JP4761461B2 - Nb-based oxide catalyst and method for producing unsaturated compound using the same - Google Patents

Description

  The present invention relates to a catalyst used in a gas phase catalytic ammoxidation reaction of propane or isobutane or a gas phase catalytic oxidation reaction, and a method for producing an unsaturated nitrile or an unsaturated carboxylic acid using the catalyst.

  Recently, instead of propylene or isobutylene, propane or isobutane is used as a raw material, and technology for producing unsaturated nitriles and unsaturated carboxylic acids by gas phase catalytic ammoxidation reaction or gas phase catalytic oxidation reaction has attracted attention. Has been proposed.

  Among them, a catalyst that is particularly attracting attention is an oxide catalyst composed of Mo—V—Te—Nb or Mo—V—Sb—Nb mainly composed of molybdenum. Etc. are disclosed. The reason for these attentions is that the selectivity of unsaturated nitriles and unsaturated carboxylic acids is relatively high, and the reaction is operated at a low temperature of 420 to 450 ° C. In such a temperature range, activation of propane induced by heat hardly occurs, and it is considered to have a relatively high selectivity.

In general, water is generated as a reaction byproduct in the gas phase catalytic ammoxidation reaction or the gas phase catalytic oxidation reaction. In a gas phase ammoxidation reaction or gas phase catalytic oxidation reaction using an oxide catalyst containing molybdenum, molybdenum combines with water generated in the gas phase ammoxidation reaction or gas phase contact oxidation reaction to reduce the vapor pressure. The molybdic acid Mo ₂ (OH) ₂ contained in the catalyst is scattered, and the molybdic acid is scattered in the gas stream. As a result, the amount of molybdenum in the catalyst decreases. (For example, refer nonpatent literature 1 and patent literature 3). For these reasons, there is a problem that the composite oxide catalyst containing molybdenum deteriorates the catalyst and causes a decrease in productivity, and the scattered molybdenum adheres to the cooling coil and reaction line of the reactor to improve the efficiency of heat removal. There is a problem that it lowers and causes dirt and blockage. For this reason, there are problems such as activation of a deteriorated catalyst and addition of molybdenum, and periodic removal of molybdenum fixed to the reactor and reaction line.

  On the other hand, as a catalyst not containing molybdenum as a main component, a catalyst containing Sb—Nb / Ta—V (see, for example, Patent Document 4) or a catalyst containing Nb—Bi—V (see, for example, Patent Document 5). Catalysts containing W-Cr-Bi (see, for example, Patent Document 6) and catalysts containing Bi-V (see, for example, Patent Document 7) are disclosed. In addition, as a catalyst having a low molybdenum content, a catalyst containing Fe—Sb—Cr—Mo containing iron as a main component (see, for example, Patent Document 8) includes a catalyst containing Fe—Sb—V—Mo (eg, Patent Document 9), a catalyst containing Nb—Sb—Cr (for example, see Patent Document 10), a catalyst having V-Sb as a main active phase (for example, see Patent Document 11), and the like are disclosed. However, these catalysts have low selectivity, yield and activity of the target product, unsaturated nitrile or unsaturated carboxylic acid. In addition, since a very high reaction temperature of about 500 ° C. or higher is required, it is disadvantageous in terms of the material of the reactor, production cost, etc. In addition, propane by a radical reaction induced by heat in a reaction of 500 ° C. or higher. Because of the activation mechanism of isobutane, it is difficult to become a catalyst that can improve selectivity and yield. Furthermore, it is said that antimony is also volatile (see, for example, Non-Patent Document 2), and a catalyst that does not have this as a main component is desired.

  For these reasons, a catalyst that is used for a gas phase catalytic ammoxidation reaction or a gas phase catalytic oxidation reaction of propane or isobutane and has a high activity at a relatively low reaction temperature without using molybdenum as a main component is desired. In addition, a catalyst having a good reaction result such as the selectivity of the target product, unsaturated nitrile and unsaturated carboxylic acid, is desired.

