JP4535608B2 - Catalyst and method for producing unsaturated nitrile using the catalyst - Google Patents

Description

【００３０】
【発明の効果】
本発明方法によれば、プロパンまたはイソブタンから高い選択率で不飽和ニトリルを製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst containing molybdenum, vanadium, antimony, niobium and aluminum used in a gas phase catalytic ammoxidation reaction of propane or isobutane, and a method for producing an unsaturated nitrile using the catalyst.
[0002]
[Prior art]
Recently, a technique for producing an unsaturated nitrile by using gas phase catalytic ammoxidation reaction or gas phase catalytic oxidation reaction using propane or isobutane as a raw material instead of propylene or isobutylene has been attracting attention, and many catalysts have been proposed.
[0003]
Among them, a catalyst system particularly attracting attention has a low reaction temperature, a relatively high unsaturated nitrile selectivity and yield, and Mo-V-Sb- composed of components having relatively low scattering properties. A catalyst system containing Nb.
Composite oxide catalysts containing Mo-V-Sb-Nb are disclosed in JP-A-9-157241, JP-A-10-28862, JP-A-10-81660, JP-A-10-330343, and JP-A-11-. No. 42434, JP-A-11-43314, JP-A-11-57479, JP-A-11-263745, JP-A-2000-1464, JP-A-2000-143244, JP-A-2000-070714 Gazette, JP-A-2000-093796, US Pat. No. 6,043,185 and the like.
The Mo—V—Sb—Nb catalyst system has a lower reaction temperature and a higher selectivity and yield of unsaturated nitrile than other catalyst systems, but is still insufficient.
[0004]
JP-A-9-157241 discloses a catalyst containing Mo—V—Sb—Nb, and Ta, W, Ti, Zr, Cr, Mn, Fe, Ru, Co, Rh are further preferable components. , Ni, Pd, Pt, B, In, Ce, alkali metals, alkaline earth metals are taught, and the presence of aluminum is stated to be undesirable in the catalyst.
[0005]
[Problem to be Solved by the Invention]
An object of the present invention is to provide a catalyst having a high selectivity of an unsaturated nitrile, which is used in producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on a catalyst for producing an unsaturated nitrile by vapor-phase catalytic oxidation of propane or isobutane in the presence of ammonia, the present inventors have further added aluminum to molybdenum, vanadium, antimony, and niobium. The inventors have found that the selectivity of unsaturated nitrile is high, and have reached the present invention.
[0007]
That is, the present invention
(1) A catalyst used for producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane, wherein the catalyst has a component composition represented by the following formula (I):
Mo ₁ V _a Sb _b Nb _c Al _d O _n (I)
(Wherein a , b, c and d represent atomic ratios per Mo atom, 0.1 ≦ a ≦ 1, 0.01 ≦ b ≦ 0.6, 0.01 ≦ c ≦ 0.3, 0 .01 ≦ d ≦ 0.5, n and its is an atomic ratio determined by the oxidation state of the constituent metal.)
(2) The catalyst according to (1), which is supported on 20 to 60% by weight of silica,
(3) The catalyst according to (1) or (2), wherein the catalyst is produced by firing at 500 ° C. to 700 ° C. in a gas atmosphere substantially free of oxygen,
(4) The catalyst according to any one of (1) to (3), wherein the catalyst is produced using aluminum oxide as a catalyst raw material,
(5) The catalyst according to any one of (1) to (4), wherein the catalyst is produced using a catalyst raw material liquid having a hydrogen peroxide / niobium molar ratio of 0.5 to 10. ,
(6) The catalyst according to any one of (1) to (5), wherein the catalyst is produced using a catalyst raw material liquid having a dicarboxylic acid / niobium molar ratio of 1 to 8.
(7) A method for producing an unsaturated nitrile, comprising using the catalyst according to any one of (1) to (6) in producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane,
It is about.
[0008]
Hereinafter, the present invention will be described in detail.
The catalyst of the present invention has a component composition represented by the following formula (I).
Mo ₁ V _a Sb _b Nb _c Al _d X _e O _n (I)
In the above formula (I), X is W, Cr, Ti, Ta, Zr, Hf, Mn, Re, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Ag, Zn, B, In, It is at least one element selected from Ge, Sn, P, Pb, Bi, Y, rare earth elements and alkaline earth metals, and preferably W, Sn, Ti, Ge, and Fe. a, b, c, d, e and n represent atomic ratios per Mo atom, and a is 0.1 ≦ a ≦ 1, preferably 0.1 ≦ a ≦ 0.5, particularly preferably 0.15 ≦. a ≦ 0.4. b is 0.01 ≦ b ≦ 0.6, preferably 0.1 ≦ b ≦ 0.4, and particularly preferably 0.13 ≦ b ≦ 0.3. c is 0.01 ≦ c ≦ 0.3, preferably 0.02 ≦ c ≦ 0.2, particularly preferably 0.03 ≦ c ≦ 0.15, and d is 0.01 ≦ d ≦ 0.5. , Preferably 0.02 ≦ d ≦ 0.3, particularly preferably 0.03 ≦ c ≦ 0.2, and e is 0 ≦ e ≦ 1, preferably 0 ≦ e ≦ 0.5, particularly preferably 0. .01 ≦ c ≦ 0.3. Here, n is an atomic ratio determined by the oxidation state of the constituent metals.
