Thermodynamic sensitivity analysis of CO2 reforming of methane based on equilibrium predictions

Abstract

Thermodynamic sensitivity analysis was conducted to evaluate the selectivity dry reforming of methane (DRM) with respect to other competing side reactions in terms of Gibbs energy minimization and equilibrium reactor compositions. Spontaneity of each reaction was evaluated by their corresponding changes in Gibbs energy as a function of reactor temperature from 100 - 1000 C. At temperatures above 700 C, all reactions considered with the exception of the Boudouard reaction are spontaneous due to their negative deltaG values. Equilibrium compositions were computed for 40 kmol of feed (CO2 + CH4) to determine its sensitivity to occurrence of reverse water-gas-shift (RWGS) reaction and changes in feed CO2/CH4 ratio. The presence of RWGS reaction results to higher reactant conversion accompanied by more severe carbon formation. The H2/CO ratio was however not affected by its occurrence. At CO2/CH4 feed ratio of 2, the product ratio was barely affected and at minimal carbon formation while CO2/CH4 ratio value of 0.5 produced a lot of carbon especially at high temperatures due to the prevalence of CH4 cracking. DRM is thus more preferable at temperatures above 700 C, devoid of RWGS and high feed CH4.