HK1018951B

HK1018951B - Improved process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation

Info

Publication number: HK1018951B
Application number: HK99104013.7A
Authority: HK
Inventors: 浜田一幸; 驹田悟
Original assignee: 旭化成株式会社
Priority date: 1997-08-11
Filing date: 1999-09-17
Publication date: 2003-03-14

Description

Improved process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation

The present invention relates to an improved process for the production of acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation. More specifically, the present invention relates to a process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, which comprises reacting propane or isobutane with ammonia and molecular oxygen in a gaseous phase in a fluidized bed reactor containing a catalyst comprising a composite oxide and a silica support having supported thereon the composite oxide, wherein the composite oxide contains molybdenum (Mo), tellurium (Te), vanadium (V) and niobium (Nb), and the reaction is carried out under conditions in which a catalyst activator comprising at least one tellurium compound and optionally at least one molybdenum compound is fed into the reactor. The process of the present invention is advantageous in that the catalyst can ensure high catalytic activity even without replacing the catalyst with a new one by interrupting the ammoxidation reaction, so that the production of acrylonitrile or methacrylonitrile by the ammoxidation of propane or isobutane can be stably carried out for a long period of time while maintaining a high yield of acrylonitrile or methacrylonitrile.

A process for producing acrylonitrile or methacrylonitrile by ammoxidation of propylene or isobutylene is known. Recently, attention has been drawn to a process for producing acrylonitrile or methacrylonitrile by the vapor-phase catalytic ammoxidation of propane or isobutane, i.e., by the vapor-phase catalytic reaction of propane or isobutane with ammonia and molecular oxygen, as an alternative to such a process using propylene or isobutylene. In addition, many catalysts for the ammoxidation of propane or isobutane have been proposed. These catalysts, especially oxide catalysts comprising tellurium, are attractive.

For example, as a catalyst for producing acrylonitrile or methacrylonitrile by ammoxidation of propane or isobutane, an oxide catalyst containing molybdenum, tellurium, vanadium and niobium is known. The above-mentioned oxide catalysts are disclosed in US 5,049,692, US 5,231,214, US 5,422,328, EP-B1-529,853, unexamined Japanese patent application laid-open Specifications 7-144132, 7-232071, 7-289907, 7-315842, 8-57319 and 8-141401.

As another example of the oxide catalyst for use in the vapor-phase catalytic ammoxidation reaction of propane or isobutane, an oxide catalyst containing molybdenum and tellurium is disclosed in unexamined japanese patent application laid-open specification No. 7-215926; in US 5,171,876 an oxide catalyst containing molybdenum, tellurium and chromium is disclosed; an oxide catalyst containing tungsten, tellurium and vanadium is disclosed in unexamined Japanese patent application laid-open Specification No. 6-228073; oxide catalysts containing vanadium, antimony and tellurium are disclosed in both US 5,079,207 and EP-a1-337,028.

However, the tellurium-containing oxide catalyst disclosed in the above patent document is disadvantageous because the catalytic activity is lowered with the lapse of time during the ammoxidation, resulting in a decrease in the yield of the desired unsaturated nitrile, i.e., acrylonitrile or methacrylonitrile.

On the other hand, a method of activating a deactivated catalyst with a substance capable of regenerating the catalytic activity of the deactivated catalyst (hereinafter such a substance is often referred to as an "activator") is known.

For example, in both of U.S. Pat. No. 4,709,070 and examined Japanese patent application publication No. 1-41135, there is disclosed a method of carrying out oxidation, ammoxidation or oxidative dehydrogenation of an organic compound in the presence of a tellurium-containing oxide catalyst, wherein a tellurium compound or a mixture of a tellurium compound and a molybdenum compound is added as a catalyst activator to the reaction system, whereby the catalytic activity of the catalyst is maintained during the reaction. However, examples in these patent documents disclose only the ammoxidation of methanol, the ammoxidation of propylene, the ammoxidation of toluene and the oxidative dehydrogenation of butene. None of the above documents describes a process for the ammoxidation of propane or isobutane in the presence of an oxide catalyst containing molybdenum, tellurium, vanadium and niobium.

In US 3,882,159, DE 3,311,521 and WO97/33863, there are disclosed processes for producing acrylonitrile or methacrylonitrile by the vapor phase ammoxidation of propylene or isobutylene in the presence of an oxide catalyst containing molybdenum, wherein the ammoxidation is conducted under the condition that a molybdenum compound is added as a catalyst activator to the reaction system. However, none of the patent documents discloses the use of a tellurium-containing oxide catalyst in the production of acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation.

It can be seen that there is currently no method for solving the above-mentioned problems arising when a tellurium-containing oxide catalyst is used for producing acrylonitrile or methacrylonitrile by the vapor phase ammoxidation of propane or isobutane, namely: during the ammoxidation, the yield of acrylonitrile or methacrylonitrile decreases due to the deactivation of the oxide catalyst with the lapse of time.

Under such circumstances, the present inventors have made extensive and intensive studies with a view toward developing an improved process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, which process can solve the above-mentioned problems occurring in the prior art, whereby the production of acrylonitrile or methacrylonitrile by the ammoxidation of propane or isobutane can be stably carried out for a long period of time while maintaining a high yield of acrylonitrile or methacrylonitrile. As a result, it has been unexpectedly found that the above object can be achieved by conducting the reaction under the condition of feeding a catalyst activator comprising at least one tellurium compound and optionally at least one molybdenum compound into a reactor, in a process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, which comprises reacting propane or isobutane with ammonia and molecular oxygen in a gas phase in a fluidized bed reactor containing a catalyst comprising a composite oxide containing molybdenum (Mo), tellurium (Te), vanadium (V) and niobium (Nb) and a silica support having the composite oxide supported thereon. The present invention has been completed based on this new finding.

Accordingly, it is a primary object of the present invention to provide a process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, which is advantageous in that: even under the condition that the catalyst is not replaced by a new catalyst by stopping the ammoxidation reaction, the high catalytic activity of the catalyst can be ensured, so that the production of acrylonitrile or methacrylonitrile by the ammoxidation of propane or isobutane can be stably carried out for a long period of time while maintaining a high yield of acrylonitrile or methacrylonitrile.

