Kinetics and Reaction Engineering Aspects of Syngas Production by the Heterogeneously Catalysed Reverse Water Gas Shift Reaction

As a contribution to the development of a process for CO2 utilisation and/or syngas production, the catalytic hydrogenation of CO2 using commercial Ni/Al12O19 and Al2O3 catalysts was studied. The experiments were performed in a down-flow fixed bed quartz reactor at atmospheric pressure. The reverse water gas shift (RWGS) reaction was examined in both the forward and reverse direction. In addition to these experiments, the consecutive reaction of CO to CH4 was also studied. The results indicate that the Ni/Al12O19 and the Al2O3 catalyst used are suitable to convert CO2 with H2 to CO and H2O at temperatures higher than 800 °C where no CH4 formation was observed. Kinetic data was obtained by systematic variation of the reaction conditions. These data were used to develop a model which explains the intrinsic and the effective kinetics (influence of internal and external diffusion) of the respective reaction. Based on the kinetic data of the RWGS reaction over the Ni/Al12O19 and the Al2O3 catalysts, technical fixed-bed reactors were simulated for the production of syngas, using a one-dimensional reactor model. The model takes into account the intrinsic kinetics, the internal and external mass transfer and the concentration and temperature gradients only in axial but not in radial direction. Two cases were considered as attractive for a technical RWGS process, isothermal and adiabatic operation in a fixed-bed tubular reactor. The differential equations for mass and heat transfer were solved by using the program Berkeley Madonna. The simulated temperature and conversion profiles within the reactor are presented. Pressure drop as well as reactor size required in a technical adiabatic fixed bed RWGS reactors were also estimated for both catalysts