CN116020545A - Ammonia oxidation catalyst containing molecular sieve, preparation method and application thereof - Google Patents
Ammonia oxidation catalyst containing molecular sieve, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an ammoxidation catalyst containing a molecular sieve, a preparation method thereof and application thereof in an aromatic nitrile preparation reaction by aromatic ammoxidation. The catalyst comprises an active molecular sieve, a carrier and an optional auxiliary agent, wherein the active molecular sieve is prepared from a composite oxide molecular sieve comprising V, al, P and optional heteroatom elements, and the heteroatom elements are at least one selected from Si, ti, fe, ni, sn and Cr. The catalyst has better reaction performance and better wear resistance, and is used for preparing the aromatic nitrile by aromatic hydrocarbon gas-phase ammoxidation, and the yield of the aromatic nitrile is higher.
Description
Technical Field
The invention belongs to the technical field of preparation of ammonia oxidation catalysts, and particularly relates to an ammonia oxidation catalyst containing a molecular sieve, and a preparation method and application thereof.
Background
The cyano-substituted aromatic hydrocarbon is also called as an aromatic nitrile compound, has wide application in the fields of medicines, pesticides, fine chemical industry, high polymers and the like, and is an important chemical raw material. The aromatic nitrile can be synthesized by two routes of an ammoxidation method and a chemical method. The ammoxidation method is a production means which is most suitable for industrialized preparation of the aromatic nitrile, and the nitrile is obtained by one step under the action of a catalyst in the presence of oxygen and ammonia. The gas phase ammoxidation of aromatic hydrocarbon features that the main and side reactions are both strong exothermic reactions, so that the selection of active components of catalyst and corresponding reaction process and reactor is important. The fluidized bed reaction system has the advantages of high heat and mass transfer efficiency, small amplification effect and the like, is suitable for chemical processes with high heat removal requirements such as aromatic hydrocarbon gas-phase ammoxidation, but the catalyst in the fluidized bed reactor is in a high-speed flowing state, and the fluidization quality control and the catalyst wear resistance strength are required to meet high requirements, so that besides the reaction performance, the strength and the wear resistance of the catalyst are core indexes for ensuring that the catalyst is applied to the reaction field.
As the active phase of the fluidized bed catalyst for preparing the aromatic nitrile by aromatic hydrocarbon gas-phase ammoxidation, vanadium oxide is the most mature and effective system, but the single-component vanadium oxide is used as the active component of the catalyst to react too severely and has poor selectivity, so that a modified component needs to be further added to prepare a composite oxide system such as V-P, V-Cr, sb-Fe and the like, and alumina, silicon carbide and silicon oxide are used as carriers to prepare spherical particles with different particle sizes, and the spherical particles are used in a fluidized bed reactor. The initial gas phase ammoxidation catalyst usually only uses an oxide system with less components, such as V-Cr-O, V-P-O, as the catalyst, so that the problems of too deep oxidation degree and low selectivity of the catalyst exist, and the strength index of the catalyst is poor. With the deep research of the field of aromatic hydrocarbon ammoxidation, the improved multicomponent vanadium oxide catalyst is widely adopted at present, and the addition of different auxiliary agents improves the performance of the catalyst from various aspects such as aromatic nitrile selectivity, catalyst strength and the like. In the 80 s of the 20 th century, the Mitsubishi gas company of Japan promoted V-Cr-B-Mo and V-Cr-B-P system catalysts, and then in the 90 s promoted V-Cr-B-P-Mo five-component catalysts to improve the reaction selectivity, the BASF reported K, fe and W modified V-Sb fixed bed catalysts, the Shanghai petrochemical institute developed multielement modified fluidized bed catalysts based on V-Cr system, and the isophthalonitrile molar yield was about 78.8%. However, the oxide is used as a catalyst, so that there is room for improvement in wear resistance and reactivity, and adaptability to various aromatic hydrocarbon raw materials is still to be enhanced.
Disclosure of Invention
The invention aims to develop a catalyst with better reaction performance and better wear resistance for preparing nitrile by ammoxidation, particularly for preparing aromatic nitrile by aromatic hydrocarbon gas-phase ammoxidation, and a preparation method thereof. The catalyst has obvious molecular sieve crystal phase structure, simple preparation process, capacity of regulating the performance of the catalyst via regulating the doping amount of hetero atom, high adaptability to various material and product, high strength and high aromatic nitrile yield.
To this end, a first aspect of the present invention provides a molecular sieve-containing ammoxidation catalyst comprising an active molecular sieve, a support and optionally an adjunct, the active molecular sieve being made from a composite oxide molecular sieve comprising V, al, P and optionally a heteroatom element selected from at least one of Si, ti, fe, ni, sn and Cr.
According to some embodiments of the invention, the active molecular sieve and the support are present in a mixed state, which means that the active molecular sieve is uniformly dispersed in the support or the support is uniformly dispersed in the active molecular sieve. In embodiments where an adjunct is present, the adjunct element is uniformly dispersed in the mixture of the support and the active molecular sieve.
