rile from nh4

8/4/2019 rile From NH4

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Acetonitrile from NH4-acetate

Acetonitrile prep

PATENT SPECIFICATION

Application Date: Oct 10, 1935 No 28007/35.

464,106 Complete

Specification

Left: Sept 23, 1936.

Complete Specification Accepted: April 12

,1937

.

PROVISIONAL SPECIFICATION

Improvements in or relating to the Manufacture of Aliphatic Acid Nitriles We, BRITISH CFLAN ES:S LIMITED, a Company incorporated in accordance with the

laws of Great Britain, of Celanese House, 22 & 23, Hanover Square, London, S W 1, HORACE FINNINGLEY OXLEY and EDW ARD BOADEN THOM AS, bot

subjects of the King of G reat Britain, of the Works of British Celanese Limited,

Spondon

, near Derby, do hereby declare the nature of this invention to be as

follows:This

invention relates to the manufacture of


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aliphatie

acid nitriles and especially acetonitrile and the nitriles of other lower fatty acids.

According to the invention an aliphatic acid nitrile is produced by decomposing by the action of heat the amm onium salt of the corresponding aliphatic acid in

presence in the free state of a quantity of the same acid The production of acetonitrile, which is an important embodiment of the invention, is thus effected by

decomposing

amllonium

acetate by the action of heat in presence of a quantity of free acetic acid.

In carrying out the process of the invention the ammonium salt to be decomposed may be heated under a fractionating column, together with a quantity of the

corresponding acid in the free state, under conditions such that the nitrile will distil off as it is produced.

In such a process the presence of a quantity of free acid equal to about 40% of that combined in the ammonium salt gives excellent results and avoids the

presence of substantial quantities of unchanged amm onium salt in the distillate.

Larger quantities of acid may be employed, if desired, although it is found that no advantage is secured by using a quantity of free acid greater than that

combined in the salt.

4,5 In practice it has been found that the quantity of free acid thus employed may be reduced very substantially by carrying out the production of the nitrile as

continuous operation This object may be achieved by heating the mixture of ammonium salt and free acid to the decomposition temperature under a

fractionating column, operated so as to permit distillation into a suitable receiver of the nitrile as it is formed, and

provid

55

ing

a continuous supply of fresh ammonium salt-acid mixture to the distillation vessel Operating in this manner it has been found possible to obtain excellent

results by supplying to 60 the distillation vessel a mixture containing free acid equal to 15-20 % of that combined in the ammonium salt Such a mixture may

be maintained in a liquid form suitable for continuous feeding by 65 warming e g to a temperature of 60-7 00 C.


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In such a process the distillation vessel may, if desired, be charged initially with a mixture containing a rather larger 70 proportion of free acid than is present i

the mixture continuously supplied; for instance the vessel may be charged with a mixture containing free acid in quantity equal to 20-50 % of the weight of 75

the acid combined in the ammonium salt employed.

The decomposition temperature

employod

may be varied according to the particular nitrile to be produced, and 80 according to other operating conditions.

In general, temperatures of 200-220 C.

are

very suitable for the production of acetonitrile, temperatures of 200-210 C.

being very satisfactory Where, as will 85 usually be the case in practice, the distillation is effected under a fractionating column, the head of the column shoul

be maintained at a temperature such that the nitrile distills over while the free 90 acid is as far as' possible returned to the distillation vessel In the production

of acetonitrile a still-

head temperature of about 92 C has been found very satisfactory in practice 95 It has been found that the production of the nitriles can be accelerated very

considerablv

by the use of an iron catalyst.

The iron

mav

he introduced into the distillation vessel in the form of a compound 100 and phosphates of iron, e g

Fe{

( 12 POG ) have been found very suitable for use in this m anner Alternatively, a distillation vessel made of a corrosive-resistant ferrous alloy such a

Stavbrite

may be 105 employed, in which case it is found that % 00 %A, a ITT-246,O the small amount of corrosion which does take place is sufficient to provide the


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iron catalyst.

