JP2021133272A - Catalyst precursor and complex oxide catalyst - Google Patents

Abstract

To provide a catalyst precursor that makes it possible to prevent both the occurrence of NOx and the degradation of catalytic performance in latter-stage firing at the same time.SOLUTION: The present disclosure provides a precursor of a complex oxide catalyst that is used when producing unsaturated aldehyde and/or unsaturated carboxylic acid from hydrocarbon. In the precursor, an amount of nitrogen left after pre-stage firing is 0.01-1.3 mass%.SELECTED DRAWING: None

Description

The present invention relates to a precursor of a composite oxide catalyst used in producing an unsaturated aldehyde and / or an unsaturated carboxylic acid from a hydrocarbon, and a composite oxide catalyst obtained by using the catalyst precursor.

A method for producing methyl acrylate or methyl methacrylate by an oxidative esterification reaction using at least one selected from propylene, isobutylene, isobutanol, and t-butyl alcohol as a raw material and unsaturated aldehyde as an intermediate. , A method consisting of two reaction steps called the direct meta method and a method consisting of three reaction steps called the direct acid method are known. According to the "Petrochemical Process" (edited by the Petroleum Society, pp. 172 to 176, Kodansha Scientific), the direct acid method is a process for producing methyl acrylate or methyl methacrylate in three steps, and is the first oxidation process. The step is a step of producing acrolein or methacrolein by subjecting at least one starting material selected from propylene, isobutylene and t-butyl alcohol to a gas phase catalytic oxidation reaction with molecular oxygen in the presence of a catalyst. The second oxidation step is a step of producing acrylic acid or methacrylic acid by subjecting acrolein or methacrolein obtained in the first oxidation step to a vapor phase catalytic oxidation reaction with molecular oxygen in the presence of a catalyst. The esterification step is a step of further esterifying acrylic acid or methacrylic acid obtained in the second oxidation step to obtain methyl acrylate or methyl methacrylate when methanol is used as the alcohol at that time. be.
On the other hand, in the direct methacrolein method, at least one selected from the group consisting of propylene, isobutylene, isobutanol, and t-butyl alcohol is used as a raw material, and a gas-phase catalytic oxidation reaction is carried out using a molecular oxygen-containing gas. In the first reaction step of producing methacrolein or methacrolein, the obtained methacrolein or methacrolein is reacted with, for example, methanol as an alcohol and molecular oxygen to produce methyl acrylate or methyl methacrylate at once. It is a method consisting of two catalytic reaction steps of the second reaction step to be produced.

There have been many reports on catalysts used in the production of unsaturated aldehydes as the main component, and many composite oxide catalysts containing Mo and Bi as essential components, which were found by Sohaio in the past, have been reported. Has been done.

For example, in Patent Document 1, since the composite oxide of Mo and Bi contains a β phase, it becomes possible to stably maintain the oxidizing power, and an unsaturated aldehyde can be obtained with a high selectivity and a high yield. Has been reported.

Japanese Unexamined Patent Publication No. 2017-2409

The composite oxide catalyst described in Patent Document 1 is produced by calcining a dried product obtained by drying a raw material slurry in three stages. However, here, the first fired body after the first firing has not been sufficiently denitrated, and a large amount of NOx may be generated in the subsequent subsequent firing, and equipment for removing it is required. It becomes. On the other hand, if the denitration is excessive, the simple oxide tends to grow in the pre-calcination, so that there is a problem that the performance of the catalyst finally obtained is deteriorated.

As a result of diligent studies to solve the above problems, the present inventors have made a precursor of a composite oxide catalyst used in producing unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons after pre-firing. We have found that the above problems can be solved by adjusting the amount of residual nitrogen to a specific range, and arrived at the present invention.
That is, the present invention is as follows.

