JPH0256937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to catalyst compositions. Specifically, the present invention relates to a composition that exhibits an excellent catalytic effect in a reaction that produces acrylonitrile by bringing propylene, ammonia, and oxygen or an oxygen-containing gas into contact in a gas phase.
Various catalyst systems have been proposed as catalysts for so-called ammoxidation, in which acrylonitrile is produced by contacting propylene, ammonia, and oxygen or an oxygen-containing gas in the gas phase, but the catalysts used in industrial implementation are is extremely small. Among these, noteworthy catalysts include oxide catalysts whose basic composition is molybdenum and bismuth, and which further includes iron and phosphorus. Various improvements have since been proposed for this type of catalyst, and typical examples include oxide catalysts containing metal elements such as molybdenum, bismuth, iron, phosphorus, nickel, and cobalt. However, these catalysts still do not sufficiently suppress side reactions, and when the reaction rate of propylene is increased, the selectivity decreases, making it difficult to obtain a sufficiently high acrylonitrile yield. Furthermore, for industrial use, it is important that the catalyst has a long life. Therefore, the present inventors conducted research to develop a catalyst with high activity and high selectivity, that is, a catalyst that can produce acrylonitrile with high selectivity even when reacting propylene at high reaction rate, and has a long life. As a result, using a catalyst containing molybdenum, tungsten, bismuth, lead, antimony, chromium, and oxygen in a specific composition range, or a catalyst in which a specific amount of iron is added to the above elements, compared to conventional molybdenum-bismuth-based catalysts, The present invention was achieved by discovering that acrylonitrile can be produced in high yield even under conditions of high propylene reaction rate, and that the life of the catalyst can be extended. The catalyst composition of the present invention has a composition formula (Mo)a(W)
b(Bi)c(Pb)d(Sb)e(Fe)f(Cr)g(O)
h (however, a, b, c, d, e, f, g, h are respectively molybdenum, tungsten, bismuth,
Representing the number of atoms of lead, antimony, iron, chromium, and oxygen, and assuming a+b=12, 0<b≦7, 0.4≦c
≦7, 2≦d≦12, 0.1/22≦e/a≦25/22,
0≦f/a≦3/22, 0<g/a≦3/22, and h represents the number of oxygen atoms necessary to satisfy the valences of each of the above components. ). In order to improve the acrylonitrile yield in the catalyst composition of the present invention, the number of atoms of each component element particularly suitable is 0<b≦5.5, 0.6 when a+b=12.
≦c≦6, 2.6≦d≦11, 1/22≦e/a≦10/
22, 0≦f/a≦2/22 and 0.05/22≦g/a
≦2/22. Furthermore, regarding iron, 0.05≦
More preferably, f/a≦2/22. The catalyst composition of the present invention may be molded as it is without using a carrier, or a molded product may be obtained using a carrier such as silica, alumina, titania, silicon carbide, or the like. The size and shape of the catalyst particles are not particularly limited, and may be formed into any shape and size such as pellets, tablets, spheres, and granules depending on the usage conditions. Molybdenum compounds used for catalyst preparation include molybdenum oxides such as molybdenum trioxide,
Molybdic acid or a salt thereof, phosphomolybdic acid or a salt thereof, etc. are used, and molybdate salts such as ammonium paramolybdate are preferably used. As the tungsten compound, tungsten oxide such as tungsten trioxide, tungstic acid or condensed acid thereof, or a salt thereof, phosphotungstic acid or a salt thereof, etc. are used. As the bismuth compound, bismuth salts such as bismuth nitrate and bismuth sulfate, and various oxides or hydroxides of bismuth are used. As lead compounds, lead salts such as lead nitrate and lead sulfate, and various lead oxides or hydroxides are used. As the antimony compound, oxides such as antimony trioxide, chlorides such as antimony trichloride, antimony metal, etc. are used. As the iron compound, iron salts such as iron nitrate and iron sulfate, and various iron oxides or hydroxides are used. As the chromium compound, chromium salts such as chromium nitrate, chromium sulfate, and ammonium dichromate, and various chromium oxides or hydroxides are used. To produce a catalyst using these raw materials, compounds of each component element are dissolved or suspended in water, and in some cases, a sol of a carrier component such as silica sol or alumina sol or a carrier powder such as titania powder is suspended. , it may be made into a uniform slurry or aqueous solution and then fired. When forming catalysts by spray drying,
