Dimethyl oxalate

Dimethyl oxalate

Colorless solid

Fixed

1.148 g · cm -3 ( 25 ° C)

50-54 ° C

163.5 ° C

• Soluble in water (60 g · l-1 at 25 ° C)
• Soluble in ethanol and ether

1.39 (20 ° C)

Attention

-756.3 KJ / mol

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Oxalate is a chemical compound from the group of oxalates, an ester of oxalic acid.

Production and representation

Dimethyl oxalate can be obtained by esterification of oxalic acid with methanol using sulfuric acid as a catalyst.

The presentation by oxidative carbonylation is possible.

The oxidative carbonylation of methanol linked in a Pd2 -catalyzed reaction under relatively mild process conditions and with high yields classical C1 - blocks from the coal-derived or biomass syngas to the C2 module dimethyl oxalate. The oxidation proceeds via dinitrogen trioxide, which is formed of (1) from nitric oxide and oxygen, and then reacts according to (2 ) with methanol to form methyl nitrite:

In the next reaction step (3 ) of the dicarbonylation reacts carbon monoxide with methyl nitrite in the vapor phase at atmospheric pressure and at temperatures between 80-120 ° C over a palladium catalyst to dimethyl oxalate:

The following empirical equation:

Shows that oxygen on the reactant dinitrogen trioxide and methyl nitrite acts as the actual oxidant. The proceedings with respect to methyl nitrite, which acts as a kind of carrier of oxidation equivalents, lossless. However, the resulting water has to be removed, as this will cause the hydrolysis of dimethyl oxalate. Interestingly, the course of the reaction depends upon X.-Z. Jiang on the nature of the carrier material from where the palladium catalyst is applied crucial. With 1% Pd/α-Al2O3 arises in a Dicarbonylierungsreaktion selectively dimethyl oxalate with 2% Pd / C produced under the same reaction conditions monocarbonylation dimethyl carbonate according to:

Alternatively, the oxidative carbonylation of methanol with 1,4-benzoquinone ( BQ ) as an oxidant in the Pd (OAc) 1/3/100 2/PPh3/BQ with mass ratio at 65 ° C and 70 atm of CO in accordance with a high yield and selectivity are performed:

Properties

Oxalate is a colorless solid, which is soluble in water.

Use

Dimethyl oxalate is used in the cosmetic industry as a chelating agent. It is also used for alkylation.

For countries with low oil deposits, but large coal reserves ( in the future perhaps also availability of biomass ), that is great potential for synthesis gas based chemistry, as at present, for example, China, the oxidative carbonylation of methanol provides a new and promising approach to the important C2 basic chemical ethylene glycol dimethyl oxalate can be converted in high yields ( 94.7 % of theory) by hydrogenation over copper-containing catalysts in ethylene glycol:

The methanol is recycled to the process of oxidative carbonylation; that is, carbon monoxide, hydrogen and oxygen are in the overall process as the only raw materials consumed. A plant with a capacity of 200,000 tons of ethylene per year after that " Coal-to - MEG " process is already in Inner Mongolia in operation, a second plant with 250,000 tons / year to the second half of 2012 in Henan Province in operating go. Other systems up to a total annual capacity of more than 1 million tons of ethylene glycol are planned.

From oxalate also as a fuel additive (so-called oxygenate ) discussed from biomass dimethyl carbonate by decarbonylation at temperatures around 100 ° C in the presence of alkali metal is accessible in accordance with:

The resulting carbon monoxide can be recycled to the initial reaction (3).

By transesterification of dimethyl oxalate with phenol in the presence of titanium catalysts, diphenyl oxalate is obtained which is similar to the dimethyl decarbonylated in liquid phase or gas phase to diphenyl carbonate. Diphenyl carbonate is used as a replacement of highly toxic phosgene in the manufacture of polycarbonates using.

Related compounds

• Oxalate C6H10O4