Chemical Engineering July 2019 - 34

Technology Profile
Epichlorohydrin Production from Propylene
By Intratec Solutions
E
pichlorohydrin, (also known
as ECH and chloromethyloxirane),
is an organochlorine
compound and a highly
reactive epoxide that is widely used
in the production of epoxy resins.
Produced with purities of greater
than 98%, epichlorohydrin is a clear,
colorless liquid. At commercial scale,
epichlorohydrin is mainly produced
via chlorohydrination of allyl chloride,
obtained in turn from the chlorination
of propylene at high-temperature.
Epichlorohydrin is mainly used in
the production of bisphenol A, a raw
material for epoxy resins, glycerol,
and elastomers.
The process
The process under analysis comprises
three major sections: allyl
chloride reaction; propylene recovery;
and epichlorohydrin (ECH) production.
Figure 1 presents a simplified
flow diagram.
Allyl chloride reaction. Initially,
chemical-grade propylene is preheated,
mixed with chlorine and fed
to a reactor where the chlorination
reaction is carried out. The reaction
occurs in the vapor phase, generating
allyl chloride and byproducts.
The chlorination products are cooled
and then directed to the prefractionator,
where a stream rich in organic
chlorides is separated from unreacted
propylene and hydrogen chloride.
The organic chlorides are routed to
two distillation columns for the removal
of light-end impurities and
heavy-end impurities.
Propylene recovery. The distillate
8
7
Spent caustic
Hydrogen
chloride
solution
CG
Propylene
1
2
3
4
Heavy
Chlorine
34
components
FIGURE 1. The diagram shows the production of epichlorohydrin from propylene and chlorine
6
Low boiling
impurities
11
5
9
Hypochlorous
acid
10
Calcium
hydroxide
slurry
Heavy
components
Calcium
chloride
RF
ST
CW
13
14
15
Allyl chloride,
chlorine, calcium
hydroxide
Hypochlorination/
epoxidation
Calcium chloride
Glycerol, hydrogen
chloride, sodium
hydroxide
Hydrochlorin./
dehydrochlorin.
n Raw material n Process n Main product
Byproducts
Calcium chloride
FIGURE 2. Several production pathways exist for epichlorohydrin
from the prefractionator is washed
countercurrently with water in an absorber,
in such a way that the HCl is
absorbed. This process forms an HCl
solution, which is removed from the
column bottom. The gaseous stream
from the overhead of the absorber is
fed to a caustic scrubber, where residual
hydrogen chloride is removed. The
washed propylene gas is compressed
in a multi-stage compressor and then
recycled to the preheating stage.
Epichlorohydrin production. The
allyl chloride stream is reacted with
hypochlorous acid, formed in turn
by chlorine dispersion in water. The
chlorohydrination reaction is conducted
in the liquid phase, adiabatically.
The liquid product from
this reaction is passed through a
separator system, which separates
the aqueous phase from the hydrocarbon
phase. The aqueous phase,
containing hypochlorous acid, is recycled,
and the hydrocarbon phase,
containing glycerol dichlorohydrins,
is
Production pathways
Epichlorohydrin is commonly produced
from allyl chloride, derived
from propylene. Production routes
based on allyl alcohol and on the
glycerol byproduct from biodiesel
production have also been used. Different
pathways for ECH production
are presented in Figure 2.
Economic performance
The total operating cost (raw materials,
utilities, fixed costs and depreciation
costs) estimated to produce
epichlorohydrin was about $1,850
per ton of epichlorohydrin in the second
quarter of 2015. The analysis
was based on a plant constructed
in the U.S. with capacity to produce
80,000 metric ton per year of ECH.
This column is based on " Epichlorohydrin
Production from Propylene
- Cost Analysis, " a report published
by Intratec. It can be found at: www.
intratec.us/analysis/epichlorohydrinproduction-cost.
n
reacted
with calcium hydroxide
to yield epichlorohydrin product.
The crude ECH stream is passed
through one stripper and two distillation
columns for the removal of
calcium chloride, light-end impurities
and heavy-end impurities.
Edited by Scott Jenkins
Editor's note: The content for this column is supplied
by Intratec Solutions LLC (Houston; www.intratec.us) and
edited by Chemical Engineering. The analyses and models
presented are prepared on the basis of publicly available
and non-confidential information. The content represents
the opinions of Intratec only. More information about the
methodology for preparing analysis can be found, along with
terms of use, at www.intratec.us/che.
Low boiling
impurities
1. Preheater
12
ECH
2. Chlorination reactor
3. Quench system
4. Prefractioner
5. Impurities removal
6. HCI absorber
7. Caustic scrubber
8. Compressor
9. Hypochlorination reactor
10. Hydrolysis reactor
11. Stripper
12. Purification columns
13. Refrigeration unit
14. Cooling tower
15. Boiler
CW Cooling water
RF Refrigeration fluid
ST steam
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JULY 2019
Epichlorohydrin
Chlorination/
hypochlorination/
epoxidation
Calcium chloride,
hydrochloric acid
Chlorination/
hydrogenation/
dehydrochlorin.
Acrolein, CI2, H2
calcium
hydroxide
Propylene,
chlorine, calcium
hydroxide
http://www.intratec.us/analysis/epichlorohydrin http://www.intratec.us http://www.intratec.us/che http://WWW.CHEMENGONLINE.COM
Chemical Engineering July 2019

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