Titanium silicalite molecular sieve catalyst as well as preparation method and application thereof

Abstract

The invention discloses a titanium silicalite molecular sieve catalyst as well as a preparation method and application thereof, and belongs to the technical field of titanium silicalite molecular sieves. The catalyst provided by the invention is composed of an oxide of a co-metal, titanium dioxide and silicon dioxide, the type of the assistant metal is at least one of iron, zinc or copper; based on the total weight of the catalyst, the oxide of the auxiliary metal accounts for 0.1-2.5 wt%, the titanium dioxide accounts for 0.5-2.5 wt%, and the balance is silicon dioxide; the average pore size of the catalyst is 10-30 nm. According to the invention, the specific pore size is combined with the specific auxiliary metal oxide, and the auxiliary metal oxide is uniformly distributed, strongly bonded and fully activated on the surface of the titanium silicalite molecular sieve by optimizing the titanium silicalite molecular sieve, so that the stability of the action effect is ensured. When the catalyst disclosed by the invention is used for epoxidation reaction of cumyl hydroperoxide and 3-chloropropene, the influence of chlorine element on CHP decomposition side reaction is effectively reduced, so that the generation of phenol is reduced.

Description

Technical Field

[0001] This invention belongs to the field of titanium-silicon molecular sieve technology, specifically relating to a titanium-silicon molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] Cumene hydroperoxide (CHP), as an important oxidant in epoxidation reactions, is widely used in the field of olefin epoxidation due to its advantages such as being environmentally friendly, having high reaction selectivity, and producing few process byproducts. However, during the reaction, CHP is prone to decomposition side reactions to generate phenol. The acidity of phenol not only increases the acidic sites on the catalyst, accelerating catalyst deactivation, but may also further trigger various side reactions such as ring-opening and polymerization, thereby affecting the stability of subsequent processes and reducing the purity of the final epoxidation product. Therefore, effectively suppressing the formation of phenol in CHP-involved epoxidation systems is one of the key issues for achieving efficient and stable production.

[0003] CN106582809A discloses an olefin epoxidation catalyst and its preparation method. By regulating the pore structure of titanium-silicon molecular sieves with a template modifier, it can improve the directional conversion efficiency of CHP at a higher propylene / CHP ratio, suppress its non-selective decomposition pathway, and thus reduce the amount of by-product phenol generated.

[0004] CN118324718A discloses a method for preparing an epoxy compound, which significantly improves the conversion rate of CHP by introducing a highly active second olefin during the reaction process and combining it with temperature synergistic control, thereby reducing the amount of CHP that can be decomposed into phenol from the source and thus reducing the content of phenol.

[0005] However, the above methods mainly target the epoxidation system of halogen-free olefins such as propylene, and do not involve the reaction process of 3-chloropropene containing active chlorine with CHP. Since 3-chloropropene more readily generates free chlorine species under reaction conditions, free chlorine significantly promotes the decomposition of CHP and exacerbates phenol formation. Phenol accumulation also threatens the stability of the epichlorohydrin synthesis process, catalyst lifetime, and product purity. Furthermore, conventional phenol suppression strategies developed for propylene systems are difficult to apply to the 3-chloropropene / CHP system.

[0006] Therefore, developing a technical solution specifically applicable to the 3-chloropropene / CHP system that can effectively inhibit phenol formation is of significant industrial application value and urgent practical importance. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies by providing a titanium-silicon molecular sieve catalyst, its preparation method, and its application, in order to solve the problem of phenol byproduct generation in the CHP method for epichlorohydrin preparation.

[0008] This invention utilizes the prepared titanium-silicon molecular sieve catalyst in the reaction system of 3-chloropropylene and cumene hydroperoxide to obtain an efficient epoxidation method with low phenol generation.

[0009] Technical solution: The objective of this invention is achieved through the following technical solution: This invention provides a titanium-silicon molecular sieve catalyst, the catalyst being composed of an oxide of a promoter metal, titanium dioxide, and silicon dioxide; wherein the promoter metal is at least one of iron, zinc, or copper; and based on the total weight of the catalyst, the oxide of the promoter metal accounts for 0.1 to 2.5 wt%, the titanium dioxide accounts for 0.5 to 2.5 wt%, and the balance is silicon dioxide; The catalyst has an average pore size of 10~30 nm.

[0010] This invention relates to a titanium-silicon molecular sieve catalyst with titanium dioxide as the active center and silicon dioxide as the support. The oxides of assisting metals, as modifying components, influence the catalytic efficiency of the titanium-silicon molecular sieve. Studies have found that in the epoxidation reaction system of 3-chloropropene and CHP, using a titanium-silicon molecular sieve catalyst modified with oxides of assisting metals such as iron, zinc, and copper, and controlling the proportion of assisting metal oxides to 0.1–2.5 wt%, can effectively reduce the impact of chlorine on the decomposition side reactions of CHP, thereby reducing the formation of phenol. Simultaneously, to ensure the complete conversion of 3-chloropropene, the titanium-silicon molecular sieve has an average pore size of 10–30 nm, a titanium dioxide content of 0.5–2.5 wt%, and the balance being silicon dioxide.

