Chemical Engineering Department

Styrene Production

What is STYRENE ?

•Chemically its IUPAC name is PHENYL ETHENE

•Its structure is:

•Styrene monomer under normal condition is liquid, colourless,odourless, flammable and Toxic liquid.

Styrene is manufactured by two methods

Dehydrogenation of ethyl benzene.

Co-product with propylene oxide

(Account for 90% of production) (account for just 10% Of production)

DEHYDROGENATION OF ETHYL BENZENE

•Ethylbenzene is dehydrogenated to styrene by the following reaction:

Reaction:

About the chemistry of reaction•The dehydrogenation of Ethyl benzene is an ENDOTHERMIC reaction (ΔH=129.4kJ/mol).•The catalyst used is Potassium promoted iron oxide for higher Selectivity and activity •At room temperature equilibrium is shifted toward the reactant side, It can be shifted toward the product side by increasing temperature to 600° C with excess of steam ;with steam EB ratio of 5:1 to 12:1.• The pressure condition is kept around 0.1 bar.•The conversion of 50 to 60% is obtained in technical reactor.•The typical byproducts of the EB dehydrogenation are (~1%) benzene and (~2%) toluene formed by catalytic dealkylation and hydrodealkylation of EB

(1) Reaction network (products and byproduct) in the dehydrogenation ofethylbenzene. •Toluene and benzene are formed by (1) dealkylation reaction(2)hydrodealkylation reaction and (3) steam dealkylation. The Coke formation andgasification with steam is also shown (4).

Advantages of using superheated steam• Shift of equilibrium towards higher EB conversion, (reduce educts partial pressure).• Supplies part of the heat needed for the endothermic reaction.•Decrease carbonaceous deposits by steam reforming reaction.•Avoid catalyst over reduction and deactivation by controlling the valence state of iron i.e. prevent reduction to metallic state and limiting it to Fe3O4 under reaction conditions.

SIGNIFICANCE OF CATALYST•The dehydrogenation of EB to St in industry is carried out over potassium promoted iron oxide catalysts.•Potassium was found to increases the activity of pure Fe2O3 (hematite) catalysts by one order of magnitude, and is believed to play a role in the removal of carbonaceous surface deposits, by catalyzing the combustion of coke with steam.•An interesting question is why potassium is clearly the most used alkali promoter in commercial styrene catalysts. This is most probably a result of secondary effects. Under operating conditions (part of) the iron oxide exists as Fe3O4 (magnetite). Smaller alkali ions like, e.g. Li+ can more easily migrate into the magnetite lattice and are no longer available for the gasification reaction. Larger ions, such as Cs+, catalyze the gasification reaction so strongly that also more St is gasified, resulting in a lower selectivity.

INDUSTRIAL PROCESS UNIT

Fire Heater

Rectors

Distillation column

Vessels

Heat Exchangers

Pump

USES OF STYRENE•It is used in packaging such as jewel cases that protect your CDs and containers that keep yogurt fresh to toys and recreational equipment, and myriad consumer electronics, construction, transportation and medical applications.• Probably the most recognizable material is polystyrene, often encountered as expanded polystyrene foam (EPS).•Other styrene-based materials include acrylonitrile-butadiene styrene (ABS), styrene-acrylonitrile (SAN), styrenebutadiene rubber (SBR), and unsaturated polyester resin (UPR), which is better known as fiberglass.• Helmets made from impact-absorbing styrene-based plastics and composites.• EPS is used in storage of transplant organs.• ‘Home Sweet Home’ Wouldn’t Be the Same Without Styrene, everything from switches, dials, keyboard, microwave , refrigerator etc. all use styrene and its product.•Getting a Safe Grip on the Road: SBR is used in tyre.

USES OF STYRENE

Health and safetyWith reliable equipment, air quality should be regularly monitored to insure that contaminants remain at a safe level.

Employees should be educated in the appropriate response should a spill or leakage occur.

Care should be taken in storage of flammable substances.

Environmental Concerns

By making energy efficiency, one can decrease the amount of fuel consumed by focus in the design of the styrene production plant.

Another way to help compensate for the environmental damage due to carbon dioxide emissions is the implementation of carbon sinks.

Plants and trees which consume carbon dioxide as a part of their metabolic cycle are examples of natural carbon sinks to reduce the effect of greenhouse gases until a permanent solution is found.

THANK YOU !