DE1468575A1 - Continuous process for the production of the mononitro compounds of benzene, toluene or chlorobenzene - Google Patents

Description

SUMITOMO CHEMICAL COMPANY, LTD., Osaka / Japan

Continuous process for producing the mononitro compounds of benzene, toluene or chlorobenzene

The present invention relates to a continuous Process for the preparation of the mononitro compounds of benzene, toluene or chlorobenzene by continuous nitration by means of "nitrating acid" (nitric acid-sulfuric acid mixture), and a device for performing this method.

Most of the conventional methods for nitrating aromatic compounds such as benzene, toluene, chlorobenzene and the like with a mixed acid consisting of nitric acid and sulfuric acid are batchwise. A continuous nitriding process is already known in which 2 or 3 successive reaction vessels are used

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(Method by Cf. Messner, in Ind. Eng. Chem., 46, 718, 1954). In the first vessel, an aromatic to be nitrated Hydrocarbon and a mixed acid for nitration are poured in continuously and left under stormy Drilling by means of a strong driving force in emulsion with each other react. The resulting liquid undergoes a second and third nitration in subsequent vessels and the reaction mass is then transferred to a separator in which it is divided into two layers nitrated product and spent acid separates. This method, however, is to maintain a uniform Emulsion of the reaction mass is difficult and a complicated apparatus is required. This suffers on the one hand the quality of the end product and, on the other hand, can be reduced due to the complex construction of the device Occasionally incidents such as explosions cannot be ruled out.

The invention now provides a continuous process for the production of 'ononitrobenzene, mononitrotoluene or mononitrochlorobenzene, the peculiarity of which is that one reaction chamber has separate streams of aromatic Starting compound by line and by nitrating acid

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at least one inlet pipe is fed through line, and that

the
the mixture reacted in the reaction space is separated in a separation zone in a phase of optionally only partially nitrated product and a second phase of spent nitrating acid, that the separated phases are discharged from the separation zone and the optionally only partially nitrated product is further nitrated in a further reactor and that part of the nitrated product is fed to the stream of aromatic starting compound in line in the circuit and mixed with it, maintaining a weight ratio of the circulating nitrated product per weight of the discharged product of zero to about 500: 1, preferably 200:

Furthermore, an apparatus for the continuous nitration of aromatic hydrocarbons is provided which is suitable for carrying out the above-mentioned method according to the invention and which is characterized by the following Features: a reactor divided into several compartments by baffles, which at one end has a Inlet for the aromatic compound feed and

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at least one inlet for the charging of nitric and sulfuric acid in at least one of the compartments

has existing mixed acid; Agitators in each coolant
division of the reactor; / for setting the temperature in the reactor; a separator connected to the other end of the reactor, in which the product is separated into the two layers of the nitrided compound phase and the spent acid phase and which has outlet openings for the withdrawal of each of these phases.

In the drawing, Fig. 1 inclines a schematic view a longitudinal section of an example of the nitriding device according to the invention. Figs. 2 and 3 show schematically the process according to the invention.

In Fig. 1, 1 and 2 represent the inlet ports for the feeds of an aromatic compound to be nitrated or a mixed acid consisting of nitric and sulfuric acid, through which these charges with constant Speed are introduced into the reaction zone. The reaction zone is through baffles 11, 12, 13, 14 and 15 divided into several departments. Each baffle has

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a hole in the middle and is attached to the inner wall of the reactor. The ones in each department Stirring surfaces are labeled 6, 7, 8, 9 and 10 and are attached to a stirrer shaft which runs through the reactor, preferably runs with the same distance between the stirring surfaces. The length of the stirring surfaces can be equal to, larger or smaller than the diameter of the plate hole and the liquid reaction mass is through the Plate holes conveyed steadily upwards. In some cases the reactor, which consists of several departments, divided by baffles, is composed and in which each individual agitator elements are created in each department are to be assembled. The batches fed in at the bottom of the lowest compartment are stirred in each department successively forwarded to the upper departments.

A separation vessel or separator 20 is located at the top of the reaction zone and preferably has one larger diameter than the reaction zone. In the separator

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the reaction mixture coming from the reaction zone is separated into the nitrated organic phase and the phase of the spent acid due to the difference in the specific gravity of the phases. In Fig. 1, 4 denotes an outlet for the nitrated organic phase and 3 an outlet for the spent acid. 19 denotes a sight glass through which a boundary layer between the separate phases can be observed. 16 denotes a water jacket into which cooling water is supplied through the inlet 17 and withdrawn from the outlet 18. Instead of the casing or in combination with it, a central and / or external cooling device can be used. The Beaktionswärme is removed by the above cooling medium and the liquid reactants are maintained depending on the nature of the nitrided material at a desired and conventionally known .konstanten temperature between about 3O ⁰ C and 8O ⁰ C.