[0011] This invention combines specific pore sizes with specific auxiliary metal oxides to achieve efficient catalytic conversion of allyl chloride while reducing the generation of free chlorine, thereby reducing phenol content.

[0012] To ensure high selectivity for epichlorohydrin, the catalyst preferably has a specific surface area of ​​195-350 m². 2 / g, with a total pore volume of 1.0~1.4mL / g.

[0013] When it is necessary to avoid phenol formation under low olefin-to-oil ratio conditions, preferably, the proportion of oxide of a single auxiliary metal is 0.05~0.95 wt% based on the total weight of the catalyst, and when the proportion of oxide of a single auxiliary metal is <0.1 wt%, the auxiliary metal is at least two of iron, zinc, or copper, to ensure that the total proportion of oxide of the auxiliary metal in the catalyst is 0.1~2.5 wt%. Correspondingly, the proportion of titanium dioxide is 0.5~2.5 wt%, with the balance being silicon dioxide.

[0014] In order to balance the conversion rate of feedstock and the selectivity of products under low olefin-to-oil ratio conditions, preferably, the auxiliary metal is at least two of iron, zinc or copper; and the average pore size of the catalyst is 15~20 nm.

[0015] This invention also provides a method for preparing the above-mentioned titanium-silicon molecular sieve catalyst, comprising the following steps: Step 1: Mix silicon source, titanium source, template agent, alkali and water in a mass ratio of 1:0.01~0.03:0.03~0.50:0.01~0.10:5~10. After crystallization, filtration, washing, drying and calcination, titanium silicon molecular sieve raw powder is obtained. Step 2: The titanium-silicon molecular sieve powder obtained in Step 1 is immersed in an aqueous solution containing a auxiliary metal salt to perform solid-liquid separation. The resulting solid is dried and treated at high temperature in an inert atmosphere at 350~550℃ to obtain a modified intermediate. Step 3: The modified intermediate obtained in Step 2 is treated by passing a high-temperature and high-pressure aqueous phase through it. The high temperature is 300~400℃ and the high pressure is 20~25MPa. After filtration and drying, the titanium-silicon molecular sieve catalyst is obtained.

[0016] The preparation method of this invention can achieve uniform distribution, strong bonding and full activation of auxiliary metal oxides on the surface of titanium-silicon molecular sieves, thereby ensuring the stability of the effect.

[0017] This invention provides a specific framework structure and pore size distribution in step one, which is beneficial for loading the auxiliary metal element. In particular, the use of alkali is important for adjusting the pore size, providing a suitable pore structure for the bonding of the auxiliary metal element. Step two, impregnation with the auxiliary metal salt followed by programmed calcination, is to obtain a fully activated auxiliary metal oxide. That is, it is not only necessary to load the specific type of auxiliary metal element, but also to fully activate the auxiliary metal element to adapt to the specific reaction. Step three, high-temperature and high-pressure water treatment, further removes impurities and promotes the full activation and further dispersion of the auxiliary metal oxide.

[0018] In this invention, the first step is to prepare titanium-silicon molecular sieve raw powder using a direct synthesis method. The silicon source and titanium source can be any conventional organic or inorganic compound in the art. The silicon source is an organosilicon and / or an inorganic silicon, where the organosilicon is tetramethyl orthosilicate, tetraethyl orthosilicate, or tetrapropyl orthosilicate; the inorganic silicon is a solution containing silica, such as silica sol; and the titanium source is at least one of tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetraisopropyl orthosilicate, tetraisooctyl or tetrabutyl orthosilicate.

[0019] To provide a more suitable environment for the bonding of the auxiliary metal elements described in this invention, the direct synthesis method was optimized by using an alkali to adjust the pH of the system to 10-11. The alkali used is at least one of ammonia, tetraC1-C3 alkyl ammonium hydroxide (such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, etc.), alkaline metal oxides (such as sodium oxide, potassium oxide, etc.), and alkaline metal hydroxides (such as sodium hydroxide, potassium hydroxide, etc.).

[0020] To obtain a suitable pore structure for impregnation with an aqueous solution of a metal salt, the template agent is at least one of the following: C2-C6 alkyl primary amines (such as butylamine, ethylamine, propylamine, pentylamine, tripentylamine, hexylamine, etc.), tri-C5-C6 alkyl tertiary amines (such as trihexylamine, tripentylamine, etc.), tetra-C2-C4 alkyl ammonium bromide (such as tetrabutylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, etc.), and tetra-C1-C3 alkyl ammonium hydroxide (such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, etc.). The template agent and the base used are not both tetra-C1-C3 alkyl ammonium hydroxide.

[0021] To match the above-mentioned material types and ratios and obtain better crystallization results, the crystallization temperature is 120~180℃, and the crystallization time is ≥27h. Furthermore, considering preparation efficiency, the crystallization time is 27~72h.

