CN107986294B - Vanadium-titanium-silicon containing molecular sieve, and synthetic method and application thereof - Google Patents
Vanadium-titanium-silicon containing molecular sieve, and synthetic method and application thereof Download PDFInfo
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- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
- C01B39/06—Preparation of isomorphous zeolites characterised by measures to replace the aluminium or silicon atoms in the lattice framework by atoms of other elements, i.e. by direct or secondary synthesis
- C01B39/08—Preparation of isomorphous zeolites characterised by measures to replace the aluminium or silicon atoms in the lattice framework by atoms of other elements, i.e. by direct or secondary synthesis the aluminium atoms being wholly replaced
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Abstract
The invention relates to the field of catalytic materials, and particularly provides a vanadium-titanium-silicon-containing molecular sieve, a synthesis method and application thereof, wherein the method comprises the following steps: (1) mixing and contacting a vanadium source, an ammonia source and optionally water to obtain a first mixture; (2) mixing a titanium source, an organic silicon source, the first mixture and optionally water in the presence of a template agent to obtain a second mixture; (3) carrying out first hydrothermal crystallization on the second mixture to obtain mixed slurry A with the solid content not higher than 20 wt%; (4) concentrating the mixed slurry A to obtain a mixed slurry B with the solid content increased by at least 50% and a liquid phase C; (5) and carrying out second hydrothermal crystallization on the mixed slurry B, and recovering to obtain the vanadium-titanium-silicon molecular sieve. The vanadium-titanium-silicon containing molecular sieve has high catalytic efficiency and good application benefit. The method of the invention has no special requirements on raw materials and simple preparation process. The method of the present invention increases the solid content, thereby increasing the capacity of the closed container.
Description
Technical Field
The invention relates to a vanadium-titanium-silicon containing molecular sieve, a synthesis method and application thereof.
Background
The vanadium-silicon molecular sieve VS-1 with MFI crystal structure is a novel vanadium-silicon molecular sieve with excellent catalytic selective oxidation performance formed by introducing transition metal vanadium into a molecular sieve framework with a ZSM-5 structure. VS-1 not only has the catalytic oxidation effect of vanadium, but also has the shape-selective effect and excellent stability of ZSM-5 molecular sieve. The VS-1 molecular sieve can adopt pollution-free low-concentration hydrogen peroxide as an oxidant in the oxidation reaction of organic matters, so that the problems of complex process and environmental pollution in the oxidation process are solved, and the VS-1 molecular sieve has the advantages of incomparable energy conservation, economy, environmental friendliness and the like in the traditional oxidation system, and has good reaction selectivity, so that the VS-1 molecular sieve has great industrial application prospect.
Disclosure of Invention
The invention aims to provide a vanadium-titanium-silicon-containing molecular sieve with high catalytic oxidation activity, a synthesis method and application thereof.
To achieve the foregoing objective and in accordance with a first aspect of the present invention, there is provided a method for synthesizing a vanadium-titanium-containing silicon molecular sieve, the method comprising: (1) mixing and contacting a vanadium source, an ammonia source and optionally water to obtain a first mixture; (2) mixing a titanium source, an organic silicon source, the first mixture and optionally water in the presence of a template agent to obtain a second mixture; (3) carrying out first hydrothermal crystallization on the second mixture to obtain mixed slurry A with the solid content not higher than 20 wt%; (4) concentrating the mixed slurry A to obtain a mixed slurry B with the solid content increased by at least 50% and a liquid phase C; (5) and carrying out second hydrothermal crystallization on the mixed slurry B, and recovering to obtain the vanadium-titanium-silicon molecular sieve.
According to a second aspect of the present invention, there is provided a vanadium-titanium-containing silicalite molecular sieve synthesized according to the method of the present invention.
According to a third aspect of the present invention, there is provided the use of a vanadium-containing titanium silicalite molecular sieve according to the present invention in oxidation reactions.
The vanadium-titanium-silicon containing molecular sieve has high catalytic efficiency and good application benefit.
The method of the invention has no special requirements on raw materials and simple preparation process.
The method of the present invention increases the solid content, thereby increasing the capacity of the closed container.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
As mentioned above, the present invention provides a method for synthesizing a vanadium-titanium-silicon containing molecular sieve, which comprises:
(1) mixing and contacting a vanadium source, an ammonia source and optionally water to obtain a first mixture;
(2) mixing a titanium source, an organic silicon source, the first mixture and optionally water in the presence of a template agent to obtain a second mixture;
(3) carrying out first hydrothermal crystallization on the second mixture to obtain mixed slurry A with the solid content not higher than 20 wt%;
(4) concentrating the mixed slurry A to obtain a mixed slurry B with the solid content increased by at least 50% and a liquid phase C;
(5) and carrying out second hydrothermal crystallization on the mixed slurry B, and recovering to obtain the vanadium-titanium-silicon molecular sieve.
According to the present invention, it is preferable that the content of the non-aqueous substance (solute) in the first mixture in the step (1) is 0.01 to 50% by weight, preferably 0.02 to 25% by weight, more preferably 0.05 to 10% by weight, and most preferably 0.1 to 5% by weight.
According to the present invention, the conditions of the mixing contact in the step (1) include: the temperature is from room temperature to 80 ℃ and/or the time is from 0.1 to 24 hours, preferably from room temperature to 60 ℃ and/or the time is from 0.5 to 12 hours. Thereby further improving the performance of the vanadium-titanium-silicon molecular sieve.
