Note: Descriptions are shown in the official language in which they were submitted.
1319~
METHOD FOR PRODUCTION OF MALEIMIDES
This invention relates to a method for the
production of maleimides. More particularly, this
invention relates to a method for the production of
maleimides by ring-closure imidation of maleinamic
acids.
Description of the Prior Art:
Maleimides are compounds useful as raw materials
for synthetic resins, medicines, and agricultural
chemicals. Researches after methods for their
production have long been under way. The most popular
method of them all effects the production of maleimides
by the dehydration cyclization of maleinamic acids with
a dehydrating agent such as acetic anhydride. One
version of this method is disclosed in U.s. Patent No.
2,444,536. This method effects the production of
maleimides by causing maleic anhydride to react upon
amines thereby forming maleinamic acids and dehydration
cyclizing and, at the same time, imidating the
maleinamic acids in the presence of acetic anhydride
and sodium acetate. ~his method, however, has the
disadvantage that the imidation requires expensive
acetlc anhydride to be used in at least an equivalent
relative to the maleinamic acid and the separation and
recovery of the formed maleimide from the imidation
reaation aolution necessitates use of a large volume of
water and, as the result, entails disposal of a large
amount of an acetic acid-containing effluent at great
expense. Thue, this method may well be called a too
expensive method for commercial production of
maleimides.
A method which has no use for such a chemical
dehydration agent as acetic anhydride is disclosed in
Briti~h Patent No. 1,041,027 and U.S. Patent No.
3,431,276. ~his method ef~ects the production of
maleimides by thermally dehydrating and cyclizing
maleinamic acids in conjunction with a solvent 8UC}l as,
for example, toluene, xylene, or
/
131~6~
chlorobenzene having a boiling point exceeding 80C and
serving as a diluent and an acid catalyst such as sulfur
trioxide, sulfuric acid, or ortho-phosphoric acid, and
distilling the system thereby causing azeotropic expulsion of
5 the consequently formed water in conjunction with the
solvent. AS compared with the method which uses acetic
anhdyride, this method proves advantageous in that it does
not require use of a large amount of such an expensive
dehydrating agent as acetic anhydride and further that the
10 formed maleimides are separated and recovered with ease.
This method nevertheless has the disadvantage that the yield
of the imidation is low as compared with that obtainable by
the method using acetic anhdyride. This disadvantage is
logically explained by a postulate that compared with the
15 method which effects the imidation by the use of acetic
anhydride, the method which effects the imidation by
performing thermal dehydration in the specific solvent as
described above involves a high reaction temperature and,
therefore, tends to induce side reactions and inevitably
20 manages to produce maleimides abounding with impurities and
further that since maleimdies are thermally unstable, the
maleimides produced at all are degenerated during the course
of the reaction. Purther, as a commercial process, this
method i5 not ecconomically satisfactory, because it requires
25 to use an expensive acid catalyst in a relatively large
amount and, moreover, produces the maleimides in a low yield.
~ here is another method which, as disclosed in
Japanese Patent Laid-Open SHO 53(1978)-68,700 and Japanese
Patent Publication SHO 57(1978)-42,043, comprises causing
30 maleic anhydride to react on amines in the presence of an
organic solvent thereby forming maleinamic acids and
subjecting the maleinamic acids as held in a state not
isolated from the reaction system to dehydration and
cyclization in the presence of such an aprotic polar solvent
35 as dimethyl formamide or dimethyl sulfoxide and an acid
catalyst. By this method, there is offered recognizable
1 3 1~
improvement in yield as compared with the second method
described above. This method, however, has these
disadvantages, that the cost of production of maleimides is
high because expensive and highly toxic aprotic polar solvent
5 such as dimethyl formamide is used in a large amount, that
the solvent such as dimethyl formamide is degenerated by the
action of an acid catalyst used in the reaction and,
therefore, the solvent is lost greatly, and that since the
aprotic polar solvent used in the reaction has a high boiling
10 point, the solvent is removed from the produced malimides
with great difficulty.
