CN116060030B

CN116060030B - Ammonia oxidation catalyst and its preparation method and application

Info

Publication number: CN116060030B
Application number: CN202111302120.3A
Authority: CN
Inventors: 李静霞; 吴粮华
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2025-07-04
Anticipated expiration: 2041-11-04
Also published as: CN116060030A

Abstract

本发明公开了一种氨氧化催化剂及其制备方法和应用。所述催化剂的活性组分包括钼和铋，载体包括二氧化硅，所述催化剂经热处理后平均孔径的变化符合Y＝(P2‑P1)/P1，其中，Y的取值小于等于4.5，P1和P2分别为催化剂在不同热处理条件下的平均孔径。该催化剂在丙烯氨氧化制丙烯腈的应用中表现出更好的长期稳定性。The present invention discloses an ammoxidation catalyst and a preparation method and application thereof. The active components of the catalyst include molybdenum and bismuth, the carrier includes silicon dioxide, and the change in the average pore size of the catalyst after heat treatment meets Y=(P2-P1)/P1, wherein the value of Y is less than or equal to 4.5, and P1 and P2 are respectively the average pore sizes of the catalyst under different heat treatment conditions. The catalyst exhibits better long-term stability in the application of propylene ammoxidation to prepare acrylonitrile.

Description

Ammonia oxidation catalyst, preparation method and application thereof

Technical Field

The invention relates to an ammoxidation catalyst, in particular to an acrylonitrile catalyst prepared by ammoxidation of propylene, a preparation method thereof and application thereof in the reaction of preparing acrylonitrile by ammoxidation of propylene.

Background

Acrylonitrile is an important chemical raw material for fiber, rubber, plastic and the like, and is mainly used for producing acrylic fiber, ABS plastic, styrene plastic, acrylamide and the like. The industrial acrylonitrile is produced mainly by using propylene as a raw material and using a fluidized bed ammoxidation method.

The technology for preparing acrylonitrile by ammoxidation of propylene has been successfully industrialized in acrylonitrile devices worldwide, but the catalyst for preparing acrylonitrile by ammoxidation of propylene is one of the core technologies of the technology, and research and development are continuously carried out so as to prepare the catalyst with more excellent comprehensive properties such as activity, selectivity and the like.

Currently, molybdenum-bismuth-iron based catalysts have been widely used industrially as relatively mature ammoxidation catalysts. The Mo-Bi catalyst may be prepared through spray drying process, including the steps of preparing metal precursor and carrier material into slurry, spray drying and roasting. For example, CN1600423a discloses a spray drying process to prepare ammoxidation catalysts.

However, in the conventional production process of acrylonitrile, there is a problem that the activity and/or selectivity of the catalyst for producing acrylonitrile by ammoxidation of propylene and the stability for long-term use are difficult to be compatible, and therefore, development of a mo—bi-based catalyst having both good activity and/or selectivity and stability for long-term use has been an object of diligent study in the art.

Disclosure of Invention

The inventors of the present invention have found through extensive studies that when an active component comprising Mo-Bi, including a carrier of silica, is used as a propylene ammoxidation catalyst, the catalyst can effectively exhibit a stable catalytic activity, particularly a stable once-through yield of acrylonitrile, during a long-period stable operation, when the average pore diameter thereof meets specific requirements as the temperature of a specific heat treatment increases. The inventors have further studied and found that, in preparing the above catalyst, a precursor having an alkali and a precursor having an acid are co-currently precipitated, so that the above catalyst can be prepared, probably because the uniform-sized crystal grains are obtained by controlling the co-current precipitation, thereby achieving the purpose of controlling the average pore diameter of the catalyst, and have completed the present invention on the basis thereof.

The invention provides an ammoxidation catalyst, a preparation method and application thereof. The catalyst has the characteristic of good long-term stability when being used for preparing acrylonitrile by propylene ammoxidation.

According to a first aspect of the present invention there is provided an ammoxidation catalyst comprising molybdenum and bismuth as active components and silica as a support, the catalyst having a change in average pore size following heat treatment which corresponds to formula (I):

Y=(P2-P1)/P1(I),

Wherein the value of Y is less than or equal to 4.5, P2 is the average pore diameter of the catalyst after heat treatment at the temperature T2 and in the water-containing atmosphere, P1 is the average pore diameter of the catalyst after heat treatment at the temperature T1 and in the water-containing atmosphere, T2 is more than T1, and T2 is less than or equal to 750 ℃.

In the catalyst of the present invention, Y is 4.5 or less, preferably 0.5 to 4.5. The value of Y may be, but is not limited to, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, etc., and more preferably 1.5 to 4.0.

In the catalyst of the present invention, the temperature T1 is 400 to 600 ℃, preferably 450 to 600 ℃, and the temperature T2 is 500 to 750 ℃, preferably 550 to 700 ℃. Further, the temperature T2 is at least 50 ℃ higher than the temperature T1.

In the catalyst of the invention, the heat treatment time is 0.5-4 h, preferably 0.5-2 h.

In the catalyst, the heat treatment is carried out under the atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein the water content of the mixed gas is 0.01-4.5%, the oxygen volume content is 10-30%, and the ratio of the gas mixture inlet amount per unit time to the mass of the catalyst is 50-500L/kg.h. The mixed gas containing water and oxygen also contains at least one of nitrogen or inert gas.

