Oligomerization of isobutene on sulfated titania: Effect of reaction conditions on selectivity

On sulfated titania prepared by gelling titanium alkoxide with sulfuric acid, isobutene oligomerization was carried out under different operating conditions. Under severe conditions [temperature 140 °C, pressure 600 psi and weight hourly space velocity (WHSV) of 2.5 h^-1], the catalyst reached 100% isobutene conversion and selectivity for C12= and C18= olefins of 54 and 39%, respectively. Meanwhile, under soft conditions (28 °C, 100 psi and 10 h^-1), conversion decreased from an initial value of 55-25% after 30 h on stream, while the selectivity for C8= increased from 42 to 60%. After 90 h on stream, catalyst activity was recovered by introducing nitrogen into the feed and the conversion then reached 90%. These results show that by varying the operating conditions over a sulfated titania catalyst, isobutene oligomerization can be controlled to the desired C8= or C12= olefin yield.