TS-1 molecular sieve, preparation method thereof and application of TS-1 molecular sieve in phenol hydroxylation reaction

Abstract

The invention relates to a TS-1 molecular sieve, a preparation method thereof and application of the TS-1 molecular sieve in phenol hydroxylation reaction, and according to the preparation method, tetraethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate and amino acid are used as raw materials, crystallization is performed firstly, and then calcination is performed to prepare the TS-1 molecular sieve. The TS-1 molecular sieve catalyst is rich in a large amount of framework titanium, has high-activity hexa-coordinated titanium species, and can be used for efficient catalysis of phenol hydroxylation reaction. Compared with the prior art, the catalyst has excellent catalytic performance and excellent para-selectivity, and is simple in process, low in cost, good in stability and easy to popularize.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve catalyst technology, and in particular to a TS-1 molecular sieve, its preparation method, and its application in the hydroxylation reaction of phenol. Background Technology

[0002] Hydroquinone is an important basic chemical raw material with wide applications, used in various industrial fields such as dye manufacturing, rubber processing, pharmaceutical synthesis, agrochemicals, and polymer material preparation. my country's industrialization of this product started relatively late, and currently relies mainly on traditional methods such as aniline oxidation, phenol oxidation-hydrolysis, and p-diisopropylbenzene oxidation. These traditional processes generally suffer from high energy consumption, low product yield, and large emissions of waste, making it difficult to meet the current demands of green manufacturing and showing a significant gap compared to international advanced technologies. Hydroquinone can be used as a rubber hardener, electroplating additive, skin antiseptic and bactericide, hair dye, and photographic developer. The production technology of hydroquinone is relatively mature, with large-scale production and ample market supply. In contrast, the production process of hydroquinone is complex, requiring advanced technology and equipment. With the increasing demand for hydroquinone, its price is more than twice that of catechol.

[0003] Titanium silicate molecular sieve catalytic systems have attracted much attention due to their environmental friendliness and process simplicity, especially in reactions such as the hydroxylation of aromatic hydrocarbons, the epoxidation of olefins, and the oxidation of alcohols and saturated hydrocarbons, exhibiting excellent shape selectivity. However, in the hydroxylation of phenol, existing technologies still have many shortcomings. Patent CN115385778B discloses a method for synthesizing hydroquinone by hydroxylation of phenol, using titanium silicate molecular sieves as catalysts to oxidize phenol with hydrogen peroxide to obtain ortho- and hydroquinones. Although the single-pass conversion rate of phenol can reach 20%-33% and the selectivity of hydroquinone can reach 90%-95%, the ratio of hydroquinone to catechol is only 2.5-3.5:1. Patent CN120024909A reports a phenol conversion rate of over 20%, a total selectivity of hydroquinone of 90%, and a hydroquinone to catechol ratio of 8:1, but the utilization rate of hydrogen peroxide is low. Furthermore, the catalyst preparation process of this patent is complex, requiring spray drying, and the tetraethyl silicate and template agent need to be added in two separate steps, making the operation cumbersome. Patent CN120243118A discloses a method for preparing TS-1 molecular sieve material with highly active six-coordinate titanium species and a method for photocatalytic degradation of tetracycline. This patent uses a hydroxyl radical initiator, Na2S2O8 solution, to generate hydroxyl radicals through a photocatalytic reaction, which then react with titanium species to form six-coordinate titanium. However, this method requires an external initiator and photocatalytic conditions, making the process complex and unsuitable for phenol hydroxylation reactions. Moreover, this method uses sodium persulfate (Na2S2O8) as a hydroxyl radical initiator, and its mechanism of action is to generate highly oxidizing free radicals under photocatalytic conditions. These free radicals may undergo non-specific oxidation or modification with titanium species, making the process difficult to control precisely and dependent on external light energy input.

[0004] In summary, the hydroxylation reaction of phenol still faces problems such as low selectivity for hydroquinone and complex catalyst preparation. Summary of the Invention

[0005] The purpose of this invention is to provide a TS-1 molecular sieve, its preparation method, and its application in the hydroxylation reaction of phenol. The TS-1 molecular sieve can efficiently catalyze the hydroxylation reaction of phenol to synthesize catechol and hydroquinone. The synthesis method is simple and has excellent phenol conversion rate and hydroquinone selectivity.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One objective of this invention is to provide a method for preparing TS-1 molecular sieves, comprising the following steps:

[0008] S1: Add tetraethyl silicate to a tetrapropylammonium hydroxide aqueous solution and stir until homogeneous. Then add a tetrabutyl titanate alcohol solution and stir to obtain a mixed solution.

