CN109721070B

CN109721070B - Method for producing titanium silicalite molecular sieve, titanium silicalite molecular sieve produced by method and ammoximation reaction method

Info

Publication number: CN109721070B
Application number: CN201711050888.XA
Authority: CN
Inventors: 林民; 史春风; 朱斌
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2017-10-31
Filing date: 2017-10-31
Publication date: 2020-12-04
Anticipated expiration: 2037-10-31
Also published as: CN109721070A

Abstract

The invention discloses a titanium-silicon molecular sieve and a production method thereof, and the method comprises the following steps: sequentially carrying out a first hydrolysis condensation reaction and a second hydrolysis condensation reaction on an organic silicon source, a titanium source, a template agent and water to obtain a hydrolysis condensation mixture, and leading out and condensing generated steam in the hydrolysis condensation reaction process; mixing the hydrolytic condensation mixture with at least part of the condensate liquid and then carrying out hydrothermal crystallization; optionally, after increasing the dry content of the hydrothermal crystallization mixture, spray forming is performed. The invention also discloses an ammoximation reaction method using the titanium silicalite molecular sieve as a catalyst. The titanium silicalite molecular sieve produced by the method can effectively inhibit the decomposition of the template agent in the hydrothermal crystallization process, and can omit the solid-liquid separation process of the mixture obtained by the hydrothermal crystallization, thereby reducing the amount of wastewater generated in the production process. When the titanium silicalite molecular sieve produced by the method is used as a catalyst for ammoximation reaction, the improved catalytic activity can be obtained.

Description

Method for producing titanium silicalite molecular sieve, titanium silicalite molecular sieve produced by method and ammoximation reaction method

Technical Field

The invention relates to the technical field of molecular sieve preparation, in particular to a production method of a titanium silicalite molecular sieve, the titanium silicalite molecular sieve produced by the method, and an ammoximation reaction method using the titanium silicalite molecular sieve as a catalyst.

Background

The titanium silicalite TS-1 is a novel titanium silicalite with excellent catalytic selective oxidation performance formed by introducing a transition metal element titanium into a molecular sieve framework with a ZSM-5 structure. TS-1 not only has the catalytic oxidation effect of titanium, but also has the shape-selective effect and excellent stability of ZSM-5 molecular sieve. As the TS-1 molecular sieve can adopt the pollution-free low-concentration hydrogen peroxide as the oxidant in the oxidation reaction of the organic matters, the problems of complex process and environmental pollution in the oxidation process are avoided, and the molecular sieve has the advantages of incomparable energy conservation, economy, environmental friendliness and the like of the traditional oxidation system and has good reaction selectivity, thereby having great industrial application prospect.

The synthesis of TS-1 was first disclosed in 1981 (USP 4410501). The method comprises the steps of firstly synthesizing a reaction mixture containing a silicon source, a titanium source and organic alkali and/or alkaline oxide serving as a template agent, carrying out hydrothermal crystallization on the reaction mixture in a high-pressure kettle at the temperature of 130-200 ℃ for 6-30 days, and then separating, washing, drying and roasting to obtain the product.

Despite intensive research efforts by researchers on the preparation of titanium silicalite molecular sieves, there are still some problems with the preparation of titanium silicalite molecular sieves, and improvements and optimizations to the existing methods of titanium silicalite molecular sieve production are needed.

Disclosure of Invention

The inventor of the invention finds that the existing titanium silicalite molecular sieve production process mainly has the following problems in the practical process:

(1) in the hydrothermal crystallization process, the template agent is decomposed, so that the quality of the titanium silicalite molecular sieve is influenced, the template agent is a raw material with higher value in the production process of the titanium silicalite molecular sieve, the template agent is difficult to recycle due to ineffective decomposition, and the feeding amount of the template agent is increased for ensuring the quality of the molecular sieve, so that the production cost of the titanium silicalite molecular sieve is obviously increased; in addition, the decomposed template agent forms an oil phase, which not only influences the crystallization of the molecular sieve, but also floats on the upper layer of the hydrothermal crystallization slurry after standing, and part of oil phase substances are attached to the inner surface of the hydrothermal crystallization kettle, so that the hydrothermal crystallization kettle is polluted, and the cleaning difficulty of the hydrothermal crystallization kettle is increased;

(2) the titanium silicalite molecular sieve product obtained by the existing method through separation, washing, drying and roasting can generate a large amount of ammonia nitrogen wastewater in the separation and washing processes, the COD value of the ammonia nitrogen wastewater is extremely high, the requirements of discharge and/or recycling can be met only after purification treatment is carried out, and the production burden of titanium silicalite molecular sieve manufacturers is increased by the purification treatment of the large amount of ammonia nitrogen wastewater.

In view of the above problems, the inventors of the present invention have conducted extensive studies and found that condensation of steam generated during the hydrolysis condensation reaction, and mixing of a mixture obtained by the hydrothermal condensation reaction with at least a portion of the condensate followed by hydrothermal crystallization can effectively inhibit decomposition of a template agent during the hydrothermal crystallization, and that the mixture obtained by the hydrothermal crystallization can be directly spray-molded, thereby avoiding generation of ammonia nitrogen wastewater and reducing energy consumption for production. The present invention has been completed based on this finding.

According to a first aspect of the present invention, there is provided a process for producing a titanium silicalite molecular sieve, the process comprising:

(1) carrying out a first hydrolysis condensation reaction on an organic silicon source, a titanium source, a template agent and water to obtain a first hydrolysis condensation mixture, carrying out a second hydrolysis condensation reaction on the first hydrolysis condensation mixture to obtain a second hydrolysis condensation mixture, and leading out and condensing generated steam in the first hydrolysis condensation reaction and the second hydrolysis condensation reaction to obtain a condensate;

(2) mixing the hydrolytic condensation mixture with at least part of the condensate, and then carrying out hydrothermal crystallization to obtain a hydrothermal crystallization mixture;

(3) optionally, increasing the dry basis content of the hydrothermal crystallization mixture to obtain slurry;

(4) and carrying out spray forming on the hydrothermal crystallization mixture or the slurry.

