DE1445972C - Process for the joint production of pyrtdine, 2 picoline and 4 picoline - Google Patents

Description

US Pat. No. 2,689,849 describes the production of 2- and 4-picoline by reacting surface activators. They are also used as acetaldehyde with ammonia in the vapor phase under organic solvents. ¹ pyridine is as basic; Use of a silica-alumina catalyst solvent commercially available, ■ also as starting ^ (12 to 18% alumina), which contains 0.1 to 5% of an element material and as a catalyst for some organic from group IV of the periodic table, beUmsionen. 2-Picoline is found written down as a solvent. However, in this process as well as in use and as a starting material or in the processes described above, no formaldehyde intermediate is used in the manufacture of dyes, and no pyridines are formed, substances, resins, disinfectants and volcanics. In British Patent 790 994 becomes a

station accelerators. In addition, 2-picoline can be described in processes according to which pyridine. and 2-vinylpyridine, which can be obtained in the 3-picoline, by formaldehyde, industry in the production of synthetic fibers, syn-acetaldehyde and ammonia via a silica ethetic rubber, adhesives and paints alumina catalyst, which is an oxide of a 3 - or is needed. 4-Picoline is the most important starting material of the 4-valent metal that is added to the vapor phase material in the production of a tuberculosis at a temperature between 400 and 500 ⁰ C to remedy, the isonicotinic acid hydrazide and is used. In this case, however, only small amounts of 2- and 4-picoline are obtained for the production of other pharmaceuticals, synthetic materials. Hence is resins and dyes. Other areas of application of this process are unsuitable if the preparation for pyridine, 2-picoline and 4-picoline are known to those skilled in the art; 2- and 4-picoline is desired in place of 3-picoline. ' will.

Until now, pyridine bases have largely been used as U.S. Patent 816,973 as well

By-products in the coal tar industry 30 described that pyridine and 3-picoline by reaction won. The capacity of the tar industry ranges from formaldehyde, acetaldehyde and ammonia in

Presence of methanol and one in manufacture of 2- and 4-picoline conventional catalyst from acetylene and ammonia can be obtained, with the proportion of acetaldehyde used should not be greater than 2 moles per 1 mole of formaldehyde.

Since, as mentioned above, large amounts of pyridine, 2-picoline and 4-picoline are required in technology and these three substances are relatively easy to separate, but the separation of _{un (} j 3-picoline is relatively expensive and cumbersome, _{un (j} thus is a real need for the recovery of these three products without 3-picoline, especially if the relative proportions of these three products

So from the German Auslegeschrift 1 105 871 45 can be varied as required, for example, a process for the production of The separation of 3-picoline makes a troublesome one

however, not enough to meet the growing demand for pyridine.

Furthermore, various processes for the chemical synthesis of these pyridine bases are already known.

The traditional methods of making pyridine and picolines are roughly divided into:

1. Process for the production of 2-picoline 4-picoline from acetaldehyde and ammonia,

2. Process for the production of pyridine 3-picoline from acetaldehyde, formaldehyde Ammonia.

and

2- and 4-picoline by passing acetaldehyde and ammonia in a mixture with water vapor at temperatures of between ¹ 250 'and 600 ° C over a catalyst consisting of alumina which has been o copper oxide or lead oxide activated by addition of 0.1 to lO ° /, known. In addition to 2- and 4-picoline, this process also produces significant amounts of 2-methyl-5-ethyIpyridine.

and expensive procedure necessary, such as it in US Pat. No. 2,728,711, according to which 4-picoline is separated off as oxalate.

The object of the invention is therefore a process for the simultaneous production of pyridine, 2-picoline and 4-picoline with high yield, and in the pure state through catalytic conversion of formaldehyde, Acetaldehyde and ammonia in the vapor phase,

In British patent specification 900 799, 55 is the same, whereby the formation of 3-picoline is suppressed

if a process for the preparation of 2-and-4 picoline. and the quantitative ratio of pyridine, 2-picoline

described, whereby ammonia and acetaldehyde in and 4-picoline correspond to the respective requirements.

Vapor form in contact with a catalyst can be heated speaking varied,

be made of aluminum oxide or aluminum es. has now been found that a mixture of

oxide and silicon and a whole range of metals 60 pyridine bases, among which pyridine, 2-picoline and

or metal compounds, with 4-picoline predominating and their content of secondary

Shem exclusion of water vapor is worked. products such as 3-picoline and other picoline derivatives,

This process is quite low at temperatures of 300 to can be obtained if a

55O "C. Gas mixture of formaldehyde, acetaldehyde and

In the USA.-Palcntschrift 2 523 580 ammonia is likewise catalytically in the vapor phase with

a process for the joint production of 2- and 4-picoline and of higher alkylpyridines described, whereby ammonia and a saturated ali-

elevated temperature is implemented, the reaction mixture contains at least 5.0 and not more than 25.0 mol of acetaldehyde per mol of formaldehyde.

