JPH11263745A - Vapor-phase catalytic oxidation of hydrocarbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain the objective product while suppressing reduction in catalytic performances, by providing a process for bringing a catalyst into contact with a specific gas in subjecting a prescribed hydrocarbon to a gas-phase catalytic oxidation in a reactor in the presence of a specified catalyst. SOLUTION: In this method for subjecting a 2-8C hydrocarbon to a gas-phase catalytic oxidation in a reactor in the presence of a compound oxide catalyst, a process or a zone for bringing at least a part of the catalyst into contact with a gas having the concentration of a combustible component lower than that of a reaction product gas and an oxygen concentration higher than that of the reaction product gas is provided to activate the deteriorated catalyst. For example, when raw material propane, raw material ammonia, a recycle gas, etc., are supplied from a reducing gas feed opening 4 and an oxidizing gas is fed from oxidizing gas feed openings 5 and 5' to the reactor 1, the oxidizing gas forms a zone having a high oxygen concentration at a regeneration zone A and the catalyst recycled as a dotted line arrow 7 is brought into contact with oxygen in the zone A and regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a reaction method for gas phase catalytic oxidation of hydrocarbons.

[0002]

2. Description of the Related Art Gas phase catalytic oxidation of hydrocarbons has been widely practiced industrially because of the usefulness of the products and the economics of the production method. Specifically, industrial methods are used to produce oxygen-containing organic compounds such as acrylic acid and maleic anhydride by a partial oxidation reaction of hydrocarbons, or nitriles such as acrylonitrile and methacrylonitrile by a catalytic oxidation reaction of hydrocarbons and ammonia. Has been implemented. In addition, a reaction for converting a saturated carbon-carbon bond into an unsaturated bond,
For example, a gas-phase catalytic oxidative dehydrogenation reaction for converting alkanes such as ethane, propane, and butane into the corresponding alkenes, that is, ethylene, propylene, butenes, and the like has been proposed.

A number of catalysts and reaction systems have been proposed for the gas phase catalytic oxidation reaction of these hydrocarbons. In particular, considering the price of the raw material, a gas-phase catalytic oxidation reaction using an alkane as a raw material rather than an alkene has attracted attention. As a catalyst for the gas phase catalytic oxidation reaction of alkanes, for example, as a catalyst for producing acrylonitrile by a gas phase catalytic oxidation reaction of propane and ammonia, Mo-Bi-
P-based catalyst (JP-A-48-16887), Mo-Cr-
Te-based catalyst (US Pat. No. 5,171,876), Mo-V-
Te-based catalysts (JP-A-2-257, JP-A-5-1482)
12, JP-A-5-208136, JP-A-6-279
No. 351, JP-A-6-287146, JP-A-7-10
No. 8101), a Mo-V-Sb-based catalyst (Japanese Unexamined Patent Publication No.
No. 157241), a Mo-Cr-Bi-based catalyst (Japanese Unexamined Patent Publication No.
215925), V-Sb-based catalysts (JP-A-47-3)
No. 3783, Japanese Patent Publication No. 50-23016, Japanese Patent Laid-Open No. 1-2
68668, JP-A-2-180637), V-Sb
-U-Ni catalyst (JP-B-47-14371), V-
Sb-WP catalysts (JP-A-2-95439) are exemplified. Regarding the production of acrylic acid by the gas phase catalytic oxidation reaction method of propane, as a proposal for a catalyst,
Bi-Mo-V-based and / or divanadyl pyrophosphate catalysts (Japanese Unexamined Patent Publication (Kokai) No. 3-170445, Abstracts of the 11th International Conference on Catalysts, pp. 1205-1214), P-Mo-Sb-W-based catalysts (Belgian application 9550049) ), Mo-V-Te-based catalysts (JP-A-6-279351) and the like have been proposed.

