KR101513300B1 - / method for producing unsaturated aldehyde and/or unsaturated carboxylic acid - Google Patents

Abstract

Unsaturated aldehydes and / or unsaturated carboxylic acids are produced in a satisfactory yield by subjecting at least one compound selected from the group consisting of propylene, isobutylene and tert-butyl alcohol to catalytic gas phase oxidation in a preferable conversion. The oxidation reaction may be carried out in such a manner that two or more catalysts composed of different specific mixed oxides in the kind and / or the content ratio of the constituent metal element (the catalyst comprises an aqueous solution containing components of the catalyst or an aqueous slurry after containing the molecular sieve The reaction tube is filled with the reaction gas so that the catalytic activity is increased from the feed gas inlet to the feed gas outlet and then the feed gas is introduced into the reaction tube .

Unsaturated aldehyde, unsaturated carboxylic acid, production

Description

METHOD FOR PRODUCING UNSATURATED ALDEHYDE AND / OR UNSATURATED CARBOXYLIC ACID Technical Field [1] The present invention relates to a process for producing unsaturated aldehyde and /

The present invention relates to a process for the production of a reaction product by feeding a feedstock gas containing at least one compound selected from the group consisting of propylene, isobutylene and tert-butyl alcohol and molecular sieve oxygen to a reaction tube to catalytically oxidize the at least one compound in a gas phase Unsaturated aldehydes and / or unsaturated carboxylic acids, including obtaining unsaturated aldehydes and / or unsaturated carboxylic acids.

Feeding at least one compound selected from the group consisting of propylene, isobutylene, and tert-butyl alcohol and a feedstock gas containing molecular sieve oxygen to a reaction tube to catalytically oxidize the at least one compound in a vapor phase As an example of the production method of the unsaturated aldehyde and / or unsaturated carboxylic acid, various types of catalysts having different catalytic activities are prepared by changing the kind or amount of the metal element constituting the catalyst, (See US Pat. Nos. 5,276,178 and JP-A-2000-351744). In this way, the catalytic activity is increased from the feed gas inlet to the feed gas outlet so as to supply the feed gas to the reaction tube.

However, this conventional method is not necessarily satisfactory in the conversion of propylene, isobutylene or tert-butyl alcohol or in the yield of unsaturated aldehyde and / or unsaturated carboxylic acid.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid in a satisfactory yield by catalytic vapor phase oxidation of at least one compound selected from the group consisting of propylene, isobutylene and tert- It is a way to do that.

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The inventors of the present invention have found out through a careful investigation that a plurality of kinds of catalysts composed of specific mixed oxides which differ in the type and / or the content ratio of the constituent metal elements (this catalyst is an aqueous solution or an aqueous slurry Is dried and then calcined in a gas atmosphere containing molecular sieve oxygen and subjected to a subsequent heat treatment in the presence of a reducing material) to the reaction tube so that the catalytic activity is increased from the feed gas inlet to the feed gas outlet And then introducing the feedstock gas into the reaction tube. Therefore, the present invention has been made based on the above findings.

Namely, the present invention relates to a process for producing an unsaturated aldehyde and / or an unsaturated carboxylic acid comprising the steps of:

Feeding a feedstock gas containing at least one compound selected from the group consisting of propylene, isobutylene and tert-butyl alcohol and molecular sieve oxygen into a reaction tube, and

Catalytically oxidizing the at least one compound in a gas phase to produce an unsaturated aldehyde and / or its corresponding unsaturated carboxylic acid,

here,

(1) at least two kinds of catalysts having different catalytic activities are charged in the reaction tube so that the catalytic activity increases from the feed gas inlet of the reaction tube to the feed gas outlet,

(2) the catalysts each independently comprise a mixed oxide represented by the following formula (I):

Mo _a Bi _b Fe _c A _d B _e C _f D _g O _x (I)

[Wherein,

Mo, Bi and Fe represent molybdenum, bismuth and iron, respectively,

A represents nickel and / or cobalt,

B represents at least one element selected from the group consisting of manganese, zinc, calcium, magnesium, tin and lead,

C represents at least one element selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony, silicon, aluminum, titanium, zirconium,

D represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium,

O represents oxygen,

wherein a, b, c, d, e, f and g satisfy the following relationship: 0 <b ≤ 10, 0 <c ≤ 10, 1 ≤ d ≤ 10, 0 ≤ e? 10, 0? f? 10 and 0 <g? 2,

x is a value determined according to the oxidation state of other elements]

(3) the catalyst is different in the kind and / or the content ratio of the metal element constituting the catalyst, and

(4) The catalyst is independently obtained by drying of an aqueous solution or aqueous slurry containing components of the catalyst, followed by calcining in a gaseous atmosphere containing molecular sieve oxygen and subsequent heat treatment in the presence of a reducing material.

