Process for preparing methylamines

A process for preparing methylamines is disclosed herein which comprises the step of reacting methanol with ammonia in the presence of a mordenite in which the ratio of the length of mordenite crystals in a c axis direction to that of the mordenite crystals in an a axis direction or a b axis direction, c/a or c/b is 2 or more, whereby the synthetic activity of the methylamines can be maintained at a high level, and the production ratio of trimethylamine can be inhibited to a low level of about several percent to predominantly produce dimethylamine and monomethylamine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process for preparing amines. More 
specifically, it relates to a process for preparing methylamines from 
methanol and ammonia by which monomethylamine and dimethylamine are 
obtained in larger amounts than trimethylamine. Still more specifically, 
it relates to a crystalline morphology of a mordenite for exerting a more 
excellent catalytic performance among mordenite catalysts which can be 
used to accelerate the reaction of methanol with ammonia. The methylamines 
which can be obtained by the present invention are useful compounds 
applicable to many uses as materials for the manufacture of various kinds 
of solvents and intermediates for synthetic organic synthetic compounds. 
2. Description of the Related Art 
Methylamines, i.e., monomethylamine, dimethylamine and trimethylamine can 
be prepared by a method which comprises reacting methanol or a mixture of 
methanol and dimethyl ether with ammonia, a method which comprises the 
catalytic hydrogenation of prussic acid, or the like. 
Thus, these methylamines can be produced as a mixture of monomethylamine, 
dimethylamine and trimethylamine, and they have corresponding uses, 
respectively. On the other hand, among these methylamines, the demand of 
dimethylamine and monomethylamine is particularly large, but that of 
trimethylamine is small under the existing circumstances. In the 
methylamines obtained by the reaction of methanol with ammonia in the 
presence of a usual amorphous silica-alumina as a catalyst, trimethylamine 
is a main component, and the yield of dimethylamine whose demand is large 
is inconveniently low. It has been disclosed that in order to overcome 
this disadvantage, a dehydrated crystalline aluminosilicate (zeolite) 
having a pore diameter of from 5 to 10 .ANG. can be used in the reaction 
of an alcohol having 1 to 18 carbon atoms with ammonia, and in this case, 
the production of the monoamine and diamine predominates over that of the 
triamine. Furthermore, it has also been disclosed that natural zeolites 
and synthetic zeolites are mentioned as some kinds of zeolites suitable 
for the above-mentioned reaction. It has further been disclosed that 
suitable examples of the natural zeolite include faujasite, analcime, 
clinoptilolite, ferrierite, chabazite, gmelinite, levynite, erionite and 
mordenite, and suitable examples of the synthetic zeolite include X type, 
Y type and A type (U.S. Pat. No. 3,384,667, 1968). 
There have also been disclosed a method which comprises mixing methanol 
with ammonia in a specific ratio, and then reacting them in the presence 
of a catalyst such as a mordenite to obtain monomethylamine in a 
particularly large amount (Japanese Patent Application Laid-open No. 
113747/1981), and another method in which monomethylamine is 
disproportionated by a crystalline aluminosilicate selected from sodium 
ion type mordenites to selectively obtain a large amount of dimethylamine 
(Japanese Patent Application Laid-open No. 46846/1981). 
Disclosed have also been a method in which a natural mineral is used as the 
mordenite in about the same manner as in the above-mentioned U.S. Pat. No. 
3,384,667 (Japanese Patent Application Laid-open No. 169444/1982), a 
method using, as the catalyst, a mordenite subjected to ion exchange with 
lanthanum ions (Japanese Patent Application Laid-open No. 49340/1983), a 
method using, as the catalyst, a mordenite in which the amount of 
ion-exchanged alkaline metal ions is limited to a specific range (Japanese 
Patent Application Laid-open No. 210050/1984 and U.S. Pat. No. 4,578,516), 
a method using a steam-treated mordenite as the catalyst (Japanese Patent 
Application Laid-open No. 227841/1984 and U.S. Pat. No. 4,582,936), a 
method using an A type zeolite containing a small amount of a binder as 
the catalyst (Japanese Patent Application Laid-open No. 69846/1983), and a 
method using a Rho type (ZK-5) zeolite as the catalyst. 
When the zeolite catalyst is used in the above-mentioned manner, the 
production of trimethylamine can be inhibited, but there is also known a 
method in which for the purpose of bringing the production of 
trimethylamine into zero or substantially zero, a mordenite having pores 
modified by a CVD (chemical vapor deposition) of silicon tetrachloride is 
used as the catalyst Japanese Patent Application Laid-open No. 
262540/1991; J. Catal., Vol. 131, p. 482 (1991); and U.S. Pat. No. 
5,137,854!. 
Another method has also been present in which a chabazite, an erionite, a 
ZK-5 or a Rho type zeolite modified by precipitating a compound of 
silicon, aluminum, phosphorus or boron thereon is used as the catalyst to 
decrease the production of trimethylamine (Japanese Patent Application 
Laid-open No. 254256/1986 and U.S. Pat. No. 4,683,334). Furthermore, there 
is also known a method in which an alcohol is reacted with ammonia in the 
presence of SAPO of a non-zeolite molecular sieve as the catalyst to 
obtain an alkylamine (Japanese Patent Application Laid-open No. 734/1990). 
As described above, by using various kinds of heretofore disclosed zeolite 
catalysts in the reaction of methanol with ammonia, the production of 
trimethylamine which is in small demand can be inhibited, and that of 
dimethylamine which is in large demand can be increased. It is well known 
from old days that among the zeolites usable for this purpose, the 
mordenites are particularly excellent in activity for the synthesis of the 
methylamines U.S. Pat. No. 3,384,667, 1968; and J. Catal., Vol. 82, p. 