[0009] S2: Add amino acids to the mixed solution of S1 and stir to obtain a pretreated solution; the amino acids are aliphatic amino acids;

[0010] S3: The pretreated solution obtained in S2 is placed in a high-pressure reactor for hydrothermal crystallization to obtain the crystallized product;

[0011] S4: The crystallized product obtained in S3 is centrifuged and washed with water until neutral, then dried and calcined to obtain the TS-1 molecular sieve.

[0012] Preferably, in step S1, the molar ratio of tetrapropylammonium hydroxide in the tetrapropylammonium hydroxide aqueous solution, tetrabutyl titanate in the tetrabutyl titanate alcohol solution, and tetraethyl silicate (calculated as SiO2) is (0.2-0.3):(0.015-0.035):1;

[0013] Preferably, in step S1, the stirring speed is 500 rpm-800 rpm and the stirring time is 2-3 h (referring to the stirring parameters after adding tetraethyl silicate to tetrapropylammonium hydroxide aqueous solution and tetrabutyl titanate alcohol solution).

[0014] Preferably, in step S1, the concentration of the tetrapropylammonium hydroxide aqueous solution is 20%wt-50%wt, and the concentration of the tetrabutyl titanate alcohol solution is 10%wt-20%wt.

[0015] Preferably, in step S1, the alcohol solvent used in the tetrabutyl titanate alcohol solution includes any one or both of ethanol and isopropanol.

[0016] Preferably, in step S2, the amino acid is selected from one or more of aliphatic neutral amino acids, acidic amino acids, or basic amino acids.

[0017] More preferably, in step S2, the aliphatic amino acid is selected from one or more of L-lysine, glycine, alanine, glutamic acid, or leucine.

[0018] More preferably, the amino acid is L-lysine.

[0019] Preferably, in step S2, the molar ratio of the amino acid to tetraethyl silicate (calculated as SiO2) is (0.025-0.1):1.

[0020] Preferably, in step S2, the stirring time is 1-2 hours and the stirring speed is 500 rpm-800 rpm.

[0021] Preferably, in step S3, the hydrothermal crystallization conditions are: heating at 110-180°C for 12-48 hours.

[0022] Preferably, in step S4, the calcination conditions are: calcination at 500-600°C for 5-6 hours in an air atmosphere.

[0023] More preferably, in step S4, the centrifugation and washing until neutral is performed at 8000rpm-120000rpm, the centrifuged product is washed with deionized water, and the centrifugation and washing are repeated 5 times until the product is neutral.

[0024] More preferably, in step S4, the drying temperature is 60℃-100℃, and the drying time is 8h-12h.

[0025] The second objective of this invention is to provide a TS-1 molecular sieve prepared according to the preparation method described above.

[0026] Preferably, the TS-1 molecular sieve has a particle size of 80-100 nm and contains six-coordinated titanium species.

[0027] The third objective of this invention is to provide an application of the TS-1 molecular sieve prepared according to the above preparation method in the hydroxylation reaction of phenol.

[0028] Preferably, the TS-1 molecular sieve is used as a catalyst for the hydroxylation reaction of phenol.

[0029] Preferably, the application process includes the following steps:

[0030] After mixing TS-1 molecular sieve, phenol and solvent, the mixture is heated to 60-80℃ with stirring. Then hydrogen peroxide is added dropwise. After the addition is complete, the temperature is maintained and the reaction continues for 6-8 hours. After the reaction is complete, the mixture is cooled to room temperature, filtered, and a sample is taken for analysis.

[0031] Preferably, the mass ratio of TS-1 molecular sieve to phenol is (0.05-0.1):1, the mass ratio of solvent to phenol is (2-4):1, and the mass ratio of hydrogen peroxide to phenol is (0.25-0.35):1.

[0032] Preferably, the solvent includes one or more of methanol, ethanol, water, and acetone.

[0033] More preferably, the solvent is methanol.

[0034] Preferably, the concentration of the hydrogen peroxide is 30-50 wt%.

[0035] More preferably, the concentration of the hydrogen peroxide is 30 wt%.

