Alkylation of isobutane by ethylene catalyzed by chlorided alumina: influence of experimental conditions
Résumé
Chlorided alumina obtained by reaction of alumina with tetrachloromethane was tested as a catalyst for alkylation of isobutane with ethylene at 273–373K. The alkylate composition and the catalyst deactivation were examined under various experimental conditions. At high isobutane/ethylene ratios the catalyst was deactivated rather slowly. A high dilution of ethylene also favoured the production of hexanes versus octanes, isopentane and heavier products, however the primary products of alkylation were largely isomerized. Whatever the dilution of ethylene, the catalyst stability was improved when the reaction temperature was lowered to 273 K. Then the isomerization of the primary products was less pronounced. Increasing the catalyst mass led to better stability, hexane production was enhanced at the expense of heavier products. Alumina catalysts treated with various chlorinating agents (hexachloroethane, thionyl chloride, hexachloropropanone, hydrogen chloride) were also examined: no marked improvement in either stability or selectivity was noted. Added metal cations did not appear beneficial either.