The catalyst of the present invention is characterized in that Al is further contained in the catalyst composed of Mo, V, Sb, and Nb. When d <0.01 or d> 0.5, the selectivity of unsaturated nitrile is lowered.
[0009]
Examples of the aluminum raw material for producing the catalyst of the present invention include aluminum halides such as aluminum oxide, aluminum hydroxide, aluminum nitrate, and aluminum chloride, aluminum alkoxides such as aluminum ethoxide, aluminum acetate, aluminum lactate, and laurin. Aluminum acid, aluminum acetylacetonate, or the like can be used. Aluminum oxide, aluminum hydroxide, and aluminum nitrate are preferable, and aluminum oxide is particularly preferable. As the aluminum oxide, α-alumina is preferable. When preparing aluminum oxide by baking aluminum hydroxide, aluminum nitrate, aluminum or the like, baking is preferably performed at 600 to 1500 ° C, and particularly preferably 800 to 1400 ° C. The catalyst of the present invention can be used by being supported on silica of preferably 20 to 60% by weight, preferably 30 to 55% by weight. If it is less than 20% by weight, the strength is small, and if it is 60% by weight or more, the strength is large, but the yield of unsaturated nitrile is low.
[0010]
The weight percentage of silica is defined by the following formula (II), where W1 is the weight of the oxide of formula (I) and W2 is the weight of silica. W1 is a weight calculated based on the charged composition and the oxidation number of the charged metal component. W2 is a weight calculated based on the charged composition.
Silica weight% = 100 × W2 / (W1 + W2) (II)
The following compounds can be used as raw materials for components other than aluminum for producing the catalyst of the present invention.
[0011]
As the molybdenum raw material, ammonium heptamolybdate, molybdenum oxide, molybdic acid, molybdenum oxychloride, molybdenum chloride, molybdenum alkoxide, and the like can be used, and ammonium heptamolybdate is preferable.
As the vanadium raw material, ammonium metavanadate, vanadium oxide (V), vanadium oxychloride, vanadium alkoxide, and the like can be used, and preferably ammonium metavanadate and vanadium oxide (V).
Antimony raw materials include antimony oxide (III), antimony oxide (IV), antimony oxide (V), metaantimonic acid (III), antimonic acid (V), ammonium antimonate (V), antimony chloride (III), chloride Organic acid salts such as antimony (III) oxide, antimony (III) nitrate, alkoxide of antimony, antimony tartrate, metal antimony, and the like can be used, and antimony (III) oxide is preferable.
As a niobium raw material, an aqueous solution in which niobic acid is dissolved in an oxalic acid aqueous solution can be suitably used. The molar ratio of oxalic acid / niobium is 1 to 10, preferably 2 to 6, particularly preferably 2 to 4. Hydrogen peroxide may be added to the obtained aqueous solution. The molar ratio of hydrogen peroxide / niobium is preferably from 0.5 to 10, particularly preferably from 2 to 6.
As raw materials for the X component, oxalates, hydroxides, oxides, nitrates, acetates, ammonium salts, carbonates, alkoxides, and the like of the X component can be used.
When silica is used as the carrier, silica sol is preferably used as a raw material. It is preferable to use a sol stabilized with ammonium ions.
[0012]
The catalyst of the present invention can be produced through the following three steps of raw material preparation, drying and firing.
<Raw material preparation process>
Ammonium heptamolybdate, ammonium metavanadate, and antimony (III) oxide are suspended in water, and preferably reacted at 70 to 100 ° C. with stirring for 1 to 5 hours. The obtained mixed liquid containing molybdenum, vanadium, and antimony is liquid-phase oxidized with air oxidation or hydrogen peroxide to obtain a mixed liquid (A).
When hydrogen peroxide is used for liquid phase oxidation, the molar ratio of hydrogen peroxide / Sb is preferably 0.5-2. It is preferable to oxidize until it becomes orange-brown visually.
[0013]
On the other hand, niobic acid is dissolved in an oxalic acid aqueous solution to prepare a niobium raw material liquid. It is preferable to add hydrogen peroxide to the niobium raw material liquid.
On the other hand, aluminum oxide liquid is prepared by suspending aluminum oxide in water.
A niobium raw material liquid and an aluminum raw material liquid are added to the mixed liquid (A).
