EA042067B1 - METHOD FOR ADIABATIC NITRATING OF AROMATIC COMPOUNDS - Google Patents

Description

The invention relates to the technical field of nitration, in particular the production of nitrated organic aromatic compounds (hereinafter also referred to synonymously as nitroaromatic compounds, nitration products, aromatic nitro products, aromatic nitro compounds, nitrated products and the like), preferably by adiabatic nitration.

In particular, the present invention relates to a process for nitration, in particular adiabatic nitration, of nitrated organic aromatic compounds (aromatic compounds) to form the corresponding nitrated organic aromatic compounds (nitroaromatic compounds).

In addition, the present invention relates to a production plant (nitration plant or plant) for nitration, in particular adiabatic nitration, of nitrated organic aromatic compounds (aromatic compounds) with the formation of nitration products in the form of corresponding nitrated organic aromatic compounds (nitroaromatic compounds), in in particular to a production plant for carrying out the method according to the invention.

Finally, the present invention relates to the use of nitrated organic aromatic compounds (nitroaromatic compounds) according to the invention.

Aromatic nitro compounds (such as nitrobenzene (MNB), mononitrotoluene (MNT), dinitrotoluene (DNT), trinitrotoluene (TNT), nitrochlorobenzene (MNCB), etc.) are usually prepared by nitration of the corresponding starting aromatic compounds (such as benzene , toluene, xylene, chlorobenzene, dichlorobenzenes, etc.), in particular by reacting the corresponding starting aromatic compounds with nitric acid in the presence of sulfuric acid as a catalyst and a water-binding component, i.e., thus, reacting the corresponding starting aromatic compounds with a nitrating acid (that is, a nitrating mixture of nitric acid and sulfuric acid, which is also called melange at the beginning of the interaction, and at the end of the interaction is also called spent (nitrating) acid).

According to the prototype, the nitration of aromatic compounds with a nitrating acid mixture of nitric acid and sulfuric acid is preferably carried out in the form of a heterogeneous liquid/liquid mixture from an organic and acid phase, and the nitrated aromatic compounds interact with nitric acid to form the corresponding aromatic nitro compounds in the acid phase. Therefore, the aromatic compound to be nitrated for this purpose must first be transferred from the organic phase to the acid phase in order to be able to react there. The nitroaromatic compound formed in the acid phase is then - after exceeding the solubility limit - isolated as an organic phase; this organic phase at the beginning of the nitration consists mainly of the nitrated aromatic compound, and at the end of the reaction, when either all of the nitric acid or all of the nitrated aromatic compound has reacted, consists mainly of the desired nitroaromatic compound.

A condition for rapid and efficient conversion of the aromatic compound is that a sufficient amount of the nitrated aromatic compound is constantly transferred from the organic phase to the acid phase. As a rule, this is achieved by creating as wide an exchange surface as possible between the two phases mentioned above, in particular by dispersing either the organic phase in an acid phase (to form an oil-in-water emulsion or an O/W emulsion) or vice versa, the acid phase in an organic phase. phase (up to a water-in-oil emulsion, or W / O-emulsion). The larger the exchange surface between the organic and acid phases (i.e., therefore, the smaller the droplet size of the dispersed phase), the more intense the conversion during nitration, such as, for example, the nitration of benzene to nitrobenzene or toluene to mononitrotoluene, etc. (as in all so-called mass transfer-controlled reactions).

For example, when nitration is carried out continuously and isothermally in stirred-tank reactors or, respectively, in cascade stirred-tank reactors in co-current and/or counter-current mode, constant conditions are created in each reactor, such as, for example, the composition of the organic phase and the acid phase, and - in in connection with this - constant physico-chemical conditions and parameters for a two-phase mixture of the organic phase and the acid phase. Nitration takes place in each reactor under always the same conditions.

By contrast, nitration proceeds quite differently in a stirred batch reactor with full backmixing, or in a tube reactor with plug flow (so-called plug flow) without backmixing. In both cases, in the course of nitration, not only the composition of the organic phase and the acid phase, but also their physicochemical conditions and, accordingly, parameters, in particular, such as density, surface tension at the interface, etc., constantly change. Under constantly changing conditions and parameters, it is very difficult or almost impossible to create a constantly identical exchange surface for a controlled transformation throughout the entire interaction time.

In addition, it is known that pure aromatic compounds, such as benzene or tolu

- 1 042067 ol, are dispersed only with difficulty in sulfuric acid or nitrating acid mixtures, and that dispersions of aromatic compounds in sulfuric acid or nitrating acid mixtures are relatively quickly destroyed again. For example, as described in patent document EP 0 373 966 A2, with a single dispersion of a nitrated aromatic compound (benzene) in melange, due to the rapid coalescence of the organic phase, only 55.3% conversion of nitric acid and, correspondingly, only 52.5% of benzene is achieved. Therefore, in a nitration in which two phases are present in the nitrating mixture (namely, on the one hand, the organic phase of the nitrated aromatic compound and the nitroaromatic compound formed, and, on the other hand, the nitrating acid mixture), it is necessary to constantly supply energy for stirring in such a way that the necessary exchange surface between the two phases remains constantly created, and thus the desired degree of conversion is achieved for a given residence time.

First of all, at the beginning of nitration (for example, in a tubular reactor), a particularly high stirring energy must be supplied in order to create and maintain a sufficiently large exchange surface between the organic phase and the acid phase, thereby initiating and accordingly stimulating, and also developing nitration. If this does not occur, due to more or less rapid coalescence of the dispersed phase, a sharp reduction in the exchange surface occurs, which causes a sharp decrease in the degree of conversion of the nitrated aromatic compound per unit time.

If, for example, in a tubular reactor, a once created dispersion of a nitrating aromatic compound (for example, benzene) in a nitrating mixture is not constantly supplied with new stirring energy along the entire length of the reactor (for example, as described in patent documents EP 1272268 A2, EP 1291078 A2 or EP 0708076 A2), in order to hinder the resulting coalescence of the organic phase dispersed in the nitrating acid by adding additional stirring energy, the nitration is stopped - which can be recognized by the fact that no more heat of nitration is released and the nitrating aromatic compound is still present in the organic phase.

This is correspondingly true for the start of the conversion: if at the start of the conversion the size of the droplets formed is not sufficiently small and thus the exchange surface is too small, e.g. in the reaction mixture, no or only a slight increase in temperature is observed, since the interaction has not begun. On the contrary, when the droplet size of the dispersed phase is small enough, and thus the exchange surface is large, under otherwise equal conditions, a rapid conversion of the nitrated aromatic compound occurs - which can be recognized by the fact that there is a rapid increase in temperature in the reaction mixture and the associated desirable high the degree of conversion of the nitrated aromatic compound to the corresponding nitroaromatic compound.

First of all, in adiabatic transformations (for example, in the adiabatic nitration of benzene to nitrobenzene), the degree of conversion, and thus the necessary duration - in addition to the exchange surface between the two phases and thus the size of the droplets of the dispersed phase - also depends on additional well-known parameters, for example, such as the concentration of sulfuric acid and nitric acid in the nitrating acid (referred to as melange at the beginning of the reaction and spent acid at the end of the reaction), the initial temperature (e.g. temperature, etc.

The degree of conversion during adiabatic nitration (for example, benzene to nitrobenzene) in a tubular reactor - based on a certain initial temperature - is characterized by an increase in temperature in the nitrating mixture due to the heat of nitration released (for example, compare patent documents EP 2168942 A1 and EP 1272268 A2). The temperature difference measured for a particular nitrating mixture (also called Delta T, or AT) can be in direct, in particular linear, correlation with the degree of conversion of nitric acid, as described, for example, in patent document EP 2168942 A1.

In order to achieve the highest possible degree of conversion at a predetermined residence time in the tubular reactor (for example, more than 98% of the nitric acid used), in addition to optimal dispersion of the nitrated aromatic compound in the melange, a suitable initial temperature is also required, thereby initiating and correspondingly stimulating the reaction, then i.e., after mixing the starting materials, the reaction proceeds in such a way that a sharp, in particular uniform, preferably exponential rise in temperature in the nitrating mixture is observed so that, for example, in the first 13% by volume of the reaction volume of the tubular reactor, at least 60% of introduced nitric acid (for example, compare patent document EP 2168942 A1). For example, this is achieved by a special arrangement of the dispersing elements for the necessary redispersion of the initially rapidly coalescing organic phase in a tubular reactor (for example, cf. EP 1 272 269 A1).

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The starting temperature can be selected, for example, in the range from 50 to 120°C. By mixing differently heated feed streams (i.e. sulfuric acid, nitric acid and a nitrated aromatic compound such as benzene, e.g. cf. the temperature is brought in by sulfuric acid in a large excess.

But by means of the initial temperature - at a given residence time - not only the degree of conversion is regulated, but also the formation of side products typical of adiabatic nitration, for example benzene to nitrobenzene, in particular, such as some di- and trinitrophenol (picric acid) and dinitrobenzene ( DNB).

By means of an initial temperature of 80 to 120°C (eg cf. US 4091042 A), preferably over 97°C, and particularly preferably 100 to 120°C (eg cf. EP 0436443 A2 or EP 2168942 A1), it is possible for residence times in the tubular reactor of less than 2 minutes (eg maximum 25 s, for example cf. EP 0 436 443 A2) to achieve a conversion of nitric acid of at least 99%.

In contrast, significantly longer residence times are required at lower initial temperatures. For example, at an initial temperature of about 80°C in prior art plants (tubular reactor) it is described as a necessary residence time of 300 s to achieve complete conversion of nitric acid (for example, compare patent documents US 8692035 B2 or WO 2010/051616 A1).

Compared to prior art plants operating at an initial temperature of 97 to 110°C, the lower initial temperatures thus require significantly larger nitration reactors, which are, however, much more expensive, since they are usually made of enamelled steel.

With a plant capacity of, for example, 20 tons of nitrobenzene (NB) per hour (i.e., 20 tons of NB/h), a tubular reactor with a diameter of 250 mm at a nitrating mixture flow rate of 1.25 m/s and a residence time of at least 300 seconds was would be 2.5 times longer (i.e. about 375 m) than the standard reactor according to the prototype with a length of 150 m at a residence time of 120 s, and all other things being equal (i.e. the same melange composition, the same phase ratio, etc.). d.).

An additional goal of optimizing plants for the adiabatic nitration of aromatic compounds, in particular benzene, is to minimize the amount of by-products in nitrobenzene. As already described in EP 0 436 443 A2, the formation of di- and trinitrobenzene is dramatically accelerated as the final temperature of the nitrating mixture increases. For these reasons also the final temperature of the nitrating mixture should not exceed 135-145°C. Then the content of nitrophenols in the crude nitrobenzene (Roh-NB) is shifted in the range from 2000 to 3000 ^ppm . The content of dinitrobenzene (DNB) at these final temperatures is shifted in the range from 200 to 250 ^ppm . The removal of these nitrophenols from the crude nitrobenzene and their destruction in the waste water, for example by thermolysis (as described in patent documents EP 0 953 546 A2 and EP 0 005 203 A2) is laborious and costly.

By lowering the initial temperature and thus also the final temperature, the formation of by-products can be substantially reduced. Each decrease in the initial temperature by 20 to 25° C. results in a halving of the content of nitrophenols in the crude nitrobenzene. Reducing the initial temperature from about 110 to about 80° C. results in a reduction in the content of nitrophenols by up to about 50%, that is, to almost 1500 ^ppm and below (for example, 1000 ^ppm ), compared with ratios such as, for example are described in EP 0436443 A2, particularly preferably up to 1000 ^ppm . The content of dinitrobenzene (DNB) similarly falls by about 100 ^ppm (compare for this, for example, also US 8692035 B2 or WO 2010/051616 A1).