[0004]

However, the initial yield and selectivity of these catalysts have been studied, but in order to use the catalyst industrially, only the yield and selectivity of the target product are required. Rather, it is necessary to stably produce the target product while preventing the performance of the catalyst from decreasing over time.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, at least a part of the composite oxide catalyst in the reactor was brought into contact with a specific gas to improve the catalytic performance. The inventors have found that the present invention can be maintained for a long time, and have reached the present invention. That is,
The gist of the present invention is to provide a method for subjecting a hydrocarbon having 2 to 8 carbon atoms to gas-phase catalytic oxidation in a reactor in the presence of a composite oxide catalyst. The present invention provides a gas phase catalytic oxidation method for hydrocarbons, which comprises a step or a zone in which the concentration of a combustible component is lower than that of a gas and the oxygen concentration is higher than that of a reaction product gas.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The hydrocarbon having 2 to 8 carbon atoms is usually an alkane having 2 to 8 carbon atoms, and specific examples thereof include ethane, propane, butane, pentane, hexane, and cyclohexane. Preferably, propane and isobutane are used. . The gas phase catalytic oxidation reaction of these hydrocarbons includes acrolein and / or acrylic acid from propane, maleic anhydride from n-butane, methacrolein and / or methacrylic acid from isobutane, and propane in the presence of ammonia. Acrylonitrile, methacrylonitrile from isobutane, and simultaneous production of acrylonitrile and acrylic acid from propane in the presence of ammonia.

The composite oxide used in the present invention generally includes a composite oxide containing molybdenum and vanadium, preferably a composite oxide containing molybdenum, vanadium and tellurium, and a composite oxide containing molybdenum, vanadium and antimony. And particularly preferably molybdenum, vanadium, X, Z and oxygen (X is at least one of tellurium and antimony, Z is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, Cobalt, rhodium,
(Indicates one or more elements selected from the group consisting of nickel, palladium, platinum, bismuth, boron, indium, phosphorus, rare earth elements, alkali metals, and alkaline earth metals.)
Is an essential component, and the proportion of each of the above essential components excluding oxygen is represented by the following formula:

[0008]

## EQU2 ## 0.25 <rMo <0.98 0.003 <rV <0.5 0.003 <rX <0.5 0.003 <rZ <0.5

(Where rMo, rV, rX, and rZ represent the mole fractions of Mo, V, X, and Z with respect to the total of the above essential components excluding oxygen). These composite oxide catalysts are particularly suitable for use in the production of acrylic acid from propane and acrylonitrile from propane in the presence of ammonia.Depending on the reaction conditions, acrylonitrile and acrylic acid can be used in the presence of ammonia in propane. Can also be manufactured at the same time.

Although the composite oxide catalyst can be used alone, it can be used as a mixture containing known carrier components such as silica, alumina, titania, zirconia, aluminosilicate, and diatomaceous earth in an amount of about 1 to 90% by weight. Can also be used. The conditions of the gas phase catalytic oxidation are different depending on the hydrocarbon as the raw material, the target substance, the catalyst, etc., but the concentration of the hydrocarbon having 2 to 8 carbon atoms in the gas supplied to the reactor is as follows:
Usually 0.1 to 70% by volume, preferably 2 to 50% by volume,
The oxygen concentration is usually 0.1 to 40% by volume, preferably 1 to 3%.
0% by volume. When performing gas phase catalytic oxidation in the presence of ammonia, the concentration of ammonia in the gas supplied to the reactor is usually 0.1 to 25% by volume, preferably 1 to 15% by volume.

For example, in the gas phase catalytic oxidation of propane and oxygen or in the gas phase catalytic oxidation of propane, ammonia and oxygen, the reaction temperature is usually 300 to 500 ° C., preferably 3 to 500 ° C.
50-480 ° C, gas space velocity SV in gas phase reaction
Is usually 100 to 10,000 hr ^-1 , preferably 300
６6000 hr ⁻¹ . The reaction is usually carried out under atmospheric pressure, but may be carried out under low pressure or low pressure. As a diluent gas for adjusting the space velocity and the oxygen partial pressure, an inert gas such as nitrogen, argon, and helium can be used.