In the case of producing a silica-supported catalyst, the catalyst raw material liquid can be obtained by adding silica sol in any step of the above-mentioned preparation sequence.
In the case of producing a catalyst containing the X component, a raw material containing the X component can be added in any step of the preparation sequence to obtain a catalyst raw material liquid.
[0014]
<Drying process>
The catalyst raw material liquid obtained in the raw material preparation step can be dried by spray drying or evaporation to dryness to obtain a dry powder. The atomization in the spray drying method can employ a centrifugal method, a two-fluid nozzle method, or a high-pressure nozzle method. As the drying heat source, air heated by steam, an electric heater or the like can be used. At this time, the dryer inlet temperature of hot air is preferably 150 to 300 ° C. Spray drying can also be performed simply by spraying the catalyst raw material liquid onto an iron plate heated to 100 ° C to 300 ° C.
[0015]
<Baking process>
An oxide catalyst can be obtained by firing the dry powder obtained in the drying step. Firing is performed using a rotary furnace, a tunnel furnace, a tubular furnace, a fluidized firing furnace, or the like, under an inert gas atmosphere such as nitrogen that does not substantially contain oxygen, preferably while circulating an inert gas, at 500 to 700 ° C., Preferably it can implement at 570-670 degreeC. The firing time is 0.5 to 5 hours, preferably 1 to 3 hours. The oxygen concentration in the inert gas is 1000 ppm or less, preferably 100 ppm or less as measured by gas chromatography or a trace oxygen analyzer. Firing can be repeated. Prior to this firing, pre-baking can be carried out at 200 ° C. to 420 ° C., preferably 250 ° C. to 350 ° C. for 10 minutes to 5 hours in an air atmosphere or under air circulation. Further, after firing, post-baking can be performed in an air atmosphere at 200 ° C. to 400 ° C. for 5 minutes to 5 hours.
[0016]
The catalyst thus produced can be used as a catalyst for producing an unsaturated nitrile by subjecting propane or isobutane to gas phase catalytic ammoxidation.
The feedstock for propane or isobutane and ammonia does not necessarily have to be high purity, and industrial grade gases can be used.
As the oxygen source supplied to the reaction system, air, air enriched with oxygen, or pure oxygen can be used. Further, helium, argon, carbon dioxide gas, water vapor, nitrogen or the like may be supplied as a dilution gas.
The molar ratio of ammonia to propane or isobutane supplied to the reaction system is 0.1 to 1.5, preferably 0.2 to 1.2. The molar ratio of molecular oxygen supplied to the reaction to propane or isobutane is 0.2 to 6, preferably 0.4 to 4.
The reaction pressure is 0.01 to 1 MPa in absolute pressure, preferably 0.1 to 0.3 MPa.
The reaction temperature is 350 ° C to 600 ° C, preferably 380 ° C to 470 ° C.
The contact time is 0.1 to 30 (g · s / ml), preferably 0.5 to 10 (g · s / ml).
For the reaction, a conventional system such as a fixed bed, a fluidized bed and a moving bed can be adopted, but a fluidized bed is preferred. The reaction may be a single flow method or a recycle method.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention will be explained with examples of ammoxidation reaction of propane. In each example, propane conversion and acrylonitrile selectivity follow the following definitions, respectively.
[0018]
Propane conversion (%) = (moles of propane reacted) / (moles of propane fed) × 100
Acrylonitrile selectivity (%) = (number of moles of acrylonitrile produced) /
(Mole number of reacted propane) × 100
[0019]
[Example 1]
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Mo 1 V 0.3 Sb 0.23 Nb 0.07} Al 0.1 O n / SiO 2 (40 wt%) as follows.
[0020]
1000 g of water, ammonium heptamolybdate [(NH 4) ₆ Mo ₇ O ₂₄ · 4H ₂ O] 250 g, ammonium metavanadate [NH ₄ VO ₃ ] 49.7 g, antimony (III) oxide [Sb ₂ O ₃ ] 47.5 g Then, the mixture was reacted at 100 ° C. for 2 hours in the atmosphere by refluxing in the atmosphere using an oil bath, and then cooled to 50 ° C., followed by addition of 689 g of silica sol having a silica content of 30% by weight. After stirring for 1 hour, 221 g of 5% by weight hydrogen peroxide water was added, and the mixture was stirred at 50 ° C. for 1 hour to carry out oxidation treatment to obtain a mixed solution (a). This oxidation treatment changed the liquid color from dark blue to brown.
17.3 g of niobic acid containing 76% by weight in terms of Nb ₂ O _{5 and} 33.7 g of oxalic acid dihydrate [H ₂ C ₂ O ₄ .2H ₂ O] are added to 120 g of water, and the mixture is stirred at 60 ° C. Then, the mixture was dissolved at 30 ° C. to obtain a niobium raw material liquid.
