JPS6325576B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improved process for the production of dimethylamine by catalytic disproportionation of monomethylamine. It is well known in the art to utilize the catalytic reaction of methanol and ammonia in the production of mono-, di- and/or trimethylamines. Various measures can be taken to facilitate the production of any one of the methylamines. For example, the following is known. in the product by using dimethyl ether with or in place of methanol, recycling undesired methylamines, changing the molar ratio of reactants, and using specific dehydrogenation or amination catalysts. It is known that the relative amounts of the various amines can be varied. Illustrating, but not exhaustively, such techniques, U.S. Pat. cocatalyst
discloses increasing the production of secondary amines using Similarly, U.S. Pat. No. 3,387,032 describes a catalytic process for obtaining increased amounts of dimethylamine from methanol and/or dimethyl ether and ammonia using silica gel-based alumina as catalyst.
discloses the use of partially deactivated alumina with steam and impregnated with silver phosphate, rhenium heptasulfide, molybdenum sulfide or cobalt sulfide. U.S. Patents 2394515 and 2394516
In a catalytic method for producing polyalkylamines with a small amount of monoalkylamine from alcohols and/or ethers having 1 to 5 carbon atoms and ammonia, an oxide or salt of aluminum as a catalyst is first coated with silica and then coated with silica. The use of coatings with vanadium salts or molybdenum oxide is disclosed. Related U.S. Pat. No. 2,349,222 uses granular alumina as a catalyst for the hydrogenation/
A catalyst coated with a dehydrogenation catalyst is used. US Pat. No. 2,456,599 discloses that higher amounts of mono- and dimethylamine and lower amounts of trimethylamine are achieved by a catalytic process in which methanol and ammonia are charged with water. U.S. Patent 1799722 and U.S. Reissue Patent 19632
discloses that by charging trimethylamine with methanol and ammonia in a catalytic process, the formation of trimethylamine is suppressed and the amount of dimethylamine is increased. US Patent 1992935
is a catalytic process for producing primary, secondary and tertiary methylamines, especially dimethylamine, from methanol and ammonia, using a dehydrated oxide as a catalyst supported on a porous, strong gel such as silica gel. Use is disclosed. British Patent No. 422,563 discloses the use of primary amines as starting materials in addition to ammonia and methanol when preparing secondary amines in a catalytic process. Restelli et al. AICh.E.Journal, Volume 12, No. 2,
292-296, March 1966, describes a study of the methyl group rearrangement reaction of monomethylamine and dimethylamine on montmorillonite, an aluminosilicate containing dehydrated magnesium/calcium oxides. For reactions at about 320-371 °C, monomethylamine is converted to dimethylamine at low conversions, the rate of which is directly proportional to the partial pressure of the amine, and therefore the adsorption of monomethylamine on the catalyst surface is rate-limiting. It turns out that there is something. US Pat. No. 1,926,691 discloses the disproportionation of monomethylamine over an oxide catalyst comprising aluminum silicate (silica-alumina) and partially dehydrated alumina. In only one example, disproportionation of monomethylamine on anhydrous alumina is highly selective for the formation of dimethylamine. It is noted that all of the disclosed oxide catalysts are equivalent in terms of being broadly classified as amination catalysts. U.S. Pat. No. 3,384,667 teaches that to produce more mono- and di-substituted amines than tri-substituted amines, a dehydrated crystalline alumino silicate with pores sized to pass the mono- and di-substituted amines but not the tri-substituted amines. It is disclosed that alcohol and ammonia may be reacted on an acid salt. Related U.S. Pat. No. 4,082,805 predominates primary aliphatic amines over secondary and tertiary amines, from _C1 to _C5 alcohols or ethers and ammonia, with structures ZSM-5, ZSM-11 or ZSM-21. over natural or synthetic dehydrated crystalline aluminosilicates at 300-500°C and 1 atm or less.
A process is disclosed under conditions of 1000 psig (7000 kPa) and charging alcohol or ether and ammonia in a ratio of 1:1 to 5:1. Currently, methylamine is generally made from amorphous silica.
It is commercially produced in a continuous process from methanol and ammonia using an alumina catalyst. At moderate methanol conversions such processes generally produce more trimethylamine than mono- and dimethylamine (at very low conversions monomethylamine is predominantly produced). Due to its expanding industrial use as a chemical intermediate, dimethylamine has become the most promising methylamine product, followed by monomethylamine. When methanol conversion is approximately 100% and equilibrium is reached, the amount of monomethylamine and dimethylamine produced is maximum.
However, the relative amounts of the three amines formed at equilibrium depend primarily on the carbon/nitrogen (C/N) ratio, ie, the methanol/ammonia ratio in the reactants.
At a carbon/nitrogen ratio of about 1, the product mixture is about 55% ammonia, 22% trimethylamine (TMA), 12% monomethylamine (MMA), and 12% dimethylamine (DMA) on a molar basis.
including. The resulting mixture is separated and methylamines, which are in low demand, are recycled. However, even if monomethylamine is recycled, only about 10% dimethylamine is obtained per pass during new equilibrium, and most of the monomethylamine is converted to trimethylamine and ammonia. At equilibrium, dimethylamine is not the predominant product at any C/N ratio. The synthesis of methylamine can be distinguished from the synthesis of ethylamine. For example, the thermodynamics of the ethylamine reaction corresponding to the reaction described above favors the formation of diethylamine when the ethyl/nitrogen ratio is about 2. The production of dimethylamine is therefore inherently more complex than the production of diethylamine by similar methods. It is therefore an object of the present invention to provide an improved process for converting monomethylamine directly to dimethylamine and ammonia, with virtually no conversion to trimethylamine, thus eliminating the need for the least demanding methylamine. This eliminates the need for generation and associated collection and recycling. Another purpose is
The object is to provide a process using a catalyst which can achieve this objective in the presence of water, such as is present with monomethylamine. Other purposes will be revealed in the future. Various novel features of the invention are set forth in more detail in the following description and accompanying drawings, as well as in the claims, for a better understanding of the structure, objects, and advantages of the invention. The present invention is a catalytic process for preparing dimethylamine from monomethylamine, which is improved from, for example, US Pat. No. 1,926,691. More specifically, it was the discovery that catalysts commonly referred to as amination catalysts can be divided into three categories depending on their selectivity in the disproportionation reaction of monomethylamine and their sensitivity to water. Class Selectivity Dry Wet (H ₂ O) Good Good Good Bad Bad Bad The class of catalysts includes, to name a few, silica-alumina, hydrogen ion-exchanged zeolites, and zeolite A, offretite, and haujasite. It is a neutral zeolite of
