PRODUCTION OF ETHYLENE GLYCOL
Manufacturing process Discrimination
The different processes followed for the production of ethylene glycol includes:
Ethylene carbonate process:
In this method, ethylene oxide is converted to an intermediate, ethylene carbonate, by
reaction with carbon dioxide, which is then hydrolyzed by water to give ethylene glycol.
This process was in use in the 1970s, but this process was replaced later by combined
ethylene oxide-glycol plants.
Halcon Acetoxylatin Process:
Two reaction steps were used in the Oxirane plant. In the first, ethylene glycol
diacatate is obtained by the oxidation of ethylene in an acetic acid solution, catalyzed by
tellurium and a bromine compound.
The reaction complex, which is quite complicated, proceeds via a tellurium-
bromoethylene complex. The oxidation, which is carried out at 90-200 °C and 20-30 atm
pressure, results in a mixture of acetates due to partial hydrolysis of the diacetate.
The reaction liquid effluent is withdrawn and processed to recover glycol acetates and
glycol and provide the recycle streams back to oxidation.
In the second step of the process, the glycol acetates are hydrolyzed to ethylene
glycol and acetic acid.
The process is obviously relatively more complex and will amount to huge capital
cost and Literature also shows that it has operating difficulties. A plant started at
Channelview in United State to produce 800 million lb/yr of ethylene glycol was shut down
after difficulties in start up.
Esterification:
Ethylene glycol can be produced by reaction of formaldehyde with carbon monoxide.
This route first produces glycolic acid which is converted by esterification and
hydrogenolysis to ethylene glycol.
HCHO +CO + H
2
0 HOCH
2

2
CH
2
OH

An expensive rhodium based catalyst catalyzes the reaction. The process is yet to be
commercialized. Union Carbide has already started work on a modified process in association
with Ube Industries. It plans to set up a commercial scale plant soon.
Oxidation of Ethylene:
This process involves the oxidation of ethylene to ethylene glycol in an aqueous
medium using an iron copper catalyst to produce Ethylene Glycol as represented in the
reaction below.

Fe-Cu
CH
2
=CH
2
+ ½ O
2
+ H
2
0 HOCH
2
CH
2
OH
Hydrolysis of Ethylene Oxide:
The reaction chemistry is quite simple; it is either acid or thermally catalyzed. It is
summarized as follows: ethylene oxide reacts with water to form ethylene glycol, and then

3CH
2
CH
2
O + H
2
O → HOCH
2
CH
2
OCH
2
CH
2
OCH
2
CH
2
O
triethylene glycol
Production Process Description
In the process either a 0.5 to 1.0% sulphuric acid (H2SO4) catalyst is used at 50 to
70oC for 30 minutes or, in the absence of the acid, a temperature of 195oC and 185 psi for 1
hour will form the diol. The formation of higher glycols is inevitable because ethelene oxide
reacts faster with ethylene glycols faster than with water. The most important variable is the
water-to-oxide ration, and the production of diethylene glycol (DEG) and triethylene glycol
(TEG) can be reduced by using a large excess of water. A 90 percent yield is realized when
the ethylene oxide/water molar ratio is 1:5-8.
The advantage of the acid-catalyzed reaction is no high pressure, however the thermal
reaction needs no corrosion resistance and no acid separation step.

As stated above this reaction can be acid or based catalysed but for this work a choice
of a neutral and high pressure and temperature reaction is made because it has the economic
advantage of having no need for corrosion resistance and no acid separation step.
The chemistry of the reaction is summarized as follows: ethylene oxide reacts with
water to form ethylene glycol, and then further reacts with ethylene glycol and higher
homologues in a series of consecutive reactions as shown in the following equations:
Step 1
CH
2
CH
2
O + H
2
O → HOCH
2
CH
2
O
ethylene glycol
Step 2
2CH
2
CH
2
O + H
2
O → HOCH
2
CH
2

