Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF T~E INVENTIO~
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The present invention is directed to a process for producing 2-
pyrrolidone from succinonitrile. lhe 2-pyrrolidone may be used to produce
polypyrrolidone (nylon-4).
Various methods have been described for producing 2-pyrrolidone.
For example, United States Patent 3~644J402 discloses a process ~or produc-
ing 2-pyrrolidone by contacting succinonitrile with hydrogen under pressure
in the presence of a hydrogenating catalyst and a niAtrogen-containing organic
solvent at a temperature of 80-200C for a period of time less than 3.7 min-
utes followed by a hydrolyzing step carried out by adding water or aqueousammonia solution into the reaction mixture from the previous step and then
heating the reaction mixture at a temperature of from 200-300 C.
Belgian Patent 839,091 also discloses a process for producing 2- :
pyrrolidone from succinonitrile wherein the reaction steps are hydrogenation
followed by hydrolysis. According to the process of the Belgiarl patent, suc-
cinonitrile is subjected to hydrogenation in the liquid phase in the presence
of ammonia at a partial hydrogen pressure between 1 and 50 atmospheres and ~-
the reaction product obtained is treated in the liquid phase at elevated tem-
perature with water. Yields disclosed in the examples of the Belgian patent
range from 78-86 mol percent.
Several patents have described a one-step method for conversion of
succinonitrile to 2-pyrrolidone such as in United States Patent 3,095,423;
3,781,298; 3,966,763; and 4,036,836. United States Patent 3,095,423 dis-
: closes yields of about 25 percent in a process where succinonitrile is heat-
ed in the presence of water at a temperature of 20-200C and in the presence
of a hydrogenation catalyst and hydrogen under a pressure of at least 500
psig. This patent also discloses that ammonia presence in the reaction zone
is advantageous as it suppresses the ~ormation of secondary amines. Cat-
alysts disclosed in the 3,095,423 patent include ruthenium oxide, platinum
oxide, supported noble metal catalysts such as platinum and palladium on
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carbon or alumlna, Raney nickel and Raney cobalt.
The aforemcntioned United States Patent 3,781,298 discloses the
reaction of succinonitrile with hydrogen in the absence of added ammonia and
in the presence of a Raney cobalt catalyst at a temperature of 250-300C and
a hydrogen pressure of about 2000-3500 psig to obtain 2-pyrrolidone. A
yield of about 62 mol percent is reported in the 3,781,298 patent.
The aforementioned United States Patent 3,966,763 discloses a one-
step hydrogenation process in the presence of water for converting succin-
onitrile to 2-pyrrolidone wherein a promoter such as added 2-pyrrolidone is
used and yields of 38-56 percent are obtained.
Another one-step process for conversion of succinonitrile to 2-
pyrrolidone is disclosed in United States Patent 4,036,836 which patent re-
ports yields of 46-59.5 mol percent using a nickel boride catalyst.
Succinic acid and maleic anhydride have also been disclosed as
feed materials for the production of gammabutyrolactone, which may be re-
acted with ammonia to produce 2-pyrrolidone. United States Patent 3,890,361
discloses conversion of succinic acidl succinic anhydride, maleic acid or
maleic anhydride to gamma-butyrolactone by contacting the feed with hydrogen
in the presence of a hydrogenation catalyst consisting of a uniform mixture
of nickel, molybdenum, and a third component selected from barium and thal-
lium. The hydrogenation is carried out at 180-300C and a pressure of 30-
200 atmospheres. ~s disclosed in United States Patent 3,975,400, gamma-
butyrolactone may be converted to the corresponding lactam, that is, 2-
pyrrolidone, by treatment with ammonia in the presence or absence of water
at 180-340C and pressures of 25-280 atmospheres.