There is no selectivity. This class of catalysts includes alumina, zeolite, and erionite, which show selectivity when prepared in anhydrous form, but lose selectivity in the presence of water. Some classes of zeolites retain high selectivity even when water is present in the system. Still more particularly, the present invention provides that a the first cation is Na, at least 2% by weight of
HNa (e.g. 2-4.3 wt% Na), Mg, Ca,
mordenite b whose first metal cation is Sr or Ba, Na, K, Mg, Ca, Sr
or Ba ferrierite, c clinoptilolite and d perioliolite, on a crystalline aluminosilicate (zeolite) catalyst selected from c clinoptilolite and d bolideite, at a temperature of 250 to 475 °C and a pressure of 1 to
It is an improved continuous production process in which monomethylamine is charged at a rate of 0.1 to 10 g/g catalyst per hour at 1000 psi (7-7000 kPa) and the monomethylamine is disproportionated to dimethylamine and ammonia. Preferably, substantially anhydrous monomethylamine and ferrierite catalyst are used at 350-400°C for 10
~500psi (70~3000kPa), especially 300psi (2000kPa),
Production is carried out at a feed rate of monomethylamine of 0.5 to 2 g/hour, especially at a feed rate of 1 g/g of catalyst. Most of the catalysts useful herein are commercially available or can be readily prepared by those skilled in the art. The following is an example of the adjustment procedure used. Sodium-hydrogen mordenite is produced by mixing an appropriate amount of sodium mordenite extrudate and an aqueous hydrochloric acid solution, leaving the mixture overnight, filtering to separate the solids, washing the recovered solids with distilled water, and then It is prepared by air drying the solid and calcining it at 400°C for 4 hours. Calcium mordenite is produced by adding 20 g of sodium mordenite to a calcium chloride aqueous solution (25 g of calcium chloride dissolved in 150 ml of distilled water), refluxing it for 3 days, decanting the supernatant liquid, and newly producing calcium chloride. An aqueous solution is added and refluxed for an additional 3 days, the solids are separated by filtration, the recovered solids are washed with distilled water to remove chloride, and the solids are then air-dried and calcined. Crystalline aluminosilicates (zeolites) other than those mentioned above, such as magnesium strontium or barium mordenite and magnesium, calcium, strontium or barium ferrierite, can be prepared by mixing 10 g of a suitable zeolite with 10 g of a suitable zeolite. Reflux the nitrate with 100ml of water,
The solids were separated by filtration, the recovered solids were washed with distilled water, and then the solids were heated at 110°C for 2 hours and at 200°C.
by an exchange reaction by drying at 400° C. for 2 hours and 400° C. for 4 hours. The process variables of the present invention are pressure and contact time. If the temperature is too low, the conversion of monomethylamine to dimethylamine will be low. If the temperature is too high, equilibration and coking (carbonization) may occur unless the contact time is reduced. When operating at very low pressures, unsuitably large reaction vessels are required, and the product must be cryocondensed for further purification; excessively high pressures require costly thick-walled vessels. . Short contact times result in low monomethylamine conversion, while long contact times result in inefficient use of the catalyst at low temperatures and equilibration coking at high temperatures. Generally, contact times of 0.1 to 60 seconds normalized to a pressure of 7 kPa give satisfactory results;
1 to 10 seconds gives favorable results. The efficiency of the catalyst used here is defined by the conversion of monomethylamine and the selectivity to dimethylamine. Here, the conversion rate expressed in % is 100
−100× [MMA/(NH ₃ +MMA+DMA+
TMA)], the selectivity expressed in % is 100×
Used to indicate [DMA/(DMA+TMA)]. In other words, the conversion rate is determined from the amount of monomethylamine (considered not converted) in the mixture of ammonia and three amines produced. The selectivity is determined from the amount of dimethylamine relative to dimethylamine and trimethylamine in the mixture formed, ie the amount of secondary amine formed from the converted portion of the (already converted) monomethylamine. The conversion of monomethylamine in the process of the invention depends on the flow rate (contact time), temperature and pressure. Optimal results are achieved by selecting conditions that compromise these variables. The attached FIGS. 1, 2 and 3, which form part of the disclosure of the present invention, show conventional amorphous silica-alumina (FIG. 1) and alumina (FIG. 2), both representative of the prior art, as catalysts. Selectivity and conversion as defined above for various experiments carried out under atmospheric pressure, at different temperatures, and at different flow rates using crystalline natural ferrierite representative of the catalyst of the process of the present invention. A plot of the rate is drawn. At uneconomically low conversion levels of monomethylamine, e.g. below about 10%, any of the three aforementioned classes of catalysts, whether the system is anhydrous or hydrous, are highly selective; i.e., the reaction is favorable for the production of dimethylamine. Correspondingly, at high levels of monomethylamine conversion, eg, above about 75%, all three classes of catalysts have low selectivity, whether the system is anhydrous or hydrous. This is because the amines approach equilibrium and coking begins. Conversion levels commonly used, e.g.
75%, the process of the present invention provides selectivity substantially superior to that with known catalysts, especially with alumina as catalyst, as disclosed in US Pat. No. 1,926,691, for example. Alternatively, as shown in Experiment 4 below, it provides substantially superior selectivity even in the presence of water, which is a feature not seen in methods using natural erionite as a catalyst. The utility of the process of the invention in the presence of water is particularly important in that the recycled monomethylamine stream isolated from the reaction of methanol and ammonia and used as a feed stream may be hydrous. The following examples are intended to illustrate certain embodiments of the invention. Some of the examples include experiments illustrating methods outside the scope of the invention for comparison. Example 1 A 3 inch (7.6 cm) long Vycor with a 0.5 inch (1.3 cm) diameter zone heated in a segmented tube furnace.
In a tubular reactor, over 3 g of sodium mordenite at atmospheric pressure, a temperature of 300-450 °C and 0.11
Monomethylamine (MMA) was passed through at a flow rate of ~0.83 g MMA/g catalyst/hour. 80/100 mesh diatomaceous earth (ChromosorbWAW) with polyethylene oxide (25% Carbowax400), 2.5%
The three amines and ammonia were measured by gas chromatography using a 10 foot (3.0 m) x 0.125 inch (0.32 cm) column packed with adsorbent containing NaOH. 65℃, He flow rate
At 20 ml/min, TMA, NH ₃ , DMA, and MMA were eluted in this order within 4 minutes. The obtained data are shown in Table 1
It was shown to.

