JPS6121459B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention produces methacrolein by vapor phase contact of isobutylene or a mixture of isobutylene and tertiary butanol and oxygen in the presence of a multipromoted oxide catalyst containing molybdenum, bismuth, and iron supported on silica at elevated temperatures. Regarding the method. A method for producing methacrolein by bringing isobutylene and oxygen into contact with a catalyst in a high-temperature gas phase is known, and a large number of catalysts have been proposed so far. For example, a metal oxide catalyst consisting of molybdenum, bismuth, iron, and sodium or potassium is known as disclosed in Japanese Patent Publication No. 50-1241, but this catalyst has low activity and is not satisfactory for industrial implementation. It's not something you should do. The present inventors have proposed an industrial catalyst for the production of methacrolein by the oxidation of isobutylene or a mixture of isobutylene and tertiary-butanol, which is particularly suitable for fluidized bed reactors, has high activity, high selectivity and has a long life. As a result of intensive research into the structure and function of the above-mentioned catalyst system in order to develop a long-lasting catalyst, we limited the composition of molybdenum, bismuth, and iron to an extremely narrow range, and selected a small amount of potassium, rubidium, and cesium as essential components. The activity, especially the selectivity, is greatly improved by using one or more elements that are present in The present invention was completed based on these findings. I came to the conclusion. That is, in the present invention, in producing methacrolein by contacting isobutylene or a mixture of isobutylene and tertiary-butanol with oxygen at high temperature in the presence of a catalyst in a gas phase, the general compositional formula A _a MoBi _b Fe _f Na _o P is obtained. _p Oq [wherein A is one or more elements selected from potassium, rubidium, cesium, a, b, f,
n, p and q each represent the atomic ratio of elemental component A, bismuth, iron, sodium, phosphorus and oxygen to one molybdenum atom, and a is 0.002 to
Numbers in the range 0.06, bf and n are respectively the formula b=(1-X)(1-Y)(1-Z)/Y+1/2Z+
p, f=X(1-Y)(1-Z)/Y and n=1/2Z, where X and Y are (0.45, 0.35), (0.45, 0.65) , (0.85,
0.50), (0.85, 0.65), Z is a number in the range of 0 to 0.6, p is a number in the range of 0 to 0.2, and q is the element in the catalyst. is the number of oxygen atoms that satisfies the valence of . ] Provides a method for producing methacrolein, characterized by using a catalyst in which 30 to 70% by weight of the composition shown in the following is supported on silica. When the catalyst of the present invention contains sodium and/or phosphorus, which are optional components, measurements such as X-ray diffraction show that some of the sodium or phosphorus may of course exist in other forms, but mainly the compound Bi ₀ .
It was found that it exists as ₅ Na ₀ . ₅ MoO ₄ or BiPO ₄ . In this case, the general compositional formula A _a MoBi _b Fe _f Na _o P _p O _q of the _catalyst of the present invention is Bi _0.5 Na _{0.5 MoO 4}
Mo (1-Z) Bi (1-X) (1-Y) (1-Z)/Y can be expressed as the following formula using BiPO ₄ as a constituent unit.
_{Fe _ _ _ _ _ _ _ _ .5} Represents the fraction of molybdenum in MoO ₄ . In addition, X and Y _{are Bi 0.5 Na 0.5} MoO ₄ among the active components of the catalyst, and other constituent parts excluding A and BiPO ₄ MO (1-Z) Bi (1-X ₎ (1-Y) _{( 1} - _Z ) _/ Y _Fe +N _Fe , Y=N _Mp /N _Mp +N
Represents the fraction defined by _Bi +N _Fe . In order to obtain effective action and characteristics, the catalyst of the present invention is characterized in that the composition ratio of the components is extremely limited as seen in the above configuration, and in particular it contains an essential trace component A. . Component A
Not only is the methacrolein selectivity relatively low for catalysts that do not contain the The selection rate decreases significantly. When using the catalyst of the present invention containing component A, a large selectivity is maintained even at substantially 100% isobutylene conversion. The amount of component A of the present invention is determined from a=0.002 to
selected from the range of 0.06, preferably a=
It ranges from 0.002 to 0.03. Component A is potassium,
One type selected from rubidium and cesium or a combination thereof can be used. When rubidium or cesium is used alone, it has the same effect of improving methachlorolene selectivity with a smaller amount than potassium. If the amount of component A used exceeds the range of the present invention, the conversion rate of isobutylene will decrease and the methacrolein selectivity will also decrease. Among the active ingredients of the catalyst of the present invention _{, Bi 0.5 Na 0} .
