DD241903A1 - PROCESS FOR PREPARING AROMATIC AND HETEROAROMATIC NITRILES - Google Patents

Abstract

The invention relates to a process for the preparation of substituted or unsubstituted aromatic and heteroaromatic nitriles by ammoxidation of pure or mixed methyl aromatics or methyl heteroaromatics in the presence of a catalyst which according to the invention a vanadium phosphate, such as (NH4) 2 (VO) 3 (P2O7) 2 or (VO) 2P2O7, contains. The ammoxidation is carried out at a temperature of 350C to 510C and a contact time of 0.5 to 2.5 seconds. The nitriles produced are important intermediates for the production of dyes, pesticides, pharmaceuticals and liquid crystal compounds for optoelectronic application.

Description

Field of application of the invention

The invention relates to a process for the preparation of substituted or unsubstituted aromatic and heteroaromatic nitriles by heterogeneously catalyzed ammoxidation. Such nitriles are versatile as organic intermediates, for example for the synthesis of dyes, pesticides, pharmaceuticals and liquid crystal compounds for optoelectronic application.

Characteristic of the known technical solutions

The preparation of substituted, for example, halogen-substituted or unsubstituted aromatic and heteroaromatic nitrites by selective heterogeneous catalytic, so-called Ammoxydation (conversion of a methyl group-CH ₃ in a nitrile group-CN) in the gas phase, of suitable in principle, methyl-containing starting compounds such. As benzene and pyridine derivatives, is known per se. Numerous examples have also been described, including for technical use, using catalysts of different composition (see, for example, in: BW Suvorov, "Oxidative Ammonolysis of Organic Compounds", Verlag Nauka, Alma Ata 1971, PM Rylander, "Catalytic Processes in Organic Conversions ", in Catalysis, Science and Technology, Vol. IV, Akademie-Verlag, Berlin 1983, page 28).

Catalysts for such methyl aromatic and methyl heteroaromatic Ammoxydationen are usually di- and polyfunctional metal oxide systems, which usually contain vanadium together with antimony, arsenic, tin, chromium, titanium, molybdenum, manganese, iron and / or cobalt.

Catalysts have also been proposed for carrying out such ammoxidations in which vanadium oxide was present in combination with phosphorus oxide. For example, an unspecified "V ₂ O ₅ -P ₂ O ₅ catalyst" has been tested for ammoxidation of toluene to benzonitrile (Chemical Age of India, Vol 28 [1977], 541) No. 4,126,631, DE-OS 2711332 and JP-PS 78.121738 propose a catalyst of the composition V ₁ P ₁ O ₂ with undefined oxygen content for the preparation of halobenzonitriles from corresponding halotoluene, which may optionally also contain other transition metals or tin but allow as well as the other proposed metal oxide catalysts no good molar yields ratio space-time yields of the respective target nitriles.

The variety and the diversity of the technical implementation of such Ammoxydationen previously proposed oxidic catalysts results overall in that the known to be ammoxidized aromatic or heteroaromatic starting compounds very different reactivities, including different Oxydationsempfindlichkeiten, z. As with respect to the unselective total oxidation to CO, CO ₂ and H ₂ O, and also from the fact that, as the previous experience shows, the specific nature of the respective substrate Ammoxydationsreaktion specifically adapted their different catalytic or operating conditions requires the Ammoxydationsprozeß to proceed with sufficient effectiveness. Selective oxidation catalysts are generally not group-specific and can therefore be used only for one reaction and technically optimized (MD Mroß in: catalysts, surfactants and mineral oil additives, edited by J. Falbe and U. Hasserodt, G.-Thieme Verlag, Stuttgart 1978, p.64). In accordance

With this general statement, as well as from other, due to the respective inorganic material nature, constitution or structure of the catalysts, reasons, it is therefore not possible to optionally differentially substituted aromatic or heteroaromatic nitriles, each with good molar yield of one and the same catalyst and space-time yield to produce and optionally also use various unseparated starting compounds, such as mixtures of isomeric methylaromatics or methyl heteroaromatics.