[1]
A precursor of a composite oxide catalyst used in the production of unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons.
A catalyst precursor having a residual nitrogen content of 0.01 to 1.3% by mass after calcination in the first stage.
[2]
A composite oxide catalyst obtained by using the catalyst precursor according to the above [1].
[3]
A metal oxide containing molybdenum, bismuth, iron, cobalt and cerium and having a composition represented by the following composition formula (1);
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula, Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, Ce is cerium, A is potassium, cesium and rubidium, and B is nickel and manganese. , Copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lantern, placeodium, neodymium and europium, indicating at least one element selected from the group, a to f are atoms of each element with respect to Mo12 atom. The ratio is shown, 0 <a ≦ 8, 0 <b ≦ 6, 1 ≦ c ≦ 12, 0 <d ≦ 8, 0.01 ≦ e ≦ 2, 0 ≦ f <2, and g is a configuration other than oxygen. The composite oxide catalyst according to the above [2], which comprises (the number of atoms of oxygen determined by the atomic value of the element).
[4]
The method for producing a composite oxide catalyst according to the above [2] or [3].
The process of mixing the raw materials that make up the catalyst to obtain a raw material slurry, and
The step of drying the raw material slurry to obtain a dried product, and
A step of obtaining a catalyst precursor by firing the dried product in the previous stage, and
A step of obtaining a composite oxide catalyst by firing the catalyst precursor in the subsequent stage, and
Including
A manufacturing method in which the first-stage firing is carried out in a temperature range of 200 to 400 ° C.
[5]
The method for producing a composite oxide catalyst according to the above [4], wherein the first-stage firing is carried out over 1 to 10 hours.
[6]
A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, which comprises a step of oxidizing a hydrocarbon using the composite oxide catalyst according to the above [2] or [3].

In the catalyst precursor of the present invention, the amount of residual nitrogen after the first-stage calcination is adjusted to a specific range, whereby both the generation of NOx and the deterioration of the catalyst performance in the second-stage calcination can be suppressed at the same time.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described, but the present invention is not limited to the following embodiments. The present invention can be modified in various ways without departing from the gist thereof.

The composite oxide catalyst precursor in this embodiment is
A precursor of a composite oxide catalyst used in the production of unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons.
The amount of residual nitrogen after firing in the first stage is 0.01 to 1.3% by mass.

The composite oxide catalyst used in producing unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons is obtained by drying the raw material slurry to obtain a dried product, and then firing the obtained dried product in the first stage firing and the second stage firing. It is manufactured by subjecting it to firing in two or more stages. Here, in the present embodiment, the "catalyst precursor" refers to those after the first-stage firing step and before the second-stage firing step, and the residual nitrogen amount of this catalyst precursor is 0.01 to 1.3% by mass. It has been adjusted to.

When the residual nitrogen content of the catalyst precursor is less than 0.01% by mass, the simple oxide easily grows in the pre-calcination step, so that the performance of the obtained composite oxide catalyst deteriorates. On the other hand, when the amount of residual nitrogen in the catalyst precursor exceeds 1.3% by mass, a large amount of NOx is generated in the subsequent firing step, and the equipment cost for removing them increases.

The method for adjusting the residual nitrogen amount of the catalyst precursor to 0.01 to 1.3% by mass is not particularly limited, but the amount of nitric acid added to the raw material slurry can be adjusted or calcination in the pre-stage calcination step. For example, adjusting the temperature and firing time.

The amount of residual nitrogen in the catalyst precursor can be measured by CHN elemental analysis. Specifically, the measurement can be performed according to the method described in Examples described later.

The catalyst precursor in the present embodiment preferably contains a metal oxide having a composition represented by the following composition formula (0).
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g '(0)
(In the formula, Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, Ce is cerium, A is potassium, cesium and rubidium, and B is nickel and manganese. , Copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lantern, placeodium, neodymium and europium, at least one element selected from the group, a to f are atoms of each element with respect to Mo12 atom. The ratio is 0 <a ≦ 8, 0 <b ≦ 6, 1 ≦ c ≦ 12, 0 <d ≦ 8, 0.01 ≦ e ≦ 2, 0 ≦ f <2, and g'is an atom of oxygen. It is a number.)

