Gas phase hydration of isobutene to tert-butyl alcohol on H4SiW12O40 as the catalyst

Catalytic hydration of isobutene in gas phase on solid dodecatungstophospho ric acid has been studied at 313-353 K hi a constant how microreactor. Besi des the main product tert-butyl alcohol (TBA) the isobutene dimer was detec ted in the gas phase the concentration of which increased with the space ti me and decreased with temperature. Selectivity to TEA was 40-80% depending on the conditions. The rate of isobutene conversion reached maximum at 328 K. Separate sorption experiments have shown that water vapour is rapidly so rbed by the whole volume of the catalyst while there is no such sorption of isobutene, which is adsorbed only on the surface. Based on these results q ualitative model of the reaction pattern was proposed including the formati on of carbenium ions on the surface. Subsequently they would react with wat er molecules supplied from the bulk of the catalyst. The latter is also the source of protons bonded by isobutene molecules. (C) 1999 Elsevier Science B.V. All rights reserved.