Determination of active centres in Re2O7-Al2O3 metathesis catalysts by titration method

A chemisorption technique has been developed for the quantitative determina tion of active centres in Re2O7-Al2O3 metathesis catalysts. Butene-2 and et hylene were used as chemical probes to generate metal-carbene species on th e active centres of the catalyst and eventually propylene as product. Catal ysts with metal loading from 2% to 8% Re were shown to contain active centr es in an amount equivalent to 0.6-2.2% Re/g catalyst. Catalysts prepared in hydrochloric acid medium contain about 5% more active centres than those p repared in aqueous medium, as measured by metathesis of propylene. It was a lso demonstrated that the surface area of the support could further influen ce the activity of the catalysts. (C) 2000 Elsevier Science B.V. All rights reserved.