Here, the above a to f are synonymous with a to f in the formula (1) of the metal oxide contained in the composite oxide catalyst described later. Further, g'is the number of oxygen atoms contained in the metal oxide before being completely oxidized by the subsequent firing, and is the number of oxygen atoms contained in the metal oxide after complete oxidation (g in the formula (1)). Is a smaller value.

[Composite oxide catalyst]
It can be obtained by using the composite oxide catalyst of the present embodiment and the catalyst precursor described above.
(1) Composition In the present embodiment, the composition of the composite oxide catalyst preferably contains Mo, Bi, Fe, Co, and Ce. Bi and Mo are indispensable for forming the composite oxide of t, and the atomic ratio a of Bi to the Mo12 atom is preferably 0 <a ≦ 8. From the viewpoint of further increasing the selectivity of the target product, 0.2 ≦ a ≦ 6 is more preferable, and 0.4 ≦ a ≦ 5 is more preferable. Ce is considered to contribute to the structural stabilization of the composite oxide of Mo and Bi. From the viewpoint of increasing heat resistance, the atomic ratio d of Ce is preferably 0 ≦ d ≦ 8, more preferably 0.1 ≦ d ≦ 5, and even more preferably 0.2 ≦ d ≦ 3.

From the viewpoint of increasing the catalytic activity without lowering the selectivity of the target product, Fe is preferably contained in industrially synthesizing the target product, like Mo and Bi. Fe _{forms a composite oxide such as Fe 2} Mo ₃ O ₁₂ , takes oxygen from the gas phase into the structure of the catalyst, supplements the lattice oxygen consumed in the reaction, and prevents the catalyst from being overreduced and deteriorated. It has a function of suppressing. The atomic ratio b of Fe to the Mo12 atom of the oxide catalyst in the present embodiment is preferably 0 <b ≦ 6, more preferably 0.5 ≦ b ≦ 5, and even more preferably 1 ≦ b ≦ 4.

In the composite oxide catalyst of the present embodiment, Co is preferably contained in industrially synthesizing the target product in the same manner as Mo, Bi and Fe. Co forms a composite oxide CoMoO ₄ and serves as a carrier for highly dispersing active species such as Bi-Mo-O and a role of taking in oxygen from the gas phase and supplying it to Bi-Mo-O and the like. Is playing. In order to obtain an unsaturated aldehyde in a high yield, it is preferable _{to combine Co with Mo to form the composite oxide CoMoO 4.} From the viewpoint of reducing the formation of a single oxide such as Co ₃ O ₄ or CoO, the atomic ratio c of Co is preferably 1 ≦ c ≦ 12, more preferably 3 ≦ c ≦ 10, and further preferably 4 ≦. c ≦ 9.

The composite oxide catalyst in the present embodiment preferably contains a metal oxide having a composition represented by the following composition formula (1).
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula, Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, Ce is cerium, A is potassium, cesium and rubidium, and B is nickel and manganese. , Copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, placeodium, neodymium and europium. The ratio is shown, 0 <a ≦ 8, 0 <b ≦ 6, 1 ≦ c ≦ 12, 0 <d ≦ 8, 0.01 ≦ e ≦ 2, 0 ≦ f <2, and g is a configuration other than oxygen. It is the number of oxygen atoms determined by the atomic value of the element.)

In the above composition formula (1), A represents potassium, cesium and / or rubidium, and is considered to play a role in neutralizing acid points such as _{MoO 3 that have not been compounded with the catalyst in the composite oxide catalyst.} The atomic ratio of the element A to the Mo12 atom is preferably 0.01 ≦ e ≦ 2 from the viewpoint of catalytic activity. By adjusting the atomic ratio e of A to this range, the catalyst is prevented from becoming basic, and the olefins and alcohols as raw materials are appropriately adsorbed on the catalyst, so that sufficient catalytic activity tends to be exhibited. ..

In the composition formula (1), B is at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, placeodium, neodymium, and europium. Is shown. Nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin and lead tend to replace some cobalt in the oxide and stabilize the crystal structure _{of CoMoO 4 in the catalyst, lanthanum,} Praseodymium, neodymium, and europium tend to form composite oxides with molybdenum to improve their activity. From the viewpoint of maintaining a balance with the formation of a preferable composite oxide crystal exhibiting catalytic performance, the upper limit of the atomic ratio f of B is preferably f <2.

