Production of Isopropanol
B.Sc. VI Sem Industrial Chemistry
By
Wasi ur Rahman
Department of Chemistry
AMU Aligarh
Introduction
• Molecular weight: 60.1
• Boiling point: 82.5 ˚C
• Melting point: - 89.5 ˚C
• Density: 786 kg/m3
Method of production
• Direct catalytic hydration of propylene.
• Hydration of propylene via sulfation and hydrolysis.
Reaction
Sulfation
• CH3CHCH2 + H2SO4 (CH3)2CH(OSO3H) (Isopropyl acid sulphate)
Hydrolysis
• Isopropyl sulphate + H2O Isopropanol + Sulfuric acid
Thus sulphuric acid is regenerated in the process.
Side reaction
Disiopropyl sulphate + H2O Diisopropyl ether + Sulfuric acid
Therefore, the primary reaction is a gas liquid reaction in which propylene is
absorbed into a tray tower fed with sulphuric acid.
Operating conditions
Room temperature but 20 – 25 atms. pressure
Reaction is highly exothermic
• Either pure propylene or a mixture of Propylene and other C2, C3 components can be
fed to a reactor.
• The hydrocarbon feed is compressed and fed to the reactor at about 20 – 25 atms
pressure.
• Sulphuric acid of about 70% acid strength is fed in a countercurrent mode to the tray
column where reactive absorption takes place. Here, sulfonation reaction takes place. -
The reaction is highly exothermic and therefore, refrigerated brine is used to control
the temperature in the absorber.
• Jacketed arrangement will be preferred for the tray absorption column to circulate the
refrigerated brine in the cooling jacket. - After reaction, the unreacted light ends such
as saturated components will leave the unit as the gas stream.
• The sulfonated product rich stream is then sent to a hydrolyzer cum stripper where
isopropanol is produced and is vaporized due to existing stripper temperatures.
• The hydrolyzer is fed with water to facilitate the conversion of the sulfonate product.
The isopropanol rich vapors then enter a caustic wash unit to remove the acidic
impurities.
• The isopropanol rich vapors then enter a partial condenser which separates the
unreacted propylene from the alcohol + ether mixture. Here, propylene is separated
as the vapour and alcohol + ether is separated as the liquid stream.
• The separated propylene gas is once again subjected to water wash to remove
soluble impurities (such as ethers and alcohols). Subsequently, pure propylene is
sent to mix with the fresh feed stream.
• Before sending to the unit, the propylene is cooled to room temperature so as to
have identification conditions as the fresh feed stock.
• The alcohol and ether enter a ether column that separates isopropyl ether which is
returned to the reactor.
• The bottom product consisting of isopropyl alcohol and water is sent to a isopropyl
alcohol column that produces water + heavy ends as the bottom product and 87 %
isoprpanol-water azeotrope mixture as the top product.
• The azeotrope is sent to an azeotropic distillation column that uses isopropyl
ether as a azeotropic agent to obtain 99 % isopropanol as the bottom
product.
• The top product is a mixture of isopropyl ether and water. The top product is
a low boiling azeotrope. This stream upon gravity settling will produce the
isopropyl ether as the top product which is sent as a reflux stream to the
azeotropic column.
• The bottom product is a mixture of isopropanol and water is recycled back to
the isopropyl alcohol column along with the bottom product generated from
the ether separating column.
Uses of Isopropanol
There may be many uses of iso-propanol, industrial as well as common uses. It
finds use in pharmaceutical applications because of the low toxicity of any
residues. Isopropanol is also used as a chemical intermediate in some industrial
processes. It is also used as a gasoline additive.