Object of the invention

It is therefore an object of the invention to provide a process for the preparation of substituted or unsubstituted aromatic and heteroaromatic nitriles by Ammoxidation, which allows, with high molar yield and high space-time yield of the respective target product, the starting materials, that is differently substituted or unsubstituted methyl aromatic and Methylheteroaromaten, widely vary and thereby optionally as starting materials and unseparated mixtures, for example of otherwise technically difficult to separate substituted meta and para isomers, to use, in the latter case, the ammoxidation in the sense of a reaction separation with different reactivity the individual components in the mixture can be used.

Explanation of the essence of the invention

The invention is therefore based on the object to develop a process for the preparation of aromatic and heteroaromatic nitriles by heterogeneously catalyzed ammoxidation with the aid of a suitable, on the one hand a large variability of the starting materials and target products and on the other hand, high yields ensuring catalyst. The object is achieved in accordance with the invention by ammoxidizing substituted or unsubstituted methylaromatics or methylheteroaromatics on a catalyst containing a vanadium diphosphate compound, where the vanadium diphosphate compound can be present either before the beginning of the ammoxidation or only during the reaction from a suitable vanadium phosphate precursor , and wherein the Ammoxydation at a reaction temperature of 350 ⁰ C to 510 ⁰ C, preferably from 360 ⁰ C to 480 ⁰ C, a residence time of 0.5 to 2.5 see, preferably from 0.7 to 1.3 sea, is performed , As well as the substrate-oxygen-ammonia mixture optionally water vapor in the molar ratio of water to ammonia from 1: 1 to 20: 1, preferably in a molar ratio of 2: 1 to 5: 1, is added. Suitable vanadium diphosphates according to the invention are, for example, the oxovanadium (IV) diphosphate (VO) ₂ PaO ₇ , the ammonium oxovanadium (IV) diphosphate (NH ₄ ) ₂ (VO) ₃ (P ₂ O ₇ ) ₂ and the ammonium vanadium (III) diphosphate NH ₄ VP ₂ O ₇ . These compounds are suitable as catalysts for the process according to the invention both when they are used as pure compounds and when they are used together with an inert carrier (eg Al ₂ Os) or with doping additives of other compounds.

However, vanadium diphosphates according to the invention can also form solid-state chemistries during the use of suitable vanadium phosphate precursor phases during the ammoxydatosis reaction. Suitable Precursorphasen according to the invention are, for example, the oxovanadium (V) monophosphate VOPO4 · nH ₂ O (with η = 0 to 2), the secondary oxovanadium (IV) monophosphate VOHPO ₄ · nH ₂ 0 (with η = 0 to 4), the primary oxovanadium (IV) monophosphate VO (H ₂ PO ₄ J ₂ and the ammonium oxovanadium (IV) diphosphate (NH ₄ J ₂ VOP ₂ O ₇ ).

The diphosphate according to the invention (NH ₄ ) ₂ (VO> 3 (P ₂ O ₇ ) is a new crystalline chemical compound which, in addition to further absorption bands, has characteristic, strong to very strong bands in the following infrared spectrum, in cm ^-1 with the usual error width have measured of about ± 3cm ^"1, wave-number layers: 3264.1430 (NH ₄ ⁺ -bands) 1178.1087, 1055,944,916 and 744 (P ₂ O ₇ ⁴ -bands: 980 (probably VO ²⁺ -band Likewise, the diphosphate (NH ₄ I ₂ VOP ₂ O _{7) is} a new crystalline chemical compound characterized by a tetragonal unit cell with the cell parameters a = 8.299 (2) A and c = 5.764 (2) A, while the other vanadium phosphate above τη compounds known per se to the invention are used according to the vanadium phosphate Precursorphasen with said & iomverhaltnis. V: P = 1: 1 are two conditions of the ammoxidation with formation of the crystalline ammonium oxovsnadium (IV) -diphosphates (NH ₄ J ₂ (VO) ₃ (P ₂ O ₇ J ₂ solid body converted in the case of precursors with pentavalent vanadium latter to the tetravalent oxidation state. Precursor phases to be used according to the invention with the atomic ratio V: P = 1: 2, such as VO (H ₂ PO ₄ J ₂ and (NH ₄ J ₂ VOP ₂ O ₇ , become reductive under the ammoxidation conditions to the crystalline ammonium vanadium (III) diphosphate NH ₄ VP ₂ O ₇ converted.

