Direct DME Synthesis from Syngas: a Technoeconomic Model-based Investigation

Dymethyl ether (DME) is of industrial interest since it is used as a precursor in many other chemical processes and it can be used as fuel in diesel engines. Nowadays, the main route to produce DME is a two-step process in which a methanol dehydration unit is connected to a methanol synthesis plant (indirect synthesis). Combining methanol synthesis and dehydration in a single reactor (direct synthesis) has attracted significant attention in recent years as it offers a theoretically higher syngas conversion per pass but leads to a more challenging downstream separation. The main contribution of this paper is a model-based comparison between an indirect DME process and two direct DME processes: a standard reactor/separation/recycle process and a once-through configuration where the unreacted syngas is used to co-produce electricity. The key-performance indicators in our analysis are the break-even price of DME, the carbon efficiency, and the energy return on energy invested. The results suggest that indirect and direct DME synthesis have similar performances both in economic terms, and in carbon and energy efficiencies terms.