CL 4003 PETROCHEMICALS AND REFINERY ENGINEERING
Department of Chemical Engineering
Birla Institute of Technology Mesra, Ranchi1
✓ Cumene is used to manufacture other chemicals such as
phenol, acetone, acetophenone, and methyl styrene.
✓ It is used as a thinner in paints, lacquers, and enamels.
✓ It is a component of high octane motor fuels.
✓ The production of cumene (isopropyl benzene) involves the
reaction of benzene with propylene in a high-temperature,
high-pressure gas-phase reactor.
C6H6 + C3H6 → C9H12
✓ There is also a sequential reaction of cumene and propylene to
form p-diisopropylbenzene (PDIB).
C9H12 + C3H6 → C12H18
✓ The benzene is kept in excess to limit the amount of DIPB
✓ Propylene obtained from refinery processes as a mixture of
propylene and propane.
✓ The mixture along with benzene is compressed to 25 atms.
✓ Eventually the mixture enters a heat integrated exchanger to
pre-heat the feed mixture.
✓ The feed mixture enters a packed bed reactor.
✓ Cold propane from the distillation column in the process is
added after every reactor with the product stream so that the
temperature of the stream is controlled.
✓ Here, propylene is the limiting reactant and therefore,
presumably all propylene undergoes conversion.
✓ Here, propane does not react but is a diluents or inert in the
system. In that way it controls the reaction temperature.
✓ The reactor units are maintained at about 250 °C.
✓ The product vapors are cooled using the heat integrated
✓ The vapors then pass to a de-propanizer which separates
propane from the product mixture.
✓ The bottom product consisting of benzene, cumene and
polyalkyl benzenes enters another distillation column which
separates benzene from the mixture of cumene and polyalkyl
benzene. The benzene stream is recycled to enter the
✓ The bottom product from the benzene column is sent to a
cumene column which produces cumene as top product and
poly alkyl benzene as bottom product.
✓ The largest end-use for phenol is in the manufacture of
bisphenol A (BPA). Although it is under regulatory pressure for
health and safety reasons, BPA is the key building block for
making polycarbonate and epoxy resins.
✓ The next largest use for phenol is in the production of phenol-
formaldehyde (PF) resins. PF resins are used primarily in wood
adhesives, for example, for bonding the layers of plies in exterior
✓ Around 98% of cumene is used to produce phenol and its co-
✓ The largest phenol derivative is bisphenol-A (BPA) which
supplies the growing polycarbonate (PC) sector.
✓ PC resins are consumed in automotive applications in place of
traditional materials such as glass and metals. Glazing and
sheet uses, such as architectural, security and glazing outlets,
are also important PC applications. The third largest use for PC
is optical media such as compact discs (CDs) and digital
versatile discs (DVDs).11
✓ BPA’s other main derivative is epoxy resins which are used in
high performance coatings, electrical-electronic laminates,
adhesives, flooring and paving applications, and composites.
✓ Phenol’s other derivatives include phenolic resins which are
largely used as durable binders and adhesives in structural
wood panels and as binders in mineral wool insulation.
✓ Another phenol derivative is caprolactam which is used mainly
to make nylon 6. It is mainly the engineering resin sector of the
nylon market that is seeing growth.
✓ The key drivers in the acetone market are methyl methacrylate
(MMA) and BPA. Nearly all MMA is used to make homopolymers
and copolymers with electronic applications such as flat screen
TVs and liquid crystal displays providing growth opportunities.
✓ In the Hock process, cumene (1, made by alkylating benzene
with propylene) is oxidized to cumene hydroperoxide (2), which
is then cleaved to a mixture of phenol (3) and acetone (4) by
treating it with H2SO4.
✓ The good news is that for every 10 kg of phenol produced, 6.2
kg of acetone is coproduced. The bad news is that for every 10
kg of phenol produced, 6.2 kg of acetone is coproduced. The
process can be good or bad, depending on the petrochemical
✓ “Two-for-one” processes sound good in concept, but they only
work commercially if the markets for both products are
changing at about the same rate. Otherwise, one product will be
in oversupply, which causes its price to fall and penalizes the
economics of the entire process. 15
✓ Fresh cumene is mixed with hydrogenated unreacted cumene,
cumene + alpha methyl styrene (recycle streams).
✓ The pre-purification step involves converting unsaturates such
as alpha methyl styrene and others to saturates. This is done by
using nickel catalyst at 100°C and feeding hydrogen to the pre-
purification reactor. The product from this unit then mixes with
the fresh cumene.
✓ The fresh cumene and processed cumene and alpha methyl
styrene are fed to the oxidation reactor. The oxidation reactor
refers to a gas-liquid reaction between air (Oxygen) and cumene.17
✓ An emulsion of cumene is prepared in the oxidation reactor by
adding alkali to it.
✓ pH is maintained in the range of 8.5 – 10.5 to suit good
✓ After reaction, vent gases are condensed and recycled back and
the product is sent to a cleavage unit.
✓ The cleavage unit consists of a stirrer and is fed with fresh and
recycled H2SO4 aqueous solution to enable the hydrolysis of
✓ The product streams from the cleavage unit enter a settler
(phase separator) which upon gravity settling yields two streams
namely the acid rich aqueous stream and the phenol rich
✓ The aqueous stream consists of the sulphuric acid and is sent
back to the cleavage unit as a recycle stream.
✓ The organic stream consists of cumene (unreacted), phenol
(product), acetone (side product), alpha methyl styrene (side
product) and acetophenone (side product).
✓ The organic stream from the gravity settler unit then enters a
scrubber fed with water. In this operation, water extracts the
remaining acids in the organic stream and produces crude
phenol stream. Water leaving the unit consists of acidified wash
✓ The crude phenol then enters a distillation unit that separates
acetone from the other components.
✓ The bottom product from this distillation column enters a
vacuum distillation column that produces cumene as a top
✓ The bottom product from the distillation column enters another
vacuum distillation unit to produce alpha methyl styrene.
✓ The bottom product of this distillation column enters the final
vacuum distillation unit to produce phenol as top product and
acetophenone as the bottom product.