Through the phase relationship between the acid phase and the organic phase - at a given concentration of nitric acid in the melange - it is possible to control the temperature rise in the nitrating mixture between the start temperature and the end temperature. At a constant phase ratio and remaining unchanged the concentration of sulfuric acid and the initial temperature in the initial melange, with an increase in the content of nitric acid in the melange and with an equal degree of conversion, the final temperature in the nitrating mixture increases, and vice versa.

As already described in EP 0 771 783 A1, for high selectivity, it is preferable that at the start of the reaction in the tubular reactor, a high initial conversion is achieved by optimal mixing. According to the prototype, various measures are described to ensure, if possible, optimal dispersion of the nitrated aromatic compound in the initial melange by the beginning of the interaction and re-dispersion (for example, compare patent documents EP 0373966 A2, EP 0489211 A1, EP 0771783 A1, EP 0779270 A1, EP 1272269 A1 , EP 1291078 A2 and EP 2168942 A1).

Optimum dispersion of a nitrated aromatic compound (e.g. benzene) into nitrates

- 3 042067 reducing acid, especially at the beginning of the nitration to initiate the reaction, is a condition for high conversion (cf. patent documents EP 1272269 A1 or EP 2168942 A1). As described in this regard in US 9284256 B2 and EP 2877442 A1, the admixture of more than 4% aliphatic hydrocarbons to nitrated benzene results in that nitration does not start, i.e. no noticeable temperature increase is observed in the nitrating mixture after mixing of the starting components, and no primary dispersion is observed, whereas, under otherwise equal conditions, with benzene at a content of less than 0.1% aliphatic hydrocarbons, nitration (as described in patent documents EP 1272269 A1 or EP 2168942 A1) begins with a sharp increase in temperature in the first 13 vol. % tubular reactor, and proceeds as intended.

In the prior art, there was no shortage of attempts to achieve improved dispersion of the nitrated aromatic compound in the nitrating acid. A measure known from the prototype to achieve this is, for example, a larger ratio of acid phase to organic phase, which should improve the dispersibility of the organic phase and reduce coalescence, as, for example, described in patent documents EP 0436443 A2 and US 8692035 B2. An additional measure known from the prototype, as follows from patent documents EP 1272268 A2 and EP 2168942 A1, consists in carrying out nitration in a tubular reactor with mixing and, respectively, dispersing elements, and in this case by means of uneven placement and, accordingly, distribution of mixing and, respectively, dispersing elements along the entire length tubular reactor to achieve that at the beginning of the interaction a uniform, in particular exponential, preferably S-shaped temperature increase is obtained, and the highest possible degree of conversion is achieved in the front section of the tubular reactor. But the measures known from the prototype are not sufficient to constantly achieve optimal dispersion of the nitrated aromatic compound in the nitrating acid, and to level the problems and disadvantages associated with insufficient dispersion and the above-described problems.

Therefore, the object of the present invention is to provide a method and a corresponding production plant (nitration plant or plant) for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds), whereby the , at least to level out the shortcomings and omissions of the prototype outlined so far.

In particular, the object of the present invention can be seen in the creation of a method and a corresponding production plant suitable for the implementation of this method (nitration plant or plant) for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds), by means of which or by which nitrated aromatic organic compounds can interact and accordingly react in a technically efficient, such as safer and simpler way to form the corresponding nitrated aromatic organic compounds (nitroaromatic compounds).

In addition, the object of the present invention can be seen in the creation of a method and a suitable production plant suitable for the implementation of this method (nitration plant or plant) for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds), moreover, within the framework of nitration the dispersion of the nitrating aromatic compounds in the nitrating acid mixture is improved, especially at the beginning of the reaction, preferably already after mixing the starting components. In this case, in particular, the dispersion of the organic phase and the acid phase should also improve under unfavorable conditions (for example, such as the presence of contaminants, such as an increased content of aliphatic compounds in the nitrated aromatic compound, at a too low initial temperature or with a low dispersion energy input) such so that the nitration can still be efficiently carried out, in particular the nitration mixture can undergo a conversion of at least 98% within a predetermined reaction time or residence time in the reactor.

Finally, the object of the present invention can also be seen in the creation of a method and a corresponding production plant suitable for the implementation of this method (nitration plant or plant) for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds), moreover, within the framework of nitration improved dispersion can already be achieved after bringing into contact (e.g. mixing) the reactants, in particular the nitrating acid phase containing nitric acid on the one hand and the organic phase containing nitrating aromatics on the other hand, preferably preventing rapid coalescence of nitrating aromatics in nitrating acid, preferably in order to initiate the nitration reaction also at lower initial temperatures compared to the prototype (namely, without requiring longer than according to the prototype with higher initial temperatures, reaction times and residence times, but other conditions being equal).

The problem statement described above is solved according to the invention - according to the first aspect

- 4 042067 of the invention - by means of the method according to claim 1 of the claims; further advantageous improvements and embodiments of the method according to the invention are the subject matter of the related dependent claims.

A further object of the present invention - according to the second aspect of the invention - is a production plant (nitration plant or plant) according to the respective independent claim for a production plant; additional, useful improvements and embodiments of this aspect of the invention are the subject matter of the dependent claims relating thereto (dependent claims on production plant).

Finally, the subject of the present invention - according to the third aspect of the invention - is the use according to the invention according to the respective independent claims on the use; additional, useful embodiments and improvements of this aspect of the invention are the subject matter of the dependent claims relating thereto (dependent claims for use).

It goes without saying that embodiments, embodiments, advantages or the like, which are hereinafter - to avoid unnecessary repetition - set forth in only one aspect of the invention, of course, are also respectively valid in relation to all other aspects of the invention.

In addition, it goes without saying that the subsequent data of values, numbers and ranges should be understood without limitation related data of values, numbers and ranges; for a person skilled in the art it is self-evident that according to a particular situation or according to the variant of application, the ranges given and, accordingly, the data may vary without going beyond the scope of the present invention.

In addition, it is true that all data of values and, respectively, parameters, or the like, subsequently indicated, can in principle be elucidated or determined by normalized and respectively standardized or explicitly indicated methods of determination, or methods of determination and, accordingly, analysis familiar to a specialist in this field of technology. .

In view of the foregoing, the present invention will now be described in more detail.

The subject of the present invention - according to the first aspect of the present invention - is thus a process for the nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds), with the formation of the corresponding nitrated aromatic organic compounds (nitroaromatic compounds), wherein the nitrated aromatic organic compounds (aromatic compounds ) are converted in nitration reactions with a nitrating acid mixture of nitric acid and sulfuric acid (that is, the so-called melange) into the corresponding nitrated aromatic organic compounds (nitroaromatic compounds), the method according to the invention being characterized in that the initial reaction mixture, which includes nitrated aromatic organic compounds compounds (aromatic compounds) and a nitrating acid mixture of nitric acid and sulfuric acid, the corresponding nitrated aromatic organic compounds (nitroaro matic compounds) and the reaction and/or nitration reaction is started and/or carried out in the presence of nitrated aromatic organic compounds (nitroaromatic compounds); and/or that the resulting nitrated aromatic organic compounds (nitroaromatic compounds) are partially returned to the nitration reaction, and the subsequent reaction and/or nitration reaction is started and/or carried out in the presence of nitrated aromatic organic compounds (nitroaromatic compounds).

The term corresponding nitrated aromatic organic compounds (nitroaromatic compounds), as used according to the invention, in the context of the present invention includes in particular those nitroaromatic compounds which can be obtained by nitration, preferably mononitration, of the introduced starting aromatic compounds. For example, mononitrobenzene (MNB) is a nitrated aromatic organic compound (nitroaromatic compound) corresponding to benzene, mononitrotoluene (MNT) corresponding to toluene, mononitrochlorobenzene corresponding to chlorobenzene, and so on.

The method according to the invention - as well as the (production) plant according to the invention described in detail later on for carrying out the method according to the invention - is associated with numerous features and advantages, which will now be discussed in detail.

The Applicant has surprisingly found within the framework of the present invention that the addition of a nitrated product to the initial reaction mixture leads to a decrease in the surface tension at the interface between the organic phase, on the one hand, and the acidic aqueous phase, respectively, the acidic phase, on the other hand (and the organic phase includes nitrated aromatic compounds and

- 5 042067 added nitrated products, as well as, if necessary, by-products of nitration, and moreover, the acidic aqueous phase, respectively, the acid phase in the initial reaction mixture, at the beginning of the interaction includes sulfuric acid, and after the addition of nitric acid, nitrating acid, respectively melange, and at the end of the interaction contains the so-called aqueous spent nitrating acid, respectively the so-called aqueous mixture of spent nitrating acid and, if necessary, parts of the nitroaromatic compound added and/or formed during the nitration dissolved in it). Thus, as a result of this, a significantly improved dispersibility and, respectively, emulsification between the organic phase, on the one hand, and the acidic aqueous phase, respectively acid phase, on the other hand, is achieved, that is, the nitrated final product, respectively the nitrated aromatic compound, thus acts in the original reaction mixture as a dispersant (dispersing agent), and accordingly as an emulsifier. In this case, so to speak, we are talking about a system-specific dispersant or emulsifier, respectively inherent in the system, since no substances foreign to the reaction that can contaminate the reaction products are used.

In general, by adding the nitrated product to the initial reaction mixture, improved, in particular internal mixing and dispersion of both phases (i.e. organic phase and acid phase) is achieved, so that in total there is an improved and accelerated exchange between both phases. This also ensures a faster conversion and a correspondingly faster nitration reaction, in particular with improved yields, in particular improved spatio-temporal yields.

Also, in the course of the reaction according to the invention, significantly fewer by-products are formed. In general, the addition of the nitrated product to the initial reaction mixture can better control the conduct of the reaction or the performance of the process and hence the nitration reaction.

In addition to shorter reaction times and faster conversions with improved yields and less formation of by-products, within the framework of the process according to the invention - compared to conventional nitration processes under otherwise equal conditions - the initial temperature for starting or initiating the reaction can also be significantly reduced, that is, within the scope of the method according to the invention, significantly lower (reaction) initial temperatures for the nitration reaction can be used, as explained in more detail below.

In general, therefore, within the scope of the present invention, an improved process, in particular adiabatic nitration, for nitrating aromatic compounds is provided, which is characterized in general by improved efficiency, in particular improved technical efficiency, as well as improved energy efficiency, and generally improved process economics, and also improved manufacturability in circulation.

In particular, within the scope of the present invention, when the nitration reaction is carried out in an adiabatic mode (for example, the adiabatic nitration of benzene to nitrobenzene in a tubular reactor), the dispersion of the nitrated aromatic compound in the nitrating acid mixture can be improved in this way, in particular already at the beginning of the reaction, preferably already after bringing into contact (e.g. mixing) of the starting components, such that even under unfavorable conditions (e.g. such as the presence of contaminants, such as an increased content of aliphatic compounds in the nitrated aromatic compound, or at too low an initial temperature, or with little energy input dispersion) the nitration can still be effectively carried out, in particular the nitration mixture can undergo a conversion of at least 98%, preferably at least 99.5%, in each case during the predetermined reaction time or respectively residence in the reactor e in terms of the degree of conversion of nitric acid in the nitrating acid mixture.