A by-product with particularly high utility value in the ammoxidation reaction is hydrocyanic acid. Cyanic acid is used for Strecker reaction with aldehydes, and cyanohydrins obtained there are converted to methyl methacrylate or amino acids. In the case of ammoxidation, a catalyst having high selectivity to hydrocyanic acid in addition to the selectivity of unsaturated nitrile is desired.
JP-A-5-208136 Japanese Patent Laid-Open No. 9-157241 JP 2005-211184 A JP-A-11-246505 JP 2000-117103 A JP-A-10-87513 JP 63-295545 A JP 2000-351760 Japanese Patent Laid-Open No. 11-246504 Japanese Patent Laid-Open No. 10-1465 JP 2005-254240 A Butten (J. Buiten), Oxidation of propylen by means of SnO2-MoO3 catalysts, "Journal of catalysis" (Netherlands), Elsevier 88, p. Ito et al. Resources and Materials 2000 Fall Meeting 2000, pp. 67-68

  The object of the present invention is a catalyst used for producing unsaturated nitrile and hydrocyanic acid by gas phase catalytic ammoxidation reaction of propane or isobutane, or unsaturated carboxylic acid by gas phase catalytic oxidation reaction, Provides a catalyst with high activity at a relatively low reaction temperature, high selectivity for unsaturated nitriles and unsaturated carboxylic acids as target products, and high selectivity to hydrocyanic acid as a by-product. It is to be.

  Under such circumstances, the present inventors have intensively studied a catalyst used for producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane or an unsaturated carboxylic acid by a gas phase catalytic oxidation reaction. As a result, a reduced oxide catalyst having a tungsten bronze structure mainly composed of Nb, which is a completely new technology, has a high selectivity for unsaturated nitriles or unsaturated carboxylic acids at a relatively low reaction temperature, and a high activity. In addition, as a secondary effect, in the case of ammoxidation, it was found that the selectivity of hydrocyanic acid was high, and the present invention was completed.

That is, in the first aspect of the present invention,
[1] An oxide catalyst used for producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane, or an unsaturated carboxylic acid by a gas phase catalytic oxidation reaction,
A reduced oxide catalyst having a tungsten bronze structure mainly composed of Nb;
[2] The reduced oxide catalyst is represented by the following formula (I):
Nb ₁ X _a O _n1 (I)
(Where
X represents at least one element selected from the group consisting of vanadium, bismuth, cerium, molybdenum and titanium,
a and n1 represent an atomic ratio per Nb1 atom, a is 0 <a <0.8, and n1 is an atomic ratio determined by the oxidation state of the constituent metals. )
The reduced oxide catalyst according to [1] above,
[3] The reduced oxide catalyst is represented by the following formula (II):
_{Nb 1 V b Bi c Y d} O n2 (II)
(Where
Y represents at least one element selected from the group consisting of cerium, molybdenum and titanium,
b, c, d and n2 represent atomic ratios per Nb atom, b and c are 0.01 ≦ b <0.8 and 0.01 ≦ c <0.8, respectively, and d is 0 ≦ d <0.8, and n2 is an atomic ratio determined by the oxidation state of the constituent metals. )
The reduced oxide catalyst according to [1] above,
[4] Any one of [1] to [3] above, wherein the reduced oxide catalyst is supported on 10 to 60% by weight of silica based on the total weight of the reduced oxide catalyst and silica. The reduced oxide catalyst according to one item,
I will provide a.

In the second aspect of the present invention,
[5] A method for producing an unsaturated nitrile by a gas phase catalytic ammoxidation reaction of propane or isobutane,
A method for producing an unsaturated nitrile, comprising the step of bringing the reduced oxide catalyst according to any one of [1] to [4] above into contact with the propane or isobutane;
[6] A method for producing an unsaturated carboxylic acid by a gas phase catalytic oxidation reaction of propane or isobutane,
A method for producing an unsaturated carboxylic acid comprising a step of bringing the reduced oxide catalyst according to any one of [1] to [4] above into contact with the propane or isobutane;
I will provide a.

  According to the reduced oxide catalyst of the present invention, it is possible to react from propane or isobutane with a high activity at a relatively low reaction temperature, and to produce an unsaturated nitrile or an unsaturated carboxylic acid with high selectivity. be able to. In addition, in the gas phase catalytic ammoxidation reaction using the reduced oxide catalyst according to the present invention, the selectivity for hydrocyanic acid, which is a useful byproduct, is high. Furthermore, since the reduced oxide catalyst according to the present invention does not contain a scattering element as a main component, troublesome operational problems such as contamination of the reactor cooling coil and reaction line do not occur.

