JPH0232017B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preparing a catalyst for the catalytic gas phase oxidation of isobutylene or tertiary-butanol with a molecular oxygen-containing gas to yield methacrolein and methacrylic acid. Specifically, the present invention provides a catalyst for catalytic gas phase oxidation of isobutylene or tertiary-butanol using a molecular oxygen-containing gas, such as air, to obtain methacrolein and methacrylic acid, particularly mainly methacrolein, with high selectivity and high yield. The purpose of this invention is to provide a method for preparing a catalyst that can be stably used industrially over a long period of time. Conventionally, many proposals have been made as catalysts for producing corresponding unsaturated aldehydes by catalytic gas phase oxidation of olefins. Examples include catalyst systems based on molybdenum and bismuth. To give specific examples, the specification of JP-A-36-3563 discloses a catalyst consisting of bismuth molybdate and bismuth phosphomolybdate, and the specification of JP-A-50-76010 uses molybdenum, cobalt, and iron as constituent elements. The catalyst is a catalyst containing iron, bismuth, phosphorus, and molybdenum as constituent elements in the specification of Japanese Patent Publication No. 39-3670, and nickel, cobalt, iron, bismuth, molybdenum, phosphorus, and arsenic in the specification of U.S. Pat. No. 3,522,299. Catalytic oxides each having as a constituent element are disclosed. On the other hand, there are catalyst systems based on tungsten and bismuth, such as U.S. Pat.
The specification of Japanese Patent Publication No. 39-18017 proposes a catalyst composition based on bismuth, cobalt, and tungsten. Furthermore, catalyst systems based on molybdenum, bismuth, and tungsten have also been proposed. For example, there are the specifications of JP-A-49-9490 and JP-A-49-14393, and the specification of JP-A-47-42241 describes molybdenum, cobalt, iron, bismuth, tungsten, silicon, and alkali metals. Elemental catalyst compositions have been proposed. However, many of these publications mainly focus on catalysts for producing acrolein and acrylic acid through catalytic gas phase oxidation of propylene, and although they do disclose catalysts for producing methacrolein, there are no examples. Even if there were no examples, most of them had very low yields and were far from being suitable for industrial use. In recent years, various improvements have been made, and some catalysts whose main purpose is to produce methacrolein have reached the level where they can be used industrially. However, when considering the use of these proposed catalysts on an industrial scale, it is difficult to obtain methacrolein and methacrylic acid with high selectivity and high yield as described in their specifications and examples. There are many. This is because the catalytic gas-phase oxidation reaction is extremely exothermic, causing local abnormally high temperature zones called hot spots to occur in the catalyst bed, causing an excessive oxidation reaction, or because the height of the catalyst packed bed is large. Another possibility is that the reaction deviates from an ideal reaction because the pressure in the catalyst layer changes sequentially from the inlet to the outlet of the catalyst layer. On the other hand, in multicomponent catalysts mainly composed of molybdenum, molybdenum easily reacts with many elements to form complex molybdenum complex salts, making it difficult to obtain homogeneous catalysts and the reproducibility of catalyst performance. However, it is quite understandable that when such a catalyst composition is used for catalyst production on an industrial scale, the performance of all the produced catalysts cannot exhibit the high level of performance as shown in the examples in the specification. As a result of intensive research, the present inventors have developed a preparation method that overcomes the drawbacks of catalyst systems containing molybdenum, bismuth, and tungsten in industrial use, and that also provides excellent reproducibility of catalyst performance in catalyst production on an industrial scale. The present invention has now been completed. That is, the present invention is based on the general formula Mo ₁₂ Bi _a W _b Fe _c A _d B _e C _f D _g O _h [where Mo is molybdenum, Bi is bismuth, W is tungsten, Fe is iron, A is cobalt (Co) and At least one element selected from nickel (Ni); B: at least one element selected from alkali metals, alkaline earth metals, and thallium (Tl); C: phosphorus (P), antimony (Sb); ), at least one element selected from tin (Sn), cerium (Ce), lead (Pb), niobium (Nb), D
is at least one element selected from silicon (SSi), aluminum (Al), titanium (Ti), and zirconium (Zr), O represents oxygen, a,
b, c, d, e, f, g, h represent the atomic ratio of each element, and when Mo is 12, a = 0.1 ~
10.0, b=0.5~10.0, a/b is 0.01~6.0, c=
0.1~10.0, d=2.0~20.0, e is 0.01~10.0, f=
0 to 10.0, g = 0 to 30, and h takes a value determined by the valence of each element], the Bi component is a mixture of a bismuth compound and a tungsten compound. The present invention provides a method for preparing a catalyst composition for producing methacrolein, which is characterized in that the catalyst composition is introduced in the form of an oxide obtained by pre-calcination at a temperature of 600 to 900°C. The catalyst obtained by the preparation method of the present invention (hereinafter referred to as the catalyst of the present invention) is characterized in that bismuth forms an extremely stable bond with tungsten and maintains its high catalytic performance even during long-term reactions. It is. This stable bond between bismuth and tungsten is formed by previously treating bismuth and tungsten at a high temperature of 600 to 900°C. Academic research on this compound consisting of bismuth and tungsten has also begun to be conducted in recent years, for example in the Journal of Catalysis.
