Synthesis factors affecting the catalytic performance and stability of Ru/C catalysts for supercritical water gasification

Abstract

Catalytic supercritical water gasification of isopropanol (450 °C, 30 MPa) over Ru/C catalysts was carried out in a fixed-bed plug flow reactor. In the absence of Ru, isopropanol decomposed to solid carbon (coke), and H₂ over the carbon support. The Ru/C catalyst was able to gasify efficiently 10 wt% isopropanol over a period of 96 h at WHSV_gRu = 1228 g_Org g_Ru⁻¹ h⁻¹ with the gas composition close to the calculated thermodynamic chemical equilibrium. The catalyst lifetime was affected by the decomposition of isopropanol to solid carbon (coke) over the carbon surface that progressively filled up the pores of the activated carbon and this resulted in a covering of the Ru nanoparticles (NPs). The Ru dispersion (D) was found to be a relevant parameter. The 0.5% Ru/C (D = 0.26) was more active than the 2% Ru/C (D = 0.14). The influence of the solvent (acetone vs. water) used during the catalyst impregnation was studied and the turnover frequency (TOF) was twice as high for the Ru/C catalyst prepared with acetone. The higher Ru dispersion and the lower content of residual chloride obtained for the catalyst prepared with acetone were both responsible.