In the context of the nitration process according to the invention, improved dispersion can be achieved already after bringing into contact (e.g. mixing) the reactants, in particular the nitrating acid phase containing nitric acid on the one hand and the organic phase containing nitrating aromatics on the other hand, preferably with preventing rapid coalescence of nitrated aromatic compounds in the nitrating acid, preferably in order to start the nitration reaction at lower initial temperatures, also compared to the prior art (namely, without the need for longer reaction times or residence times than in the prior art process with higher initial temperatures, but other things being equal). In particular, by means of the embodiment of the method according to the invention, it can be achieved that even at (reaction) initial temperatures below 100° C., preferably below 95° C., particularly preferably below 90° C., nitration can be initiated or started in such a way that no will require a longer reaction time or residence time, respectively, than in the method according to the prototype with higher initial temperatures, but other things being otherwise equal conditions.

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Thus, by means of the present invention, nitrated aromatic organic compounds (i.e., aromatic compounds) can be converted and accordingly reacted in a more technically efficient, such as safer and simpler way to form the corresponding nitrated aromatic organic compounds (nitroaromatic compounds).

Thus, within the scope of the present invention, it has surprisingly been found that by admixing a nitrated product (e.g., nitrobenzene in the case of benzene nitration) to the initial reaction mixture, a significantly improved primary dispersion of the nitrating aromatic compound is observed (in particular, characterized by a sharp rise in temperature in the nitrating mixture after initiating nitration primary dispersion) as well as the reduced coalescence tendency of this dispersion.

In other words, the subject matter of the invention is therefore in particular a generally improved, preferably adiabatic process for the preparation of nitroaromatic compounds (such as nitrobenzene, nitrotoluene, nitrochlorobenzene, etc.), preferably by adiabatically reacting the corresponding starting aromatic compounds (such as benzene, toluene, chlorobenzene, etc.) with nitric acid in the presence of sulfuric acid as dewatering agent and catalyst, preferably in a tubular reactor, and preferably using a stoichiometric excess of a nitrated aromatic compound, moreover, to the reaction mixture, respectively the initial reaction mixture, a part of the corresponding nitroaromatic compound is added, respectively admixed (for example, nitrobenzene in the case of benzene nitration).

As described in more detail below, the method according to the invention can be carried out in a quite universal way: thus, a part of the nitroaromatic compound used, respectively admixed (for example, nitrobenzene in the case of benzene nitration), for example, necessary for the nitration of regenerated or fresh sulfuric acid, can be added and /or nitrated aromatic compound, before the primary co-dispersion of additional starting materials (i.e. sulfuric acid and nitric acid), and/or only part of the nitrated aromatic compound before primary co-dispersion of additional starting materials (i.e. sulfuric acid and nitric acid, and the rest parts of the nitrated aromatic compound), etc., and combinations of these options are also possible. In principle, this is determined only by the fact that by the beginning of the nitration reaction there are sufficient amounts of the nitroaromatic compound in the initial reaction mixture to ensure efficient dispersion of the organic and acid phases.

The following describes specific, advantageous or preferred embodiments of the method according to the invention.

As previously described, in the context of the process according to the invention, the conversion and/or the nitration reaction is preferably carried out under adiabatic reaction conditions.

In addition, according to a particular embodiment of the present invention, the conversion and/or the nitration reaction is carried out in particular as a mononitration.

According to a further particular embodiment of the present invention, the operation is usually carried out in such a way that the initial reaction mixture and the nitrated aromatic organic compounds (nitroaromatic compounds) under the selected reaction conditions are in the form of a liquid-liquid mixture of an organic phase on the one hand and an acid phase, in particularly the acidic aqueous phase, on the other hand. In this case, in particular, the organic phase may contain nitrated aromatic organic compounds (aromatic compounds) and nitrated aromatic organic compounds (nitroaromatic compounds), and/or, in particular, the acidic phase (i.e., in particular, the acidic aqueous phase) may include nitric acid, sulfuric acid and, as appropriate, water (as well as, as appropriate, the proportions of the nitroaromatic compound added and/or formed during nitration, dissolved in it).

In the context of the process according to the invention, nitrated aromatic organic compounds (aromatic compounds) and a nitrating acid mixture of nitric acid and sulfuric acid, as well as (added or returned) nitrated aromatic organic compounds (aromatic nitro compounds) form the (initial) nitrating mixture (i.e. initial nitrating mixture , respectively, the nitrating mixture available at the beginning of the interaction and/or nitration reaction); that is, in other words, the nitrating mixture includes the nitrating mixture (that is, the initial nitrating mixture, respectively, the nitrating mixture present at the beginning of the interaction and / or the nitration reaction) in the initial reaction mixture, which includes nitrating aromatic organic compounds (aromatic compounds) and a nitrating acid mixture nitric acid and sulfuric acid, as well as nitrated aromatic organic compounds (aromatic nitro compounds).

In contrast, the nitrating mixture obtained or respectively formed after the reaction and/or at the end of the nitration reaction comprises at least essentially spent nitrating acid and nitrated aromatic organic compounds (aromatic nitro compounds), and

- 7 042067 also, as the case may be, small amounts of unreacted nitrated aromatic organic compounds (aromatic compounds) (along with incidental impurities and by-products).

According to the present invention, in principle almost any nitrated aromatic organic compound (aromatic compound) can be nitrated.

According to a particular embodiment of the present invention, the nitrated aromatic organic compounds (aromatic compounds) under selected reaction conditions may be liquid. In particular, nitrated aromatic organic compounds (aromatic compounds) at standard pressure (1.01325 bar) and at temperatures up to 70°C, in particular below 50°C, preferably below 25°C, particularly preferably below 10°C, are in liquid aggregate state. This allows the reaction to be carried out efficiently.

In particular, the nitrated aromatic organic compounds (aromatic compounds) may be selected, as appropriate, from halogenated mono- or polycyclic aromatic organic compounds.

According to a particular embodiment of the present invention, the nitrated aromatic organic compounds (aromatic compounds) used for nitration can be selected in particular from the group of benzene, mononitrobenzene (MNB), halogenated benzenes, in particular mono and dichlorobenzenes, mononitrated halogenated benzenes, toluene, mononitrotoluene (MNT), dinitrotoluenes (DNT) and xylenes, as well as their mixtures and combinations. Benzene is especially preferred.

According to the present invention, in principle almost any nitrated aromatic organic compound (nitroaromatic compound) can be obtained.

With regard to the resulting nitrated aromatic organic compounds (nitroaromatic compounds), they, in particular, under the selected reaction conditions can be liquid. In particular, nitrated aromatic organic compounds (nitroaromatic compounds) at standard pressure (1.01325 bar) and at temperatures up to 70°C, in particular below 50°C, preferably below 25°C, particularly preferably below 10°C, are in liquid aggregate state. This enables efficient execution of the method.

In particular, the resulting nitrated aromatic organic compounds (nitroaromatic compounds) may be selected, as appropriate, from halogenated mono- or polycyclic mono-, di- or trinitrated aromatic organic compounds.

According to a particular embodiment of the present invention, the resulting nitrated aromatic organic compounds (nitroaromatic compounds) can be selected from the group of mononitrobenzene (MNB), dinitrobenzenes (DNB), halogenated mono- and dinitrobenzenes, in particular mono- and dinitrated mono- and dichlorobenzenes, mononitrotoluenes ( MNT), dinitrotoluenes (DNT), trinitrotoluene, and mono- and dinitrated xylenes, as well as mixtures and combinations thereof. Mononitrobenzene is particularly preferred.

According to one preferred embodiment of the present invention, benzene is used as the nitrated aromatic organic compound (aromatic compound), and mononitrobenzene (MNB) is obtained as the nitrated aromatic organic compound (nitroaromatic compound).

According to a conventional embodiment of the process according to the invention, the nitration reaction and/or reaction can be completed by separating the acidic aqueous phase (acid phase) and/or by separating the phases of the resulting nitrating mixture into spent nitrating acid and crude nitrated aromatic organic compounds (crude nitroaromatic compounds), after which preferably follows the washing of the crude nitrated aromatic organic compounds (crude nitroaromatic compounds) with a washing medium, in particular in one or more washing steps, preferably with a final separation of the used washing medium, to obtain washed and thus freed from impurities (i.e. purified) nitrated aromatics organic compounds (nitroaromatic compounds).

According to a preferred embodiment of the present invention, the washing is carried out in at least two washing stages, whereby at least one acid washing stage (acid washing) and at least one neutral washing stage (neutral washing) can be provided.

Most preferably, the washing may comprise (i) at least one first acidic washing step (acid washing), preferably with water or mineral acid as the washing medium, (ii) at least one second alkaline (basic) washing step. medium, a washing step (basic wash), preferably using a base as the washing medium, and (iii) at least one third, carried out in a neutral medium, a washing step (neutral washing), preferably with water as the washing medium (namely, in the above sequence , respectively, the order from the first to the third washing).

- 8 042067

According to a particular embodiment of the present invention, the used washing medium can be recirculated and/or recycled and/or returned for washing, in particular after cleaning.

Thus, as previously explained in detail, washing of crude nitroaromatic compounds to remove nitrating mixture acids dissolved and suspended in them, nitrophenols, and other acidic and other impurities still extractable by the washing agent usually involves three washing steps (for example, see F. Meissner et al. ., Industrial and Engineering Chemistry, vol. 46, pp. 718-724 (1954), Ullmanns Enzyklopadie der Technischen Chemie, 4th ed., vol. 384-386 H. Hermann et al., Industrial Nitration of Toluene to Dinitrotoluene, Proceedings of the American Chemical Society Symposium (ACS), Series 623 (1996), pages 234-249, editors: L.F. Albright, R.V.C. Carr, R.J. Schmitt; patent documents US 6288289 B1; EP 1816117 B1). Water can usually be used as the washing medium, and the washing is usually carried out as a liquid-liquid washing (ie, at temperatures at which the nitroaromatic compound to be washed is present as a liquid). In addition, according to the present invention, the condensate of the secondary steam from the subsequent concentration of the spent nitrating acid can also be used as the washing medium in the acid washing (washing step (i)), and respectively in the alkaline washing (washing step (ii)).

As outlined above, a three-step wash typically includes the following steps:

(i) acid washing with water to remove dissolved and suspended mineral acids such as, for example, sulfuric acid, nitric acid and nitrose (acid washing);

(ii) basic, respectively alkaline washing in the presence of a base (alkaline washing), for example, using sodium carbonate (soda), sodium bicarbonate, sodium sulfite, sodium hydrosulfite, ammonia, caustic soda, caustic potash, etc. (for example, see patent documents US 4482769 A, US 4597875 A or US 6288289 B1), to remove weakly acid contaminants dissolved in the crude nitroaromatic compound, such as nitrophenols, nitrocresols, nitrobenzoic acids, decomposition products after oxidative cleavage of phenols, or aliphatic or cyclic hydrocarbons, etc., such as, for example, oxalic acid, etc., or asymmetric isomers in the case of TNT (basic wash);

(iii) neutral washing to remove residual traces of alkali and further reduce trace impurities still remaining in the product (neutral washing).

The purpose of these washing steps is to obtain, in particular, in addition to a pure product, as little waste water as possible per tonne of product in which the washed-out contaminants are present, so that they can be removed economically.

