Titanium-containing molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieve preparation, and discloses a titanium-containing molecular sieve and a preparation method and application thereof.The preparation method of the titanium-containing molecular sieve comprises the steps that 1, a pure silicon molecular sieve and / or a silicon-aluminum molecular sieve are / is pretreated, framework silicon or framework aluminum is partially removed, and a molecular sieve with framework hydroxyl vacancy is obtained, the pretreatment comprises acid treatment and / or alkali treatment; and (2) carrying out solid-phase titanium supplementing treatment on the molecular sieve with the skeleton hydroxyl vacancy obtained in the step (1) and a titanium-containing compound. According to the method, the titanium-containing molecular sieve with relatively high catalytic oxidation activity can be prepared.

Description

Technical Field

[0001] The invention relates to the field of molecular sieve preparation, and in particular to a titanium-containing molecular sieve and a preparation method and application thereof. Background Art

[0002] The isolated framework four-coordinated Ti and six-coordinated Ti in the titanium silicalite TS-1 can combine with hydrogen peroxide to generate Ti-OOH as an oxygen supply intermediate to oxidize the reactants. The new generation of green oxidation reactions with titanium silicalite TS-1 with MFI crystal form as the main component of the catalyst and hydrogen peroxide as the oxidant has been applied to the production process of industrial products such as cyclohexanone oxime and propylene oxide. Most of these processes have the advantages of mild reaction conditions and no by-products, and have formed a substitute for processes such as the production of cyclohexanone oxime by the hydroxylamine method and the production of propylene oxide by the chlorohydrin method. However, due to the micropore pore size of the MFI crystal form of TS-1 (0.51×0.55nm and 0.53×0.56nm), the selectivity of TS-1 catalytic oxidation is poor for larger reactant molecules. Therefore, the development of large-pore titanium silicalite with larger pore size can expand the scope of green oxidation reactions with hydrogen peroxide as the oxidant, which is of practical significance.

[0003] TS-1 with MFI crystal form can be prepared by hydrothermal synthesis. However, titanium silicalite molecular sieves with larger pore sizes, such as Ti-MWW and Ti-BEA molecular sieves, require the addition of additives during the hydrothermal synthesis process. Ti is also difficult to enter the MWW and BEA frameworks during this process, but tends to self-polymerize to form anatase with no catalytic oxidation activity. Therefore, researchers generally use a post-synthesis method to pre-treat Ti-free MWW and BEA molecular sieves, and then add Ti to their frameworks to prepare Ti-MWW and T-BEA molecular sieves.

[0004] The literature (Corma A, Díaz U, Fornés V, et al. Ti / ITQ-2, a new material highly active and selective for the epoxidation of olefins with organic hydroperoxides [J]. Chemical Communications, 1999 (9): 779-780.) reports a method for preparing Ti-MWW. First, a layered MWW precursor of pure silicon is prepared, and then it is converted into a pure silicon MWW molecular sieve. Then, dichlorotitacenene dissolved in chloroform is mixed with the molecular sieve and stirred for a period of time, and then a certain amount of triethylamine and chloroform mixture is added. The solid product is recovered and calcined to obtain a Ti-MWW molecular sieve with isolated four-coordinated titanium. In this process, Cl in dichlorotitacenene is substituted with the hydroxyl group on the surface of the pure silicon MWW molecular sieve. The obtained Ti-MWW has a certain catalytic activity in the epoxidation reaction of cyclohexene.

[0005] The literature (Krijnen S, Sánchez P, Jakobs BTF, et al. A controlled post-synthesis route to well-defined and active titanium Beta epoxidation catalysts [J]. Microporous and mesoporous materials, 1999, 31 (1-2): 163-173.) used oxalic acid and nitric acid to dealuminate the aluminum-containing BEA molecular sieve, and found that a large number of nested hydroxyl groups appeared in the dealuminated BEA molecular sieve. The BEA molecular sieve was loaded into a fluidized bed, and chemical vapor deposition was performed with TiCl4 for 30 minutes. After that, the unreacted TiCl4 was purged with nitrogen and calcined in air for 4 hours. The Ti-BEA finally obtained showed certain catalytic activity in the epoxidation reaction of 1-hexene and cyclohexene.

[0006] The literature (Wolf P, Hammond C, Conrad S, et al. Post-synthetic preparation of Sn-, Ti-and Zr-beta: a facile route to water tolerant, highly active Lewis acidic zeolites [J]. Dalton Transactions, 2014, 43 (11): 4514-4519.) also first used nitric acid to dealuminate the aluminum-containing BEA molecular sieve, and then used the wet impregnation method to impregnate the dealuminated BEA molecular sieve with TBOT ethanol solution. After fully drying, the obtained solid product was calcined in air to obtain Ti-BEA molecular sieve. However, a large amount of Ti in the obtained Ti-BEA molecular sieve exists in the form of TiO2, which limits its catalytic oxidation performance.

[0007] In summary, the preparation of large-pore titanium silicate molecular sieves is relatively difficult, the process involves many steps, and the Ti in the obtained large-pore titanium silicate molecular sieves easily forms TiO2 with no catalytic oxidation activity, which limits the catalytic oxidation performance of the obtained large-pore titanium silicate molecular sieves. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a titanium-containing molecular sieve and a preparation method and application thereof. The method can produce a titanium-containing molecular sieve with high catalytic oxidation activity.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a titanium-containing molecular sieve, characterized in that the method comprises the following steps:

[0010] (1) pre-treating pure silicon molecular sieve and / or silicon aluminum molecular sieve to partially remove framework silicon or framework aluminum to obtain a molecular sieve with framework hydroxyl vacancies, wherein the pre-treatment includes acid treatment and / or alkali treatment;

[0011] (2) subjecting the molecular sieve with framework hydroxyl vacancies obtained in step (1) to solid phase titanium supplementation treatment with a titanium-containing compound.

