WO2002016031A2

WO2002016031A2 - Catalyst for ammoxidation and method for producing nitrile compound using the catalyst

Info

Publication number: WO2002016031A2
Application number: PCT/JP2001/007155
Authority: WO
Inventors: Yasushi Kuroda; Yoko Ohmori; Katsuyuki Tsuji; Tsutomu Nozawa; Tetsuo Nakajo; Katsuomi Takehira
Original assignee: Showa Denko K. K.
Priority date: 2000-08-21
Filing date: 2001-08-21
Publication date: 2002-02-28
Also published as: AU7879201A; WO2002016031A3

Abstract

An ammoxidation catalyst is provided, characterized in that a crystalline composite oxide containing vanadium and chromium and having a specific powder X-ray diffraction peak pattern is used as the catalyst component in practicing gas phase ammoxidation of an organic compound having an alkyl group. Also provided are a method for producing a nitrile compound using the catalyst and a method for evaluating the performance of a gas phase ammoxidation catalyst using powder X-ray diffraction.

Description

DESCRIPTION

CATALYST FOR AMMOXIDATION AND METHOD FOR PRODUCING NITRILE COMPOUND USING THE CATALYST

Cross Reference to Related Application

This application is based on U.S. Provisional Application No. 60/256,913, filed on December 21, 2000. Technical Field The present invention relates to a catalyst for use in the production of a nitrile compound using so-called gas phase ammoxidation and also relates to a method for producing a nitrile compound using the catalyst. More specifically, the present invention relates to a catalyst for use in the production of a nitrile compound by contacting an organic compound with ammonia and oxygen in gas phase at an elevated temperature in the presence of a catalyst, which ensures the production of an objective product in a higher yield with good efficiency. The present invention also relates to a method for producing a nitrile compound by using the catalyst. The present invention has a great effect on the production of an aromatic nitrile compound, particularly phthalonitriles. Background Art Nitrile compounds are a useful compound as an intermediate of medical or agrochemical preparations, as a starting material of functional resins or as a raw material of dyes and pigments. It is known that the most inexpensive production method therefor is a gas phase ammoxidation method using an organic compound having an alkyl group.

With respect to the catalyst system for use in this reaction, a method using a catalyst system comprising V- Cr has been long known. For example, Japanese Examined Patent Publication (Kokoku) Nos. 35-15689 and 41-19690 have proposed an oxide catalyst system comprising V-Cr supported on alumina. Regarding the V-Cr catalyst system, various improved systems have been proposed thereafter. Examples thereof include a catalyst system comprising V-Cr-B (Japanese Examined Patent Publication No. 45-19284) and a catalyst system comprising V-Cr-P (Japanese Examined Patent Publication No. 50-1264).

The ammoxidation method using such a catalyst system has various problems to be solved for its implementation on a commercial basis, for example, the yield of the product is low, or generation of carbon dioxide or combustion of ammonia occurs due to combustion of an organic compound used as the starting material.

Some of these reports have studied the correlation between the structure of a specific crystalline substance present in the composite metal oxide containing vanadium and chromium as essential components and its catalytic performance. However, depending on the type of the catalysts, some of them are deficient in crystallinity and some of them are mixtures of multiple crystalline substances, and therefore there are many cases in which it is difficult to elucidate the catalytic performance based on the structure of a specific crystalline substance. In general, the catalytic performance depends greatly on the composition or crystal structure thereof. Nevertheless, this has been elucidated for only a very small number of catalyst systems.

Japanese Examined Patent Publication No. 43-27218 has proposed a catalyst system obtained by calcining a precipitate having a V/Cr atomic ratio in the vicinity of 1.5/1, which is produced from ammonium metavanadate and chromium nitrate, at a temperature higher than the exothermic transition point of 500 to 750 °C. In this patent, X-ray diffraction pattern and infrared spectroscopic spectrum are shown. However, the X-ray diffraction pattern reveals that the compound has low crystallinity, and this pattern clearly differs from the peak pattern obtained by powder X-ray diffraction shown in the present invention. Moreover, the crystal structure is not specified. Furthermore, although high performance is attained for the ammoxidation of β- picoline or γ-picoline, the catalytic performance in the production of other aromatic nitrile compounds is insufficient for implementation on a commercial base.

Some papers have made a study of composite oxides of vanadium and chromium and reported on the ammoxidation catalytic performance thereof. For example, in Bull. Chem. Soc. Jpn. , Vol. 41, page 716 (1968), Ito et al. report the results of analysis on catalyst components effective in the ammoxidation reaction of m-xylene. However, the crystal structure was not determined. Furthermore, although a peak pattern by powder X-ray diffraction is shown, as compared with the powder X-ray diffraction peaks shown in the present invention, the number of peaks which can be confirmed is less and the peak intensity ratio greatly differs. In Bull. Chem. Soc . Jpn . , Vol. 51, page 1685 (1978), Takehira et al. report on the analysis of composite oxide catalysts comprising vanadium and chromium, with studies of liquid phase oxidation of cyclohexane using the catalyst. In this report, however, the catalytic capability in gas phase is not studied at all and the crystal structure of a catalyst component is not clarified.

