CN111484031B - Modified titanium-silicon molecular sieve, preparation method and application thereof, and thioether oxidation method - Google Patents

Abstract

The invention relates to the field of molecular sieves, and discloses a modified titanium silicalite molecular sieve, a preparation method and application thereof, and a thioether oxidation method, wherein the molecular sieve comprises the following components: titanium element, aluminum element, silicon element and oxygen element, wherein the molecular sieve satisfies X _1‑1.8 /X _0.4‑0.9 ＝C，0.1<C<0.5. The preparation method of the molecular sieve comprises the following steps: carrying out acidic steam modification on a titanium-silicon molecular sieve; (2) Mixing and contacting the titanium-silicon molecular sieve modified in the step (1) with an aluminum source, an alkali source and water; (3) And (3) carrying out heat treatment on the solid product obtained in the step (2) in an alkaline steam atmosphere. The modified titanium silicalite molecular sieve provided by the invention is used for thioether oxidation, and the selectivity of sulfone can be effectively improved.

Description

Modified titanium-silicon molecular sieve, preparation method and application thereof, and sulfide oxidation method

technical field

The invention relates to the field of molecular sieves, in particular to a modified titanium-silicon molecular sieve, a preparation method and application thereof, and a sulfide oxidation method.

Background technique

Titanium-silicon molecular sieve is a molecular sieve whose skeleton is composed of silicon, titanium and oxygen elements, and has broad application prospects in petroleum refining and petrochemical industry. Among them, TS-1 molecular sieve is a new type of titanium-silicon molecular sieve with excellent catalytic selective oxidation performance formed by introducing transition metal element titanium into the molecular sieve framework with 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. Although titanium-silicon molecular sieves have achieved industrial applications in some catalytic oxidation fields (such as the process of preparing cyclohexanone oxime by catalytic ammoxidation of cyclohexanone), the catalytic performance of titanium-silicon molecular sieves is still poor, so that it is restricted in other industrial applications. limit.

Sulfones are important sulfur-containing compounds. For example, dimethyl sulfone is a white crystalline powder, easily soluble in water, ethanol, benzene, methanol and acetone, and slightly soluble in ether. Dimethyl sulfone is used in industry as a high-temperature solvent and raw material for organic synthesis, as a stationary liquid for gas chromatography, as a analytical reagent, as a food additive, and as a drug. As an organic sulfide, dimethyl sulfone can enhance the ability of the human body to produce insulin, and at the same time, it can also promote the metabolism of carbohydrates. It is a necessary substance for the synthesis of human collagen.

At present, sulfone can be prepared by oxidation of thioether. When oxidizing sulfide (especially peroxide) is used to oxidize sulfide, the oxidation product is mainly a mixture of sulfoxide and sulfone. Therefore, how to adjust the selectivity of the target product (sulfone) according to production needs is an important research content of the thioether oxidation process.

Contents of the invention

The object of the present invention is to provide a modified titanium silicon molecular sieve, its preparation method and application, and a thioether oxidation method in order to overcome the problem of low selectivity of sulfone in the thioether oxidation process in the prior art. Using the modified titanium-silicon molecular sieve provided by the invention for sulfide oxidation can effectively improve the selectivity of sulfone.

In order to achieve the above object, the first aspect of the present invention provides a modified titanium-silicon molecular sieve, the molecular sieve includes: titanium element, aluminum element, silicon element and oxygen element, wherein the molecular sieve satisfies X _1-1.8 /X _0.4-0.9 = C, 0.1<C<0.5, X _0.4-0.9 is the ratio of the molecular sieve’s micropore diameter in the range of 0.4-0.9nm to the total micropore diameter distribution, X _1-1.8 is the molecular sieve’s micropore diameter in the range of 1-1.8nm The proportion of the total micropore size distribution.

Preferably, the surface silicon-titanium ratio of the molecular sieve is not lower than the bulk phase silicon-titanium ratio, the silicon-titanium ratio refers to the molar ratio of silicon oxide to titanium oxide, and more preferably, the surface silicon-titanium ratio and the bulk phase The ratio of the phase silicon to titanium ratio is 1.2-5.

The second aspect of the present invention provides a method for preparing the above-mentioned modified titanium-silicon molecular sieve, the method comprising:

(1) carry out acidic steam modification with titanium silicon molecular sieve;

(2) The titanium silicon molecular sieve after step (1) modification is mixed with aluminum source, alkali source and water contact;

(3) Under an alkaline steam atmosphere, heat-treat the solid product obtained in step (2).

Preferably, a silicon source is also added during the contacting process in step (2), more preferably the silicon source is an organosilicon source, and even more preferably the hydrolysis rate of the organosilicon source is 40-60%.

The third aspect of the present invention provides the application of the modified titanium silicate molecular sieve of the present invention in sulfide oxidation.

According to a fourth aspect of the present invention, the present invention provides a method for thioether oxidation, the method comprising: contacting a liquid mixture with a catalyst under thioether oxidation conditions, the liquid mixture containing thioether, at least one An oxidant and optionally at least one solvent, the catalyst contains the modified titanium-silicon molecular sieve of the present invention or the modified titanium-silicon molecular sieve prepared by the preparation method of the present invention.

The modified titanium-silicon molecular sieve with special physical and chemical characteristic structure of the present invention can achieve better catalytic effect when used in the reaction of sulfide oxidation. That is, because the material of the present invention has a micropore size distribution in the range of 1-1.8nm, and X _1-1.8 /X _0.4-0.9 =C, 0.1<C<0.5, it is beneficial to the diffusion of reactants and product molecules in the catalytic reaction , which is beneficial to the thioether oxidation reaction and can effectively modulate the selectivity of the target product sulfone.

The inventors of the present invention found in the research process that the titanium-silicon molecular sieve can be modified by acidic steam, then mixed and contacted with aluminum source, alkali source and water, and then heat-treated in an alkaline steam atmosphere. A modified titanium-silicon molecular sieve with a special characteristic structure, for example, has a micropore size distribution in the range of 1-1.8nm.

In a preferred situation of the present invention, during the contact process of step (2), an optional silicon source is simultaneously introduced so that the surface silicon-titanium ratio of the modified titanium-silicon molecular sieve is not lower than the bulk phase silicon-titanium ratio, and the obtained modified titanium-silicon molecular sieve It is more beneficial to effectively adjust the selectivity of the target product sulfone when it is used in the oxidation reaction of thioether.

The modified titanium-silicon molecular sieve provided by the invention has a special physical and chemical characteristic structure, and is used for sulfide oxidation reaction, which is beneficial to adjust the selectivity of the target product (sulfone).

