Propylene ammoxidation catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of industrial catalysts, in particular to a propylene ammoxidation catalyst and a preparation method and application thereof. The propylene ammoxidation catalyst comprises a carrier and active components, wherein the active components comprise Mo, Bi, at least one alkaline earth metal element, at least one alkali metal element and at least one group VIII metal element in the fourth period; in a hydrogen temperature programmed reduction H2-TPR test, the catalyst starts to have a reduction peak in a range of 350-390 DEG C; the reduction rate is 4 * 10 <-4 > a.u. / DEG C to 8 * 10 <-4 > a.u. / DEG C within the range of 420 DEG C to 450 DEG C. The propylene ammoxidation catalyst has a low reduction temperature and a fast reduction rate in hydrogen temperature programmed reduction H2-TPR characterization, and has good reaction activity and long-term stability when being used for preparing acrylonitrile through propylene ammoxidation.

Description

Technical Field

[0001] This invention relates to the field of industrial catalysts, specifically to a propylene ammoxidation catalyst, its preparation method, and its application. Background Technology

[0002] Acrylonitrile is an important organic chemical raw material, serving as a raw material for the production of chemicals such as acrylic fiber, ABS resin, polyacrylonitrile, and carbon fiber, with a wide range of applications and promising prospects. After decades of development, the mainstream production method for acrylonitrile currently involves the reaction of propylene, ammonia, and air in a fluidized bed reactor under the action of catalyst particles made from active metals such as molybdenum, bismuth, and iron, and supported by silica. Studies have shown that the uniform dispersion of active metals into small particles within the catalyst is beneficial for improving catalyst activity and long-term operational stability. In practical industrial applications, the active components of the catalyst often undergo sintering and agglomeration due to prolonged high-temperature operation, resulting in decreased activity and hindering the normal operation of the reaction unit. Therefore, addressing the issue of particle size and uniform distribution of active components in propylene ammoxidation catalysts is a crucial research direction for maintaining the activity and stability of acrylonitrile catalysts.

[0003] CN107398288A discloses an acrylonitrile catalyst, using silica, alumina, montmorillonite, and other support modifiers as composite supports, containing a general formula A. a B b La c Fe d Bi e Mo 13.6 O x The active component is a metal oxide, which effectively solves the problems of low catalyst selectivity and poor stability, and can be used in the industrial production of acrylonitrile by ammoxidation of propylene.

[0004] CN109772356A discloses an acrylonitrile catalyst, its preparation method, and its application. The catalyst comprises a silica support and a substrate having the general formula Bi. a Fe b Ni c Mg d Ce e A f B g C h Mo 12 O x The active component is a metal oxide, wherein B is selected from one or more elements in the group consisting of praseodymium, europium, terbium, and dysprosium. By adding ammonia water stabilizer to the silica sol carrier, the prepared acrylonitrile catalyst can not only meet the high catalyst load requirements of industrial expansion units, but also reduce the generation of carbonyl compounds acrolein and acrylic acid, thereby improving the unit's operating cycle.

[0005] CN112584929A discloses a method for manufacturing a catalyst for ammonia oxidation and a method for manufacturing acrylonitrile, wherein the catalyst comprises the general formula Mo. 12 Bi a Fe b X c Y d Z e O f A composite metal oxide is formed, wherein Y represents one or more elements selected from cerium, chromium, lanthanum, neodymium, yttrium, praseodymium, samarium, aluminum, gallium, and indium. The solid phase of the catalyst precursor slurry contains an aggregate containing a metal and a support. The primary metal particles constituting the aggregate have a particle size of less than 1 μm and an average particle size of more than 40 nm and less than 200 nm. A catalyst for ammonia oxidation with high acrylonitrile yield is prepared by controlling the size of the solid phase particles in the slurry.

[0006] Although the above technical solutions have improved the catalytic activity of the propylene ammoxidation catalyst to acrylonitrile to some extent, they have not yet solved the problem of uneven dispersion of active components in the support, and there is still room for improvement in the long-term operational stability of the catalyst. Therefore, it is urgent to develop a propylene ammoxidation catalyst with good activity and stability. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of large particle size and poor dispersibility of active metal components in existing propylene ammoxidation catalysts, which agglomerate into lumps. This invention provides a propylene ammoxidation catalyst, its preparation method, and its applications. In the hydrogen-programmed temperature reduction (H2-TPR) characterization, this propylene ammoxidation catalyst exhibits a low reduction temperature and a fast reduction rate, indicating that the active component particles are small and uniformly composited with the support, resulting in good dispersibility. This catalyst demonstrates good reactivity and long-term stability in the ammoxidation of propylene to acrylonitrile.

[0008] To achieve the above objectives, the first aspect of the present invention provides a propylene ammoxidation catalyst, the catalyst comprising a support and an active component, the active component comprising Mo, Bi, at least one alkaline earth metal element, at least one alkali metal element, and at least one group VIII metal element of period 4.

[0009] In the hydrogen-programmed temperature reduction (H2-TPR) test, the catalyst began to show a reduction peak in the range of 350℃-390℃; the reduction rate was 4×10⁻⁶ in the range of 420℃-450℃. -4 au / ℃-8×10 -4 au / ℃.

[0010] Preferably, the general formula of the active component is: Mo12 Bi a A b B c C d O x ,in,

[0011] A is a metal element of Group VIII in the fourth period, preferably selected from at least two of Fe, Co and Ni;

[0012] B is an alkaline earth metal element, preferably selected from at least one of Mg, Ca and Sr;

[0013] C is an alkali metal element, preferably selected from at least one of K, Cs and Rb;

[0014] a, b, c, d, and x represent the number of atoms of each element;

[0015] The value of a ranges from 0.05 to 8;

[0016] The value of b ranges from 0.05 to 12;

[0017] The value of c ranges from 0.05 to 8;

[0018] The value of d ranges from 0.02 to 2;

[0019] x represents the number of oxygen atoms required to satisfy the valence of other elements.