In the device described here, the continuous nitration reaction of aromatic compounds with a mixed acid or a mixture of nitric and sulfuric acids is always smooth and uniform. The aromatic compounds and the mixed acid will be at the bottom of the reactor

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fed at constant speed. They react together uniformly as they move through the successive departments be directed with effective movement in each department. Eventually, the nitrated product becomes continuous conveyed into the separator.

The composition of the reaction mixture in each reaction compartment of the reactor is therefore always constant. The reaction Toll takes place at a constant rate and the resulting nitro compound and the consumed Acids are withdrawn from the separator at a constant rate.

The baffle plate can be a perforated plate of the diameter which is the same as the inner diameter of the reactor. Any type of perforated plate can be used, for example plates with a hole in the center or with a number of small holes on the surface. The plate can also be in the form of a grid or sieve.

The number of divisions can be arbitrarily selected, but 3 to 10 or more divisions are usually used.

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As illustrated in Figure 1, the inlet pipe for the mixed acid feed may be at the bottom of the reactor to be appropriate. In some cases, if desired or necessary, the inlet tube can be attached to any of the sequential Departments, for example, attached to the middle department. Also, two can or several inlet pipes for the supply of the mixed acid at any one of the compartments, for example at the Floor and middle section.

In Fig. 2 of the accompanying drawings, which illustrates a circuit system of the present method using the Nitrierungsvorrichtung set forth in Figure 1, the desired nitrated product is withdrawn through the tube 8 and ¹ divided into two parts. Part of the product is withdrawn through the pipe 9 ', while the other part of the connection is fed back into the reactor through the circuit line 10', on the way of which the line ^{10f is} connected to the feed line for the outlet connection. Accordingly, the aromatic compound charge is always fed in combination with the nitrated product. In Fig. 2 1 ¹ and 2 'denote the mixed acid feed

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tank or the feed tank for the aromatic compound. 3 !, 4 'and 5 ¹ indicate flow meters, 6 ¹ a circulation pump and 7 ¹ a discharge line for used acid. Since the fresh charge of the aromatic compound to be nitrated is introduced into the reactor together with part of the nitrated product, the reaction mixture in the lowest compartment of the reactor is extremely uniform and smooth.

Since the reaction mixture in the lowest section of the reaction zone contains an aromatic compound to be nitrated in combination with the nitrated product, in this process is the concentration of the aromatic compound in the reaction mixture is lower than the concentration in a process in which no nitrated product is added will; in addition, the nitrated product serves to emulsify the reaction mixture. Hence the reaction proceeds temperate and is not accompanied by higher nitro compounds as by-products, in contrast to the stormy one exothermic reaction when an aromatic compound containing no nitrated product is mixed directly with an Mixed acid, as is the case with conventional processes.

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As mentioned above, the mixed acid can be supplied through an inlet pipe which is at the bottom or at the any department is provided. In some cases, it can pass through two or more inlet pipes on any one of the Department to be introduced. For example, if it is fed through two pipes, one of which is at the bottom and the other is attached approximately to the middle compartment, so there will be better uniformity both the temperature as well as the acid concentration ensures the formation of higher nitro compounds reduced to a minimum as by-products.

The degree of circulation can be selected within a wider range. The inventive The device and the method according to the invention create many advantages over the conventional one Nitriding apparatus or conventional methods, even in the extreme case where no circulation occurs will. The effectiveness of the device according to the invention and the method according to the invention is, however, much wider increased if one uses the circulation system mentioned above

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applies. The weight ratio of the circulating nitrided product per weight of the discharged product can be zero up to an order of magnitude of about 500, preferably about 200.

The invention can also be carried out more effectively when using two or more of the above-mentioned reactors in combination. This is illustrated in FIG. 3. In Fig. 3, 1 "and 2" "represent the mixed acid and aromatic compound feed tanks and the aromatic compound, respectively. Of these tanks the mixed acid and aromatic compound are introduced into the bottom of the first reactor. The aromatic compound is continuously nitrated by the mixed acid, while, as shown in Figures 1 and 2, it passes through the first reactor. The reaction product resulting in the first reactor is withdrawn through the outlet 7 ″ for the nitrated organic phase, while the phase of the partial Used acid is discharged through the outlet 6 "provided for this purpose. Part of the nitrated organic phase the circuit line 8 ″ together to the first reactor with the aromatic compound fed in from the feed tank 2 "is fed back into the circuit. The remaining part of the