In the catalyst disclosed by the invention, the active components comprise molybdenum and bismuth, the weight content of the molybdenum is 15% -55%, preferably 20% -45% in terms of MoO ₃, and the weight content of the bismuth is 0.5% -3.5%, preferably 1.0% -3.5% in terms of Bi ₂O₃, based on the weight of the catalyst.

In the catalyst of the present invention, the atomic ratio of Bi/Mo is preferably 0.008 to 0.25, and more preferably 0.01 to 0.20. Among them, the atomic ratio of Bi/Mo is exemplified by, but not limited to, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, etc.

In the catalyst of the present invention, the active component may further include Fe, rare earth elements, alkali metal elements, alkaline earth metal elements, and metal element a. The rare earth element is at least one selected from La, ce, pr, nd, sm. The alkali metal element is at least one selected from Li, na, K, rb and Cs. The alkaline earth metal element is at least one selected from Be, mg, ca, sr and Ba. The metal element A is at least one selected from W, V, zr, P, nb, ni, co, cr, mn, tl, au, ag, pt, ru, rh, pd, ti, sb, in, sn, te, and more preferably, the metal element A is at least one selected from Co, mn, P, pd, nb.

In the catalyst, based on the weight of the catalyst, the weight content of molybdenum calculated by MoO ₃ is 15% -55%, preferably 20% -45%, the weight content of bismuth calculated by Bi ₂O₃ is 0.5% -3.5%, preferably 1.0% -3.5%, the weight content of Fe calculated by Fe ₂O₃ is 1% -12%, preferably 1.5% -11%, the weight content of rare earth element calculated by oxide of rare earth element is 1.5% -8.5%, preferably 2.5% -5.0%, the weight content of alkali metal element calculated by oxide is 0.01% -0.60%, preferably 0.05% -0.55%, the weight content of alkaline earth metal calculated by oxide is 0.01% -4.0%, preferably 0.5% -3.5%, and the weight content of metal element A calculated by oxide is 0.01% -15%, preferably 0.05% -14%.

In the catalyst of the present invention, preferably, the atomic ratio of Bi/Mo in the active component is 0.008 to 0.25, preferably 0.01 to 0.20, wherein the atomic ratio of Bi/Mo is exemplified by, but not limited to, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, etc.; the atomic ratio of Fe/Bi is 1.0 to 7.0, preferably 2.0 to 6.0, wherein the atomic ratio of Fe/Bi is not limited to 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, etc., the atomic ratio of rare earth element+alkali metal element+alkaline earth metal element)/Mo is 0.05 to 0.40, preferably 0.10 to 0.35, wherein the atomic ratio of (rare earth element+alkali metal element+alkaline earth metal element)/Mo is 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, etc., and the atomic ratio of A/Mo is 0.01 to 1.0, preferably 0.02 to 0.9.

In the catalyst of the invention, the carrier can also contain other components, and the other components can be at least one of zirconia, molecular sieve, cerium oxide, titanium oxide and calcium oxide. Based on the weight of the carrier, the content of SiO ₂ is 20% -100%, preferably 30% -100%, and the content of other components is below 20%, preferably 0% -15%.

In the catalyst, the weight of the catalyst is taken as a reference, the content of active components in terms of oxide is 20% -80%, and the content of carriers is 20% -80%.

In the catalyst of the present invention, the pore size distribution of the catalyst is such that the pore volume occupied by pores having a pore size of less than 5nm and more than 80nm is 10% or less, preferably 8% or less, and more preferably 7% or less of the total pore volume.

According to the invention, the catalyst is in the form of particles with an average particle size of 30 to 70. Mu.m, preferably 40 to 60. Mu.m.

The second aspect of the invention provides a preparation method of the catalyst, which comprises the following steps:

(1) The alkaline material containing molybdenum and the carrier precursor and the acidic material containing bismuth as the active component precursor are subjected to concurrent precipitation reaction to obtain slurry I;

(2) And (3) carrying out spray drying and heat treatment on the slurry I to obtain the catalyst.

In the method of the present invention, the carrier precursor in step (1) comprises silica sol. In the silica sol, the solid content is 20-50wt% based on the silica, and the average particle size is 10-35 nm.

In the method, in the alkaline material containing molybdenum and the carrier precursor in the step (1), the mass concentration of the material is controlled to be 20% -55%. Solvents which may be present in the alkaline material are, for example, alcohols and water, in particular C1-C6-monoalcohols (such as ethanol) and water, preferably water. These solvents may be used alone or in combination of plural kinds in an arbitrary ratio.

In the method, in the acid material of the bismuth-containing active component precursor in the step (1), the mass concentration of the material is controlled to be 20% -60%. Solvents which may be present in the acidic material are, for example, alcohols and water, in particular C1-C6-monoalcohols (such as ethanol) and water, preferably water. These solvents may be used alone or in combination of plural kinds in an arbitrary ratio.

In the method of the invention, the time of the parallel flow precipitation in the step (1) is 10-40 min, preferably 10-25 min. Further, after the materials are added, the materials are further stirred and mixed for 10-30 min, preferably 10-25 min.

In the method, the temperature of the parallel flow precipitation in the step (1) is controlled to be 20-60 ℃.

