Dimethyl ether

Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH₃OCH₃, (sometimes ambiguously simplified to C₂H₆O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor to other organic compounds and an aerosol propellant that is currently being demonstrated for use in a variety of fuel applications.

Dimethyl ether was first synthesised by Jean-Baptiste Dumas and Eugene Péligot in 1835 by distillation of methanol and sulfuric acid.<ref>Ann. chim. phys., 1835, [2] 58, p. 19 </ref>

Production

Approximately 50,000 tons were produced in 1985 in Western Europe by dehydration of methanol:<ref name=Ullmann>Manfred Müller, Ute Hübsch, "Dimethyl Ether" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. {{#invoke:doi|main}}</ref>

Template:Chem2

The required methanol is obtained from synthesis gas (syngas).<ref name=ChemSystems>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Other possible improvements call for a dual catalyst system that permits both methanol synthesis and dehydration in the same process unit, with no methanol isolation and purification.<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. The two-step process is relatively simple and start-up costs are relatively low. A one-step liquid-phase process is in development.<ref name=ChemSystems/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

From biomass

Dimethyl ether is a synthetic second generation biofuel (BioDME), which can be produced from lignocellulosic biomass.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The EU is considering BioDME in its potential biofuel mix in 2030;<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It can also be made from biogas or methane from animal, food, and agricultural waste,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> or even from shale gas or natural gas.<ref>Template:Cite book</ref>

The Volvo Group is the coordinator for the European Community Seventh Framework Programme project BioDME<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> where Chemrec's BioDME pilot plant is based on black liquor gasification in Piteå, Sweden.<ref>Chemrec press release September 9, 2010 Template:Webarchive</ref>

Applications

The largest use of dimethyl ether is as the feedstock for the production of the methylating agent, dimethyl sulfate, which entails its reaction with sulfur trioxide:

Template:Chem2

Dimethyl ether can also be converted into acetic acid using carbonylation technology related to the Monsanto acetic acid process:<ref name=Ullmann/>

Template:Chem2

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 (Template:Convert), but the same property facilitates its removal from reaction mixtures. Dimethyl ether is the precursor to the useful alkylating agent, trimethyloxonium tetrafluoroborate.<ref>Template:OrgSynth</ref>

Niche applications

A mixture of dimethyl ether and propane is used in some over-the-counter "freeze spray" products to treat warts by freezing them.<ref>Template:Cite news</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In this role, it has supplanted halocarbon compounds (Freon).

Dimethyl ether is also a component of certain high temperature "Map-Pro" blowtorch gas blends, supplanting the use of methyl acetylene and propadiene mixtures.<ref name="MAP-Plus">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Dimethyl ether is also used as a propellant in aerosol products. Such products include hair spray, bug spray and some aerosol glue products.

Research

Fuel

File:Chemrec 5 - small.JPG

Installation of BioDME synthesis towers at Chemrec's pilot facility

A potentially major use of dimethyl ether is as substitute for propane in LPG used as fuel in household and industry.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Dimethyl ether can also be used as a blendstock in propane autogas.<ref>Template:Cite journal</ref>

It is also a promising fuel in diesel engines,<ref>nycomb.se, Nycomb Chemicals company Template:Webarchive</ref> and gas turbines. For diesel engines, an advantage is the high cetane number of 55, compared to that of diesel fuel from petroleum, which is 40–53.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} topsoe.com</ref> Only moderate modifications are needed to convert a diesel engine to burn dimethyl ether. The simplicity of this short carbon chain compound leads to very low emissions of particulate matter during combustion. 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>{{#invoke:citation/CS1|citation |CitationClass=web }}, Conference on the Development and Promotion of Environmentally Friendly Heavy Duty Vehicles such as DME Trucks, Washington DC, March 17, 2006</ref>

At the European Shell Eco Marathon, an unofficial World Championship for mileage, vehicle running on 100 % dimethyl ether drove 589 km/L (169.8 cm³/100 km), fuel equivalent to gasoline with a 50 cm³ displacement 2-stroke engine. As well as winning they beat the old standing record of 306 km/liter (326.8 cm³/100 km), set by the same team in 2007.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

To study the dimethyl ether for the combustion process a chemical kinetic mechanism<ref>Template:Cite journal</ref> is required which can be used for Computational fluid dynamics calculation.

Refrigerant

Dimethyl ether is a refrigerant with ASHRAE refrigerant designation R-E170. It is also used in refrigerant blends with e.g. ammonia, carbon dioxide, butane and propene. Dimethyl ether was the first refrigerant. In 1876, the French engineer Charles Tellier bought the ex-Elder-Dempster a 690 tons cargo ship Eboe and fitted a methyl-ether refrigerating plant of his design. The ship was renamed Le Frigorifique and successfully imported a cargo of refrigerated meat from Argentina. However the machinery could be improved and in 1877 another refrigerated ship called Paraguay with a refrigerating plant improved by Ferdinand Carré was put into service on the South American run.<ref>A history of the frozen meat trade, page 26-28</ref><ref name ="ASHRAE refrigerants">http://www.ashrae.org/technology/page/1933#et Template:Webarchive ASHRAE list of refrigerants</ref>

Safety

Unlike other alkyl ethers, dimethyl ether resists autoxidation.<ref>A comparative study on the autoxidation of dimethyl ether (DME) comparison with diethyl ether (DEE) and diisopropyl ether (DIPE), Michie Naito, Claire Radcliffe, Yuji Wada, Takashi Hoshino, Xiongmin Liu, Mitsuru Arai, Masamitsu Tamura. Journal of Loss Prevention in the Process Industries, Volume 18, Issues 4–6, July–November 2005, Pages 469–473 DOI</ref> Dimethyl ether is also relatively non-toxic, although it is highly flammable. On July 28, 1948, a BASF factory in Ludwigshafen suffered an explosion after 30 tonnes of dimethyl ether leaked from a tank and ignited in the air. 200 people died, and a third of the industrial plant was destroyed.<ref>Welt im Film 167/1948 Template:Webarchive. filmothek.bundesarchiv.de</ref>

Data sheet

Vapor pressure

Experimental vapor pressures of dimethyl ether<ref>Template:Cite journal</ref>

Temperature (K)	Pressure (kPa)
233.128	54.61
238.126	68.49
243.157	85.57
248.152	105.59
253.152	129.42
258.16Template:Figure space	157.53
263.16Template:Figure space	190.44
268.161	228.48
273.153	272.17
278.145	321.87
283.16Template:Figure space	378.66
288.174	443.57
293.161	515.53
298.172	596.21
303.16Template:Figure space	687.37
305.16Template:Figure space	726.26
308.158	787.07
313.156	897.59
316.154	968.55
318.158	1018.91
323.148	1152.35
328.149	1298.23
333.157	1457.5Template:Figure space
333.159	1457.76
338.154	1631.01
343.147	1818.8Template:Figure space
348.147	2022.45
353.146	2242.74
353.158	2243.07
358.145	2479.92
363.148	2735.67
368.158	3010.81
373.154	3305.67
378.15Template:Figure space	3622.6Template:Figure space
383.143	3962.25
388.155	4331.48
393.158	4725.02
398.157	5146.82
400.378	5355.8Template:Figure space

See also

• Methanol economy

External links

• Template:Usurped
• NOAA site for NFPA 704
• XTL & DME Institute