According to a second aspect of the invention, there is provided a titanium silicalite molecular sieve produced by the process of the first aspect of the invention.

According to a third aspect of the present invention, there is provided an ammoximation reaction method, comprising contacting cyclohexanone, ammonia and hydrogen peroxide with a titanium silicalite molecular sieve under ammoximation reaction conditions, wherein the titanium silicalite molecular sieve is the titanium silicalite molecular sieve of the second aspect of the present invention.

The titanium silicalite molecular sieve produced by the method not only can effectively inhibit the decomposition of the template agent in the hydrothermal crystallization process, but also can omit the processes of solid-liquid separation and washing of the mixture obtained by the hydrothermal crystallization, thereby greatly reducing the amount of wastewater generated in the production process.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The organic silicon source may be any of various materials capable of forming silica under hydrolytic condensation conditions, and may be, for example, one or more selected from silicon-containing compounds represented by formula I,

in the formula I, R₁、R₂、R₃And R₄Each is C₁-C₄Alkyl group of (1). Said C is₁-C₄Alkyl of (2) includes C₁-C₄Straight chain alkyl of (2) and C₃-C₄Specific examples thereof may include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and tert-butyl.

Preferably, the silicon source is one or more than two selected from methyl orthosilicate, ethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate and n-butyl orthosilicate.

The titanium source can be a titanium source commonly used in the technical field of molecular sieve preparation. In particular, the titanium source may be an organic titanium source (e.g. an organic titanate) and/or an inorganic titanium source (e.g. an inorganic titanium salt). The inorganic titanium source may be TiCl₄、Ti(SO₄)₂、TiOCl₂One or more of titanium hydroxide, titanium oxide, titanium nitrate and titanium phosphate. The organic titanium source can be one or more than two of fatty titanium alkoxide and organic titanate. The titanium source is preferably an organic titanium source, more preferably an organic titanate, and still more preferably of the formula M₄TiO₄The organic titanate shown, wherein 4M can be same or different, and each is preferably C₁-C₄Alkyl group of (1). The titanium source is particularly preferably one or two or more of tetraisopropyl titanate, tetra-n-propyl titanate, tetrabutyl titanate, and tetraethyl titanate.

The template agent can be a template agent commonly used in the technical field of molecular sieve preparation, and specifically can be one or more than two of urea, amine, alcohol amine and quaternary ammonium hydroxide.

The quaternary ammonium base may be various organic quaternary ammonium bases, the amine may be an organic compound having at least one amino group in a molecular structure, and the alcohol amine may be an organic compound having at least one amino group and at least one hydroxyl group in a molecular structure.

Specifically, the quaternary ammonium base can be a quaternary ammonium base shown in a formula II,

in the formula II, R₅、R₆、R₇And R₈Are the same or different and are each 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.

The amine may be an aliphatic amine of formula III,

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.

The alcohol amine may be an aliphatic alcohol amine represented by formula IV,

(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. Preferably, the alcohol amine is monoethanolamine,One or more of diethanolamine and triethanolamine.

Specific examples of the templating agent may include, but are not limited to, one or more of urea, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, ethylamine, n-butylamine, butanediamine, hexamethylenediamine, monoethanolamine, diethanolamine, and triethanolamine.

Preferably, the templating agent is a quaternary ammonium base, more preferably tetraethylammonium hydroxide and/or tetrapropylammonium hydroxide.

According to the method of the present invention, in step (1), the amounts of the organic silicon source, the titanium source, the template and water can be selected conventionally. Generally, the molar ratio of the organic silicon source, the titanium source, the templating agent, and the water may be 100: (0.005-10): (0.005-40): (200-10000), preferably 100: (0.05-8): (0.5-30): (500- & ltSUB & gt 5000- & gt), more preferably 100: (0.2-8): (5-25): (800-4000), more preferably 100: (1-6): (10-20): (1200-3000), the organic silicon source is SiO₂The titanium source is calculated as TiO₂In terms of NH, the template agent₃And (6) counting.

In the step (1), an organic silicon source, a titanium source, a template and water may be simultaneously added to the reaction kettle to perform a first hydrolysis condensation reaction, or the template and water may be prepared into an aqueous solution containing the template, the titanium source and the organic silicon source are prepared into a mixture containing the titanium source and the organic silicon source, and the aqueous solution containing the template and the mixture containing the titanium source and the organic silicon source are simultaneously added to the reaction kettle to perform the first hydrolysis condensation reaction.

The mixture containing the titanium source and the organic silicon source can be obtained by mixing the titanium source and the organic silicon source. Preferably, the mixture containing the titanium source and the organic silicon source can be obtained by a method comprising the following steps: the titanium source and the organic silicon source are mixed with stirring at 0 to 60 ℃, preferably 15 to 40 ℃, more preferably 20 to 30 ℃ for 1 to 2 hours.

The aqueous solution containing the templating agent may be obtained by dispersing the templating agent in water, the mixing may be performed at a temperature of 20-60 deg.C, preferably 15-40 deg.C, more preferably 20-30 deg.C, the mixing may be continued for 1-2 hours, and the templating agent may be provided in pure form or in the form of a concentrated solution.

The first hydrolytic condensation reaction may be carried out at a temperature of 35 to 80 c, preferably 40 to 60 c. Generally, the duration of the first hydrolytic condensation reaction may be from 1 to 20 hours, preferably from 5 to 18 hours, more preferably from 10 to 15 hours.

In the step (1), the first hydrolytic condensation reaction may be carried out under normal pressure (i.e., 1 atm), or may be carried out under pressure. Generally, the first hydrolytic condensation reaction may be carried out at a pressure of-0.2 MPa to 0MPa, the pressure being a gauge pressure.

The second hydrolytic condensation reaction may be carried out at a temperature of 70 to 98 deg.C, preferably 80 to 96 deg.C, more preferably 90 to 95 deg.C. The duration of the second hydrolytic condensation reaction may be from 1 to 15 hours, preferably from 3 to 12 hours, more preferably from 6 to 10 hours.

