Catalyst for propylene ammoxidation reaction as well as preparation method and application thereof

Abstract

The invention provides a catalyst for propylene ammoxidation reaction and a preparation method and application thereof, and the preparation method comprises the following steps: uniformly mixing a metal salt solution with a first silicon source and alkaline silica sol, and then mixing with a second silicon source to obtain slurry; and carrying out spray drying and roasting on the slurry to obtain the catalyst for propylene ammoxidation reaction, wherein the first silicon source comprises one or more of acidic silica sol, tetraethoxysilane and potassium silicate, and the second silicon source is a solid silicon source. According to the preparation method disclosed by the invention, the acid-base property of the catalyst can be adjusted by introducing the liquid first silicon source, the composition of the catalyst is further regulated and controlled, and the selectivity of byproducts CO and CO2 in the propylene ammoxidation reaction is reduced; in addition, the solid second silicon source is added to provide a core for drying and forming of the catalyst, distribution of catalyst particles is more concentrated, the mechanical strength of the catalyst is enhanced, and the use stability of the catalyst and the conversion rate and selectivity of a catalytic reaction are improved.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a catalyst for propylene ammoxidation reaction and a preparation method and application thereof. Background Art

[0002] Acrylonitrile (AN) is an important chemical raw material and polymerization monomer, which is widely used in the production of acrylic fiber, acrylonitrile-butadiene-styrene copolymer, styrene-acrylonitrile copolymer, nitrile rubber, nylon, etc. In addition, polyacrylamide used as an oil recovery surfactant and polyacrylonitrile fiber used to produce carbon fiber are also synthesized from acrylonitrile. In recent years, the global demand for acrylonitrile has increased year by year, and the production process of large-scale acrylonitrile has also been continuously developed and improved.

[0003] The industrial production of AN has a history of more than 80 years, and has adopted the cyanoethanol method, acetylene-hydrocyanic acid method, acetaldehyde-hydrocyanic acid method, etc. With the rapid development of production technology, the current production processes of AN mainly include propylene ammoxidation method, propane ammoxidation method and biomass method. In 1959, Sohio Company (now owned by BP Company) developed a propylene ammoxidation process for producing AN using propylene, liquid ammonia and oxygen in the air as raw materials. In 1960, industrial production was achieved. At present, AN devices around the world basically use propylene ammoxidation method. The propylene ammoxidation method uses a fluidized bed reactor, which has the advantages of cheap and easy raw materials, simple process, low product cost and stable quality. The main by-products are hydrocyanic acid, acetonitrile, ammonium sulfate, etc. The technical core of the propylene ammoxidation reaction to produce acrylonitrile lies in the catalyst. Especially in industrial production, the catalytic performance of the catalyst and its durability in the process have become factors that need to be focused on. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention discloses a catalyst for propylene ammoxidation reaction and a preparation method and application thereof. Compared with traditional catalysts, the prepared catalyst can provide more acid sites, a higher specific surface area, and better wear resistance. The catalyzed propylene ammoxidation reaction has high raw material conversion rate and product selectivity.

[0005] In order to achieve the above technical objectives, on the one hand, the present invention provides a method for preparing a catalyst for propylene ammoxidation reaction, wherein a metal salt solution is uniformly mixed with a first silicon source and an alkaline silica sol, and then mixed with a second silicon source to obtain a slurry; the slurry is spray-dried and calcined to obtain the catalyst for propylene ammoxidation reaction; wherein the first silicon source includes one or more of acidic silica sol, tetraethyl orthosilicate and potassium silicate, and the second silicon source is a solid silicon source.

