Review for the Direct Synthesis of Dimethyl Carbonate

Abstract

This review summarizes the state-of-the-art for direct synthesis of dimethyl carbonate (DMC) from carbon dioxide and methanol. In addition, conventional and alternative processes are also discussed in order to understand the advantages and disadvantages of the direct synthesis of DMC. Furthermore, the major applications of DMC are described: solvent, fuels additive, and building block for organic synthesis. The major drawbacks of the direct synthesis of DMC are the low yield and reaction rate, mostly induced by the highly stable carbon dioxide molecules. The development of novel catalyst and strategies to enhance the DMC yield -such as dehydrating agents that remove the water from the reacting mixture -are pointed out as the key solution for this route. Therefore, the main catalysts (homogeneous and heterogeneous catalysts) used so far are presented, together with the respective operating conditions and catalyst performance. The use of different dehydrating agents to increase the DMC yield is also discussed.

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

“…Organic carbonates (OCs) are promising candidates as green replacements of conventional noxious solvents and fuel additives as well as for the development of innovative intermediates in the pharma, lubricant and polymer industries [55–56]. Before the 1980’s, the industrial synthesis of the simplest representative of the series, dimethyl carbonate (DMC), was based on the phosgenation of methanol, which used a lethal chemical reagent such as phosgene (Scheme 6, top).…”

Homogeneously Catalyzed Synthesis of (Higher) Alcohols (C1–C4) from the Combination of CO2/CO/H2

“…However, the equilibrium of the direct esterification of carbon dioxide and methanol is unfavorable , wherefore the reaction only proceeds when the by‐product water is effectively removed from the reaction mixture. This was attempted, e.g., by the use of dehydrating agents like 2‐cyanopyridine , molecular sieves , ionic liquids , or for the similar diethyl carbonate by the separation of water through a membrane . The stoichiometrically used dehydrating agent 2‐cyanopyridine in a continuous flow setup at 120 °C (∼10 min residence time) leads to excellent conversion and selectivity, but the subsequent dehydration of the produced 2‐picolinamide for recycling is unfavorable (17 days at 165 °C) .…”

Fixation of carbon dioxide into dimethyl carbonate over titanium-based zeolitic thiophene-benzimidazolate framework

“…The reported methods, however, often require longer reaction time, high temperature and pressure to accomplish the synthesis. Alternatively, oxidative carbonylation of methanol 16, 17 , transesterification of cyclic carbonates 12 , methanolysis of urea 12 have been deployed but these methods suffer from low yield and diminished atom efficiency resulting in the generation of large amount of chemical waste along with compromised yield.…”