Japanese Patent Laid-Open SHO 54(1979)-30,155
discloses a method for producing an oligoimide by using, as a
catalyst, a mixturé of an - inorganic or organic
15 acid-containing acid with a quaternary ammonium salt of the
acid. The quaternary ammonium salt which is used as mixed
with an acid catalyst in this method, however, is an ammonium
salt of the nitrogen atom of which has been at least
disubstituted. Specifically, this is an expensive interphase
20 catalyst such as dimethyldialkyl ammonium methane sulfonate
or tetraoctyl ammonium methane sulfonate. The method, thus
necessitating use of such a compound as indicated aobve, is
inevitably judged to be an expensive approach. For this
method to maintain a highly satisfactory yield of imidation,
25 however, it is essential that the reaction should be
continued with the ratio of the acid catalyst to the
quaternary ammonium salt rigidly controlled within a certain
range. When the catalyst which has been used once in the
reaction is used again, the imidation cannot be obtained in a
30 highly satisfactory yield because the ratio is varied in the
presence of the used catalyst. An effort to attain efficient
reuse of the used catalyst, therefore, entails as a problem
the fact that the management for maintenance of catalytic
activity as by subjecting the used catalyst to purifying and
35 readjusting treatments calls for immense labor.
1 3 ~
Japanese Patent Laid-Open SHO 60(1985)-109,562
discloses a method for the production of monomaleimide
by the cyclizing imidation of maleinamic acid in a mixed
solvent containing a nonpolar solvent such as toluene or
xylene and a polar solvent such as dimethyl sulfoxide or
N-methyl pyrrolidone in a specific ratio in the presence
of an acid catalyst such as p-toluenesulfonic acid or
m-toluenesulfonic acid and a mixed catalyst containing
the acid catalyst and an ammonium salt such as, for
example, the salt thereof with maleinamic acid. In this
method, however, since the acid catalyst and the polar
solvent in the mixed solvent react with each other to
form a complicate complex (which is widely variable with
the rat$o of the amounts of the two compounds and the
temperature, for example), it is the complicate catalyst
system composed of the complex just mentioned, the acid,
and the salt that substantially produces a catalytic
activity. Thus, the yield of the imidation is affected
to a great extent by the composition of the three
components mentioned above. When the reaction is
carried out batchwise, it does not entail any
appreciable disadvantage. When the reaction is carried
out in ~uch operation system as require the catalyst
and the solvent to be used in a recycling manner,
however, it entails various drawbacks. To be specific,
this method renders the selection of reaction conditions
complicate because the amount of the complicate complex
produced owing to the use of the polar solvent is varied
and the catalyst is varied in quality from one batch to
another. Thls is eguivalent to a statement that the
method under discussion has the disadvantage that it is
unfit for a continuous reaction.
Thls invention is directed towards the provision of
an improved method for the production of maleimides of
high purity in a high yield by a safe and simple
13~9~
procedure, which may be effected easily by a continuous
reaction.
In accordance with the present invention, there is
provided a method for the production of a maleimide by
dehydration and ring-closure of maleinamic acid obtained
by the reaction of maleic anhydride with an amine, which
method is characterized by effecting ring-closure
imidation of the maleinamic acid by heating the
maleinamic acid in a water-insoluble or water-immiscible
inert organic solvent in the presence of a catalyst
supported on a solid carrier at least one catalyst
inqredient selected from the group consisting of (a) an
acid, (b) an amine salt produced from the amine and the
acid, and (c) a mixture of the amine salt and the acid.
We have long been continuing a study on the
reactions for synthesis of maleimides. Particularly, we
have devoted our study to development of a catalyst for
use in the ring-closure imidation reaction. The study
has resulted in a finding that an aid, an amine salt
produced by the neutralization of the amine used as the
raw material for the maleimide with the acid or a
mixture of the amine ~alt with an acid supported on a
solid carrier manlfests a catalytic activity of
unusually high selectivity on the cyclizing imidation
reaction. This invention has been perfected as the
result.
In the light of the long cherished theory that the
presence o~ an oxygen-containing acid is indispensable
to the reaction of ring-closure imidation, it is liter-
ally an amazing fact that the use of the amine saltproduced by the neutralization brlngs about an unusually
high catalytic activity in the reaction o~ ring-closure
imidation.