313 (1983)!. However, in the case that the mordenites employed are those 
prepared by a hydrothermal synthesis method or the natural mordenites, the 
activity for the synthesis of the methylamines and the performance for the 
production inhibition of trimethylamine are fairly different among these 
kinds of mordenites, even if a mordenite content, an impurity content, a 
cation composition and the like are substantially similar and even if 
values obtained by a standard powder X-ray diffraction and pore diameters 
obtained from the adsorption isotherm of argon at a liquid argon 
temperature are at similar levels. This difference is not so large in the 
case of the synthetic mordenites, but it is particularly noticeable in the 
case of the natural mordenites. 
U.S. Pat. No. 3,384,667 (1968) has suggested that zeolites having a pore 
diameter of from 5 to 10 .ANG. are used in order to predominantly obtain a 
monoalkylamine and a dialkylamine from an alcohol having 1 to 15 carbon 
atoms and ammonia, and as one of these zeolites, a natural mordenite is 
suitable. However, it is not disclosed at all which kind of natural 
mordenite is suitable. In Japanese Patent Publication No. 27335/1990, it 
is described that in preparing the methylamines from methanol and ammonia, 
a natural mordenite having an effective pore diameter of from 1 to 5 .ANG. 
is suitable as the catalyst, but a more detailed description is not 
disclosed at all therein. That is to say, with regard to characteristics 
of the mordenites, particularly the natural mordenites suitable for the 
manufacture of the methylamines from methanol and ammonia, any standards 
for selection have not been established, and it has been difficult to 
prepare the catalyst for efficiently accelerating the reaction, while 
sufficiently inhibiting the production of trimethylamine. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a method for preparing 
methylamines in the presence of a mordenite as a catalyst having a 
crystalline morphology particularly suitable for the preparation of the 
methylamines without the above-mentioned problems, i.e., the industrial 
preparation of the methylamines in which the production of dimethylamine 
and monomethylamine is increased and that of trimethylamine is 
sufficiently inhibited. 
The present inventors have conducted intensive research regarding a method 
for industrially preparing the methylamines in the presence of a mordenite 
as a catalyst so as to inhibit the production of trimethylamine to an 
extremely low level and to increase the production of dimethylamine. As a 
result, it has been found that when there is used, as a starting material 
of the catalyst, a mordenite in which the ratio of the length of the 
crystal of the mordenite used as the catalyst in a c axis direction to 
that of the crystal in an a axis direction or a b axis direction, c/a or 
c/b is 2 or more, more preferably 3 or more, the production of 
trimethylamine can be inhibited to a sufficiently low level and the 
methylamines can be efficiently prepared. In consequence, the present 
invention has now been completed. 
That is to say, the present invention is directed to a process for 
preparing methylamines which comprises the step of reacting methanol or 
methanol and dimethyl ether with ammonia in the presence of a mordenite in 
which the ratio of the length of a mordenite crystal in a c axis direction 
to that of the mordenite crystal in an a axis direction or a b axis 
direction, c/a or c/b is 2 or more. 
When the mordenite in which the ratio of the length of the mordenite 
crystal in the c axis direction to that of the mordenite crystal in the a 
axis direction or the b axis direction, c/a or c/b is 2 or more is used as 
the catalyst or a starting material for the preparation of the catalyst in 
manufacturing the methylamines by the reaction of methanol with ammonia, 
the synthetic activity of the methylamines can be maintained at a high 
level and the production ratio of trimethylamine can be decreased to a low 
level of few percent, whereby a step can be omitted in which 
trimethylamine is recycled through a reaction system to disproportionate 
trimethylamine, with the result that the process for preparing the 
methylamines can be simplified and the amount of utilities to be used can 
be decreased. Hence, it is apparent that the process for preparing the 
methylamines of the present invention is industrially advantageous.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A conventional mordenite which has often been used in the synthetic 
reaction of methylamines is a crystalline aluminosilicate represented by 
Na.sub.8 (Al.sub.8 Si.sub.40 O.sub.96)24H.sub.2 O (Atlas of Zeolite 
Structure Types, W. M. Meier and D. H. Olson, 1987, Butter worths). 
Alternatively, the mordenite may be represented by Me.sub.1/n (AlSi.sub.5 
O.sub.12)3H.sub.2 O (Me is an n-valent alkali metal atom, an alkaline 
earth metal atom or a hydrogen atom) (Japanese Patent Laid-open Nos. 
169444/1982 and 210050/1984 and the like). 
In either case, the Si/Al ratio and the silica/alumina ratio (SiO.sub.2 
/Al.sub.2 O.sub.3) of the conventional mordenite is about 5 and 10, 
respectively, irrespective of the natural mordenite or the synthetic 
mordenite (Zeolon made by Norton Co., Ltd, LZM-8 made by UCC, CM-180 made 
by La Grande Paroisse Co., Ltd. or the like). The mordenites having such a 
silica/alumina ratio as to be far over 11 are not known except special 
synthetic products. 
Thus, the mordenite which can be used in the process of the present 
invention has a silica/alumina ratio of 10 or more. If a silica/alumina 
ratio of about 10 is necessary, the conventional synthetic or natural 
mordenite can be used. If a silica/alumina ratio of 11 or more is 
necessary, the mordenite can be subjected to a usual treatment such as an 
acid treatment or a steam treatment. Alternatively, the mordenite having 
such a silica/alumina ratio can be prepared by obtaining a gel-like slurry 
having a composition of 
EQU (10+n)Na.sub.2 O(3+n)Al.sub.2 O.sub.3 (87-n)SiO.sub.2 
(wherein n is from 0 to 4) from an aqueous sodium silicate solution and an 
aqueous aluminum chloride solution, and then subjecting the slurry to 
hydrothermal synthesis at 130 to 250.degree. C. for 10 hours to several 
days Am. Mineral, Vol. 65, p. 1012 (1972)!. 
In the structure of the mordenite by X-ray diffractometry, as shown in FIG. 