  The following embodiment is an example for explaining the present invention, and is not intended to limit the present invention only to this embodiment. The present invention can be implemented in various forms without departing from the gist thereof.

The oxide catalyst according to the present invention is a reduced oxide catalyst having a tungsten bronze structure mainly composed of Nb. Here, the term “having Nb as the main component” means a catalyst in which Nb has the highest content among elements other than oxygen constituting the oxide catalyst. The term “tungsten bronze structure” generally refers to A _x WO ₃ (A = H, Li, Na, K, Rb, Cs, Ca, Sr, Ba, In, Tl, Ge, Sn, Pb. Well known as a cationic element such as Cu, Ag, x ≧ 0), and is a structure in which unit blocks of oxygen octahedron (WO ₆ ) are connected together sharing a vertex and a ridge (for example, crystal structure handbook (Kyoritsu) Publication) p832, 4th edition experimental chemistry course 16 inorganic compound (Maruzen) p448, Lars Kihlberg, Renu Sharma, J. Microsc. Spectrosc. Electron., 7, 387 (1982) etc.). Depending on how the vertices and edges are shared, a wide variety of structures can be used. For example, a bronze structure having a perovskite-type bronze structure, a five-membered ring, a six-membered ring, a seven-membered ring, etc. An intergrowth bronze structure or the like is known. In this specification, the term “tungsten bronze structure” is used as a structure name, but it does not mean that the compound skeleton is formed of tungsten and oxygen, but has a tungsten bronze structure. Refers to all structures known as.

  In the present invention, one feature of the reduced oxide having a tungsten bronze structure is that it has a layered structure. Therefore, in the X-ray diffractogram measured by CuKα rays, the interplanar spacing of the layers (with the c axis as the plane vector). 22.5 ± 1 °, preferably 22.5 ± 0.5 °, more preferably 22.5 ± 0.2 °, still more preferably 22.5 ± 0.1 corresponding to (001)) It has a strong peak at °. The peak intensity corresponding to the above face spacing is the strongest among the peaks attributed to the reduced oxide having a tungsten bronze structure, or the second to the third strongest. In the reduced oxide catalyst according to the present invention, a peak not attributed to the reduced oxide having a tungsten bronze structure may or may not exist, and the size of the peak not attributed does not matter.

  As an example showing a reduced tungsten bronze structure according to the present invention, in an X-ray diffraction diagram measured by CuKα rays, 22.5 ° ± 0.5 ° (P1 peak), 28.4 ° ± 0.5 ° (P2 Peak), 36.7 ° ± 0.5 ° (P3 peak), 46.3 ° ± 0.5 ° (P4 peak). Preferably, they are 22.5 ° ± 0.2 °, 28.4 ± 0.2 °, 36.7 ° ± 0.2 °, and 46.3 ° ± 0.2 °. More preferably, they are 22.5 ° ± 0.1 °, 28.4 ± 0.1 °, 36.7 ° ± 0.1 °, 46.3 ° ± 0.1 °. When the P1 peak intensity is 1, the P2 peak intensity is preferably 0.2 to 1.5, the P3 peak intensity is 0.03 to 0.6, and the P4 peak intensity is preferably 0.01 to 0.5.

In one preferred embodiment of the oxide catalyst according to the present invention, the composition of the oxide catalyst mainly composed of Nb is a reduced oxide catalyst represented by the following formula (I):
Nb ₁ X _a O _n1 (I)
(Where
X represents at least one element selected from the group consisting of vanadium, bismuth, cerium, molybdenum and titanium,
a and n1 represent an atomic ratio per Nb1 atom, a is 0 <a <0.8, and n1 is an atomic ratio determined by the oxidation state of the constituent metals. ).
Here, a is preferably 0.02 ≦ a ≦ 0.5, more preferably 0.03 ≦ a ≦ 0.3, and still more preferably 0.04 ≦ a ≦ 0.2.