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nitrated organic phase is transferred from the first device through the pipe 9 ″ into the second reactor. The partially consumed acid, which is drawn off from the first reactor, is introduced into the second reactor through the pipe 6 ″ provided for this purpose. In the second reactor, the nitrated organic phase and the partially consumed acid from the first reactor react with one another in a manner similar to that in the first reactor. A part of the compound nitrided through the outlet pipe 14 ″ in the second reactor is fed back to the lower part of the second reactor through the circulation line 15 ″ in the circuit. The remaining part of the nitrided compound is drawn off through the outlet line 16 ". The acid Ttf consumed in the second reactor is discharged through the outlet line 13". In this figure, 3 ", 4", 10 "and 11" indicate flow meters, and 5 "and 12" indicate circulating pumps.

In the process as shown in FIG. 3, the first reactor treats a mixture of an aromatic compound fed in with its nitration product together with the mixed acid fed in. For this reason, the

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Reaction extremely moderate and uniform compared to feeding only one aromatic compound and one

this

Mixed acid are carried out. In "iner two-stage nitration, it is advantageous to perform the nitration in the first Eeaktor up to about 90 to 98 # and to complete the remaining nitration in the second reactor substantially. If an essentially complete nitration is carried out in a reactor, an increase in the reaction temperature is necessary, which, however, can reduce the yield of the final nitro compound as a result of the formation of undesirable, higher nitro compounds as by-products. A higher nitration yield is therefore achieved if the reactors according to the invention and the process according to the invention are used in two stages. For this purpose, it is necessary to use a temperature in the second reactor which is higher, for example about 3 to 20 ° C., preferably 5 to 15 ^° C., higher than in the first reactor.

In this two-stage nitration, the mixed acid can be introduced into the reaction zone of the first reactor in at least one compartment. The mixed acid can therefore, for example, from the middle department or from the middle and the

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Lower departments are fed out. In some cases, if desired, the amount to be introduced into the second reactor, partially used acid can be combined with fresh mixed acid before the introduction to increase the power to strengthen the acid.

According to the process according to the invention, the maintenance of the emulsification state in the reaction mixture during the reaction is much easier than in the case of the conventional processes attributable to recycling of part of the nitrided product.

The product obtained according to the invention in both single-stage and two-stage nitration has a extremely excellent quality. The product contains a far lower proportion of more highly nitrated by-products than the product obtained by conventional methods. Accordingly, the withdrawn from the separator of the reactor can In many cases, the product can be used as a raw material for various production processes. If another If purification is desired, the product can be washed with water, dehydrated or dried and distilled in Vacuum clean.

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According to the invention, benzene, toluene, chlorobenzene are nitrated, resulting in the corresponding mononitro compounds; Nitrobenzene, mitrotoluene and the like are on the other hand nitrable with the formation of the corresponding dinitro compounds.

The mixed acid used in the invention preferably contains 30 to 50 * nitric acid, 50 to 60 * sulfuric acid and 5 to 15 * water. The withdrawn from the separator Used acid contains sulfuric acid and a small amount of nitric acid, which can be used to make fresh mixed acid after removing the organic impurities.

The mixed acid amount, based on the amount of aromatic compound, which is fed to the reaction zone, can be freely selected within the limits known in the conventional nitriding processes, with an amount by weight of about 1 to 5 times per amount of the aromatic Connection is preferred.

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The method according to the invention will now be illustrated further with the aid of the following examples.

example 1

Benzene is mononitrated using the oil device shown in FIG. Benzene and a mixed acid with a content of 33% by weight nitric acid are introduced at the bottom of the reactor in an amount of 12 kg per day and 30 kg per day, respectively. The reaction zone is maintained at 4O ⁰ C, and the agitator rotated at 300 rev / min. Part of the nitrobenzene formed is recycled at a rate of 2.5 liters / min. The yield is 98 # and 18.2 kg of nitrobenzene are obtained per day.

Example 2

Toluene is mononitrated as in Example 1. Toluene and the same mixed acid as in Example 1 are introduced at the bottom of the reaction apparatus in a constant amount of 20 kg per day and 41.6 kg per day, respectively. The temperature in the reactor is kept at 40 ^° C., and the stirrer rotates at 300 rpm. Part of the nitrotoluene formed is in an amount of

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1 liter per minute returned to the circuit. The reaction yield is 98 #, and there are 28.5 kg of nitrotoluene per Day received.

