Disproportionating method of trimethylamine

Upon subjecting trimethylamine with ammonia and optionally, a methylamine to a disproportioning reaction to reduce the proportion of the trimethylamine, use of a zeolite as a catalyst, said zeolite being mordenite, clinoptilolite or the like at least 80% of whose ion-exchangeable cations being in the form of hydrogen ions, makes it possible to efficiently conduct the reaction at a low reaction temperatures and also to suppress by-production of impurities such as acetonitrile.

BACKGROUND OF THE INVENTION 
(i) Field of the Invention 
This invention relates to a method for reducing the proportion of 
trimethylamine by a disproportionating reaction, said trimethylamine being 
by-produced in a small amount upon preparation of dimethylamine and 
monomethylamine through a reaction between methanol and ammonia in the 
presence of a shape-selective catalyst. More specifically, this invention 
pertains to a catalyst useful in allowing the disproportionating reaction 
to proceed efficiently and also in suppressing by-production of trace 
components which are formed in the disproportionating reaction. 
(ii) Description of the Related Art 
As catalysts for the disproportionation of trimethylamine, those having 
solid acidity are known to show catalytic ability for many years. As those 
exhibiting solid acidity, alumina, silica-alumina, silica-magnesia, 
alumina-titania, silica-titania, silica-zirconia, alumina-zirconia, solid 
phosphoric acid, large pore zeolites and the like are known to be 
effective for the disproportionating reaction. Among these solid acid 
catalysts, proposed and widely employed are those composed primarily of 
silica and/or alumina, specifically, silica-alumina catalysts (Japanese 
Patent Laid-Open No. 169445/1982, Japanese Patent Publication No. 
47172/1987, U.S. Pat. No. 4,485,261) and rhenium-ion-exchanged zeolite Y 
(REY zeolite), i.e., "SK-500" (trade name; product of Union Carbide 
Corporation, U.S.A.; U.S. Pat. No. 4,398,041). 
The above-described conventional catalysts proposed to date do not have 
sufficient catalytic activities. A reaction temperature of 375.degree. C. 
or higher is needed to achieve sufficient conversion of trimethylamine 
especially with an amorphous silica-alumina catalyst. This 
disproportionating reaction is an equilibrium reaction. Although a 
somewhat higher temperature is advantageous for the conversion at 
equilibrium, it may be sufficient in balance if the conversion at 
equilibrium available at about 300.degree. C. is obtained. There is a 
demand for a catalyst which exhibits sufficient activities in a 
temperature range of about 280.degree.-380.degree. C., because this 
disproportionating reaction is an endothermic reaction and therefore, heat 
of reaction should be supplied from the outside to the catalyst layer. The 
lower the reaction temperature, the more advantageous in both apparatus 
and energy for supplying heat of reaction. From such a viewpoint, the 
above-described REY zeolite has the advantage that it shows activities at 
a lower temperature than an amorphous silica-alumina catalyst. According 
to the results of a test conducted by the present inventors, however, REY 
zeolite has been found to involve the problem that reaction 
by-products--for example, acetonitrile, acetone, propionitrile and 
propyl-amine--are formed in trace amounts. These trace by-products 
accumulate in the course of separation and purification of the reaction 
products, and cause the problem that the efficiency of the separation is 
lowered. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a disproportionating 
method of trimethylamine, which is free of the drawbacks described above. 
More specifically, the object is to provide a method which allows a 
disproportionating reaction of trimethylamine to efficiently proceed at a 
reaction temperature lower than that needed when amorphous solid acid 
catalysts used widely to date, typified by silica-alumina catalysts, are 
employed and is free from by-production of trace components such as 
acetonitrile, acetone, propionitrile and/or propylamine. 
The present inventors have conducted extensive research with a view toward 
developing a disproportionating method of trimethylamine, which is free of 
the above-described problems. As a result, it has been found that use of a 
zeolite with its ion-exchangeable cations having been sufficiently 
exchanged by hydrogen ions as a catalyst for the disproportionating 
reaction of trimethylamine allows the disproportionating reaction to 
efficiently proceed at temperatures lower than those needed for 
conventional catalysts without by-production of acetonitrile, acetone, 
propionitrile, propylamine and/or the like in trace amounts, leading to 
the completion of the present invention. 