In the step (1), the second hydrolytic condensation reaction may be performed under normal pressure (i.e., 1 atm), or may be performed under reduced pressure. Generally, the second hydrolytic condensation reaction may be carried out at a pressure of-0.2 MPa to 0MPa, the pressure being a gauge pressure.

In the step (1), the titanium source and the organic silicon source are subjected to hydrolysis condensation reaction, and simultaneously release a small molecular compound, usually alcohol. These small molecule compounds volatilize to form vapor which escapes from the reaction system. According to the method of the invention, the escaping vapour is condensed and the condensate is collected.

The condensate contains water and alcohol. In general, the alcohol may be present in an amount of 80 to 96% by weight, preferably 83 to 95% by weight, more preferably 88 to 92% by weight, and the water may be present in an amount of 4 to 20% by weight, preferably 5 to 17% by weight, more preferably 8 to 12% by weight, based on the total amount of the condensate. In addition to water and alcohol, the condensate also contains nitrogen, which is typically derived from the templating agent. The concentration of nitrogen element in the condensate may be 0.01 to 50mmol/L, preferably 0.02 to 20mmol/L, more preferably 0.04 to 5mmol/L, and still more preferably 0.05 to 3 mmol/L. Particularly preferably, the concentration of nitrogen element in the condensate is 0.5-1.5mmol/L, so that the decomposition of the template agent in the hydrothermal crystallization process can be better inhibited.

According to the process of the invention, in step (2), the entire condensate may be mixed with the hydrolytic condensation mixture, or part of the condensate may be mixed with the hydrolytic condensation mixture. Preferably, the condensate may be used in an amount of 1 to 50 parts by weight, preferably 2 to 40 parts by weight, relative to 100 parts by weight of the hydrolytic condensation mixture. More preferably, the condensate is used in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the hydrolytic condensation mixture. Further preferably, the condensate is used in an amount of 10 to 25 parts by weight with respect to 100 parts by weight of the hydrolytic condensation mixture, so that the decomposition of the template agent during hydrothermal crystallization can be inhibited and the quality of the molecular sieve obtained by hydrothermal crystallization can be further improved.

In step (2), the hydrolytic condensation mixture may be mixed with a portion of the condensate at a temperature of 20 to 80 ℃, preferably 40 to 60 ℃ for 1 to 6 hours, preferably 1 to 3 hours. The mixing may be carried out by means of stirring.

In the step (2), the hydrothermal crystallization may be performed under conventional conditions. According to the method of the present invention, a titanium silicalite molecular sieve having a desired crystal form can be obtained even if hydrothermal crystallization is performed at a lower temperature for a shorter time than existing hydrothermal crystallization conditions under the same remaining conditions. According to the method of the present invention, in the step (2), the hydrothermal crystallization is preferably performed at a temperature of 120-. The duration of the hydrothermal crystallization is preferably 6 to 30 hours, more preferably 9 to 25 hours. The hydrothermal crystallization is usually carried out under autogenous pressure, and pressure may be additionally applied during the hydrothermal crystallization. Preferably, the hydrothermal crystallization is performed under autogenous pressure.

According to the method of the present invention, step (3) may be performed or step (3) may not be performed.

According to the method of the present invention, in one embodiment, step (3) is not performed, and the hydrothermal crystallization mixture is directly fed to step (4) for spray forming, which further simplifies the process and further reduces the material and energy consumption of the operation.

According to the method of the invention, in another embodiment, the method comprises the step (3) of increasing the dry content of the hydrothermal crystallization mixture to obtain a slurry, and the slurry is sent to the step (4) for spray forming. From the viewpoint of further improving the quality of the titanium silicalite molecular sieve particles obtained by spray molding, it is preferable to increase the dry content of the hydrothermal crystallization mixture to 25 to 45% by weight, and more preferable to increase the dry content of the hydrothermal crystallization mixture to 28 to 40% by weight. In the invention, the dry content is the mass percentage of the hydrothermal crystallization mixture after drying the hydrothermal crystallization mixture at 120 ℃ for 8 hours.

According to this embodiment, in one example, supplemental titanium silicalite molecular sieves are added to the hydrothermal crystallization mixture to increase the dry basis content of the hydrothermal crystallization mixture. The added complementary titanium silicalite molecular sieves can be titanium silicalite molecular sieves with the topological structures consistent with those of the titanium silicalite molecular sieves prepared in the step (1) and the step (2), and can also be titanium silicalite molecular sieves with the topological structures different from those of the titanium silicalite molecular sieves prepared in the step (1) and the step (2). Preferably, the topology structure of the titanium silicalite molecular sieve prepared by the step (1) and the step (2) is consistent with that of the complementary titanium silicalite molecular sieve, and more preferably, the topology structure of the titanium silicalite molecular sieve prepared by the step (1) and the step (2) and that of the complementary titanium silicalite molecular sieve are both titanium silicalite molecular sieves with MFI structures, such as titanium silicalite TS-1.

In this embodiment, the hydrothermal crystallization mixture and the complementary titanium silicalite molecular sieves can be uniformly mixed by a conventional method. For example, the hydrothermal crystallization mixture and the complementary titanium silicalite molecular sieve can be uniformly mixed by stirring.

In this embodiment, the conditions for mixing the hydrothermal crystallization mixture and the complementary titanium silicalite molecular sieves are not particularly limited, and may be performed under conventional conditions. For example, the hydrothermal crystallization mixture may be mixed with the complementary titanium silicalite molecular sieves uniformly at a temperature of 20 to 100 ℃, preferably 30 to 60 ℃, more preferably 30 to 40 ℃. The mixing duration is based on the capability of uniformly mixing the hydrothermal crystallization mixture and the supplementary titanium silicalite molecular sieve. Generally, the duration of the mixing may be from 0.1 to 12 hours, preferably from 0.5 to 6 hours, more preferably from 1 to 3 hours.

According to this embodiment, in another example, the hydrothermal crystallization mixture may be subjected to distillation to remove a portion of the liquid phase material, thereby adjusting the dry content of the resulting slurry to be in the range of 25 to 45 wt%, preferably 28 to 40 wt%. The distillation may be atmospheric distillation or vacuum distillation, and is preferably atmospheric distillation.