According to some embodiments of the invention, the catalyst has an average particle size of 40-100 μm, e.g., 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, and any value in between.
According to some embodiments of the invention, the active molecular sieve comprises at least one of an AFI-configured molecular sieve, an AEL-configured molecular sieve, a CHI-configured molecular sieve, and an MFI-configured molecular sieve.
According to some embodiments of the invention, the auxiliary agent is selected from at least one of the group W, mo, B, te, IA elements and group IIA elements and their oxides.
According to some embodiments of the invention, the support is selected from the group consisting of SiO 2 、Al 2 O 3 、TiO 2 、ZrO 2 At least one of MgO and molecular sieves.
According to some embodiments of the invention, the active molecular sieve is present in an amount of 10 to 70wt%, based on the total weight of the catalyst.
According to some embodiments of the invention, the promoter is present in an amount of 0 to 10wt%, based on the total weight of the catalyst.
According to some embodiments of the invention, the support is present in an amount of 30 to 90wt%, based on the total weight of the catalyst.
According to some embodiments of the invention, the mole ratio of V to Al atoms in the composite oxide molecular sieve is (0.01-1): 1.
According to some embodiments of the invention, the mole ratio of P to Al atoms in the composite oxide molecular sieve is (0.8-1.2): 1.
According to some embodiments of the invention, the molar ratio of the heteroatom element to Al in the composite oxide molecular sieve is (0 to 0.8): 1.
according to some preferred embodiments of the present invention,the composite oxide molecular sieve comprises a molecular sieve having the general formula xV 2 O 5 ·Al 2 O 3 ·yP 2 O 5 ·zM·wH 2 And O, wherein M is the heteroatom element, x=0.05-0.5, y=0.9-1.1, z=0-0.4 and w=30-70.
According to some embodiments of the invention, the active molecular sieve is made from the composite oxide molecular sieve by a hydrothermal treatment that results in an XRD crystalline retention of 20-90% of the composite oxide molecular sieve.
According to some embodiments of the invention, the hydrothermal treatment utilizes air for the hydrothermal treatment.
According to some embodiments of the invention, the water vapor treatment is carried out by passing through a gas stream having a water vapor content of 50-100%. Wherein the water vapor content is the total mole content of water vapor in the air flow. The other gas in the gas stream is not specifically limited so long as the purpose of the hydrothermal treatment can be achieved, and for example, the other gas in the gas stream may be air.
According to some embodiments of the invention, the temperature of the hydrothermal treatment is 450-750 ℃.
According to some embodiments of the invention, the hydrothermal treatment is for a time period of 1-8 hours.
The manner of the hydrothermal treatment according to the present invention is not particularly limited, and as long as the hydrothermal treatment can be performed, a conventional hydrothermal treatment method in the art may be employed, for example, the drying of the composite oxide molecular sieve may be performed in a tube furnace or a muffle furnace into which a water vapor atmosphere is introduced.
According to some preferred embodiments of the invention, the active molecular sieve is a V, si doped phosphorus aluminum molecular sieve having an AFI, AEL structure.
According to some preferred embodiments of the present invention, the composite oxide molecular sieve is produced by a process comprising the steps of:
(1) Mixing a vanadium source, an aluminum source, a phosphorus source and optionally the heteroatom source with water to form a mixed solution I;
(2) Mixing a template agent with the mixed solution I to form a mixed solution II;
(3) Aging and crystallizing the mixed solution II, cooling, performing solid-liquid separation, and drying to obtain the composite oxide molecular sieve;
according to some embodiments of the present invention, the amount of vanadium source, aluminum source, phosphorus source, and optionally the heteroatom source added during the preparation of the composite oxide molecular sieve is calculated as the gel oxide molar ratio V during hydrothermal synthesis 2 O 5 :Al 2 O 3 :P 2 O 5 :M:R:H 2 O＝0.01～1:1:0.8～1.2:0～0.8:0.5～5:20～100。
According to some embodiments of the invention, the amount of water added in step (1) is in combination with the vanadium source, aluminum source, phosphorus source and optionally a heteroatom source, wherein V 2 O 5 、Al 2 O 3 、P 2 O 5 And the molar ratio of the total amount of the hetero atoms is (2.5 to 67): 1.
according to some embodiments of the invention, the amount of water used in step (1) is (20-100) in molar ratio to the aluminium in the aluminium source: 1.
according to some embodiments of the invention, the molar ratio of the amount of template added in step (2) to Al in the aluminum source is (0.5-4.5): 1.
according to some embodiments of the invention, in step (1), the vanadium source, the aluminum source, the phosphorus source and optionally the heteroatom source are added to water, wherein the order of their addition to water is not specifically limited, so that they can be mixed with water to form a mixed solution. In some preferred embodiments, the aluminum source, the vanadium source (or heteroatom source), the heteroatom source (or vanadium source), and the phosphorus source are added sequentially to the water.