The method for the production of an maleimide
according to this invention resides in causing dehydra-
tion and ring-closure imidation of a maleinamic acid
131969~
obtained by the reaction of maleic anhydride with an
amine to be carried
6 13i9~9~
out in a water-insoluble or water-immiscible inactive
organic solvent in the presence of a catalyst produced
by supporting on a solid carrier (a) an acid (b) or the
amine salt (c) or a mixture of the amine salt with the
acid.
The maleinamic acids to be used in this invention
are easily obtained generally by the reaction of primary
amines with maleic anhydride. They are desired to be
compounds represented by the following general formula
I.
o
CH -- ~ - OH
CH - C -- NH -- R (I)
o
wherein R denotes a member selected from the class
consisting of alkyl of l to 20 carbon atoms, phenyl,
benzyl, cyclohexyl, pyridyl, and quinolyl groups, and
the same groups as mentioned above and possessed of
halogen, carboxyl, or nitro substituents; providing that
said alkyl groups or phenyl groups are more desirable
than the other groups mentioned.
Examples of the primary amine particularly useful
as the raw material for the maleinamic acid in this
invention include methylamine, ethylamine, n-
propylamine, isopropylamine, n-butylamine, sec-
butylamine, isobutylamine, tert-butylamine, n-
hexylamine, n-dodecylamine, allylamine, benzylamine,
cyclohexylamine, aniline, nitroaniline, aminomono-
chloroaniline, dichloroaniline, toluidines, xylidines,
and ethylanilines.
Synthesis of a maleinamic acid proceeds virtually
stoichiometrically. For example, the maleinamic acid
can be synthesized by causing the amine in an amount of
0.8 to 1.5 mols, preferably 0.9 to 1.2 mols, to react
upon each mol of maleic anhydride.
B'
131~6~6
The organic solvent to be used in the present
invention is desired to be capable of permitting the
water formed by the reaction of dehydration and
cyclization to be expelled from the reaction system
through azeotropic distillation therewith, insoluble or
immiscible in water, inert, and incapable of partici-
pating in the reaction. Examples of the organic solvent
meeting this description are benzene, toluene, oil
fractions boiling at temperatures in the range of 50~ to
120C, xylenes, ethyl benzene, isopropyl benzene,
cumene, mesitylene, tert-butyl benzene, pseudo-cumene,
trimethyl hexane, octane, tetrachloroethane, nonane,
chlorobenzene, ethyl cyclohexane, oil fractions boiling
at temperatures in the range of 120 to 170C, m-
dicyclobenzene, sec-butyl benzene, p-dichlorobenzene,
decane, p-cymene, o-dichlorobenzene, butyl benzene,
decahydronaphthalene, tetrahydronaphthalene, dodecane,
naphthalene, cyclohexyl benzene, and oil fractions
boiling at temperatures in the range of 170~ to 250C.
From the standpoint of enabling this reaction to proceed
smoothly under satisfactorily economic conditions, the
amount o~ this solvent to be used in the reaction is in
the range of 1 to 20 times, preferably 3 to 7 times (by
volume), the amount of maleinamic acid.
Further, the solvent is selected on the condition
that it should possess a boiling point suiting the
prevalent reaction conditions in due consideration of
the solubility of the maleimide, price, and ease of
handling. When the separation of the maleimide and the
solvent after completion of the reaction demands an
important consideration, there are times when the
reaction performed by the use of a solvent of a low
boiling point under application o~ pressure may prove
to be more advantageous.
As a catalyst, there i8 used an inorganic or
organic monobasic or polybasic acid such as p-
7 13l9~96
toluenesulfonic acid, orthophosphoric acid,
metaphosphoric acid, pyrophosphoric acid, benzene
sulfonic acid, or trichloroacetic acid. As the
catalyst, there is used an amine salt which is obtained
by subjecting the acid with an amine as a raw material
for the production of maleimide.
~3~9~9g
This amine salt is preferred to be such that at least one of
the protons of the monobasic acid or polybasic acid is
substituted with an amine.