Separation of the nitrile produced from the distillate obtained may be effected in any desired manner, for instance by fractional distillation, if desired, after the

addition of sufficient acetic acid to convert all the acetate present into acid acetate and thus prevent distillation of ammonia.

The aqueous nitriles contaminated with the ammonium salt of the corresponding acid obtained in the process of the present invention may be purified very

efficiently by a process comprising salting out the nitrile with the am monium salt This may be effected by

neutralising

with ammonia free acid contained in the crude nitrile, and if necessary, adding a further quantity of the ammonium salt.

Such a salting out process produces in the case of acetonitrile an upper layer of aqueous nitrile of 95 % concentration, which, o-n fractionation, yields first a

constant boiling nitrile-water mixture containing 84 % nitrile and subsequently the anhydrous nitrile It is possible by this means to obtain the bulk of the nitrile

contained in the crude product in an anhydrous condition.

Fractionation of the amm onium acetate layer

irom

the salting out operation yields a distillate consisting of aqueous 35 nitrile containing free ammonia which can be used in

neutralising

a further batch of crude nitrile, and so likewise can ammonia obtained from the 84 % nitrile obtained by fractionating the 40 salted out product The residue

from the fractionation of the ammonium acetate layer consists of amm onium acetate and the acid acetate and is available for use as starting material in the

pro 45

duction

of a further quantity of nitrile.

While the invention has been described above more particularly with regard to the manufacture of acetonitrile it is not limited in this respect and may be

applied 50 to the m anufacture of other aliphatic acid nitriles For example, by employing ammonium propionate as starting material

propionitrile

may be produced and likewise from ammonium butyrate 55 there may be obtained


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butyronitrile

.

Dated this 9th day of October, 1935.

STEPHENS &

ALLEN,

Chartered Patent Agents, Celanese House, 22 & 23, Hanover Square, London, W l.

COMPLETE SPECIFICATION

Improvements in or relating to the Manufacture of Aliphatic Acid Nitriles We, BRITISH CE LANE

Sn

, L

Im

I

Tn

D, a Company incorporated in accordance with the laws of Great Britain, of Celanese go House, 22 & 23, Hanover S quare, London, W.1, HORACE

FINNINGLEY OX:LY and E

Dw

ARD BOADEN T

Hom

As, both subjects of the King of Great Britain, of the Works of British Celanese Limited, d B

Spondon

, near Derby, do hereby declare the nature of this invention and in what manner the sam e is to be performed, to be particularly described and ascertained in

and by the following statement:-

This invention relates to the manufacture of aliphatic acid nitriles and especially acetonitrile and the nitriles of other lower fatty acids.


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According to the invention an aliphatic acid nitrile is produced by decomposing by the action of heat the amm onium salt of the corresponding aliphatic acid in

presence in the free state of a quantity of the same acid The production of

aceionitrile

, which is an important embodiment of the invention, is thus effected by decomposing ammonium acetate by the action of heat in presence of a quantity of

free acetic acid.

In carrying out the, process of the 85 invention the ammonium salt to be decomposed may be heated under a fractionating column, together with a quantity of

the corresponding acid in the free state, under conditions such that the 90 nitrile will distil off as it is produced.

In such a process the presence of a quantity of free acid equal to about 40% of that combined in the ammonium salt gives

excelent

results and avoids the 95 presence of substantial quantities of unchanged amm onium salt in the distillate.

Larger quantities of acid may be employed, if desired, although it is found that no advantage is secured by 100 using a quantity of free acid greater than that

combined in the salt.

