Transesterification of dimethyl carbonate with phenol to diphenyl carbonate over hexagonal Mg(OH)2 nanoflakes. Issue 1 (27th November 2014) - Wang, Qiang
Abstract : Hexagonal Mg(OH)2 nanoflakes were synthesized, which showed excellent catalytic activities for the transesterification of dimethyl carbonate with phenol. Abstract : Hexagonal Mg(OH)2 nanoflakes were synthesized via a hydrothermal method in the presence of polyethylene glycol 20000 (PEG-20000). X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were applied to characterize the composition, morphologies and structure of the Mg(OH)2 nanoflakes. Brunauer–Emmett–Teller (BET) analysis was performed to investigate the porous structure and surface area of the as-obtained nanoflakes. The transesterification of dimethyl carbonate (DMC) with phenol to produce diphenyl carbonate (DPC) was carried out over the hexagonal Mg(OH)2 nanoflakes. The evaluation results showed that the hexagonal Mg(OH)2 nanoflakes had better activity and excellent selectivity to target products compared with many conventional ester exchange catalysts. Compared with other catalysts, such as AlCl3, ZnCl2, and irregular Mg(OH)2 synthesized via a hydrothermal method without PEG-20000, which all have been widely used as catalysts for this transesterification reaction, Mg(OH)2 nanoflakes were more stable and showed a relatively high activity with a low catalyst amount. The transesterification reaction process was also analyzed with the classic thermodynamic theory, and when the reaction was carried out at 453 K, with a molar ratio of phenol to DMC of 2 : 1, a reaction time of 13 h, and a catalyst amount of 0.2% (molar ratio to phenol), the selectivity of the transesterification reaction reached 92.3%. Moreover, the deactivated hexagonal Mg(OH)2 nanoflakes could be easily reactivated by calcination under vacuum, and the regenerated Mg(OH)2 nanoflakes showed the catalytic activity almost as high as that of the fresh sample.