In the step (4), the conditions for spray forming may be selected conventionally, and the present invention is not particularly limited thereto. Generally, the inlet temperature for spray forming may be 200-450 deg.C, preferably 250-400 deg.C.

According to the method of the present invention, the molecular sieve particles obtained by spray forming can be used directly, for example, as a catalyst; the catalyst may be used after calcination, for example, as a catalyst after calcination. The conditions for the calcination in the present invention are not particularly limited, and the calcination may be carried out under conventional conditions. Specifically, the calcination may be carried out at a temperature of 300-800 ℃, preferably at a temperature of 450-650 ℃, more preferably at a temperature of 500-600 ℃. The duration of the calcination may be from 2 to 12 hours, preferably from 2 to 6 hours. The calcination may be performed in an air atmosphere or an inert atmosphere.

The titanium silicalite molecular sieve prepared by the method of the first aspect of the invention has an increased external specific surface area compared to titanium silicalite molecular sieves prepared by conventional methods. Specifically, the external specific surface area of the titanium-silicon molecular sieve prepared by the conventional method is generally 20-30m²The titanium silicalite molecular sieves prepared by the process of the first aspect of the invention typically have an external specific surface area of from 35 to 80m²A/g, preferably of 40 to 75m²/g。

The bulk density of the titanium silicalite molecular sieve prepared by the process of the first aspect of the invention is in the range of 0.2 to 0.4 g/mL. The bulk density of titanium silicalite molecular sieves prepared by conventional methods is typically in the range of 0.6 to 0.8 g/mL.

According to the ammoximation reaction method of the present invention, the ammoximation reaction conditions are not particularly limited, and may be carried out under conventional conditions.

In general, the molar ratio of cyclohexanone, ammonia and hydrogen peroxide may be 1: 0.2-5: 0.5-2, preferably 1: 1-3: 0.8-1.5.

The contacting may be carried out in a solvent or in the absence of a solvent. The solvent may be one or more of alcohol, nitrile, ether, ester and water. Specific examples of the solvent may include, but are not limited to, one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, methyl t-butyl ether, acetonitrile, and water. Preferably, the solvent is tert-butanol. The amount of the solvent used in the present invention is not particularly limited, and may be selected conventionally. Generally, the solvent may be used in an amount of 10 to 5000 parts by weight, preferably 100-4000 parts by weight, more preferably 1000-3000 parts by weight, relative to 100 parts by weight of cyclohexanone.

According to the cyclohexanone ammoximation reaction process of the present invention, the contact of cyclohexanone, ammonia and hydrogen peroxide may be carried out at a temperature of 40 to 100 deg.C, preferably 60 to 95 deg.C, more preferably 70 to 90 deg.C. The contacting can be carried out in a fixed bed reactor or in a slurry bed reactor. When the cyclohexanone is contacted in a fixed bed reactor, the liquid hourly volume space velocity of the cyclohexanone can be 0.1-50h^-1Preferably 0.2 to 25h^-1More preferably 1-20h^-1More preferably 2 to 15 hours^-1. When the slurry bed reactor is used for contact, the weight ratio of cyclohexanone to titanium silicalite molecular sieve can be 100: 1-50, preferably 100: 2-20.

The present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.

In the following production examples and production comparative examples, X-ray diffraction analysis (XRD) was performed on a Siemens D5005 type X-ray diffractometer; the infrared spectroscopic analysis was performed on a Nicolet 8210 type fourier infrared spectrometer.

In the following preparation examples and preparation comparative examples, the molar composition of the molecular sieve was measured on an X-ray fluorescence spectrometer of model 3271E, manufactured by japan physical motors corporation; the external specific surface area and the pore volume are measured by adopting a BET method; the bulk density was determined using the method specified in GB/T6286-.

In the following preparation examples and comparative preparations, the decomposition rate of the template agent in the hydrothermal crystallization process was calculated by the following method:

the decomposition rate (%) of the template (1-the weight of the oil phase separated after hydrothermal crystallization/the total weight of the template added before crystallization) × 100%, wherein the weight of the oil phase separated after hydrothermal crystallization and the total weight of the template added before crystallization are both calculated as N element.

In the following preparation examples and preparation comparative examples, the dry content means a solid content in percentage by mass of the hydrothermal crystallization mixture obtained by drying the hydrothermal crystallization mixture at 120 ℃ for 8 hours under normal pressure (i.e., 1 atm).

In the following experimental examples and experimental comparative examples, the content of each component in the obtained reaction solution was analyzed by gas chromatography, and on the basis, the conversion of cyclohexanone and the selectivity of caprolactam were calculated by the following formulas, respectively:

cyclohexanone conversion (%) × 100 [ (% by mole of added cyclohexanone-by mole of unreacted cyclohexanone)/mole of added cyclohexanone ];

caprolactam selectivity (%) × 100% in terms of molar amount of caprolactam produced by the reaction/(molar amount of cyclohexanone added-molar amount of unreacted cyclohexanone).

Preparative examples 1-10 are illustrative of the titanium silicalite molecular sieves of the present invention and methods for their production.

Reference example 1

This reference is made to the preparation of molecular sieves TS-1 by the method described in Zeolite, 1992, Vol.12, pp.943-950, which is used to illustrate the synthesis of titanium silicalite TS-1 by conventional hydrothermal crystallization.

At room temperature (20 ℃), 22.5 g of ethyl orthosilicate (silicon ester 28, available from xirkat chemical trade ltd, yokkang) was mixed with 7.0 g of tetrapropylammonium hydroxide, and 59.8 g of distilled water was added, and after stirring and mixing, hydrolysis was carried out at normal pressure and 60 ℃ for 1.0 hour to obtain a hydrolyzed solution of ethyl orthosilicate, a solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropyl alcohol was slowly added under vigorous stirring, and the resulting mixture was stirred at 75 ℃ for 3 hours to obtain a clear transparent colloid. Placing the colloid in a stainless steel sealed reaction kettle, and standing at a constant temperature of 170 ℃ for 3 days to obtain a mixture of crystallized products; the mixture was filtered, washed with water, and dried at 110 ℃ for 60 minutes to obtain a molecular sieve raw powder. The molecular sieve raw powder is roasted for 3 hours at the temperature of 550 ℃ in the air atmosphere to obtain the molecular sieve.