The diphosphates (NH ₄ J ₂ (VOJs (P ₂ O ₇ ) and NH ₄ VP ₂ O ₇ thus formed do not change any further under the reaction conditions of the ammoxidation, and the diphosphate (VO) ₂ P _{2 to} be used according to the invention also remains the same O ₇ stable.

The Ammoxidation reaction is carried out on the catalysts used in the invention in a conventional manner by reacting the substituted or unsubstituted Hethylaromaten- or heteroaromatic with ammonia and oxygen or air, in addition varying amounts of inert gas or water vapor can be detected. The necessary amount of ammonia and oxygen may correspond to the stoichiometric amount, but it is also possible to apply an excess to increase the nitrile selectivity. Excess ammonia, which is neither consumed in the reaction nor totally oxygenated, can be separated after passing through the reactor and recycled to the reaction. The reaction temperature for optimum reaction control depends on the type of catalyst or catalyst precursor used and on the nature of the substrate and on the other reaction conditions (catalyst loading, residence time, etc.). As a rule, the optimum reaction temperature is between 400 ⁰ C (in some cases even less, as in the case of the ammoxidation of γ-picoline) and at most 510 ⁰ C. Above 520/530 ⁰ C, there is irreversible damage to the used or Vanadium diphosphate catalysts formed from the precursor phases. The optimal contact time (residence time) of the reaction gas mixture also depends on the type of catalyst or catalyst precursor used, as well as on the nature of the substrate and on the other reaction conditions. In the case of rupture, riif is necessary 1 3cor-711 vary

The use of the process according to the invention for the preparation of substituted and unsubstituted aromatic and heteroaromatic nitriles is basically possible in all types of reactors which are suitable for heterogeneously catalyzed gas phase oxidation. Preferably, the process is carried out in a fixed bed tubular reactor. The use of the contact can in this case be such that the vanadium phosphate compound can be used undiluted as a catalyst, diluted with inert material or with other active materials or as a supported catalyst. The contacts themselves can be introduced into the reactor without being diluted or mixed with inert material or with another catalytically active component.

By varying the substrate, the amount of metered air (or oxygen), ammonia and optionally other additives and by choosing the appropriate reaction parameters, a change from the synthesis of one substituted nitrile to another is possible in a simple manner. A more effective separation process is possible, for example, by scrubbing the reaction gases with toluene and caustic. The nitrile compound produced according to the invention dissolves in the toluene phase. Ammonia is driven off by the caustic and can be recycled, acidic by-products, such as hydrogen cyanide formed by decomposition reactions under certain conditions, are dissolved in the caustic.

The separation of the products proves to be generally in accordance with this procedure as simple, because a particular advantage of the method is that the desired nitriles in high selectivity (by-products generally formed only by some total oxidation) arise. Degradation reactions to other nitriles (also to hydrocyanic acid) as well as formation of other organic components (aldehydes, acids) can usually not be detected under optimal reaction conditions.

The reaction to various substituted nitriles (also in a mixture) can be carried out on the same catalyst in a standard apparatus, with substrate change, only the amount of substrate dosage, the amount of reactants (ammonia, air or oxygen, optionally water vapor or inert gases), the temperature control of the reactor and the procedure of the reaction gas scrubber or the cycle of the extractant including the usually distillative separation of product and extractant must be changed.

When changing the feed substrate, it is advisable to carry out intermediate rinsing of the reactor and of the separation system with an inert gas (for example nitrogen) which does not cause an oxidative or reductive change in the catalytic system.

A particular advantage of the process according to the invention is that the ammoxidation reaction on the vanadium diphosphate catalysts can be carried out with great variability of the starting materials to give various target products, at the same time ensuring high molar and space-time yields. The Vanadiumdiphosphatphasen acting as a catalyst are stable under reaction conditions and therefore particularly suitable for industrial use in the context of the task of the invention. The process according to the invention can be extended as desired in the choice of further suitable ammoxidation substrates, without the scope of the process thereby being impaired in any way.