[Table] The selection of process conditions is important. temperature is 400
As the ~450° C. range is reached, MMA conversion increases to about 80% or higher, but selectivity decreases as TMA-rich equilibrium conditions are approached. If the temperature is kept below the operational range, the MMA conversion will drop to no more than 15%, for example, but the selectivity will approach 100%. Preferably, the process conditions are selected such that the MMA conversion is at least 15% and the selectivity is at least 80%. For sodium mordenite, 250-450
A selectivity of 80% or more can be obtained at 1 to 10 g MMA/g catalyst/hour at atmospheric pressure. Example 2 Using substantially the same method as described in Example 1, a variety of catalysts within the scope of the present invention were prepared.
Through MMA. Table 2 shows these data and, as a comparative experiment, catalysts outside the scope of the present invention, namely calcium erionite, erionite, γ-Al ₂ O ₃ , η-Al ₂ O ₃ , 2 Less than % by weight
Sodium-hydrogen mordenite with Na,
Hydrogen mordenite, amorphous standard amination catalyst
SiO ₂ /Al ₂ O ₃ , Bentonite/Volclay, Rhyofluorite-erionite, Pd/SiO ₂ ,
and zeolites 4A, 5A and Na-ZSM-
This is the data of 5. Comparative experiments were labeled "C".

