Study On The Isobutene Oligomerization

The hydrogenated diisobutene and triisobutene can be used as gasoline blending components to improve the octane number and reduce the lead content. Diisobutene is raw material of isononyl alcohol, tert-octyl phenol, pesticide emulsifier and polymerization degree regulator, triisobutene can be used to produce epoxy curing agents, lubricant additives, rust inhibitors and so on. As the oligomerization of isobutene has attracted considerable attention as a method to obtain diisobutene and triisobutene, it is of great importance to study the mechanism of isobutene oligomerization.For cationic oligomerization of isobutene, a variety of isomers will be produced by isomerization such as methyl group shift, hydride group shift and tail-to-tail coupling. Structures of isomers of diisobutene and triisobutene were deduced from the reaction mechanism. The quantum chemistry method was also used to predict the possibility of different isomers. Isobutene oligomerization took place in batch reactor in the presence of a strong acidic ion exchange resin Amberlyst-35. All products were analyzed by GC-MS method to confirm the results of the above theoretical analysis. It was found that there are five isomers in diisobutene, seven isomers in triisobutene and three isomers in tetraisobutene. This research provided a useful platform for further development of isobutene oligomerization.The kinetics of isobutene oligomerization was conducted in a batch reactor over a temperature range of313.15-343.15K in the presence of Amberlyst-35as catalyst and isooctane as solvent. Products are essentially dimers and trimers inspected by gas chromatography. A consecutive reaction based on Eley-Rideal mechanism was proposed through theoretical analysis and experimental research, and the kinetic equation of isobutene oligomerization was presented according to the mechanism. The activation energy for dimerization and trimerization in this model were156.49kJ/mol and110.02kJ/mol respectively. The influencing factors on the yield of triisobutene were mainly studied including the temperature and pressure. The experimental results showed that when the feed flow rate was1.2mL/min, the amount of catalyst was1g, the highest yield of triisobutene reached68.07%at pressure1.3MPa and temperature80℃.The differences between1-butene and isobutene oligomerization under the same experimental condition were also studied. The influence of catalyst on conversion of raw material, the structure and its yield of product were researched. This research supplemented and verified the mechanism of isobutene oligomerization.