[0022] The filtration, washing, and drying processes in step one can be performed using conventional methods in this field, such as washing with water until neutral after filtration, and then drying at 100~200℃ or under vacuum at 50~80℃.

[0023] To ensure the activity of the obtained catalyst and to maintain suitable catalyst mechanical strength under the high-pressure environment of step three, preferably, the calcination in step one employs a two-stage gradient heating method, with a heating rate of 2~3℃ / min. The first stage raises the temperature to 400~450℃, and the second stage continues to raise it to 500~700℃. Calcination can be carried out in an inert atmosphere or in air; considering process cost, it can be carried out in air.

[0024] To coordinate the hydrolysis rates of the titanium and silicon sources under the conditions of step one of this invention and to construct a good pore structure, preferably, in step one, the stirring and mixing temperature is 15~55℃, the stirring speed is ≥400 r / min, and the stirring time is ≥60 min. Further, considering both preparation cost and efficiency, the stirring speed is 400~800 r / min, and the stirring time is 60~240 min.

[0025] In step two of this invention, the solid obtained from impregnation is subjected to high-temperature treatment at an inert atmosphere of 350~550℃, which is beneficial for the formation of suitable activation centers by the auxiliary metal element. Under this high-temperature condition, the auxiliary metal salt is preferably a chloride or nitrate of the auxiliary metal; the mass concentration of the aqueous solution containing the auxiliary metal salt is 0.1~20wt%.

[0026] The amount of aqueous solution containing the auxiliary metal salt is determined according to the target auxiliary metal oxide loading, and either an excess solution impregnation method or an equal volume impregnation method can be used. When using the excess solution impregnation method, the mass concentration of the aqueous solution containing the auxiliary metal salt is preferably 5~20wt%; when using the equal volume impregnation method, the mass concentration of the aqueous solution containing the auxiliary metal salt is preferably 0.1~5.0wt%. To ensure the effective loading of the auxiliary metal element, the impregnation temperature is preferably 60~90℃, the impregnation time is ≥5h, such as 5~15h, and the high temperature treatment maintenance time is ≥4h, such as 4~8h.

[0027] Step three of this invention involves removing harmful impurities that hinder the reaction through high-temperature and high-pressure aqueous phase treatment. Furthermore, to further activate and fully disperse the auxiliary metal oxide, the preferred high temperature is 375-400℃ and / or the preferred high pressure is 23-25 ​​MPa. The duration of the high-temperature and high-pressure aqueous phase treatment is ≥4 hours, but can be 4-10 hours to consider cost. The volume ratio of the aqueous phase to the modified intermediate is preferably just right or excessive, i.e., ≥1. Considering both cost and treatment effect, the preferred volume ratio of the aqueous phase to the modified intermediate is 1-5:1.

[0028] Through steps one, two, and three described above, a titanium-silicon molecular sieve catalyst suitable for catalyzing the reaction of 3-chloropropene with cumene hydroperoxide is obtained. To further improve the hydrophobicity of the titanium-silicon molecular sieve, it can be further alkylated. This silanization treatment can be performed using conventional methods in the art. For example, the titanium-silicon molecular sieve catalyst can be contacted with a silanizing agent at 90–350°C. This contact can be a liquid-phase contact or a gas-phase contact, and the reaction can be maintained at this temperature for 3–18 hours to obtain the silanized titanium-silicon molecular sieve. The silanizing agent can be selected from at least one of organosilanes, organosiliconamines, organosiliconamides, or organosilazanes. Examples include hexamethyldisilazane, hexamethylchlorosilazane, heptamethyldisilazane, heptamethylchlorosilazane, trimethylchlorosilane, trimethylbromosilane, trimethyliodosilane, dimethylchlorosilane, tetramethyldisilazane, dimethyldiethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, and trimethylethoxysilane. Typically, the mass ratio of the silylating agent to the titanium-silicon molecular sieve catalyst is 0.1 to 0.5. The titanium-silicon molecular sieve catalyst of the present invention can achieve good catalytic performance without further alkylation treatment; therefore, the present invention preferably does not perform alkylation treatment on the titanium-silicon molecular sieve catalyst.

[0029] The present invention also provides the application of the above-mentioned titanium-silicon molecular sieve catalyst in the epoxidation reaction of cumene hydroperoxide solution with 3-chloropropene to produce epichlorohydrin.

[0030] The titanium-silicon molecular sieve catalyst of the present invention can maintain good catalytic activity over a wide temperature range and under a wide pressure condition. The corresponding reaction conditions are as follows: using a cumene solution of cumene hydroperoxide with a mass concentration of 10~50wt% as the oxidant, a molar ratio of 3-chloropropene to cumene hydroperoxide of 1~15, an epoxidation reaction temperature of 40~160℃, and an epoxidation reaction pressure of 0.1~5.0MPa.

