Preferential oligomerization of isobutene in mixtures of isobutene and 1-butene over 12-tungstosilicic acid supported on silica

H 4SiW 12O 40/SiO 2 shows high activity and selectivity for preferential oligomerization of isobutene in a mixture of isobutene and 1-butene. Here selectivity is defined as the fraction of isobutene converted against the total conversion. ▪ Preferential oligomerization of isobutene in a mixture of isobutene and 1-butene (molar ratio of 1:1) over H 4SiW 12O 40/SiO 2 was investigated with different loadings of H 4SiW 12O 40. The catalytic performance of H 4SiW 12O 40/SiO 2 was compared with those of typical solid acids, such as H-β, SiO 2-Al 2O 3, and SO 4 2−/ZrO 2. H 4SiW 12O 40/SiO 2 was superior in activity and selectivity for isobutene oligomerization (defined as the fraction of isobutene converted against the total conversion) compared to other catalysts. The activity was sensitive to the H 4SiW 12O 40 loading on SiO 2, reaching a maximum at around 40 wt.%, due to the change in the acid amount of the outermost surface as determined by temperature-programmed desorption of benzonitrile. The selectivity for isobutene oligomerization also changed with the H 4SiW 12O 40 loading. The highest selectivity (∼95%) was achieved using 10 wt.% H 4SiW 12O 40/SiO 2 at 293 K, due to the absence of strong acid sites on the outermost surface. In the conversion of linear butene (1- and 2-butene), an induction period occurred when 10 wt.% H 4SiW 12O 40/SiO 2 was used, because linear butene cannot adsorb on the acid sites when isobutene is present in the reaction mixture.