[0020] A second aspect of the present invention provides a method for preparing the propylene ammoxidation catalyst described in the first aspect, comprising the following steps:

[0021] (1) The solution II containing the precursor of Mo element is mixed with the first part of the carrier precursor to obtain the first mixed solution;

[0022] (2) The first mixed solution is mixed with solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and the remaining carrier precursor to obtain slurry.

[0023] (3) The slurry is dried and calcined to obtain a propylene ammoxidation catalyst.

[0024] The third aspect of the present invention provides the application of the propylene ammoxidation catalyst described in the first aspect above or the propylene ammoxidation catalyst prepared by the method described in the second aspect above in the production of acrylonitrile by the propylene ammoxidation reaction.

[0025] Through the above technical solution, the present invention has the following beneficial effects:

[0026] (1) The propylene ammoxidation catalyst provided by the present invention contains a silica support and specific active components. The acrylonitrile catalyst has a lower reduction temperature and a faster reduction rate in the hydrogen programmed temperature reduction (H2-TPR) characterization, indicating that the active components in the propylene ammoxidation catalyst have small particles and are uniformly compounded with the support, and have good dispersibility. The catalyst has good reactivity and long-term stability when used in the ammoxidation of propylene to acrylonitrile.

[0027] (2) The method for preparing propylene ammoxidation catalyst provided by the present invention involves adding a support precursor to the active metal precursor in steps, so that the precipitation reaction during the slurry formation process is carried out in a relatively mild manner. The slurry will not form large particles due to rapid co-precipitation caused by acid-base reaction, resulting in uneven composite of active components and support. This makes the active component particles in the propylene ammoxidation catalyst smaller and more uniformly distributed. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0029] Figure 1 This is a graph showing the H2-TPR test data of the propylene ammoxidation catalyst prepared in Example 1 of this invention;

[0030] Figure 2 This is a graph showing the H2-TPR test data of the propylene ammoxidation catalyst prepared in Comparative Example 1 of this invention. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] The first aspect of the present invention provides a propylene ammoxidation catalyst, the catalyst comprising a support and an active component, the active component comprising Mo, Bi, at least one alkaline earth metal element, at least one alkali metal element, and at least one group VIII metal element of period IV;

[0033] In the hydrogen-programmed temperature reduction (H2-TPR) test, the catalyst began to show a reduction peak in the range of 350℃-390℃; the reduction rate was 4×10⁻⁶ in the range of 420℃-450℃. -4 au / ℃-8×10 -4au / ℃.

[0034] In this invention, the propylene ammoxidation catalyst contains a silica support and specific active components. The acrylonitrile catalyst exhibits a low reduction temperature and a fast reduction rate in hydrogen temperature programmed reduction (H2-TPR) characterization, indicating that the active components have small particle size and are uniformly composited with the support, resulting in good dispersibility. The catalyst has good reactivity and long-term stability when used in the ammoxidation of propylene to acrylonitrile.

[0035] In this invention, hydrogen temperature-programmed reduction (H2-TPR) technology was used to characterize the catalyst's reduction activity using an Anton Pacanta Chem BET Pulsar instrument with TPR functionality. This instrument features a specially designed quartz sample chamber and uses thermocouples located in the sample bed to precisely measure the sample temperature. Different heating rates are achieved through integrated intelligent PID control. A TCD detector located downstream of the sample monitors changes in the concentration of reactant gases in the inert carrier stream. Proprietary acquisition software provides online collection and data processing. A cold trap is used to collect any vapors generated during the reaction. Approximately 1 gram of sample was added to the quartz sample chamber for the experiment, and the sample was heated from room temperature (25°C) to 800°C using three different heating rates.

[0036] In some embodiments of the present invention, preferably, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst begins to show a reduction peak in the range of 350°C to 390°C. For example, it can be 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, or any value within the range of the two aforementioned values. More preferably, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst begins to show a reduction peak in the range of 360°C to 380°C. In the present invention, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst begins to be reduced within the above temperature range, and the H2 reduction TCD signal begins to significantly increase.

[0037] In some embodiments of the present invention, preferably, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst has a reduction rate of 4 × 10⁻⁶ in the range of 420°C to 450°C. -4 au / ℃-8×10 -4 au / ℃, for example, can be 4×10 -4 au / ℃, 4.5×10 -4 au / ℃, 5×10 -4 au / ℃, 5.5×10 -4 au / ℃, 6×10 -4 au / ℃, 6.5×10-4 au / ℃, 7×10 -4 au / ℃, 7.5×10 -4 au / ℃, 8×10 -4 au / ℃, and any value within the range of the two values ​​above, more preferably, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst has a reduction rate of 5 × 10⁻⁶ ℃ in the range of 420℃-450℃. -4 au / ℃-6×10 -4 au / ℃.

[0038] In this invention, during the hydrogen temperature-programmed reduction (H2-TPR) test, the reduction rate of the catalyst = (TCD signal) / (TCD signal). 450 -TCD signal 420 ) / 30℃, unit au / ℃, where TCD signal 450 and TCD signal 420 These are the TCD signal intensities at 450℃ and 420℃ in the H2-TPR spectrum, respectively, in au.

[0039] In this invention, the acrylonitrile catalyst exhibits a low reduction temperature in the hydrogen temperature-programmed reduction (H2-TPR) characterization and a fast reduction rate in the industrial propylene ammoxidation to acrylonitrile reaction temperature range of 420℃-450℃. This indicates that the active component has small particle size and is uniformly composited with the support, resulting in good dispersibility. Furthermore, the propylene ammoxidation catalyst exhibits higher reactivity due to the presence of uniformly dispersed small-particle active components.

