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 partia lly 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 cat alyst 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 adsorp tion measurements at 200-degrees-C, the evolution of surface acidity s trength distribution has been attained. The fast deactivation of very strong acidic sites is concluded.