CN105523972B

CN105523972B - Thioether oxidation method

Info

Publication number: CN105523972B
Application number: CN201410514186.2A
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: 2014-09-29
Filing date: 2014-09-29
Publication date: 2020-04-28
Anticipated expiration: 2034-09-29
Also published as: CN105523972A

Abstract

The invention discloses a thioether oxidation method, which comprises the step of contacting a liquid mixture with a titanium silicalite molecular sieve under the oxidation reaction condition, wherein the liquid mixture contains thioether, at least one oxidant, at least one alkaline substance and optionally at least one solvent, and the method also comprises the step of improving the quality of the alkaline substance in the liquid mixture and optionally improving the quality of the oxidant in the liquid mixture when the selectivity of a target oxidation product is lower than an expected value. The method can maintain the selectivity of the target oxidation product at a higher level for a long time, effectively prolong the one-way service life of the titanium-silicon molecular sieve used as the catalyst, and reduce the regeneration frequency of the catalyst.

Description

Thioether oxidation method

Technical Field

The invention relates to a thioether oxidation method.

Background

The sulfoxide is an important sulfur-containing compound, such as dimethyl sulfoxide (DMSO), which is a sulfur-containing organic compound, is a colorless transparent liquid at normal temperature, and has the characteristics of high polarity, high hygroscopicity, flammability, high boiling point, non-proton and the like. Dimethyl sulfoxide is soluble in water, ethanol, acetone, diethyl ether and chloroform, is an inert solvent with strong polarity, and is widely used as a solvent and a reaction reagent. Moreover, dimethyl sulfoxide has high selective extraction capacity and can be used as an extraction solvent for separating alkane from aromatic hydrocarbon, such as: dimethyl sulfoxide can be used for extracting aromatic hydrocarbon or butadiene, and can be used as a processing solvent and a spinning solvent in acrylonitrile polymerization reaction, as a synthetic solvent and a spinning solvent for polyurethane, and as a synthetic solvent for polyamide, chlorofluoroaniline, polyimide and polysulfone. Meanwhile, in the pharmaceutical industry, dimethyl sulfoxide can be directly used as a raw material and a carrier of certain medicines, and also has the effects of diminishing inflammation, relieving pain, promoting urination, tranquilizing and the like, so that dimethyl sulfoxide is often used as an active component of an analgesic medicine to be added into the medicines. In addition, dimethyl sulfoxide can also be used as a capacitance medium, an antifreeze, brake oil, a rare metal extractant and the like.

At present, the sulfoxide is generally prepared by a thioether oxidation method, and usable oxidizing agents include nitric acid, peroxides, ozone, and the like.

When oxidizing thioether with oxidant, especially peroxide, titanium silicalite molecular sieve is used as catalyst, so as to raise the conversion rate of oxidant and the selectivity of target oxidation product. However, as the reaction time increases, the catalytic performance of the titanium silicalite molecular sieve tends to decrease, resulting in a decrease in oxidant conversion and/or selectivity to the desired oxidation product. When the reaction is carried out in a fixed bed reactor, the titanium silicalite molecular sieve needs to be regenerated in or out of the reactor due to the reduction of the catalytic performance of the titanium silicalite molecular sieve, so that the shutdown of the reactor is caused, the production efficiency is influenced, and the operation cost of the device is increased.

When the regenerated catalyst is put into operation again, particularly after being regenerated in a reactor, the activity fluctuation of the catalyst is large, and the catalyst can be stabilized for a long time, so that the selectivity of a target oxidation product is reduced, the operation efficiency of the device is reduced, and the operation condition is adjusted by a subsequent separation and purification process, so that the operation complexity is increased; meanwhile, it is necessary to combine operations such as raising the reaction temperature to achieve smooth operation of the reaction, but these measures tend to accelerate catalyst deactivation.

Therefore, for the thioether oxidation reaction using the titanium silicalite as the catalyst, how to prolong the one-way service life of the titanium silicalite as the catalyst and reduce the regeneration frequency is one of the key links for improving the production efficiency and reducing the operation cost.

Disclosure of Invention

The invention aims to solve the defects of thioether oxidation reaction using a titanium silicalite molecular sieve as a catalyst, and provides a thioether oxidation method, which can effectively prolong the one-way service life of the titanium silicalite molecular sieve as the catalyst and stabilize the selectivity of a target oxidation product at a higher level in a long-period continuous operation process.

The invention provides a thioether oxidation method, which comprises the steps of contacting a liquid mixture with a titanium silicalite molecular sieve under an oxidation reaction condition, wherein the liquid mixture contains thioether, at least one oxidant, at least one alkaline substance and at least one optional solvent, the method also comprises an adjustment step when the selectivity of a target oxidation product is reduced to meet the condition 1, the adjustment step is stopped until the selectivity of the target oxidation product is improved to meet the condition 2,

condition 1, selectivity S of target oxidation product at a certain time t_tSelectivity S with initial target oxidation product₀Ratio S of_t/S₀S is not less than 0.85_t/S₀<1；

Condition 2, target oxidation product selectivity S' and initial target oxidation product selectivity S₀Ratio S'/S of₀S'/S is more than or equal to 0.9₀≤1；

The adjusting step is an adjusting step A or a combination of the adjusting step A and the adjusting step B,

adjusting step A: improving the quality of the alkaline substance in the liquid mixture;

and B, an adjusting step: improving the quality of the oxidizing agent in the liquid mixture.

According to the method for oxidizing thioether of the present invention, in the case that the target oxidation product selectivity determined by the reaction mixture output from the reactor is lower than the expected value during the long-time continuous operation, the adjustment step of increasing the quality of the alkaline substance in the liquid mixture as the feed and optionally increasing the quality of the oxidizing agent in the liquid mixture as the feed is performed, so that the target oxidation product selectivity which originally shows a descending trend can be increased. Therefore, the selectivity of the target oxidation product can be always maintained at a higher level in the long-time continuous operation process, and on one hand, the condition that the operation condition needs to be adjusted according to the composition of a reaction mixture in the subsequent separation and purification process is avoided; on the other hand, the one-way service life of the titanium silicalite molecular sieve used as the catalyst is effectively prolonged, the regeneration frequency of the catalyst is reduced, and the stable operation time of the device is prolonged.

Detailed Description

The invention provides a thioether oxidation method, which comprises the step of contacting a liquid mixture with a titanium silicalite molecular sieve under the oxidation reaction condition, wherein the liquid mixture contains thioether, at least one oxidant, at least one basic substance and at least one optional solvent.

In the present invention, "at least one" means one or more (e.g., two or more); "optional" means with or without.

The oxidizing agent may be any of various substances commonly used to oxidize thioethers. Preferably, the oxidizing agent is a peroxide. The peroxide is a compound containing an-O-O-bond in the molecular structure, and can be selected from hydrogen peroxide, organic peroxide and peracid. The organic peroxide is a substance obtained by substituting one or two hydrogen atoms in a hydrogen peroxide molecule with an organic group. The peracid refers to an organic oxyacid having an-O-O-bond in the molecular structure. Specific examples of the peroxide may include, but are not limited to: hydrogen peroxide, tert-butyl hydroperoxide, cumene peroxide, cyclohexyl hydroperoxide, peracetic acid and propionic acid. Preferably, the oxidizing agent is hydrogen peroxide, which further reduces the separation cost. The hydrogen peroxide may be hydrogen peroxide in various forms commonly used in the art.

From the viewpoint of further improving the safety of the process according to the invention, the process according to the invention preferably uses hydrogen peroxide in the form of an aqueous solution. The concentration of the aqueous hydrogen peroxide solution may be conventional in the art, for example: 20-80 wt%. Aqueous solutions of hydrogen peroxide at concentrations meeting the above requirements may be prepared by conventional methods or may be obtained commercially, for example: can be 30 percent by weight of hydrogen peroxide, 50 percent by weight of hydrogen peroxide or 70 percent by weight of hydrogen peroxide which can be obtained commercially.

The amount of the oxidizing agent to be used may be selected depending on the desired oxidation product, and is not particularly limited. Generally, the molar ratio of oxidizing agent to thioether may be in the range of 0.1 to 5: 1, in the above range. From the viewpoint of further improving the selectivity for sulfoxide, the molar ratio of the oxidizing agent to the thioether is preferably in the range of 0.1 to 2: 1, more preferably in the range of 0.2 to 1: 1, in the above range.

According to the method, a titanium silicalite molecular sieve is used as a catalyst for the contact reaction of thioether and an oxidant. The titanium-silicon molecular sieve is a general term of a type of zeolite with titanium atoms replacing a part of silicon atoms in a lattice framework and can be represented by a chemical formula xTiO₂·SiO₂And (4) showing. The content of titanium atoms in the titanium silicalite molecular sieve is not particularly limited in the invention, and can be selected conventionally in the field. Specifically, x may be 0.0001 to 0.05, preferably 0.01 to 0.03, more preferably 0.015 to 0.025.

