Subcritical and supercritical water gasification of lignocellulosic biomass impregnated with nickel nanocatalyst for hydrogen production

Abstract

Advanced concepts in thermochemical biomass conversion are indispensable today for efficient generation of high-quality energy products. One of such strategies used in this study is the impregnation of nickel catalyst into lignocellulosic biomasses (pinewood and wheat straw) for hydrothermal water gasification. The nickel-impregnated feedstocks were gasified in subcritical and supercritical water to study the impacts of temperature (300, 400 and 500 °C), biomass-to-water ratio (1:5 and 1:10) and residence time (15, 30 and 45 min) at 23-25 MPa. The gasification of nickel-impregnated biomasses showed considerably higher total gas yields (9.5-16.2 mmol/g) and hydrogen yields (2.8-5.8 mmol/g) with greater carbon gasification efficiency (19.6-32.6%) when compared to non-catalytic gasification. Furthermore, hydrogen yields from nickel-impregnated biomasses were favored at an optimal temperature of 500 °C, biomass-to-water ratio of 1:10 and residence time of 45 min at 23-25 MPa. The nickel particles doped into the lignocellulosic matrix acted as nanocatalysts by providing active sites for enhancing hydrogen production in supercritical water. Copyright © 2016 Hydrogen Energy Publications, LLC.