[Table] Mordenite
0.69 350 42 97

【table】

Table: Example 3 As mentioned above, the monomethylamine that is preferably disproportionated is anhydrous. The purpose of this example is to demonstrate that the catalyst of the process of the invention is relatively insensitive to water. The starting monomethylamine therefore does not need to be anhydrous. As can be seen from Table 3, the moisture in MMA (60% H ₂ O, 40% MMA) has no obvious effect on the selective disproportionation of MMA on sodium mordenite. η− outside the scope of the present invention
In the case of Al ₂ O ₃ , there is an effect. Other examples and experiments included herein also further demonstrate the distinction between the catalysts of the present invention and prior art catalysts. The data shown in Table 3 were obtained under the following conditions:
3g sodium mordenite or η-
Al ₂ O ₃ , 3 ml/h liquid charge (40% MMA in H ₂ O) in an apparatus similar to that described in Example 1 and a nitrogen carrier of 10 ml/min.

[Table] Example 4 In this example, sodium mordenite, which is suitable as a disproportionation catalyst for MMA, was used. Anhydrous MMA is heated as steam at a rate of 0.45 to 1.15 g/g Na mordenite/hour to 0.125 inches (0.32 cm).
Sodium mordenite extruded from 120
A cylindrical reactor measuring 0.125 inches (0.32 cm) by 6 inches (15.2 cm) containing 100 g
Charged at a gauge pressure of 350 psig (700-2400 kPa) and a temperature of 300°C. The reactor temperature was controlled by a thermocouple placed in the center of the catalyst bed. Analysis was performed by gas chromatography as described in Example 1. The experimental data are summarized in Table 4.

