CN113828323B - Additional catalyst for acrylonitrile production, preparation method and application - Google Patents

Additional catalyst for acrylonitrile production, preparation method and application Download PDF

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CN113828323B
CN113828323B CN202010590862.XA CN202010590862A CN113828323B CN 113828323 B CN113828323 B CN 113828323B CN 202010590862 A CN202010590862 A CN 202010590862A CN 113828323 B CN113828323 B CN 113828323B
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catalyst
molybdenum oxide
composition
molybdenum
acrylonitrile
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CN113828323A (en
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张顺海
吴粮华
李静霞
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/85—Chromium, molybdenum or tungsten
    • B01J23/88—Molybdenum
    • B01J23/887—Molybdenum containing in addition other metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8876—Arsenic, antimony or bismuth
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • B01J23/28—Molybdenum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/24—Preparation of carboxylic acid nitriles by ammoxidation of hydrocarbons or substituted hydrocarbons
    • C07C253/26—Preparation of carboxylic acid nitriles by ammoxidation of hydrocarbons or substituted hydrocarbons containing carbon-to-carbon multiple bonds, e.g. unsaturated aldehydes
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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Abstract

The invention provides a supplemental catalyst for acrylonitrile production, a preparation method and application thereof. The additional catalyst for producing acrylonitrile provided by the invention comprises molybdenum oxide and a composition; the weight ratio of the composition to the molybdenum oxide is 4-50; the silicon mass content in the molybdenum oxide is 1% -3%; and the particle size of the molybdenum oxide is 10 micrometers-50 micrometers; according to the XRD spectrum of the molybdenum oxide, the 2 theta of the crystal phase of the molybdenum oxide is the strongest peak when the angle is 25.8+/-1 DEG, the angle of 12.8+/-1 DEG is the next strongest peak, and the angle of the third strongest peak is 39.1+/-1 deg. The additional catalyst provided by the invention is used for propylene ammoxidation reaction, so that higher acrylonitrile yield can be obtained under higher propylene load, and the catalyst can be kept stable for a long time.

Description

Additional catalyst for acrylonitrile production, preparation method and application
Technical Field
The invention relates to a fluidized bed catalyst for producing acrylonitrile by propylene ammoxidation, in particular to a supplemental catalyst for producing acrylonitrile, a preparation method and application thereof.
Background
Acrylonitrile is an important organic chemical raw material, and more than 95% of acrylonitrile is produced through propylene ammoxidation. In order to obtain the fluidized bed catalyst with high activity and high selectivity, a series of improvements are continuously explored. These improvements are mostly related to the catalyst active components, focusing on the collocation between the catalyst active components to improve the activity and selectivity of the catalyst, thereby achieving the improvement of the single pass yield of acrylonitrile and the improvement of the production load. The single pass yield of the fresh catalyst acrylonitrile can reach more than 80%, the activity of the catalyst can be gradually reduced after the catalyst is used for a long time in an industrial device, and the single pass yield of the catalyst acrylonitrile is reduced by more than 1 percent after the catalyst is generally used for two years, so that the economic benefit of the device is affected. Because of the high price of the catalyst, the whole tower is less adopted for replacement due to economic reasons. It is common in industry to maintain the reaction performance by supplementing the catalyst or regenerating the catalyst with reduced activity.
The fluidized bed catalyst for producing acrylonitrile by propylene ammoxidation in the prior art adopts a Mo-Bi-Fe catalyst. Wherein the essential component Mo is easy to sublimate and lose under the action of high temperature and reaction atmosphere, especially steam, so that the composition of the catalyst formula is changed and deviates from the optimal formula. In addition, in long-term operation, certain components with oxidation-reduction properties in the catalyst are excessively reduced, the structure of an active phase of the catalyst is changed, the particle size distribution of the catalyst is changed to cause the change of fluidization state, carbon deposition in a pore canal of the catalyst and other factors, so that the performance of the ammoxidation catalyst is reduced.
For example, CN201210412584.4 discloses a fluidized bed catalyst for preparing unsaturated nitrile by ammoxidation, a preparation method and an application catalyst thereof, wherein the catalyst is Mo 12 Bi 1.2 Fe 2.2 Ni 6.6 Co 1.0 Ce 0.7 Sm 0.2 Sb 0.01 K 0.07 +46％SiO 2 The method is used for ammoxidation reaction, and the single pass yield of the obtained acrylonitrile is high. However, in the long-term operation of the catalyst, the loss of Mo component still exists, so that the activity of the catalyst is reduced, and the long-term stability is affected.
