SKELETAL ISOMERIZATION OF 1-BUTENE TO ISOBUTENE OVER MG-ZSM-22

ZSM-22s, ion-exchanged with various cations, were prepared and examine d as catalysts with respect to the skeletal isomerization of 1-butene to isobutene in a continuous flow reactor. Mg-ZSM-22 gave the best yie ld for isobutene. The order of the catalysts with respect to the yield for isobutene was proportional to the ratio of Lewis acidity to Brons ted acidity. The Lewis acid site was found to be responsible for impro vement in catalytic activity, as well as suppression of coke formation . The role of Lewis acidity in the skeletal isomerization of 1-butene was confirmed by experiments involving the addition of water to the fe ed. The effect of impregnated boron or phosphorus was clearly observed . Phosphorus poisoned not only the strong acid sites, but also the act ive sites responsible for the skeletal isomerization of l-butene, whil e boron mainly poisoned the strong acid sites, which resulted in a dec rease in side reactions and an increase in isobutylene selectivity. (C ) 1997 Elsevier Science B.V.