Studies Of A Mixed Butylenes Oligomerization Catalyst Derived From Ferric Sulfate And Nickel Sulfate

A great quantity of C4 alkenes is produced by refineries and petrochemical plants, but the chemical utilization rate of C4 alkenes is low. In recent years, oligomerization of C4 alkenes to synthesize higher alkenes which are high-value-added products has attracted much attention of investigators. So the development of oligomerization catalyst is very important. In this paper, Fe-Ni/γ-Al₂O₃, a member of mixed butylenes oligomerization was prepared by impregnation ofγ-Al₂O₃ with an aqueous solution of Fe₂(SO₄)₃ and NiSO₄.The effect of preparation conditions of Fe-Ni/γ-Al₂O₃ unmolded catalyst and molded catalyst were investigated. And the comparison of Fe-Ni/γ-Al₂O₃ catalyst and alumina-silica ball catalyst was also studied to find advantages and disadvantages of Fe-Ni/γ-Al₂O₃ catalyst. And the reason of the deactivation of Fe-Ni/γ-Al₂O₃ catalyst was also studied.The research showed that, the single Fe₂(SO₄)₃, NiSO₄ orγ-Al₂O₃ can not catalyze mixed butylenes oligomerization; the optimum preparation conditions of Fe-Ni/γ-Al₂O₃ unmolded catalyst were thatγ-Al₂O₃ was prepared by pseudoboehmite calcined under 500℃, the drying time was 7h, the Fe/Ni atomic ratio was 2:1, the SO₄2- loading is 1.4 mmol/g·γ-Al₂O₃, the mixture of H3PO₄ and NH4H2PO₄ was the best promoter; through NaOH poisoning, it was proved that the acid sites directly related to mixed butylenes oligomerization; the optimum conditions of catalyst molding were that the particle diameter of pseudoboehmite was less-than 40um, the W/P ratio was 2.25 ml/g, the time of kneading was 30⁴0min, the binder loading was 10w%, the mass fraction of peptizer was 12%; although the method of support molding was easy, but the stability of molded catalyst was very bad, because the separation of the active components from support was serious; Fe-Ni/γ-Al₂O₃ catalyst showed high activity in the initial period and good dimmer selectivity, its stability was not good;Through the regeneration experiment and the BET surface areas, it was proved that the coke formation caused the deactivation of Fe-Ni/γ-Al₂O₃ catalyst.