Example 3

Chlorobenzene is mononitrated as in Example 1. Chlorobenzene and the same mixed acid as in Example 1 are introduced at the bottom of the reaction device in a constant amount of 18 kg per day and 30.6 kg per day, respectively. The temperature of the reactor is kept at 60 ^° C. and the stirrer rotates at 30 rpm. The chloronitrobenzene formed is recirculated to the reactor in an amount of 2 liters per minute. The yield is 98 # and 24.5 kg of chloronitrobenzene are obtained per day.

Example 4

Beniol is mononitrated using the reaction apparatus shown in FIG. Benzene and the same Mixed acid as in Example 1 is fed in at the bottom of the first reactor in an amount of 79.2 kg per day. The temperatures the first and the second reactor are kept at 40 ° and 50 ° and the stirrers rotate at 300 rpm,

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A portion of the nitrobenzene formed is circulated in each reactor in an amount of 2.5 liters per minute returned. The reaction in the first reactor is 943 * and that in the second reactor 99 *. 120 kg of nitrobenzene per day were obtained.

Example 5

Toluene is mononitrated as in Example 4. Toluene and the same mixed acid as in Example 1 are introduced at the bottom of the first reactor in an amount of 132 kg per day and 274 kg per day, respectively. The temperatures of the first and second reactor are maintained at 35 ° and 40 ⁰ C and the stirrer rotating at 300 rev / min. Part of the nitrotoluene formed is recirculated to the first and the second reactor in an amount of 2.0 liters per minute and 1 liter per minute, respectively. The conversion in the first and in the second reactor is 93 * and 98 *, respectively. 188 kg of nitrotoluene are obtained per day.

Example 6

Chlorobenzene is mononitrated as in Example 4. Chlorobenzene to be the same mixed acid as in Example 1 at the bottom of the first reactor in an amount of 118 kg per day

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or 200 kg per day imported. The temperature of the first and second reactor is maintained at 45 ° and 60 ⁰ C and the stirrer rotating at 300 o / min. A portion of the chloronitrobenzene formed is returned to each reactor in the circuit in an amount of 2 liters per minute. The conversion in the first and second reactor is 90) C and £ 98. 160 kg of chloronitrobenzene are obtained per day.

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Claims (5)

Patent claims: 1.j Continuous process for the production of the mononitro compounds of benzene, toluene or chlorobenzene by continuous nitration by means of "nitrating acid" (nitric acid-sulfuric acid mixture), characterized in that that a reaction space (21) separate streams of aromatic starting compound through line (1) and of nitrating acid through at least one inlet pipe through line (2) that the mixture reacted in the reaction space (21) in a separation zone (22) in a phase of possibly only partially nitrided product and a second phase spent nitrating acid separates that one diverts the separated phases from the separation zone (22) and that optionally nitrated only partially nitrated product in a further reactor (21) and that one part of the nitrated product fed to the stream of aromatic starting compound in line (2) in circulation and mixed with this, a weight ratio of the circulating nitrated product per weight from zero to
of the discharged product / to about 500: 1, preferably 200: adheres to. - 21 909806/1061 2. The method according to claim 1, characterized in that a weight ratio of about 200: 1 is maintained. 3. The method according to claim 1 and 2, characterized in that the mixed stream of aromatic starting compound and nitrated product to the reaction space, which consists of several, vertically one above the other and provided with stirrers compartments, at the bottom End that one introduces the nitrating acid stream in at least one of the departments and that one at the top of the The reaction mixture exiting the reaction space is fed to a separation zone arranged above the reaction space. 4. The method according to claim 3, characterized in that the nitrating acid stream is introduced into that department, which is also the mixed stream of aromatic starting compound and nitrated product is fed. 5. The method according to claim 3 and 4, characterized in that that you have two of the existing fleaktionsraum and separation zone 409806/1061 - 22 - Units consecutively switched to perform the nitration in two stages, to drive the reaction space of the second stage at a temperature which is higher by 3 to 2O ⁰ C than the temperature in the reaction space of the first stage. ι 6Λ device for carrying out the method according to claim 1 to 5, characterized by one or two series-connected units, one Unit has the following characteristics: a) a vertically arranged reaction chamber, which is divided into several compartments arranged one above the other by means of deflection plates is divided, each of the compartments is provided with a stirring device, b) an inlet at the lower end of the reaction space for the supply of the mixed stream of aromatic starting compound and nitrided product, c) at least one inlet into at least one of the compartments for the supply of the nitrating acid stream, - 23 909806/1061 d) coolant for temperature control of the reaction room, e) a separation zone for separation which is arranged at the upper end of the reaction space and is connected to it of the reaction mixture into a phase of nitrated product and a second phase of spent nitrating acid, f) Means for deriving the separate phases from the Separation zone and g) means for recycling part of the nitrated product into the stream of the aromatic starting compound. 909806/1061