In the present invention, the non-aqueous material content (solute content) refers to the weight percentage of materials other than water in the total mixture, i.e., non-aqueous material/(non-aqueous material + water) × 100 wt%.
According to the process of the present invention, it is preferable that the solid content of the mixed slurry A is 10 to 18% by weight.
According to the process of the present invention, it is preferable that the solid content of the mixed slurry B is increased by 50 to 500% relative to the solid content of the mixed slurry a.
According to the process of the present invention, the method of concentration is not particularly required, and the object is to remove the solvent to increase the solid content, such as filtration, centrifugation and the like.
According to the invention, the preferred weight ratio of the source of ammonia to the source of vanadium is (5-50000): 100, preferably (10-10000): 100, more preferably (50-5000): 100, most preferably (100-: 100. thereby further improving the performance of the vanadium-titanium-silicon molecular sieve.
According to the invention, the organic silicon source is preferably: a titanium source: a vanadium source: template agent: the molar ratio of water is 100: (0.5-5): (0.5-5): (5-50): (200-; preferably 100: (1-4): (1-4): (6-15): (300-800), wherein the organic silicon source is SiO2The titanium source is calculated as TiO2The vanadium source is calculated by vanadium element, the template agent is N or OH-And (6) counting.
According to the present invention, preferably, the method further comprises: and mixing the liquid phase C with the obtained vanadium-titanium-silicon containing molecular sieve, and then carrying out third hydrothermal crystallization.
According to the present invention, it is preferred that the third hydrothermal crystallization is carried out under a closed condition, and sequentially undergoes the stage (1), the stage (2) and the stage (3), wherein the stage (1) is treated at 80-150 ℃, preferably at 110-.
According to a preferred embodiment of the present invention, it is preferred that the phases (1) and (3) satisfy one or both of the following conditions:
condition 1: the temperature of stage (1) is lower than the temperature of stage (3), preferably the temperature of stage (1) is 10-50 ℃ lower than the temperature of stage (3), preferably 20-40 ℃ lower;
condition 2: the time of stage (1) is less than the time of stage (3), preferably the time of stage (1) is 5-24 hours, preferably 6-12 hours shorter than the time of stage (3).
According to a preferred embodiment of the invention, the temperature of stage (2) is reduced to not more than 50 ℃, preferably to 30 to 50 ℃, and the residence time is at least 1 hour, preferably to 1 to 5 hours.
According to the method of the present invention, the temperature-raising rate and the temperature-lowering rate for adjusting the temperature to the respective stage temperatures may be selected depending on the type of the reactor specifically used, and are not particularly limited. In general, the ramp rate for raising the temperature to the stage (1) temperature may be from 0.1 to 20 deg.C/min, preferably from 0.1 to 10 deg.C/min, more preferably from 1 to 5 deg.C/min. The rate of temperature decrease from the stage (1) temperature to the stage (2) temperature may be from 1 to 50 deg.C/min, preferably from 2 to 20 deg.C/min, more preferably from 5 to 10 deg.C/min. The rate of temperature increase from the stage (2) temperature to the stage (3) temperature may be 1-50 deg.C/min, preferably 2-40 deg.C/min, more preferably 5-20 deg.C/min.
According to the method of the present invention, the conditions for the first hydrothermal crystallization can be selected from a wide range as long as it is ensured that the mixed slurry a having a solid content of not more than 20% by weight is obtained, and for example, the temperature may be 80 to 130 ℃.
According to the method of the present invention, the time for the first hydrothermal crystallization can be selected from a wide range, and can be adjusted appropriately according to the temperature, for example, can be 12 to 96 hours.
According to the method of the present invention, the conditions for the second hydrothermal crystallization can be selected from a wide range as long as the vanadium-titanium-silicon containing molecular sieve is obtained, and for example, the temperature can be 140-.
According to the method of the present invention, the time for the second hydrothermal crystallization can be selected in a wide range, and can be adjusted appropriately according to the temperature, for example, the time can be 6 to 24 hours.
According to the present invention, it is preferable that the ammonia source is one or more of ammonia gas, liquid ammonia, and an organic solution of ammonia and ammonia; preferably one or more of ammonia gas, liquid ammonia and aqueous ammonia, and the organic solution of ammonia is, for example, an alcoholic solution of ammonia, and more preferably aqueous ammonia.
According to the method of the present invention, the organic silicon source may be various silicon-containing compounds capable of forming silica under hydrolytic condensation reaction conditions. Specifically, the organic silicon source may be one or more selected from silicon-containing compounds represented by formula I,
in the formula I, R1、R2、R3And R4Each is C1-C4Alkyl of (2) including C1-C4Straight chain alkyl of (2) and C3-C4Branched alkyl groups of (a), for example: r1、R2、R3And R4Each may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.
Specifically, the organic silicon source may be one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, and tetra-n-butyl orthosilicate. In a particular embodiment of the invention, ethyl orthosilicate or methyl orthosilicate is used.
According to the invention, the selectable range of the template agent is wide, and the template agent can be determined according to the type of the titanium silicon molecular sieve to be prepared, such as one or more of quaternary ammonium base compound, aliphatic amine compound and aliphatic alcohol amine compound.