[0031] To enable the titanium-silicon molecular sieve catalyst of this invention to achieve good feed conversion, epichlorohydrin selectivity, and low phenol production under low olefin-to-oil ratio conditions, the molar ratio of 3-chloropropene to cumene hydroperoxide can be <10, thereby reducing the numerous problems caused by excessive 3-chloropropene recycling. Preferably, the molar ratio of 3-chloropropene to cumene hydroperoxide is greater than 1.0 and less than 1.5, such as 1.02 to 1.10. The corresponding epoxidation reaction temperature is 40 to 90°C, the epoxidation reaction pressure is 0.1 to 1.0 MPa, and the mass concentration of the cumene hydroperoxide solution is 20 to 50 wt%. Beneficial effects

[0032] (1) This invention combines specific pore sizes with specific auxiliary metal oxides. By optimizing the titanium silicon molecular sieve, the influence of chlorine on the decomposition side reaction of CHP is effectively reduced, thereby reducing the generation of phenol.

[0033] (2) The preparation method of the present invention achieves uniform distribution, strong bonding and full activation of the auxiliary metal oxide on the surface of titanium silicon molecular sieve, thereby ensuring the stability of the effect.

[0034] (3) When the titanium-silicon molecular sieve catalyst prepared in this invention is used in the epoxidation reaction of cumene hydroperoxide solution with 3-chloropropene to generate epichlorohydrin, it achieves efficient catalytic conversion of chloropropene while hindering the side reaction of 3-chloropropene on the decomposition of cumene hydroperoxide and reducing the content of phenol byproducts. Detailed Implementation

[0035] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0036] The specific surface area, average pore size, and total pore volume of this invention are determined according to the method in "HB / T5764-2020 Determination of Pore Structure of Petroleum Refining Catalysts"; the content of each component is determined by XRF (X-ray fluorescence spectrometer) elemental analyzer.

[0037] Example 1: Preparation of Titanium-Silicon Molecular Sieves (1) Tetramethyl orthosilicate, tetrabutyl titanate, template agent tetrabutylammonium bromide, 5% ammonia water and deionized water were mixed in a mass ratio of 1:0.01:0.1:0.1:8 until the solution pH was 10~11. The mixture was stirred at 15℃ and 400r / min for 150min. Then it was crystallized at 150℃ for 27h. After filtration and washing until neutral, it was dried at 100℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 2℃ / min, and the temperature was raised to 430℃. The heating rate in the second stage was 3℃ / min, and the temperature was raised to 600℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) Using the equal volume impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 3% aqueous solution of auxiliary metal salt (containing zinc chloride, copper nitrate and ferric nitrate in a mass ratio of 1:1:1) at 75°C for 5 hours. Then, solid-liquid separation was carried out, and the obtained solid was dried at 180°C and treated at 400°C under a nitrogen atmosphere for 5 hours to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 400°C and 20MPa for 8 hours at a volume ratio of water to modified intermediate of 2:1. After solid-liquid separation, it was dried at 180°C to obtain the titanium-silicon molecular sieve catalyst C-1#.

[0038] Example 2 Preparation of Titanium-Silicon Molecular Sieves (1) Tetraethyl orthosilicate, tetrapropyl titanate, trihexylamine template agent, sodium hydroxide and deionized water were mixed in a mass ratio of 1:0.02:0.08:0.03:8 until the pH of the solution was 10~11. The mixture was stirred at 55℃ and 500r / min for 200min. Then it was crystallized at 150℃ for 72h. After filtration and washing until neutral, it was dried at 150℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 2℃ / min, and the temperature was raised to 400℃. The heating rate in the second stage was 2℃ / min, and the temperature was raised to 500℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) Using the equal volume impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 0.1% ferric chloride aqueous solution at 60°C for 15 hours, followed by solid-liquid separation. The resulting solid was dried at 150°C and treated at 350°C under a nitrogen atmosphere for 4 hours to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 300°C and 25MPa for 10 hours according to the volume ratio of water to modified intermediate of 5:1. After solid-liquid separation, it was dried at 150°C to obtain the titanium silicon molecular sieve catalyst C-2#.

[0039] Example 3 Preparation of Titanium-Silicon Molecular Sieves (1) Tetrapropyl orthosilicate, tetraisopropyl titanate, tetraethylammonium bromide template agent, tetrapropylammonium hydroxide base and deionized water were mixed in a mass ratio of 1:0.03:0.2:0.05:8 until the pH of the solution was 10~11. The mixture was stirred at 15℃ and 400r / min for 80min. Then it was crystallized at 120℃ for 55h. After filtration and washing until neutral, it was dried under vacuum at 50℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 3℃ / min, and the temperature was raised to 400℃. The heating rate in the second stage was 2.5℃ / min, and the temperature was raised to 600℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) The titanium silicon molecular sieve powder was impregnated in a 5% copper chloride aqueous solution at 75°C for 10 hours using the excess impregnation method. Then, solid-liquid separation was carried out. The obtained solid was dried at 120°C and treated at 500°C under a nitrogen atmosphere for 7 hours to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 375°C and 23MPa for 8 hours at a volume ratio of 1:1 between water and the modified intermediate. After solid-liquid separation, the mixture was dried at 120°C to obtain the titanium-silicon molecular sieve catalyst C-3#.