Other features and advantages of the present invention will be described in detail in the following detailed description.

Detailed ways

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Neither the endpoints nor any values of the ranges disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed herein.

The present invention provides a modified titanium-silicon molecular sieve, the molecular sieve includes: element, aluminum element, silicon element and oxygen element, wherein, the molecular sieve satisfies X _1-1.8 /X _0.4-0.9 =C, 0.1<C<0.5, X _0.4-0.9 is the ratio of the micropore diameter of molecular sieve in the range of 0.4-0.9nm to the total micropore diameter distribution, X _1-1.8 is the ratio of the micropore diameter of molecular sieve in the range of 1-1.8nm to the total micropore diameter distribution Proportion.

According to a preferred embodiment of the present invention, 0.25<C<0.5. The molecular sieve provided by the present invention not only has a pore size distribution in the range of 0.4-0.9nm, but also has a distribution in the range of 1-1.8nm, and the ratio of the micropore diameter in the range of 1-1.8nm to the total micropore diameter distribution is the same as that in the 0.4nm range. The ratio of the micropore diameter in the range of -0.9nm to the total micropore diameter distribution is C, 0.1<C<0.5, preferably, 0.25<C<0.5, more preferably, 0.3<C<0.5. Adopt the molecular sieve of preferred technical scheme of the present invention, when being used for thioether oxidation reaction, be more conducive to the diffusion of reactant and product molecule in the catalytic reaction, not only can further improve the conversion rate of oxidant (for example peroxide), also can More effectively modulate the selectivity of target products such as sulfones. In the present invention, the test method of micropore diameter can be carried out according to conventional methods, and the present invention has no special requirements, and is well known to those skilled in the art, such as using _N2 static adsorption and other methods for testing. In the present invention, the pore size distribution is measured on ASAP2405 static nitrogen adsorption instrument of Micromeritics Company.

What needs to be specially explained here is that if the pore size distribution of micropores accounts for less than 1% of the total pore size distribution in the range of 1-1.8nm, the pore distribution of this part of the micropores is ignored, that is, it is considered to be in the range of 1-1.8nm There is no micropore distribution in the nm range, as is known to those skilled in the art. Therefore, the present invention has a micropore diameter in the range of 1-1.8nm under the _N2 static adsorption test, which means that the ratio of the micropore diameter distribution in the range of 1-1.8nm to the total micropore diameter distribution is >1%. . Microporous molecular sieves prepared by conventional direct hydrothermal synthesis, the proportion of micropore size distribution in the range of 1-1.8nm to the total micropore size distribution is less than 1%, and the common treatment and modification methods are used to treat the modified micropores For molecular sieves, the ratio of micropore size distribution in the range of 1-1.8nm to the total micropore size distribution is also low, <10%, generally <1%.

According to the molecular sieve of the present invention, preferably the molecular sieve satisfies _Tw / _Tk =D, 0.2<D<0.5, more preferably, 0.25<D<0.45, wherein, _Tw is the micropore volume of the molecular sieve, and _Tk is The total pore volume of the molecular sieve. In the present invention, the test method of the pore volume can be carried out according to the conventional method, and the present invention has no special requirements, and is well known to those skilled in the art, such as using _N2 static adsorption and other methods for testing.

According to the molecular sieve of the present invention, preferably, the molar ratio of silicon element: titanium element: aluminum element of the molecular sieve is 100: (0.1-10): (0.01-5), preferably 100: (0.2-5): ( 0.2-4), more preferably the molar ratio of silicon: titanium: aluminum is 100: (0.5-4): (0.5-4), the most preferred silicon: titanium: aluminum molar ratio is 100: (1-4): (0.5-4).

In the present invention, X-ray fluorescence spectrometry (XRF) is used to measure the content of titanium element, silicon element and aluminum element in the molecular sieve. The test methods are all carried out according to conventional methods, without special requirements, which are well known to those skilled in the art, and will not be repeated here.

According to the modified titanium-silicon molecular sieve of the present invention, preferably, the surface silicon-titanium ratio of the molecular sieve is not lower than the bulk phase silicon-titanium ratio, and the silicon-titanium ratio refers to the molar ratio of silicon oxide to titanium oxide; more preferably, The ratio of the surface silicon-titanium ratio to the bulk silicon-titanium ratio is 1.2-5; more preferably, the ratio of the surface silicon-titanium ratio to the bulk silicon-titanium ratio is 1.5-4.5.

In the present invention, the surface silicon-titanium ratio is measured by X-ray photoelectron spectroscopy, and the bulk silicon-titanium ratio is measured by X-ray fluorescence spectroscopy.

The aforementioned modified titanium-silicon molecular sieve of the present invention has the advantage of micropore size distribution in the range of 1-1.8nm, and preferably, the surface silicon-titanium ratio is not lower than the bulk phase silicon-titanium ratio. The present invention has no special requirements on the preparation method of the aforementioned modified titanium-silicon molecular sieve, as long as the modified titanium-silicon molecular sieve with the above structure can be prepared.

The present invention also provides a method for preparing the modified titanium-silicon molecular sieve of the present invention, the method comprising:

(1) carry out acidic steam modification with titanium silicon molecular sieve;

(2) The titanium silicon molecular sieve after step (1) modification is mixed with aluminum source, alkali source and water contact;

(3) Under an alkaline steam atmosphere, heat-treat the solid product obtained in step (2).

According to a specific embodiment of the present invention, the acid steam modification refers to contacting the titanium silicon molecular sieve with acid steam. Preferably, the acidic steam modification in step (1) includes: contacting the titanium silicon molecular sieve with acidic steam for acidic steam modification.

In the present invention, the source of the acidic steam is not particularly limited, and it can be any way to obtain the acidic steam. Specifically, the acidic steam can be formed by heating the aqueous acid solution, or the acidic steam can be formed by passing superheated steam through the aqueous acid solution. In the present invention, the acid vapor is obtained by heating an acid aqueous solution as an example for illustration.

Preferably, the acidic steam is obtained by heating an aqueous acid solution, and the concentration of the aqueous acid solution is >0.1 mol/L, more preferably ≥1 mol/L, even more preferably 1-15 mol/L. In the present invention, the main solvent of the acid aqueous solution is water, and other solvent additives can also be added as required. The characteristics of the modified titanium-silicon molecular sieve prepared in this way are more obvious, such as the pore volume and the distribution of micropores in the range of 1-1.8nm.

