Catalytic activities of bulk tungstophosphoric acid (HPW) and its supported forms on activated carbon were investigated in the vapor phase etherification reaction of isoamylene with ethanol in a continuous flow reactor. Tungstophosphoric acid (H3PW12O40 center dot 11H(2)O) was supported on activated carbon having a surface area of 796 m(2)/g, at two different loading levels (25% and 31%) by aqueous impregnation technique and the kinetic experiments were done in a temperature range between 353 and 370 K. Supported HPW catalysts containing the same amount of HPW yielded much higher conversion than bulk HPW at 353 K. Decrease of isoamylene conversion values with an increase in temperature on the supported catalysts was explained by the role of active carbon surface as a reservoir for the reactants. HPW was found to be highly immobilized on the active carbon surface keeping most of its activity after being excessively washed with ethanol. Results also indicated that activity of HPW was higher than the activities of both Amberlyst-15 and another heteropoly acid, namely molybdophosphoric acid. (C) 2007 Elsevier B.V. All rights reserved.