On the other hand, some papers concern the determination of structure of composite oxides comprising vanadium and chromium. For example, in Eur. J. Solid State Inorg. Chem. _r Vol. 32, page 577 (1995), Touboul et al. report a new structure of vanadium-chromium composite oxide, which has not been reported heretofore, and named this crystal structure as "CrV0₄-I". Heretofore, the catalytic performance of the composite oxide having this crystal structure has not been reported at all. As such, with respect to conventionally known V-Cr system catalysts, the crystal structure of a catalyst component effective for the ammoxidation reaction is not clearly known. Since the relationship between the crystal structure and the catalytic performance in the ammoxidation reaction is not clarified, the catalyst is specified only by the preparation method of the catalyst, and this leads to the poor reproducibility of the catalytic performance or deterioration in the catalytic performance due to unknown causes. In view of the yield of objective substance, the catalytic performance is still in need of improvement. If the crystal structure of a compound which can work as an effective catalyst in the objective reaction can be specified, this, it is believed, will have great significance. Disclosure of Invention Accordingly, an object of the present invention is to provide a catalyst for use in producing a nitrile compound by a gas phase ammoxidation, wherein the catalyst ensures high yield and has a long life. Another object of the present invention is to provide a method for producing a nitrile compound using the catalyst. Still another object of the present invention is to provide a method for evaluating the performance of a gas phase ammoxidation catalyst.

As a result of extensive investigations to attain the above-described objects, the present inventors have found that in practicing the gas phase ammoxidation of an organic compound having an alkyl group, if a crystalline composite oxide containing vanadium and chromium and having a specific powder X-ray diffraction peak pattern is used as a catalyst component, the objective nitrile compound can be obtained in a high yield.

It has also been found that this catalyst component has main scattered light peaks on specific Raman shifts, as determined by Raman spectrometry. In other words, a catalyst component having a specific crystal structure is very effective in the gas phase ammoxidation reaction. Based on these findings, the present invention comprising the following matters has been accomplished.

[1] A gas phase ammoxidation catalyst comprising a crystalline composite oxide comprising vanadium and chromium, wherein the pattern of spacings d (A) and relative intensities [shown by % in ( ) ] of said crystalline composite oxide is, as determined by powder X-ray diffraction analysis using Cu-Kαl radiation, within an experiment error, 6.44(25), 3.26(22), 3.21(100), 3.19(35), 3.16(20), 3.02(16), 2.58(11), 2.14(24), 1.71(13) and 1.64(10).

[2] The gas phase ammoxidation catalyst as in [1], wherein as determined by Raman spectrometry, the Raman shift of said crystalline composite oxide has scattered light peaks at 900 to 930 cm^"1, and at 880 to 900 cm^"1 and has no scattered light peak at 940 to 1000 cm^"1.

[3] The gas phase ammoxidation catalyst as in [1], wherein as determined by Raman spectrometry, the Raman shift of said crystalline composite oxide has scattered light peaks at 900 to 930 cm^"1, at 880 to 900 cm^"1 and at 940 to 1,000 cm^"1, and the intensity of the scattered light peak at 940 to 1,000 cm^"1 is lower than those of the scattered light peaks at 900 to 930 cm^"1 and at 880 to 900 cm^"1.

[4] The gas phase ammoxidation catalyst as in [1], wherein the ratio of vanadium to chromium is from 1: 0.7 to 1: 1.5 in terms of atomic ratio.

[5] The gas phase ammoxidation catalyst as in [1], wherein said crystalline composite oxide further comprises one or more elements selected from the group consisting of tungsten, molybdenum, iron, antimony, zirconium, phosphorus, boron, titanium, magnesium, calcium, strontium and barium.

[6] The gas phase ammoxidation catalyst as in [5], wherein said one or more elements is calcium and/or tungsten.

[7] A method for producing a gas phase ammoxidation catalyst comprising a crystalline composite oxide comprising vanadium and chromium, characterized in by performing a calcination of the composite oxide at about 400 to about 650°C while passing a gas containing oxygen. [8] The method for producing a gas phase ammoxidation catalyst as in [7], wherein pH of a solution containing metal components of the catalyst is adjusted with ammonia, amine or a solution thereof, and then evaporated to dryness or supported on a support, followed by drying and calcination. [9] A method for producing a nitrile compound, comprising reacting an organic compound having one or more alkyl groups with ammonia and oxygen in gas phase in the presence of the gas phase ammoxidation catalyst claimed in [1] to [6], thereby converting the alkyl group into a nitrile group.

[10] The method for producing a nitrile compound as in [ 9 ] , wherein the organic compound having one or more alkyl groups is an aromatic compound having one or more alkyl substituents, and the nitrile compound is a corresponding aromatic nitrile compound.

[11] The method for producing a nitrile compound as in [10], wherein the aromatic compound having one or more alkyl substituents is a compound having one or more methyl groups on a benzene ring, and the aromatic nitrile compound is a corresponding compound having one or more nitrile group on the benzene ring.

[12] The method for producing a nitrile compound as in [11], wherein the compound having one or more methyl groups on a benzene ring is toluene, o-xylene, m-xylene or p-xylene, and the compound having one or more nitrile groups on a benzene ring is a corresponding benzonitrile, o-phthalonitrile, isophthalonitrile or terephthalonitrile .

