Oxidative condensation/esterification of furfural with ethanol using preformed Au colloidal nanoparticles. Impact of stabilizer and heat treatment protocols on catalytic activity and stability

The oxidative condensation of furfural and ethanol has been studied using supported gold colloidal nano particles. The influence of the nature of stabilizer (polyvinylalcohol, polyvinylpyrrolidone), the choice of thermal treatment and washing for removing the stabilizer, on the catalytic performance has been evaluated. Variation of the mean gold particle size and surface coverage of the gold nanoparticles onto the support surface were achieved by modifying the stabilizer to Au weight ratio. Thus, the mean gold particle size was varied in the range of 3-8 nm. The catalytic results showed that the choice of stabilizer, the stabilizer to Au weight ratio, thermal treatment of the catalyst, affect catalytic activity and selectivity/yield to the desired products. When PVA was the chosen stabilizer, the highest yield to furan-2-acrolein (33%) was attained with a PVA to Au weight ratio of 2.4. On the contrary, when PVP was the stabilizer, the best catalytic performance was achieved in its absence, with the yield of furan-2-acrolein reaching 21%. These results showed the strong impact of stabilizer to control catalytic activity and to enhance, in the case of PVA, the yield to the target product, whereas a strong negative effect was observed with PVP. Moreover, a mild thermal treatment of the catalyst and a washing step for the removal of the stabilizer from the catalyst had a positive effect on the catalytic performance.