[0012] Preferably, the pretreatment includes a first acid treatment and a second acid treatment; the concentration of the acid solution used in the first acid treatment is more than 3 times the concentration of the acid solution used in the second acid treatment, preferably 10-150 times.

[0013] The second aspect of the present invention provides a titanium-containing molecular sieve prepared by the method described in the first aspect.

[0014] The third aspect of the present invention provides the use of the titanium-containing molecular sieve described in the second aspect in olefin epoxidation reaction, especially in olefin epoxidation reaction with carbon number of 4-12.

[0015] Through the above technical scheme, the present invention obtains a molecular sieve with framework hydroxyl vacancies by pre-treating the molecular sieve in liquid phase or gas phase; then, a large amount of isolated four-coordinated and six-coordinated titanium can be effectively introduced into the molecular sieve by solid phase titanium supplementation. The titanium-containing molecular sieve obtained by the method of the present invention has good catalytic activity in the catalytic oxidation reaction of macromolecular olefins. The method provided by the present invention has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the FTIR spectrum of the macroporous molecular sieve with framework hydroxyl vacancies obtained in Example 1;

[0017] Figure 2 is the UV-Vis spectrum of the macroporous molecular sieve with framework hydroxyl vacancies obtained in Example 1;

[0018] Figure 3 is the UV-Vis spectrum of the titanium-containing molecular sieve obtained in Example 1;

[0019] Figure 4 This is the UV-Vis spectrum of the titanium-containing molecular sieve obtained in Comparative Example 1. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The first aspect of the present invention provides a method for preparing a titanium-containing molecular sieve, the method comprising the following steps:

[0022] (1) pre-treating pure silicon molecular sieve and / or silicon aluminum molecular sieve to partially remove framework silicon or framework aluminum to obtain a molecular sieve with framework hydroxyl vacancies, wherein the pre-treatment includes acid treatment and / or alkali treatment;

[0023] (2) subjecting the molecular sieve with framework hydroxyl vacancies obtained in step (1) to solid phase titanium supplementation treatment with a titanium-containing compound.

[0024] The present invention has a wide range of selection for the type of molecular sieve used, which can be a pure silicon molecular sieve, a silicon-aluminum molecular sieve, or a mixture of a pure silicon molecular sieve and a silicon-aluminum molecular sieve.

[0025] The molar ratio of silicon oxide to aluminum oxide in the silicon-aluminum molecular sieve of the present invention is selected in a wide range, preferably 5-80, more preferably 5-40.

[0026] According to a preferred embodiment of the present invention, the molecular sieve in step (1) is at least one of MEL molecular sieve, BEA molecular sieve, MTW molecular sieve and MWW molecular sieve; further preferably, the molecular sieve in step (1) is BEA molecular sieve and / or MWW molecular sieve. The above molecular sieves are used for the pretreatment of the present invention, and the solid phase titanium supplementation treatment in step (2) is more conducive to improving the catalytic oxidation performance of the titanium-containing molecular sieve.

[0027] The pretreatment in step (1) of the present invention is aimed at partially removing framework silicon or framework aluminum. Specifically, for pure silicon molecular sieve, the pretreatment is aimed at partially removing framework silicon, and for silicon aluminum molecular sieve, the pretreatment is aimed at partially removing framework aluminum.

[0028] According to the present invention, the molecular sieve obtained after pretreatment has framework hydroxyl vacancies which can be determined by FTIR characterization, for example, from Figure 1 It can be seen that 3750-3000cm -1 An obvious infrared absorption peak appeared at , indicating the large-scale generation of skeleton hydroxyl vacancies.

[0029] According to the present invention, preferably, the pretreatment method of the present invention can effectively avoid excessive dissolution of the molecular sieve framework and promote the generation of hydroxyl vacancies in the molecular sieve framework.

[0030] In the present invention, the pretreatment includes alkaline treatment and / or acid treatment. For example, acid treatment or alkaline treatment can be used alone, or the two can be combined. When the two are combined, there is no particular limitation on the order of acid treatment and alkaline treatment. It is preferred to perform acid treatment first and then alkaline treatment.

[0031] According to the present invention, preferably, the specific operation mode of the acid treatment includes: under pretreatment conditions, the pure silicon molecular sieve and / or silicon aluminum molecular sieve is contacted with an acid. The acid can be provided by an acid solution (the solvent includes but is not limited to water). It can be contacted with the pure silicon molecular sieve and / or silicon aluminum molecular sieve in a liquid phase state, which is hereinafter referred to as liquid phase acid treatment in the present invention, or it can be contacted with the pure silicon molecular sieve and / or silicon aluminum molecular sieve in a gas phase state, which is hereinafter referred to as gas phase acid treatment in the present invention.

