Propylene oxide

Colorless liquid

Liquid

0.83 g · cm -3 ( 20 ° C)

-112 ° C

34 ° C.

588 hPa ( 20 ° C)

Well in water (405 g · l-1 at 20 ° C)

Risk

Not assigned because carcinogenic

380 mg · kg -1 ( LD50, rat, oral)

-123.0 KJ / mol

Template: Infobox chemical / molecular formula search available

1,2-epoxypropane or propylene oxide (PO) is a heterocyclic organic compound from the group of epoxides ( oxiranes ). The highly flammable, soluble in water and alcohol, colorless liquid having an ethereal odor. Propylene oxide is produced from propene and used mainly for the production of water-soluble propylene glycol derivatives, but can also be used as anti-corrosion additive for pesticides, cooling fluids and disinfectants. The epoxide is propylene oxide is not a naturally occurring substance, its presence in the atmosphere is attributed to industrial emissions and their further processing. It is believed that it does not contribute to the propagation of the ozone hole.

Production

In 1985, the production of propylene oxide amounted to about 2.9 Mt worldwide in 1991 to about 4.2 Mt, 4.8 Mt in 2001 and 2008, approximately 5.5 Mt The installed worldwide annual production capacity was on January 1, 2002 5.8 Mt

A direct oxidation of propylene with oxygen to propylene oxide, as in the preparation of ethylene oxide from ethylene, is technically possible, but uneconomical because the reaction with a low selectivity and the formation occurs more oxidation products that need to be time-consuming separated. In this respect, the methods described below have prevailed.

Chlorohydrin

In the chlorohydrin are of propene with chlorine and water (in which hypochlorous acid is produced in situ) generated chloropropanols which are present in two isomeric forms ( 1-chloro -propan- 2-ol, 2 -chloro- propan-1- ol). In a second reaction step, these may be reacted with hydroxide ion to give propylene oxide and water. The hydroxide ions are recovered from milk of lime Ca (OH) 2, so that as a by-product of calcium chloride CaCl 2 is obtained ( 100 kg of propylene oxide are 200 kg of calcium chloride ). This leads to a large waste load.

The propylene oxide Herstellkapazitätsanteil after the chlorohydrin was 1985 run at about 55%, about 52 % in 1991 and 2010, only around 34%.

Oxirane - method ( Prileschajew reaction)

The epoxidation of propene in the catalytic reaction Prileschajew reaction with a hydroperoxide, which strongly reactive peroxide reacts with the double bond of the propene.

In styrene variant ethylbenzene is converted with oxygen into the corresponding peroxide, which reacts with propylene to propylene oxide. The resulting parallel 1-phenylethanol ( Phenylmethylcarbinol ) is reacted with alumina to the elimination of water to styrene.

In isobutane variant iso -butane is converted by oxidation in tert- butyl hydroperoxide reacts with propylene to give propylene oxide and t- butanol. The tert- butanol can then be attributed to hydrogen back into iso- butane by dehydration in iso- butene and this.

HPPO process

In this the Prileschajew reaction similar process, the reaction of propylene with hydrogen peroxide (English abbreviation HP ) are:

Since the only by-product water is formed, this method is considered to be particularly economical and environmentally friendly. It requires an upstream system for the production of hydrogen peroxide, but does have in contrast to the other methods, no infrastructure and markets for byproducts. The SKC has taken in Ulsan ( South Korea) in 2008, the first commercial-scale plant for the production of propylene oxide by the Evonik / Uhde HPPO process in operation. The plant has a capacity of 100,000 tonnes per year. Another, much larger facility, which uses a similar method was established in Antwerp in 2008 and is jointly operated by BASF and Dow Chemical.

Enantiomerically pure propylene oxide

The synthesis of Propylenoxidenantiomeren goes from (R) - or of (S)- alanine. This is first reacted with retention with sodium nitrite and hydrochloric acid to 2- Chloropropionic. After reduction with lithium aluminum hydride to the alcohol and cyclization with sodium hydroxide, with inversion, the (S) - or (R ) -propylene oxide obtained.

Reactivity

Propylene tends less to as self-polymerization of ethylene oxide, but such can be initiated by catalysts such as the salts of aluminum, iron or tin chloride, as well as bases, acids, and alkali metals, and be explosive. Propylene oxide is similar to ethylene oxide, hence the name Methyloxirane in the reaction behavior. With water in the slow cooling, at high temperatures of 200-220 ° C. A rapid hydrolysis to 1,2- propanediol ( propylene glycol ); This is utilized for the industrial synthesis of 1,2 -propanediol.

Toxicity

Propylene oxide has been shown to be carcinogenic in animal experiments (cancer-causing ) and mutagenic ( mutagenic ). The also acutely harmful substance irritates the skin, eyes and respiratory tract, its vapors cause a narcotic effect; a harmful concentration of airborne particles can come at temperatures around 20 ° C. Its inclusion may be administered orally, pulmonary, or percutaneously through the skin thus, effected. With continuous or repeated exposure may cause sensitization. As a marine pollutant, the substance is classified in water hazard class 3.

Animal experiments have shown that inhalation of propylene oxide to a concentration of 150 ppm has no detectable effect. Continuous contact of the animals with the fabric it came to the depression of the CNS and eye and respiratory irritation. Since the odor threshold in air between 100 and 350 ppm, but is maximum permissible workplace concentration of only 2.5 ppm, the characteristic smell of the substance can not be used as an indicator of propylene oxide.