In the method of the invention, the acid material of the precursor of the active component containing bismuth in the step (1) also comprises precursors of Fe, rare earth elements, alkali metal elements, alkaline earth elements and metal elements A. The rare earth element is at least one selected from La, ce, pr, nd, sm. The alkali metal element is at least one selected from Li, na, K, rb and Cs. The alkaline earth metal element is at least one selected from Be, mg, ca, sr and Ba. The metal element A is at least one selected from W, V, zr, P, nb, ni, co, cr, mn, tl, au, ag, pt, ru, rh, pd, ti, sb, in, sn, te, preferably at least one selected from Co, mn, P, pd, nb. Further, the atomic ratio of Bi/Mo is 0.008 to 0.25, preferably 0.01 to 0.20, the atomic ratio of Fe/Bi is 1.0 to 7.0, preferably 2.0 to 6.0, the atomic ratio of (rare earth element+alkali metal element+alkaline earth metal element)/Mo is 0.05 to 0.40, preferably 0.10 to 0.35, and the atomic ratio of A/Mo is 0.01 to 1.0, preferably 0.02 to 0.9.

In the method of the present invention, in the step (1), the Mo element precursor is not particularly limited, and may be an oxide of Mo or any substance that can form the oxide after firing, and specifically, for example, an oxide, hydroxide, inorganic acid salt, organic acid salt and ammonium salt of an oxo acid (including hydrates of these compounds) of Mo, among which a water-soluble inorganic acid salt, a water-soluble organic acid salt and ammonium salt of an oxo acid are preferable, and an ammonium salt of an oxo acid of Mo is more preferable, such as (NH ₄)₆Mo₇O₂₄ or a hydrate thereof; the Bi element precursor, the rare earth element precursor, the alkali metal element precursor, the alkaline earth metal element precursor and the metal A element precursor are not particularly limited, the oxide of the corresponding element or any substance which can form the oxide after firing can be used, and specifically, for example, oxide, hydroxide, inorganic acid salt and organic acid salt of the corresponding element (including hydrate of these compounds) can be mentioned, preferably water-soluble inorganic acid salts and water-soluble organic acid salts, more preferably halides, alkoxides, nitrates and acetates, these precursors may be used alone or in combination of plural kinds in any ratio.

In the method, the spray drying condition in the step (2) comprises the drying heat source being air, the drying temperature being 250-350 ℃, preferably 300-350 ℃, the drying time being 0.1-2.0 h, preferably 0.2-1.0 h, and the average diameter of spray droplets being 20-200 mu m, preferably 40-180 mu m.

In the method of the invention, the heat treatment in the step (2) is high-temperature roasting treatment in an aqueous atmosphere. Preferably, the heat treatment is carried out under the conditions that the temperature is 500-750 ℃ and the time is 0.2-4 h. The heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein the water volume content of the mixed gas is 0.01% -4.5%, the oxygen volume content is 10% -30%, and the ratio of the gas mixture inlet amount per unit time to the mass of the catalyst is 50-500L/kg.h. The mixed gas containing water and oxygen also contains at least one of nitrogen or inert gas.

In a third aspect, the present invention provides a process for producing acrylonitrile by ammoxidation of propylene, comprising the step of subjecting propylene to ammoxidation reaction in the presence of the above-mentioned catalyst or the catalyst obtained by the above-mentioned production process to produce acrylonitrile.

In the method, the reaction conditions for preparing the acrylonitrile by ammoxidation of the propylene comprise the mol ratio of propylene/ammonia gas/air calculated by O ₂ of 1:1.1-1.35:1.8-2.5, the reaction temperature of 420-440 ℃, the reaction pressure calculated by gauge pressure of 0.03-0.14 MPa and the weight hourly space velocity of 0.04-0.10 h ^-1.

Compared with the prior art, the invention has the following beneficial effects:

1. the catalyst has good stability and can show stable catalytic activity in the long-period stable operation process.

2. When the catalyst is used for the reaction for preparing the acrylonitrile by ammoxidation of the propylene, the reduction amplitude of the yield of the acrylonitrile is obviously reduced along with the extension of the reaction time, and the single-pass yield of the acrylonitrile can be still kept high after long-period operation.

Detailed Description

The following detailed description of embodiments of the invention is provided, but it should be noted that the scope of the invention is not limited by these embodiments, but is defined by the appended claims.

In the invention, the measurement method of the average particle size adopts a Markov MS2000 laser particle sizer for measurement. Before testing the sample, the circulating water of the device needs to be opened. The refractive index of the catalyst was selected before the measurement of the sample, and the refractive index of SiO ₂ was 1.45 as the refractive index of the measurement sample. The background is measured before the sample is measured, the sample is added to 10% of the shading degree after the measurement, and the average value is selected after three measurements are carried out.

In the present invention, the "oxide" refers to the most stable oxide at normal temperature and pressure, such as Na oxide refers to Na ₂ O, ni oxide refers to NiO, and Fe oxide refers to Fe ₂O₃.

In the invention, the pore diameter of the catalyst is measured by using a Tristar2000 of America microphone instrument company to measure the average pore diameter (diameter) of N ₂ adsorption and desorption of the sample. The samples were first degassed at 250 ℃ under vacuum for 2 hours, after which the N ₂ adsorption-desorption curve of the samples was measured at liquid nitrogen temperature (-196 ℃) with the average pore size being obtained according to the BJH method.

Unless explicitly indicated, all percentages, parts, ratios, etc. mentioned in this specification are by weight unless otherwise clear to the routine knowledge of a person skilled in the art.

