The feasibility study of the octane-enhancing process: isobutylene dimerization using C4 mixture

The dimerization of isobutylene to diisobutylene in C4 mixture was evaluated using various catalysts such as nickel salts system, zeolite system and acidic ion exchange resin. There were shown that the strong acidic type ion exchange resin (Amberlyst 15) under 6 kg/cm2 and 60 degrees C gave rise to 90% conversion and more than 60% selectivity to diisobutylene with acceptable amounts of oligomer as a best catalyst. Therefore, Amberlyst 15 was employed to investigate the optimum reaction condition. In the batch reaction, since the catalyst activity was increased with the increasing reaction temperature, the reaction time should be shortened appropriately to prevent a high yield of oligomer. The reaction rate was increased by the increased amount of catalyst without much change in the product composition. The formation of oligomer was inhibited when a small amount of organic solvents (methyl tert-butyl ether) are attended. In the fixed-bed study, the results indicate that the increase in reaction temperature was accompanied by the increase in reaction rate, however, the selectivity to the dimer was affected. Higher WHSV will enhance the selectivity but reduce the conversion. Conclusively, the appropriate reaction condition was 45 degrees C with WHSV of 10.