Volume 31, pages 200-208 (1973) reveals the existence of various bismuth-tung states.
Experiments conducted by the present inventors have also shown that these compounds are active in the oxidation of isobutylene or tertiary-butanol at high temperatures exceeding 400°C, but the level of activity is very satisfactory for industrial use. By further combining this bismuth tungstate with molybdenum, iron, and other metal elements, we have created a catalyst composition with good thermal stability, excellent catalytic performance at low temperatures, and high space-time yield. It turned out that it was possible to grow.
It is true that a proposal to separately prepare a mixture of bismuth and tungsten and add it to the remaining catalyst components has already been made in some of the specifications of JP-A-55-47144 and JP-A-49-9490. However, in this case, firing was not performed under conditions that would form a stable bismuth-tungsten compound in advance. In contrast, in the catalyst of the present invention, bismuth and tungsten are pretreated at high temperatures, and by using this, a high-quality catalyst with extremely good reproducibility can be obtained in the preparation method, and the conventional bismuth and molybdenum compound can be obtained. It has been found that this is extremely advantageous as an industrial preparation method compared to catalyst systems based on Furthermore, surprisingly, in the present invention, bismuth is substantially bonded extremely strongly to tungsten, and even after being made into a multicomponent catalyst, bismuth compounds that are unbonded to tungsten, such as bismuth trioxide, bismuth As a result of X-ray diffraction analysis, it became clear that no molybdate was produced. That is, it was recognized that in the catalyst of the present invention, bismuth and tungsten maintain a strong bond and are further combined with other catalyst constituent elements in a complex manner. The results of the same X-ray diffraction analysis confirmed that there was almost no change in the bonding state even after isobutylene or tert-butanol was subjected to oxidation over a long period of time. Furthermore, the catalyst produced according to the present invention was able to lower the reaction temperature and increase the methacrolein yield compared to conventional catalysts. According to the findings of the present inventors, it has become clear that as a catalyst that provides high selectivity to methacrolein, a catalyst whose shape is further specified as follows is recommended. That is, a ring-shaped catalyst having an outer diameter of 3.0 to 10.0 mm, a length of 0.5 to 2.0 times the outer diameter, and openings in the length direction such that the inner diameter is 0.1 to 0.7 times the outer diameter. This is a catalyst for producing methacrolein, characterized in that the catalyst composition is represented and specified by the above general formula. It has been found that specifying the shape of the catalyst of the present invention in this way has the following effects. (i) By making the catalyst into the ring shape specified above, the geometric surface area of the catalyst increases,
As the conversion rate of isobutylene increases,
In addition, the pore diffusion of methacrolein generated within the catalyst pores is faster than that of a cylindrical catalyst due to the shortening of the path during desorption and diffusion.