In another preferred embodiment of the oxide catalyst according to the present invention, the composition of the oxide catalyst containing Nb as a main component is a reduced oxide catalyst represented by the following formula (II):
_{Nb 1 V b Bi c Y d} O n2 (II)
(Where
Y represents at least one element selected from the group consisting of cerium, molybdenum and titanium,
b, c, d and n2 represent atomic ratios per Nb atom, b and c are 0.01 ≦ b <0.8 and 0.01 ≦ c <0.8, respectively, and d is 0 ≦ d <0.8, and n2 is an atomic ratio determined by the oxidation state of the constituent metals. ).
Here, b is preferably 0.02 ≦ b ≦ 0.5, more preferably 0.03 ≦ b ≦ 0.3, and further preferably 0.04 ≦ b ≦ 0.2. c is preferably 0.02 ≦ c ≦ 0.5, more preferably 0.03 ≦ c ≦ 0.3, and still more preferably 0.04 ≦ c ≦ 0.2. Further, d is preferably 0 ≦ d ≦ 0.5, more preferably 0 ≦ d ≦ 0.2, and further preferably 0 <d ≦ 0.1. In the above formulas (I) and (II), the values of the atomic ratios a, b, c, and d per Nb atom indicate the composition ratio of the constituent elements charged.

  The reduced oxide catalyst according to the present invention is represented by the above formulas (I) and (II). As optional components of these central compositions, Cr, W, Al, Ta, Zr, Hf, Mn, At least one selected from Re, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Ag, Zn, B, In, Ge, Sn, P, Pb, Y, Ga, rare earth elements and alkaline earth metals Seed elements may be added. Preferably, it is at least one element selected from W, Al, Zr, Ge, Sn, Re, B, In, P, Y, and a rare earth element. The addition amount of the optional component is less than 0.8 with respect to the number of moles of Nb, and particularly preferably less than 0.2.

  Further, the reduced oxide catalyst according to the present invention can be used by being supported on a carrier. As the carrier, a known carrier can be used, and preferably, for example, silica. The weight of silica is preferably 10 to 60% by weight, more preferably 20% to 50% by weight. When the weight of silica is less than 10% by weight, the strength is small, and when the weight is 60% by weight or more, the strength is large.

The weight percent of silica is defined by the following formula (III), where W1 is the weight of the oxide of formula (I) or formula (II), 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) (III)

  The reduced oxide catalyst having a tungsten bronze structure containing Nb as the main component of the present invention is an oxide catalyst produced reductively. A firing method or a hydrothermal synthesis method may be used. An atmosphere in which air is diluted with an inert gas, an inert gas atmosphere, an atmosphere in which a reducing gas such as organic matter, ammonia or hydrogen coexists with air, an atmosphere in which the oxygen concentration is diluted than air, such as a reducing gas atmosphere, or an oxygen-containing gas such as air It is an oxide catalyst produced by firing in an atmosphere in which a reducing gas coexists with or by hydrothermal synthesis. Preferably, it is an oxide catalyst produced by calcining a catalyst precursor obtained using an organic substance, ammonium ion or the like as a raw material in the catalyst raw material preparation step in an inert gas atmosphere.

  The following compounds can be used as raw materials for producing the reduced oxide catalyst in the present invention. As a raw material of niobium, niobic acid, niobium oxide, an aqueous solution in which niobic acid is dissolved in a dibasic acid, or the like can be used. 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, and more preferably 2 to 4. Hydrogen peroxide may be added to the obtained aqueous solution. The molar ratio of hydrogen peroxide / niobium is preferably 0.5 to 10, more preferably 2 to 6.

  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).

  As a bismuth raw material, bismuth nitrate pentahydrate, bismuth oxide, bismuth hydroxide, bismuth carbonate, bismuth acetate, bismuth acetate, etc. can be used, and bismuth nitrate is preferred.

  In addition, when using silica as a support | carrier, a silica sol is used suitably as a raw material.

The manufacturing method of the oxide catalyst according to the present invention will be described using the case of manufacturing through the following three steps of raw material preparation, drying and firing.
<Raw material preparation process>
Niobic acid is dissolved in an oxalic acid aqueous solution to prepare a niobium raw material liquid. At this time, hydrogen peroxide water may be added to the niobium raw material liquid. Bismuth nitrate is dissolved in an aqueous nitric acid solution to prepare a bismuth raw material liquid. A vanadium raw material liquid is prepared by dissolving ammonium metavanadate in water. A vanadium raw material liquid is added to the niobium raw material liquid, and then a bismuth raw material liquid is added to prepare a catalyst raw material liquid. The catalyst raw material used in the raw material preparation step preferably contains an organic substance such as oxalic acid or ammonium ions as in this example.
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 other components, a catalyst raw material liquid can be obtained by adding a raw material containing an optional component in any step of the above blending sequence.

