Partial oxidative gasification of sewage sludge in supercritical water with multi-component catalyst

A new -Mn-Cu- mixture catalyst with components of 50.9 wt% CuMn₂O₄, 46.1 wt% CuO and 3.0 wt% Mn₂O₃ was made by a co-precipitation method firstly. We adopted the multi-component catalyst together with activated carbon (AC) and Na₂CO₃ (N) for the first time to conduct supercritical water partial oxidative gasification (SWPO) of sewage sludge at 450 °C, 25 MPa, 0.3 of oxidation coefficient and 5 h of residence time, so as to improve H₂ production and organics removal. The results show that MnO₂-AC-N, CuO-AC-N and -Mn-Cu-AC-N could obviously improve H₂ yield and removal efficiency of organics in sewage sludge SWPO. At -Mn-Cu-AC-N conditions, H₂ yield and X_COD (removal efficiency of chemical oxygen demand) were 202.4 mL/L and 95.6 wt%, much higher than 48.7 mL/L and 86.2 wt% obtained without catalyst, respectively. The -Mn-Cu-AC-N catalyst seemingly had the best catalytic effect on gas formation as well as on organics removal in sewage sludge SWPO among MnO₂-AC-N, CuO-AC-N and -Mn-Cu-AC-N. Potential catalytic reaction pathways were proposed as well.