Module: 3 Lecture: 18 ETHYLENE GLYCOL

Module:3
Lecture:18 Ethylene glycol
Dr. N. K. Patel
Module: 3
Lecture: 18
ETHYLENE GLYCOL
INTRODUCTION
Ethylene glycol is an odourless, colourless, syrupy, sweet-tasting organic
liquid. It is widely used as an automotive antifreeze and a precursor to
polymers.
Ethylene glycol was first prepared by Charles-AdolpheWurtz in 1856 but
was reported in 1859. He first treated "ethylene iodide" (C2H4I2) with silver
acetate and then hydrolyzed the resultant "ethylene diacetate" with
potassium hydroxide. Wurtz named as glycol because it was intermediate to
ethyl alcohol and glycerine. In 1860, Wurtz prepared ethylene glycol from the
hydration of ethylene oxide. Prior to world war I, there is no commercial
application of ethylene glycol. After first world warit was synthesized from
ethylene dichloride in Germany and used as a substitute for glycerol in the
explosives industry.
In 1917 semicommercial production of ethylene glycol via ethylene
chlorohydrin was started in USA. The first large-scale commercial glycol plant
was erected by union carbide corporation in 1925. Almost all dynamite
manufacturers used ethylene glycol up to 1929.
Du pont, USA produce ethylene glycol form formaldehyde. This process
is the latest in the manufacturing of ethylene glycol. In this process
hydroformylation of formaldehyde produce glycolaldehyde an intermediate
in the manufacturer of ethylene glycol.
MANUFACTURE
Ethylene glycol was manufactured from ethylene from cracked
petroleum by the following two processes.
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Module:3
Lecture:18 Ethylene glycol
Dr. N. K. Patel
1. Via ethylene oxide (70% yield)
Raw material
Basis -1000kg ethylene glycol (70% yield)
Ethylene
865kg
Oxygen
180kg
Water
203kg
Reaction
Manufacture process
Water or 1% H2SO4
To ejector
Silver oxide
catalyst
Oxidation
tower
Hydrator
Distillation
Ethylene
Steam
Air
Ethylene glycol
(di and tri-ethylene
glycol)
Figure: Manufacture of Ethylene glycol via ethyleneoxide
Block diagram of manufacturing process
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Lecture:18 Ethylene glycol
Dr. N. K. Patel
Diagram with process equipment
Animation
In the oxidation tower, pure ethylene and air was passed under
atmospheric pressure over silver oxide catalyst at about 300 0C temperature.
Ethylene - air mole ratio should be kept at 1:10. While contact time should be
kept about one second. So, 60 – 70% ethylene was converted into ethylene
oxide. Ethylene oxide was then passed in to the hydrator where it was
hydrated at 1950C with water for 1hr in a tower or may be hydrated with 1%
H2SO4 at 600C for 1.5hr to yield ethylene glycol.
The crude glycol then run into the distillation column where it was
distilled under reduced pressure. Di- and tri-ethylene glycol was separated
out from the bottom of the distillation column while impurities was ejected
from top of the column.
2. Via ethylene chlorohydrin
Raw material
Basis -1000kg ethylene glycol(70% yield)
Lime
315kg
Ethylene
320kg
Chlorine
200kg
Sodium bicarbonate
950kg
Reaction
Manufacture process
Block diagram of manufacturing process
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Module:3
Lecture:18 Ethylene glycol
Dr. N. K. Patel
Diagram with process equipment
Animation
To ejector
Sodium
bicarbonate
Distillation
tower
Chlorinator
Lime
bed
Steam
Tower
Ethylene
Steam jacket vessel
Chlorine
Ethylene glycol
Figure: Manufacture of Ethylene glycol via ethylenechlorohydrin
Ethylene was passed over bed of hydrated lime at pressure of 200atm
at 2000C so, that it contained about 28gms of ethylene per litre of alkali
solution. The solution was pumped into a chlorination chamber under the
same pressure, where it was reacted with chlorine to form calcium
oxychloride (CaOCl2), which rapidly decomposed to form calcium chloride
and hypochlorous acid. The ethylene was reacted with hypochlorous acid to
produce ethylene chlorohydrin.
