Kinetic model for reactions of indole under supercritical water gasification conditions

• Simplifed network of indole SCWG.
• Detailed kinetic modelling of indole SCW.
• Reaction rate analysis of the model.

We developed a quantitative kinetics model for the homogeneous decomposition and gasification of indole in supercritical water at 550–650 °C based on a reaction network with 17 separate reaction pathways. The model accurately describes the effects of time, temperature, and initial concentrations on the concentrations of intermediate products such as aniline, toluene, and benzene as well as the terminal gaseous products such as H2, CH4, and CO2. Modeling revealed that three steps are most important for H2 production. Ring-opening of indole to form aniline is the fastest such step during the first few minutes at 600 °C, depletion of the large variety of gasifiable products dominates at times between 5 and 55 min, and water gas shift is the main H2-producing reaction at longer times. The model also revealed that some of the potential pathways were kinetically insignificant at 600 °C. Such paths included methanation, gasification of benzene, steam reforming of indole, and formation of CO, CO2, and C2H6 from intermediate products.