[13] The method for producing a nitrile compound as in [11], wherein the compound having one or more methyl groups on a benzene ring is o-xylene, m-xylene or p- xylene, and the compound having one or more nitrile groups on a benzene ring is a corresponding o- phthalonitrile, isophthalonitrile or terephthalonitrile. [14] The method for producing a nitrile compound as in [11], wherein the compound having one or more methyl groups on a benzene ring is o-xylene, and the compound having one or more nitrile groups on a benzene ring is o- phthalonitrile .

[15] A method for evaluating the performance of a gas phase ammoxidation catalyst using X-ray powder diffraction.

[16] The evaluation method as in [15], further using Raman spectrometry. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows the powder X-ray diffraction pattern of Catalyst 1 obtained in Catalyst Preparation Example 1. Fig. 2 shows the Raman spectrometry chart of Catalyst 1 obtained in Catalyst Preparation Example 1.

Fig. 3 shows the powder X-ray diffraction pattern of Comparative Catalyst 1 obtained in Comparative Catalyst Preparation Example 1.

Fig. 4 shows the Raman spectrometry chart of Comparative Catalyst 1 obtained in Comparative Catalyst Preparation Example 1.

Best Mode for Carrying Out the Invention The present invention is described in detail below. The organic compound having one or more alkyl groups for use in the present invention is a compound containing carbon and hydrogen as essential component elements and having one or more alkyl groups. A compound comprising only carbon and hydrogen may be used but a compound additionally containing elements such as oxygen, nitrogen and halogen may also be used. The organic compound is preferably an olefin or an aromatic compound having one or more alkyl substituents. Examples of the olefin include propylene, isobutene, 2-pentene and 2-hexene. Examples of the aromatic compound having (an) alkyl substituent(s) include compounds having (a) methyl group(s) on the benzene ring, such as toluene, o-xylene, m-xylene, p-xylene, mesitylene, 1,2,3-trimethylbenzene, 1,2,4- trimethylbenzene, 1 ,2, 3 ,4-tetramethylbenzene, 1,2,3,5- tetramethylbenzene, 1,2,4,5-tetramethylbenzene, pentamethylbenzene and hexamethylbenzene, and compounds having (a) methyl group(s) on the naphthalene ring, such as 1-methylnaphthalene, 2-methylnaphthalene, 1,2- dimethylnaphthalene, 2 ,3-dimethylnaphthalene, 1,3- dimethylnaphthalene, 1,4-dimethylnaphthalene, 2,6- dimethylnaphthalene, 1 , 2 ,3-trimethylnaphthalene, 1,6,7- trimethylnaphthalene, 2 , 6 , 7-trimethylnaphthalene, 1,4,5- trimethylnaphthalene, 1 ,4, 6-trimethylnaphthalene, 2,3,5- trimethylnaphthalene, 2,3, 6-trimethylnaphthalene, 1,4,5, 8-tetramethylnaphthalene and 2,3,6,7- tetramethylnaphthalene .

The aromatic compound having one or more alkyl substituent includes compounds having (a) halogen substituent(s) or (an) alkoxy substituent (s) , and examples thereof include monochlorotoluenes, dichlorotoluenes, monochloroxylenes, dichloroxylenes, monobromotoluenes , dibromotoluenes , monobromoxylenes , dibromoxylenes , monomethoxytoluenes , dimethoxytoluenes , monomethoxyxylenes and dimethoxyxylenes . Among these, preferred are toluene, o-xylene, m- xylene and p-xylene, more preferred are o-xylene, m- xylene and p-xylene, and most preferred is o-xylene. The nitrile compound obtained by the production method of the present invention is a compound in which the alkyl group of the above-described organic compound having an alkyl group is converted into a nitrile group.

For example, in the case where the starting material is toluene, benzonitrile is obtained, and when the starting material is o-, - or p-xylene, corresponding o-, m- or p-phthalonitrile is obtained.

For the organic compound having one or more alkyl group used in the present invention, even an industrial grade product which is not a special high-purity product may be used as it is.

The ammonia and oxygen for use in the present invention each may be even an industrial grade product which is not a special high-purity product. The oxygen source is usually air but air increased in its oxygen concentration or on the contrary, air diluted with nitrogen or the like may also be used. The oxygen source is preferably air. The diluting gas may be nitrogen, argon, helium or carbon dioxide. Even water vapor may be used therefor. The diluting gas is preferably general- purpose nitrogen. Water vapor having an effect of suppressing combustion may be added to the reaction system in a slight amount.

The catalyst for use in the present invention is described below.

The catalyst for use in the present invention is characterized by comprising a crystalline composite oxide of vanadium and chromium and having at least an powder X- ray diffraction peak shown in Table 1.

Table 1

1) The d value varies within the error range but the order of peak positions does not change.

2) A value assuming that the peak intensity at d=3.21±0.1 is 100.

