Study Of Isobutane/1-butene Alkylation Performance Over Al, Pt Promoted SO₄^2-/ZrO₂Catalysts

Iso-octane was an ideal component with high octane number in clean gasoline, which was now mainly produced by the alkylation between isobutane and1-butene with liquid acid. The alkylation with liquid acid had shortcomings such as corroding equipments and polluting the environment. However, alkylation process with solid acid was a good alternative to the traditional one due to its environmental friendly.The sulfated zirconia-based catalysts promoted with Al and Pt were prepared. The effects of the preparation conditions of Al-promoted SZ samples on the alkylation performance were investigated. The impact of the reaction condition on the catalytic performance was also studied. The physico-chemical properties were characterized. A correlation was established between catalytic activity and physico-chemical properties.The experimental results showed that the alkylation performance over sulfated zirconia-based catalyst which was prepared by shaping pseudo-boehmite with Zr(OH)4powder before impregnating sulfuric acid (denoted as ZA-S) was relatively better. As the Al content increased, the alkylation activity of the catalysts was improved while their cracking activity was decreased due to serious polymerization. In addition, the enhancement of calcination temperature of the sulfated carrier first led to an obvious increase in the cracking activity of Z5A-S and a decrease in the alkylation activity. The further rise of calcination temperature resulted in high polymerization activity and low alkylation activity. The alkylation activity descended to a great extent as the reaction temperature was raised. The suitable preparation conditions of catalyst were as follows:20wt%of Al content,500℃of calcination temperature of sulfated Zr(OH)4-Al(OH)3. The content of iso-octanes in liquid products reached to33%when reaction was conducted under an appropriate temperature of25℃. It could be concluded that the acid sites with medium acid strength were in favor of the alkylation between isobutane and1-butene. Besides, the addition of Pt improved the initial alkylation activity and lowered the initial cracking activity of Z5A-S, which might be related with the formation of large amount of n-butane.