Noble metal free carbon encapsulated CoNi alloy catalyst for total hydrogenation of 5‐hydroxymethylfurfural to tetrahydrofurandiol in aqueous media

The selective hydrogenation of 5‐(hydroxymethyl)furfural (HMF) into 2,5‐bis‐(hydroxymethyl)tetrahydrofuran (BHMTHF) in flow reactor using water as a green solvent, has been achieved on a non‐noble metal catalyst based on monodispersed CoNi alloy nanoparticles covered by a thin carbon layer. The alloyed catalyst containing CoNi (molar ratio 1 : 1) was prepared in a one‐step synthesis following a hydrothermal method. Total conversion of HMF with 91 % selectivity to BHMTHF was achieved. The reaction network has been stablished, in which the carbonyl group of HMF is first reduced to alcohol giving the 2,5‐bis‐(hydroxymethyl)furan (BHMF) with an apparent activation energy of 25 KJ/mol, and then the double bonds of the furan ring are hydrogenated (apparent Ea=31 KJ/mol). Formation of byproducts, mainly proceed from furan ring opening and ring rearrangement processes of BHMF, promoted by water. BHMTHF resulted a compound highly stable under reaction conditions. The fixed bed flow reactor was maintained operational for 65 h without observing any loss of catalytic activity and selectivity.