[0006] In the above technical solution, three different types of silicon sources are used to prepare the catalyst for propylene ammoxidation reaction, wherein the alkaline silica sol is the structural agent of the acrylonitrile catalyst, providing the catalyst with a catalytic reaction area; the first silicon source is a liquid silicon source including one or more of acidic silica sol, tetraethyl orthosilicate and potassium silicate. By using the liquid first silicon source to partially replace the structural agent of the traditional acrylonitrile catalyst, the acidic position and specific surface area of ​​the prepared catalyst can be increased, and the pore morphology can be adjusted, which can reduce the selectivity of byproducts CO and CO2, and can also load more active components by changing the effective specific surface area; further, in the above technical solution, after the metal salt solution, the first silicon source and the alkaline noble solvent are evenly mixed, the solid silicon is introduced. Source, during the granulation process, the slurry will adhere to the solid silicon source particles as the core and further dry into balls, so that the catalyst particle size distribution is more concentrated, and at the same time, the wear resistance of the catalyst is improved, and the overall specific surface area of ​​the catalyst is increased, thereby accelerating the external diffusion of materials on the catalyst surface during the catalytic reaction and reducing the side reaction of excessive oxidation; the above technical scheme gradually adds the first silicon source, alkaline silica sol and the second silicon source as the catalyst silicon source during the catalyst preparation process, so that the wear resistance coefficient of the prepared catalyst product can be maintained within a moderate range, which is beneficial to the catalyst not being easy to break or the catalytic performance being lost in the process of catalyzing the preparation of acrylonitrile with propylene, ammonia and air as raw materials, and the catalytic reaction maintains a high conversion rate and acrylonitrile selectivity.

[0007] It should be noted that the present invention does not limit the specific operation sequence for uniformly mixing the metal salt solution with the first silicon source and the alkaline silica sol. Those skilled in the art can, through non-creative labor, choose to uniformly mix the metal salt solution with the first silicon source first and then mix it with the alkaline silica sol, or can choose to uniformly mix the metal salt solution with the alkaline silica sol first and then mix it with the first silicon source, or can mix the metal salt solution with the first silicon source and the alkaline silica sol simultaneously, and the technical solutions thus formed are all within the protection scope of the present invention.

[0008] In a further example of the present invention, the amount of the first silicon source, the alkaline silica sol, and the second silicon source is explored and optimized. Optionally, in terms of silicon element, the mass ratio of the first silicon source, the alkaline silica sol, and the second silicon source is (2-8.4): (41.4-54): (2.25-11.2); based on a large amount of experimental data, the present invention further prefers the mass ratio of the first silicon source, the alkaline silica sol, and the second silicon source to be (2-5.6): (41.4-54): (4.5-8.4).

[0009] The type of the first silicon source in the above technical solution is not limited. In a further example of the present invention, the first silicon source is optimized. Optionally, the pH value of the acidic silica sol is 2-4, and the mass content of silicon dioxide is 30%-40%. Optionally, the colloidal particle size of the acidic silica sol is 50%-100% of the colloidal particle size of the alkaline silicon sol, so that more specific surface area can be obtained by adding acidic silica sol with finer particle size, further promoting the loading of more active components, thereby improving the catalytic performance of the catalyst. Optionally, the mass concentration of the tetraethyl orthosilicate (in terms of silicon dioxide) is greater than 25% to increase the specific surface area and active centers of the catalyst and improve the loading capacity of the carrier.

[0010] The above technical solution does not limit the type of the second silicon source. In a further example of the present invention, the second silicon source is optimized. Optionally, the second silicon source includes at least one of diatomaceous earth and fumed silica. Further optionally, when the second silicon source is diatomaceous earth, the input amount of the diatomaceous earth accounts for 4-20% of the mass of silicon dioxide in the catalyst, preferably 8-15%; further optionally, when the second silicon source is fumed silica, the input amount of the fumed silica accounts for 4-8% of the mass of silicon dioxide in the catalyst, calculated as silicon dioxide. Furthermore, the specific surface area of ​​the diatomaceous earth is 40-46m 2 / g; further, the particle size of the fumed silica is 2-5 μm. The optimization of the second silicon source can adjust the wear resistance index of the prepared catalyst to a suitable range and improve the catalytic performance of the catalyst.