[0032] According to the present invention, preferably, the specific operation mode of the alkali treatment includes: under pretreatment conditions, the pure silicon molecular sieve and / or silicon aluminum molecular sieve is contacted with a base. The base can be provided by an alkaline solution (solvent includes but is not limited to water). It can be contacted with the pure silicon molecular sieve and / or silicon aluminum molecular sieve in a liquid phase state, which is hereinafter referred to as liquid phase alkali treatment in the present invention, or it can be contacted with the pure silicon molecular sieve and / or silicon aluminum molecular sieve in a gas phase state, which is hereinafter referred to as gas phase alkali treatment in the present invention.

[0033] In the present invention, the base may be an organic base and / or an inorganic base; the acid may be an organic acid and / or an inorganic acid.

[0034] According to the present invention, preferably, the acid treatment uses an organic acid and / or an inorganic acid. The organic acid includes but is not limited to an organic carboxylic acid and / or an organic sulfonic acid, preferably an organic carboxylic acid.

[0035] Preferably, the organic carboxylic acid is selected from at least one of formic acid, acetic acid, butyric acid, oxalic acid and succinic acid, and more preferably is selected from at least one of formic acid, acetic acid and oxalic acid.

[0036] Preferably, the organic sulfonic acid is selected from at least one of methanesulfonic acid, ethanesulfonic acid and benzenesulfonic acid.

[0037] The present invention has a wide range of selection for the type of the inorganic acid. Preferably, the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid, more preferably nitric acid and / or hydrofluoric acid.

[0038] According to the present invention, preferably, the alkali treatment uses an organic base and / or an inorganic base.

[0039] Preferably, the organic base is an organic amine compound, further preferably selected from at least one of aliphatic amines, aromatic amines, alcohol amines and organic quaternary ammonium bases, more preferably an organic quaternary ammonium base, most preferably, the organic quaternary ammonium base is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0040] Preferably, the inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate and aqueous ammonia.

[0041] According to a preferred embodiment of the present invention, the alkali used in the alkali treatment is at least one selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and ammonia water.

[0042] As described above, the pretreatment may be liquid phase pretreatment or gas phase pretreatment, and the present invention has a wide range of selection for the two.

[0043] According to a preferred embodiment of the present invention, the pretreatment is carried out under liquid phase pretreatment conditions, and the pretreatment comprises: mixing the molecular sieve with an acid solution or an alkaline solution, and then treating at 60-200° C. for 0.5-24 h.

[0044] In this preferred embodiment, the molecular sieve in terms of SiO2 and the molecular sieve in terms of H + Acid or OH - The molar ratio of the base is preferably 1:0.01-0.5, more preferably 1:0.1-0.5.

[0045] The present invention has a wide range of acid solution concentration and alkaline solution concentration under liquid phase pretreatment conditions. Preferably, the acid solution concentration is 5-20 mol / L, more preferably 10-15 mol / L. Preferably, the alkaline solution concentration is 0.1-1 mol / L, more preferably 0.2-0.6 mol / L.

[0046] According to another preferred embodiment of the present invention, the pretreatment is carried out under gas phase pretreatment conditions, and the pretreatment comprises: gasifying the acid solution or the alkaline solution and contacting it with the molecular sieve, the contact temperature is 120-300°C, and the contact time is 0.5-36h.

[0047] The gas phase pretreatment used in the present invention can be carried out in a fixed bed reactor. Specifically, the molecular sieve can be loaded into the fixed bed reactor; the acid solution or the alkaline solution is gasified and then passed into the fixed bed, and the treated product is recovered after treatment.

[0048] In the gas phase pretreatment process of the present invention, preferably, the molecular sieve in terms of SiO2 and the molecular sieve in terms of H + Acid or OH - The molar ratio of the base is 1:0.01-2, more preferably 1:0.1-0.5.

[0049] In the present invention, the alkali treatment and the acid treatment can be carried out in one step or in steps. For pure silicon molecular sieve, alkali treatment is preferably used. For silicon aluminum molecular sieve, only acid treatment can be used to remove the framework aluminum, or acid treatment or alkali treatment can be carried out after acid treatment to partially remove the framework silicon and further increase the number of framework hydroxyl vacancies.

[0050] According to a specific embodiment of the present invention, pure silicon molecular sieve is treated with liquid phase alkali. The molecular sieve (in terms of SiO2) and the alkali (in terms of OH) - The molar ratio of 1:0.01-0.5 is 1:0.01-0.5, and after treating at 60-200° C. for 0.5-24 h, the product is filtered, washed with water (preferably washed to neutrality), and recovered after drying.

[0051] In a preferred embodiment, the molecular sieve (in terms of SiO2) and the base (in terms of OH - The molar ratio of the above-mentioned catalyst is 1:0.01-0.25. The treatment temperature is 60-190° C. The treatment time is 0.5-12 hours.

[0052] In a more preferred embodiment, the molecular sieve (in terms of SiO2) and the base (in terms of OH - The molar ratio of the above-mentioned catalyst is 1:0.05-0.2. The treatment temperature is 80-170° C. The treatment time is 2-12 hours.

[0053] According to a specific embodiment of the present invention, the silicon aluminum molecular sieve is subjected to liquid phase acid treatment. The molecular sieve (in terms of SiO2) and the acid (in terms of H + After treating at 60-200° C. for 0.5-24 h, the product is filtered, washed with water (preferably to neutrality), and recovered after drying.

[0054] In a preferred embodiment, the molecular sieve (in terms of SiO2) and the acid (in terms of H + The molar ratio of the above-mentioned catalyst is 1:0.1-0.5. The treatment temperature is 60-140° C. The treatment time is 0.5-12 h.