[0040] In some embodiments of the present invention, preferably, the general formula of the active component is: Mo 12 Bi a A b B c C d O x ,in,

[0041] A is a metal element of Group VIII in the fourth period, preferably selected from at least two of Fe, Co and Ni;

[0042] B is an alkaline earth metal element, preferably selected from at least one of Mg, Ca and Sr;

[0043] C is an alkali metal element, preferably selected from at least one of K, Cs and Rb;

[0044] a, b, c, d, and x represent the number of atoms of each element;

[0045] The value of a ranges from 0.05 to 8, preferably from 0.1 to 4, and more preferably from 1 to 3;

[0046] The value of b ranges from 0.05 to 12, preferably from 0.1 to 8, and more preferably from 2 to 7;

[0047] The value of c ranges from 0.05 to 8, preferably from 0.1 to 4, and more preferably from 0.5 to 3;

[0048] The value of d ranges from 0.02 to 2, preferably from 0.05 to 1;

[0049] x represents the number of oxygen atoms required to satisfy the valence of other elements.

[0050] In this invention, by introducing Mo, Bi, alkaline earth metals, alkali metals, and Group VIII metals from the fourth period as essential components, the synergistic effect between elements is fully utilized through a reasonable combination, which is beneficial to improving the stability and catalytic activity of the propylene ammoxidation catalyst. Among them, Mo and Bi are the main active phases of the catalyst, which play a role in adsorbing and activating propylene and ammonia during the propylene ammoxidation process; the Group VIII metals from the fourth period are mainly metal components with variable valence states, which are promoters of lattice oxygen migration and catalyst redox; alkali metals and alkaline earth metals mainly play the roles of structural and electronic aids, as well as acid-base regulation.

[0051] In some embodiments of the present invention, preferably, based on the total amount of the propylene ammoxidation catalyst, the content of the support is 35-65 wt%, more preferably 45-55 wt%; and the content of the active component is 35-65 wt%, more preferably 45-55 wt%.

[0052] In this invention, controlling the content of the support and active components in the propylene ammoxidation catalyst within the above-mentioned range is beneficial to improving the activity and stability of the catalyst, ensuring high selectivity of the catalyst for acrylonitrile, and extending the service life of the catalyst.

[0053] In this invention, the type of support is not particularly limited and can be any support commonly used in the art for propylene ammoxidation catalysts. Preferably, the support is selected from at least one of silica, alumina, and titanium dioxide, and more preferably silica.

[0054] A second aspect of the present invention provides a method for preparing the propylene ammoxidation catalyst described in the first aspect, comprising the following steps:

[0055] (1) The solution II containing the precursor of Mo element is mixed with the first part of the carrier precursor to obtain the first mixed solution;

[0056] (2) The first mixed solution is mixed with solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and the remaining carrier precursor to obtain slurry.

[0057] (3) The slurry is dried and calcined to obtain a propylene ammoxidation catalyst.

[0058] The present invention also provides a method for preparing a propylene ammoxidation catalyst, comprising the following steps:

[0059] (1) The solution II containing the precursor of Mo element is mixed with the first part of the carrier precursor to obtain the first mixed solution;

[0060] (2) The first mixed solution is mixed with solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and the remaining carrier precursor to obtain slurry.

[0061] (3) The slurry is dried and calcined to obtain a propylene ammoxidation catalyst.

[0062] In the preferred embodiment, the amounts and types of each metal component, and the amounts and types of the carrier, are selected as described in the first aspect above, and will not be repeated here. The further limitations on the method described below also apply to this scheme.

[0063] In this invention, the inventors discovered that the crucial determining step for the size of the active metal component in the propylene ammoxidation catalyst and the uniformity of its composite with the support lies in the slurry formation step. During this process, the active metal component precursor undergoes hydrolysis and precipitation to form amorphous small particles, which then composite with the support precursor. The active metal component precursor and the support precursor solution undergo rapid hydrolysis and precipitation reactions. Therefore, effectively controlling this process can prevent the formation of large precipitated particles, thereby maintaining a small size of the active metal component in the final propylene ammoxidation catalyst and ensuring its uniform distribution with the support. To address this, the inventors employ a stepwise method of adding the support precursor to the active metal component precursor, allowing the precipitation reaction to proceed more gently during slurry formation. This prevents the rapid co-precipitation of large particles due to acid-base reactions in the slurry, which could lead to uneven composite of the active component and the support. Consequently, the active component particles in the propylene ammoxidation catalyst are small and have good uniform distribution. This catalyst exhibits good reactivity and long-term stability when used in the ammoxidation of propylene to acrylonitrile.

[0064] In some embodiments of the present invention, preferably, the Mo element precursor, Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor are water-soluble salts corresponding to active metal elements.

[0065] In this invention, preferably, the water-soluble salt containing Mo is selected from at least one of water-soluble inorganic salts, water-soluble organic salts, and oxyacid ammonium salts containing Mo, preferably an oxyacid ammonium salt, and more preferably (NH4)6Mo7O. 24 Or its hydrate. In this invention, preferably, the water-soluble salt containing Bi, alkaline earth metal, alkali metal, and Group VIII metal of period four is preferably a water-soluble inorganic salt and / or a water-soluble organic salt of the corresponding active metal element. More preferably, the water-soluble salt containing Bi, alkaline earth metal, alkali metal, and Group VIII metal of period four is independently selected from at least one of nitrate, acetate, halide, and alkoxide of the corresponding active metal element, preferably a nitrate.