[0040] Example 4 Preparation of Titanium-Silicon Molecular Sieves (1) Tetrabutyl orthosilicate, tetraoctyl titanate, tetramethylammonium hydroxide template agent, sodium oxide and deionized water were mixed in a mass ratio of 1:0.02:0.4:0.01:8 until the pH of the solution was 10~11. The mixture was stirred at 30℃ and 500r / min for 60min. Then it was crystallized at 180℃ for 55h. After filtration and washing until neutral, it was dried under vacuum at 60℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 2.5℃ / min, and the temperature was raised to 430℃. The heating rate in the second stage was 2.5℃ / min, and the temperature was raised to 600℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) Using the excess impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 10% aqueous solution of auxiliary metal salt (the auxiliary metal salt contained in the mass ratio of zinc nitrate and copper chloride was 1:1) at 60°C for 10h, and then solid-liquid separation was performed. The obtained solid was dried at 150°C and treated at high temperature at 450°C under a nitrogen atmosphere for 6h to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 380°C and 24MPa for 4 hours according to the volume ratio of water to modified intermediate of 3:1. After solid-liquid separation, it was dried at 150°C to obtain the titanium silicon molecular sieve catalyst C-4#.

[0041] Example 5: Preparation of Titanium-Silicon Molecular Sieves (1) 30% silica sol, tetramethyl titanate, template agent (ethylamine, propylamine and hexylamine in a mass ratio of 1:1:1), potassium hydroxide and deionized water were mixed in a mass ratio of 1:0.01:0.5:0.06:10 until the pH of the solution was 10~11. The mixture was stirred at 30℃ and 800r / min for 240min. Then it was crystallized at 180℃ for 27h. After filtration and washing until neutral, it was dried under vacuum at 80℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 2.5℃ / min, and the temperature was raised to 450℃. The heating rate in the second stage was 2℃ / min, and the temperature was raised to 700℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) The titanium silicon molecular sieve powder was impregnated in an aqueous solution of 18% zinc nitrate at 90°C for 5 hours using the excess impregnation method. Then, solid-liquid separation was carried out. The obtained solid was dried at 180°C and treated at high temperature in a nitrogen atmosphere at 550°C for 8 hours to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 400°C and 24MPa for 10 hours according to the volume ratio of water to modified intermediate of 1:1. After solid-liquid separation, it was dried at 180°C to obtain the titanium silicon molecular sieve catalyst C-5#.

[0042] Example 6 Preparation of Titanium-Silicon Molecular Sieves The only difference from Example 5 is that: in step (2), the excess impregnation method is used, the titanium silicon molecular sieve powder is impregnated in a 20% zinc nitrate aqueous solution at 90°C for 15 hours, and then solid-liquid separation is performed. The obtained solid is dried at 180°C and treated at high temperature at 550°C under a nitrogen atmosphere for 8 hours to obtain the modified intermediate; the remaining conditions are the same as in Example 5, and the titanium silicon molecular sieve catalyst C-6# is obtained.

[0043] Example 7 Preparation of Titanium-Silicon Molecular Sieves (1) Mix 25% silica sol, tetraethyl titanate, tetrapropylammonium hydroxide template agent, 10% ammonia water and deionized water in a mass ratio of 1:0.03:0.3:0.08:5 until the solution pH is 10~11, stir at 55℃ and 800r / min for 100min, then crystallize at 120℃ for 72h, filter and wash until neutral, dry at 200℃, and then perform two-stage gradient heating calcination in air. The first stage heating rate is 3.0℃ / min, rising to 450℃, and the second stage heating rate is 2.0℃ / min, rising to 600℃. After calcination, titanium silicon molecular sieve raw powder is obtained. (2) Using the equal volume impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 5% aqueous solution of auxiliary metal salt (containing copper nitrate and iron nitrate in a mass ratio of 1:1) at 90°C for 15h. Then, solid-liquid separation was carried out, and the obtained solid was dried at 200°C and treated at high temperature in a nitrogen atmosphere at 350°C for 6h to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 390°C and 25MPa for 4 hours at a volume ratio of water to modified intermediate of 5:1. After solid-liquid separation, it was dried at 200°C to obtain the titanium silicon molecular sieve catalyst C-7#.

[0044] Example 8 Preparation of Titanium-Silicon Molecular Sieves (1) Tetraethyl orthosilicate, tetrabutyl titanate, template agent tripentylamine, tetramethylammonium hydroxide and deionized water were mixed in a mass ratio of 1:0.02:0.03:0.08:8 until the pH of the solution was 10~11. The mixture was stirred at 40℃ and 600r / min for 200min. Then it was crystallized at 160℃ for 52h. After filtration and washing until neutral, it was dried under vacuum at 70℃. Then it was calcined in air in a two-stage gradient heating process. The heating rate in the first stage was 2.5℃ / min, and the temperature was raised to 450℃. The heating rate in the second stage was 2.5℃ / min, and the temperature was raised to 600℃. After calcination, titanium silicon molecular sieve raw powder was obtained. (2) Using the excess impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 20% aqueous solution of auxiliary metal salt (the auxiliary metal salt contained in zinc chloride and ferric chloride with a mass ratio of 1:1) at 60°C for 10h. Then, solid-liquid separation was carried out, and the obtained solid was dried at 150°C and treated at high temperature in a nitrogen atmosphere at 450°C for 6h to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 350°C and 22MPa for 6 hours according to the volume ratio of water to modified intermediate of 4:1. After solid-liquid separation, it was dried at 150°C to obtain the titanium silicon molecular sieve catalyst C-8#.