Preferably, the acid in the aqueous acid solution is an organic acid and/or an inorganic acid, more preferably an inorganic acid; wherein the inorganic acid can be one or more of HCl, sulfuric acid, perchloric acid, nitric acid and phosphoric acid; The organic acid may be a C1-C10 organic carboxylic acid, preferably one or more of formic acid, acetic acid, propionic acid, naphthenic acid, peroxyacetic acid and peroxypropionic acid.

According to a preferred embodiment of the present invention, the temperature of the acid steam modification is 40-200°C, more preferably 60-180°C, further preferably 80-150°C.

According to the method of the present invention, the time for the acidic steam modification can be determined according to needs. For the present invention, the preferred time is 0.5-360 h, more preferably 1-240 h, and more preferably 2-120 h.

According to the method of the present invention, preferably, the molar ratio of titanium-silicon molecular sieve to acidic steam is 100:(0.5-40), more preferably 100:(1-15), further preferably 100:(5-15), most preferably It is preferably 100: (5-12), wherein, the titanium silicon molecular sieve is counted as SiO ₂ , and the acid vapor is counted as H ⁺ .

According to the method of the present invention, preferably, the method of the present invention further includes: before the titanium-silicon molecular sieve is subjected to acidic steam modification, first roasting the titanium-silicon molecular sieve. In the present invention, the optional range of the roasting conditions is relatively wide, and the preferred roasting conditions for the present invention include: the roasting temperature is 300-800°C, preferably 550-600°C; the roasting time is 2-12h , preferably 2-4h, the firing atmosphere includes air atmosphere.

In the method described in the present invention, step (1) can be carried out in a fixed bed reactor.

In the present invention, specifically, after the acidic steam passes through the titanium-silicon molecular sieve in the fixed-bed reactor, it can be recycled in the process of forming acidic steam, and the acidic steam that has passed through the titanium-silicon molecular sieve in the fixed-bed reactor can also be directly recycled The titanium-silicon molecular sieve is modified by acidic steam by passing it into a fixed-bed reactor.

In the present invention, the aluminum source is a substance that can provide aluminum, preferably the aluminum source is one or more of aluminum sol, aluminum salt, aluminum hydroxide and aluminum oxide, and the aluminum sol preferably has a content of 10-50% by weight.

In the present invention, the aluminum salt can be an inorganic aluminum salt and/or an organic aluminum salt, the organic aluminum salt is preferably a C1-C10 organic aluminum salt, and the inorganic aluminum salt can be, for example, aluminum sulfate, sodium metaaluminate , one or more of aluminum chloride and aluminum nitrate.

According to a preferred embodiment of the present invention, in step (2), the molar ratio of the modified titanium-silicon molecular sieve: aluminum source: alkali source: water is 100: (0-10): (0.5-50) : (20-1000), further preferably the modified titanium-silicon molecular sieve: aluminum source: alkali source: the molar ratio of water is 100: (0.2-5): (1-20): (100-800), It is further preferred that the molar ratio of the modified titanium-silicon molecular sieve: aluminum source: alkali source: water is 100: (0.5-3): (5-15): (200-600), wherein the modified Titanium silicon molecular sieve is counted as SiO ₂ , aluminum source is counted as Al ₂ O ₃ , and alkali source is counted as N or OH ^- .

According to the method of the present invention, the optional range of the type of the alkali source is relatively wide, and it can be an organic alkali source and/or an inorganic alkali source, wherein the inorganic alkali source can be ammonia or a cation that is an alkali metal or an alkaline earth metal Alkali, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, barium hydroxide, etc., the organic alkali source can be urea, aliphatic amine compounds, aliphatic alcohol amine compounds and quaternary ammonium One or more of alkali compounds. Preferably, the alkali source is one or more of ammonia, aliphatic amines, aliphatic alcohol amines and quaternary ammonium bases.

In the present invention, the quaternary ammonium base can be various organic quaternary ammonium bases, and the aliphatic amine can be a compound formed after at least one hydrogen in various _NH is replaced by an aliphatic hydrocarbon group (preferably an alkyl group) , the aliphatic alcohol amine can be a compound formed after at least one hydrogen in various _NH3 is replaced by a hydroxyl-containing aliphatic hydrocarbon group (preferably an alkyl group).

Specifically, the quaternary ammonium base may be a quaternary ammonium base as shown in formula II, the aliphatic amine may be an aliphatic amine represented by formula III, and the aliphatic alcohol amine may be an aliphatic amine represented by formula IV Alcoholamine:

In formula II, each of R ⁵ , R ⁶ , R ⁷ and R ⁸ is a C ₁ -C ₄ alkyl group, including a C ₁ -C ₄ straight chain alkyl group and a C ₃ -C ₄ branched chain alkyl group, for example : each of R ⁵ , R ⁶ , R ⁷ and R ⁸ may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.

R ⁹ (NH ₂ ) _n (Formula III)

In formula III, n is an integer of 1 or 2. When n is 1, R ⁹ is C ₁ -C ₆ alkyl, including C ₁ -C ₆ straight chain alkyl and C ₃ -C ₆ branched chain alkyl, such 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, R ⁹ is C ₁ -C ₆ alkylene, including C ₁ -C ₆ straight chain alkylene and C ₃ -C ₆ branched chain alkylene, such 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, butylenediamine and hexamethylenediamine

(HOR ¹⁰ ) _m NH _(3-m) (Formula IV)

In formula IV, m R ^10s are the same or different, and each is a C ₁ -C ₄ alkylene group, including a C ₁ -C ₄ straight chain alkylene group and a C ₃ -C ₄ branched chain alkylene group, 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.

According to a preferred embodiment of the present invention, in order to further improve the pore order of the synthesized modified titanium-silicon molecular sieve, preferably the alkali source is sodium hydroxide, ammonia water, ethylenediamine, n-butylamine, butanediamine One or more of amine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, tetraethylammonium hydroxide and tetrapropylammonium hydroxide.

Wherein, when the alkali source contains ammonia water, the molar ratio of the alkali source is based on ammonia in molecular form NH ₃ and ion form NH ₄ ⁺ .

In the present invention, when the alkali source contains both N and ^OH- , unless otherwise specified, the alkali source is calculated as ^OH- .

According to the method of the present invention, preferably the alkali source is provided in the form of an alkali solution, more preferably the pH of the alkali solution is >9.

According to the method of the present invention, in step (2), preferably the modified titanium-silicon molecular sieve in step (1) is mixed with aluminum source, alkali source and water to contact for a period of time, preferably, the conditions of contact include: The temperature is 20-80°C, more preferably 40-70°C, and the contact time is 0.5-12h, more preferably 1-8h.

