Capturing methanol and dimethoxymethane gases with ionic liquids

In this work, ionic liquid (IL) as green solvent was first proposed for capturing methanol and dimethoxymethane (DMM) gases released in the fuel synthesis process. The hydrophilic IL [EMIM][BF4] was selected from 192 kinds of ILs by the COSMO-RS model. The separation mechanism was revealed at the molecule level in combination with the quantum chemistry calculation. The vapor-liquid equilibrium (VLE) data for the binary mixture of methanol (or DMM) and [EMIM][BF4] were experimentally obtained and compared with the prediction of UNIFAC-Lei model. It was found that the popular UNIFAC-Lei model can predict the VLE of the methanol + [EMIM][BF4] and DMM + [EMIM][BF4] mixtures well. Moreover, the methanol and DMM capture experiments using [EMIM][BF4] as absorbent were carried out, demonstrating the good separation performance. Furthermore, a rigorous equilibrium EQ stage model including the UNIFAC-Lei model parameters was built for simulating and optimizing the methanol and DMM capture processes using [EMIM][BF4] and the conventional benchmark solvent triethylene glycol (TEG) as absorbents at industry level. This work confirmed that capturing methanol and DMM gases with ILs is a typical process intensification method.