[0036] This invention provides a TS-1 molecular sieve and its preparation method. By adding amino acids to a traditional hydrothermal synthesis system, a stable Ti-(amino acid) complex is formed through the coordination of amino acids with Ti precursors. On one hand, this complex serves as a stable titanium source during molecular sieve crystallization (hydrothermal crystallization), directionally providing highly catalytically active TiO6 (six-coordinate titanium species), while simultaneously improving the effective utilization rate of the Ti precursor, promoting the successful embedding of more titanium elements into the molecular sieve framework. This ultimately yields a TS-1 molecular sieve with excellent crystal structure, high framework titanium content, and abundant six-coordinate titanium species. On the other hand, the introduction of amino acids regulates the crystal growth of TS-1, forming smaller, more crystallized nanocrystals. This reduces diffusion limitations of reactants and products within the pores and optimizes the distribution of active sites, thereby more fully leveraging the microporous shape-selective catalytic advantages of TS-1 and improving the selectivity of smaller para-products.

[0037] This invention creatively utilizes aliphatic amino acids as green and mild ligands. The amino (-NH2) and carboxyl (-COOH) groups in the amino acid molecule can act as bidentate ligands, reacting with tetrabutyl titanate to produce Ti. 4+ Ions undergo reversible chelation coordination to form a well-defined Ti-(amino acid) complex. This complex has the following advantages: (1) It can effectively inhibit Ti crystallization in an alkaline environment during hydrothermal crystallization. 4+ (1) Hydrolysis and precipitation improve the stability and utilization of titanium source; (2) As a “pre-assembled” titanium precursor, it is easier to be introduced into the framework site during the growth of molecular sieve crystals, and directionally induce the generation of highly active six-coordinated titanium species (TiO6); (3) The steric hindrance effect of amino acids can fine-tune the crystal growth of molecular sieves, forming nanocrystals with smaller particle size and better crystallinity. Therefore, this invention achieves precise control of titanium species through molecular-level coordination chemistry, and the catalyst obtained in the end exhibits higher activity, selectivity and hydrogen peroxide utilization in the phenol hydroxylation reaction.

[0038] The TS-1 molecular sieve prepared by this invention can be applied to the reaction of phenol hydroxylation to prepare hydroquinone, and the above-mentioned structural advantages are fully utilized: the highly active six-coordinate titanium species and the high framework titanium content ensure that the catalyst can efficiently catalyze the phenol hydroxylation reaction under mild reaction conditions, increasing the phenol conversion rate to 21.6%; the smaller nanocrystal size helps to guide the reaction to generate para products in a directional manner and promote product diffusion, thereby increasing the para selectivity to 92.8%.

[0039] Furthermore, the process used in this invention is simple to operate and has low raw material costs, avoiding the high cost problem caused by complex processes. This makes the TS-1 molecular sieve not only have excellent catalytic performance, but also significant economic benefits. It is easy to promote and apply in the large-scale preparation process of phenol hydroxylation products, effectively solving the technical pain points of low catalytic efficiency, poor selectivity and high difficulty in industrialization of traditional TS-1 molecular sieves.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) This invention provides a TS-1 molecular sieve and its preparation method. It is prepared by first crystallizing tetraethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate and amino acids, and then calcining. The TS-1 molecular sieve can be used as a catalyst in the hydroxylation reaction of phenol, showing excellent catalytic performance and excellent para-selectivity, and the synthesis method is simple.

[0042] (2) Based on the traditional hydrothermal synthesis method, this invention successfully synthesized TS-1 molecular sieve with excellent crystal form, high framework titanium content and six-coordinate titanium species by introducing amino acids, thereby significantly improving its catalytic performance.

[0043] (3) The TS-1 molecular sieve catalyst in this invention uses amino acid-assisted synthesis. The amino acid coordinates with the Ti precursor to form a stable Ti-(amino acid) complex. During the crystallization process, these complexes can provide a stable TiO6 species with high catalytic activity, and the species can remain stable during calcination. At the same time, this coordination also improves the effective utilization rate of the Ti precursor, allowing more Ti content to be introduced into the TS-1 molecular sieve, thereby increasing the conversion rate of phenol (up to 21.6%).

[0044] (4) This invention introduces amino acid regulation to control the growth of TS-1 crystals, resulting in nanocrystals with smaller particle size and higher crystallinity, which enhances the shape-selective catalytic effect of the microporous system and effectively improves the selectivity of para-products (up to 92.8%).