Currently, one of the ways to maintain acrylonitrile yields is to employ a method of catalyst regeneration. CN1110193a regenerates the catalyst by replenishing ammonium molybdate and under a nitrogen-air mixed atmosphere. Both US4609635 and US4052332 employ a method of impregnating a catalyst having reduced activity with a solution containing certain constituents of the catalyst and then calcining the catalyst. CN200910056808.0 describes a method for maintaining the activity of the catalyst by regeneration, which comprises supplementing the corresponding molybdenum content, roasting at 550-700 ℃ under the condition that the roasting atmosphere is at least two selected from air, nitrogen or water vapor to obtain the regenerated catalyst, but the maintenance time of the regenerated catalyst cannot be long, and the stable operation of the production device is affected. In addition, only external regeneration of the reactor can be adopted, and the production is influenced.
Another method is a method of adding a catalyst. CN1061163a discloses a supplemental catalyst for keeping the activity of the molybdenum catalyst of the acrylonitrile fluidized bed stable, the composition of each element of the supplemental catalyst is the same as or close to that of the original molybdenum catalyst, and only the molybdenum content is higher than that of the original molybdenum catalyst, but by adopting the method, the supplemental catalyst has low activity, the single pass yield of the acrylonitrile is below 78%, and the catalyst cannot stably and efficiently run for a long period.
Disclosure of Invention
One of the technical problems to be solved by the invention is to provide a new additional catalyst for acrylonitrile production, which can maintain stable catalyst performance for a long time in the acrylonitrile production process and improve the production efficiency and economic benefit of the device.
The second technical problem to be solved by the invention is to provide a preparation method of the additional catalyst.
The invention provides an application of the additional catalyst in preparing acrylonitrile by ammoxidation of propylene.
The present invention provides in a first aspect a supplemental catalyst for acrylonitrile production comprising molybdenum oxide and a composition; the weight ratio of the composition to the molybdenum oxide is 4-50;
wherein the silicon mass content in the molybdenum oxide is 1% -3%; and the particle size of the molybdenum oxide is 10 micrometers-50 micrometers; the molybdenum oxide XRD spectrum information is shown in the following table:
2θ(°) relative intensity (I/I) 0 )×100
12.8±1 70-93
23.3±1 15-38
25.8±1 100
27.3±1 18-32
39.1±1 45-65
As shown in the table, the molybdenum oxide crystal phase 2 theta was the strongest peak at 25.8.+ -. 1 °, the second strongest peak at 12.8.+ -. 1 °, and the third strongest peak at 39.1.+ -. 1 °.
In the additional catalyst, the composition contains a carrier and an active component, wherein the active component is a Mo-Bi-Fe catalyst, and the mass ratio of Mo in the composition to Mo in the unsaturated nitrile bulk catalyst prepared by ammoxidation of olefin is 2.0-1.0.
Further, the molybdenum oxide XRD spectrum information is shown in the following table:
further, the chemical general formula of the active components of the composition in terms of atomic ratio may be as follows:
A a Q b Fe c Ni d Bi e Mo 12 O x
wherein: a is at least one selected from Li, na, K, rb and Cs elements; q includes at least one selected from Be, mg, ca, sr and Ba elements;
wherein, the value range of a is 0.01-2.50; b has a value of 0.01-15.00; c has a value range of 0.01-5.00; d has a value ranging from 1.00 to 10.00; e has a value range of 0.01-5.00; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst.
Further, the carrier of the composition in the supplemental catalyst may be present in an amount of 30 to 70wt% by weight and the active component may be present in an amount of 30 to 70wt% by weight. The carrier in the composition may include at least one selected from silica, alumina, titania and zirconia.
Further, in the catalyst-supplementing composition, the active component Q may be preferably B and L, wherein B is at least one of Be, mg, ca, sr and Ba, and L is at least one of Nb, pr, yb, tm and Er, and the chemical formula of the active component in atomic ratio may be expressed as:
A a B m L n Fe c Ni d Bi e Mo 12 O x
wherein:
b is at least one selected from Be, mg, ca, sr and Ba elements;
l is at least one selected from Nb, pr, yb, tm and Er elements;
m has a value range of 0.10-10.00;
the value range of n is 0.01-5.00.
