A comparative study of SiO2 supported Rh-Sn catalysts prepared by different methods in the hydrogenation of citral

The hydrogenation of citral(3,7-dimethyl-2,6-octadienal) on bimetallic silica supported Rh-Sn catalysts was investigated. The performance of the catalyst was evaluated under exactly the same conditions (5 MPa, 399 K) using different preparation methods, namely coimpregnation, successive impregnation, and an organometallic route. The organometallic-route catalyst was taken as the reference and its performance was in good agreement with those in the literature. All preparation methods create active sites suitable for the formation of unsaturated alcohols. The coimpregnated catalyst is shown to be as selective as the organometallic one. This performance could be attributed to an intimate contact between the metals. Temperature programmed reduction (TPR) profiles support the catalytic reaction results and reveal distinct interaction degrees for each catalyst. The coimpregnation appears as a potential method to prepare bimetallic Rh-Sn catalysts. (C) 2000 Elsevier Science B.V. All rights reserved.