1, a wide 12-membered ring pore (a maximum pore size=6.5-7.0 .ANG.) and a 
longitudinally slender 8-membered ring pore are arranged in parallel with 
a c axis direction, and these pores are connected to the 8-membered ring 
pores in a b axis direction. In an a axis direction, no pores are 
observed, and thus in a surface vertical to the a axis, the pores are not 
opened. Furthermore, in the a axis and b axis directions, bonds are fewest 
at the position indicated by a wave line in the front view of FIG. 1, and 
so cleavage easily occurs at this position. According to the observation 
of the side view of FIG. 1, any surface on which the cleavage particularly 
easily occurs is not present in the c axis direction. 
In the process of the present invention, as a catalyst or a starting 
material of the catalyst, there can be used the mordenite, particularly 
the natural mordenite having the above-mentioned mordenite crystal 
morphology in which the ratio of the length of the mordenite crystal in 
the c axis direction to that of the mordenite crystal in the a axis 
direction or the b axis direction, c/a or c/b is 2 or more, preferably 3 
or more. The value of c/a or c/b can usually easily be known by observing 
an enlarged image of from 200,000 to 1,000,000 times of a mordenite sample 
through an electron microscope. A mordenite having the axially long 
cylindrical crystals corresponds to the above-mentioned mordenite. It can 
be clearly known by observing an electron diffraction pattern in situ 
which part of the crystals observed by the electron microscope corresponds 
to the c axis. Alternatively, the value of c/a or c/b can also easily be 
judged from the image of the mordenite sample enlarged 400 to 2,000 times 
by a scanning electron microscope (SEM). In particular, the natural 
mordenite in which long fibrous crystals are observed by SEM (the value of 
c/a or c/b is extremely large) is particularly preferable as the starting 
material of the catalyst. 
Most morphologies of the mordenite crystals in which the value of c/a or 
c/b is less than 2 are from spherical to elliptical, rectangularly 
parallelepipedic and cylindrical having short axis. If the mordenite 
having such a crystalline morphology is used as the starting material of 
the catalyst, it is difficult to prepare the preferable catalyst. 
All of the crystalline morphologies confirmed by the observation are not 
required to have a c/a or c/b ratio of 2 or more. If the reaction of 
methanol with ammonia is carried out in the presence of the catalyst 
obtained by using the mordenite containing that having a c/a or c/b ratio 
of 2 or more, preferably 3 or more as the starting material, the 
production of trimethylamine can be sufficiently inhibited with a high 
conversion of methanol. In the crystalline morphologies, the ratio of the 
crystalline morphology having a c/a or c/b ratio of 2 or more, preferably 
3 or more is preferably 30% or more, more preferably 40% or more. Usually 
in most cases, the length of the a axis or the b axis of the mordenite 
crystals which can be used in the process of the present invention is in 
the range of from about 20 to 1000 nm, and the length of the c axis is in 
the range of from about 40 to 100,000 nm. In general, the hydrogen ion 
type mordenite is often used because of exerting a high activity, but the 
mordenite in which part of the hydrogen ions are replaced with a small 
amount of alkali metal ions or alkaline earth metal ions can also be used. 
The synthetic or the natural mordenite can be obtained in the form of an 
alkali metal ion type, and so the hydrogen ion type mordenite can be 
prepared by thermal decomposition after ion exchange with ammonium ions. 
Alternatively, the alkali metal ion type mordenite may be treated with a 1 
to 3N mineral acid to obtain the hydrogen ion type which is a precursor of 
the catalyst. 
The natural mordenite is a mixture of a mordenite component and other 
components. In the mordenite which is often used, the amount of alkali 
metals and alkaline earth metals is substantially zero in the mordenite 
component. In general, the amount of these metals is preferably in the 
range of from 0.1 to 1%. In the mordenite which is often used, the amounts 
of sodium, potassium and the total of calcium and magnesium present in 
feldspars and clays which are components other than the mordenite are in 
the range of from about 0.2 to 0.5%, about 0.2 to 5% and about 0.2 to 5%, 
respectively. The content of the alkali metals and the alkaline earth 
metals in the mordenite component and the other components can be measured 
separately in the mordenite, in the clays and in the feldspars by means of 
an analytical electron microscope. 
The sodium ions in the mordenite can be substantially completely replaced 
with hydrogen ions by the above-mentioned ion exchange treatment. The 
amount of the remaining sodium ions is in the range of from about 0.1 to 
0.2%, but potassium ions, calcium ions and magnesium ions remain in some 
amount on occasion. Even if the amount of these remaining substances 
fluctuates, the activity and the trimethylamine production inhibiting 
performance of the finally obtained catalyst are scarcely affected. In 
addition, quartz, the feldspars, the amorphous clays and the like which 
might be contained as impurities in the catalyst have little influence on 
the performance of the finally obtained catalyst. A mordenite content in 
the natural mordenite which is often used is in the range of from about 40 
to 80%, and the catalyst finally obtained from this natural mordenite has 
a satisfactory performance. 
Even if the mordenite content is less than 40%, the synthetic reaction of 
the methylamines can proceed, but the space time yield of the catalyst 
deteriorates and the volume of a reaction vessel required to from a unit 
amount of the product increases, which is economically inconvenient. In 
general, a catalyst having a mordenite content of 40% or more can be used. 
The mordenite converted from the alkali metal ion type into the hydrogen 
ion type usually has a high activity but is insufficient in the 
performance of inhibiting the production of trimethylamine. Also with 
regard to the mordenite which remains converted into the hydrogen ion 
type, the production ratio of trimethylamine is largely different between 
the mordenite having a c/a or c/b ratio of 2 or more and the mordenite 
having a c/a or c/b ratio of less than 2, the above-mentioned c/a or c/b 
ratio being the feature of the present invention. Even in this case, the 
difference of a pore diameter is not substantially observed between both 
the mordenites. As a technique for sufficiently imparting the 
trimethylamine production inhibiting performance to the mordenite, there 
can be used one or a combination of two or more of a method in which the 
ion exchange of a suitable cation is carried out, a method in which an 
outer surface is subjected to a dealuminumation treatment, a method in 
which a treatment is carried out by the use of high-temperature and 
high-pressure steam, and a method in which an outer surface is subjected 
to a silylation treatment. 
