Supercritical water gasification of waste water produced from hydrothermal liquefaction of microalgae over Ru catalyst for production of H2 rich gas fuel

Abstract

Ru supported on activated carbon (C), Al2O3, CeO2, MgO, TiO2, and ZrO2 were prepared and employed to boost supercritical water gasification (SCWG) of microalgae hydrothermal liquefaction (HTL) downstream water at 600 °C for 1 h. Effects of catalysts, water density, and Ru/C loading on total organic carbon (TOC) reduction, carbon gasification efficiency (CGE), and gas yield were examined. All the Ru catalysts showed a positive effect on TOC reduction and converted organics in the HTL downstream water to fuel gas, with H2 and CH4 as the two most abundant component. With the addition of Ru/C, almost complete removal of TOC, the highest CGE, and H2 yield were achieved due to its largest metal dispersion. With the addition of Ru/C, increasing water density and catalyst loading favored TOC reduction and CGE increase as well as the total gas yield. The highest H2 content of 50% and yield of 2.62 mmol/g(aq.) were obtained at the highest catalyst loading of 12.0 mg(Ru/C)/mL(aq.). This study suggested that SCWG with the addition of Ru/C was a promising strategy to produce fuel gas rich in H2, from the organics in the microalgae HTL downstream water.