3 4

The usual reaction temperatures are 400 to mixes, and the mixture is then mixed with gaseous

500 ⁰ C, and the proportion of ammonia is 0.5 to ammonia added. Mixing the reaction

10 moles per mole of total aldehyde. : Participation takes place preferably before the initiation

When carrying out the inventive method in the reaction zone. The reaction mixture should

Each catalyst and each reaction temperature can be used, if possible, up to the vicinity of the reaction temperature

condition that are preheated during manufacture.

of pyridine bases by catalytic conversion in any case, the aldehydes and ammonia of the vapor phase using aldehydes should only then be mixed with one another or in contact with ammonia; it must be placed the other after both isolated on min-molar ratio of acetaldehyde to formaldehyde ίο least about 250 ⁰ C have been preheated. If it is noted which the most important characteristic forms aldehydes and ammonia at a temperature of the invention. ^; .; brought into contact with each other below 250 ° C ■ A gaseous mixture of form can be formed, so they form adducts that continuously clog the reaction aldehyde, acetaldehyde and ammonia and then the reaction gas is introduced into a Prevent flow through the reaction vessel.
Contains catalyst or is filled with it and the temperature in the reaction zone can be kept within a higher temperature can be varied within the range from 400 to 550 ⁰ C,

Various, preferably between 430 and 480 ^° C., can be used in the reaction vessel.
Catalyst types such as fixed bed, fluidized bed and fluidized bed. The contact time of the gaseous reaction bed catalysts are used. As mentioned above, the mixture can range from 0.1 to 7 seconds, each can be used in the production of:. .. ■ · ... ·. ,, _; _, ·; ■ '.-. ■ ·. ■■'.-.-. · | D borrowed catalyst can be used. As an example _: In general, the reaction is carried out under normal conditions silica, alumina, silica-alumina or atmospheric pressure, but it can and silica-magnesia, with silica-clay also happening at pressure, is preferable to earth is. The content of alumina in which the slightly above or slightly below atmospheric pressure is ■ silica-alumina catalyst is within one. . ■■ "■. ■■ .. ■ '■. ·.'.> ■..

large area variable, albeit em silica. The gas flowing out of the reaction vessel after the reaction of alumina catalyst with - 5 to 25 percent by weight can be treated in the usual way! Clay is most suitable. It is also advisable to get the desired pyridine bases; worth finding a suitable cocatalyst with the above. For example. the derived gas-J called main catalyst such as silica-alumina-shaped product condenses to combine the oily layer. Suitable. Co-Kätalysatoreh are separated, over a desiccant, such as solid metals of the II., III., IV. And VIII. Group, the alkali hydroxide, dried and then fractionated periodic table and oxides of these metals. 35 distilled, with pyridine, 2- and 4-picoline in pure form. In practice, at least one of the metals Zn, Cd, should be obtained. . ;:
Th, Co and their oxides used as co-catalyst Not only the substance itself can be used as formaldehyde. The amount of cocatalyst can be any other product, such as an aqueous 0.1 to 15 percent by weight, based on the total formaldehyde solution, paraformaldehyde, trioxane, weight of the catalyst. : 40 methylal, methyl-hemiformal or a mixture of The addition of the co-catalyst to the main two or more of these substances, are used, catalyst, ζ. B. silica-alumina can develop in the usual way under the reaction conditions formaldehyde, that is, by common precipitation. In the same way, instead of acetaldehyde I or impregnation can take place. A substance according to the invention, such as paraldehyde or a mixture catalyst, can be used, for example, from acetaldehyde and paraldehyde, according to the following process: To a freshly made from which acetaldehyde sodium silicate prepared under the conditions of the reaction can develop by adding an acid. Therefore it must be noted that silica gel is an aqueous solution of an aluminum that contains the expressions "formaldehyde" and salt and a cadmium or zinc salt in the form of "acetaldehyde", which in the invention and in the andes nitrate, sulfate or chloride are added. The 50 Proverbs are used not only on the mixing is done with stirring with alkali, z. B. an aqueous aldehyde itself, but also added to the above mentioned ammonia solution to relate aluminum and substances from which the cadmium or zinc in question can be developed together in the form of the hydroxide aldehyde,
to precipitate on the silica. The mass is then washed with water to remove any water-soluble material, material can be removed, shaped, dried and e.g. B. from 0.5 to 10 moles, preferably 1.5 moles from Ibis. The catalyst so prepared retains total aldehyde per mole.