[0055] In a more preferred embodiment, the molecular sieve (in terms of SiO2) and the acid (in terms of H + The molar ratio of the above-mentioned catalyst is 1:0.25-0.5. The treatment temperature is 60-90° C. The treatment time is 2-8 hours.

[0056] According to a specific embodiment of the present invention, pure silicon molecular sieve is treated with gas phase alkali. The molecular sieve (in terms of SiO2) and the alkali (in terms of OH) - The molar ratio is 1:0.1-2. The treatment temperature is 120-300°C and the treatment time is 2-36h.

[0057] In a preferred embodiment, the molecular sieve (in terms of SiO2) and the alkali (in terms of OH - The molar ratio is 1:0.1-1. The treatment temperature is 170-300°C and the treatment time is 6-24h.

[0058] In a more preferred embodiment, the molecular sieve (in terms of SiO2) and the base (in terms of OH - The molar ratio is 1:0.1-0.5. The treatment temperature is 170-200°C and the treatment time is 6-18h.

[0059] According to a specific embodiment of the present invention, the silicon aluminum molecular sieve is subjected to a two-step acid treatment. In the first acid treatment, the molecular sieve (in terms of SiO2) is treated with an acid (in terms of H + The molar ratio of the molecular sieve (in terms of SiO2) to the acid (in terms of H + The molar ratio of the above-mentioned catalyst is 1:0.25-0.5. The treatment temperature is 60-90° C. The treatment time is 2-8 hours.

[0060] According to a specific embodiment of the present invention, the silicon aluminum molecular sieve is treated with acid and then with alkali. In the first acid treatment, the molecular sieve (in terms of SiO2) is treated with an acid (in terms of H + The molar ratio of the molecular sieve (in terms of SiO2) to the alkali (in terms of OH) is 1:0.25-0.5. The treatment temperature is 60-90°C. The treatment time is 2-8h. In the second step of alkali treatment, the molecular sieve (in terms of SiO2) and the alkali (in terms of OH) are mixed. - The molar ratio of the above-mentioned catalyst is 1:0.05-0.2. The treatment temperature is 80-170° C. The treatment time is 2-12 hours.

[0061] According to a particularly preferred embodiment of the present invention, the pretreatment includes a first acid treatment and a second acid treatment; the concentration of the acid solution used in the first acid treatment is more than 3 times the concentration of the acid solution used in the second acid treatment, preferably 10-150 times, for example, 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, 100 times, 110 times, 120 times, 130 times, 140 times or 150 times, more preferably 10-50 times. The use of this preferred embodiment is more conducive to promoting the removal of skeleton aluminum and the generation of skeleton hydroxyl vacancies. In this manner, preferably, the concentration of the acid solution used in the first acid treatment is 10-15 mol / L.

[0062] According to a preferred embodiment of the present invention, the method further comprises, after the pretreatment, optionally drying the product obtained by the pretreatment, and then calcining. The present invention has no particular limitation on the drying conditions. Preferably, the drying conditions include: a temperature of 40-120°C and a time of 0.5-12h; preferably, a temperature of 60-120°C and a time of 2-12h. Preferably, the calcination conditions include: a calcination temperature of 400-600°C and a calcination time of 1-6h, more preferably, a calcination temperature of 450-550°C and a calcination time of 2-4h.

[0063] According to the present invention, preferably, step (2) of subjecting the molecular sieve having framework hydroxyl vacancies obtained in step (1) to solid phase titanium supplementation treatment with a titanium-containing compound comprises: mixing the molecular sieve having framework hydroxyl vacancies obtained in step (1) with the titanium-containing compound, and then calcining at 350-600°C for 2-12h, more preferably calcining at 450-550°C for 2-4h.

[0064] In order to further optimize the effect of the solid phase titanium treatment, preferably, the method further comprises, before the calcination, grinding the molecular sieve with framework hydroxyl vacancies obtained in step (1) and the titanium-containing compound, and then drying. The present invention has no particular limitation on the grinding and drying conditions, which are more conducive to the mixing of the two. Preferably, the grinding time is 0.5-2h. Preferably, the grinding is carried out at room temperature.

[0065] According to a preferred embodiment of the present invention, the drying conditions include: temperature of 40-120° C., time of 0.5-12 h; preferably, temperature of 60-80° C., time of 2-4 h.

[0066] In order to further optimize the effect of solid phase titanium supplementation and the performance of the oxidation reaction, preferably, the molar ratio of the molecular sieve calculated as SiO2 to the titanium-containing compound calculated as Ti is 1:0.005-0.1, preferably 1:0.01-0.05.

[0067] According to a preferred embodiment of the present invention, the titanium-containing compound is selected from at least one of an organic titanium source and an inorganic titanium source, and is more preferably an organic titanium source.

[0068] Preferably, the organic titanium source has a structure as shown in formula (1):

[0069]

[0070] Wherein R1, R2, R3, and R4 are independent groups, and contain at least one C1-C4 alkoxy group; preferably, R1, R2, R3, and R4 contain at least one halo group, more preferably contain at least two halo groups, and further preferably, the carbon number of the remaining alkoxy groups is greater than 1.

[0071] According to the present invention, preferably, the organic titanium source is selected from at least one of Ti(C2H5O)3Cl, Ti(C2H5O)2Cl2, Ti(C2H5O)Cl3, Ti(C3H7O)3Cl, Ti(C3H7O)2Cl2, and Ti(C3H7O)Cl3. This preferred embodiment is more conducive to improving the catalytic performance of the prepared molecular sieve.

