Hydrogenation of CO ₂ into Methanol and Dimethyl Ether on a Mixture of Commercial CuO/ZnO/MgO and HZSM5 Catalysts: Effect of Optimizing the Temperature Profile along the Reactor

The optimal temperature progression (OTP) theory was applied to the catalytic hydrogenation of CO2 into methanol and dimethyl ether. The reaction kinetics was studied experimentally on a mixture of the CuO/ZnO/Al2O3/MgO (CZA-C) catalyst and HZSM-5 zeolite between 26 and 36 bar and at temperatures between 463 and 583 K. Isothermal and OTP behaviors of the reactors were compared in terms of CO2 conversion and production of valuable molecules. OTP depends heavily on the inlet temperature and demonstrated its significant advantage over an isothermal reactor operation in a simple reversible and balanced reaction. However, in the case of a complex scheme involving several exothermic and endothermic reactions, the benefits were more moderate. Extrapolation to industrial scale demonstrated the feasibility of designing an OTP reactor, enhancing CO2 conversion and productivity by continuously promoting the methanol synthesis, and reducing the competing reverse water gas shift reaction rate along the reactor by lowering the outlet temperature.