Synthesis of Methanol and Dimethyl Ether from CO2 and H2 Under Flow-Circulation Conditions

Abstract

In the context of utilization of carbon dioxide emissions, a study of the CO₂ conversion to methanol and dimethyl ether (DME) under flowcirculation conditions, when a part of converted gas returns to the reactor, was carried out. Experimental data on the synthesis of methanol (commercial catalyst Megamax 507) and direct synthesis of DME (Megamax 507/commercial zeolite ZVM, weight ratio 1/1) are reported. In the methanol synthesis from syngas, vol.%: H2 – 76.6, CO₂ – 19.8, N2 – 3.6 performed at 240–260 °C and pressure 5.3 MPa, a high conversion of CO₂ was reached: 84–99.6% at a low selectivity of the side reaction (CO synthesis, not higher than 4.7 %). The maximum specific yield of methanol at 260 °C was 1.24 kg(kgcat·h)^–1. Special-purpose experiments demonstrated that the methanol synthesis is accompanied by a small heating (up to 10 °C) at the catalyst bed inlet, which testifies to polytropicity of the reactor. In the synthesis of DME, the DME yield referred to bifunctional catalyst was within 0.16–0.33 kg(kgcat·h)^–1 depending on the conditions. Therewith, the conversion of methanol to DME was not lower than 42 %, the conversion of CO₂ was within 79–96 %, and the DME synthesis proceeded under nearly isothermal conditions.