Introduction to Dimethyl Ether

Dimethyl ether (DME) also known as methyl ether, methyl oxide and wood ether, is the organic compound with the formula CH3OCH3. The simplest ether, it is a colourless liquid or compressed gas that is a useful precursor to other organic compounds and an aerosol propellant. DME consists of two methyl groups bonded to a central oxygen atom, as expressed by its chemical formula CH3-O-CH3. It has been used in a variety of consumer applications viz., personal care (e.g., hairspray, shaving creams, foams and anti perspirants), household products, automotive, paints, food products, insect control, animal products and other related applications. It is commonly used in organic synthesis as a reaction solvent for systems requiring volatile polar solvents and is also promising as a clean-burning hydrocarbon fuel.

DME can be produced from natural gas—providing an alternative way of its utilization, in competition to such technologies as Fischer-Tropsch synthetic fuels—as well as from other carbon-containing feed stocks, including coal and biomass. DME has replaced CFC gases (freons) as an environmentally friendly and safe aerosol propellant, which is one of its major current applications. Potential future uses of DME include an alternative automotive fuel, a substitute for other fuels in power generation and in the household and a source of hydrogen for fuel cells. Worldwide DME production grew from 100,000-150,000 tons per annum in the 1990s to some 200,000 tons in the mid-2000s.

With the chemical structure somewhat similar to methanol, DME contains oxygen and no carbon-carbon bonds, thus seriously limiting the possibility of forming carbonaceous particulate emissions during combustion. However, unlike methanol, DME has a high enough cetane number to perform well as a compression-ignition fuel. Also unlike methanol, DME is a gas at ambient temperature and pressure, so it must be stored under pressure as a liquid similar to LPG (liquefied petroleum gas). When used as a diesel fuel, DME provides reduced PM (Particulate Matter) and NOx emissions.

The physical properties of DME (density, viscosity, etc.) are so different from the diesel fuel that the entire fuel system must be redesigned. It seems clear that DME, like perhaps some other alternative fuels, would be able to produce many larger emissions reductions than it is possible with diesel fuel. Therefore, from today’s perspective, the DME fuel is more likely to be used in certain niche applications, rather than provide a wide-scale alternative to liquid diesel fuels.