A Study On Preparation Of PAO Over Immobilized AlCl₃ Catalyst

The catalyst of AlCl₃ immobilized onγ-Al₂O₃ with meso- and macro-pore bimodal structure was prepared and investigated in the oligomerization of 1-decene in the suspension bed reactor. The effects of some parameters, including catalyst preparation method,γ-alumina pore structure, catalyst particle size, volume ratio of heptane to 1-decene, reaction temperature, single reaction time and solvent, on the activity and stability of catalyst were investigated. And the mechanism of deactivation of the immobilized AlCl₃ catalyst was discussed.The catalyst prepared by two-step method exhibited higher activity and excellent stability. 20-60 mesh of the catalyst with meso- and macro- pore is favorable, because it can increase diffusibility of products. The results indicate that lower reaction temperature is preferred to prolonging catalyst lifetime; longer reaction time, proper solvent and higher volume ratio of heptane to 1-decene are favourable to reaction progress, that promote diffusibility of reactants and products. It was observed that the stability of the catalyst is the best under the reaction conditions of heptane/1-decene (volume ratio) of 4, reaction temperature of 80℃, and single reaction time of 3 hours.The mechanism of deactivation of the immobilized AlCl₃ catalyst was discussed. Characterization of the deactivated catalyst indicated that the main reasons of the deactivation of catalyst in the oligomerization of 1-decene are not the loss of chloride immobilized on the catalyst, water, 1-decyne or thiofuran in feed. While 1-decene strongly combined with the active sites of catalyst by chemical adsorption is contributed to the deactivation of catalyst. It reduces the number of the active sites of catalyst, as a result the catalyst deactived easily.Al₂(SO₄)₃/γ-Al₂O₃ catalysts were prepared by impregnation and calcined in dry air at 400℃for 4 hours. The catalysts loaded with 10 wt. % of Al₂ (SO₄)₃ and ZnO (ZnO/Al₂(SO₄)₃ molar ratio of 1) showed high oligomerization activities for isobutene. Selectivity of dimer and trimer is 90% under the condition of 20℃, LHSV 4.0h^-1 and isobutene concentration of 22% and isobutene conversion of 97%.