Nuclear chemistry

Methane

Catalysis

Engineering

Yield (engineering)

Metallurgy

Materials science

Cellulose

Autoclave

Inorganic chemistry

Chemical engineering

Supercritical fluid

Hydrogen

Organic chemistry

Chemistry

Carbon dioxide

Hydrogen production

Frontiers of Chemical Engineering in China

Cellulose, one of the important components of biomass, was gasified in supercritical water to produce hydrogen-rich gas in an autoclave which was operated batch-wise under high-pressure. K2CO3 and Ca(OH)2 were selected as the catalysts (or promoters). The temperature was kept between 450°C and 500°C while pressure was maintained at 24–26 MPa. The reaction time was 20 min. Experimental results showed that the two catalysts had good catalytic effect and optimum amounts were observed for each catalyst. When 0.2 g K2CO3 was added, the hydrogen yield could reach 9.456 mol·kg−1 which was two times of the H2 amount produced without catalyst. When 1.6 g Ca(OH)2 was added, the H2 yield was 8.265 mol·kg−1 which is lower than that obtained using K2CO3 as catalyst but is still 1.7 times that achieved without catalyst. Comparing with the results obtained using K2CO3 or Ca(OH)2 alone, the use of a combination of K2CO3 and Ca(OH)2 could increase the H2 yield by up to 2.5 times that without catalyst and 25% and 45% more than that obtained using K2CO3 and Ca(OH)2 alone, respectively. It was found that methane was the dominant product at relatively low temperature. When the temperature was increased, the methane reacts with water and is converted to hydrogen and carbon dioxide.

Hydrogen production by catalytic gasification of cellulose in supercritical water