[0045] (5) The TS-1 molecular sieve prepared by this invention is rich in framework titanium and six-coordinated titanium active species, which can efficiently activate hydrogen peroxide to generate hydroxyl radicals through homolytic cracking. At the same time, the introduction of amino acids inhibits the formation of non-framework titanium (anatase TiO2) that easily leads to ineffective decomposition of hydrogen peroxide. Therefore, the utilization rate of hydrogen peroxide is significantly improved (up to 86.4%).

[0046] (6) The TS-1 molecular sieve process of the present invention is simple and low in cost. It can be used as a catalyst in the hydroxylation reaction of phenol and is easy to promote and use in the preparation process of large-scale hydroxylation products of phenol. Attached Figure Description

[0047] Figure 1 The image shows a transmission electron microscope image of the TS-1 molecular sieve prepared in Example 1 of this invention (the scale bar in Figure A is 100 nm, and the scale bar in Figure B is 50 nm).

[0048] Figure 2 The image shows the XRD pattern of the TS-1 molecular sieve prepared in Example 1 of this invention.

[0049] Figure 3 The image shows the UV-Vis absorption spectrum of the TS-1 molecular sieve prepared in Example 1 of this invention.

[0050] Figure 4 The image shows the Fourier Transform Infrared (FT-IR) spectrum of the TS-1 molecular sieve prepared in Example 1 of this invention.

[0051] Figure 5 This is a gas chromatogram of the product obtained by the TS-1 molecular sieve prepared in Example 1 of the present invention after phenol hydroxylation reaction. Detailed Implementation

[0052] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiment.

[0053] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0054] A method for preparing TS-1 molecular sieve includes the following steps:

[0055] S1: Add tetraethyl silicate to a tetrapropylammonium hydroxide aqueous solution and stir until homogeneous. Then add a tetrabutyl titanate alcohol solution and stir to obtain a mixed solution.

[0056] S2: Add amino acids to the mixed solution of S1 and stir to obtain a pretreated solution; the amino acids are aliphatic amino acids;

[0057] S3: The pretreated solution obtained in S2 is placed in a high-pressure reactor for hydrothermal crystallization to obtain the crystallized product;

[0058] S4: Wash the crystallized product obtained in S3 with water until neutral, and then calcine it to obtain the TS-1 molecular sieve;

[0059] In step S1, the molar ratio of tetrapropylammonium hydroxide in the tetrapropylammonium hydroxide aqueous solution, tetrabutyl titanate in the tetrabutyl titanate alcohol solution, and tetraethyl silicate (calculated as SiO2) is (0.2-0.3):(0.015-0.035):1; the stirring speed is (500 rpm)-(800 rpm) and the stirring time is 2-3 h; the concentration of the tetrapropylammonium hydroxide aqueous solution is (20 wt%)-(50 wt%), the concentration of the tetrabutyl titanate alcohol solution is (10 wt%)-(20 wt%), and the alcohol solvent used in the tetrabutyl titanate alcohol solution includes any one or both of ethanol and isopropanol;

[0060] In step S2, the amino acid includes one or more of L-lysine, glycine, alanine, glutamic acid, or leucine; the molar ratio of the amino acid to tetraethyl silicate (calculated as SiO2) is (0.025-0.1):1; the stirring time is 1-2 hours, and the stirring speed is (500 rpm)-(800 rpm).

[0061] In step S3, the hydrothermal crystallization conditions are: heating at 110-180℃ for 12-48 hours;

[0062] In step S4, the calcination conditions are: calcination at 500-600℃ for 5-6 hours in an air atmosphere;

[0063] The TS-1 molecular sieve prepared by the above method has a particle size of 80-100 nm and contains six-coordinated titanium species.

[0064] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0065] Example 1:

[0066] This embodiment provides a TS-1 molecular sieve, the preparation method of which is as follows:

[0067] S1: Mix 51.36 g of tetrapropylammonium hydroxide (25 wt%) aqueous solution with 46.86 g of tetraethyl silicate and stir for 3 h until the solution is clear. Then, add 1.98 g of tetrabutyl titanate dropwise to 13.98 g of ethanol to obtain a tetrabutyl titanate alcohol solution. Add the tetrabutyl titanate alcohol solution to the above clear solution and continue stirring for 3 h.