For the gas phase catalytic oxidation, a known reactor such as a fluidized bed reactor and a fixed bed flow reactor is used. Since gas phase catalytic oxidation is an exothermic reaction, a fluidized bed reactor is preferably used. By performing the gas phase catalytic oxidation, a gas containing a reaction product, that is, a reaction product gas is discharged from the reactor. When the reaction of the gas phase catalytic oxidation is continuously performed, the activity of the catalyst gradually decreases, and the selectivity and the conversion rate decrease. A feature of the present invention is that the catalyst thus degraded has a combustible component concentration lower than that of the reaction product gas, preferably less than half the concentration of the reaction product gas, more preferably substantially zero, and The gas is brought into contact with a gas having an oxygen concentration higher than that of the reaction product gas, preferably 0.5 to 75% by volume, and more preferably 1 to 50% by volume (hereinafter also referred to as "regeneration treatment").

The combustible component is a component other than oxygen and an inert gas present in the reaction product gas. For example, when a gas phase catalytic reaction of propane is carried out in the presence of ammonia,
The combustible components in the reaction product gas include unreacted acrylonitrile and ammonia such as hydrocyanic acid, acetonitrile, propylene, carbon monoxide, and acrylic acid, in addition to acrylonitrile.

[0014] By contacting with such a gas having a combustible component concentration lower than the reaction product gas and an oxygen concentration higher than the reaction product gas, the deteriorated catalyst can be activated. The catalyst used for the regeneration treatment is a catalyst whose activity has been reduced by performing a gas phase catalytic oxidation reaction. When the composite oxide catalyst is exposed to a hydrocarbon gas phase catalytic oxidation reaction atmosphere for a long time, the composite oxide catalyst gradually becomes a reduced state, the activity is degraded, and the reduced catalyst is replaced by the catalyst of the present invention. It is presumed that the regeneration treatment can suppress the deterioration of the catalytic activity structure.

If the deterioration exceeds the threshold value, irreversible deterioration of the catalytically active structure occurs, and even if the regeneration treatment of the present invention is performed, the recovery of the activity becomes insufficient. For example, in a composite oxide catalyst containing molybdenum as a main component, when molybdenum is reduced, the activity of the catalyst decreases. Specifically, when the oxidation number of molybdenum of the catalyst before subjecting to the gas phase catalytic oxidation reaction is +6, before the catalyst is subjected to the gas phase catalytic oxidation reaction and the oxidation number of molybdenum becomes smaller than +5,
It is effective to perform the reproduction processing of the present invention. If the reduction proceeds until the oxidation number of molybdenum becomes smaller than +5, the reduction becomes irreversible, and it is not easy to return to the state of +6 even with the treatment of the present invention.

The temperature at which the regeneration process is performed is usually 300 to 50
0 ° C., preferably 350-480 ° C. By performing the reaction at a temperature similar to the gas phase contact reaction temperature, it is possible to reduce the loss of time required to reach a predetermined temperature. The time is usually 1 second to 5 hours, preferably 5 seconds to 2 hours.
Time. In the regeneration process, a part of the catalyst is continuously or batch-extracted from the reactor and subjected to the regeneration process.Then, the catalyst is returned to the reactor or the gas composition supplied to the reactor is changed to remove the entire catalyst in the reactor. Even if it is performed in a regeneration process step that regenerates at once, by devising the position of the supply port of the reducing gas such as hydrocarbons, ammonia, etc. and the oxidizing gas such as oxygen to the reactor to be supplied to the reactor Even if the reaction is carried out in a regeneration treatment zone in which a part of the reactor is kept at a condition where the concentration of combustible components is lower than the reaction product gas and the oxygen concentration is higher than the reaction product gas, and a part of the catalyst is regenerated. Good.

FIG. 1 shows an example of a cross-sectional model of a fluidized bed reactor having a regeneration treatment zone A. In FIG. 1, raw material propane, raw material ammonia, recycled gas, and the like are supplied to the reactor 1 through a reducing gas supply port 4,
The oxidizing gas such as oxygen is supplied from the oxidizing gas supply ports 5 and 5 'to a region partitioned by the partition plate 2 having a notch so as not to hinder circulation of the catalyst. The oxidizing gas supplied to the reactor passes through the dispersion plate 3 to form a zone having a high oxygen concentration at the location A, and the circulating catalyst as indicated by the dotted arrow 7 is mixed with oxygen at the location A. It is regenerated by contact.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples unless it exceeds the gist. The propane conversion (%), the selectivity (%) of acrylonitrile and acrylic acid, and the yield (%) of acrylonitrile and acrylic acid in the following Examples and Comparative Examples are each represented by the following formulas.

[0019]

## EQU3 ## Conversion of propane (%) = (moles of propane consumed / moles of supplied propane) × 100 Selectivity for acrylonitrile (%) = (moles of acrylonitrile formed / moles of propane consumed) × 100 Acrylonitrile yield (%) = (moles of acrylonitrile produced / moles of propane supplied) × 100 Selectivity of acrylic acid (%) = (moles of produced acrylic acid / moles of propane consumed) × 100 acrylic acid Yield (%) = (moles of acrylic acid produced /
Number of moles of propane supplied) x 100

Reference Example 1 Preparation of Composite Oxide Catalyst A composite oxide having an empirical formula of Mo ₁ V _0.3 Te _0.23 Nb _0.12 On and silica as a carrier were mixed with a composite oxide / Si
A catalyst mixed at a ratio of O ₂ = 90/10 (weight ratio) was prepared as follows. To 5.68 liters of warm water, 1.380 kg of ammonium paramolybdate, 0.275 kg of ammonium metavanadate, 0.413 of telluric acid
kg was dissolved to prepare a uniform aqueous solution. Further, 0.972 kg of a 20% by weight silica sol and 2.105 kg of an aqueous niobium ammonium oxalate solution having a niobium concentration of 0.446 mol / kg were mixed with the aqueous solution to prepare a slurry. The slurry was dried to remove water. Then, the dried product is removed for about 30 minutes until the smell of ammonia disappears.
After heat treatment at 0 ° C., it was baked at 600 ° C. for 2 hours in a nitrogen stream.

Reference Example 2 Preparation of Composite Oxide Catalyst Silica, which is a composite oxide carrier whose empirical formula is represented by Mo ₁ V _0.3 Sb _0.2 Nb _0.05 On, was mixed with composite oxide / SiO.
A catalyst mixed at a ratio of ₂ = 90/10 (weight ratio) was prepared as follows. 122 g of ammonium metavanadate and 102 g of antimony trioxide in 2.1 liters of warm water
Was added thereto, and the slurry was heated at 90 ° C. for 6 hours to remove water and concentrated to about ３. This is called slurry A. On the other hand, 614 g of ammonium paramolybdate was added and dissolved in 1.23 kg of warm water, and then heated to 40 ° C. to prepare an aqueous solution containing molybdenum. Also, hot water 4.
77 g of niobium ammonium oxalate was dissolved in 62 kg, and then heated to 40 ° C. to prepare an aqueous solution containing niobium. The slurry and the aqueous solution were cooled to about 30 ° C., and the above-mentioned aqueous solution containing molybdenum, then 400 g of a silica sol having a silica content of 20% by weight, and the above-mentioned aqueous solution containing niobium were added to slurry A, followed by stirring and mixing. The water was removed by a spray drier and dried. Next, the dried product was heated at about 300 ° C. until the smell of ammonia disappeared, and then calcined at 600 ° C. for 2 hours in a nitrogen stream.

Example 1 0.55 g of the composite oxide catalyst of Reference Example 1 was charged into a fixed bed flow type reactor, the temperature of the reactor was set at 370 ° C., and propane: ammonia: oxygen: nitrogen = 1: 0.4: 3.15: 11.85 molar ratio, gas space velocity about 900 h ^-1 , and gas based space velocity of propane WHSV 0.109 h ^-1 , gas is supplied for 30 minutes to perform gas phase catalytic oxidation. Then, the supply of propane and ammonia was stopped, the temperature of the reactor was set at 380 ° C., and the supply of only oxygen and nitrogen (oxygen concentration: 21% by volume) was continued for 10 minutes to perform a regeneration treatment. Thereafter, the reactor was again set to 37
The temperature was set to 0 ° C., and a mixed gas of propane, ammonia, oxygen, and nitrogen was supplied for 30 minutes under the same conditions as at the beginning to perform gas phase catalytic oxidation. In this manner, the gas phase catalytic oxidation was repeated for 30 minutes / the regeneration treatment for 10 minutes. Only the time during which the gas phase catalytic oxidation reaction was performed is integrated, and the reaction results after 100 hours and 200 hours are shown in Table 1.

