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Dimethyl ether is an organic compound that is used to make other molecules. Also known as DME, it functions as a reagent in chemistry laboratories. It is currently being used as a substitute for liquefied petroleum gas. Also, DME is being heavily studied as a biofuel to replace diesel in engines. As of 2010, there are numerous pilot plants around the world to use this compound as diesel fuel for vehicles.
The classical way to produce DME is by reacting methanol with sulfuric acid. The methanol undergoes a dehydration reaction, meaning it loses a molecule of water, producing the desired product. Industrial dimethyl ether production generally starts with natural gas, producing through synthetic gas to methanol and then to DME. There are new procedures to make dimethyl ether in a single step.
As a biofuel, DME can be produced from the waste products of paper mills. One advantage to this, as compared to other biofuels sources, is that the raw materials come from the forestry industry. No food is lost to the production of this compound. There is concern about other biofuels production that use edible crops as a source of biomass.
The delignification process of removing the insoluble fibers from wood produces a lot of waste called black liquor. This biomass waste can now be used as a source to make DME inexpensively. This process produces dramatically fewer greenhouse gases than methods for making traditional diesel fuel. If biofuel production does not meet the growing demand for DME, there are always the industrial ways of manufacturing.
It is fairly straightforward to modify a diesel engine to use DME as fuel. There are several benefits to this. This fuel can be used with much lower injection pressures, greatly simplifying the fuel injection equipment needed. There are no particulate, carbon monoxide, or sulfur emissions produced in an engine designed to use DME. This clean-burning fuel meets the emission standards of the United States, Japan, and Europe. With the combination of worldwide industrial, governmental, and institutional interest in this fuel, it is predicted to become widely used.
Dimethyl ether is also used to synthesize organic compounds, such as dimethyl sulfate. This chemical is an intermediate in the production of many other molecules. DME is also used to make acetic acid and as a propellant in aerosol cans.
The dimethyl ether structure is CH3OCH3, and it is the simplest ether. Ethers are notorious for reacting with air to produce explosive oxygen compounds called peroxides. DME is less likely to react in such a manner, however. Nonetheless, it is good laboratory practice to put the date of arrival on a container of ether, so one does not keep them around dangerously long.
The boiling point of dimethyl ether is -9° F (-23° C). It is a colorless gas with a small degree of solubility in water. It is generally stable, but is extremely flammable.