According to the method of the present invention, in step (3), the source of the alkaline steam atmosphere is not particularly limited. Specifically, the alkaline steam atmosphere may be provided by alkaline steam. The present invention has no special limitation on the source of the alkaline steam, which can be formed by heating the alkaline aqueous solution to form acidic steam, or by passing superheated steam through the alkaline aqueous solution to form alkaline steam. In the present invention, the alkaline steam is obtained by heating an alkaline aqueous solution as an example for illustration.

According to a preferred embodiment of the present invention, the concentration of the alkaline aqueous solution is >0.1 mol/L, preferably ≥1 mol/L, more preferably 1-10 mol/L. In the present invention, the main solvent of the alkaline aqueous solution is water, and other solvent additives can also be added as required. The characteristics of the modified titanium-silicon molecular sieve prepared in this way, such as the micropore volume accounting for the total pore volume of the molecular sieve, are more obvious.

The alkali in the alkaline aqueous solution of the present invention can be the same as the selection range of the alkali source described in the above step (2), and the types of the two can be the same or different, and the present invention is not particularly limited to this.

According to a preferred embodiment of the present invention, in the alkaline steam (which can be formed by heating the alkaline aqueous solution), the volume concentration of the alkaline gas is 0.02-50%, preferably 0.1-25%, more preferably 3-10%.

Step (3) of the present invention can be carried out in a fixed bed reactor or a reactor. In the step (3) described in the alkaline steam atmosphere, the solid product obtained in the step (2) (which can be separated by filtration) is heat-treated. The specific embodiment can be to obtain the alkaline steam by heating the alkaline aqueous solution, and the alkali The alkaline steam is passed into the reactor to provide an alkaline steam atmosphere.

According to a preferred embodiment of the present invention, in step (3), the conditions of the heat treatment include: the temperature is 100-200°C, more preferably 120-180°C, further preferably 140-170°C.

According to the method of the present invention, preferably, the heat treatment time can be determined according to needs. For the present invention, the heat treatment time is preferably 0.5-96h, preferably 2-48h, more preferably 6-24h.

According to the method of the present invention, the pressure of the heat treatment is preferably 0-5 MPa, more preferably 0.2-2 MPa, more preferably 1-1.5 MPa, and the pressure is measured by gauge pressure.

According to the method of the present invention, preferably, the method of the present invention further includes: calcining the molecular sieve obtained in step (3). The optional range of the roasting conditions is relatively wide, and the preferred roasting conditions for the present invention include: the roasting temperature is 300-800°C, preferably 350-600°C; the roasting time is 2-12h, preferably 2 -4h, the firing atmosphere includes an air atmosphere; more preferably, the firing conditions include: first firing at 450-600°C in a nitrogen atmosphere for 0.5-6h, and then firing at 450-600°C in an air atmosphere for 0.5-12h.

According to a preferred embodiment of the present invention, a silicon source is also added in the contact process described in step (2). The present invention has no particular limitation on the silicon source, and can be any material in the art that can provide silicon, such as The silicon source may be an organic silicon source and/or an inorganic silicon source, more preferably an organic silicon source.

Specifically, the organosilicon source can be, for example, one or more selected from the silicon-containing compounds shown in formula I,

In formula I, each of R ₁ , R ₂ , R ₃ and R ₄ is a C ₁ -C ₄ alkyl group, including a C ₁ -C ₄ straight chain alkyl group and a C ₃ -C ₄ branched chain alkyl group, for example : each of R ₁ , R ₂ , R ₃ and R ₄ can 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. Tetraethyl orthosilicate or methyl orthosilicate is used as an example in a specific embodiment of the present invention, but the scope of the present invention is not limited thereby.

According to the method of the present invention, the optional range of the type of the inorganic silicon source is relatively wide. For the present invention, preferably the inorganic silicon source is silica sol and/or silica gel, and the silica gel or silica sol in the present invention can be each Various forms of silica gel or silica sol obtained by various production methods.

According to a preferred embodiment of the present invention, the hydrolysis rate of the organosilicon source is 40-60%. In the prior art, during the synthesis of molecular sieves using organosilicon sources, the organosilicon sources need to be hydrolyzed. Usually, the hydrolysis rate of the organosilicon sources is above 70% by weight, usually above 90% by weight. In the present invention, preferably, the hydrolysis rate of the organosilicon source is controlled to 40-60% by weight, preferably 40-50% by weight, which is more conducive to regulating the pore size distribution of the modified titanium-silicon molecular sieve, and more conducive to improving the catalytic performance of the molecular sieve.

In the present invention, the hydrolysis rate of the organic silicon source refers to the weight percentage of the weight of the hydrolyzed organic silicon source in the mixture obtained in step (2) relative to the weight percentage of the organic silicon source fed during mixing. The hydrolyzed organosilicon source refers to the organosilicon source in which at least one of the hydrolyzable groups connected to silicon atoms in the organosilicon source undergoes hydrolysis to form a hydroxyl group. In the present invention, the hydrolysis amount of the hydrolyzed organosilicon source in the mixture can be measured by conventional quantitative analysis methods such as gas chromatography, and then the hydrolysis rate can be calculated.

According to a preferred embodiment of the present invention, in terms of _SiO2 , the molar ratio of the modified titanium silicon molecular sieve to the silicon source is 100: (0.1-10), more preferably 100: (0.5-5), most preferably is 100: (1-5). Using the preferred embodiment of the present invention, the surface silicon-titanium ratio of the obtained molecular sieve material is not lower than the bulk phase silicon-titanium ratio. In addition, the molecular sieve material obtained by this preferred embodiment has more micropore pore size distribution in the range of 1-1.8nm , which is particularly beneficial for thioether oxidation reactions. The contact time in step (2) can be selected according to the contact temperature and expected hydrolysis rate.

The present invention also provides the modified titanium-silicon molecular sieve of the present invention and the application of the modified titanium-silicon molecular sieve prepared by the method of the present invention in sulfide oxidation. In the thioether oxidation reaction, the modified titanium-silicon molecular sieve and the modified titanium-silicon molecular sieve obtained by the method of the invention can effectively adjust the selectivity of the target product.

According to a fourth aspect of the present invention, the present invention provides a method for thioether oxidation, the method comprising: contacting a liquid mixture with a catalyst under thioether oxidation conditions, the liquid mixture containing thioether, at least one An oxidant and optionally at least one solvent, the catalyst contains the modified titanium-silicon molecular sieve of the present invention or the modified titanium-silicon molecular sieve prepared by the preparation method of the present invention.

According to the method of the present invention, the amount of the catalyst used can be the amount of the catalyst capable of realizing the catalytic function. Specifically, the liquid hourly space velocity of the thioether may be 0.01-20h ^-1 , preferably 0.1-10h ^-1 , for example 1-5h ^-1 .