Further, the value of a is preferably in the range of 0.05-1.50, and non-limiting specific point values of a may be 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, etc. Further, non-limiting specific point values of m may be 0.20, 0.40, 0.60, 0.80, 1.00, 1.50, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, 3.80, 4.20, 4.80, 5.20, 5.80, 6.20, 6.80, 7.20, 7.80, 8.20, 8.40, 8.60, 8.80, 9.20, 9.60, 9.80, and the like. Further, non-limiting specific point values of n may be 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, 4.20, 4.60, 4.80, and the like. Further, the value of c is preferably in the range of 0.05-3.50, and non-limiting specific point values of c may be 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, etc. Further, d preferably ranges from 1.50 to 9.00, and non-limiting specific points of d within this range may be 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, 3.00, 3.20, 3.40, 3.80, 4.20, 4.80, 5.20, 5.80, 6.20, 6.80, 7.20, 7.80, 8.20, 8.80, etc. Further, the value of e is preferably in the range of 0.05-3.00, and non-limiting specific point values of e may be 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.60, 1.80, 2.00, 2.20, 2.40, 2.60, 2.80, etc.
Further, the average particle size of the composition in the supplemental catalyst is 20-80 microns.
Further, the weight ratio of the composition to molybdenum oxide in the supplemental catalyst is preferably in the range of 6 to 45, and non-limiting specific values may be 7.0, 9.0, 11.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, etc.
The bulk catalyst for preparing unsaturated nitrile by ammoxidation of olefin used in the present invention refers to a catalyst conventionally used in the art for preparing unsaturated nitrile by ammoxidation of olefin, for example, a Mo-Bi-Fe-based catalyst is not limited to Mo-Bi-Fe, and may contain at least one of alkali metal element, alkaline earth metal element, lanthanide metal, etc. The conventional preparation method of the bulk catalyst comprises the following steps: and respectively dissolving the compounds of the corresponding component elements in water, mixing and stirring, mixing with carrier sol to obtain catalyst slurry, spray-drying the slurry, and roasting in an oxidizing atmosphere to obtain the bulk catalyst. The average particle size of the bulk catalyst is typically 25-75 microns.
Further, the bulk catalyst for preparing unsaturated nitrile by ammoxidation of olefin used in the present invention may be the same as or different from the composition of the additional catalyst.
The second aspect of the invention provides a method for preparing a supplemental catalyst, comprising the steps of:
uniformly mixing the composition and the molybdenum oxide to obtain the additional catalyst;
the preparation steps of the composition in the additional catalyst are as follows: respectively dissolving the compounds of the corresponding component elements in water, mixing and stirring, mixing with carrier sol to obtain catalyst slurry, spray drying the slurry, and roasting in an oxidizing atmosphere to obtain a composition;
the preparation steps of the molybdenum oxide in the additional catalyst are as follows: carrying out desulfurization treatment on molybdenum concentrate containing silicon, then carrying out reduction treatment, cooling, and oxidizing under the temperature programming condition and in the oxidizing atmosphere to obtain a molybdenum oxide precursor; and then roasting the molybdenum oxide precursor in an inert atmosphere, and sieving the roasted molybdenum oxide particles by 10-50 microns to obtain the molybdenum oxide.
Further, the preparation method of the composition comprises the following steps:
(a) The material I is obtained after the raw materials of the A are dissolved; dissolving the raw material of molybdenum to obtain a material II; the material III is obtained after the raw materials of Q and the raw materials of Fe, bi and Ni are dissolved;
(b) Mixing the material I with the carrier sol, sequentially adding the material II and the material III under stirring to obtain catalyst slurry, and spray-drying the catalyst slurry to obtain a composition precursor;
(c) The composition precursor is baked in an oxidizing atmosphere to obtain the composition.
Further, in the preparation method of the composition, after the catalyst slurry is prepared, before spray drying, the composition preferably further comprises: a step of heat-treating the catalyst slurry; the temperature of the heat treatment is 80-150 ℃; the heat treatment time is 1-50 minutes.
Further, in the preparation method of the composition, the process conditions of the spray drying are not particularly limited, and those skilled in the art can reasonably select and do not need to pay creative effort.
Further, in the preparation method of the composition, the roasting temperature is 500-700 ℃, and the roasting time is 0.25-4 hours.
Further, in the preparation method of the composition, the raw material of molybdenum in the composition is preferably at least one of molybdenum oxide or ammonium molybdate; the raw materials of A, B, L, fe, ni and Bi are nitrate, oxalate, hydroxide, oxide or salt which can be decomposed into oxide.
Further, in the preparation method of molybdenum oxide, the desulfurization treatment method comprises the following steps: roasting the molybdenum concentrate containing silicon for 2-6 hours at 500-650 ℃ in oxygen-enriched or air atmosphere until the sulfur content cannot be detected.