According to some embodiments of the invention, the vanadium source is selected from at least one of an oxide of vanadium, a salt of vanadium, and an organic compound containing vanadium, such as V 2 O 5 Sodium metavanadate, sodium vanadate, ammonium metavanadate, vanadyl oxalate and the like.
According to some embodiments of the invention, the aluminum source is selected from at least one of aluminum salts, aluminum oxides, aluminum hydroxides, and aluminum-containing organic compounds, such as pseudo-boehmite, aluminum isopropoxide, aluminum hydroxide, activated alumina, and the like.
According to some embodiments of the invention, the phosphorus source is selected from at least one of a phosphorus-containing acid, a phosphorus-containing salt, and a phosphorus oxide, such as phosphoric acid, monoammonium phosphate, pyrophosphoric acid, and the like.
According to some embodiments of the invention, the heteroatom is selected from acids, oxides and organic compounds containing the heteroatom which are soluble or homogeneously dispersible in water, the heteroatom being selected from at least one of Si, ti, fe, ni, sn and Cr, for example silica sol, tiCl 4 N-butyl titanate, ferric nitrate, nickel nitrate, stannic chloride, chromium nitrate and the like.
According to some embodiments of the invention, the templating agent is a nitrogen-containing organic compound, preferably at least one of an organic amine templating agent and an organic ammonium templating agent, such as at least one of triethylamine, diethylamine, di-n-propylamine, tripropylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.
According to some embodiments of the present invention, the manner and time of mixing in steps (1) and (2) are not specifically limited, and may be selected from methods conventional in the art, provided that the added raw materials are sufficiently mixed to form a mixed solution. In some embodiments, the mixed solution is formed by continuous stirring.
According to some embodiments of the invention, the temperature of the aging in step (3) is 75-95 ℃.
According to some embodiments of the invention, the aging time in step (3) is 1-8 hours.
According to some embodiments of the invention, the crystallization in step (3) is performed at a temperature of 140-220 ℃.
According to some embodiments of the invention, the crystallization in step (3) is for a period of 8-48 hours.
According to some embodiments of the invention, the crystallization is performed in a crystallization kettle.
The manner of solid-liquid separation, washing and drying in the step (3) is not particularly limited, and the solid-liquid separation and solvent removal may be carried out by a method conventional in the art, in accordance with the present invention, so as to obtain a dried final composite oxide molecular sieve solid. In some embodiments, the drying is performed by drying at 80-120 ℃ for 4-8 hours.
In a second aspect, the present invention provides a method for preparing a catalyst according to the first aspect of the present invention, comprising the steps of:
step (a): mixing an active molecular sieve with water to obtain a mixed solution a;
optional step (b): mixing the mixed solution a with an auxiliary compound to obtain a mixed solution b;
step (c): mixing the mixed solution a or the mixed solution b with a carrier to obtain a mixed solution c;
step (d): and (3) carrying out spray forming on the mixed solution c to obtain catalyst precursor particles, and roasting to obtain the catalyst.
Step (e): and forming the obtained catalyst precursor particles to obtain the catalyst.
According to some embodiments of the present invention, the active molecular sieve in step (a) may be a milled active molecular sieve powder, the particle size of which is not specifically limited, so as to facilitate uniform dispersion in water.
According to some embodiments of the invention, in step (a), the amount of water added is not specifically defined, and depends on the concentration required for subsequent spray forming. According to some preferred embodiments of the invention, the water is used in such an amount that the total weight of the dry basis of the raw materials added in step (a), optionally step (b) and step (c) is 20-50% by weight of the total weight of the resulting mixed liquor c. In some embodiments, the total dry weight of the added raw materials is active molecular sieve powder, siO in the carrier 2 And the total weight of the oxide form of the auxiliary compound.
According to the invention, the auxiliary compound is a salt, oxide or organic compound of the auxiliary that is capable of being dissolved or homogeneously dispersed in water.
According to some embodiments of the invention, specific examples of the starting materials for the carrier include, but are not limited toNot limited to silica sol, alumina sol, pseudo-boehmite, rutile/anatase TiO 2 And meta-titanic acid.
According to some embodiments of the invention, in step (c), the mixing is performed in a colloid mill to uniformly disperse the carrier in the mixed liquid b to form the mixed liquid c.
According to some embodiments of the invention, the spray-formed outlet temperature is 150-200 ℃.
According to some embodiments of the invention, the firing temperature is 400-700 ℃.
According to some embodiments of the invention, the firing time is from 6 to 12 hours.
According to the invention, the active molecular sieve containing the active component is synthesized in situ and is subjected to further hydrothermal treatment to form the active molecular sieve with good crystallization performance, so that the combination degree of the active component and the molecular sieve is reduced, the wear resistance of the ammoxidation catalyst is improved, and meanwhile, the better catalytic performance is ensured.
In a third aspect, the present invention provides the use of a catalyst according to the first aspect of the present invention and/or a catalyst prepared according to the second aspect of the present invention in the ammoxidation of aromatic hydrocarbons to give aromatic nitriles, in particular in the gas phase ammoxidation of aromatic hydrocarbons to give aromatic nitriles.
