US3434802A - Apparatus for the staged nitration of aromatic hydrocarbons - Google Patents

Description

March 25, 1969 TOISCHER ETAL 3,434,802

APPARATUS FOR THE STAGED NITRATION 0F AROMATIC HYDROCARBONS Filed Oct. 22, 1965 Sheet 3 of 2 E XTRACTION N I TRATING APPA RATUS APPARA TU S E S Fig.2

NITRAT/NG CONVERTIBLE NITRATING APPA RATU$ES I XTRACTI ON APPARATUS Q I w i STORAGE TAN K I 41 40 43 aroma: 42 /TANKS 44 l INVENTORS Karl Engelbert Ludwig Toischer 8 Horst Sigurd Max Bergmunn BY a? ATTORNEYS United States Patent 3,434,802 APPARATUS FOR THE STAGED NITRATION OF AROMATIC HYDROCARBONS Karl Engelbert Ludwig Toischer and Horst Sigurd Max Bergmann, Cologne-Marienburg, Germany, assignors to Josef Meissner GmbH & Co. KG, Cologne-Bayenthal, Germany Filed Oct. 22, 1965, Ser. No. 502,194 Claims priority, application Germany, Oct. 23, 1964, M 62,855 Int. C]. (3071) 11/00; C07c 79/10 US. Cl. 23-260 Claims ABSTRACT OF THE DISCLOSURE A two stage system for the selective production of either a monoor dinitro-product, including a first stage for converting raw material into a mono nitro product and a second stage having a convertible nitrating-extraction unit, and valved conduit means for connecting the second stage in cascade with the first stage and connecting the convertible unit as a nitrating unit to produce a dinitro product at the output of the second stage or for connecting both stages in parallel and connecting the convertible unit as an extraction unit for causing both stages to produce a mononitro-product.

The present invention relates to nitrating system, and particularly to a two-stage system for nitrating aromatic hydrocarbons.

Systems for producing a dinitro-product are usually multistage systems which are so constructed that the nonnitrated starting material is nitrated in a first stage to form a mononitro-product which is then nitrated in a second stage to form a dinitro-product.

Both nitro-products are commercially salable as such and can then be processed further elsewhere, so that it is desirable to be able to produce both nitro-products in a single system. One way in which this was previously sought to be done was, if only the mononitro-product was to be made in a two-stage system, to disconnect the second nitrating stage and to produce the mononitro-product in the first nitrating stage only. It is true that this made it possible to produce different nitrated products in a multiple-stage system, depending on the particular manufacturing process selected, but the drawback of this was that whenever a mononitro-product was to be produced, a substantial part of the system as a whole remained unused.

It is, therefore, a primary object of the present invention to provide a system which overcomes the abovedescribed drawback.

It is a more specific object of the present invention to provide a two-stage system which is used to full capacity even when the system is used to produce only a mononitro-product.

In accordance with the present invention, this is achieved by providing a system which is primarily composed of a first stage for producing a mononitro-product and a second stage for producing a dinitro-product. The system also includes converter means which are connectable in the second stage for enabling it to produce a mononitro-product. In addition, selectively openable and closeable fluid conveyor lines are connected to the two stages and between the second stage and the supplementary means for permitting the fluid flow pattern through the system to be switched between a first configuration in which the second stage is fed by the output of the first stage, and the supplementary means are disconnected, for producing a dinitro-product at the output from the second Patented Mar. 25, 1969 'ice stage, and a second configuration in which the two stages are connected in parallel, and the supplementary means are operatively connected in the second stage, for producing a mononitro-product in both stages.

In accordance with a further feature of the present invention, a plurality of temporary storage tanks are provided for storing the substances removed from the various apparatuses of the two stages when it is desired to change over from one process to another.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a flow diagram of a two-stage nitrating system according to the present invention.

FIGURE 2 shows the arrangement of the discharge receptacles when a different starting material is to be nitrated in the system.