_{5 Regarding} MoO ₄ , component A and other constituent elements other than BiPO ₄ , molybdenum, bismuth, and iron, the index X representing the fraction of iron to bismuth and the index Y representing the relative ratio of molybdenum are Four coordinate points (0.45, 0, 35), (0.45,
0.65), (0.85, 0.50), and (0.85, 0.65). If the combination of X and Y is outside this range, a high methacrolein selectivity cannot be obtained even if component A is added. If the value of Y is larger than this range, not only will the yield of methacrolein be low, but also the escape of molybdenum will be significant, causing troubles such as clogging of the reaction system. The amount of sodium, which is one of the optional components of the catalyst in the present invention, is selected from the range of Z= ₀ to _0.6 using an index representing the relative proportion of Bi _0.5 Na _0.5 MoO ₄ . Particularly preferably, Z=0 to 0.45. If the values of X and Y are within the limited range of the present invention and contain a trace amount of component A within the range of the present invention, when sodium is not present, that is, Z=
A catalyst having excellent activity and selectivity can be obtained even at 0. However, if the value of Y is relatively large within the range of the present invention, such as 0.55 to 0.65, the degree of escape of molybdenum will be relatively large, but the addition of sodium to such a catalyst system will reduce the escape of molybdenum. effectively suppress. When the value of Y is relatively small, the degree of molybdenum escape is sufficiently suppressed even without the addition of sodium, and it can be used for industrial implementation. In order to use the catalyst stably for a long time, it is necessary to suppress the escape of molybdenum, and for this purpose, the value of Z is sufficient within the range of the present invention. If used in excess of this range, not only will expensive bismuth and molybdenum be consumed, but also the yield of methacrolein will decrease. In the catalyst used in the present invention, silica is used as a carrier. Silica itself is inert compared to other carriers, exhibits the effect of a binder without substantially impairing the selectivity of the catalyst itself, and imparts high wear resistance to the catalyst. other carriers,
For example, when titania or zirconia is applied to the catalyst used in the present invention, the effect as a binder is extremely small, and when alumina is used, even though it has a binder effect, the selectivity of the catalyst is greatly reduced. Furthermore, even if the catalyst used in the present invention contains 1% by weight of aluminum, the selectivity will decrease. The amount of silica used is 30~
Selected from a range of 70% by weight. Especially preferably
It is 40-60% by weight. Silica usage is 30% by weight
Strong wear resistance can be obtained with the above conditions. however,
If it exceeds 70% by weight, not only will the catalytic active component be diluted and sufficient activity will not be obtained, but the selectivity will also be greatly reduced. The amount of phosphorus, which is another optional component, is selected from the range p=0 to 0.2 using an index representing the relative proportion of _BiPO4 . By adding a small amount of phosphorus within this range to the catalyst of the present method, the wear resistance strength of the catalyst can be further improved. The addition of phosphorus refines the particle size of suspended matter in the slurry and improves its dispersibility in the preparation of a raw material slurry in the catalyst manufacturing process described below. It is believed that this allows the silica sol, which is preferably used as a carrier silica source, and the active ingredient to be homogeneously mixed in the slurry, resulting in excellent body abrasion strength in the final form of the catalyst. Phosphorus can be used beyond the scope of the present invention, but will not increase the wear strength any further. Since phosphorus is present primarily as BiPO ₄ in the final catalyst form, using large amounts of phosphorus is not advantageous as it consumes expensive bismuth. When a catalyst is used industrially, its action must last for a long time under the reaction conditions. As mentioned above, the catalyst of the present invention not only has improved activity and selectivity at the initial stage of use, but also has the characteristics required from this point of view, namely:
It has a stable catalyst component and excellent wear resistance, and maintains high activity and selectivity over a long period of time. The production of methacrolein of the present invention can be carried out in either a fluidized bed reactor or a fixed bed reactor. Generally, when a fluidized bed reactor is used, heat can be easily removed and a uniform reaction temperature can be obtained, making it suitable for large-scale production. Generally, when a catalyst is used in a fluidized bed reactor, it is abraded due to collisions between catalyst particles or between particles and the vessel wall, but the catalyst of the present invention can sufficiently withstand this. The catalyst of the present invention can be suitably produced through three steps: first preparing a raw material slurry, then spray drying the slurry, and finally heat-treating and calcining the dried product. Silica sol can be suitably used as the carrier silica source for the catalyst, and phosphoric acid can be suitably used as the phosphorus source. molybdenum,
