Page 98 - Chemical and process design handbook

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ALLYL ALCOHOL

o
Allyl alcohol (2-propen-1-ol, CH =CHCH OH, boiling point: 96.9 , den-
2 2
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sity: 0.8520, flash point: 25 C) is the simplest unsaturated alcohol and is a
colorless corrosive liquid with a pungent odor. The vapor can cause severe
irritation and injury to eyes, nose, throat, and lungs. Allyl alcohol is misci-
ble with water and miscible with many polar organic solvents and aromatic
hydrocarbons, but is not miscible with n-hexane. It forms an azeotropic
mixture with water and a ternary azeotropic mixture with water and organic
solvents.
There are four processes for industrial production of allyl alcohol. One
involves the alkaline hydrolysis of allyl chloride.
–
–
CH =CHCH Cl (+ OH ) → CH =CH–CH OH (+ Cl )
2 2 2 2
In this process, the amount of allyl chloride, 20 wt % aqueous sodium
hydroxide (NaOH) solution, water, and steam are controlled as they are
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added to the reactor and the hydrolysis is carried out at 150 C, 200 psi
(1.4 MPa) and pH 10 to 12. Under these conditions, conversion of allyl
chloride is near quantitative (97 to 98 percent), and allyl alcohol is selec-
tively produced in 92 to 93 percent yield. The main by-product is diallyl
ether (CH =CHCH OCH CH=CH ). At high alkali concentrations, the
2 2 2 2
amount of by-product, diallyl ether, increases, and at low concentrations,
conversion of allyl chloride does not increase.
A second process has two steps. The first step is oxidation of propylene
to acrolein and the second step is reduction of acrolein to allyl alcohol by
a hydrogen transfer reaction, using isopropyl alcohol.
CH CH=CH + O → CH =CHCH=O + H O
3 2 2 2 2
CH =CHCHO + (CH ) CHOH → CH =CHCH OH + CH COCH
2 3 2 2 2 3 3
Another process is isomerization of propylene oxide in the presence of
a catalyst (lithium phosphate, Li PO ).
3 4
[
CH CHCH O → CH =CHCH OH
3 2 2 2
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