The titanium silicalite molecular sieve can be common titanium silicalite molecular sieves with various topologies, such as: the titanium silicalite molecular sieve can be selected from titanium silicalite molecular sieve with MFI structure (such as TS-1), titanium silicalite molecular sieve with MEL structure (such as TS-2), titanium silicalite molecular sieve with BEA structure (such as Ti-Beta), titanium silicalite molecular sieve with MWW structure (such as Ti-MCM-22), titanium silicalite molecular sieve with MOR structure (such as Ti-MOR), titanium silicalite molecular sieve with TUN structure (such as Ti-TUN), titanium silicalite molecular sieve with two-dimensional hexagonal structure (such as Ti-MCM-41 and Ti-SBA-15), titanium silicalite molecular sieve with other structure (such as Ti-ZSM-48), etc. The titanium silicalite molecular sieve is preferably selected from a titanium silicalite molecular sieve with an MFI structure, a titanium silicalite molecular sieve with an MEL structure and a titanium silicalite molecular sieve with a BEA structure, and more preferably is a titanium silicalite molecular sieve with an MFI structure.

According to the method, the titanium silicalite molecular sieve is preferably a hollow titanium silicalite molecular sieve, so that better catalytic effect can be obtained. The hollow titanium silicalite molecular sieve is a titanium silicalite molecular sieve with an MFI structure, crystal grains of the titanium silicalite molecular sieve are of a hollow structure, the radial length of a cavity part of the hollow structure is 5-300 nanometers, and the titanium silicalite molecular sieveAt 25 ℃ P/P₀The benzene adsorption amount measured under the conditions of 0.10 and the adsorption time of 1 hour is at least 70 mg/g, and a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption of the titanium silicalite molecular sieve. The hollow titanium silicalite molecular sieves are commercially available (e.g., molecular sieves sold under the designation HTS, commercially available from the shogaku corporation, han, south of the lake) and can also be prepared according to the method disclosed in CN 1132699C.

According to the method of the present invention, the contact form of the titanium silicalite molecular sieve and the liquid mixture is not particularly limited, and the titanium silicalite molecular sieve can be filled in a catalyst bed layer of a fixed bed reactor, and the liquid mixture passes through the catalyst bed layer, so that the thioether and the oxidant are subjected to a contact reaction in the presence of the titanium silicalite molecular sieve; the liquid mixture can also be mixed with a titanium silicalite molecular sieve to form slurry, so that the thioether can be in contact reaction with an oxidant in the presence of the titanium silicalite molecular sieve.

When the liquid mixture is mixed with the titanium silicalite molecular sieve to form slurry, various methods can be adopted to carry out liquid-solid separation on the slurry after the contact reaction is finished, so as to obtain the liquid material containing the target oxidation product. For example: the liquid material may be subjected to liquid-solid separation by a membrane separation device.

When the titanium silicalite molecular sieve is filled in the catalyst bed layer of the fixed bed reactor, the number of the catalyst bed layers can be one or more. When the number of the catalyst beds is plural, the catalyst beds may be located in different regions of one reactor, or may be located in a plurality of reactors.

In one embodiment of the invention, the catalyst bed comprises a first catalyst bed and a second catalyst bed, through which the liquid mixture flows in sequence, i.e. the first catalyst bed is located upstream of the second catalyst bed, based on the direction of flow of the liquid mixture. The types of the titanium silicalite molecular sieves filled in the first catalyst bed layer and the second catalyst bed layer can be the same or different. Preferably, the titanium silicalite molecular sieve filled in the first catalyst bed layer is a hollow titanium silicalite molecular sieve, and the titanium silicalite molecular sieve filled in the second catalyst bed layer is a titanium silicalite molecular sieve other than the hollow titanium silicalite molecular sieve, such as one or more of other titanium silicalite molecular sieves with MFI structures (e.g., titanium silicalite TS-1), titanium silicalite molecular sieves with two-dimensional hexagonal structures (e.g., titanium silicalite Ti-MCM-41) and titanium silicalite molecular sieves with BEA structures (e.g., titanium silicalite Ti-Beta), so that the deactivation rate of the titanium silicalite molecular sieve can be further delayed. More preferably, the titanium silicalite molecular sieve filled in the first catalyst bed layer is a hollow titanium silicalite molecular sieve, and the titanium silicalite molecular sieve filled in the second catalyst bed layer is a titanium silicalite molecular sieve TS-1, so that a better catalytic effect can be obtained, and the one-way service life of the titanium silicalite molecular sieve is further prolonged.

When the catalyst bed layer contains a first catalyst bed layer and a second catalyst bed layer, the weight ratio of the titanium silicalite molecular sieve filled in the first catalyst bed layer to the titanium silicalite molecular sieve filled in the second catalyst bed layer can be 0.5-20: 1, preferably 1 to 20: 1, more preferably 2 to 10: 1.

where the catalyst bed comprises a first catalyst bed and a second catalyst bed, each of the first catalyst bed and the second catalyst bed may comprise one or more catalyst beds. When the first catalyst bed layer and/or the second catalyst bed layer contains a plurality of catalyst bed layers, the plurality of catalyst bed layers may be connected in series, may also be connected in parallel, and may also be a combination of series and parallel, for example: the catalyst beds are divided into a plurality of groups, the catalyst beds in each group are connected in series and/or in parallel, and the groups are connected in series and/or in parallel. The first catalyst bed and the second catalyst bed can be arranged in different areas of the same reactor or in different reactors.

When the catalyst bed comprises a first catalyst bed and a second catalyst bed, the superficial velocities of the liquid mixture flowing through the first catalyst bed and the second catalyst bed can be the same or different. Preferably, the superficial velocity of the liquid mixture flowing through the first catalyst bed isDegree v₁Superficial velocity through the second catalyst bed is v₂Wherein v is₁＜v₂Therefore, the single-pass service life of the titanium silicalite molecular sieve can be further prolonged. More preferably, v₂/v₁1.5-10. Further preferably, v₂/v₁＝2-5。

In the present invention, the superficial velocity (flow velocity) refers to the mass flow (in kg/s) of the liquid mixture and the area (in m) of a certain cross section of the catalyst bed in the whole course of passing through the catalyst bed in a unit time²Meter) of the measured values. The mass of the liquid mixture fed to the fixed bed reactor per unit time can be taken as the "mass flow rate of the liquid mixture through the entire catalyst bed per unit time". In the present invention, there is no particular requirement for the superficial velocity of the liquid mixture in the first catalyst bed, and it may be generally in the range of 0.001 to 200 kg/(m)²S).

Various methods can be employed to adjust the superficial velocity of the liquid mixture in the first catalyst bed and the second catalyst bed. For example, the superficial velocity of the liquid mixture can be adjusted by selecting the cross-sectional area of the catalyst bed. Specifically, the cross-sectional area of the first catalyst bed may be made larger than that of the second catalyst bed so that v₁＜v₂. Specifically, the inner diameter of the first catalyst bed layer is D₁The inner diameter of the second catalyst bed layer is D₂Wherein D is₁＞D₂，D₁/D₂Preferably 1.5 to 10, more preferably 2 to 5. Methods for determining the cross-sectional area of a catalyst bed based on the desired superficial velocity are well known to those skilled in the art and will not be described in detail herein.

When the catalyst bed layer contains a first catalyst bed layer and a second catalyst bed layer, the residence time of the liquid mixture in the first catalyst bed layer is T₁The total residence time in the catalyst bed is T, typically T₁0.2-0.96% of/T, preferably, T₁and/T is 0.3-0.95. More preferably, T₁0.5-0.85, which can obtain furtherThe one-way service life of the catalyst is prolonged, and a better reaction effect can be obtained.

According to the method, when the catalyst bed layer comprises a first catalyst bed layer and a second catalyst bed layer, materials can be supplemented between the first catalyst bed layer and the second catalyst bed layer according to specific conditions, and when the first catalyst bed layer and/or the second catalyst bed layer is/are a plurality of catalyst bed layers, fresh materials can be supplemented between the first catalyst bed layers and/or between the second catalyst bed layers according to specific conditions. For example: the thioethers, oxidants and/or solvents are replenished between the first catalyst bed and the second catalyst bed, between the first catalyst beds and/or between the second catalyst beds. However, it should be noted that the liquid mixture flows through all of the first catalyst bed (i.e., all of the way through the first catalyst bed) and all of the second catalyst bed (i.e., all of the way through the second catalyst bed), and the liquid mixture does not include fresh material introduced between the first catalyst beds, between the second catalyst beds, and between the first catalyst beds and the second catalyst beds, and the superficial velocity described above is determined by the liquid mixture and is not affected by whether fresh material is introduced or not.

According to the method of the invention, the catalyst bed layer can be only filled with the titanium silicalite molecular sieve, and can also contain the titanium silicalite molecular sieve and inactive filler. The amount of the titanium silicalite molecular sieve in the catalyst bed layer can be adjusted by filling the inactive filler in the catalyst bed layer, so that the reaction speed can be adjusted. When the catalyst bed layer contains the titanium silicalite molecular sieve and the inactive filler, the content of the inactive filler in the catalyst bed layer can be 5-95 wt%. The inactive filler means a filler having no or substantially no catalytic activity for oxidation reaction, and specific examples thereof may include, but are not limited to: one or more of quartz sand, ceramic rings, and ceramic chips.

