Dimethyl ether

Dimethyl ether
IUPAC name	methoxymethane
Other names	DME, methyl ether, methoxymethane, wood ether, dimethyl oxide, Demeon, Dymel A
Identifiers
CAS number	115-10-6 Y
UN number	1033
RTECS number	PM3780000
SMILES	COC
Properties
Molecular formula	C2H6O CH3OCH3
Molar mass	46.07 g/mol
Appearance	colourless gas with typical smell
Density	1.97 g/L, gas (1.59 × that of air) 668 kg/m3, liquid
Melting point	−138.5 °C (134.6 K)/(−217.3 °F) 242.37 °R
Boiling point	−23.6 °C (254.6 K)/(−12.82 °F) 446.85 °R
Solubility in water	328 g/L (20 °C)
Solubility	soluble in acetone, chloroform, ethanol, ether
Structure
Dipole moment	1.30 D (gas)
Hazards
MSDS	External MSDS
R-phrases	R12
S-phrases	(S2), S9, S16, S33
Flash point	−41 °C (232.2 K)/(−41.8 °F) 417.87 °R
Autoignition temperature	350 °C
Related compounds
Related ethers	diethyl ether crown ether polyethylene glycol
Related compounds	methanol
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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. Dimethyl ether is also promising as a clean-burning hydrocarbon fuel.

Production

Today, DME is primarily produced by converting hydrocarbons, predominantly sourced from natural gas (and to a lesser extent via gasification of coal), 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).^[1] 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.^[2] 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.^[1][3]

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.^[1][4]

Applications

Dimethyl ether has two primary applications: as a propellant in aerosol canisters, and as a precursor to dimethyl sulfate.^[2][5] 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:

CH₃OCH₃ + SO₃ → (CH₃O)₂SO₂

Dimethyl ether can also be converted into acetic acid using carbonylation technology related to the Monsanto acetic acid process:^[2]

(CH₃)₂O + 2 CO + H₂O → 2 CH₃CO₂H

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), but the same property facilitates its removal from reaction mixtures. Dimethyl ether is the precursor to the useful alkylating agent, trimethyloxonium tetrafluoroborate.^[6]

Fuel

DME is a promising fuel in diesel engines,^[7] 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.^[8] 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, dimethyl ether meets even the most stringent emission regulations in Europe (EURO5), U.S. (U.S. 2010), and Japan (2009 Japan).^[9] DME is being developed as a synthetic biofuel (BioDME), which can be manufactured from lignocellulosic biomass.^[10] Currently the EU is considering BioDME in its potential biofuel mix in 2030,^{[citation needed]} the Volvo Group is the coordinator for the European project BioDME.^[11][12] and Mobil is using it in their methanol to gasoline process. The image below illustrates some of processes from various raw materials to DME.

Treating warts

A mixture of dimethyl ether and propane is used in an over-the-counter device to treat warts, by freezing them.^[13][14]

Safety

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

References

1. ^ ^{a b c} Dimethyl Ether Technology and Markets 07/08-S3 Report, ChemSystems, December 2008.
2. ^ ^{a b c} Manfred Müller, Ute Hübsch, “Dimethyl Ether” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
3. ^ P.S. Sai Prasad et al., Fuel Processing Technology, 2008, 89, 1281.
4. ^ Air Products Technology Offerings
5. ^ demeon.com, Akzo Nobel DME
6. ^ T. J. Curphey (1988), "Trimethyloxonium tetrafluoroborate", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P1019 ; Coll. Vol. 6: 1019 
7. ^ nycomb.se, Nycomb Chemicals company
8. ^ http://www.topsoe.com/site.nsf/all/BBNN-5PNJ3F?OpenDocument topsoe.com
9. ^ 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
10. ^ http://www.biodme.eu/
11. ^ http://www.volvo.com/group/global/en-gb/newsmedia/pressreleases/NewsItemPage.htm?channelId=2184&ItemID=47984&sl=en-gb
12. ^ http://www.volvo.com/group/global/en-gb/volvo+group/ourvalues/environment/renewable_fuels/biodme/biodme.htm
13. ^ "A Pharmacist's Guide to OTC Therapy: OTC Treatments for Warts". July 2006. http://www.pharmacytimes.com/issue/pharmacy/2006/2006-07/2006-07-5674. 
14. ^ http://www.fda.gov/cdrh/pdf3/K030838.pdf

External links

• The International DME Association
• dimethyl ether 3D view and pdb-file