According to some embodiments of the invention, the aromatic hydrocarbon is a monomethyl-substituted aromatic hydrocarbon, a polymethylsubstituted aromatic hydrocarbon, or a methyl-substituted organic compound containing a similar aromatic ring.
According to the present invention, the methyl-substituted organic compound having an aromatic-like ring means an organic compound in which a parent ring is at least one carbon on a benzene ring, preferably 1 to 3 carbons are substituted with a hetero atom such as nitrogen, oxygen, sulfur, and hydrogen attached to the parent ring is substituted with a methyl group, such as 2-methylpyridine, 3-methylpyridine, 2-methylpyrazine, etc.
According to some embodiments of the invention, the aromatic hydrocarbons are toluene, meta-xylene, ortho-xylene, and 3-methylpyridine.
According to some embodiments of the invention, the application comprises the steps of reacting an aromatic hydrocarbon, an oxygen source, and NH 3 The reaction is carried out in the presence of the catalystThe aromatic nitrile is prepared.
According to some embodiments of the invention, the oxygen source is an oxygen-containing gas, such as oxygen, air, or the like.
According to some embodiments of the invention, the concentration of aromatic hydrocarbon in the feed mixture is 0.1-10% vol, preferably in the range of 0.2-5% vol, when air is used as the oxygen source for the reaction.
According to some embodiments of the invention, in the reaction, NH 3 The ratio of the number of moles of feed to the number of moles of aromatic hydrocarbon is more than 1 time the stoichiometric theoretical value of the reaction, preferably in the range of 2.5 to 12 times.
According to some embodiments of the invention, the ratio of moles of oxygen feed to moles of aromatic hydrocarbon is more than 2 times the stoichiometric theoretical value of the reaction occurring, preferably ranging from 4 to 15 times. Typically too low an oxygen content will result in lower conversion of the reaction, while too high an oxygen content will result in increased product of the deep oxidation reaction, both of which will reduce the yield of aromatics.
According to some embodiments of the invention, the temperature of the reaction is 350-450 ℃. The inventor finds in experiments that the reaction conversion rate is lower when the reaction temperature is lower than 350 ℃; when the reaction temperature is higher than 450 ℃, the deep oxidation is aggravated, COx, HCN and demethylated products are generated by the reaction, and NH 3 Greatly increases oxidation and reduces aromatic hydrocarbon yield.
According to some embodiments of the invention, the gas phase ammoxidation reaction system is at atmospheric pressure, while a pressurized system may also be suitable.
According to some preferred embodiments of the invention, the reaction is carried out in a fluidized bed reactor.
According to the invention, the catalyst can be applied to a fluidized bed reactor with common design, generally only the fluidization quality is required to be ensured, abnormal fluidization phenomena such as channeling, bubbles, slugging and the like are avoided as much as possible, and meanwhile, the back mixing degree of air flow is reduced, so that the higher product yield can be ensured.
Compared with the prior art, the invention has the following advantages:
(1) The catalyst has higher reaction performance and better wear resistance.
(2) The invention can adjust the composition of the active molecular sieve according to different aromatic hydrocarbon raw materials, is applicable to the gas-phase ammoxidation of various aromatic hydrocarbon compounds, optimizes the reaction performance of the catalyst, and can keep the yield of the aromatic nitrile at a higher level and obtain good technical effect when being used for preparing the aromatic nitrile by the gas-phase ammoxidation of the aromatic hydrocarbon.
Drawings
Fig. 1 is the XRD characterization result of the catalyst in example 1.
Detailed Description
In order that the invention may be more readily understood, the invention will be described in detail below with reference to the following examples and the accompanying drawings, which are provided for illustration only and are not to be construed as limiting the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The materials used in the examples, unless otherwise specified, are commercially available products or conventional products which can be synthesized by known methods.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The data measurement or calculation method in the embodiment of the invention is as follows:
1. in the embodiment of the invention, the aromatic hydrocarbon conversion rate, the aromatic nitrile selectivity and the aromatic nitrile yield are defined as follows:
2. the method for measuring and calculating the crystallization retention degree comprises the following steps: obtaining XRD spectrum of molecular sieve sample by X-ray powder diffraction method, fine scanning 2 theta=20-30 deg. to obtain spectrum of characteristic peak at 3 position in the range, and calculating total area A by integral mode 1 And with the total area A of the sample with higher crystallinity 0 Comparing to obtain A 1 /A 0 The crystallinity retention for the samples.
3. The method for measuring and calculating the catalyst attrition rate comprises the following steps: the catalyst was loaded in the attrition tester using the straight tube test method and a gas stream was introduced, followed by a continuous 5 hour test to remove the first 1 hour attrition, followed by a 4 hour average percent attrition per hour as attrition index.
4. Catalyst evaluation was carried out using
The reaction was carried out in a fluidized bed reactor having a length of 1800mm, a catalyst loading of 550g and a reaction system pressure of 0.01MPa.