concentration of the ethylene glycol produced to discourage the formation of higher glycols.
Production Process Description
Ethylene Oxide and water a passed into a Continous Stirring Tank Reactor which
operates a temperature of 195oC and pressure 185 psi for 1 hour will form the diol. Since the
formation of higher glycols is inevitable because ethelene oxide reacts faster with ethylene
glycols faster than with water then the water-to-oxide ration must be manipulated to reduce if
not eliminate the production of diethylene glycol (DEG) and triethylene glycol (TEG). This is
done by using a large excess of water. In this work, the ethylene oxide/water molar ratio is 1:
7 and the yield of Ethylene glycol is 90%. This Plant is designed to produced 10000kg/yr of
Ethylene Glycol.
The crude Ethylene produced from the reactor is dehydrated and recovered as highly
pure overhead stream from a distillation column with a partial condenser. The Distillate from
the partial condenser is mainly water and is recycled back to the reactor and mixed with
incoming water. The flow sheet for this sequence is shown below
P
Fig: Shows the Flow sheet for the Production of Ethylene Glycol Simulated on Aspen
Hysis
MATERIAL BALANCE FOR THE REACTOR
Reaction Stoichiometry:
CH
2
CH
2
O + H
2
O → HOCH
2
CH
2
O

-5
kmol/sec of ethylene glycol must be produced
from the reactor to be feed into the column.
From Literature, the yield of Ethylene Glycol in the reactor is 90%
Yield of 90% implies
Moles of ethylene oxide used up in the reaction/total moles of ethylene Oxide = 90/100
5.38x10
-5
kmol/moles of ethylene oxide = 0.9
Therefore, moles of ethylene oxide = 5.38x10
-5
/0.9 = 5.97x10
-5
kmol of ethylene Oxide is
used up during the reaction but 5.97x10
-5
/0.9 = 6.63x10
-5
kmol/sec of Ethylene is actually feed
into the reactor
Mass of ethylene Oxide required per second = 44kg/kmol x 6.63x10
-5
kmol = 2.92x10
-3
kg
Unreacted Ethylene oxide = 6.63x10
-5
kmol/sec - 5.38x10
-5
kmol/moles = 6.6x10

Therefore
Amount of water left unconverted = Total Water fed – Amount that took part in the reaction
= 4.64x10
-4
kmol – 5.97x10
-5
kmol = 4.04x10
-4
kmol
=4.04x10
-4
kmol x 18kg/kmols = 7.27x10
-3
kg/sec of Water
=7.27x10
-3
/1000 = 7.27x10
-6
m
3
/sec of Water
ENERGY BALANCE FOR THE REACTOR
Equation of the reaction
C
2
H
4(g)
+ H
2
0

c – the Temperature of water available
Degree of approach is taken as 10
0
c
CP of water = 4.180kj/kgk
Thus
8.91x10
-3
kj/s = mCPDT = m x 4.180 x (35-25) +273k
Where 25
0
c – the Temperature of water available
Degree of approach is taken as 10
0
c
CP of water = 4.180kj/kgk
m = 8.91x10
-3
/ 1162.04= 7.67 x 10
-6
kg/s
Thus 7.67 x 10
-6
kg/s of water must be feed into the cooler system around the reactor to
maintain at operational temperature.
MATERIAL BALANCE FOR THE DISTILLATION COLUNM
Ethylene Glycol has a boiling point of 197.6
0
c while water has a boiling point of
100

Therefore
Bottoms (B) = 5.33x10
-5
kmol/s + 4.04x10
-6
kmol/s = 5.734x10
-5
kmol/s
Distillate (D)
Specification
100% Water
Distillate (D) = F – B = 4.64x10
-4
kmol/s - 5.734x10
-5
kmol/s = 4.07x10
-4
kmol/s
L+D=T
Where
L=Flow of Condensate returned to the column
D=Flow of condensate taken out as Distillate
T=Flow of vapour leaving the first stage of the column
Reflux Ration = L/D
At 2.5reflux, L/D=2.5
L=2.5D = 2.5x4.07x10
-4
kmol/s = 1.02x10
-3
kmol/s

specified as 0.99. It was noted that the HYSIS Estimate of the other Distillate flow, Bottoms
flow etc were very close to the manual calculations made for them. The result of the
simulation is shown below along with the condenser and heater duties.
ETHYLENE GLYCOL/WATER SPLITTER FLOW
SHEET
SPECIFICATION FOR THE REACTOR EFFLUENT
(COLUMN INPUT) DISTILLATE ESTIMATE
BOTTOMS ESTIMATE
class="bi x4 yd0 w8 h11"