The sequential reaction from methacrolein to methacrylic acid, acetic acid, carbon dioxide, and carbon monoxide decreases. (ii) As expected, by using a ring-shaped catalyst, pressure loss in the catalyst layer is reduced, making it possible to reduce power costs for blowers in industrial production. (iii) Furthermore, the catalyst of the present invention has the advantage that the catalyst life is extended. In other words, the use of a ring-shaped catalyst increases the heat removal effect in the locally abnormally high temperature zone that occurs because catalytic gas phase oxidation is generally extremely exothermic, and the above-mentioned methacrylic acid, acetic acid, and carbon dioxide , the reduction in heat generation due to the sequential reaction to carbon monoxide together lowers the temperature of the hot spot, which reduces the rate of increase in pressure drop caused by the scattering of molybdenum, one of the catalyst components, during the reaction, reducing the catalyst. This results in a longer lifespan. The catalyst of the present invention has a composition range shown by the above general formula, and its preparation method can be selected from various methods as long as it has the above-mentioned characteristics. First, an example of a preferred method for producing a bismuth-tungsten bond is shown below. First, a bismuth compound such as bismuth nitrate, bismuth hydroxide, bismuth oxide and a tungsten compound such as ammonium paratungstate or tungsten oxide are mixed well with a small amount of water and dried at 600-900°C, preferably 700-850°C.
Process and crush at high temperatures. It is better to make the powder smaller, but it is wasteful to make it finer than necessary.
About 100 meshes or less is sufficient. In this way, a bismuth-tungsten compound can be obtained. Next, a specific example of preparing a catalyst is shown below. Add an iron compound such as an aqueous solution of iron nitrate to an aqueous solution of a molybdenum compound such as ammonium molybdate in advance, and when using cobalt as the element A shown in the general formula, use an aqueous solution of cobalt nitrate, for example, and use an alkali metal as B. When using an alkali metal source, use an alkali metal hydroxide or nitrate, when using phosphorus as C, use a phosphoric acid aqueous solution, and when using silicon as D, use colloidal silica, etc., and mix each aqueous solution thoroughly, and the resulting mud Add the previously pulverized bismuth tungsten binder to the mixture, mix well and concentrate, and mold the resulting clay-like material, then heat at 350°C to 650°C, preferably 400°C to 600°C. Calcinate at high temperature under air circulation to obtain the finished catalyst. Note that, if necessary, a powdered carrier material may be added to the slurry. The carrier is selected from silica gel, alumina, silicon carbide, diatomaceous earth, titanium oxide, Celite (trade name), etc., and silica gel, titanium oxide, and Celite are particularly suitable. The oxygen-containing compound of bismuth and tungsten, which is a feature of the present catalyst, has an atomic ratio of bismuth to tungsten of 0.01 to 6.0, preferably 0.1 to 4.0. In other words, a bismuth-tungsten compound with an atomic ratio exceeding 6.0 cannot form a stable bond, and during catalyst preparation or long-term use of the catalyst, the bonds of bismuth tungsten are broken and bismuth recombines with other components, causing the catalyst to deteriorate. This is because it disrupts the bond balance of each component and does not produce desirable results. Of course, in addition to satisfying such an atomic ratio, high-temperature treatment conditions are also essential. Oxygen-containing compounds of bismuth and tungsten form stable compounds when treated in this temperature range, and when incorporated into the catalyst composition of the present invention, their catalytic performance is raised to an extremely high level. . Heat treatment of a compound of bismuth and tungsten at a low temperature below 600°C will not stabilize it in the catalyst composition even if its atomic ratio satisfies the above range, and it will not be stabilized during catalyst preparation or during catalyst preparation. This is undesirable because it causes the bond balance in the catalyst composition to collapse during use. Furthermore, treatment at a high temperature exceeding 900° C. is also not preferred because it is difficult to obtain a stable bond of bismuth and tungsten and the bond is likely to change in the catalyst composition. The catalyst raw materials in the present invention are not limited to the above-mentioned compounds, and for bismuth and tungsten, bismuth halides such as bismuth chloride, bismuth salts of organic acids such as bismuth carbonate, bicarbonate, bismuth hydroxide, and bismuth acetate are used. Alkali metal salts of tungstic acid such as sodium tungstate, tungsten halides such as tungsten chloride, etc. are used as appropriate, but when halides or alkali salts are used, thorough cleaning is required after passing through the slurry. It goes without saying that there is. Regarding molybdenum, iron, and other catalyst raw materials, not only nitrates and organic acid salts, but also any compounds that can form their respective oxides in catalyst preparation can be used. Of course, compounds containing two or three of the elements constituting the above catalyst may also be used. In addition to the above methods, any method can be used to prepare the catalyst as long as each catalyst component in the catalyst composition can be uniformly mixed. For example, the preparation of bismuth and tungsten can be used. powder, powdered cobalt,
It is mixed with a mixture of oxides such as nickel, iron, molybdenum, phosphorus, antimony, tin, cerium, silicon, aluminum, titanium, etc., and a binder such as carboxymethyl cellulose that disappears by baking is added and kneaded uniformly. A desired catalyst composition can be obtained in the same manner. 250 to 450 using the catalyst obtained in this way.
