CN105985271A - Dimethyl sulfone preparation method - Google Patents

Abstract

The invention discloses a method for preparing dimethyl sulfone. The method comprises contacting a liquid mixture with a titanium-silicon molecular sieve as a catalyst under oxidation reaction conditions to obtain a mixture containing dimethyl sulfone. The liquid mixture Containing dimethyl sulfoxide and at least one peroxide, wherein the titanium silicate molecular sieve is filled in the tubes of the tube reactor to form a catalyst bed, and the method also includes adding to the The space between the row tubes is fed with cooling medium to exchange heat with the row tubes. According to the method of the present invention, in the process of oxidizing dimethyl sulfoxide to prepare dimethyl sulfone, the reaction heat released in the reaction process is removed in time, and during long-term continuous operation, not only can higher dimethyl sulfoxide be obtained The conversion rate of sulfoxide, the selectivity of dimethyl sulfone and the effective utilization rate of oxidant, and the activity and stability of the catalyst are good, and it has a longer service life.

Description

A kind of preparation method of dimethyl sulfone

technical field

The invention relates to a preparation method of dimethyl sulfone.

Background technique

Dimethyl sulfone is white crystalline powder, easily soluble in water, ethanol, benzene, methanol and acetone, slightly soluble in ether. Potassium permanganate cannot be discolored at room temperature, and strong oxidizing agents can oxidize dimethyl sulfone to methanesulfonic acid. Aqueous solution of dimethyl sulfone is neutral. At 25°C, there is a small amount of sublimation, and the sublimation speed is accelerated at 60°C, so the drying of dimethyl sulfone products should be carried out at low temperature and vacuum.

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. Dimethyl sulfone can promote wound healing, and it can also play a role in the synthesis and activation of vitamin B, vitamin C, and biotin required for metabolism and nerve health. It is called "natural beautifying carbon substance". The skin, hair, nails, bones, muscles and various organs of the human body contain dimethyl sulfone. Dimethyl sulfone mainly exists in the ocean and soil in nature, and is absorbed as a nutrient during plant growth. Human beings can get it from Ingested in vegetables, fruits, fish, meat, eggs, milk and other foods, once lacking, it will cause health disorders or diseases. It is the main substance for the human body to maintain the balance of biological sulfur elements. It has therapeutic value and health care functions for human diseases. Essential medicines for survival and health assurance. In foreign countries, dimethyl sulfone is widely used as a nutritional product as important as vitamins, but the research on the application of dimethyl sulfone in my country has not been carried out well. Therefore, dimethyl sulfone is not only a high-tech product, but also a high value-added fine chemical product. The product is new, the market potential is great, the profit is outstanding, and it has broad prospects for production and application development.

At present, dimethyl sulfone, as the product of further oxidation of dimethyl sulfoxide, is the main by-product of dimethyl sulfoxide production. In addition, dimethyl sulfone can also be obtained directly from dimethyl sulfoxide by nitric acid oxidation. Specifically, dimethyl sulfoxide can be oxidized with nitric acid at 140-145° C., cooled after the reaction, and filtered to obtain a crude product of white needle crystals. After vacuum distillation, the fraction at 138-145°C (98.42kPa) is collected as the finished product.

Contents of the invention

The inventors of the present invention found in the research process that when dimethyl sulfoxide is oxidized to prepare dimethyl sulfone, if titanium silicate molecular sieve is used as a catalyst, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone can be effectively improved , while also being able to obtain a high conversion rate of dimethyl sulfoxide.

Adopt titanium silicon molecular sieve as catalyst, when dimethyl sulfoxide is oxidized to prepare dimethyl sulfone, can carry out in fixed-bed reactor, but especially in fixed-bed reactor when aspect ratio is small (as aspect ratio＜10 ) in a fixed-bed reactor for contact reaction, the local temperature in the catalyst bed is prone to be too high during the reaction process, and the problem of overheating occurs, which leads to a decrease in catalyst activity, shortens the catalyst regeneration cycle, and affects the reaction efficiency.

The present invention aims to overcome the above-mentioned shortcomings that exist when adopting a fixed-bed reactor, especially a fixed-bed reactor with a small aspect ratio (such as aspect ratio<10), to prepare dimethyl sulfone from dimethyl sulfoxide by an oxidation method, and provides A method for preparing dimethyl sulfone, which can effectively avoid the above-mentioned shortcomings in fixed-bed reactors with small aspect ratios (such as aspect ratio<10).

The invention provides a method for preparing dimethyl sulfone, which comprises contacting a liquid mixture with a titanium-silicon molecular sieve as a catalyst under oxidation reaction conditions to obtain a mixture containing dimethyl sulfone, the liquid mixture Containing dimethyl sulfoxide, at least one peroxide, and optionally at least one solvent, wherein the titanium-silicon molecular sieve is packed in the tubes of the tube-and-tube reactor to form a catalyst bed, and the method also includes performing During the contact process, a cooling medium is sent into the space between the tubes to exchange heat with the tubes.

According to the method of the present invention, in the process of oxidizing dimethyl sulfoxide to prepare dimethyl sulfone, the reaction heat released in the reaction process is removed in time, and during long-term continuous operation, not only can higher dimethyl sulfoxide be obtained The conversion rate of sulfoxide, the selectivity of dimethyl sulfone and the effective utilization rate of oxidant, and the activity and stability of the catalyst are good, and it has a longer service life.

detailed description

The invention provides a method for preparing dimethyl sulfone, which comprises contacting a liquid mixture with a titanium-silicon molecular sieve as a catalyst under oxidation reaction conditions to obtain a mixture containing dimethyl sulfone, the liquid mixture Contains dimethylsulfoxide, at least one peroxide and optionally at least one solvent. In the present invention, "optionally" means containing or not.

The method according to the present invention is carried out in a tubular reactor, wherein the titanium silicon molecular sieve is packed in the tubular reactor to form a catalyst bed, and dimethyl sulfoxide and peroxide are mixed with During the contact process of titanium-silicon molecular sieve, a cooling medium is sent into the space between the tubes to exchange heat with the tubes, so that the heat released during the reaction process can be removed in time, which can effectively prevent the catalyst bed from overheating. phenomenon, and effectively improve the effective utilization of the oxidant, while also improving the conversion rate of dimethyl sulfoxide and the selectivity of dimethyl sulfone.

According to the method of the present invention, the titanium-silicon molecular sieve is a general term for a type of zeolite in which titanium atoms replace a part of silicon atoms in the lattice framework, and can be represented by the chemical formula xTiO ₂ ·SiO ₂ . The present invention has no special limitation on the content of titanium atoms in the titanium-silicon molecular sieve, which can be a conventional choice in the field. Specifically, x may be 0.0001-0.05, preferably 0.01-0.03, more preferably 0.015-0.025.

The titanium-silicon molecular sieve can be a common titanium-silicon molecular sieve with various topological structures, for example: the titanium-silicon molecular sieve can be a titanium-silicon molecular sieve selected from the MFI structure (such as TS-1), the titanium-silicon molecular sieve of the MEL structure ( Such as TS-2), titanium-silicon molecular sieves with BEA structure (such as Ti-Beta), titanium-silicon molecular sieves with MWW structure (such as Ti-MCM-22), titanium-silicon molecular sieves with hexagonal structure (such as Ti-MCM-41, Ti- One of SBA-15), titanium-silicon molecular sieves with MOR structure (such as Ti-MOR), titanium-silicon molecular sieves with TUN structure (such as Ti-TUN) and titanium-silicon molecular sieves with other structures (such as Ti-ZSM-48) or Two or more.

