JPS6115051B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing methacrolein and methacrylic acid by vapor phase catalytic oxidation of isobutyraldehyde using a novel catalyst. Conventionally, several types of catalysts have been proposed for the production of methacrolein and methacrylic acid from isobutyraldehyde, but none of them are industrially satisfactory. For example, according to JP-A-48-78112, a method using phosphomolybdic acid in which molybdenum is partially replaced with vanadine or tungsten is used as a catalyst;
A method using a catalyst containing phosphorus-thallium-oxygen as essential components has been proposed. However, according to these methods, a considerable amount of carbon oxide is produced, and the product is mainly methacrolein, and the yield of methacrylic acid is about 35% at most. Methacrylic acid is industrially more useful, and a higher yield of methacrylic acid is more advantageous in terms of catalyst performance. The present inventors have conducted intensive research on catalysts for obtaining methacrolein and methacrylic acid from isobutyraldehyde, especially methacrylic acid, with high selectivity and high yield. It was found that methacrylic acid can be obtained by If the catalyst of the present invention is used, the conversion rate of isobutyraldehyde can be almost 100% if the conditions are selected, and it is also possible to make methacrolein or methacrylic acid the main product by controlling the reaction temperature. It is possible. Furthermore, it has been found that this catalyst system has an extremely long life. The present invention was obtained based on these new findings. That is, the present invention uses the general formula Mo _a P _b Zr _c X _d V _e Y _f O _g (wherein X represents at least one element selected from potassium, rubidium, cesium, and thallium, preferably selected from potassium and cesium, and Y is selected from lithium, sodium, magnesium, and calcium, preferably selected from lithium and sodium. Indicates the element, a, b,
c, d, e, f and g are molybdenum, respectively;
Represents the atomic ratio of phosphorus, zirconium, X, vanadine, Y, and oxygen, and when a=12, b=
0.5-3, preferably 1-2, c=0.5-5, preferably 0.5-2, d=1-3, e=0.1-4, preferably 0.2-1, f=0-0.5, preferably 0-
0.3, and g is a value determined from the oxidation numbers of other elements. However, when X is other than thallium, Y represents an element selected from lithium and sodium, and f≠0. ) The present invention provides a method for producing methacrolein and methacrylic acid, which is characterized by using a catalyst represented by: As a method for preparing the catalyst, methods known in the field of oxidation reactions, such as evaporation to dryness, etc. may be used.
Although it is possible to mix oxides as they are as catalyst preparation reagents, metal salts, metal acids, or a base, etc., are acceptable. Common examples thereof include nitrates, organic acid salts, ammonium salts, hydroxides, heteropolyacids, and the like. The prepared catalyst is heated at 150-500°C, preferably 200-450°C in a stream of air for 1-40 hours, preferably 2 hours.
- It is preferred to bake for 30 hours. Although the catalyst used in the method of the present invention can be used without a carrier, it is preferred industrially to use a carrier. Specific examples of the carrier include silicon carbide, fused alumina, pumice, and the like. The amount of the catalyst component supported on the carrier varies somewhat depending on the catalyst preparation method employed, but usually the weight of the active component as a catalyst is 10 to 400 parts by weight, preferably 25 to 400 parts by weight, based on 100 parts by weight of the carrier. 200 parts by weight is suitable. According to the present invention, a raw material gas containing isobutyraldehyde and molecular oxygen, preferably mixed with an inert gas and water vapor, is passed over the catalyst of the present invention at high temperature to produce methacrolein and methacrylic acid with high selectivity. It can be obtained in high yield. The reaction conditions for the catalytic reaction vary somewhat depending on the performance of the individual catalyst employed, and there are interrelationships with conditions such as reaction temperature and space velocity, so it cannot be generalized, but they are approximately as follows. (1) Reaction temperature: 200-400℃, preferably 250-350℃
°C (2) Reaction pressure: 0.5 to 2 atm (absolute) (3) Space velocity: 500 to 2000 hr ^-1 (0 °C, 1 atm standard) (4) Molar ratio of water vapor and isobutyraldehyde;
(1-50):1 Furthermore, although air is usually used as the oxygen source, it is of course possible to use pure oxygen. The molar ratio of oxygen and isobutyraldehyde is (1 to
20):1 is preferable, but if economic considerations are taken into account, preferably (1 to 3):1. In addition, the above-mentioned inert gases include nitrogen, carbon dioxide, helium, argon, and lower saturated hydrocarbons (methane, ethane, propane, butane, etc.).