(2) Components other than metal oxide The composite oxide catalyst for producing unsaturated aldehyde / unsaturated carboxylic acid in the present embodiment may contain a carrier for supporting the metal oxide. A catalyst containing a carrier is preferable in that the metal oxide is highly dispersed and the supported metal oxide is provided with high abrasion resistance, but when producing an unsaturated aldehyde / unsaturated carboxylic acid in a fixed bed reactor. In addition, when a tablet-molded catalyst is used, the carrier may not be included. When the catalyst is molded by the extrusion molding method, it is preferable to include a carrier component. Examples of the carrier include silica, alumina, titania, and zirconia. In general, silica is a preferred carrier in that it is itself inert compared to other carriers and has a good binding action on metal oxides without reducing selectivity for the target product. Further, the silica carrier is also preferable in that it easily imparts high wear resistance to the supported metal oxide. When the catalyst is molded by the extrusion molding method, the content of the carrier with respect to the entire catalyst is preferably 5 to 10% by mass.

When the catalyst is used in a fluidized bed reactor, it is preferable to use silica as a carrier from the same viewpoint as described above. From the viewpoint of making the apparent specific gravity appropriate and improving the fluidity, the content of the carrier in the catalyst is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the catalyst. More preferably, it is 60% by mass or less. When strength such as a catalyst for fluidized bed reaction is required, the content of the carrier is 20% by mass or more with respect to the total mass of the catalyst from the viewpoint of having sufficient crushing resistance and wear resistance for practical use. It is preferably 30% by mass or more, and more preferably 40% by mass or more.

[Manufacturing method of composite oxide catalyst]
The method for producing the composite oxide catalyst of the present embodiment is preferably
The process of mixing the raw materials that make up the catalyst to obtain a raw material slurry, and
The step of drying the raw material slurry to obtain a dried product, and
A step of obtaining a catalyst precursor by firing the dried product in the previous stage, and
A step of obtaining a composite oxide catalyst by firing the catalyst precursor in the subsequent stage, and
including.
Hereinafter, preferred embodiments of a method for producing a composite oxide catalyst having each of the above steps will be described.

(1) Preparation of Raw Material Slurry In the first step, the catalyst raw materials of each metal element constituting the catalyst are mixed to obtain a raw material slurry. Molybdenum, bismuth, cerium, iron, cobalt, potassium, rubidium, cesium, nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lantern, placeodium, neodymium, and europium are the sources of each element. Examples thereof include ammonium salts, nitrates, hydrochlorides and organic acid salts which are soluble in water or nitrate, and oxides, hydroxides, carbonates and the like may be used. In the case of an oxide, a dispersion liquid dispersed in water or an organic solvent is preferable, and more preferably, the oxide is dispersed in water, and when dispersed in water, a polymer or the like is used to disperse the oxide. Dispersion stabilizer may be included. The particle size of the oxide is preferably 1 to 500 nm, more preferably 10 to 80 nm. When producing a catalyst containing a silica carrier, it is preferable to add silica sol as a silica raw material to the raw material slurry.

From the viewpoint of uniformly dispersing the slurry in the raw material slurry, water-soluble polymers such as polyethylene glycol, methyl cellulose, polyvinyl alcohol, polyacrylic acid and polyacrylamide, amines, aminocarboxylic acids, oxalic acid, malonic acid, etc. Polyvalent carboxylic acids such as succinic acid and organic acids such as glycolic acid, apple acid, tartaric acid and citric acid can also be added as appropriate. The amount of the water-soluble polymer or organic acid added is not particularly limited, but it is preferable to add the water-soluble polymer or the organic acid in the range of 0 to 30% by mass with respect to the metal oxide from the viewpoint of the balance between the uniformity and the production amount.