[0066] In this invention, the conditions for dissolving the active metal in solution I and solution II are not particularly limited, as long as the corresponding active metal can be fully dissolved to obtain solution I and solution II. In this invention, the type of solvent in solution I is not particularly limited; for example, it can be water and / or a C1-C6 monohydric alcohol, preferably water. The types of solvents in solution I and solution II can be the same or different; preferably, the types of solvents in solution I and solution II are the same. In this invention, the amount of solvent used is not particularly limited, as long as it can achieve the dissolution of the active metal precursor and facilitate slurry stirring; those skilled in the art can conventionally select the appropriate amount.

[0067] In this invention, the type of carrier precursor is not particularly limited and can be any carrier precursor conventionally used in the art. Preferably, the carrier precursor is selected from at least one of silica sol, fumed silica, and silicon-based molecular sieves, and is preferably silica sol. In this invention, the silica sol has a solid content of 25-40 wt% based on silica.

[0068] In this invention, the method and conditions for the first mixing in step (1) are not particularly limited, as long as it is ensured that the first portion of the carrier precursor is mixed evenly with the solution II. Preferably, the Mo element precursor in the solution II is immediately mixed with the first portion of the carrier precursor after dissolution to obtain the first mixed solution.

[0069] In this invention, the solution II containing the Mo element precursor and the carrier precursor are generally alkaline, while the other active metal element precursor solutions are strongly acidic. Therefore, acid-base reactions are likely to occur during the mixing process to form a slurry, forming colloidal or micro-particle precipitates. By using the method described above to mix solution II with the first part of the carrier precursor, the resulting first mixed solution is uniform and free of precipitates.

[0070] In some embodiments of the present invention, preferably, in step (2), the method includes: S1, adding a solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and a second portion of carrier precursor to the first mixed solution for a second mixing to obtain a second mixed solution; S2, adding a third portion of carrier precursor to the second mixed solution for a third mixing to obtain the slurry.

[0071] In this invention, adding a support precursor to the active metal precursor solution through the steps described above is more conducive to promoting the uniform distribution of active metal elements on the support, and more conducive to the precipitation reaction during the slurry formation process to proceed more gently. The slurry will not rapidly form large particles due to acid-base reaction co-precipitation, which would lead to uneven composite of active components and support, resulting in smaller active component particles and better uniform distribution in the final catalyst.

[0072] In this invention, preferably, the method in step S1 includes: 1) adding a solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor to the first mixed solution for mixing; 2) adding a second portion of carrier precursor to the mixed solution obtained in step 1) for a second mixing to obtain a second mixed solution.

[0073] In this invention, the method and conditions for mixing the first mixed solution with the solution I containing the Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor, and Group VIII metal element precursor of period four are not particularly limited, as long as the first mixed solution and the solution I are mixed uniformly. Preferably, the active metal element precursor in the solution I is dissolved and then immediately mixed with the first mixed solution. The method and conditions for the second mixing in this invention are not particularly limited. Preferably, the second portion of the carrier precursor is added immediately after mixing with the solution I for the second mixing.

[0074] In this invention, the method described above is used to mix the first mixed solution, solution I, and the second part of the carrier precursor to avoid rapid precipitation or agglomeration due to excessively high local acid or alkaline concentrations, resulting in unevenly distributed large particles. This yields a mixed slurry with uniformly dispersed active components, which is beneficial for improving the uniformity and activity of the propylene ammonia oxidation catalyst.

[0075] In this invention, the method and conditions for the third mixing are not particularly limited, as long as it is ensured that the third portion of the carrier precursor is mixed evenly with the second mixed solution. Preferably, the third portion of the carrier precursor is mixed with the second mixed solution 5-10 minutes after the second portion of the carrier precursor is added.

[0076] In this invention, controlling the time interval between adding the third part of the carrier precursor and adding the second part of the carrier precursor within the above-mentioned range is more conducive to slowing down the reaction rate, allowing the active metal elements more time to be evenly distributed on the carrier, and also helps to improve the stability and service life of the catalyst.

[0077] In this invention, unless otherwise specified, the sum of the masses of the second and third portions of the carrier precursor is the mass of the remaining portion of the carrier precursor. That is, based on the total amount of the carrier precursor, the sum of the content of the first portion of the carrier precursor and the content of the remaining portion of the carrier precursor is 100 wt%. In this invention, the amounts of the first, second, and third portions of the carrier precursor have a wide range of selection. Preferably, based on the total amount of the carrier precursor, the content of the first portion of the carrier precursor is 40-60 wt%, for example, it can be 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or any value within the range of the above two values, preferably 45-55 wt%; the content of the second portion of the carrier precursor is 20-40 wt%, for example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or any value within the range of the above two values, preferably 25-35 wt%; the content of the third portion of the carrier precursor is 10-30 wt%, for example, it can be 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any value within the range of the above two values, preferably 15-25 wt%.

[0078] In this invention, controlling the amounts of the first, second, and third portion of the support precursor within the aforementioned range helps ensure a uniform distribution of the active metal elements on the support, thereby improving the catalytic performance of the catalyst. Even better results are achieved within the preferred range.

[0079] In some embodiments of the present invention, preferably, the method in step (2) further includes boiling the product obtained by mixing. The conditions for boiling the product are not particularly limited and can be conventional boiling conditions in the art. Preferably, the boiling conditions include: a mixing temperature of 100-160°C, preferably 120-150°C, under stirring conditions; and a mixing time of 10-40 min, preferably 20-30 min.

[0080] In this invention, the stirring method and conditions are not particularly limited, and conventional stirring methods and conditions used in the art can be adopted. Preferably, the stirring speed is 150-250 r / min.

