Chemical Engineering January 2017 - 27

Technology Profile
Ethylene Glycol Production from Synthesis Gas
By Intratec Solutions
E
thylene glycol, also known as
monoethylene glycol (MEG), is
a major chemical commodity,
widely used in the production
of polyethylene terephthalate (PET)
bottle-grade resins and polyester fibers.
These materials, in turn, are used
to manufacture textiles, soft drink and
water bottles, tire cords and more.
MEG was first synthesized via the
hydrolysis of ethylene glycol diacetate.
Now, it can be made from multiple raw
materials, such as coal, natural gas and
ethylene. Globally, it is mainly produced
from ethylene via an ethylene oxide intermediate.
This process generates diand
tri-ethylene glycol along with MEG.
The process
In the process described here, ethylene
glycol is produced from synthesis gas
(syngas), a gaseous mixture of carbon
monoxide (CO) and hydrogen (H2). CO
is first converted to dimethyl oxalate
(DMO), which is then hydrogenated to
form ethylene glycol (Figure 1).
Carbonylation. The CO and H2 in the
feed syngas are separated. The recovered
CO is fed to the carbonylation
reactors along with a recycled stream
from the nitrite regeneration section
(discussed below) that contains an
intermediate (methyl nitrite). Methyl
nitrite reacts with CO to produce the
intermediate DMO and nitric oxide
(NO). The product from the carbonylation
reactors is partially condensed,
generating a gaseous stream, rich in
unconverted CO and NO, and a liquid
stream, rich in DMO. The former is directed
to the nitrite-regeneration section,
and the latter is directed to the
DMO hydrogenation section.
Syngas
CO
1
H2
Oxygen
CW
2
CW
3 CW
BFW ST
FIGURE 1. The diagram shows production of fiber-grade
ethylene glycol from synthesis gas via dimethyl oxalate
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5
Fiber-grade MEG
Heavies to fuel
JANUARY 2017
27
Methanol
Water to
waste
ST
4
6
7
CW
RF
Methyl-nitrite-rich stream
1,200
1,100
1,000
900
800
700
600
500
2006
2007
2008
2009
DMO hydrogenation. The DMO-rich
stream is fed to the hydrogenation reactors
along with H2 recovered from
the syngas feed. DMO reacts with H2
to produce the final product, ethylene
glycol and methanol. A few byproducts
from undesired side reactions
also form. The product stream from
the hydrogenation reactors is partially
condensed, and the condensate
is directed to the purification section.
Uncondensed vapor (mostly H2) is
compressed and recycled to the hydrogenation
reactors.
Purification. The purification system
consists of a series of distillation steps
to separate fiber-grade ethylene glycol
from methanol and other byproducts
formed during DMO hydrogenation.
Methanol is recovered from an intermediate
distillation column and is recycled
to the nitrite-regeneration section.
Nitrite regeneration. The recovered
NO stream from the carbonylation section
is mixed with O2 and contacted
in a reactive absorber with methanol,
which is recycled from the purification
section, as well as from a distillation
column downstream. These chemicals
CW
ST
RF
2010
2011
FIGURE 2. This graph
shows the yearly average
prices for MEG in the U.S.
2012
2013
2014
react to produce methyl nitrite and water.
The top product stream from the
nitrite reactor is partially condensed
to remove most of its water and the
resulting methyl-nitrite-rich stream is
recycled to the carbonylation section.
The reactor bottom product is directed
to a water-removal distillation column.
Economic performance
Variable costs (raw materials and utilities)
for manufacturing MEG from syngas
in the U.S., using data from Q1
2013, are estimated to be $600/ton
of product. Historical yearly average
prices for MEG are shown in Figure 2.
This column is based on " Ethylene
glycol production from Syngas
- Cost Analysis, " a report published
by Intratec. It can be found at: www.
intratec.us/analysis/ethylene-glycolproduction-cost.
n
Edited
by Scott Jenkins
Editor's note: The content for this column is supplied by Intratec
Solutions LLC (Houston; www.intratec.us) and edited by
Chemical Engineering. The analyses and models presented are
prepared on the basis of publicly available and non-confidential
information. The content represents the opinions of Intratec only.
More information about the methodology for preparing analysis
can be found, along with terms of use, at www.intratec.us/che.
8
9
10
1. Syngas separation
2. Carbonylation reactors
3. DMO hydrogenation reactors
4. H2
recycle compressor
5. MEG purification system
6. Methyl nitrite reactor
7. Water removal column
8. Cooling tower
9. Steam boiler
10. Refrigerant system
CW Cooling water
ST Steam
RF Refrigerant
BFW Boiler feed water
Average price ($/ton)
http://www.intratec.us/analysis/ethylene-glycol http://www.intratec.us http://www.intratec.us/che http://WWW.CHEMENGONLINE.COM
Chemical Engineering January 2017

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