[0072] According to the present invention, preferably, the inorganic titanium source is selected from one or more of titanium tetrachloride, titanium trichloride and titanium tetrabromide, more preferably titanium tetrachloride and / or titanium trichloride.

[0073] The second aspect of the present invention provides a titanium-containing molecular sieve prepared by the method described in the first aspect. The titanium-containing molecular sieve has good catalytic performance when used in olefin epoxidation reaction.

[0074] The third aspect of the present invention provides the use of the titanium-containing molecular sieve described in the second aspect in the epoxidation reaction of olefins. The molecular sieve provided by the present invention is particularly suitable for the epoxidation reaction of macromolecular olefins. Preferably, the olefin is selected from olefins with a carbon number of 4-12, which can be aliphatic hydrocarbons or cycloolefins. Most preferably, the olefin is dicyclopentadiene. The molecular sieve provided by the present invention is used in dicyclopentadiene, which is more conducive to improving the conversion rate of dicyclopentadiene and the selectivity of the epoxidation product.

[0075] There is no particular limitation on the specific operation mode of the epoxidation reaction. Preferably, the olefin epoxidation reaction comprises: contacting an olefin, an oxidant and optionally a solvent with a titanium-containing molecular sieve under olefin epoxidation conditions.

[0076] According to the present invention, preferably, the olefin epoxidation conditions include: a reaction temperature of 20-200° C. and a reaction time of 0.1-16 hours.

[0077] In the epoxidation reaction, the present invention has a wide range of selection of the amount of molecular sieve, olefin and oxidant. Preferably, the mass ratio of the titanium-containing molecular sieve to the olefin is 1:5-20. Preferably, the molar ratio of the olefin to the oxidant is 1:1-5.

[0078] According to the present invention, preferably, ammonium chloride is also added to the olefin epoxidation reaction. In this preferred manner, ammonium chloride is used to generate complex intermediates with reactants, which can effectively improve the catalytic oxidation effect of the molecular sieve of the present invention, and improve the conversion rate of reactants and the selectivity of products.

[0079] According to the present invention, preferably, the mass ratio of the titanium-containing molecular sieve to ammonium chloride is 1:0.01-0.2, preferably 1:0.05-0.15.

[0080] The present invention has a wide range of solvent types to choose from, and those skilled in the art can select the solvent according to conventional means, and it only needs to be able to provide an environment for the epoxidation reaction, preferably tert-butyl alcohol.

[0081] The present invention has a wide range of choices for the type of the oxidant, and those skilled in the art can select it according to conventional means, as long as it can oxidize the olefin. Preferably, the oxidant is hydrogen peroxide, preferably provided in the form of hydrogen peroxide (there is no particular limitation on mass concentration).

[0082] The present invention will be described in detail below through examples.

[0083] In the following examples, the infrared hydroxyl spectrum of the molecular sieve with framework hydroxyl vacancies was measured on a Nicolet 870 Fourier transform infrared spectrometer. The sample was pressed into a self-supporting sheet and placed in an infrared cell at 1×10 -3 The samples were treated at 450 °C for 3 h under Pa conditions, and the infrared hydroxyl spectrum of the samples was measured.

[0084] The framework titanium content of the molecular sieve was characterized by UV-Vis, the instrument was a Cary 300 Agilent UV-Vis spectrometer, and the test range was 180-800nm.

[0085] The reaction product was analyzed by gas chromatography, and the analysis results were quantified by external standard method. The chromatographic analysis conditions were: Agilent-6890 chromatograph, HP-5 capillary column, injection volume 0.5 μL, injection port temperature 280°C. The column temperature was maintained at 45°C for 5 min, then increased to 250°C at a rate of 15°C / min and maintained for 1 min. FID detector, detector temperature 280°C.

[0086] Example 1

[0087] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 12M nitric acid (in terms of H + The product was filtered, washed with water until neutral, recovered, and mixed with 0.5M nitric acid (in terms of H + The mixture was mixed with 2,4-dihydro-1,2-dihydro-2-nitro-1-propene (2,2-dihydro-1-propene) in a molar ratio of 1:0.5 and stirred at 60°C for 2h. The product was filtered, washed with water until neutral, recovered, dried at 110°C for 12h, and calcined at 550°C for 2h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0088] The molecular sieve was mixed with Ti(C2H5O)2Cl2 in a nitrogen atmosphere at a Si / Ti molar ratio of 50 and ground for 0.5 h. The obtained product was dried at 60°C for 2 h and calcined at 550°C for 4 h. The obtained solid product was recovered and recorded as Ti-BEA-A.

[0089] Figure 1 This is the FTIR spectrum of BEA molecular sieve rich in framework hydroxyl vacancies. It can be seen from the figure that 3750-3000cm -1 An obvious infrared absorption peak appeared at , indicating the large-scale generation of skeleton hydroxyl vacancies.

[0090] Figure 2 This is the UV-Vis spectrum of the BEA molecular sieve rich in framework hydroxyl vacancies obtained in Example 1. There is no obvious spectrum peak in the figure, indicating that the obtained BEA molecular sieve does not contain titanium element.

[0091] Figure 3 This is the UV-Vis spectrum of the titanium-containing molecular sieve obtained in Example 1. In the figure, obvious peaks appear at 190nm-330nm, indicating that in the Ti-BEA molecular sieve obtained by solid-phase titanium supplementation, titanium enters the BEA molecular sieve framework and mainly exists in the form of isolated four-coordinated skeleton, while a small amount exists in the form of isolated six-coordinated titanium.

