Porous LaFeO3 Prepared by an in Situ Carbon Templating Method for Catalytic Transfer Hydrogenation Reactions

Catalytic transfer hydrogenation is an attractive route for the synthesis of biomass-derived chemicals. However, development of efficient, low-cost, and stable catalysts for that reaction is still a challenge. Here, we report on the preparation and testing of a non-noble perovskite oxide (LaFeO3) catalyst synthesized by an in situ carbon templating method. We show that our catalyst is quite active and selective toward the hydrogenation of unsaturated organics. Compared to an analogous LaFeO3 catalyst prepared by a more traditional method, using citric acid, the new LaFeO3 exhibited a more porous structure, a La-enriched surface composition, and abundant oxygen vacancies, all characteristics that improve contact with the reactants. In the case of the conversion of furfural to furfuryl alcohol (FOL) using iso-propanol as hydrogen donor, the new LaFeO3 showed a furfural conversion of 90% and a selectivity to FOL of 94%, significantly higher than with the reference LaFeO3 prepared by the traditional sol-gel method (60 and 91%, respectively). Moreover, our new LaFeO3 catalyst can be recovered after a calcination treatment, with no appreciable changes in its structure or activity, a test that we repeated six times, and can promote the hydrogenation of other carbonyl compounds containing electron-withdrawing groups. A reaction mechanism is proposed in which metal cations are the adsorption sites for iso-propanol and oxygen vacancies are the adsorption sites for furfural, and where the conversion proceeds following an acid-base mechanism. We believe that the novel use of perovskites as catalysts for hydrogenation reactions reported here may be easily extendable to other processes, and that our carbon-templating synthetic approach offers a way to synthesize viable perovskite catalysts with high surface areas for optimized activity.