In the invention, the quaternary ammonium base can be various organic quaternary ammonium bases, and the aliphatic amine can be various NH3In which at least one hydrogen is substituted with an aliphatic hydrocarbon group (preferably an alkyl group), which may be a variety of NH3Wherein at least one hydrogen is substituted with a hydroxyl-containing aliphatic hydrocarbon group (preferably an alkyl group).
Specifically, the quaternary ammonium base may be a quaternary ammonium base represented by formula II, the aliphatic amine may be an aliphatic amine represented by formula III, and the aliphatic alcohol amine may be an aliphatic alcohol amine represented by formula IV:
in the formula II, R5、R6、R7And R8Each is C1-C4Alkyl of (2) including C1-C4Straight chain alkyl of (2) and C3-C4Branched alkyl groups of (a), for example: r5、R6、R7And R8Each may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.
R9(NH2)n(formula III)
In the formula III, n is an integer of 1 or 2. When n is 1, R9Is C1-C6Alkyl of (2) including C1-C6Straight chain alkyl of (2) and C3-C6Such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl and n-hexyl. When n is 2, R9Is C1-C6Alkylene of (2) including C1-C6Linear alkylene of (A) and (C)3-C6Such as methylene, ethylene, n-propylene, n-butylene, n-pentylene or n-hexylene. More preferably, the aliphatic amine compound is one or more of ethylamine, n-butylamine, butanediamine and hexamethylenediamine
(HOR10)mNH(3-m)(formula IV)
In the formula IV, m are R10Are the same or different and are each C1-C4Alkylene of (2) including C1-C4Linear alkylene of (A) and (C)3-C4Branched alkylene groups of (a), such as methylene, ethylene, n-propylene and n-butylene; m is 1, 2 or 3. More preferably, the aliphatic alcohol amine compound is one or more of monoethanolamine, diethanolamine and triethanolamine.
The templating agent used in the embodiments of the present invention is tetrapropylammonium hydroxide, hexamethylenediamine, or n-butylamine.
In the present invention, the titanium source may be an inorganic titanium source and/or an organic titanium source.
According to a preferred embodiment of the invention, the titanium source is an inorganic titanium salt and/or an organic titanate.
In the present invention, the inorganic titanium salt is selected from various hydrolyzable titanium salts, and may be selected from TiX, for example4、TiOX2Or Ti (SO)4)2And the like, wherein X is halogen, preferably chlorine, wherein preferably the inorganic titanium salt is selected from TiCl4、Ti(SO4)2And TiOCl2One or more of (a).
In the present invention, the organic compound isThe titanate is preferably of the formula M4TiO4Wherein M is preferably an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 2 to 4 carbon atoms, and 4M may be the same or different, preferably the organotitanate is selected from one or more of isopropyl titanate, n-propyl titanate, tetrabutyl titanate and tetraethyl titanate, tetrabutyl titanate being used in the specific embodiment of the present invention as an example, but not thereby limiting the scope of the present invention.
According to a preferred embodiment of the present invention, the vanadium source is preferably an oxide of vanadium, a halide of vanadium, vanadic acid (HVO)3) Orthovanadic acid (H)3VO4) Pyrovanadic acid (H)4V2O7、H3V3O9) Vanadate (corresponding salt of the aforementioned vanadate), carbonate of vanadium, nitrate of vanadium, sulfate of vanadium, and hydroxide of vanadium. Including but not limited to sodium vanadate, ammonium metavanadate, vanadium pentoxide, vanadium oxytrichloride, potassium metavanadate, vanadyl sulfate, vanadium acetylacetonate, and the like.
According to the method of the present invention, preferably the method further comprises: and (3) contacting the obtained vanadium-titanium-silicon-containing molecular sieve (including or not including a product which is mixed with the liquid phase C and then subjected to hydrothermal crystallization) with a modification solution containing nitric acid and at least one peroxide for modification treatment.
According to the method of the present invention, preferably, the method further comprises drying the solid product after the modification treatment.
According to the synthesis method of the present invention, preferably, in the modification treatment, the molar ratio of the vanadium-titanium-silicon containing molecular sieve as the raw material to the peroxide is 1: 0.01 to 5, preferably 1: 0.05 to 3, more preferably 1: 0.1-2, the molar ratio of the peroxide to the nitric acid is 1: 0.01 to 50, preferably 1: 0.1 to 20, more preferably 1: 0.2 to 10, more preferably 1: 0.5 to 5, particularly preferably 1: 0.6-3.5, wherein the vanadium-titanium-silicon molecular sieve is calculated by silicon dioxide.
According to the method of the present invention, it is preferable that the concentrations of the peroxide and the nitric acid in the modification liquid are each 0.1 to 50% by weight, preferably 0.5 to 25% by weight, and more preferably 5 to 15% by weight.
According to the method of the invention, preferably in the modification treatment, the vanadium-titanium-silicon containing molecular sieve as the raw material is contacted with the modification solution at a temperature of 10-350 ℃, preferably 20-300 ℃, more preferably 50-250 ℃, and even more preferably 60-200 ℃, the contact is carried out in a container with a pressure of 0-5MPa, the pressure is gauge pressure, and the duration of the contact is 1-10 hours, preferably 3-5 hours.
According to the process of the present invention, preferably the peroxide is selected from the group consisting of hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexyl hydroperoxide, peroxyacetic acid and peroxypropionic acid.