[0021]
After adding 7.2 g of aluminum oxide (Wako Pure Chemicals, product code 012-01965) to 50 g of water, it was vigorously suspended for 1 hour to obtain an aluminum raw material liquid. When the XRD of the aluminum oxide was measured, it was α-type aluminum oxide (α-alumina) having high crystallinity.
The niobium raw material liquid was added to the mixed liquid (a), and then the aluminum raw material liquid was added. Thereafter, the mixture was stirred at 50 ° C. for 30 minutes in an air atmosphere to obtain a catalyst raw material liquid.
The obtained catalyst raw material liquid was dried using a centrifugal spray dryer under conditions of an inlet temperature of 230 ° C. and an outlet temperature of 120 ° C. to obtain a fine spherical dry powder. 100 g of the obtained dry powder was filled in a quartz container, and while rotating the container, 600 Ncc / min. The catalyst was obtained by calcination at 640 ° C. for 2 hours under a nitrogen gas flow. The oxygen concentration of the nitrogen gas used was 1 ppm as a result of measurement using a trace oxygen analyzer (306WA type, manufactured by Teledyne Analytical Instruments). The composition of the catalyst and the main production factors are listed in Table 1.
[0022]
<Propane Ammoxidation Test>
Catalyst W = 0.35 g is packed into a fixed bed type reaction tube having an inner diameter of 4 mm, reaction temperature T = 420 ° C., propane: ammonia: oxygen: helium = 1: 0.7: 1.7: 5.3 molar ratio. Were mixed at a flow rate F = 4.0 (ml / min). At this time, the pressure P was 0 MPa as a gauge pressure. The contact time is 2.1 (= W / F × 60 × 273 / (273 + T) × ((P + 0.101) /0.101)) (g · s / ml). Analysis of the reaction gas was performed by on-line gas chromatography. The obtained results are shown in Table 1.
[0023]
[Example 2]
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Mo 1 V 0.3 Sb 0.23 Nb 0.07} Al 0.05 O n / SiO 2 (40 wt%) as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 3.6 g was added instead of 7.2 g of aluminum oxide, and 681 g was used instead of 689 g of silica sol.
[0024]
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1. The obtained results are shown in Table 1.
[Example 3]
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Mo 1 V 0.3 Sb 0.23 Nb 0.07} Al 0.3 O n / SiO 2 (40 wt%) as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 21.6 g was added instead of 7.2 g of aluminum oxide and 721 g was used instead of 689 g of silica sol.
[0025]
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1. The obtained results are shown in Table 1.
[Comparative Example 1]
<Catalyst preparation>
A catalyst having a composition formula of Mo ₁ V _0.3 Sb _0.23 Nb _0.07 O _n / SiO ₂ (40 wt%) was prepared as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that aluminum oxide was not added and 673 g was used instead of 689 g of silica sol.
[0026]
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1. The obtained results are shown in Table 1.
[Comparative Example 2]
[0027]
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Mo 1 V 0.3 Sb 0.23 Nb 0.07} Al 0.6 O n / SiO 2 (40 wt%) as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 43.3 g was added instead of 7.2 g of aluminum oxide and 770 g was used instead of 689 g of silica sol.
[0028]
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1. The obtained results are shown in Table 1.
[0029]
[Table 1]

[0030]
【The invention's effect】
According to the method of the present invention, an unsaturated nitrile can be produced with high selectivity from propane or isobutane.

Claims (7)

A catalyst used for producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane, wherein the catalyst has a component composition represented by the following formula (I).
Mo ₁ V _a Sb _b Nb _c Al _d O _n (I)
(Wherein a , b, c and d represent atomic ratios per Mo atom, 0.1 ≦ a ≦ 1, 0.01 ≦ b ≦ 0.6, 0.01 ≦ c ≦ 0.3, 0 .01 ≦ d ≦ 0.5, n and its is an atomic ratio determined by the oxidation state of the constituent metal.)   The catalyst according to claim 1, which is supported on 20 to 60% by weight of silica.   The catalyst according to claim 1 or 2, wherein the catalyst is produced by firing at 500 ° C to 700 ° C in a gas atmosphere substantially free of oxygen.   The catalyst according to any one of claims 1 to 3, wherein the catalyst is produced using aluminum oxide as a catalyst raw material. Either the serial mounting of the catalyst of claims 1 to 4 wherein the catalyst is characterized in that the molar ratio of hydrogen peroxide / niobium is produced using a catalyst raw material solution is 0.5 to 10.   The catalyst according to any one of claims 1 to 5, wherein the catalyst is produced using a catalyst raw material liquid having a dicarboxylic acid / niobium molar ratio of 1 to 8.   A method for producing an unsaturated nitrile, comprising using the catalyst according to any one of claims 1 to 6 in producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane.