Optimization and Reaction Kinetics Studies on Copper-Cobalt Catalyzed Liquid Phase Hydrogenation of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran

In the present work, hydrogenation of biomass derived 5-hydroxymethylfurfural (HMF) into fuel additive 2,5-dimethylfuran (DMF) is studied over Cu-Co/Al catalyst. The influence of various operating parameters such as temperature, pressure, catalyst amount, time and HMF concentration on the conversion HMF to DMF was optimized using well known Taguchi method as statistical tool. According to Taguchi method, under optimum reaction conditions viz. temperature 220 °C, pressure 30 bar, reaction time 6 h, catalyst loading 0.5 g, and HMF concentration of 0.2 wt%, maximum DMF yield (87 %) was recorded. Analysis of variance suggested that temperature and pressure are the most influencing factor. Mechanistic study suggested that DMF can be obtained via C = O hydrogenation over Cu metal due to preferential adsorption of HMF on Cu metal which further undergoes acid catalyzed hydrogenolysis and resulted DMF. The initial rates of reaction HMF to BHMF varied linearly with hydrogen pressure at different temperatures, catalysts loading, and reactant substrate concentration. These observations indicate first order kinetics for HMF disappearance. According to power-law model, the order with respect to HMF was found to be 0.9. The experimental data could also be explained using Langmuir-Hinshelwood kinetics. A competitive hydrogen with dissociative adsorption on catalysts surface and surface reaction as the rate-controlling step provided the best fit of the experimental data.