The sources of bismuth, iron, sodium, potassium, rubidium and cesium are preferably used in the form of ammonium salts, nitrates, hydrochlorides, sulfates or organic acid salts soluble in water or nitric acid. Particular sources of molybdenum include its ammonium salts, bismuth, iron, sodium, potassium,
The sources of rubidium and cesium are preferably used in the form of their respective nitrates. To prepare the raw material slurry, first add phosphoric acid to the silica sol while stirring, then add an aqueous solution of ammonium molybdate, and finally add dilute nitric acid and add selected from bismuth nitrate, ferric nitrate, sodium and potassium nitrate, rubidium nitrate, or cesium nitrate. This can be suitably carried out by adding a mixed solution in which one or more of the above substances are dissolved. A slurry of fine suspended solids uniformly dispersed in the silica colloid sol is thus obtained. If phosphorus is not added during this preparation process, a highly sedimentary and non-uniform slurry will result. The slurry is then dried using a known spray dryer to obtain spherical dry fine particles. Atomization of the raw material slurry can be carried out by any of the centrifugal, two-fluid nozzle, or high-pressure nozzle methods commonly used in industrial practice, but the centrifugal method is particularly preferred. In the centrifugal system, the particle size can be distributed between 10 and 150 microns, which is suitable for use in a fluidized bed reactor, by adjusting the rotation speed of the disk and the feed rate of the slurry. Finally, the dried product is heat-treated and fired using a conventional tunnel or rotary kiln. Firing temperature is 600-750℃, preferably 620-730℃
It can be carried out in the range of ℃. The firing time may vary depending on the firing temperature, but is selected within the range of 1 to 20 hours. The raw materials, isobutylene and tertiary-butanol, do not necessarily have to be of high purity, and can be used even if they contain some impurities. Air is usually used as the oxygen source. The volume ratio of isobutylene to air is 1:8 to 20, especially 1:
A range of 9 to 15 is preferred. Furthermore, water vapor or an inert gas can be introduced as necessary. The reaction temperature is preferably in the range of 360 to 500°C, particularly 380 to 430°C. The reaction pressure may be normal pressure, but the reaction may be carried out under increased pressure if necessary. The contact time between the raw material mixed gas and the catalyst is between 0.3 and 15 seconds, preferably between 0.5 and 10 seconds. As described above, by using a catalyst with a specific composition, the method of the present invention significantly improves the selectivity of methacrolein by oxidation of isobutylene or a mixture of isobutylene and tertiary-butanol, and also provides long-term stability and durability of the catalyst itself. This is an extremely advantageous method for implementation on an industrial scale to improve wear resistance. Hereinafter, the present invention will be described in more detail with reference to Examples. Example (1) Production of catalyst Composition index: X=0.7, Y=0.54, Z=0.a(k)=
0.006, p=0.1, and the empirical formula of the 50 wt% silica-supported catalyst, i.e. its active component, is
A catalyst having _{MoBi 0.36 Fe 0.60 K 0.006 P 0.1 Oq} was produced as follows _. Take 5,000 g of silica sol (Snowtex N manufactured by Nissan Chemical) containing 30% by weight of SiO ₂ , add 61.2 g of 85% by weight of phosphoric acid to it while stirring, and then add ammonium 7-molybdate [(MH ₄ ) to 2,400 g of water. Add a solution containing 948 g of ₆ Mo ₇ O ₂₄・4H ₂ O, and finally add 1000 g of 13.3% by weight nitric acid in advance.
921g of bismuth nitrate [Bi(NO ₃ ) _{3.5H 2} O],
A mixed solution of 1293 g of ferric nitrate [Fe(NO ₃ ) _{3.9H 2} O] and 3.26 g of potassium nitrate [KNO ₃ ] was added. The raw material slurry thus obtained was sent to a cocurrent type spray dryer and dried. Atomization of the raw material slurry was performed using a centrifugal atomization device equipped with a dish-shaped rotor, which was installed in the center of the upper part of the dryer. The obtained dry powder was calcined in a tunnel kiln to obtain a catalyst. This will be referred to as catalyst 1. Thirty-four other catalysts with various compositions were manufactured using the same method. These catalysts were subjected to the following isobutylene oxidation test, molybdenum escape test, and abrasion test. (2) Isobutylene oxidation reaction test (A) 600 g of each catalyst prepared in (1) was placed in a fluidized bed reactor with a diameter of 3 inches and equipped with 16 mesh stainless wire mesh, and the reaction temperature was set at 400°C. The pressure was maintained at 0.5Kg/ ^cm2 in gauge pressure, and the volume ratio of isobutylene, water vapor, and air was 1:3:13.
of mixed gas was sent at a rate of 420 per hour in terms of NTP. The contact time under reaction conditions was 3.1 seconds. The test results for this reaction are shown in Table 1 along with the composition of the catalyst used. (3) Isobutylene oxidation reaction test (B) Fill a glass reaction tube with an inner diameter of 8 mm with 1 g of the various catalysts prepared in (1), and maintain it at 380 to 400°C.