The solution of ethylene chlorohydrin from chlorinator was withdrawan
and run into steam jacket vessel. The steam jacket vessel was fitted with
stirrer. The solution was treated with sodium carbonate at about 70 – 800C. For
the complete hydrolysis treatment, reaction was continued for about 5 – 6hrs.
After hydrolysis process ethylene glycol form vessel was passed into distillation
tower under reduced pressure. About 65 - 70% ethylene glycol yield was
obtained.
Engineering aspects
An uncatalyzed hydrolysis of ethylene oxide to ethylene glycols also
form bi and tri ethylene glycols. The current process gives dependent
production of ethylene glycol and diethylene glycol.
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Module:3
Lecture:18 Ethylene glycol
Dr. N. K. Patel
 Effect of water ratio
Different glycols are produced by varying the ratio of water to ethylene
oxide. Excess amount of water promotes ethylene glycol selectivity. Removal
of water requires capital investment in evaporators and increases energy
consumption. These factors limits the amount of excess water which can be
used for control of the uncatalyzed selectivity of ethylene glycol.
PROPERTIES
Monoethylene glycol
 Molecular formula
 Molecular weight
 Appearance
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Odour
Boiling point
Freezing point
Vapour pressure
Autoignition temperature
Flash point
Lower explosive limits
Density
Solubility
: C2H6O2
: 62.07gm/mole
: Colourless hygroscopic liquid, absorbs
twice its weight of water at 100%
relative humidity
: Slightly sweet odour
: 197.50C
: -130C
: 0.05mm at 200C
: 4000C
: 111.10C
: 3.2%
: 1.113gm/cm3 at 250C
: Miscible with water, aldehydes and
pyridine, slightly miscible with ether and
insoluble in chlorinated hydrocarbon,
benzene, petroleum and oils
Diethylene glycol
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Molecular formula
Molecular weight
Appearance
Odour
Boiling point
Melting point
Freezing point
Vapour pressure
: C4H10O3 [(HOC2H4)2O]
: 106.12gm/mole
: Colourless hygroscopic syrupy liquid
: Odourless
: 245.80C
: -6.50C
:-8.00C
: 1mm at 91.80C
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Module:3
Lecture:18 Ethylene glycol
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Autoignition temperature
Flash point
Density
Solubility
Dr. N. K. Patel
: 228.890C
: 123.890C
: 1.118gm/cm3 at 200C
: Miscible with water, ether, alcohol,
acetone, ethylene glycol and insoluble
in carbontetrachloride, benzene
Triethylene glycol
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Molecular formula
Molecular weight
Appearance
Odour
Boiling point
Melting point
Freezing point
Vapour pressure
Autoignition temperature
Flash point
Density
Lower explosive limits
Upper explosive limits
Solubility
: C6H14O4 [(HOC2H4)3O]
: 150.17gm/mole
: Colourless hygroscopic liquid
: Odourless
: 285.00C
: -7.20C
: -7.30C
: 1mm at 114.00C
: 371.110C
: 176.670C
: 1.127gm/cm3 at 150C
: 0.9%
: 9.2%
: Miscible with water, benzene, alcohol,
toluene and sparingly soluble in ether
and insoluble in petroleum ether
USES
 Ethylene glycol is mostly used as antifreeze agent
 Used as coolant and heat transfer agent for example it is used in as
medium for convective heat transfer
 As chilled water air conditioning system
 Important precursor to polyester fiber and resins as it is used in
manufacturing of polyethylene terephthalate which is used for plastic
bottles for soft drinks
 Because of its high boiling point and affinity to water, it is a useful
desiccant
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