Production of Alcohols from Cellulose by Supercritical Methanol Depolymerization and Hydrodeoxygenation

The reaction pathway and products of cellulose supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHDO) were investigated. Monoalcohols, diols, alcohol ethers, and methyl esters were produced from cellulose at 300 degrees C with a CuMgAI mixed metal-oxide catalyst. Time course experiments show that cellulose is rapidly solubilized and depolymerized within 1 h with C-2-C-4 diols being intermediates. Experiments with glucose - C-13(6) show that methanol is incorporated in all liquid products accounting for approximately 30-40% of the carbon in these products. Experiments with model compounds (dihydroxyacetone, isosorbide, and S-hydroxymethylfurfural) indicate that the reaction pathway for cellulose occurs primarily through retroaldol condensation of solubilized cellulose followed by recondensation with methanol. Methanol produces H-2, CO, and CO2 through reformation with 30% of the generated H2 being incorporated into the liquid products. Analysis of the liquid products with Fourier transform ion cyclotron resonance MS (FT-ICR MS) measured C-7-C-12 partially oxygenated species with 2-6 double bond equivalence which could not be detected via gas chromatography (GC). We conclude that the reaction pathway occurs through rapid solubilization and depolymerization of cellulose followed by retro-aldol condensation to C-2-C-4 oxygenates. Retro-aldol condensation products undergo hydrodeoxygenation and extensive carbon-carbon coupling to produce C-2-C-7 alcohols or other oxygenates.