Further, in the preparation method of the molybdenum oxide, the cooling is to cool the material to the room temperature of 300 ℃.
Further, in the preparation method of molybdenum oxide, the reducing atmosphere may be a gas commonly used in the art with reducing property, for example, but not limited to, CO, pure hydrogen, etc., and the reducing atmosphere is preferably a mixture of hydrogen and inert gas, and the reducing temperature is preferably 800-1000 ℃.
Further, in the preparation method of the molybdenum oxide, the temperature programming is 1 ℃/min-30 ℃/min, preferably 5 ℃/min-20 ℃/min, the temperature of the oxidation process is 500-700 ℃, preferably 655-700 ℃ and the oxidation time is 0.5-2h.
Further, in the preparation method of molybdenum oxide, the inert gas atmosphere may be inert gas commonly used in the art, for example, but not limited to, nitrogen, helium, etc. or a mixture thereof. The preferred range of firing temperatures is 650-700 ℃. The roasting time is preferably in the range of 0.5 to 3 hours.
Further, in the preparation method of the composition and the preparation method of molybdenum oxide, the oxidizing atmosphere may employ a gas commonly used in the art having oxidizing property, such as, but not limited to, a gas derived from oxygen enrichment, pure oxygen, air, etc., preferably air.
The third aspect of the invention provides the application of the additional catalyst in preparing acrylonitrile by ammoxidation of propylene.
Further, the application comprises adding the additional catalyst into a reaction system for preparing acrylonitrile by ammoxidation of propylene. The reaction system for preparing acrylonitrile by ammoxidation of propylene is preferably a fluidized bed reaction system.
Further, in the application, the additional catalyst is continuously added in the presence of the bulk catalyst for preparing unsaturated nitrile by ammoxidation of olefin, and the additional mode is a continuous additional mode.
Further, in the application, the additional catalyst is added at a rate of 0.3 to 0.7 kg/ton acrylonitrile, and the additional catalyst controls the catalyst density of the bed layer to be 330 to 520kg/m 3 。
Further, in the application, the reaction temperature is 410-460 ℃; the molar ratio of propylene to ammonia to oxygen is 1 (1.05-1.35) to 1.7-2.5; the catalyst loading WWH can be 0.04-0.12h -1 The method comprises the steps of carrying out a first treatment on the surface of the The reaction pressure is 30-100KPa.
Further, in the application, the oxygen is not particularly limited, and oxygen-containing gases commonly used in the art, such as, but not limited to, oxygen-enriched, pure oxygen, air, and the like, may be used.
The specifications of propylene, ammonia and molecular oxygen required for acrylonitrile production by the additional catalyst of the invention are the same as those of acrylonitrile production by other ammoxidation. Although the low molecular saturated hydrocarbon content in the raw propylene has no effect on the reaction, the propylene concentration is preferably more than 85 mol% from the economical viewpoint. The ammonia may be fertilizer grade liquid ammonia. The molecular oxygen required for the reaction may be pure oxygen, oxygen-enriched or air from a technical point of view, but air is preferred from an economical and safety point of view.
The product recovery refining process for preparing acrylonitrile by adding the catalyst can use the existing production process without any modification. I.e. the effluent gas from the fluidized bed reactor is passed through a neutralization column to remove unreacted ammonia and the total organic product is absorbed by means of low temperature water. The absorption liquid is subjected to extractive distillation, dehydrocyanic acid and dehydration treatment to obtain a high-purity acrylonitrile product.
According to the technical scheme, the primary activity of the bulk catalyst is high, but molybdenum is easy to sublimate, and the like. The catalyst contains silicon-containing molybdenum oxide with specific crystal phase and performance, a small amount of silicon oxide and molybdenum oxide form a chemically stable structure to form Mo-Si-O chemical bond, so that the performance of the molybdenum oxide is changed, and the molybdenum oxide has a granular structure with certain strength, and has the characteristics of stable production of an acrylonitrile device, high acrylonitrile yield and the like. The additional catalyst of the invention is used for propylene ammoxidation reaction, so that higher acrylonitrile yield can be obtained under higher propylene load, and the catalyst can be kept stable for a long time.
Drawings
FIG. 1 is an XRD diffraction pattern of molybdenum oxide prepared in accordance with example 1;
fig. 2 is an XRD diffractogram of molybdenum oxide prepared in comparative example 1.
