Oriented Conversion of a LA/HMF Mixture to GVL and FDCA in a Biphasic Solvent over a Ru Single-Atom/Nanoparticle Dual-Site Catalyst

Abstract

The industrial use of lignocellulose is limited by the copresence of C5 and C6 carbohydrates in this feedstock and the low selectivity of the corresponding catalytic conversion reaction, which collectively result in suboptimal product yields and necessitate energy-intensive purification/separation processes. Herein, we designed a composite dual-site Ru single-atom (SA)/Ru nanoparticle (NP) catalyst for the hydrogenation of levulinic acid (LA) and the oxidation of 5-hydroxymethyl furfural (HMF) in a biphasic solvent (γ-valerolactone (GVL)-saturated aqueous Na2CO3). Ru-SAs activated LA, while Ru-NPs boosted H2 dissociation to promote the hydrogenation of LA to GVL and ensured the efficient oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). The SA/NP site design increased the oriented conversion efficiency of complex substrates, and the alternate hydrogenation–oxidation process ensured the stability of catalyst activity. The biphasic solvent system not only facilitated the mass transfer process but also allowed the spontaneous and non-energy-intensive separation of the produced GVL and FDCA. The obtained results pave the way for the design of SA/NP dual-site catalysts for the one-pot oriented conversion of complex substrates and the facile separation of products.