If spray drying is performed after adjusting the pH of the spray raw material slurry to 1 to 6, a catalyst with excellent impact resistance can be obtained. When ammonium paramolybdate and ammonium paratungstate are used as molybdenum compounds and tungsten compounds, respectively, in the production of catalysts, a solubility promoter such as ammonia is added to an aqueous solution containing these salts to increase their solubility in water. It is preferable to add. When bismuth nitrate or bismuth sulfate is used as the bismuth compound, it is preferable to use an acidic nitric acid aqueous solution or a sulfuric acid acidic aqueous solution, respectively. Furthermore, when using antimony trioxide as an antimony compound, it may be used by dissolving it in an organic aqueous solution such as tartaric acid, but when using antimony trioxide powder, the slurry containing each catalyst component must be uniformly stirred. It is preferable to adjust the pH to 7 or less and heat treat at 40° C. or higher for 1 to 8 hours. In this case, the iron compound can be added to the slurry after the heat treatment, if desired. The firing temperature and firing time after catalyst formation are not particularly limited, but the firing temperature is usually 400~400℃.
The temperature is selected to be 800°C, preferably 500 to 750°C, and baked for 5 minutes to 4 hours. To explain the reaction in which the catalyst composition of the present invention is used, acrylonitrile is produced by contacting propylene, ammonia, and oxygen or an oxygen-containing gas in the gas phase in the presence of the following catalyst. The raw material gas propylene does not necessarily have to be of high purity, and may contain a gas substantially inert to the reaction, for example, a saturated hydrocarbon such as propylene. Air is used industrially as the oxygen-containing gas. The molar ratio of oxygen to propylene to be supplied is preferably 1 to 4 times, preferably 1.5 to 2.5 times. The molar ratio of ammonia to propylene is preferably 0.8 to 2.5 times, preferably 0.9 to 1.5 times. The reaction is usually carried out under normal pressure, but may be carried out under reduced pressure or increased pressure, if necessary. The reaction temperature is usually 360-540℃, preferably
The temperature is 400-500℃. Also, the space velocity of the raw material gas is
Range 100-3000hr ^-1 , preferably 200-2000hr ^-1
You can choose from the range as appropriate. The catalyst composition of the present invention can be used in either fixed bed or fluidized bed mode. As explained in detail above, according to the ammoxidation of propylene using the catalyst composition of the present invention, acrylonitrile is produced with a high selectivity even when the reaction rate of the raw material gas is increased. can be manufactured. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In this specification, the reaction rate, selectivity, and acrylonitrile yield are defined by the following formula. Reaction rate (%) = Number of moles of propylene consumed/Number of moles of propylene supplied x 100 Selectivity (%) = Number of moles of acrylonitrile produced/Number of moles of propylene consumed x 100 Example 1 Ammonium paratungstate (NH ₄ ) ₁₀ W ₁₂ O ₄₁・5H ₂ 0.0392 g of 1 wt.
A solution of 3.030 g of (NO ₃ ) ₂ dissolved in 5.9 ml of water, ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ .
A solution of 2.225 g of 4H ₂ O dissolved in 11.5 ml of 5% by weight aqueous ammonia and a solution of 1.164 g of bismuth nitrate dissolved in 1.8 ml of 10% by weight nitric acid aqueous solution were added.