Example 1
1. Preparation of the catalyst
Using triethylamine as a template agent, pseudo-boehmite as an aluminum source, 85% phosphoric acid as a P source, silica sol as a silicon source, and a catalyst prepared by the following steps of 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.2:1:1.1:0.25:1.5:50 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Triethylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 90℃for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 180deg.C for 16 hr to obtain AFI structure molecular sieve, filtering, washing, drying, and performing hydrothermal treatment at 450deg.C for 2 hr. The crystallinity retention of the obtained product is 65% of the molecular sieve raw powder before the hydrothermal treatment.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in water required to prepare the catalyst to give a dispersed slurry, wherein the slurry dry basis content was 25wt%.
According to SiO 2 Weighing silica sol accounting for 50wt% of the mass of the catalyst, mixing the silica sol with dispersion slurry containing molecular sieve, then introducing the mixture into a colloid mill for grinding treatment, introducing the treated slurry into a spray dryer, drying the sprayed catalyst fine particles at 120 ℃ for 12 hours, and roasting the catalyst fine particles at 550 ℃ for 8 hours, wherein the average particle size of the catalyst is 90 mu m.
2. Catalyst performance evaluation:
the reaction raw material is m-xylene mX
The molar ratio of the feed is mX to NH 3 :O 2 Catalyst loading 0.070h =1:8:8 -1 。
The reaction temperature was 425 ℃.
Reaction results:
the conversion of meta-xylene is 99.7%;
isophthalonitrile selectivity 81.0%;
the yield of isophthalonitrile was 80.8%.
The catalyst attrition rate was 1.1%.
Example 2
1. Preparation of the catalyst
Using triethylamine as a template agent, pseudo-boehmite as an aluminum source, 85% phosphoric acid as a P source, silica sol as a silicon source, V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.2:1:1.1:0.1:1.5:50 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Triethylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 95℃for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 180deg.C for 14 hr to obtain AFI structure molecular sieve, filtering, washing, drying, and performing hydrothermal treatment at 450deg.C for 2 hr. The crystallinity retention of the obtained product is 76% of the original powder before treatment.
The molecular sieve sample was weighed at 49.8wt% based on the mass of the catalyst and dispersed in water required to prepare the catalyst to obtain a dispersed slurry, wherein the dry content of the slurry was 25wt%.
According to SiO 2 Weighing silica sol accounting for 49.8 weight percent of the mass of the catalyst, and adding TeO 3 Tellurium acid accounting for 0.4wt% of the total mass of the catalyst is mixed with dispersing slurry containing molecular sieve, then the mixture is introduced into a colloid mill for grinding treatment, the treated slurry is introduced into a spray dryer, the outlet temperature of the dryer is 180 ℃, the sprayed catalyst fine particles are dried for 12 hours at 120 ℃, and the catalyst fine particles are roasted for 8 hours at 550 ℃, and the average particle size of the catalyst is 85 mu m.
2. Catalyst performance evaluation:
the reaction raw material is m-xylene mX
The molar ratio of the feed is mX to NH 3 :O 2 =1:10:8, catalyst loading 0.080h -1 。
The reaction temperature was 415 ℃.
Reaction results:
meta-xylene conversion 92.1%;
m-methylbenzonitrile selectivity 53.5%;
the yield of m-tolunitrile was 49.3%.
The catalyst attrition rate was 1.3%.
Example 3
1. Preparation of the catalyst
Din-propylamine is used as a template agent, pseudo-boehmite is used as an aluminum source, 85% phosphoric acid is used as a P source, silica sol is used as a silicon source, and V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.3:1:1.1:0.3:1.5:40 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Di-n-propylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 95℃for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 170 ℃ for 24 hours, filtering, washing and drying the molecular sieve product, and performing hydrothermal treatment at 500 ℃ for 3 hours. The crystallinity retention of the obtained product is 68% of the raw powder before treatment.
Molecular sieve samples are weighed according to the weight percentage accounting for 50 percent of the mass of the catalyst, and are dispersed into water required for preparing the catalyst to obtain dispersed slurry, wherein the dry basis content of the slurry is 30 percent.
According to SiO 2 Weighing silica sol accounting for 50wt% of the mass of the catalyst, mixing the silica sol with dispersion slurry containing molecular sieve, then introducing the mixture into a colloid mill for grinding treatment, introducing the treated slurry into a spray dryer, drying the sprayed catalyst fine particles at 120 ℃ for 12 hours at the outlet temperature of 180 ℃, and roasting the catalyst fine particles at 600 ℃ for 4 hours, wherein the average particle size of the catalyst is 80 mu m.
2. Catalyst performance evaluation:
the reaction raw material is toluene T
The molar ratio of the feed is T to NH 3 :O 2 =1:6:8, catalyst loading 0.060h -1 。
The reaction temperature was 425 ℃.
Reaction results:
toluene conversion 99.5%;
m-methylbenzonitrile selectivity 83.5%;
the yield of m-tolunitrile was 83.1%.