Preferably, the titanium-silicon molecular sieve is one or more selected from the group consisting of MFI-structured titanium-silicon molecular sieves, MEL-structured titanium-silicon molecular sieves, hexagonal-structured titanium-silicon molecular sieves and BEA-structured titanium-silicon molecular sieves. More preferably, the titanium-silicon molecular sieve is a titanium-silicon molecular sieve with an MFI structure, such as TS-1 molecular sieve.

From the perspective of further improving the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant, and the selectivity of dimethyl sulfone, in a preferred embodiment of the present invention, at least part of the titanium-silicon molecular sieve is MFI structure of titanium-silicon molecular sieve, and the crystal grain of the titanium-silicon molecular sieve is a hollow structure, the radial length of the cavity part of the hollow structure is 5-300 nanometers, and the titanium-silicon molecular sieve is at 25°C, P/P ₀ = 0.10. The benzene adsorption measured under the condition of adsorption time of 1 hour is at least 70 mg/g, and there is a hysteresis loop between the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption of the titanium silicon molecular sieve. Herein, the titanium-silicon molecular sieve with this structure is called hollow titanium-silicon molecular sieve. The hollow titanium-silicon molecular sieve can be obtained commercially (for example, the molecular sieve with the trademark HTS purchased from Hunan Jianchang Petrochemical Co., Ltd.), or can be prepared according to the method disclosed in CN1132699C.

In this preferred embodiment, the titanium-silicon molecular sieves may all be hollow titanium-silicon molecular sieves, or may be a combination of hollow titanium-silicon molecular sieves and other types of titanium-silicon molecular sieves, such as combining hollow titanium-silicon molecular sieves with other MFI structures of titanium Silicon molecular sieves (such as titanium-silicon molecular sieve TS-1), titanium-silicon molecular sieves of hexagonal structure and titanium-silicon molecular sieves of BEA structure are used in combination. When the hollow titanium-silicon molecular sieve is used in combination with other types of titanium-silicon molecular sieves, it is preferable to use the flow direction of the liquid mixture as a reference, and the hollow titanium-silicon molecular sieve is located upstream of other titanium-silicon molecular sieves (that is, the hollow titanium-silicon molecular sieve Molecular sieves and other titanium-silicon molecular sieves are loaded in the reaction zone so that the liquid mixture is in contact with the hollow titanium-silicon molecular sieves and other titanium-silicon molecular sieves), so that higher effective utilization of the oxidant and selection of target oxidation products can be obtained sex. The mass ratio of the hollow titanium-silicon molecular sieve to other titanium-silicon molecular sieves may be 1-10:1, preferably 2-5:1. In actual operation, it can be realized by packing the hollow titanium-silicon molecular sieve and other titanium-silicon molecular sieve layers in a fixed-bed reactor, and making the hollow titanium-silicon molecular sieve upstream of other titanium-silicon molecular sieves.

According to the method of the present invention, in a more preferred embodiment, the titanium-silicon molecular sieve is hollow titanium-silicon molecular sieve and titanium-silicon molecular sieve TS-1, and the hollow titanium-silicon molecular sieve and titanium-silicon molecular sieve TS-1 are The order of filling in the pipeline is such that, based on the flow direction of the liquid mixture, the hollow titanium-silicon molecular sieve is located upstream of the titanium-silicon molecular sieve TS-1 (that is, the liquid mixture is successively connected with the hollow titanium-silicon molecular sieve contact with titanium-silicon molecular sieve TS-1), which can not only further extend the service life of the titanium-silicon molecular sieve as a catalyst, but also further improve the selectivity for dimethyl sulfone and the effective utilization rate of the oxidant.

In various industrial devices that use titanium-silicon molecular sieves as catalysts, such as ammoximation reaction, hydroxylation reaction and epoxidation reaction devices, usually after the device has been running for a period of time, the catalytic activity of the catalyst decreases, and it needs to be carried out in the device or External regeneration, when it is difficult to obtain satisfactory activity even with regeneration, it is necessary to discharge the catalyst from the unit (i.e., replace the catalyst), and the discharged catalyst (i.e., discharge agent or spent catalyst) is currently treated The method is usually stacking and burying. On the one hand, it takes up valuable land resources and storage space. On the other hand, the production cost of titanium-silicon molecular sieve is relatively high, and direct disposal also causes great waste. The inventors of the present invention found in the research process that if these unloading agents (that is, unloaded titanium-silicon molecular sieves) are regenerated and contacted with dimethyl sulfoxide and an oxidizing agent under oxidation reaction conditions, higher The conversion rate of dimethyl sulfoxide and the selectivity of dimethyl sulfone can be obtained, and a higher effective utilization rate of the oxidant can be obtained. The conversion rate of dimethyl sulfoxide and the selectivity of dimethyl sulfone are more stable in the continuous reaction process. Therefore, according to the method of the present invention, at least part of the titanium-silicon molecular sieve is preferably a regenerated reaction device using a titanium-silicon molecular sieve as a catalyst (except the dimethyl sulfide oxidation reaction device and the dimethyl sulfoxide oxidation reaction device) unloading agent. The discharge agent may be the discharge agent discharged from various reaction devices using titanium silicate molecular sieve as the catalyst, for example, it may be the discharge agent discharged from the oxidation reaction device. Specifically, the unloading agent is one or more than two of the unloading agent of the ammoximation reaction device, the unloading agent of the hydroxylation reaction device and the discharge agent of the epoxidation reaction device. More specifically, the discharge agent can be one or both of the discharge agent of the cyclohexanone ammoximation reaction device, the discharge agent of the phenol hydroxylation reaction device and the discharge agent of the propylene epoxidation reaction device. more than one species.

The conditions for regenerating the unloading agent are not particularly limited, and can be appropriately selected according to the source of the unloading agent, for example: high-temperature roasting and/or solvent washing.

The activity of the regenerated unloading agent varies according to its source. Generally, the activity of the regenerated unloading agent may be 5-95% of the activity of the titanosilicate molecular sieve when fresh (ie, the activity of fresh titanosilicate molecular sieve). Preferably, the activity of the regenerated unloading agent may be 10-90% of the fresh activity of the titanium-silicon molecular sieve, more preferably 30-55% of the fresh activity. When the activity of the regenerated unloading agent is 30-55% of the activity of the titanium-silicon molecular sieve when it is fresh, not only can a higher effective utilization rate of the oxidant be obtained, but also a satisfactory conversion of dimethyl sulfoxide can be obtained. rate and dimethyl sulfone selectivity. The activity of the fresh titanium-silicon molecular sieve is generally above 90%, usually above 95%.

The activity is measured by the following method: the regenerated unloading agent and fresh titanium-silicon molecular sieve are respectively used as catalysts for the ammoximation reaction of cyclohexanone, and the conditions of the ammoximation reaction are: titanium-silicon molecular sieve, 36% by weight of Ammonia water (calculated as _NH3 ), 30% by weight of _hydrogen peroxide (calculated as H2O2), tert _- butanol and cyclohexanone in a mass ratio of 1:7.5:10:7.5:10 were reacted at 80°C for 2 hours under atmospheric pressure . Calculate respectively the conversion rate of cyclohexanone when the unloading agent and fresh titanium-silicon molecular sieve are used as catalysts through regeneration, and use it as the activity of the unloading agent and fresh titanium-silicon molecular sieve through regeneration respectively, wherein the conversion of cyclohexanone Rate=[(molar amount of cyclohexanone added−molar amount of unreacted cyclohexanone)/molar amount of cyclohexanone added]×100%.

