Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to the treatment of
adiponitrile with weak-acid cation exchange resins and in par- -
ticular to a process for reducing the amount of basic impuri-
ties in crude adiponitrile in which the crude adiponitrile is
- treated with a weak-acid cation exchange resin in the presence
of water.
One of the more important uses o~ adiponitrile at
the present time is in the manufacture o~ hexamethylene diamine.
Thiæ diamine may be used aæ a detergent, as an emulsi~ying agent
or, in particular, as an intermediate in the manufacture of
polymers. A catalytic hydrogenation reaction is usually employed
to con~ert adiponitrile to hexamethylene diamine.
There are several method~ for synthesizing adiponitrile.
In paxticular, adiponitrile may be obtainea by reacting adipic
acld with ammonia in the presence Or a dehydrating catalyst, for
example, by the techniques disclosed in U. S. Patent 2,200,734 ~ ;
- Or Arnold and Lazier which issued May 14, 1940 and in U.S. Patent
2,273,633 of M. ~. A. Fluchaire which issued February 17, 1942.
Adiponltrlle, especially adiponitrile obtained rrom adipic acid,
; 20 contains impurlties, ~ome Or which boil at temperatures close
to the boiling point o~ adiponitrile. 2-Cyanocyclopentylidene-
imine, hereinafter ~ometimes rererred to as CPI, i~ an example ;
such ~n impurity. Close boiling impuritie~ fre~uently cannot
be removed erriciently in indu~trial scale di~tillation columns.
Impurltie~ in the adiponitrilc may lead to impuritie~ in sub-
~ ~oquont derivatlve~, in partlcular in hexamethylene dlamine,
- that are dirrlcult to remove. Failurc to remove these latter
impuritie~ may ro~ult in inrerior and variable propertles, e~-
.; ,....... . . .
pecially in polymer~ manuractured u5ing ~uch impure hexamethyl~
ene di~mine. Tcchnique8 for the purirication Or adiponitrile
are known in the axt. ~or example, adiponitrlle may be treated
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with a solid acidic catalyst in the presence o~ water and at a
temperature of at least 140C to remove 2-cyanocycl~pentylidene-
imine. The solid acidic cataly~ts may be sllica-alu~ina catalysts,
cryst~lline aluminosilicate~, boron phosphate or titania-alumina.
Such treatmcnt is deæcribed in Canad~an Patent 912,036 o~ B. J.
Kershaw which issued October 10, 1972.
Adiponitrile, especially adiponitrile obtained ~rom
the reaction o~ adlpic acid with ammonia, may also contain
impurities in the form of cyclic amines, especially N-hetero-
cyclic compounds. Examples of such impurities are 2-methyl-4-
amino-5,6-trimethylene pyrimidine, hereinafter sometimes re-
ferred to as MAP, 2-Pm~no-3,4,5,6 bis(trimethylene) pyridine,
.~ hereinafter so_etimes referred to as ABP, and 2-cyclopentyl-4-
amino-5,6-trimethylene pyr~m~dine, hereinafter sometimes re-
~erred to as VAP. Such N-heterocyclic compounds may cauae prob-
lems in the hydrogenation of adiponitrile to hexamethylene diamine
or in the subsequent purification o~ he~amethylene diamine.
It has now been ~ound that basic impurities, e~pecially
N-heterocycllc compound~, may bo removed from crude adiponitrile
~y treating the adiponitrile with a weak-acid cation exchange
resin, ~uch ro~ins being discu~sed hereinafter.
Accordingly, the pre~ent invention provide~ a procee~
for reducing the amount of basic impurities in crude adiponitrile,
said process comprlsing the steps of treating crude adiponitrile
with a weak-acid cation exchange resin in the presence of water
and at a temperature in the range of from 20C up to the temper- - ~-
ature ~t which degradation o~ the weak-acid catlon exchange resin
becomes slgnl~lcant, said resin being in its hydrogen form, and ~-~
separating adiponitrile there~rom.
In a pre~erred embodiment of the process o~ the present
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;~0438~3
invention the temperature is in the range 20 C to 140 C and
especially in the range 25C to 100 C.
In a further embodiment the adiponitrile is adipo-
nitrile manufactured ~rom adipic acid and ammonia.
In another embodiment the adiponitrile being treated
contains at least 1% by weight o~ water.
Cation exchange resins are usually classi~ied as being
of three general types. Strong-acid cation exchange resins have
a che lcal activity similar to sulphuric acid and commercially
are usually nuclear sulphonic acid or methylene sulphonic acid
resins. Intermediate-acid cation exchange resins have a che_ical
activity ~m~lar to phosphoric acid and commercially are usually
phosphonic acid, phosphonous acid or phosphoric acid resins.