The present invention therefore provides a method for disproportionating 
trimethylamine by subjecting the trimethylamine and ammonia or the 
trimethylamine, ammonia and a methylamine to a disproportionating reaction 
to reduce the proportion of the trimethylamine. The disproportionating 
reaction is conducted in the presence of at least one zeolite selected 
from the group consisting of mordenite, clinoptilolite, heulandite, 
canncrinite, ferrierite, gmelinite, stilbite, mazzite, offretite and ZSM-5 
zeolite, at least 80% of whose ion-exchangeable cations are in the form of 
hydrogen ions. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
It has heretofore been considered that among zeolites, those having a pore 
diameter of approximately 5 to 7 .ANG.--such as mordenite and 
clinoptilolite--other than faujasite (pore diameter: 7.4 .ANG.) and the 
like can hardly induce a disproportionating reaction of trimethylamine 
within their pores and the disproportionating reaction primarily proceeds 
on their outer surfaces alone because the molecular size of trimethylamine 
is 6.1 .ANG.(Japanese Patent Laid-Open No. 169445/1982 and U.S. Pat. No. 
4,485,261). It is also known that outer surfaces of a zeolite account for 
5-10% or so of its entire surfaces. It is disclosed that, when a catalyst 
having a smaller pore diameter such as mordenite is used, the time of 
contact between a reactant or reactants and the catalyst has to be 
prolonged sufficiently (Japanese Patent Laid-Open No. 169445/1982 and U.S. 
Pat. No. 4,485,261). 
Further, it is disclosed that, since 5 A zeolite, macroporous 
H-chabazite-erionite and H-mordenite are shape-selective, they are suited 
for the reaction between methanol and ammonia but are not suited for the 
disproportionating reaction of trimethylamine; for the disproportionating 
reaction, SiO.sub.2 --Al.sub.2 O.sub.3, H--Y and REY zeolites are suited 
(U.S. Pat. No. 4,398,041). 
According to research conducted by the present inventors, it has been 
unexpectedly found that a zeolite having a small pore diameter like 
mordenite or clinoptilolite can sufficiently promote the 
disproportionating reaction of trimethylamine even at a temperature lower 
than those required for amorphous solid acid catalysts employed widely to 
date, such as silica-alumina catalysts, can set the time of contact 
between the reactant and the catalyst either equal to or shorter than 
those needed for the silica-alumina catalysts and, when exchangeable 
cations are sufficiently exchanged with hydrogen ions, can minimize trace 
by-products such as acetonitrile to substantially zero. 
Namely, byproducts such as acetone, acetonitrile, propionitrile and 
propylamine are formed where exchangeable cations in a zeolite have been 
substituted by cations of an alkali metal, an alkaline earth metal or 
rhenium. A zeolite whose cations have been sufficiently exchanged with 
protons however do not practically form these impurities. 
The zeolite or zeolites usable in the practice of the method of this 
invention are each either synthetic or natural. Described specifically, 
the followings are examples of zeolites usable in the method of the 
present invention and their compositions and maximum pore diameters. 
______________________________________ 
Maximum 
pore 
diameter 
Kind Composition (nm) 
______________________________________ 
Mordenite 
Na.sub.8 (Al.sub.8 Si.sub.40 O.sub.96)24H.sub.2 O 
0.67 .times. 0.70 
Clinoptilolite 
Na.sub.6 (Al.sub.6 Si.sub.30 O.sub.72)24H.sub.2 O 
0.44 .times. 0.72 
Heulandite 
Ca.sub.4 (Al.sub.8 Si.sub.28 O.sub.72)24H.sub.2 O 
0.76 .times. 0.30 
Canncrinite 
Na.sub.6 (Al.sub.6 Si.sub.6 O.sub.24)CaCO.sub.3.24H.sub.2 
0.59 
Ferrierite 
Na.sub.2 Mg.sub.2 (Al.sub.6 Si.sub.30 O.sub.72)18H.sub.2 
0.54 .times. 0.42 
Gmelinite 
(Na.sub.2 Ca).sub.4 (Al.sub.8 Si.sub.16 O.sub.48)24H.sub.2 
0.70 
Stilbite Na.sub.4 Ca.sub.8 (Al.sub.20 Si.sub.52 O.sub.144)56H.sub.2 
0.61 .times. 0.49 
Mazzite (Na.sub.2 K.sub.2 CaMg).sub.5 (Al.sub.10 Si.sub.26 O.sub.72)28H.s 
ub.2 O 0.74 
Offretite 
(CaMg).sub.1.5 K(Al.sub.4 Si.sub.14 O.sub.36)14H.sub.2 O 
0.67 
ZSM-5 Na.sub.n (Al.sub.n Si.sub.96-n O.sub.192)16H.sub.2 O 
0.56 .times. 0.53 
______________________________________ 
Each of these zeolites can be used at the silica/alumina ratio in the 
above-described composition without any modification. In the method of the 
present invention, it is also possible to use that obtained by increasing 
the silica/alumina ratio upon hydrothermal synthesis of any one of the 
above zeolites or a high-silica zeolite with a high silica/alumina ratio 
attained by increasing the silica/alumina ratio of any one of the above 
zeolites in accordance with a method such as an acid treatment or steam 
treatment. 