Examples of the cation suitable for the above-mentioned purpose include 
sodium ions, magnesium ions, and ions of a rare earth element-such as 
lanthanum. In a typical example, the concentration of sodium ions is first 
regulated to be in the range of from 0.3 to 1% by weight by ion exchange 
(U.S. Pat. No. 4,578,516), and the obtained mordenite is then treated with 
water vapor at 300 to 500.degree. C. under atmospheric pressure to 30 
kg/cm.sup.2 G for an interval of several hours to 100 hours (U.S. Pat. No. 
4,582,936) to obtain a catalyst which can inhibit the production of 
trimethylamine to about 5 to 10%. 
Methods using the catalyst in which the magnesium ions or the ions of a 
rare earth element such as lanthanum are ion-exchanged are described in 
detail in Japanese Patent Application Laid-open No. 49340/1983 and J. 
Catal., Vol. 82, p. 313 (1983). The catalyst obtained by the ion exchange 
of the magnesium ions or the ions of a rare earth element such as 
lanthanum can be further treated with the steam to further increase the 
inhibition effect of the production of trimethylamine. 
If the catalyst is brought into contact with an amine compound prior to the 
high-temperature and high-pressure pressure steam treatment, the 
inhibition effect of the trimethylamine production can be further 
increased. This method is described in U.S. Pat. No. 5,382,696. 
A treatment technique suitable to obtain the catalyst by which the 
production of trimethylamine can be suppressed to about several percent is 
a method in which the outer surface of the mordenite is subjected to 
silylation with a suitable silylating agent. The size of the molecule of 
the silylating agent to be used is larger than the diameter of the pores 
in the mordenite, and therefore the only outer surface of the mordenite is 
selectively silylated. No particular restriction is put on the treatment 
method with the silylating agent, but there can be used a treatment in a 
gaseous phase by CVD (chemical vapor deposition) and a treatment in a 
liquid phase in which the silylating agent is dissolved in a suitable 
solvent. In order to manufacture a great deal of the catalyst, the method 
of the liquid phase treatment is often employed. 
One example of the preferable silylation treatment method in the liquid 
phase will be described. Prior to the treatment of the mordenite with the 
silylating agent in the liquid phase, the moisture content in the pores of 
the mordenite is regulated to a predetermined level. The moisture content 
in the mordenite is preferably in the range of from 3 to 40% by weight, 
more preferably 4 to 30% by weight. If the moisture content is outside the 
above-mentioned range, it is difficult to obtain the silylated catalyst by 
which the production of trimethylamine can be maintained at a low value of 
about 1%. The regulation of the moisture content in the mordenite can be 
carried out by various techniques, and for example, the following method 
is convenient. The mordenite which has undergone the ion exchange into the 
hydrogen ion type, deionized water washing, filtration and drying is 
calcined at 400 to 600.degree. C. to once bring the moisture content in 
the pores of the mordenite into substantially zero. Next, the mordenite is 
allowed to adsorb the moisture of water having a saturated vapor pressure 
at about 0 to 50.degree. C., so that a moisture content of from 3 to 40% 
by weight is given to the mordenite. In the case of a laboratory scale, 
the mordenite is placed in the upper part of a desiccator containing water 
in its lower part, and it is then allowed to stand at room temperature for 
10 to 30 hours, whereby a moisture content of from 5 to 20% by weight can 
be given to the mordenite. As another method for giving a predetermined 
moisture content to the mordenite, the mordenite may be treated with an 
aqueous acid solution to convert the same into the hydrogen ion type, and 
the thus treated mordenite may be air-dried, and then dried at 100 to 
160.degree. C., whereby a moisture content of from 3 to 30% by weight can 
be given to the mordenite. According to this method, a trace amount of the 
acid is occluded together with moisture in the pores of the mordenite, and 
the acid can conveniently perform a catalytic function. That is to say, 
the acid slowly diffuses into the surface of the mordenite to smoothly 
advance the silylation reaction. 
Examples of the silylating agent which can be used in the silylation 
treatment include alkoxides of silicon such as tetramethoxysilane and 
tetraethoxysilane, silicon tetrachloride, dimethyl dichlorosilane, 
trimethyl chlorosilane, tetramethyl disilazane and hexamethyl disilazane. 
The liquid phase silylation treatment of the mordenite is usually carried 
out by dissolving the silylating agent in a suitable solvent. Examples of 
the solvent include aliphatic and alicyclic hydrocarbons such as hexane, 
octane and cyclohexane and aromatic hydrocarbons such as benzene, toluene 
and xylene. It is preferable to select the suitable solvent in compliance 
with the used silylating agent. 
The amount of the silylating agent is usually in the range of from 1 to 10% 
to the employed mordenite in terms of silicon dioxide as a silicon content 
in the silylating agent. The concentration of the silylating agent in the 
solvent is usually in the range of from 2 to 30% by weight. If a moisture 
content in the solvent which can be used in the silylation treatment is 
high, the silylating agent is hydrolyzed and it is consumed in vain. Thus, 
the moisture content in the solvent for use in the silylation treatment is 
preferably low. 
The mordenite is dispersed in the solution of the above-mentioned 
silylating agent, whereby a silicon compound is deposited and fixed on the 
mordenite. 
The temperature at which the silylation treatment is carried out is from 
room temperature to the boiling point of the solution, and it is usually 
in the range of from 20 to 200.degree. C. When the treatment is done under 
pressure, the treatment temperature can be further raised. 
