DD149510A5 - PROCESS FOR THE PRODUCTION OF METHYLAMINES - Google Patents

Abstract

The invention relates to a process for the preparation of methylamines from a mixture of methanol and ammonia in excess in the vapor phase at elevated temperature, wherein the reaction mixture is passed through a catalyst containing acid-activated montmorillonite.

Description

2ί 9796 A-Berlin, the 15th -SO

B7 091 11

AP C 07 JÖ / 219 Irr

Process for the preparation of methylamines

Field of application of the invention

The present invention relates to a process for the preparation of methylamines by reaction of nol and ammonia in the gas phase at elevated tem eraser, and possibly under elevated pressure in the presence of _a silica / alumina catalyst.

Characteristic of the known technical solutions

For the catalytic synthesis of the methylamines from Ammo "ia k and methanol by first preparing a vapor mixture of methanol and ammonia - with ammonia predominates -" is thereafter Is & respond t in a reactor at temperatures of unge-Fafer 200 to about 500 ⁰ C at a pressure "the bar is located between the atmospheric pressure and about 50, by conduction through a catalyst bed ·

For this synthesis, a large number of catalysts has been proposed; these are, for example, metal oxides, such as aluminum oxide, zirconium oxide, thorium oxide, silicitic oxide, tungsten oxide and copper oxide, pure or in admixture, with or without addition of carriers. For the same purpose, various metal salts have also been proposed, in particular diammonium hydrogen phosphate, aluminum phosphate, aluminum sulfate, thorium sulfate or mixtures these salts with oxides such as those mentioned above, alone or with the addition of carriers such as pumice, activated carbon, diatomaceous earth, quartz, asbestos, etc.

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Economically, all of the above-mentioned catalysts share the common disadvantage that they are based on relatively expensive raw materials and are produced by processes which are also relatively expensive.

A more favorable way in this respect would be to start directly from abundant mineral resources in nature. For this reason, in U.S. Patent No. 1,875, for the synthesis of methylamines, natural aluminum silicates are proposed, such as Indianaite, blue clay, crushed brick, Doucil, a feldspar, and Putnam clay. Ladder, the results obtained with this category of natural aluminosilicates are not very good as far as the production of dimethylamine, the most popular methylamine, is concerned. In fact, according to this US patent, especially the production of monomethylamine is sought. However, it turns out that even if this is the desired product, the process described is not satisfactory due to its low productivity.

Synthetic silica / alumina catalysts were also used for the synthesis of methylamines.

Thus, according to DE patent 1 543 731, artificial catalysts of the silica / alumina type are prepared from a silica gel on which an alumina gel is precipitated. Thereafter, the catalyst is partially deactivated with steam under pressure and then impregnated with silver phosphate or rhenium, molybdenum or cobalt sulfide. The results obtained with these catalysts are better than those of the above-mentioned U.S. Patent 1,875,747, but the cost of the raw materials and the production are

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considerably higher. In addition, this method also has shortcomings in its productivity. According to the applicant's knowledge, the primary production of dimethylamine provided for in that patent could never be realized in industrial practice. In Example 1 below, it is shown that these catalysts produce much trimethylamine at the beginning of the conversion and the trimethylamine formed at the beginning is difficult to convert to dimethylamine.

Object of the invention

It would be ideal to find among the natural minerals catalytic substances which retain the advantage of the low cost by which they excel and at the same time have a very high and highly selective catalytic activity.

Explanation of the essence of the invention

The invention has for its object to provide a process for the preparation of methylamines, are used in the course, occurring new catalysts.

According to this invention, a process for the preparation of methylamines is provided which is characterized. in that a mixture of methanol and ammonia - with ammonia predominating - is passed in the vapor phase at elevated temperature over a Krtalysator containing acid-activated montmorillonite.

The montmorillonite ideally has the formula AIp (OH) ₂ /~Si.0 _10>< 7 + η H ₂ O. It has the peculiarity that

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its lattice consisting of two outer layers of silicon dioxide tetrahedra and a middle layer of alumina octahedrons reversibly swells by intercalation of water between the layers, however, the silicon ions of the outer layers may be partially covered by aluminum (beidelite) and the aluminum ions of the middle layer by iron ( Nontronite), magnesium (hectorite), etc. Likewise, some clays, such as bentonite, contain a certain amount of montmorillonite. It will be understood that all of these natural compounds, after being activated by an acid, are useful as catalysts for the synthesis of methylamines according to the process of the present invention. For more information on montmorillonite and its natural derivatives, see in particular the ULLMAN Encyclopedia of Industrial Chemistry, 3rd Edition, Volume 4, 1953, page 541 ff., And the work of RE GRIM, "Clay Mineralogy", McGraw-Hill Book Co. , I _n c. 1,953th

For their industrial applications, montmorillonite and the clays which contain it are subjected to an activation process with a strong mineral acid such as, for example, hydrochloric acid, sulfuric acid or phosphoric acid. As a result of this treatment, the structure of the original lattice of montmorillonite is more or less deeply altered, thereby maintaining its catalytic properties.

