Catalytic supercritical water gasification of glucose with in-situ generated nickel nanoparticles for hydrogen production

Abstract

Hydrogen production from catalytic supercritical water gasification of glucose with in-situ generated nickel nanoparticles in a quartz tube reactor is demonstrated. The effects of various operating parameters such as the presence of catalyst, resident time, reaction temperature and feed concentration on the gasification performances are studied. The results show that both the carbon gasification efficiency and the hydrogen gasification efficiency of glucose in supercritical water were improved with in-situ generated nickel nanoparticles as catalyst compared to those without catalyst. The catalyst promotes the water-gas shift reaction and CO methanation reaction, resulting in increased yields of H2, CH4 and CO2 and decreased yield of CO. At the presence of catalyst, 10 wt% glucose solution exhibits the best gasification performances at 500 °C. Highly dispersed nickel nanoparticles identified by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) are assumed to be generated via supercritical hydrothermal synthesis through hydrolysis, dehydration and in-situ reduction. However, the in-situ generated nano-nickel catalyst underwent an activation to deactivation transition due to carbon deposition on the surface of nickel nanoparticles. Regeneration strategies of the deactivated catalysts need further study for practical application.