[0081] In this invention, the stepwise addition of the carrier precursor is beneficial for the active metal elements and the carrier to come into more complete contact during the slurry boiling process, and for the co-precipitation reaction to occur more gently, resulting in a slurry with uniform dispersion of active components and less agglomeration, thereby giving the acrylonitrile catalyst better uniformity, dispersibility and stability.

[0082] In this invention, preferably, in step (3), the slurry is dried to obtain powder. The drying process is preferably spray drying. The spray drying method and conditions are not particularly limited, and conventional spray drying methods and conditions used in the art can be employed. Preferably, the spray drying conditions include: a spray drying temperature of 320-480℃, preferably 350-400℃, under an air atmosphere; a spray drying time of 0.2-4h, preferably 0.5-1.5h; and an average droplet diameter of 30-130μm, preferably 30-120μm.

[0083] In this invention, preferably, in step (3), the dried powder is calcined. The calcination method and conditions are not particularly limited, and conventional calcination methods and conditions used in the art can be employed. Preferably, the calcination conditions include: a calcination temperature of 400-800℃, preferably 450-640℃, under an oxygen-containing atmosphere; and a calcination time of 3-8 hours, preferably 4-6 hours.

[0084] The third aspect of the present invention provides the application of the propylene ammoxidation catalyst described in the first aspect above or the propylene ammoxidation catalyst prepared by the method described in the second aspect above in the production of acrylonitrile by the propylene ammoxidation reaction.

[0085] The propylene ammoxidation catalyst provided by this invention contains a silica support and specific active components. The active components have small particle sizes and are uniformly compounded with the support, exhibiting good dispersibility. In H2-TPR characterization, it shows a low reduction temperature and a fast reduction rate. When used in the ammoxidation of propylene to acrylonitrile, this catalyst exhibits good reactivity and long-term stability.

[0086] In some embodiments of the present invention, preferably, the method for the propylene ammoxidation reaction comprises: propylene reacting with ammonia and oxygen in the presence of the propylene ammoxidation catalyst to produce acrylonitrile. In the present invention, the oxygen can be provided by any oxygen-containing gas, preferably air. The volume content of oxygen in the air is not less than 10%.

[0087] In this invention, the molar ratio of propylene, ammonia, and oxygen has a wide range of possible choices. Preferably, the molar ratio of propylene, ammonia, and oxygen is 1:1-1.5:9-11, and more preferably 1:1.1-1.3:9.5-10.

[0088] In this invention, the conditions for the ammonia oxidation reaction are not particularly limited, and conventional ammonia oxidation conditions used in the art can be adopted. Preferably, the conditions for the ammonia oxidation reaction include: a reaction temperature of 420-440℃, a reaction pressure of 0.06-0.12 MPa, and a catalyst loading of 0.08-0.12 h⁻¹. -1 In this invention, the reaction pressure refers to gauge pressure.

[0089] The present invention will be described in detail below through embodiments.

[0090] In the following examples and comparative examples, the reduction activity of the catalyst was characterized using hydrogen temperature-programmed reduction (H2-TPR) technology. The specific testing methods are the same as those described in the specific implementation methods, and will not be repeated here.

[0091] In the following examples and comparative examples, gas chromatography was used to analyze the composition of the gaseous products.

[0092] Propylene conversion rate (%) = (moles of propylene reacted / moles of propylene fed) × 100%

[0093] Acrylonitrile selectivity (%) = (moles of acrylonitrile produced / moles of propylene reacted) × 100% Acrylonitrile single-pass yield (%) = (moles of acrylonitrile produced / moles of propylene fed) × 100%

[0094] Example 1

[0095] (1) Take 416.8g of (NH4)6Mo7O 24• Dissolve 4H2O in 800mL of hot water to obtain solution II. Then, immediately add 640g of silica sol with a mass fraction of 40% to solution II and stir to mix evenly to obtain the first mixed solution.

[0096] (2) Add solution I obtained by heating 114.5g of Bi(NO3)3·5H2O, 228.8g of Ni(NO3)2·6H2O, 158.9g of Fe(NO3)3·9H2O, 60.5g of Mg(NO3)2·6H2O and 7.7g of CsNO3 until dissolved and fully mixed to the first mixed solution, stir and mix evenly, and then immediately add 380g of silica sol with a mass fraction of 40% and mix for 8 minutes to obtain the second mixed solution;

[0097] (3) Immediately add 230g of silica sol with a mass fraction of 40% to the second mixed solution and mix to obtain a third mixed solution. Heat the third mixed solution at a temperature of 150℃ and a rotation speed of 200r / min for 20min to form a slurry.

[0098] (4) The slurry is spray-dried at 350°C for 1 hour to obtain powder particles. The powder particles are then calcined in air at 640°C for 4 hours to obtain a propylene ammoxidation catalyst.

[0099] In this embodiment, the propylene ammoxidation catalyst contains 50 wt% silica support and 50 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs 0.2 O 46.1 .

[0100] Figure 1 This is a graph showing the H2-TPR test data of the propylene ammoxidation catalyst described in this embodiment. Figure 1 It can be seen that a reduction peak appears at 367.5℃, and the reduction rate is 5.84 × 10⁻⁶ between 420℃ and 450℃ (the reaction temperature for the ammoxidation of propylene to acrylonitrile in industrial production). -4 au / ℃.

[0101] Example 2

[0102] (1) Take 461.2g of (NH4)6Mo7O 24• Dissolve 4H2O in 800mL of hot water to obtain solution II. Then, immediately add 576g of silica sol with a mass fraction of 40% to solution II and stir to mix evenly to obtain the first mixed solution.