According to the method of the present invention, the titanium silicalite molecular sieve can be raw powder of the titanium silicalite molecular sieve, and can also be a formed titanium silicalite molecular sieve, preferably a formed titanium silicalite molecular sieve. The formed titanium silicalite molecular sieve generally contains a titanium silicalite molecular sieve as an active component and a carrier as a binder, wherein the content of the titanium silicalite molecular sieve can be selected conventionally. Generally, the content of the titanium silicalite molecular sieve can be 5 to 95 wt%, preferably 10 to 95 wt%, more preferably 70 to 90 wt% based on the total amount of the shaped titanium silicalite molecular sieve; the carrier may be contained in an amount of 5 to 95% by weight, preferably 5 to 90% by weight, more preferably 10 to 30% by weight. The support for the shaped titanium silicalite molecular sieve may be of conventional choice, such as alumina and/or silica. Methods of making the shaped titanium silicalite molecular sieves are well known in the art and will not be described in detail herein. The particle size of the shaped titanium silicalite molecular sieve is not particularly limited, and may be appropriately selected according to the specific shape. In particular, the shaped titanium silicalite molecular sieves may have an average particle size of from 4 to 10000 microns, preferably from 5 to 5000 microns, more preferably from 40 to 4000 microns, such as from 50 to 1000 microns. The average particle size is a volume average particle size and can be measured by a laser particle sizer.

In various reaction (generally referred to as non-thioether oxidation) devices using titanium silicalite molecular sieves as catalysts, such as ammoximation, hydroxylation and epoxidation devices, generally, after the devices operate for a period of time, the catalytic activity of the catalysts is reduced, and the catalysts need to be regenerated in or out of the devices, when the satisfactory activity is difficult to obtain even if the regeneration is carried out, the catalysts need to be discharged from the devices (i.e. the catalysts are replaced), and the discharged catalysts (i.e. discharging agents or waste catalysts) are generally buried in a pile up manner in the current precious treatment method, so that land resources and storage space are occupied on one hand, and on the other hand, the titanium silicalite molecular sieves are high in production cost and are not directly discarded, so that great waste is caused.

During the research, the inventor of the present invention found that if these discharging agents are regenerated, the obtained regenerating agent is used as the catalyst used in the method of the present invention, and high catalytic activity can still be obtained.

According to the process of the present invention, at least part of the titanium silicalite is preferably the discharge agent of the regenerated reaction apparatus using titanium silicalite as catalyst. The discharging agent may be discharged from various apparatuses using a titanium silicalite as a catalyst, and may be discharged from an oxidation reaction apparatus, for example. The oxidation reaction may be various oxidation reactions, for example, the discharging agent may be one or more of a discharging agent of an ammoximation reaction apparatus, a discharging agent of a hydroxylation reaction apparatus, and a discharging agent of an epoxidation reaction apparatus, and specifically may be one or more of a discharging agent of a cyclohexanone ammoximation reaction apparatus, a discharging agent of a phenol hydroxylation reaction apparatus, and a discharging agent of an epoxidation reaction apparatus for propylene.

The conditions for regenerating the discharging agent are not particularly limited, and may be appropriately selected depending on the source of the discharging agent, for example: high temperature calcination and/or solvent washing.

The activity of the regenerated discharging agent varies depending on its source. Typically, the activity of the regenerated discharging agent may be 5-95% of its activity when fresh (i.e. the activity of the fresheners). Preferably, the activity of the regenerated discharging agent may be 10 to 90% of its activity when fresh, more preferably 10 to 60% of its activity when fresh. When the activity of the regenerated discharging agent is 10-60% of the activity of the regenerated discharging agent in the fresh state, not only can satisfactory selectivity of the target oxidation product be obtained, but also a further improved effective utilization rate of the oxidizing agent can be obtained. On the premise of considering the effective utilization rate of the oxidant, the activity of the regenerated discharging agent is 30-55% of the activity of the regenerated discharging agent in fresh from the viewpoint of further improving the selectivity of a target oxidation product. The activity of the fresh titanium silicalite molecular sieve is generally more than 95%.

The activity was determined by the following method: the regenerated discharging agent and fresh agent are respectively used as catalysts for cyclohexanone ammoximation reaction, and the ammoximation reaction conditions are as follows: catalyst (calculated by titanium silicon molecular sieve) and 36 wt% ammonia water (calculated by NH)₃Calculated as H), 30 wt% of hydrogen peroxide (calculated as H)₂O₂Calculated by mass ratio of 1: 7.5: 10: 7.5: 10, reacting for 2h at 80 ℃ under atmospheric pressure. Respectively calculating the conversion rate of cyclohexanone when the regenerated discharging agent and the fresh agent are used as catalysts, and taking the conversion rate as the activity of the regenerated discharging agent and the fresh agent, wherein,conversion of cyclohexanone [ (molar amount of cyclohexanone charged-molar amount of unreacted cyclohexanone)/molar amount of cyclohexanone charged]×100％。

When at least a part of the catalyst is the regenerated reactor discharge agent, the content of the regenerated reactor discharge agent is preferably 5% by weight or more based on the total amount of the catalyst, so that a higher effective utilization rate of the oxidant can be obtained. According to the method of the present invention, even when the whole catalyst is the discharged agent of the regenerated reaction device, high catalytic activity can be obtained.

According to the method of the present invention, the titanium silicalite molecular sieve is used as a catalyst, and the dosage of the titanium silicalite molecular sieve is not particularly limited, so as to realize the catalytic function. The choice may be made according to the form of contact of the titanium silicalite with the liquid mixture. For example, when mixing a titanium silicalite with the liquid mixture to form a slurry, the weight ratio of thioether to titanium silicalite may be from 0.1 to 50: 1, preferably 1 to 50: 1, such as 1-25: 1; when the titanium silicalite molecular sieve is filled in a catalyst bed layer of a fixed bed reactor, the weight hourly space velocity of the thioether can be 0.05-100h^-1Preferably 0.1 to 50h^-1(e.g. 2-20 h)^-1). In the invention, the weight hourly space velocity is based on the total amount of the titanium-silicon molecular sieves in all catalyst bed layers.

According to the process of the present invention, the liquid mixture contains at least one basic substance, which enables further improvement of the selectivity for sulfoxide. The alkaline substance is a substance whose pH value of the aqueous solution is more than 7. Specific examples of the alkaline substance may include, but are not limited to: ammonia (i.e., NH)₃) Amine, quaternary ammonium base and M¹(OH)_n(wherein, M¹Is an alkali metal or alkaline earth metal, n is an alkyl group with M¹The same integer as the valence of (1).

As the basic substance, ammonia may be introduced in the form of liquid ammonia, an aqueous solution, or a gas. The concentration of ammonia as an aqueous solution (i.e., aqueous ammonia) is not particularly limited and may be conventionally selected, for example, from 1 to 36% by weight.

As the baseThe amine is a substance formed by partially or completely replacing hydrogen on ammonia by hydrocarbyl, and comprises primary amine, secondary amine and tertiary amine. The amine may in particular be a substance of the formula I and/or C₃-C₁₁The heterocyclic amine of (a) is a heterocyclic amine,

in the formula I, R₁、R₂And R₃Each may be H or C₁-C₆Of (e.g. C)₁-C₆Alkyl group of) and R)₁、R₂And R₃Not H at the same time. Herein, C₁-C₆Alkyl of (2) includes C₁-C₆Straight chain alkyl of (2) and C₃-C₆Specific examples thereof may include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl and n-hexyl.

Specific examples of amines may include, but are not limited to: methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, isopropylamine, diisopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, sec-butylamine, diisobutylamine, triisobutylamine, tert-butylamine, n-pentylamine, di-n-pentylamine, tri-n-pentylamine, neopentylamine, isopentylamine, diisopentylamine, triisopentylamine, tert-pentylamine, n-hexylamine, and n-octylamine.

The heterocyclic amine is a compound having a nitrogen atom on the ring and a lone pair of electrons on the nitrogen atom. The heterocyclic amine may be, for example, one or more of substituted or unsubstituted pyrrole, substituted or unsubstituted tetrahydropyrrole, substituted or unsubstituted pyridine, substituted or unsubstituted hexahydropyridine, substituted or unsubstituted imidazole, substituted or unsubstituted pyrazole, substituted or unsubstituted quinoline, substituted or unsubstituted dihydroquinoline, substituted or unsubstituted tetrahydroquinoline, substituted or unsubstituted decahydroquinoline, substituted or unsubstituted isoquinoline, and substituted or unsubstituted pyrimidine.

As the basic substance, the quaternary ammonium base may specifically be a substance represented by the formula II,

in the formula II, R₄、R₅、R₆And R₇Each may be C₁-C₆Of (e.g. C)₁-C₆Alkyl groups of (ii). Said C is₁-C₆Alkyl of (2) includes C₁-C₆Straight chain alkyl of (2) and C₃-C₆Specific examples thereof may include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, isopentyl, tert-pentyl and n-hexyl.

Specific examples of the quaternary ammonium base may include, but are not limited to: tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (including tetra-n-propylammonium hydroxide and tetraisopropylammonium hydroxide), tetrabutylammonium hydroxide (including tetra-n-butylammonium hydroxide, tetra-sec-butylammonium hydroxide, tetra-isobutyl ammonium hydroxide and tetra-tert-butylammonium hydroxide), and tetrapentylammonium hydroxide.