The pattern of powder X-ray diffraction peak shown in Table 1 is similar to the pattern of X-ray diffraction peak of the crystal structure named as "CrV0₄-l" by Touboul et al. in Eur. J. Solid State Inorcr. Chem., Vol. 32, page 577 (1995). More specifically, this catalyst component is assigned to a composite oxide of V:Cr (1:1 by atomic ratio) having a monoclinic crystal structure where four (Cr0₄) units form a cluster which is surrounded by (V0₄) units.

It was first found by the present inventors that a composite oxide of vanadium and chromium, having a crystal structure named "CrV0₄-I", is a catalyst component effective for the ammoxidation reaction of an organic compound having an alkyl group.

The catalyst of the present invention is not critical with respect to the ratio between vanadium and chromium. The matter of importance is to have a crystal component having the powder X-ray diffraction pattern shown in Table 1, and other V compounds or Cr compounds may also be mixed thereto. That is, a mixture of "CrV0₄- I" with V₂0₅ or Cr₂0₃ may also be used. Furthermore, a vanadium and chromium composite oxide having a different crystal form may also be contained therein. However, in the process for synthesizing "CrV0₄-I", preferably, at least the ratio of V:Cr charged therein should be set within the range of from 1.0:0.7 to 1.0:1.5. If the composition ratio departs from the above-described range, although it may depend on the synthesis method of "CrV0₄- I", it may be difficult to obtain "CrV0₄-I". The catalyst of the present invention is characterized in that, as determined by Raman spectroscopy, the Raman shift thereof has main scattered light peaks at 900 to 930 cm^"1 and at 880 to 900 cm^"1, and in the range from 940 to 1,000 cm^"1, there is no scattered light peak nor a scattered light peak having an intensity higher than those of the above-described two main scattered light peaks. The chemical background thereof is not clearly known but it is presumed that a metal-oxygen chemical bond in a specific chemical bonding state effectively acts on the objective ammoxidation reaction.

In particular, with respect to the Raman scattering derived from the vanadium-oxygen bond, detailed studies are reported by Hardcastle et al. in J. Phys . Chem. , Vol. 95, page 5031 (1991). Referring to this report, it is presumed that the above-described two main scattered light peaks correspond to the four-coordination type vanadium-oxygen bond in "CrV0₄-I", more specifically, the peak at 900 to 930 cm^"1 corresponds to the bond distance of 1.64 A and the peak at 880 to 900 cm^"1 corresponds to the bond distance of 1.66 A. In many cases, the peak at from 900 to 930 cm^"1 appears most strongly, and the peak at from 880 to 900 cm^"1 appears as the second-strongest. In the range from 940 to 1000 cm^"1, a scattering derived from vanadium-oxygen bonds having different bond orders or different bond distances is observed.

The present inventors have found that if a peak having an intensity higher than that of either of the above-described two main scattered light peaks is present within this range, a sufficiently high catalytic performance is not exhibited. In general, among these two main scattered light peaks, the peak at 880 to 900 cm^"1 has lower intensity, and therefore a peak of higher intensity than this peak should not exist in the range from 940 to 1,000 cm^"1. If a peak of higher intensity is present within this range, an undesirable side reaction such as combustion will be promoted, and thereby the selectivity of objective ammoxidation reaction will be decreased.

Therefore, if there is a peak in the range of 940 - 1000 cm^"1, its intensity should be below 90%, preferably below 50%, more preferably below 30% relative to the peak at 880 - 900 cm^"1. Most preferably, the peak at 940 - 1000 cm^-1 should be a negligible one.

The catalyst of the present invention may comprise only a crystalline composite oxide having the powder X- ray diffraction peak shown in Table 1, but may additionally contain a metal component other than vanadium and chromium. The component added is preferably a metal oxide comprising one or more elements selected from the group consisting of tungsten, molybdenum, iron, antimony, zirconium, phosphorus, boron, titanium, magnesium, calcium, strontium and barium. This metal oxide may be a mixture of single metal oxides or may be a composite oxide. The additive may form a composite oxide with "CrV0₄-I". However, if the formed composite metal oxide shows a pattern clearly different from the powder X-ray diffraction peak pattern shown in Table 1, the catalyst is out of the scope of the present invention. The catalyst of the present invention may be used as a catalyst merely consisting of the above-described crystalline composite oxide and the additional metal component, but may also be used by supporting it on an oxide support. If the latter, examples of the oxide support which can be used include alumina, silica, silica alumina, titania, zirconia and magnesia.

The catalyst of the present invention may be prepared by a method commonly used in this technical field. For example, a method comprising dissolving a compound containing the metal components of the catalyst in a solvent such as water or alcohol, followed by evaporating to dryness (or supporting on a support), and then drying and calcining, may be used. Alternatively, a method comprising suspending a certain component, stirring this suspension in a solution containing other components under heating to react the suspended and the dissolved components, separating these components, followed by evaporating to dryness (or supporting on a support), and then drying and calcining, may be used. Furthermore, a method of co-pulverizing a plurality of powdered metal compounds and then calcining the product may also be used. The starting material of a metal component may be an oxide containing the metal component or a compound in the form of a salt or a complex. Usually, an oxide is used as it is or a compound which can easily be converted into an oxide is used.