The catalyst attrition rate was 1.4%.
Example 4
1. Preparation of the catalyst
Tetraethylammonium hydroxide is used as a template agent, pseudo-boehmite is used as an aluminum source, 85% phosphoric acid is used as a P source, silica sol is used as a silicon source, V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.3:1:1:0.1:1.2:60 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Tetraethylammonium hydroxide was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 85 ℃ for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 180deg.C for 10 hr to obtain AFI structure molecular sieve, filtering, washing, drying, and performing hydrothermal treatment at 550deg.C for 4 hr. The crystallinity retention of the obtained product is 50% of the original powder before treatment.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in water required to prepare the catalyst to give a dispersed slurry, wherein the slurry dry basis content was 35wt%.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in the water required to prepare the catalyst.
According to SiO 2 Weighing silica sol accounting for 50wt% of the mass of the catalyst, mixing the silica sol with dispersion slurry containing molecular sieve, then introducing the mixture into a colloid mill for grinding treatment, introducing the treated slurry into a spray dryer, drying the sprayed catalyst fine particles at 120 ℃ for 12 hours at the outlet temperature of 170 ℃, and roasting the catalyst fine particles at 550 ℃ for 4 hours, wherein the average particle size of the catalyst is 80 mu m.
2. Catalyst performance evaluation:
the reaction raw material is 3-methylpyridine (3-Picoline)
The molar ratio of the feed is 3-Picoline to NH 3 :O 2 Catalyst negative = 1:5:6Charge 0.070h -1 。
The reaction temperature was 380 ℃.
Reaction results:
3-methylpyridine conversion 99.8%;
3-cyanopyridine selectivity 94.5%;
the yield of 3-cyanopyridine was 94.3%.
The catalyst attrition rate was 1.3%.
Example 5
1. Preparation of the catalyst
Using triethylamine as a template agent, pseudo-boehmite as an aluminum source, 85% phosphoric acid as a P source, silica sol as a silicon source, V 2 O 5 :Al 2 O 3 :P 2 O 5 :R:H 2 Molecular sieve gels were prepared with o=0.2:1:1.1:1.5:50 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Triethylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 85 ℃ for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 180deg.C for 18 hr to obtain AFI structure molecular sieve, filtering, washing, drying, and performing hydrothermal treatment at 600deg.C for 2 hr. The crystallinity retention of the obtained product is 47% of the raw powder before treatment.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in water required to prepare the catalyst to give a dispersed slurry, wherein the slurry dry basis content was 35wt%.
Molecular sieve samples were weighed at 49wt% of the catalyst mass and dispersed in the water needed to prepare the catalyst.
According to SiO 2 Weighing silica sol accounting for 49wt% of the mass of the catalyst, and adding MoO 3 Ammonium molybdate accounting for 0.5 percent of the total mass of the catalyst and Sb 2 O 3 0.5wt% of total catalyst mass of potassium antimonate and molecular sieveAfter the dispersion slurry is mixed, the mixture is introduced into a colloid mill for grinding treatment, the treated slurry is introduced into a spray dryer, the outlet temperature of the dryer is 180 ℃, the sprayed catalyst fine particles are dried for 12 hours at 120 ℃, and the catalyst fine particles are roasted for 8 hours at 560 ℃, wherein the average particle diameter of the catalyst is 90 mu m.
2. Catalyst performance evaluation:
the reaction raw material is o-xylene mX
The feed ratio is mX: NH 3 :O 2 =1:12:8, catalyst loading 0.080h -1 。
The reaction temperature was 415 ℃.
Reaction results:
the conversion of o-xylene is 95.6%;
phthalonitrile selectivity 77.4%;
the yield of m-tolunitrile was 74.0%.
The catalyst attrition rate was 1.4%.
Example 6
1. Preparation of the catalyst
Using triethylamine as a template agent, pseudo-boehmite as an aluminum source, 85% phosphoric acid as a P source, silica sol as a silicon source, V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.2:1:1:0.2:2.7:62 ratio (R is template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Triethylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 85 ℃ for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 190 deg.c for 16 hr to obtain CHI structure molecular sieve, filtering, washing and drying to obtain molecular sieve product, and hydrothermal treating at 450 deg.c for 3 hr. The crystallinity retention of the obtained product is 71% of the raw powder before treatment.
Molecular sieve samples are weighed according to the weight percentage accounting for 50 percent of the mass of the catalyst, and are dispersed into water required for preparing the catalyst to obtain dispersed slurry, wherein the dry basis content of the slurry is 30 percent.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in the water required to prepare the catalyst.
According to SiO 2 Weighing silica sol accounting for 50wt% of the mass of the catalyst, mixing the silica sol with dispersion slurry containing molecular sieve, then introducing the mixture into a colloid mill for grinding treatment, introducing the treated slurry into a spray dryer, drying the sprayed catalyst fine particles at 120 ℃ for 12 hours, and roasting the catalyst fine particles at 550 ℃ for 8 hours, wherein the average particle size of the catalyst is 90 mu m.