[0045] Example 9 Preparation of Titanium-Silicon Molecular Sieves Tetrabutyl orthosilicate, tetramethylammonium hydroxide (TMA) template agent, sodium oxide, and deionized water were mixed at a mass ratio of 1:0.4:0.01:8 until the solution pH reached 10-11. The mixture was stirred at 30°C and 500 rpm for 60 min, then crystallized at 180°C for 55 h. After filtration and washing until neutral, the mixture was dried under vacuum at 60°C and then subjected to a two-stage gradient calcination in air. The first stage heating rate was 2.5°C / min, reaching 430°C, and the second stage heating rate was 2.5°C / min, reaching 600°C. The resulting mesoporous silica support was obtained after calcination. Mesoporous silica support was added to the reactor and the temperature was raised to 450°C. Then, titanium tetrachloride was introduced into the reactor at a mass ratio of titanium tetrachloride to silicon dioxide of 1.1:1. After sufficient heat preservation, the temperature was lowered to 110°C. Then, it was washed with deionized water until neutral and dried at 180°C to obtain titanium silicon molecular sieve raw powder. (3) Using the excess impregnation method, the titanium silicon molecular sieve raw powder was impregnated in a 10% aqueous solution of auxiliary metal salt (the auxiliary metal salt contained in the mass ratio of zinc nitrate and copper chloride was 1:1) at 60°C for 10h, and then solid-liquid separation was performed. The obtained solid was dried at 150°C and treated at high temperature at 450°C under a nitrogen atmosphere for 6h to obtain the modified intermediate. (4) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 380°C and 24MPa for 4 hours according to the volume ratio of water to modified intermediate of 3:1. After solid-liquid separation, it was dried at 150°C to obtain the titanium silicon molecular sieve catalyst C-9#.

[0046] Example 10 Preparation of Titanium-Silicon Molecular Sieves The only difference from Example 4 is that in step (1), tetrabutyl orthosilicate, tetraoctyl titanate, tetramethylammonium hydroxide template agent, sodium oxide and deionized water are mixed in a mass ratio of 1:0.02:0.4:0.01:8 until the solution pH is 10~11, and stirred at 30℃ and 310r / min for 50min, then crystallized at 180℃ for 55h, filtered and washed until neutral, dried under vacuum at 60℃, and then calcined in air in a two-stage gradient heating process. The first stage heating rate is 2.5℃ / min, reaching 430℃, and the second stage heating rate is 2.5℃ / min, reaching 600℃. After calcination, titanium silicon molecular sieve raw powder is obtained; the other conditions are the same as in Example 4, and the titanium silicon molecular sieve catalyst C-10# is obtained.

[0047] Example 11 Preparation of Titanium-Silicon Molecular Sieves The only difference from Example 4 is that step (3) is not performed. All other conditions are the same as in Example 4. The modified intermediate obtained in step (2) is used as the titanium-silicon molecular sieve catalyst C-11#.

[0048] Example 12 Preparation of Titanium-Silicon Molecular Sieves The only difference from Example 4 is that in step (1), tetrabutyl orthosilicate, tetraoctyl titanate, tetramethylammonium hydroxide template agent, sodium oxide and deionized water are mixed in a mass ratio of 1:0.02:0.4:0.01:8 until the solution pH is 10~11, and stirred at 30℃ and 500r / min for 60min. Then, it is crystallized at 180℃ for 55h, filtered and washed until neutral, dried under vacuum at 60℃, and then calcined in air at 600℃ to obtain titanium silicon molecular sieve raw powder. The remaining conditions are the same as in Example 4 to obtain the titanium silicon molecular sieve catalyst C-12#.

[0049] Example 13 Preparation of Titanium-Silicon Molecular Sieves The only difference from Example 4 is that: in step (2), the excess impregnation method is used, and the titanium silicon molecular sieve powder is impregnated in an aqueous solution of 10% auxiliary metal salt (the auxiliary metal salt is zinc nitrate and copper chloride with a mass ratio of 1:1) at 60°C for 10h, and then solid-liquid separation is performed. The obtained solid is dried at 150°C and treated at high temperature at 300°C under a nitrogen atmosphere for 6h to obtain the modified intermediate; the remaining conditions are the same as in Example 4, and the titanium silicon molecular sieve catalyst C-13# is obtained.