The process of recovering the product according to the method of the present invention is well known to those skilled in the art, and includes, in no way in particular, filtration or natural settling of the product, washing, drying, calcining and the like.
The invention provides a vanadium-titanium-containing silicon molecular sieve obtained by the method.
The invention provides application of the vanadium-containing titanium silicalite molecular sieve in oxidation reaction.
The vanadium-titanium-containing silicon molecular sieve of the invention is suitable for oxidation reaction of various molecules, such as phenol, alkane, aldehyde, alcohol, ketone, olefin and the like. The vanadium-titanium-silicon containing molecular sieve has high catalytic activity. The advantages of the present invention are illustrated in the examples of the present invention by the oxidation of phenol.
The invention provides a phenol oxidation method, which comprises the step of contacting phenol, an oxidant and a catalyst, wherein the catalyst contains the vanadium-containing titanium silicalite molecular sieve.
The conditions of the contacting according to the process of the present invention may be chosen as is conventional in the art, and for the purposes of the present invention, preferred contacting conditions include: the temperature is 40-150 ℃, preferably 40-120 ℃; the pressure is 0.1-3.0MPa, preferably 0.1-2.5 MPa; the time is 0.1-24h, and the molar ratio of the phenol to the oxidant is 1: 1-20, preferably 1: 2-15.
According to the process of the present invention, the mass ratio of phenol to catalyst is preferably from 0.5 to 150: 1.
according to the method of the present invention, preferably the contacting is carried out in the presence of a solvent, wherein the mass ratio of the solvent to the catalyst is preferably 1 to 200: 1, preferably 2-150: 1; more preferably, the solvent is selected from one or more of water, alcohol, linear or branched ketone, acid and nitrile, and preferably the solvent is one or more of water, C1-C5 alcohol, C2-C6 linear or branched ketone, C2-C8 nitrile and C2-C5 acid.
According to the process of the present invention, the solvent is preferably selected from one or more of water, methanol, ethanol, n-propanol, isopropanol, tert-butanol, isobutanol, acetone, butanone, acetonitrile, propionitrile, phenylacetonitrile, acetic acid and propionic acid, more preferably the solvent is selected from one or more of acetonitrile, acetone, methanol, acetic acid and water.
According to the process of the present invention, the order of addition is not particularly critical, and phenol may be added first, or an oxidizing agent or a solvent may be added first.
According to the process of the present invention, preferably the oxidizing agent is one or more of hydrogen peroxide, tert-butyl hydroperoxide, cumene peroxide, cyclohexyl hydroperoxide, peracetic acid and peroxopropionic acid.
According to the method, after the contact reaction, the material after the reaction can adopt a common distillation or rectification method, and after the target product is separated, the unreacted phenol raw material and the like can be directly returned to the reaction device again for continuous reaction without separation and purification.
The following examples further illustrate the invention but are not intended to limit the invention thereto.
Comparative example 1
(1) Mixing vanadium source vanadium nitrate, ammonia water (the concentration is 20 weight percent), tetrabutyl titanate, tetrapropyl ammonium hydroxide and tetraethyl orthosilicate, and then carrying out hydrothermal crystallization; silicon source: a titanium source: a vanadium source: template agent: water (mol) ═ 100: 2: 1: 15: 1000, parts by weight; a vanadium source: ammonia source (weight ratio) 2: 20;
hydrothermal crystallization: after a first stage 6h at 140 ℃ in a sealed reaction kettle, cooling the mixture to 30 ℃ and staying for a second stage for 2h, continuously performing a third stage 12h at 170 ℃ in the sealed reaction kettle (wherein, the heating rate from room temperature to the first stage temperature is 2 ℃/min, the cooling rate from the first stage temperature to the second stage treatment temperature is 5 ℃/min, and the heating rate from the second stage treatment temperature to the third stage temperature is 10 ℃/min);
(4) and finally, cooling to room temperature and relieving pressure, filtering, washing, drying and roasting the product in the reaction kettle for 5 hours at 550 ℃ to obtain the vanadium-titanium-silicon molecular sieve sample DB-1.
Comparative example 2
(1) Mixing vanadium nitrate as a vanadium source with ammonia water (the concentration is 20 weight percent) to contact to obtain a mixture; a vanadium source: ammonia source (weight ratio) 2:20, solute content 1 wt%, conditions of mixed contact including: at 30 ℃, normal pressure and 4 hours;
(2) then mixing the mixture with tetrabutyl titanate, tetraethyl orthosilicate and tetrapropyl ammonium hydroxide; mixing, and performing hydrothermal crystallization at 160 deg.C for 120 hr; silicon source: a titanium source: a vanadium source: template agent: water (mol) ═ 100: 2: 1: 15: 1000, parts by weight; and filtering, washing, drying and roasting the product in the reaction kettle for 5 hours at 550 ℃ to obtain the vanadium-titanium-silicon molecular sieve sample DB-2.
