Dimethylether

• Methoxymethane
• Holzether
• Methyl ether
• Methyloxid
• DME

Colorless gas with ethereal odor

Gaseous

• 2.11 g · l-1 (0 ° C, 1013 hPa)
• 0.74 g · cm -3 ( -25 ° C)

-141.5 ° C

-24.82 ° C

510 kPa ( 20 ° C)

Little in water ( 70 g · l-1 at 20 ° C)

1.30 D ( 4.3 × 10-30 C · m)

Risk

1910 mg · m- 3, 1000 ml · m-3

1 (relative to 100 years)

-184.1 KJ / mol

Template: Infobox chemical / molecular formula search available

Dimethyl ether is the simplest ether; it contains two methyl groups as organic radicals. Dimethylether is polar and is in liquid form, as solvent use.

• 3.1 DME as a fuel

Properties

Dimethyl ether is ( at normal conditions ) of colorless, slightly narcotic -acting, non-toxic, extremely flammable gas. The compound boils at -24 ° C. The heat of vaporization at boiling point of 21.51 kJ / mol. Vacuum up to 34% soluble in water.

Thermodynamic properties

The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 4.11475, B = C = -30.604 894.669 and in the temperature range of from 194.93 to 248.24 K.

Production

It can be, for example, by condensation of 2 molecules of methanol säurenkatalysierte won ( elimination of water ):

Dimethyl ether as a by- product of the methanol synthesis and is usually produced directly from synthesis gas. As a source for the synthesis gas are particularly coal, natural gas and biogas and syngas from biomass gasification of high interest.

In the synthesis is a two step process, in which by means of appropriate catalysts (usually CuO/ZnO/Al2O3 ) at temperatures of 270 ° C and a pressure of 5 to 10 MPa first methanol is prepared, in one second step in the presence of an acid catalyst (usually aluminum) dehydrogenated within the same process. Secluded dimethyl still contains small amounts of methanol and water.

Use

High-purity dimethyl ether is widely used as a propellant for example in hair spray and spray paint. Technical dimethyl ether is an alternative to LPG with excellent burning properties. An azeotropic mixture of dimethyl ether and ammonia yields the refrigerant R723.

A large amount of dimethyl ether produced is reacted with sulfur trioxide (SO3) to dimethyl sulfate ( C2H6O4S ), which is needed as a basis for a number of chemical processes and products.

Until the 1980s, this was the main use of dimethyl ether, 1998, of the 50,000 tonnes produced in Central Europe about 15,000 tonnes converted to dimethyl sulfate.

Dimethyl ether is also an intermediate product for the preparation of alkenes like ethene ( ethylene ) and propene ( propylene ) from methanol or natural gas in the so-called methanol -to- olefin technology, as alternative to the method of oil currently in use ( "steam cracking" ) was developed.

DME as a fuel

Due to a cetane number of 55 to 60 to dimethyl ether can be used as a substitute for diesel fuel in diesel engines. Here are just slight modifications to the engine needed, primarily relating to the injection pump and the installation of a pressure tank, similar to LPG. Dimethyl ether burns in a diesel engine very clean without soot formation. The calorific value is 28.4 MJ / kg.

According to the Biofuels Directive 2003 -30- EC dimethyl ether is considered as a biofuel, if he " produced from biomass and intended for use as biofuel is " and will replace long-term LNG. As a raw material base for the production of synthesis gas from black liquor is intended to serve the paper and pulp industry. The first factory for the production of biologically produced dimethyl ether was built in 2012 in Piteå in Sweden.

Misfortune

With the explosion of a tank car filled with dimethyl ether on the BASF site in Ludwigshafen am Rhein on July 28, 1948 207 people died, there were 3,818 injured, and 3,122 buildings were affected.