It means a gas that is substantially inert to the reaction, and a mixture of these gases can also be used. The reaction product can be separated and recovered by a commonly used method, such as condensation followed by extraction or distillation. Analysis in the following examples was by gas chromatography. Further, the conversion rate of isobutyraldehyde, the yield of methacrylic acid, methacrolein, and carbon oxide, and the selectivity were determined by the following formulas. Note that in the examples below, these mole percentages are simply %
It is written as Conversion rate (mol%) Supplied isobutyraldehyde (mol) - unreacted isobutyraldehyde (mol) / supplied isobutyraldehyde (mol) x 100 Selectivity to methacrylic acid (methacrolein) (mol%) Produced methacrylic acid ( methacrolein) (molar ratio)/supplied isobutyraldehyde (mol) - unreacted isobutyraldehyde (mol) x 100 Selectivity to CO ₂ (CO) (mol %) CO ₂ (CO) produced (mol)/supplied Isobutyraldehyde produced (mol) - Unreacted isobutyraldehyde (mol) x 25 Selectivity to acetic acid (mol%) Acetic acid produced (mol) / Supplied isobutyraldehyde (mol) - Unreacted isobutyraldehyde (mol) x
50 Yield of methacrolein and methacrylic acid (mol%) (conversion rate) x (selectivity to methacrolein + selectivity to methacrylic acid) x 1/100 Example 1 45.6 g (12.5 mmol) of phosphomolybdic acid was placed in a flask. ) was dissolved in 200 c.c. of distilled water. To this, add 3.08 g (25 mmol) of zirconium dioxide powder and 0.75% (6.5 mmol) of 85% orthophosphoric acid, and
Time refluxed. After cooling the liquid, transfer it to a beaker and add 1.08 g (9.25 g) of ammonium metavanadate.
aqueous solution containing (mmol) and thallium nitrate
A mixture of aqueous solutions containing 13.32 g (50 mmol) was added with good stirring. The resulting suspension was evaporated to dryness over a water bath. The contents were transferred to a crucible and fired in a Matsufuru furnace at 300°C for 2 hours. After cooling, it was ground in a mortar. 20 g of granular molten alumina carrier (particle size: 3 mmφ) was placed in a beaker, and while water was being sprayed, the above catalyst component powder was sprinkled little by little, and the mixture was thoroughly stirred to coat the carrier. The powder was dried by blowing hot air from time to time, and the same operation was repeated many times to prevent moisture from oozing out onto the surface, so that a total of 30 g of powder was adhered to the carrier. The obtained product was placed in a crucible and fired again in a Matsufuru furnace at 400°C for 3 hours to obtain a catalyst.
The atomic ratio of the active ingredients excluding oxygen contained in this catalyst is Mo:P:Zr:Tl:V≒12:1.3:1:2:
It was 0.37. A quartz reaction tube with an inner diameter of 20 mm was filled with 25 c.c. of catalyst.
A raw material gas consisting of 4.0 mol % of isobutyraldehyde, 40.0 mol % of air, and 56.0 mol % of water vapor was passed through the tube at a space velocity of 1000 hr ^-1 (based on 0° C. and 1 atm). The reaction temperature (the highest temperature in the catalyst layer) was controlled to be 320°C. The yield of methacrylic acid was highest around this temperature. Table of reaction results 1000 hours after the start of the reaction.
Shown in 1. Table 1 shows that the activity of the catalyst is very stable and the yield of methacrylic acid is also at a high level. Example 2 An experiment was carried out in exactly the same manner as in Example 1, except that the reaction temperature was significantly lowered to 270°C. The results are shown in Table-1. As is clear from Table 1, even if the reaction temperature is lowered in this way, the conversion rate of isobutyraldehyde remains low.
100%, and the main product was methacrolein. This shows that the main product can be changed by controlling the reaction temperature. Comparative Example 1 Example 1 except that orthophosphoric acid was not used.
The catalyst was prepared and tested exactly as described above. Activity was almost completely gone. Example 3 Take 43.2 g (300 mmol) of molybdenum trioxide and 2.02 g (17.5 mmol) of 85% orthophosphoric acid in a flask, add 200 c.c. of distilled water, and then add 3.08 g (25 mmol) of zirconium dioxide. and refluxed for 48 hours. Transfer the obtained liquid to 1 beaker and add 1.08 g (9.25 g) of ammonium metavanadate here.
aqueous solution containing 13.32 g of thallium nitrate (mmol)
A mixture of aqueous solutions containing (50 mmol) was added, stirred well, and evaporated to dryness over a hot water bath. The subsequent handling was carried out in the same manner as in Example 1 to prepare a catalyst, and the reaction test was conducted in the same manner as in Example 1. The results are shown in Table-1. Perhaps because the amount of phosphorus used was small, the yield of methacrylic acid was somewhat low even at the optimum temperature for methacrylic acid. Example 4 A catalyst was prepared and tested in exactly the same manner as in Example 1, except that the amount of orthophosphoric acid used was increased. Compared to Example 1, the selectivity to methacrylic acid decreased and the selectivity to methacrolein increased. Comparative Example 2 A catalyst was prepared and tested in exactly the same manner as in Example 1, except that the amount of orthophosphoric acid used was increased. The conversion rate is
It did not reach 100%, and the selectivity to methacrylic acid also decreased significantly. Examples 5 and 6, Comparative Examples 3 and 4 Catalysts were prepared and tested in exactly the same manner as in Example 1, except that the amount of zirconium dioxide used was changed. The results are shown in Table-1. These results show that addition of an appropriate amount of zirconium is useful for increasing the selectivity of methacrylic acid.