The above, as well as additional objectives, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, and the appended claims.

In the present invention, there is provided a process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, which comprises:

reacting propane or isobutane with ammonia and molecular oxygen in a gaseous phase in a fluidized bed reactor containing a catalyst comprising a composite oxide and a silica carrier having the composite oxide supported thereon, wherein the composite oxide contains molybdenum (Mo), tellurium (Te), vanadium (V) and niobium (Nb),

wherein the reaction is carried out with the addition of a catalyst activator to the reactor, the activator comprising at least one tellurium compound and optionally at least one molybdenum compound.

In order to facilitate an understanding of the invention, the main features and various preferred embodiments of the invention will be described in detail below. 1. A process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, said process comprising:

wherein the reaction is carried out with the addition of a catalyst activator to the reactor, the activator comprising at least one tellurium compound and optionally at least one molybdenum compound. 2. The process according to item 1 above, wherein the silica support is present in an amount of 10 to 60% by weight based on the total weight of the composite oxide and the silica support, and wherein the composite oxide is represented by the following formula (1):

Mo₁Te_aV_bNb_cX_dO_n (1)

wherein:

x is at least one element selected from the group consisting of tantalum, tungsten, chromium, titanium, zirconium, antimony, bismuth, tin, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, aluminum, indium, thallium, phosphorus, and alkaline earth metals; and

a. b, c, d and n are the atomic ratios of tellurium, vanadium, niobium, X and oxygen relative to molybdenum, respectively,

wherein

0.01≤a≤1.0；

0.1≤b≤1.0；

0.01≤c≤1.0；

D is more than or equal to 0 and less than or equal to 1.0; and

n is a number determined by and corresponding to the valence requirements of the other elements present in the composite oxide of formula (1). 3. The process according to item 1 or 2 above, wherein the at least one tellurium compound is selected from the group consisting of metallic tellurium, an inorganic tellurium compound and an organic tellurium compound, and the at least one molybdenum compound is selected from the group consisting of ammonium heptamolybdate (ammonium heptamolybdate), molybdic acid, molybdenum dioxide and molybdenum trioxide. 4. The process according to item 3 above, wherein the inorganic tellurium compound is at least one tellurium compound selected from the group consisting of telluric acid, tellurium dioxide and tellurium trioxide, and the organic tellurium compound is at least one tellurium compound selected from the group consisting of methyltellurol and dimethyltelluroxide. 5. The method according to item 1 or 2 above, wherein the at least one tellurium compound is telluric acid and the at least one molybdenum compound is ammonium heptamolybdate.

The present invention will be described in more detail below.

In the process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation according to the present invention, propane or isobutane is reacted with ammonia and molecular oxygen in a gaseous phase in a fluidized-bed reactor containing a catalyst comprising a composite oxide and a silica carrier having the composite oxide supported thereon, wherein the reaction is carried out under the condition that a catalyst activator is added to the reactor.

The above-mentioned composite oxide contained in the catalyst used in the process of the present invention contains molybdenum (Mo), tellurium (Te), vanadium (V) and niobium (Nb).

In the process of the present invention, the addition of the above-mentioned activating agent is particularly important for obtaining the excellent effects of the present invention. Specifically, in the process of the present invention, the catalyst which has been deactivated in the course of the ammoxidation can be easily reactivated by adding an activating agent. Therefore, the production of (meth) acrylonitrile by the ammoxidation of propane or isobutane can be stably carried out for a long period of time while maintaining a high yield of (meth) acrylonitrile.

On the other hand, if the ammoxidation of propane or isobutane is carried out in the presence of the catalyst defined in the present invention but the above-mentioned activating agent is not added, then troubles are caused because the catalyst is deactivated in a short period of time, thereby disadvantageously resulting in a decrease in the yield of the desired (meth) acrylonitrile.

In the present invention, it is preferable that the silica support is present in an amount of 10 to 60% by weight based on the total weight of the composite oxide and the silica support, and it is preferable that the composite oxide is represented by the following formula (1):

Mo₁Te_aV_bNb_cX_dO_n (1)

wherein:

x is at least one element selected from the group consisting of tantalum, tungsten, chromium, titanium, zirconium, antimony, bismuth, tin, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, aluminum, gallium, indium, thallium, phosphorus, and alkaline earth metals; and

wherein

0.01≤a≤1.0，

More preferably 0.05. ltoreq. a.ltoreq.0.5;

0.1≤b≤1.0，

more preferably 0.2. ltoreq. b.ltoreq.0.6;

0.01≤c≤1.0，

more preferably 0.05. ltoreq. c.ltoreq.0.5;

0≤d≤1.0，

more preferably 0. ltoreq. d.ltoreq.0.1;

and

n is a number determined by and corresponding to the valence requirements of the other elements present in the composite oxide of formula (1).

Further, when an activator is added during the ammoxidation reaction using a catalyst other than the catalyst defined in the present invention, the above-mentioned excellent effects cannot be obtained. Examples of the catalyst other than the catalyst defined in the present invention include oxide catalysts containing only Mo and Te as active component elements, oxide catalysts containing only Mo, Te and Cr as active component elements, and oxide catalysts containing only V, Sb and Te as active component elements.

The activator used in the process of the invention comprises at least one tellurium compound and optionally at least one molybdenum compound. A molybdenum compound is optionally used as an auxiliary activator. When a molybdenum compound is used as the auxiliary activator, the molybdenum compound may be added to the reactor separately from the tellurium compound or together with the tellurium compound.

In the present invention, it is preferable to use a tellurium compound which can be converted into an oxide of tellurium under the conditions of ammoxidation of propane or isobutane. Specific examples of the tellurium compound include metallic tellurium; inorganic tellurium compounds, such as telluric acid, tellurium dioxide and tellurium trioxide, organic tellurium compounds, such as methyltellurol and dimethyltelluroxide. Among them, telluric acid is preferable.

In the present invention, when a molybdenum compound is used in the activator, it is preferable to use a molybdenum compound which can be converted into an oxide of molybdenum under the conditions of ammoxidation of propane or isobutane. Specific examples of the molybdenum compound include ammonium heptamolybdate, molybdic acid, molybdenum dioxide and molybdenum trioxide. Among them, ammonium heptamolybdate is preferred.

