Hydrotalcite supported bimetallic (Ni-Cu) catalyst: A smart choice for one-pot conversion of biomass-derived platform chemicals to hydrogenated biofuels

Abstract

The production of drop-in biofuels 2,5-dimethylfuran (DMF), 2,5-dimethyltetrahydrofuran (DMTHF) from biomass-derived hydrocarbons usually incorporates precious metals as a catalyst. Herein, we developed a bimetallic (Ni-Cu) supported on hydrotalcite (HT) catalyst and applied for catalytic hydrogenation of 5-hydroxymethylfurfural (HMF) and 2,5-bis(hydroxymethyl)furan (BHMF) to 2,5-dimethylfuran (DMF) and other valuable fuel additives at a relatively low temperature (85–130 °C) and pressure (6–20 bar). The effect of other process parameters like reaction time, solvent and catalyst loading on DMF yield was also investigated. Ni-Cu/HT was found to be exceptionally active and selective catalyst for hydro-deoxygenation of HMF to DMF and other high-energy furanics. Ni-Cu/HT was applied under mild reaction condition for hydrogenation of BHMF to DMF and 100% BHMF conversion and 83% DMF yield was obtained at 85 °C and 6 bar hydrogen pressure and 100 mg catalyst loading. 78% over-hydrogenated product (DMTHF) yield was observed at higher catalyst loading (200 mg) at 130 °C. The excellent activity of Ni-Cu/HT catalyst for hydrogenation and deoxygenation is attributed to synergistic-cooperation of Ni and Cu and metal stability owing to hydrotalcite support. Moreover, the acid-base properties of HT also contributed to superior activity of Ni-Cu/HT catalyst by facilitating HMF, BHMF and formic acid adsorption and activation and by promoting hydrogenolysis of C-O ester bond. A detailed characterization of as-synthesized Ni-Cu/HT by TPR, BET, XPS, TEM, HRTEM, FESEM, EDX, powder XRD and FTIR techniques was carried out to examine its structural and morphological features.