The time required for the silylation treatment depends mainly upon the 
treatment temperature and the like. When a treatment temperature in the 
vicinity of room temperature is used, the treatment time is usually in the 
range of from 3 to 30 hours, and when a treatment temperature of from 60 
to 90.degree. C. is used, the treatment time is usually in the range of 
from 1 to 10 hours. 
The mordenite which has just been treated is separated from the treatment 
solution by a usual technique such as filtration or centrifugal 
separation, and then heated under the atmosphere of an inert gas such as 
nitrogen or heated under reduced pressure to remove the organic solvent 
which adheres to the mordenite or which is adsorbed by the mordenite. 
Next, the mordenite is subjected to a heat treatment (calcination) at 300 
to 600.degree. C. under an atmosphere of nitrogen, air or oxygen to obtain 
the catalyst. If the mordenite which is the starting material is already 
molded into grains or tablets, it can be directly used as the catalyst. If 
the mordenite is in the form of powder, it is extruded in a conventional 
manner or molded into tablets, thereby obtaining the catalyst. 
The amount of SiO.sub.2 formed by the silylation treatment followed by the 
calcination is preferably in the range of from 1 to 10% by weight, more 
preferably 1 to 8% by weight based on the weight of the catalyst. This 
value depends upon the outer surface area of the mordenite to be used, and 
therefore it is preferable to experimentally decide the optimum value. 
The raw materials which can be used in the method of the present invention 
are methanol or a mixture of methanol and dimethyl ether and ammonia. In 
addition, a methylamine such as monomethylamine may be mixed with the 
reaction materials. With regard to the molar ratio of ammonia to methanol 
or the like, the mols of ammonia per mol of methanol or the like are 0.5 
or more, preferably in the range of from 1 to 5, but in general, it is 
often in the range of from 1 to 3. 
The flow rate of a reaction gas which is fed to a catalyst layer is in the 
range of from 200 to 5000 liters/hr./liter of the catalyst in terms of SV, 
and a reaction pressure is in the range of from 1 to 40 kg/cm.sup.2 G, 
preferably 10 to 30 kg/cm.sup.2 G. In the practice of the reaction, a 
catalyst layer temperature is in the range of from 250 to 450.degree. C., 
preferably 270 to 360.degree. C. 
A reactor which can be used to practice the method of the present invention 
is a usual fixed bed or a fluidized bed reactor. 
From a gas at the outlet of the reactor, methylamines are isolated and 
collected by a separation-purification device. However, in the method of 
the present invention, the production of trimethylamine is about several 
percent, and therefore the separation step of trimethylamine can be 
simplified and a step for recycling trimethylamine through a reaction 
system is unnecessary. Thus, the whole manufacturing process can be 
simplified. 
Now, the present invention will be described in more detail with reference 
to examples and comparative examples, but the scope of the present 
invention should not be limited to these examples. 
EXAMPLE 1 
A natural mordenite obtained in Oga, Akita Prefecture, Japan was used as a 
starting material for a catalyst to prepare the catalyst. With regard to 
this natural mordenite, when it was observed at a magnification of 200,000 
times through an electron microscope, the length of the c axis of 
mordenite crystals was in the range of from 300 to 400 nm and the length 
of the a axis or the b axis of the mordenite crystals was in the range of 
from 100 to 150 nm, and thus the ratio of c/a or c/b was in the range of 
from 2 to 4. The pore diameter of the mordenite calculated on the basis of 
the adsorption of argon at a liquid argon temperature was 6.2 .ANG.. 
Afterward, 110 g of the natural mordenite (a mordenite content=about 65%) 
having a granule diameter of from 2 to 3 mm was poured into 1 liter of 2N 
hydrochloric acid, followed by shaking at 35.degree. C. for 10 hours. The 
mordenite was collected by filtration and then poured into 1 liter of 
fresh 2N hydrochloric acid, followed by shaking at 35.degree. C. for 10 
hours again. Next, the mordenite was collected by filtration, air-dried, 
and then dried at 140.degree. C. to obtain the mordenite having pores in 
which 9% of moisture and a trace amount of hydrochloric acid were 
occluded. The thus obtained mordenite was of a substantially complete 
hydrogen ion type and had an Na content of 0.14%. 
Into 100 g of a toluene solution in which 4.5 g of tetraethoxysilane was 
dissolved, 50 g of the above-mentioned hydrogen ion type mordenite was 
added, and the mixture was then shaken at room temperature (20-25.degree. 
C.) for 10 hours. Afterward, the mordenite was collected by filtration, 
heated at 300.degree. C. for 2 hours in a nitrogen gas flow, and then 
further heated 500.degree. C. for 4 hours in an air flow. The resultant 
granular mordenite was directly used as a catalyst for a reaction. The 
degree of silylation on the catalyst corresponded to 2.5% by weight based 
on the catalyst in terms of SiO.sub.2. 
Next, a stainless steel reaction tube having an inner diameter of 1 inch 
was filled with 40 g (60 ml) of the above-mentioned catalyst, and the 
reaction tube was then heated from the outside in a sand fluidized bath. 
Methanol and ammonia were fed at flow rates of 20 g/hr and 21 g/hr, 
respectively, to the reaction tube under pressure via an evaporator, and 
the reaction was then carried out at 300.degree. C. under a pressure of 19 
kg/cm.sup.2 G. 
After 130 hours had elapsed since the start of the reaction, gas at the 
outlet of the reaction tube was analyzed. As a result, it was found that 
the conversion of methanol was 93%, the selectivities of monomethylamine, 
dimethylamine and trimethylamine were 34.8%, 63.1% and 2.1%, respectively. 
