Tungsten catalysts supported on activated carbon - II. Skeletal isomerization of 1-butene

Tungsten catalysts supported on activated carbon were used in the isomeriza tion reaction of 1-butene. The results obtained were compared with those of other tungsten catalysts supported on Al2O3, SiO2, and TiO2. When the cata lysts supported on activated carbon were pretreated in He flow, at either 6 23 or 748 K, the activity to produce isobutene increased linearly with the surface acidity of the catalysts, and the specific activity after pretreatm ent at 623 K was higher than that after pretreatment 748 K. The activity to produce isobutene did not decrease with reaction time and no dimerization by-products were obtained. After the pretreatments at 973 and 1223 K, there was a loss of activity with reaction time, and by-products from the dimeri zation of butenes appeared. The presence of water vapor in the reaction mix ture was also studied. The catalysts supported on Al2O3, SiO2, and TiO2 and pretreated under the same conditions, at both 623 and 748 K, showed a decr ease in activity to produce isobutene with reaction time and the catalyst s upported on Al2O3 was the most active. Results show the importance of the s upport in these kinds of catalysts and seem to indicate that the activated carbon, due to its surface basicity, moderates the surface acidity of the t ungsten oxide particles. Therefore, with a lower surface acidity of the cat alyst it has an activity similar to that found with the Al2O3-W catalysts b ut without deactivation. (C) 2000 Academic Press.