[0092] Comparative Example 1

[0093] Titanium-containing molecular sieves were prepared by the method described in the literature (Wolf P, Hammond C, Conrad S, et al. Post-synthetic preparation of Sn-, Ti-and Zr-beta: a facile route to water tolerant, highly active Lewis acidic zeolites [J]. Dalton Transactions, 2014, 43 (11): 4514-4519.). First, the Beta molecular sieve with a silicon-aluminum molar ratio of 25 was pretreated in nitric acid with a concentration of 13M for dealumination at a temperature of 100°C for 20 hours, and the mass volume ratio of the molecular sieve to nitric acid was 20 mL / g. After washing to neutrality, it was recovered and dried at 110°C for 12 hours. After that, TBOT (tetrabutyl titanate) was used for impregnation, and the molar ratio of the molecular sieve (in terms of SiO2) to the titanium source (in terms of Ti) was 1:0.03. After standing at room temperature for 12 hours, it was dried at 110°C for 12 hours and calcined at 550°C for 3 hours. The solid product obtained is recovered as D-BEA.

[0094] Figure 4 This is the UV-Vis spectrum of the titanium-containing molecular sieve obtained in Example 1, wherein the spectrum peak at 190-330 nm is relatively broad, indicating that the proportion of isolated tetracoordinate titanium in the skeleton is relatively low, and the proportion of isolated hexacoordinate titanium is relatively high.

[0095] Example 2

[0096] The pure silicon BEA molecular sieve produced by Changling Catalyst Factory was used as raw material for gas phase alkali treatment. The BEA molecular sieve (in terms of SiO2) was transferred into a fixed bed reactor and 0.6M ammonia water was used as the alkali source (in terms of OH - The molecular sieve was treated with gas phase alkali (calculated). The molecular sieve and alkali molar ratio was 1:0.2, the alkali treatment temperature was 170°C, and the alkali treatment time was 12h. The ammonia atmosphere was replaced by air atmosphere, the molecular sieve was dried at 110°C for 12h, and then calcined at 550°C for 2h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0097] The molecular sieve was mixed with Ti(C2H5O)2Cl2 in a nitrogen atmosphere at a Si / Ti molar ratio of 50 and ground for 0.5 h. The obtained product was dried at 60°C for 2 h and calcined at 550°C for 4 h. The obtained solid product was recovered and recorded as Ti-BEA-B.

[0098] Example 3

[0099] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 12M nitric acid (in terms of H+ The product was filtered, washed with water until neutral, recovered, and dried at 110°C for 12h. The obtained molecular sieve (in terms of SiO2) was mixed with 1M formic acid (in terms of H + The mixture was mixed with 2,4-dihydro-1,2 ...

[0100] The molecular sieve was mixed with Ti(C2H5O)3Cl in a nitrogen atmosphere at a Si / Ti molar ratio of 40 and ground for 0.5 h. The obtained product was dried at 80°C for 2 h and calcined at 550°C for 3 h. The obtained solid product was recovered and recorded as Ti-BEA-C.

[0101] The molecular sieve was transferred into a fixed bed reactor, replaced with nitrogen three times, and then Ti(CH3CH2O)2Cl2 was used as the titanium source to perform vapor phase titanium supplementation at 200°C for 8 hours. The molar ratio of the molecular sieve (in terms of SiO2) to Ti(CH3CH2O)2Cl2 (in terms of Ti) was 1:2. After the reaction was completed, the reaction temperature was maintained, replaced with nitrogen three times, and replaced with air, and calcined at 550°C for 6 hours. The solid product was recovered and recorded as Ti-BEA-C.

[0102] Example 4

[0103] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 12M nitric acid (in terms of H + The product was filtered, washed with water until neutral, recovered, and dried at 110°C for 12h. The obtained molecular sieve (in terms of SiO2) was mixed with 0.5M TEAOH (in terms of OH) - The product was filtered, washed with water until neutral, recovered, dried at 110°C for 12h, and calcined at 550°C for 4h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0104] The molecular sieve was mixed with Ti(C2H5O)3Cl in an air atmosphere at a Si / Ti molar ratio of 50 and ground for 1 hour. The obtained product was dried at 70°C for 2 hours and calcined at 550°C for 3 hours. The obtained solid product was recovered and recorded as Ti-BEA-D.

[0105] Example 5

[0106] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 1M formic acid (in terms of H + The mixture was mixed with 2,4-dihydro-1,2 ...

[0107] The molecular sieve was mixed with Ti(C3H7O)2Cl2 in an air atmosphere at a Si / Ti molar ratio of 40 and ground for 1 hour. The obtained product was dried at 80°C for 2 hours and calcined at 550°C for 3 hours. The obtained solid product was recovered and recorded as Ti-BEA-E.

[0108] Example 6

[0109] Pure silicon BEA molecular sieve produced by Changling Catalyst Factory was used as raw material for liquid phase alkali treatment. BEA molecular sieve (in terms of SiO2) was mixed with 0.5M TBAOH (in terms of OH - The molar ratio of molecular sieve to alkali source is 1:0.25, the alkali treatment temperature is 180°C, and the alkali treatment time is 8h. The product is filtered, washed with water until neutral, recovered, dried at 110°C for 10h, and then calcined at 550°C for 3h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0110] The molecular sieve was mixed with Ti(C2H5O)3Cl in an air atmosphere at a Si / Ti molar ratio of 40 and ground for 1 hour. The obtained product was dried at 70°C for 2 hours and calcined at 550°C for 3 hours. The obtained solid product was recovered and recorded as Ti-BEA-F.