Weak-acid cation exchange resins, which are used in the process ;
o~ the pre6ent invention, have a chemio~l activity similar to
acetlc acid and commercially are usually carboxylic acid or
phenolic resins. me classes of lon exchange resins are dis-
cussed in greater detail in "DUOLITE* Ion-Exchange Manual" ob-
tainable from Diamond Shamrock Chemical Company.
In the process of the present inventlon crude adipo-
nitrile is treated with a weak-acid cation exchange resin.
In the process the adiponitrile may be treated by contacting
the adiponitrile and re~in in a continuous proces6 or in a batch
.:
process, the ~ormer being pre~erred. Preferably, the adiponitrile ~ ~-
is passed throu6h a ~ixed bed o~ weak-acid cation exchange resln.
` In a preferred embodiment the adiponitrile i8 adiponitrlle manu-
~actured ~rom adipic acid and ammonia,
*denotes trade mark
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While the adiponitrile treated by the process of the
present invention is de~cribed as "crude adiponitrile" the
adiponitrile being treated is preferably adiponitrile that
has been subjected to partial puri~ication, e.g., by distill-
ation.
me treatment of adiponitrile according to the pro-
cess of the present invention is carried out in the presence
of water. me temperature at which the adiponitrile is treated
may be in the range of from about 20C up to the temperature
at which the weak-acid cation exchange resin exhibit~ si~nificant
degradation. Such degradation may affect the properties of
the catlon exchange resin and/or the properties and especially
the impurities in the adiponitrile after treatment. In par-
ticular, the adiponitrile after treatment mQy contain decomp-
osition products of the cation exchange resin. me temperature
at which decomposition of the cation e~change re~in may become
significant will depend on the actual resin being used and, in
part, on the process conditiona. Pre~erably the upper temper-
ature limit is not in excess of 140C. Pre~erred temperatures
are in the range 20 to 100C and in particular 25 to 50C.
As stated above the treatment of the adiponitrile is
carried out in the presence Or water. The water content oP the
adiponitrile is preferably in the range from about 1% to a ratio
o~ water to adiponitrile of about 2:1, on a weight basi~. me
upper limit o~ water is determined primarily by practical con-
~ideratlons. In an embodiment of the proceæs oP the pregent in-
ven 40n the treatment o~ adiponitrile is carried out in the pres-
ence o~ at least 5% by weight of water. A particularly prePerred
range of water is 5-10% by weight.
me pre~sure used in the process of the present in- ~-
vention is not critical. The pre~sure will depend primarily
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on other process variables, for example, temperature and the
water content o~ the adiponitrile.
In a pre~erred embodiment of the process o~ the
present invention the adiponitrile is substantially ~ree of
ammonia.
In the process of the present invention amines es- ~
pecially the aforementioned cyclic amines are removed ~rom ~ ;
the adiponitrile by retention on the weak-acid cation ex-
- change resin. After a period of time it may become desirable
to remove said amines from the weak-acid cation exchange
resin and thereby regenerate the resin for further use. The
res~n may be regenerated by contacting with an amount of a
strong acid, for example, hydrochloric or sulphuric acid, that
is slightly in excess of the stoichiometric amount of acid ~ f
required to con~ert the resin to its acid or hydrogen form.
The resin i8 used in the process of the present invention in
its acid or hydrogen form. Preferably the resin is regener-
- ated at about ambient temperature~. The relatively low amount
~f acid required ~or regeneration o~ weak-acid cation exchange 20 resins, as compared with strong-acid cation exchange resins,
may hare advantages with respect to the control of polluti~n
from the proce~s.
Adiponitrile purified by the process described herein
i8 particularly useful in the manufacture of hexamethylene
diamine u8ing an iron catalyst as is di~closed in Canadian patent
application 234 356 Or B. J. Kershaw filed on the s&me d&te
as the present application.
A~ iB exemplifi~d hereina~ter the treatment of adlpo-
~ nitrile with a weak-acid cation exchange resin in the presence 30 of water results in e~sentially no hydroly~is of 2-cyanocyclo-
pent~lideneimine. ~uch hydrolysis would result in the ~orm-
ation o~ ammonla, which would be adsorbed by the resin thereby
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reducing the capacity of the resin for removing other amines. The
process of the present invention may, therefore, offer advantages
over the treatment of adiponitrile with a strong-acid cation
exchange resin in the presence of water, 2-cyanocyclopentyl-
ideneimine being hydrolyzed by strong-acid cation exchange
resins in the presence of water.
me process of the present invention is illustrated
by the following examples. The adiponitrile used in the
examples had been manufactured ~rom adipic acid and ammonia.
