In-depth understanding of soluble base deactivation during the carbonate transesterification process

Soluble strong bases such as NaOH or CH 3 ONa were industrially applied in production of multiple carbonates via the transesterification route. However, the catalytic efficiency decreased significantly after recycling and insoluble solids were formed, leading to a complicated and non-eco-friendly manufacture process. In this study, the influence of Na-based soluble basic catalysts (C 4 H 9 ONa, C 2 H 5 ONa, CH 3 ONa, NaOH, Na 2 CO 3 , and NaHCO 3 ) structures, amounts, reusability, reaction atmospheres, and different reactants treatment were systematically studied for in-depth understanding the deactivated processes and mechanism. The results indicated dimethyl carbonate (DMC) was responsible for the deactivation and with decreasing the pK b (alkalinity coefficient) value, the alkali strength, nucleophilicity, and catalyst efficiency increased. The properties of fresh, DMC-treated and recycled NaOH or CH 3 ONa samples were characterized by means of XRD, FT-IR, Raman, TG, and SEM. Nearly all the characterizations proved that the final deactivation species was Na 2 CO 3 after long-time treatment or recycle. A possible deactivation mechanism of soluble bases during the transesterification process was proposed. The presence of trace H 2 O was the induction of CH 3 ONa deactivation, whereas the interaction between DMC and NaOH led to the formation of Na 2 CO 3 . This finding will contribute to the development of strategies to design homogeneous catalysts with high activity and stability for carbonate transesterification.