In practice it has been found that the quantity of free acid thus em ployed may be reduced very substantially by carry 105

ing

out the production of the nitrile as a continuous operation This object may be achieved by heating the mixture of ammonium salt and free acid to the

decompqsition

temperature under a

frac

110 464,1 OU a 464,106

tion

ating

column, operated so as to permit distillation into a suitable receiver of the nitrile as it is formed, and providing a continuous supply of fresh ammonium salt-


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acid mixture to the distillation vessel Operating in this manner it has been found possible to obtain excellent results by supplying to the distillation vessel a

mixture containing free acid equal to 15-90 % of that combined in the ammonium salt Such a m ixture may be maintained in a liquid form suitable for

continuous feeding by warming e g to a temperature of 60-700 C.

In such a process the distillation vessel may, if desired, be charged initially with a mixture containing a rather larger proportion of free acid than is present in

the mixture continuously supplied; for instance the vessel may be charged with a mixture' containing free acid in quantity equal to 20-50 % of the weight of the

acid combined in

tbh

ammonium salt employed.

The decomposition temperature employed may be varied according to the particular nitrile to be produced, and according to other operating conditions.

In general, temperatures of 200-2290 C.

are

very suitable for the production of acetonitrile, temperatures of 200-210 C.

being very satisfactory Where, as will usually be the case in practice, the distillation is effected under a fractionating column, the head of the column should be

maintained at a temperature such that the nitrile distills over while the free acid is as far as possible returned to the distillation vessel In the production of

acetonitrile a still-head temperature of about, 920 C has been found very satisfactory in practice.

It has been found that the production of the nitriles can be accelerated very considerably by the use of an iron catalyst.

The iron may be introduced into the distillation vessel in the form of a compound and phosphates of iron, e g

Fe(

l 12 P 4), have been found very suitable for use in this manner Alternatively, a, distillation vessel made of a corrosive-resistant ferrous alloy such a


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Staybrite

may be em ployed, in which case it is found that the small amount of corrosion which does take place is sufficient to provide, the iron catalyst.

Separation of the nitrile produced from the distillate obtained may be effected in ( any desired manner, for instance by fractional distillation, if desired, after the

addition of sufficient acetic acid to convert all the acetate present into acid acetate and thus prevent distillation of ammonia.

The aqueous nitriles

conlandnated

with the ammonium salt of the corresponding acid obtained in the process of the present invention may be purified very efficiently by a process comprising

Malt 70

ing

out the nitrile with the ammonium salt This may be

efiected

by

neutralising

with ammonia free acid contained in the crude nitrile, and if necessary adding a further quantity of the

ammllo

75

nium

salt.

Such a salting out process produces in the case of acetonitrile an upper layer of aqueous nitrile of 95 % concentration, which, on fractionation, yields first a

con 80

stant

boiling nitrile-water mixture containing 84 % nitrile and subsequently the anhydrous nitrile It is possible by this means to obtain the bulk of the nitrile contained

in the crude product in an 85 anhydrous condition.

Fractionation of the amm onium acetate layer from the salting out operation yields a distillate consisting of aqueous nitrile containing free ammonia w hich 90

can be used in


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neutralising

a further batch of crude nitrile, and so likewise can ammonia obtained from the 84 % nitrile obtained by fractionating the salted out product The residue from

95 the fractionation of the ammonium acetate layer consists of ammonium acetate and the acid acetate and is available for use as starting material in the

production of a further quantity of nitrile 100 While the invention has been described above more particularly with regard to the manufacture of acetonitrile it is

not limited in this respect and may be applied to the m anufacture of other aliphatic acid 105 nitriles For example, by employing ammonium propionate as

starting material

propionitrile

may be produced and likewise from ammonium

butvrate

there may be obtained

butyronitrile

110 The following Example illustrates the invention as applied to the production of

acetonitrile:EXAMPLE

.

A mixture of about 88 %

amnionium

115 acetate and 12 % acetic acid, prepared by adding acetic acid to ammonium carbonate, is continuously fed to a still provided with a

Viigreux

column and containing either a quantity of the feed mixture 120 or a residue from a previous operation


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rile from nh4

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