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 carboxymethylcellulose, 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_H2 ) and potential yield of hydrogen production (Y_PH2) 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 G_E, G_HE, G_CE 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 pro duction 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.