Reverse Boudouard reforming produces CO directly suitable for the production of methanol from CO₂ and CH₄

We report the development of a novel process for the production of CO from CO2 and CH4, with CO suitably pure for use in conventional low-pressure methanol synthesis processes over Cu-ZnO-Al2O3 catalysts. The experimentally achieved yield of 3.07 molCO molCH4- 1 is substantially higher than the 2 molCO molCH4- 1 that is produced, at best, by the dry reforming process. We demonstrate the production of 84-mol%-pure CO (the remainder being CO2) for the first time without any dilution gas or further gas separation required. The syngas prepared by the addition of hydrogen is directly suitable for methanol synthesis, with a stoichiometric number (S = (H2 - CO2)/(CO + CO2)) of 2.05 and a CO2 concentration < 5 mol%, which is achieved in a single packed-bed reactor operated in a cyclic manner. Each cycle consists of two steps, with the CH4 reactant fed in the first step, and the CO2 reactant fed in the second step. After each step, the direction of the gas flow is reversed. Methane cracking produces solid carbon and gaseous H2 in the first step, which is then oxidised by the lattice oxygen of an oxygen storage material to H2O, while CO2 is reduced to CO by the uptake of oxygen by the oxygen storage material in the second step. This is followed by the further production of CO by gasification of the solid carbon by CO2 through the reverse Boudouard reaction. Hence, we refer to this novel process as "reverse Boudouard reforming".