Chemical Engineering May 2020 - 28

Technology Profile
Vinyl Chloride Production from Ethylene and Chlorine
By Intratec Solutions
V
inyl chloride
(also known
as vinyl chloride monomer,
VCM and chloroethene) is an
organochloride compound.
At room temperature, VCM is a gas
with a sweet, ethereal odor, but in
industrial processes, it is most often
handled as a liquid (melting point =
-13°C). VCM is a major commodity
chemical, mainly used in the production
of the polymer polyvinyl chloride
(PVC). For this use alone, VCM is
among the top 20 petrochemicals in
world production. To a lesser extent,
VCM is used in furniture and automobile
upholstery, wall coverings,
housewares and automotive parts.
The process
This analysis describes the production
of VCM from ethylene and chlorine
via a balanced process (Figure
1). The process comprises four major
sections: (1) oxychlorination; (2) direct
chlorination; (3) ethylene dichloride
(EDC) cracking; and (4) purification.
Oxychlorination.
Hydrogen
chloride
(HCl) is reacted with ethylene
and oxygen, yielding EDC and water.
Oxychlorination is conducted
above 200°C. High conversion and
selectivity are obtained with metallic
chloride catalysts. The EDC obtained
is partially condensed and
compressed before it is fed to a
series of columns for
purification.
High-boiling and low-boiling compounds
are recovered and converted
to CO2, water and HCl, which is
recycled to the reaction.
Hydrogen chloride
7
2
1
Oxygen
Ethylene
Chloride
8
6
RF
RW
FIGURE 1. The diagram shows a production process for VCM
28
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM MAY 2020
15
16
3
4
5
Wastewater
Vinyl chloride
monomer
CW
ST
17
18
9
10
11
12
13
14
Production pathways
Originally, production of VCM on
a commercial
scale
was
based
on the reaction of HCl with acetyEthylene,
chlorine
Ethylene,
chlorine
Ethane,
chlorine
Chlorination/
oxychlorination
Direct
chlorination
Chlorination/
oxychlorination
n
Raw material n Process n Main product
Direct chlorination. Ethylene is
chlorinated to produce EDC. The
direct chlorination reaction is carried
out in the liquid phase, using EDC
itself as the solvent. The reaction is
conducted with a slight excess of
ethylene, leading to a conversion of
almost 100% and selectivity higher
than 99%.
EDC cracking. EDC from the direct
chlorination and the oxychlorination
reactions is preheated, vaporized
and thermally cracked to yield VCM,
HCl and unreacted EDC. 60% conversion
of EDC is typical, with selectivity
to VCM greater than 96%.
Purification. The VCM obtained is
partially condensed before it is fed
to a series of columns, where HCl,
EDC, VCM and impurities are separated.
Hydrogen chloride is
recovered
and recycled to oxychlorination.
Unconverted EDC is returned to
EDC purification, while VCM product,
with acidity content below 0.1
ppm, is stored.
Vinyl chloride
Cracking
Oxychlorination
Hydrochlorination
Ethylene
dichloride
Ethylene,
ethylene
dichloride
Acetylene, HCI
FIGURE 2. Several pathways exist for making VCM
lene derived from calcium carbide.
Throughout the 20th century, as ethylene
became plentiful, new production
routes for VCM were developed,
with ethylene and chlorine as main
raw materials. Figure 2 presents different
pathways for VCM production.
Economic performance
The total operating cost (raw materials,
utilities, fixed costs and depreciation
costs) estimated to produce
VCM was about $500 per ton of
VCM in the second quarter of 2016.
The analysis was based on a plant
constructed in the U.S. with the capacity
to produce 500,000 metric
tons per year of VCM.
This column is based on " Vinyl
Chloride Production from Ethylene
and Chlorine - Cost Analysis, " a report
published by Intratec. It can be
found at: www.intratec.us/analysis/
vinyl-chloride-production-cost. n
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.
1. Oxychlorination
1. Oxychlorination
2. Oxychlorination quench
3. Condensation & compression
4. Heads column
5. High-boil column
6. Vacuum column
7. Byproduct recovery
8. Chlorination reactor
9. EDC cracking
10. EDC quench
11. HCI column
12. VCM column
13. HCI stripper
14. Hydrogenation
15. Refrigeration system
16. Chiller
17. Cooling tower
18. Boiler
RW Chilled water
CW Cooling water
RF Refrigeration fluid
ST Steam
2. Oxychlorination quench
3. Condensation & compression
4. Heads column
5. High-boil column
6. Vacuum column
7. By-product recovery
8. Chlorination reactor
9. Cracking
10. EDC quench
11. HCI column
12. VCM column
13. HCI stripper
14. Hydrogenation
15. Refrigeration system
16. Chiller
17. Cooling tower
18. Boiler
RW Chilled water
CW Cooling water
RF Refrigeration fluid
ST Steam
http://www.intratec.us/analysis/ http://www.intratec.us http://www.intratec.us/che http://WWW.CHEMENGONLINE.COM
Chemical Engineering May 2020

Table of Contents for the Digital Edition of Chemical Engineering May 2020