Referring now to the drawings, and first to FIGURE 1 thereof, there is shown a system according to the present invention which can be used either for producing a dinitro-product or a mononitro-product. The system is composed of a group of supply tanks 30-34 for supplying fluids for use in the process, a first reaction stage, or mono-stage, I having an extraction apparatus 10, nitrating apparatuses 11-12, and separators 14 and 15, and a second reaction stage II, which may be either a monostage or a di-stage, having a convertible nitrating-extraction apparatus 20, nitrating apparatuses 21-22, and separators 24 and 25. The system is also equipped with suitable dosing devices 13 and 130, and selectively openable and closeable conduits 100, 101, 110, 111, 121, 140, 141, -152, 200, 201, 210, 211, 220-224, 241 and 250-253 are provided for conveying fluids to and from the various apparatuses and separators.

As shown in FIGURE 2, the system is also equipped with a plurality of storage tanks 40-44 connected to store the contents of the various apparatuses 10-12 and 20-22 when the system is to be changed over from a pure mononitration to a dinitration, or vice versa, or when a different material is to be nitrated, or when the apparatuses have to be cleaned or repaired.

For purposes of explanation, the system will be described in conjunction with a proces for producing a dinitro-product, namely, dinitrotoluene. The mono-stage I contains three aparatuses 10, 11 and 12, while the distage II likewise contains three ap aratuses 20, 21 and 22, the convertible apparatus 20 acting as a nitrating apparatus for this process. The mono-stage I includes two separators 14 and 15 and the di-stage II two separators 24 and 25. However, the separator 24, which constitutes the converter means for the system, is connected so as to be switched into and out of the system and is provided for the case when the stage II is to be used for the production of a mononitro-product.

Both stages I and II have associated with them tanks 30, 31, 32, 33 and 34 as well as dosing devices 13, 130, whose flow control elements, shown schematically, control the flow of the individual media. The tanks 30, 32 and 33, as well a the dosing devices 13 and 130, come into play for the production of the dinitrotoluene as well as for the production only for the mononitrotoluene, toluene being supplied by tank 30 and acid by tanks 32 and 33. The flow control elements, as well as their conduits, will be described below in conjunction with the operation of the system. The tanks 31, 32 and 34 are provided if the system is to be switched over for the nitrating of benzene, benzene being supplied by tank 31 and acid by tank 32 and 34.

The apparatuses 20, 21 and 22 as well as the lines which lead from the di-stage to the mono-stage are heated when the system is to be used for manufacturing a dinitroproduct. If the starting medium is chlorobenzene, the apparatuses 10, 11 and 12 are also equipped so a to be heated. The heating means themselves are provided with suitable means which make it possible for them to be turned on and off.

The discharge receptacles or tanks 40, 41, 42, 43, 44 shown in FIGURE 2 are generally provided even when the system is to be used for nitrating a single starting material either into a dinitro-product or into a mononitroproduct, in which case the dinitro-product will be transferred, the spent acid of the di-stage, however, then being discharged into the receptacle 40.

All of the tanks 30-34 and 40-44, the apparatuses 12 and 20-22, the dosing devices 13 and 130, and the separators 14, 15, 24 and 25 are constituted by wellknown, commercially available devices and hence will not be described in detail in the present specification.

When toluene is to be nitrated into dinitrotoluene, the units are interconnected as represented by the heavy and light solid lines in FIGURES 1 and 2. Thus, the toluene is passed from tank 30 via the dosing device 13 and the line 100 to the first apparatus 10 of the mononitrating stage I. The second component supplied to the apparatus 10 is constituted by spent or residuary acid which was separated in the separator from the finished mononitro product, this acid reaching the apparatus 10 via a line 151. The spent acid is extracted from the toluene and is delivered, together with the already nitrated toluene, via line 101 to the second separator 14 of this first nitrating stage I.

