Highly selective etherification of fructose and 5-hydroxymethylfurfural over a novel Pd-Ru/MXene catalyst for sustainable liquid fuel production

Sustainable liquid fuel production from bio-oil compounds has attracted considerable attention in recent years. The catalytic etherification of 5-hydroxymethylfurfural (HMF) to ethoxymethylfurfural (EMF) is an effective approach for the production of liquid fuels. However, the development of high-performance and chemically stable catalysts has remained challenging. In this work, ultra-small Pd-Ru NPs were successfully immobilized on the surfaces of 2D MXene nanosheets (Pd-Ru/MXene) via fish sperm DNA-assisted microwave process. HR-TEM imaging results with SAED analysis showed that the hexagonal closed-pack (hcp) Pd-Ru NPs were grown on the surfaces of sheet-like MXene, thus enhancing the specific surface area of 117 m² g⁻¹ and providing a higher density of the acid-base sites. Furthermore, Pd-Ru/MXene was employed for the etherification of HMF into EMF. The results showed that the Pd-Ru/MXene catalyst exhibited 98% EMF yield and 100% HMF conversion with the prolonged usage of catalyst for five consecutive reuse cycles. Additionally, fructose was directly converted into EMF with a higher yield of 82% over the Pd-Ru/MXene catalyst at lower reaction conditions. The recyclability test of the used Pd-Ru/MXene catalyst demonstrated its chemical stability under prolonged usage for several hours and is therefore suitable for commercial renewable liquid fuel production. Novelty Statement: The catalytic transformation of biomass into diesel-miscible biofuel is a sustainable route for liquid fuel production and has recently attracted massive attention. The chemically stable and high-performance Pd-Ru/MXene catalyst was successfully prepared and characterized. The study demonstrated that the Pd-Ru/MXene catalyst exhibits superior catalytic activity toward the direct conversion of fructose and 5-hydroxymethylfurfural (5-HMF) into 5-ethoxymethylfurfural (5-EMF), which is a promising conversion method for the production of biofuels from biomass.