Comparative Example 1 0.55 g of the composite oxide catalyst of Reference Example 1 was charged into a fixed bed flow type reactor, and the temperature of the reactor was set at 370 ° C., and propane: ammonia: oxygen: nitrogen Gas was supplied at a molar ratio of 1: 0.4: 3.15: 11.85, a gas space velocity of about 900 h ^-1 , and a propane-based mass space velocity WHSV of 0.109 h ^-1 to perform a gas phase catalytic oxidation reaction. . Immediately after the start of the reaction, 100 hours later, 200 hours
Table 1 shows the reaction results after the lapse of time. The oxygen concentration of the reaction product gas at the reactor outlet and the combustible components (acrylonitrile, acrylic acid, hydrocyanic acid, acetonitrile,
10 hours after the start of the reaction, the total concentration of carbon monoxide, propylene, propane, and ammonia) was 11.3,
It was 6.8% by volume.

<Example 2> [0024] Except that the gas phase catalytic oxidation reaction of propane and ammonia shown in Example 1 was changed to gas phase catalytic oxidation 60 minutes / regeneration treatment 6 minutes, gas phase catalytic oxidation was performed in the same manner as in Example 1. An oxidation reaction was performed. Only the time during which the gas phase catalytic oxidation reaction was performed is integrated, and the reaction results after 100 hours and 200 hours are shown in Table 1.

Example 3 0.2 g of the composite oxide catalyst of Reference Example 1 was charged into a fixed bed flow-type reactor, the temperature of the reactor was set to 400 ° C., and propane: ammonia: oxygen: nitrogen. Gas is supplied for 25 minutes at a molar ratio of 1: 0.3: 1.5: 3.5, a gas hourly space velocity of about 1500 h ⁻¹ , and a mass-based hourly space velocity of propane of 0.984 h ⁻¹ to perform gas phase catalytic oxidation. Then, the supply of propane and ammonia was stopped, the temperature of the reactor was set to 400 ° C., and the supply of only oxygen and nitrogen (oxygen concentration 30% by volume) was continued for 10 minutes to perform a regeneration treatment. Thereafter, the temperature of the reactor was set again to 400 ° C., and a mixed gas of propane, ammonia, oxygen, and nitrogen was supplied for 25 minutes under the same conditions as at the beginning to perform gas phase catalytic oxidation. In this manner, the gas phase catalytic oxidation was repeated for 25 minutes / regeneration treatment for 10 minutes. Only the time during which the gas phase catalytic oxidation reaction was performed is integrated, and the reaction results after 100 hours and 1000 hours are shown in Table 1.

Comparative Example 2 0.2 g of the composite oxide catalyst of Reference Example 1 was charged into a fixed bed flow type reactor, and the temperature of the reactor was set to 400 ° C., and propane: ammonia: oxygen: nitrogen A gas was supplied at a molar ratio of 1: 0.3: 1.5: 3.5, a gas hourly space velocity of about 1500 h ^-1 , and a mass hourly space velocity of propane of 0.984 h ^-1 to perform a gas phase catalytic oxidation reaction. . Table 1 shows the reaction results immediately after the start of the reaction, 100 hours later, and 1000 hours later. The concentration of oxygen in the reaction product gas at the outlet of the reactor and the concentration of the total amount of combustible components were 6.4 and 16.
It was 3% by volume.