The method for preparing the raw material slurry is not particularly limited as long as it is a commonly used method. For example, a solution in which an ammonium salt of molybdenum is dissolved in warm water and water or nitrate using bismuth, cerium, iron, cobalt and alkali metal as nitrates It can be prepared by mixing a solution dissolved in an aqueous solution. The concentration of metal elements in the raw material slurry after mixing is usually 1 to 50% by mass, preferably 10 to 40% by mass, and more preferably 20 to 40% by mass from the viewpoint of the balance between uniformity and production amount. ..

The content of nitric acid contained in the raw material slurry is preferably 0.1 to 1.2% by mass, more preferably 0.1 to 1.2% by mass, from the viewpoint of achieving the residual nitrogen content of the catalyst precursor of 0.01 to 1.3% by mass. Is 0.3 to 1.1% by mass, more preferably 0.4 to 1.0% by mass. When the content of nitric acid contained in the raw material slurry is less than 0.1% by mass, precipitation of bismuth compounds and simple oxides are formed, which tends to hinder the formation of a preferable composite oxide crystal phase. If it exceeds 0% by mass, α phase and γ tend to be easily generated.

When an aqueous solution or dispersion of ammonium salt is mixed with an aqueous solution or dispersion of nitrate, a precipitate is formed to form a slurry. Before adjusting the pH of the slurry, it is preferable to grind the solid content in the slurry using a homogenizer or the like. As described above, when the composition has a high Bi content, the nitric acid content in the slurry tends to be high and the dispersibility tends to be low, so that the homogenizer treatment is particularly effective. From the viewpoint of crushing the solid content to a smaller size and facilitating the compounding of each element, the rotation speed of the homogenizer is preferably 5000 to 30000 rpm, more preferably 1000 to 20000 rpm, and 15000 to 20000 rpm. Is even more preferable. The homogenizer treatment time depends on the number of revolutions and the amount of solid content, but is generally preferably 5 minutes to 2 hours. If the homogenizer treatment is not performed, simple oxides are likely to be produced.

If the raw material slurry is not homogeneous, the catalyst composition after firing becomes inhomogeneous, and it becomes difficult to form a homogeneously composited crystal structure. Therefore, when the obtained oxide is not sufficiently composited, the slurry is prepared. Attempting to optimize the process is a preferred embodiment. The above-mentioned raw material slurry preparation step is an example and is not limited, and the order of addition of each element source may be changed, the nitric acid concentration may be adjusted, or an aqueous ammonia or aqueous nitric acid solution may be used as a slurry. The pH and viscosity of the slurry may be modified by adding the slurry. In order to form a preferable composite oxide crystal phase, it is important to prepare a homogeneous slurry, and from this viewpoint, the pH of the raw material slurry is preferably adjusted to 8.0 or less. The pH of the raw material slurry is more preferably 0.1 to 7.0, still more preferably 0.3 to 6.0. If the pH of the raw material slurry exceeds 8.0, precipitation of a bismuth compound or simple oxide tends to be formed, which tends to hinder the formation of a preferable composite oxide crystal phase. If the pH is less than 0.1, α phase or γ Tends to be easily generated.

(2) Drying In the second step, the raw material slurry obtained in the first step is dried to obtain a dried product. The drying method is not particularly limited and can be carried out by a generally used method, and can be carried out by any method such as an evaporation drying method, a spray drying method and a vacuum drying method. The spray drying method can be performed by methods such as a centrifugal method, a two-fluid nozzle method, and a high-pressure nozzle method, which are usually industrially performed, and as the drying heat source, air heated by steam, an electric heater, or the like is used. Is preferable. At this time, the temperature at the inlet of the dryer of the spray dryer is usually 150 to 400 ° C, preferably 180 to 400 ° C, and more preferably 200 to 350 ° C.

(3) Firing In the third step, the dried product obtained in the second step is calcined. The firing can be performed using a firing furnace such as a rotary furnace, a tunnel furnace, or a muffle furnace. The method of firing the dried product also differs depending on the raw material used. For example, when the raw material contains nitrate ions, it is preferable to perform the following two-step firing.