[0111] Example 7

[0112] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 12M nitric acid (in terms of H + The mixture was mixed with 2,4-dihydro-1,4-dihydro-2-nitro-1-propene (2,4-dihydro-1-nitro-1-propene) in a molar ratio of 1:0.5 and stirred at 90°C for 8h. The product was filtered, washed with water until neutral, recovered, dried at 110°C for 12h, and calcined at 450°C for 3h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0113] The molecular sieve was mixed with TiCl4 in an air atmosphere at a Si / Ti molar ratio of 30 and ground for 0.5 h. The obtained product was dried at 60°C for 2 h and calcined at 550°C for 3 h. The obtained solid product was recovered and recorded as Ti-BEA-G.

[0114] Example 8

[0115] The BEA molecular sieve with a silicon-aluminum molar ratio of 10 produced by Changling Catalyst Factory was used as raw material for liquid phase acid treatment. The BEA molecular sieve (in terms of SiO2) was mixed with 6M acetic acid (in terms of H + The mixture was mixed with 2,4-dihydro-1 ...

[0116] The molecular sieve was mixed with TiCl4 in an air atmosphere at a Si / Ti molar ratio of 30 and ground for 0.5 h. The obtained product was dried at 60°C for 2 h and calcined at 550°C for 3 h. The obtained solid product was recovered and recorded as Ti-BEA-H.

[0117] Example 9

[0118] The BEA molecular sieve with a silicon-aluminum ratio of 10 produced by Changling Catalyst Factory was used as raw material for gas phase acid treatment. The BEA molecular sieve (in terms of SiO2) was transferred into a fixed bed reactor and heated to 10M formic acid (in terms of H + The product was filtered, washed with water until neutral, recovered, dried at 110°C for 12h, and calcined at 500°C for 3h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0119] The molecular sieve was mixed with TiCl4 in an air atmosphere at a Si / Ti molar ratio of 40 and ground for 1 hour. The obtained product was dried at 60°C for 2 hours and calcined at 550°C for 3 hours. The obtained solid product was recovered and recorded as Ti-BEA-I.

[0120] Example 10

[0121] Pure silicon BEA molecular sieve produced by Changling Catalyst Factory was used as raw material for liquid phase alkali treatment. BEA molecular sieve (in terms of SiO2) was mixed with 0.6M ammonia water (in terms of OH - The molar ratio of molecular sieve to alkali source is 1:0.5, the alkali treatment temperature is 80°C, and the alkali treatment time is 12h. The product is filtered, washed with water until neutral, recovered, dried at 110°C for 12h, and calcined at 500°C for 3h to obtain a BEA molecular sieve rich in framework hydroxyl vacancies.

[0122] The molecular sieve was mixed with TiCl4 in an air atmosphere at a Si / Ti molar ratio of 30 and ground for 0.5 h. The obtained product was dried at 60°C for 2 h and calcined at 550°C for 3 h. The obtained solid product was recovered and recorded as Ti-BEA-J.

[0123] Test Example 1

[0124] This test example is used to illustrate the effect of the titanium-containing molecular sieve obtained by the method of the present invention on the epoxidation reaction of dicyclopentadiene.

[0125] The epoxidation reaction of dicyclopentadiene was carried out in a 250 mL three-necked flask reaction device with an automatic temperature-controlled water bath, magnetic stirring and condensation reflux system. The samples prepared in the above embodiments and comparative examples were added into a three-necked flask according to the sample amount of 1.0 g, 13.2 g (0.1 mol) of dicyclopentadiene, 0.1 g of ammonium chloride, and 148.2 g (2 mol) of solvent tert-butyl alcohol, and placed in a water bath with a preset reaction temperature of 60°C. A peristaltic pump was used to dropwise add 28.3 g (0.25 mol) of hydrogen peroxide with a mass fraction of 30 wt%. The reaction was stopped after 8 h, the temperature was rapidly lowered, and the liquid product was separated by suction filtration, and the composition was determined. The results are listed in Table 1.

[0126] Conversion rate of dicyclopentadiene (%) = (moles of dicyclopentadiene in the raw material - moles of dicyclopentadiene in the product) / moles of dicyclopentadiene in the raw material × 100%;

[0127] Epoxidation product selectivity (%) = number of moles of epoxidation product generated in the product / number of moles of dicyclopentadiene consumed to generate all products × 100%.

[0128] Table 1

[0129]

[0130]

[0131] It can be seen from the results in Table 1 that Example 1 and Example 3, which were pretreated by the two-step method under the preferred conditions of the present invention and then supplemented with titanium in the solid phase, have significantly excellent catalytic performance in the epoxidation reaction of dicyclopentadiene.

[0132] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a titanium-containing molecular sieve, characterized in that: The method comprises the following steps: (1) pre-treating pure silicon molecular sieve and / or silicon aluminum molecular sieve to partially remove framework silicon or framework aluminum to obtain a molecular sieve with framework hydroxyl vacancies, wherein the pre-treatment includes acid treatment and / or alkali treatment; (2) subjecting the molecular sieve with framework hydroxyl vacancies obtained in step (1) to solid phase titanium supplementation treatment with a titanium-containing compound.