When at least part of the titanium-silicon molecular sieve is the regenerated reaction device discharge agent, based on the total amount of the titanium-silicon molecular sieve, the content of the regenerated reaction device discharge agent is preferably more than 5% by weight (such as 50% by weight above), so that not only can better improve the effective utilization rate of the oxidant, but also the reaction process is more stable and easy to control, and can also obtain higher dimethyl sulfoxide conversion rate and dimethyl sulfone selectivity. According to the method of the present invention, even if all the titanium-silicon molecular sieves are the regenerated reaction device unloading agent (that is, based on the total amount of the titanium-silicon molecular sieve, the content of the regenerated unloading agent is 100% by weight), still can Satisfactory conversion rate of dimethyl sulfoxide, effective utilization rate of oxidant and selectivity of dimethyl sulfone were obtained.

In a preferred embodiment of the invention, prior to the use of the titanium-silicon molecular sieve as a catalyst, the method according to the invention preferably contacts at least part of the titanium-silicon molecular sieve with at least one acid as modifier. This can further prolong the service life of the catalyst while further improving the selectivity of dimethyl sulfone. For the purpose of clarity, hereinafter, the titanium-silicon molecular sieve that has been contacted with an acid will be referred to as a modified titanium-silicon molecular sieve.

The content of the modified titanium-silicon molecular sieve can be selected according to specific conditions. The titanium-silicon molecular sieve may be all modified titanium-silicon molecular sieves, or partially modified titanium-silicon molecular sieves. Generally, based on the total amount of the titanium-silicon molecular sieve, the content of the modified titanium-silicon molecular sieve can be more than 10% by weight (such as 10-100% by weight), preferably more than 50% by weight.

As a modifying agent, the acid is a generalized acid, which can be one or more of inorganic acids, organic acids and acid salts. The organic acid can be carboxylic acid and/or sulfonic acid, such as C ₁ -C ₆ aliphatic carboxylic acid, C ₆ -C ₁₂ aromatic carboxylic acid, C ₁ -C ₆ aliphatic sulfonic acid and C ₆ -C ₁₂ aromatic sulfonic acid. Preferably, the acid is one or more of acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, perchloric acid and hydrobromic acid. The acid is preferably provided in the form of an aqueous solution, and the concentration of the acid in the aqueous solution of the acid can be selected according to the type of the acid, and is not particularly limited. Generally, the concentration of the acid in the aqueous solution of the acid can be 0.01-50% by weight, preferably 10% by weight. -40% by weight.

Compared with the titanium-silicon molecular sieve before acid treatment, the condition of treating the titanium-silicon molecular sieve with acid is such that in the ultraviolet-visible (UV-Vis) spectrum of the titanium-silicon molecular sieve after contact, the absorption between 240-300nm The peak height of the peak is reduced by more than 2% (generally 2-20%, such as 3-6%), and the pore volume measured by static nitrogen adsorption method is reduced by more than 1% (generally 1-10%, such as 1.5-3%) .

Generally, the titanium-silicon molecular sieve is calculated as silicon dioxide, and the molar ratio of the titanium-silicon molecular sieve to the acid can be 1:0.01-10, preferably 1:0.05-8, more preferably 1:0.1-5, such as 1: 0.5-5. The contacting may be performed at a temperature of 0-200°C, preferably 20-180°C, more preferably 50-100°C, further preferably 60-90°C. The contact time can be selected according to the contact temperature and the type of acid. Generally, the contacting time may be 0.1-72 hours, preferably 0.5-24 hours (such as 5-24 hours).

According to the method of the present invention, the titanium-silicon molecular sieve may be a titanium-silicon molecular sieve raw powder, or a shaped titanium-silicon molecular sieve, preferably a shaped titanium-silicon molecular sieve. The formed titanium-silicon molecular sieve contains a carrier (that is, a binder) and a titanium-silicon molecular sieve, wherein the content of the carrier is based on the ability to bind the titanium-silicon molecular sieve together to form a molded body with a certain strength. Generally, based on the total amount of the shaped titanium-silicon molecular sieve, the content of the titanium-silicon molecular sieve can be 5-95% by weight, preferably 10-95% by weight, more preferably 40-95% by weight, and even more preferably 60% by weight. -95% by weight (such as 70-90% by weight); the content of the carrier can be 5-95% by weight, preferably 5-90% by weight, more preferably 5-60% by weight, further preferably 5-40% by weight % (such as 10-30% by weight). The carrier of the shaped titanium silicate molecular sieve can be conventionally selected, such as alumina and/or silica. The method for preparing the shaped titanium-silicon molecular sieve is well known in the art and will not be described in detail herein. The particle size of the shaped titanium-silicon molecular sieve is also not particularly limited, and can be properly selected according to the specific shape. Generally, the average particle size of the shaped titanium-silicon molecular sieve can be 5-2000 microns, preferably 100-1000 microns, such as 200-600 microns. The average particle size is a volume average particle size, which can be measured by a laser particle size analyzer.

According to the method of the present invention, the titanium-silicon molecular sieve is used as a catalyst, and its dosage is based on the ability to realize the catalytic function. In actual operation, the amount of titanium-silicon molecular sieve can be expressed by the weight hourly space velocity of the liquid mixture. Generally, the weight hourly space velocity of the liquid mixture may be 0.1-500h ^-1 , preferably 5-300h ^-1 (such as 50-100h ^-1 ). The weight hourly space velocity is based on all the titanium-silicon molecular sieves packed in the tubular reactor.

According to the method of the present invention, the tubes of the tube-and-tube reactor can be further filled with fillers, which can adjust the amount of catalyst in the catalyst bed, thereby adjusting the reaction speed and the processing capacity of the reactor. The content of the filler can be properly selected according to the expected reaction speed and the processing capacity of the reactor, so as to meet the specific use requirements. Generally, the filler content in the catalyst bed may be 5-70% by weight, preferably 30-70% by weight, more preferably 30-50% by weight.

In the present invention, the type of the filler is not particularly limited, and it can be various commonly used fillers, for example, it can be selected from Raschig rings, Pall rings, stepped rings, arc saddles, rectangular saddles and metal ring rectangular saddles. Specific examples of the filler may be θ rings and/or β rings.

When the catalyst bed is also filled with fillers, the filler and the catalyst can be packed in the tubular reactor in the form of a mixture of the two; The packing layers are packed in the tubes of the tube-and-tube reactor at intervals; a combination of the above two methods can also be used.

According to the method of the present invention, 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 point of view of further improving the safety of the method according to the invention, the method according to the invention preferably uses 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.

The amount of the peroxide used can be conventionally selected and is not particularly limited. Generally, the molar ratio of dimethyl sulfoxide to peroxide can be 1:0.1-10, preferably 1:0.2-8, more preferably 1:1-5, such as 1:1.5-3.5.

According to the method of the present invention, the liquid mixture may or may not contain a solvent. Preferably, the liquid mixture also contains at least one solvent. The solvent can be various liquid substances that can not only dissolve dimethyl sulfoxide and peroxide or promote the mixing of the two, but also can promote the dissolution of dimethyl sulfone. 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.

The amount of the solvent can be properly selected according to the amount of dimethyl sulfoxide and peroxide. Preferably, the mass ratio of dimethyl sulfoxide to the solvent is 1:0.1-100. More preferably, the mass ratio of dimethyl sulfoxide to the solvent is 1:1-50.

Before bringing the liquid mixture into contact with the titanium-silicon molecular sieve, the method according to the present invention preferably further comprises adding at least one acid to the liquid mixture as a pH adjuster, the acid being added in an amount such that the liquid The pH value of the mixture is preferably in the range of 0.5-5.5, more preferably in the range of 1-5, which can further improve the selectivity for dimethyl sulfone, while also obtaining a higher conversion rate of dimethyl sulfoxide and effective utilization of oxidants. Although the pH of the liquid mixture is generally between 3.5 and 4 when the peroxide is a peracid, if an acid is added to the liquid mixture, the pH of the liquid mixture is adjusted below 3.5 to If it is not lower than 1, the above effects can still be obtained. The pH value of the liquid mixture refers to the pH value of the liquid mixture measured at 25° C. and 1 standard atmospheric pressure.