<Drying process>
The catalyst precursor liquid obtained in the raw material preparation step can be dried by spray drying or evaporation to dryness to obtain a catalyst precursor. 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.

<Baking process>
An oxide catalyst can be obtained by calcining the catalyst precursor obtained in the drying step. For the firing, a rotary furnace, a tunnel furnace, a tubular furnace, a fluidized firing furnace or the like is used. The firing atmosphere is an atmosphere in which air is diluted with an inert gas, an inert gas atmosphere, an atmosphere in which a reducing gas such as organic matter or ammonia coexists with air, an atmosphere in which the oxygen concentration is diluted than air, such as a reducing atmosphere, or an oxygen-containing atmosphere such as air It is an atmosphere in which reducing gas coexists with gas. More preferably, it is carried out while circulating an inert gas such as nitrogen that does not substantially contain oxygen. The oxide catalyst according to the present invention is preferably reduced more than the maximum oxidation number of each element, and as a method thereof, a raw material containing an organic substance or an ammonium salt is used as a catalyst raw material, and is fired in an inert atmosphere. Such an oxide catalyst can be obtained. The baking temperature is 500 to 900 ° C, preferably 550 to 670 ° C. 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, more preferably 10 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 performed at 200 ° C. to 420 ° C., preferably at 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.

  The catalyst thus produced should be used as a catalyst for the production of unsaturated nitriles by gas phase catalytic ammoxidation of propane or isobutane, or by the gas phase catalytic oxidation of propane or isobutane. Can do.

  The feedstock of propane or isobutane and ammonia used for the gas phase catalytic ammoxidation reaction or the gas phase catalytic oxidation reaction in the present invention does not necessarily have to be highly pure, and an industrial grade gas can be used. As the oxygen source supplied to the reaction system, air, air enriched with oxygen, or pure oxygen can be used. Furthermore, helium, argon, carbon dioxide gas, water vapor, nitrogen, or the like may be supplied as a dilution gas.

  In the case of gas phase catalytic ammoxidation, the molar ratio of ammonia supplied to the reaction system to propane or isobutane 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.

  In the case of gas phase catalytic oxidation, the molar ratio of molecular oxygen supplied to the reaction system to propane or isobutane is 0.1 to 10, preferably 0.1 to 5. Although addition of water vapor to the reaction system is preferred, the molar ratio of water vapor supplied to the reaction to propane or isobutane is 0.1 to 70, preferably 0.5 to 40.

  The reaction pressure is 0.01 to 1 MPa in absolute pressure, and preferably 0.1 to 0.3 MPa. The reaction temperature is 350 ° C. to 600 ° C., preferably 380 ° C. to 490 ° C., more preferably 400 to 470 ° C. The contact time is 0.05 to 30 (g · s / ml), preferably 0.1 to 10 (g · s / ml). The gas phase catalytic ammoxidation reaction or the gas phase catalytic oxidation reaction may employ a conventional method such as a fixed bed, a fluidized bed, or a moving bed, but a fluidized bed is preferred. The reaction may be a single flow method or a recycle method.

  The present invention will be described in more detail with reference to the following examples and comparative examples of the present invention, but these are illustrative and the present invention is not limited to the following specific examples. Those skilled in the art can implement the present invention by making various modifications to the embodiments shown below, and such modifications are included in the scope of the claims of the present application.

In the following, the present invention will be described with reference to examples of propane ammoxidation reaction and propane oxidation reaction. In each example, propane conversion, acrylonitrile selectivity, and acrylic acid selectivity follow the following definitions, respectively.
Propane conversion (%) = (moles of propane reacted) / (moles of propane fed) × 100
Acrylonitrile selectivity (%) = (number of moles of acrylonitrile produced) / (number of moles of reacted propane) × 100
Cyanic acid selectivity (%) = ((moles of cyanide produced) / 3) / (moles of reacted propane) × 100
Contact time (s · g / ml) = W / F × 60 × 273 / (273 + T) × ((P + 0.101) /0.101))
Here, W is the catalyst weight (g), F is the gas flow rate (ml / s), T is the reaction temperature (° C.), P is the gauge pressure (MPa)
Activity ((s · g / ml) ⁻¹ ) = − Ln (1- (conversion / 100)) / t
Here, t is the contact time (s).