Accordingly, as a starting material of vanadium, vanadium pentoxide is used as it is or a vanadium compound which can easily be converted into an oxide. Examples of the vanadium compound which can easily be converted into an oxide include ammonium metavanadate, vanadyl sulfate and vanadium salts of an organic acid such as oxalic acid and tartaric acid. Preferably, vanadium pentoxide is used as it is or vanadyl oxalate obtained by the reaction between ammonium metavanadate and oxalic acid or between vanadium pentoxide and oxalic acid is used.

Examples of the starting material of chromium include chromic acid, chromium nitrate, chromium hydroxide, ammonium chromate, ammonium bichromate and chromium salts of an organic acid such as oxalic acid and tartaric acid. Preferably, chromic acid or chromium nitrate is used as it is or chromium oxalate obtained by the reaction of chromic acid with oxalic acid is used.

Examples of the starting material of tungsten include tungsten oxide, ammonium paratungstate, ammonium metatungstate and complex compounds with oxalic acid, tartaric acid or citric acid.

Examples of the starting material of molybdenum include molybdenum oxide, ammonium molybdate, carbonylmolybdenum and complex compounds with oxalic acid, tartaric acid or citric acid.

Examples of the starting material of iron include iron(II) oxide, iron(III) oxide, iron(II) nitrate, iron(III) nitrate and complex compounds with oxalic acid, tartaric acid or citric acid.

Examples of the starting material of antimony include antimony(III) oxide, antimony(V) oxide and complex compounds with oxalic acid, tartaric acid or citric acid.

Examples of the starting material of zirconium include zirconium oxide, zirconium nitrate, zirconium hydroxide and zirconium acetate.

Examples of the starting material of phosphorus include phosphoric acid and ammonium phosphate.

Examples of the starting material of boron include boric acid. Examples of the starting material of titanium include titanium oxide, tetraethoxytitanium and titanium nitrate.

Examples of the starting material of magnesium include magnesium nitrate, magnesium acetate and magnesium oxalate.

Examples of the starting material of calcium include calcium nitrate, calcium oxalate and calcium acetate.

Examples of the starting material of strontium include strontium nitrate and strontium acetate. Examples of the starting material of barium include barium nitrate, barium oxalate and barium acetate.

Examples of the solvent used in the preparation of the catalyst of the present invention by the method comprising dissolving a compound containing metal components of the catalyst in a solvent, followed by evaporating to dryness (or supporting on a support), and then drying and calcination, include water, alcohol, hydrocarbon halogenide, hydrocarbon, and those containing nitrogen, phosphorus or sulfur. A mixed solvent may also be used. In general, water or alcohol is used and among these, water is most preferred.

Before the solution containing metal components of the catalyst is evaporated to dryness or supported on a support, ammonia, amine or a solution thereof may be added so as to appropriately adjust the pH.

The catalyst of the present invention may be used as a catalyst merely consisting of the above-described crystalline composite oxide and the additional metal component. In the case of preparing the catalyst from a solution, a solution containing the catalyst component is evaporated to dryness and then calcined, thereby obtaining the catalyst component powder. In the case of preparing the catalyst through suspension in a solution, the suspended component is separated by filtration, dried and calcined, thereby obtaining the catalyst component powder. Also, powdered starting materials may be mixed as they are, co-pulverized and then calcined, thereby obtaining the catalyst component powder. The powder obtained is used as it is or may used after molding it. Also, the catalyst may be prepared by mixing a solution containing the catalyst component with a component which can work as a support, such as silica sol, and then spray-drying the solution. In this case, the powdered catalyst obtained by the spray drying is calcined before use.

The catalyst for use in the present invention may be a supported catalyst. For supporting the catalyst component on a support, examples of the method include the following methods. A support is dipped in a solution containing the catalyst component to impregnate the support with the catalyst component, excess liquid content is separated using a net or a filter paper, and then the support impregnated with the catalyst component is dried, whereby the catalyst component is supported on the support. In the case of preparing the catalyst component powder by a method without using a solution, the obtained catalyst component powder and a support can be suspended in a liquid while removing the liquid by distillation, whereby the catalyst component is supported on the support.

The drying is generally performed under heating at 60 to 200°C in air, preferably at 80 to 150°C in air.

The calcination is performed at 300 to 800 °C for a few hours while passing a gas containing oxygen. The calcination temperature is preferably 400 to 650 °C. The gas containing oxygen is not limited but air is preferred. Before the main calcination, preliminary calcination may be performed. A method for producing a nitrile compound using the catalyst prepared by the above-described method is described below.

The molar ratio of oxygen to the organic compound is preferably on the order of 3 to 15 times, and the molar ratio of ammonia to the organic compound is preferably on the order of 2 to 40 times. Use of a gas mixture wherein the content of the starting material organic compound is 0.1 to 5 vol% is preferred because good results can be obtained. Therefore, it is desired to vary the amount of oxygen or ammonia in order to satisfy this condition. The reaction temperature is from 300 to 600°C, preferably from 320 to 580 °C, more preferably from 350 to 550 °C. If the reaction temperature is 600 °C or more, the production of carbon dioxide gas, hydrocyanic acid and the like increases, and the yield of aromatic nitrile decreases. The residence time of the starting material gas mixture on the catalyst is from 0.1 to 25 seconds, preferably from 0.5 to 10 seconds. The reaction may be performed under atmospheric pressure, applied pressure or reduced pressure. However, the reaction is preferably performed in the range from atmospheric pressure to 300 kPa (gauge pressure).