[Table] Examples 5 to 10 These examples demonstrate that the method of the present invention
This demonstrates that even when using MMA, it is possible to carry out the experiment even in a water-containing system. If you look at the results,
The catalyst of the process of the invention is found to be effective in both systems. Process conditions are substantially the same as described in Example 1. Data for these examples are summarized in Tables 5-10, respectively.
Some of the data in these tables is a reprint of the data listed in Tables 1-4.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Experiments 1 to 4 The following experiments are outside the scope of the present invention because the catalysts of the present method do not exhibit the selectivity exhibited by the catalysts of the present method regardless of the presence or absence of water in the system. This is to demonstrate the use of an amination catalyst in a reaction. The conditions used for the reaction were substantially the same as those described in the previous examples. Data for Experiments 1-4 are summarized in Tables 11-14. Experiments 1 and 2 demonstrated the use of catalysts that were non-selective in both dry and wet systems. Data from Experiment 1, along with data not shown in Table 11, are included in Experiment 1.
Illustrated in the figure. Experiments 3 and 4 demonstrated the use of catalysts that were selective in dry systems but non-selective in wet systems. The data of experiment 3 is
It is illustrated in FIG. 2 along with data not shown in Table 13. Experiment 3 is based on η included in Example 3.
- The method of the aforementioned US Pat. No. 1,926,691 is shown as well as a comparative experiment using _{Al 2} O ₃ .

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】 [Brief explanation of the drawing]

The accompanying drawings form a specific part of the disclosure of the present invention, and together they include a plot (Figure 3) showing the selectivity of the catalyst of the process of the present invention in the conversion of monomethylamine to dimethylamine. Conventional amorphous silica-alumina catalysts (1st
Figure 2) and a normal alumina catalyst (Figure 2) are compared with each other.
More specifically, these figures provide plots showing the percentage of dimethylamine in the dimethylamine/trimethylamine products obtained at various conversions of monomethylamine. These figures are based on examples and experimental data. It can be seen that the silica-alumina catalyst shown in FIG. 1 is non-selective in both dry and hydrous systems. It can be seen that the alumina catalyst shown in FIG. 2 has selectivity in a dry system, but is non-selective in a water-containing system. It can be seen that the natural ferrierite catalyst shown in FIG. 3 has selectivity in both dry and hydrous systems.

Claims (1)

[Claims] 1. A continuous production method for disproportionating monomethylamine to dimethylamine and ammonia, comprising:
The method of production includes monomethylamine in which a the first cation is Na and at least 2% by weight of Na.
b Mordenite whose first metal cation is HNa, Mg, Ca, Sr or Ba
or Ba ferrierite, c clinoptilolite and d phillipsite, on a crystalline aluminosilicate catalyst selected from
At a temperature of 250 to 475°C, a pressure of 7 to 7000 kPa, and a monomethylamine charging rate of 0.1 to 10 g/g catalyst per hour,
An improved method for producing dimethylamine, characterized by passing the monomethylamine at a conversion rate of 15 to 75%. 2. The method according to claim 1, comprising:
The temperature is 350~400℃, the pressure is 70~
3000 kPa, and a method in which the monomethylamine feeding rate is 0.5 to 2 g/g catalyst per hour. 3. The method according to claim 1, comprising:
A method in which the monomethylamine is anhydrous. 4. The method according to claim 1, comprising:
A method in which the monomethylamine is mixed with water. 5. The method according to claim 1, comprising:
A method in which the catalyst is sodium mordenite. 6. The method according to claim 1, comprising:
A method in which the catalyst is hydrogen-sodium mordenite with at least 2% by weight Na. 7. A method according to claim 1, comprising:
A method in which the catalyst is calcium mordenite. 8. The method according to claim 1, comprising:
A method in which the catalyst is natural ferrierite. 9. The method according to claim 1, comprising:
A method in which the catalyst is natural ferrierite ion-exchanged with calcium.