Propylene carbonate transesterification

The transesterification reaction was carried out in a 50 mL stainless steel autoclave equipped with a magnetic stirrer. For each typical reaction, quaternary ammonium salt (2 mmol), propylene carbonate (25 mmol) and excess methanol (200 mmol) were charged into the reactor, and the CO2 was introduced at room temperature to a preset pressure. The reaction was started by stirring when the desired tranperature and pressure were attained The reachon was performed in a batch operation... 

Z Dong. Synthesis of propylene carbonate by transesterification. Hangzhou Chemical Engineering, (3) 39-96,1979. 

Solid base catalysts have gradually gained importance in the catalytic field due to their well-known advantages of non-corrosive and easier product separation[l]. However, in contrast to the extensive application of solid acid catalysts, the utilization of solid bases was limited for their rapid catalytic deactivation [2]. The deactivation problem was also foimd in the continuous synthesis of dimethyl carbonate (DMC). DMC has attracted more and more attention in recent years because of its low toxic and nicely biodegradable property [3,4]. Transesterification between methanol and propylene carbonate (PC) or ethylene carbonate (EC) is an attractive route for the synthesis of DMC. Both acid and base catalysts catalyze the reaction, and base catalyst was reported to be more effective [5]. Among bases, CaO showed unique catalytic activity for the transesterification reaction with high yield and selectivity [6]. Unfortunately, when CaO based catalyst was employed in the continuous synthesis of DMC, its activity gradually decayed with time-on-stream due to... 

In this work, a stable base catalyst was obtained by adding Cap2 into Zr02. Such a base catalyst had both high activity and stability towards the transesterification of propylene carbonate and methanol, being subjected to continuous product of dimethyl carbonate at catalytic distillation for 200h without any obvious loss of activity. The effect of preparation method and calcination temperature on the structure and catalytic performance of CaFa-ZrOa was also investigated. 

CaF2-Zr02 prepared by coprecipitation and calcinated at 800 C showed high stability towards the transesterification of propylene carbonate with methanol as shown in Fig 7. The conversion of propylene carbonate remained at about 95% for 200h and no obvious loss of activity was observed. A detailed characterization of used catalyst was carried out, and the results was shown in... 

It is interesting to remark that other reactive materials which will readily undergo transesterification analogous to that of propylene carbonate with methanol are trialkyl borates, tetraalkyl titanates, and trialkyl phosphates in an alkaline environment. Also gas injection of methyl borate (and carbon dioxide) has been found to enhance the results of wood composites bonded with formaldehyde-based resins [29], just as the addition of propylene carbonate and glycerol triacetate have been shown to do in wood composites bonded with phenolic resins. 

MALDI-TOF analysis also revealed that transesterification reactions between propylene carbonate and diols containing six or more carbon atoms in the molecule, carried out in esence of a coordination catalyst, lead to almost pure oligocarbonate diols. When ethylene carbonate (EtC) was used, the resultant polymer contained a different combinahon of ethylene carbonate and ethylene oxide units. The transesterification with EtC, carried out in the presence of catalysts, such as K2CO3 and CsF, leads to oligomers with high amoxmts of oxyethylene fragmenfs. ... 

Juarez et al. showed that ceria nanocrystallites are a moderately active catalyst for the transesterification of propylene carbonate (PC) by methanol to DMC at 140°C. The presence of gold nanoparticles on the ceria at an appropriate loading significantly increased the activity and selectivity towards transesterification (Table 13.4). 

Scheme 3.3 Synthesis of phosphorus-containing poly(propylene ether carbonate)s via transesterification of dimethyl H-phosphonate with poly(propylene ether carbonate)diol.

The SEs were first synthesized in 1956 by Osipow and coworkers [101] by the transesterification reaction between sucrose and a methyl ester of a fatty acid in the presence of a basic catalyst and dimethyl formamide (Fig. 41). However, because of the toxicity of DMF and other similar solvents, and because of the difficulty in removing DMF, from the reaction product, other methods were investigated. One of these methods, a microemulsion process, used sucrose, the methyl ester of a fatty acid, propylene glycol, sodium soap, and a potassium carbonate catalyst, all entailing time-consuming and costly steps [102,103]. 

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