Dimethyl carbonate manufacture

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). 

Scheme 5.4 Daicel phosgene-free I DPI manufacture using dimethyl carbonate.

Dimethyl Carbonate. An industrial process to manufacture dimethyl carbonate through the oxidative carbonylation of methanol catalyzed by cuprous chloride has been developed and commercialized by EniChem.197,198 The reaction occurs in two steps. Cupric methoxy chloride is formed in the first oxidation step [Eq. (7.21)], which is then reduced to yield dimethyl carbonate and regenerate cuprous chloride [Eq. (7.22)] ... 

Pacheco MA, Marshall CL (1997) Review of dimethyl carbonate (DMC) manufacture and its characteristics as a fuel additive. Energ Fuel 11(1) 2—29... 

Table 3.5.2 Compilation of the most important secondary battery technologies. Energy densities compiled from various manufacturers data sheets and references [4,7-9] (EC/DMC, ethylene carbonate/dimethyl carbonate EMS (ethyl methyl sulphone)). 

As with the chloroformates, a large number of carbonates (e.g. diethyl carbonate, dimethyl carbonate, and diphenyl carbonate) are commercially available. Manufacturers of chloroformates are usually also manufacturers of carbonates. 

Because of the toxicity of phosgene, research on nonphosgene routes to isocyanates and polycarbonates has intensified over the past decade. Eni-Chem of Italy has commercialized a process to manufacture dimethyl carbonate (DMC) by oxidative carbonylation of methanol. Dimethyl carbonate can be used as an intermediate for the production of polycarbonates. A description of the nonphosgenation chemistry for producing DMC and polycarbonates is included in Section II.A in this chapter. 

In Reppe reactions organic substrates are reacted with carbon monoxide in the presence of a metal carbonyl catalyst (or their precursors). Industrial chemicals such as acetic acid, methyl formate, formamide, di-methylformamide, formic acid, methyl methacrylate, and the emerging nonphosgene intermediates for isocyanates and dimethyl carbonate for polycarbonates are manufactured via Reppe reactions. 

Oxidative carbonylation of alcohols in the presence of CO provides an economically viable route to dialkyl carbonates and/or oxalates (Eqs. (8.4) and (8.5)), both of which have important industrial applications. Dialkyl carbonates (e.g., dimethyl carbonate, propylene carbonate) are excellent solvents for a variety of organic substances [14]. Dialkyl oxalates have utility as solvents, C2 building blocks in fine chemicals synthesis, and intermediates in the manufacture of oxamide (as a fertilizer) [15]. Hydrogenation of dialkyl oxalates provides an alternative route to ethylene glycol that is independent of oil-derived resources [15,16]. 

A cyclic process for producing triphosgene, in which dimethyl carbonate chlorination is coupled with triphosgene methanolysis (i.e. a manufacturing process essentially based on methanol and chlorine as raw materials), has been claimed in the past [78, 79]. The cost of manufacturing the product in this way is considerably lower than that using the traditional liquid-phase photochlorination of DMC. 

Phosgene (COCI2) is one of the most toxic chemicals known. It was used as mustard gas in World War I. Currendy, phosgene is used as a raw material in the manufacture of pesticides and urethanes. It has been suggested that dimethyl carbonate (DMC, CH3-0-(C=0)-0-CH3) can serve as a reactant in many of the same processes that use phosgene [6]. This is an example of an alternative feedstock. 

Alkoxyhydroxybenzophenonesulfonic acids are used in the manufacture of cosmetic sunscreen additives they are synthesized by sulfonation of the parent alkoxyhydroxybenzophenones with chlorosulfonic acid at temperatures in the range (—20 to 100 °C) using an aliphatic or aromatic ester solvent. " For instance, 2-hydroxy-4-methoxybenzophenone reacts with chlorosulfonic acid (2.6 equivalents) in ethyl acetate at 0-5 °C (30 minutes), then at room temperature (12 hours) to yield 4-hydroxy-2-methoxybenzophenonesulfonic acid (80%). " The sulfonation may also be effected in excellent yield (95.3%), by reacting the substrate with an equimolar amount of chlorosulfonic acid in dimethyl carbonate at 10-35 °C (1 hour). " In this example, of course, the sulfonation is greatly... 

Great efforts have been made in electrolyte development to achieve desirable hthium-ion conductivity, dielectric constant, viscosity, and thermal stabihty. The solvent systems include single solvent [35, 36] and cosolvent [37-44]. A mixture of ethylene carbonate (EC) and dimethyl carbonate/ethyl methyl carbonate (DMC/EMC) has been widely adopted by researchers and manufacturers [45-48]. liPFe is the preferred salt due to its overall performance [49]. An overview of electrolyte development is provided by Ahmad [49], and electrolyte processing has also been discussed elsewhere [50]. In addition, the introduction of hthium-ion... 

Pachecoa, M.A. Marshall, C.L. Review of Dimethyl Carbonate (DMC) Manufacture and Its Characteristics as a Fuel Additive. Energy and Fuels 1997,11,2-29. 

Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

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