View source for Dimethyl ether

{{chembox
| Watchedfields = changed
| verifiedrevid = 306043924
|   Name = Dimethyl ether
|   ImageFile = DiMeether.png
|   ImageSize = 200px
|   ImageFile2 = Dimethyl-ether-3D-balls.png
|   ImageSize2 = 200px
|   ImageName = Dimethyl ether
|   IUPACName = methoxymethane
|   OtherNames = Carbinic acid anhydride<br />
DME, methyl ether, methoxymethane, wood ether, dimethyl oxide, Demeon, Dymel A
| Section1 = {{Chembox Identifiers
|   SMILES = COC
|   CASNo_Ref = {{cascite}}
| CASNo = 115-10-6
|   RTECS = PM3780000
|   UNNumber = 1033
  }}
| 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 = 71 g/L (20 °C)
|   SolubleOther = soluble in [[acetone]], [[chloroform]], [[ethanol]], [[ether]]
|   MeltingPt = −138.5 °C (134.6 K)/(−217.3 °F) 242.37 °R
|   BoilingPt = −23.6 °C (254.6 K)/(−12.82 °F) 446.85 °R
  }}
| Section3 = {{Chembox Structure
|   MolShape = 
|   Dipole = 1.30 [[Debye|D]] (gas)
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS = [http://msds.chem.ox.ac.uk/DI/dimethyl_ether.html Oxford MSDS]
|   MainHazards = highly flammable
|   Autoignition = 235 C
|   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''' (DME) is the [[organic compound]] with the formula CH<sub>3</sub>OCH<sub>3</sub>. The simplest [[ether]], it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant.  When combusted, dimethyl ether produces minimal NOx and CO, though HC and soot formation are significant. DME can act as a clean fuel when burned in engines properly optimized for DME.

==Production==
Today, DME is primarily produced by converting hydrocarbons sourced from [[natural gas]] or  [[coal]] via gasification to synthesis gas ([[syngas]]).  Synthesis gas is then converted into [[methanol]] in the presence of catalyst (usually copper-based), with subsequent methanol dehydration in the presence of a different catalyst (for example, silica-alumina) resulting in the production of DME.  As described, this is a two-step (indirect synthesis) process that starts with methanol synthesis and ends with DME synthesis (methanol dehydration).<ref name=ChemSystems>[http://www.chemsystems.com/reports/search/docs/abstracts/0708S3_abs.pdf Dimethyl Ether Technology and Markets 07/08-S3 Report, ChemSystems, December 2008.]</ref>  The same process can be conducted using organic waste or biomass. Approximately 50,000 tons were produced in 1985 in Western Europe using the methanol dehydration process.<ref name=Ullmann>Manfred Müller, Ute Hübsch, “Dimethyl Ether” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.</ref>  
Alternatively, DME can be produced through direct synthesis, using a dual catalyst system that permits both methanol synthesis and dehydration in the same process unit, with no methanol isolation and purification, a procedure that, by eliminating the intermediate methanol synthesis stage, the licensors claim promises efficiency advantages and cost benefits.<ref name=ChemSystems/><ref>P.S. Sai Prasad et al., Fuel Processing Technology, 2008, 89, 1281.</ref>

Both the one-step and two-step processes above are commercially available.  Currently, there is more widespread application of the two-step process since it is relatively simple and start-up costs are relatively low.  It is worth mentioning that there is a developing one-step liquid-phase process.<ref name=ChemSystems/><ref>[http://www.airproducts.com/Technology/product_offering.asp?reg=GBL&intProductTypeCategoryId=95&intRegionalMarketSegment=0 Air Products Technology Offerings]</ref>

==Applications==
The largest use of dimethyl ether is currently (2010) as substitute for propane in LPG used as fuel in household and industry<ref>[http://aboutdme.org/aboutdme/files/ccLibraryFiles/Filename/000000001519/IDA_Fact_Sheet_1_LPG_DME_Blends.pdf IDA Fact Sheet DME/LPG Blends 2010 v1]</ref>. The largest use of DME for this purpose is in China. Dimethyl ether has two other primary applications: as a propellant in [[aerosol spray|aerosol canisters]], and as a precursor to [[dimethyl sulfate]].<ref name=Ullmann/><ref>[http://www.demeon.com/ demeon.com, Akzo Nobel DME]</ref> As an aerosol propellant, dimethyl ether is useful as a somewhat polar solvent.  It can also be used as a refrigerant.

