DD256129A1 - 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 nitriles by selective heterogeneous catalytic, so-called Ammoxidation (conversion of a methyl group -CH _{3 in a} nitrile group - CN) in the gas phase, of suitable in principle for this purpose, methyl-containing starting compounds such. As benzene and pyridine derivatives, is known per se. Numerous examples have already 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, PN 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 combinations with phosphorus oxide. For example, an unspecified "V2O5 P2O5 catalyst" has been tested for the ammoxidation of toluene to benzonitrile (Chemical Age of India, VoI 28 [1977], 541). U.S. Patent Nos. 4,124,631, 2,711,332 and U.S. Patent Nos. 4,246,231; JP-PS 78.121738 proposes a catalyst of the composition V ₁ P ₁ O ₂ with undefined oxygen content for the preparation of halobenzonitriles from corresponding halotenthenes, which may optionally also contain other transition metals or tin.These vanadium oxide / phosphorus oxide catalysts, however, make it possible as well as the others proposed Metal oxide catalysts do not give good molar yields or space-time yields of the respective target nitriles.

The diversity and the diversity of the oxide catalysts previously proposed for the technical implementation of such ammoxidations results overall from the fact that the aromatic or heteroaromatic starting compounds to be ammoxidized have very different reactivities, for example with respect to 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 ammoxidation reaction specifically requires its adapted different catalytic or operating conditions in order to allow the ammoxidation process to proceed with sufficient effectiveness. Selective oxidation catalysts are generally not group-specific and can therefore only be used 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 and from other, due to the respective, only poorly understood inorganic nature, constitution or structure of the catalysts reasons, it is therefore not possible to one and the same catalyst optionally differently substituted aromatic or heteroaromatic nitriles, each with good molar yield and space-time yield to produce and optionally also different unseparated starting compounds, such as mixtures of isomeric methylaromatics or Methyiheteroaromaten use.

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 nitrites by Ammoxydation, 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 and methyl methacrylates , to vary widely 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 Ammoxydation also in the sense of a reaction separation with different reactivity of Single 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 that substituted or unsubstituted methyl aromatics or Methyiheteroaromaten on a catalyst containing a vanadium diphosphate compound, wherein the vanadium diphosphate compound either before the start of Ammoxydation present or may be formed only during the reaction of a suitable vanadium phosphate precursor and wherein the ammoxidation at a reaction temperature of 350 ⁰ C to 510 ° C, preferably from 380 ⁰ C to 480 ⁰ C, a residence time of 0.5 to 2.5 see, preferably from 0.7 to 1.3 see, optionally, water vapor in the molar ratio of water to ammonia of 1: 1 to 20: 1, preferably in a molar ratio of 2: 1 to 5: 1, is added to the substrate-oxygen-ammonia mixture. Suitable vanadium diphosphates according to the invention are, for example, the oxovanadium (IV) diphosphate (VO) ₂ P ₂ O ₇ , the ammonium oxovanadium (IV) diphosphate (NH ₄ J ₂ (VO) ₃ (P ₂ O ₇ I ₂ and the ammonium vanadium (III) diphosphate NH ₄ VP ₂ O _7. These compounds are useful as catalysts for the process of the invention both when used as pure compounds and when used together with an inert support (eg Al ₂ O ₃ ) or with doping additions of other compounds.

Vanadium diphosphates according to the invention can also form solid-state chemistries during the use of suitable vanadium phosphate precursor phases during the ammoxidation reaction. Suitable Precursorphasen according to the invention are, for example, the oxovanadium (V) monophosphate VOPO ₄ · nH ₂ 0 (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 ) ₂ and the ammonium oxovanadium (IV) diphosphate (NH ₄ I ₂ VOP ₂ O ₇ ).

The diphosphate (NH ₄ ) ₂ (VO) ₃ (P ₂ O ₇ ) ₂ according to the invention is a novel crystalline chemical compound which, in addition to other absorption bands, exhibits characteristic, strong to very strong bands in the infrared spectrum of the following, in cm " ^{1, the} usual error range of zirca + 3cm " ¹ measured wavenumber layers have: 3264,1430 (NH ₄ ⁺ bands), 1178,1087,1055, 944,916 and 744 (P ₂ O ₇ ⁴ bands; 980 (probably VO ²⁺ bands) is also the diphosphate (NH ₄ I ₂ VOP ₂ O ₇ 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 phosphates mentioned above The vanadium phosphate precurosorphases to be used according to the invention having the atomic ratio V: P = 1: 1 are formed under the conditions of ammoxidation with formation of the crystalline ammonium oxovanadium (IV) diphosphate (NH ₄ ) ₂ (VO) ₃ (P ₂ 0 ₇ ) ₂ solid state chemis In the case of precursors with pentavalent vanadium, the latter is reduced 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 I 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 ) ₂ (VO) ₃ (P ₂ O ₇ ) ₂ 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) to be used in accordance with the invention also remains the same. ₂ P ₂ O ₇ stable.