Example 1
(1) Mixing vanadium nitrate as a vanadium source with ammonia water, and contacting to obtain a mixture; a vanadium source: ammonia source (weight ratio) 2:20, solute content 1 wt%, conditions of mixed contact including: at 30 ℃, normal pressure and 4 hours;
(2) then mixing the mixture with tetrabutyl titanate, tetraethyl orthosilicate and tetrapropyl ammonium hydroxide; after mixing, carrying out first hydrothermal crystallization at 120 ℃ for 72 hours to obtain mixed slurry A (the solid content is 18 weight percent); silicon source: a titanium source: a vanadium source: template agent: water (mol) ═ 100: 2: 1: 15: 1000, parts by weight;
(3) filtering the mixed slurry A to obtain mixed slurry B (the solid content is 40 weight percent) and a liquid phase C;
(4) carrying out second hydrothermal crystallization on the mixed slurry B at the temperature of 170 ℃ for 24 hours, filtering, washing, drying, roasting and recovering to obtain a vanadium-titanium-silicon molecular sieve;
(5) mixing the obtained vanadium-titanium-silicon-containing molecular sieve with a liquid phase C, and then carrying out third hydrothermal crystallization:
and (3) third hydrothermal crystallization: after a first stage 6h at 140 ℃ in a sealed reaction kettle, cooling the mixture to 30 ℃ and staying for a second stage for 2h, continuously performing a third stage 12h at 170 ℃ in the sealed reaction kettle (wherein, the heating rate from room temperature to the first stage temperature is 2 ℃/min, the cooling rate from the first stage temperature to the second stage treatment temperature is 5 ℃/min, and the heating rate from the second stage treatment temperature to the third stage temperature is 10 ℃/min);
(6) and finally, cooling to room temperature and relieving pressure, filtering, washing, drying and roasting the product in the reaction kettle for 5 hours at 550 ℃ to obtain a vanadium-titanium-silicon molecular sieve sample A.
The method is characterized in that: the crystal structure type of the vanadium-titanium-silicon containing molecular sieve of sample A is MFI.
Example 2
(1) Mixing vanadium source vanadyl sulfate and ammonia water to obtain a mixture; a vanadium source: ammonia source (weight ratio) 2:10, solute content 2 wt%, conditions of mixed contact including: at 40 ℃, normal pressure for 3 hours;
(2) then mixing the mixture with isopropyl titanate, tetramethyl orthosilicate and n-butylamine, and carrying out first hydrothermal crystallization at 100 ℃ for 50 hours to obtain mixed slurry A (the solid content is 15 wt%); silicon source: a titanium source: a vanadium source: template agent: 100 parts of water: 3: 2: 35: 3000A;
(3) filtering the mixed slurry A to obtain mixed slurry B (the solid content is 30 weight percent) and a liquid phase C;
(4) carrying out second hydrothermal crystallization on the mixed slurry B at the temperature of 160 ℃ for 30 hours, filtering, washing, drying, roasting and recovering to obtain a vanadium-titanium-silicon molecular sieve;
(5) mixing the obtained vanadium-titanium-silicon-containing molecular sieve with a liquid phase C, and then carrying out third hydrothermal crystallization:
and (3) third hydrothermal crystallization: after the mixture is cooled to 50 ℃ and stays for 5 hours in the second stage, the mixture is continuously subjected to a third stage 16 hours in the sealed reaction kettle at the temperature of 170 ℃ (wherein the heating rate of the temperature rising from the room temperature to the first stage temperature is 1 ℃/min, the cooling rate of the temperature rising from the first stage temperature to the second stage temperature is 10 ℃/min, and the heating rate of the temperature rising from the second stage temperature to the third stage temperature is 20 ℃/min);
(6) and finally, cooling to room temperature and relieving pressure, filtering, washing, drying and roasting the product in the reaction kettle for 5 hours at 550 ℃ to obtain a vanadium-titanium-silicon molecular sieve sample B.
The method is characterized in that: the crystal structure type of the vanadium-titanium-silicon containing molecular sieve of sample B is MFI.
Example 3
(1) Mixing vanadium hydroxide from a vanadium source with ammonia water to contact to obtain a mixture; a vanadium source: ammonia source (weight ratio) 2:10, solute content 5 wt%, conditions of mixing contact including: at 50 ℃, normal pressure for 5 hours;
(2) then mixing the mixture with tetraethyl titanate, tetraethyl orthosilicate and hexamethylene diamine, and carrying out first hydrothermal crystallization after mixing at the temperature of 80 ℃ for 96 hours to obtain mixed slurry A (the solid content is 10 weight percent); silicon source: a titanium source: a vanadium source: template agent: water (mol) ═ 100: 4: 3: 25: 2000;
(3) filtering the mixed slurry A to obtain mixed slurry B (the solid content is 50 weight percent) and a liquid phase C;
(4) carrying out second hydrothermal crystallization on the mixed slurry B at the temperature of 150 ℃ for 24 hours, filtering, washing, drying, roasting and recovering to obtain a vanadium-titanium-silicon molecular sieve;
(5) mixing the obtained vanadium-titanium-silicon-containing molecular sieve with a liquid phase C, and then carrying out third hydrothermal crystallization:
and (3) third hydrothermal crystallization: after the mixture is cooled to 40 ℃ and stays for 1h in the second stage, the mixture is continuously subjected to a third stage for 12h in the sealed reaction kettle at the temperature of 160 ℃ (wherein the heating rate of the mixture from the room temperature to the first stage is 5 ℃/min, the cooling rate from the first stage to the second stage is 5 ℃/min, and the heating rate from the second stage to the third stage is 5 ℃/min);
(6) and finally, cooling to room temperature and relieving pressure, filtering, washing, drying and roasting the product in the reaction kettle for 5 hours at 550 ℃ to obtain a vanadium-titanium-silicon molecular sieve sample C.