It is preferred not to use the activator in a supported form for the following reasons. For example, when silica-supported tellurium dioxide is used as an activator, it is difficult for such an activator to maintain its ability to reactivate a deactivated catalyst for a long period of time, and thus it is difficult to stably produce (meth) acrylonitrile for a long period of time while maintaining a high yield of (meth) acrylonitrile.

In the present invention, the method of adding the activating agent to the fluidized-bed reactor is not particularly limited. An example of a method of adding an activator to a reactor using a reactor connected to an activator conduit separate from a raw material gas conduit can be given. In this process, a powdered activator is fed into the reactor through an activator conduit together with a gas, for example, air or nitrogen. In this case, when the activator is added to the dense phase of the reactor (where the catalyst is present in high concentration), the activator may be thoroughly mixed with the catalyst to achieve sufficient contact of the activator and catalyst.

In the present invention, the activator may be added continuously or in a batch manner.

The time required to obtain satisfactory reactivation of the catalyst after addition of the activator is generally from 2 to 10 hours.

There is no particular limitation in the frequency of addition of the activator and the amount of activator added to the reactor. For example, the frequency and amount of addition can be appropriately determined by a simple method in which the activator is added to the reactor in portions while monitoring the results of the ammoxidation reaction.

In the method of the present invention, the frequency of addition of the activator is not particularly limited as long as the effects of the present invention are achieved. However, for example, when the process of the present invention is carried out on an industrial scale, the activator is preferably added once within 1 to 30 days, more preferably once within 1 to 7 days.

In the process of the present invention, the amount of tellurium compound to be added as an activator to the reactor is preferably 20% by weight or less, more preferably 10% by weight or less, in terms of the amount of tellurium atoms, per time, based on the amount of tellurium atoms originally contained in the catalyst.

In the process of the present invention, when at least one molybdenum compound is added as an optional activator, the amount of the molybdenum compound to be added to the reactor is preferably 10% by weight or less, more preferably 5% by weight or less, in terms of the amount of molybdenum atoms, per time, based on the amount of molybdenum atoms originally contained in the catalyst.

For example, a molybdenum compound may be added as part of the activator when a loss of molybdenum is detected in the catalyst. The loss of molybdenum from the catalyst can be determined, for example, by subjecting a sample of the catalyst to X-ray fluorescence analysis.

The mechanism of the deactivation of the tellurium-containing composite oxide-based catalyst has not been completely explained. In general, when acrylonitrile or methacrylonitrile is produced by the ammoxidation of propane or isobutane in the presence of a tellurium-containing oxide catalyst, the tellurium contained in the catalyst is continuously lost with time during the reaction, and the yield of the desired unsaturated nitrile is also decreased with the loss of tellurium from the catalyst. However, in such ammoxidation, it was occasionally observed that the yield of acrylonitrile or methacrylonitrile slightly increased in the initial stage of the ammoxidation in spite of the fact that the tellurium content of the catalyst decreased with time. Therefore, in the ammoxidation using a tellurium-containing oxide catalyst, the decrease in the yield of acrylonitrile or methacrylonitrile cannot be simply explained by the loss of tellurium from the catalyst.

The mechanism by which the activator used in the process of the present invention regenerates or maintains the catalytic activity of a catalyst comprising a composite oxide containing molybdenum, tellurium, vanadium and niobium has not yet been fully explained. It is envisaged that during the ammoxidation using a fluidized bed reactor containing a catalyst comprising a composite oxide containing molybdenum, tellurium, vanadium and niobium, the activator (typically in the form of particles) interacts with the composite oxide either on the outer surface of the particles of the composite oxide or on the interior of the particles of the composite oxide (wherein the activator is contacted with the interior of the particles of the composite oxide by, for example, the vapour form of the activator), whereby the interaction between the activator and the particles of the composite oxide brings about a repairing effect on the damaged crystal structure of the composite oxide which has undergone reductive breakdown which is specific to the type of catalyst used in the process of the present invention.

In fact, if experiments are conducted to carry out the process of the invention and the X-ray diffraction patterns of the catalyst are examined before and after addition of the activator and these X-ray diffraction patterns of the catalyst are compared, the comparison tends to indicate that the damaged crystalline structure portion of the catalyst has been repaired to some extent. However, in many cases, observations have shown that there is no significant difference between these X-ray diffraction patterns of the catalyst, despite the fact that the catalytic activity of the catalyst has indeed been regenerated by the addition of the activator. Therefore, the mechanism of activation of the catalyst involved in the process of the present invention cannot be explained only by means of the repair phenomenon of the damage of the crystal structure observed with the X-ray diffraction method.

The method for preparing the catalyst used in the method of the present invention will be described below.

The source of each component element of the composite oxide of the ammonia oxidation catalyst used in the method of the present invention is not particularly limited. Representative examples of sources of the elements of the composite oxide component of the catalyst include ammonium heptamolybdate [ (NH) as a source of molybdenum₄)₆Mo₇O₂₄·4H₂O]Telluric acid (H) as a source of tellurium₆TeO₆) Ammonium metavanadate (NH) as a vanadium source₄VO₃) Niobium (Nb) as a niobium source₂O₅·nH₂O)。

Examples of sources of other constituent elements of the composite oxide of the catalyst used in the process of the present invention include nitrates, oxalates, acetates, hydroxides, oxides, ammonium salts and carbonates of elements such as tantalum, tungsten, chromium, titanium, zirconium, antimony, bismuth, tin, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, aluminum, gallium, indium, thallium, phosphorus and alkaline earth metals.

The silica support source for the composite oxide of the catalyst is preferably silica sol.

The catalyst used in the process of the present invention can be prepared by conventional methods. For example, the catalyst may be prepared by a process comprising the steps of: (1) preparing a raw material mixture (e.g., a slurry of raw materials), (2) drying the raw material mixture obtained in the above-mentioned step (1) to obtain a dried catalyst precursor, and (3) calcining the dried catalyst precursor obtained in the above-mentioned step (2).

Hereinafter, a preferred embodiment of the above-mentioned method for preparing the catalyst used in the method of the present invention, which comprises the above-mentioned steps (1), (2) and (3), is explained.

In step (1), a raw material mixture is prepared. For this purpose, a solution (solution a) was first prepared by dissolving ammonium heptamolybdate, telluric acid and ammonium metavanadate in water.

Further, niobic acid and oxalic acid were dissolved in water to obtain a solution (solution B).

As mentioned above, the composite oxide of the catalyst used in the process of the present invention optionally contains at least one constituent element selected from the group consisting of tantalum, tungsten, chromium, titanium, zirconium, antimony, bismuth, tin, hafnium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, zinc, aluminum, gallium, indium, thallium, phosphorus and alkaline earth metals. Nitrate, oxalate, acetate, hydroxide, oxide, ammonium salt, carbonate, etc. of at least one of the above-mentioned constituent elements are dissolved in water to obtain a solution or slurry (the solution or slurry is "solution C").

And adding the solution B, the solution C and silica sol into the solution A in sequence to obtain a raw material mixture. The order of addition of solution B, solution C and silica sol may be changed as appropriate.

In step (2), the raw material mixture obtained in step (1) above is spray-dried. The spray drying of the raw material mixture is generally carried out by a centrifugal method, a two-phase side-stream nozzle method or a high-pressure nozzle method to obtain a dried spherical particulate catalyst precursor. In this case, it is preferable to use air, steam, or the like that has been heated by an electric heater as the drying heat source. The spray dryer temperature at the inlet of the dryer section is preferably 150-.

The spray drying is preferably carried out under conditions such that the resulting oxide catalyst after calcination in the below-mentioned step (3) has a particle diameter of 5 to 120 μm and an average particle diameter of about 50 μm.

In step (3), the dried particulate catalyst precursor obtained in the above step (2) is calcined. The calcination of the dried particulate catalyst precursor is carried out in an atmosphere of an inert gas substantially free of oxygen, such as nitrogen, argon or helium, preferably in an inert gas stream at 500-700 c, preferably 550-650 c, for 0.5-20 hours, preferably 1-8 hours, to obtain the oxide catalyst.

Calcination may be carried out using a kiln, for example, a rotary kiln, a tunnel kiln, a muffle kiln, and a fluidized combustion kiln.

The dried catalyst precursor obtained in the above step (2) may be heat-treated in air or in an air stream at a temperature of 200 and 400 ℃ for 1 to 5 hours before the calcination in step (3).

In the process of the present invention, acrylonitrile or methacrylonitrile is produced by the vapor phase ammoxidation of propane or isobutane in the presence of the above-obtained oxide catalyst using a fluidized bed reactor.

It is not necessary to use propane or isobutane and ammonia in very high purity in the process of the invention, as long as it is technical.

Examples of sources of molecular oxygen include air, oxygen-enriched air, and pure oxygen. Further, such a molecular oxygen source may be diluted with helium, argon, nitrogen, carbon dioxide, steam, or the like.

In the process of the present invention, the catalytic ammoxidation of propane or isobutane in the gas phase can be carried out under the following conditions. The molar ratio of [ propane or isobutane: ammonia: molecular oxygen ] is generally from 1: 0.3 to 1.5: 0.5 to 10, preferably from 1: 0.8 to 1.2: 1 to 5. The ammoxidation temperature is generally 350 ℃ to 500 ℃, preferably 380 ℃ to 470 ℃. The ammoxidation pressure is usually from 0.5 to 5atm, preferably from 1 to 3 atm. The contact time between the gas feed and the catalyst is generally in the range of from 0.1 to 10sec g/cc, preferably from 0.5 to 5sec g/cc.

In the process of the present invention, the contact time during the catalytic ammoxidation of propane or isobutane is determined according to the following formula: contact time (sec. g/cc) (W/F) × 273/(273+ T)

Wherein:

w is the weight (g) of the catalyst contained in the fluidized bed reactor;

f is the flow rate of the gas feed (Ncc/sec) [ Ncc is the cc measured at standard temperature and pressure (0 ℃, 1atm) ]; and

t is the reaction temperature (. degree. C.).

The present invention is described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

In the following examples and comparative examples, acrylonitrile was produced by ammoxidation of propane.

The results of the ammoxidation were evaluated by the propane conversion (%), the acrylonitrile selectivity (%) and the acrylonitrile yield (%) which are defined as follows, respectively:

example 1 (preparation of Ammonia Oxidation catalyst)

An oxide catalyst comprising a silica carrier supporting a composite oxide, wherein SiO is used as a reference based on the total weight of the composite oxide and the silica carrier, is prepared as follows₂Expressed, the silica support is present in an amount of 25 wt%, and wherein the composite oxide can be expressed as: mo₁Te_0.23V_0.31Nb_0.11O_n。

1173.9g of ammonium heptamolybdate [ (NH) were added to 4840g of water₄)₆Mo₇O₂₄·4H₂O]352.2g of telluric acid (H)₆TeO₆) And 241.9g of ammonium metavanadate (NH)₄VO₃) While stirring at about 60 ℃ to give an aqueous solution (solution A).

1190g of Water was charged with 126.0g of niobic acid (Nb)₂O₅76.6% by weight) and 274.7g of oxalic acid (H)₂C₂O₄·2H₂O) while stirring at about 60 ℃ to give an aqueous solution (solution B).

To the solution A, the solution B and 1167g of SiO were added₂Silica sol in an amount of 30 wt% was stirred to obtain a raw material mixture.

The resulting raw material mixture was spray-dried with a centrifugal spray dryer at inlet and outlet temperatures of 240 ℃ and 145 ℃, respectively, to obtain a dried particulate catalyst precursor.

The resulting catalyst precursor was heat-treated at 250 ℃ for 2 hours in air to obtain a composite oxide. 700g of the resulting composite oxide was packed in an SUS tube (diameter: 2 inches) and calcined at 600 ℃ and a nitrogen flow (Ncc is cc measured at standard temperature and pressure, i.e., at 0 ℃ and 1atm) at a flow rate of 600Ncc/min for 2 hours to obtain an oxide catalyst. An additional 700g of the oxide mixture was calcined in substantially the same manner to prepare a sufficient amount of the oxide catalyst for the desired ammoxidation. (ammoxidation of propane)

800g of the oxide catalyst prepared above was charged in a fluidized bed SUS reaction tube (inner diameter: 82mm) in which 12 wire nets (16 mesh) parallel to each other were installed in the vertical direction of the vertical inner wall of the reaction tube, wherein the distance between the adjacent wire nets was 1 cm. A gas mixture having a molar ratio of propane, ammonia and air of 1: 1.2: 14 was fed into the reaction tube from the lower portion of the reaction tube at a flow rate of 104Ncc/sec, and ammoxidation of propane was carried out to produce acrylonitrile. The temperature of the ammoxidation was 430 ℃ and the pressure of the ammoxidation was atmospheric pressure. The contact time (contact time) between the oxide catalyst and the gas mixture feed was 3.0sec g/cc.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 86.5%, the selectivity for acrylonitrile was 60.5% and the yield of acrylonitrile was 52.3%. The results of the ammoxidation were further evaluated 2 days and 6 days after the start of the ammoxidation, and the results obtained are shown in Table 1.

Then, as an activator, telluric acid (H) in powder form was used as follows₆TeO₆) Added to the reaction tube in portions.

7 days after the start of the ammoxidation, a first 10g portion of the telluric acid was fed into the reaction tube together with a nitrogen gas stream through an activator conduit connected to the reaction tube. The results of the ammoxidation were evaluated 2 hours after the addition of telluric acid, and it was found that the results of the ammoxidation were improved as compared with the results of the evaluation 6 days after the start of the ammoxidation (i.e., the day before the addition of telluric acid). After 5 hours of addition of telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 86.8%, the selectivity for acrylonitrile was 60.5% and the yield of acrylonitrile was 52.5%.

In addition, a second part (8g), a third part (6g), a fourth part (7g) and a fifth part (7g) of telluric acid were fed to the reaction tube in the substantially same manner as described above 15, 20, 26 and 32 days after the start of the ammoxidation. During this period, the acrylonitrile yield is maintained at 50-53%.

After 38 days from the start of the reaction, another one was prepared by passing 6g of telluric acid (H) in a manner essentially as described above₆TeO₆) And 10g of ammonium heptamolybdate [ (NH)₄)₆Mo₇O₂₄.4H₂O]The powdered activator obtained by mixing was added to the reaction tube. The results of the ammoxidation were evaluated 40 days after the start of the ammoxidation, and it was found that the conversion of propane was 87.0%, the selectivity for acrylonitrile was 60.2% and the yield of acrylonitrile was 52.4%.

The amount of the activator added to the reaction tube and the evaluation results 2 hours, 2, 6, 7 and 40 days after the start of ammoxidation are shown in Table 1.

TABLE 1

Time after start of ammoxidation	Activating agent (g)		Ammoxidation of propane
	Activating agent (g)		Ammoxidation of propane			Telluric acid	Ammonium heptamolybdate	Conversion (%)	Selectivity (%)	Yield (%)
	2 hours	0	0	86.5	60.5	Telluric acid	Ammonium heptamolybdate	Conversion (%)	Selectivity (%)	Yield (%)	52.3
2 days	2 hours	0	0	86.5	60.5	0	0	87.4	60.3	52.7	52.3
2 days	6 days	0	0	89.3	54.3	0	0	87.4	60.3	52.7	48.5
7 days	6 days	0	0	89.3	54.3	10	0	86.8	60.5	52.5	48.5
7 days	15 days	8	0	-	-	10	0	86.8	60.5	52.5	-
20 days	15 days	8	0	-	-	6	0	-	-	-	-
20 days	26 days	7	0	-	-	6	0	-	-	-	-
32 days	26 days	7	0	-	-	7	0	-	-	-	-
32 days	For 38 days	6	10	-	-	7	0	-	-	-	-
40 days	For 38 days	6	10	-	-	0	0	87.0	60.2	52.4	-

Example 2 (ammoxidation of propane under stringent reaction conditions)

Ammoxidation of propane was carried out using the catalyst prepared in example 1 in the following manner to observe the deactivation and reactivation of the catalyst.

45g of the catalyst prepared in example 1 was charged into a fluidized-bed borosilicate heat-resistant glass reaction tube (inner diameter: 25mm) in which 8 wire nets (16 mesh) parallel to each other were installed in the vertical direction of the vertical inner wall of the reaction tube, wherein the distance between the adjacent wire nets was 1 cm. A gas mixture having a molar ratio of propane, ammonia and air of 1: 1.2: 14 was fed into the reaction tube from the lower portion of the reaction tube at a flow rate of 5.83Ncc/sec, and ammoxidation of propane was carried out to produce acrylonitrile. The temperature of the ammoxidation was 430 ℃ and the pressure of the ammoxidation was atmospheric pressure. The contact time (contact time) between the catalyst and the gas mixture feed was 3.0sec g/cc.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 87.1%, the selectivity for acrylonitrile was 60.3% and the yield of acrylonitrile was 52.5%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 430 ℃ to 490 ℃. Under severe reaction conditions (ammoxidation temperature: 490 ℃), ammoxidation was continuously carried out for about 10 hours, and then the ammoxidation temperature was returned to 430 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 60.3%, the selectivity for acrylonitrile was 44.2% and the yield of acrylonitrile was 26.7%.

Then, telluric acid (H) was added as described below₆TeO₆) Added to the reaction tube in portions. In the same manner as in example 1, 1.0g of a first portion of telluric acid was charged into a reaction tube. About 2 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 80.1%, the selectivity for acrylonitrile was 53.2% and the yield of acrylonitrile was 42.6%. This shows that the results of ammoxidation after the addition of the first portion of telluric acid are improved as compared with the results of the ammoxidation under severe reaction conditions and the results of the evaluations before the addition of the first portion of telluric acid. 0.7g of a second portion of the telluric acid and 0.3g of a third portion of the telluric acid were added to the reaction tube 7 hours and 12 hours after the addition of the first portion of the telluric acid, respectively. 17 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 88.5%, the selectivity for acrylonitrile was 58.9% and the yield of acrylonitrile was 52.1%.

The results of example 2 are shown in tables 2 and 3. Comparative example 1 (preparation of Ammonia Oxidation catalyst)

The oxide catalyst of US 4,709,070 example 12 was prepared as follows, wherein the oxide catalyst is represented by the formula:

Fe₁₀Sb₂₅Wo_0.25Te_1.0O_67.8(SiO₂)₃₀。

636.5g of ferric nitrate [ Fe (NO) was added to 700g of water₃)₃·9H₂O]While stirring, an aqueous solution (solution A) was obtained.