[1] First stage firing (first firing)
In the first-stage firing, the temperature of the dried product is raised from room temperature to a temperature range of 200 to 400 ° C., and the temperature is maintained in the temperature range of 200 to 400 ° C. to obtain a catalyst precursor. In the pre-stage firing, the temperature is preferably raised to a temperature range of 200 to 300 ° C, more preferably 230 to 280 ° C. The purpose of the first-stage firing is to gradually burn the ammonium nitrate remaining in the dried body and the nitric acid derived from the raw material metal nitrate, and the time for holding in the temperature range of 200 to 400 ° C. is preferably 1 to 10 hours. , More preferably 2-9 hours. The rate of temperature rise is preferably 20 to 100 ° C./h, more preferably 35 to 80 ° C./h. If the temperature of the first-stage calcination is too high or the time is too long, the simple oxide tends to grow in the first-stage calcination stage, so that it becomes difficult to form a preferable composite oxide crystal phase in the second-stage calcination described later. .. Therefore, it is preferable that the upper limits of the temperature and time in the first firing are set to such an extent that the formation of simple oxides does not occur.

[2] Second-stage firing In the second-stage firing, the catalyst precursor obtained in the first-stage firing is fired at a higher firing temperature. The post-stage firing may be performed in one stage or in two or more stages. A mode in which the subsequent firing is carried out in one stage will be described below.

In the second-stage calcination in the first stage, the catalyst precursor obtained in the first-stage calcination is held at a temperature in the range of 460 to 700 ° C. to obtain a composite oxide catalyst. The temperature in the subsequent firing is preferably 500 to 600 ° C, more preferably 500 to 580 ° C. The purpose of the subsequent calcination is to form a composite oxide in the catalyst precursor and to grow its crystals. The holding time in the subsequent firing is usually 3 to 48 hours, preferably 3 to 24 hours, and more preferably 3 to 10 hours.

Subsequently, an embodiment in which the latter-stage firing is carried out in two stages of the second firing and the third firing will be described below.

In the second firing, the catalyst precursor obtained in the previous firing is gradually heated to over 400 ° C. to 460 ° C. and held at a temperature in the range of over 400 ° C. to 460 ° C. to obtain a second firing body. .. In the second firing, the temperature is preferably raised to a set temperature over 1 to 10 hours. The heating rate does not have to be constant at all times. The heating time is preferably 1 to 5 hours, more preferably 2 to 4 hours. The second calcination is intended to facilitate the uniform formation of a preferable composite oxide crystal phase. According to the findings of the present inventors, since the crystal structure is affected by the product of the firing temperature and the firing time, it is preferable to appropriately set the firing temperature and the firing time. From the viewpoint of facilitating the formation of a preferable composite oxide crystal phase, the temperature in the second firing is preferably 420 to 450 ° C., more preferably 430 to 450 ° C. The holding time in the second firing is preferably 0.5 to 6 h, more preferably 0.5 to 5 h, and even more preferably 0.5 to 3 h. If the holding time of the second firing is too long, it becomes difficult for the crystal structure of the preferable composite oxide crystal phase to grow in the third firing described later. Therefore, it is preferable to set the upper limit of the temperature and time of the second firing to such an extent that the α phase and the γ phase are not generated.

In the third firing, the second fired body obtained in the second firing is held at a temperature in the range of 460 to 700 ° C. to obtain a composite oxide catalyst. The temperature in the third firing is preferably 500 to 600 ° C, more preferably 500 to 580 ° C. The purpose of the third firing is to grow the crystals obtained in the second firing body. The holding time in the third firing is usually 3 to 48 hours, preferably 3 to 24 hours, and more preferably 3 to 10 hours.

[3] Method for producing unsaturated aldehyde / unsaturated carboxylic acid The unsaturated aldehyde and / or unsaturated carboxylic acid can be produced by subjecting a hydrocarbon to an oxidation reaction using the composite oxide catalyst in the present embodiment. can.
Examples of the hydrocarbon used as a raw material include propylene, isobutylene, isobutanol, t-butyl alcohol and the like, and among them, unsaturated hydrocarbons such as propylene and isobutylene are preferable.