Example 1
<Catalyst preparation>
Composition formula was prepared a catalyst represented by Nb ₁ V _0.12 Bi _0.12 O _n as follows.
To 2350 g of water, 200 g of niobic acid containing 76% by weight in terms of Nb ₂ O _{5 and} 389.5 g of oxalic acid dihydrate [H ₂ C ₂ O ₄ .2H ₂ O] were added, and the mixture was stirred at 60 ° C. After heating and dissolving, the mixture was cooled at 30 ° C. to obtain a niobium raw material liquid.
Bismuth nitrate pentahydrate [Bi (NO ₃ ) ₃ .5H ₂ O] (66.6 g) was dissolved in 200 g of a 10 wt% nitric acid aqueous solution to obtain a bismuth raw material liquid.
16.1 g of ammonium metavanadate [NH ₄ VO ₃ ] was dissolved in 211 g of 5 wt% hydrogen peroxide solution to obtain a vanadium raw material liquid.
The vanadium raw material liquid was added to the niobium raw material liquid, and then the bismuth raw material liquid was added 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 microspherical catalyst precursor. 10 g of the obtained catalyst precursor was pre-baked in air at 250 ° C. for 2 hours, and then filled in a quartz container, and 350 Ncc / min. Was then calcined at 600 ° C. for 2 hours under a nitrogen gas flow to obtain an oxide catalyst.

<X-ray diffraction measurement>
X-ray diffraction was measured using an MXP-18 type X-ray diffractometer manufactured by Mac Science. The sample preparation method and X-ray diffraction conditions are as follows.
(Sample preparation)
About 0.5 g of the oxide catalyst was placed in an agate mortar , pulverized by hand for 2 minutes using an agate pestle, and classified to obtain a catalyst powder having a particle size of 53 μm or less. The obtained catalyst powder was placed in a depression (length 20 mm, width 16 mm rectangular, depth 0.2 mm) on the surface of the XRD measurement sample stage, and pressed using a flat stainless steel spatula, The surface was flattened.
(Measurement conditions) The X-ray diffraction pattern was obtained under the following conditions.
X-ray source: CuKα1 + CuKα2, detector: scintillation counter, spectral crystal: graphite, tube voltage: 40 kV, tube current: 190 mA, divergence slit: 1 °, scattering slit: 1 °, light receiving slit: 0.3 mm, scan speed: 1 ° / min, sampling width: 0.02 °, scan method: 2θ / θ method.
The X-ray diffraction pattern had peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °. As a result of assigning the diffraction peaks, the structure of the same type as that of No. 1840 (K. Kato, S. Tamura., Acta Cryst. B, 31, 673 (1975)) recorded in Inorganic Crystal Database (ICSD) is obtained. And a reduced oxide having a tungsten bronze structure.

<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 = 450 ° C. (external temperature), propane: ammonia: oxygen: helium = 1: 0.7: 1.7: 5. A mixed gas having a molar ratio of 3 was allowed to flow at a flow rate F = 45 (ml / min). At this time, the pressure P was 0 MPa as a gauge pressure. The contact time is 0.18 (= 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.

(Example 2)
<Catalyst preparation>
A catalyst having a composition formula of Nb ₁ V _0.12 Bi _0.12 O _n / SiO ₂ (10 wt%) was prepared as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 73 g of silica sol having a silica content of 30% by weight was added to the catalyst raw material liquid.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 _{Nb 1 V 0.12 Bi 0.12 Ce 0.02} O n as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 10 g of cerium nitrate hexahydrate [Ce (NO ₃ ) ₃ .6H ₂ O] was added to the bismuth raw material liquid.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 4
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Nb 1 V 0.12 Bi 0.12 Al 0.01} O n as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 0.58 g of aluminum oxide [Al ₂ O ₃ ] was added to the catalyst raw material liquid.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 5)
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Nb 1 V 0.12 Bi 0.12 Mo 0.01} O n as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 2.0 g of ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O] was added to the vanadium raw material liquid.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 6)
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Nb 1 V 0.08 Bi 0.05 Mo 0.05} O n as follows.
Use 27.7 g instead of 66.6 g of bismuth nitrate pentahydrate [Bi (NO ₃ ) ₃ .5H ₂ O], and 10.7 g instead of 16.1 g of ammonium metavanadate [NH ₄ VO ₃ ]. The catalyst preparation of Example 1 was repeated except that 10 g of ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O] was added to the vanadium raw material liquid and no pre-calcination was performed. Prepared.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1 except that the catalyst W was changed to 0.20 g instead of 0.35 g and the mixed gas flow rate F was changed to 50 (ml / min) instead of 45 (ml / min). I went. The obtained results are shown in Table 1.