To 350g of water was added 10.2g of ammonium paratungstate [ (NH)₄)₁₀W₁₂O₄₁·5H₂O]And 36.2g of telluric acid (H)₆TeO₆) While stirring at about 95 ℃ to give an aqueous solution (solution B).

The above solution B, 568.9g of antimony trioxide powder (Sb)₂O₃) And 937g SiO₂Silica sol with a content of 30% by weight was added to the above solution A while stirring, followed by addition of an aqueous ammonia solution (NH)₃Content 15 wt.%) until the pH of the resulting mixture was 2, resulting in a starting mixture.

The obtained raw material mixture was spray-dried under substantially the same conditions as in example 1 to obtain a dried particulate catalyst precursor.

The obtained catalyst precursor was calcined at 500 ℃ for 4 hours in air, and then calcined at 850 ℃ for 1 hour to obtain a catalyst. (ammoxidation of propane under stringent reaction conditions)

The above-mentioned catalyst was subjected to ammoxidation of propane in the following manner to observe the deactivation and reactivation of the catalyst.

Ammoxidation was carried out in the same manner as in example 2 using 45g of the above catalyst except that the ammoxidation reaction temperature was 500 ℃ and the contact time was 5.0 sec. g/cc.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 31.4%, the selectivity for acrylonitrile was 27.4% and the yield of acrylonitrile was 8.6%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 500 ℃ to 550 ℃. Under severe reaction conditions (ammoxidation temperature 550 ℃), ammoxidation was continuously carried out for about 10 hours, and then, the ammoxidation temperature was returned to 500 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 23.2%, the selectivity for acrylonitrile was 18.0% and the yield of acrylonitrile was 4.2%.

Then, telluric acid (H) was added as described below₆TeO₆) Is added in portions to the reactionAnd is applied to the pipe. 0.3g of a first portion of the telluric acid was added to the reaction tube. About 5 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 25.0%, the selectivity for acrylonitrile was 16.8% and the yield of acrylonitrile was 4.2%.

About 10 hours after the addition of the first portion of the telluric acid, 0.2g of a second portion of the telluric acid was added to the reaction tube, and the subsequent ammoxidation was monitored to judge whether the results of the ammoxidation improved. As a result, no improvement was found in the results of the ammoxidation.

The results of comparative example 1 are shown in tables 2 and 3. Comparative example 2 (preparation of Ammonia Oxidation catalyst)

The oxide catalyst of US 4,709,070 example 13 was prepared as follows, wherein the oxide catalyst is represented by the formula:

Fe₁₀Sb₂₅Cu₃Mo_0.5W_0.3Te_1.5O_73.4(SiO₂)₆₀。

468.9g of ferric nitrate [ Fe (NO) were added to 500g of water₃)₃·9H₂O]And 84.1g of copper (II) nitrate [ Cu (NO)₃)₂·3H₂O]While stirring, an aqueous solution (solution A) was obtained.

To 300g of water was added 10.2g of ammonium heptamolybdate [ (NH)₄)₆Mo₇O₂₄·4H₂O]9.0g of ammonium paratungstate [ (NH)₄)₁₀W₁₂O₄₁·5H₂O]And 40.0g of telluric acid (H)₆TeO₆) While stirring at about 95 ℃ to give an aqueous solution (solution B).

Solution B, 419.1g of antimony trioxide powder (Sb)₂O₃) And 1381g SiO₂Silica sol with a content of 30% by weight was added to the above solution A while stirring, followed by addition of an aqueous ammonia solution (NH)₃Content 15 wt.%) until the pH of the product mixture was 2, giving a starting mixture.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 32.0%, the selectivity for acrylonitrile was 28.3% and the yield of acrylonitrile was 9.1%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 500 ℃ to 550 ℃. Under severe reaction conditions (ammoxidation temperature 550 ℃), ammoxidation was continuously carried out for about 10 hours, and then, the ammoxidation temperature was returned to 500 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 24.1%, the selectivity for acrylonitrile was 21.2% and the yield of acrylonitrile was 5.1%.

Then, telluric acid (H) was added as described below₆TeO₆) Added to the reaction tube in portions. 0.3g of a first portion of the telluric acid was added to the reaction tube. About 5 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 25.8%, the selectivity for acrylonitrile was 19.4% and the yield of acrylonitrile was 5.0%.

The results of comparative example 2 are shown in tables 2 and 3. Comparative example 3 (preparation of Ammonia Oxidation catalyst)

A catalyst composition comprising a silica carrier supporting an oxide catalyst, wherein the silica carrier is present in an amount of 20% by weight based on the total weight of the silica carrier and the oxide catalyst, and wherein the oxide catalyst comprises a catalyst described in example 4 of Japanese unexamined patent application publication Specification No. 7-215926 and may be expressed as Mo₁Te_0.5Al_8.0O_nThe composite oxide of (3).

To 2,200g of water was added 222.3g of ammonium heptamolybdate [ (NH)₄)₆Mo₇O₂₄·4H₂O]And 145.0g of telluric acid (H)₆TeO₆) While stirring at 60 ℃ to give an aqueous solution (solution A).

3,752.2g of aluminum nitrate [ Al (NO) was added to 1,100g of water₃)₃·9H₂O]While stirring at about 60 ℃ to give an aqueous solution (solution B).

To the above solution A, 667g of SiO were added₂Silica sol in an amount of 30 wt% and the above solution B were stirred at the same time to obtain a raw material mixture.

The obtained catalyst precursor was calcined at 650 ℃ for 3 hours in air to obtain a catalyst. (ammoxidation of propane under stringent reaction conditions)

Ammoxidation was carried out in the same manner as in example 2 using 45g of the above catalyst except that the ammoxidation reaction temperature was 500 ℃ and the contact time was 7.6 sec. g/cc.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 77.6%, the selectivity for acrylonitrile was 37.9% and the yield of acrylonitrile was 29.4%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 500 ℃ to 550 ℃. Under severe reaction conditions (ammoxidation temperature 550 ℃), ammoxidation was continuously carried out for about 10 hours, and then, the ammoxidation temperature was returned to 500 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 54.0%, the selectivity for acrylonitrile was 22.8% and the yield of acrylonitrile was 12.3%.