Detailed Description
The propylene conversion, acrylonitrile selectivity and single pass yield in the present invention are defined as follows:
in the present invention, XRD analysis was performed on a BRUKER D8ADVANCE diffractometer using a Cu ka radiation source (λ= 0.15406 nm), ni monochromator. Under the working condition, the pipe pressure is 40kV, the pipe flow is 250mA, the scanning speed is 12 degrees/min, and the test 2 theta range is 5-80 degrees.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
[ example 1 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 56.6 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 600 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 950 ℃ in the atmosphere of hydrogen and nitrogen mixed gas to obtain granular molybdenum powder with the silicon mass content of 1.8%; heating the molybdenum powder cooled to 200 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 675 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst.
The crystal phase structure of the prepared molybdenum oxide is shown in figure 1. The information of the XRD spectrum of molybdenum oxide is shown in the table below, and according to the table, the molybdenum oxide has a maximum peak at 25.8 degrees 2 theta, a secondary maximum peak at 12.8 degrees and a third maximum peak at 39.1 degrees.
2θ(°) Relative intensity (I/I) 0 )×100
12.8 78.2
23.3 20.3
25.8 100
27.3 18.2
39.1 50.7
2. Catalyst evaluation
The performance evaluation of the additional catalyst was carried out in an acrylonitrile unit fluidized bed reactor of 8 ten thousand tons/year scale. The reaction conditions are as follows:
the reaction temperature is 435 DEG C
Reaction pressure 70kPa
Catalyst loading was 140 tons
Catalyst propylene load (WWH) 0.080 hours -1
Raw material ratio (mol) C 3 H 6 /NH 3 Oxygen=1/1.15/1.9.
The unsaturated nitrile bulk catalyst prepared by ammoxidation of olefin is as follows: 50% K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 11.8 O x +50％SiO 2 . The catalyst particle size was 58.1 microns.
The commercial unit was fed with catalyst of the type described in example 1 by continuous feeding at a rate of 0.4 kg/ton acrylonitrile and the bed catalyst density was controlled at 400kg/m 3 。
The composition and properties of the additional catalyst are shown in Table 1, and the catalytic performance results are shown in Table 2.
[ example 2 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 57.5 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 620 ℃ to carry out desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing under the atmosphere of a mixed gas of hydrogen and nitrogen at 850 ℃ to prepare granular molybdenum powder with the silicon mass content of 1.2%; heating the molybdenum powder cooled to 150 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 695 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
(3) 380 grams of catalyst composition and 20 grams of molybdenum oxide were uniformly mixed to obtain a make-up catalyst. The additional catalyst composition and properties are shown in Table 1.
The prepared molybdenum oxide XRD spectrum is the same as that of example 1, the information of the molybdenum oxide XRD spectrum is shown in the table, according to the table, the molybdenum oxide crystal phase 2 theta is the strongest peak when the angle is 25.8 degrees, the 12.8 degrees is the second strongest peak, and the third strong peak is 39.1 degrees. The evaluation conditions were the same as in example 1, and the performance results are shown in Table 2.
2θ(°) Relative intensity (I/I) 0 )×100
12.8 72.2
23.3 22.5
25.8 100
27.3 19.8
39.1 52.4
[ example 3 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide and 15 g of waterAnd heating and dissolving to obtain a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 60.1 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 610 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing under the mixed gas atmosphere of hydrogen and nitrogen at 980 ℃ to obtain granular molybdenum powder with the silicon mass content of 3%; heating the molybdenum powder cooled to 200 ℃ to 700 ℃ at a programmed heating rate of 10 ℃ per minute under the air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under nitrogen atmosphere at 655 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst. The additional catalyst composition and properties are shown in Table 1.
The information of XRD spectrum of the prepared molybdenum oxide is shown in the following table, wherein the molybdenum oxide crystal phase 2 theta is the strongest peak at 25.8 degrees, the second strongest peak at 12.8 degrees and the third strongest peak at 39.1 degrees.
