Sorption-enhanced dimethyl ether synthesis-Multiscale reactor modeling

As an opportunity for the attenuation of atmospheric CO2 emissions, conversion of carbon dioxide into valuable oxygenates as fuel additives or fuel surrogates was explored conceptually in terms of a potentially feasible dimethyl ether (DME) conversion process. Incentives for application of conventional CO2-DME conversion process are insufficient due to low CO2 conversion, and DME yield and selectivity. In-situ H2O removal by adsorption (sorption-enhanced reaction process) can lead to the displacement of the water gas shift equilibrium and therefore, the enhancement of CO2 conversion into methanol and the improvement of DME productivity. A two-scale, isothermal, unsteady-state model has been developed to evaluate the performance of a sorption-enhanced DME synthesis reactor. Modeling results show that under H2O removal conditions, methanol and DME yields and DME selectivity are favoured and the methanol selectivity decreases. The increase of methanol and DME yields and DME selectivity becomes more important at higher CO2 feed concentration because a relatively large amount of water is produced followed by a large quantity of water removed from the system. Also, the drop in the fraction of unconverted methanol becomes more important when CO2 feed concentration is higher and the dehydration reaction is favoured. Therefore, application of the sorption-enhanced reaction concept allows the use of CO2 as a constituent of the synthesis gas as the in-situ H2O removal accelerates the reverse water gas shift reaction. (C) 2011 Elsevier Ltd. All rights reserved.