===Feedstock===
Several thousand tons of dimethyl ether are consumed annually for the production of the methylating agent, [[dimethyl sulfate]], which entails its reaction with [[sulfur trioxide]]:
: CH<sub>3</sub>OCH<sub>3</sub>  +  SO<sub>3</sub>   →   (CH<sub>3</sub>O)<sub>2</sub>SO<sub>2</sub>

Dimethyl ether can also be converted into [[acetic acid]] using [[carbonylation]] technology related to the [[Monsanto acetic acid process]]:<ref name=Ullmann/>
: (CH<sub>3</sub>)<sub>2</sub>O  +  2 CO  +  H<sub>2</sub>O   →   2 CH<sub>3</sub>CO<sub>2</sub>H

===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]] (&minus;23 °C), but the same property facilitates its removal from reaction mixtures.  Dimethyl ether is the precursor to the useful [[alkylating agent]], [[trimethyloxonium tetrafluoroborate]].<ref>{{OrgSynth | author = T. J. Curphey | collvol = 6 | year = 1988| collvolpages = 1019 | prep = CV6P1019| title = Trimethyloxonium tetrafluoroborate}}</ref>

===Fuel===
DME is a promising fuel in [[diesel engines]],<ref>[http://www.nykomb.se/index.php?s=Chemicals nycomb.se, Nycomb Chemicals company]</ref> [[petrol engine]]s (30% DME / 70% LPG), and [[gas turbines]] owing to its high [[cetane number]], which is 55, compared to diesel's, which is 40–53.<ref>http://www.topsoe.com/site.nsf/all/BBNN-5PNJ3F?OpenDocument topsoe.com</ref> 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, NO<sub>x</sub>, 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).<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>  DME is being developed as a synthetic biofuel (BioDME), which can be manufactured from [[lignocellulosic biomass]].<ref>http://www.biodme.eu/</ref> Currently the EU is considering BioDME in its potential biofuel mix in 2030,{{Fact|date=September 2008}} the [[Volvo]] Group is the coordinator for the European project BioDME.<ref>http://www.volvo.com/group/global/en-gb/newsmedia/pressreleases/NewsItemPage.htm?channelId=2184&ItemID=47984&sl=en-gb</ref><ref>http://www.volvo.com/group/global/en-gb/volvo+group/ourvalues/environment/renewable_fuels/biodme/biodme.htm</ref> and  [[Mobil]] is using it in their [[methanol to gasoline]] process.  The image below illustrates some of processes from various raw materials to DME.
[[Image:DME Process diagram.jpg|none|center|600px]]

In 2009 a team of university students from Denmark won the Urban Concept/Internal Combustion class at the European Shell Eco Marathon (The Shell Eco Marathon is an unofficial World Championship for mileage) with a vehicle running on 100% DME. The vehicle drove 589 km/liter, fuel equivalent to gasoline with a 50 ccm 2-stroke engine operating by the Diesel principle. As well as winning they beat the old standing record of 306 km/liter, set by the same team in 2007 <ref>[http://www.ecocar.mek.dtu.dk/Achievements.aspx The Danish Ecocar Team - List of achievements]</ref>

===Treating [[warts]]===
A mixture of dimethyl ether and [[propane]] is used in an over-the-counter device to treat warts, by freezing them.<ref>{{cite news | url = http://www.pharmacytimes.com/issue/pharmacy/2006/2006-07/2006-07-5674 | date = July 2006 | title = A Pharmacist's Guide to OTC Therapy: OTC Treatments for Warts}}</ref><ref>http://www.fda.gov/cdrh/pdf3/K030838.pdf</ref>

==Safety==
Unlike other alkyl ethers, it resists [[autoxidation]].  Dimethyl ether is also relatively non-toxic, although it is highly flammable.
== References ==
<references/>

==External links ==
* [http://www.aboutdme.org/ The International DME Association]
* [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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