2. •Chemically its IUPAC name is PHENYL ETHENE
•Its structure is:
•Styrene monomer under normal condition is
liquid, colourless,odourless, flammable and Toxic liquid.
4. DEHYDROGENATION OF ETHYL BENZENE
•Ethylbenzene is dehydrogenated to styrene by the following
reaction:
5. •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
6. (1) Reaction network (products and byproduct) in the dehydrogenation of
ethylbenzene.
•Toluene and benzene are formed by (1) dealkylation reaction
(2)hydrodealkylation reaction and (3) steam dealkylation. The Coke formation and
gasification with steam is also shown (4).
7. • 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.
8. •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.
12. •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.
13.
14. With 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.
15. 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.