COMATIVE EXAMPLE 1 
A natural mordenite obtained in Kawarago, Miyagi Prefecture, Japan was used 
as a starting material for a catalyst to prepare the catalyst. With regard 
to the crystalline morphology of this natural mordenite, when it was 
observed at a magnification of 200,000 times through an electron 
microscope, the ratio of the length of the c axis of mordenite crystals to 
the length of the a axis or the b axis of the mordenite crystals was in 
the range of from 1 to 1.5. The amount and composition of quartz, 
feldspars, amorphous clays which were the impurities of the natural 
mordenite were of the same level as in the starting material of Example 1. 
The pore diameter of the mordenite calculated on the basis of the 
adsorption of argon at a liquid argon temperature was 6.0 .ANG.. 
Next, 110 g of the natural mordenite (a mordenite content=about 68%) having 
a particle diameter of from 2 to 3 mm was added into 1 liter of 2N 
hydrochloric acid, followed by shaking at 35.degree. C. for 10 hours. 
Afterward, the mordenite was separated, and 1 liter of fresh 2N 
hydrochloric acid was then added to the separated mordenite, followed by a 
similar treatment for 10 hours. Next, the mordenite was collected by 
filtration, air-dried, and then dried at 140.degree. C. to obtain the 
mordenite having pores in which 9% of moisture and a trace amount of 
hydrochloric acid were occluded. In the thus obtained mordenite, an Na 
content was 0.13%, and the amount of the other remaining cations was about 
the same as in Example 1. Into 100 g of a toluene solution containing 4.5 
g of tetraethoxysilane, 50 g of the obtained mordenite was thrown, and the 
mixture was then shaken at room temperature for 10 hours. Afterward, the 
mordenite was collected by filtration, heated at 300.degree. C. for 2 
hours in a nitrogen gas flow, and then further heated 500.degree. C. for 4 
hours in an air flow to prepare the catalyst. The degree of silylation was 
2.6% by weight based on the catalyst in terms of SiO.sub.2. 
Next, the same reaction tube as in Example 1 was filled with 40 g of the 
above-mentioned catalyst, and the synthesis of methylamines was tested 
under the same reaction conditions as in Example 1. After 130 hours had 
elapsed since the start of the reaction, gas at the outlet of the reaction 
tube was analyzed. As a result, it was found that the conversion of 
methanol was 88%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 35.2%, 58.5% and 6.3%, respectively. 
That is to say, when the methylamines are synthesized by the use of the 
catalyst prepared by employing, as the starting material, the mordenite 
having the crystalline morphology in which the ratio of c/a or c/b is less 
than 2, the conversion of methanol is lower and the amount of 
trimethylamine formed as a by-product is larger, as compared with a case 
where the mordenite having a c/a or c/b ratio of 2 or more is used as the 
starting material. In consequence, it is apparent that the employment of 
the mordenite having a c/a or c/b ratio of less than 2 cannot lead to 
preferable results. 
EXAMPLE 2 TO 4 
Natural mordenites having c/a or c/b ratios of more than 2 sampled at 
different points in Itado, Akita Prefecture, Japan were used as starting 
materials for catalysts and the same procedure as in Example 1 was carried 
out to prepare the catalysts, and the synthetic reaction of methylamines 
was tested under the same reaction conditions as in Example 1. The 
obtained results are shown in Table 1. 
COMATIVE EXAMPLES 2 AND 3 
Various natural mordenites having c/a or c/b ratios of less than 2 were 
used as starting materials for catalysts and the same procedure as in 
Example 1 was carried out to prepare the catalysts, and the synthetic 
reaction of methylamines was tested under the same reaction conditions as 
in Example 1. The obtained results are shown in Table 1. 
TABLE 1 
______________________________________ 
Mordenite MeOH 
c/a Content (%) 
Conversion (%) 
______________________________________ 
Example 2 3-10 64 92.8 
Example 3 10-50 71 91.5 
Example 4 10-30 68 93.6 
Comp. Ex. 2.sup.a 
1-1.5 72 89.1 
Comp. Ex. 3.sup.b 
1-1.5 65 87.8 
______________________________________ 
Selectivity (%) of Methylamines 
Mono-form Di-form Tri-form 
______________________________________ 
Example 2 34.7 62.8 2.5 
Example 3 35.1 63.0 1.9 
Example 4 35.9 61.9 2.2 
Comp. Ex. 2.sup.a 
37.0 56.5 6.5 
Comp. Ex. 3.sup.b 
38.3 55.5 6.2 
______________________________________ 
Note: 
.sup.a It was sampled in Amagouchi, Shimane Prefecture, Japan. 
.sup.b It was sampled in Tenei, Fukushima Prefecture, Japan. 
EXAMPLE 5 
A natural mordenite sampled in Kawazu, Shizuoka Prefecture, Japan was used 
as a starting material for a catalyst to prepare the catalyst. When this 
natural mordenite was observed at a magnification of 600 times through an 
SEM, it was apparent that the mordenite had a long fibrous crystal 
morphology. The c/a or c/b ratio of the mordenite crystals was mainly in 
the range of from 30 to 500. 