2. The method according to claim 1, wherein: The molecular sieve in step (1) is at least one selected from MEL molecular sieve, BEA molecular sieve, MTW molecular sieve and MWW molecular sieve; Preferably, the molecular sieve in step (1) is BEA molecular sieve and / or MWW molecular sieve.

3. The method according to claim 1, wherein: The acid treatment uses an organic acid and / or an inorganic acid, wherein the organic acid is an organic carboxylic acid and / or an organic sulfonic acid, preferably at least one of formic acid, acetic acid, butyric acid, oxalic acid, and succinic acid, and more preferably at least one of formic acid, acetic acid, and oxalic acid; the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, and preferably nitric acid and / or hydrofluoric acid.

4. The method according to claim 1, wherein: The alkali treatment uses an organic base and / or an inorganic base, wherein the organic base is an organic amine compound, preferably at least one selected from aliphatic amines, aromatic amines, alcohol amines and organic quaternary ammonium bases; Preferably, the organic quaternary ammonium base is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; Preferably, the inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate and ammonia water; Further preferably, the alkali used in the alkali treatment is at least one selected from tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and ammonia water.

5. The method according to any one of claims 1 to 4, wherein: The pretreatment is carried out under liquid phase pretreatment conditions, and the pretreatment comprises: mixing the molecular sieve with an acid solution or an alkaline solution, and then treating at 60-200° C. for 0.5-24 hours; Among them, the molecular sieve in terms of SiO2 and the + Acid or OH - The molar ratio of the alkali is 1:0.01-0.5; Preferably, the concentration of the acid solution is 5-20 mol / L, more preferably 10-15 mol / L; Preferably, the concentration of the alkaline solution is 0.1-1 mol / L, more preferably 0.2-0.6 mol / L.

6. The method according to any one of claims 1 to 5, wherein: The pretreatment includes a first acid treatment and a second acid treatment; the concentration of the acid solution used in the first acid treatment is more than 3 times the concentration of the acid solution used in the second acid treatment, preferably 10-150 times; Preferably, the concentration of the acid solution used in the first acid treatment is 10-15 mol / L.

7. The method according to any one of claims 1 to 4, wherein: The pretreatment is carried out under gas phase pretreatment conditions, and the pretreatment includes: gasifying the acid solution or the alkaline solution and contacting it with the molecular sieve, the contact temperature is 120-300° C., and the contact time is 0.5-36 hours; Preferably, the molecular sieve in terms of SiO2 and the molecular sieve in terms of H + Acid or OH - The molar ratio of the alkali is 1:0.01-2.

8. The method according to any one of claims 1 to 7, wherein: The method further comprises, after the pretreatment, optionally drying the product obtained by the pretreatment and then calcining it; Preferably, the calcination conditions include: a calcination temperature of 400-600° C. and a calcination time of 1-6 h, more preferably, a calcination temperature of 450-550° C. and a calcination time of 2-4 h.

9. The method according to any one of claims 1 to 8, wherein: Step (2) solid phase titanium supplementation treatment of the molecular sieve with framework hydroxyl vacancies obtained in step (1) with a titanium-containing compound comprises: mixing the molecular sieve with framework hydroxyl vacancies obtained in step (1) with the titanium-containing compound, and then calcining at 350-600° C. for 2-12 hours; preferably calcining at 450-550° C. for 2-4 hours; Preferably, the method further comprises, before the calcination, mixing the molecular sieve having framework hydroxyl vacancies obtained in step (1) with a titanium-containing compound, grinding the mixture, and then drying the mixture; Preferably, the solid phase titanium supplementation treatment is performed under an inert atmosphere.

10. The method according to any one of claims 1 to 9, wherein: The molar ratio of the molecular sieve calculated as SiO2 to the titanium-containing compound calculated as Ti is 1:0.005-0.1, preferably 1:0.01-0.

05.

11. The method according to any one of claims 1 to 10, wherein: The titanium-containing compound is selected from at least one of an organic titanium source and an inorganic titanium source; Preferably, the organic titanium source has a structure as shown in formula (1): Wherein R1, R2, R3, and R4 are independent groups, and at least one of them contains a C1-C4 alkoxy group; preferably, at least one of R1, R2, R3, and R4 contains a halogenated group; Further preferably, the organic titanium source is selected from at least one of Ti(C2H5O)3Cl, Ti(C2H5O)2Cl2, Ti(C2H5O)Cl3, Ti(C3H7O)3Cl, Ti(C3H7O)2Cl2, and Ti(C3H7O)Cl3; Preferably, the inorganic titanium source is selected from one or more of titanium tetrachloride, titanium trichloride and titanium tetrabromide.

12. The titanium-containing molecular sieve prepared by the method according to any one of claims 1 to 11.

13. Use of the titanium-containing molecular sieve according to claim 12 in olefin epoxidation reaction; Preferably, the olefin is selected from at least one olefin having 4 to 12 carbon atoms; Preferably, the olefin epoxidation reaction comprises: contacting an olefin, an oxidant, and optionally a solvent with a titanium-containing molecular sieve under olefin epoxidation conditions; Preferably, the olefin epoxidation conditions include: a mass ratio of the titanium-containing molecular sieve to the olefin of 1:5-20, a molar ratio of the olefin to the oxidant of 1:1-5, a reaction temperature of 20-200°C, and a reaction time of 0.1-16 hours.

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