As the basic substance, M¹(OH)_nIs a hydroxide of an alkali metal or a hydroxide of an alkaline earth metal, and may be, for example, sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide and calcium hydroxide.

According to the method of the present invention, the alkaline substance may be used as it is, or the alkaline substance may be used after being prepared into a solution.

According to the process of the invention, the amount of said alkaline substance can be chosen according to the composition of the liquid mixture. Generally, the molar ratio of the basic substance to the thioether may be in the range of from 0.00001 to 0.1: 1, preferably in the range of 0.00002 to 0.05: 1, more preferably in the range of 0.00005 to 0.005: 1, in the above range.

According to the process of the present invention, the liquid mixture may or may not contain a solvent. Preferably, the liquid mixture containsAt least one solvent, which allows a better control of the speed and intensity of the reaction. In the present invention, the kind of the solvent is not particularly limited, and the solvent may be any of various solvents commonly used in the oxidation reaction of a thioether. Preferably, the solvent is water, C₁-C₁₀Alcohol of (1), C₃-C₁₀Ketone (b), C₂-C₁₀Nitrile and C₁-C₆At least one of carboxylic acids (b). Preferably, the solvent is water, C₁-C₆Alcohol of (1), C₃-C₈Ketone and C₂-C₅One or more of the nitriles of (a). More preferably, the solvent is one or more of water, methanol, ethanol, n-propanol, isopropanol, tert-butanol, isobutanol, and acetone. Further preferably, the solvent is one or more of water, methanol, acetone and tert-butanol.

The amount of the solvent used in the present invention is not particularly limited, and may be selected according to the amounts of the thioether and the oxidizing agent. Generally, the molar ratio of the solvent to the thioether may be from 1 to 100: 1, preferably 2 to 80: 1 (e.g., 5-40: 1).

According to the process of the invention, the thioether may be any of various compounds containing an-S-bond, preferably the thioether is selected from thioethers having 2 to 18 carbon atoms, more preferably dimethyl sulfide and/or dimethyl sulfide.

According to the method of the present invention, when the target oxidation product selectivity decreases to satisfy the condition 1, the method further comprises performing the adjusting step, and stopping the adjusting step until the target oxidation product selectivity increases to satisfy the condition 2,

According to the method of the present invention, when condition 2 is satisfied, the improvement of the quality of the alkaline substance in the liquid mixture as the feed is stopped and the quality of the alkaline substance is maintained to the value at which condition 2 is satisfied; in the method of the present invention, further comprising adjusting step B, when condition 2 is satisfied, stopping increasing the mass of the oxidizing agent in the liquid mixture and maintaining the mass of the oxidizing agent at a value satisfying condition 2.

When the condition 1 is met, the adjustment step is carried out, so that the selectivity of the target oxidation product which originally shows a descending trend can be increased, the selectivity of the target oxidation product is increased to a higher level, the one-way service life of the titanium-silicon molecular sieve is prolonged, and the selectivity of the target oxidation product is maintained at a higher level for a long time.

Under the premise of prolonging the one-way service life of the titanium silicalite molecular sieve, from the viewpoint of further prolonging the stable operation time of the device, in the condition 1, S_t/S₀<0.9。

In the present invention, the target oxidation product selectivity (the number of moles of target oxidation product/moles of thioether involved in the reaction in the obtained reaction mixture) × 100%;

wherein the number of moles of thioether involved in the reaction-the number of moles of thioether added-the number of moles of thioether in the resulting reaction mixture.

The target oxidation product selectivity S can be determined by continuously monitoring the composition of the reaction mixture output from the reactor during the course of the reaction₀、S_tAnd S'. When the reactor is a plurality of reactors, the target oxidation product selectivity S is determined by the reaction mixture output by the reactor at the end of the material flow based on the flowing direction of the liquid mixture₀、S_tAnd S'.

In the present invention, the initial target oxidation product selectivity S₀Stabilized by a reactorAfter the run, the composition of the first reaction mixture output from the reactor was determined. For example, a reaction mixture obtained within 0.5 to 10 hours of stable operation of the reactor may be used as the initial reaction mixture.

The composition of the reaction mixture output from the reactor can be determined by conventional methods, such as gas chromatography.

Although it is sufficient to increase the mass of the basic substance in the liquid mixture when the condition 1 is satisfied, or to increase the mass of the basic substance in the liquid mixture and increase the mass of the oxidizing agent in the liquid mixture until the condition 2 is satisfied, in the adjustment step a, the mass of the basic substance in the liquid mixture is preferably increased in the range of 0.01 to 10%/day; in the adjusting step B, the mass of the oxidant in the liquid mixture is preferably increased by 0.02-5%/day, so that the one-way service life of the titanium silicalite molecular sieve is longer, and the reaction is performed more smoothly. In the present invention, "amplitude" refers to a step size between two adjacent numerical values.

According to the method of the present invention, various methods can be employed to improve the quality of the alkaline substance and the oxidizing agent in the liquid mixture. For example: the amounts of alkaline substance and oxidizing agent added in formulating the liquid mixture can be increased to improve the quality of the alkaline substance and oxidizing agent in the liquid mixture. When the alkaline substance and the oxidizing agent are provided in the form of solutions, respectively, the quality of the alkaline substance and the quality of the oxidizing agent in the liquid mixture can be improved by increasing the concentration of the alkaline substance in the alkaline substance solution and the concentration of the oxidizing agent in the oxidizing agent solution. In increasing the quality of the oxidizing agent in the liquid mixture by increasing the concentration of the oxidizing agent in the oxidizing agent solution, the amount of the oxidizing agent solution may be kept constant or may be adjusted accordingly (e.g., the amount of the oxidizing agent solution may be decreased to keep the ratio between the thioether and the oxidizing agent constant), as long as the quality of the oxidizing agent in the liquid mixture is ensured to be increased. In practice, at least part of the solvent may be mixed with the basic substance and the oxidizing agent to prepare a basic substance solution and an oxidizing agent solution while effecting the reaction in the presence of at least one solvent.

The magnitude of the increase in the quality of the alkaline substance and optionally of the oxidizing agent in the liquid mixture during the long-term continuous operation can be the same or different according to the process of the invention. In general, the mass of the alkaline substance and optionally the mass of the oxidizing agent can be increased to a lower extent in the early stages of the reaction and to a higher extent in the latter stages of the reaction.

According to the method of the present invention, the maximum value of the mass of the basic substance and the mass of the oxidizing agent in the liquid mixture is based on the fact that stabilization of the target oxidation product to a desired level can be achieved by increasing the mass of the basic substance and optionally the mass of the oxidizing agent, respectively. Generally, the maximum molar ratio of the basic substance to the thioether may be not higher than 0.1: 1, preferably not higher than 0.05: 1. the maximum molar ratio of oxidant to thioether may be no more than 5: 1, preferably not higher than 2: 1.

according to the process of the invention, the amount of the remaining material is generally kept constant during the adjustment step, but can be adjusted accordingly, provided that the mass of the alkaline substance and the mass of the oxidizing agent in the liquid mixture are increased.

According to the method of the invention, the adjusting step is an adjusting step a, or a combination of an adjusting step a and an adjusting step B.

The adjustment step a may be used alone, that is, when the condition 1 is satisfied, only the adjustment step a may be performed.

The conditioning step a may also be used in combination with the conditioning step B.

When the adjustment step a and the adjustment step B are used in combination, in the first embodiment, when the condition 1 is satisfied, the adjustment step a and the adjustment step B are performed, and in this case, the adjustment step a and the adjustment step B may be performed synchronously or asynchronously, preferably asynchronously, which is more advantageous in terms of operation and easier in terms of reaction control.

When the adjustment step a and the adjustment step B are used in combination, in the second embodiment, when the condition 1 is satisfied, the adjustment step a or the adjustment step B is performed, and the adjustment step a or the adjustment step B is performedAt least one conditioning step A, such as 1-5 (preferably 1-3) conditioning steps A, is carried out between two adjacent conditioning steps B. That is, the condition 1 is satisfied n times, where n₁When the condition 1 is not met, the adjusting steps A and n are carried out₂When the condition 1 is satisfied, the adjusting steps B and n are carried out₁+n₂＝n，n₁≥n₂E.g. n₁/n₂1-5, n is preferred₁/n₂＝1-3。

When the adjustment step a and the adjustment step B are used in combination, in the third embodiment, when the condition 1 is satisfied, the adjustment step a or the adjustment step B is performed, in which the adjustment step B is performed at least once, such as 1 to 5 times (preferably 1 to 3 times), between two adjacent adjustment steps a. That is, n' times satisfy the condition 1, where n₁When the condition 1 is satisfied, the adjusting steps B and n are performed₂When the condition 1 is satisfied, the adjustment steps A and n are performed₁’+n₂’＝n，n₁’≥n₂', such as n₁’/n₂' 1 to 5, preferably n₁’/n₂’＝1-3。

Preferably, conditioning step a is used in combination with conditioning step B, which is more effective in extending the catalyst's single pass service life and achieving higher target oxidation product selectivity.

