Hydrogen production by catalytic gasification of cellulose in supercritical water

Cellulose, one of the important compositions of biomass, was gasified in supercritical water to produce hydrogen-rich gas in a high-pressure bath autoclave. K₂CO₃ and Ca(OH)₂ were selected as catalysts, and the reaction condition was controlled as follows: the temperature is 450-500°C, pressure ranges from 24-26 MPa and reaction time is 20 min. The experimental results show that two catalysts have good catalytic effect and each of them has its own optimum added amount for the gasification. Hydrogen production can reach 9.456 mol·kg^-1 when 0.3 g K₂CO₃ is added, which is 2 times the H₂ amount achieved when no catalyst is used. And the H₂ production of 8.265 mol·kg^-1 is achieved when 1.6 g Ca(OH)₂ is added, though it is worse than that when K₂CO₃ is used, it is 1.7 times the amount achieved when no catalyst is used. Comparing with using K₂CO₃ or Ca(OH)₂ alone, using the mixed catalyst composed of K₂CO₃ and Ca(OH)₂ can increase the H₂ production by 25% and 45% correspondingly. It was found that the methane production is dominant at relatively low temperature, and the methane might be converted to hydrogen and carbon dioxide by reacting with water when the temperature is increased.