Then, telluric acid (H) was added as described below₆TeO₆) Added to the reaction tube in portions. 1.0g of a first portion of the telluric acid was added to the reaction tube. About 5 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 56.2%, the selectivity for acrylonitrile was 22.2% and the yield of acrylonitrile was 12.5%.

About 10 hours after the addition of the first portion of the telluric acid, 0.7g of a second portion of the telluric acid was added to the reaction tube, and the subsequent ammoxidation was monitored to judge whether the results of the ammoxidation improved. As a result, no improvement was found in the results of the ammoxidation.

The results of comparative example 3 are shown in tables 2 and 3. Comparative example 4 (preparation of Ammonia Oxidation catalyst)

The oxide catalyst comprising silica and alumina carrier supporting a composite oxide in example 1 of U.S. Pat. No. 5,171,876 was prepared as follows, wherein SiO is used as the basis of the total weight of the composite oxide, the silica carrier and the alumina carrier₂The silica support is present in an amount of 25% by weight, expressed as Al₂O₃The alumina support is present in an amount of 25 wt% and wherein the oxide catalyst is represented by the formula: mo₁Te_0.5Cr_0.5Mg_0.5O_n。

To 3,100g of water was added 306.6g of ammonium heptamolybdate[(NH₄)₆Mo₇O₂₄·4H₂O]And 199.9g of telluric acid (H)₆TeO₆) Stirring was carried out at about 60 ℃ to obtain an aqueous solution (solution A).

To 1,500g of water was added 345.4g of chromium nitrate [ Cr (NO)₃)₃·9H₂O]And 222.8g of magnesium nitrate [ Mg (NO)₃)₂·6H₂O]While stirring at about 60 ℃ to give an aqueous solution (solution B).

To the solution A were added the above solution B and 833g of silica Sol (SiO)₂Content 30% by weight) and 1, 250g of alumina sol (Al)₂O₃Content 20 wt%), while stirring, to give a raw material mixture.

The resulting catalyst precursor was calcined at 290 ℃ for 3 hours, then at 425 ℃ for 3 hours, and finally at 610 ℃ for 3 hours in air to obtain a catalyst. (ammoxidation of propane under stringent reaction conditions)

Ammoxidation was carried out in the same manner as in example 2 using 45g of the above catalyst except that the ammoxidation temperature was 470 ℃.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 15.0%, the selectivity for acrylonitrile was 60.2% and the yield of acrylonitrile was 9.0%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 470 ℃ to 520 ℃. Under severe reaction conditions (ammoxidation temperature: 520 ℃), ammoxidation was continuously carried out for about 10 hours, and then, the ammoxidation temperature was returned to 470 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 12.5%, the selectivity for acrylonitrile was 28.8% and the yield of acrylonitrile was 3.6%.

Then, telluric acid (H) was added as described below₆TeO₆) Added to the reaction tube in portions. 1.4g of a first portion of telluric acid was added to the reaction tube. About 5 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 14.0%, the selectivity for acrylonitrile was 25.1% and the yield of acrylonitrile was 3.5%.

About 10 hours after the addition of the first portion of the telluric acid, 0.7g of a second portion of the telluric acid was added to the reaction tube, and the subsequent ammoxidation was monitored to judge whether the results of the ammoxidation improved or not. As a result, no improvement was found in the results of the ammoxidation.

The results of comparative example 4 are shown in tables 2 and 3. Comparative example 5 (preparation of Ammonia Oxidation catalyst)

A catalyst composition comprising a silica support supporting an oxide catalyst, wherein the silica support is present in an amount of 25% by weight, based on the total weight of the silica support and the oxide catalyst, and wherein the oxide catalyst comprises a catalyst described in example 1 of unexamined Japanese patent application laid-open Specification No. 6-228073 and may be represented by W₁V_0.3Te_0.23Nb_0.12O_nThe composite oxide of (3).

To 4,000g of water was added 311.5g of ammonium paratungstate [ (NH)₄)₁₀W₁₂O₄₁·5H₂O]63.4g of telluric acid (H)₆TeO₆) And 42.1g of ammonium metavanadate (NH)₄VO₃) While stirring at 95 ℃ to give an aqueous solution (solution A).

To 240g of water was added 24.8g of niobic acid (Nb)₂O₅76.6% by weight and 54.0g of oxalic acid (H)₂C₂O₄·2H₂O) while stirring at about 60 ℃ to give an aqueous solution (solution B).

417g of the above solution A was addedSiO₂Silica sol in an amount of 30 wt% and solution B were stirred simultaneously to obtain a raw material mixture.

80g of the obtained catalyst precursor was loaded on a SUS tube (inner diameter: 1 inch) and calcined at 600 ℃ for 2 hours in a nitrogen gas stream at a flow rate of 150Ncc/min to obtain a catalyst. (ammoxidation of propane under stringent reaction conditions)

Ammoxidation was carried out in the same manner as in example 2 using 45g of the above catalyst except that the ammoxidation temperature was 450 ℃.

About 2 hours after the start of the ammoxidation, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 65.3%, the selectivity for acrylonitrile was 21.0% and the yield of acrylonitrile was 13.7%.

About 5 hours after the start of ammoxidation, the ammoxidation temperature was raised from 450 ℃ to 500 ℃. Under severe reaction conditions (ammoxidation temperature 500 ℃), ammoxidation was continuously carried out for about 10 hours, and then, the ammoxidation temperature was returned to 450 ℃. Subsequently, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 36.6%, the selectivity for acrylonitrile was 18.6% and the yield of acrylonitrile was 6.8%.

Then, telluric acid (H) was added as described below₆TeO₆) Added to the reaction tube in portions. 0.8g of a first portion of the telluric acid was added to the reaction tube. About 5 hours after the addition of the first portion of the telluric acid, the results of the ammoxidation were evaluated, and it was found that the conversion of propane was 37.0%, the selectivity for acrylonitrile was 17.6% and the yield of acrylonitrile was 6.5%.

About 10 hours after the addition of the first portion of the telluric acid, 0.5g of a second portion of the telluric acid was added to the reaction tube, and the subsequent ammoxidation was monitored to judge whether the results of the ammoxidation improved. As a result, no improvement was found in the results of the ammoxidation.

