SummaryBenzene (C6H6), also called benzol (coal naphtha), is an aromatic flammable hydrocarbon liquid produced by coking coal in steel industries and is synthesised from natural gas.
Around the world benzene is used to produce organic chemicals, including medicines, dyes and plastics, and directly as a solvent and a component of petrol. In Australia benzene is almost exclusively used by Huntsman Chemicals to produce styrene and some phenol. Extraction from petrol Benzene, together with the other aromatics methylbenzene, ethylbenzene and the xylenes is a major component of petrol, typically representing between 25 and 30 per cent of the blend . Of these aromatics, benzene is normally a minority component representing one-tenth of the aromatic content (ie. 3 per cent) of the petrol. Petrols with reduced benzene are produced by installing a separate benzene extraction process which results in benzene rich or pure benzene streams.
Benzene is also a component of petroleum, typically around 3 per cent by mass. Given Australia’s production of some 13 million tonnes of petrol per year, this represents the production of some 400 000 tonnes per year - over three-times current usage by Huntsman (and four-times the level of imports).
In 1993 (and before the Huntsman part acquisition of Chemplex), Shell Australia was quoted in European Chemical News (17 May page 18) as having considered a benzene extraction plant at one of its refineries but is “uncertain whether a local and dependent market can be found”. The aromatic components of petrol are to a small degree present in the original crude oil and are thus also produced in some of the distillation streams which involve separation only (ie. with no chemical conversion). Most aromatics such as benzene are produced as part of the reforming process where there is a high degree of chemical conversion to compounds of' a higher octane value. Benzene, toluene and alkyl benzenes are largely produced this way within the reforming process. They are thus components of reformate which is a blend stream for petrol. The benzene, toluene, alkyl benzenes are only present as part of the reformate stream.
To a small degree the aromatics components in petrol can be altered by selecting a different crude feedstock and in the case of benzene, by selecting the distillation cut point of the reformer feed (naphtha) to exclude the benzene precursors. However, this is not an optimal procedure as it reduces the reformate octane, which then has to be made up by more severe processing on other units. Such additional processing adds to the cost and energy consumption in the refining process.
It is relevant to note that during 1996 under state legislation in the USA, Reformulated Gasoline will be marketed in certain states and regions. This petrol will cost more (though also containing oxygenates) and is promoted as containing lower aromatic hydrocarbons (ie. including benzene). The implication is that these hydrocarbons can be extracted from petrol but the economics appears to be marginal. Benzene can also be produced by the steam cracking of LPG and reforming but a competitive plant would have to produce about 300 000 tpa - three times Australia’s market. Of course it could also be produced by a petroleum refinery with indications of that intention. Legislated reductions in the content of benzene in petroleum could substantially impact on refinery and production economics.
The value and quantity of imports of benzene can only be estimated as it is declared confidential by the ABS under their guidelines (which apply if there is less than about three producers or traders). Imports of benzene are believed to be around 50 000 tpa. Benzene is imported as a component of the estimated 60 000 tonnes of imported BTX (benzene, toluene [methyl benzene] and xylene) used by Huntsman to produce benzene (by dealkylation).
The only commercial supply of benzene in Australia is from BHP’s coking plants at Whyalla and Point Kembla collectively producing around 20 000 tpa . Benzene is produced as a mixture with other aromatic hydrocarbons as BTX.