All analyses are on a weight basis.
EXAMPLE I
To 50 ml o~ a crude adiponitrile referred to herein-
after as adiponitrile #1, the composition of which is given `
in Table I hereinafter, were added 3 ml of water and 2 g of
DUOLITE CC-3, a weak-acid cation exchange resin obtainable from
Diamond Shamrock Chemical Company. The resulting mixture was
stirred for 30 minutes~at ambient temperature and then filtered.
The filtrate of treatea adiponttrile ~o obtained was analyzed
by gas chromatography. The results were as follows:
Before Treatment* After Treatment* Removal of
_omponent with Resin (%) with Resin (%) Impurity (%)
MAP - 0.040 0.0079 80
ABP 0.071 0.019 75
CPI 0.35 0.35 0
*Analy~es are on a solution ba~is, i.e., adiponitrile plus water.
EXAMPLE II `
To show the effect of water, Example I was repeated
except th~t no water was added to the adiponitrile. The re-
sults were as follows: -
Be~ore Tre~tment A~ter Treatment Removal of
Impurity _with Re~in (%) with Re~in (%~ Impurity (%)
: .-... .
o o40 o.o38 5
.~. . . ..
, , .
,
..
EXAMPLE III
:. -: . .
To 50 ml o~ a crude adi~onitrile re~erred to herein-
after as adiponitrile #2, the composition o~ which is gi~en -
in Table I hereinafter, were added water and DUOLITE CC-3 cation
exchange resin. The resulting mixture was stirred ~or 30
minutes and a sample of the adiponitrile was analyzed by gas
chromatography. A ~urther analysis was made after a total
o~ 60 minutes treatment. me results are given in Table II.
me hydrolysis product of CPI, 2-cyanocyclopentanone,
was not detected in any of the samples.
EXAMPLE IV
,
Approxlmately 37 g of DUOLITE CC-3 cation exchange
resin were placed in a glass column o~ approximately 2.5 cm
internal diameter. 60 ml of water were mixed with one litre
of adiponitrile #l and the resulting solution was pa~sed down
through the glass column. The contact time of adiponitrile
with the cation exchange resin was approximately 2.5 minutes.
Samples of the treated adiponitrile eluting from the glass
column were taken periodically and analyzea by gas chromato-
graphy. The results were as follows:
Sample~ MAP(%) Removal of ABP (%) Removal o~
' MAP (%) ABP (%)
.
Treated #1 0.0055 86 0.012 83
Treated #2 0.0085 79 0.012 83
Treated #3 0.015 63 0.023 68
*Treated #l - after 100 ml of treated mixture had eluted from ~-
the column, the next 100 ml was collectea and thl~
sample taken therefrom. -~
Treated #2 - after 400 ml Or treated mixture had eluted from
the column, the next 200 ml was collected and this
sa~ple taken therefrom.
Treated #3 - sample taken from the f~nal 70 ml eluted from the
column.
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After treatment of the adiponitrile the cation ex-
change re~in ln the column was treated with 40 ml o~ 15%
hydro~hloric acid and then washed with distilled water until
the eluent was free of acid. A solution o~ 30 ml of water
in 500 ml o~ adiponitrile #1 was then passed down through
the cation exchange resin as described above. The result~
were:
Sample* MAP (~) Removal of ABP (~) Removal of
MAP (%) , ABP (%)
10Treated #1 0.0026 94 0.023 67
Treated #2 o.oo63 84 0.022 69
Treated #3 0.0078 81 0.025 65
*Treated #l - ~ample taken from the fir~t 100 ml o~ eluent.
Treated #2 - after 100 ml of treated mixture had eluted from
the column, the next 300 ml was collected and
thiB sample taken thererrom.
Treated #3 - sample taken ~rom the last 100 ml of eluent.
TABLE I
Impurlty*~ Adiponitrile #1 Adiponitrile #2
; 20 MAP 0.042 0.028
ABP 0.075 0.062
VAP 0.075
CPI o.35 0.15
-cyanovalerlc acld 1.0
~ -cyanovaleramlde 0.5 0.13
: adipl m~ de 0.6
N.B. all analyses expre8sed as percentages on a weight/volume
ba~is, remaining component essentlally adiponitrile.
** MAP - 2-methyl-4-amino-5,6-trimethylene pyrimidine ;;~
ABP ~ 2-amino-3,4,5,6-bis (tr~mPthylene) pyridine
VAP - 2-cyclopentyl-4-amino-5,6-trimethylene pyrimidine
CPI _ 2-cyanocyclopentylideneim~ne
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