DEACTIVATION AND ACIDITY DETERIORATION OF A SIO2/AL2O3 CATALYST IN THE ISOMERIZATION OF CIS-BUTENE

The evolution of acidity of a SiO2/Al2O3 catalyst in the isomerization of cis-butene has been studied. The catalyst deactivation takes place by blockage of active sites by slightly evolved coke, which is partially soluble in dichloromethane and pyridine and is slightly aromatic. The blockage of active sites has no incidence on the porous structure and on the catalyst surface area. By combining the results for the catalyst in different deactivation states, corresponding to calorimetric and thermogravimetric measurements of tert-butylamine desorption at a programmed temperature, the evolution of the average value of acidity strength has been determined. In addition, from tert-butylamine adsorption measurements at 200-degrees-C, the evolution of surface acidity strength distribution has been attained. The fast deactivation of very strong acidic sites is concluded.