Biomass Hydrogen SCWG Gasification Magnesia Nickel compounds Oil palm frond Palm oil Specific surface area Supercritical water Supported catalyst CAO Catalysis Catalyst activity Catalyst selectivity Catalyst supports Catalytic gasification Catalytic performance Catalytic reactions Cell contraction Copper oxides Crystal structure Crystallite size Cubic crystal structures FRUIT BUNCHES GLUCOSE HYDROTHERMAL GASIFICATION Hydrogen production LIGNIN METAL-CATALYSTS