Example 3 0.55 g of the composite oxide catalyst of Reference Example 2 was charged into a fixed bed flow type reactor, and the temperature of the reactor was set at 380 ° C., and propane: ammonia: oxygen: nitrogen = 1: 0.4: 3.15: 11.85 molar ratio, gas space velocity about 900 h ^-1 , and gas based space velocity of propane WHSV 0.109 h ^-1 , gas is supplied for 30 minutes to perform gas phase catalytic oxidation. Then, the supply of propane and ammonia was stopped, the temperature of the reactor was set at 380 ° C., and the supply of only oxygen and nitrogen (oxygen concentration: 21% by volume) was continued for 10 minutes to perform a regeneration treatment. Thereafter, the reactor was again charged to 38
The temperature was set to 0 ° C., and a mixed gas of propane, ammonia, oxygen, and nitrogen was supplied for 30 minutes under the same conditions as at the beginning to perform gas phase catalytic oxidation. In this manner, the gas phase catalytic oxidation was repeated for 30 minutes / the regeneration treatment for 10 minutes. Only the time during which the gas phase catalytic oxidation reaction was performed is integrated, and the reaction results after 100 hours and 1000 hours are shown in Table 1.

Comparative Example 3 0.55 g of the composite oxide catalyst of Reference Example 2 was charged into a fixed bed flow type reactor, and the temperature of the reactor was set to 380 ° C., and propane: ammonia: oxygen: nitrogen Gas was supplied at a molar ratio of 1: 0.4: 3.15: 11.85, a gas space velocity of about 900 h ^-1 , and a propane-based mass space velocity WHSV of 0.109 h ^-1 to perform a gas phase catalytic oxidation reaction. . Immediately after the start of the reaction, 100 hours later, 1000
Table 1 shows the reaction results after the lapse of time. The oxygen concentration of the reaction product gas at the reactor outlet and the total concentration of combustible components were 11.2 and 10 hours after the start of the reaction, respectively.
It was 6.4% by volume.

[0029]

[Table 1]

[0030]

According to the present invention, the activity of the catalyst can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a model diagram of a cross section of a fluidized bed type reactor used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor 2 Partition plate 3 Dispersion plate 4 Reducing gas supply port 5, 5 'Oxidizing gas supply port 6 Reaction product gas outlet 7 Catalyst movement A Regeneration zone

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C07C 255/08 C07C 255/08 // C07B 61/00 300 C07B 61/00 300

Claims (7)

[Claims] 1. A method for subjecting a hydrocarbon having 2 to 8 carbon atoms to gas-phase catalytic oxidation in a reactor in the presence of a composite oxide catalyst, wherein at least a part of the composite oxide catalyst in the reactor is reacted with a reaction product gas. A gas phase catalytic oxidation method for hydrocarbons, comprising a step or zone of contacting with a gas having a lower concentration of a combustible component and a higher oxygen concentration than a reaction product gas. 2. The gas phase catalytic oxidation method according to claim 1, wherein the hydrocarbon having 2 to 8 carbon atoms is subjected to gas phase catalytic oxidation in the presence of ammonia. 3. The method according to claim 2, wherein unsaturated nitrile is produced. 4. The method according to claim 1, wherein an unsaturated carboxylic acid is produced. 5. The method according to claim 1, wherein the hydrocarbon is propane and / or isobutane.
Item 8. A gas phase catalytic oxidation method according to item 1. 6. The catalyst according to claim 1, wherein the catalyst is molybdenum, vanadium, X, Z.
And oxygen (X is at least one of tellurium and antimony, Z is niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel,
Palladium, platinum, bismuth, boron, indium, phosphorus, a rare earth element, an alkali metal, and at least one element selected from the group consisting of alkaline earth metals) as essential components, and excluding oxygen. The existence ratio is expressed by the following formula: 0.25 <rMo <0.98 0.003 <rV <0.5 0.003 <rX <0.5 0.003 <rZ <0.5 (where rMo , RV, rX, and rZ each represent a mole fraction of Mo, V, X, and Z with respect to the sum of the essential components excluding oxygen). The gas phase catalytic oxidation method according to claim 1 or 2. 7. A method for regenerating a gas-catalyzed oxidation catalyst, comprising contacting a gas having a lower concentration of a combustible component than a reaction product gas and having a higher oxygen concentration than the reaction product gas.