The reaction form is usually a gas phase flow fixed bed or a fluidized bed form. In the fluidized bed form, fine powder of catalyst is generally liable to mix into the product during the process. Therefore, in the case where the mixing of fine powder into the product is undesirable, use of the gas phase flow fixed bed is advantageous . The construction material of the reactor varies depending on the kind of the starting materials or the reaction conditions, but stainless steel or carbon steel is generally used therefor.

When the reaction is performed by a continuous flow system for a long time, the activity of the catalyst slightly reduces and the conversion rate would also decreases. In this case, an effective means for preventing this reduction is to adjust the reaction temperature or the contact time, thereby maintaining the conversion rate. Means for controlling the oxygen amount may also be used. The present invention is described below by referring to Examples. However, the present invention is not limited thereto by any means. Catalyst Preparation Example 1:

To 40.35 g of ammonium metavanadate (NH₄V0₃), 60 ml of water and 91.5 g of oxalic acid dihydrate

( (C00H)₂ ^«2H₂0) were added and dissolved with stirring under heat at 80 to 90 °C. Separately, 34.5 g of chromic acid anhydride (Cr0₃) was dissolved by adding 50 ml of water thereto, and in a bath at 50 to 60 °C, 142.0 g of oxalic acid dihydrate was added by portions and dissolved therein. Thus-obtained vanadyl oxalate solution and the chromium oxalate solution were mixed and stirred in a bath at 50 to 60 °C for 30 minutes. Insofar as observed with the eye, the obtained solution was uniform. From this solution, water was removed by distillation using a rotary evaporator and the residue was placed in a drier at 120 °C and dried. Thereafter, while passing air, the dried product was calcined at 550°C for 8 hours. As such, Catalyst 1 was obtained. The powder X-ray diffraction pattern of Catalyst 1 is shown in Fig. 1. In the measurement by X-ray powder diffraction, the measuring apparatus used was Rigaku Rotary Flex, the X-ray source used was CuKαl, the output was 50 kV-180 mA, the slit was DSl/2°-SSl/2°-RS 0.15 mm, the scan speed was 5°/min and the measured range was from 5 to 90°. The diffraction peaks of Fig. 1 are shown in Table 2. Table 2

1) A value assuming that the peak intensity at d=3.21 is 100. As seen from these results, Catalyst-1 contained

"CrV0₄-I" named by Touboul et al. as the main component.

The chart obtained by the Raman spectrometry of Catalyst 1 is shown in Fig. 2. In the Raman spectrometry, the measuring apparatus used was Model NR- 1800 Laser Raman Spectrophotometer manufactured by Nippon Bunko, the excitation light used was argon ion laser (wavelength: 514.5 nm) , the laser output was 5 mW at the sampling point, the irradiation time was 120 seconds, the integration was performed twice, and the measured range was from 300 to 1,900 cm^"1.

On use for the reaction, the catalyst was pressure- molded, the obtained tablet was crushed and sieved, and that passing through the sieve having an opening between 0.7 and 1.7 mm was used. Catalyst Preparation Example 2:

To 40.35 g of ammonium metavanadate (NH₄V0₃), 300 ml of water was added and dissolved with stirring under heat at 80 to 90 °C. Separately, 200 ml of water was added to 138.0 g of chromium nitrate nonahydrate (Cr (N0₃)₃*9H₂O) and the resulting solution was dissolved. The thus- obtained solution containing vanadium and solution containing chromium were mixed, and while measuring the pH by a pH meter, aqueous ammonia was added. When the pH of the solution reached 10, the addition of aqueous ammonia was stopped and the solution (suspension) was stirred in a bath at 80 to 90 °C for 3 hours.

From this solution, water was removed by distillation using a rotary evaporator and the residue was placed in a drier at 120 °C and dried. Thereafter, the product was calcined at 550 °C for 8 hours while passing air. As such, Catalyst 2 was obtained. The powder X-ray diffraction pattern of Catalyst 2 was the same as in Fig. 1, and notable changes were not observed in the d value and the intensity ratio of main peaks.

The chart obtained in the Raman spectrometry of Catalyst

2 was the same as in Fig. 2 and no notable change was observed.

Comparative Catalyst Preparation Example 1 : A vanadyl oxalate solution and a chromium oxalate solution were prepared in the same manner as in Catalyst Preparation Example 1. These solutions were mixed such that the atomic ratio between V and Cr became 1:0.66. After mixing, the mixed solution was stirred in a bath at 50 to 60 °C for 30 minutes. Insofar as observed with the eye, the solution was uniform. The thus-obtained solution was subjected to removal of solvent by distillation and drying in the same manner as in Catalyst Preparation Example 1, and thereafter, while passing air, calcined at 600 °C for 8 hours. As such, Comparative Catalyst 1 was obtained.