As the catalyst, a mixture of the amine salt with
5 the inorganic or organic acid can also be used. This mixed
catalyst produces desirable results when the amine salt
content thereof at least exceeds 40 mol%, preferably falls in
the range of 50 to 80 mol~.
Further the catalyst is obtained by supporting on a
10 solid carrier either the amine salt or a mixture of the amine
salt just mentioned with the inorganic or organic acid can be
effectively used. Furthermore, when the catalyst is
supported on the solid carrier, the amine content may be zero
percent. That is to say, sole acid catalyst may be used.
~he amount of the catalyst to be used falls in the
range of 2 to 400 mol~, preferably 20 to 200 mol%, as an acid
component contained in the catalyst, based on the amount of
the maleinamic acid, wherein the acid component contained in
the catalyst means both an acid component which constitutes
20 the amine salt and free acid.
Examples of the solid carrier to be used
advantageously herein include natural minerals such as
kaolins, clay, talc, chalk, quartz, bentonite,
montmorillonite, and diatomaceous earth; synthetic minerals
25 such as highly dispersed silicic acid, alumina, silicates,
activated carbon, gypsum, iron oxide red, titanium dioxide,
silica, silica-alumina, and zirconium oxide; and natural
rocks such as calcite, marble, pumice, sepiolite, and
dolomite.
Such an inorganic carrier is used in the form of
powder, in the form of granules obtained by pelletizing and
classifying the relevant substance, or in the form of a
honeycomb.
It is also permissible to use an organic carrier.
35 A granular carrier of polyfluorocarbon, polystyrene, or
phenol resin can be effectively used. The catalysis is
1 31 ~
obtained with particularly desirable results when the carrier
is made of such a porous substance as diatomaceous earth,
silica gel or activated carbon. As typical examples of the
cmmercially available carrier usable effectively herein
5 include a product of diatomaceous earth (marketed by Showa
Chemical Industry Co., ~td. under trademark designation of
"Radiolight") and products of silica gel (marketed by
Fuji-Davison Chemical Co., Ltd. under trademark designations
of "Carriact" "SYLOID," and "Microbead Silica Gel"), a
1~ product of silica gel (marketed by Wako-Junyaku Industry Co.,
Ltd. under trademark designation of "Wakogel"), and a product
of activated carbon (marketed by Taiyo Kaken Co., Ltd. under
trademark designation of "BAC".
Though the amount of the carrier-supported catalyst
15 to be used is variable with the physical properties of the
carrier used therein, it is generally in the range of 0.5 to
500 ~ by weight, desirably 5 to 200 ~ by weight, and
particularly desirably 10 to 100 % by weight, based on the
amount of the carrier.
As means for supporting the catalyst on the
carrier, any of the conventional methods such as the
immersion method and the spray can be adopted. The catalyst
may be supported directly on the carrier or it may be
supported in an organic solvent or an aqeous solution.
When the amine salt obtained by the reaction of
neutralization of the amine as the raw material with an acid
is used as the catalyst either independently or in a form
mixed with an acid, the acid catalyst may be supported first
on the carrier and then caused to react with the amine or the
30 amine salt or the mixture of the amine salt with an acid may
be prepared in advance and subsequently supported on the
carrier. It is provided, however, that when the amine salt
is used by itself, since the amine salt is solid at normal
room temperature, it must be supported on the carrier in the
35 form of an agueous solution.
13~6~6
The amount of the catalyst o~ the foregoing
description to be used is in the range of 2 to 400 mol%,
preferably 20 to 200 mol%, based on the amount of the
maleinamic acid to be contained as an acid component, part or
S the whole of the acid destined to serve as the catalyst may
be neutralized with an amine.
In the reaction of neutralization, the reaction may
be carried out in the presence of a metal-containing compound
and a stabilizer when occasion demands.
The catalyst produced as described above is
insoluble in the organic solvent to be used in the present
invention. In the reaction system, therefore, this catalyst
assumes a state separated into the two layers, an organic
layer and an layer. This state remains intact during and
15 after the reaction. Moreover, the catalyst remains
substantially unchanged before and after the reaction. The
catalyst system of this nature itself, therefore, can be
utilzied in situ in the next cycle of reaction without being
recovered and refined in the meantime.