[0011] The above technical solution does not limit the content of carrier silica in the prepared catalyst. In a further example of the present invention, the content of carrier silica in the catalyst is optimized. The catalyst prepared by the present invention includes an active component and carrier silica, the active component includes a composite metal oxide, and optionally, the mass of silica in the catalyst accounts for 45%-56% of the mass of the catalyst, that is, the mass of the active component accounts for 44%-55%, and the catalyst activity and stability of the catalyst are improved by optimizing the active component and the carrier.

[0012] The control conditions of the spray drying and calcining operations in the above technical scheme are not limited. In a further example of the present invention, the temperature of the calcining operation is optimized. Optionally, the temperature of the calcining operation is 550-630°C, preferably 570-610°C, so that organic and inorganic impurities on the surface of the catalyst can be removed, more catalytic active centers can be formed, and the activity and selectivity of the catalyst can be improved. It should be noted that the present invention does not limit the equipment and facilities of the calcining operation. It can be selected to be calcined in a rotary kiln. Those skilled in the art can select suitable calcining equipment through non-creative labor, and the technical solutions formed thereby are all within the scope of protection of the present invention. It should be noted that the granulation method of the catalyst of the present invention is not limited, and spray granulation is preferred to effectively ensure that the particle size of the catalyst is uniform; further, the present invention is also not limited to the equipment and facilities of spray granulation and drying, and can be selected to be dried and formed in a spray granulation tower, a spray dryer, or a centrifugal spray dryer. Those skilled in the art can select suitable calcining equipment through non-creative labor, and the technical solutions formed thereby are all within the scope of protection of the present invention.

[0013] On the other hand, the present invention provides a catalyst for propylene ammoxidation reaction prepared by the above preparation method.

[0014] Furthermore, the composition of the active components in the catalyst is optimized. Optionally, the active component of the catalyst is a composite metal oxide, and the stoichiometric composition of the composite metal oxide is Mo 30 Bi b Ni c Fe d Mg e B f C g O x , wherein B includes one or more of aluminum, lithium, sodium, and potassium, and C includes one or more of lanthanum, cerium, praseodymium, scandium, and yttrium; b, c, d, e, f, g, and x represent the molar ratios of the corresponding elements. Further optionally, in the stoichiometric composition of the catalyst, b is in the range of 2-2.2, c is in the range of 10-12, d is in the range of 2.5-3, e is in the range of 1.5-1.9, f is in the range of 0.25-0.4, g is in the range of 0.8-1.5, and x is a value that satisfies the charge balance of the catalyst.

[0015] It should be noted that the present invention does not limit the preparation process of the salt solution, and the salt solution of molybdenum and the salt solutions of other metals other than molybdenum can be prepared separately; further, the salt solution of molybdenum can be obtained by dissolving molybdic acid, potassium molybdate, sodium molybdate or ammonium molybdate in water; further, it can be an aqueous solution of ammonium molybdate; further, the present invention does not limit the types of salts of other metal elements, and can be soluble salts, such as nitrates, chlorides, sulfates, etc., and can be further selected as nitrates of other metal elements. Those skilled in the art can set it according to actual conditions.

[0016] Furthermore, the particle size of the catalyst is 40-80 μm; further, the specific surface area of ​​the catalyst is 36-40 m 2 / g. The above technical solution can not only make the catalyst particle size distribution more concentrated by adding the second solid silicon source, but also increase the specific surface area of ​​the catalyst as a whole, accelerate the external diffusion of materials on the catalyst surface during the catalytic reaction, and reduce the side reaction of excessive oxidation.

