ethylbenzene : ENVIRONMENTAL, HEALTH & SAFETY Guidelines
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1.2 Manufacturing

Commercially, almost all ethylbenzene (> 99 %) is produced by alkylating benzene with ethylene, except for a very small fraction that is recovered from mixed C8 aromatics (xylenes) by superfractioning.

Ethylbenzene and styrene units are almost always installed together, with matching capacities. In a typical ethylbenzene-styrene complex, energy economy is realized by advantageously integrating the energy flows of the two units. The alkylation is exothermic, while the subsequent dehydrogenation to styrene is endothermic.

The reaction of benzene and ethylene takes place on an acidic catalyst (Lewis acids):
C6H6 + CH2=CH2 ↔ C6H5CH2CH3

The newest technologies utilize synthetic zeolites installed in fixed-bed reactors to catalyze the alkylation in the liquid phase. Another proven route uses narrower-pore synthetic zeolites, also installed in fixed-bed reactors, to effect the alkylation in the vapour phase. A considerable quantity of ethylbenzene is still produced by alkylation with homogeneous aluminum chloride catalyst in the liquid phase, though the recent trend in the industry has been to retrofit such units with zeolite technology.

Several facilities built in the United States, Europe and Japan during the 1960’s recovered ethylbenzene by fractionation of mixed xylenes (C8 aromatics) produced mainly in refinery catalytic reforming units. Mixed-xylenes capacity worldwide was 36 million tonnes in 2002. This practice has largely been discontinued, due to poor economics that result from high energy and investment costs, as well as small economies of scale (mixed xylenes only contain about 20 % ethylbenzene) in comparison to the conventional alkylation routes.

For more details on production technologies and the latest technology trends, please refer to Reference 2 of the Bibliography.


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