Dimethyl ether
569315
215279166
2008-05-27T14:20:37Z
Stephan Leeds
140154
my typo; letter "x" to "×" where clearly the latter was intended
{{Chembox new
| Name = Dimethyl ether
| ImageFile = dimethylether_structure.png
| ImageSize = 200px
| ImageName = Dimethyl ether
| IUPACName = methoxymethane
| OtherNames = DME, wood ether<br />dimethyl oxide<br />Demeon, Dymel A
| Section1 = {{Chembox Identifiers
| SMILES = COC
| CASNo = 115-10-6
| RTECS = PM3780000
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>2</sub>H<sub>6</sub>O<br />CH<sub>3</sub>OCH<sub>3</sub>
| MolarMass = 46.07 g/mol
| Appearance = colourless gas with<br />typical smell
| Density = 1.97 g/L, gas (1.59 × that of air)<br />668 kg/m<sup>3</sup>, liquid
| Solubility = 328 g/100 mL (20 °C)
| MeltingPt = −138.5 °C (134.6 K)/(−217.3 °F) 242.37 °R
| BoilingPt = −23 °C (254 K)/(−12.82 °F) 446.85 °R
}}
| Section3 = {{Chembox Structure
| MolShape =
| Dipole = 1.30 [[Debye|D]] (gas)
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [[Dimethyl ether chemdata supplement#Material Safety Data Sheet|External MSDS]]
| MainHazards = highly flammable
| FlashPt = {{convert|-41|°C|K}}/(−41.8 °F) 417.87 °R
| RPhrases = {{R12}}
| SPhrases = {{S2}}, {{S9}}, {{S16}}, {{S33}}
}}
| Section8 = {{Chembox Related
| Function = [[ether]]s
| OtherFunctn = [[diethyl ether]]<br />[[crown ether]]<br />[[polyethylene glycol]]
| OtherCpds = [[methanol]]}}
}}
'''Dimethyl ether''', also known as '''methoxymethane''', '''oxybismethane''', '''methyl ether''', '''wood ether''', and '''DME''', is a colorless [[gaseous]] [[ether]] with an ethereal [[odor]]. Dimethyl ether gas is water [[soluble]]. It has the formula CH<sub>3</sub>OCH<sub>3</sub> or as its [[empirical formula]] C<sub>2</sub>H<sub>6</sub>O (which it shares with [[ethanol]]). Dimethyl ether is used as an [[aerosol spray#Propellant|aerosol spray propellant]], and is used in conjunction with [[propane]] to give a thermic expansion that lowers temperature to −60 °C. This property is useful in [[cryogenic]] freezing of common [[warts]] found on the human body. Dimethyl ether is also a clean-burning alternative to [[liquified petroleum gas]], [[liquified natural gas]], [[diesel]] and [[gasoline]]. It can be made from [[natural gas]], [[coal]], or [[biomass]].
==Production==
Conventional DME production uses the methanol dehydration method.<ref>[http://www.demeon.com/ProductionProcess/ demeon.com, production process]</ref> For mass production of DME as a fuel other methods are being considered, the main one being DME synthesis from hydrogen and CO gas, also known as [[syngas]].<ref>[http://www.jfe-holdings.co.jp/en/dme/02-seizo.html JFE-holdings.co.jp, dme]</ref>
DME can be produced from methanol by combining two methanol molecules to produce a DME molecule and a water molecule.<ref name=dehydrcat>[http://www.int.gov.br/questao/pdf/dehydration_catalyst.pdf gov.br, dehydration catalyst]</ref> This is a reversible reaction.<ref name=dehydrcat/> This can be shown in the following equation:
: methanol → dimethyl ether + water
: 2CH<sub>3</sub>OH → CH<sub>3</sub>OCH<sub>3</sub> + H<sub>2</sub>O
There are various companies developing this method of DME production, the most active one being JFE Holding in Japan.{{Fact|date=February 2007}} The DME-synthesis method has a better overall efficiency because with methanol dehydration,{{Fact|date=February 2007}} the methanol is firstly produced from a base source such as LPG, NG or coal via synthesis and then this is converted into DME.{{Fact|date=February 2007}}
This method attempts to cut out the intermediate methanol production and produce DME from LPG, NG, coal or even biomass in one process.{{Fact|date=February 2007}}
DME production from solid raw materials such as [[biomass]] and [[coal]] requires more processes than DME production from gases such as [[NG]] and [[LPG]]. This is because the solid materials need go through the [[gasification]] process to produce the [[syngas]] required for the DME-synthesis. To allow for more efficient gasification the biomass and coal have various preparation processes; such as chipping of the biomass or producing slurry of the coal. To ensure that the DME produced is clean there are various gas scrubbing, cleaning and purification processes. DME production from methane can simply use a [[methane reformer|methane reforming]] method to produce the syngas for the DME synthesis.
The image below shows a simple representation of the various processes from raw materials to DME.
[[Image:DME_Process_diagram.jpg|none|500px]]
==Applications==
DME is used as:<ref>[http://www.demeon.com/ demeon.com, Akzo Nobel DME]</ref>
* A refrigerant
* A (co-)blowing agent for foam
* A propellant for aerosol products
* A solvent
* An extraction agent
* A chemical reaction medium
* A fuel for welding cutting and brazing
* A multi-purpose fuel
===As a fuel===
DME can be used as a fuel in [[diesel engines]],<ref>[http://www.nykomb.se/index.php?s=Chemicals nycomb.se, Nycomb Chemicals company]</ref> [[Petrol_engine|petrol engines]] (30% DME / 70% LPG) and [[gas turbines]].
It works particularly well in diesel engines due to its high [[cetane number]], which is greater than 55 compared to diesel which is 38–53.<ref>[http://www.topsoe.com/site.nsf/all/BBNN-5PNJ3F?OpenDocument topsoe.com, Haldor Topsoe Chemicals Company]</ref>. only moderate modification are needed to convert a diesel engine to run on DME. The simplicity of this short carbon chain compound leads during combustion to very low emissions of particulate matter, NO<sub>x</sub>, CO and no SO<sub>x</sub>, meeting even the most stringent emission regulations in Europe (EURO5), U.S. (U.S. 2010) and Japan (2009 Japan).<ref>http://www.japantransport.com/conferences/2006/03/dme_detailed_information.pdf, ''Conference on the Development and Promotion of Environmentally Friendly Heavy Duty Vehicles such as DME Trucks'', Washington DC, March 17, '''2006'''</ref>
Currently the EU is considering DME in its potential biofuel mix in 2030.<ref>[http://www.refuel.eu/biofuels/bio-dme/ refuel.eu, EU Refuel biofuel project]</ref> and [[Mobil]] is using it in their [[methanol to gasoline]] process.
===Solvent===
Like [[ammonia]] (NH<sub>3</sub>), dimethyl ether can be [[condense]]d (liquified) and used as a solvent. Clearly there are limitation on the maximum temperature (e.g. the [[boiling]]/[[reflux]] temperature i.e. −23 °C) which the solvent can be used. One advantage of using dimethyl ether as a solvent is that is readily removed by evaporation, especially from a product which has a relatively low boiling point.
== References ==
<references/>
==External links ==
* [http://www.aboutdme.org/] the International DME Association
* [http://www.afrox.com/templ-files/Safety/93_Dimethylether.pdf] Material Safety Data Sheet
* [http://www.welsch.com/e/index.php5?chap=6&moduletype=moleculeviewer&searchword=all&post_site=1] dimethyl ether 3D view and pdb-file
[[Category:Aerosol propellants]]
[[Category:Ethers]]
[[Category:Fuels]]
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