Fresh catalyst was used for the acrylonitrile-making reaction by ammoxidation of propylene, and propylene conversion, acrylonitrile selectivity and acrylonitrile single pass yield were calculated as evaluation catalyst performance indices. Wherein, the propylene conversion, the acrylonitrile selectivity and the acrylonitrile single pass yield are defined as follows:

Propylene conversion (%) = moles of propylene reacted/moles of propylene feed x 100%;

Acrylonitrile selectivity (%) = moles of acrylonitrile produced/moles of propylene reacted x 100%;

acrylonitrile single pass yield (%) = moles of acrylonitrile produced/moles of propylene feed x 100%.

[ Example 1]

836.6 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 684g of water, 2750 g of silica sol with 40% weight concentration is added at 50 ℃ to form slurry I, the mass concentration of the slurry I is 46.8%, 2.46 g of KOH and 175.9 g of Bi (NO ₃)₃·5H₂ O, 532.7 g of Ni (NO ₃)₂·6H₂ O, 78.1 g of Pr (NO ₃)₃·6H₂ O), 808.2 g of Fe (NO ₃)₃·9H₂ O, 139.5 g of Mg (NO ₃)₂·6H₂ O) are dissolved in 195g of water, the mass concentration of the solution I is 49.5%, the slurry I and the solution I are respectively subjected to parallel flow precipitation through a separating funnel in a parallel flow mode, the mass concentration of the slurry I is controlled at 40 ℃ for 20min, after the material is added, stirring and mixing are carried out for 30min, the prepared slurry II is subjected to micro-ball forming in a spray dryer, the drying temperature is 300 ℃, the drying time is 0.5h, the average diameter of spray droplets is 100 mu m, the prepared particles, then the mass concentration of the solution I and the solution I is 49.5% by volume of the catalyst is mixed in a mixed gas atmosphere (the volume of the catalyst is 200 ℃ and the required volume of the catalyst is 2 kg/1 kg/700 ℃ in the atmosphere) of water at the temperature of 40 ℃ and the temperature of 40 ℃ respectively).

The composition of the catalyst obtained according to the above steps is represented by the following formula:

50％K_0.10Fe_5.46Ni_5.0Mg_1.5Pr_0.5Bi_1.0Mo₁₃O_x+50％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 9.0nm, P2 was 32.0nm, y= (32.0-9.0)/9.0 = 2.6, wherein pores with a pore size of less than 5nm and greater than 80nm occupied a pore volume of 2.5% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation of the catalyst after heat treatment at the temperature of T1 are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.2% and the acrylonitrile selectivity was 85.1%.

[ Example 2]

704.9 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 577g of water, 4400 g of silica sol with the weight concentration of 30% is added under the condition of 50 ℃ to form slurry I, the concentration of the slurry I is 35.6%, 3.11 g of KOH and 74.1 g of Bi (NO ₃)₃·5H₂ O, 444.7 g of Co (NO ₃)₂·6H₂ O, 132.8 g of Nd (NO ₃)₃·6H₂ O, 374.2 g of Fe (NO ₃)₃·9H₂ O, 117.5 g of Mg (NO ₃)₂·6H₂O、101.8g Mn(NO₃)₂) are dissolved in 94g of water), the concentration of the solution I is 43.6%, the slurry I and the solution I are respectively subjected to parallel flow precipitation in a parallel flow mode through a separating funnel, the control time is 30min under the condition of 50 ℃, after the material is added, stirring and mixing are carried out for 30min, the prepared slurry II is subjected to micro-forming in a spray dryer, the drying temperature is 300 ℃, the average diameter of liquid drops is 100 mu m, two spray samples are prepared, then the mixed gas mixture is prepared in a mixed gas atmosphere of 0.5 vol% and the volume of oxygen is 200.25 vol% relative to the catalyst (the required gas is 550 ℃ per volume of the catalyst is 200 ℃ per volume of the gas is 2 kg).

40％K_0.15Fe_3.0Co_5.0Mn_1.0Mg_1.5Nd_1.0Bi_0.5Mo₁₃O_x+60％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 8.5nm, P2 was 28.0nm, y= (28.0-8.5)/8.5 = 2.3, wherein pores with a pore size of less than 5nm and greater than 80nm occupied a pore volume of 2.8% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation of the catalyst after heat treatment at the temperature of T1 are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.5% and the acrylonitrile selectivity was 85.1%.

[ Example 3]

1071.4 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 877g of water, 4400 g of silica sol with the weight concentration of 30% is added under the condition of 50 ℃ C.) to form slurry I, the concentration of the slurry I is 37.7%, 10.27 g of RbNO ₃ and 112.7 g of Bi (NO ₃)₃·5H₂ O and 675.9 g of Co (NO ₃)₂·6H₂ O) and 184.4 g of La (NO ₃)₃·6H₂ O and 568.7 g of Fe (NO ₃)₃·9H₂ O) and 164.5 g of Ca (NO ₃)₂·6H₂ O and 3.98 g of CrO ₃) are dissolved in 226g of water, the concentration of the solution I is 43% are obtained, the slurry I and the solution I are respectively subjected to parallel flow precipitation through a separating funnel in a parallel flow mode, the control time is 30min under the condition of 60 ℃ C.), after the materials are added, the slurry II is formed, the prepared slurry is subjected to microsphere forming in a spray dryer, the drying temperature is 300 ℃ C., the drying time is 0.5h, the average diameter of spray droplets is 100 mu m, the concentration of Ca (the concentration of the catalyst is 200% by volume per volume of the catalyst is 200 ℃ C.) and the required to be mixed in the air at the volume ratio of 200 ℃ C.25.25 kg of the catalyst (the volume ratio of the catalyst is prepared by volume of the two samples) after the two samples are prepared).

