1-Octene

1-Octene is a higher olefin, or alkene, with a formula C₈H₁₆. 1-Octene is an alpha-olefin, meaning that the double bond is located at the alpha (primary) position, endowing this compound with higher reactivity and thus useful chemical properties. 1-Octene is one of the industrially important linear alpha olefins.

Physical properties

1-Octene is a clear colorless flammable liquid that is immiscible with water.

Refractive index: 1.4087

Flashpoint: 13 °C

Critical temperature: 560.1 °F (293.4 °C)

Critical pressure: 375 psia (2.59 MPa absolute)

Critical density: 0.244 g/ml

Synthesis

Industrially, 1-octene is commonly manufactured by two main routes: oligomerization of ethylene and by Fischer-Tropsch synthesis followed by purification. Another route to 1-octene which has been used commercially on a small scale is dehydration of alcohols. Prior to the 1970s 1-octene was also manufactured by thermal cracking of waxes, whereas linear internal octenes were also manufactured by chlorination/dehydrochlorination of linear paraffins.

There are five commercial processes which oligomerize ethylene to 1-octene. Four of these processes produce 1-octene as a part of a wide distribution of alpha-olefins. Typically, 1-hexene content of the entire distribution of alpha-olefins ranges from about 25% of the distribution in the Ethyl (Innovene) process to about 8% of distribution in some modes of the Gulf (CP Chemicals) and Idemitsu processes.

The only commercial process to isolate 1-octene from a wide mixture of C₈ hydrocarbons is practiced by Sasol Ltd., a South African oil and gas and petrochemical company. Sasol commercially employs Fischer-Tropsch synthesis to make fuels from synthesis gas derived from coal and recovers 1-octene from these fuel streams, where the initial 1-octene concentration in a narrow distillation cut may be 60%, with the remainder being vinylidenes, linear and branched internal olefins, linear and branched paraffins, alcohols, aldehydes, carboxylic acids and aromatic compounds.

Synthesis of 1-octene as a part of multi-product ethylene oligomerization process or a Fischer-Tropsch process is covered in an article on linear alpha olefins.

Although several processes have been proposed in patents or in technical literature, there is not a viable commercial process which produces only 1-octene.

Applications

The primary, even overwhelming, use of 1-octene is as a comonomer in production of polyethylene. High density polyethylene (HDPE) and linear low density polyethylene (LLDPE) use approximately 2-4% and 8-10% of comonomers, respectively.

Another significant use of 1-octene is for production of linear aldehyde via OXO Synthesis (hydroformulation) for later production of the short-chain fatty acid nonanoic acid, a carboxylic acid, by oxidation of an intermediate aldehyde or linear alcohols for plasticizer application by hydrogenation of the aldehyde.

Synonyms

Octene-1, octylene; 1-n-ctene; hexylethylene; oct-1-ene; octene.

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