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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.

The heterogeneous catalysis of lactic acid (88 wt %) esterification with ethanol in the presence of Amberlyst 15-wet was studied for catalyst loading of 1.2−3.9 wt %, initial molar ratio of reactants of 1.1−2.8, and temperature from 50 to 90 °C. In this work a methodology based on the UNIQUAC model was developed to determine the thermodynamic equilibrium constant since in the literature there is inconsistency concerning the temperature dependence of the thermodynamic equilibrium constant. A simplified Langmuir−Hinshelwood kinetic model was used to predict the experimental data. The proposed rate law is r = k c(a Eth a La − a EL a W/K)/(1 + K Eth a Eth + K W a W)2; the kinetic parameters are the preexponential factor, k c,0 = 2.70 × 107 mol·g-1·min-1, and the activation energy, E a = 49.98 kJ/mol. The equilibrium reaction constant is K = 19.35 exp(−515.13/T (K)) with reaction enthalpy 4.28 kJ/mol. The model reasonably predicts the kinetic experimental data, and it will be very useful to apply to the design and optimization of industrial hybrid reactive separation processes.