The high-silica zeolite catalyst with an increased silica/alumina ratio 
features relatively less deposit of carbonaceous substances during a 
long-term operation than low-silica zeolites and can hence minimize the 
reduction in catalytic activities. 
A zeolite inherently having a high silica/alumina ratio (hereinafter 
abbreviated as the "R ratio"), instead of an R ratio increased 
specifically by a troublesome procedure such as an acid treatment, also 
features less deposit of carbonaceous substances and a smaller reduction 
in catalytic activities even when employed in a log-term operation. 
Among a group of zeolites usable in the present invention, those inherently 
having a high R ratio, for example, 10 or greater--mordenite (R ratio: 
10), clinoptilolite (R ratio: 10), ZSM-5 (R ratio&gt;20) and the like--are 
therefore particularly preferred catalysts. 
Faujasite (corresponding to synthetic Y zeolite) has a pore diameter as 
large as 0.74 nm. Its initial catalytic activities are excellent. However, 
its R ratio is 4.6, carbonaceous substances deposit in a relatively large 
amount and, when employed in a long-term operation, faujasite gives 
results inferior in the deterioration of activities to mordenite. 
In the method of the present invention, exchangeable cations in a zeolite 
to be employed as a catalyst are fully exchanged with hydrogen ions to 
minimize, to substantially zero, acetonitrile and the like which are 
by-produced upon the disproportionating reaction. The functional exchange 
attainment to a H-type zeolite is 80% or higher, preferably 90% or higher. 
To exchange cations of a zeolite, which has been exchanged with an alkali 
metal, an alkaline earth metal or the like, with hydrogen ions, there are 
two methods, one featuring an exchange treatment in a gas phase and the 
other an exchange treatment in a liquid phase. 
To conduct the treatment in a gas phase, the zeolite is treated with vapor 
of ammonium chloride at 250.degree.-300.degree. C. and is then heated to 
400.degree.-600.degree. C. or is treated at 400.degree. C. with ammonia 
gas and is then heated to 500.degree.-600.degree. C., whereby the zeolite 
is converted into a hydrogen ion form. To treat the zeolite in the liquid 
phase, the zeolite to be exchanged is immersed in an aqueous solution of 
an ammonium salt such as ammonium nitrate or ammonium chloride, so that 
the zeolite is subjected to ion exchange. The concentration of the aqueous 
solution of the ammonium salt is often adjusted in a range of 0.1 to 2N. 
The aqueous solution of the ammonium salt is used in an amount equivalent 
to the amount of the ammonium salt 2 to 10 times as much as the amount of 
cations contained in the zeolite and to be ion-exchanged. The temperature 
upon conducting the ion exchange can range from room temperature to the 
boiling point of the aqueous solution of the ammonium salt. The time 
required for the ion exchange is often in a range of 1-30 hours. The ion 
exchange in the liquid phase can be conducted by conducting the above 
procedures once or more, generally, twice to thrice, whereby more than 90% 
of the ion-exchangeable cations can be replaced by ammonium ions. The 
zeolite which has been converted into the NH.sub.4.sup.+ -form is 
thoroughly washed with deionized water. The resulting mixture is subjected 
to solid-liquid separation. The solid phase is dried and then heated to 
400.degree.-600.degree. C., whereby the zeolite is converted into H.sup.+ 
-form for use in the present disproportionating reaction. Where the 
zeolite to be used is mordenite, clinoptilolite or ZSM-5 zeolite, alkali 
metal or alkaline earth metal ions can be directly exchanged with hydrogen 
ions by an aqueous solution of an acid such as hydrochloric acid, nitric 
acid or sulfuric acid. Here, the concentration of the acidic aqueous 
solution is generally 6N or lower, especially in a range of 0.5--3N. The 
amount of the acid to be used is often 2-10 times the amount of cations 
which are contained in the zeolite and are to be exchanged. In the case of 
the ion exchange by the acid, 90% or more of ion-exchangeable cations can 
also be exchanged with hydrogen ions by repeating the ion-exchanging 
procedures once or more. The zeolite converted into the H.sup.+ -form by 
the acidic aqueous solution is similarly washed with deionized water. The 
resulting mixture is subjected to solid-liquid separation. The solid phase 
so obtained is dried and then calcined at 400.degree.-700.degree. C. into 
a catalyst. 
