Supported Palladium Catalysts for the Selective Hydrogenation of Furfural with Polymethylhydrosiloxane
M. Esther Medina Ruiz, Rocío Maderuelo‐Solera, Carmen P. Jiménez‐Gómez, Ramón Moreno‐Tost, Irene Malpartida, Cristina García‐Sancho, Juan Antonio Cecilia, Christophe Len, J. Mérida‐Robles, Pedro Maireles‐Torres
Abstract
A series of Pd-based catalysts supported on oxides with different acid–base properties has been prepared, characterized, and used for the valorization of furfural into value-added chemicals, with polymethylhydroxysiloxane (PMHS) as a reducing agent being an alternative to the use of hydrogen gas and alcohols as hydrogen donors. PMHS is a polymeric waste product of the silicone industry and is also recognized as a sustainable reductant for epoxide hydrosilylations and diastereoselective radical reduction in organic chemistry. Moreover, it is nontoxic, water/air insensitive, and soluble in most organic solvents due to its low viscosity. So, PMHS has been employed for the reduction of furfural in the presence of supported Pd catalysts. Although all catalysts tested are catalytically active, those supported on Al 2 O 3 and SiO 2 showed complete conversion after 30 min of reaction at 303 K, whereas 27.7% was attained using MgO as support. 1PdAl 2 O 3 (1 wt % Pd) catalyst was initially very selective to furfuryl alcohol (80.4% yield of FOL), which was hydrogenated to tetrahydrofurfuryl alcohol (THFA) at longer reaction times, reaching yields of 48.8 and 33.4% of FOL and THFA, respectively, after 6 h. By increasing the amount of Pd until 5 wt %, the reaction evolves toward the formation of more hydrogenated products (THFA), although the amount of nondetected products also increases. The best FOL productivity data has been achieved with 1PdAl 2 O 3, with a TOF value of 397 h –1 (mol FOL ·mol Pd –1 ·h –1 ) at 303 K after 30 min, with 180 μL of PMHS in ethanol, as solvent, while increasing both the amount of Pd to 2.5 wt % (2.5PdAl 2 O 3 ) and that of PMHS until 360 μL; under similar experimental conditions, 100 mol THFA mol Pd –1 ·h –1 can be produced.