The spent acid which has been separated out is eliminated via a line 140, while the nitrated toluene is applied to the main nitrating apparatus 11 via a further line 141. This main nitrating apparatus 11 additionally has delivered to it, via a line 111, concentrated nitric acid from tank 33 and, via a further line 251, spent acid which was separated out in the separator 25 of the second nitrating stage. After a suitable time interval, the reaction mixture is delivered via a line 120 to the last nitrating apparatus 12 and from there, via a line 121, to the separator 15. The finished mononitrotoluene is conveyed from this separator 15 via a line 150 to the nitrating stage II and, more particularly, to the first nitrating apparatus 21 thereof, which apparatus also receives, via lines 210 and 211, fresh sulfuric acid and concentrated nitric acid from tank 32 and 33, respectively. From there the mixture i delivered successively via lines 220 and 221, respectively, to the other nitrating apparatuses 22 and 20. The apparatus 22 receives still more fresh acid, via the lines 223 and 224. The mixture passes from the last nitrating apparatus 20, via the line 201, to the separator 25 where the dinitrotoluene and the spent acid are separated from each other. The dinitrotoluene passes via a line 252 to a scrubber 300, the spent acid being delivered, via line 251, to the main nitrating apparatus 11 of the nitrating stage I.

If the system is to be switched over to work with a different starting material, such as benzene for example, then the entire system can be drained, after which the manufacture of dinitrobenzene can start. In order to prevent the loss of the semifinished product and the acids in the system, discharge receptacles are provided for storing these media until the system is once more to produce dinitrotoluene. The variou discharge receptacles are shown in FIGURE 2 to be connected to receive the various media. The contents of the apparatuses 20, 21 and 22 are separated into dinitrotoluene and spent acid, the dinitrotoluene being transferred and sent to the scrubber, whereas the spent acid of all three nitrating apparatuses 20, 21 and 22 is drained into the receptacle 40. It should be noted that each nitrating apparatus does not have to have its own discharge receptacle. Instead, only as many receptacles as necessary have to be provided and utilized to obtain products of the desired quality. Consequently, the contents of the apparatuses 11 and 12 can be collected in a common receptacle 42, while a separate receptacle 41 is provided to receive the contents of the extraction apparatus 10.

If the system is now to be used to produce no dinitrotoluene, but only mononitrotoluene as the final product, only the nitrating stage II has to be drained. The stage I can be separated from stage II by closing suitable ones of the illustrated valves and production in stage I can be continued even while stage II is being drained.

If, however, the system is to be changed over completely, as will be described below, so that the starting material is to differ and a mononitro-product is to be the final product, the entire system has to be drained.

After all of the apparatuses have been drained, the line 150 is closed and the apparatuses .10, .11 and 12 as well as 20, 21 and 22 are filled, as will be described in detail below, the units now being connected as shown by the dot-dash lines and the light solid lines. Thus, benzene is supplied from the tank 31, the benzene flowing, firstly, via the dosing device 13 and the line into the apparatus .10 of stage I, and, secondly, via the dosing device 130 and line 200 into the convertible apparatus 20 of stage II, which now functions as an extraction apparatus. Spent acid is supplied to both of the last-named apparatuses, the apparatus 10 being supplied from the separator 15 via the line 151 and the apparatus 20 being supplied from the separator 24 via the line 241. In these apparatuses the spent acid is extracted by means of the freshly supplied benzene after which it is separated from the benzene in the separators 14 and 25, respectively, and passed on the the lines .140 and 250, respectively. At the same time, nitrated benzene separated in separators 14 and 25 is conveyed to apparatuses 11 and 21, respectively, via lines 141 and 253, respectively.

Concurrently, fresh acid is supplied to the apparatuses 11 and 21, sulfuric acid being supplied from tank 32 via the lines and 210, respectively, and diluted nitric acid being supplied from the tank 34 via lines .111 and 211, respectively. The lines 223 and 224 are closed off.

The mixtures produced in apparatuses 11 and 21 are transferred to apparatuses 12 and 22, respectively, via lines and 220, respectively, where they go through the final process reaction. The outputs from the latter apparatuses flow through lines 121 and 222, respectively, to separators 15 and 24, respectively, where the spent acid is separated from the finished mononitrobenzene. The finished mononitrobenzene is conveyed to scrubber 300 from separators 15 and 24 via line 152 and the spent acid is returned to apparatuses 10 and 20 via lines .151 and 241, respectively.