2θ(°) Relative intensity (I/I) 0 )×100
12.8 78.5
23.3 25.8
25.8 100
27.3 23.5
39.1 50.6
[ example 4 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
3.60 g of potassium nitrate and 4.65 g of cesium nitrate are added with 15 g of water and dissolved after heating, so as to obtain a material I; 512.6 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 500 g of hot water at 80 ℃ to obtain a material II; 11.6 g of bismuth nitrate Bi (NO 3 ) 3 ·5H 2 O, 84.9 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 387.5 g Nickel Ni nitrate (NO 3 ) 2 ·6H 2 O, 146.8 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 258.2 g praseodymium nitrate Pr (NO) 3 ) 3 ·6H 2 O, 139.6 g cobalt nitrate Co (NO) 3 ) 2 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 750 g of silica sol with the weight concentration of 40%, sequentially adding the material II and the material III under stirring, fully stirring to obtain slurry, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 55.8 microns, wherein the composition is as follows:
70％K 0.15 Cs 0.1 Fe 1.5 Ni 5.5 Co 2.0 Ca 1.5 Pr 2.5 Bi 0.1 Mo 12.0 O x +30％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 600 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 950 ℃ in the atmosphere of hydrogen and nitrogen mixed gas to obtain granular molybdenum powder with the silicon mass content of 1.9%; heating the molybdenum powder cooled to 200 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 675 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
(3) The additional catalyst was obtained by uniformly mixing 350 g of the catalyst composition with 50 g of molybdenum oxide. The additional catalyst composition and properties are shown in Table 1.
The XRD spectrum of the prepared molybdenum oxide is the same as that of example 1.
[ comparative example 1 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 56.6 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
reducing 800 g of ammonium molybdate in a mixed gas atmosphere of hydrogen and nitrogen at 900 ℃ to prepare powdery molybdenum powder; and oxidizing the molybdenum powder cooled to 200 ℃ for 1 hour in an air atmosphere at 450 ℃ and cooling to obtain molybdenum oxide.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst. The additional catalyst composition and properties are shown in Table 1.
The structure of the molybdenum oxide crystal phase is shown in figure 2. The XRD spectrum of molybdenum oxide is shown in the following table, the molybdenum oxide has a strongest peak when the 2 theta of the crystal phase is 12.8 degrees, a second strongest peak when the 25.8 degrees is the second strongest peak, and a third strongest peak is 39.1 degrees.
2θ(°) Relative intensity (I/I) 0 )×100
12.8 105.5
23.3 12.4
25.8 100
27.3 10.5
39.1 49.2
2. Catalyst evaluation the same as in example 1
The performance results are shown in Table 2.
[ comparative example 2 ]
1. Preparation of additional catalyst
Roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 600 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 950 ℃ in the atmosphere of hydrogen and nitrogen mixed gas to obtain granular molybdenum powder with the silicon mass content of 1.8%; heating the molybdenum powder cooled to 200 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 675 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
Only 400 g of molybdenum oxide was used as additional catalyst. The additional catalyst composition and properties are shown in Table 1.
The XRD spectrum of the prepared molybdenum oxide is the same as that of example 1.
2. Catalyst evaluation the same as in example 1
The composition is not added, only molybdenum oxide is added, and the molybdenum oxide alone has no catalytic activity and cannot be kept stable for long-time operation. After 3 months, the propylene conversion rate was reduced from 98.5% at the initial stage to 96.7%, the acrylonitrile selectivity was reduced from 84.1% at the initial stage to 81.5%, and the reduction tendency was remarkable, and the stability was not maintained for a long period of time.
[ comparative example 3 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 56.6 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 880 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 1000 ℃ in the atmosphere of a mixed gas of hydrogen and nitrogen to obtain granular molybdenum powder with the silicon mass content of 10%; heating the molybdenum powder cooled to 200 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 600 ℃, cooled and sieved to obtain 10-50 microns of molybdenum oxide.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst. The composition and properties of the additional catalyst are shown in Table 1.
The information of the XRD spectrum of molybdenum oxide is shown in the table below, and according to the table, the molybdenum oxide has a maximum peak at 25.8 degrees 2 theta, a secondary maximum peak at 12.8 degrees and a third maximum peak at 39.1 degrees.
2θ(°) Relative intensity (I/I) 0 )×100
12.8 67
23.3 40
25.8 100
27.3 38
39.1 43
2. The catalyst was evaluated in the same manner as in example 1 and the performance results are shown in Table 2.
[ comparative example 4 ]
1. Preparation of additional catalyst
(1) The preparation method of the composition comprises the following steps:
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 56.6 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere at 610 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 950 ℃ in the atmosphere of hydrogen and nitrogen mixed gas to obtain granular molybdenum powder with the silicon mass content of 1.8%; heating the molybdenum powder cooled to 200 ℃ to 680 ℃ at a programmed heating rate of 10 ℃ per minute under an air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 675 ℃, cooled and sieved to obtain the molybdenum oxide with the diameter of 0.01-9 microns.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst. The additional catalyst composition and properties are shown in Table 1.
The XRD spectrum of the prepared molybdenum oxide is the same as that of example 1. The evaluation conditions were the same as in example 1.