As a pH adjuster, the type of the acid can be conventionally selected. Generally, the acid can be inorganic acid and/or organic acid, such as one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid and acetic acid, preferably hydrochloric acid and/or sulfuric acid. Pure acids or aqueous solutions of acids can be used. The mixing of the acid with the dimethyl sulfoxide and oxidizing agent and other components of the liquid mixture such as solvents can be done inside the reactor or outside the reactor.

The acid is used in an amount that enables the pH of the liquid mixture to meet the aforementioned requirements.

According to the method of the present invention, when the dimethyl sulfoxide and the oxidizing agent are brought into contact with the titanium-silicon molecular sieve, the pressure in the column tube can be conventionally selected. Generally, the pressure inside the array tube can be 0-3MPa, preferably 0.1-2MPa, more preferably 0.5-1.5MPa, and the pressure is measured by gauge pressure.

According to the method of the present invention, the tube-and-tube reactor can be various common tube-and-tube reactors. In the present invention, there is no special limitation on the specification of the tube-and-tube reactor, which can be conventionally selected. Specifically, the inner diameter (inner diameter) of the tubes in the tube-and-tube reactor may be 0.5-10 cm, preferably 1-8 cm. The filling ratio of the tubes in the reactor can be 5-95% by volume, preferably 10-90% by volume, generally 50-85% by volume. The filling rate refers to the percentage value of the space occupied by the tubes to the total volume of the inner space of the reactor.

According to the method of the present invention, a cooling medium is fed into the space between the tubes (that is, the shell side of the tube-and-tube reactor) during the contact reaction. The type and amount of the cooling medium can be selected according to the specific reaction conditions, so as to control the temperature of the catalyst bed in the tube side of the tube array within a predetermined temperature range. Generally, the heat exchange conditions between the cooling medium and the tubes are such that the temperature in the catalyst bed is in the range of 0-180°C, preferably in the range of 20-160°C, more preferably in the range of 30-150°C In the range, such as in the range of 50-100 ° C. The cooling medium is a fluid substance with thermal conductivity, specifically water, alcohol, silicone oil, etc., and is preferably water from the perspectives of availability and cost. The temperature at which the liquid mixture enters the catalyst bed can be conventionally selected. From the perspective of reducing the impact of the lower temperature of the liquid mixture on the temperature distribution of the catalyst bed, it is preferable to send the liquid mixture into the catalyst bed after being heated (eg heated to a predetermined temperature of the catalyst bed).

With the prolongation of the continuous operation time of the tubular reactor, the activity of the titanium-silicon molecular sieve as the catalyst decreases, resulting in a decrease in the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone. At this time, the catalyst is generally Regenerate to restore its activity. The inventors of the present invention found in the research process that when the conversion rate of the oxidant decreases, increasing the temperature of the catalyst bed can make the activity of the catalyst that originally showed a downward trend rise, thereby improving the conversion rate of dimethyl sulfoxide and the effective utilization rate of the oxidant The selectivity of dimethyl sulfone and dimethyl sulfone is maintained at a higher level for a longer period of time, which prolongs the regeneration period of the titanium-silicon molecular sieve, thereby prolonging the stable operation time of the device.

Therefore, in a preferred embodiment, the method according to the present invention further includes an adjustment step performed at least once, and the adjustment step is performed when condition 1 is met, so as to increase the conversion rate of the oxidant until condition 2 is met and stop the adjustment step,

Condition 1. The ratio C _t /C ₀ of the oxidant conversion rate C _t to the initial oxidant conversion rate C ₀ at a certain time t is 0.8≤C _t /C ₀ <1;

Condition 2, the ratio C'/C _{0 of the oxidant conversion rate C' to the initial oxidant conversion rate C 0 is} 0.85≤C'/C ₀ ≤1;

The adjustment step is to increase the temperature of the catalyst bed until the conversion rate of the oxidant satisfies the condition 2, then maintain the temperature of the catalyst bed.

According to this preferred embodiment, the deactivation speed of the titanium-silicon molecular sieve as a catalyst can be delayed, and the single-pass service life of the titanium-silicon molecular sieve can be extended.

On the premise of prolonging the single-pass service life of titanium-silicon molecular sieves, from the perspective of further prolonging the stable operation time of the device, in condition 1, 0.85≤C _t /C ₀ <0.9; in condition 2, 0.9≤C'/C ₀ .

In the present invention, the oxidant conversion ratio=(the molar number of the oxidant participating in the reaction/the molar number of the added oxidant)×100%;

Wherein, the number of moles of the oxidizing agent participating in the reaction=the number of moles of the added oxidizing agent−the number of moles of the remaining oxidizing agent in the obtained reaction mixture.

The oxidant conversions C ₀ , C _t and C' can be determined by continuously monitoring the composition of the reaction mixture output from the tubular reactor during the reaction. When the tubular reactor is a plurality of tubular reactors, based on the flow direction of the liquid stream, the oxidant conversion rate C ₀ , C _t and C'.

In the present invention, the initial oxidant conversion rate _C0 is determined by the composition of the first batch of reaction mixture output from the reactor after the reactor runs stably. For example, the reaction mixture obtained within 0.5-10 hours of stable operation of the reactor can be used as the first batch of reaction mixture.

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

According to this preferred embodiment, although when condition 1 is met, it is sufficient to increase the temperature of the catalyst bed until the oxidant conversion rate C' satisfies condition 2, but it is preferred to increase the temperature of the catalyst bed in the range of 0.01-2°C/day, In this way, on the one hand, a longer single-pass service life of the titanium-silicon molecular sieve can be obtained, and on the other hand, the selectivity of the target oxidation product can be maintained at a high level for a long time. More preferably, the temperature of the catalyst bed is increased by 0.02-1°C/day. According to the method of the present invention, in the continuous reaction process, the temperature increase range of the catalyst bed can be different, the temperature of the catalyst bed can be increased with a lower range in the early stage of the reaction, and the temperature of the catalyst bed can be increased with a higher range in the later stage of the reaction. layer temperature.

According to this preferred embodiment, the method of increasing the temperature of the catalyst bed or maintaining the temperature of the catalyst bed can be selected according to the specific operation mode of the device. For example: adjusting the operating conditions of the heating device used to heat the catalyst bed, adjusting the operating conditions of the cooling medium used to exchange heat for the catalyst bed to remove the heat of reaction, adjusting one of the temperatures of the liquid mixture one or a combination of two or more.

According to this preferred embodiment, the initial temperature of the catalyst bed depends on the operating conditions of the device. Preferably, the initial temperature of the catalyst bed is not more than 120°C, which is more conducive to practical operation on the one hand, and on the other hand can obtain a longer single-pass service life of the titanium-silicon molecular sieve. The initial temperature of the catalyst bed refers to the temperature of the catalyst bed when the device achieves stable operation. According to this preferred embodiment, the final temperature of the catalyst bed is generally not more than 180°C, preferably not more than 160°C

According to this preferred embodiment, when the temperature of the catalyst bed is adjusted, other reaction conditions, such as pressure, feed space velocity, and raw material ratio can remain unchanged.

