Hydrogen production from cellulose, lignin, bark and model carbohydrates in supercritical water using nickel and ruthenium catalysts

In this study, the catalytic activity and hydrogen selectivity of Ni/alpha-Al2O3, Ni/hydrotalcite, Raney nickel, Ru/C and Ru/gamma-Al2O3 catalysts for hydrothermal hydrogen production from lignocellulosic biomass have been evaluated. The feedstocks included glucose, cellulose, fructose, xylan, pulp, lignin and bark The experiments were carried out at 380 degrees C in a batch reactor with 2 wt% feed concentration. It was found that the gasification of glucose, fructose, cellulose, xylan and pulp resulted in comparable gas yields (+/- 10% at 60 min), whereas lignin was substantially harder to gasify. Interestingly, gasification yield of bark which has a high lignin content was comparable to those of carbohydrates after 60 min reaction time. For a given feedstock, catalyst type affected both the gasification yield and the product distribution. Ni/alpha-Al2O3 and Ni/hydrotalcite catalysts were not only highly active for the gasification of carbohydrates, but also had better hydrogen selectivity when compared to Raney nickel, Ru/C and Ru/gamma-Al2O3. In particular, gasification of bark in the presence of these catalysts resulted in negligible amounts of alkanes. (c) 2012 Elsevier B.V. All rights reserved.