Methanol and Dimethyl Ether Synthesis from CO₂ and H₂ in the Flow-Circulation Mode

Abstract

Processes of converting CO₂ to methanol and dimethyl ether (DME) in a flow-circulation mode where the converted gas is partially returned to the reactor are studied to address the issue of utilizing carbon dioxide emissions. Experimental data are presented on methanol synthesis (industrial catalyst MegaMax 507) and the direct synthesis of DME (MegaMax 507/industrial zeolite TsVM in a mass ratio of 1 : 1). In methanol synthesis from synthesis gas (composition, vol %: Н₂ 76.6, СО₂ 19.8, and N₂ 3.6), high СО₂ conversion of 84–99.6% is achieved at 240–260°С and a pressure of 5.3 MPa with low selectivity in regard to the side reaction (<4.7% synthesis of CO). The maximum specific productivity of methanol at 260°C is 1.24 kg (kg_cat h)⁻¹. Experiments performed under special conditions show that slight heating (up to 10°C) is observed at the inlet into the catalyst bed under methanol synthesis condition, thus indicating that the reactor is of polytropic type. In the synthesis of DME, the yield of DME per weight amount of a bifunctional catalyst lies within the range of 0.08–0.17 kg (kg_cat h)⁻¹, depending on the conditions of the reaction. In addition, the conversion of methanol in DME is no lower than 42%, СО₂ conversion lies in the range of 79–96%, and DME synthesis proceeds almost under isothermal conditions.