According to a particular embodiment of the present invention, it is most preferably provided that the spent nitrating acid remaining after the reaction and/or the nitration reaction, after the separation of the crude nitrated aromatic organic compounds (crude nitroaromatic compounds), is recycled and/or recycled and/or recycled. in the nitration reaction, in particular after concentration and/or after the addition of fresh nitric and/or sulfuric acid. In this way, the efficiency of the method is further increased.

In addition, the amount of nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or nitration reaction can also vary within wide limits.

According to a particular embodiment of the present invention, it can most preferably be provided that the amount of nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or nitration reaction is chosen in such a way that the amount of added and/or returned to the reaction and/or nitration reaction of nitrated aromatic organic compounds (nitroaromatic compounds) provides a reduction in surface tension at the interface between the organic phase and the acid phase, and / or the amount of added and / or returned nitrated aromatic organic compounds (nitroaromatic compounds) leads to improved dispersibility, in particular emulsification, organic phase and acid phase.

Equally, according to again a particular embodiment of the present invention, it can be provided that the amount of nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the interaction and/or nitration reaction is chosen in such a way that the weight amount of added and/or of the returned nitrated aromatic organic compounds (nitroaromatic compounds), based on the nitrated and/or converted nitrated aromatic organic compounds (aromatic compounds), is present or, respectively, varies in the range from 0.01 to 60 wt.%, in particular in the range from 0 1 to 50% by weight, preferably in the range of 5 to 45% by weight, particularly preferably in the range of 10 to 40% by weight.

- 9 042067

Again, according to a further specific embodiment of the present invention, it can be provided that the amount of nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or nitration reaction is chosen in such a way that the weight amount of added and/or returned nitrated aromatic organic compounds compounds (nitroaromatic compounds), based on sulfuric acid in the nitrating acid mixture of nitric acid and sulfuric acid, is a value in the range from 0.01 to 10 wt.%, in particular in the range from 0.2 to 5 wt.%, preferably in the range from 0.5 to 3 wt.%, particularly preferably in the range from 1 to 2 wt.%.

Also in view of the different mode of execution of the method according to the invention, the method according to the invention can be flexibly and almost arbitrarily adapted and adjusted accordingly to the given conditions (eg equipment-related conditions).

Thus, the introduction of nitrated aromatic organic compounds (nitroaromatic compounds) is carried out in a wide variety of technological stages and positions corresponding to the invention of the method. In particular, it can be provided that the nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or the nitration reaction are used and/or introduced in at least one of the following positions (i)-(iv): ( i) to the initial reaction mixture of all other reactants; and/or (ii) to the sulfuric acid of the nitrating acid mixture of nitric acid and sulfuric acid, in particular before obtaining the nitrating acid mixture of nitric acid and sulfuric acid; and/or (iii) a nitrating acid mixture of nitric acid and sulfuric acid; and/or (iv) nitrated nitrated aromatic organic compounds (aromatic compounds). In principle, combinations of two or more of these options can also be taken into account.

In addition, the selection of returned nitrated aromatic organic compounds (nitroaromatic compounds) can be carried out in a wide variety of technological stages and positions corresponding to the invention of the method. In particular, it can be provided that the nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or the nitration reaction come from at least one of the following positions (i) to (iv): (i ) from crude nitrated aromatic organic compounds (crude nitroaromatic compounds), preferably after separation of the acidic aqueous phase (acidic phase) and/or after phase separation of the obtained nitrating mixture into spent nitrating acid and crude nitrated aromatic organic compounds (crude nitroaromatic compounds); and/or (ii) from washed nitrated aromatic organic compounds (nitroaromatic compounds), in particular after acidic and neutral washings; and/or (iii) from washed, in particular obtained after acid and neutral washing, and also subjected to stripping or distillation of nitrated organic compounds (nitroaromatic compounds); and/or (iv) from nitrated aromatic organic compounds (nitroaromatic compounds) separated from the secondary steam condensate after concentrating the spent nitrating acid. In principle, combinations of two or more of these options can also be taken into account here.

According to one particular embodiment of the present invention, it can advantageously be provided that the nitrated organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or the nitration reaction are introduced and/or added both to the organic phase and to the acid phase of the starting material. reaction mixture. In this way, an equilibrium distribution of the added and/or recycled nitrated aromatic organic compounds (nitroaromatic compounds) in the two phases mentioned above (organic phase on the one hand and acid phase on the other hand) is achieved particularly quickly and efficiently. In particular, it can be additionally provided in this embodiment that nitrated aromatic organic compounds (nitroaromatic compounds) are added to the organic phase, based on the organic phase, in an amount of from 0.1 to 35% by weight, in particular from 10 to 25 wt.%, and/or that to the acid phase, based on the acid phase, nitrated aromatic organic compounds (nitroaromatic compounds) are added in an amount of from 0.01 to 3 wt.%, in particular from 0.1 to 2 wt.% , preferably from 0.5 to 1.5 wt.%, particularly preferably from 1.1 to 1.5 wt.%.

According to a particular embodiment of the process according to the invention, the treatment can in particular be carried out in such a way that the spent nitrating acid formed after the reaction and/or the nitration reaction, after separation of the crude nitrated aromatic organic compounds (crude nitroaromatic compounds) and after subsequent concentration and, if necessary, , adding fresh nitric and/or sulfuric acid, is involved in recirculation and/or in the circulation circuit, and/or is again returned to the nitration reaction, and nitrated aromatic organic compounds (nitroaromatic compounds) added and/or returned to the reaction and/or nitration reaction introduced and/or added to concentrated and, as the case may be, supplemented with fresh nitrogen and/or sulfuric

- 10 042067 acids, and/or subjected to nitration nitrated aromatic organic compounds (aromatic compounds). In particular, in this particular embodiment, nitrated aromatic organic compounds (aromatic compounds) are preferably added and/or introduced immediately before the start of the reaction and/or simultaneously with the last reaction component (reactant), preferably immediately before the primary dispersion initiating the reaction and/or nitration reaction. .

Again, according to a further special embodiment of the process according to the invention, the treatment can be carried out in such a way that the spent nitrating acid formed after the reaction and/or the nitration reaction is recycled after separation of the crude nitrated aromatic organic compounds (crude nitroaromatic compounds) and after subsequent concentration and/or or to the circulation loop as recirculating acid and/or recycled back to the nitration reaction, whereby first a dispersion is created from concentrated recirculating acid and nitrated aromatic organic compounds (aromatic compounds) and also nitrated aromatic organic compounds (nitroaromatic compounds), and then to nitric acid is added to the dispersion, in particular, it is dispersed in it, and thus the nitration reaction is initiated. In particular, in this particular embodiment, nitric acid is preferably added and/or introduced immediately before the start of the reaction and/or simultaneously with the last reaction component (reactant), preferably immediately before the primary dispersion initiating the reaction and/or nitration reaction.

As stated above, taking into account the technological regime according to the invention, the method according to the invention can be flexibly and almost arbitrarily adapted and adapted accordingly to given conditions (for example, conditions associated with the equipment). In this regard, the (reaction) initial temperature can also vary within wide limits.

In this case, it can usually be provided that the initial temperature for the reaction and/or the nitration reaction is selected in the range from 70 to 120°C, in particular from 80 to 120°C, preferably from 80 to 110°C, particularly preferably from 85 to 105 °C.

As explained earlier in connection with the advantages and features of the process according to the invention, according to a preferred embodiment of the process according to the invention, it can be provided that the starting temperature for the reaction and/or the nitration reaction is at most 120°C, in particular at most 100°C, preferably not higher than 95°C, particularly preferably not higher than 90°C.

In particular, the execution of the method according to the invention leads to the fact that the nitration reaction, also in comparison with the prototype, can start at lower initial temperatures (namely, without the need for longer reaction times or residence times than in the method according to the prototype with higher initial temperatures, but other things being equal otherwise). In particular, as a result of the execution of the process according to the invention, it can be achieved that even at (reaction) initial temperatures below 100° C., preferably below 95° C., particularly preferably below 90° C., nitration can thus be initiated and accordingly started, without no longer reaction time or residence time is required than in the prior art process with higher initial temperatures, but other things being otherwise equal.

With regard to the nitrating acid mixture of nitric acid and sulfuric acid used according to the invention as nitrating agent, it can in particular be an aqueous nitrating acid mixture of nitric acid and sulfuric acid.

It is usually provided here that the nitrating acid mixture of nitric acid and sulfuric acid used, based on the nitrating acid mixture of nitric acid and sulfuric acid, contains sulfuric acid in quantities of from 60 to 79% by weight, in particular from 62 to 75% by weight. , preferably from 65 to 72 wt.%, and nitric acid in amounts of from 1 to 8 wt.%, in particular from 2 to 6 wt.%, preferably from 3 to 5 wt.%. In this case, a proportion of up to 100% by weight is water.

According to a particular embodiment of the method according to the invention, the treatment can in particular be carried out in such a way that the nitrating acid mixture of nitric acid and sulfuric acid is used in such quantities that the stoichiometric ratio of the nitrated aromatic organic compounds (aromatic compounds) to be nitrated to that present in the nitrating agent used acid mixture of nitric acid and sulfuric acid nitric acid is a value in the range from 1.0 to 1.5, in particular in the range from 1.05 to 1.15.

According to one preferred embodiment of the process according to the invention, the procedure can in particular be such that the nitrating acid mixture of nitric acid and sulfuric acid is used in such quantities that the volumetric phase ratio of the spent nitrating acid to the nitrated organic compounds (nitroaromatic compounds) is in the range from 3:1 to 25:1, in particular in the range from 4:1 to 15:1, preferably in the range from 5:1 to 8:1.

- 11 042067

According to the usual procedure, the method according to the invention and accordingly the reaction and/or the nitration reaction can be carried out in a reactor, in particular in a tubular reactor.

According to one embodiment of the process according to the invention, the sequence of operations can in particular be such that the process and, accordingly, the reaction and/or the nitration reaction is carried out in a reactor, in particular in a tubular reactor, wherein the reaction time and/or residence time of the reaction mixture in the reactor , in particular in a tubular reactor, is selected such that the nitric acid of the nitrating acid mixture of nitric acid and sulfuric acid undergoes a conversion of at least 98%, in particular at least 99%, preferably at least 99.5%.

According to a further embodiment of the process according to the invention, the procedure can in particular be such that the process and, accordingly, the reaction and/or nitration reaction is carried out in a tubular reactor. In this case, the reaction time and/or residence time of the reaction mixture in the tubular reactor can be from 10 to 180 seconds, in particular from 30 to 180 seconds, preferably from 40 to 120 seconds, particularly preferably from 60 to 90 seconds. In addition, in this embodiment, the procedure can be such that the reaction time and/or the residence time of the reaction mixture in the tubular reactor does not exceed 180 s, in particular 120 s. In addition, in this embodiment, the flow rate of the reaction mixture in the tubular reactor is chosen such that plug flow is created (slug flow conditions), in particular without back mixing. In particular, it can be provided in this embodiment that the reaction mixture flows through the tubular reactor under plug flow conditions (plug flow conditions), in particular without back mixing. In particular, the flow velocity of the reaction mixture in the tubular reactor may be from 0.01 to 10 m/s, in particular from 0.1 to 5 m/s, preferably from 0.2 to 3 m/s, particularly preferably from 0. 5 to 2 m/s, even more preferably 0.8 to 1.5 m/s.

