Supercritical water gasification of phenol over Ni-Ru bimetallic catalyst: Intermediates and kinetics

Phenol is gasified in supercritical water at 400−500 °C under a pressure of 25 MPa over Ni-Ru bimetallic catalyst. Several liquid products including cyclohexanol, 2-methyl cyclopentanone, toluene, alkylphenol etc. are identified and possible reaction paths among them are proposed. Gaseous products consist of H₂, CH₄ and CO₂. We develop a quantitative kinetic model based on a simplified reaction network in which intermediates are lumped. The model accurately captures the trends of concentration variation for phenol and gaseous products. Steam reforming of phenol to form CO is the main source of H₂ and nearly all CH₄ is formed from methanation of CO under 450 °C. Concentration of H₂ is most sensitive to steam reforming to form CO₂ while steam reforming to form CO strongly affects CH₄ production at 450 °C. The model has predictive capacity when varying initial phenol loading while it lose some accuracy for a higher water density condition.