60％Rb_0.15Fe_3.0Co_5.0Cr_0.1Ca_1.5La_1.0Bi_0.5Mo₁₃O_x+40％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 7.6nm, P2 was 29.0nm, y= (29.0-7.6)/7.6=2.8, wherein pores with a pore size of less than 5nm and greater than 80nm accounted for 3.6% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 98.8% and the acrylonitrile selectivity was 86.9%.

[ Example 4]

869.5 G (NH ₄)₆Mo₇O₂₄·4H₂ O in 711g water, 50 ℃ C.) of silica sol with a concentration of 40% by weight and 110gZrO ₂ g were added to form slurry I with a concentration of 47.3% by weight, 8.34 g RbNO ₃, 91.4 g Bi (NO ₃)₃·5H₂ O, 553.7 g Ni (NO ₃)₂·6H₂ O), 65.7 g Sm (NO ₃)₃·6H₂ O, 384.6 g Fe (NO ₃)₃·9H₂ O, 119.7 g Sr (NO ₃)₂·6H₂ O, 21.5 g H ₃PO₄ and 3.81 g CrO ₃) were dissolved in 129g water, a concentration of 46% by weight of solution I was obtained, slurry I and solution I were co-current precipitated by means of a separating funnel, at a temperature of 60 ℃ C., a control time of 30min, after the addition of the materials was completed, stirring and mixing for 30min, the slurry II was formed, the slurry was subjected to micro-forming in a spray dryer with a drying temperature of 300 ℃ C., a drying time of 0.5H, a diameter of 100 μm and a liquid droplet concentration of 300.600 kg of air was prepared by mixing the two catalysts (volume: 1.600 vol% by volume, a ratio of water was prepared by spraying the two catalysts was prepared at a volume of 200 vol% by volume of water, respectively, and a ratio of 1.600 vol% of air was prepared by spraying catalyst was prepared).

50％Rb_0.15Fe_2.5Ni_5.0Cr_0.1Sr_1.5Sm_1.0P_0.5Bi_0.5Mo₁₃O_x+45％SiO₂+5％ZrO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 6.5nm, P2 was 27.0nm, y= (27.0-6.5)/6.5 = 3.2, wherein pores with a pore size of less than 5nm and greater than 80nm accounted for 3.9% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.5% and the acrylonitrile selectivity was 85.6%.

[ Example 5]

890.9 G (NH ₄)₆Mo₇O₂₄·4H₂ O in 729g of water, at 50 ℃ C.) of silica sol ₂ with a concentration of 40% by weight was added to form slurry I with a concentration of 45.6% by weight, 8.54 g of RbNO ₃, 93.7 g of Bi (NO ₃)₃·5H₂ O, 567.3 g of Ni (NO ₃)₂·6H₂ O), 67.3 g of Sm (NO ₃)₃·6H₂ O, 315.3 g of Fe (NO ₃)₃·9H₂ O, 122.6 g of Sr (NO ₃)₂·6H₂O、10.3gPd(NO₃)₂ in 129g of water) were dissolved to obtain a solution I with a concentration of 47.1% by weight, the slurry I and the solution I were co-current precipitated by means of a separating funnel, at 60 ℃ C.) for 30min, after the completion of the addition of the materials, stirred and mixed for 30min to form slurry II, the prepared slurry was subjected to micro-molding in a spray dryer with a drying temperature of 300 ℃ C., a drying time of 0.5h, and a spray droplet average diameter of 100. Mu.m, and then mixed gas was prepared in a mixed atmosphere of 3.35 vol. Water with a required concentration of oxygen (at 200.35 vol. 3.35% by volume, 3.1% by volume, the ratio of the catalyst was prepared by volume).

50％Pd_0.1Rb_0.15Fe_2.0Ni_5.0Cr_0.1Sr_1.5Sm_1.0Bi_0.5Mo₁₃O_x+50％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 5.8nm, P2 was 26.50nm, y= (26.5-5.8)/5.8=3.6, and wherein pores with a pore size of less than 5nm and greater than 80nm accounted for 1.4% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 98.3% and the acrylonitrile selectivity was 83.8%.

[ Example 6]

35G (NH ₄)₆Mo₇O₂₄·4H₂ O in 805g water, adding 2750 g silica sol ₂ with 40% weight concentration at 50 ℃ C.) to form slurry I, mixing 8.54 g RbNO ₃ and 103.5 g Bi (NO ₃)₃·5H₂ O, 626.6 g Ni (NO ₃)₂·6H₂ O, 36.7 g Pr (NO ₃)₃·6H₂ O, 261.2 g Fe (NO ₃)₃·9H₂ O, 164.1 g Mg (NO ₃)₂·6H₂ O, 4.71g CrO ₃、13.22gNb₂(C₂O₄)₅) in 144g water, obtaining solution I, concentration of solution I being 47.3%), co-current precipitating the slurry I and the solution I by a separating funnel, stirring and mixing for 30min at 60 ℃ C., forming slurry II, forming micro-pellets in a spray dryer, drying at 300 ℃ C., drying time of 0.5h, spraying average diameter of 100 μm, preparing a mixture of two catalysts with water content of 200.3% by volume per volume of air at 550 ℃ C., and air volume of air sample of 550 ℃ C., respectively, preparing a mixture of the catalyst is 500.25.3% by volume, and the catalyst is prepared by mixing the mixture of the two catalysts at 200 ℃ C. And air sample volume of air is prepared at 550 ℃ C.1.1.1.1.

