Dimethyl carbonate transesterification

For the methyl acetate synthesis, dynamic modeling effects are investigated, whereas for other systems, the focus is on different steady-state issues, for example the influence of liquid-liquid separation, operational conditions and different column internals (ethyl acetate) or selectivity effect (dimethyl carbonate transesterification). The comparison between the simulation and experimental data made for all RD case studies proves that the rate-based approach is capable of predicting correct process behavior, both steady state and dynamic. 

An analogue of the transesterification process has also been demonstrated, in which the diacetate of BPA is transesterified with dimethyl carbonate, producing polycarbonate and methyl acetate (33). Removal of the methyl acetate from the equihbrium drives the reaction to completion. Methanol carbonylation, transesterification using phenol to diphenyl carbonate, and polymerization using BPA is commercially viable. The GE plant is the first to produce polycarbonate via a solventiess and phosgene-free process. 

Synthesis of dimethyl carbonate by transesterification of ethylene carbonate and methanol using quaternary ammonium salt catalysts... 

Yun-Jin Fang and Wen-De Xiao, Experimental and modeling studies on a homogeneous reactive distillation system for dimethyl carbonate synthesis by transesterification, Separation and purification technology, 34 (2004) 255. 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

This method of transesterification is of high technical interest. Particularly the reaction of bisphenol A with diphenyl carbonate is a preferred phosgene-free process because biphenyl carbonate can be obtained directly from phenol and dimethyl carbonate.The latter is an industrial product made from CO and methanol. 

Alkylene CCs have been prepared through the transesterification of appropriate glycols with dialkyl carbonates (usually diethyl or dimethyl carbonate) in the presence of a suitable catalyst. One of the first such examples was the synthesis of six-membered CCs by the transesterification of propane-1,3-diols with DEC catalyzed by sodium ethanolate (Equation 7.31) [289], The reaction was carried out at temperatures between 293 and 333 K, and a conversion yield of 40% was obtained. 

Wei T, Wang M, Wei W et al (2003) Synthesis of dimethyl carbonate by transesterification over CaO/carbon composites. Green Chem 5(3) 343-346... 

Yang Z-Z, He L-N, Dou X-Y et al (2010) Dimethyl carbonate synthesis catalyzed by DABCO-derived basic ionic liquids via transesterification of ethylene carbonate with methanol. Tetrahedron Lett 51(21) 2931-2934... 

Bhanage BM, Fujita S-i, Ikushima Y (2003) Transesterification of urea and ethylene glycol to ethylene carbonate as an important step for urea based dimethyl carbonate synthesis. Green Chem 5(4) 429-432... 

Yang Z-Z, Dou X-Y, Wu F et al (2011) NaZSM-5-catalyzed dimethyl carbonate synthesis via the transesterification of ethylene carbonate with methanol. Can J Chem 89(5) 544-548... 

In addition to ordinary titanium alkoxides of the type Ti(OR)4, a heterogeneous catalyst, TS-1 treated with K2CO3 before the reaction, proved effective in the transesterification of ethylene carbonate to dimethyl carbonate with methanol [532]. 

Transesterification of ethylene carbonate with methyl acetate in the presence of DBU gave dimethyl carbonate and 1,2-ethanediol acetate in 4% conversion (85EUP150962). 

SCHEME 6.9 Synthesis of dimethyl carbonate and diphenyl carbonate by transesterification. 

The direct polyesterification reaction of diacids with glycols is the most important industrial synthetic route to polyester polyols. The second most important synthetic route is the transesterification reaction between dimethyl esters of dicarboxylic or dibasic acids (dimethyl adipate, dimethyl terephthalate, dimethyl carbonate or even polyethylene terephthalate) and glycols (reaction 8.2) [1, 3-8]. 

Aliphatic polycarbonates (polyesters of carbonic acid) are obtained by the transesterification reaction of dialkyl carbonates (for example dimethyl carbonate) with aliphatic diols. A typical example is the polycondensation of dimethyl carbonate with 1,6 hexanediol (reaction 8.3) [4-8] ... 

W B Kim, J S Lee. Gas phase transesterification of dimethyl carbonate and phenol over surpported titanium dioxide. JCatal 185 307-313, 1999. 

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. 

Transesterification of dimethyl carbonate by phenol, catalysed with dioctyl tin oxide and titanium tetra-isopropoxide, has been effected by passage of the mixture through 5A molecular sieve at 175-185°C under pressure (203 Bar). Unreacted starting materials were removed separately by heating at 185-195X for 2 hours to give diphenyl carbonate in 85% yield (ref. 15). 

CO purity, 234 derivatives, 232 dimethyl carbonate, 252 membrane material of construction, 92 nonphosgene chemistry, 252-254 phosgene chemistry, 232-234 Scheiten-Baumann synthesis, 232, 233 transesterification, 233, 253, 254 Polyester fiber, 129, 132, 205 Polyester polyols, 229 Polyether polyols, 147, 148, 229 Polyethylene, 132, 183, 266 Polymerization ... 

Reactions that require phosgene are dangerous, and dimethyl carbonate (DMC) 33 is the most promising phosgene substitute. Current industrial processes for DMC synthesis are oxidative carbonylation of methanol and transesterification of ethylene carbonate with methanol. Hence, the direct reaction of CO2 and methanol (Scheme 58) is regarded as an attractive, next-generation process, but the limitation... 

In this section, four examples illustrating the application of the rate-based approach discussed above to the RD modeling are presented. The systems selected are methyl acetate synthesis, MTBE synthesis, ethyl acetate synthesis and transesterification of dimethyl carbonate. In the first example, dynamic process modeling is highlighted, whereas in three other examples, different aspects of steady-state modeling are discussed. 

The transesterification of dimethyl carbonate (DMC) to diethyl carbonate (DEC) represents a complex reaction system including five components and three binary azeotropes shown in Table 10.5. The characteristics of some binary mixtures of the substances involved in the reaction system have been investigated by Franchesconi and coworkers [114-116], Luo et al. [117-119] and Rodriguez et al. [120, 121], resulting in a good description of the required thermodynamic properties. 

Pyo, S.H., Hatti-Kaul, R., 2012. Selective, green synthesis of six-membered cyclic carbonates by Upase-catalyzed chemospecific transesterification of diols with dimethyl carbonate. Advanced Synthesis Catalysis 354, 797—802. 

The transesterification of dimethyl carbonate with phenol was recognised early as an appropriate reaction step to replace the direct phosgene process for making chloride-free polycarbonates for optical applications (Scheme 21.11). 

The solventless reaction in the presence of diallq ltin(iv) complexes led to a conversion of 42% with 78% selectivity to diphenyl carbonate. Starting from phenyl acetate, total conversion was obtained at 220 "C with higher selectivity to diphenyl carbonate (95%). Transesterification with higher alcohols was also examined, giving better conversion due to higher nucleophilicity compared to phenol. However, a steric effect was evidenced as fert-butanol was unreactive. Transesterification of ethylene carbonate (l,3-dioxolan-2-one) with methanol to dimethyl carbonate was also reported early. " Today, both transesterifications with methanol and phenol are integrated into the value chain of bisphenol-A polycarbonate production and commercialised by Asahi Kasei Corporation (Scheme 21.12). ... 

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