One-step conversion of succinic acid or maleic anhydride to 2-
pyrrolidone is disclosed in United States Patent 3,812,148; 3,812,149; and
3,884,936. The 3,812,148 patent discloses reacting succinic acid or its
precursor with hydrogen and ammonia in an aqueous system at a mol ratio of
ammonia to succinic acid of from 1.3:1 to 1.7:1, a temperature of 250 to
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275C, a pressure of 1500 to 2000 psig, and in the presence of a ruthenium
on alumina catalyst. The 3,812,1~9 patent is similar except that a rhodium
catalyst is used. Both of these patents report mol percent yields of 2-
pyrrolidone up to 90 or 95 percent. United States Patent 3,~84,936 also
discloses a one-step preparation of 2-pyrrolidone by reaction of maleic acid
or maleic anhydride with hydrogen and ammonia ln an aqueous system with a
mol ratio of ammonia to maleic acid or anhydride of from 1:1 to 1.2:1 and
using a palladium on carbon catalyst.
The present invention, which is a two~step process for the produc-
tion of 2-pyrrolidone, involves a nitrile hydrolysis step as will be de-
scribed in more detail below. The hydrolysis of nitrile groups has been
disclosed in the art ~see for example Morrison and Boyd, Organic Chemistry,
second edition, 1966, Page 588).
SUMMARY OF T~IE INVENTION
According to the present invention, a process is provided for pro-
ducing 2-pyrrolidone which process comprises (a) contacting succinonitrile
with water at a temperature between 150 and 300C and a pressure between 50
and 10,000 psig to thereby hydrolyze succinoni~rile and (b) contacting the -~
hydrolyzed succinonitrile with hydrogen in ~he presence of a heterogeneous
hydrogenation catalyst and at a temperature between 200 and 300C and a pres-
sure between 100 and 10,000 psig to thereby obtain 2-pyrrolidone.
Among other factors, the present invention is based on my finding
that, starting with a succinonitrile feed, hydrolysis followed by hydrogena--
tion in accordance with the present invention produces a high yield of 2-
pyrrolidone. The high yield from this process is particularly unexpected in
view of the fact that the sequence of steps used in the present invention,
that is, hydrolysis followed by hydrogenation, is the reverse of the two-
step sequenc0 taught by the prior art for obtaining 2-pyrrolidone from suc-
cinonitrile.
Preferably, the hydrolysis of the succinonitrile in accordance
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with thc present invention is carricd out at a temperature between about
180 and 250C. A temperature of about 190-230C is particularly preferred.
Preferred pressures Eor the hydrolysis step are sufficient to maintain water
in the liquid phase present in the hydrolysis reaction zone at the elevated
temperature used for hydrolysis. Usually the pressure is maintained between
lO0 and 1000 psig.
Preferred molar ratios for water to succinonitrile in the feed to
the hydrolysis step are between about 200:1 and 2:1, more preferably between
about 30:1 and 5:1. Residence time for the hydrolysis step may be 0.1 to 20
hours, preferably 0.25 to 4 hours~
The hydrolysis step can be cataly~ed by added acids or bases.
~lowever, strong acids or bases tend to be quenched in activity by the car-
boxyl and ammonium products of the hydrolysis. Also their presence compli-
cates product recovery. Therefore, it is pre:Eerred to not use these cat-
alysts. Some advantage in hydrolysis rate can be obtained by adding ammonia
or carboxyl-containing compounds to alter the equal proportion of these weak
basic and acidic groups which are formed in the hydrolysis reaction. This
can be achieved in two simple ways: (1) some ammonia, which is a net by-
product from the two-step process, can be recycled to the hydrolysis step,
or (2) some hydrolysis product can be recycled to that zone af~er stripping
out some ammonia.
The hydrolysis conditions are preferably maintained so that at
least one of the nitrile groups of succinonitrile is converted to a carboxyl
type group, i.e., to an amide or a carboxyl group or its ammonium salt. The
other nitrile group of the succinonitrile can remain unreacted for a reaction
product which is suitable for ~he second step of the present invention, that
is, the hydrogenatlon/cycli~ation step.
In accordance with this invention, preferably the hydrolysis con-
ditions are such that at least a portion of the succinonitrile is converted
to succinic acid-type products, such as various amides and ammoniu~ salts.