[0017] On the other hand, the present invention provides a method for synthesizing acrylonitrile, wherein in the presence of the above catalyst, propylene, ammonia and air are used as raw materials to undergo propylene ammoxidation reaction to obtain acrylonitrile.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the preparation method of the catalyst for propylene ammoxidation reaction of the present invention adopts a liquid first silicon source, alkaline silica sol and a solid second silicon source, which can increase the effective specific surface area of ​​the prepared catalyst to load more effective components and improve the catalytic performance; the introduction of the liquid first silicon source can adjust the acidity and alkalinity of the catalyst, further better regulate the product composition, and reduce the selectivity of by-products CO and CO2 in the propylene ammoxidation reaction; in addition, the addition of the solid second silicon source provides a core for the catalyst drying and molding, so that the distribution of catalyst particles is more concentrated, fine powder and coarse powder are reduced, the mechanical strength of the catalyst is enhanced, the stability of the catalyst is improved, and the catalyst is easy to load and use, thereby improving the conversion rate and selectivity of the catalytic reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 The particle size distribution of the catalysts prepared in Example 1, Example 2 and Comparative Example 3 is shown. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, i.e., not intended to limit the scope of protection of the present invention.

[0022] It should be noted that the wear index in the embodiments of the present invention is measured using the equipment and detection method specified in NB / SH / T0964-2017 Straight Tube Method for Determination of Wear Index of Catalytic Cracking Catalysts; a Quantachrome brand physical adsorption instrument is used to detect the specific surface area of ​​the prepared catalyst; and a laser particle size analyzer is used to detect the particle size distribution of the prepared catalyst.

[0023] Example 1

[0024] A method for preparing a catalyst for propylene ammoxidation reaction, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 45.9% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 30.5g of cerium nitrate, 182g of iron nitrate, and 100g of chlorine nitrate. g, 91.5 g of magnesium nitrate, and 7.7 g of potassium nitrate; then, add 30% acidic silica sol into the second metal salt solution and mix evenly to obtain a second precursor, wherein the mass of the acidic silica sol in terms of silicon dioxide accounts for 5.6% of the mass of the finished catalyst; the first precursor and the second precursor are evenly mixed, and diatomaceous earth is added to obtain a solution in the form of a suspension, and the beating is continued at 80°C for 4h, and the slurry is evenly mixed to obtain the slurry, wherein the mass of the diatomaceous earth in terms of silicon dioxide accounts for 4.5% of the mass of the finished catalyst.

[0025] The slurry enters a spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to a calcination furnace and calcined at 590°C for 2 hours to finally obtain 1152g of a finished catalyst product. The particle size D[0.5] / um of the finished catalyst product is 59.3μm, and the specific surface area is about 38.5m 2 / g, the wear index is 0.424%, and the particle size distribution of the finished catalyst is as follows Figure 1 .

[0026] Example 2

[0027] A method for preparing a catalyst for propylene ammoxidation reaction, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 42% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 30.5g of cerium nitrate, 182g of iron nitrate, nitric acid 91.5 g of magnesium and 7.7 g of potassium nitrate; then, add 30% acidic silica sol into the second metal salt solution and mix evenly to obtain a second precursor, wherein the mass of the acidic silica sol in terms of silicon dioxide accounts for 5.6% of the mass of the finished catalyst; the first precursor and the second precursor are evenly mixed, and then fumed silica is added to obtain a solution in the form of a suspension, and the slurry is continuously beaten at 80°C for 4 hours, and the slurry is evenly mixed to obtain the slurry, wherein the mass of the fumed silica in terms of silicon dioxide accounts for 8.4% of the mass of the finished catalyst.

[0028] The slurry enters a spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to a calcination furnace and calcined at 590°C for 2 hours to finally obtain 1152g of a finished catalyst. The particle size D[0.5] / um of the finished catalyst is 59.5μm, and the specific surface area is about 39.7m 2 / g, the wear index is 0.411%, and the particle size distribution of the finished catalyst is as follows Figure 1 .