If the system is now to be switched over once again in order to manufacture dinitrotoluene, the apparatuses 10, 11 and 12 and 20, 21 and 22 are again drained. This time the contents of apparatuses 10 and 20 flow into the receptacle 43 while the contents of the apparatuses .11, 12, 21 and 22 flow into the receptacle 44.

The contents of the receptacles 40, 41 and 42 is once again quickly pumped into the system, via conduits (not shown) connected inputs for the various apparatuses so that the system is rapidly prepared to begin a new production cycle and the necessity of an extended warm-up period is eliminated. If necessary, the system can be flushed after each draining.

If yet a third starting material is to be nitrated in the same system, all that need be done is to provide the lnecessary number of additional discharge receptacles which are connected into the system in the manner described above.

It will thus be seen that, in accordance with the present invention, there is provided a two-stage system in which, for the production of a mono-product, not only the stage intended for the production of the mono-product but also the second nitrating stage is used, even though the second nitrating stage is itself not primarily designed for the production of the mono-product. It has been found, however, as explained above, that relatively simple means suffice to adapt the second stage for the production of the mononitro-product, so that the relatively minor additional costs are more than offset by the fact that there is now obtained a system which has twice the production capacity for a monoproduct than a system in which only the first stage is suitable for the manufacture of the monoproduct.

As described above, this result is, in accordance with the invention, achieved in that the second nitrating stage, this being the so-called di-stage, is equipped with additional parts, which can be switched in and out and which are normally intended solely for the first nitarting stage, the so-called mono-stage. Furthermore, the material to be nitrated and the nitrating acid can be made to flow, selectively, into either of two conduit systems, whose inlets can be selectively opened or closed. One of these systems leads solely to the mono-stage, except for certain bypass lines, and from there to the dinitrating stage. The other system leads both to the mono-stage and the di-stage, and the discharge from the mono-stage to the inlet of the di-stage can be disconnected and connected to lead to the washing device, or scrulbber.

It will also be appreciated that the present invention is applicable to installations which are designed for nitrating but a single aromatic hydrocarbon, for example, toluene, which is to be converted either to mononitrotoluene or dinitrotoluene, or to systems in which one or several hydrocarbons is to be nitrated into a monoand/ or dinitro-product.

If, in such multiple-purpose system, different starting materials are to be nitrated to different extents, the system must, before it is charged with a different starting material, be emptied and, if necessary, flushed, depending on the degree of purity which the end product is to have.

In order to avoid the loss of the intermediate product which is still in the system at the time the system is switched over from one type of operation to the other, there are provided the above-described discharge receptacles for each of the materials to be treated in the system, into which the material can be drained and from which the material can once again be fed to the system after it has again been switched over to operation for the particular material involved. It will be seen from the above that there are as many receptacles or tanks per material as there are different process steps, there being suflicient receptacles to receive materials in substantially different conversion states. Thus, each two-stage system would have one container for each of the stages, there being an additional receptacle for discharging the extraction vessel of the mono-stage. If still other starting materials are to be selectively nitrated in the system, additional discharge receptacles will be provided for these materials, the number of receptacles depending on the number of starting materials to be treated. The provision of these receptacles is particularly significant and useful if not only the starting material is to be changed, but each of the various starting materials is to be subjected to a mononitration as well as to a dinitration.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. For example, while the system described above has been described in conjunction with a process for converting toluene to dinitrotoluene and a process for converting benzene to mononitrobenzene, the operation for converting toluene to mononitrotoluene and the conversion of benzene to dinitrobenzene can be carried out analogously. Similarly, the invention is not limited to these particular hydrocarbons, inasmuch as various other aromatic hydrocarbons, as, for example, chlorobenzene or xylene, can be nitrated. All that is important is that the system be equipped with the supplementary equipment customarily needed for the nitration of the particular hydrocarbon involved, these additional pieces of equipment, which are well known per se to the chemical engineer, being connected into the system in such a manner that they can readily be switched into or out of the system.

