Characterization of Molecular Structure of Butene Oligomerization Products and Its Effect on Catalytic Cracking to Produce Propene
The reaction performance of C4 olefins was investigated using a small fixed fluidized bed catalytic cracker.Based on characterizing the molecular structure of butene oligomerization products,the paper studies the reaction modes in the catalytic cracking of oligomerization products and 1-octene,and also analyzes the influence of reaction temperature on the selectivity of propene.The experimental results show that the reactivity of 2-butylene is lower than that of 1-butylene and the conversion of butene is hardly higher than 70％over Y and ZSP zeolite catalyst.Both of the oligomerization products(denoted as OP-1 and OP-2)consist mainly of C8 olefins.Almost 90％of C8 olefins is trimethylpentene in OP-1,in which 2,4,4-trimethylpentene accounts for over 82％;dimethylhexene has a similar content with trimethylpentene in OP-2,dominated by dimethyl-2-hexene;the molecular structure of oligomerization products can affect β-cracking type,and trimethylpentene produces propylene and butene mainly through A-type cracking(3°→3°),while C8 olefins with few substituents prefer to produce propylene and butene via the cracking modes of B1(2°→3°),B2(3°→2°),C(2°→2°)and D2(2°→1°).Furthermore,high temperature can help propylene and butene to produce aromatic hydrocarbons via cyclization dehydrogenation reaction,and the catalytic cracking of oligomerization products can increase propylene production in a suitable temperature range(620-640 ℃).
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