The above-mentioned mordenite was crushed, and the resultant particles 
having a diameter of from 2.5 to 4.0 mm were collected by a sieve. Next, 
300 g of the mordenite particles was thrown into 2.5 liters of 3N sulfuric 
acid, and the mixture was then gently shaken at 30.degree. C. for 10 
hours. The solid phase was collected by filtration, and then thrown into 
2.5 liters of fresh 3N sulfuric acid, and the mixture was further shaken 
for 10 hours. The solid phase was collected by filtration, dried at 
140.degree. C., and calcined at 600.degree. C. for 5 hours to obtain a 
hydrogen ion type mordenite. Afterward, 100 g of this hydrogen ion type 
mordenite was immersed in 400 g of a 0.01N aqueous sodium nitrate solution 
for 1 minute, and then immediately washed with deionized water to obtain 
an NaH type mordenite having a sodium content of 0.95% by weight. This 
mordenite was dried, and then calcined at 600.degree. C. to obtain the 
catalyst. Next, a stainless steel reactor having an inner diameter of 1 
inch was filled with 40 g of this catalyst, and the synthesis of 
methylamine was carried out for 15 hours under the same conditions as in 
Example 1 and the reaction was then discontinued. Next, steam at 
450.degree. C. and 15 kg/cm.sup.2 G was caused to flow through a catalyst 
layer at an SV of 500 for 15 hours, and the synthesis of methylamines was 
then tested at a reaction temperature of 300.degree. C. under the same 
reaction conditions as in Example 1. After 150 hours had elapsed since the 
start of the reaction, gas at the outlet of the reactor was analyzed. As a 
result, it was found that the conversion of methanol was 92%, the 
selectivities of monomethylamine, dimethylamine and trimethylamine were 
32.4%, 60.5% and 7.1%, respectively. 
EXAMPLE 6 
In a 0.1N aqueous sulfuric acid solution, 120 g of the hydrogen ion type 
mordenite prepared in Example 5 was immersed, and after filtration, the 
mordenite was dried at 140.degree. C. for 6 hours. Next, the mordenite was 
allowed to stand overnight at room temperature in the air atmosphere, 
whereby the pores of the mordenite were allowed to occlude a moisture 
content of about 8%. Consequently, not only the moisture but also a trace 
amount of sulfuric acid were occluded in the pores of the mordenite. 
The mordenite in which the moisture content had been adjusted was thrown 
into 0.3 liter of a 0.15 mol/liter solution of tetraethoxysilane in 
toluene, and the mixture was then gently shaken at room temperature for 13 
hours to carry out a silylation treatment. Next, the solid phase was 
collected by filtration, dried at 140.degree. C. under reduced pressure, 
and calcined at 600.degree. C. for 5 hours under an air atmosphere to 
obtain a catalyst. The degree of the silylation was 2.2% by weight based 
on the catalyst in terms of SiO.sub.2. 
A stainless steel reactor having an inner diameter of 1.5 inches was filled 
with 100 g of this catalyst, and the reactor was then heated from the 
outside in a sand fluidized bath. Methanol and ammonia were fed at flow 
rates of 55 g/hr and 55 g/hr, respectively, to a catalyst layer under 
pressure via an evaporator, and a reaction was then carried out at 
294.degree. C. under a pressure of 19 kg/cm.sup.2 G. After 150 hours had 
elapsed since the start of the reaction, gas at the outlet of the reactor 
was analyzed. As a result, it was apparent that the conversion of methanol 
was 95%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 35.4%, 63.0% and 2.0%, respectively. The reaction was 
further continued for 800 hours, and after the reaction, the conversion of 
methanol was 94%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 35.6%, 62.5% and 1.9%, respectively. 
EXAMPLE 7 
A part of a hydrogen ion type mordenite prepared in Example 5 was directly 
used as a catalyst (c/a or a/b=30-500). 
The same reactor as in Example 1 was filled with 40 g of the 
above-mentioned catalyst, and the synthesis reaction of methylamines was 
then tested under the same reaction conditions as in Example 1. After 100 
hours had elapsed since the start of the reaction, gas at the outlet of 
the reactor was analyzed. As a result, it was found that the conversion of 
methanol was 96.7%, the selectivities of monomethylamine, dimethylamine 
and trimethylamine were 24.2%, 48.6% and 27.2%, respectively. 
COMATIVE EXAMPLE 4 
A mordenite (c/a or a/b=1-1.5) used in Comparative Example 1 was treated 
with 2N hydrochloric acid to convert the same into a hydrogen ion type, 
and this type mordenite was directly used as a catalyst. 
The same reactor as in Example 1 was filled with 40 g of the 
above-mentioned catalyst, and the synthesis reaction of methylamines was 
then tested under the same reaction conditions as in Example 1. After 100 
hours had elapsed since the start of the reaction, gas at the outlet of 
the reactor was analyzed. As a result, it was found that the conversion of 
methanol was 94.9%, the selectivities of monomethylamine, dimethylamine 
and trimethylamine were 21.4%, 38.6% and 40.0%, respectively. 
EXAMPLE 8 
A hydrogen ion type mordenite prepared by the same procedure as in Example 
5 was immersed in a 0.1N aqueous sodium nitrate solution for 3 minutes, 
collected by filtration, dried, and then calcined at 500.degree. C. to 
obtain a catalyst (c/a or a/b=30-500). A sodium content in the catalyst 
was 0.95% by weight. Next, a glass reaction tube having an inner diameter 
of 15 mm was filled with 5 g of this catalyst, and it was then heated in 
an electric furnace. Methanol and ammonia were fed to the reaction tube at 
flow rates of 2.5 g/hr and 2.5 g/hr, respectively, and a reaction was then 
carried out at 320.degree. C. under atmospheric pressure. Afterward, gas 
at the outlet of the reaction tube was analyzed, and as result, it was 
found that the conversion of methanol was 87%, the selectivities of 
monomethylamine, dimethylamine and trimethylamine were 36.1%, 51.4% and 
12.5%, respectively. 
EXAMPLE 9 
A hydrogen ion type mordenite prepared by the same procedure as in Example 
5 was immersed in a 0.1N aqueous lanthanum nitrate solution for 10 
minutes, collected by filtration, dried, and then calcined at 500.degree. 
C. to obtain a catalyst (c/a or a/b=30-500). A lanthanum content in the 
catalyst was 2.1% by weight. Next, this catalyst was brought into contact 
with water vapor at 500.degree. C. under atmospheric pressure at an SV of 
500 .sup.hr-1 for 3 hours to carry out a steam treatment. 