The oxidizing agent can be various substances commonly used in the art that can oxidize thioethers to form sulfones. The method of the invention is especially suitable for the occasion of preparing sulfone by using peroxide as an oxidant to oxidize thioether, which can significantly improve the effective utilization rate of peroxide and reduce the cost of thioether oxidation. The peroxide refers to a compound containing -O-O-bond in its molecular structure, which can be selected from hydrogen peroxide, hydroperoxide and peracid. The hydroperoxide refers to a substance obtained by replacing one hydrogen atom in a hydrogen peroxide molecule with an organic group. The peracid refers to an organic oxyacid containing -O-O-bonds in its molecular structure. Specific examples of the peroxide may include, but are not limited to, hydrogen peroxide, t-butyl hydroperoxide, cumene peroxide, cyclohexyl hydroperoxide, peracetic acid, and peroxypropionic acid. Preferably, the oxidizing agent is hydrogen peroxide, which can further reduce the separation cost. The hydrogen peroxide may be hydrogen peroxide commonly used in the art in various forms.

From the viewpoint of further improving the safety of the method of the present invention, it is preferable to use hydrogen peroxide in the form of an aqueous solution. According to the method of the present invention, when the hydrogen peroxide is provided in the form of an aqueous solution, the concentration of the aqueous hydrogen peroxide solution can be a conventional concentration in the field, for example: 20-80% by weight. The aqueous solution of hydrogen peroxide whose concentration meets the above requirements can be prepared by conventional methods, and can also be obtained commercially, for example: it can be commercially available 30% by weight hydrogen peroxide, 50% by weight hydrogen peroxide or 70% by weight hydrogen peroxide.

According to the method of the present invention, the thioether can be various compounds containing -S-bonds, preferably the thioether is selected from thioethers with 2-18 carbon atoms, more preferably dimethyl sulfide or benzene methyl sulfide. In the embodiments of the present invention, dimethyl sulfide is taken as an example for illustration, but the present invention is not limited thereto.

According to the method of the present invention, preferably, the molar ratio of sulfide to oxidant is 1:(0.1-10), more preferably 1:(0.2-5), and still more preferably 1:(0.2-3).

According to the method of the invention, the liquid mixture may or may not contain a solvent, preferably it contains a solvent. Preferably, said contacting is performed in the presence of at least one solvent. In this way, by adjusting the content of the solvent in the liquid mixture, the speed of the reaction can be adjusted to make the reaction more stable. The solvent can be various liquid substances that can not only dissolve the thioether and the oxidizing agent or promote the mixing of the two, but also dissolve the target oxidation product. Generally, the solvent may be selected from water, C ₁ -C ₆ alcohols, C ₃ -C ₈ ketones and C ₂ -C ₆ nitriles. Specific examples of the solvent may include, but are not limited to: water, methanol, ethanol, n-propanol, isopropanol, t-butanol, isobutanol, acetone, methyl ethyl ketone, and acetonitrile. Preferably, the solvent is selected from water and C ₁ -C ₆ alcohols. More preferably, the solvent is at least one of acetone, methanol and water. Adopting this preferred embodiment is more conducive to improving the degree of mixing among the reactants in the reaction system, enhancing diffusion, and more conveniently adjusting the severity of the reaction.

The amount of the solvent can be properly selected according to the amount of thioether and oxidant. Generally, the molar ratio of the solvent to the thioether may be 0.1-100:1, preferably 2-80:1.

According to the method of the present invention, the oxidation reaction conditions depend on the target oxidation product. Generally, the thioether oxidation reaction can be carried out at a temperature of 0-120°C, preferably at a temperature of 20-80°C; in terms of gauge pressure, the pressure in the reactor can be 0-5MPa, preferably 0.1-3MPa .

The thioether oxidation method provided by the invention can be carried out in a fixed-bed reactor.

The method according to the present invention may also include separating the reaction mixture output from the fixed-bed reactor to obtain target oxidation products and unreacted reactants. The method for separating the reaction mixture can be a conventional choice in the art and is not particularly limited. The separated unreacted reactants can be recycled.

The present invention will be described in detail below in conjunction with the examples, but the scope of the present invention is not limited thereby.

In the following examples and comparative examples, the reagents used are all commercially available analytical reagents, and the pressures are all measured by gauge pressure.

The pore volume and pore size distribution of the samples were measured on the ASAP2405 static nitrogen adsorption instrument of Micromeritics Company, and the specific data are shown in Table 1.

The composition of titanium, silicon and aluminum elements of the samples was measured on a 3271E X-ray fluorescence spectrometer of Rigaku Electric Co., Ltd., and the specific data are shown in Table 1.

In the present invention, the surface silicon-titanium ratio is measured by the ESCALab250 X-ray photoelectron energy spectrometer of Thermo Scientific Company, and the bulk phase silicon-titanium ratio is measured by the 3271E X-ray fluorescence spectrometer of Rigaku Electric Co., Ltd., the surface silicon-titanium ratio/bulk phase silicon The titanium ratios are listed in Table 1.

In the following examples, the amount of hydrolyzed organic silicon source is measured by gas chromatography. The gas chromatograph used is Agilent6890N equipped with thermal conductivity detector TCD and HP-5 capillary column (30m*320μm*25μm). Wherein, the inlet temperature was 180°C, the column temperature was 150°C, nitrogen was used as the carrier gas, and the flow rate of the carrier gas was 25 mL/min. The specific method is as follows: take a certain amount of the mixture and inject it from the gas chromatograph inlet, after passing through the chromatographic column, use TCD to detect and quantify by external standard method. Use the following formula to calculate the hydrolysis rate of organosilicon source:

X _{organosilicon source} %=[(m ^o _{organosilicon source} -m _{organosilicon source} )/m ^o _{organosilicon source} ]×100%

In the formula, X _{organosilicon source} represents the hydrolysis rate of organosilicon source; m ^o _{organosilicon source} represents the quality of added organosilicon source; m _{organosilicon source} represents the mass of unhydrolyzed organosilicon source.

In the following examples, titanium-silicon molecular sieves were prepared by the method described in Zeolites, 1992, Vol.12, pages 943-950.

The acidic steam in the following examples and comparative examples is obtained by heating the aqueous solution of hydrochloric acid, the concentration of the aqueous solution of hydrochloric acid is 2mol/L.

The alkaline steam in the following examples and comparative examples was obtained by heating an aqueous solution of tetrapropylammonium hydroxide, wherein the volume concentration of the formed alkaline gas was 5%.