The ammoxidation reaction is carried out on the catalysts used according to the invention in a manner known per se by reacting the substituted or unsubstituted methylaromatics or heteroaromatics with ammonia and oxygen or air, wherein additionally varying amounts of inert gas or water vapor can be added. The necessary amount of ammonia and oxygen may correspond to the stoichiometric amount, but it is also possible to use an excess to increase the NitriISelektivität. 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 ° C results in 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 used or of the catalyst precursor and on the nature of the substrate and on the other reaction conditions.

In general, the contact time between 0.5 and 2.5see, preferably from 0.7 to 1.3sec, to 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 as well as by choosing the appropriate reaction parameters, a change from the synthesis of one substituted nitrile to another is easily possible. 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 alkali metal hydroxide solution and can be recycled; acidic by-products, such as hydrocyanic acid formed by decomposition reactions under certain conditions, are dissolved in the alkali metal hydroxide solution.

The separation of the products generally proves to be simple according to this procedure because a particular advantage of the process according to the invention is that the desired nitriles are formed in high selectivity (by-products in general Tiur formed by some total oxidation). 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 monitor 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 any 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 phosphate 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 adversely affected 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 from the outside by a customary alkali metal nitrate / nitrite salt (melt bath) A mixture of the substrate to be ammoxidized, ammonia, oxygen (in the form of air) and a metered system was introduced 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, VOPO ₄ · 2H ₂ O, prepared, pressed into tablets and produced therefrom grit with a grain size of about 1.2 mm. After initially in a preliminary experiment, the dihydrate grit outside the reactor tube by heating in air to 200 ⁰ C in grit, consisting of the anhydrous a-oxovanadium (V) -phosphate, Ci-VOPO ₄ , was then found that the same dehydration to a-V0P0 _{4 occurs} in the course of the heating of dihydrate grit in the reactor to the ammoxidation reaction temperature, without affecting the catalytic results.

To 30 ml of Ci-VOPO ₄ or VOPO ₄ -2H ₂ O chippings introduced into the reactor, at a reaction temperature of 440 ° C. and a residence time of 1.0 sec, a yield of p-methoxybenzonitrile of 67.6 mol% was 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 62.0 g per liter of catalyst per hour.

Examination of the spent catalyst grain removed from the reactor revealed that it contained the new crystalline ammonium oxovanadium (IV) diphosphate of the formula

(NH ₄ I ₂ (VO) ₃ (P ₂ O ₇ I ₂₎ , which was recognized, among other things, by its characteristic infrared spectrum, ie, the precursor a-V0P0 ₄ present at the beginning of the ammoxidation was reductively converted 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 was fractionated). ν

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

Table 1

Eg substrate toluene molar ratio T yield sales RZA m-methoxytoluene substrate: ⁰ C mol% mol% g / l-h o-methoxytoluene NH ₃ O ₂ = H ₂ O 2 o-Chlortoluen 1: 8: 7: 40 410 90.5 98.0 108.5 3 m-Chlortoluen 1: 8: 7: 44 460 41.5 67.0 40.1 4 p-Chlortoluen 1: 8: 7: 44 440 65.1 85.0 59.5 5 p-bromotoluene 1: 10: 7: 30 454 69.6 87.5 72.4 6 2-picoline 1: 7: 7: 29 475 50.0 79.6 51.6 7 3-picoline 1: 7: 7: 30 468 92.9 96.3 94.3 8th 4-picoline 1: 7: 7: 28 456 90.8 97.6 129.9 9 Mixture of 45% 1: 3: 5: 21 429 61.0 88.9 61.1 10 p-Methoxytoluene and 1: 3: 5: 21 452 82.8 97.5 79.6 11 55% m-methoxytoluene 1: 3: 5: 21 408 91.0 99.8 90.6 12 p-Methoxybenzbnitril m-Wlethoxybenzonitril 1: 8: 7: 44 440 68,1 ^υ 82.7 ³¹ 80.4 p-Methoxytoluenumsatz 18.3 ²¹ 44.8 ⁴⁾ 27.9 1) m-Methoxytoluenumsatz 2) = Reaction temperature 3) RZA: = space-time yield 4) T:

Examples 13 to 22

It was prepared according to the information in J. Solid State Chem. 5 (1972), p 432, the ^ modification of oxovanadium (V) -phosphate, / 3-VOPO ₄ , and this in the form of 30ml grit in the reactor filled. 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 listed in Example 1 was detected in used catalyst grain, that is, the / 3-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) ₂ P ₂ O ₇ , prepared and added in the form of 30 ml of chippings 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 or 1.2 sec to the corresponding nitriles are listed in Table 3. In these two cases, examination of the spent catalyst grain, which was carried out, among other things, by X-ray diffraction, revealed that the diphosphate (VO) ₂ P ₂ O ₇ used remained unchanged after the ammoxidations.

