Thermally self-sufficient process for single-step coproduction of methanol and dimethyl ether by CO2 hydrogenation

Abstract

Methanol and DME are highly efficient fuels and relevant building blocks that can be synthesized by CO2 hydrogenation. While several alternatives for methanol production by CO2 hydrogenation have already been developed at a commercial scale, DME production is still based on methanol dehydration. In this sense, the development of bifunctional methanol synthesis/dehydration catalysts is a clear opportunity for the simultaneous coproduction of methanol and DME in a single-step process. Although a few alternatives for DME-methanol coproduction have been proposed, either they need external fuels or refrigerants, or part of the CO2 used as raw material is purged, resulting in a loss of methanol and DME yields. This work presents a novel thermally self-sufficient process that hydrogenates CO2 into methanol and DME in a single reactor at 100 % yield (only water as a byproduct at 0.94 kgwater/kgproduct), that only consumes air, cooling water (0.006 m3water/kgproducts) and electricity (net CO2 emissions of −1.20 or 0.64 kgCO2eq/kgproducts when the plant is operated with green or grey electricity, respectively). The innovative design, based on the combination of a top-divided wall column, an integrated heat network, and limited pressure drop in the reaction-separation loop, results in a thermally self-sufficient process that uses only 0.76 kWh per kg products.