[0103] (2) 126.7g of Bi(NO3)3·5H2O, 227.9g of Ni(NO3)2·6H2O, 193.5g of Fe(NO3)3·9H2O, 12.7g of Co(NO3)2·6H2O, 67.0g of Mg(NO3)2·6H2O and 5.5g of KNO3 were heated until dissolved and fully mixed. The resulting solution I was added to the first mixed solution and stirred until homogeneous. Then, 342g of silica sol with a mass fraction of 40% was immediately added and mixed. The mixture was stirred for 8 minutes to obtain the second mixed solution.

[0104] (3) Immediately add 207g of silica sol with a mass fraction of 40% to the second mixed solution and mix to obtain a third mixed solution. Heat the third mixed solution at a temperature of 150℃ and a rotation speed of 200r / min for 20min to form a slurry.

[0105] (4) The slurry is spray-dried at 350°C for 1 hour to obtain powder particles. The powder particles are then calcined in air at 640°C for 4 hours to obtain a propylene ammoxidation catalyst.

[0106] In this embodiment, the propylene ammoxidation catalyst contains 45 wt% silica support and 55 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.2 Ni 3.6 Co 0.2 Mg 1.2 K 0.25 O 46.2 .

[0107] According to the hydrogen-programmed temperature reduction (H2-TPR) test, the propylene ammoxidation catalyst described in this example showed a reduction peak at 372.3℃, and the reduction rate in the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 5.62 × 10⁻⁶. -4 au / ℃.

[0108] Example 3

[0109] (1) Take 431.2g of (NH4)6Mo7O 24• Dissolve 4H2O in 800mL of hot water to obtain solution II. Then, immediately add 640g of silica sol with a mass fraction of 40% to solution II and stir to mix evenly to obtain the first mixed solution.

[0110] (2) 118.5g of Bi(NO3)3·5H2O, 148.0g of Ni(NO3)2·6H2O, 205.6g of Fe(NO3)3·9H2O, 38.5g of Ca(NO3)2·4H2O and 6.0g of RbNO3 were heated until dissolved and fully mixed to obtain solution I, which was added to the first mixed solution. The mixture was stirred and mixed evenly. Then, 380g of silica sol with a mass fraction of 40% was immediately added and mixed. The mixture was stirred for 8 minutes to obtain the second mixed solution.

[0111] (3) Immediately add 230g of silica sol with a mass fraction of 40% to the second mixed solution and mix to obtain a third mixed solution. Heat the third mixed solution at a temperature of 150℃ and a rotation speed of 200r / min for 20min to form a slurry.

[0112] (4) The slurry is spray-dried at 350°C for 1 hour to obtain powder particles. The powder particles are then calcined in air at 640°C for 4 hours to obtain a propylene ammoxidation catalyst.

[0113] In this embodiment, the propylene ammoxidation catalyst contains 50 wt% silica support and 50 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.5 Ni 2.5 Ca 0.8 Rb 0.2 O 50 .

[0114] According to the hydrogen-programmed temperature reduction (H2-TPR) test, the propylene ammoxidation catalyst described in this example showed a reduction peak at 374.0℃, and the reduction rate was 5.75 × 10⁻⁶ °C between 420℃ and 450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile). -4 au / ℃.

[0115] Example 4

[0116] The method is the same as in Example 1, except that...

[0117] In step (1), (NH4)6Mo7O 24 The amount of 4H2O used was 385.1g;

[0118] In step (2), the amount of Bi(NO3)3·5H2O is 105.8g, the amount of Ni(NO3)2·6H2O is 264.3g, the amount of Fe(NO3)3·9H2O is 293.7g, Mg(NO3)2·6H2O is replaced by Ca(NO3)2·4H2O and the amount is 34.3g, and CsNO3 is replaced by NaNO3 and the amount is 3.1g.

[0119] In this embodiment, the propylene ammoxidation catalyst contains 50 wt% silica support and 50 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 4.0 Ni 5.0 Ca 0.8 Na 0.2 O 49.7 .

[0120] According to the hydrogen-programmed temperature reduction (H2-TPR) test, the propylene ammoxidation catalyst described in this example showed a reduction peak at 383.2℃, and the reduction rate in the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 4.78 × 10⁻⁶. -4 au / ℃.

[0121] Example 5

[0122] The method is the same as in Example 1, except that...

[0123] In step (1), the amount of silica sol with a mass fraction of 40% is 427g;

[0124] In step (2), the amount of silica sol with a mass fraction of 40% is 253g;

[0125] In step (3), the amount of silica sol with a mass fraction of 40% is 153g.

[0126] In this embodiment, the propylene ammoxidation catalyst contains 40 wt% silica support and 60 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs 0.2 O 46.1 .

[0127] According to the hydrogen-programmed temperature reduction (H2-TPR) test, the propylene ammoxidation catalyst described in this example began to show a reduction peak at 385.5℃, and the reduction rate in the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 4.31 × 10⁻⁶. -4 au / ℃.

[0128] Example 6

[0129] The method is the same as in Example 1, except that...

[0130] In step (1), the amount of silica sol with a mass fraction of 40% is 530g;

[0131] In step (2), the amount of silica sol with a mass fraction of 40% is 450g;

[0132] In step (3), the amount of silica sol with a mass fraction of 40% is 270g.

[0133] In this embodiment, the propylene ammoxidation catalyst contains 50 wt% silica support and 50 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs 0.2 O 46.1 .

[0134] According to the hydrogen-programmed temperature reduction (H2-TPR) test, the propylene ammoxidation catalyst described in this example began to show a reduction peak at 358.0℃, and the reduction rate in the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 6.23 × 10⁻⁶. -4 au / ℃.

[0135] Example 7

[0136] The method is the same as in Example 1, except that...

[0137] In step (2), the amount of silica sol with a mass fraction of 40% is 610g; the resulting second mixed solution is heated at 150°C for 20min to form a slurry; step (3) is not performed.