The term "ion-exchangeable cations in a zeolite" indicate alkali metal 
cations and/or alkaline earth metal cations contained in the zeolite. How 
much of these cations have been exchanged with hydrogen ions by the above 
exchanging operation can be determined by performing a calculation on the 
basis of chemical analysis date of the zeolite so obtained. 
If the zeolite subjected to the ion-exchanging treatment is in a briquette 
form or has been formed into tablets, it is used, as is, as a catalyst. If 
it is in a powdery form, it is extruded into pellets or compressed into 
tablets in a manner known per se in the art for use as a catalyst. In some 
instances, it can be granulated into microspheres by a spray drier for use 
as a fluidized bed catalyst. The particle sizes of these microspheres may 
preferably be distributed over a range of 20-100 .mu.m. 
The disproportionating reaction of trimethylamine in the present invention 
can be practiced by bringing the trimethylamine along with ammonia into 
contact with the above-described catalyst layer or a mixture of the 
trimethylamine, ammonia and methylamines composed primarily of 
monomethylamine into contact with the 10 above-described catalyst layer. 
Whichever reaction method is followed, the starting materials which are to 
be fed to the catalyst layer upon practicing the disproportionating 
reaction may contain dimethylamine, methanol, dimethyl ether and/or the 
like in small amounts. In the present disproportionating reaction, the 
composition of disproportionated products is determined by the ratio of 
nitrogen atoms to carbon atoms contained in the starting materials of the 
reaction, the N/C ratio, irrespective of the composition of the starting 
materials of the reaction. In the method of the present invention, an N/C 
ratio in a range of 1-50, especially 3-30 is often used. 
The temperature of the catalyst layer upon conducting the reaction may 
preferably be in a range of 270.degree.-400.degree. C. Usually, a 
temperature in a range of 280.degree.-80.degree. C. is often employed. The 
preferred reaction pressure may be from atmospheric pressure to 50 atm. A 
reaction pressure in a range of 10-30 atm is often used. The feed rate of 
the starting materials of the reaction to the catalyst layer can be in a 
range of 500-20,000 Nm.sup.3 /m.sup.3 hr when expressed in terms of gas 
hourly space velocity (hereinafter abbreviated as "GHSV". GHSV in a range 
of 1,000-10,000 Nm.sup.3 /m.sup.3 hr is often employed. 
A reactor for use in the present invention can be of the usual fixed bed or 
fluidized bed type. In the case of the fixed bed type, a shell-and-tube 
reactor or an adiabatic reactor can be used. 
A description will next be made of advantageous effects of the present 
invention. 
The method according to the present invention can bring about such an 
industrial merit that the disproportionating reaction of trimethylamine 
can proceed at a temperature lower than those required when 
conventionally-known amorphous silica-alumina catalysts are used and the 
supply of reaction heat can hence be facilitated. Further, the method of 
the present invention can practically achieve complete prevention of 
by-production of trace impurities such as acetonitrile, thereby making it 
possible to avoid a reduction in separation efficiency 
The method of the present invention can effectively be used in combination 
with a step for producing, from ammonia and methanol, methylamines 
composed mainly of dimethylamine, monomethylamine as a by-product and not 
more than 5 percent of trimethylamine as a further by-product, i.e., in 
combination with a step for producing methylamines, in which a zeolite 
modified with a silicon compound and having a high shape-selectivity is 
used as a catalyst.

The present invention will hereinafter be described specifically by 
examples and comparative examples. 