The results of comparative example 5 are shown in tables 2 and 3.

TABLE 2

	Catalyst and process for preparing same	Reaction temperature (. degree.C.)	Temperature (. degree.C.) of stringent reaction conditions	The amount (g) of activator (telluric acid) added
	Catalyst and process for preparing same	Reaction temperature (. degree.C.)	Temperature (. degree.C.) of stringent reaction conditions	The amount (g) of activator (telluric acid) added	Example 2	Mo₁Te_0.23V_0.31Nb_0.11O_n25% by weight of SiO₂	430	490	1.0+0.7+0.3
Comparative example 1	Fe₁₀Sb₂₅W_0.25te_1.0O₆ _7.8(SiO₂)₃₀	500	550	0.3(+0.2)	Example 2	Mo₁Te_0.23V_0.31Nb_0.11O_n25% by weight of SiO₂	430	490	1.0+0.7+0.3
Comparative example 1	Fe₁₀Sb₂₅W_0.25te_1.0O₆ _7.8(SiO₂)₃₀	500	550	0.3(+0.2)	Comparative example 2	Fe₁₀Sb₂₅Cu₃Mo_0.5W_0.3Te_1.5O_73.4(SiO₂)₆₀	500	550	0.3(+0.2)
Comparative example 3	Mo₁Te_0.5Al_8.0O_n20% by weight of SiO₂	500	550	1.0(+0.7)	Comparative example 2	Fe₁₀Sb₂₅Cu₃Mo_0.5W_0.3Te_1.5O_73.4(SiO₂)₆₀	500	550	0.3(+0.2)
Comparative example 3	Mo₁Te_0.5Al_8.0O_n20% by weight of SiO₂	500	550	1.0(+0.7)	Comparative example 4	Mo₁Te_0.5Cr_0.6Mg_0.5O_n/(25% by weight SiO₂+ 25% by weight of Al₂O₃)	470	520	1.4(+0.7)
Comparative example 5	W₁V_0.3Te_0.23Nb_0.12O_n25% by weight of SiO₂	450	500	0.8(+0.5)	Comparative example 4		470	520	1.4(+0.7)

TABLE 3

Results 2 hours after the start of the reaction			Results after stringent reaction conditions			Results after addition of activator
Results 2 hours after the start of the reaction			Results after stringent reaction conditions			Results after addition of activator			Conversion (%)	Selectivity (%)	Yield (%)	Conversion (%)	Selectivity (%)	Yield (%)	Conversion (%)	Selectivity (%)	Yield (%)
Example 2	87.1	60.3	52.5	60.3	44.2	26.7	88.5	58.9	Conversion (%)	Selectivity (%)	Yield (%)	Conversion (%)	Selectivity (%)	Yield (%)	Conversion (%)	Selectivity (%)	Yield (%)	52.1

Comparative example 1	31.4	27.4	8.6	23.2	18.0	4.2	25.0	16.8	4.2
Comparative example 1	31.4	27.4	8.6	23.2	18.0	4.2	25.0	16.8	4.2	Comparative example 2	32.0	28.3	9.1	24.1	21.2	5.1	25.8	19.4	5.0
Comparative example 3	77.6	37.9	29.4	54.0	22.8	12.3	56.2	22.2	12.5	Comparative example 2	32.0	28.3	9.1	24.1	21.2	5.1	25.8	19.4	5.0
Comparative example 3	77.6	37.9	29.4	54.0	22.8	12.3	56.2	22.2	12.5	Comparative example 4	15.0	60.2	9.0	12.5	28.8	3.6	14.0	25.1	3.5
Comparative example 5	65.3	21.0	13.7	36.6	18.6	6.8	37.0	17.6	6.5	Comparative example 4	15.0	60.2	9.0	12.5	28.8	3.6	14.0	25.1	3.5

INDUSTRIAL APPLICABILITY

As described above, in the process of the present invention, acrylonitrile or methacrylonitrile is produced from propane or isobutane by the vapor-phase ammoxidation of propane or isobutane in a fluidized-bed reactor containing a catalyst comprising a composite oxide containing molybdenum (Mo), tellurium (Te), vanadium (V) and niobium (Nb), wherein the reaction is carried out under conditions in which a catalyst activator comprising a tellurium compound and optionally a molybdenum compound is fed into the reactor. The process of the present invention is advantageous in that the catalyst of the present invention can ensure high catalytic activity even without replacing the catalyst with a new one by interrupting the ammoxidation reaction, so that the production of acrylonitrile or methacrylonitrile by the ammoxidation of propane or isobutane can be stably carried out for a long period of time while maintaining a high yield of acrylonitrile or methacrylonitrile.

Claims

1. A process for producing acrylonitrile or methacrylonitrile from propane or isobutane by ammoxidation, comprising:

wherein the reaction is carried out under conditions in which an activator for the catalyst is added to the reactor, the activator comprising at least one tellurium compound and optionally at least one molybdenum compound.

2. The process according to claim 1, wherein the silica support is present in an amount of 10 to 60% by weight, based on the total weight of the composite oxide and the silica support, wherein the composite oxide is represented by the following formula (1):

Mo₁Te_aV_bNb_cX_dO_n(1) wherein:

wherein

0.01≤a≤1.0；

0.1 ≤ b≤1.0；

0.01≤c≤1.0；

D is more than or equal to 0 and less than or equal to 1.0; and

3. The process according to claim 1 or 2, wherein the at least one tellurium compound is selected from the group consisting of metallic tellurium, inorganic tellurium compounds and organic tellurium compounds, and the at least one molybdenum compound is selected from the group consisting of ammonium heptamolybdate, molybdic acid, molybdenum dioxide and molybdenum trioxide.

4. The method according to claim 3, wherein the inorganic tellurium compound is at least one tellurium compound selected from the group consisting of telluric acid, tellurium dioxide and tellurium trioxide, and the organic tellurium compound is at least one tellurium compound selected from the group consisting of methyltellurol and dimethyltelluroxide.

5. The process according to claim 1 or 2, wherein said at least one tellurium compound is telluric acid and said at least one molybdenum compound is ammonium heptamolybdate.