According to the present invention, it is preferred that the unsaturated aldehyde and / or the corresponding unsaturated carboxylic acid is replaced with a satisfactory yield by catalytic gas phase oxidation of a good conversion of at least one compound selected from the group consisting of propylene, isobutylene and tert- . &Lt; / RTI &gt;

In the present invention, it is preferable that the feedstock gas containing at least one compound selected from the group consisting of propylene, isobutylene, and tert-butyl alcohol and molecular sieve oxygen is increased in catalytic activity from the feedstock gas inlet to the feedstock gas outlet To a reaction tube filled with a plurality of kinds of catalysts having different catalytic activities. The more types of catalyst, the more efficient the reaction results or the temperature control in the reaction tube, but the more catalyst preparation or charging becomes more complicated. Considering these factors, it is preferable to use two kinds of catalysts.

The catalyst used in the present invention is each independently mixed oxide represented by the following formula (I)

Mo _a Bi _b Fe _c A _d B _e C _f D _g O _x (I)

[Wherein,

Mo, Bi and Fe represent molybdenum, bismuth and iron, respectively,

A represents nickel and / or cobalt,

B represents at least one element selected from the group consisting of manganese, zinc, calcium, magnesium, tin and lead,

C represents at least one element selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony, silicon, aluminum, titanium, zirconium,

D represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium,

O represents oxygen,

wherein a, b, c, d, e, f and g satisfy the following relationship: 0 <b ≤ 10, 0 <c ≤ 10, 1 ≤ d ≤ 10, 0 ≤ e? 10, 0? f? 10 and 0 <g? 2,

x is a value determined by the oxidation state of other elements].

The catalysts differ in the kind and / or the content ratio of the metal elements constituting the catalyst. A "different catalyst in the kind of the metal element constituting the catalyst" means that at least one element in the group A, B, C or D of a comparative catalyst is different from any element in the corresponding group of another catalyst to be compared . In addition, "different catalysts in the ratio of the content of the metal element constituting the catalyst" means that the values b, c, d, e, f and g when a is set to 12 and a The values of b, c, d, e, f and g in one catalyst are compared with those of the other catalysts when the values of b, c, d, e, Quot; and &quot;

Preferably, the catalyst comprises a mixed oxide represented by the following formula (II): &lt; RTI ID = 0.0 &gt;

Mo _a Bi _b Fe _c Co _d Sb _f Cs _g O _x (II)

[Wherein,

Mo, Bi, Fe, Co, Sb and Cs represent molybdenum, bismuth, iron, cobalt, antimony and cesium,

wherein a, b, c, d, f and g satisfy the following relationship: when a is set to 12, 0 <b ≤ 10, 0 <c ≤ 10, 1 ≤ d ≤ 10, 0 ≤ f ≤ 10 and 0 < g? 2,

x is a value determined by the oxidation state of other elements].

Also in this case, the catalysts differ in the kind and / or the content ratio of the metal elements constituting the catalyst.

In a more preferred embodiment for its charge state in the catalyst and reaction tube, two catalysts are charged in a reaction tube, and a catalyst comprising a mixed oxide of the formula (II) when f is not zero is used as a feedstock (II) in the case where f is 0, is filled in the reaction tube on the side of the feed gas outlet side, and the catalyst in the reaction tube on the side of the feed gas inlet side is filled with the other catalyst Molybdenum, bismuth, iron, and cobalt are respectively the same as those in the catalyst in the feed gas outlet side reaction tube.

Hereinafter, a method for producing a catalyst used in accordance with the present invention will be described as follows. The catalysts having different catalytic activities used in the present invention are produced independently of each other. As a raw material for such a catalyst, a compound of each element such as an oxide, a nitrate, a sulfate, a carbonate, a hydroxide, an oxo acid and its ammonium salt and a halogen compound constituting the catalyst is mixed with a ratio . For example, molybdenum trioxide, molybdic acid, ammonium paramolybdate, or the like can be used as the molybdenum compound. Bismuth oxide, bismuth nitrate, bismuth sulfate and the like can be used as a bismuth compound. Iron (III) nitrate, iron (III) sulfate, iron (III) chloride and the like can be used as iron compounds. Cobalt nitrate, cobalt sulfate, cobalt chloride and the like can be used as a cobalt compound. Antimony trioxide, antimony (III) chloride, and the like can be used as the antimony compound. Cesium nitrate, cesium carbonate, cesium hydroxide and the like can be used as a cesium compound.

In the present invention, an aqueous solution or an aqueous slurry is prepared by mixing a raw material of a catalyst with water and drying the solution or slurry. The dried mixture is then calcined under a gaseous atmosphere containing molecular sieve oxygen. Some raw materials of catalyst such as antimony compounds can be added after drying. Each step can be carried out according to a conventional method (see, for example, JP-A-59-46132, JP-A-60-163830 and JP-A-2000-288396). For example, drying can be carried out using a kneader, a box dryer, a drum-type through air dryer, a spray dryer, a flush dryer and the like. The molecular sieve oxygen concentration in the gas containing molecular sieve oxygen is usually 1 to 30% by volume, preferably 10 to 25% by volume. Normally, ambient air or pure oxygen is used as the source of molecular sieve oxygen. Such a source may be diluted with nitrogen, carbon dioxide, water, helium, argon, etc., if necessary, and then used as a gas containing molecular sieve oxygen. The calcination temperature is usually 300 to 600 占 폚, preferably 400 to 550 占 폚. The calcination time is usually 5 minutes to 40 hours, preferably 1 hour to 20 hours.

The calcined product calcined is heat treated in the presence of a reducing material. This treatment which is carried out in the presence of a reducing substance will hereinafter be referred to briefly as "reduction treatment ".

Examples of reducing materials include, for example, hydrogen, ammonia, carbon monoxide, hydrocarbons, alcohols, aldehydes and amines. Optionally, two or more of such reducing materials may be used. Preferably, the hydrocarbons, alcohols, aldehydes and amines each have from 1 to about 6 carbon atoms. Examples of hydrocarbons include saturated aliphatic hydrocarbons such as methane, ethane, propane, n-butane and isobutane, unsaturated aliphatic hydrocarbons such as ethylene, propylene, alpha -butylene, beta -butylene and isobutylene, aromatic hydrocarbons such as benzene . Examples of the alcohols include saturated aliphatic alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol, allyl alcohol, crotyl alcohol and metal Unsaturated aliphatic alcohols such as allyl alcohol, and aromatic alcohols such as phenol. Examples of such aldehydes include unsaturated aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, saturated aliphatic aldehydes such as n-butylaldehyde and isobutylaldehyde, acrolein, crotonaldehyde and methacrolein. Examples of such amines include saturated aliphatic amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine and triethylamine, unsaturated aliphatic amines such as allylamine and diallylamine, and aromatic amines such as aniline .

The reduction treatment is usually carried out by heat-treating the calcined product in a gas atmosphere containing a reducing material. The concentration of the reducing material in the gas is usually 0.1 to 50% by volume, preferably 1 to 30% by volume. The reducing material can be diluted with nitrogen, carbon dioxide, water, helium, argon, etc., and as a result, such concentration can be obtained. The molecular sieve oxygen is allowed to exist as long as it does not affect the reducing treatment effect. However, the presence of molecular sieve oxygen may not be allowed.

The temperature for the reduction treatment is usually 200 to 600 占 폚, preferably 250 to 550 占 폚. The reduction treatment time is usually 5 minutes to 20 hours, preferably 30 minutes to 10 hours. It is preferable that the calcined product is placed in a tubular or box-shaped container, and the container is subjected to a reducing treatment while keeping the gas containing the reducing material in communication therewith. At this time, if necessary, the gas released from the vessel can be circulated or reused.