The catalytic properties of the acid-activated montmorillonites have been known for a long time and are exploited in industry, especially in the catalytic cracking of petroleum components, in polymerization, hydrogenation, dehydrogenation, alkylation, dehydration, isomerization, etc. (see DE patents 1 051 271, 1 051 864,

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1 086 241 and 1 089 168). But acid-activated montmorillonites have not yet been proposed and used as catalysts for methylamine synthesis,

Compared with the prior art aluminosilicates, the activated montmorillonites of the invention have the following advantages:

1. They are more selective because they favor the formation of dimethylamine.

2. At the same time, the conversion of methanol is more than 96 % and the yield of amines relative to the converted methanol is more than 98 %,

3. Your life is longer.

The activated montmorillonite used in the present invention as a catalyst may be in the form of solid or hollow grains, spheres or cylinders varying in size from 0.2 to 10 mm. The spatial density of activated montmorillonite may vary between 0.4 and 1.2 kg / liter,

The raw materials used in the process according to the invention are methanol and ammonia.

The methanol and ammonia used may be of pure technical or lucid economic reasons.

The molar ratio of methanol to ammonia in the gas mixture fed to the reactor can vary between 0.3: 1 and 1: 1. It is in no way advantageous to use a ratio of less than 0.3: 1, since then one would have to return too much unused ammonia. The operating procedures applicable to the invention

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conditions are the same as those generally used in the preparation of methylamines by catalytic reaction of an excess of ammonia with methanol in the gas phase, in a temperature range of 200 to 500 ⁰ C _1, preferably from 350 to 450 ⁰ C, and below a pressure which is between the atmospheric pressure and about 100 bar, preferably between 10 and 50 bar.

The contact time of the methanol-ammonia gas mixture with the catalyst used according to the invention is not critical, and contact times between 1 and 20 seconds can be used. Contact time refers to the ratio of the apparent volume of the catalyst (in ml) to the amount of gas mixture of methanol and ammonia, expressed in ml per second, under normal conditions of temperature and pressure (O ⁰ C and 1.013 bar).

There are no limitations on the type of equipment used to carry out the method of the invention. The process can be carried out continuously or batchwise. The catalyst bed may be a solid bed or a fluidized bed.

At the outlet of the reactor, the gas mixture is separated by known methods, such as stepwise distillation, into its various constituents.

After separation of the various constituents of the effluent reactor product can, if desired, the formed mono- and / or trimethylamine partially or completely recycled to the reaction in addition

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increase the yield of dimethylamine and at the same time reduce its formation.

Ausführungsbeispiei

In the following examples which, without limitation, demonstrate the process of this invention, commercially available products are used as activated montmorillonites, namely, the K-catalysts from SÜD-CHEMIE; these are trade brochures that company, such as "K-catalysts, Süd-Chemie AG Munich" 9/1977, S _s ites 1 and 4 described.

Example 1 (example for comparison)

In this example, the artificial silica / alumina catalyst is used, the preparation of which is described in Example 1 of DE Patent 1 543 731; this catalyst still contains 0.1% by weight of metallic silver when dried,

The reactor used is a tube of pyrex glass 5 cm in length with an inside diameter of 8 mm through which runs a concentric sleeve into which a thermocouple slides. This pipe is housed in an oven. The catalyst mass stored in the middle of the tube consists of 1 g of the aforementioned catalyst; its grain size is between 0.42 and 0.59 mm. While the temperature in the reactor is maintained at 423 + _ 0.5 ° C, passing through him a benäres gas mixture CH.-OH-NH, (molar ratio CH ₃ OHcNH ₃ equal to 0.54: 1), which at 423 ⁰ C. preheated, man working at atmospheric pressure.

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Analysis of the composition of the gas mixture coming from the reactor is carried out by gas phase chromatography in a stainless steel column. For this chromatography, a stationary phase is used which consists of polystyrene in the form of spheres, the surface of which is treated by a silane (PORAPAK / S) and impregnated to 10 % with a mixture of tetraethylenepentamine and potassium hydroxide.

The results obtained are summarized in the table below, in which

- the "contact time" (in seconds) is the quotient of the apparent volume (expressed in ml) of the catalyst and the volume flow expressed in ml per second. These "contact times" allow estimating the performance of a catalyst in industrial practice. In fact, from the value of contact time, one can easily derive the volume that the reactor must have in order to secure a given production. The longer the contact time, the larger the reactor must be for a given production. In this way, not only the actual apparatus (reactor) is expensive, but also the amount of catalyst is larger;

MMA = monomethylamine;

DMA = dimethylamine;

TMA = triethylamine;

DME = dimethyl ether;

the weight percentages of MMA, DMA, TMA, CH, OH and DME are expressed in relation to the total weight DME + MMA + DMA + TMA + CHOH (substances which are most difficult to separate);

the weight ratio ΓΤΜΑ / DMA is the ratio of the weight of TMA to the weight of DMA. This ratio

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makes it possible to estimate the DMA selectivity in the ratio: to TMA selectivity, with the smallest ratio being the most favorable.

