A critical review of the technologies to obtain pure dimethyl carbonate from its azeotropic mixture with methyl alcohol

Abstract Dimethyl carbonate (DMC) is used in many applications: pharmaceuticals, composites, flavors and in lithium ion batteries. There is a huge industrial demand for pure DMC (worth ∼2 billion USD as in 2025), which is expected to increase in the future. Most production routes of DMC involve methyl alcohol (MeOH) as a reactant. The industrial requirement is high purity DMC (>99.9 mass %) with least water and MeOH (<0.01 mass % each). In order to obtain pure DMC, it is necessary to effectively overcome the minimum boiling azeotrope of MeOH and DMC (70 mass % MeOH, 63.75 °C). A number of methods are reported in the literature for this industrially important separation and purification. This review has undertaken to critically evaluate various separation and purification methods for this mixture: azeotropic distillation; extractive distillation; reactive distillation; pressure swing distillation; adsorption; liquid-liquid extraction and membrane based separations. Combination of two (or more) processes can bring in unforeseen advantages and this review also discusses such hybrid separations. Miscellaneous process technologies are also discussed in brief. Techno-economic considerations are highlighted. Recommendations are provided based on detailed literature review. Schematics and tables are provided so as to present the compiled data in a concise way.