According to a particular embodiment of the process according to the invention, the procedure can in particular be such that the process and the corresponding reaction and/or nitration reaction are carried out in a tubular reactor, the tubular reactor being equipped with one or more, preferably multiple, mixing elements (dispersing elements), in particular, to supply additional stirring energy. In this embodiment, the mixing elements can be designed as sheets, in particular baffles or baffles, as diaphragms, as a static mixer or as a flow divider. In particular, it can be provided that a mixing energy of 10 to 1000 J/l, preferably 10 to 500 J/l, particularly preferably 20 to 200 J/l, is supplied by means of the mixing elements. In addition, in particular, it can be provided that the pressure drop per mixing element is from 0.1 bar to 3.0 bar (0.01 to 0.3 MPa), preferably from 0.3 to 1.5 bar (0.03-0.15 MPa), particularly preferably 0.3 to 0.8 bar (0.03-0.08 MPa). In this embodiment, it can preferably be provided that the mixing elements are placed in the tubular reactor in such a way that in the first 10-30 vol.% of the reactor, the degree of conversion of nitric acid in the nitrating acid mixture of nitric acid and sulfuric acid is at least 40%, in in particular at least 50%, preferably at least 60%. In this embodiment, it can also preferably be provided that the mixing elements are placed in the tubular reactor in such a way that the degree of conversion of the nitric acid used at the end of the tubular reactor is at least 98%, preferably at least 99%, particularly preferably 99.5% .

Finally, according to a further special embodiment of the process according to the invention, it can be provided that the process and the reaction and/or the nitration reaction take place in a reactor, in particular a tubular reactor, where a dispersing device, preferably a mixer, is placed upstream of the reactor, in particular the tubular reactor. , in particular, to create a dispersion or emulsion, in particular, the initial reaction mixture or nitrating mixture. In this embodiment, the dispersing device, in particular the mixer, is made in the form of a tank with a stirrer, a jet mixer (Jet-Mixer) or a pump, in particular a vane centrifugal pump. In this case, according to the particular configuration of this embodiment, the dispersing device, in particular the mixing device, can be in the form of a pump, in particular a vane centrifugal pump. However, according to another particular configuration of this embodiment, the dispersing device, in particular the mixing device, can be in the form of a jet mixer (Jet-Mixer); in particular, in this case, the jet mixer can preferably create a central working jet and a medium surrounding the working jet, in particular in the form of an annular jet. In particular, in this embodiment, it can be provided that the dispersing device, in particular the mixing device, is located before the reactor, in particular the tubular reactor, preferably immediately before it, and the dispersing device passes into the reactor, or, in particular, the dispersing device built into the reactor and/or is an integral part of the reactor.

- 12 042067

In a particularly preferred embodiment, the process according to the invention is carried out as follows, the process being described by way of example for the nitration of benzene to nitrobenzene. However, the method according to the invention can also be applied to all other aromatic compounds which are difficult to disperse in sulfuric acid and, accordingly, nitrating acid (such as toluene, xylenes, chlorobenzenes, etc.).

The fundamental process for the adiabatic nitration of benzene to nitrobenzene and the reactor used for this are described, for example, in EP 1272268 A2, EP 1291078 A2 and EP 2168942 A1.

In general terms, in adiabatic nitration, which is also preferably used in the process according to the invention, melange (nitrating acid mixture or nitrating acid), typically, for example, with a sulfuric acid content by weight of from 60 to 79% by weight, in particular from 62 to 75 wt.%, preferably 65 to 72 wt.%, and with a weight content of nitric acid of 1 to 8 wt.%, preferably 2 to 6 wt.%, particularly preferably 3 to 5 wt.%, miscible with nitrated benzene, preferably in a stoichiometric ratio of benzene to nitric acid from 1.0 to 1.5, preferably from 1.05 to 1.15, in a dispersing device. The phase ratio between the organic phase and the acid phase in the nitrating mixture is controlled by the concentration of nitric acid in the melange used: in the case of melange with 4.5% by weight of nitric acid, with a 10% by weight excess of benzene, a melange/benzene ratio of 16 is obtained, 3. Then at the end of the reaction, the nitrating mixture, in which all the heat of reaction accumulates, is obtained with a spent acid/product ratio of about 10.3. The temperature increase in the nitrating mixture, that is, the difference (AT) between the final and initial temperatures, when nitric acid is converted into a product by more than 99%, is uniquely determined by the phase ratio. If the phase ratio is smaller, for example due to a higher nitric acid content in the melange, the difference (AT) between the end and start temperature is larger, and vice versa.

After mixing the reaction components, the two-phase mixture of organic and acidic phases is dispersed in such a way that nitration begins, for example, in a tubular reactor, which is discernible by a sharp increase in temperature in the nitrating mixture. The initial temperature is obtained as the temperature of the mixture of the individual feed streams, and is shifted for adiabatic nitration, in particular benzene to nitrobenzene, typically in the range from 70 to 120°C, in particular in the range from 80 to 120°C, preferably in the range from 80 up to 110°C, particularly preferably in the range from 85 to 105°C. In particular, the starting temperature for the reaction and/or nitration reaction is at most 120°C, in particular at most 100°C, preferably at most 95°C, particularly preferably at most 90°C.

As a rule, the residence time of the nitrating mixture in the tubular reactor at the end of which at least 98%, preferably over 99% of the nitric acid introduced is converted is from 30 to 180 seconds, preferably not more than 120 seconds, particularly preferably from 60 to 90 With. The flow velocity of the nitrating mixture in the pipe can then be from 0.1 to 5.0 m/s, preferably from 0.2 to 3.0 m/s, particularly preferably from 0.5 to 2.0 m/s, most preferably from 0.8 to 1.5 m/s, thereby creating a so-called plug flow (slug flow conditions) without back mixing in the tubular reactor. By adjusting the hourly output of the product, the values of the content of nitric acid in the melange, the residence time and the flow rate in the tubular reactor, the choice of dimensions of the tubular reactor is uniquely determined.

According to a particular embodiment, the mélange can initially preferably be obtained by combining sulfuric acid and nitric acids. Then, in the second stage, the nitrated aromatic compound is dispersed in this melange. Then the initial temperature is obtained as the temperature of the mixture of individual flows of the initial components. The temperatures of the feed streams are preferably controlled such that the desired initial temperature is reached after mixing.

Apart from the selection of a suitable initial temperature, the control of the temperature difference (AT) between the final and initial temperatures, as well as the final temperature of the nitrating mixture itself, an important condition for the possible complete conversion of nitric acid while maintaining the predetermined residence times is such a dispersion of the nitrated aromatic compound in the melange, that immediately after the purposefully carried out primary dispersion, the nitration is initiated so that the desired temperature rise in the nitrating mixture occurs (which is known from the prototype and familiar to the person skilled in the art). For this purpose, the nitrating aromatic compound can be dispersed in the mélange, for example, through specially shaped nozzles (for example, cf. documents EP 0489211 A1 or EP 0779270 A1), or by means of a jet mixer (for example, cf. patent document EP 0771783 A1), or by using specially formed diaphragms (for example, cf. patent documents EP 1272268 A2 or EP 1291078 A2),

- 13 042067 which are preferably also used for redispersion.

Regardless of the dispersion method used, the primary dispersion of phases in each other, for example benzene in a large excess of melange, results in the most unfavorable surface tensions at the interface between the phases, as a result of which optimal dispersion is difficult.

In addition, energy-generated dispersions of pure nitrated aromatics in mélange tend to coalesce rapidly.

The surface tensions at the interface between the nitroaromatic compound and the aqueous phase (eg, between nitrobenzene and water) are noticeably lower than the surface tensions at the interface between the nitrated aromatic compound (eg, benzene) and water. By adding the nitrated product according to the invention prior to the initial reaction-initiating initial dispersion, the interfacial tensions between the phases are effectively and significantly reduced, whereby improved dispersion is achieved at the onset and the tendency of the initially created dispersion to coalesce is reduced.

For the additional addition of the nitrated product according to the invention to the nitration mixture before the start of the nitration as an additional component along with sulfuric acid, nitric acid and the aromatic compound to be nitrated (e.g. benzene), preferably for adiabatic nitration in a tubular reactor, in particular shortly before the start reaction, that is, before the first primary dispersion initiating nitration, various addition sequences are possible. In particular, the introduction of a returned product can be performed

a) before adding a nitrating aromatic compound (e.g. benzene) and before mixing nitric acid into concentrated and recycled sulfuric acid (circulating acid), and/or

b) before adding the nitrating aromatic compound (e.g. benzene) shortly after admixing the nitric acid to the melange, and/or

c) together with a nitrating aromatic compound, and/or

d) as a partial flow of nitrating emulsion before phase separation into recycle acid or melange, and/or

e) also as a combination of points a) to c), in particular in such a way that part of the introduced nitrated product (eg nitrobenzene) is introduced into the aqueous phase according to a) and/or b), and another part together with the nitrated aromatic compound according to With).

The addition of the nitrated aromatic compound as a second reactive component to the nitrating mixture, along with nitric acid, is preferably carried out in cases a) e), in particular always at the end, preferably shortly before the primary dispersion initiating the transformation.

In addition to these variants, in particular also admixing the nitrating aromatic compound into the nitrating mixture as the last component before the primary dispersion, it is particularly advantageous to introduce nitric acid as the second nitrating agent into the nitrating mixture as the last component before the primary dispersion.

It has turned out to be particularly advantageous that after each addition of the starting material to the concentrated recycle sulfuric acid of the main part of the nitrating mixture, a suitable mixing device (e.g. static mixer, diaphragms, jet mixer, etc.) produces a homogeneous mixing with the recycle acid (in the case of nitric acid ) or pre-dispersion in recycled sulfuric acid (in the case of recycled nitrated product or nitrated aromatic compound) in such a way that only a slight pressure drop occurs in this mixing device.

The product (eg nitrobenzene) introduced into the concentrated recycled acid, into the melange or into the nitrated aromatic compound (eg benzene) can likewise be taken from the various stages of the process, i.e.:

A) in the form of crude nitrobenzene, in particular after phase separation of the nitrating mixture from spent nitrating acid and nitrobenzene, before or after cooling, and preferably before treatment with washing medium (this crude nitrobenzene, in addition to the product, also contains from 2 to 10% benzene, dissolved nitrophenols and traces of sulfuric acid, from about 0.2 to 0.25%, and waste acid in the form of a microemulsion, but not water); and/or

B) in the form of partially purified acid-free nitrobenzene after acid washing (this nitrobenzene from acid washing, in addition to all nitrophenols, still contains all excess benzene, and is saturated with water); and/or

C) as purified nitrobenzene after neutral washing (this nitrobenzene from neutral washing still contains only traces of nitrophenols, from about 2 to 60 ^ppm , and still all excess benzene, and is also saturated with water); and/or

D) in the form of secondary steam separated from the condensate after concentrating the spent ki-

- 14 042067 slots for recirculating acid (this nitrobenzene, about 10-15% of the product, from the condensate after the concentration of the spent acid, to a certain extent does not contain nitrophenols, also contains still small residues of benzene, and is also saturated with water); and/or

E) in the form of a final product, after separation of excess benzene, does not contain water or is saturated with water; and/or

F) in addition, in the form of a partially withdrawn nitrating emulsion before phase separation with subsequent return to the nitration process; and/or

G) combinations A) to F).

It is advantageous to return the still benzene-containing nitrobenzene according to the above positions A) to C), and particularly advantageously the still benzene-containing nitrobenzene after the above positions B) and C), in order to minimize the formation of by-products, especially dinitrobenzene from nitrobenzene, with traces of nitric acid in recycled acid.

When adding the product to the concentrated recycle acid before adding the nitric acid and respectively to the melange, in particular from 0.1 to 5.0 wt.%, preferably from 0.5 to 3.0 wt.%, particularly preferably from 1 .1 to 2.0 wt.% recycle acid.

By diluting nitrated benzene with nitrobenzene so that nitrobenzene is added to the benzene/nitrobenzene mixture in an amount of 0.1 to 50%, preferably 5.0 to 45%, particularly preferably 11 to 40%, an effective reduction in surface tension by the interface between the organic and acid phases.

Both when adding the nitrated product (eg nitrobenzene) directly to the recycle acid, and when adding the product (eg nitrobenzene) to the nitrated aromatic compound, it is useful to predisperse the nitrated product and, accordingly, the mixture of nitrated product and nitrated aromatic compound, and known holding time, the duration of which depends on the quality of the pre-dispersion of the organic phase introduced into the recirculating acid, whereby the equilibrium distribution of the nitrated product between the acid and the organic phase can be controlled, before an optimally modified surface tension at the interface between the two phases containing the nitrated product comes into play.

In order to shorten this holding time before the initial dispersion, it is particularly advantageous to add the nitrated product (eg nitrobenzene) to the recirculating acid or to the melange in such an amount that the solubility limit of the added product in the respective acid is exceeded. Then a mixture of nitrated product and acid already consisting of two phases is formed.

When the nitrated aromatic compound is added to this mixture, the acid-undissolved part of the added nitrated product immediately mixes with the nitrated aromatic compound, so that a mixture of benzene and nitrobenzene as an organic phase is obtained already before the initial dispersion. The two phases, which in each case contain nitrobenzene, thus contribute to the reduction in interfacial tension desired for primary dispersion.

An additional possibility of shortening the residence time in the tubular reactor before primary dispersion, and thereby accelerating the achievement of an approximate equilibrium distribution of the added product between both phases, is that the product (for example, nitrobenzene) is introduced into the recirculating acid both via the acid phase and via the organic phase , namely, in particular in such a way that the acid phase can introduce, for example, from 0.1 to 2.0 wt.%, preferably from 0.5 to 1.5 wt.%, particularly preferably from 1.1 to 1.5 wt.% nitrobenzene, based on the amount of recirculating acid, and/or that the organic phase of nitrated benzene and nitrobenzene can add, for example, from 0.1 to 32 wt.%, preferably from 11.0 to 25 wt. %, nitrobenzene.

In addition to the options of adding the nitrated aromatic compound as the last component before initially dispersing the fully formed nitrating mixture as described above, it is equally useful to first pre-disperse the mixture of recycled acid, nitrated product and nitrated aromatic compound, and then add nitric acid to the nitrating mixture. acid as the last component, namely, in particular, in such a way that, by means of a suitable mixing device, nitric acid is not only uniformly distributed in a fraction of a second in the aqueous phase, and not only does the pre-dispersed nitrating mixture remain contained, but additional dispersion is achieved and the resulting an even larger exchange surface between the dispersed organic phase and the homogeneous acid phase.

The above invention and the process according to the invention are in principle applicable to any adiabatic nitration process known from the prior art, preferably for the adiabatic nitration process in combination with a tubular reactor, in which the nitration starts with pure starting materials, in particular with hardly dispersible aromatic compounds.

- 15 042067 mi (preferably benzene) and with pure melange (an aqueous nitrating acid mixture of nitric acid and sulfuric acid), by supplying mechanical stirring energy, as, for example, described in patent documents EP 0373966 A2, EP 0436443 A2, EP 0489211 A1, EP 0708076 A2, EP 0771783 A1, EP 0779270 A1, EP 1272268 A2, EP 1291078 A2, EP 2168942 A1, EP 2354117 A1 and EP 2473477 A1.

A further object of the present invention - according to the second aspect of the present invention - is a production plant (i.e. nitration plant, respectively plant) for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds) to nitrated products in the form of the corresponding nitrated aromatic organic compounds (nitroaromatic compounds), in particular, a production plant for carrying out the method described so far according to the present invention, the production plant comprising the following blocks and devices:

(a) a nitration unit for nitration, in particular adiabatic nitration, of nitrated aromatic organic compounds (aromatic compounds) to form nitrated products in the form of the corresponding nitrated aromatic organic compounds (nitroaromatic compounds), in particular in one or more reactors for carrying out the nitration reaction, preferably in a tubular reactor;

(b) if necessary, placed in the production line downstream of the nitrating unit, at least one separating device, in particular a cleaning device (separator), in particular for separating the spent nitrating acid from the crude nitrated products;

(c) placed in the production line downstream of the nitrating unit and, if applicable, the separation device present, at least one washing unit for carrying out the washing of the nitrated products with the washing medium, in particular in one or more washing steps;

(d) placed in the production line downstream of the washing unit, a separating device, in particular a cleaning device (separator), for separating the washed nitrated product from the washing medium;

moreover, the production plant also includes at least one return device for partially returning the nitrated product to the nitrating block, in particular to the initial reaction mixture of the nitrating block.

According to a preferred embodiment of the present invention, it is provided that the nitrating unit comprises at least one tubular reactor as a reactor.

In particular, according to a preferred embodiment of the production plant according to the invention, it can be provided that the nitrating unit comprises at least one tubular reactor as a reactor, the tubular reactor being equipped with one or more, preferably multiple, mixing elements (dispersing elements), in particular for supplying additional mixing energy. In this embodiment, the mixing elements can in particular be designed as sheets, in particular baffles or baffles, as diaphragms, as a static mixer or as a flow divider. In addition, in this embodiment, the mixing elements can in particular be configured such that a mixing energy of 10 to 1000 J/l, preferably 10 to 500 J/l, particularly preferably 20 to 200 J/l. In addition, in particular, in this embodiment, it can be provided that in the operating state the pressure drop per mixing element is from 0.1 to 3.0 bar (0.01-0.3 MPa), preferably from 0. 3 to 1.5 bar (0.03-0.15 MPa), particularly preferably 0.3 to 0.8 bar (0.03-0.08 MPa). In addition, according to a particular configuration of this embodiment, it can be provided that the mixing elements are placed in the tubular reactor in such a way that in the first 10-30 vol.% of the reactor, the degree of conversion of nitric acid in the nitrating acid mixture of nitric acid and sulfuric acid is at least 40%, in particular at least 50%, preferably at least 60%. Finally, according to a particular configuration of this embodiment, it can be provided that the mixing elements are placed in the tubular reactor in such a way that the degree of conversion of the nitric acid used at the end of the tubular reactor is at least 98%, preferably at least 99%, particularly preferably 99, 5%.

In addition, according to a special embodiment of the production plant according to the invention, it can be provided that a dispersing device, preferably a mixing device, in particular for creating a dispersion or emulsion, in particular the initial reaction mixture or nitrating mixture.

In this embodiment, the dispersing device, in particular the mixing device, can be made in the form of a tank with a stirrer, a jet mixer (Jet-Mixer) or a pump, in part

- 16 042067 vane centrifugal pump. In this case, according to the particular configuration of this embodiment, the dispersing device, in particular the mixing device, can be in the form of a pump, in particular a vane centrifugal pump. In this case, according to another particular configuration of this embodiment, the dispersing device, in particular the mixing device, can be in the form of a jet mixer (Jet-Mixer), in particular, the jet mixer preferably creates a central working jet and a medium surrounding the working jet, in in particular, in the form of an annular jet. In particular, in this embodiment, it can be provided that the dispersing device, in particular the mixing device, is located before the reactor, in particular the tubular reactor, preferably immediately before it, and, in particular, the dispersing device passes into the reactor or, in particular, the dispersing device is built into the reactor and/or is an integral part of the reactor.

With regard to the washing unit located in the production line downstream of the nitrating unit and, if necessary, the separation device present, this washing unit can usually include at least one dispersing device, in particular at least one mixing device, for bringing into contact and emulsification of the crude nitrated product, on the one hand, and the washing medium, on the other hand, and a tubular reactor located downstream of the dispersing device for introducing the crude nitrated product emulsion formed in the dispersing device, on the one hand, and the washing medium, on the other on the other hand, in particular, wherein the tubular reactor is designed in such a way that during the passage of the emulsion through the tubular reactor it is possible to remove the contaminants originally present in the crude nitrated products and/or that during the passage of the emulsion through the tubular reactor the impurities present in crude nitrated products, contaminants pass into the washing medium and/or are neutralized as a result.

It goes without saying that traditional washing devices (eg mixer-settlement devices, extraction columns, etc.) can also be additionally present.

Typically, a wash unit for carrying out a wash can be formed from at least two wash stages, in particular at least one acid wash and at least one neutral wash.

According to a preferred embodiment, it can in particular be provided that the washing unit (W) for carrying out the washing is formed from at least three washing stages. In particular, the washing comprising at least three washing steps can include: (i) at least one first washing step carried out in an acidic medium (acidic washing), preferably with water or mineral acid as washing medium, (ii) at least at least one second alkaline (basic) wash step (basic wash), preferably using a base wash medium, and (iii) at least one third neutral wash step (neutral wash), preferably with water as a wash medium.

As has been explained so far in connection with the method according to the invention, in view of the execution of the method according to the invention, the method according to the invention can be flexibly and almost arbitrarily adapted to the given conditions (eg equipment-related conditions). Thus, in particular - as described above - the introduction and selection of nitrated aromatic organic compounds (nitroaromatic compounds) can be carried out in a wide variety of technological stages and positions corresponding to the invention of the method. This also finds its embodiment in relation to the production plant according to the invention.

Thus, according to a particular embodiment of the present invention, the return device provided in the production plant according to the invention for partially returning the nitrated product to the nitrating block can in particular be designed and/or arranged in such a way that the partially returned nitrated products are withdrawn from at least one of following positions (i)-(iv) of the product stream: from crude nitrated aromatic organic compounds (crude nitroaromatic compounds), preferably after separation of the acidic aqueous phase (acid phase), and/or after separation of the phases of the obtained nitrating mixture into spent nitrating acid and crude nitrated aromatic organic compounds (crude nitroaromatic compounds); and/or (ii) from washed nitrated aromatic organic compounds (nitroaromatic compounds), in particular after acidic and neutral washings; and/or (iii) from washed, in particular obtained after acid and neutral washing, and also subjected to stripping or distillation of nitrated organic compounds (nitroaromatic compounds); and/or (iv) from nitrated aromatic organic compounds (nitroaromatic compounds) separated from the secondary steam condensate after concentrating the spent nitrating acid. In principle, combinations of two or more of these options can also be taken into account here.

In addition, according to a further special embodiment of the present invention, the return device provided in the production plant according to the invention

- 17 042067 The means for partially returning the nitrated product to the nitrating block can in particular be designed and/or arranged in such a way that the partially returned nitrated products are used and/or added in at least one of the following positions (i)-(iv ) product stream: (i) to the initial reaction mixture of all other reactants; and/or (ii) to the sulfuric acid of the nitrating acid mixture of nitric acid and sulfuric acid, in particular before obtaining the nitrating acid mixture of nitric acid and sulfuric acid; and/or (iii) a nitrating acid mixture of nitric acid and sulfuric acid; and/or (iv) nitrated nitrated aromatic organic compounds (aromatic compounds). In principle, combinations of two or more of these options can also be taken into account.

Finally, according to a further special embodiment of the production plant according to the invention, it can be provided that the production plant also includes at least one recycling device for reuse in the recycling of spent nitrating acid. In this way, the economics of the process and the efficiency of the process can be further improved. In particular, in this particular embodiment, the recycling device may include a device for concentrating the spent nitrating acid and, if necessary, a device for adding fresh nitric and/or sulfuric acids.