The method according to the present invention may also include separating the contacted mixture containing dimethyl sulfone to separate dimethyl sulfone and unreacted dimethyl sulfoxide therein. In the present invention, the method for separating dimethyl sulfone from the contacted mixture is not particularly limited, and it can be a conventional choice in the art. For example, dimethyl sulfone can be obtained by fractional distillation of the mixture obtained by contacting. The separated unreacted dimethyl sulfoxide can be recycled.

The present invention will be described in detail below in conjunction with examples and comparative examples. The following examples will further illustrate the present invention, but do not thereby limit the scope of the present invention.

In the following examples and comparative examples, unless otherwise specified, the reagents used are commercially available analytical reagents, the titanium-silicon molecular sieves used are fresh titanium-silicon molecular sieves, and the pressures are gauge pressure.

In the following examples, the titanium-silicon molecular sieve TS-1 used was prepared according to the method described in Zeolites, 1992, Vol.12: 943-950, and its titanium oxide content was 2.5% by weight; the hollow titanium-silicon molecular sieve used was purchased from Hunan The brand name of Jianchang Petrochemical Co., Ltd. is the hollow titanium-silicon molecular sieve of HTS, and its titanium oxide content is 2.5% by weight; the titanium-silicon molecular sieve Ti-MCM-41 used is according to Corma et al. Prepared by the method described in, its titanium oxide content is 3% by weight; The titanium-silicon molecular sieve Ti-Beta used is described in J.Chem.Soc.Chem.Commun., 1997,677-678 according to Takashi Tatsumi et al. prepared by the method, and its titanium oxide content is 2.6% by weight.

In the following examples 3, 12 and 16, the pore volume and ultraviolet absorption peak of the titanium-silicon molecular sieve before and after modification were characterized by static nitrogen adsorption method and solid ultraviolet-visible diffuse reflectance spectrometry respectively. Wherein, the solid ultraviolet-visible diffuse reflectance spectrum (UV-Vis) is measured on the SHIMADZU UV-3100 type ultraviolet-visible spectrometer; the pore volume is measured on the ASAP 2405 type static nitrogen adsorption instrument of Micromeritics Company.

In the following examples and comparative examples, gas chromatography was used to analyze the content of each component in the reaction solution, and on this basis, the following formulas were used to calculate the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone. sex:

Conversion rate of dimethyl sulfoxide (%)=[(molar amount of added dimethyl sulfoxide-molar amount of unreacted dimethyl sulfoxide)/molar amount of added dimethyl sulfoxide]×100 %;

Effective utilization rate of oxidant (%)=[the molar amount of dimethyl sulfone produced by the reaction/(the molar amount of added oxidant-the molar amount of unreacted oxidant)]×100%

Dimethyl sulfone selectivity (%)=[the molar amount of dimethyl sulfone produced by the reaction/(the molar amount of dimethyl sulfoxide added-the molar amount of unreacted dimethyl sulfoxide)]×100%.

Examples 1-23 illustrate the method of the invention.

Example 1

With the molding titanium-silicon molecular sieve (volume average particle diameter is 200 μm, titanium-silicon molecular sieve is TS-1 as catalyst, take the total amount of molding titanium-silicon molecular sieve as a benchmark, the content of titanium-silicon molecular sieve TS-1 is 80% by weight, as viscous The content of the silicon oxide of binder is 20% by weight, is denoted as catalyst C1) is packed in the tube of tube-and-tube reactor (the internal diameter of tube is 2cm, and the quantity of tube is 21, and the filling rate of tube is 50 vol%), a catalyst bed with a height of 1.5 m was formed.

Dimethyl sulfoxide, hydrogen peroxide (provided as a 40% by weight aqueous solution) as an oxidant, and methanol as a solvent were mixed to form a liquid mixture, which was heated to 60°C. Then, the liquid mixture is sent from the bottom into the tubes of the tube-and-tube reactor to contact and react with the catalyst bed. Among them, in the liquid mixture, the molar ratio of dimethyl sulfoxide to oxidant hydrogen peroxide is 1:1.5, the mass ratio of dimethyl sulfoxide to solvent methanol is 1:8, and the weight hourly space velocity of the liquid mixture is 80h ^-1 , the pressure inside the tube is 0.6MPa. During the reaction process, the catalyst bed is heated to a temperature of 60°C through the heating wires installed in the catalyst bed, and at the same time cooling water is sent into the shell side of the reactor to remove the heat of reaction, so that the temperature in the catalyst bed remains is 60°C.

The reaction mixture obtained when the reaction was carried out to 0.5 hour and 200 hours was analyzed by gas chromatography, and the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone were calculated. The results are listed in Table 1.

Example 2

Adopt the same method as Example 1 to prepare dimethyl sulfone, the difference is that in the shaped titanium-silicon molecular sieve (volume average particle size is 200 μm) as the catalyst (referred to as catalyst C2), the titanium-silicon molecular sieve is a hollow titanium-silicon molecular sieve, Based on the total amount of the shaped titanium-silicon molecular sieve, the content of the hollow titanium-silicon molecular sieve is 80% by weight, and the content of silicon oxide as a binder is 20% by weight.

The results obtained at 0.5 hour and 200 hours of reaction are listed in Table 1.

Example 3

Adopt the same method as Example 1 to prepare dimethyl sulfone, the difference is that the shaped titanium silicate molecular sieve is processed by the following method before being used as a catalyst and packed in the column tube:

The shaped titanium silicon molecular sieve was mixed with hydrochloric acid (concentration is 36% by weight aqueous solution), the obtained mixture was stirred and reacted at 90° C. for 5 hours, and the temperature of the obtained reaction mixture was lowered to room temperature and filtered, and the obtained solid phase substance was Dry at 120°C to constant weight to obtain a modified titanium-silicon molecular sieve. Among them, the titanium-silicon molecular sieve is calculated as _SiO2 , and the molar ratio of titanium-silicon molecular sieve to HCl is 1:0.4. After characterization, compared with the raw material titanium-silicon molecular sieve, the peak height of the absorption peak between 240-300nm in the UV-Vis spectrum of the obtained modified titanium-silicon molecular sieve is reduced by 3.0%, and the pore volume measured by the static nitrogen adsorption method is 1.8% reduction.

The results obtained at 0.5 hour and 250 hours of reaction are listed in Table 1.

Example 4

The same method as in Example 1 was used to prepare dimethyl sulfone, except that hydrochloric acid (concentration of 30% by weight) was also added to the liquid mixture, and the amount of hydrochloric acid adjusted the pH value of the liquid mixture from 6.1 to 5.

The results obtained at 0.5 hour and 220 hours of the reaction are listed in Table 1.

Example 5

The same method as in Example 1 was used to prepare dimethyl sulfone. The difference was that, under the condition that the loading amount of the formed titanium-silicon molecular sieve in each tube was constant, the catalyst C2 was first filled in the tubes, and then the catalyst C1 was loaded. (That is, the liquid mixture first passes through the catalyst C2, and then passes through the catalyst C1), wherein the mass ratio of the catalyst C2 to the catalyst C1 is 1:1.

The results obtained at 0.5 hours and 240 hours are listed in Table 1.

Example 6

The same method as in Example 5 was used to prepare dimethyl sulfone, except that the mass ratio of catalyst C2 to catalyst C1 was 2:1 under the condition that the total catalyst loading was constant.

The results obtained at 0.5 hour and 300 hours of reaction are listed in Table 1.

Example 7

Adopt the same method as Example 6 to prepare dimethyl sulfone, the difference is that, under the condition that the loading amount of catalyst C1 and catalyst C2 is constant, the catalyst C1 is first loaded in the column tube, and then the catalyst C2 (that is, liquid The mixture is passed first over catalyst C1 and then over catalyst C2).

The results obtained at 0.5 hours and 180 hours are listed in Table 1.