(Example 7)
<Catalyst preparation>
Composition formula was prepared a catalyst represented by Nb ₁ V _0.16 Bi _0.20 O _n as follows.
111 g was used instead of 66.6 g of bismuth nitrate pentahydrate [Bi (NO ₃ ) ₃ .5H ₂ O], and 21.4 g was used instead of 16.1 g of ammonium metavanadate [NH ₄ VO ₃ ]. Prepared the catalyst by repeating the catalyst preparation of Example 1.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 8)
<Catalyst preparation>
Composition formula was prepared a catalyst represented by _{Nb 1 V 0.12 Bi 0.12 Ti 0.01} O n as follows.
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that 0.9 g of titanium oxide anatase type [TiO ₂ ] was added to the catalyst raw material liquid.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<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 9
<Catalyst preparation>
Composition formula was prepared a catalyst represented by Nb ₁ V _0.41 Bi _0.30 O _n as follows.
Except for using 166 g instead of 66.6 g of bismuth nitrate pentahydrate [Bi (NO ₃ ) ₃ .5H ₂ O] and 54 g instead of 16.1 g of ammonium metavanadate [NH ₄ VO ₃ ]. The catalyst preparation of Example 1 was repeated to prepare a catalyst.
<X-ray diffraction measurement>
It was a reduced oxide having a tungsten bronze structure having peaks at 22.5 °, 28.4 °, 36.7 °, and 46.3 °.
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1 except that the mixed gas flow rate F was changed to 35 (ml / min) instead of 45 (ml / min). The obtained results are shown in Table 1.

(Comparative Example 1)
<Catalyst preparation>
A catalyst was prepared by repeating the catalyst preparation of Example 1 except that instead of the nitrogen gas flow of Example 1 and under the flow of air only.
<Propane Ammoxidation Test>
The obtained catalyst was subjected to the same conditions as in Example 1 except that the mixed gas flow rate F was changed to 4 (ml / min) instead of 45 (ml / min). The obtained results are shown in Table 1.

  According to the reduced oxide catalyst of the present invention, it is possible to react from propane or isobutane with a high activity at a relatively low reaction temperature, and to produce an unsaturated nitrile or an unsaturated carboxylic acid with high selectivity. be able to. In addition, in the gas phase catalytic ammoxidation reaction using the reduced oxide catalyst according to the present invention, the selectivity for hydrocyanic acid, which is a useful byproduct, is high. Furthermore, since the reduced oxide catalyst according to the present invention does not contain a scattering element as a main component, troublesome operational problems such as contamination of the reactor cooling coil and reaction line do not occur.

Claims (2)

An oxide catalyst used for producing an unsaturated nitrile by a gas-phase catalytic ammoxidation reaction of propane or isobutane or an unsaturated carboxylic acid by a gas-phase catalytic oxidation reaction, and has a tungsten bronze structure mainly composed of Nb A reduced oxide catalyst ,
The reduced oxide catalyst is represented by the following formula (II):
_{Nb 1 V b Bi c Y d} O n2 (II)
(Where
Y represents at least one element selected from the group consisting of cerium, molybdenum and titanium,
b, c, d and n2 represent atomic ratios per Nb atom, b and c are 0.01 ≦ b <0.8 and 0.01 ≦ c <0.8, respectively, and d is 0 ≦ d <0.8, and n2 is an atomic ratio determined by the oxidation state of the constituent metals. )
And
In the X-ray diffraction pattern measured by CuKα ray, 22.5 ° ± 0.5 °, 28.4 ° ± 0.5 °, 36.7 ° ± 0.5 °, 46.3 ° ± 0.5 A reduced oxide catalyst characterized by having a peak at °. The reduced oxide catalyst according to claim 1, wherein the reduced oxide catalyst is supported on 10 to 60% by weight of silica based on the total weight of the reduced oxide catalyst and silica.