The reduction treatment usually causes mass loss. This can be due to the lattice oxygen atom loss of the catalyst. The mass loss is preferably 0.05 to 6% by mass, and more preferably 0.1 to 5% by mass. If the mass loss exceeds 6 mass% due to excessive reduction, the mass loss can be recovered by performing the calcination again in a gas atmosphere containing molecular sieve oxygen. The mass loss can be calculated using the following equation:

Mass loss (%) = 100 x [(weight of calcined product before reduction treatment) - (weight of catalyst after reduction treatment)] / (weight of calcined product before reduction treatment)

In the reduction treatment, the reducing substance itself, the decomposition product derived from the reducing substance and the like may remain in the catalyst even after the reduction treatment depending on the type of the reducing substance used, the heat treatment conditions and the like. In this case, the mass loss can be calculated by calculating the weight after the reduction treatment by measuring the weight of the residual material in the catalyst and then subtracting the mass of the residual material from the weight of the catalyst containing the residual material. A typical residual material is carbon, and therefore the mass of the residual material can be measured, for example, by total carbon (TC) analysis.

The catalyst is usually shaped into the desired shape and then used in the process of the present invention. When molding, the catalyst may be molded into a ring, pellet, sphere or the like by tablet compression, extrusion molding or the like. The shape of the catalyst used in the present invention may be the same or different. The molding may be performed before or after calcination in a gas atmosphere containing molecular sieve oxygen, or may be carried out after the reduction treatment. At the time of molding, inorganic fibers and the like which are substantially inactive to the intended oxidation reaction can be added, for example, as mentioned in JP-A-9-52053, in order to improve the mechanical strength of the catalyst.

Thus, a catalyst having another catalytic activity is produced. The catalytic activity of each catalyst is determined by catalytically oxidizing molecular sieve oxygen and at least one raw material compound selected from the group consisting of propylene, isobutylene, and tert-butyl alcohol in the presence of a vapor phase catalyst and measuring the conversion of the compound Can be evaluated. The gas phase catalytic oxidation is carried out by charging the catalyst in the reaction tube such that the conversion is increased from the feed gas feed inlet to the feed gas outlet and feeding the feed gas containing molecular sieve oxygen and the raw material compound do. In the industrial production, it is preferable to use a fixed bed multitubular reactor including the aforementioned reaction tube.

Normally, air is used as a source of molecular sieve oxygen. In addition to raw material compounds and molecular sieve oxygen, the feedstock gas may include nitrogen, carbon dioxide, carbon monoxide, water vapor, and the like.

By the above-mentioned vapor-phase catalytic oxidation, acrolein and / or acrylic acid can be produced with satisfactory yield from propylene. Alternatively, methacrolein and / or methacrylic acid may be prepared in a satisfactory yield from isobutylene or tert-butyl alcohol.

The reaction temperature is usually 250 to 400 ° C. The reaction pressure may be reduced, but is usually normal to 500 kPa. The molecular sieve oxygen content is usually 1 to 3 mol per 1 mol of the raw material compound. The space velocity SV of the feedstock gas is typically 500 to 5000 hr &lt; ^-1 &gt; per hour at STP (standard temperature and pressure).

[Example]

Examples of the present invention are shown below, but the present invention is not limited in any way by the examples. In an embodiment, the "ml / min" unit representing the flow rate of the gas is in STP unless otherwise stated. In an embodiment, conversion (%) and yield are defined as follows:

(%) = 100 x [(moles of isobutylene introduced) - (moles of unreacted isobutylene)] / (moles of isobutylene introduced)

Total yield (%) = 100 x (total moles of methacrolein and methacrylic acid) / (moles of isobutylene introduced)

Reference Example  One

Production of catalyst a (catalyst not subjected to reduction treatment)

4414 g of ammonium molybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O] was dissolved in 5000 g of hot water to form solution A. Separately, 2020 g of iron (III) nitrate [Fe (NO ₃ ) ₃ .9H ₂ O], 4366 g of cobalt nitrate [Co (NO ₃ ) ₂ .6H ₂ O] and 195 g of cesium nitrate [CsNO ₃ ] Was dissolved in 2000 g of hot water, and then 970 g of bismuth nitrate [Bi (NO ₃ ) ₃ .5H ₂ O] was further dissolved to form solution B. Solution B was added to Solution A while stirring to form a slurry. The slurry was then dried with a flash drier to give a dried product. 6 parts by mass of silica alumina fiber (RFC400-SL, manufactured by Saint-Gobain) was added to 100 parts of the dried material. The resulting mixture was shaped into a ring having an outer diameter of 6.3 mm, an inner diameter of 2.5 mm and a length of 6 mm, followed by calcination at 525 ° C for 6 hours in an air stream to obtain catalyst a. The catalyst contained 0.96 bismuth atoms, 2.4 iron atoms, 7.2 cobalt atoms and 0.48 cesium atoms per 12 molybdenum atoms.