Example 8

The same method as in Example 5 was used to prepare dimethyl sulfone, except that the mass ratio of the catalyst C2 to the catalyst C1 was 5:1 under the condition that the total loading amount of the catalyst was not changed.

The results obtained at 0.5 hour and 300 hours of reaction are listed in Table 1.

Example 9

The same method as in Example 5 was used to prepare dimethyl sulfone, except that the mass ratio of the catalyst C2 to the catalyst C1 was 10:1 under the condition that the total loading amount of the catalyst was not changed.

The results obtained at 0.5 hour and 250 hours of reaction are listed in Table 1.

Example 10

Adopt the method identical with embodiment 8 to prepare dimethyl sulfone, difference is, catalyst C1 replaces with the same amount of catalyst C3, and the preparation method of catalyst C3 is as follows:

Mix titanium-silicon molecular sieve Ti-Beta with silica sol (silicon oxide content is 30% by weight) and water evenly, wherein the mass ratio of titanium-silicon molecular sieve Ti-Beta, silica sol calculated as silicon oxide and water is 1:0.2: 1.5. The obtained mixture was granulated by rolling balls, and the obtained wet granules were calcined at 550° C. for 5 hours, thereby obtaining a catalyst C3 having an average particle diameter of 200 μm. Wherein, in the catalyst C3, the content of the titanium-silicon molecular sieve Ti-Beta is 80% by weight.

The results obtained for 0.5 hours and 230 hours of reaction are listed in Table 1.

Example 11

Adopt the method identical with embodiment 8 to prepare dimethyl sulfone, difference is, catalyst C1 replaces with the same amount of catalyst C4, and the preparation method of catalyst C4 is as follows:

Titanium-silicon molecular sieve Ti-MCM-41 is mixed with silica sol (silicon oxide content is 30% by weight) and water, wherein, the mass ratio of titanium-silicon molecular sieve Ti-MCM-41, silica sol and water calculated as silicon oxide is 1:0.2:1.5. The obtained mixture was granulated by rolling balls, and the obtained wet granules were calcined at 550° C. for 5 hours, thereby obtaining a catalyst C4 having an average particle diameter of 200 μm. Wherein, in the catalyst C4, the content of the titanium silicon molecular sieve Ti-MCM-41 is 80% by weight.

The results obtained for 0.5 hours and 220 hours of reaction are listed in Table 1.

Comparative example 1

The catalyst C1 is packed in a fixed bed reactor (single tube) to form a catalyst bed (aspect ratio of 2.5:1), wherein the number of catalyst bed is 1 layer. Mix dimethyl sulfoxide, oxidizing agent and solvent according to the same ratio as in Example 1, and send the obtained liquid phase mixture into a fixed bed reactor to contact and react with a catalyst bed containing a shaped titanium-silicon molecular sieve. Wherein, in terms of dimethyl sulfoxide, the feed rate of the liquid-phase mixture in the fixed-bed reactor is the same as in Example 1, and the temperature and pressure in the fixed-bed reactor are also the same as those in the tube-and-tube reactor of Example 1. same temperature and pressure.

The reaction mixture obtained when the reaction was carried out to 0.5 hour and 100 hours was analyzed by gas chromatography, and the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone were calculated. The results are listed in Table 1.

Table 1

Comparing Example 1 with Comparative Example 1, it can be seen that compared with the use of a single-tube fixed-bed reactor, the method of the present invention is used to prepare dimethyl sulfone, and in a long-term continuous reaction process, a higher disulfone The conversion rate of methyl sulfoxide, the selectivity of dimethyl sulfone and the effective utilization rate of oxidant, and the stability of the catalyst are good, and the service life is longer.

Comparing Example 1 with Example 3, it can be seen that treating the titanium-silicon molecular sieve with acid and using it as a catalyst can obtain higher dimethyl sulfone selectivity; and the catalyst shows a longer service life.

Comparing Example 1 with Example 4, it can be seen that adjusting the pH value of the liquid phase mixture in contact with the titanium-silicon molecular sieve with an acid can obtain higher dimethyl sulfone selectivity, and can further prolong the service life of the catalyst .

Examples 12-18 The following methods were used to measure the activity of titanium silicon molecular sieves.

Titanium silicon molecular sieve, 36% by weight of ammonia water (calculated as _NH3 ), 30% by weight of _hydrogen peroxide (calculated as H2O2), tert _- butanol and cyclohexanone in mass ratio=1:7.5:10:7.5:10 After mixing, stir and react at 80°C for 2 hours under atmospheric pressure, filter the reactant, analyze the composition of the liquid phase by gas chromatography, and use the following formula to calculate the conversion rate of cyclohexanone and use it as the activity of titanium silicon molecular sieve ,

The conversion rate of cyclohexanone=[(the molar amount of cyclohexanone added−the molar amount of unreacted cyclohexanone)/the molar amount of cyclohexanone added]×100%.

Example 12

(1) Preparation of modified titanium-silicon molecular sieves

The raw material molecular sieve used is the shaped titanium-silicon molecular sieve TS-1 (volume average particle diameter of 300 μm, based on the total amount of the shaped titanium-silicon molecular sieve TS-1, which will be unloaded from the cyclohexanone ammoximation reaction process, and the titanium-silicon molecular sieve The content of TS-1 is 75% by weight, and the content of silicon oxide as a binder is 25% by weight) to regenerate and obtain, its activity is 45%, and the activity when fresh is 95%, and the regeneration condition is: Calcined in air atmosphere at 550°C for 4h.

The raw material molecular sieve is mixed with hydrochloric acid (concentration is the aqueous solution of 20% by weight), the mixture obtained is stirred and reacted at 80° C. for 6 hours, the temperature of the reaction mixture obtained is dropped to room temperature and filtered, and the solid phase substance obtained is heated at 120° C. Dry to constant weight to obtain a modified titanium-silicon molecular sieve (referred to as catalyst C3). Among them, the titanium-silicon molecular sieve is calculated as _SiO2 , and the molar ratio of titanium-silicon molecular sieve to HCl is 1:1. After characterization, compared with the raw material titanium-silicon molecular sieve, the absorption peak height between 240-300nm in the UV-Vis spectrum of the obtained modified titanium-silicon molecular sieve is reduced by 4.4%, and the pore volume measured by the static nitrogen adsorption method is reduced. 2.3%.

(2) the catalyst C3 that step (1) is obtained is filled in the tubes of the tube-and-tube reactor (the inner diameter of the tubes is 5cm, the number of the tubes is 16, and the filling rate of the tubes is 75% by volume), A catalyst bed was formed with a height of 2 meters.

Dimethyl sulfoxide, hydrogen peroxide (provided as a 40% by weight aqueous solution) as an oxidant, and methanol as a solvent were mixed to form a liquid mixture. Next, phosphoric acid (concentration: 30% by weight) was added to the liquid mixture to adjust the pH of the liquid mixture to 3.5. Then, after the liquid mixture is heated to 50°C, it is sent from the bottom into the tubes of the tube-and-tube reactor to contact and react with the catalyst bed layer containing the titanium-silicon molecular sieve. Wherein, in the liquid mixture, the molar ratio of dimethyl sulfoxide to oxidant hydrogen peroxide is 1:2.5, the mass ratio of dimethyl sulfoxide to solvent methanol is 1:5, and the weight hourly space velocity of the liquid mixture is 100h ^-1 , the pressure inside the tube is 1.5MPa. During the reaction process, the catalyst bed is heated to a temperature of 50°C by means of a heating wire installed in the catalyst bed, and at the same time, cooling water is sent into the shell side of the reactor to remove the heat of reaction, so that the temperature in the catalyst bed remains is 50°C.

