Towards a low carbon economy via sorptionenhanced water gas shift and alcohol reforming

Hydrogen (H2) is one of the most important raw materials in the chemical and refinery industries. H2 is also regarded as a future “energy vector” due to its potential to act as an ultraclean fuel in the heat, power, and transport sectors. Therefore, development of efficient, low carbon routes to produce H2 is essential to meet its current and growing demand. In particular, this has placed an imperative on improving the efficiency of steam reforming of hydrocarbons (SRH), this process being considered the most feasible and economic route to large scale H2 production. The water gas shift reaction (WGS) is one of the most important stages of SRH, but is equilibrium limited and requires improvements in energy efficiency. In this study, we demonstrate that the overall efficiency of the WGS can be improved by removing CO2 in situ and co-feeding alcohols such as methanol and ethanol. The feasibility of this novel concept is investigated by conducting thermodynamic analyses of the alcohol reforming/WGS (alcohol-to-shift) reactions for H2 production alone and with simultaneous CO2 adsorption (sorption-enhanced, SEalcohol-to-shift). To this end, a non-stoichiometric approach based on the minimisation of the Gibbs free energy is used. The results show that adding alcohols to the feed facilitates autothermal operation of the shift unit and significantly increases the amount of H2 produced. The H2 productivity can be further enhanced by adsorbing CO2 in situ. The theoretical studies presented here are carried out under relevant operating conditions for SRH and aim to serve as a guideline for future work on alcohol-to-shift processes enhanced by adsorption.