Comparison of Kinetic Models for Biogas Steam Reforming Reactor Design According to Complexity and the Heat of Reaction Effect

Biogas reforming is being considered an alternative source of hydrogen and synthesis gas for gas-to-liquid technologies. In this context, our focus is on the rapid design of pilot-scale reactors based on simple and robust kinetic models. Thus, we present an evaluation of kinetic models of NiMo2C/Al2O3 for biogas steam reforming, sourced from sugar cane industrial residues, in Brazil. Comparing the NiMo2C/Al2O3 to catalysts from the literature (Ni/Al2O3, Ni/MgO). The models' complexity are taken into account according to the Akaike Information Criterion (AIC). Simple models are shown to be superior, with the simplest one being the best: a second-order power law model for CH4 and zeroth-order for water, which was validated considering the effects of reactor total pressure, temperature and feed H2O/CH4 ratio. Within model comparison, it was included for the first time─to the best of our knowledge, the effect of temperature variation caused by the heat of the methane steam reforming and water–gas shift reactions. The inclusion of the energy balance in the parameter estimation step improved the quality of the kinetic fit, providing strong evidence that the isothermal operation assumption, often used in differential reactors, may not always be true. In such cases, it is possible to extract kinetic parameters by adding the energy balance to the kinetic model. Finally, the model is applied to the simulation of a pilot scale biogas steam reforming reactor.