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Dimethyl ether

Names
Systematic IUPAC name Methoxymethane
Other names Demeon Dimethyl oxide Dymel A Methyl ether Wood ether
Identifiers
CAS Number	115-10-6
3D model (JSmol)	Interactive image
Abbreviations	DME
Beilstein Reference	1730743
ChEBI	CHEBI:28887
ChEMBL	ChEMBL119178
ChemSpider	7956
ECHA InfoCard	100.003.696
EC Number	204-065-8
KEGG	C11144
MeSH	Dimethyl+ether
PubChem CID	8254
RTECS number	PM4780000
UNII	AM13FS69BX
UN number	1033
CompTox Dashboard (EPA)	DTXSID8026937
InChI InChI=1S/C2H6O/c1-3-2/h1-2H3Key: LCGLNKUTAGEVQW-UHFFFAOYSA-N InChI=1/C2H6O/c1-3-2/h1-2H3Key: LCGLNKUTAGEVQW-UHFFFAOYAU
SMILES COC
Properties
Chemical formula	C2H6O
Molar mass	46.069 g·mol
Appearance	Colourless gas
Odor	Typical
Density	1.97 mg cm
Melting point	−141 °C; −222 °F; 132 K
Boiling point	−24 °C; −11 °F; 249 K
Solubility in water	71 g dm (at 20 °C)
log P	0.022
Vapor pressure	>100 kPa
Dipole moment	1.30 D
Thermochemistry
Heat capacity (C)	65.57 J K mol
Std enthalpy of formation (ΔfH298)	-184.1 kJ mol
Std enthalpy of combustion (ΔcH298)	-1.4604 MJ mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220
Precautionary statements	P210, P410+P403
NFPA 704 (fire diamond)	1 4 1
Flash point	-41 °C
Explosive limits	27%
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Dimethyl ether (DME) is the organic compound with the formula CH₃OCH₃. The simplest ether, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. When combusted, DME produces minimal NOx and CO, though HC and soot formation is 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). 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. 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.

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.

Applications

The largest use of DME is currently (2010) as substitute for propane in LPG used as fuel in household and industry. The largest use of DME for this purpose is in China. DME has two other primary applications: as a propellant in aerosol canisters, and as a precursor to dimethyl sulfate. As an aerosol propellant, DME is useful as a somewhat polar solvent. It can also be used as a refrigerant.

Feedstock

Several thousand tons of DME are consumed annually for the production of the methylating agent, dimethyl sulfate, which entails its reaction with sulfur trioxide:

CH₃OCH₃ + SO₃ → (CH₃O)₂SO₂

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

(CH₃)₂O + 2 CO + H₂O → 2 CH₃CO₂H

Laboratory reagent and solvent

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

Fuel

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 55, compared to diesel's, 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, NO_x, CO. For these reasons as well as being sulfur-free, DME meets even the most stringent emission regulations in Europe (EURO5), U.S. (U.S. 2010), and Japan (2009 Japan). Mobil is using DME in their methanol to gasoline process.

DME is being developed as a synthetic second generation 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 Community Seventh Framework Programme project BioDME where Chemrec's BioDME pilot plant based on black liquor gasification is nearing completion in Piteå, Sweden.

The image below illustrates some of processes from various raw materials to DME.

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

Refrigerant

DME is also gaining popularity as a refrigerant with ASHRAE refrigerant designation R-E170. DME is also used in refrigerant blends with e.g. butane and propene.

Treating warts

A mixture of DME and propane is used in an over-the-counter device to treat warts, by freezing them.

Safety

Unlike other alkyl ethers, DME resists autoxidation. DME is also relatively non-toxic, although it is highly flammable.

References

1. "dimethyl ether - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
2. ^ Dimethyl Ether Technology and Markets 07/08-S3 Report, ChemSystems, December 2008.
3. ^ Manfred Müller, Ute Hübsch, “Dimethyl Ether” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
4. P.S. Sai Prasad et al., Fuel Processing Technology, 2008, 89, 1281.
5. Air Products Technology Offerings
6. IDA Fact Sheet DME/LPG Blends 2010 v1
7. demeon.com, Akzo Nobel DME
8. T. J. Curphey (1988). "Trimethyloxonium tetrafluoroborate". Organic Syntheses; Collected Volumes, vol. 6, p. 1019.
9. nycomb.se, Nycomb Chemicals company
10. http://www.topsoe.com/site.nsf/all/BBNN-5PNJ3F?OpenDocument topsoe.com
11. 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
12. http://www.biodme.eu/
13. Biofuels in the European Union, 2006
14. http://www.volvo.com/group/global/en-gb/newsmedia/pressreleases/NewsItemPage.htm?channelId=2184&ItemID=47984&sl=en-gb
15. http://www.volvo.com/group/global/en-gb/volvo+group/ourvalues/environment/renewable_fuels/biodme/biodme.htm
16. Chemrec press release September 9, 2010
17. The Danish Ecocar Team - List of achievements
18. http://www.mecanica.pub.ro/frigo-eco/R404A_DME.pdf 101110
19. http://www.ashrae.org/technology/page/1933#et ASHRAE list of refrigerants
20. "A Pharmacist's Guide to OTC Therapy: OTC Treatments for Warts". July 2006.
21. http://www.fda.gov/cdrh/pdf3/K030838.pdf

External links

• The International DME Association

• Aerosol propellants
• Ethers
• Fuels