In the following examples, unless otherwise specified, the pressure is gauged.

Example 1

This example illustrates the methods and products provided by the invention.

(1) Pack 10g of titanium-silicon molecular sieve into a fixed-bed reactor, feed acidic steam therein, contact titanium-silicon molecular sieve with acidic steam to carry out acidic steam modification, the temperature of said acidic steam modification is 100°C, time The molar ratio of titanium-silicon molecular sieve to acidic steam is 100:10, titanium-silicon molecular sieve is calculated as _SiO2 , and acidic steam is calculated as H ⁺ .

(2) At 40°C, mix the titanium-silicon molecular sieve modified in step (1), aluminum sulfate from aluminum source, tetraethyl orthosilicate from organic silicon source, aqueous sodium hydroxide solution (pH is 10) and water, and wait After hydrolysis of tetraethyl orthosilicate (the hydrolysis rate of organic silicon source is 50%), the obtained mixture is filtered and separated to obtain a solid product, wherein, the modified titanium-silicon molecular sieve: aluminum source: silicon source: alkali source: water The molar ratio is 100:3:5:10:600, the modified titanium-silicon molecular sieve and the silicon source are calculated as SiO ₂ , the aluminum source is calculated as Al ₂ O ₃ , and the alkali source is calculated as ^OH- .

(3) Place the solid product obtained in step (2) in a reactor, feed alkaline steam into the reactor until the pressure in the reactor is 1.3 MPa, close the reactor, and heat treat at 140° C. for 12 hours; Molecular sieves were calcined at 450°C for 2h in a nitrogen atmosphere, and then calcined at 550°C for 2h in an air atmosphere to obtain modified titanium-silicon molecular sieve S-1.

Example 2

This example illustrates the methods and products provided by the invention.

(1) Pack 10g of titanium-silicon molecular sieve into a fixed-bed reactor, feed acidic steam therein, contact titanium-silicon molecular sieve with acidic steam to carry out acidic steam modification, the temperature of said acidic steam modification is 150°C, time The molar ratio of titanium silicon molecular sieve to acid steam is 100:12, titanium silicon molecular sieve is calculated as _SiO2 , and acid steam is calculated as H ⁺ .

(2) At 50° C., the modified titanium-silicon molecular sieve in step (1), aluminum source aluminum sol (content is 20% by weight), organosilicon source methyl orthosilicate, tetrapropyl ammonium hydroxide aqueous solution ( pH is 14) mixed with water, and after methyl orthosilicate is hydrolyzed (the hydrolysis rate of the organic silicon source is 60%), the obtained mixture is filtered and separated to obtain a solid product, wherein, the modified titanium-silicon molecular sieve: aluminum source : Silicon source: Alkaline source: Water _molar ratio is 100:1:2:15:400, modified titanium silicon molecular sieve and silicon source are calculated as _SiO2 , aluminum source is calculated as _Al2O3 , alkali source is calculated as OH ^- meter.

(3) Place the solid product obtained in step (2) in a reactor, feed alkaline steam into the reactor until the pressure in the reactor is 1MPa, close the reactor, and heat treat at 170°C for 6h; heat-treated molecular sieve Calcined at 500° C. for 2 h in a nitrogen atmosphere, and then calcined at 500° C. for 2 h in an air atmosphere to obtain the modified titanium-silicon molecular sieve S-2.

Example 3

This example illustrates the methods and products provided by the invention.

(1) Pack 10g of titanium-silicon molecular sieve into a fixed-bed reactor, feed acidic steam therein, contact titanium-silicon molecular sieve with acidic steam to carry out acidic steam modification, the temperature of said acidic steam modification is 80 DEG C, time For 15h, the molar ratio of titanium-silicon molecular sieve to acidic steam is 100:5, titanium-silicon molecular sieve is calculated as _SiO2 , and acidic steam is calculated as H ⁺ .

(2) At 60°C, mix the titanium-silicon molecular sieve modified in step (1), aluminum hydroxide from aluminum, methyl orthosilicate from organic silicon, aqueous sodium hydroxide (pH 12) and water, and wait After hydrolysis of methyl orthosilicate (the hydrolysis rate of organic silicon source is 55%), the obtained mixture is filtered and separated to obtain a solid product, wherein, the modified titanium silicon molecular sieve: aluminum source: silicon source: alkali source: water The molar ratio is 100:0.5:1:5:300, the modified titanium-silicon molecular sieve and the silicon source are calculated as SiO ₂ , the aluminum source is calculated as Al ₂ O ₃ , and the alkali source is calculated as ^OH- .

(3) Place the solid product obtained in step (2) in a reactor, feed alkaline steam into the reactor until the pressure in the reactor is 1.5MPa, close the reactor, and heat treat at 150°C for 18h; Molecular sieves were calcined at 450°C for 2h in a nitrogen atmosphere, and then calcined at 500°C for 2h in an air atmosphere to obtain modified titanium-silicon molecular sieve S-3.

Example 4

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that in step (1), the molar ratio of the titanium-silicon molecular sieve to the acidic steam is 100:2 to obtain the modified titanium-silicon molecular sieve S-4.

Example 5

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that in step (1), the molar ratio of titanium-silicon molecular sieve to acidic steam is 100:30 to obtain modified titanium-silicon molecular sieve S-5.

Example 6

This example illustrates the methods and products provided by the invention.

According to the method of Example 2, the difference is that the acid steam modification temperature is 200° C. to obtain modified titanium-silicon molecular sieve S-6.

Example 7

This example illustrates the methods and products provided by the invention.

According to the method of Example 3, the difference is that the temperature of the acidic steam modification is 50° C. to obtain the modified titanium-silicon molecular sieve S-7.

Example 8

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that after the tetraethyl orthosilicate is hydrolyzed (the hydrolysis rate of the organic silicon source is 100%), the obtained mixture is separated by filtration. A modified titanium silicate molecular sieve S-8 was obtained.

Example 9

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that the silicon source tetraethyl orthosilicate is not added in the step (2). A modified titanium silicate molecular sieve S-9 was obtained.

Example 10

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that the heat treatment temperature in step (3) is 100°C. A modified titanium-silicon molecular sieve S-10 was obtained.

Example 11

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that the heat treatment temperature in step (3) is 200°C. A modified titanium-silicon molecular sieve S-11 was obtained.

Example 12

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that step (3) does not include the process of roasting the heat-treated molecular sieve. A modified titanium-silicon molecular sieve S-12 was obtained.

Example 13

This example illustrates the methods and products provided by the invention.