In this sense, the exemplary embodiments show a selection of possibilities of using different catalyst systems according to the invention and the ammoxidation of various substrates or substrate mixtures according to the invention. The choice is arbitrary and can be expanded arbitrarily.

embodiments example 1

For ammoxidation, a fixed bed reactor in the form of a stainless steel tube with an inner diameter of 16 mm was used. The reactor tube was heated externally by a conventional alkali metal nitrate / nitrite molten salt bath. Using a dosing system, a mixture of the substrate to be ammoxidized, ammonia, oxygen (in the form of air) and water vapor was passed through the catalyst precursor bed filled into the tube. The product gas mixture coming from the reactor tube was analyzed for its constituents in the usual way by quantitative gas chromatography and infrared spectrometry.

The substrate used was p-methoxytoluene. The molar ratio of substrate: NH ₃ : O ₂ : H ₂ O was adjusted according to 1: 8: 7: 44. As Katalysatorprecursor was according to the information in Z. Anorg. General Chemie 338 (1965), p.266, Oxovanadium (V) -phosphate dihydrate, VOPO4.2H ₂ O, prepared, pressed into tablets and produced therefrom with a particle size of about 1.2 mm. After first converting the dihydrate grit outside the reactor tube by heating in air to 200 ° C in chippings consisting of the anhydrous a-oxovanadium (V) -phosphate, CI-VOPO4, in a pre-consumption, it was found that the same Dehydration to CI-VOPO4 also occurs in the course of heating dihydrate grit in the reactor to the AmmOxydations reaction temperature, and without affecting the catalytic results.

At a reaction temperature of 440 ° C and a residence time of 1, Osec was injected into the reactor 30ml Ci-VOPO ₄ - relationship VOPO ₄ · 2H ₂ O-chippings, a yield of p-methoxybenzonitrile of 67.7 mol .-% achieved, wherein the conversion of p-methoxytoluene was 89.9%. CO ₂ was formed in an amount of 16 mol% and CO in an amount of 2.2 mol%. The space-time yield of nitrile was 62.0g per liter. Catalyst and hour.

Examination of the spent catalyst beads removed from the reactor revealed that it contained the novel crystalline ammonium oxovanadium (IV) diphosphate of the formula (NH ₄ ) ₂ (VO) 3 <P ₂ O 7) ₂ , which was described, inter alia, by hand of its characteristic infrared spectrum. The precursor a-V0P0 ₄ present at the beginning of the ammoxidation was thus converted into a reduction during the same.

Examples 2 to 12

In a manner analogous to Example 1, nitrile syntheses were carried out by ammoxidation of other, unsubstituted and differently substituted methylaromatics or methylheteroaromatics and also of a mixture of substituted methylaromatics. The analysis of the reaction products was carried out analogously to Example 1. In some cases, the nitriles formed were isolated from a scrubber by extraction with toluene (after distilling off the toluene, the residue

The results obtained at residence times of 1.0 to 1.3 are summarized in Table 1. In all these examples, the conversion of the used a-V0P0 ₄ -Precursors was detected on the used catalyst grain to the cited in Example 1 diphosphate.

Table 1 substratum molar ratio T yield sales RZA Ex. substrate: ⁰ C Mol .-% Mol .-% g / l-h NH ₃ : O ₂ : H ₂ O toluene 1: 8: 7: 40 410 90.5 98.0 108.5 2 m-methyloxy 3 töluen 1: 8: 7: 44 460 41.5 67.0 40.1 o-methoxy 4 toluen 1: 8: 7: 44 440 65.1 85.0 59.5 o-chloro- 5 toluen 1: 10: 7: 30 454 69.6 87.5 72.4 m-chloro- 6 toluen 1: 7: 7: 29 475 50.0 79.6 51.6 p-chloro- 7 toluen 1: 7: 7: 30 468 92.9 96.3 94.3 p-bromo- 8th toluen 1: 7: 7: 28 456 90.8 97.6 129.9 2-picoline 1: 3: 5: 21 429 61.0 88.9 61.1 9 3-picoline 1: 3: 5: 21 452 82.8 97.5 79.6 10 ' 4-picoline 1: 3: 5: 21 408 91.0 99.8 90.6 11 Mixture off 12 45% p-meth oxytoluen 1: 8: 7: 44 440 68, I ¹¹ 82,7 ³⁾ 80.4 and 55% 18.3 ²⁾ 44.8 ⁴⁾ 27.9 m-methoxy toluen 1 p-methoxybenzonitrile 3 p-methoxytoluene conversion 2m-methoxybenzonitrile 4m-methoxytoluene conversion

