Influence of the activation temperature on the physicochemical properties and catalytic activity of La-X zeolites for isobutane/cis-2-butene alkylation

The influence of the activation temperature on the physicochemical properties and catalytic activity of La-X zeolites for isobutane/cis-2-butene alkylation was investigated. Under optimal activation conditions, molecularly adsorbed water was detected by in situ IR and 1H MAS NMR spectroscopy, as well as temperature programmed desorption. Bridging hydroxyl groups were not involved in hydrogen bonding of these water molecules. Isobutane/cis-2-butene adsorption together with isobutane/n-butene alkylation indicates that the water left on the catalyst after activation at 423–453 K promotes the rate of hydride transfer with respect to that of alkene addition. As a consequence, the catalyst lifetime in alkylation was shorter for the sample activated at higher temperatures (553 K) than for those having molecular water adsorbed in the zeolite pores.