The powder X-ray diffraction pattern of Comparative Catalyst 1 is shown in Fig. 3. The measuring method was the same as in Catalyst Preparation Example 1. The diffraction peaks of Fig. 3 are shown in Table 3. Table 3

1) A value assuming that the peak intensity at d=2.52 is 100. As seen from these results, in Comparative Catalyst 1, a component having a crystal structure completely different from that of "CrV0₄-l" named by Touboul et al. was its main component. Even examining its small peaks, there were no peaks for "CrV0₄-l". The chart obtained in the Raman spectrometry of Comparative Catalyst 1 is shown in Fig. 4. The method in the Raman spectrometry was the same as in Catalyst Preparation Example 1. Catalyst Preparation Example 3 :

In a solution containing vanadium and chromium obtained in Catalyst Preparation Example 1, an α-alumina support (produced by Norton, low surface area alumina/silica, α-alumina content: 89%, silica content: 10%, specific surface area: 0.05 m²/g) was dipped, and after the dipping while keeping the temperature at 60°C, the support was pulled out, dried at 120°C, and while passing air, calcined at 550 °C for 8 hours. As such, Catalyst 3 was obtained.

The powder X-ray diffraction pattern of Catalyst 3 corresponds to the pattern of Fig. 1 where the peak pattern of the support was superposed, and notable changes were not observed in the d value and the intensity ratio of main peaks ascribable to the catalyst component. Also, the chart obtained by the Raman spectroscopy was the same as in Fig. 2 and no notable change was observed.

On use for the reaction in Examples, the catalyst was crushed in a mortar and sieved, and that passing through a sieve having an opening of 0.7 to 1.7 mm was used.

Comparative Catalyst Preparation Example 2:

In the solution containing vanadium and chromium obtained in Comparative Catalyst Preparation Example 1 , the α-alumina support used in Catalyst Preparation Example 3 was dipped and treated in the same manner as in Catalyst Preparation Example 3. As such, Comparative Catalyst 2 was obtained.

The powder X-ray diffraction pattern of Comparative Catalyst 2 corresponds to the pattern of Fig. 1 where the peak pattern of the support was superposed, and notable changes were not observed in the d value and the intensity ratio of main peaks ascribable to the catalyst component. Also, the chart obtained by the Raman spectroscopy was the same as in Fig. 2 and no notable change was observed.

Catalyst Preparation Example 4:

To the solution containing vanadium and chromium obtained in Catalyst Preparation Example 1, an ammonium metatungstate solution (containing 50% by mass of W component as W0₃) and a solution obtained by dissolving calcium acetate monohydrate (Ca(CH₃C00)₂*H₂0) in a small amount of water were added such that the atomic ratio of V:Cr:W:Ca contained in the entire solution became 1:1:0.1:0.02. The obtained solution was stirred in a bath at 60°C for 1 hour. Insofar as observed with the eye, the solution was uniform.

In this solution, the α-alumina support used in Catalyst Preparation Example 3 was dipped and treated in the same manner as in Catalyst Preparation Example 3. As such, Catalyst 4 was obtained. Examples Example 1 (reaction example: production of o- p thalonitrile from o-xylene)

In the reaction, an atmospheric pressure fixed bed flow-type reaction apparatus was used. The reaction tube used was constructed by inserting a stainless steel tube having an outer diameter of 3 mm through a stainless steel tube having an inner diameter of 10 mm and then fixing these tubes, so that the reaction temperature in the catalyst layer could be measured. 7 ml of Catalyst 1 was filled into the reaction tube, and then the reaction tube was externally heated to 340 °C. After controlling the flow rate of each of helium gas, oxygen gas and ammonia gas, they were mixed in a mixer and then introduced into a vaporization chamber. O-xylene and water were fed to the vaporization chamber at constant flow rates, vaporized therein by heating the chamber to 200°C, mixed with the above-described three kinds of gases, and then fed to the catalyst layer in the reaction tube. The total amount of gases fed was 7 L/hr and the composition of gases fed was o-xylene/NH₃:0₂:He:H₂0 = 1:20:10:64:5 (by volume). The reaction gas passing through the catalyst layer was captured by an air cooled trap and a solution trap, and the gases passing through the traps were gas-collected. After collecting the product at 340 °C, the reaction temperature was elevated to 350 °C, and the product was collected in the same manner. The products were analyzed by gas chromatography. The carbon dioxide gas was analyzed by allowing the gas to be absorbed into an alkali solution and then determining the quantity using titration. The amount of ammonia combusted was calculated from a value obtained by the quantitation of nitrogen gas at the reactor outlet. The results obtained are shown in Table 4.

Examples 2 to 4 and Comparative Examples 1 and 2 (reaction example: production of o-phthalonitrile from o- xylene )

The reactions were performed in the same manner as in Example 1 except for using Catalyst 2 , 3 or 4 or Comparative Catalyst 1 or 2. The results obtained are shown in Table 4.

Table 4

1) The yield of C0₂ is shown by a value based on xylene.

2) The combustion ratio of ammonia is shown by a value based on ammonia fed.