T = reaction temperature RZA = space-time yield

Examples 13 to 22

It was prepared according to the information in J. Solid State Chem. 5 (1972), p 432, the ß-modification of oxovanadium (V) -phosphate, ß-VOPO ₄ , and this filled in the form of 30ml grit in the reactor , Otherwise, as in Examples 1 to 12, nitrile syntheses were carried out by ammoxidation of various substrates.

The results obtained at residence times of 0.8 to 1.3 sec are summarized in Table 2.

In all these cases, the presence of the diphosphate given in Example 1 was found in spent catalyst

that is, the P-VOPO _{4 used also} acted as a precursor compound. .; - ... .. ·.

Examples 23 and 24

It was according to the instructions in DD-WP 113210 Oxovanadium (IV) diphosphate, (VO> 2P2O7, prepared and added in the form of 30 ml grit in the reactor.

The results of the analogous to the previous examples Ammoxydation of p-Methoxytoluen and p-chlorotoluene at residence times of 0.7 and 1.2 see to the corresponding nitriles are listed in Table 3. In these two cases, examination of the spent catalyst grain, which was carried out by powder-X-ray analysis, revealed that the diphosphate (VO> 2P2O7 used remained unchanged after the ammoxidation.

Example 25

By solid-state reduction of β-VOPO ₄ with boiling Ethyiglycoi and washing the product with water and acetone and drying in air at room temperature, oxovanadium (IV) hydrogen phosphate, VOHPO ₄ , was prepared and added to the reactor in the form of 30 ml chippings , Ammoxidation of p-chlorotoluene with a residence time of 1.1 see gave the results shown in Table 3.

substratum molar ratio T yield - sales • , 98.9 ³¹ 5- 241903 Table 2 substrate: ° c Mol .-% Mol .-% 47.5 ⁴¹ Ex. NH ₃ : O ₂ : H ₂ O RZA p-methoxy- g / l-h toluen 1: 8: 7: 44 439 67.7 87.5 13 o-chloro- toluen 1: 10: 4: 28 475 72.8 85.0 62.1 14 o-chloro- toluen 1: 10: 5: 48 482 70.8 82.6 142.7 15 m-chloro- toluen 1: 7: 7: 29 460 26.1 46.3 72.4 16 p-chloro- toluen 1: 7: 7: 29 450 92.9 96.3 47.8 17 p-bromo- toluen 1: 7: 7: 28 441 90.8 98.6 94.3 18 2-picoline 1: 3: 5: 21 432 64.1 90.7 3-picoline 1: 3: 5: 21 446 81.1 99.6 189.4 19 4-picoline 1: 3: 5: 21 379 94.7 98.8 63.0 20 Mixture off 80.9 21 50% p-chloro- 93.9 22 toluenund 1: 7: 7: 30 450 94.5 ¹¹ 50% m-chloro- 26,6 ²⁾ toluen 51.3 1 p-chlorobenzonitrile 3 p-chlorotoluene conversion 13.5 2 m-chlorobenzonitrile 4 m-chlorotoluene conversion T = reaction temperature RZA = space-time yield

In used catalyst core, the hydrogen phosphate used was no longer present, it was as a conversion product listed in Example 1 diphosphate before.

Example 26

It was according to the information in Inorg. Chem. 23 (1984), p. 1308, the hemihydrate of the oxovanadium (IV) hydrogen phosphate, VOHPO ₄ 0.5H ₂ O, prepared and on 30 ml of chippings used therefrom the ammoxidation of p-chlorotoluenes with a residence time of 1.2 see made.

The results are shown in Table 3.

In used catalyst grain the hemihydrate used was no longer present, it had been converted during the ammoxidation to form the diphosphate given in Example 1.

Example 27

It was the new, tetragonal crystallizing ammonium oxovanadium (IV) diphosphate of the formula (NH ₄ I ₂ VOP ₂ O ₇ represented.