[0029] Example 3

[0030] A method for preparing a catalyst for propylene ammoxidation reaction, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 42% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 71.9g of bismuth nitrate, 672.12g of nickel nitrate, 30.5g of cerium nitrate, 218.4g of iron nitrate, 9 1.5g, potassium nitrate 7.7g; then, add 28% of tetraethyl orthosilicate to the second metal salt solution and mix evenly to obtain a second precursor, wherein the mass of the 28% tetraethyl orthosilicate calculated as silicon dioxide accounts for 5.6% of the mass of the finished catalyst; the first precursor and the second precursor are evenly mixed, and then fumed silica is added to obtain a solution in the form of a suspension, and the slurry is continuously beaten at 80°C for 4h, and the slurry is evenly mixed to obtain the slurry, wherein the mass of the fumed silica calculated as silicon dioxide accounts for 8.4% of the mass of the finished catalyst.

[0031] The slurry enters a spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to a calcination furnace and calcined at 590°C for 2 hours to finally obtain 1222g of a finished catalyst product. The particle size D[0.5] / um of the finished catalyst product is 59.6μm, and the specific surface area is about 39.3m 2 / g, and the wear index is 0.435%.

[0032] Example 4

[0033] A method for preparing a catalyst for propylene ammoxidation reaction, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 42% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 57.18g of cerium nitrate, and 182g of iron nitrate. , 115.9g of magnesium nitrate, 12.3g of potassium nitrate; then, the potassium silicate solution is added to the second metal salt solution and mixed evenly to obtain a second precursor, wherein the mass of the potassium silicate solution calculated as silicon dioxide accounts for 5.6% of the mass of the finished catalyst; the first precursor and the second precursor are mixed evenly, and then fumed silica is added to obtain a solution in the form of a suspension, and the slurry is continuously beaten at 80°C for 4h, and the slurry is evenly mixed to obtain the slurry, wherein the mass of the fumed silica calculated as silicon dioxide accounts for 8.4% of the mass of the finished catalyst.

[0034] The slurry enters a spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to a calcination furnace and calcined at 590°C for 2 hours to finally obtain 1179g of a finished catalyst product. The particle size D[0.5] / um of the finished catalyst product is 59.3μm, and the specific surface area is about 39.5m 2 / g, and the wear index is 0.440%.

[0035] Example 5

[0036] A method for preparing a catalyst for propylene ammoxidation reaction. The conditions in the catalyst preparation method of this embodiment are the same as those in Example 1, except that the dried and formed catalyst particles are transferred to a calcining furnace and calcined at 570° C. for 2 h to finally obtain 1155 g of a finished catalyst; the particle size D[0.5] / um of the finished catalyst is 59.2 μm, and the specific surface area is about 40.2 m 2 / g, and the wear index is 0.465%.

[0037] Example 6

[0038] A method for preparing a catalyst for propylene ammoxidation reaction. The conditions in the catalyst preparation method of this embodiment are the same as those in Example 1, except that the dried and formed catalyst particles are transferred to a calcining furnace and calcined at 610° C. for 2 h to finally obtain 1150 g of a finished catalyst; the particle size D[0.5] / um of the finished catalyst is 58.9 μm, and the specific surface area is about 36.3 m 2 / g, and the wear index is 0.383%.

[0039] Comparative Example 1

[0040] A method for preparing a catalyst, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 50.4% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 30.5g of cerium nitrate, 182g of ferric nitrate, 91.5g of magnesium nitrate, and 7.7g of potassium nitrate; then adding 30% of acidic silica sol to the second metal salt solution and mixing evenly to obtain a second precursor, wherein the mass of the acidic silica sol in terms of silicon dioxide accounts for 5.6% of the mass of the finished catalyst; the first precursor and the second precursor are evenly mixed, slurried at 80°C for 4h, and evenly mixed to obtain the slurry.

[0041] The slurry enters a spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to a calcination furnace and calcined at 590°C for 2h to finally obtain 1150g of a finished catalyst. The particle size D[0.5] / um of the finished catalyst is 57.8μm, and the specific surface area is about 36.4m 2 / g, and the wear index is 0.432%.