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1. The molecular sieve property parameters are listed in table 4.

Preparation of example 1

(1) A50 wt% concentrated solution of tetrapropylammonium hydroxide (the solvent for this concentrated solution is water) was added to deionized water at 20 ℃ under 1 atm with stirring, and mixed for 1 hour to obtain an aqueous solution containing a template.

Tetrabutyl titanate as a titanium source and ethyl orthosilicate (silicon ester 28, same as in reference example 1) as an organic silicon source were mixed at 20 ℃ and 1 atm with stirring for 1 hour to obtain a mixture containing the titanium source and the organic silicon source.

An aqueous solution containing a template agent and a mixture containing a titanium source and an organic silicon source were fed into a reaction vessel in the proportions shown in Table 1, and a first hydrolytic condensation reaction and a second hydrolytic condensation reaction were sequentially carried out with stirring under the reaction conditions shown in Table 1 to obtain a hydrolytic condensation mixture.

In the hydrolysis condensation reaction process, nitrogen is used for auxiliary purging, steam in the reaction kettle is taken out, the taken steam is condensed by adopting condensed water, the condensate enters a condensate storage tank, and the composition of the condensate is listed in table 2.

(2) And (2) feeding the hydrolysis condensation mixture obtained in the step (1) into a hydrothermal crystallization kettle, adding the condensate collected in the step (1) into the hydrothermal crystallization kettle, and stirring for 3 hours at the temperature of 40 ℃. The amounts of condensate used relative to 100 parts by weight of the hydrolytic condensation mixture (on a dry basis) are listed in Table 3.

Next, the hydrothermal crystallization kettle was sealed, the temperature in the hydrothermal crystallization kettle was raised to the hydrothermal crystallization temperature, and hydrothermal crystallization was performed under autogenous pressure, and the conditions of hydrothermal crystallization and the decomposition rate of the template agent during hydrothermal crystallization are shown in table 3.

After the hydrothermal crystallization was completed, the temperature in the hydrothermal crystallization kettle was naturally decreased to 30 ℃, the hydrothermal crystallization kettle was opened, titanium silicalite TS-1 (prepared by the same method as in reference example 1) was added to the hydrothermal crystallization kettle, and after stirring for 2 hours, the resulting slurry (dry basis content 28 wt%) was discharged.

(3) The resulting slurry was spray molded to obtain molecular sieve particles, the spray molding conditions being listed in table 4. And roasting the molecular sieve particles at 580 ℃ for 2 hours in an air atmosphere to obtain the molecular sieve.

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1. The parameters of the properties of the molecular sieve particles obtained are listed in Table 4。

Preparation of comparative example 1

The titanium silicalite molecular sieve is produced by the same method as the preparation example 1, except that in the step (2), the condensate collected in the step (1) is not added into the hydrothermal crystallization kettle, but the hydrolysis condensation mixture obtained in the step (1) is fed into the hydrothermal crystallization kettle, stirred for 3 hours at the temperature of 40 ℃, and then the hydrothermal crystallization kettle is sealed for hydrothermal crystallization.

Through detection, five-finger diffraction characteristic peaks which are special for an MFI structure exist in the XRD crystal phase of the obtained molecular sieve between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1.

Preparation of comparative example 2

A titanium silicalite molecular sieve was produced in the same manner as in preparation example 1, except that in step (2), the condensate collected in step (1) was replaced with an equal weight of deionized water.

Preparation of comparative example 3

A titanium silicalite molecular sieve was produced in the same manner as in preparative example 1, except that in step (2), the condensate collected in step (1) was replaced with an equal weight of ethanol.

Through detection, five-finger diffraction characteristic peaks which are special for an MFI structure exist in the XRD crystal phase of the obtained molecular sieve between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. On the upper partThe characterization result shows that the prepared molecular sieve is the titanium silicalite TS-1.

Preparation of comparative example 4

A titanium silicalite molecular sieve was produced in the same manner as in preparation example 1, except that in step (2), the condensate collected in step (1) was replaced with an equal weight of a mixture of water and ethanol (composition listed in table 2).

Preparation of comparative example 5

A titanium silicalite molecular sieve was produced in the same manner as in preparation example 1, except that in step (2), the condensate collected in step (1) was replaced with a mixed solution of water, ethanol and tetrapropylammonium hydroxide (composition shown in table 2) in equal weight.

Preparation of example 2

The titanium silicalite molecular sieve is produced by the same method as the preparation example 1, except that in the step (3), the titanium silicalite molecular sieve TS-1 is not added into the hydrothermal crystallization kettle, but the mixture obtained by hydrothermal crystallization is directly sprayed and formed.

Through detection, five-finger diffraction characteristic peaks which are special for an MFI structure exist in the XRD crystal phase of the obtained molecular sieve between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The presence of all-silicon molecules in the vicinityThe characteristic absorption peak absent from the sieve indicates that titanium has entered the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1.

Preparation of example 3

A titanium silicalite molecular sieve was produced in the same manner as in preparation example 1, except that, in step (1), the hydrolytic condensation reaction was carried out under the reaction conditions as listed in table 1.

Preparation of example 4

Preparation of example 5

(1) Tetrapropylammonium hydroxide was mixed with deionized water at 25 ℃ and 1 atm under stirring for 1.5 hours to obtain an aqueous solution containing a template.

The titanium source and the organic silicon source were mixed with stirring at 25 ℃ under 1 atm for 1.5 hours to obtain a mixture containing the titanium source and the organic silicon source.

Tetrapropylammonium hydroxide as a template, tetraisopropyl titanate as a titanium source, ethyl orthosilicate (silicon ester 40, available from sierkat chemical trade ltd, york, hong kong) as an organic silicon source, and water were fed into a reaction vessel in the proportions shown in table 1, and first hydrolysis and second hydrolysis were sequentially carried out with stirring according to the reaction conditions shown in table 1 to obtain a hydrolysis-condensation mixture.