Next, 3.43 g of commercially available antimony trioxide Sb ₂ O ₃ powder
was mixed with 14.2 ml of water, 2.80 ml of 25% aqueous ammonia, and 5.3 g of tartaric acid, heated to dissolve it, weighed out 1/10 of the resulting liquid, added it to the above slurry, and then added ferric nitrate Fe. (NO ₃ ) ₃・9H ₂ O0.115g
A solution of Cr dissolved in 3 ml of water and chromium nitrate Cr
(NO ₃ ) Add a solution of 0.138 g of ₃・9H ₂ O dissolved in 3 ml of water, adjust the pH to 2.2 by adding a 10% by weight aqueous solution, and while stirring, no longer generates NO ₂ on the hot plate. It was heated to dryness. The obtained solid was formed into a tablet with a diameter of 6 mm and a thickness of 3 mm, calcined at 700° C. for 2 hours under air circulation, and then ground to obtain a granular catalyst of 16 to 24 meshes. The composition _of the _catalyst thus obtained was MO _11.86 W _0.14 Bi ₂ .
_{26Pb8.61Sb2.21Fe0.27Cr0.32O52.2 ,} and _{the ratio of} silica as _{a carrier to catalyst component} was 40:60 ₍ weight ratio). 1 ml of this catalyst was packed into a heat-resistant glass reactor with an inner diameter of 4 mm, a mixed gas with a molar ratio of propylene: ammonia: air = 1:1.2:10 was supplied to the reactor at a space velocity of 500 hr ^-1 , and the reaction was carried out at 460°C. I let it happen. As a result, the propylene reaction rate was 98.6%, and the acrylonitrile selectivity was 86.2% (acrylonitrile yield was
85.0%). Examples 2 to 6 Catalysts having the compositions shown in Table 1 were prepared in the same manner as in Example 1, and the reactions were carried out in the same manner as in Example 1 at the reaction temperatures shown in the table. The results are also shown in Table 1.
Shown below. Comparative Example 1 Example except that the addition of ferric nitrate Fe(NO ₃ ) ₃ ·9H ₂ O in Example 1 was omitted and the amount of chromium nitrate Cr(NO ₃ ) ₃ ·9H ₂ O was increased. The same experiment as 1 was repeated. The catalyst composition and reaction results are shown in Table 2. Comparative Example 2 The same experiment as in Example 3 was repeated except that antimony was not used in Example 3. The catalyst composition and reaction results are shown in Table 2. Example 7 Example 1 except that the addition of ferric nitrate Fe(NO ₃ ) ₃ ·9H ₂ O in Example 1 was omitted and the amount of chromium nitrate Cr(NO ₃ ) ₃ ·9H ₂ O was increased. The same experiment was repeated. Table 1 shows the catalyst composition and reaction results.

【table】

[Table] Example 8 A fluidized catalyst having the same composition as in Example 1 was prepared as follows. Ammonium paratungstate (NH ₄ ) ₁₀ W ₁₂ O ₄₁・5H ₂ A solution of 78.4 g of 1 wt % ammonia water dissolved in 1 wt.