However, when the amount of zirconium used was too large, the selectivity of methacrylic acid decreased significantly. Comparative Example 5 A catalyst was prepared in exactly the same manner as in Example 1, except that thallium nitrate was not used, and the catalyst was tested under the same conditions except that the reaction temperature was 310°C. Table 1 shows the results.
It was shown to. During this reaction, the color of the catalyst changed drastically compared to other Examples (eg Example 1). That is, in Example 1, the color was yellow-green when unreacted and turned green during reaction, but in this case, the color changed to almost blue during reaction. Therefore, measurements were also conducted when the reaction time was 10 hours. It can be seen that the catalytic activity changes significantly over time and the stability is low. Examples 7 and 8 A catalyst was prepared and tested in exactly the same manner as in Example 1, except that the amount of thallium nitrate used was changed. The results are shown in Table-1. Whether the thallium content was high or low, the selectivity for methacrylic acid slightly decreased and the selectivity for methacrolein increased. Comparative Example 6 A catalyst was prepared and tested in exactly the same manner as in Example 1, except that the amount of thallium nitrate used was considerably increased.
The results are shown in Table-1. The total yield of methacrolein and methacrylic acid was significantly reduced. Examples 9 and 10 A catalyst was prepared and tested in exactly the same manner as in Example 1, except that the amount of ammonium metavanadate used was changed. The results are shown in Table-1. When the amount of vanadine was small, the selectivity to acetic acid and carbon oxides tended to increase, and when the amount was large, the selectivity to methacrolein increased, while the selectivity to methacrylic acid decreased. Comparative Examples 7 and 8 Catalysts were prepared and tested in exactly the same manner as in Example 1, except that ammonium metavanadate was not used or a large amount was used and the reaction temperature was 315°C or 330°C. The results are shown in Table-1. As is clear from Table 1, the total yield of methacrolein and methacrylic acid was low. Examples 11 and 12 An aqueous solution containing 0.962 g (3.75 mmol) of magnesium nitrate or 0.820 g (5.0 mmol) of calcium nitrate was added to the aqueous thallium nitrate solution prepared as a catalyst in Example 1. A catalyst was otherwise prepared and tested in the same manner as in Example 1. The results are shown in Table-1. Compared to the results of Example 1, the production of carbon oxides was somewhat suppressed. Furthermore, the total yield of methacrylic acid and methacrolein at high methacrylic acid yield was slightly higher than in Example 1, suggesting that the addition of calcium or magnesium had some effect. Reference Examples 1 to 3 Potassium nitrate, rubidinium nitrate, cesium nitrate, etc. are used instead of thallium nitrate, and further,
Example 1 except that the reaction temperature was 310°C or 330°C
The catalyst was prepared and tested exactly as described above. The results are shown in Table-1. Examples 13-15 Instead of magnesium nitrate, lithium hydroxide,
A catalyst was prepared and tested in exactly the same manner as in Example 11, except that sodium nitrate was used and potassium nitrate, rubidium nitrate, and cesium nitrate were used in place of thallium nitrate. The results are shown in Table-1. Lithium and sodium also showed similar effects as magnesium and calcium. Examples 16-18 Catalysts were prepared in exactly the same manner as in Example 1, except that thallium and potassium, thallium and rubidium, and thallium and cesium were used as the X component, and lithium, sodium, and lithium were used as the Y component, respectively. Tested. The results are shown in Table-1. All showed high methacrylic acid selectivity.

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Claims (1)

[Claims] 1. In producing methacrolein and methacrylic acid by gas phase catalytic oxidation of isobutyraldehyde with a gas containing molecular oxygen, the general formula Mo _a P _b Zr _c X _d V _e Y _f O _g (Here, X represents at least one element selected from potassium, rubidium, cesium, and thallium, and Y represents an element selected from lithium, sodium, magnesium, and calcium, and a, b, c, d, e, f and g represent the atomic ratio of molybdenum, phosphorus, zirconium, X, vanadine, Y and oxygen, respectively, and when a=12, b=0.5-3, c=0.5-5, d=1 −
3, e=0.1-4, f=0-0.5 and g are numerical values determined from the oxidation numbers of other elements. However, when X is other than thallium, Y represents an element selected from lithium and sodium, and f≠0. ) A method for producing methacrolein and methacrylic acid, characterized by using a catalyst represented by: