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.