The method is characterized in that: the crystal structure type of the vanadium-titanium-silicon containing molecular sieve of sample C is MFI.
Example 4
Mixing the vanadium-titanium-silicon molecular sieve A obtained in example 1 with HNO3(HNO3The mass concentration of the vanadium-titanium-silicon molecular sieve D is 10%) and hydrogen peroxide (the mass concentration of the hydrogen peroxide is 7.5%) are mixed, the obtained mixture is stirred and reacted for 5 hours in a closed container at 70 ℃, the temperature of the obtained reaction mixture is reduced to room temperature, then the obtained reaction mixture is filtered, and the obtained solid-phase substance is dried to constant weight at 120 ℃, so that the modified vanadium-titanium-silicon molecular sieve D is obtained. Wherein, the vanadium-titanium-silicon containing molecular sieve TS-1 is SiO2The molar ratio of the vanadium-titanium-silicon-containing molecular sieve to the hydrogen peroxide is 1: 0.1. this sample was similar in its spectral characteristics to the sample of example 1 by X-ray diffraction.
Example 5
Mixing the vanadium-titanium-silicon containing molecular sieve B obtained in the example 2 with HNO3(HNO3The mass concentration of the vanadium-titanium-containing silicon molecular sieve E is 10%) and hydrogen peroxide (the mass concentration of the hydrogen peroxide is 5%) are mixed, the obtained mixture is stirred and reacted for 4 hours in a closed container at 120 ℃, the temperature of the obtained reaction mixture is reduced to room temperature, then the obtained reaction mixture is filtered, and the obtained solid-phase substance is dried to constant weight at 120 ℃, so that the modified vanadium-titanium-containing silicon molecular sieve E is obtained. Wherein, the vanadium-titanium-silicon containing molecular sieve TS-1 is SiO2The molar ratio of the vanadium-titanium-silicon-containing molecular sieve to the hydrogen peroxide is 1: 0.4. this sample was similar in its spectral characteristics to the sample of example 2 by X-ray diffraction.
Example 6
Mixing the vanadium-titanium-silicon containing molecular sieve C obtained in example 3 with HNO3(HNO315%) and an aqueous solution of hydrogen peroxide (the mass concentration of hydrogen peroxide is 8%), stirring the obtained mixture in a closed container at 150 ℃ for 3 hours, cooling the obtained reaction mixture to room temperature, and then carrying outFiltering, and drying the obtained solid-phase substance at 120 ℃ to constant weight to obtain the modified vanadium-titanium-containing silicon molecular sieve F. Wherein, the vanadium-titanium-silicon containing molecular sieve TS-1 is SiO2The molar ratio of the vanadium-titanium-silicon-containing molecular sieve to the hydrogen peroxide is 1: 2. this sample was similar in its spectral characteristics to the sample of example 3 by X-ray diffraction.
Example 7
A molecular sieve was prepared as in example 1, except that in the third hydrothermal crystallization, the crystallization temperature in the first stage was 110 ℃. The product was then recovered according to the procedure of example 1, with an XRD crystallographic phase diagram in accordance with comparative example 1.
Example 8
The molecular sieve was prepared according to the method of example 1, except that in the third hydrothermal crystallization, the crystallization time was 12h in the first stage, and the temperature was reduced to 70 ℃ and stayed for 2h in the second stage. The product was then recovered according to the procedure of example 1, with an XRD crystallographic phase diagram in accordance with comparative example 1.
Example 9
The molecular sieve was prepared according to the method of example 1 except that the vanadium-containing titanium silicalite molecular sieve obtained in step (4) was used directly as a product.
Test example 1
This test example is intended to illustrate the reaction effect of the molecular sieve obtained by the method of the present invention and the molecular sieve obtained by the method of the comparative example for the hydroxylation reaction of phenol.
The samples prepared in the above examples and comparative examples were prepared according to the following sample: phenol: acetone ═ 1: 18: 26 weight ratio in a three-neck flask with a condenser, heating to 50 ℃, and stirring according to the weight ratio of phenol: hydrogen peroxide ═ 3: 1, hydrogen peroxide was added at a concentration of 27.5% by weight, and the reaction was carried out at this temperature for 2.5 hours, and the product distribution was measured on an Agilent6890N chromatograph using an HP-5 capillary column (30 m.times.0.25 mm), and the results are shown in Table 1.
Wherein:
wherein the diphenols include catechol, resorcinol, and hydroquinone.
TABLE 1
| Sample source | Phenol conversion rate,% | Selectivity for hydroquinone,% |
| Comparative example 1 | 16.6 | 47 |
| Comparative example 2 | 18.5 | 49 |
| Example 1 | 22.8 | 61 |
| Example 2 | 23.7 | 59 |
| Example 3 | 24.4 | 62 |
| Example 4 | 24.5 | 64 |
| Example 5 | 25.3 | 65 |
| Example 6 | 26.2 | 64 |
| Example 7 | 20.8 | 58 |
| Example 8 | 21.9 | 60 |
| Example 9 | 21.3 | 59 |
From the results in table 1, it can be seen that the vanadium-titanium-silicon containing molecular sieve prepared according to the method of the present invention has high catalytic activity, and when used in the phenol hydroxylation reaction, the phenol conversion rate and the hydroquinone selectivity are both significantly higher than those obtained from the sample prepared by the method of the comparative example.