A glass reaction tube having an inner diameter of 15 mm was filled with 5 g 
of this catalyst, and it was then heated in an electric furnace. Methanol 
and ammonia were fed to the reaction tube at flow rates of 2.5 g/hr and 
2.5 g/hr, respectively, and a reaction was then carried out at 320.degree. 
C. under atmospheric pressure. Afterward, gas at the outlet of the 
reaction tube was analyzed, and as a result, it was found that the 
conversion of methanol was 90%, the selectivities of monomethylamine, 
dimethylamine and trimethylamine were 37.1%, 52.9% and 10.0%, 
respectively. 
EXAMPLE 10 
A hydrogen ion type mordenite prepared in Example 5 was brought into 
contact with water vapor at 500.degree. C. under atmospheric pressure at 
an SV of 500 .sup.hr-1 for 3 hours to obtain a catalyst. 
A glass reaction tube having an inner diameter of 15 mm was filled with 5 g 
of this catalyst, and it was then heated in an electric furnace. Methanol 
and ammonia were fed to the reaction tube at flow rates of 2.5 g/hr and 
2.5 g/hr, respectively, and a reaction was then carried out at 32020 C. 
under atmospheric pressure. Afterward, gas at the outlet of the reaction 
tube was analyzed, and as a result, it was found that the conversion of 
methanol was 91%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 35.9%, 51.0% and 13.1%, respectively. 
EXAMPLE 11 
A synthetic mordenite (made by Zeocat Corporation) having the crystalline 
morphology of a needle form and a c/a or c/b ratio of 4-8 was used as a 
starting material for a catalyst. 
The above-mentioned mordenite which had been converted into a hydrogen ion 
type was calcined at 500.degree. C., and it was then allowed to stand at 
room temperature in the air, whereby a moisture content of 9% by weight 
was occluded in the pores of the mordenite. Next, 10 g of the mordenite 
was thrown into a solution obtained by dissolving 1.0 g of tetraethyl 
orthosilicate in 9 g of benzene, and silylation was then carried out at 
room temperature (20-25.degree. C.) for 30 hours, while the mixture was 
slowly stirred. Afterward, the mordenite was collected by filtration, 
dried, and calcined at 500.degree. C. to prepare a catalyst. The degree of 
the silylation on the catalyst was 3% by weight in terms of SiO.sub.2. 
A glass reaction tube having an inner diameter of 15 mm was filled with 5 g 
of this catalyst, and it was then heated in an electric furnace to carry 
out a methylamine synthesis test. That is to say, methanol and ammonia 
were fed to the reaction tube at flow rates of 2.5 g/hr and 2.5 g/hr, 
respectively, and a reaction was then carried out at 310.degree. C. under 
atmospheric pressure. Afterward, gas at the outlet of the reaction tube 
was analyzed, and as a result, it was found that the conversion of 
methanol was 91%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 34.5%, 61.9% and 3.6%, respectively. 
COMATIVE EXAMPLE 5 
A synthetic mordenite (made by Toyo Soda Mfg Co., Ltd.) having the 
crystalline morphology of a globular form and a c/a or c/b ratio of less 
than 2 was used as a starting material for a catalyst. 
The above-mentioned mordenite which had been converted into a hydrogen ion 
type was calcined at 500.degree. C., and it was then allowed to stand at 
room temperature in the air atmosphere, whereby a moisture content of 8% 
by weight was occluded in the pores of the mordenite. Next, 10 g of the 
mordenite was thrown into a solution obtained by dissolving 1.0 g of 
tetraethyl orthosilicate in 9 g of benzene, and silylation was then 
carried out at room temperature (20-25.degree. C.) for 30 hours, while the 
mixture was slowly stirred. Afterward, the mordenite was collected by 
filtration, dried, and calcined at 500.degree. C. to prepare the catalyst. 
The degree of the silylation on the catalyst was 3% by weight in terms of 
SiO.sub.2. 
A glass reaction tube having an inner diameter of 15 mm was filled with 5 g 
of this catalyst, and it was then heated in an electric furnace to carry 
out a methylamine synthesis test. That is to say, methanol and ammonia 
were fed to the reaction tube at flow rates of 2.5 g/hr and 2.5 g/hr, 
respectively, and a reaction was then carried out at 310.degree. C. under 
atmospheric pressure. Afterward, gas at the outlet of the reaction tube 
was analyzed, and as a result, it was found that the conversion of 
methanol was 90%, the selectivities of monomethylamine, dimethylamine and 
trimethylamine were 32.0%, 58.5% and 9.5%, respectively. 
The mordenites used in the examples and the comparative examples are all 
shown together in Table 2. 
TABLE 2 
______________________________________ 
Mordenite 
______________________________________ 
Example 1 Oga, Akita Prefecture 
Comp. Ex. 1 Kawarago, Miyagi Prefecture 
Example 2 Itado, Akita Prefecture (A) 
Example 3 Itado, Akita Prefecture (B) 
Example 4 Itado, Akita Prefecture (C) 
Comp. Ex. 2 Amagouchi, Simane Prefecture 
Comp. Ex. 3 Tenei, Fukushima Prefecture 
Example 5 Kawazu, Shizuoka Prefecture 
Example 6 Kawazu, Shizuoka Prefecture 
Example 7 Kawazu, Shizuoka Prefecture 
Comp. Ex. 4 Kawarago, Miyagi Prefecture 
Example 8 Kawazu, Shizuoka Prefecture 
Example 9 Kawazu, Shizuoka Prefecture 
Example 10 Kawazu, Shizuoka Prefecture 
Example 11 Synthetic mordenite 
(made by Zeocat Corporation, 
having crystalline morphology of 
needle form) 
Comp. Ex. 5 Synthetic mordenite 
(made by Toyo Soda Mfg Co., Ltd., 
having crystalline morphology of 
globular form) 
______________________________________ 
Note: The mordenites in Examples 2 to 4 were sampled at different points 
in the same district.