2. Catalyst performance evaluation:
the reaction raw material is m-xylene mX
The feed ratio is mX: NH 3 :O 2 Catalyst loading 0.070h =1:8:8 -1 。
The reaction temperature was 425 ℃.
Reaction results:
the conversion of meta-xylene is 99.2%;
isophthalonitrile selectivity 78.8%;
the yield of isophthalonitrile was 78.2%.
The catalyst attrition rate was 1.2%.
Example 7
1. Preparation of the catalyst
Using triethylamine as a template agent, pseudo-boehmite as an aluminum source, 85% phosphoric acid as a P source, silica sol as a silicon source, V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 :R:H 2 Molecular sieve gels were prepared with o=0.2:1:1.1:0.25:1.5:50 ratio (R as template). The method comprises the following specific steps:
(1) Adding pseudo-boehmite and V into water in turn under stirring 2 O 5 And mixing with phosphoric acid.
(2) Triethylamine was added dropwise to give a gel precursor.
(3) After aging the gel precursor at 90℃for 4 hours, it was transferred to a stainless steel kettle.
(4) Crystallizing at 180 deg.c for 16 hr to obtain AFI structure molecular sieve, and vacuum filtering, washing and drying to obtain the final product.
Molecular sieve samples were weighed at 50wt% of the catalyst mass and dispersed in water required to prepare the catalyst to give a dispersed slurry, wherein the slurry dry basis content was 25wt%.
According to SiO 2 Weighing silica sol accounting for 50wt% of the mass of the catalyst, mixing the silica sol with dispersion slurry containing molecular sieve, then introducing the mixture into a colloid mill for grinding treatment, introducing the treated slurry into a spray dryer, drying the sprayed catalyst fine particles at 120 ℃ for 12 hours at the outlet temperature of 180 ℃, and roasting the catalyst fine particles at 550 ℃ for 8 hours, wherein the average particle size of the catalyst is 110 mu m.
2. Catalyst performance evaluation:
the reaction raw material is m-xylene mX
The feed ratio is mX, NH3 and O 2 Catalyst loading was 0.070h-1 =1:8:8.
The reaction temperature was 425 ℃.
Reaction results:
the conversion of meta-xylene is 99.3%;
isophthalonitrile selectivity 79.5%;
the yield of isophthalonitrile was 78.9%.
The catalyst attrition rate was 1.2%.
Comparative example 1
1. Preparation of the catalyst
Respectively by V 2 O 5 、Al(OH) 3 、H 3 PO 4 Ethyl orthosilicate as raw material, oxalic acid is added to aid dissolution according to V 2 O 5 :Al 2 O 3 :P 2 O 5 :SiO 2 The active phase was prepared in a ratio of =0.2:1:1:0.2. Mixing the raw materials to obtain the blue slurry. According to the adding amount of the active phase and the silica sol being 1:1, further adding the silica sol, slowly adding the silica sol into the solution under the stirring condition to obtain mixed slurry, heating and evaporating under the stirring condition, and controlling the solid content to be 35％。
The slurry is spray dried and formed, the gas inlet temperature of a spray dryer is 300 ℃, the gas outlet temperature is 180 ℃, the sprayed catalyst fine particles are dried for 12 hours at 120 ℃, and are roasted for 8 hours at 550 ℃, and the average particle size of the catalyst is 150 mu m.
2. Catalyst performance evaluation:
the reaction raw material is m-xylene mX
The feed ratio is mX, NH3 and O 2 Catalyst loading 0.060h-1 =1:8:8.
The reaction temperature was 425 ℃.
Reaction results:
the conversion of meta-xylene is 99.3%;
isophthalonitrile selectivity 66.5%;
the yield of isophthalonitrile was 66.2%.
It should be noted that the above-described embodiments are only for explaining the present invention and do not constitute any limitation of the present invention. The invention has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the invention as defined in the appended claims, and the invention may be modified without departing from the scope and spirit of the invention. Although the invention is described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, as the invention extends to all other means and applications which perform the same function.
Claims (10)
1. A molecular sieve-containing ammoxidation catalyst comprising an active molecular sieve, a carrier and optionally an auxiliary agent, wherein the active molecular sieve is prepared from a composite oxide molecular sieve comprising V, al, P and optionally a heteroatom element, and the heteroatom element is at least one selected from Si, ti, fe, ni, sn and Cr.
2. The catalyst according to claim 1, characterized in that the average particle size of the catalyst is 40-110 μm.
3. The catalyst of claim 1 or 2, wherein the active molecular sieve comprises at least one of an AFI-configured molecular sieve, an AEL-configured molecular sieve, a CHI-configured molecular sieve, and an MFI-configured molecular sieve; and/or the auxiliary agent is selected from at least one of W, mo, B, te, IA group element and IIA group element and oxides thereof; and/or the carrier is selected from SiO 2 、Al 2 O 3 、TiO 2 、ZrO 2 At least one of MgO and a molecular sieve type carrier;
preferably, the active molecular sieve is present in an amount of 10 to 70wt% and/or the adjunct is present in an amount of 0 to 10wt% and/or the support is present in an amount of 30 to 90wt%, based on the total weight of the catalyst.