Weight percent DME Weight percent MMA TABLE 1 Weight percent CH ₃ OH Weight ratio TMA / DMA 6.5 4.5 2.6 1.7 20.0 21.0 22.0 22.7 16.3 10.0 9.0 8.5 2.83 2.57 2.31 2.25 Contact time Example .2 Weight percent DMA Weight percent TMA 2.22 4.00 5.50 5.73 14.9 18.0 20.0 20.6 42.2 46.3 46.3 46.3

The procedure is as in B _e ispiel 1, but the molar ratio of methanol: Ammonial <0.55: 1, the reaction temperature is 424 + _ 0.5 C, and the catalyst consists of 1 g according to the invention activated montmorillonite (catalyst sold by SOD-CHEMIE K 306), which is comminuted to a grain size of 0.42 to 0.59 mm.

This catalyst has a surface index of 190

2 3

to 250 m / g, a pore volume of 0.19 cm / g at 14 nm and of 0.30 cm / g at 80 nm, a compressive strength of 78.4 N and a bulk density of about 650 g / l.

Table 2 shows the results obtained:

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TABLE 2

Con- Weight- Weight-, Weight-, Weight-% Time percent percent, percent, percent

DME MKA DMA TMA Methanol TMA / DMA

1.4 4 17.7 14.9 33 ,8th 29.5 2.26 2.34 2 20.9 20.4 38 18.4 1.86 5.39 - 26.2 25.3 42 , 6 5.3 1.68 5.5 - 26.0 26.0 43 5.0 1.65

This table shows the superiority of the catalyst used in this example over the catalyst used in Example 1, namely:

a) One achieves a weight ratio TMA / DMA of 2.26 for a contact time of 1.4 s, while in Example 1 a contact time of 5.73 s is necessary to achieve an approximately equal ratio. Furthermore, this ratio may decrease to 5.5 at a contact time of 5.5 seconds.

As a result, in the process of the invention, DMA selectivity is higher compared to THA selectivity for significantly smaller contact times.

b) The formation of DME is significantly lower, and it is close to zero for 5 s contact times.

The amine yield is ^x in relation to the converted methanol so very high (less by-products).

c) The conversion of the methanol is much stronger for contact times of 5 s. 11 -

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By "conversion of methanol" is meant the weight percent of this alcohol converted by flow through the reactor.

Example 3

The procedure is essentially as in Example 1; however, the reactor has a larger inside diameter (28 mm), the molar ratio of methanol: ammonia is 0.58: 1 and the reaction temperature 440 + _ 0.5 ⁰ C.

The catalyst is the same as in the previous example except that it has the form of spheres of 4 to 5 mm with a volume density of about 650 g / l. The amount of catalyst used is larger (5 g) than in the previous example.

Table 3 below gives the results as a function of the conversion of methanol,

TABLE 3

Conversion- weight- weight-

weight-, weight-, weight-

of percent meth- od percent percent percent _ΤΜΔ / ηΜΛ

nol DME MMA DMA TMA Methanol ^Im / ^UMA

83 ,1 1 , 7 16 3 18 6 40 5 22 7 2 , 18 88 O , 7 19 , 5 22 6 40 8th 17 1 80 99 2 - 26 2 28 2 44 5 ο, 9 1 , 58

Table shows that with the catalysts of the present invention it is possible to obtain an excellent conversion.

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Conversion of methanol (99.3 %) with a very favorable weight ratio TMA / DMA to achieve.

Example 4

This example was realized on an industrial scale. The catalyst of Example 3 is placed in an industrial reactor containing a 10,000 liter catalytic charge.

The reaction takes place under a pressure of 20 bar and at a temperature of 420.degree.

At a charge of 0.36 kg methanol / kg catalyst per hour, the molar amine yield relative to the converted methanol is 99 % and the conversion of the methanol is 97.3 %. At the reactor exit, it can be seen that, on average and for an operating time of calculated one month, the weight ratio TMA / DMA is 1.68.

At a charge of 0.325 kg methanol / kg catalyst / hour, the amine yield is 98.9 % and the conversion of methanol 98.4 %.

After 11 months of operation at a charge of 0.325 kg methanol / kg catalyst / hour, the conversion of methanol still 96.6 % and the amine yield 98 ', 3 %,

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Claims (4)

796 15. 8. 1980 AP C 07 C / 219 796 - 13 - invention claim A process for the preparation of methylamines, characterized in that a mixture of methanol and an excess of ammonia in the vapor phase at elevated temperature is passed through a catalyst containing acid-activated montmorillonite. 2. The method according to item 1, characterized in that the molar ratio of the methanol to the ammonia between 0.3: 1 and 1: 1 varies. Method according to points 1 and 2, characterized in that the reaction takes place at a temperature which is between 200 and 500 ^° C, preferably between and 450 ^° C. 4. Process according to items 1 to 3, characterized in that the reaction proceeds under a pressure which is between atmospheric pressure and about 100 bar, preferably between 10 and 50 bar.