New approaches to immobilization of aluminium chloride on gamma-Al2O3

The method of preparation of AlCl3 catalyst immobilized on gamma -Al2O3 was investigated. AlCl3 generated by reacting CCl4 with pure gamma -Al2O3 at 5 00 degreesC and gamma -Al2O3 with bimodal meso- and macro-pore structure we re used as immobilizing agent and support, respectively, to prepare the cat alyst. The effect of various factors of immobilization conditions on cataly tic property in isobutene polymerization was examined. The catalyst, in whi ch the mass fraction of AlClx is about 7.5 and x=2.2, showed a high activit y, selectivity and stability, and no considerable differences in the cataly tic behavior were found in the following ranges: reaction temperature, 300 similar to 400 degreesC; reaction time, 0.5 similar to 4.0 h; flow of CCl4 of adding, 1.15 similar to2.01 mL/h for 15 mL gamma -Al2O3. Additionally, i t was shown that the catalytic property in isobutene polymerization is not only dependent on the nature of support, but also on its geometric structur e. Compared with the catalysts having micro-porous and meso-porous structur e which showed a poor stability, the catalyst with meso- and macro-pore bim odal structure exhibited a very high stability, and was supposed to be most suitable one, and it was ascribed to that in the case of the latter, harmf ul influence of intraparticle diffusion caused by "pore clogging" of large product molecules in the pore channel effectively reduced.