According to the method of the present invention, the oxidation reaction conditions are dependent on the target oxidation product. In general, the temperature of the catalyst bed may be in the range from 0 to 120 ℃ and preferably in the range from 20 to 80 ℃. The pressure in the reactor may be in the range of 0 to 5MPa, preferably 0.5 to 3.5MPa, the pressure being in gauge pressure.

According to the method of the present invention, when the catalyst beds include the first catalyst bed and the second catalyst bed described above, the temperature of the first catalyst bed and the temperature of the second catalyst bed may be the same or different. From the viewpoint of ease of operation, the temperature of the first catalyst bed layer is the same as the temperature of the second catalyst bed layer. From the viewpoint of further improving the selectivity of the target oxidation product and further prolonging the one-way service life of the titanium silicalite molecular sieve, the temperature of the first catalyst bed layer is preferably higher than that of the second catalyst bed layer. More preferably, the temperature of the first catalyst bed is 5-30 ℃, such as 10-20 ℃ higher than the temperature of the second catalyst bed.

The method according to the present invention may further comprise separating the reaction mixture output from the fixed-bed reactor to obtain the target oxidation product (e.g., sulfoxide) and unreacted reactants. The method for separating the reaction mixture may be a method conventionally selected in the art, and is not particularly limited. The separated unreacted reactant can be recycled.

The method of the invention is adopted to oxidize the thioether, which can effectively prolong the one-way service life of the titanium silicalite molecular sieve used as the catalyst and reduce the regeneration frequency of the titanium silicalite molecular sieve. The method is particularly suitable for oxidizing thioether to prepare sulfoxide, and the reaction mixture with stable sulfoxide content can be obtained by the method, so that the subsequent products can be conveniently separated and purified.

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 examples and comparative examples, titanium silicalite TS-1 was used according to Zeolite, 1992, Vol.12: 943-950, with a titanium oxide content of 2.5% by weight; the hollow titanium silicalite molecular sieve used is a hollow titanium silicalite molecular sieve purchased from Hunan Jian Chang petrochemical Co Ltd and sold under the trademark HTS, and the titanium oxide content of the hollow titanium silicalite molecular sieve is 2.5 wt%.

In the following examples and comparative examples, the reagents used were all commercially available analytical grade reagents, and the pressures were measured as gauge pressures.

In the following examples and comparative examples, the contents of the respective components in the obtained reaction liquid were analyzed by gas chromatography, and on the basis of which the sulfoxide selectivity was calculated by the following formulas, examples 11 to 18 and 21 further calculate the effective utilization rate of the oxidizing agent:

sulfoxide selectivity (moles of sulfoxide/moles of thioether involved in the reaction in the resulting reaction mixture) × 100%;

the effective oxidant utilization factor (moles of sulfoxide/moles of oxidant participating in the reaction in the obtained reaction mixture) × 100%.

Wherein the moles of thioether involved in the reaction-the moles of thioether remaining in the resulting reaction mixture-are the moles of thioether added;

the moles of oxidant participating in the reaction-the moles of oxidant added-the moles of oxidant remaining in the resulting reaction mixture.

The following examples 4, 11-18 and 21 were tested for catalyst activity using the following method:

catalyst, 36 wt% ammonia (as NH)₃Calculated as H), 30 wt% of hydrogen peroxide (calculated as H)₂O₂Calculated), tert-butyl alcohol and cyclohexanone in a mass ratio of 1: 7.5: 10: 7.5: 10 stirring and reacting at 80 ℃ under atmospheric pressure for 2 hours, filtering the reaction product, analyzing the composition of the obtained liquid phase by gas chromatography, calculating the conversion rate of cyclohexanone by the following formula and using the conversion rate as the activity of the catalyst,

conversion (%) of cyclohexanone ═ molar amount of charged cyclohexanone-molar amount of unreacted cyclohexanone)/molar amount of charged cyclohexanone ] × 100%.

Examples 1-21 illustrate the process of the present invention.

Example 1

Catalyst (i.e. shaped titanium silicalite TS-1, spherical catalyst with volume average particle size of 500 μm, titanium silicalite TS-1 content in catalyst 80 wt%, silicon oxide content of 20 wt%, density of 0.76 g/cm)³) The catalyst is filled in a fixed bed reactor to form a catalyst bed, wherein the number of the catalyst beds is 1.

A liquid mixture of dimethyl sulphide, hydrogen peroxide as oxidant (provided in the form of 30 wt% hydrogen peroxide), acetone as solvent and ammonia (initial concentration of 10 wt%) was fed from the bottom of the fixed bed reactor and passed through the catalyst bed. Wherein the molar ratio of dimethyl sulfide to hydrogen peroxide is 1: 0.5, the molar ratio of dimethyl sulfide to solvent acetone is 1: 10, dimethyl sulfide and NH₃Is 1;0.005, weight hourly space velocity of dimethyl sulfide of 2h^-1. The temperature in the catalyst bed was 45 ℃ and the pressure in the fixed bed reactor was 0.8 MPa.

Continuously monitoring the composition of the reaction mixture withdrawn from the reactor during the course of the reaction, in the presence of the dimethyl sulphoxide-selective S_tWith initial (sample determination at 0.5 hour after reaction) selectivity S of dimethyl sulfoxide₀Ratio S of_t/S₀S is not less than 0.85_t/S₀<At 0.9 (i.e., when condition 1 is satisfied), NH in the liquid mixture is increased by 0.01 to 10%/day₃By increasing the NH content of the ammonia₃While the amount of ammonia water is kept constant) until the selectivity of dimethyl sulfoxide S' is equal to the initial selectivity of dimethyl sulfoxide S₀Ratio S'/S of₀S'/S is more than or equal to 0.9₀When the NH content of the liquid mixture is less than or equal to 1 (namely, when the condition 2 is satisfied), the increase of NH content in the liquid mixture is stopped₃And remains at the elevated value.

The reaction was carried out for 660 hours, and the concentration of aqueous ammonia at the end of the reaction was 29% by weight. The selectivity for dimethyl sulfoxide determined from the reaction mixtures obtained after the reaction had proceeded for 0.5 hour and 660 hours is listed in table 1.

Comparative example 1

Dimethyl sulfide was oxidized by the same method as in example 1, except that the basic substance (i.e., NH) in the liquid mixture was not changed during the reaction₃) The quality of (c). The results of the reaction for 0.5 hour and 360 hours are shown in Table 1.

Example 2

Dimethyl sulfide was oxidized by the same method as in example 1, except that NH in the liquid mixture was increased by 0.01 to 10%/day when the condition 1 was satisfied for the 1 st time during the reaction₃By increasing the amount of NH in the ammonia₃While the amount of the aqueous ammonia solution remains unchanged) until condition 2 is satisfied, the increase of NH in the liquid mixture is stopped₃The amount of (c) is maintained at the elevated value; on the 2 nd occasion that condition 1 is satisfied, the quality of the hydrogen peroxide in the liquid mixture is increased in the range of 0.02 to 5%/day (by increasing the concentration of hydrogen peroxide in hydrogen peroxide)While the amount of aqueous hydrogen peroxide solution is kept constant) until condition 2 is met, the increase in the mass of hydrogen peroxide in the liquid mixture is stopped and kept at the increased value, and so on (i.e. the NH in the liquid mixture is increased by 0.01-10%/day when condition 1 is met an odd number of times), and so on (i.e. the NH in the liquid mixture is increased by 0.01-10%/day₃Until condition 2 is satisfied; when condition 1 is satisfied an even number of times, the mass of hydrogen peroxide in the liquid mixture is increased in the range of 0.02 to 5%/day until condition 2) is satisfied.

The reaction was carried out for 770 hours, and at the end of the reaction, the concentration of ammonia water was 20% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 42% by weight. The results of the reaction for 0.5 hour and 770 hours are shown in Table 1.

Example 3

Dimethyl sulfide was oxidized in the same manner as in example 2, except that the titanium silicalite TS-1 in the catalyst was replaced with an equivalent amount of hollow titanium silicalite (i.e., a shaped hollow titanium silicalite, catalyst density of 0.70g/cm³). The reaction was carried out for 770 hours, and the concentration of ammonia water at the end of the reaction was 18% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 39% by weight. The results of the reaction for 0.5 hour and 770 hours are shown in Table 1.

Example 4

Dimethyl sulfide was oxidized by the same method as in example 2, except that the catalyst was obtained by regenerating a shaped catalyst (spherical catalyst having a volume average particle diameter of 500 μm) discharged from the cyclohexanone ammoximation reaction process, the catalyst containing 80% by weight of titanium silicalite TS-1 and 20% by weight of silica, under the regeneration conditions: calcining at 550 deg.C in air atmosphere for 4 h. The activity of the regenerated catalyst was 50%, and its activity when fresh was 95%. The reaction was carried out for 800 hours, and the concentration of ammonia water at the end of the reaction was 16% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 37% by weight. The results of the reaction for 0.5 hour and 800 hours are shown in Table 1.