EXAMPLE 1 
In 2,500 ml of a 1N aqueous solution of ammonium chloride, 300 g of powdery 
synthetic mordenite (silica/alumina ratio: 10) were added, followed by 
external heating for 4 hours under reflux. The resultant mixture was then 
separated into a solid phase and a liquid phase. To the solid phase so 
obtained, a fresh supply (3,000 ml) of a 1N aqueous solution of ammonium 
chloride was added, followed by reflux for 4 hours, whereby NH.sub.4.sup.+ 
-form mordenite was obtained. Subsequent to separation of the mixture into 
a solid phase and a liquid phase, the solid phase was thoroughly washed 
with deionized water, dried at 120.degree. C. and then calcined at 
600.degree. C. for 3 hours under air circulation, whereby H.sup.+ -form 
mordenite was prepared. From data of a chemical analysis of the mordenite 
so obtained, it was found that 97.5% of ion-exchangeable cations in the 
mordenite had been exchanged with hydrogen ions. The resultant mordenite 
was compressed into cylindrical tablets of 3 mm in diameter and 3 mm in 
height and were provided for use as a catalyst. 
A stainless-steel reactor having an internal diameter of 25 mm was packed 
with 20 ml of the catalyst so obtained, followed by external heating over 
a fluidized sand bath. 
A liquefied gas mixture of ammonia and trimethylamine (N/C ratio: 10.1) was 
fed to the catalyst layer at GHSV of 4,000/hr, followed by a reaction at 
330.degree. C. and 20 atm. As a result of an analysis of components at an 
outlet of the reactor 150 hours after the reaction was started, it was 
found that the conversion of trimethylamine was 60.8% and no trace 
by-products such as acetonitrile were detected practically (20 ppm or 
less). The conversion of trimethylamine reached 60.9% when the analysis 
was conducted after the reaction was continued for 800 hours and further, 
no deterioration of the catalyst was recognized. 
This example clearly indicates that H.sup.+ -form mordenite shows high 
activities at lower temperatures than SiO.sub.2 --Al.sub.2 O.sub.3 
catalysts widely used to date for the disproportionating reaction and 
hence, prolongation of the contact time is not needed. This example also 
teaches that mordenite having a large R ratio features less deposit of 
carbonaceous substances and no deterioration of the catalytic activities 
will be observed even in a long-term operation. 
EXAMPLE 2 
In 2,000 ml of a 2N aqueous solution of hydrochloric acid, 300 g of natural 
mordenite (mordenite content: 74%) having a granule size range of 2-3 mm 
were added, followed by gentle stirring at room temperature for 5 hours. 
After the resultant mixture was separated into a solid phase and a liquid 
phase, the solid phase was added with a fresh supply (2,000 ml) of a 2N 
aqueous solution of hydrochloric acid and then treated as above. The 
resultant mixture was subjected to solid-liquid separation. The solid 
phase was washed with deionized water, dried, and then calcined at 
550.degree. C. for 4 hours, whereby a catalyst was prepared. It was found 
that 98.2% of ion-exchangeable cations in the mordenite had been exchanged 
with hydrogen ions. A stainless-steel reactor having an internal diameter 
of 25 mm was packed with 20 ml of the mordenite so obtained, followed by 
external heating over a fluidized sand bath. 
A liquefied gas mixture of ammonia and trimethylamine (N/C ratio: 10.1) was 
fed to the catalyst layer at GHSV of 3,200/hr, followed by a reaction at 
330.degree. C. and 20 atm. As a result of an analysis of components at an 
outlet of the reactor 150 hours after the reaction was started, it was 
found that the conversion of trimethylamine was 61.1% and no trace 
by-products such as acetonitrile were detected practically (20 ppm or 
less). 
Comparative Example 1 
A reactor similar to that employed in Example 1 was packed with 20 ml of an 
amorphous silica-alumina catalyst (alumina content: 13%) having a granule 
size range of 2-3 mm. A liquefied gas mixture of ammonia and 
trimethylamine (N/C ratio: 10.3) was fed to the catalyst layer at GHSV of 
4000/hr, followed by a reaction at 330.degree. C. and 20 atm. 
As a result of an analysis of components at an outlet of the reactor 150 
hours after the reaction was started, it was found that the conversion of 
trimethylamine was 18.5%. 
Comparative Example 2 
From mordenite similar to that employed in Example 1, a catalyst whose 
ion-exchange rate to hydrogen ions was 70% was prepared. Using the 
catalyst so obtained and the same reactor as that employed in Example 1, a 
liquefied gas mixture of ammonia and trimethylamine (N/C ratio: 5) was fed 
to the catalyst layer at GHSV of 1,500/hr, followed by a reaction at 
350.degree. C. and 20 atm. The results of an analysis of components at the 
outlet of the reactor 150 hours after the reaction was started were as 
follows: 
The conversion of trimethylamine was 57.2%, and the total amount of 
by-products, that is, acetonitrile, acetone, propionitrile and 
propylamine, was 1,200 ppm. 