Hereinafter, specific examples of the method for producing an unsaturated aldehyde / unsaturated carboxylic acid will be described, but the production method of the present embodiment is not limited to the following specific examples.

(1) Method for Producing Methacrolein or Acrolein Methacrolein and / or methacrylic acid can be obtained, for example, by carrying out a vapor-phase catalytic oxidation reaction of isobutylene and t-butyl alcohol using the composite oxide catalyst of the present embodiment. be able to. In the gas-phase catalytic oxidation reaction, the molecular oxygen concentration of 1 to 10% by volume of isobutylene, t-butyl alcohol, propylene alone, or a mixed gas thereof is 1 to 1 in the catalyst layer in the fixed bed reactor. A raw material gas composed of a mixed gas to which a molecular oxygen-containing gas and a diluting gas are added is introduced so as to have a volume of 20% by volume. The concentration of isobutylene, t-butyl alcohol, propylene, or a mixed gas thereof is usually 1 to 10% by volume, preferably 6 to 10% by volume, and more preferably 7 to 9% by volume. The reaction temperature is 300 to 480 ° C, preferably 350 ° C to 450 ° C, and more preferably 400 ° C to 450 ° C. The pressure is normal pressure to 5 atm, and can be performed by introducing the raw material gas at a space velocity of 400 to 4000 / hr [Normal temperature pressure (NTP) conditions]. The molar ratio of oxygen to isobutylene, t-butyl alcohol, propylene alone, or a mixture thereof is usually 1. from the viewpoint of controlling the outlet oxygen concentration of the reactor in order to improve the yield of unsaturated aldehyde. It is 0 to 2.0, preferably 1.1 to 1.8, and more preferably 1.2 to 1.8.

The molecular oxygen-containing gas, e.g., pure oxygen gas, and N ₂ O, include gas containing oxygen such as air, air from an industrial point of view are preferred. Examples of the diluting gas include nitrogen, carbon dioxide, water vapor and a mixed gas thereof. The mixing ratio of the molecular oxygen-containing gas and the diluted gas in the mixed gas preferably satisfies the condition of 0.01 <molecular oxygen / (molecular oxygen-containing gas + diluted gas) <0.3 in terms of volume ratio. .. Further, the concentration of molecular oxygen in the raw material gas is preferably 1 to 20% by volume.

Water vapor in the raw material gas is necessary from the viewpoint of preventing caulking to the catalyst, but when suppressing the by-product of carboxylic acids such as acrylic acid, methacrylic acid, and acetic acid, reduce the water vapor concentration in the diluted gas as much as possible. Is preferable. The water vapor in the raw material gas is usually used in the range of 0 to 30% by volume.

The present embodiment will be described in more detail with reference to the following examples, but the present embodiment is not limited to the examples described below. The atomic ratio of oxygen atoms in the composite oxide catalyst is determined by the valence conditions of other elements. In Examples and Comparative Examples, the atomic ratios of oxygen atoms in the formula representing the composition of the catalyst. Is omitted. The composition ratio of each element in the composite oxide catalyst was calculated from the composition ratio of the charged material.

<Manufacturing example 1>
The bulk composition is represented by Mo ₁₂ Bi _1.1 Fe _1.9 Co _7.4 Ce _0.5 Cs _0.4 K _{0.2 Og} (g is the number of oxygen atoms required to satisfy the valence requirements of other elements present). A composite oxide catalyst was produced.

<Measurement of residual nitrogen amount in the first fired body>
The amount of residual nitrogen in the catalyst precursor after the first calcination was measured by the CHN method. As the CHN method measuring device, MICRO ORDER JM10 manufactured by J-Science Lab was used.

<Calculation of NOx generation amount>
The residual nitrogen of the first fired body is released as NOx during the subsequent firing. Since the residual nitrogen content of the second-stage fired product was 0 wt%, it was considered that the entire amount was released as NOx, and the generated amount was calculated.

<Calculation of required air volume>
When NOx is generated, the emission control concentration is determined by the equipment. Therefore, it is necessary to introduce air that sufficiently satisfies the emission regulation concentration with respect to the amount of NOx generated during the subsequent firing, and the required amount of air at that time is calculated.