Example 5

Dimethyl sulfide was oxidized by the same method as in example 2, except that, under the condition that the total loading of the molded titanium silicalite molecular sieve was not changed, the molded hollow titanium silicalite molecular sieve was filled (same as in example 3) and then the molded titanium silicalite molecular sieve TS-1 was filled (same as in example 1), thereby forming a catalyst bed layer, i.e., the liquid mixture first passed through the catalyst bed layer formed by the molded hollow titanium silicalite molecular sieve and then passed through the catalyst bed layer formed by the molded titanium silicalite molecular sieve TS-1. Wherein the weight ratio of the formed hollow titanium silicalite molecular sieve to the formed titanium silicalite molecular sieve TS-1 is 2: 1. the reaction was carried out for 840 hours, the concentration of ammonia at the end of the reaction being 17% by weight and the concentration of hydrogen peroxide in hydrogen peroxide being 36% by weight. The results of the reaction for 0.5 hour and 840 hours are shown in Table 1.

Example 6

The dimethyl sulfide is oxidized by the same method as that in the example 5, except that under the condition that the total loading amount of the formed titanium silicalite molecular sieve is not changed, the formed titanium silicalite molecular sieve TS-1 is firstly filled, and then the formed hollow titanium silicalite molecular sieve is filled, so as to form a catalyst bed layer, wherein the weight ratio of the formed titanium silicalite molecular sieve TS-1 to the formed hollow titanium silicalite molecular sieve is 1: 2. the reaction was carried out for 700 hours, and the concentration of ammonia water at the end of the reaction was 24% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 45% by weight. The results of the reaction for 0.5 hour and 700 hours are shown in Table 1.

Example 7

The dimethyl sulfide is oxidized by the same method as that in the example 5, except that under the condition that the total loading amount of the formed titanium silicalite molecular sieve is not changed, the formed hollow titanium silicalite molecular sieve is firstly filled, and then the formed titanium silicalite molecular sieve TS-1 is filled, so as to form a catalyst bed layer, wherein the weight ratio of the formed hollow titanium silicalite molecular sieve to the formed titanium silicalite molecular sieve TS-1 is 1: 1. the reaction was carried out for 760 hours, and the concentration of ammonia water at the end of the reaction was 21% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 40% by weight. The results of the reaction for 0.5 hour and 760 hours are shown in Table 1.

Example 8

Dimethyl sulfide is oxidized by the same method as in example 5, except that under the condition that the total loading of the formed titanium silicalite molecular sieve is not changed, a formed hollow titanium silicalite molecular sieve is filled first, and then a formed titanium silicalite molecular sieve TS-1 is filled, wherein the weight ratio of the formed hollow titanium silicalite molecular sieve to the formed titanium silicalite molecular sieve TS-1 is 1: 2. the reaction was carried out for 730 hours, and the concentration of ammonia water at the end of the reaction was 22% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 41% by weight. The results of the reaction for 0.5 hour and 730 hours are shown in Table 1.

Example 9

Dimethyl sulfide was oxidized by the same method as in example 5, except that the weight ratio of the formed hollow titanium silicalite molecular sieve to the formed titanium silicalite molecular sieve TS-1 was 8: 1. the reaction was carried out for 840 hours, the concentration of ammonia at the end of the reaction being 16% by weight and the concentration of hydrogen peroxide in hydrogen peroxide being 37% by weight. The results of the reaction for 0.5 hour and 840 hours are shown in Table 1.

Example 10

Dimethyl sulfide was oxidized by the same method as in example 5, except that the weight ratio of the formed hollow titanium silicalite molecular sieve to the formed titanium silicalite molecular sieve TS-1 was 20: 1. the reaction was carried out for 740 hours, and the concentration of ammonia water at the end of the reaction was 21% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 42% by weight. The results of the reaction for 0.5 hour and 740 hours are shown in Table 1.

TABLE 1

Comparing examples 1 and 2 with comparative example 1, it can be seen that the selectivity of the target oxidation product can be stably maintained at a high level for a long time by using the method of the present invention, thereby effectively prolonging the single-pass service life of the titanium silicalite molecular sieve.

Comparing examples 2 and 3 with examples 4-10, it can be seen that the hollow titanium silicalite molecular sieve and titanium silicalite TS-1 are used in combination, and the hollow titanium silicalite molecular sieve is located upstream of the titanium silicalite TS-1, namely: the reactant firstly passes through the catalyst bed layer formed by the hollow titanium silicalite molecular sieve and then passes through the catalyst bed layer formed by the titanium silicalite molecular sieve TS-1, so that the one-way service life of the catalyst can be further prolonged.

Comparing example 1 with example 2, it can be seen that the combined use of increasing the quality of the alkaline substance in the liquid mixture and increasing the quality of the oxidant in the liquid mixture as the adjusting step can further prolong the one-way service life of the titanium silicalite molecular sieve as the catalyst.

Examples 11-20 relate to the following four catalysts.

C1: the formed hollow titanium silicalite molecular sieve discharged from the propylene epoxidation reaction process is a spherical catalyst with the volume average particle diameter of 800 mu m and the density of 0.69g/cm³) The catalyst is obtained by regeneration, the catalyst contains 85 wt% of hollow titanium-silicon molecular sieve and 15 wt% of silicon oxide, and the regeneration conditions are as follows: calcining at 570 deg.C in air atmosphere for 4 h. The activity of the regenerated catalyst was 30% (its activity in fresh was 96%).

C2: the formed titanium silicalite TS-1 (spherical catalyst with volume average particle diameter of 800 μm and density of 0.75 g/cm) discharged from the propylene epoxidation reaction process³) The catalyst is obtained by regeneration, the catalyst contains 85 wt% of titanium silicalite TS-1 and 15 wt% of silicon oxide, and the regeneration conditions are as follows: calcining at 570 deg.C in air atmosphere for 4 h. The activity of the regenerated catalyst was 30% (its activity in fresh was 95%).

C3: forming the C1 freshly formed hollow titanium silicalite molecular sieve.

C4: forming the fresh forming titanium silicalite TS-1 of C2.

Example 11

The embodiment adopts a reducing fixed bed reactor, the reducing fixed bed reactor is provided with two catalyst bed layers with different inner diameters and used for filling the titanium silicalite molecular sieve, and a conical inner diameter transition area is arranged between the two catalyst bed layers, wherein the catalyst is not filled. Taking the flowing direction of the liquid material in the reactor as a reference, the upstream catalyst bed layer is called a first catalyst bed layer, the downstream catalyst bed layer is called a second catalyst bed layer, the first catalyst bed layer and the second catalyst bed layer are both filled with catalyst C1, and the weight ratio of the filling amount of the catalyst in the first catalyst bed layer to the filling amount of the catalyst in the second catalyst bed layer is 5: 1, the ratio of the inner diameter of the first catalyst bed layer to the inner diameter of the second catalyst bed layer is 2: 1.

dimethyl sulfide, hydrogen peroxide (provided in the form of 27.5 wt% hydrogen peroxide) as an oxidant, methanol as a solvent and pyridine (mixed with methanol to prepare an alkaline substance solution for use, wherein the initial concentration of the pyridine in the alkaline substance solution is 12 wt%) are mixed to form a liquid mixture, and the liquid mixture is fed from the bottom of a fixed bed reactor and flows through a first catalyst bed layer and a second catalyst bed layer in sequence. Wherein the molar ratio of dimethyl sulfide to hydrogen peroxide is 1: 0.3, the molar ratio of dimethyl sulfide to solvent methanol (excluding methanol in the alkaline solution) is 1: 20, initial molar ratio of dimethyl sulfide to pyridine 1: 0.0002 weight hourly space velocity of dimethyl sulfide (based on the total amount of titanium silicalite molecular sieves in the first catalyst bed and the second catalyst bed) is 2.5h^-1. The temperature of the first catalyst bed layer and the second catalyst bed layer is 35 ℃, and the pressure in the fixed bed reactor is controlled to be 0.5 MPa.

Continuously monitoring the composition of the reaction mixture withdrawn from the reactor during the course of the reaction, in the presence of the dimethyl sulphoxide-selective S_tWith initial (reaction carried out to 2 hours sampled) selectivity S of dimethyl sulfoxide₀Ratio S of_t/S₀S is not less than 0.85_t/S₀<When 0.9 (i.e., when the condition 1 is satisfied), the amount of pyridine in the liquid mixture is increased (by increasing the concentration of pyridine in the basic substance solution while the amount of the basic substance solution is kept constant) by 0.01 to 10%/day until the dimethyl sulfoxide selectivity S' and the initial dimethyl sulfoxide selectivity S are satisfied₀Ratio S'/S of₀S'/S is more than or equal to 0.9₀When the value is less than or equal to 1 (namely, when the condition 2 is satisfied), the improvement of the quality of the pyridine is stopped and is maintained as the improved value.

The reaction was carried out for 740 hours, and the pyridine concentration in the alkaline solution at the end of the reaction was 28% by weight. The selectivity to dimethyl sulfoxide and the effective utilization rate of the oxidizing agent determined from the reaction mixture obtained after the reaction proceeded for 2 hours and 740 hours are shown in table 2.

Comparative example 2

Dimethyl sulfide was oxidized by the same method as in example 11, except that the quality of pyridine in the liquid mixture was not changed during the reaction.

The results of the 2-hour and 400-hour reactions are shown in Table 2.

Example 12

Dimethyl sulfide was oxidized by the same method as in example 11 except that the temperature of the first catalyst bed was controlled to 35 ℃ and the temperature of the second catalyst bed was controlled to 25 ℃.