Example 25

By solid-reduction of / 3-VOPO ₄ with boiling ethyl glycol and washing the product with water and acetone and air-drying 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.

p-methoxytoluene molar ratio T yield • Sales -5- 256 129 o-Chlortoluen substrate: ⁰ C mol% mol% Table 2 o-Chlortoluen NH ₃ : O ₂ : H ₂ O RZA Eg substrate m-Chlortoluen 1: 8: 7: 44 439 67.7 87.5 g / l-h p-Chlortoluen 1: 10: 4: 28 475 72.8 85.0 p-bromotoluene 1: 10: 5: 48 482 70.8 82.6 62.1 13 2-picoline 1: 7: 7: 29 460 26.1 46.3 142.7 14 3-picoline 1: 7: 7: 29 450 92.9 96.3 72.4 15 4-picoline 1: 7: 7: 28 441 90.8 98.6 47.8 16 Mixture of 50% 1: 3: 5: 21 432 64.1 90.7 94.3 17 p-chlorotoluene and 50% 1: 3: 5: 21 446 81.1 99.6 189.4 18 m-Chlortoluen 1: 3: 5: 21 379 94.7 98.8 63.0 19 p-chlorobenzonitrile 80.9 20 m-chlorobenzonitrile 1: 7: 7: 30 450 94.5 ¹⁾ 98.9 ³¹ 93.9 21 p-Chlortoluenumsatz 26,6 ²⁾ 47.5 ⁴ⁱ 22 m-Chlortoluenumsatz 51.3 = Reaction temperature 13.5 RZA = space-time yield 1) 2) 3) 4) T =

In used catalyst grain, 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 .5 H ₂ O, and the 30 ml chippings used therefrom, the ammoxidation of p-chlorotoluene at a residence time

made by 1,2sec.

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 formula (NH ₄ I ₂ VOP ₂ O ₇ dargestp!) - This was done by heating a mixture of vanadium (V) oxide, V ₂ O ₅ , and secondary ammonium phosphate, (NH ₄ I ₂ HPO ₄ , with the atomic ratio N: V: P = 12: 1: 6 for two hours at 320 ° C, leaching the heating product with water, and

Wash and dry the remaining crystals.

30 ml of chippings of this diphosphate were introduced into the reactor and the ammoxidation of p-chlorotoluene in a

Dwell time of 1.25sec made.

The results are shown in Table 3.

In this case, examination 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 had been reduced, 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 I 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 available, it was up to this

the ammonium vanadium (III) diphosphate given in Example 27.

Table 3

substratum

molar ratio

substrate:

NH ₃ : O ₂ : H ₂ O

Yield mol%

Sales mol%

RZA g / lh

28, w w ....

T = reaction temperature

RZA = space-time yield

p-Methoxytolüen

p-Chlortoluen

p-Chlortoluen

p-Chlortoluen

p-Chlortoluen

p-Chlortoluen

1: 8: 10: 33

1: 5: 7: 29

1: 7: 7: 36

1: 5: 7: 29

1: 7: 7: 30

1: 7: 7: 29

450 454 477 450 476 465

69.3 93.5 90.5 93.7 94.9 94.3

91.6 98.5 97.3 99.2 98.5 98.0

53.0 96.4 77.4 96.6 88.4 87.2

Claims (3)

-ι- zbö iza invention claim: 1. A process for the preparation of substituted or unsubstituted aromatic and heteroaromatic nitrites by catalytic ammoxidation of pure or mixed methyl aromatic or methyl heteroaromatic, characterized in that these substrates are ammoxidiert on a catalyst containing a vanadium diphosphate compound, wherein the vanadium diphosphate compound either before the beginning of Ammoxidation present or only during the reaction of a suitable vanadium phosphate precursor can be formed solid state chemical, and wherein the ammoxidation at a reaction temperature of 350 ° C to 51O ⁰ C, preferably from 38O ⁰ C to 48O ⁰ C, a residence time of 0.5 to 2.5 seconds, preferably from 0.7 to 1.3 see, and 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. 2. The method according to item 1, characterized in that the catalyst as vanadium diphosphate, the oxovanadium (IV) diphosphate (VO) ₂ P2O ₇ , the ammonium oxovanadium (IV) diphosphate (NH ₄ J ₂ (VO) ₃ (P ₂ O ₇ ) Z and / or the ammonium vanadium (III) diphosphate contains NH ₄ VP ₂ O ₇ , wherein the catalyst may also be composed exclusively, that is without further constituents, of 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 0mitn = 0bis4 , the primary oxovanadium (IV) monophosphate VO (H ₂ P0 ₄ ) ₂ and / or the ammonium oxovanadium (IV) diphosphate (NH ₄ J ₂ VOP ₂ O _{7 is} used.