℃ reaction temperature, under pressure of normal pressure to 10 atmospheres, 1-10% by volume of isobutylene or tert-butanol, 3-20% by volume of oxygen, 0-60% by volume of water vapor and 20-80% by volume of nitrogen gas. , contact time of raw material gas consisting of inert gas such as carbon dioxide 1.0 ~
It reacts in 10.0 seconds. Furthermore, the catalyst according to the present invention can be used in both fixed bed reactions and fluidized bed reactions.
The selection can also be made appropriately by those skilled in the art. EXAMPLES Hereinafter, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited to the following examples unless it goes against the gist thereof. In addition, the reaction rate, selectivity, and single flow yield in this invention shall be defined as follows. Reaction rate (mol%) = Number of moles of reacted isobutylene or tertiary-butanol / Number of moles of supplied isobutylene or tertiary-butanol x 100 Selectivity (mol%) = Number of moles of methacrolein produced / Number of moles of reacted isobutylene or tertiary-butanol Number of moles of Libutanol x 100 Single flow yield (mol%) = Number of moles of methacrolein produced/Number of moles of supplied isobutylene or tertiary butanol x 100 Example 1 291g of bismuth nitrate was added with 62ml of concentrated nitric acid. Dissolved in 1000 ml of acidified distilled water. To this aqueous solution, 660 ml of aqueous ammonia (28%) was added to obtain a white precipitate. This was washed separately with water, and 278 g of tungsten trioxide was added to the obtained white cake-like substance and thoroughly mixed, followed by drying at 230°C for 16 hours and further heat treatment at 750°C for 2 hours under air circulation.
The obtained yellow lumps were crushed to less than 100 mesh to obtain yellow powder. X-ray diffraction analysis of this powder revealed that d = 2.973, 3.207, as shown in the previous literature.
Bi ₂ (WO ₄ ) ₃ with peaks at 2.706, 1.648, 1.915 and peaks at d=3.632, 3.817, 3.739, 2.610
It was found that it was a mixture of WO ₃ and no bismuth oxide peak was observed. Separately, add 1060g of ammonium molybdate to distilled water.
873g of cobalt nitrate in 8000ml of aqueous solution
Aqueous solution of ferric nitrate dissolved in 600ml of distilled water
An aqueous solution of 71 g dissolved in 400 ml of distilled water, 150 g of silica sol containing 20% by weight of silica, and an aqueous solution of 25 g of potassium nitrate dissolved in 300 ml of distilled water were added and stirred at room temperature. The resulting suspension was concentrated by heating, dried, and then ground. Add the previous yellow powder to this powder and mix thoroughly, then add distilled water and mix well.