Example  One

Preparation of catalyst A (reduced catalyst)

After the catalyst a was charged into the glass tube, a mixed gas of hydrogen / nitrogen (5/95, volume) was flowed through the glass tube and reduction treatment was performed at 350 ° C for 8 hours to prepare the catalyst A. The catalyst contained 0.96 bismuth atoms, 2.4 iron atoms, 7.2 cobalt atoms and 0.48 cesium atoms per 12 molybdenum atoms, similar to catalyst a, and the mass loss due to the reduction treatment was 0.90 mass%.

Reference Example  2

Preparation of catalyst b (catalyst not subjected to reduction treatment)

Catalyst b was prepared in the same manner as in Reference Example 1, except that 2.54 parts by mass of antimony trioxide (Sb ₂ O ₃ ) was added to 100 parts by mass of the dry substance of Reference Example 1 and the calcination temperature was changed to 546 ° C . The catalyst contained 0.96 bismuth atoms, 0.48 antimony atoms, 2.4 iron atoms, 7.2 cobalt atoms, and 0.48 cesium atoms per 12 molybdenum atoms.

Example  2

Preparation of Catalyst B (Reduced Catalyst)

Catalyst b was filled in a glass tube, and a mixed gas of hydrogen / nitrogen (5/95, volume) was flowed through a glass tube to perform reduction treatment at 350 ° C for 8 hours to prepare catalyst B. Similar to catalyst b, the catalyst contained 0.96 bismuth atoms, 0.48 antimony atoms, 2.4 iron atoms, 7.2 cobalt atoms, and 0.48 cesium atoms per 12 molybdenum atoms, and the mass loss due to the reduction treatment was 1.28 mass %.

Reference Example  3

Production of catalyst c (catalyst not subjected to reduction treatment)

Catalyst c was prepared in the same manner as in Reference Example 1, except that the amount of cesium nitrate used was changed to 273 g. The catalyst contained 0.96 bismuth atoms, 2.4 iron atoms, 7.2 cobalt atoms and 0.67 cesium atoms per 12 molybdenum atoms.

Example  3

Preparation of Catalyst C (Reduced Catalyst)

The catalyst c was filled in a glass tube, and then a mixed gas of hydrogen / nitrogen (5/95, volume) was flowed through a glass tube to perform reduction treatment at 350 ° C for 8 hours to prepare catalyst C. The catalyst contained 0.96 bismuth atoms, 2.4 iron atoms, 7.2 cobalt atoms and 0.67 cesium atoms per 12 molybdenum atoms, similar to catalyst c, and the mass loss due to the reduction treatment was 0.77 mass%.

Reference Example  4

Preparation of catalyst d (catalyst not subjected to reduction treatment)

6 parts by weight of silica alumina fiber (RFC400-SL, Saint-Gobain TM Co., Ltd.) and 2.54 parts by weight of antimony trioxide (Sb ₂ O ₃₎ was added to the dried substance 100 parts by weight produced in Reference Example 3. The resulting mixture was shaped into a ring having an outer diameter of 6.3 mm, an inner diameter of 2.5 mm and a length of 6 mm and then calcined at 490 ° C for 6 hours in an air stream to obtain catalyst d. The catalyst contained 0.96 bismuth atoms, 0.29 antimony atoms, 2.4 iron atoms, 7.2 cobalt atoms, and 0.67 cesium atoms per 12 molybdenum atoms.

Example  4

Preparation of Catalyst D (Reduced Catalyst)

Catalyst d was filled in a glass tube and then a mixed gas of hydrogen / nitrogen (5/95, volume) was flowed through a glass tube and reduction treatment was carried out at 350 ° C for 8 hours to prepare catalyst D. The catalyst contained 0.96 bismuth atoms, 0.29 antimony atoms, 2.4 iron atoms, 7.2 cobalt atoms and 0.67 cesium atoms per 12 molybdenum atoms, similar to catalyst d, and the mass loss due to the reduction treatment was 1.17 mass %.