Test example 2
The catalyst molecular sieves prepared in comparative example and example were reacted according to test example 1, then centrifuged and dried, and then phenol oxidation reaction was continued according to the reaction conditions of test example 1, and a reaction-separation-reaction cycle was repeated, and the results after 4 cycles are shown in table 2.
TABLE 2
| Sample source | Phenol conversion rate,% | Selectivity for hydroquinone,% |
| Comparative example 1 | 11.5 | 37 |
| Comparative example 2 | 13.5 | 40 |
| Example 1 | 22.6 | 59 |
| Example 2 | 23.4 | 58 |
| Example 3 | 24.2 | 60 |
| Example 4 | 24.4 | 61 |
| Example 5 | 25.1 | 63 |
| Example 6 | 26.1 | 62 |
| Example 7 | 20.6 | 57 |
| Example 8 | 21.6 | 59 |
| Example 9 | 21.1 | 57 |
As can be seen from the data in table 2, the catalyst of the present invention has high stability.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (33)
1. A method for synthesizing a vanadium-titanium-silicon-containing molecular sieve is characterized by comprising the following steps:
(1) mixing and contacting a vanadium source, an ammonia source and optionally water to obtain a first mixture, wherein the content of non-water substances in the first mixture in the step (1) is 0.01-50 wt%, and the mixing and contacting conditions in the step (1) comprise the following steps: the temperature is between room temperature and 80 ℃, and the time is 0.1 to 24 hours;
(2) mixing a titanium source, an organic silicon source, the first mixture and optionally water in the presence of a template agent to obtain a second mixture;
(3) carrying out first hydrothermal crystallization on the second mixture to obtain mixed slurry A with the solid content not higher than 20 wt%;
(4) concentrating the mixed slurry A to obtain a mixed slurry B with the solid content increased by at least 50% and a liquid phase C;
(5) and carrying out second hydrothermal crystallization on the mixed slurry B, and recovering to obtain the vanadium-titanium-silicon molecular sieve.
2. The synthetic method according to claim 1, wherein,
in the step (1), the content of non-water substances in the first mixture is 0.02-25 wt%; and/or
The mixing and contacting conditions in the step (1) comprise the following steps: the temperature is between room temperature and 60 ℃, and the time is 0.5-12 h.
3. The method according to claim 1, wherein the non-aqueous substance content of the first mixture in step (1) is 0.05-10 wt%.
4. The method of claim 1, wherein the non-aqueous material content of the first mixture in step (1) is 0.1-5 wt.%.
5. The synthetic method according to claim 1 or 2, wherein,
the solid content of the mixed slurry A is 10-18 wt%; and/or
The solid content of the mixed slurry B is increased by 50-500% relative to that of the mixed slurry A; and/or
The weight ratio of the ammonia source to the vanadium source is (5-50000): 100, respectively; and/or
An organic silicon source: a titanium source: a vanadium source: template agent: the molar ratio of water is 100: (0.5-5): (0.5-5): (5-50): (200-; wherein the organic silicon source is SiO2The titanium source is calculated as TiO2Counting vanadium source by vanadium element, counting template agent by N or OH-And (6) counting.
6. A synthesis process according to claim 1 or 2, wherein the weight ratio of ammonia source to vanadium source is (10-10000): 100, respectively; and/or
An organic silicon source: a titanium source: a vanadium source: template agent: the molar ratio of water is 100: (1-4): (1-4): (6-15): (300-800), wherein the organic silicon source is SiO2The titanium source is calculated as TiO2Counting vanadium source by vanadium element, counting template agent by N or OH-And (6) counting.
7. A synthesis process according to claim 1 or 2, wherein the weight ratio of ammonia source to vanadium source is (50-5000): 100.
8. the synthesis process according to claim 1 or 2, wherein the weight ratio of ammonia source to vanadium source is (100- & 2000): 100.
9. the method of synthesis of claim 1 or 2, wherein the method further comprises: and mixing the liquid phase C with the obtained vanadium-titanium-silicon-containing molecular sieve, and then carrying out third hydrothermal crystallization, wherein the third hydrothermal crystallization is carried out under a closed condition and sequentially passes through a stage (1), a stage (2) and a stage (3), the stage (1) is treated at 80-150 ℃ for 6-72 hours, the stage (2) is cooled to not higher than 70 ℃ and the retention time is at least 0.5 hour, and the stage (3) is heated to 120-phase 200 ℃ and then treated for 6-96 hours.
10. The synthesis method according to claim 9, wherein the stage (1) is treated at 140 ℃ for 6-72 hours, the stage (2) is cooled to 70 ℃ or less and the retention time is 1-5 hours, and the stage (3) is heated to 180 ℃ and then treated for 12-20 hours.
11. The synthesis method according to claim 9, wherein the stage (1) is treated at 140 ℃ for 6-8 hours, the stage (2) is cooled to 70 ℃ or less and the retention time is 1-5 hours, and the stage (3) is heated to 170 ℃ and 160 ℃ and then treated for 12-20 hours.
12. The synthesis process as claimed in claim 9, wherein stage (1) is treated at 130-140 ℃ for 6-8 hours.
13. The synthesis method according to claim 9, wherein stage (1) and stage (3) satisfy one or both of the following conditions:
condition 1: the temperature of the stage (1) is lower than that of the stage (3);
condition 2: the time of the stage (1) is less than the time of the stage (3);
the temperature of the stage (2) is reduced to not higher than 50 ℃ and the retention time is at least 1 hour.
