HEALTH AND SAFETY

Health and Safety

Health and Safety

Health and Safety during the Styrene production process

The ethylbenzene dehydrogenation process remains dominant for making styrene; some styrene is coproduced in the manufacture of propylene oxide. The process for making styrene from toluene via stilbene and that for making styrene from toluene and methanol are not yet economic. Costs for these processes are presented. Copolymers of styrene with maleic anhydride, methyl methacrylate, and acrylic acid, respectively, are also evaluated. The copolymer with acrylic acid has a low molecular weight. We also evaluated the manufacture of p-methylstyrene from toluene and ethylene. Costwise p-methylstyrene is barely competitive with styrene. Its polymers have some performance advantages over those of styrene, but these are not sufficient to justify substantial replacement. With surplus production capacity for styrene already in place, the growth of p-methylstyrene is expected to be slow.

Chemical Properties and Possible Danger

Styrene

Styrene (C6H5CH=CH2), also known as Phenylethylene, Vinyl-benzene, Styrol or cinnamene, is a clear, colourless liquid with a distinctive aromatic odour. Styrene is a solvent which is used for the preparation of Polystyrene, synthetic rubber and other polymers with higher molecular mass. Styrene is not completely soluble in water. Only around 300 ppm of Styrene is soluble in water in laboratory conditions. Therefore, Styrene is a highly toxic substance for marine species if it is spilled in the sea or ocean.

To produce Styrene the process used in this case study only requires the dehydrogenation of Ethylbenzene in the presence of steam over a catalyst in a fixed bed adiabatic reactor.

Catalytic dehydrogenation of ethylbenzene (EB) to styrene was introduced in the

1940s and currently accounts for about 85% of commercial production . This

endothermic and equilibrium-limited reaction is carried out primarily over iron oxide

based catalysts in either an adiabatic or isothermal reactor with short contact time in order

to prevent polymerization of the styrene. The reaction system is complicated. The major

reaction is the dehydrogenation of ethylbenzene to styrene and hydrogen with

ethylbenzene conversion of 65-70% and styrene selectivity of 90-97%:

C6H5CH2CH3 ( C6H5CH=CH2 + H2

Styrene is a volatile liquid with low toxicity following brief exposure. Liquid styrene is severely irritating to eyes and is a skin irritant, causing redness and local swelling and possibly some local tingling. If swallowed, vomiting should not be induced as it might enter and damage the lungs. Inhalation of styrene vapours may lead to respiratory irritation. Repeated or prolonged exposure to high concentrations of styrene vapours can impact the central nervous system and result in drowsiness. Effects on the visual system may cause a decrease in colour perception, but this does not lead to functional colour vision deficits. Exposures of laboratory animals to high styrene concentrations have resulted in hearing loss. In a workplace situation, hearing loss may be more related to exposure to noise, but high concentrations of hydrocarbons may contribute to this effect. Styrene monomer has been under scrutiny from regulators, health agencies and scientific bodies for many years. In terms of carcinogenicity, styrene was classified as a possible human carcinogen in 2002 by IARC ...