[0138] In this embodiment, the propylene ammoxidation catalyst contains 50 wt% silica support and 50 wt% active component, the general formula of which is Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs0.2 O 46.1 .

[0139] Hydrogen-programmed temperature reduction (H2-TPR) tests showed that the propylene ammoxidation catalyst described in this comparative example exhibited a reduction peak at 385.2℃, and the reduction rate within the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 4.37 × 10⁻⁶. -4 au / ℃.

[0140] Comparative Example 1

[0141] (1) Take 416.8g of (NH4)6Mo7O 24 • 4H2O was dissolved in 800mL of hot water (80℃) to obtain solution II. 1250g of silica sol with a mass fraction of 40% was weighed and added to solution II. The mixture was stirred and mixed evenly immediately. Then, 114.5g of Bi(NO3)3·5H2O, 228.8g of Ni(NO3)2·6H2O, 158.9g of Fe(NO3)3·9H2O, 60.5g of Mg(NO3)2·6H2O and 7.7g of CsNO3 were heated at 80℃ until dissolved and fully mixed to obtain solution I. The resulting mixed solution was heated at 150℃ and 200r / min for 20min to form a slurry.

[0142] (2) The slurry is spray-dried at 350°C for 1 hour to obtain powder particles. The powder particles are then calcined in air at 640°C for 4 hours to obtain a propylene ammoxidation catalyst.

[0143] The propylene ammoxidation catalyst prepared in this comparative example contained 50 wt% silica support and 50 wt% active component, the general formula of which was Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs 0.2 O 46.1 .

[0144] Figure 2 This is a graph showing the H2-TPR test data of the propylene ammoxidation catalyst described in this comparative example. Figure 2 It can be seen that a reduction peak appears at 393.0℃, and the reduction rate is 3.72 × 10⁻⁶ between 420℃ and 450℃ (the reaction temperature for the ammoxidation of propylene to acrylonitrile in industrial production). -4 au / ℃.

[0145] Comparative Example 2

[0146] The method described in Example 1 is different,

[0147] In step (1), (NH4)6Mo7O 24 The amount of 4H2O used is 323g;

[0148] In step (2), the amount of Bi(NO3)3·5H2O used is 1.5g, the amount of Ni(NO3)2·6H2O used is 354.7g, the amount of Fe(NO3)3·9H2O used is 369.6g, the amount of Mg(NO3)2·6H2O used is 156.4g, and the amount of CsNO3 used is 65.4g.

[0149] The propylene ammoxidation catalyst prepared in this comparative example contained 50 wt% silica support and 50 wt% active component, the general formula of which was Mo. 12 Bi 0.02 Fe 6.0 Ni 8.0 Mg 4.0 Cs 2.2 O 58.1 .

[0150] Hydrogen-programmed temperature reduction (H2-TPR) tests showed that the propylene ammoxidation catalyst described in this comparative example exhibited a reduction peak at 412.3℃, and the reduction rate within the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 2.30 × 10⁻⁶. -4 au / ℃.

[0151] Comparative Example 3

[0152] The method described in Example 1 is different,

[0153] In step (1), the amount of silica sol with a mass fraction of 40% is 875g;

[0154] In step (2), the amount of silica sol with a mass fraction of 40% is 225g;

[0155] In step (3), the amount of silica sol with a mass fraction of 40% is 150g;

[0156] The propylene ammoxidation catalyst prepared in this comparative example contained 50 wt% silica support and 50 wt% active component, the general formula of which was Mo. 12 Bi 1.2 Fe 2.0 Ni 4.0 Mg 1.2 Cs 0.2 O 46.1 .

[0157] Hydrogen-programmed temperature reduction (H2-TPR) tests showed that the propylene ammoxidation catalyst described in this comparative example exhibited a reduction peak at 395.6℃, and the reduction rate within the range of 420℃-450℃ (the industrial reaction temperature for the ammoxidation of propylene to acrylonitrile) was 3.06 × 10⁻⁶. -4 au / ℃.

[0158] Test case

[0159] The propylene ammoxidation catalysts prepared in the examples and comparative examples were subjected to ammoxidation in a fluidized bed reactor with an inner diameter of 38 mm to obtain acrylonitrile. The conditions for the ammoxidation reaction included: a reaction temperature of 420 °C, a reaction pressure of 0.085 MPa, and a catalyst propylene loading (WWH) of 0.12 h⁻¹. -1 Raw material ratio (molar): C3 ＝ / NH3 / air (as oxygen) = 1 / 1.26 / 9.6. Samples were taken and analyzed after 3 hours and 500 hours of operation. The results of propylene conversion, propylene selectivity, and acrylonitrile single-pass yield are shown in Table 1.

[0160] Table 1

[0161]

[0162] As can be seen from the results in Table 1, the propylene ammoxidation catalyst prepared by the method provided in this invention exhibits high propylene conversion, propylene selectivity, and acrylonitrile single-pass yield in the ammoxidation of propylene to acrylonitrile, indicating that the propylene ammoxidation catalyst has good reactivity. Furthermore, the propylene conversion, propylene selectivity, and acrylonitrile single-pass yield of the propylene ammoxidation catalyst after 500 hours of operation decreased by 0.12%, 0.25%, and 0.35%, respectively, compared to those after 3 hours of operation (taking Example 1 as an example), and the decrease was not significant, indicating that the propylene ammoxidation catalyst has good long-term stability.

[0163] Based on Example 1, Comparative Examples 1-3 and Table 1, it can be seen that, compared with Example 1, Comparative Example 1 uses a one-step addition of the support precursor, the content of the active component in Comparative Example 2 is not within the range limited by the present invention, and the proportion of the support added in Comparative Example 3 is not within the range limited by the present invention, resulting in a significant reduction in the reaction activity and long-term stability of the prepared propylene ammoxidation catalyst.