[0042] Comparative Example 2

[0043] A method for preparing a catalyst, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 41.4% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 30.5g of cerium nitrate, 182g of iron nitrate, 91.5g of magnesium nitrate, and 7.7g of potassium nitrate; the first precursor and the second metal salt solution are evenly mixed, diatomaceous earth is added to obtain a suspension solution, pulping is carried out at 80°C for 4h, and the slurry is evenly mixed to obtain the slurry, wherein the mass of the diatomaceous earth in terms of silicon dioxide is 3.6% of the mass of the finished catalyst.

[0044] The slurry enters the spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to the calcination furnace and calcined at 590°C for 2h to finally obtain 1163g of the finished catalyst product. The particle size D[0.5] / um of the finished catalyst product is 60.3μm, and the specific surface area is about 35.8m 2 / g, and the wear index is 0.785%.

[0045] Comparative Example 3

[0046] A method for preparing a catalyst, specifically, using desalted water to dissolve 530g of ammonium molybdate to obtain a first metal salt solution, the first metal salt solution is mixed with alkaline silica sol to obtain a first precursor, wherein the mass of silicon dioxide in the alkaline silica sol is 56% of the mass of the finished catalyst; using desalted water to dissolve other salts except molybdenum salt to obtain a second metal salt solution, the second metal salt solution includes 59.9g of bismuth nitrate, 560.1g of nickel nitrate, 30.5g of cerium nitrate, 182g of iron nitrate, 91.5g of magnesium nitrate, and 7.7g of potassium nitrate; the first precursor and the second metal salt solution are evenly mixed, pulped at 80°C for 4h, and evenly mixed to obtain the slurry.

[0047] The slurry enters the spray granulation tower for drying to obtain shaped catalyst particles. The inlet temperature of the granulation tower is 300°C and the outlet temperature is above 110°C. The dried shaped catalyst particles are transferred to the calcination furnace and calcined at 590°C for 2h to finally obtain 1160g of the finished catalyst product. The particle size D[0.5] / um of the finished catalyst product is 66.4μm, and the specific surface area is about 35.9m 2 / g, the wear index is 0.418%; the particle size distribution of the finished catalyst is as follows Figure 1 , larger particles appeared in the catalyst prepared in Comparative Example 3.

[0048] Depend on Figure 1It can be confirmed that the particle size distribution of the catalyst prepared by the present invention is more concentrated. By comparing the wear index of the catalyst, it can be confirmed that the wear index of the catalyst prepared by the present invention for propylene ammoxidation reaction is within a reasonable range, which can avoid the catalyst being broken during the catalytic process due to an excessively large wear index, which not only affects the catalyst effect but also may block the pipeline of the subsequent process, and can also avoid the loss of catalytic activity due to an excessively small wear index, and further avoid the enrichment of such catalyst in the reactor to affect the catalyst effect.

[0049] Test Case

[0050] In the test examples of the present invention, the catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were used to carry out propylene ammoxidation reaction with propylene, ammonia and air as raw materials to prepare acrylonitrile.

[0051] A method for synthesizing acrylonitrile, specifically, sieving catalyst agglomerates larger than 80 mesh, catalyzing propylene ammoxidation reaction in a DN50 fixed fluidized bed device, the reaction temperature is 440°C, the space velocity is 0.08h -1 , the molar ratio of propylene, ammonia and air is 1:1.2:10.3; after the reaction is completed, stop feeding the raw gas and purge the reactor; use chromatography to detect the content of each product online. Among them, propylene conversion rate = 100% - (propylene concentration in the gas at the rear end of the reactor × gas flow rate at the rear end of the reactor) / propylene feed amount, acrylonitrile selectivity = (acrylonitrile concentration in the gas at the rear end of the reactor × gas flow rate at the rear end of the reactor) / (propylene feed amount × propylene conversion rate), the selectivity calculation method of acetonitrile, hydrocyanic acid, acrolein, acrylic acid, CO2, CO is the same as the acrylonitrile selectivity calculation method.