Examples 5 to 7 and Comparative Examples 3 to 5 (reaction example: ammoxidation reaction of m-xylene or p-xylene) The reactions were performed in the same manner as in Example 1 except for using any one of Catalyst 1, Comparative Catalyst 1, Catalyst 3 and Comparative

Catalyst 2, using as a starting material m-xylene or p- xylene in place of o-xylene, and setting the composition of gases fed to (m- or p-xylene) :NH₃:0₂ : He: H₂0 = 1:8:8:78:5 (by volume). The results obtained are shown in Table 5.

Table 5

1) The yield of C0₂ is shown by a value based on xylene.

Example 8 (catalyst life test):

Using Catalyst 4, a reaction was performed in the same manner as in Example 1, and the product obtained at the point where the reaction was continued at 480 °C for 8,000 hours was analyzed. As a result, the yield of o- phthalonitrile was 76%. Effects of the Invention

By using the catalyst according to the present invention, a nitrile compound can be produced from an organic compound having an alkyl group with good efficiency. The catalyst found in the present invention has high selectivity of nitrile compounds, deteriorates less even when in use for a long time and ensures a long life. Furthermore, the crystal in the catalyst component is specified and the reproducibility of the catalytic performance is greatly elevated.

It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and use may be made without departing from the inventive scope of this application.

Claims

1. A gas phase ammoxidation catalyst comprising a crystalline composite oxide comprising vanadium and chromium, wherein the pattern of spacings d (A) and relative intensities [shown by % in ( ) ] of said crystalline composite oxide is, as determined by powder X-ray diffraction analysis using Cu-Kαl radiation, within an experiment error, 6.44(25), 3.26(22), 3.21(100), 3.19(35), 3.16(20), 3.02(16), 2.58(11), 2.14(24), 1.71(13) and 1.64(10).

2. The gas phase ammoxidation catalyst as claimed in claim 1, wherein as determined by Raman spectrometry, the Raman shift of said crystalline composite oxide has scattered light peaks at 900 to 930 cm^"1 and at 880 to 900 cm^"1, and has no scattered light peak at 940 to 1000 cm^"1.

3. The gas phase ammoxidation catalyst as claimed in claim 1, wherein as determined by Raman spectrometry, the Raman shift of said crystalline composite oxide has scattered light peaks at 900 to 930 cm^"1, at 880 to 900 cm^"1 and at 940 to 1,000 cm^"1, and the intensity of the scattered light peak at 940 to 1,000 cm^"1 is lower than those of the scattered light peaks at 900 to 930 cm^"1 and at 880 to 900 cm^"1.

4. The gas phase ammoxidation catalyst as claimed in claim 1, wherein the ratio of vanadium to chromium is from 1: 0.7 to 1: 1.5 in terms of atomic ratio.

5. The gas phase ammoxidation catalyst as claimed in claim 1, wherein said crystalline composite oxide further comprises one or more elements selected from the group consisting of tungsten, molybdenum, iron, antimony, zirconium, phosphorus, boron, titanium, magnesium, calcium, strontium and barium.

6. The gas phase ammoxidation catalyst as claimed in claim 5, wherein said one or more elements is calcium and/or tungsten.

7. A method for producing a gas phase ammoxidation catalyst comprising a crystalline composite oxide comprising vanadium and chromium, characterized in by performing a calcination of the composite oxide at about 400 to about 650 °C while passing a gas containing oxygen.

8. The method for producing a gas phase ammoxidation catalyst as claimed in claim 7, wherein pH of a solution containing metal components of the catalyst is adjusted with ammonia, amine or a solution thereof, and then evaporated to dryness or supported on a support, followed by drying and calcining.

9. A method for producing a nitrile compound, comprising reacting an organic compound having one or more alkyl groups with ammonia and oxygen in gas phase in the presence of the gas phase ammoxidation catalyst claimed in any one of claims 1 to 6, thereby converting the alkyl group into a nitrile group.

10. The method for producing a nitrile compound as claimed in claim 9, wherein the organic compound having one or more alkyl groups is an aromatic compound having one or more alkyl substituents, and the nitrile compound is a corresponding aromatic nitrile compound.

11. The method for producing a nitrile compound as claimed in claim 10, wherein the aromatic compound having one or more alkyl substituents is a compound having one or more methyl groups on a benzene ring, and the aromatic nitrile compound is a corresponding compound having one or more nitrile groups on the benzene ring.

12. The method for producing a nitrile compound as claimed in claim 11, wherein the compound having one or more methyl groups on a benzene ring is toluene, o- xylene, m-xylene or p-xylene, and the compound having one or more nitrile groups on a benzene ring is a corresponding benzonitrile, o-phthalonitrile, isophthalonitrile or terephthalonitrile.

13. The method for producing a nitrile compound as claimed in claim 11, wherein the compound having one or more methyl groups on a benzene ring is o-xylene, m- xylene or p-xylene, and the compound having one or more nitrile groups on a benzene ring is a corresponding o- phthalonitrile, isophthalonitrile or terephthalonitrile.

14. The method for producing a nitrile compound as claimed in claim 11, wherein the compound having one or more methyl groups on a benzene ring is o-xylene, and the compound having one or more nitrile groups on a benzene ring is o-phthalonitrile.

15. A method for evaluating the performance of a gas phase ammoxidation catalyst using X-ray powder diffraction.

16. The evaluation method as claimed in claim 15, further using Raman spectrometry.