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is the organic compound with the formula CH3
. The simplest ether
, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. Dimethyl ether is also promising as a clean-burning hydrocarbon fuel.
Dimethyl ether is produced by the dehydration of methanol:
- 2 CH3OH → CH3OCH3 + H2O
Approximately 50,000 tons were produced in 1985 in Western Europe alone. In principle, it could also be manufactured by partial hydrogenation
of carbon monoxide, which in turn can be obtained from many sources of hydrocarbons, including biomass.
Dimethyl ether has two primary applications: as a propellent in aerosol cannisters
, and as a precursor to dimethyl sulfate
. As an aerosol propellent, dimethyl ether is useful as a somewhat polar solvent.
Several thousand tons of dimethyl ether are consumed annually for the production of the methylating agent, dimethyl sulfate
, via the reaction with sulfur trioxide
- CH3OCH3 + SO3 → (CH3O)2SO2
This compound is also converted to acetic acid using technology related to the Monsanto acetic acid process:
- (CH3)2O + 2 CO + H2O → 2 CH3CO2H
Laboratory reagent and solvent
Dimethyl ether is a low-temperature solvent and extraction agent that is used as a solvent in specialised laboratory procedures. Its usefulness is limited by its low boiling point (−23 °C), but the same property facilitates its removal from reaction mixtures. Dimethyl ether is the precursor to the useful alkylating agent
, trimethyloxonium tetrafluoroborate
DME is a promising fuel in diesel engines
, petrol engines
(30% DME / 70% LPG), and gas turbines
owing to its high cetane number
, which is greater than 55 compared to diesel, which is 40–53. Only moderate modification are needed to convert a diesel engine to burn DME. The simplicity of this short carbon chain compound leads during combustion to very low emissions of particulate matter, NOx
, CO. 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). DME is being developed as a synthetic biofuel (BioDME), which can be manufactured from lignocellulosic biomass
. Currently the EU is considering BioDME in its potential biofuel mix in 2030, the Volvo
Group is the coordinator for the European project BioDME. and Mobil
is using it in their methanol to gasoline
process. The image below illustrates some of processes from various raw materials to DME.
A mixture of dimethyl ether and propane
is used in an over-the-counter device to treat warts, by freezing them.
Unlike other alkyl ethers, it resists autoxidation
. Dimethyl ether is also relatively non-toxic, although it is highly flammable.