[0052] The catalysts used in the specific test examples, the conversion rates of raw materials, and the product yields are shown in Table 1.

[0053] Table 1

[0054]

[0055] It should be noted that the above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions; the dimensional data of this embodiment does not necessarily limit the technical solution, but only shows one of the specific working conditions. For ordinary technicians in the technical field to which the present invention belongs, several simple improvements and modifications can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for propylene ammoxidation reaction, characterized in that: The metal salt solution is mixed evenly with the first silicon source and alkaline silica sol, and then mixed with the second silicon source to obtain a slurry; the slurry is dried and calcined to obtain the catalyst for propylene ammoxidation reaction; wherein the first silicon source includes one or more of acidic silica sol, tetraethyl orthosilicate and potassium silicate, and the second silicon source is a solid silicon source.

2. The method for preparing a catalyst for propylene ammoxidation according to claim 1, characterized in that: Calculated in terms of silicon element, the mass ratio of the first silicon source, the alkaline silica sol, and the second silicon source is (2-8.4): (41.4-54): (2.25-11.2); preferably (2-5.6): (41.4-54): (4.5-8.4).

3. The method for preparing a catalyst for propylene ammoxidation according to claim 1, characterized in that: The pH value of the acidic silica sol is 2-4, and the mass content of silicon dioxide is 30%-40%; Preferably, the colloidal particle size of the acidic silica sol is 50%-100% of the colloidal particle size of the alkaline silica sol.

4. The method for preparing a catalyst for propylene ammoxidation according to claim 1, characterized in that: The second silicon source includes at least one of diatomaceous earth and fumed silica; Preferably, when the second silicon source is diatomaceous earth, the input amount of the diatomaceous earth accounts for 4-20% of the mass of silicon dioxide in the catalyst, preferably 8-15%; when the second silicon source is fumed silica, the input amount of the fumed silica accounts for 4-8% of the mass of silicon dioxide in the catalyst, calculated as silicon dioxide; Preferably, the specific surface area of ​​the diatomaceous earth is 40-46m 2 / g; Preferably, the fumed silica particle size is 2-5 μm.

5. The method for preparing a catalyst for propylene ammoxidation according to claim 1, characterized in that: The mass of silicon dioxide in the catalyst accounts for 45%-56% of the mass of the catalyst.

6. The method for preparing a catalyst for propylene ammoxidation according to claim 1, characterized in that: The calcination temperature is 550-630°C, preferably 570-610°C.

7. A catalyst for propylene ammoxidation reaction prepared by the preparation method according to any one of claims 1 to 6.

8. The catalyst for propylene ammoxidation according to claim 7, characterized in that: The active component of the catalyst is a composite metal oxide, and the stoichiometric composition of the composite metal oxide is Mo 30 Bi b Ni c Fe d Mg e B f C g O x , wherein B includes one or more of aluminum, lithium, sodium, and potassium, and C includes one or more of lanthanum, cerium, praseodymium, scandium, and yttrium; b, c, d, e, f, g, and x represent the molar ratios of the corresponding elements respectively; Preferably, in the stoichiometric composition of the catalyst, b is in the range of 2-2.2, c is in the range of 10-12, d is in the range of 2.5-3, e is in the range of 1.5-1.9, f is in the range of 0.25-0.4, g is in the range of 0.8-1.5, and x is a value that satisfies the charge balance of the catalyst.

9. The catalyst for propylene ammoxidation according to claim 7, characterized in that: The particle size of the catalyst is 40-80 μm; And / or, the specific surface area of ​​the catalyst is 36-40m 2 / g; And / or, the loading amount of the catalyst active component is 44%-55%.

10. A method for synthesizing acrylonitrile, characterized in that: In the presence of the catalyst for propylene ammoxidation reaction according to any one of claims 7 to 9, propylene ammoxidation reaction is carried out with propylene, ammonia and air as raw materials to obtain acrylonitrile.

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