A gas in which isobutylene, oxygen, and water vapor are mixed at a molar ratio of 1:2:3 is diluted with helium until the isobutylene concentration is 3% by volume, and the contact time is 1 to 1.5 seconds. I passed it. The reaction pressure at this time was atmospheric pressure. The test results for this reaction are shown in Table 2 along with the composition of the catalyst used. Note that rubidium nitrate and cesium nitrate were used as the rubidium and cesium sources in the examples. In addition, sodium nitrate was used as the sodium source in all cases. Further, the total conversion of isobutylene and the yield of methacrolein in Tables 1 and 2 were determined according to the following definitions. Total conversion rate of isobutylene (%) = Carbon weight of reacted isobutylene / Carbon weight of supplied isobutylene x 100 Yield of methacrolein (%) = Carbon weight of produced methacrolein / Carbon weight of supplied isobutylene x 100

【table】

[Table] (4) Oxidation reaction test of a mixture of isobutylene and tert-butanol Using the catalyst No. 1 prepared in (1), a reaction was carried out using the apparatus of (3) Isobutylene oxidation reaction test (B). I went there. At this time, the catalyst was 1g, the temperature was 400℃,
The pressure was atmospheric pressure, the contact time was 1 second, and the molar ratio of isobutylene and tert-butanol was 1:1.
Using a gas mixture such that the sum of isobutylene and tertiary-butanol, oxygen and water vapor are mixed in a molar ratio of 1:2:3, the sum of isobutylene and tertiary-butanol is 3% by volume. diluted with helium until diluted with helium. As a result of testing this reaction, the yield of methacrolein was
It was 79.5%. However, methacrolein yield (%) = carbon weight of produced methacrolein/sum of carbon weights of supplied isobutylene and tertiary butanol x 100. (5) Molybdenum fugitive test The molybdenum fugitive rate was determined by accurately weighing about 10 g of the catalyst in a magnetic dish, and calculating the weight loss rate of the catalyst after leaving it in the presence of air at 750°C for 100 hours. It was confirmed by elemental analysis after the test that the decrease in catalyst weight was due to sublimation and escape of MoO ₃ . Table 3 shows the measurement results of molybdenum fugitiveness. As is clear from Table 3, catalysts 32 and 29, in which the value of Y exceeds the range of the present invention, have a large degree of escape. By introducing Z in comparative catalyst 29, comparative catalyst 32
Although the degree of escape is further suppressed, as shown in Table 2, the yield of methacrolein is low. In the catalyst of the present invention, the value of Y is within a limited range, and the degree of escape is effectively suppressed by the introduction of Z.

[Table] (6) Wear test The wear level of the catalyst is measured using the Test Methods for Synthetic Cracking Catalyst, which is normally performed as a test method for FCC catalysts.
Catalysts), American Cyanamids, Inc., 6/
31-4M-1/57], approximately 50 g of catalyst was accurately weighed into a vertical tube with a diameter of 1.5 inches and equipped with a perforated disc with three 1/64-inch orifices at the bottom.
Air was flowed through the Kongming disk at a rate of 15 CF/hour to cause vigorous catalyst fluidization. The degree of wear of the catalyst is 5~
It was determined as the ratio of the weight of the catalyst that was atomized and escaped from the top of the vertical tube during 20 hours to the initial input amount. Table 4 shows the measurement results of the degree of catalyst wear. As is clear from Table 4, comparative catalysts 33 and 34 with a low silica content are very susceptible to wear, whereas the catalyst of the present invention with an appropriate silica content has a low wear rate, and even when phosphorus is added, This shows that it is effectively suppressed.

【table】

Claims (1)

[Claims] 1. In producing methacrolein by contacting isobutylene or a mixture of isobutylene and tertiary-butanol with oxygen in the presence of a catalyst in the gas phase at high temperature, the general compositional formula A _a MoBi _b Fe _f Na _o P _p O _q [wherein A is one or more elements selected from potassium, rubidium, cesium, a, b, f,
n, p and q are elemental components A, bismuth, iron, sodium,
Represents the atomic ratio of phosphorus and oxygen, a is 0.002
A number in the range of ~0.06, b, f and n are respectively the formula b=(1-X)(1-Y)(1-Z)/Y+1/2Z
+P, f=X(1-Y)(1-Z)/y and n=1/2Z
where X and Y are (0.45, 0.35),
(0.45, 0.65), (0.85, 0.50), (0.85, 0.65) 4
The number inside the rectangle formed by connecting two coordinate points,
Z is a number in the range of 0 to 0.6, p is a number in the range of 0 to 0.2, and q is the number of oxygen atoms that satisfies the valence of the element in the catalyst] at 30 to 70% by weight. A method for producing methacrolein, characterized by using a catalyst supported on silica.