When this catalyst layer is to be used in the next
cycle of reaction, the organic layer and the catalyst layer
exi~ting at the end of the reaction may be separated one from
the other at a temperature in the range of 120 to 250C, and
the catalyst layer consequently recovered may be put to use
25 directly in the next cycle of reaction.
As concerns the manner of use o the supported
catalyst of the foregoing description, the catalyst may be
used as added in the form of powdered catalyst to a stirring
type reaction kettle or it may be used as granulated and
30 packed in the form of a fixed bed in a flow type reaction
tube.
There are times when the reaction can be carried
out, as disclosed in U.S. Patent No. 4,623,734, in the
presence of a metal-containing compound and a stabilizer.
35 The metal-containing compound to be used in this case is
selected from among oxides, acetates, maleates, succinates,
-- 10 --
69~
nitrates, phosphates, chlorides, and sulfates of at least one
metal selected from the group consisting of zinc, chromium,
palladium, cobalt, nickel, iron, and aluminum. Among other
compounds enumerated above, zinc acetate proves to be
5 particularly effective. The amount of the metal-containing
compound to be used is in the range of 0.005 to 0.5 mol%,
preferably 0.01 to 0.1 mol~, as metal, based on 1 mol of the
maleinamic acid.
Examples of the stabilizer to be used
10 advantageously herein include methoxy benzoquinone,
p-methoxyphenol, phenothiazine, hydro~uinone, alkylated
diphenyl amines, methylene blue, tert-butyl catechol,
tert-butyl hydroquinone, zinc dimethyldithiocarbamate, copper
dimethyldithiocarbamate, copper dibutyldithiocarbamate,
15 copper salicylate, thiodipropionic esters,
mercaptobenzimidazole, triphenyl phosphite, alkylphenols, and
alkylbisphenols.
The stabilizer plays the part of enabling the
maleimide which is produced by the reaction of imidation to
20 retain stably during the course of the imidation without
being degenerated at the elevated temperature of the
reaction.
Concerning the amount of the stabilizer to be
added, the addition of the ~tabilizer in a minute amount is
25 not suffici0ntly effective and the addition thereof in an
unduly large amount is undesirable because it entails the
drawback that the excess of stabilizer finds its way into the
final product. The amount of the stabilizer to be
effectively used is in the range of 0.005 to 0.5 mol%,
30 preferably 0.05 to 0.3 mol%, based on 1 mol of the maleinamic
acid.
Regarding the manner of working out the present
invention, first maleic anhydride prepared as a solution in
an organic solvent and an amine compound added thereto are
35 allowed to react with each other at a temperature not
exceeding 150C, preferably falling in the range of 30 to
13~9~
120C, for a period of 15 to 120 minutes, preferabl~ 30 to
60 minutes to produce maleinamic acid. Then, the reaction
system in which the maleinamic acid is left unisolated, the
catalyst or the catalyst layer separated from the reaction
5 system of the preceding cycle of reaction, and optionally the
metal-containing compound and/or the stabilizer are combined
and heated at a temperature in the range of 120 to 250C,
preferably 130 to 220C, for a period in the range of one
hour to 15 hours, preferably 3 to 7 hours to effect the
10 reaction in a continuous pattern with the formed water
expelled from the system through azeotropic distillation or
to effect the reaction in a batchwise pattern with the
expulsion of the formed water carried out at the end of the
reaction. As the result, the maleimide is produced in a high
15 yield.
The maleimide which is consequently obtained is a
compound represented by the general formula II, for example.
CH - C~ (II)
CH - C /
o
wherein R has the same meaning as defined above. Typical
examples of the maleimides include N-methyl maleimide,
25 N-ethyl maleimide, N-n-propyl maleimide, N-isopropyl
maleimide, N-n-butyl maleimide, N-sec-butyl maleimide,
N-tert-butyl maleimide, N-n-hexyl maleimide, N-n-dodecyl
maleimide, N-allyl maleimide, N-benzyl maleimide,
N-cyclohexyl maleimide, N-phenyl maleimide, N-nitrophenyl
30 maleimide, N-hydroxyphenyl maleimide, N-methoxyphenyl
maleimide, N-ethoxyphenyl maleimide, N-monochlorophenyl
maleimide, N-dichlorophenyl maleimide, N-monomethylphenyl
maleimide, N-dimethylphenyl maleimide, and N-ethylphenyl
maleimide. Of course, the maleimides which this invention is
35 intended to embrace are not limited to the examples cited
above.
1319~36
This invention which has been described above
brings about the following advantages.
(1) This invention permits a maleimide of high purity
to be produced in a high yield because the catalyst
system produced by supporting on a solid carrier the
amine salt obtained from the acid and the amine as the
raw material and/or the acid possesses a catalytic
activity of high selectivity on the reaction of
ring-closure imidation.
(2) Since the catalyst is supported on the solid
carrier and, therefore, the separation of the reaction
solution and the catalyst can be easily effected, the
reaction can be easily carried out in a continuous
pattern and, what is more, the productivity of the
process can be enhanced to a great extent.
(3) Since the catalyst is lost only nominally, the cost
of the catalyst can be substantially disregarded.
As described in (1) through (3), this invention
permits a maleimide to be easily produced inexpensively
and safely.
Now, the present invention will be described more
specifically below with re~erence to working examples.
Example 1
In a beaker having an inner volume of 200 ml, 20g
of orthophosphoric acid was placed and then 30 g of
diatomaceous earth (product of Showa Chemical Industry
Co., Ltd. marketed under trademark designation of
"Radiolight #200") was added thereto to effect
deposition of the orthophosphoric acid on the
diatomaceous earth.
A flask provided with a thermometer, a condenser
incorporating therein a water separator, a dropping
funnel, and a stirrer was charged with a solution of 55
g of maleic anhydride in 50 g of xylene. Then, the
inner temperature of the flask was ad~usted to 80~C and
a solution of 50 g of aniline in 400 g of xylene was
.~
~3~9~
13a
added piecemeal thereto over a period of 30 minutes, to
synthesize a slurry solution of N-phenyl maleinamic acid
in xylene.
B~
i3~9~
The slurry solution thus obtained and the catalyst
prepared in the beaker in advànce were left reacting at 140C
for three hours. After the reaction was completed, the
reaction solution was separated from the catalyst layer. It
5 was then cooled to 80C, washed with water, and thereafter
distilled under a vacuum to expel xylene and obtain 83 g of
crystals of N-phenyl maleimide. The purity of the crystals,
on analysis by liquid chromatography, was found to be 87.4 %
by weight. The yield of this product was 78.0 % based on
10 aniline used as aniline.
Example 2
The procedure of Example 1 was faithfully repeated,
excepting 0.034 g of zinc acetate and 0.01 g of copper
dibutyl dithiocarbamate were added instead during the course
15 of imidation. As the result, there were obtained 93 g of
crystals of N-phenyl maleimide. The purity of the crystals,
on analysis by liquid chromatography, was found to be 94.3 %
by weight. The yield thereof was 94.3 mol% based on aniline
used as the raw material.
20 Example 3
In a Meyer's flask having an inner volume of 300
ml, 100 g of xylene and 20 g of orthophosphoric acid were
dispersed Then, the same diatomaceous earth as used in
Example 1 was introduced therein to effect deposition of the
25 orthophosphoric acid on the diatomaceous earth. Then it was
reacted with 9.5g of aniline. The procedure of Example 2 was
repeated, excepting the deposited catalyst mentioned above
was used as a catalyst for the imidation. Consequently,
there were obtained g2 g of crystals. The purity of the
30 crystals, on analysis by liquid chromatography, was found to
be 98.5 % by weight. The yield thereof was 97~5 mol% based
on aniline used as the raw material.
After the reaction was completed, in the reactor
containing the used catalyst intact, a total of 20 cycles of
35 the imidation were carried out. The yield of reaction in the
- 14 -
.
1319~
20th cycle was 98.1 mol%. The catalyst after the 20th cycle
of reaction showed the same a~tributes as the catalyst after
the first cycle of reaction.
Control 1
The procedure of Example 1 was repeated, excepting
the orthophosphoric acid was not deposited on diatomaceous
earth. As the result, there were obtained 82 g of crystals
of N-phenyl maleimide. The purity of the crystals, on
analysis by liquid chromatography, was found to be 74.8 % by
10 weight. The yield of the product was 66.0 mol~, based on
aniline used as the raw material.
Control 2
The procedure of Example 2 was repeated, excepting
the orthophosphoric acid was not deposited on diatomaceous
15 earth. Consequently, there were obtained 85 g of crystals of
N-phenyl maleimide. The purity of the crystals, on analysis
by liquid chromatography, was found to be 90.2 % by weight.
The yield of this product was 80.5 mol% based on aniline used
as the raw material.
20 Control 3
The procedure of Example 3 was repeated, excepting
the orthophosphoric acid was not deposited on diatomaceous
earth. Consequently, there were obtained 90 g of crystals of
N-phenyl maleimide. The purity of the crystals, on analysis
25 by liquid chromatography, was found to be 91.7 % by weight.
The yield of this product was 88.8 mol% based on aniline used
a8 the raw material.
Example 4
In a meyer's flask having an inner volume of 300
30 ml, 60 g of orthophosphoric acid was placed and stirred with
g of a granular silica gel carrier (product of
Fuji-Davison chemical Co., Ltd. mar]seted under trademark
designation of "Carriact-30") to effect deposition of the
acid on the carrier.
,~ 1319~
Subsequently, 100 g of orthoxylene was added
thereto and the Meyer's flask was kept cooled in a water
bath and 37 g of cyclohexylamine was added dropwise
thereto, to effect partial conversion of the carried
acid into an amine salt.
Separately, a flask provided with a thermometer, a
condenser incorporating therein a water separator, a
dropping funnel, and a stirrer was charged first with
100 g of orthoxylene and then with loo g of maleic
anhydride and heated to an inner temperature of 100C,
to effect dissolution of the maleic anhydride.
Subsequently, a solution of 100 g of cyclo-
hexylamine in 600 g of orthoxylene was added dropwise in
a stirred state over a period of one hour, to synthesize
a slurry solution of N-cyclohexyl maleinamic acid in
orthoxylene.
Then, the slurry solution and the carried catalyst
and 0.1 g of copper dibutyl dithiocarbamate added
thereto were left reaction for seven hours by being
heated and stirred at 143C, with the water formed by
the reaction continuously expelled by distillation in
combination with the oroxylene ~rom the reaction system
in the meantime.
A~ter the reaction was completed, the reaction
solution was analyzed for N-cyclohexyl maleimide by gas
chromatography. Thus, the yield of N-cyclohexyl
maleimide was found to be 97.8 mol% based on cyclohexyl
amine used as the raw material.
Example 5
In a beaker having an inner volume of 500 ml, 100 g
of sul~uric acid and 200 g of silica gel (product o~
Wako Junyaku marketed under trademark designation o~
"Wako Gel C100") were stirred to e~ect support o~ the
acid on the silica gel. Separately, a reactor wa~
prepared by furnishing a glass flask having an inner
volume of 1 liter with a thermometer, a stirrer, and a
~. ~ '
13î~
16a
water separator. Then, a solution of 53 g of powdered
maleic anhydride in 50 g of
~ la;~J
131~3~
p-cymene was placed in the reactor. Subsequently, the inner
temperature of the reactor -was adjusted to 130C and a
solution of 40 g of n-butylamine in 400 g of p-cymene was
added piecemeal thereto in a dropwise manner over a period of
5 30 minutes, to synthesize a solution of N-(n-butyl)
maleinamic acid.
The solution thus obtained and the supported
catalyst, 0.034 g of zinc acetate, and 0.065 g of
p-methoxyphenol added thereto were left reacting at 180C,
lO with the formed water continuously expelled in combination
with the p-cymene from the reaction system in the meantime.
After the reaction was completed, the reaction
solution was analyzed for the concentration of N-(n-butyl)
maleimide. As the result, the yield of the product was found
15 to be 80.4 mol~O.