(2) And (2) feeding the hydrolysis condensation mixture obtained in the step (1) into a hydrothermal crystallization kettle, adding the condensate collected in the step (1) into the hydrothermal crystallization kettle, and stirring for 2 hours at the temperature of 50 ℃. The amounts of condensate used relative to 100 parts by weight of the hydrolytic condensation mixture (on a dry basis) are listed in Table 3.

After the hydrothermal crystallization is completed, the temperature in the hydrothermal crystallization kettle is naturally reduced to 40 ℃, the hydrothermal crystallization kettle is opened, the titanium silicalite TS-1 (prepared by the same method as in reference example 1) is added into the hydrothermal crystallization kettle, and after stirring for 1 hour, the obtained slurry (with the dry basis content of 38 weight percent) is output.

(3) The resulting slurry was spray molded to obtain molecular sieve particles, the spray molding conditions being listed in table 4. And roasting the molecular sieve particles at 520 ℃ for 5 hours in an air atmosphere to obtain the molecular sieve.

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1. The properties of the resulting molecular sieve particles are set forth in table 4.

Preparation of comparative example 6

The titanium silicalite molecular sieve is produced by the same method as that of preparation example 5, except that in the step (2), the condensate collected in the step (1) is not added into the hydrothermal crystallization kettle, but the hydrolysis condensation mixture obtained in the step (1) is fed into the hydrothermal crystallization kettle, stirred at the temperature of 50 ℃ for 2 hours, and then the hydrothermal crystallization kettle is sealed for hydrothermal crystallization.

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1The characteristic absorption peak which the all-silicon molecular sieve does not have appears in the vicinity, and the titanium enters the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1.

Preparation of comparative example 7

A titanium silicalite molecular sieve was produced in the same manner as in preparation example 5, except that in step (2), the condensate collected in step (1) was replaced with a mixed solution of water, ethanol and tetrapropylammonium hydroxide (composition shown in table 2) of equal weight.

Preparation of example 6

Titanium silicalite molecular sieves were produced in the same manner as in preparative example 5 except that the condensate was used in the amounts shown in Table 3 relative to 100 parts by weight of the hydrolytic condensation mixture (on a dry basis).

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1Presence of all silicon in the vicinityThe molecular sieve does not have a characteristic absorption peak indicating that titanium has entered the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1.

Preparation of example 7

The titanium silicalite molecular sieve is produced by the same method as that of preparation example 5, except that in the step (3), the titanium silicalite molecular sieve TS-1 is not added into the hydrothermal crystallization kettle, but the mixture obtained by hydrothermal crystallization is directly sprayed and formed.

Preparation of example 8

(1) Tetrapropylammonium hydroxide was mixed with deionized water at 30 ℃ and 1 atm under stirring for 1 hour to obtain an aqueous solution containing a template.

Tetrabutyl titanate as a titanium source and ethyl orthosilicate (silicon ester 40, available from xiekatt chemical trade co., yokohong) as an organosilicon source were mixed at 30 ℃ and 1 atm under stirring for 1 hour to obtain a mixture containing the titanium source and the organosilicon source.

(2) And (2) feeding the hydrolysis condensation mixture obtained in the step (1) into a hydrothermal crystallization kettle, adding the condensate collected in the step (1) into the hydrothermal crystallization kettle, and stirring for 1 hour at the temperature of 60 ℃. The amounts of condensate used relative to 100 parts by weight of the hydrolytic condensation mixture (on a dry basis) are listed in Table 3.

After the hydrothermal crystallization is finished, opening the hydrothermal crystallization kettle after the temperature in the hydrothermal crystallization kettle naturally drops to 40 ℃, and distilling the hydrothermal crystallization mixture at normal pressure to obtain slurry with the dry basis content of 30 weight percent.

(3) The resulting slurry was spray molded to obtain molecular sieve particles, the spray molding conditions being listed in table 4. And roasting the molecular sieve particles at 500 ℃ for 6 hours in an air atmosphere to obtain the molecular sieve.

Preparation of comparative example 8

The titanium silicalite molecular sieve is produced by the same method as that of preparation example 8, except that in step (2), the condensate collected in step (1) is not added into the hydrothermal crystallization kettle, but the hydrolysis condensation mixture obtained in step (1) is fed into the hydrothermal crystallization kettle, stirred for 1 hour at the temperature of 60 ℃, and then the hydrothermal crystallization kettle is sealed for hydrothermal crystallization.

Through detection, in an XRD spectrogram of the obtained molecular sieve, a five-finger diffraction characteristic peak which is specific to an MFI structure exists between 22.5-25.0 degrees of 2 theta, and the molecular sieve is shown to have the MFI structure similar to TS-1. Fourier infrared spectrum at 960cm^-1Presence of all-silicon molecular sieves in the vicinity thereofIndicating that titanium has entered the sample framework. The above characterization results show that the prepared molecular sieve is a titanium silicalite TS-1.

Preparation of comparative example 9

A titanium silicalite molecular sieve was produced in the same manner as in preparative example 8, except that in step (2), the condensate collected in step (1) was replaced with a mixed solution of water, ethanol and tetrapropylammonium hydroxide (composition shown in table 2) of equal weight.

Preparation of comparative example 10

The titanium silicalite molecular sieve was produced in the same manner as in preparation example 8, except that in step (1), the hydrolysis condensation reaction was carried out without purging with nitrogen, and the vapor generated by the reaction was condensed and refluxed back to the reaction vessel. In the step (2), condensate is not added into the hydrothermal crystallization kettle, but the hydrolysis condensation mixture obtained in the step (1) is sent into the hydrothermal crystallization kettle, stirred for 1 hour at the temperature of 60 ℃, and then the hydrothermal crystallization kettle is sealed for hydrothermal crystallization.