According to the method of Example 1, the difference is that in step (3), the heat-treated molecular sieve is calcined at 550° C. for 4 hours in an air atmosphere. A modified titanium silicate molecular sieve S-13 was obtained.

Comparative example 1

According to the method of Example 1, the difference is that step (1) acid steam modification process is not included. A modified titanium silicate molecular sieve D-1 was obtained.

Comparative example 2

According to the method of embodiment 1, the difference is that step (2) mixing contact process is not included. The modified titanium silicate molecular sieve D-2 was obtained.

Comparative example 3

According to the method of Example 1, the difference is that step (3) alkaline steam modification process is not included. The modified titanium silicate molecular sieve D-3 was obtained.

Table 1

In Table 1:

C=X _1-1.8 /X _0.4-0.9 , X _0.4-0.9 is the ratio of the micropore diameter of the molecular sieve in the range of 0.4-0.9nm to the total micropore diameter distribution, X _1-1.8 is the molecular sieve in the range of 1-1.8nm The ratio of the micropore diameter to the total micropore diameter distribution;

D= _Tw / _Tk , _Tw is the micropore volume of the molecular sieve, and _Tk is the total pore volume of the molecular sieve;

Silicon:titanium:aluminum refers to the molar ratio of silicon element:titanium element:aluminum element.

It can be seen from the results in Table 1 that:

The pore size distribution of the molecular sieve prepared by the preferred method of the present invention, the ratio of the micropore volume to the total pore volume, the molar ratio of silicon element: titanium element: aluminum element, the ratio of the surface silicon-titanium ratio to the bulk phase silicon-titanium ratio and other data are fully satisfied. All features of the product of the present invention. In contrast, the titanium silicon material obtained in Comparative Examples 1-3, its pore size distribution, the ratio of the micropore volume to the total pore volume, the silicon element: titanium element: the molar ratio of aluminum element and other data cannot meet all the characteristics of the product of the present invention .

test case

The catalyst (the molecular sieve prepared in the examples and comparative examples in the catalyst was pressed into tablets, and the particle size was 10-20 mesh) was packed in a fixed bed reactor to form a catalyst bed, and the aspect ratio of the catalyst bed was 10.

Dimethyl sulfide, hydrogen peroxide (provided as 30% by weight hydrogen peroxide) as oxidizing agent and acetone as solvent were mixed to form a liquid mixture which was fed from the bottom of the fixed bed reactor and flowed through Catalyst bed. Among them, the molar ratio of dimethyl sulfide to hydrogen peroxide is 1:1, the molar ratio of dimethyl sulfide to acetone is 1:8, the weight hourly space velocity of dimethyl sulfide is 1.5h ^-1 , the reaction The temperature is 60°C. During the reaction, water is used as the heat exchange medium to exchange heat with the catalyst bed to remove the heat of reaction. During the reaction, the pressure in the fixed-bed reactor is controlled to 1 MPa.

During the continuous reaction process, the composition of the reaction mixture output from the reactor was monitored and the conversion rate of dimethyl sulfide and the relative amount of sulfone selectivity increase in the product were calculated. The results obtained after 0.5 hours of reaction were listed in Table 2.

Dimethyl sulfide conversion rate (%)=[(molar amount of dimethyl sulfide added-molar amount of unreacted dimethyl sulfide)/molar amount of dimethyl sulfide added]×100 %;

The relative amount (%) of sulfone selectivity increase in the product=(the molar number of sulfone in the reaction mixture obtained by the test example-the molar number of sulfone in the reaction mixture obtained by the test reference ratio)/the mole number of sulfone in the reaction mixture obtained by the test reference ratio Number of moles x 100%.

The present invention uses the titanium-silicon molecular sieve described above as a reference example.

Table 2

As can be seen from the data in Table 2, the titanium-silicon molecular sieve with special physical and chemical characteristic structure of the present invention is used in the reaction of thioether oxidation, which is conducive to adjusting the selectivity of the target product (sulfone), and can obtain better catalytic effect.

The preferred embodiments of the present invention have been described in detail above, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (43)

1. A modified titanium silicalite molecular sieve, comprising: titanium element, aluminum element, silicon element and oxygen element, wherein the molecular sieve satisfies X _1-1.8 /X _0.4-0.9 ＝C，0.1<C<0.5，X _0.4-0.9 The ratio of the pore diameter of the micropores of the molecular sieve in the range of 0.4-0.9nm to the distribution quantity of the total pore diameter, X _1-1.8 Is the proportion of the pore diameter of the micropores of the molecular sieve in the range of 1-1.8nm in the distribution quantity of the pore diameter of the total micropores.

2. The modified titanium silicalite molecular sieve of claim 1,

the molecular sieve satisfies X _1-1.8 /X _0.4-0.9 ＝C，0.25<C<0.5，X _0.4-0.9 The ratio of the pore diameter of the micropores of the molecular sieve in the range of 0.4-0.9nm to the total pore diameter distribution, X _1-1.8 Is the ratio of the micropore diameter of the molecular sieve in the range of 1-1.8nm to the total micropore diameter distribution.

3. The modified titanium silicalite molecular sieve of claim 1, wherein the molecular sieve satisfies T _w /T _k ＝D，0.2<D<0.5，T _w Is the micropore volume of the molecular sieve, T _k Is the total pore volume of the molecular sieve.

4. The modified titanium silicalite molecular sieve of claim 3, wherein the molecular sieve satisfies T _w /T _k ＝D，0.25<D<0.45，T _w Is the micropore volume of the molecular sieve, T _k Is the total pore volume of the molecular sieve.

5. The modified titanium silicalite molecular sieve of claim 1, wherein the molar ratio of elemental silicon: titanium element: the molar ratio of aluminum elements is 100: (0.1-10): (0.01-5).

6. The modified titanium silicalite molecular sieve of claim 5, wherein the molar ratio of elemental silicon: titanium element: the molar ratio of aluminum elements is 100: (0.2-5): (0.2-4).

7. The modified titanium silicalite molecular sieve of any one of claims 1 to 6, wherein the molecular sieve has a surface silicon to titanium ratio of not less than a bulk silicon to titanium ratio, the silicon to titanium ratio being the molar ratio of silicon oxide to titanium oxide.

8. The modified titanium silicalite molecular sieve of claim 7,

the ratio of the surface silicon-titanium ratio to the bulk silicon-titanium ratio is 1.2-5.

9. The modified titanium silicalite molecular sieve of claim 8,

the ratio of the surface silicon-titanium ratio to the bulk silicon-titanium ratio is 1.5-4.5.