The catalyst was molded into a pellet with a length of 7 mm and dried, and then calcined at 500°C for 6 hours under air circulation to obtain a finished catalyst. The composition of this catalyst, excluding oxygen, was Bi _1.2 W _2.4 Fe _0.35 Mo ₁₂ Co _6.0 K _0.5 Si _1.0 in atomic ratio (hereinafter, the catalyst composition will be expressed in the same manner). When the resulting catalyst was subjected to X-ray diffraction analysis, the bismuth tungstate peak was observed as is, and no peaks related to bismuth combined with other elements other than oxygen, such as bismuth molybdate, were observed. The thus obtained catalyst was packed into a steel reaction tube with an inner diameter of 25.4 mmφ to a layer length of 3000 mm, the external heating medium (molten salt) was heated to 340°C, and 6% by volume of isobutylene, 13.2% by volume of oxygen, and 10.0% by volume of water vapor were added. Volume %, nitrogen
A raw material gas having a composition of 70.8% by volume was introduced and the reaction was carried out for a contact time of 2.5 seconds (in terms of NTP), and the results shown in Table 1 were obtained. The analysis was performed using gas chromatography. After reacting with this catalyst for 5,000 hours, it was extracted and subjected to X-ray analysis, and no changes were observed compared to the catalyst before use. Comparative Example 1 A catalyst having the following composition was prepared in the same manner as in Example 1 except that the high-temperature treated product of bismuth and tungsten was not used. Fe _0.35 Mo ₁₂ Co _6.0 K _0.5 Si _1.0 The obtained catalyst was reacted under the same conditions as in Example 1, and the results shown in Table 1 were obtained. Comparative Example 2 A catalyst having the following composition was prepared in the same manner as in Example 1 except that tungsten trioxide was not used. Bi _1.2 Fe _0.35 Mo ₁₂ Co _6.0 K _0.5 Si _1.0 The obtained catalyst was reacted under the same conditions as in Example 1, and the results shown in Table 1 were obtained. Comparative Example 3 In Example 1, bismuth and tungsten were
A catalyst having the same composition as the catalyst in Example 1 was obtained by carrying out the same procedure except that heat treatment was performed at 500° C. for 2 hours. The obtained catalyst was reacted under the same conditions as in Example 1, and the results shown in Table 1 were obtained. Example 2 873 g of bismuth nitrate was dissolved in 1840 ml of distilled water which had been made acidic by adding 160 ml of concentrated nitric acid and heated to 80°C.
297 g of sodium tungstate was dissolved in 3500 ml of water, the pH of the solution was adjusted to 2.2 with nitric acid, heated to 80° C., and added to the bismuth nitrate solution with stirring. The resulting white precipitate was separated and washed with water until no sodium ions were detected. The obtained white cake was treated in the same manner as in Example 1 to obtain a yellow powder. Separately, add 1060g of ammonium molybdate to 8000ml.
cobalt nitrate 873 in an aqueous solution dissolved in distilled water.
Aqueous solution of g dissolved in 800 ml of distilled water, nitric acid 2nd
An aqueous solution of 242 g of iron dissolved in 700 ml of distilled water, 150 g of silica sol containing 20% by weight of silica, and an aqueous solution of 25.6 g of rubidium hydroxide dissolved in 100 ml of distilled water were added and stirred at room temperature. After adding 90 ml of concentrated nitric acid and 500 g of ammonium nitrate to the resulting suspension, the above yellow powder was added,
The mixture was concentrated under heating and stirring, molded and dried in the same manner as in Example 1, and then calcined at 500° C. for 6 hours under air circulation to obtain a catalyst having the following composition. Bi _3.6 W _1.8 Fe _1.2 Mo ₁₂ Co ₆ Rb _0.5 Si _1.0 The obtained catalyst was reacted under the same conditions as in Example 1, and the results shown in Table 1 were obtained. Example 3 485 g of bismuth nitrate was dissolved in 1000 ml of distilled water which had been made acidic by adding 104 ml of concentrated nitric acid. 1100 ml of ammonia water (28%) was added to this aqueous solution to obtain a white precipitate. This was washed separately with water, and 278 g of tungsten trioxide was added to the obtained white cake-like substance and thoroughly mixed, dried at 230°C for 16 hours, and further treated at 750°C for 2 hours under air circulation. The obtained yellow lumps were crushed to less than 100 mesh to obtain yellow powder. Separately, add 1060g of ammonium molybdate to distilled water.
873g of cobalt nitrate was dissolved in 8000ml of aqueous solution.
1000ml of 323g of ferric nitrate dissolved in 800ml of aqueous solution
150 g of silica sol containing 20% by weight of silica and 48.7 g of cesium nitrate in an aqueous solution dissolved in ml of distilled water.
