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 degrees C, pressure 600 psi and weight hourly space velocity (WHSV) of 2.5 h(-1)], the catalyst reached 100% isobutene conversion and selectivity for C-12(=) and C-18(=) olefins of 54 and 39%, respectively. Meanwhile, under soft conditions (28 degrees 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 C-8(=) increased from 42 to 60%. After 90 It 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 C-8(=) or C-12(=) olefin yield. (c) 2005 Elsevier B.V. All rights reserved.