Sorption-enhanced DME synthesis provides high flexibility: evidence from modelling four industrial use cases†

Abstract

Sorption-enhanced dimethyl ether synthesis (SEDMES) is a powerful technology to produce dimethyl ether (DME) from residual industrial gas streams or captured CO₂ and renewable H₂. In situ water removal by zeolites shifts the thermodynamic equilibrium of the reaction towards product formation. Sorption enhancement proved to provide a single-pass CO₂ conversion above state of the art values. Building knowledge on prior optimisation of a CO₂–H₂ feed, this work extends modelling of SEDMES to a design study for four distinct industrial feeds, with progressively higher CO content. The trade-offs between DME productivity and carbon distribution over the products were studied. The impact of process parameters such as cycle duration, feed flow, operating pressure, temperature, reactant stoichiometry, amount of inert gases and the presence of CO was analysed in detail, including the impact of flexible operation and turndown. Results show that higher CO feed concentrations enhance the DME productivity but complicate the purification due to increased CO₂ by-product formation. Variations in the feed H₂–C ratio affected by-product selectivity, with lower ratios reducing CO₂ and methanol formation, potentially simplifying downstream processing. Pressure and temperature were identified as critical design parameters. Higher operating pressures consistently enhanced DME productivity in all cases, while a moderate temperature increase above 250 °C proved to be beneficial as well. Moreover, the process demonstrated resilience under lower feed flow conditions (factor 3 in turn down ratio) that could potentially be caused by renewable electricity fluctuations, without compromising the performance.

Keywords: Dimethyl ether; CO₂ utilisation; Modelling; Sorption enhanced reaction; Pressure-swing adsorption (PSA); Syngas.