50％Nb_0.1Rb_0.10Fe_1.5Ni_5.0Cr_0.1Mg_1.5Pr_0.2Bi_0.5Mo₁₃O_x+50％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 9.1nm, P2 was 38.5nm, y= (38.5-9.1)/9.1=3.2, wherein pores with a pore size of less than 5nm and greater than 80nm occupied 1.2% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.1% and the acrylonitrile selectivity was 86.1%.

Comparative example 1

836.6 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 684g of water, 2750 g of silica sol with a weight concentration of 40% is added at 50 ℃ C.) to form slurry I, the concentration of the slurry I is 46.8%, 2.46 g KOH and 175.9 g Bi (NO ₃)₃·5H₂ O, 532.7 g Ni (NO ₃)₂·6H₂ O), 78.1 g Pr (NO ₃)₃·6H₂ O), 808.2 g Fe (NO ₃)₃·9H₂ O, 139.5 g Mg (NO ₃)₂·6H₂ O) are dissolved in 195g of water, the concentration of the solution I is 49.5%, the slurry I is added into the solution I, stirring and mixing are carried out for 30min, the slurry II is formed, the prepared slurry is subjected to microsphere forming in a spray dryer, the drying temperature is 300 ℃, the drying time is 0.5h, and the average diameter of spray droplets is 100 mu m, so as to obtain particles, two spray samples are prepared, then the mixed gas of N ₂ with a volume content of water of 0.5% and a volume content of oxygen is 25% is introduced into the mixed gas atmosphere, the mixed gas has a unit time of 49.5% relative to the mass of the catalyst at 200 ℃ C.1 kg/T, and the required calcination ratio is carried out at 200 ℃ C.1 h, respectively, and the calcination is carried out at 1 h.

50％K_0.10Fe_5.46Ni_5.0Mg_1.5Pr_0.5Bi_1.0Mo₁₃O_x+50％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 5.2nm, P2 was 39.0nm, y= (39.0-5.2)/5.2=6.5, wherein pores with a pore size of less than 5nm and greater than 80nm occupied 7.2% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.2% and the acrylonitrile selectivity was 79.6%.

Comparative example 2

704.9 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 577g of water, 4400 g of silica sol with a weight concentration of 30% is added at 50 ℃ C.) to form slurry I, the concentration of the slurry I is 35.6%, 3.11 g KOH, 74.1 g Bi (NO ₃)₃·5H₂ O, 444.7 g Co (NO ₃)₂·6H₂ O), 132.8 g Nd (NO ₃)₃·6H₂ O, 374.2 g Fe (NO ₃)₃·9H₂ O, 117.5 g Mg (NO ₃)₂·6H₂O、101.8g Mn(NO₃)₂ is dissolved in 94g of water) to obtain solution I, the concentration of the solution I is 43.6%, the solution I is added into the slurry I, stirring and mixing are carried out for 30min, slurry II is formed, the prepared slurry is subjected to microsphere forming in a spray dryer, the drying temperature is 300 ℃, the drying time is 0.5h, the average diameter of spray droplets is 100 mu m, and the particles are obtained, samples are prepared after two spray, the mixed gas of N ₂ with a volume content of water of 0.5% and a volume content of oxygen of 25% is introduced into the mixed gas atmosphere, the mixed gas has a unit time of passing through the catalyst at 200 ℃ C.550 ℃ C.1 kg/T, and the required calcination is carried out at 1h respectively.

40％K_0.15Fe_3.0Co_5.0Mn_1.0Mg_1.5Nd_1.0Bi_0.5Mo₁₃O_x+60％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 7.1nm, P2 was 38.0nm, y= (38.0-7.1)/7.1=6.4, wherein pores with a pore size of less than 5nm and greater than 80nm accounted for 7.5% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 99.7% and the acrylonitrile selectivity was 80.9%.

[ Comparative example 3]

1071.4 G (NH ₄)₆Mo₇O₂₄·4H₂ O, 184.4 g La (NO ₃)₃·6H₂ O dissolved in 907g water, 50 ℃ C.) of silica sol with a concentration of 30% by weight was added to form slurry I, the concentration of slurry I was 37.7%, 10.27 g RbNO ₃, 112.7 g Bi (NO ₃)₃·5H₂ O, 675.9 g Co (NO ₃)₂·6H₂ O, 568.7 g Fe (NO ₃)₃·9H₂ O, 164.5 g Ca (NO ₃)₂·6H₂ O, 3.98 g CrO ₃) dissolved in 196g water, the concentration of solution I was 43%), slurry I and solution I were Co-current precipitated by a separating funnel, the control time was 30min at 90 ℃ C.), after the addition of the materials, 10.27 g RbNO ₃, 112.7 g Bi (NO ₃)₃·5H₂ O, 675.9 g Co) (NO ₃)₂·6H₂ O, 568.7 g Fe (NO ₃)₃·9H₂ O, 164.5 g Ca) (NO ₃)₂·6H₂ O, 3.98 g CrO ₃) were formed in a parallel flow manner, the mixture was prepared by a spray-type air-phase of 200 ℃ C., and a volume ratio of 200.25% by volume of the catalyst was prepared by mixing the two catalysts in a spray dryer at a temperature of 90 ℃ C., 200 ℃ C., at a temperature of 200.25 ℃ C., respectively, and a volume ratio of air was prepared by mixing the two catalysts of the catalyst was prepared by mixing.