Comparative Example  One

Oxidation using catalyst A (catalyst A monolayer)

14.30 ml of the catalyst A was diluted with 30 g of silicon carbide (SHINANO-RUNDUM GC F16, manufactured by Shinano Electric Refining Co., Ltd.) and filled in a glass reaction tube having an inner diameter of 18 mm. A mixed gas of isobutylene / oxygen / nitrogen / steam (1.0 / 2.2 / 6.2 / 2.0, moles) was supplied to the reaction tube at a flow rate of 157.5 ml / min to perform an oxidation reaction at a reaction temperature of 330 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  2

Oxidation using catalyst A (catalyst A monolayer)

The oxidation reaction was carried out in the same manner as in Comparative Example 1, except that the reaction temperature was changed to 340 캜. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  3

Oxidation using catalyst A (catalyst A monolayer)

The oxidation reaction was carried out in the same manner as in Comparative Example 1, except that the reaction temperature was changed to 350 캜. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  4

Oxidation using catalyst B (catalyst B monolayer)

An oxidation reaction was carried out in the same manner as in Comparative Example 1, except that Catalyst A was changed to Catalyst B. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  5

Oxidation using catalyst C (catalyst C monolayer)

The oxidation reaction was carried out in the same manner as in Comparative Example 1 except that the catalyst A was replaced with the catalyst C and the reaction temperature was changed to 340 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  6

Oxidation using catalyst D (catalyst D monolayer)

The oxidation reaction was carried out in the same manner as in Comparative Example 1 except that the catalyst A was replaced with the catalyst D and the reaction temperature was changed to 350 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Example  5

Oxidation using Catalysts B and A (Catalyst B / catalyst A bilayer)

7.15 ml of the catalyst B was diluted with 15 g of silicon carbide (SHINANO-RUNDUM GC F16, manufactured by Shinano Electric Refining Co., Ltd.) into a glass reaction tube having an inner diameter of 18 mm, filled into the region of the inlet side of the feed gas, 7.15 ml of the catalyst A was diluted with 15 g of silicon carbide (SHINANO-RUNDUM GC F16, manufactured by Shinano Electric Refining Co., Ltd.) and filled into the region of the outlet side of the feed gas. A mixed gas of isobutylene / oxygen / nitrogen / steam (1.0 / 2.2 / 6.2 / 2.0, moles) was supplied to the reaction tube at a flow rate of 157.5 ml / min to perform an oxidation reaction at a reaction temperature of 330 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Example  6

Oxidation using catalysts C and A (Catalyst C / catalyst A bilayer)

The oxidation reaction was carried out in the same manner as in Example 5, except that the catalyst B was replaced with the catalyst C and the reaction temperature was changed to 340 캜. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Example  7

Oxidation using Catalysts D and A (Catalyst D / catalyst A bilayer)

The oxidation reaction was carried out in the same manner as in Example 5 except that the catalyst B was replaced with the catalyst D and the reaction temperature was changed to 350 캜. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  7

Oxidation using catalyst b and a (catalyst b / catalyst a bilayer)

Oxidation reaction was carried out in the same manner as in Example 5, except that Catalyst B and Catalyst A were changed to Catalyst b and Catalyst a, respectively. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  8

Oxidation using catalysts c and a (catalyst c / catalyst a bilayer)

The oxidation reaction was carried out in the same manner as in Example 5, except that catalyst B and catalyst A were replaced with catalyst c and catalyst a, respectively, and the reaction temperature was changed to 340 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

Comparative Example  9

Oxidation using catalysts d and a (catalyst d / catalyst a bilayer)

The oxidation reaction was carried out in the same manner as in Example 5, except that catalyst B and catalyst A were replaced with catalyst d and catalyst a, respectively, and the reaction temperature was changed to 350 ° C. The conversion of isobutylene and the total yield of methacrolein and methacrylic acid are shown in Table 1.

