Dry reforming of methane with a Ni-based catalyst: a kinetic and thermodynamic analysis

The dry reforming of methane (DRM) was conducted using a Ni-SiO2 catalysts. It was evaluated the catalyst's stability within the temperature range of 973-1033 K under low spatial time conditions (kinetic regime) in the reactor. The catalyst deactivated more rapidly at high temperatures, contrary to the prediction based on chemical equilibrium calculations. To understand this behavior, it was investigated the impact of reactor operating conditions by simulating the reactor using a pseudo-homogeneous model and comparing the results with the chemical equilibrium prediction. The simulations revealed that, at high spatial times (W/FCH4), the reactions considered for the DRM process closely approach equilibrium. In contrast, at low spatial times, the reactive system deviates from chemical equilibrium, with the water gas shift and disproportionation of CO being the most favored. This results in increased coke production, which leads to faster catalyst deactivation. The effect is attributed to the kinetic inhibition of CO2 adsorption, hindering the activation of this molecule at high spatial time. The spatial time in the reactor, whether high or low, strongly depends on the intrinsic catalytic activity of the catalyst. Thus, when studying catalytic solids, the operating conditions of the reactor should be taken into account to avoid erroneous interpretations of the experimental data when evaluating their performance (for example, catalyst selectivity or resistance against deactivation by coke).