The molybdenum oxide in the added catalyst has finer granularity, so that the subsequent system is blocked due to easy running loss, and the granularity distribution in the reactor bed is poor, and the fluidization effect is poor. After 3 months, the propylene conversion rate was reduced from 98.5% at the initial stage to 97.3%, the acrylonitrile selectivity was reduced from 84.1% at the initial stage to 81.1%, and the reduction tendency was remarkable, and the stability was not maintained for a long period of time.
[ comparative example 5 ]
1. Preparation of additional catalyst
(1) Process for the preparation of a composition
8.12 g of potassium hydroxide is added with 15 g of water and is dissolved after heating, thus obtaining a material I; 319.1 g of ammonium heptamolybdate (NH) 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in 300 g of hot water at 80 ℃ to obtain a material II; 109.1 g of bismuth nitrate Bi (NO) 3 ) 3 ·5H 2 O, 177.0 g of calcium nitrate Ca (NO 3 ) 2 ·4H 2 O, 242.2 g nickel Ni Nitrate (NO) 3 ) 2 ·6H 2 O, 110.1 g ferric nitrate Fe (NO) 3 ) 3 ·9H 2 O, 162.8 g of neodymium nitrate Nd (NO) 3 ) 3 ·6H 2 O is mixed, 120 g of water is added, and the mixture is heated and dissolved to be used as a material III.
Mixing the material I with 1250 g of silica sol with 40% weight concentration, adding the material II and the material III in sequence under stirring, obtaining slurry after full stirring, carrying out heat treatment on the slurry at 100 ℃ for 25 minutes, then carrying out microsphere forming on the heat-treated slurry in a spray dryer according to a conventional method, and finally roasting the slurry in a rotary roasting furnace with the inner diameter of 89 mm and the length of 1700 mm (phi 89 multiplied by 1700 mm) at 585 ℃ for 2.0 hours to obtain a catalyst composition with the average particle size of 56.6 microns, wherein the composition is as follows:
50％K 0.80 Ca 5.00 Nd 2.50 Fe 1.80 Ni 5.50 Bi 1.50 Mo 12.0 O x +50％SiO 2
(2) The preparation method of the molybdenum oxide comprises the following steps:
roasting 800 g of molybdenum concentrate containing silicon for 3 hours in an air atmosphere of a rotary oxidation furnace at 670 ℃ to perform desulfurization treatment until XRD can not detect molybdenum sulfide crystal phase; reducing at 800 ℃ in the atmosphere of a mixed gas of hydrogen and nitrogen to prepare granular molybdenum powder with the silicon mass content of 1.8%; heating the molybdenum powder cooled to 150 ℃ to 660 ℃ at a programmed heating rate of 10 ℃ per minute under the air atmosphere, and oxidizing the molybdenum powder into a molybdenum oxide precursor for 1 h; the molybdenum oxide precursor is roasted for 1 hour under the nitrogen atmosphere at 675 ℃, cooled and sieved to obtain the molybdenum oxide with the size of 50-1000 microns.
(3) 360 grams of the catalyst composition and 40 grams of molybdenum oxide were uniformly mixed to obtain a supplemental catalyst. The additional catalyst composition and properties are shown in Table 1.
The XRD spectrum of the prepared molybdenum oxide is the same as that of example 1. The evaluation conditions were the same as in example 1.
The molybdenum oxide in the added catalyst has coarse granularity, and the granularity distribution in the reactor bed layer is poor, so that the fluidization effect is poor. After 3 months, the propylene conversion rate was reduced from 98.5% at the initial stage to 96.5%, the acrylonitrile selectivity was reduced from 84.1% at the initial stage to 81.8%, and the reduction tendency was remarkable, and the stability was not maintained for a long period of time.
Table 1 composition and properties of each additional catalyst of examples and comparative examples
Table 2 performance results for each of the examples and comparative examples
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Claims (15)

1. A supplemental catalyst for maintaining long term stable production of acrylonitrile units comprising molybdenum oxide and a composition; the weight ratio of the composition to the molybdenum oxide is 4-50;
wherein the silicon mass content in the molybdenum oxide is 1% -3%; and the particle size of the molybdenum oxide is 10 micrometers-50 micrometers; the molybdenum oxide XRD spectrum information is shown in the following table:
2θ（°） relative intensity (I/I) 0 )×100 12.8±1 75-92 23.3±1 18-33 25.8±1 100 27.3±1 19-27 39.1±1 47-60
In the additional catalyst, the composition contains a carrier and an active component, wherein the active component is a Mo-Bi-Fe catalyst, and the mass ratio of Mo in the composition to Mo in the catalyst for preparing unsaturated nitrile body by ammoxidation of olefin is 2.0-1.0;
in the additional catalyst, the preparation steps of the molybdenum oxide are as follows: carrying out desulfurization treatment on molybdenum concentrate containing silicon, then carrying out reduction treatment, cooling, and oxidizing under the temperature programming condition and in the oxidizing atmosphere to obtain a molybdenum oxide precursor; and then roasting the molybdenum oxide precursor in an inert atmosphere, and sieving the roasted molybdenum oxide particles by 10-50 microns to obtain the molybdenum oxide.
