Sorption enhanced dimethyl ether synthesis for high efficiency carbon conversion: Modelling and cycle design

Dimethyl ether is one of the most promising alternative fuels under consideration worldwide. Both the conventional indirect DME synthesis and the improved direct DME synthesis process are constrained by thermodynamics, which results in limited product yield, extensive separations and large recycle streams. Sorption enhanced DME synthesis is a novel process for the production of DME. The in situ removal of H2O ensures that the oxygen surplus of the feed no longer ends up in CO2 as is the case for direct DME synthesis. As a result CO2 can be converted directly to DME with high carbon efficiency, rather than being the main byproduct of DME production. The sorption enhanced DME synthesis process is a promising intensification, already achieving over 80 % single-pass CO2 conversion for a non-optimized system. The increased single-pass conversion requires less downstream separation and smaller recycle streams, especially for a CO2-rich feed. A key optimization parameter for the process performance is the adsorption capacity of the system. This capacity can be improved by optimizing the reactive adsorption conditions and the regeneration procedure. In this work, a detailed modelling study is performed to investigate the impact of various process parameters on the operating window and the interaction between different steps in a complete sorption enhanced DME synthesis cycle, and to compare its performance to other direct DME synthesis processes. The development of sorption enhanced DME synthesis, with its high efficiency carbon conversion, could play a significant role in the energy transition in which the carbon conversion will become leading.