New approaches to immobilization of aluminum chloride on γ-alumina and its regeneration after deactivation

Abstract

The preparation of an AlCl3 catalyst immobilized on γ-Al2O3 and its regeneration after deactivation have been studied. AlCl3, generated by reacting CCl4 with γ-Al2O3, was carried by N2 to a reactor containing the γ-Al2O3 support. The immobilized AlCl3 catalyst with meso- and macro-pore bimodal structure was shown to be suitable for isobutene oligomerization. The amount of AlCl3 immobilized on the support in terms of AlCl x (x = 2.2) was 7.5 wt%. The catalyst exhibited excellent catalytic properties for isobutene polymerization under mild conditions. The average molecular weight of the product was 1000–2500, and its distribution was narrow, around 2.0 in the reaction temperature range 10–40 °C. This catalyst showed nearly perfect reactive specificity to isobutene polymerization and remarkable stability. After 2000 h of continuous running, the conversion dropped from 99 to 57%, the selectivity was maintained with little change at about 90%, and the average molecular weight was within the range 1000–1200 under the conditions T = 32 ± 1 °C, LHSV = 2.0 h-1, and P = 1.0 MPa. Reneration of the deactivated catalyst was satisfactorily accomplished by treating the used catalyst with a saturated solution of AlCl3 in CCl4 either in situ or ex situ. The activity recovery can be as high as 96%, and the deactivated catalyst can be regenerated repeatedly.