Preparation of example 9

Titanium silicalite molecular sieves were produced in the same manner as in preparative example 8, except that the condensate was used in the amounts shown in Table 3 relative to 100 parts by weight of the hydrolytic condensation mixture (on a dry basis).

Preparation of example 10

The titanium silicalite molecular sieve is produced by the same method as that of preparation example 8, except that in step (3), the titanium silicalite molecular sieve TS-1 is not added into the hydrothermal crystallization kettle, but the mixture obtained by hydrothermal crystallization is directly sprayed and formed.

TABLE 1

TABLE 2

Numbering	Alcohol content (% by weight)	Nitrogen content (mmol/L)
			Preparation of example 1	90	1.23
Preparation of comparative example 4	90	0
			Preparation of comparative example 5	90	1.23
Preparation of example 3	82	2.39
			Preparation of example 4	95	0.09
Preparation of example 5	89	0.89
			Preparation of comparative example 7	89	0.89
Preparation of example 8	93	0.57
			Preparation of comparative example 9	92	0.53

TABLE 3

TABLE 4

The results of preparation examples 2, 7 and 10 demonstrate that, with the method of the present invention, the hydrothermal crystallization mixture obtained by hydrothermal crystallization can be directly spray-molded without adding additional titanium silicalite molecular sieves and adhesives or precursors thereof, thereby simplifying the operation process and reducing the material and energy consumption of the operation.

The results of preparation examples 1, 5 and 8 and preparation comparative examples 1 to 10 demonstrate that the method of the present invention for producing a titanium silicalite molecular sieve can effectively inhibit the ineffective decomposition of the template agent in the hydrothermal crystallization process, increase the amount of the template agent recycled, reduce the consumption of the template agent, and further reduce the production cost of the titanium silicalite molecular sieve by mixing at least part of the condensate generated in the hydrolysis condensation reaction process with the hydrolysis condensation mixture and then carrying out hydrothermal crystallization.

Experimental examples 1-10 are provided to illustrate the cyclohexanone ammoximation reaction method of the present invention.

Experimental examples 1 to 10

Experimental examples 1 to 10 the cyclohexanone ammoximation reaction was carried out by using the titanium silicalite molecular sieves prepared in preparation examples 1 to 10 as catalysts for the cyclohexanone ammoximation reaction, respectively, in the following manner.

The titanium silicalite molecular sieves prepared in preparation examples 1 to 10 were respectively loaded in a fixed bed reactor to form a catalyst bed (the aspect ratio of the catalyst bed is 5), cyclohexanone, ammonia, hydrogen peroxide (the concentration of hydrogen peroxide is 30 wt%) and a solvent were fed into the fixed bed reactor according to the ratio in table 5, and reacted under the reaction conditions listed in table 5. The reaction was continued for 80 hours. And collecting the reaction product output from the fixed bed reactor, measuring the composition of the reaction product, and calculating the conversion rate of cyclohexanone and the selectivity of caprolactam.

Each preparation example was repeated to prepare 3 batches of titanium silicalite molecular sieves, each batch of titanium silicalite molecular sieves was subjected to 3 sets of parallel experiments, each preparation example was subjected to 9 sets of experiments in total, and average values of cyclohexanone conversion and caprolactam selectivity obtained in the 9 sets of experiments were taken as the evaluation results of the catalytic performance of the titanium silicalite molecular sieves prepared in the preparation examples, and the specific results are listed in table 5.

Experimental comparative examples 1 to 10

The cyclohexanone ammoximation reaction was carried out in the same manner as in examples 1 to 10, except that the titanium silicalite molecular sieves prepared in comparative examples 1 to 10 were each used as a catalyst. The results of the experiment are listed in table 5.

Reference Experimental example 1

The cyclohexanone ammoximation reaction was carried out in the same manner as in examples 1 to 10, except that the titanium silicalite molecular sieve prepared in reference example 1 was used as the catalyst. The results of the experiment are listed in table 5.

TABLE 5

The results of experimental examples 1-10 confirm that the titanium silicalite molecular sieve prepared by the method of the invention can obtain more excellent catalytic performance as the catalyst of cyclohexanone ammoximation reaction.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for producing a titanium silicalite molecular sieve, the method comprising:

(4) and carrying out spray forming on the hydrothermal crystallization mixture.

2. The method according to claim 1, wherein in the step (1), the molar ratio of the organic silicon source, the titanium source, the template and the water is 100: (0.005-10): (0.005-40): (200-10000), the organic silicon source is SiO₂The titanium source is calculated as TiO₂In terms of NH, the template agent₃And (6) counting.

3. The method according to claim 2, wherein in the step (1), the molar ratio of the organic silicon source, the titanium source, the template and the water is 100: (0.05-8): (0.5-30): (500-5000), the organic silicon source is SiO₂The titanium source is calculated as TiO₂In terms of NH, the template agent₃And (6) counting.

4. The method of claim 3, wherein in step (1), the molar ratio of the organic silicon source, the titanium source, the templating agent, and the water is 100: (0.2-8): (5-25): (800-4000), the organic silicon source is SiO₂The titanium source is calculated as TiO₂In terms of NH, the template agent₃And (6) counting.

5. The method of claim 4, wherein in step (1), the molar ratio of the organic silicon source, the titanium source, the template agent and the water is 100: (1-6): (10-20): (1200-3000), the organic silicon source is SiO₂The titanium source is calculated as TiO₂In terms of NH, the template agent₃And (6) counting.

6. The method according to any one of claims 1 to 5, wherein the organic silicon source is selected from silicon-containing compounds of formula I,

in the formula I, R₁、R₂、R₃And R₄Each is C₁-C₄Alkyl group of (1).

7. The method according to claim 6, wherein the organic silicon source is one or more selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, and n-butyl orthosilicate.

8. The method of any one of claims 1-5, wherein the titanium source is TiCl₄、Ti(SO₄)₂、TiOCl₂One or more than two of titanium hydroxide, titanium oxide, titanium nitrate, titanium phosphate, tetraisopropyl titanate, tetra-n-propyl titanate, tetrabutyl titanate and tetraethyl titanate.

9. The method of any one of claims 1-5, wherein the templating agent is one or more of urea, amine, alcohol amine, and quaternary ammonium base.