When used under the invention As mentioned above, the main feature is the conditions its activity for about 10 hours. Invention in the particular molar ratio of The regeneration of the used catalyst can easily convert acetylalhydrate to formaldehyde in the reaction by passing hot air over the mixture, because the invention only applies to the Her-catalyst bed take place, with carbon and refers to the position of pyridine, 2-picoline and 4-picoline the surface deposited organic sub- and is based on the observation that the die-cutting to be burned down. ratio of acetaldehyde to formaldehyde the gaseous reactants formaldehyde, 65 yield of pyridine, 2-picoline and 4-picoline as well Acetaldehyde and ammonia can segregate with each other reducing the formation of 3-picoline are .. Or first of all, they are influenced in a decisive manner. In particular, it was found aldehyde gas and acetaldehyde gas with one another that, as shown in the examples explained later

It can be seen that the yield increases with the increase in the molar ratio of acetaldehyde to formaldehyde Pyridine decreases and the yield of both 2-picoline and 4-picoline increases, while the yield increases in 3-picoline drops to a much lower value, and that therefore the molar ratio of the aldehydes is within the specific range of the invention can be selected appropriately, depending on the particular need for pyridine or 2- and 4-picoline.

Thus, according to the invention, acetaldehyde must be used in an amount of not less than 5.0 moles, but not more than 25.0 moles of formaldehyde can be used. When the amount of acetaldehyde is below 5.0 moles per mole Formaldehyde, the formation of 3-picoline, which makes it difficult to isolate 4-picoline, would be unnecessary increase. So in order to ensure a degree of purity of over 90% for the separated 4-picoline, the molar ratio of acetaldehyde to formaldehyde must not be less than 5. On the other hand, if the If the amount of acetaldehyde is more than 25.0 moles per mole of formaldehyde, the pyridine yield would be great become small, which would be incompatible with the aim of the invention, even if the formation of 3-picoline would be greatly reduced.

The invention is illustrated by means of the following examples. In the examples, all yields are on Pyridine and picolines based on the carbon contained in the aldehydes used, and it it was assumed that no other bases were formed. That is, the yield of pyridine was calculated assuming that this pyridine yield is theoretically 100% when the all of the carbon contained in the aldehydes used to form pyridine and not to Formation of picolines would serve. The same assumption was made with regard to the two picolins did.

example 1

40

An aqueous solution containing a 37% aqueous solution of formaldehyde and acetaldehyde in a molar ratio of 10 moles to 1 mole of acetaldehyde, formaldehyde, was g at a rate of 4.3 per minute evaporated and preheated to a temperature of about 25O ⁰ C. On the other hand, a stream of ammonia gas was generated at normal temperature and pressure, which had a rate of 1.9 liters per minute and was preheated to a temperature of about 250 ° C. The two gas streams were mixed with one another and passed through a catalyst layer which contained 350 ecm of a silica-alumina catalyst consisting of 82% silica, 15% alumina and 3% zinc oxide. The temperature of the catalyst layer was kept ^{at 440 ° C. during the reaction.} The gas mixture flowing out, consisting of the reaction product and unreacted material, was cooled and condensed. Solid sodium hydroxide was added to the condensed liquid in order to separate out dry, crude pyridine bases (greenish-gray oily products). The crude pyridine bases were carefully fractionally distilled to separate pyridine, 2- and 4-picoline. The yield and purity of the pyridine bases obtained in this way were as follows: pyridine, yield 14.7% (purity 98%); 2-picoline, yield 18.9% (purity 98%); 4-picoline, yield 17.5% (purity 89%).

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Claims (5)

Patent claims: 1. Process for the joint production of pyridine, 2-picoline and 4-picoline by catalytic Conversion of formaldehyde, acetaldehyde and ammonia in the vapor phase at increased Temperature, characterized in that the reaction mixture is at least 5.0 and Contains no more than 25.0 moles of acetaldehyde per mole of formaldehyde. 2. The method according to claim 1, characterized in that a in the production of 2- and 4-picoline from acetaldehyde and ammonia commonly used catalyst, e.g. B. silica, Alumina, Silica - Alumina, or Silica - Magnesia is used. 3. The method according to claim 2, characterized in that it is the catalyst Silica-alumina with or without the addition of a cocatalyst, this cocatalyst from a metal of the IL, III., IV. and VIII. Group of the Periodic Table or from consists of an oxide of these metals. 4. The method according to claim 1, characterized in that the molar ratio of ammonia to the total aldehydes is 0.5 to 10, preferably 1 to 1.5. 5. The method according to any one of the preceding claims, characterized in that the reaction temperature is ^{400 to 550 0} C, preferably 430 to 480 ^{0 C.} 009527/290