Selective Synthesis of Renewable Diesel Fuel Precursors via C–C Condensation of Biomass-Derived Furans Using a Niobium Oxide Nanocatalyst
Mudavath Arun Kumar, Bhattu Swapna, Pavan Narayan Kalbande, Lavanya Yalagandula, Satyapaul A. Singh, Putla Sudarsanam
Abstract
The carbon–carbon (C–C) condensation of biomass-derived molecules represents a promising approach for the production of renewable fuel precursors. We developed a highly selective catalytic route for the C–C condensation of biomass-derived furans (furfural and 2-methylfuran) for the synthesis of a C-15 diesel precursor using a recyclable heterogeneous Nb 2 O 5 nanocatalyst at solvent-free conditions. The shape-engineering of Nb 2 O 5 particles (nanorods) and thermal treatment at 300 °C for 2 h (Nb 2 O 5 NR3) provided a higher concentration of acid sites with optimum Brønsted acid sites, which are the vital active sites for the condensation of furfural with 2-methylfuran. The X-ray photoelectron spectroscopy (XPS) studies showed the presence of more oxygen vacancy defects and electron-deficient Nb 5+ sites in the Nb 2 O 5 NR3 catalyst. By optimizing the reaction conditions, a 94% yield of C-15 diesel precursor with 99% conversion of furfural was achieved using the Nb 2 O 5 NR3 catalyst under mild reaction conditions. The versatile efficiency of the Nb 2 O 5 NR3 catalyst is showcased for the synthesis of diverse renewable diesel fuel precursors by using various substituted furans and benzaldehydes. The structure and morphological stability of the Nb 2 O 5 NR3 catalyst were elucidated by powder X-ray diffraction, XPS, and transmission electron microscopy studies. The good reusability of Nb 2 O 5 nanocatalyst for up to 5 cycles and sustainable green chemistry metrics show the practical feasibility of this catalytic approach for the C–C condensation of biomass-based furans.