyclization and internal splitting prevail; their ratio is controlled by the hydrogen pressure. The ratio of 2-methylpentane to 3-methylpentane is related to the ratio of internal to terminal rupture. Terminal splitting prevails at highest temperature. Aromatization increases with temperature but seems to be independent of the other reactions. The results are interpreted in terms of three different surface states. These correspond to Pt—H, Pt—C—H and Pt—C under increasing severity of conditions.