EXAMPLE 3 
From mordenite similar to that employed in Example 1, a catalyst whose 
ion-exchange rate to hydrogen ions was 83% was prepared. Using the 
catalyst so obtained and the same reactor as that employed in Example 1, a 
liquefied gas mixture of ammonia and trimethylamine (N/C ratio: 5) was fed 
to the catalyst layer at GHSV of 1,500/hr, followed by a reaction at 
350.degree. C. and 20 atm. The results of an analysis of components at the 
outlet of the reactor 150 hours after the reaction was started were as 
follows: 
The conversion of trimethylamine was 60.4%, and the total amount of 
by-products, that is, acetonitrile, acetone, propionitrile and 
propylamine, was 380 ppm. Example 4. 
In 2,000 ml of a 2N aqueous solution of hydrochloric acid, 300 g of natural 
clinoptilolite (clinoptilolite content: 75%) having a particle size range 
of 2-3 mm were added, followed by gentle shaking at room temperature for 4 
hours. After the resultant mixture was separated into a solid phase and a 
liquid phase, the solid phase was separated, followed by the addition of a 
fresh supply (2,000 ml) of a 2N aqueous solution of hydrochloric acid, The 
solid phase was treated for four hours at room temperature. The resultant 
mixture was then subjected to solid-liquid separation. The solid phase so 
obtained was washed with deionized water, dried, and then calcined at 
500.degree. C. for 4 hours, whereby a catalyst was prepared. The 
ion-exchange rate to hydrogen ions of the catalyst so obtained was 95%. 
A reactor similar to that employed in Example 1 was packed with 20 ml of 
the catalyst so obtained to conduct disproportionation of trimethylamine. 
One hundred hours after the reaction was started under conditions similar 
to those employed in Example 1, an outlet gas at the outlet of the reactor 
was analyzed. As a result, it was found that the conversion of 
trimethylamine was 56.1% and no trace byproducts such as acetonitrile was 
detected practically (20 ppm or less). 
EXAMPLE 5-12 
In each example, a glass-made reactor having an internal diameter of 18 mm 
was packed with a zeolite catalyst having a granule size range of 1-2 mm. 
To the catalyst layer, a liquefied gas mixture (N/C ratio: 10) of ammonia 
and trimethylamine was fed at GHSV of 1,000/hr, followed by a reaction at 
atmospheric pressure. Results obtained using various zeolites are 
presented in Table 1. The reaction temperature was 350.degree. C. and in 
each of the catalysts, the fractional attainment of exchangeable cations 
to a H-type zeolite was 90% or higher. 
TABLE 1 
______________________________________ 
Conversion 
Example of TMA* By-product 
No. Kind of zeolite 
(%) (ppm) 
______________________________________ 
5 Heulandite 53.8 30 
6 Canncrinite 46.1 25 
7 Ferrierite 51.0 20 
8 Gmerlinite 40.3 30 
9 ZMS-5 (Si/Al = 25) 
58.5 37 
10 Stilbite 46.9 35 
11 Mazzite 49.0 20 
12 Offretite 51.8 20 
______________________________________ 
*TMA: Trimethylamine 
Comparative Example 3 
In a reactor and under conditions similar to those employed in Example 1, a 
disproportionating reaction of trimethylamine was conducted using REY 
zeolite as a catalyst. 
The results of an analysis of components at an outlet of the reactor 150 
hours after the beginning of the reaction were as follows: 
The conversion of trimethylamine was 67.3%, and the total amount of 
by-products, that is, acetonitrile, acetone, propionitrile and propylamine 
was 1,800 ppm. 
Comparative Example 4 
In a reactor and under the same conditions similar to those employed in 
Example 1, a disproportionating reaction of trimethylamine was conducted 
using H-Y zeolite (fractional attainment of exchangeable cations to a 
H-type zeolite: 90%) as a catalyst. 
As a result of an analysis of components at an outlet of the reactor 150 
hours after the beginning of the reaction, it was found that the 
conversion of trimethylamine was 64.1% and substantially no by-products 
such as acrylonitrile were observed practically (&lt;20 ppm). 
The reaction was continued further. An analysis of components at the outlet 
of the reactor 800 hours after the beginning of the reaction indicated 
that the conversion of triethylamine dropped to 57.8%. 
It has hence been found that in the case of a zeolite having a low R ratio, 
a decrease in catalytic activities is inevitable in a long-term operation.