The reaction was carried out for 770 hours, and the pyridine concentration in the basic substance solution at the end of the reaction was 26% by weight. The selectivity to dimethyl sulfoxide and the effective utilization rate of the oxidizing agent determined from the reaction mixture obtained after the reaction was carried out for 2 hours and 770 hours are shown in table 2.

Example 13

Dimethyl sulfide was oxidized by the same method as in example 11, except that the initial molar ratio of dimethyl sulfide to hydrogen peroxide was 1: 0.3, in the reaction process, when the condition 1 is met for the first time, the quality of the hydrogen peroxide in the liquid mixture is improved (namely, the step B is adjusted) in a range of 0.02-5%/day (the concentration of the hydrogen peroxide in the hydrogen peroxide is improved, and meanwhile, the using amount of the hydrogen peroxide is kept unchanged) until the condition 2 is met, the quality of the hydrogen peroxide is stopped to be improved and is kept at an increased value; when the condition 1 is satisfied at the 2 nd and 3 rd times, the amount of pyridine in the liquid mixture is increased (by increasing the concentration of pyridine in the alkaline substance solution while the amount of alkaline substance solution is kept constant) in a range of 0.01 to 10%/day (i.e., the adjustment step a) until the condition 2 is satisfied, the mass of pyridine is stopped from being increased and kept at the increased value, and so on (i.e., when the condition 1 is satisfied, the adjustment step a or the adjustment step B is performed, wherein the adjustment step a is performed twice between two adjacent adjustment steps B).

The reaction was carried out for 840 hours, and at the end of the reaction, the pyridine concentration in the alkaline substance solution was 21 wt%, and the hydrogen peroxide concentration in hydrogen peroxide was 36 wt%. The results of the reaction for 2 hours and 840 hours are listed in table 2.

Example 14

Dimethyl sulfide was oxidized by the same method as in example 13, except that the temperature of the first catalyst bed was controlled to 50 ℃ and the temperature of the second catalyst bed was controlled to 35 ℃.

The reaction was carried out for 870 hours, and at the end of the reaction, the concentration of pyridine in the alkaline solution was 20% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 34% by weight. The results of the 2 hour and 870 hour reactions are shown in Table 2.

Example 15

Dimethyl sulfide was oxidized by the same method as in example 14 except that the catalyst C1 in the second catalyst bed was replaced with an equal amount of catalyst C2.

The reaction was carried out for 980 hours, and at the end of the reaction, the pyridine concentration in the alkaline solution was 18 wt%, and the hydrogen peroxide concentration in hydrogen peroxide was 35 wt%. The results of the reactions for 2 hours and 980 hours are shown in Table 2.

Example 16

Dimethyl sulfide was oxidized by the same method as in example 15, except that the total catalyst loading was kept constant so that the weight ratio of catalyst C1 to catalyst C2 was 10: 1, the ratio of the inner diameters of the first catalyst bed layer and the second catalyst bed layer is 5: 1 (inner diameter of second catalyst bed same as example 15).

The reaction was carried out for 980 hours, and at the end of the reaction, the pyridine concentration in the alkaline solution was 17 wt%, and the hydrogen peroxide concentration in hydrogen peroxide was 35 wt%. The results of the reactions for 2 hours and 980 hours are shown in Table 2.

Example 17

Dimethyl sulfide was oxidized by the same method as in example 15 except that, under the condition that the loading of the first catalyst bed and the second catalyst bed was constant, the ratio of the inner diameters of the first catalyst bed to the second catalyst bed was 1: 1 (inner diameter of second catalyst bed same as example 15).

The reaction was carried out for 820 hours, and at the end of the reaction, the pyridine concentration in the alkaline substance solution was 21% by weight, and the hydrogen peroxide concentration in hydrogen peroxide was 36% by weight. The results of the 2 hour and 820 hour reactions are shown in Table 2.

Example 18

Dimethyl sulfide was oxidized by the same method as in example 15 except that, under the condition that the loading of the first catalyst bed and the second catalyst bed was constant, the ratio of the inner diameters of the first catalyst bed to the second catalyst bed was 1: 2 (inner diameter of second catalyst bed is the same as in example 15).

The reaction was carried out for 780 hours, and at the end of the reaction, the concentration of pyridine in the alkaline substance solution was 22% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 36% by weight. The results of the 2-hour and 780-hour reactions are shown in Table 2

Example 19

Dimethyl sulfide was oxidized in the same manner as in example 15 except that the catalyst C1 was replaced by an equal amount of catalyst C3 and the catalyst C2 was replaced by an equal amount of catalyst C4.

The reaction was carried out for 880 hours, and at the end of the reaction, the pyridine concentration in the alkaline substance solution was 23 wt%, and the hydrogen peroxide concentration in hydrogen peroxide was 34 wt%. The results of the reactions for 2 hours and 880 hours are listed in table 2.

Example 20

Dimethyl sulfide was oxidized in the same manner as in example 15 except that catalyst C1 and catalyst C2 were each replaced with the same amount of catalyst C3.

The reaction was carried out for 800 hours, and at the end of the reaction, the concentration of pyridine in the alkaline substance solution was 25% by weight, and the concentration of hydrogen peroxide in hydrogen peroxide was 37% by weight. The results of the reaction for 2 hours and 800 hours are shown in Table 2.

TABLE 2

Comparing examples 15, 17 and 18, it can be seen that the single pass life of the catalyst can be further extended by passing the liquid mixture through the upstream catalyst bed at a lower superficial velocity and then through the downstream catalyst bed at a higher superficial velocity.

Example 21

The catalyst used in this example was obtained by regenerating a shaped hollow titanium silicalite molecular sieve (a spherical catalyst with a volume average particle size of 250 μm) discharged from a phenol hydroxylation reaction process, the catalyst containing 85 wt% hollow titanium silicalite molecular sieve and 15 wt% silica, the regeneration conditions being: calcining at 570 deg.C in air atmosphere for 4 h. The activity of the regenerated catalyst was 40% (its activity when fresh was 96%).

The catalyst is filled in a fixed bed reactor to form a catalyst bed layer, wherein the number of the catalyst bed layers is 1.

The dimethyl benzene sulfide, tert-butyl hydroperoxide (mixed with acetonitrile to prepare an oxidant solution, the initial concentration of the tert-butyl hydroperoxide in the oxidant solution is 10 wt%), acetonitrile (excluding acetonitrile in the oxidant solution and an alkaline substance solution) as a solvent and tetramethylammonium hydroxide (mixed with the acetonitrile to prepare the alkaline substance solution, the initial concentration of the tetramethylammonium hydroxide in the alkaline substance solution is 20 wt%) are mixed to form a liquid mixture, and the liquid mixture is fed into a fixed bed reactor and flows through a catalyst bed layer. Wherein the molar ratio of the methyl phenyl sulfide to the tert-butyl hydroperoxide is 1: 1, the molar ratio of the thioanisole to the solvent acetonitrile (excluding acetonitrile in the oxidant solution and the alkaline substance solution) is 1: initial molar ratio of thioanisole to tetramethylammonium hydroxide of 1: 0.00005, weight hourly space velocity of thioanisole of 10h^-1. The temperature in the catalyst bed was 70 ℃ and the initial pressure in the fixed bed reactor was controlled to 2.5 MPa.

Continuously monitoring the composition of the reaction mixture withdrawn from the reactor during the course of the reaction, the selectivity S for the first sulphoxybenzoate_tWith initial (reaction carried out to 2 hours sampled) selectivity S of benzyl sulfoxide₀Ratio S of_t/S₀S is not less than 0.85_t/S₀<0.9 (i.e., satisfiesCondition 1), increasing the mass concentration of tetramethylammonium hydroxide in the liquid mixture (by increasing the concentration of tetramethylammonium hydroxide in the alkaline solution while the amount of alkaline solution is kept constant) by 0.01-10%/day until the selectivity S' to benzyl sulfoxide is equal to the initial selectivity S to benzyl sulfoxide₀Ratio S'/S of₀S'/S is more than or equal to 0.9₀When the mass concentration of the tetramethylammonium hydroxide is less than or equal to 1 (namely, when the condition 2 is met), stopping increasing the mass concentration of the tetramethylammonium hydroxide and keeping the mass concentration of the tetramethylammonium hydroxide at the increased value (namely, adjusting the step A); when the condition 1 is met for the 2 nd to 4 th times, the quality of the tert-butyl hydroperoxide in the liquid mixture is improved by 0.02 to 5 percent/day (which is realized by increasing the concentration of the tert-butyl hydroperoxide in the oxidant solution and correspondingly reducing the dosage of the oxidant solution so as to keep the molar ratio of the methyl phenyl sulfide to the tert-butyl hydroperoxide unchanged) until the condition 2 is met, the improvement of the quality of the tert-butyl hydroperoxide is stopped and is kept at the improved value (namely, the adjusting step B), and so on (namely, when the condition 1 is met, the adjusting step A or the adjusting step B is carried out, wherein the adjusting step B is carried out three times between two adjacent adjusting steps A).