In the examples and comparative examples, the selectivity used to show the reaction results is defined by the following equation, respectively.
Selectivity = (number of moles of produced compound / number of moles of reacted raw material) x 100

[Example 1]
Ammonium heptamolybdate was dissolved in warm water at about 90 ° C. (Liquid A). Further, bismuth nitrate, iron nitrate, cesium nitrate, cerium nitrate, potassium nitrate, and cobalt nitrate were dissolved in an aqueous nitric acid solution of 18% by mass, and warm water at about 90 ° C. was added (solution B). Both liquids A and B were mixed to obtain a raw material slurry. This raw material slurry was sent to a spray dryer and spray-dried at an inlet temperature of 250 ° C. and an outlet temperature of about 140 ° C. to obtain a catalyst precursor (dried product). The obtained catalyst precursor was heated in air from room temperature to 400 ° C. at a heating rate of 100 ° C./h and held for 6 hours to perform pre-calcination to obtain a catalyst precursor. The amount of residual nitrogen in the obtained catalyst precursor was measured by the CHN method. The results are shown in Table 1. The obtained catalyst precursor was heated to 540 ° C. for 2 hours in air and held at 540 ° C. for 3 hours for subsequent firing to obtain a composite oxide catalyst. "As a reaction evaluation of the catalyst, 4.0 g of the catalyst was filled in a SUS reaction tube with a jacket having a diameter of 14 mm, and at a reaction temperature of 390 ° C., 8.3% by volume of isobutylene, 13.3% by volume of oxygen, and 3.0% by volume of water vapor. A mixed gas having an inert gas capacity of 75.4% was aerated at a flow rate of 120 mL / min (NTP) to carry out a methacrolein synthesis reaction. The reaction evaluation results are shown in Table 1.

[Examples 2 to 11]
The synthetic reaction of methacrolein was carried out by the same method as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.

[Comparative Examples 1 to 3]
The synthetic reaction of methacrolein was carried out by the same method as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.

The present invention is used in producing unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons and has industrial potential as an oxide catalyst.

Claims (6)

A precursor of a composite oxide catalyst used in the production of unsaturated aldehydes and / or unsaturated carboxylic acids from hydrocarbons.
A catalyst precursor having a residual nitrogen content of 0.01 to 1.3% by mass after calcination in the first stage. A composite oxide catalyst obtained by using the catalyst precursor according to claim 1. A metal oxide containing molybdenum, bismuth, iron, cobalt and cerium and having a composition represented by the following composition formula (1);
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula, Mo is molybdenum, Bi is bismuth, Fe is iron, Co is cobalt, Ce is cerium, A is potassium, cesium and rubidium, and B is nickel and manganese. , Copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lantern, placeodium, neodymium and europium, indicating at least one element selected from the group, a to f are atoms of each element with respect to Mo12 atom. The ratio is shown, 0 <a ≦ 8, 0 <b ≦ 6, 1 ≦ c ≦ 12, 0 <d ≦ 8, 0.01 ≦ e ≦ 2, 0 ≦ f <2, and g is a configuration other than oxygen. The composite oxide catalyst according to claim 2, which comprises (the number of atoms of oxygen determined by the atomic value of the element). The method for producing a composite oxide catalyst according to claim 2 or 3.
The process of mixing the raw materials that make up the catalyst to obtain a raw material slurry, and
The step of drying the raw material slurry to obtain a dried product, and
A step of obtaining a catalyst precursor by firing the dried product in the previous stage, and
A step of obtaining a composite oxide catalyst by firing the catalyst precursor in the subsequent stage, and
Including
A manufacturing method in which the first-stage firing is carried out in a temperature range of 200 to 400 ° C. The method for producing a composite oxide catalyst according to claim 4, wherein the first-stage firing is carried out over 1 to 10 hours. A method for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid, which comprises a step of oxidizing a hydrocarbon using the composite oxide catalyst according to claim 2 or 3.