60％Rb_0.15Fe_3.0Co_5.0Cr_0.1Ca_1.5La_1.0Bi_0.5Mo₁₃O_x+40％SiO₂, The catalyst was subjected to an average pore size measurement wherein P1 was 6.7nm, P2 was 39.0nm, y= (39.0-6.7)/6.7=4.8, and wherein pores with a pore size of less than 5nm and greater than 80nm accounted for 7.6% of the total pore volume.

The reaction conditions for producing acrylonitrile by propylene ammoxidation with the above catalyst calcined at T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 98.5% and the acrylonitrile selectivity was 77.1%.

[ Comparative example 4]

836.6 G (NH ₄)₆Mo₇O₂₄·4H₂ O is dissolved in 684g of water, 2750 g of silica sol with 40% weight concentration is added at 50 ℃ to form slurry I, the mass concentration of the slurry I is 46.8%, 2.46 g of KOH and 175.9 g of Bi (NO ₃)₃·5H₂ O, 532.7 g of Ni (NO ₃)₂·6H₂ O, 78.1 g of Pr (NO ₃)₃·6H₂ O) and 808.2 g of Fe (NO ₃)₃·9H₂ O and 139.5 g of Mg (NO ₃)₂·6H₂ O) are dissolved in 195g of water, the mass concentration of the solution I is 49.5%) are added, the slurry I and the solution I are respectively and parallelly precipitated in a parallel flow mode through a separating funnel, the control time is 20min at 40 ℃, after the material is added, stirring and mixing are carried out for 30min, the prepared slurry II is subjected to microsphere forming in a spray dryer, the drying temperature is 300 ℃ and the drying time is 0.5h, the average diameter of spray droplets is 100 mu m, the obtained particles are then baked at the air atmosphere for 1h, and the required catalyst is prepared.

50％K_0.10Fe_5.46Ni_5.0Mg_1.5Pr_0.5Bi_1.0Mo₁₃O_x+50％SiO₂,

The reaction conditions for producing acrylonitrile by propylene ammoxidation by the catalyst are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 ℃, the reaction pressure was 0.084MPa, the catalyst loading was 300 grams, the catalyst propylene loading (WWH) was 0.085 hours ^-1, and the feed ratio (mol): C ₃ ^＝/NH₃/air=1/1.25/9.6. After 300 hours of operation, the reaction result was that the propylene conversion was 96.1% and the acrylonitrile selectivity was 78.3%.

Table 1 composition and evaluation results of catalyst particles obtained in each of examples and comparative examples

The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. An ammonia oxidation catalyst, wherein the active components of the catalyst include molybdenum and bismuth, the carrier includes silicon dioxide, and the change in average pore size of the catalyst after heat treatment conforms to formula (I):

Y=（P2-P1）/P1（I），

Wherein, the value of Y is less than or equal to 4.5, P2 is the average pore size of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, P1 is the average pore size of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere, and T2 is greater than T1, T2 is less than or equal to 750°C; temperature T1 is 400-600°C; temperature T2 is 500-750°C; the heat treatment time is 0.5-4h; temperature T2 is at least 50°C higher than temperature T1;

The active components include molybdenum and bismuth. Based on the weight of the catalyst, the weight content of the molybdenum calculated as MoO ₃ is 15% to 55%, and the weight content of the bismuth calculated as Bi ₂ O ₃ is 0.5% to 3.5%; the atomic ratio of Bi/Mo is 0.008 to 0.25;

The method for preparing the catalyst comprises the following steps:

(1) a basic material containing molybdenum and a carrier precursor and an acidic material containing bismuth as an active component precursor are subjected to a co-current precipitation reaction to obtain a slurry I;

(2) The slurry I is spray-dried and heat-treated to obtain the catalyst.

2. The catalyst according to claim 1, characterized in that the value of Y is 0.5~4.5.

3. The catalyst according to claim 2, characterized in that the value of Y is 1.5 to 4.0.

4. The catalyst according to claim 1, characterized in that the temperature T1 is 450-600°C; the temperature T2 is 550-700°C;

And/or, the heat treatment time is 0.5~2h.

5. The catalyst according to claim 1 is characterized in that the heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein the water volume content of the mixed gas is 0.01% to 4.5%, the oxygen volume content is 10% to 30%, and the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 50 to 500 L/kg·h.

6. The catalyst according to claim 1, characterized in that the active components include molybdenum and bismuth, and based on the weight of the catalyst, the weight content of the molybdenum calculated as _MoO3 is 20% to 45%, and the weight content of the _bismuth calculated as _Bi2O3 is 1.0% to 3.5%.

7. The catalyst according to claim 1, characterized in that in the active component, the atomic ratio of Bi/Mo is 0.01-0.20.

8. The catalyst according to claim 1 is characterized in that the active components also include Fe, rare earth elements, alkali metal elements, alkaline earth metal elements and metal element A; the metal element A is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn and Te.

9. The catalyst according to claim 8, characterized in that the metal element A is selected from at least one of Co, Mn, P, Pd and Nb.