10. A method of preparing a modified titanium silicalite molecular sieve as claimed in any one of claims 1 to 9, comprising:

(1) Carrying out acid steam modification on the titanium silicalite molecular sieve;

(2) Mixing and contacting the titanium-silicon molecular sieve modified in the step (1) with an aluminum source, an alkali source and water;

(3) And (3) carrying out heat treatment on the solid product obtained in the step (2) in an alkaline steam atmosphere.

11. The method of claim 10, wherein the acid steam modification of step (1) comprises: contacting a titanium silicalite molecular sieve with acid steam to modify the acid steam; the temperature of the acidic steam modification is 40-200 ℃; the time for modifying the acid steam is 0.5-360h.

12. The preparation method according to claim 11, wherein the temperature of the acid steam modification is 60-180 ℃; the time for modifying the acid steam is 1-240h.

13. The preparation method according to claim 12, wherein the temperature of the acid steam modification is 80-150 ℃; the time for modifying the acid steam is 2-120h.

14. The method of claim 11, wherein the acid vapor is obtained by heating an aqueous acid solution having a concentration >0.1mol/L.

15. The preparation method according to claim 14, wherein the acidic vapor is obtained by heating an aqueous acid solution having a concentration of 1mol/L or more.

16. The method of claim 15, wherein the acid vapor is obtained by heating an aqueous acid solution having a concentration of 1 to 15mol/L.

17. The production method according to claim 14,

the acid in the aqueous acid solution is an organic acid and/or an inorganic acid.

18. The method of any one of claims 10-17, wherein the molar ratio of the titanium silicalite molecular sieves to the acid vapor is 100: (0.5-40), wherein the titanium-silicon molecular sieve is SiO ₂ Acid steam is counted as H ⁺ And (6) counting.

19. The method of claim 18, wherein the molar ratio of titanium silicalite molecular sieves to acid vapor is 100: (1-15), wherein the titanium silicalite is SiO ₂ Acid steam is counted as H ⁺ And (6) counting.

20. The preparation method of claim 19, wherein the molar ratio of the titanium silicalite molecular sieve to the acid vapor is 100: (5-15), wherein the titanium silicalite is SiO ₂ Acid steam is counted as H ⁺ And (6) counting.

21. The preparation method according to any one of claims 10 to 17, wherein in the step (2), the modified titanium silicalite molecular sieve:an aluminum source: alkali source: the molar ratio of water is 100: (0-10): (0.5-50): (20-1000), wherein the modified titanium silicalite molecular sieve is SiO ₂ In terms of aluminum source, al is calculated ₂ O ₃ The alkali source is N or OH ^- And (6) counting.

22. The production method according to claim 21,

modified titanium silicalite molecular sieve: the molar ratio of the aluminum source is 100: (0.2-5).

23. The production method according to claim 22,

modified titanium silicalite molecular sieve: the molar ratio of the aluminum source is 100: (0.5-3).

24. The production method according to any one of claims 10 to 17,

the contact temperature in the step (2) is 20-80 ℃.

25. The production method according to any one of claims 10 to 17,

the alkali source is one or more of ammonia, aliphatic amine, aliphatic alcohol amine and quaternary ammonium hydroxide; the aluminum source is one or more of aluminum sol, aluminum salt, aluminum hydroxide and aluminum oxide.

26. The production method according to any one of claims 10 to 17, wherein the alkaline steam atmosphere is provided by alkaline steam obtained by heating an alkaline aqueous solution.

27. The production method according to claim 26,

the volume concentration of the alkaline gas in the alkaline steam is 0.02-50%.

28. The production method according to claim 27, wherein,

the volume concentration of the alkaline gas in the alkaline steam is 0.1-25%.

29. The production method according to claim 28,

the volume concentration of the alkaline gas in the alkaline steam is 3-10%.

30. The production method according to any one of claims 10 to 17, wherein in step (3), the conditions of the heat treatment include: the temperature is 100-200 ℃; the time is 0.5 to 96 hours; the pressure is 0-5MPa in gage pressure.

31. The production method according to claim 30, wherein in step (3), the conditions of the heat treatment include: the temperature is 120-180 ℃; the time is 2-48h; the pressure is 0.2-2MPa in gauge pressure.

32. The production method according to claim 31, wherein in step (3), the conditions of the heat treatment include: the temperature is 140-170 ℃; the time is 6-24h.

33. The production method according to any one of claims 10 to 17, wherein the method further comprises: roasting the molecular sieve obtained in the step (3), wherein roasting conditions comprise: the roasting temperature is 300-800 ℃, the roasting time is 2-12h, and the roasting atmosphere comprises air atmosphere.

34. The method of claim 33, wherein the firing conditions include: the roasting temperature is 350-600 ℃, the roasting time is 2-4h, and the roasting atmosphere comprises air atmosphere.

35. The production method according to claim 34, wherein,

the roasting conditions comprise: roasting at 450-600 deg.c in nitrogen atmosphere for 0.5-6 hr, and roasting at 450-600 deg.c in air atmosphere for 0.5-12 hr.

36. The method according to any one of claims 10 to 17, wherein a silicon source is further added during the contacting in step (2), and the silicon source is an organic silicon source and/or an inorganic silicon source.

37. The production method according to claim 36,

the silicon source is an organic silicon source.

38. The method of claim 37, wherein,

the silicon source is one or more selected from silicon-containing compounds shown in formula I,

in the formula I, R ₁ 、R ₂ 、R ₃ And R ₄ Each independently is C ₁ -C ₄ Alkyl group of (1).

39. The method of claim 36, wherein,

with SiO ₂ In terms of the molar ratio of the modified titanium-silicon molecular sieve to the silicon source is 100: (0.1-10).

40. The production method according to claim 36,

the hydrolysis rate of the organic silicon source is 40-60%.

41. Use of the modified titanium silicalite molecular sieve of any one of claims 1 to 9 and the modified titanium silicalite molecular sieve prepared by the preparation method of any one of claims 10 to 40 in the oxidation of thioethers.

42. A method of oxidizing a thioether, the method comprising: contacting a liquid mixture with a catalyst under thioether oxidation conditions, wherein the liquid mixture contains thioether, at least one oxidant and at least one solvent, and the catalyst contains the modified titanium silicalite molecular sieve as defined in any one of claims 1 to 9 or the modified titanium silicalite molecular sieve prepared by the preparation method as defined in any one of claims 10 to 40.

43. The method of claim 42, wherein,

the thioether is dimethyl sulfide and/or dimethyl sulfide; the oxidant is peroxide, and the molar ratio of the thioether to the oxidant is 1: (0.1-10), the thioether oxidation conditions comprising: the temperature is 0-120 ℃, and the pressure is 0-5MPa in gauge pressure.