Key words: isomerization, n-alkanes, zeolite catalysts
The skeletal isomerization of n-butane, n-hexane and n-heptane in the supercritical (SC) conditions is studied over H-forms of zeolites (mordenite, beta, ZSM-5) at 260÷450 °C and 80÷130 bars. The isomerization of n-hexane and n-heptane is accompanied by such side processes as oligomerization and cracking. Selectivity with respect to the formation of branched isomers of these hydrocarbons does not exceed 70 and 30 %, respectively. ZSM-5 is shown to be the most durable catalyst, however selectivity towards the formation of branched isomers does not exceed 30 % even at 260—280 °C; it decreases down to 3 % at 400—450 °C. The fraction of aromatization products in these conditions does not exceed 15 %. The effect of the addition of C6—C7 n-alkanes onto the isomerization of n-pentane over H-mordenite in SC conditions (260 °C, 120 bars) is studied. It is demonstrated that the gradual decrease of activity is due to the formation of higher hydrocarbons.
doi:10.1134/S1990793110070067