14. The synthesis method according to claim 9, wherein stage (1) and stage (3) satisfy one or both of the following conditions:
condition 1: the temperature of the stage (1) is 10-50 ℃ lower than that of the stage (3),
condition 2: the time of the stage (1) is 5-24 hours shorter than that of the stage (3).
15. The synthesis method according to claim 9, wherein stage (1) and stage (3) satisfy one or both of the following conditions:
condition 1: the temperature of the stage (1) is 20-40 ℃ lower than that of the stage (3),
condition 2: the time of the stage (1) is 6-12 hours shorter than that of the stage (3).
16. The synthetic method according to claim 1 or 2, wherein,
the conditions of the first hydrothermal crystallization include: the temperature is 80-130 ℃, and the time is 12-96 h;
the conditions of the second hydrothermal crystallization include: the temperature is 140 ℃ and 180 ℃, and the time is 6-24 h.
17. The synthetic method according to claim 1 or 2, wherein,
the ammonia source is one or more of ammonia gas, liquid ammonia, ammonia water and an organic solution of ammonia; and/or
The template agent is one or more of quaternary ammonium base compound, aliphatic amine compound and aliphatic alcohol amine compound; and/or
The organic silicon source is one or more selected from silicon-containing compounds shown in formula I,
in the formula I, R1、R2、R3And R4Each is C1-C4Alkyl groups of (a); and/or
The titanium source is inorganic titanium salt and/or organic titanate; and/or
The vanadium source is one or more of vanadium oxide, vanadium acid, vanadate, vanadium halide, vanadium carbonate, vanadium nitrate, vanadium sulfate and vanadium hydroxide.
18. The synthesis method according to claim 1 or 2, wherein the ammonia source is one or more of ammonia gas, liquid ammonia and aqueous ammonia.
19. The synthesis process according to claim 1 or 2, wherein the ammonia source is aqueous ammonia.
20. The method of synthesis of claim 1 or 2, wherein the method further comprises: and (2) contacting the obtained vanadium-titanium-silicon molecular sieve with a modification solution containing nitric acid and at least one peroxide for modification treatment, wherein in the modification treatment, the molar ratio of the vanadium-titanium-silicon molecular sieve as a raw material to the peroxide is 1: (0.01-5), the molar ratio of the peroxide to the nitric acid is 1: (0.01-50), wherein the vanadium-titanium-silicon containing molecular sieve is calculated by silicon dioxide.
21. The synthesis method of claim 20, wherein in the modification treatment, the molar ratio of the vanadium-titanium-containing silicon molecular sieve as the raw material to the peroxide is 1: (0.05-3); the molar ratio of the peroxide to the nitric acid is 1: (0.1-20), wherein the vanadium-titanium-silicon containing molecular sieve is calculated by silicon dioxide.
22. The synthesis method of claim 20, wherein in the modification treatment, the molar ratio of the vanadium-titanium-containing silicon molecular sieve as the raw material to the peroxide is 1: (0.1-2); the molar ratio of the peroxide to the nitric acid is 1: (0.2-10), wherein the vanadium-titanium-silicon containing molecular sieve is calculated by silicon dioxide.
23. The synthesis method of claim 20, wherein in the modification treatment, the molar ratio of the peroxide to the nitric acid is 1: (0.5-5).
24. The synthesis method of claim 20, wherein in the modification treatment, the molar ratio of the peroxide to the nitric acid is 1: (0.6-3.5).
25. The synthesis method according to claim 20, wherein the concentrations of the peroxide and nitric acid in the modification solution are each 0.1 to 50 wt%; wherein the peroxide is selected from the group consisting of hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexyl hydroperoxide, peracetic acid, and perpropionic acid.
26. The synthesis method according to claim 25, wherein the concentrations of the peroxide and nitric acid in the modification solution are each 0.5 to 25 wt%.
27. The synthesis method according to claim 25, wherein the concentrations of the peroxide and nitric acid in the modification solution are each 5 to 15 wt%.
28. The synthesis method of claim 20, wherein in the modification treatment, the vanadium-titanium-containing silicon molecular sieve as a raw material is contacted with the modification solution at a temperature of 10-350 ℃, the contact is carried out in a container with a pressure of 0-5MPa, the pressure is gauge pressure, and the contact duration is 1-10 hours.
29. The synthesis method according to claim 20, wherein in the modification treatment, the vanadium-titanium-containing silicon molecular sieve as a raw material is contacted with the modification solution at a temperature of 20-300 ℃; the duration of the contact is 3 to 5 hours.
30. The synthesis method according to claim 20, wherein in the modification treatment, the vanadium-titanium-containing silicon molecular sieve as a raw material is contacted with the modification solution at a temperature of 50-250 ℃.
31. The synthesis method according to claim 20, wherein in the modification treatment, the vanadium-titanium-containing silicon molecular sieve as a raw material is contacted with the modification solution at a temperature of 60-200 ℃.
32. A vanadium titanium containing molecular sieve obtainable by the process of any one of claims 1 to 31.
33. Use of the vanadium-containing titanium silicalite molecular sieve of claim 32 in oxidation reactions.
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