This was done by heating a mixture of VanadiumfVJ-oxide ¹ , V ₂ Os, and secondary ammonium phosphate, (NH ₄ I ₂ HPO ₄ ,, with the atomic ratio N: V: P = 12: 1: 6 for two hours at 32O ⁰ C. Leaching of the heating product with water, and washing and drying of the remaining crystals.

It was filled * 30ml grit of this diphosphate in the reactor and made the ammoxidation of p-chlorotoluene at a residence time of 1.25sec.

The results are shown in Table 3.

In this case, investigation of the used catalyst carried out, inter alia, by means of powder X-ray, revealed that the ammonium oxovanadium (IV) diphosphate used during the ammoxidation completely gave rise to the crystalline ammonium vanadium (III) diphosphate of the formula NH ₄ VP ₂ O ₇ , which is already known (see Izvest, Akad., Nauk, Latv., SSR, Khim., Ser., 1979, p.

Example 28

It was prepared according to the information in Z. Chem. 8 (1968), p 307, the oxovanadium (IV) dihydrogen phosphate VO (H ₂ PO ₄ J ₂ and to 30 ml grit the ammoxidation of p-chlorotoluene at a residence time of 1.1 lake made.

The results are shown in Table 3.

In used catalyst grain, the oxovanadium (IV) dihydrogen phosphate used was no longer present, it was for the listed in Example 27 ammonium vanadium (III) diphosphate before.

Table 3 substratum molar ratio T yield sales RZA Ex. substrate: ⁰ C Mol .- "/. Mol .-% g / l-h NH ₃ : O ₂ : H ₂ O p-methoxy- 23 toluen 1: 8: 10: 33 450 69.3 91.6 53.0 p-chloro- 24 toluen 1: 5: 7: 29 454 93.5 98.5 96.4 p-chloro- 25 toluen 1: 7: 7: 36 477 90.5 97.3 77.4 p-chloro- 26 toluen 1: 5: 7: 29 450 93.7 99.2 96.6 p-chloro- 27 toluen 1: 7: 7: 30 476 94.9 98.5 88.4 p-chloro- 28 toluen 1: 7: 7: 29 465 94.3 98.0 87.2

T = reaction temperature RZA = space-time yield

Claims (3)

Invention claim: 1. A process for the preparation of substituted or unsubstituted aromatic and heteroaromatic nitriles by catalytic ammoxidation of pure or mixed methyl or methyl heteroaromatics, characterized in that these substrates are ammoxidized on a catalyst containing a vanadium diphosphate compound, wherein the vanadium diphosphate compound either before the start the ammoxidation may be present or may only be formed chemically during the reaction from a suitable vanadium phosphate precursor body, and wherein the ammoxidation at a reaction temperature of 350 ° C to 510 ⁰ C, preferably from 380 ⁰ C to 480 ⁰ C, a residence time of 0.5 water to steam in the molar ratio of water to ammonia of 1: 1 to 20: 1, preferably in a molar ratio of 2: 1, to 2.5 sea, preferably from 0.7 to 1.3 sea, is carried out, and the substrate-oxygen-ammonia mixture is added to 5: 1. 2. The method according to item 1, characterized in that the catalyst as vanadium diphosphate, the oxovanadium (IV) diphosphate (VO) ₂ P ₂ O ₇ , the ammonium oxovanadium (IV) diphosphate (NH ₄ I ₂ (VO) ₃ ( PaO ₇ J ₂ and / or the ammonium vanadium (III) diphosphate NH ₄ VP ₂ O ₇ , wherein the catalyst may also be composed exclusively, that is without further constituents, from one of these diphosphates or mixtures thereof. 3. The method according to item 1 and 2, characterized in that as a precursor oxovanadium (V) monophosphate VOPO ₄ nH ₂ O with η = 0 to 2, the secondary oxovanadium (IV) monophosphate VOHPO ₄ · nH ₂ O with η = 0 to 4, the primary oxovanadium (IV) monophosphate VO (H ₂ PO ₄ J ₂ and / or the ammonium oxovanadium flVJ diphosphate (NH ₄ J ₂ VOP ₂ O _{7 is} used.