[0164] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A propylene ammoxidation catalyst, characterized in that, The catalyst includes a support and an active component, wherein the active component includes Mo, Bi, at least one alkaline earth metal element, at least one alkali metal element, and at least one group VIII metal element of period 4. In the hydrogen-programmed temperature reduction (H2-TPR) test, the catalyst began to show a reduction peak in the range of 350℃-390℃; the reduction rate was 4×10⁻⁶ in the range of 420℃-450℃. -4 au / ℃-8×10 -4 au / ℃.

2. The propylene ammoxidation catalyst according to claim 1, wherein, In the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst began to show a reduction peak in the range of 360℃-380℃; And / or, in the hydrogen temperature-programmed reduction (H2-TPR) test, the catalyst exhibits a reduction rate of 5 × 10⁻⁶ in the range of 420 °C–450 °C. -4 au / ℃-6×10 -4 au / ℃.

3. The propylene ammoxidation catalyst according to claim 1 or 2, wherein, The general formula of the active component is: Mo 12 Bi a A b B c C d O x ,in, A is a metal element of Group VIII in the fourth period, preferably selected from at least two of Fe, Co and Ni; B is an alkaline earth metal element, preferably selected from at least one of Mg, Ca and Sr; C is an alkali metal element, preferably selected from at least one of K, Cs and Rb; a, b, c, d, and x represent the number of atoms of each element; The value of a ranges from 0.05 to 8, preferably from 0.1 to 4; The value of b ranges from 0.05 to 12, and is preferably from 0.1 to 8; The value of c ranges from 0.05 to 8, and is preferably from 0.1 to 4; The value of d ranges from 0.02 to 2, preferably from 0.05 to 1; x represents the number of oxygen atoms required to satisfy the valence of other elements.

4. The propylene ammoxidation catalyst according to any one of claims 1-3, wherein, Based on the total amount of the propylene ammoxidation catalyst, the content of the support is 35-65 wt%, preferably 45-55 wt%; the content of the active component is 35-65 wt%, preferably 45-55 wt%.

5. The propylene ammoxidation catalyst according to any one of claims 1-4, wherein, The carrier is selected from at least one of silicon dioxide, aluminum oxide and titanium oxide, preferably silicon dioxide.

6. A method for preparing the propylene ammoxidation catalyst according to any one of claims 1-5, wherein, Includes the following steps: (1) The solution II containing the precursor of Mo element is mixed with the first part of the carrier precursor to obtain the first mixed solution; (2) The first mixed solution is mixed with solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and the remaining carrier precursor to obtain slurry. (3) The slurry is dried and calcined to obtain a propylene ammoxidation catalyst.

7. The method according to claim 6, wherein, The precursors of Mo, Bi, alkaline earth metals, alkali metals, and group VIII metals in the fourth period are water-soluble salts corresponding to active metal elements. Preferably, the water-soluble salt containing Mo is an oxyacid ammonium salt containing Mo; the water-soluble salts containing Bi, alkaline earth metals, alkali metals and Group VIII metals of the fourth period are each independently selected from at least one of the nitrates, acetates, halides and alkoxides of the corresponding active metal elements, preferably nitrates; Preferably, the carrier precursor is selected from at least one of silica sol, fumed silica and silicon-based molecular sieves, and more preferably silica sol.

8. The method according to claim 6 or 7, wherein, In step (2), the method includes: S1, adding a solution I containing Bi element precursor, alkaline earth metal element precursor, alkali metal element precursor and fourth period group VIII metal element precursor and a second part of carrier precursor to the first mixed solution for a second mixing to obtain a second mixed solution; S2, adding a third part of carrier precursor to the second mixed solution for a third mixing to obtain the slurry; Preferably, based on the total amount of the carrier precursor, the content of the first portion of the carrier precursor is 40-60 wt%, preferably 45-55 wt%; the content of the second portion of the carrier precursor is 20-40 wt%, preferably 25-35 wt%; and the content of the third portion of the carrier precursor is 10-30 wt%, preferably 15-25 wt%. Preferably, the method in step (2) further includes boiling the product obtained by mixing, wherein the boiling conditions include: under stirring conditions, the mixing temperature is 100-160℃, preferably 120-150℃; and the mixing time is 10-40 min, preferably 20-30 min. Preferably, the stirring speed is 150-250 r / min.

9. The method according to any one of claims 6-8, wherein, The drying process is spray drying, and the conditions for spray drying include: spray drying in an air atmosphere, a spray drying temperature of 300-450℃, preferably 350-400℃; a spray drying time of 0.2-4h, preferably 0.5-1.5h; and an average diameter of spray droplets of 30-130μm, preferably 30-120μm. Preferably, the calcination conditions include: a calcination temperature of 400-800℃, preferably 450-640℃, under an oxygen-containing atmosphere; and a calcination time of 3-8h, preferably 4-6h.

10. The application of a propylene ammoxidation catalyst according to any one of claims 1-5 or a propylene ammoxidation catalyst prepared by the method according to any one of claims 6-9 in the production of acrylonitrile by propylene ammoxidation reaction; Preferably, the method for the propylene ammoxidation reaction includes: In the presence of the propylene ammoxidation catalyst, propylene undergoes an ammoxidation reaction with ammonia and oxygen to produce acrylonitrile; Preferably, the molar ratio of propylene, ammonia and oxygen is 1:1-1.5:9-11, more preferably 1:1.1-1.3:9.5-10; Preferably, the conditions for the ammonia oxidation reaction include: a reaction temperature of 420-440℃, a reaction pressure of 0.06-0.12 MPa, and a catalyst loading of 0.08-0.12 h⁻¹. -1 .

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