ZSM-5 as a support for Ru-containing catalysts of levulinic acid hydrogenation: Influence of the reaction conditions and the zeolite acidity

Levulinic acid (LA) is a substance, which can be obtained from cellulosic biomass and hydrogenated to gammavalerolactone (GVL) - important platform chemical. This work describes the study of a ruthenium-containing catalysts synthesized by the impregnation of HZSM-5 having different silicate modulus (40, 80 or 400) with ruthenium precursor, which resulted in formation of oxidized Ru(III) and Ru(IV) species on the catalyst surface. Synthesized catalysts allowed more than 98% of LA conversion for 60 min of the reaction and 100% GVL selectivity while working at relatively mild conditions (100 degrees C, 1 MPa of H2) in aqueous medium. It was demonstrated that the observed catalytic activity mainly depends on two factors: (i) concentration of strong Lewis acid centers on the catalyst surface and (ii) surface content of RuO2, since the synthesized catalysts needed no preliminarily activation procedure.