[0050] Example 14 Preparation of Titanium-Silicon Molecular Sieves The difference from Example 4 is that after obtaining the titanium-silicon molecular sieve catalyst in step (3), the titanium-silicon molecular sieve is silanized with hexamethyldisilazane at 350°C; the other conditions are the same as in Example 4, and the silanized titanium-silicon molecular sieve catalyst is obtained, which is denoted as C-14#.

[0051] Comparative Example 1 The only difference from Example 2 is that step (2) is omitted, while all other conditions are the same as in Example 2, resulting in a titanium-silicon molecular sieve catalyst without auxiliary metal oxides, denoted as C-D1#.

[0052] Comparative Example 2 The only difference from Example 3 is that in step (1), tetrapropyl orthosilicate, tetraisopropyl titanate, and the template agent tetraethylammonium bromide are mixed with deionized water at a mass ratio of 1:0.03:0.2:8 until the solution pH is 8-9. The mixture is stirred at 15°C and 400r / min for 80 min, then crystallized at 120°C for 55 h. After filtration and washing until neutral, the mixture is dried under vacuum at 50°C and then calcined in air in a two-stage gradient heating process. The heating rate in the first stage is 3°C / min, reaching 400°C, and the heating rate in the second stage is 2.5°C / min, reaching 600°C. After calcination, titanium silicon molecular sieve raw powder is obtained. All other conditions are the same as in Example 3, and titanium silicon molecular sieve catalyst is obtained, denoted as C-D2#.

[0053] Comparative Example 3 The only difference from Example 5 is that in step (1), 30% silica sol, tetramethyl titanate, template agent hexylamine, potassium hydroxide and deionized water are mixed in a mass ratio of 1:0.01:0.8:0.12:10 until the solution pH is 10~11, and stirred at 30℃ and 800r / min for 240min. Then, it is crystallized at 180℃ for 27h, filtered and washed until neutral, and then dried under vacuum at 80℃. Then, it is calcined in air in a two-stage gradient temperature rise. The first stage temperature rise rate is 2.5℃ / min, rising to 450℃, and the second stage temperature rise rate is 2℃ / min, rising to 700℃. After calcination, titanium silicon molecular sieve raw powder is obtained. All other conditions are the same as in Example 5, and titanium silicon molecular sieve catalyst is obtained, which is denoted as C-D3#.

[0054] Comparative Example 4 30% silica sol, tetramethyl titanate, template agent (ethylamine, propylamine, and hexylamine in a mass ratio of 1:1:1), potassium hydroxide, and deionized water were mixed in a mass ratio of 1:0.04:0.5:0.06:10 until the pH of the solution was 10-11. The mixture was stirred at 30℃ and 800 rpm for 240 min, then crystallized at 180℃ for 27 h. After filtration and washing until neutral, the mixture was dried under vacuum at 80℃. Then, a two-stage gradient heating calcination was carried out in air. The first stage heating rate was 2.5℃ / min, reaching 450℃, and the second stage heating rate was 2℃ / min, reaching 700℃. After calcination, titanium-silicon molecular sieve raw powder was obtained. (2) The titanium silicon molecular sieve raw powder was impregnated in a 25% zinc nitrate aqueous solution at 90°C for 15 hours using the excess impregnation method. Then, solid-liquid separation was carried out, and the obtained solid was dried at 180°C and treated at high temperature at 550°C under a nitrogen atmosphere for 8 hours to obtain the modified intermediate. (3) The modified intermediate was placed in a reaction vessel, and the aqueous phase was introduced into the reaction vessel at 400°C and 24MPa for 10 hours according to the volume ratio of water to modified intermediate of 1:1. After solid-liquid separation, it was dried at 180°C to obtain the titanium silicon molecular sieve catalyst C-D4#.

[0055] The titanium-silicon molecular sieves prepared in the above embodiments and comparative examples were characterized in terms of average pore size, total pore volume, specific surface area, and composition. The results are shown in Tables 1 and 2.

[0056] Table 1. Characterization results of titanium-silicon molecular sieves in Examples 1-9

[0057] Table 2 Characterization results of titanium-silicon molecular sieves in Examples 10-14 and Comparative Examples 1-4

[0058] As can be seen from the data in Table 1-2, the preparation method of the present invention can produce titanium-silicon molecular sieves with average pore size and auxiliary metal oxide content within the range of the present invention. However, the titanium-silicon molecular sieve of Comparative Example 1 does not contain auxiliary metal oxides. The titanium-silicon molecular sieve of Comparative Example 2 with reduced alkali content has a smaller average pore size. The titanium-silicon molecular sieve of Comparative Example 3 with excessive alkali has a larger average pore size. The titanium-silicon molecular sieve of Comparative Example 4 with excessive titanium source and auxiliary metal source has exceeded the range of titanium content and auxiliary metal oxide content. Application Examples

