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

Preferential oligomerization of isobutene in a mixture of isobutene and 1-butene (molar ratio of 1:1) over H4SiW12O40/SiO2 was investigated with different loadings of H4SiW12O40. The catalytic performance of H4SiW12O40/SiO2 was compared with those of typical solid acids, such as H-β, SiO2-Al2O3, and SO42−/ZrO2. H4SiW12O40/SiO2 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 H4SiW12O40 loading on SiO2, 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 H4SiW12O40 loading. The highest selectivity (∼95%) was achieved using 10 wt.% H4SiW12O40/SiO2 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.% H4SiW12O40/SiO2 was used, because linear butene cannot adsorb on the acid sites when isobutene is present in the reaction mixture.

H4SiW12O40/SiO2 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.Figure optionsDownload as PowerPoint slide