Experimental research on catalysts and their catalytic mechanism for hydrogen production by gasification of peanut shell in supercritical water

Abstract

Peanut shell, mixed with sodium carboxymethyl-cellulose, was gasified at a temperature of 450°C and a pressure range from 24 to 27 MPa with the presence of different catalysts, including K2CO3, ZnCl2 and Raney-Ni. The experimental results show that different catalysts have greatly different effects on the reaction. Gasification efficiency (GE), hydrogen gasification efficiency (GHE), carbon gasification efficiency (GCE), yield of hydrogen production \((Y_{H_2 } )\) and potential yield of hydrogen production \((Y_{PH_2 } )\) are applied to describe the catalytic efficiency. From the result of gaseous components, ZnCl2 has the highest hydrogen selectivity, K2CO3 is lower, and Raney-Ni is the lowest, but Raney-Ni is the most favorable to gasify biomass among the three catalysts, and its GE, GHE, GCE reach 126.84%, 185.71%, 94.24%, respectively. As expected, hydrogen selectivity increased and CH4 reduced rapidly when the mixture of ZnCl2 and Raney-Ni is used under the same condition. The optimization mixture appeared when 0.2 g of ZnCl2 was added to 1 g of Raney-Ni, 43.56 g·kg−1 of hydrogen production was obtained. In addition, the catalytic mechanisms of different catalysts were analyzed, and the possible reaction pathway was brought forward, which helped to explain the experiment phenomena and results correctly.