[0059] This invention utilizes the aforementioned titanium-silicon molecular sieve catalyst for the preparation of epichlorohydrin. The preparation method involves adding the titanium-silicon molecular sieve catalyst, 3-chloropropene, and an oxidizing solution to a batch reactor for an epoxidation reaction. The titanium-silicon molecular sieve is used at 1.0 wt% of the total raw material. The oxidizing solution is a cumene hydroperoxide solution with a mass concentration of 20-50 wt%. The molar ratio of 3-chloropropene to cumene hydroperoxide (CHP) is 1.02-8:1. The epoxidation reaction pressure is 0.1-1.0 MPa, and the temperature is 40-90℃. The characterization results of the epoxidation reaction are shown in Tables 3 and 4. The calculation methods for the raw material conversion rate and product selectivity are as follows: Cumene hydrogen peroxide conversion rate (CHP%) = (1 - moles of cumene hydrogen peroxide remaining after reaction / moles of cumene hydrogen peroxide added before reaction) × 100%; Epichlorohydrin selectivity (ECH%) = [moles of epichlorohydrin / (moles of propylene chloride added before reaction - moles of propylene chloride remaining after reaction)] × 100%; The phenol content was determined using liquid chromatography with external standard method.

[0060] Table 3 Catalytic effects of C-1#~C-8# titanium-silicon molecular sieves

[0061] Table 4 Catalytic Effects of C-9#~C-D4# Titanium-Silicon Molecular Sieves

[0062] The data in the table show that the titanium-silicon molecular sieve prepared using this invention can effectively reduce phenol formation while maintaining both the conversion rate of cumene hydroperoxide and the selectivity of epichlorohydrin. Furthermore, this invention can achieve good catalytic performance under low olefin-to-oil ratio conditions, thereby reducing the energy consumption problem of excessive olefin recycling. In contrast, the comparative catalysts all have higher phenol content and poorer feed conversion and product selectivity.

[0063] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A titanium-silicon molecular sieve catalyst, characterized in that, The catalyst is composed of an oxide of a promoter metal, titanium dioxide, and silicon dioxide; wherein the promoter metal is at least one of iron, zinc, or copper; and by total weight of the catalyst, the oxide of the promoter metal accounts for 0.1 to 2.5 wt%, the titanium dioxide accounts for 0.5 to 2.5 wt%, and the balance is silicon dioxide. The catalyst has an average pore size of 10~30 nm.

2. The titanium-silicon molecular sieve catalyst according to claim 1, characterized in that, The catalyst has a specific surface area of ​​195~350 m². 2 / g, with a total pore volume of 1.0~1.4mL / g.

3. The titanium-silicon molecular sieve catalyst according to claim 1, characterized in that, The oxide percentage of a single promoter metal is 0.05 to 0.95 wt% based on the total weight of the catalyst, and when the oxide percentage of a single promoter metal is < 0.1 wt%, the promoter metal is at least two of iron, zinc, or copper.

4. The titanium-silicon molecular sieve catalyst according to claim 1, characterized in that, The type of auxiliary metal is at least two of iron, zinc or copper; the average pore size of the catalyst is 15~20 nm.

5. The method for preparing the titanium-silicon molecular sieve catalyst according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Mix silicon source, titanium source, template agent, alkali and water in a mass ratio of 1:0.01~0.03:0.03~0.50:0.01~0.10:5~10. After crystallization, filtration, washing, drying and calcination, titanium silicon molecular sieve raw powder is obtained. Step 2: The titanium-silicon molecular sieve powder obtained in Step 1 is immersed in an aqueous solution containing a auxiliary metal salt to perform solid-liquid separation. The resulting solid is dried and treated at high temperature in an inert atmosphere at 350~550℃ to obtain a modified intermediate. Step 3: The modified intermediate obtained in Step 2 is treated by passing a high-temperature and high-pressure aqueous phase through it. The high temperature is 300~400℃ and the high pressure is 20~25MPa. After filtration and drying, the titanium-silicon molecular sieve catalyst is obtained.

6. The preparation method according to claim 5, characterized in that, In step one, the calcination adopts a two-stage gradient heating, with a heating rate of 2~3℃ / min. In the first stage, the temperature is raised to 400~450℃, and in the second stage, it is raised to 500~700℃.

7. The preparation method according to claim 5, characterized in that, In step one, the mixing temperature is 15~55℃, the mixing speed is ≥400r / min, and the mixing time is ≥60min.

8. The preparation method according to claim 5, characterized in that, In step two, the auxiliary metal salt is a chloride or nitrate of an auxiliary metal; the mass concentration of the aqueous solution containing the auxiliary metal salt is 0.1~20wt%.

9. The use of the titanium-silicon molecular sieve catalyst according to any one of claims 1 to 4 in the epoxidation reaction of cumene hydroperoxide solution with 3-chloropropene to produce epichlorohydrin.

10. The application according to claim 9, characterized in that, The molar ratio of 3-chloropropene to cumene hydroperoxide is greater than 1.0 and less than 1.5, the epoxidation reaction temperature is 40~90℃, the epoxidation reaction pressure is 0.1~1.0MPa, and the mass concentration of the cumene hydroperoxide solution is 20~50wt%.

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