Dimerization of isobutene to isooctene over NiO-WO3/Al2O3 catalysts

Abstract

NiO-WO3/Al2O3 catalysts were prepared by incipient wetness impregnation method. The catalytic performance was determined in the dimerization of isobutene under 150 ºC and atmospheric pressure. The effect of different weight percents of nickel and tungsten on the catalytic activity were investigated. The results showed that NiO-WO3/Al2O3 catalysts gave higher isobutene conversion and selectivity to isooctene than NiO/Al2O3 catalysts. Tungsten oxide increased the acidity of catalyst and improved the selectivity to isooctene. The 1Ni-4W/Al2O3 catalyst was the best ratio of nickel and tungsten that gave the highest catalytic performance. This ratio of nickel and tungsten was used in the study of different weight percents of silica in SiO2-Al2O3 supports and different preparation methods of alumina. The results in this part showed that the SiO2-Al2O3 support without metal gave higher yield to isooctene because silica-alumina possessed strong acid sites and higher total acidity of catalyst which increased the isobutene conversion. The 40SiO2-Al2O3 Al2O3 catalyst gave the highest catalytic performance. For the effect of different preparation methods of alumina including solvothermal, co-precipitation, and calcination from gibbsite, the 1Ni-4W/Al2O3-GIB catalyst gave the highest catalytic performance because calcination from gibbsite method improved the structure and acidity of catalyst that gave the high catalytic performance with low coke formation.