4. The catalyst according to any one of claims 1 to 5, wherein the molar ratio of V to Al atoms in the composite oxide molecular sieve is (0.01 to 1): 1, and/or the molar ratio of P to Al atoms in the composite oxide molecular sieve is (0.8 to 1.2): 1, and/or the molar ratio of the heteroatom element to Al in the composite oxide molecular sieve is (0 to 0.8): 1, a step of;
preferably, the composite oxide molecular sieve comprises a molecular sieve having the general formula xV 2 O 5 . Al 2 O 3 . yP 2 O 5 . zM . wH 2 And O, wherein M is the heteroatom element, x=0.05-0.5, y=0.9-1.1, z=0-0.4 and w=30-70.
5. The catalyst of any one of claims 1-4, wherein the active molecular sieve is prepared from the composite oxide molecular sieve by a hydrothermal treatment that results in an XRD crystalline retention of the resulting active molecular sieve of 20-90% of the composite oxide molecular sieve;
preferably, the water vapor content of the hydrothermal treatment is 50-100%, and/or the temperature of the hydrothermal treatment is 450-750 ℃, and the time of the hydrothermal treatment is 1-8h.
6. The catalyst of any one of claims 1-5, wherein the composite oxide molecular sieve is produced by a process comprising the steps of:
(1) Mixing a vanadium source, an aluminum source, a phosphorus source and optionally a heteroatom source with water to form a mixed solution I;
(2) Mixing a template agent with the mixed solution I to form a mixed solution II;
(3) Aging and crystallizing the mixed solution II, cooling, performing solid-liquid separation, and drying to obtain the composite oxide molecular sieve;
preferably, the amount of water added in step (1) is in combination with the vanadium source, aluminum source, phosphorus source and optionally a heteroatom source, wherein V 2 O 5 、Al 2 O 3 、P 2 O 5 And the molar ratio of the total amount of the hetero atoms is (2.5 to 67): 1, preferably the amount of water to the aluminum in the aluminum source is (20-100) in molar ratio: 1 and/or the molar ratio of the template agent to Al in the aluminum source in step (2) is (0.5-4.5): 1, a step of;
more preferably, the temperature of the aging is 75-95 ℃, the time of the aging is 1-8 hours, and/or the temperature of the crystallization is 140-220 ℃, and the time of the crystallization is 8-48 hours.
7. The catalyst according to claim 6, wherein the vanadium source is selected from at least one of vanadium oxides, vanadium salts and vanadium-containing organic compounds, and/or the aluminum source is selected from at least one of aluminum salts, aluminum oxides, aluminum hydroxides and aluminum-containing organic compounds, and/or the phosphorus source is selected from at least one of phosphoric acid, phosphorus-containing salts and phosphorus-containing oxides, and/or the heteroatom is selected from acids, oxides and organic compounds containing the heteroatom which are soluble or homogeneously dispersible in water, and/or the templating agent is a nitrogen-containing organic compound, preferably at least one of an organic amine templating agent and an organic ammonium templating agent, such as at least one of triethylamine, diethylamine, di-n-propylamine, tripropylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.
8. The method for preparing a catalyst according to any one of claims 1 to 7, comprising the steps of:
step (a): mixing an active molecular sieve with water to obtain a mixed solution a;
optional step (b): mixing the mixed solution a with an auxiliary compound to obtain a mixed solution b;
step (c): mixing the mixed solution a or the mixed solution b with a carrier to obtain a mixed solution c;
step (d): spraying and forming the mixed solution c to obtain catalyst precursor particles, and roasting to obtain the catalyst;
step (e): and forming the obtained catalyst precursor particles to obtain the catalyst.
9. The process according to claim 9, wherein in step (a) the water is used in such an amount that the total weight of the dry basis of the raw materials added in step (a), optional step (b) and step (c) is 20-50% by weight based on the total weight of the obtained mixed liquor c; and/or the mixing of step (c) is performed by a colloid mill;
preferably, the outlet temperature of the spray formation in step (d) is 150-200 ℃;
more preferably, the temperature of the calcination is 400-700 ℃, and the time of the calcination is 6-12h.
10. Use of a catalyst according to any one of claims 1 to 7 and/or a catalyst prepared according to the preparation method of claim 8 or 9 in the ammoxidation of an aromatic hydrocarbon to prepare an aromatic nitrile, preferably wherein the aromatic hydrocarbon is a monomethyl-substituted aromatic hydrocarbon, a polymethyl-substituted aromatic hydrocarbon or a methyl-substituted organic compound containing a similar aromatic ring; more preferably the application will be aromatic hydrocarbon, oxygen source and NH 3 The aromatic nitrile is produced by the reaction in the presence of the catalyst, and it is further preferable that the reaction is carried out in a fluidized bed reactor.
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