The reaction mixture obtained when the reaction was carried out to 0.5 hour and 400 hours was analyzed by gas chromatography, and the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone were calculated. The results are listed in Table 2.

Example 13

The same method as in Example 12 was used to prepare dimethyl sulfone, except that the step (1) was not carried out, but the raw material molecular sieve in the step (1) was directly loaded in the tubular reactor.

The results obtained at 0.5 hour and 300 hours of reaction are listed in Table 2.

Example 14

The same method as in Example 13 was used to prepare dimethyl sulfone, except that the catalyst loaded in the tubular reactor was the freshly formed titanium-silicon molecular sieve TS-1 used as the raw material molecular sieve in Example 12.

The results obtained at 0.5 hours and 240 hours are listed in Table 2.

Example 15

Dimethyl sulfone was prepared by the same method as in Example 12, except that in step (2), phosphoric acid was not used, and the pH of the liquid mixture was 6.8.

The results obtained at 0.5 hour and 340 hours of the reaction are listed in Table 2.

Example 16

(1) Preparation of modified titanium-silicon molecular sieves

The raw material molecular sieve that uses is the molding hollow titanium-silicon molecular sieve that will be unloaded from the phenol hydroxylation reaction device (volume average particle diameter is 500 μ m, take the total amount of molding hollow titanium-silicon molecular sieve as a benchmark, and the content of the hollow titanium-silicon molecular sieve is 70 wt. %, the content of silicon oxide as an oxidant is 30% by weight) to regenerate and obtain, its activity is 50%, and the activity when fresh is 96%. The regeneration condition is: roasting in air atmosphere at 570 ° C for 4h.

Raw material molecular sieves are mixed with acetic acid (mass concentration is the aqueous solution of 32% by weight), the obtained mixture is stirred and reacted at 60 ℃ for 24 hours, and the temperature of the obtained reaction mixture is down to room temperature and then filtered, and the obtained solid phase substance is filtered at 120 °C and dried to constant weight to obtain a modified titanium-silicon molecular sieve (referred to as catalyst C4). Among them, the titanium-silicon molecular sieve is calculated as SiO ₂ , and the molar ratio of the titanium-silicon molecular sieve to CH ₃ COOH is 1:5. After characterization, compared with the raw material molecular sieve, the absorption peak height between 240-300nm in the UV-Vis spectrum of the obtained modified titanium-silicon molecular sieve is reduced by 5.1%, and the pore volume measured by the static nitrogen adsorption method is reduced by 2.6%. .

(2) Preparation of dimethyl sulfone

The catalyst C4 prepared by step (1) is packed in the tubes of the tube-and-tube reactor (the internal diameter of the tubes is 1 cm, the number of the tubes is 108, and the filling rate of the tubes is 83% by volume), forming a height of 1.2 meters of catalyst bed.

Dimethyl sulfoxide, cumene peroxide as an oxidizing agent, and acetone as a solvent were mixed to form a liquid mixture. Next, sulfuric acid (concentration: 20% by weight) was added to the liquid mixture to adjust the pH of the liquid mixture from 6.7 to 1.5. Then, after the liquid mixture is heated to 90°C, it is sent from the bottom into the tubes of the tube-and-tube reactor to contact and react with the catalyst bed. Among them, in the liquid mixture, the molar ratio of dimethyl sulfoxide to the oxidant cumene peroxide is 1:3, the mass ratio of dimethyl sulfoxide to the solvent acetone is 1:20, and the weight hourly space velocity of the liquid mixture is 60h ^-1 , the pressure inside the tube is 2MPa. During the reaction process, the catalyst bed is heated to a temperature of 90°C by means of a heating wire installed in the catalyst bed, and at the same time, cooling water is sent into the shell side of the reactor to remove the heat of reaction, so that the temperature in the catalyst bed remains is 90°C.

The reaction mixture obtained when the reaction was carried out for 0.5 hour and 360 hours was analyzed by gas chromatography, and the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone were calculated. The results are listed in Table 2.

Example 17

The catalyst used in this embodiment (referred to as catalyst C5) is the shaped titanium-silicon molecular sieve TS-1 (volume average particle diameter of 600 μm, the total amount of the shaped titanium-silicon molecular sieve TS-1 is Standard, the content of titanium silicon molecular sieve TS-1 is 80% by weight, and the content of silicon oxide as a binder is 20% by weight) to regenerate and obtain, its activity is 30%, and the activity when it is fresh is 95%, The regeneration condition is: roasting in air atmosphere at 550°C for 4h.

The catalyst C5 is packed in the tubes of the tube-and-tube reactor (the internal diameter of the tubes is 8cm, the number of the tubes is 50, and the filling rate of the tubes is 80% by volume), forming a catalyst bed with a height of 1.2 meters .

Dimethyl sulfoxide, peracetic acid as an oxidizing agent, and water as a solvent are mixed to form a liquid mixture. Then, after the liquid mixture is heated to 120° C., it is sent from the bottom into the tubes of the tube-and-tube reactor to contact and react with the catalyst bed layer containing titanium-silicon molecular sieves. Wherein, in the liquid mixture, the molar ratio of dimethyl sulfoxide to oxidant peracetic acid is 1:3.5, the mass ratio of dimethyl sulfoxide to solvent water is 1:15, and the weight hourly space velocity of the liquid mixture is 80h ^-1 , the pressure inside the tube is 2MPa. During the reaction process, the catalyst bed was heated to a temperature of 120°C by means of heating wires arranged in the catalyst bed, and at the same time, cooling water was fed into the shell side of the reactor so that the temperature in the catalyst bed was maintained at 120°C.

The reaction mixture obtained when the reaction was carried out to 0.5 hour and 300 hours was analyzed by gas chromatography, and the conversion rate of dimethyl sulfoxide, the effective utilization rate of the oxidant and the selectivity of dimethyl sulfone were calculated. The results are listed in Table 2.

Example 18

Adopt the same method as Example 17 to prepare dimethyl sulfone, the difference is that under the condition that the loading amount of the formed titanium-silicon molecular sieve in each column tube is constant, the catalyst used is catalyst C5 and fresh agent (forming catalyst C5 fresh agent), wherein the mass ratio of the catalyst C5 to the fresh agent is 2:1.

The results obtained at 0.5 hour and 250 hours of reaction are listed in Table 2.

Table 2

The results of Examples 12-18 confirm that even if at least part of the titanium silicalite molecular sieve is derived from the regenerated reaction device discharge agent, a higher conversion rate of dimethyl sulfoxide and a selectivity of dimethyl sulfone can be obtained, and it is possible to obtain Higher effective utilization rate of oxidant, and higher activity retention rate of catalyst during long-term continuous reaction process.

Example 19

Adopt the same method as Example ₈ to prepare dimethyl sulfone, the difference is that during the reaction, the composition of the reaction mixture output from the reactor is continuously monitored, and when the oxidant conversion C _t and the initial oxidant conversion C When the ratio C _t /C ₀ is 0.85≤C _t /C ₀ <0.9, the heating power of the heating wire in the catalyst bed and the feed temperature of the liquid mixture are kept constant under the condition , by reducing the amount of cooling medium, the temperature of the catalyst bed can be increased by 0.02-2°C/day until the ratio C'/C _{0 of the oxidant conversion rate C' to the initial oxidant conversion rate C 0 is} 0.9≤C' When /C ₀ ≤1, stop reducing the amount of cooling medium and keep the amount of cooling medium.

At 820 hours of reaction time, the temperature in the catalyst bed was 84°C. During the continuous reaction process, the composition of the reaction mixture output from the reactor is monitored and the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone are calculated. The results obtained in 0.5 hours and 820 hours are shown in Table 3 listed in .

