Dimethyl ether

Applications

The largest use of dimethyl ether is as the feedstock for the production of the methylating agent, dimethyl sulfate, which entails its reaction with sulfur trioxide:

${\displaystyle {\text{CH}}_3^{}{\text{OCH}}_3^{}+{\text{SO}}_3^{}⟶{({\text{CH}}_3^{})}_2^{}{\text{SO}}_4^{}}$

Dimethyl ether can also be converted into acetic acid using carbonylation technology related to the Monsanto acetic acid process:

${\displaystyle {\text{CH}}_3^{}-\text{O}-{\text{CH}}_3^{}+2\text{CO}+{\text{H}}_2^{}\text{O}⟶2{\text{CH}}_3^{}\text{COOH}}$

Laboratory reagent and solvent

Dimethyl ether is a low-temperature solvent and extraction agent, applicable to specialised laboratory procedures. Its usefulness is limited by its low boiling point (−23 °C (−9 °F)), but the same property facilitates its removal from reaction mixtures. Dimethyl ether is the precursor to the useful alkylating agent, trimethyloxonium tetrafluoroborate.

Niche applications

A mixture of dimethyl ether and propane is used in some over-the-counter "freeze spray" products to treat warts by freezing them. In this role, it has supplanted halocarbon compounds (Freon).

Dimethyl ether is also a component of certain high temperature "Map-Pro" blowtorch gas blends, supplanting the use of methyl acetylene and propadiene mixtures.

Dimethyl ether is also used as a propellant in aerosol products. Such products include hair spray, bug spray and some aerosol glue products.

Research

Fuel

A potentially major use of dimethyl ether is as substitute for propane in LPG used as fuel in household and industry. Dimethyl ether can also be used as a blendstock in propane autogas.

It is also a promising fuel in diesel engines, and gas turbines. For diesel engines, an advantage is the high cetane number of 55, compared to that of diesel fuel from petroleum, which is 40–53. Only moderate modifications are needed to convert a diesel engine to burn dimethyl ether. The simplicity of this short carbon chain compound leads to very low emissions of particulate matter during combustion. For these reasons as well as being sulfur-free, dimethyl ether meets even the most stringent emission regulations in Europe (EURO5), U.S. (U.S. 2010), and Japan (2009 Japan).

At the European Shell Eco Marathon, an unofficial World Championship for mileage, a vehicle running on 100% dimethyl ether achieved a fuel economy of 0.170L/100 km, fuel equivalent to gasoline with a 50 cm³ displacement 2-stroke engine.

To study the dimethyl ether for the combustion process a chemical kinetic mechanism is required which can be used for Computational fluid dynamics calculation.

Refrigerant

Dimethyl ether is a refrigerant with ASHRAE refrigerant designation R-E170. It is also used in refrigerant blends with e.g. ammonia, carbon dioxide, butane and propene. Dimethyl ether was the first refrigerant. In 1876, the French engineer Charles Tellier bought the ex-Elder-Dempster a 690 tons cargo ship Eboe and fitted a methyl-ether refrigerating plant of his design. The ship was renamed Le Frigorifique and successfully imported a cargo of refrigerated meat from Argentina. However the machinery could be improved and in 1877 another refrigerated ship called Paraguay with a refrigerating plant improved by Ferdinand Carré was put into service on the South American run.

Safety

Unlike other alkyl ethers, dimethyl ether resists autoxidation. Dimethyl ether is also relatively non-toxic, although it is highly flammable. On July 28, 1948, a BASF factory in Ludwigshafen suffered an explosion after 30 tonnes of dimethyl ether leaked from a tank and ignited in the air. 200 people died, and a third of the industrial plant was destroyed.

Data sheet

Routes to produce dimethyl ether

Vapor pressure