An aqueous solution prepared by dissolving the above in 300 ml of distilled water was added to each, and the mixture was stirred at room temperature. After adding 90 ml of concentrated nitric acid and 500 g of ammonium nitrate to the resulting suspension, the above yellow powder was added, concentrated under heating and stirring, molded in the same manner as in Example 1, and then calcined at 500°C under air circulation for 6 hours to obtain the following. A catalyst with the following composition was obtained. Bi _2.0 W _2.4 Fe _1.6 Mo ₁₂ Co ₆ Si _1.0 Cs _0.5 The obtained catalyst was reacted under the same conditions as in Example 1, and the results shown in Table 1 were obtained. Examples 4 to 8 Catalysts having the compositions shown in Table 1 were prepared in the same manner as in Example 1. The oxidation reaction conditions and results of isobutylene are shown in Table 1. The raw materials used were nickel, thallium, barium,
Strontium, calcium, magnesium, cerium, zirconium, nitrates are used as lead sources, phosphoric acid is used as phosphorus source, niobium pentoxide is used as niobium source, antimony trioxide is used as antimony source, and titanium dioxide is used as titanium source. there was. Example 9 A catalyst with the same composition and preparation method as in Example 1 was molded into a ring shape with an outer diameter of 6.0 mm, a length of 6.6 mm, and a hole diameter of 2.0 mm, and the same reaction as in Example 1 was carried out, and the results are shown in Table 1. I got the results. Example 10 Using the catalyst of Example 2 and using tertiary-butanol in place of isobutylene, 6% by volume of tertiary-butanol, 13.2% by volume of oxygen, and 4% by volume of water vapor.
A raw material gas having a composition of 76.8% by volume and nitrogen was introduced, and the reaction was carried out at a contact time of 2.5 seconds and a molten salt temperature of 330°C, and the following results were obtained. Tertiary-butanol reaction rate 100% Isobutylene selectivity 1.5% Methacrolein 〃 85.2% Methacrylic acid 〃 2.6% Isobutylene single stream yield 1.5% Methacrolein 〃 85.2% Methacrylic acid 〃 2.6%

【table】

[Table] Comparative example 4 In Example 1, bismuth and tungsten were
A catalyst having the same composition as the catalyst in Example 1 was obtained by carrying out the same procedure except that the heat treatment was performed at 950° C. for 2 hours. When the obtained catalyst was reacted under the same conditions as in Example 1, the isobutylene conversion rate was 93.6%, the methacrolein selectivity was 85.0%, and the methacrylic acid selectivity was
It was 3.1%. Also using this catalyst 2000
After reacting for a period of time, it was extracted and subjected to X-ray analysis, and it was found that a bismuth molybdate compound was produced, albeit in a small amount. Example 11 In Example 1, bismuth and tungsten were
The same procedure was carried out except that heat treatment was performed at 650℃ for 2 hours.
A catalyst having the same composition as the catalyst in Example 1 was obtained.
When the obtained catalyst was reacted under the same conditions as in Example 1, the isobutylene conversion rate was 98.9%, the methacrolein selectivity was 85.1%, and the methacrylic acid selectivity was 2.5%. Further, after performing a reaction using this catalyst for 5,000 hours, it was extracted and subjected to X-ray analysis, and no change was observed compared to the catalyst before use. Example 12 In Example 1, bismuth and tungsten were
The same procedure was carried out except that heat treatment was performed at 850℃ for 2 hours.
A catalyst having the same composition as the catalyst in Example 1 was obtained.
When the obtained catalyst was reacted under the same conditions as in Example 1, the conversion of isobutylene was 97.8%, the selectivity of methacrolein was 84.9%, and the selectivity of methacrylic acid was 2.8%. In addition, after 5000 hours of reaction using this catalyst, it was extracted and subjected to X-ray analysis.
No changes were observed with the catalyst before use.

Claims (1)

[Claims] 1 The general formula composition used in producing methacrolein by catalytic gas phase oxidation of isobutylene or tertiary-butanol is Mo ₁₂ Bi _a W _b Fe _c A _d B _e C _f D _g O _h (However, A is at least one element selected from cobalt and nickel, B is at least one element selected from alkali metals, alkaline earth metals, and thallium, and C is phosphorus, antimony, and tin. At least one selected from , cerium, lead, and niobium
The seed element D represents at least one element selected from silicon, aluminum, titanium, and zirconium, and a, b, c, d, e, f, g, h
represents the atomic ratio of each element, and when molybdenum is 12, a=0.1-10.0, b=0.5-10.0, a/b is 0.01-6.0, c=0.1-10.0, d=2.0-
20.0, e is 0.01~10.0, f=0~10.0, g=0~
30, and h is a value determined by the valence of each element.
A method for preparing a catalyst composition for producing methacrolein, which comprises introducing the catalyst composition in the form of an oxide obtained by calcination at a temperature of 600 to 900°C.