Added to 32.37Kg of silica sol. Next, 710.7 g of commercially available antimony trioxide Sb ₂ O ₃ powder was mixed with 2.9 g of water, 580 ml of 25 wt% aqueous ammonia, and 1089 g of tartaric acid, heated to dissolve it, and the resulting solution was added to the above slurry under stirring, followed by addition of nitric acid. Lead Pb ( _NO3 ) ₂ 6.06
A solution of Kg dissolved in water 11.3, ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄・4H ₂ O 4.450Kg
A solution of 5% by weight of ammonia water dissolved in 8.5% of aqueous ammonia,
Bismuth nitrate Bi (NO ₃ ) ₃・5H ₂ O2.328Kg dissolved in 10% by weight nitric acid aqueous solution 2.70%, nitric acid 2
A solution of iron Fe (NO ₃ ) ₃・9H ₂ O242 g dissolved in 2.75 g of water and chromium nitrate Cr (NO ₃ ) ₃・9H ₂ O274.3
A solution prepared by dissolving 2.5 g of water was added thereto, and 97% by weight nitric acid was added to adjust the pH to 2.8. The slurry thus obtained was homogenized using a homogenizer and spray-dried using a conventional method using a spraying device with a rotating disk to form fine particles.The slurry was then placed in a rotary firing furnace at a temperature of 670°C and a residence time of 14 minutes. A catalyst with an average particle size of 58μ was obtained by continuous firing under the following conditions. Next, 1850 g of this catalyst was packed into a fluidized bed reactor with an inner diameter of 2.5 inches, and a mixed gas with a molar ratio of propylene: ammonia: air = 1:1.1:12.7 was added to the catalyst so that the load of propylene per unit time on the catalyst was
0.068hr ^-1 (supplied propylene g/hr/gcat) was supplied to the reactor at a temperature of 480℃ and a pressure of 0.85.
The reaction was carried out at Kg/cm ² G. It took about 100 hours to reach steady state. The results are shown in Table-3. Comparative Example 3 350 g of commercially available antimony trioxide Sb ₂ O ₃ powder was added to a solution of 261 g of ammonium paratungstate (NH ₄ ) ₁₀ W ₁₂ O ₄₁・5H ₂ O dissolved in 1% by weight aqueous ammonia (3.3 g) with stirring. . To this, 32.6 kg of 20% by weight silica sol was added with stirring, followed by a solution of 6.29 kg of lead nitrate Pb (NO ₃ ) ₂ dissolved in 11.7 kg of water, ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄・4H ₂ A solution of 4.450Kg of O4 dissolved in 5% by weight ammonia water 8.5% and a solution of 2.328Kg of bismuth nitrate dissolved in 10% by weight nitric acid aqueous solution 2.7% were added, and the pH of the slurry was adjusted to 4.2 using 67% by weight nitric acid. did. Next, a solution of 15.4 g of phosphotungstic acid P ₂ O ₅ 24Wo ₃ 41.85H ₂ O dissolved in 1 part of water and a solution of 13.8 g of potassium carbonate K ₂ CO ₃ dissolved in 500 ml of water were added to the slurry. The mixture was charged into a three-necked flask and heated under reflux at 100°C for 3 hours. Slurry is heated through heat treatment.
The pH increased from 4.2 to 5.0, so it was adjusted to 4.2 again, and then homogenized using a homogenizer, and spray-dried using a conventional method using a spray device with a rotating disk. The obtained microparticles are placed in a rotary firing furnace,
Continuous firing was performed at a temperature of 685°C and a residence time of 14 minutes to obtain a catalyst with an average particle size of 50μ. The composition of the _catalyst thus obtained _was Mo _{11.2 W 0.8} Bi _{2.1 Pb 8.4} Sb _{1.07 K 0} .
₀₃ P _0.03 O _49.28 , and _the ratio of silica as _a carrier to catalyst component was 40:60 (weight ratio). 1850 g of this catalyst was charged into the same reactor as in Example 8, and the reaction was carried out under the same reaction conditions as in Example 8. The results are shown in Table 4.

【table】

【table】

Claims (1)

[Claims] 1 Compositional formula (Mo)a(W)b(Bi)c(Pb)d(Sb)e
(Fe)f(Cr)g(O)h (a, b, c, d, e, f, g, h are respectively molybdenum, tungsten, bismuth,
Indicates the number of atoms of lead, antimony, iron, chromium, and oxygen, and when a+b=12, 0<b≦7, 0.4
≦c≦7, 2≦d≦12, 0.1/22≦e/a≦25/
22, 0≦f/a≦3/22, 0<g/a≦3/22, and h indicates the number of atoms necessary to satisfy the valence of each component. ) A catalyst composition for producing acrylonitrile from propylene, ammonia and oxygen or an oxygen-containing gas.