What is claimed is:

1. A two-stage system for nitrating different aromatic hydrocarbons, comprising, in combination:

(a) a plurality of supply sources containing different hydrocarbons to be nitrated and reagents for effectuating the nitrations;

(b) dosing means for delivering the required doses of a selected hydrocarbon and selected reagents for nitration;

(c) first valved piping means connected between said sources and said dosing means;

((1) a first processing stage for producing a mononitro product and including an extraction apparatus, a plurality of nitrating apparatuses connected in cascade, and a first separator having an input connected to the output of said extraction apparatus, a first output connected to supply nitrated material to said nitrating apparatuses, and a second output for eliminating spent acid separated in said separator;

(e) a second processing stage including a plurality of nitrating apparatuses connected in cascade, a convertible nitrating-extraction apparatus, and a second separator having an input, a first output connected for delivering separated spent acid to said convertible apparatus, and a second output for delivering nitrated material out of said system;

(f) conduit means connected between said dosing means and said apparatuses of said stages for supplying selected reagents to the first nitrating apparatus in cascade in each said stage;

(g) second valved piping means connected between said apparatuses of said first stage and said apparatuses of said second stage; and

(h) third valved piping means connected in said second stage between said nitrating apparatus and both said convertible apparatus and said second separator thereof:

(i) the valves of said piping means being selectively operable between:

(1) a first condition which operatively connects said dosing means, said apparatuses and said separators in a dinitrating configuration in which: said dosing means supply a selected bydrocarbon only to said extraction apparatus of said first stage and supply selected reagents to the last apparatus in cascade in said second stage; the nitrated material produced in said first stage is delivered to said nitrating apparatuses of said second stage; and the entire output of said nitrating apparatuses of said second stage is delivered to said convertible apparatus, which then functions as a nitrating apparatus whose output contains the desired dinitro product, so that said second separator is effectively disconnected from said system; and

(2) a second condition which operatively connects said dosing means, said apparatuses and said separators in a mononitrating configuration in which: said dosing means supply a selected hydrocarbon to said extraction apparatus of said first stage and to said convertible apparatus of said second stage, said convertible apparatus then functioning as an extraction apparatus; all of the nitrated material produced in said first stage is removed from said system; the entire output of said nitrating apparatuses of said second stage is delivered to said input of said second separator; and the nitrated material contained in the output of said convertible apparatus is delivered to said nitrating apparatuses of said second stage.

2. An arrangement as defined in claim 1 wherein said first stage further comprises a second separator having an input connected to receive the output from said nitrating apparatuses, a first output connected to convey spent acid separated in said second separator to said extraction apparatus, and a second output connected to convey the mononitro product separated in said second separator, and wherein said second valved means are connected to said second output of said second separator for selectively conveying the mononitro product to said second stage when the valves are in said first condition and conveying such product to subsequent treating apparatus when the valves are in said second condition.

3. An arrangement as defined in claim 1 wherein said second stage further comprises a third separator having an input connected to receive the output from said convertible apparatus, a first output connected for the outflow of spent acid separated in said first separator, and a second output connected for the outflow of the nitro product separated in said third separator, and wherein said second and third valved means are connected to said third separator outputs for selectively conveying the spent acid from said first output thereof to said first stage only when the valves are in said first condition and for selectively operatively connecting said second output of said third separator to an input of said two nitrating apparatuses of said second stage only when the valves are in said second condition and to subsequent treating apparatus only when the valves are in said first condition.

4. An arrangement as defined in claim 1 further comprising a plurality of storage receptacles selectively connectable to said first and second stages, with each of said receptacles being connectable for receiving at least one of the fluids present in said stages.

5. An arrangement as defined in claim 4 wherein a first group of said receptacles is selectively connectable for receiving the fluids present in said stages only when a dinitro product was previously being produced and a second group of said receptacles is selectively connectable for receiving the fluids present in said stages only when a mononitro product alone was previously being produced.

References Cited UNITED STATES PATENTS 3,266,872 8/1966 Terao et al. 23266 XR 2,951,746 9/1960 Kouba et al. 23266 2,357,531 9/1944 Mather et a1 23-288 XR JAMES H. TAYMAN, JR., Primary Examiner.

U.S. Cl. X.R.

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