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Conditions suitable for converting a relatively large portion of the sucin-
onitrile to the succinic acid compouncls involve a higher teMperature or
longer times than is ~Ised for conversion of only one of the nitrile groups
of succinonitrile to a carboxyl-type group.
For the hydrogenation step, the temperature may range from about
20C to 300C depending on the product of the hydrolysis step. In one em-
bodiment of this invention, the hydrolysis mixture would be conducted through
a two~stage hydrogenation. In the first low temperature stage, at about 20-
150C, any residual nitrile groups are hydrogenated. In the second stage,
at about 200-300C, carboxyl type groups are hydrogenated and ring closure ;
to 2-pyrrolidone occurs. If relatively mild hydrolysis conditions were em-
ployed and a considerable number of nitrile groups remained, the two-step
approach may be desired. If more severe hydrolysis was performed, the low ~-
temperature stage may be unnecessary. In either case, the final hydrogena-
tion temperature preferably is between about 200-300C. More preFerably the
temperature is between about 210-280C, most preferably about 215-255C. A
temperature of about 235C has been found particularly suitable for the hy- ~ ;
drogenation step of the present invention.
Preferred pressure for the hydrogenation step is between 100 and
10,000 psig, preferably about 200-2500 psig. The pressure preferably is
sufficient to maintain water and ammonia in the liquid phase.
The feed to the hydrogenation step of the present invention can be
the total efflucnt mixture from the preceeding hydrolysis step of the pro-
cess or a portion of the ammonia and/or water may be removed before feeding
the hydrolysis step reaction product to the hydrogenation step. Preferably,
the entire mixture or substantially the entire mixture resulting from the
hydrolysis step is fed to the hydrogenation step of the present invention.
In the hydrolysis step, ammonia will be formed to the extent that
the nitrile groups of succinonitrile are conver~ed to carboxyl groups. Thus,
the theoretical maximum amount of ammonia which can be formed in the hydrol-
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ysis step is 2 mols per mol of succinonitrile feed to the hydrolysls step.
If the succinonitrile is hydrolyzed only as far as the amide, which usually
will not be the case~ then it is preferred to add some ammonia to the hydro-
genation zone feed as there will be little or no ammonia in the hydrolysis
step effluent which is typically fed to the hydrogenation zone. The hydro-
genation reaction zone conditions preferably are maintained so that at least
0.10 mol, and usually no more than 5.0 mols of ammonia, are present per mol
of succinic reactant. More preferably the amount of ammonia is between 0.25
and 2 mols of ammonia per mol of succinic reactant.
The term "succinic reactant" is used in a general sense to cover
the hydrolyzed succinonitrile, whether partially or completely hydrolyzed -
and whether it contains carboxyl or amide groups. If the succinic reactant
in the hydrogenation step is in the form of an amide, ammonia will be evolved
in the hydrogenation/cyclization reaction by which 2-pyrrolidone is produced
in the hydrogenation zone. Thus, the ammonia content in the hydrogenation
zone is maintained not only by ammonia which may be fed to the hydrogenation
step-as part of the reaction effluent of the hydrolysis step~ or as a sep-
arately added ammonia stream, but also the ammonia which may be generated
from the feed to the hydrogenation reaction zone while the feed is being con-
verted to 2-pyrrolidone.
Preferably, the hydrogenation reaction is carried out in liquid
phase with water being the liquid medium. The mol ratio of water to succinic
reactant preferably is between 1:1 and ~00:1, more preferably between 2:1 and
50:1 in the hydrogenation step reaction zone. Similar to the situation with
ammonia, water may be added separately to the reaction zone if desired and
also the amount of water in the reaction zone will be increased by the con~
version of the succinic reactant to 2-pyrrolidone. In the case of conversion
of succinic acid to 2-pyrrolidone, 3 mols of water are generated, and in the
conversion of beta-cyanopropionic acid to 2-pyrrolidone, l mol of water will
be formed, while in the conversion of beta-cyanopropionamide to 2-pyrrol-
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idone, one mol of ammonia will be formed~ but no water.