[Table 1]

catalyst Reaction temperature
(° C) transform (%) Total yield (%) Inlet / outlet Reduction treatment Comparative Example 1 Catalyst A monolayer U 330 96.3 79.8 Comparative Example 2 Catalyst A monolayer U 340 99.6 80.6 Comparative Example 3 Catalyst A monolayer U 350 100.0 79.7 Comparative Example 4 Catalyst B monolayer U 330 80.3 69.5 Comparative Example 5 Catalyst C monolayer U 340 98.4 81.8 Comparative Example 6 Catalyst D monolayer U 350 93.4 80.1 Example 5 Catalyst B / Catalyst A Yes / No 330 99.1 83.1 Example 6 Catalyst C / Catalyst A Yes / No 340 99.0 82.7 Example 7 Catalyst D / Catalyst A Yes / No 350 99.1 84.6 Comparative Example 7 Catalyst b / catalyst a No / No 330 90.9 78.3 Comparative Example 8 Catalyst c / catalyst a No / No 340 96.7 81.3 Comparative Example 9 Catalyst d / catalyst a No / No 350 99.1 81.9

Claims (9)

A process for preparing an unsaturated aldehyde and / or unsaturated carboxylic acid comprising the steps of: Feeding a feedstock gas containing at least one compound selected from the group consisting of propylene, isobutylene and tert-butyl alcohol and molecular sieve oxygen into a reaction tube, and Catalytically oxidizing the at least one compound in a gas phase to produce an unsaturated aldehyde and / or its corresponding unsaturated carboxylic acid, here, (1) at least two kinds of catalysts having different catalytic activities are charged in the reaction tube so that the catalytic activity increases from the feed gas inlet of the reaction tube to the feed gas outlet, (2) the catalysts each independently comprise a mixed oxide represented by the following formula (I): Mo _a Bi _b Fe _c A _d B _e C _f D _g O _x (I) [Wherein, Mo, Bi and Fe represent molybdenum, bismuth and iron, respectively, A represents nickel and / or cobalt, B represents at least one element selected from the group consisting of manganese, zinc, calcium, magnesium, tin and lead, C represents at least one element selected from the group consisting of phosphorus, boron, arsenic, tellurium, tungsten, antimony, silicon, aluminum, titanium, zirconium, D represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, O represents oxygen, wherein a, b, c, d, e, f and g satisfy the following relationship: 0 <b ≤ 10, 0 <c ≤ 10, 1 ≤ d ≤ 10, 0 ≤ e? 10, 0? f? 10 and 0 <g? 2, x is a value determined according to the oxidation state of other elements] (3) the catalyst is different in the kind and / or the content ratio of the metal element constituting the catalyst, and (4) The catalyst is subjected to a subsequent heat treatment in an atmosphere of a gas containing a calcining and reducing material in a gas atmosphere containing molecular sieve oxygen after drying an aqueous solution or an aqueous slurry containing the components of the catalyst, Lt; / RTI &gt; The method according to claim 1, wherein the heat treatment is carried out while flowing a gas containing a reducing material. The process according to claim 1 or 2, wherein the catalyst comprises a mixed oxide each independently represented by the following formula (II): Mo _a Bi _b Fe _c Co _d Sb _f Cs _g O _x (II): [Wherein, Mo, Bi, Fe, Co, Sb and Cs represent molybdenum, bismuth, iron, cobalt, antimony and cesium, wherein a, b, c, d, f and g satisfy the following relationship: when a is set to 12, 0 <b ≤ 10, 0 <c ≤ 10, 1 ≤ d ≤ 10, 0 ≤ f ≤ 10 and 0 < g? 2, x is a value determined by the oxidation state of other elements]. The method according to claim 1 or 2, wherein the number of kinds of catalysts charged in the reaction tube is two. 5. The process according to claim 4, wherein a catalyst containing a mixed oxide of the formula (II) in which f is not 0 is charged in the feed gas inlet side reaction tube, and another mixed oxide containing the mixed oxide of the formula (II) The ratio of molybdenum, bismuth, iron and cobalt in the catalyst packed in the reaction tube on the inlet side of the feed gas inlet is different from that of the other catalyst packed in the reaction tube on the side of the feed gas outlet The same as the content ratio of the components. The method according to claim 1 or 2, wherein the calcination is carried out at 300 to 600 占 폚. The method according to claim 1 or 2, wherein the heat treatment is performed at 200 to 600 캜. 3. The process according to claim 1 or 2, wherein the mass loss of the catalyst due to the heat treatment is 0.05 to 6 mass%. 3. The method according to claim 1 or 2, wherein the reducing material is selected from the group consisting of hydrogen, ammonia, carbon monoxide, a hydrocarbon having 1 to 6 carbon atoms, an alcohol having 1 to 6 carbon atoms, an aldehyde having 1 to 6 carbon atoms, and an amine having 1 to 6 carbon atoms &Lt; / RTI &gt;