10. The catalyst according to claim 8, characterized in that, based on the weight of the catalyst, the weight content of the molybdenum calculated as _MoO3 is 15% to 55%, the weight content of the bismuth calculated as _Bi2O3 is 0.5% to _3.5 %, the weight content of the Fe element calculated as _Fe2O3 is 1% to 12%, the weight content of the _alkali metal element calculated as oxide is 0.01% to 0.60%, the weight content of the alkaline earth metal calculated as oxide is 0.01% to 4.0%, and the weight content of the metal element A calculated as oxide is 0.01% to 15%.

11. The catalyst according to claim 10, characterized in that, based on the weight of the catalyst, the weight content of the molybdenum calculated as _MoO3 is 20% to 45%, the weight content of the bismuth calculated as _Bi2O3 is 1.0% to _3.5 %, the weight content of the Fe element calculated as _Fe2O3 is 1.5% to 11%, the weight content of the _alkali metal element calculated as oxide is 0.05% to 0.55%, the weight content of the alkaline earth metal calculated as oxide is 0.5% to 3.5%, and the weight content of the metal element A calculated as oxide is 0.05% to 14%.

12. The catalyst according to claim 10, characterized in that, in the catalyst, the atomic ratio of Bi/Mo is 0.008-0.25; and/or the atomic ratio of Fe/Bi is 1.0-7.0; and/or the atomic ratio of (rare earth element+alkali metal element+alkaline earth metal element)/Mo is 0.05-0.40; and/or the atomic ratio of A/Mo is 0.01-1.0.

13. The catalyst according to claim 12, characterized in that, in the catalyst, the atomic ratio of Bi/Mo is 0.01-0.20; and/or the atomic ratio of Fe/Bi is 2.0-6.0; and/or the atomic ratio of (rare earth element+alkali metal element+alkaline earth metal element)/Mo is 0.10-0.35; and/or the atomic ratio of A/Mo is 0.02-0.9.

14. The catalyst according to claim 1, 8 or 10, characterized in that, based on the weight of the catalyst, the content of the active component in terms of oxide is 20% to 80%, and the content of the carrier is 20% to 80%.

15. The catalyst according to claim 1, characterized in that the catalyst is in granular form with an average particle size of 30-70 μm.

16. The catalyst according to claim 15, characterized in that the catalyst is in granular form with an average particle size of 40-60 μm.

17. A method for preparing the catalyst according to any one of claims 1 to 16, comprising the following steps:

(2) The slurry I is spray-dried and heat-treated to obtain the catalyst.

18. The preparation method according to claim 17, characterized in that the carrier precursor in step (1) comprises silica sol; the silica sol has a solid content of 20wt% to 50wt% in terms of silicon dioxide and an average particle size of 10 to 35nm;

And/or, in the alkaline material containing molybdenum and a carrier precursor described in step (1), the material mass concentration is controlled at 20% to 55%;

And/or, in the acidic material of the bismuth-containing active component precursor described in step (1), the material mass concentration is controlled at 20% to 60%.

19. The preparation method according to claim 17, characterized in that the time of the parallel flow precipitation in step (1) is 10-40 minutes, and the temperature is controlled at 20-60°C.

20. The preparation method according to claim 19, characterized in that the time of the parallel flow precipitation in step (1) is 10 to 25 minutes.

21. The preparation method according to claim 19, characterized in that in step (1), after the materials are added, they are further stirred and mixed, and the mixing time is 10 to 30 minutes.

22. The preparation method according to claim 19, characterized in that in step (1), after the materials are added, they are further stirred and mixed, and the mixing time is 10 to 25 minutes.

23. The preparation method according to any one of claims 17 to 22, characterized in that the acidic material of the bismuth-containing active component precursor in step (1) further includes precursors of Fe, rare earth elements, alkali metal elements, alkaline earth metal elements and metal element A.

24. The preparation method according to claim 17, characterized in that the spray drying conditions in step (2) include: the drying heat source is air, the drying temperature is 250-350°C, the drying time is 0.1-2.0h, and the average diameter of the spray droplets is 20-200μm;

And/or, the heat treatment in step (2) is a high-temperature calcination treatment in a water-containing atmosphere.

25. The preparation method according to claim 24, characterized in that the spray drying conditions in step (2) include: drying temperature of 300-350°C, drying time of 0.2-1.0h, and average diameter of spray droplets of 40-180 μm.

26. The preparation method according to claim 24, characterized in that the conditions of the heat treatment in step (2) are as follows: temperature of 500-750°C, time of 0.2-4h, and the heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein the volume content of water in the mixed gas is 0.01%-4.5%, the volume content of oxygen is 10%-30%, and the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 50-500L/kg·h.

27. A method for preparing acrylonitrile by ammoxidation of propylene, comprising: in the presence of a catalyst according to any one of claims 1 to 16 or a catalyst prepared by the preparation method according to any one of claims 17 to 26, subjecting propylene to an ammoxidation reaction to produce acrylonitrile.

28. The method according to claim 27, characterized in that the reaction conditions for preparing acrylonitrile by ammoxidation of propylene include: the molar ratio of propylene/ammonia/air (in terms of _O2) is 1:1.1-1.35:1.8-2.5, the reaction temperature is 420-440°C, the reaction pressure is 0.03-0.14 MPa in terms of gauge pressure, and the weight hourly space velocity is 0.04-0.10 h ^-1 .