With regard to further details regarding the production plant according to the invention, in order to avoid unnecessary repetitions, reference may be made to the above-mentioned embodiments of the method according to the invention, which respectively apply to the production plant according to the invention.

A further subject of the present invention - according to a third aspect of the present invention - is the use of nitrated aromatic organic compounds (nitroaromatic compounds) as a dispersant (dispersing agent), in particular an emulsifier, for nitration, in particular nitration reactions, of the corresponding unnitrated aromatic organic compounds.

On the other hand, a further subject of the present invention according to this aspect of the invention is the use of nitrated aromatic organic compounds (nitroaromatic compounds) to reduce the surface tension at the interface between the organic phase and the acid phase, and/or to improve the dispersibility of the organic phase and the acid phase during nitration, in in particular in nitration reactions corresponding to unnitrated aromatic organic compounds.

Finally, again, a further subject of the present invention according to this aspect of the invention is the use of nitrated aromatic organic compounds (nitroaromatic compounds) to increase yields and/or to reduce the formation of by-products and/or to reduce overall reaction times and/or to reduce initial reaction temperatures during nitration, in particular in the nitration reactions of the corresponding unnitrated aromatic organic compounds.

Within the context of the applications according to the invention, the overall procedure can be such that the nitrated aromatic organic compounds (aromatic compounds) are converted in a preferably adiabatic nitration reaction under the action of a nitrating acid mixture of nitric acid and sulfuric acid into the corresponding nitrated aromatic organic compounds (nitroaromatic compounds );

moreover, the corresponding nitrated aromatic organic compounds (nitroaromatic compounds) are introduced into the initial reaction mixture, which includes nitrated aromatic organic compounds (aromatic compounds) and a nitrating acid mixture of nitric acid and sulfuric acid, and the conversion and/or nitration reaction begins and/or is carried out in the presence of nitrated aromatic organic compounds (nitroaromatic compounds); and/or wherein the resulting nitrated aromatic organic compounds (nitroaromatic compounds) are partially returned to the nitration reaction, and the subsequent conversion and/or nitration reaction is started and/or carried out in the presence of nitrated aromatic organic compounds (nitroaromatic compounds).

With regard to further details regarding the applications according to the invention, in order to avoid unnecessary repetitions, reference may be made to the above-mentioned embodiments of the process according to the invention and the production plant according to the invention, which respectively apply to the applications according to the invention.

Additional advantages, properties, aspects and features of the present invention will follow from the following description of the drawings shown in FIGS. 1, 2a-d and 3, preferred embodiments according to the invention.

As shown:

fig. 1 is a schematic representation of the method according to the invention and the production plant according to the invention according to the preferred

- 18 042067 embodiment of the present invention;

fig. 2a-d are schematic representations of various embodiments of the method according to the invention and, accordingly, of the production plant according to the invention according to additional preferred embodiments of the present invention (Fig. 2b, c) in comparison with the prototype (Fig. 2a);

fig. 3 again represents a further schematic representation of the method according to the invention and the production plant according to the invention according to a preferred embodiment of the present invention, according to again a further preferred embodiment of the present invention.

Fig. 1 shows a schematic representation of one embodiment of the process according to the invention for various ways of returning the product to the nitrating mixture, using the example of the nitration of benzene to nitrobenzene, while in FIG. 2b-d schematically represent the most important of the various possible additions and sequences of addition of various starting materials using the example of the nitration of benzene to nitrobenzene.

As shown in FIG. 1, in the dosing and premixing unit PM of the tubular reactor TR, which is directly connected to this tubular reactor, into concentrated recirculating sulfuric acid 3, which is fed through a suitable pump P (for example, a centrifugal pump) at a certain inlet pressure P1 (at least equal to the sum of all values of the pressure drop in the tubular reactor, including the final pressure P2) into the PM dosing and premixing unit, the initial nitric acid 1, benzene 2 and the returned nitrobenzene 9, 12, 13, 14 and 15 are introduced in a predetermined and, accordingly, defined sequence . The nitric acid dissolves completely and homogeneously in the recirculating acid. The benzene 2 and the returned nitrobenzene 9, 12, 13, 14 or 15 form a two-phase initial nitrating mixture 4 with the recycle acid (sulfuric acid)/nitric acid (=mélange) and are pre-dispersed. The temperature in this nitrating mixture 4 of melange, benzene and nitrobenzene is obtained as the temperature of the mixture (i.e. starting temperature) from the temperatures of the individual feed streams (1, 2, 3 and/or 9, 12, 13, 14, 15) and is selected in the range from 80 to 120°C, so that after the initial dispersion in the FD disperser, nitration begins. The initial substances pre-mixed in the PM dosing and pre-mixing unit are then dispersed in each other in such a way that a sufficiently large exchange surface (phase boundary) is formed between the organic and acid phases, thereby nitration is initiated and accordingly begins or starts, which can be detected by the largest sharp increase in temperature in the nitrating mixture 4 after the dispersing device FD. By means of the additional dispersing elements RD1 and RD _n distributed in the tubular reactor TR, the coalescence caused by the reduction of the interface between the organic and acidic phases is counteracted during the passage of the nitrating mixture through the tubular reactor TR. At the outlet of the tubular reactor, a nitrating mixture 5 (now a mixture of spent acid and product) is obtained with a final temperature typically in the range of 120 to 145° C., and with a pressure P2 in the phase separator S. The pressure P2 is selected in such a way that flash evaporation of highly volatile components in the nitrating mixture 5 is reliably prevented, especially in crude nitrobenzene (a mixture of aliphatic compounds, benzene and nitrobenzene in the case of nitration of benzene to nitrobenzene), in the phase separator.

In addition, as shown in FIG. 1, after phase separation in the phase separation device S, the partial stream 13 of crude nitrobenzene, which, in addition to sulfuric acid, dissolved and in the form of a microemulsion, also contains all contaminants (for example, such as unreacted benzene, nitrophenols, etc.) , before or after cooling, can be returned to nitration through the PM dosing and premixing unit. The bulk of the crude nitrobenzene 6 in the W-water wash (with or without added bases) is purified from all acidic compounds (eg, mineral acids, nitrophenols, etc.) in one to three washing steps. The partial stream 14 of this mixture 7 of nitrobenzene and benzene withdrawn from the one or more washing washing steps is preferably returned to the nitration. The main amount of the mixture 7 of nitrobenzene and benzene, which is freed from all mineral acids and nitrophenols to trace levels, can then, for example, be purified from unreacted benzene 10 and highly volatile aliphatic impurities by distillation or stripping in a DS purification unit. The isolated benzene 10, after separation of excess aliphatic compounds, is returned to nitration. The fully purified nitrobenzene 8 can also be diverted to a partial stream 9 to be returned to the nitration.

Finally, as shown in FIG. 1, from the waste acid 11 separated in the device S for phase separation at a temperature of 120 to 145°C (for example, by flash evaporation in the evaporator AR), the water formed during nitration and contained in nitric acid and nitrobenzene dissolved up to the solubility limit are completely removed, as well as traces of other volatile components (such as benzene, nitric acid, aliphatic compounds, etc.). Secondary steam condensate formed during the flash evaporation of spent acid, which is a mixture of water and pure

- 19 042067 nitrobenzene 12 (which makes up about 10 to 15% of the total nitrobenzene formed) is usually combined with the crude nitrobenzene 6 from the phase separator S and subjected to further processing. According to the method according to the invention, this pure nitrobenzene 12 from the vapor condensate can also be completely returned to the nitration after phase separation.

In addition, the nitrobenzene from the nitration can be returned to the nitration circulation loop in such a way that a partial stream 15 of the nitrating mixture 5 is returned before phase separation.

An additional but not shown variant of the method according to the invention is that the nitrobenzene is returned from the waste water treatment step, for example from the waste water stripping.

With respect to those shown in FIG. 2a-d images are given, in particular, the following explanations.

In FIG. 2a shows for comparison corresponding to the prototype the usual sequence of admixing to the recirculating sulfuric acid of the starting components, nitric acid and benzene. First, nitric acid 1 is added to recirculating acid 3 and homogeneously mixed with recirculating acid 3. Nitratable benzene 2 is mixed into the resulting melange (stream 3 + 1), and the resulting initial nitrating mixture 4 or the initial reaction mixture (melange / benzene) is dispersed in the dispersing unit FD with each other so that a sufficiently large exchange surface (phase boundary) arises, thereby starting nitration, distinguishable by the largest sharp rise in temperature in the initial nitrating mixture 4 after the dispersing device FD.

In FIG. 2b the addition of starting nitric acid 1, benzene 2 and nitrobenzene from various sources 9, 12, 13, 14 or 15 to the recycled sulfuric acid is carried out according to the invention, namely in sequence first nitrobenzene from sources 9, 12, 13, 14 or 15, then nitric acid 1, and finally benzene 2. Before adding nitric acid, nitrobenzene can be pre-dispersed in recycled sulfuric acid 3. Nitric acid is mixed as quickly as possible homogeneously, and after adding benzene to the melange/nitrobenzene mixture, the initial nitrating mixture 4 is is dispersed in the dispersing device FD, which creates a sufficiently large exchange surface (interface), thereby starting nitration, which can be distinguished by the largest sharp rise in temperature in the initial nitrating mixture 4 after the dispersing device FD.

In FIG. 2c the addition of feed nitric acid 1, benzene 2 and nitrobenzene from various sources 9, 12, 13, 14 or 15 to recirculating sulfuric acid 3 is done in sequence first nitrobenzene from sources 9, 12, 13, 14 or 15, nitric acid 1, and finally, benzene 2, which is a mixture of benzene and nitrobenzene from sources 9, 12, 13, 14, or 15. Nitrobenzene may be pre-dispersed in recirculating sulfuric acid 3 before adding nitric acid to recirculating acid 3. Nitric acid as quickly as possible , is mixed uniformly, and after adding benzene to the mixture of benzene/nitrobenzene to the mixture of melange (nitrating acid) and nitrobenzene, the initial nitrating mixture 4 is so dispersed in the dispersing device FD that a sufficiently large exchange surface (phase boundary) is created, thereby starting nitration, which can be distinguished by the largest sharp rise in temperature in the initial nitrating mixture 4 after disp pulling device FD.

Finally, in FIG. 2d addition of starting materials, i.e. nitric acid 1, benzene 2 and nitrobenzene from various sources 9, 12, 13, 14 or 15, to recirculating sulfuric acid 3 is carried out in the following sequence: addition of nitrobenzene from sources 9, 12, 13 to recirculating acid , 14 or 15, then benzene 2 itself and/or as a mixture with nitrobenzene, or in separate streams from sources 9, 12, 13, 14 or 15. The nitrobenzene/benzene mixture is pre-dispersed in recycled acid before adding nitric acid. Finally, nitric acid is added and mixed as quickly as possible homogeneously. This initial nitrating mixture is dispersed in the dispersing device FD in such a way that a sufficiently large exchange surface (interface) is created, thereby starting and accordingly starting nitration, which can be distinguished by the largest sharp rise in temperature in the initial nitrating mixture 4 after the dispersing device FD.

