Catalytic Supercritical Water Gasification of Biomass for Hydrogen Production

Abstract

With a focus on rice husk, this study explores the possibilities of supercritical water gasification (SCWG) for the effective synthesis of hydrogen from biomass. Compared to conventional fossil fuels, biomass is a possible substitute, and SCWG provides an energy- and environmentally friendly method of producing hydrogen. The need to maximize catalytic efficiency and reduce this process's environmental impact is what motivates the study. The main focus is on Ni/eggshell catalysts, with the goal of filling up important information gaps about catalytic activity, stability, and the generation of clean hydrogen from biomass sources that are renewable. This research assesses the performance of Ni/eggshell catalysts in biomass SCWG and seeks to establish the suitable working conditions that would yield the highest levels of hydrogen with negligible levels of by-products. The catalyst synthesized with three loadings (5 wt%, 10 wt%, and 20 wt%) in the production of hydrogen in SCW at three different temperatures (370°C, 450°C, and 500°C) and two residence time (60 minutes and 80 minutes) Also, it reviews the Ni/eggshell catalysts in the aspects of activity, stability, and impact on the environment in SCWG. Ni/eggshell proved to be very active in SCWG of rice husk biomass especially with moderate loading of Ni, (10 wt% provided adequate active sites with least chance of particle sintering). According to the experiments, the best conditions for hydrogen production were the temperature 500°C; the residence time of 80 minutes, and the catalyst loading of 10 wt%. These conditions gave the highest gas yields and hydrogen content, and the least solid residues implied that the biomass was almost fully converted. The SEM and XRD studies revealed that there are no morphological changes, and the Ni particles were effectively dispersed and uniformly distributed on the CaO support, thus the catalytic activity was constant. According to the obtained FTIR and XRD results, the catalyst was stable in the course of the reaction.