Hydrogen production from glucose by supercritical water gasification with Ni/Zr(Ce,Y)O_2-Δ catalysts

Catalytic supercritical water gasification (SCWG) of glucose over Ni/Zr(Ce,Y)O_2-δ catalysts was conducted in a batch reactor at 500 °C, 23–24 MPa with 10 wt.% feed concentration. The catalysts were prepared by carbonate co-precipitation method and the effects of nickel molar content and CeO₂ loading on gasification performances were investigated. The catalytic gasification experiments with Ni_x/Zr_0.8Y_0.2O_2-δ (x = 0.1, 0.2, 0.3, 0.5, 0.7) (NZY) catalysts showed that carbon gasification efficiency increased gradually with the increase of nickel content, but hydrogen yield gradually increased then leveled off. The maximum hydrogen yield of 22 mol kg⁻¹, about 10 times of that without catalyst, was obtained with Ni_0.5/Zr_0.8Y_0.2O_2-δ (NZY582) catalyst, and carbon gasification efficiency and total gasification efficiency were 66% and 90%, respectively. In order to achieve higher gasification efficiency, the Zr(Y)O_2-δ support was modified by adding CeO₂. The results showed that using Ni_0.5/Zr_0.4Ce_0.4Y_0.2O_2-δ (NZCY5442) catalyst, carbon gasification efficiency reached 76%, about 15% higher than that of NZY582 catalyst, and methane yield increased by 1.9 times, while hydrogen yield decreased by 23%. Various characterization techniques were carried out on the reduced and used catalysts and it was found that the catalysts exhibited excellent hydrothermal stability and good anti-carbon deposition capability.