Kinetic Study of CaO-Catalyzed Transesterification of Cyclic Carbonates with Methanol

Abstract

Simultaneous catalytic contributions of CaO in the liquid phase (homogeneous) and in the solid phase (heterogeneous) for transesterification are considered in the kinetic analysis, because sparingly soluble CaO has significant catalytic activity. Experimental concentration−time profiles were obtained at different catalyst loadings, propylene carbonate (PC) concentrations, and methanol concentrations in a temperature range of 20−60 °C in a stirred batch reactor for both the homogeneous and heterogeneous reactions. Kinetic models based on power-law rate forms were evaluated and discriminated to fit the experimental data. Reaction orders of 1 for PC, 2 for methanol, and 1 for both DMC and PG fit the experimental data best for the homogeneous reaction, whereas orders of 0.35 for PC, 1.9 for methanol, and 0 for both DMC and PG fit the experimental data best for the heterogeneous reaction. The heterogeneous CaO catalyst (E a = 56.8 kJ/mol) was found to be more active than the homogeneous CaO catalyst (E a = 82.4 kJ/mol). The reaction-order and activation-energy differences may be attributed to different reaction pathways for homogeneous-and heterogeneous-CaO-catalyzed transesterifications. Different reaction mechanisms were proposed for the homogeneous and heterogeneous reactions, respectively. It is observed that kinetic models based on mechanisms fit better than power-law models, especially for the heterogeneous reaction. The kinetic model for the homogeneous reaction suggests the formation of active species CH 3 O − . Then, PC gets activated by the CH 3 O − to form the first intermediate, which then forms the second intermediate by reaction with one mole of methanol. This is followed by a reaction of the second intermediate with another molecule of methanol to form the final products, DMC and PG. However, for the heterogeneous-CaO-catalyzed reaction, adsorption of PC and dissociative adsorption of methanol on the surface of the active species is assumed to occur simultaneously. Then, the adsorbed PC and methanol react to directly form the final products, DMC and PG. The good fits of the kinetic models with the experimental data suggest that the proposed homogeneous-and heterogeneous-reaction mechanisms represent the transesterification of propylene carbonate satisfactorily.

Effect of Cobalt Doping on the Stability of CaO‐Based Catalysts for Dimethyl Carbonate Synthesis via the Transesterification of Propylene Carbonate with Methanol

“…The surface basic sites of catalysts could activate methanol, and it was possible that the higher the basicity of the catalyst was, the easier it was for methanol was to be activated and thus easily promoted the catalytic activity for the synthesis of DMC [27,50] . To investigate the effect of the number of moderate basic sites on the catalyst activity, the DMC yield was correlated with the number of moderate basic sites, and the results are shown in Figure 8a.…”

Neighboring Group Participation and Internal Catalysis Effects on Exchangeable Covalent Bonds: Application to the Thriving Field of Vitrimer Chemistry

“…75 Bases are also common catalysts, for instance magnesium hydroxide, 76 calcium salts 77,78 or sodium alkoxides. 74,79 All the catalyzed mechanisms described are associative, 69,71,74,[76][77][78][79][80] though they are slightly different depending on the type of catalysis employed (Scheme 3).…”

High Conversion of Palm Olein to Ethyl Esters Using a Strong Anion Exchange Resin: Study of the Operational Parameters

“…Furthermore, heterogeneous catalysis facilitates catalyst reuse and the implementation of continuous processing. 9,10 As disadvantages one can mention the higher costs and special temperature and pressure requirements. 11,12 A strong anion exchange resin, with its quaternary ammonium as fixed-ion and a hydroxyl as counterion (see Figure 1), can be used as heterogeneous catalysts on the transesterification reaction.…”