Fig. 3 shows a further schematic representation of the method according to the invention and the production plant according to the invention according to the present invention in accordance with a particular embodiment of the present invention: according to FIG. 3, in the nitrating block N, nitration is first carried out, in particular under adiabatic conditions, of nitrated aromatic organic starting compounds (aromatic compounds) to the corresponding nitrated aromatic organic compounds (nitroaromatic compounds), according to the reaction mixture described so far (i.e., starting reaction mixture from nitrated aromatic compounds and a nitrating acid mixture of nitric acid and sulfuric acid, as well as the addition of an appropriate nitrated product). In the production line downstream of the nitrating unit N there is a separating device S, in particular

- 20 042067 cleaning device (separator) for separating spent nitrating acid and, accordingly, a mixture of spent nitrating acid, from nitrated crude products. In the production line, downstream of the nitrating unit N and the separating device S, there is a washing device W for carrying out washing of the nitrated crude product as described above, so that subsequently (after separating the washing medium and, if necessary, drying the washed nitrated product), washed and purified nitrated NP products.

The plant according to the invention and the operating mode according to FIG. 3 differ as described above in that a return device R is additionally provided for partially returning the nitrated product to the initial reaction mixture, which makes it possible to perform the process according to the invention as described above. In this case, the return device according to the invention is designed in such a way that the nitrated product is withdrawn from the most diverse areas of the production plant according to the invention and, accordingly, from the most diverse areas of the process according to the invention, and can be returned, as described in detail before (for example, in the form of a two-phase nitrating mixture directly after nitration and/or also as nitrated crude product after separation of spent nitrating acid, and/or before washing, from washing or after washing, in particular after acidic or after neutral washing, and/or as pure nitrobenzene from the spent nitrating acid concentration step acid in an RA recycle unit, or as a purified and optionally dried nitrated end product, combinations of these possibilities being possible).

The partial return of the nitrated product to the initial reaction mixture is associated with the advantages described in detail earlier, in particular, the improvement in the dispersibility of the organic phase and the acid phase, and thereby the improvement of the reaction conditions as a whole (i.e., improved yields, reduced formation of by-products, more low start temperatures, improved energy efficiency, improved processability, etc.).

As shown in FIG. 3 and already explained above, according to a further specific embodiment of the production plant according to the invention, it can be provided that the production plant also includes at least one recycling device RA for recycling the spent nitrating acid. In particular, as previously explained, in this particular embodiment, the recycling device RA includes a device for concentrating the spent nitrating acid and, if necessary, a device for adding fresh nitric and/or sulfuric acids.

Therefore, in general, within the framework of the present invention, an improved process for the nitration of nitrated aromatic organic compounds (aromatic compounds), as well as a (production) installation according to the invention for carrying out this process, are presented, which are characterized in general by improved efficiency, in particular improved technical efficiency, and also improved energy efficiency, and generally improved process economics, and also improved manufacturability.

Additional embodiments, alterations, variations, modifications, or the like of the present invention may be readily apparent and feasible to those skilled in the reading of the description, without departing from the scope of the present invention.

The present invention is clearly illustrated by means of the following embodiments, however, without limiting the present invention to them.

Implementation examples

Example 1. Comparative example.

In a tubular reactor with an internal volume of 231 ml, which is equipped with 17 mixing elements (a combination of static mixing elements and diaphragms) at uneven distances from each other, 762 g/h of benzene (10% excess) and 15.4 kg/h melange with 65.73% sulfuric acid and 4.99% nitric acid. The primary dispersion benzene is introduced into the reactor through a nozzle at an internal pressure of about 9 bar (0.9 MPa). With an 80 second residence time of the nitrating mixture (with a spent acid/product phase ratio of 11.7 by weight and 9.6 by volume, respectively) in the reactor, the flow rate of the nitrating mixture is 0.42 m/s. The temperature in the reactor after the fifth mixing element after the primary dispersion is 98°C, and at the end of the reactor 121°C. The residual content of nitric acid in the spent nitrating acid is 1200 ^ppm (corresponding to the degree of conversion of nitric acid 97%). The temperature rise in the nitrating mixture is 41°C. The crude nitrobenzene contains - along with an excess of added benzene - less than 120 ^ppm dinitrobenzene (DNB) and less than 1200 ^ppm nitrophenols, with a very small proportion of picric acid.

Example 2 (according to the invention).

A mixture of 762 g/h benzene (10% excess) and 190.5 g/h recycled from nitration formed is dosed into a tubular reactor as described in example 1 at an initial temperature of 80° C.

- 21 042067 nitrobenzene (correspondingly 25% of the input benzene), as well as 15.4 kg / h of melange with a sulfuric acid content of 65.73% and nitric acid 4.99%. The benzene/nitrobenzene primary dispersion mixture is introduced into the reactor through a nozzle at an internal pressure of about 9 bar (0.9 MPa). With a 78 second residence time of the nitrating mixture (with a spent acid/product phase ratio of 10.2 by weight and respectively 8.0 by volume) in the reactor, the flow rate of the nitrating mixture is 0.43 m/s. The temperature in the reactor after the fifth mixing element after the primary dispersion is 102°C, and at the end of the reactor 122.1°C. The residual content of nitric acid in the spent nitrating acid is less than 200 ^ppm (corresponding to a degree of conversion of nitric acid of 99.5%). The temperature rise in the nitrating mixture is 42.1°C. The crude nitrobenzene contains, along with an excess of added benzene, about 80 ^ppm dinitrobenzene (DNB) and less than 900 ^ppm nitrophenols, with a very small proportion of picric acid.

Example 3 (according to the invention).

A mixture of 15.4 kg/h of melange containing 65.73% sulfuric acid and 4.99% nitric acid, as well as 190.5 g/ h returned from the nitrobenzene formed during nitration (respectively 1.31% melange), and 762 g/h benzene (10% excess), and nitrobenzene is pre-dispersed in melange before adding benzene. The primary dispersion benzene is introduced into the reactor through a nozzle into a mixture of melange and nitrobenzene at an internal pressure of about 9 bar (0.9 MPa). With a 78 second residence time of the nitrating mixture with a spent acid/product phase ratio of 10.2 by weight and 8.0 by volume, respectively, the nitrating mixture flow rate in the reactor is 0.43 m/s. The temperature in the reactor after the fifth mixing element after the primary dispersion is 102°C, and at the end of the reactor 122.1°C. The residual content of nitric acid in the spent nitrating acid is less than 200 ^ppm (corresponding to a degree of conversion of nitric acid of 99.5%). The temperature rise in the nitrating mixture is 42.1°C. The crude nitrobenzene contains, along with an excess of added benzene, about 80 to 90 ^ppm dinitrobenzene (DNB) and less than 900 ^ppm nitrophenols, with a very small proportion of picric acid.

Example 4 (according to the invention).

A mixture of 15.4 kg/h of melange containing 65.73% sulfuric acid and 4.99% nitric acid, and 160 g/h of nitrobenzene ( respectively 1.1% recycled acid), as well as a mixture of 762 g/h of benzene (10% excess) and 76 g/h of nitrobenzene (respectively 10% of dosed benzene), the nitrobenzene being pre-dispersed in the mélange before the benzene is added. The benzene/nitrobenzene primary dispersion mixture is introduced into the reactor through a nozzle into the mélange/nitrobenzene mixture at an internal pressure of about 9 bar (0.9 MPa). With a 78 second residence time of the nitrating mixture with a spent acid/product phase ratio of 10.2 by weight and respectively 8.0 by volume, the nitrating mixture flow rate in the reactor is 0.43 m/s. The temperature in the reactor after the fifth mixing element after the primary dispersion is 102°C, and at the end of the reactor 122.1°C. The residual content of nitric acid in the spent nitrating acid is less than 200 ^ppm (corresponding to a degree of conversion of nitric acid of 99.5%). The temperature rise in the nitrating mixture is 42.1°C. The crude nitrobenzene contains, along with an excess of added benzene, from about 80 ^ppm dinitrobenzene (DNB) and less than 900 ^ppm nitrophenols, with a very small proportion of picric acid.

Claims (4)

CLAIM 1. The method of adiabatic nitration of nitrated aromatic organic compounds with the formation of the corresponding nitrated aromatic organic compounds, wherein the nitrated aromatic organic compounds are converted in nitration reactions with a nitrating acid mixture of nitric acid and sulfuric acid into the corresponding nitrated aromatic organic compounds, to the initial reaction mixture, which includes: (i) nitrating aromatic organic compounds; and (ii) a nitrating acid mixture of nitric acid and sulfuric acid, the corresponding nitrated aromatic organic compounds are added, and the nitration reaction is started and carried out in the presence of nitrated aromatic organic compounds; and the resulting nitrated aromatic organic compounds are partially returned to the nitration reaction, and the subsequent nitration reaction is started and carried out in the presence of nitrated aromatic organic compounds; the nitration reaction is carried out under adiabatic reaction conditions; the nitration reaction is carried out in a tubular reactor, and the amount of nitrated aromatic organic compounds added to the nitration reaction is chosen so that the weight amount of nitrated aromatic organic compounds added to the nitration reaction, based on sulfuric acid of the nitrating acid mixture, is nitrogen - 22 042067 noic acid and sulfuric acid, is a value in the range from 0.2 to 10 wt.%; the spent nitrating acid formed after the nitration reaction, after separation of the crude nitrated aromatic organic compounds and after subsequent concentration and addition of at least one of fresh nitric acid and sulfuric acid, is reused and again returned to the nitration reaction, in which the nitrated aromatic organic compounds added for the nitration reaction have origin from at least one of the following positions (i)-(iv): (i) from crude nitrated aromatic organic compounds after separation of the acidic aqueous phase (acid phase) of the resulting nitrating mixture, (ii) from washed nitrated aromatic organic compounds, (iii) from washed, stripped or distilled or dried nitrated aromatic organic compounds compounds, (iv) from nitrated aromatic organic compounds separated from the secondary steam condensate after concentration of spent nitrating acid, wherein the nitrating acid mixture of nitric acid and sulfuric acid is used in such quantities that the stoichiometric ratio of nitrated aromatic organic compounds subjected to nitration to that present in the nitrating acid used a mixture of nitric acid and sulfuric acid nitric acid is a value in the range from 1.05 to 1.15; the nitrating acid mixture of nitric acid and sulfuric acid is used in such quantities that the volumetric phase ratio of the spent nitrating acid to nitrated organic compounds is in the range from 3:1 to 25:1, the residence time of the reaction mixture in the tubular reactor is chosen in such a way that nitric the acid of the nitrating acid mixture of nitric acid and sulfuric acid undergoes a conversion of at least 99%, while the residence time of the reaction mixture in the tubular reactor is from 10 to 180 s, the tubular reactor is equipped with numerous mixing elements to supply additional stirring energy, and the pressure drop in calculation per mixing element is from 0.1 to 3.0 bar. 2. The method according to claim 1, wherein the nitrated aromatic organic compounds added for the nitration reaction are added at least one of the following positions (i)-(iv): (i) to the initial reaction mixture of all reactants; (ii) to sulfuric acid of a nitrating acid mixture of nitric acid and sulfuric acid, (iii) to a nitrating acid mixture of nitric acid and sulfuric acid; (iv) nitrated nitrated aromatic organic compounds. 3. The method according to claim 1, in which the nitrated aromatic organic compounds added for the nitration reaction are added to both the organic phase and the acid phase of the initial reaction mixture. 4. The method according to claim 1, in which the nitrated aromatic organic compounds added for the nitration reaction are added to both the organic phase and the acid phase of the initial reaction mixture, and the nitrated aromatic organic compounds are added to the organic phase, based on the organic phase, in 0.1 to 35% by weight, and nitrated aromatic organic compounds are added to the acid phase, based on the acid phase, in an amount of 0.01 to 3% by weight.