NEW CATALYST OF SO42- AL2O3-ZRO2 FOR N-BUTANE ISOMERIZATION/

The catalytic behavior of Al-promoted sulfated zirconia for n-butane i somerization at low temperature in the absence of H-2 and at high temp erature in the presence of H2 was studied. The addition of Al enhances the activity and stability of the catalysts for reaction at 250 degre es C and in the presence of H-2 significantly. After on stream for 120 h, the n-butane conversion of the catalyst containing 3 mol% Al2O3 ke eps steadily at 88% of its equilibrium conversion and no observable tr end of further deactivation has been observed. The difference in behav ior of the promoted and unpromoted catalysts at low and high temperatu re is associated with a change of reaction mechanism from bimolecular to monomolecular. Experimental evidence is presented to show that the promoting effect of Al is different from that of the transition metals . Microcalorimetric measurements of NH3 adsorption on catalysts reveal that the remarkable activity and stability of the Al-promoted catalys ts are caused by an enhancement in the number of acid sites effective for the isomerization reaction.