10. The method of claim 9, wherein the templating agent is a quaternary ammonium base represented by formula II,

in the formula II, R₅、R₆、R₇And R₈Are the same or different and are each C₁-C₄Alkyl group of (1).

11. The method of claim 10, wherein the templating agent is tetraethylammonium hydroxide and/or tetrapropylammonium hydroxide.

12. The process according to claim 1, wherein the first hydrolytic condensation reaction is carried out at a temperature of 35-80 ℃ and the duration of the first hydrolytic condensation reaction is 1-20 hours.

13. The process according to claim 12, wherein the first hydrolytic condensation reaction is carried out at a temperature of 40-60 ℃ and the duration of the first hydrolytic condensation reaction is 5-18 hours.

14. The process according to claim 13, wherein the duration of the first hydrolytic condensation reaction is 10-15 hours.

15. The process according to any one of claims 1 and 12 to 14, wherein the second hydrolytic condensation reaction is carried out at a temperature of 70 to 98 ℃.

16. The process according to claim 15, wherein the second hydrolytic condensation reaction is carried out at a temperature of 80-96 ℃.

17. The process according to claim 16, wherein the second hydrolytic condensation reaction is carried out at a temperature of 90-95 ℃.

18. The process according to claim 15, wherein the duration of the second hydrolytic condensation reaction is from 1 to 15 hours.

19. The process according to claim 18, wherein the duration of the second hydrolytic condensation reaction is 3-12 hours.

20. The process according to claim 19, wherein the duration of the second hydrolytic condensation reaction is 6-10 hours.

21. A method according to any one of claims 1 to 5 and 12 to 14, wherein the condensate comprises water and alcohol, the alcohol being present in an amount of 80 to 96 wt% and the water being present in an amount of 4 to 20 wt%, based on the total amount of the condensate.

22. A method according to claim 21, wherein the condensate comprises water and alcohol, the alcohol being present in an amount of 83-95 wt% and the water being present in an amount of 5-17 wt%, based on the total amount of the condensate.

23. A method according to claim 22, wherein the condensate comprises water and alcohol, the alcohol being present in an amount of 88-92% by weight and the water being present in an amount of 8-12% by weight, based on the total amount of the condensate.

24. The method of any of claims 1-5 and 12-14, wherein the condensate contains nitrogen.

25. The method of claim 24, wherein the concentration of elemental nitrogen in the condensate is 0.01 to 50 mmol/L.

26. The method of claim 25, wherein the concentration of elemental nitrogen in the condensate is 0.02 to 20 mmol/L.

27. The method of claim 26, wherein the concentration of elemental nitrogen in the condensate is 0.04 to 5 mmol/L.

28. The method of claim 27, wherein the concentration of elemental nitrogen in the condensate is 0.05 to 3 mmol/L.

29. The method of claim 28, wherein the concentration of elemental nitrogen in the condensate is 0.5 to 1.5 mmol/L.

30. The process according to any one of claims 1 to 5 and 12 to 14, wherein in step (2), the condensate is used in an amount of 1 to 50 parts by weight relative to 100 parts by weight of the hydrolytic condensation mixture.

31. The process according to claim 30, wherein in step (2), the condensate is used in an amount of 2 to 40 parts by weight with respect to 100 parts by weight of the hydrolytic condensation mixture.

32. The process according to claim 31, wherein in step (2), the condensate is used in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the hydrolytic condensation mixture.

33. The process according to claim 32, wherein in step (2), the condensate is used in an amount of 10 to 25 parts by weight with respect to 100 parts by weight of the hydrolytic condensation mixture.

34. The process according to any one of claims 1 to 5 and 12 to 14, wherein in step (2) the hydrolytic condensation mixture is mixed with a portion of the condensate at a temperature of 20 to 80 ℃ for 1 to 6 hours with stirring.

35. The process according to claim 34, wherein in step (2), the hydrolytic condensation mixture is mixed with part of the condensate at a temperature of 40-60 ℃ for 1-3 hours with stirring.

36. The method as claimed in claim 1, wherein, in the step (2), the hydrothermal crystallization is performed at a temperature of 120-190 ℃.

37. The method as claimed in claim 36, wherein, in the step (2), the hydrothermal crystallization is carried out at a temperature of 140 ℃ to 185 ℃.

38. The method as claimed in claim 37, wherein, in the step (2), the hydrothermal crystallization is performed at a temperature of 160-180 ℃.

39. The method as claimed in claim 36, wherein the duration of the hydrothermal crystallization in step (2) is 6-30 hours.

40. The method as claimed in claim 39, wherein the duration of the hydrothermal crystallization in step (2) is 9-25 hours.

41. The method according to claim 1, wherein the method further comprises step (3): and (3) increasing the dry basis content of the hydrothermal crystallization mixture to obtain slurry, wherein the method for increasing the dry basis content comprises the steps of adding a supplementary titanium silicalite molecular sieve into the hydrothermal crystallization mixture or distilling the hydrothermal crystallization mixture, and in the step (4), carrying out spray forming on the slurry.

42. The method as claimed in claim 41, wherein in the step (3), the dry content of the hydrothermal crystallization mixture is increased to 25-45 wt%, wherein the dry content is a percentage of the mass of the hydrothermal crystallization mixture after drying at 120 ℃ for 8 hours.

43. The method as claimed in claim 42, wherein in the step (3), the dry content of the hydrothermal crystallization mixture is increased to 28-40 wt%, wherein the dry content is a percentage of the mass of the hydrothermal crystallization mixture after drying the hydrothermal crystallization mixture at 120 ℃ for 8 hours.

44. A titanium silicalite molecular sieve prepared by the method of any one of claims 1 to 43 having an external specific surface area of from 35 to 80m²/g。

45. A cyclohexanone ammoximation reaction process comprising contacting cyclohexanone, ammonia and hydrogen peroxide with a titanium silicalite molecular sieve under ammoximation reaction conditions, wherein the titanium silicalite molecular sieve is the titanium silicalite molecular sieve of claim 44.