The amount of hydrogen which is fed to the hydrogenation reaction
zone preferably is sufficient so that there is between 2:1 and 200:1 mols of
hydrogen per mol of succinic reactant, that is per mol of the hydrolyzed
succinonitrile feed to the hydrogenation zone. In any case, preferably suf-
ficient hydrogen is fed to maintain an appreciable hydrogen partial pressure
on top of that required to maintain liquid phase reaction conditions for the
succinic reactant in the presence of liquid water. The elevated pressure
preferably is between 500 and 2,500 psig, more preferably between 1,000 and
2,000 psig.
Suitable hydrogenation catalysts for the hydrogenation step in-
clude the Group VIII metals, namely, iron, cobalt, nickel, ruthenium, rhod-
ium, palladium, osmium, iridium, and platinum. Preferred Group VIII hydro-
genation metals include cobalt, nickel, ruthenium, rhodium, palladium, irid-
ium, and platinum. Particularly preferred Group VIII metals are cobalt,
nickel, palladium, and ruthenium.
The Group VIII metal preferably is supported, for example, on an
inorganic refractory material such as alumina or silica or alumina-silica
mixtures. Zirconia is a particularly preferred support.
Raney cobalt or Raney nickel catalysts can be used for the hydro-
genation step. The Raney cobalt or Raney nickel are prepared in accordance
with the known methods for preparing these hydrogenation catalysts.
A particularly preferred hydrogenation catalyst is ruthenium on
refractory support such as alumina, silica, silica-alumina, carbon, or zir-
conia. A particularly preferred supported ruthenium catalyst is ruthenium
on æirconia as described in more detail in commonly assigned application of
H. Y. Lew and W. Alan Sweeney, ti~led "Preconditioned Ruthenium Catalysts
And Processes For Preparing Pyrrolidone" and filed on about March 1, 1978,
the disclosure of which application is incorporated herein by reference.
Preferred amounts of the Group VIII metal or metals on the above-
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mentioned supports ~re 0.1 to 25 weight percent, more preferably 0.2 to 10
weight percent.
Preferably, the amount of catalyst used in the hydrogenation reac-
tion zone is 0.01 to 5.0, more preferably 0.02 to 20 parts by weight of the
succinic reactant feed.
EXAMPLES -
To a 5-gallon stirred stainless steel autoclave there was charged
21.25 mols of succinonitrile, ~.6 mols of succinic anhydride, and 352 mols
of water. It was charged at room temperature and then heated to 210C.
The contents were held at this temperature, and at a pressure of about 240
psig, with stirring for about 3 hours.
Succinic anhydride was included as an acid catalyst for the hydrol-
ysis; however, other laboratory runs determined that this was not required.
A 2,000 gram portion of the reaction product, that is, of the total
effluent from the above 5-gallon reactor, was charged to a one-gallon reactor
at room temperature. A hydrogenation catalyst in the amount of 150 grams of
1.8 weight percent ruthenium on zirconia was charged to the one-gallon reac-
tor in the form of a powder. The reactor was pressurized with added hydro-
gen gas at room temperature to a pressure between 1,500 and 1,900 psig.
The reactor was then heated to 235C with stirring of the contents.
The temperature was held at 235C ~or about 20 hours.
The product from this hydrogenation step was chromatographically
analyzed; the yield of 2-pyrrolidone was 89 mol percent based on succinon-
itrile fed to the hydrolysis step.
In a repeat run on the hydrogenation step, a yield of about 90 mol
percent was obtained, thus confirming the previous high yield of 89 percent.
In this repeat run, a one-liter reaction vessel was used for the hydrogena-
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tion step and the feed was a portion of the total reaction product from the
5-gallon hydrolysis step as previously described. The reaction conditions
~0 for this repeat hydrogenation run were generally similar except that a res-
idence time of only I2 hours was used for the hydrogenation step.
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