The reaction was carried out for 970 hours, and at the end of the reaction, the concentration of tetramethylammonium hydroxide in the alkaline substance solution was 24% by weight, and the concentration of t-butylhydroperoxide in the oxidizing agent solution was 32% by weight. The results of the 2 hour and 970 hour reactions are listed in table 3.

TABLE 3

The results of examples 4, 11 to 18 and 21 demonstrate that the process of the present invention can achieve a good reaction effect even when a discharging agent is used as a catalyst, and can achieve a higher effective utilization rate of an oxidizing agent, enabling effective reuse of a spent catalyst.

Claims

1. A thioether oxidation method comprises the steps of contacting a liquid mixture with a titanium silicalite molecular sieve under oxidation reaction conditions, wherein the liquid mixture contains thioether, at least one oxidant, at least one alkaline substance and at least one optional solvent, the oxidant is peroxide, the method further comprises the step of performing an adjustment step when the selectivity of a target oxidation product is reduced to meet the condition 1, the adjustment step is stopped until the selectivity of the target oxidation product is improved to meet the condition 2, the target oxidation product is sulfoxide,

and B, an adjusting step: increasing the mass of the oxidizing agent in the liquid mixture;

wherein the maximum molar ratio of the basic substance to the thioether is not higher than 0.05: 1, the maximum molar ratio of oxidizing agent to thioether is not higher than 2: 1;

the alkaline substance is selected from ammonia, a substance shown in formula I, pyridine and quaternary ammonium base,

in the formula I, R₁、R₂And R₃Each is H or C₁-C₆And R is alkyl of₁、R₂And R₃Not H at the same time.

2. The method according to claim 1, wherein when condition 1 is satisfied, either the adjustment step a or the adjustment step B is performed, and at least one adjustment step a is performed between two adjacent adjustment steps B; or, when the condition 1 is satisfied, performing the adjusting step a or the adjusting step B, and performing the adjusting step B at least once between two adjacent adjusting steps a.

3. The method according to claim 1 or 2, wherein, in condition 1, S_t/S₀<0.9。

4. The process according to claim 1, wherein the molar ratio of basic substance to thioether is between 0.00001-0.05: 1 in the range of; the molar ratio of the oxidant to the thioether is between 0.2 and 1: 1, in the above range.

5. The method according to claim 1 or 4, wherein the mass of the alkaline substance is increased in an amplitude of 0.01-10%/day; and/or

The mass of the oxidizing agent in the liquid mixture is increased in the range of 0.02 to 5%/day.

6. The method of claim 1, wherein the titanium silicalite molecular sieves are loaded in a catalyst bed of a fixed bed reactor, the catalyst bed comprises a first catalyst bed and a second catalyst bed, the first catalyst bed is located upstream of the second catalyst bed based on a flow direction of the liquid mixture, and the titanium silicalite molecular sieves loaded in the first catalyst bed are the same as or different from the titanium silicalite molecular sieves loaded in the second catalyst bed.

7. The method of claim 6, wherein the titanium silicalite molecular sieve filled in the first catalyst bed layer is a hollow titanium silicalite molecular sieve, crystal grains of the hollow titanium silicalite molecular sieve are of a hollow structure, the radial length of a cavity part of the hollow structure is 5-300 nanometers, and the titanium silicalite molecular sieve has a P/P ratio at 25 ℃ of P/P₀The benzene adsorption amount measured under the conditions of 0.10 and 1 hour of adsorption time is at least 70 mg/g, and a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption of the titanium silicalite molecular sieve; and

the titanium silicalite molecular sieve filled in the second catalyst bed layer is a titanium silicalite molecular sieve TS-1.

8. The method of claim 6 or 7, wherein the weight ratio of the titanium silicalite molecular sieves packed in the first catalyst bed to the titanium silicalite molecular sieves packed in the second catalyst bed is 0.5-20: 1.

9. the method of claim 8, wherein the weight ratio of the titanium silicalite molecular sieves packed in the first catalyst bed to the titanium silicalite molecular sieves packed in the second catalyst bed is 2-10: 1.

10. a process as claimed in claim 6 or claim 7, wherein the superficial velocity of the liquid mixture flowing through the first catalyst bed is v₁Superficial velocity through the second catalyst bed is v₂，v₁＜v₂。

11. The method of claim 10, wherein v₂/v₁＝1.5-10。

12. The method of claim 11, wherein v, v₂/v₁＝2-5。

13. The process of claim 8, wherein the superficial velocity of the liquid mixture flowing through the first catalyst bed is v₁Superficial velocity through the second catalyst bed is v₂，v₁＜v₂。

14. The method of claim 13, wherein v, v₂/v₁＝1.5-10。

15. The method of claim 14, wherein v₂/v₁＝2-5。

16. The method of claim 6 or 7, wherein the liquid mixture is inResidence time in the first catalyst bed of T₁The total residence time in the catalyst bed is T, T₁/T＝0.2-0.96。

17. The method of claim 16, wherein T is₁/T＝0.5-0.85。

18. The process of claim 8, wherein the residence time of the liquid mixture in the first catalyst bed is T₁The total residence time in the catalyst bed is T, T₁/T＝0.2-0.96。

19. The method of claim 18, wherein T is₁/T＝0.5-0.85。

20. The process of claim 10, wherein the residence time of the liquid mixture in the first catalyst bed is T₁The total residence time in the catalyst bed is T, T₁/T＝0.2-0.96。

21. The method of claim 20, wherein T is₁/T＝0.5-0.85。

22. The process of claim 6 or 7, wherein the temperature of the first catalyst bed is higher than the temperature of the second catalyst bed.

23. The process of claim 22, wherein the temperature of the first catalyst bed is 5-30 ℃ higher than the temperature of the second catalyst bed.

24. The method of claim 8, wherein the temperature of the first catalyst bed is higher than the temperature of the second catalyst bed.

25. The process of claim 24, wherein the temperature of the first catalyst bed is 5-30 ℃ higher than the temperature of the second catalyst bed.

26. The method of claim 10, wherein the temperature of the first catalyst bed is higher than the temperature of the second catalyst bed.

27. The process of claim 26, wherein the temperature of the first catalyst bed is 5-30 ℃ higher than the temperature of the second catalyst bed.

28. The method of claim 16, wherein the temperature of the first catalyst bed is higher than the temperature of the second catalyst bed.

29. The process as claimed in claim 28, wherein the temperature of the first catalyst bed is 5-30 ℃ higher than the temperature of the second catalyst bed.

30. The method of any one of claims 1 and 6-7, wherein the contacting is performed at a temperature of 0-120 ℃.

31. The method of any one of claims 1 and 6 to 7, wherein at least a portion of the titanium silicalite is a recycled discharging agent of the reaction apparatus using the titanium silicalite as a catalyst, and the discharging agent is one or more of a discharging agent of an ammoximation reaction apparatus, a discharging agent of a hydroxylation reaction apparatus, and a discharging agent of an epoxidation reaction apparatus.

32. The method of claim 8, wherein at least a portion of the titanium silicalite molecular sieves are recycled discharging agents for a reaction apparatus using the titanium silicalite molecular sieves as catalysts, and the discharging agents are one or more of discharging agents for an ammoximation reaction apparatus, a hydroxylation reaction apparatus, and an epoxidation reaction apparatus.

33. The method of claim 10, wherein at least a portion of the titanium silicalite molecular sieves are recycled discharging agents for a reaction apparatus using the titanium silicalite molecular sieves as catalysts, and the discharging agents are one or more of discharging agents for an ammoximation reaction apparatus, a hydroxylation reaction apparatus, and an epoxidation reaction apparatus.

34. The method of claim 16, wherein at least a portion of the titanium silicalite is a regenerable discharging agent for a reaction apparatus with titanium silicalite as a catalyst, and the discharging agent is one or more of a discharging agent for an ammoximation reaction apparatus, a discharging agent for a hydroxylation reaction apparatus, and a discharging agent for an epoxidation reaction apparatus.

35. The method of claim 22, wherein at least a portion of the titanium silicalite is a regenerable discharging agent for a reaction unit with titanium silicalite as a catalyst, and the discharging agent is one or more of a discharging agent for an ammoximation reaction unit, a discharging agent for a hydroxylation reaction unit, and a discharging agent for an epoxidation reaction unit.

36. The method of claim 30, wherein at least a portion of the titanium silicalite is a regenerable discharging agent for a reaction unit with titanium silicalite as a catalyst, and the discharging agent is one or more of a discharging agent for an ammoximation reaction unit, a discharging agent for a hydroxylation reaction unit, and a discharging agent for an epoxidation reaction unit.

37. The process according to any one of claims 1, 2, 4, 6 and 7, wherein the oxidizing agent is selected from hydrogen peroxide, tert-butyl hydroperoxide, cumene peroxide, cyclohexyl hydroperoxide, peracetic acid and propionic acid.

38. The method according to any one of claims 1, 2, 4, 6 and 7, wherein the sulfide is dimethyl sulfide and/or benzyl sulfide.

39. The method of claim 1, wherein the quaternary ammonium base is a material of formula II,

in the formula II, R₄、R₅、R₆And R₇Each may be C₁-C₆Alkyl group of (1).

40. The method of claim 39, wherein the quaternary ammonium base is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetrapentylammonium hydroxide.