2. The make-up catalyst of claim 1 wherein the active components of the composition are of the formula:
A a Q b Fe c Ni d Bi e Mo 12 O x
wherein: a is at least one selected from Li, na, K, rb and Cs elements; q includes at least one selected from Be, mg, ca, sr and Ba elements;
wherein, the value range of a is 0.01-2.50; b has a value of 0.01-15.00; c has a value range of 0.01-5.00; d has a value ranging from 1.00 to 10.00; e has a value range of 0.01-5.00; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst.
3. The supplemental catalyst of claim 1, wherein the supplemental catalyst comprises a carrier of the composition in an amount of 30-70wt% by weight, and the active component in an amount of 30-70wt% by weight; the carrier in the composition comprises at least one selected from the group consisting of silica, alumina, titania and zirconia.
4. A process for preparing a make-up catalyst according to any one of claims 1 to 3, comprising the steps of:
uniformly mixing the composition and the molybdenum oxide to obtain the additional catalyst;
in the additional catalyst, the preparation steps of the composition are as follows: respectively dissolving the compounds of the corresponding component elements in water, mixing and stirring, mixing with carrier sol to obtain catalyst slurry, spray drying the slurry, and roasting in an oxidizing atmosphere to obtain a composition;
in the additional catalyst, the preparation steps of the molybdenum oxide are as follows: carrying out desulfurization treatment on molybdenum concentrate containing silicon, then carrying out reduction treatment, cooling, and oxidizing under the temperature programming condition and in the oxidizing atmosphere to obtain a molybdenum oxide precursor; and then roasting the molybdenum oxide precursor in an inert atmosphere, and sieving the roasted molybdenum oxide particles by 10-50 microns to obtain the molybdenum oxide.
5. The method of preparing the composition according to claim 4, wherein the method further comprises, after preparing the catalyst slurry, before spray drying: a step of heat-treating the catalyst slurry; the temperature of the heat treatment is 80-150 ℃; the heat treatment time is 1-50 minutes.
6. The method according to claim 4, wherein the firing temperature is 500 to 700 ℃ and the firing time is 0.25 to 4 hours.
7. The method according to claim 4, wherein in the method for producing molybdenum oxide, the desulfurization treatment is carried out by: roasting the molybdenum concentrate containing silicon for 2-6 hours at 500-650 ℃ in oxygen-enriched or air atmosphere until the sulfur content cannot be detected.
8. The method according to claim 4, wherein the reducing atmosphere is a reducing gas having a reducing temperature of 800 to 1000 ℃.
9. The method according to claim 8, wherein in the method for producing molybdenum oxide, the reducing atmosphere is a mixture of hydrogen and an inert gas.
10. The method according to claim 4, wherein the temperature programming is 1 ℃/min-30 ℃/min, the oxidation process is 500-700 ℃ and the oxidation time is 0.5-2h.
11. The method according to claim 10, wherein the temperature programming is 5 ℃ to 20 ℃ per minute, and the oxidation process is 655 to 700 ℃.
12. Use of the supplemental catalyst according to any of claims 1-4 in the ammoxidation of propylene to acrylonitrile.
13. The use according to claim 12, comprising adding the additional catalyst to the reaction system for the ammoxidation of propylene to acrylonitrile in a continuous manner.
14. The use according to claim 12, wherein the additional catalyst is added at a rate of 0.3 to 0.7 kg/ton acrylonitrile, the additional catalyst controlling the bed catalyst density to 330 to 520kg/m 3 。
15. The use according to claim 12, wherein the reaction temperature is 410-460 ℃; the molar ratio of propylene to ammonia to oxygen is 1 (1.05-1.35) to 1.7-2.5; the WWH of the catalyst load is 0.04-0.12h -1 The method comprises the steps of carrying out a first treatment on the surface of the The reaction pressure is 30-100KPa.
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