Example 20

Adopt the same method as Example 12 to prepare dimethyl sulfone, the difference is that during the reaction, the composition of the reaction mixture output from the reactor is continuously monitored, and between the oxidant conversion rate C _t and the initial _oxidant conversion rate C When the ratio C _t /C ₀ is 0.85≤C _t /C ₀ <0.9, under the condition that the amount of cooling medium and the feed temperature of the liquid mixture are kept constant, by increasing the catalyst bed The heating power of the heating wire in the middle increases the temperature of the catalyst bed in the range of 0.02-1°C/day until the ratio C'/C _{0 of the oxidant conversion rate C' to the initial oxidant conversion rate C 0 is} 0.9≤C' When /C ₀ ≤1, stop increasing the heating power of the heating wire and keep the heating power of the heating wire.

At 900 hours of reaction, the temperature in the catalyst bed was 72°C. During the continuous reaction process, the composition of the reaction mixture output from the reactor is monitored and the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone are calculated. The results obtained in 0.5 hours and 900 hours of reaction are shown in Table 3 listed in .

Example 21

Adopt the same method as Example 14 to prepare dimethyl sulfone, the difference is that during the reaction, the composition of the reaction mixture output from the reactor is continuously monitored, and between the oxidant conversion rate C _t and the initial _oxidant conversion rate C When the ratio C _t /C ₀ is 0.85≤C _t /C ₀ <0.9, when the heating power of the heating wire in the catalyst bed is kept constant and the consumption of the cooling medium is constant, By increasing the feed temperature of the liquid mixture, the temperature of the catalyst bed is increased in the range of 0.02-1°C/day until the ratio C'/ _C0 of the oxidant conversion rate C' to the initial oxidant conversion rate _C0 is 0.9≤C When '/C ₀ ≤1, stop increasing the feed temperature of the liquid mixture and maintain the feed temperature of the liquid mixture.

At 700 hours of the reaction, the temperature in the catalyst bed was 75°C. During the continuous reaction process, the composition of the reaction mixture output from the reactor is monitored and the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone are calculated. The results obtained in 0.5 hours and 700 hours of reaction are shown in Table 3 listed in .

Example 22

Dimethyl sulfone was prepared by the same method as in Example 8, except that the reaction was continued for 500 hours.

During the continuous reaction process, the composition of the reaction mixture output by the reactor is monitored and the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone are calculated, and the results obtained in 0.5 hours and 500 hours of reaction are shown in Table 3 listed in .

Example 23

Dimethyl sulfone was prepared by the same method as in Example 12, except that the reaction was continued for 600 hours.

During the continuous reaction process, the composition of the reaction mixture output by the reactor is monitored and the conversion rate of dimethyl sulfoxide, the effective utilization rate of oxidant and the selectivity of dimethyl sulfone are calculated. The results obtained in 0.5 hours and 600 hours of reaction are shown in Table 3 listed in .

table 3

The results of Examples 19-23 confirm that during the reaction process, when the oxidant conversion rate decreases, by increasing the temperature of the catalyst bed, the catalytic activity of the titanium-silicon molecular sieve as a catalyst can be maintained at a relatively high level for a long period of time , delay the deactivation speed of the titanium-silicon molecular sieve as a catalyst, and prolong the single-pass service life of the catalyst.

Claims (15)

1. a preparation method of dimethyl sulfone, the method comprises under oxidation reaction conditions, a kind of liquid mixture is contacted with the titanium silicon molecular sieve as catalyst, obtains the mixture containing dimethyl sulfone, and described liquid mixture contains two Methyl sulfoxide, at least one peroxide, and optionally at least one solvent, wherein the titanium-silicon molecular sieve is packed in the tubes of the tube-and-tube reactor to form a catalyst bed, and the method also includes performing the During the contact process, a cooling medium is sent into the space between the tubes to exchange heat with the tubes. 2. The method according to claim 1, wherein at least part of the titanium-silicon molecular sieve is the unloading agent of the reaction device using the titanium-silicon molecular sieve as a catalyst through regeneration, and the unloading agent is an ammoximation reaction device One or more of the unloading agent, the unloading agent of the hydroxylation reaction device and the unloading agent of the epoxidation reaction device. 3. The method according to claim 1 or 2, wherein at least part of the titanium-silicon molecular sieve has undergone the following process before being used as a catalyst: contacting with at least one acid at a temperature of 0-200°C for 0.1-72 Hour. 4. The method according to claim 3, wherein the acid is acetic acid and/or hydrochloric acid. 5. The method according to claim 3, wherein the titanium-silicon molecular sieve is calculated as silicon dioxide, and the molar ratio of the titanium-silicon molecular sieve to the acid is 1:0.01-10. 6. The method according to any one of claims 1-5, wherein the titanium-silicon molecular sieve is a titanium-silicon molecular sieve having an MFI structure. 7. The method according to claim 6, wherein at least part of the titanium-silicon molecular sieve is a hollow titanium-silicon molecular sieve, the grain of the hollow titanium-silicon molecular sieve is a hollow structure, and the radial length of the cavity part of the hollow structure is 5-300nm, and the benzene adsorption measured by the titanium-silicon molecular sieve under the conditions of 25°C, P/P ₀ =0.10, and adsorption time of 1h is at least 70mg/g. The low-temperature nitrogen adsorption of the titanium-silicon molecular sieve is There is a hysteresis loop between the adsorption isotherm and the desorption isotherm. 8. The method according to claim 7, wherein the catalyst is a hollow titanium-silicon molecular sieve and a titanium-silicon molecular sieve TS-1, and the packing of the hollow titanium-silicon molecular sieve and the titanium-silicon molecular sieve TS-1 in the column tube The sequence is such that, based on the flow direction of the liquid mixture, the hollow titanium-silicon molecular sieve is located upstream of the titanium-silicon molecular sieve TS-1. 9. The method according to claim 8, wherein the mass ratio of the hollow titanium-silicon molecular sieve to the titanium-silicon molecular sieve TS-1 is 1-10:1. 10. The method according to any one of claims 1-9, wherein the method further comprises feeding at least one acid into the liquid mixture in an amount such that the pH of the liquid mixture is between In the range of 0.5-5.5. 11. The method according to any one of claims 1-10, wherein the method further comprises at least one adjustment step, and the adjustment step is carried out when condition 1 is satisfied, until condition 2 is satisfied to improve the oxidant conversion rate When the adjustment step is stopped, Condition 1. The ratio C _t /C ₀ of the oxidant conversion rate C _t to the initial oxidant conversion rate C ₀ at a certain time t is 0.8≤C _t /C ₀ <1; Condition 2, the ratio C'/C _{0 of the oxidant conversion rate C' to the initial oxidant conversion rate C 0 is} 0.85≤C'/C ₀ ≤1; The adjustment step is to increase the temperature of the catalyst bed until the conversion rate of the oxidant satisfies the condition 2, then maintain the temperature of the catalyst bed. 12. The method according to claim 11, wherein the temperature of the catalyst bed is increased by 0.01-2°C/day. 13. The method according to claim 11 or 12, wherein the initial temperature of the catalyst bed is not more than 120°C. 14. The method according to any one of claims 11-13, wherein in condition 1, 0.85≤C _t /C ₀ <0.9; in condition 2, 0.9≤C'/C. 15. The method according to any one of claims 1-14, wherein the mol ratio of dimethyl sulfoxide to the peroxide is 1:0.1-10, and the conditions of the heat exchange make the catalyst in the column tube The temperature of the bed layer is in the range of 0-180°C, and the weight hourly space velocity of dimethyl sulfoxide is in the range of 0.1-500h ^-1 .