MTBE SYNTHESIS ON PARTIALLY ALKALI-EXCHANGED HY ZEOLITES

The influence of the acid strength of zeolites upon gas-phase formatio n of MTBE from methanol and isobutene was studied detached from other parameters such as structure, framework composition, and site density. A series of partially ion-exchanged HY zeolites which had been ion-ex changed to the same extent by Li, Na, and Rb was used, yielding materi als with similar concentrations of protons but different acid strength s. All zeolites exhibited similar initial activities for the formation of MTBE at temperatures below 100-degrees-C, although for other acid- catalyzed reactions such as 1-butene isomerization an increase in the activities with increasing acid strength of the zeolites had been prev iously observed. Steady-state activities, however, were found to be st rongly influenced by the different deactivation behavior of the invest igated samples. For the partially Rb-exchanged sample, blockage of por es (probably by isobutene oligomers) caused an expressed decrease in r ate of reaction during the first 30 min on stream. The presence of exc ess methanol in the pores is regarded as a possible cause for the simi larity of the initial reaction rates. (C) 1994 Academic Press, Inc.