Reaction-extraction platforms towards CO2-derived cyclic carbonates catalyzed by ionic liquids by COSMO models
Alejandro BELINCHON ABENOJAR1, Elisa HERNANDEZ MUÑOZ 1, Pablo NAVARRO TEJEDOR 1, Ruben SANTIAGO 1, Cristian MOYA 1, Jesus LEMUS1, Daniel HOSPITAL-BENITO1, Rola EL-BIJOU1, Jose Francisco PALOMAR1
1Chemical Engineering Department, Universidad Autónoma de Madrid, madrid, Spain
Global warming solutions mainly consist of reducing the current alarming CO2 levels in the atmosphere. Two main strategies are implemented to achieve said purpose: Carbon Capture and Storage (CCS), which aims to concentrate CO2 and store it, and Carbon Capture and Utilization (CCU), which uses CO2 as feedstock of new processes to produce value-added compounds.
The utilization of CO2 can take various routes to produce different compounds but, among all of them, cyclic carbonates stand out for their potential application as extractive solvents. The cyclic carbonates are synthesized by cycloaddition of CO2 with epoxides but, due to the stability of CO2, the presence of catalysts is necessary. Ionic liquids (ILs) are gaining importance as effective catalysts in several reactions that convert CO2 into value-added products due to the high yields obtained. The challenge to design a CO2 conversion process based on ILs is to solve the product/catalyst separation efficiently and sustainably, especially dealing with a homogeneous catalytic step. The common strategy proposed in the literature consists of a distillation step in which the ionic liquid is obtained as pure compound in the residue and the carbonate is recovered as distillate. Nevertheless, cyclic carbonates generally present a high boiling point, which requires high reboiler temperatures, incompatible with ionic liquids thermal stability. This distillation can be achieved by displaying extreme vacuum conditions, but it implies high electricity expenses.
In this work, a multiscale approach based on commercial simulators is used to design a liquid-liquid separation strategy to solve the separation process. ILs can be classified in Hydrophobic ionic liquids are soluble in fatty alcohols, while hydrophilic ionic liquids are soluble in water. Thus, those solvents can potentially be used to separate them from the products of CO2 conversion. This strategy is applied to different carbonates, which proves the universal applicability of this technique. Carbonates and ionic liquids recoveries were calculated, as well as carbonates purities and global energy consumption. The results show that, in most cases, this novel strategy can reduce the operating costs in comparison with the conventional carbonate distillation.