[0068] S2: Add 2.14 g of L-lysine to the above mixed solution and stir for 2 h to obtain a pretreated solution;

[0069] S3: Place the pretreatment solution in a hydrothermal autoclave with a polytetrafluoroethylene liner and hydrothermally crystallize at 160°C for 24 hours.

[0070] S4: The obtained product was centrifuged at 10,000 rpm, then washed with deionized water, and the centrifugation and washing were repeated 5 times until the sample was neutral. It was then dried at 80°C for 12 h, and finally calcined in a muffle furnace at 550°C for 6 h to obtain the TS-1 molecular sieve of this embodiment.

[0071] The TEM image of the TS-1 molecular sieve prepared in this embodiment is shown below. Figure 1 As shown, the TS-1 molecular sieve exhibits a uniformly dispersed crystal structure with a particle size range of 80-100 nm.

[0072] XRD pattern as follows Figure 2 As shown, the five characteristic peaks at 7.92°, 8.79°, 23.08°, 23.91°, and 24.38° indicate that the TS-1 molecular sieve has a typical MFI structure. The absence of obvious amorphous SiO2 peaks in the figure indicates good crystallinity.

[0073] UV-vis spectrum as follows Figure 3 As shown, the peak at 210 nm is due to the electronic transition of empty orbitals between titanium and oxygen atoms, corresponding to the four-coordinate titanium species in the framework. The absorption peak at 260 nm is mainly attributed to the six-coordinate titanium species in the molecular sieve, and the absorption peak around 330 nm belongs to TiO2. Therefore, it can be seen that the TS-1 molecular sieve prepared in this embodiment not only contains four-coordinate titanium species but also successfully introduces six-coordinate titanium species.

[0074] FT-IR spectrum as shown Figure 4 As shown, 960cm -1 The characteristic peak at 800 cm⁻¹ is attributed to the stretching vibration of the Si-O bond in the Si-O-Ti structure. -1 The characteristic peak at 960 cm⁻¹ corresponds to the antisymmetric and symmetric stretching vibrations of the [SiO₄] tetrahedral unit. -1 With 800cm -1 The relative intensity ratio (I960 / I800) of the two peaks can be used to evaluate the relative content of framework titanium species in the molecular sieve. A higher I960 / 800 value indicates a higher content of Ti species in the framework. In this example, the I960 / 800 ratio of the TS-1 molecular sieve is as high as 1.48, proving that it has successfully introduced a high content of framework titanium.

[0075] Example 2:

[0076] This embodiment provides a TS-1 molecular sieve, the preparation method of which is as follows:

[0077] S1: Mix 51.36 g of tetrapropylammonium hydroxide (25 wt%) aqueous solution with 46.86 g of tetraethyl silicate and stir for 3 h until the solution is clear. Then, add 1.98 g of tetrabutyl titanate dropwise to 13.98 g of ethanol to obtain a tetrabutyl titanate alcohol solution. Add the tetrabutyl titanate alcohol solution to the above clear solution and continue stirring for 3 h.

[0078] S2: Add 1.48g of L-lysine to the above mixed solution and stir for 2 hours to obtain a pretreated solution;

[0079] S3: Place the pretreatment solution in a hydrothermal autoclave with a polytetrafluoroethylene liner and hydrothermally crystallize at 160°C for 24 hours.

[0080] S4: The obtained product was centrifuged at 10,000 rpm, then washed with deionized water, and the centrifugation and washing were repeated 5 times until the sample was neutral. It was then dried at 80°C for 12 h, and finally calcined in a muffle furnace at 550°C for 6 h to obtain the TS-1 molecular sieve of this embodiment.

[0081] Example 3:

[0082] This embodiment provides a TS-1 molecular sieve, the preparation method of which is as follows:

[0083] S1: Mix 51.36 g of tetrapropylammonium hydroxide (25 wt%) aqueous solution with 46.86 g of tetraethyl silicate and stir for 3 h until the solution is clear. Then, add 1.98 g of tetrabutyl titanate dropwise to 13.98 g of ethanol to obtain a tetrabutyl titanate alcohol solution. Add the tetrabutyl titanate alcohol solution to the above clear solution and continue stirring for 3 h.

[0084] S2: Add 0.82g of L-lysine to the above mixed solution and stir for 2h to obtain a pretreated solution;

[0085] S3: Place the pretreatment solution in a hydrothermal autoclave with a polytetrafluoroethylene liner and hydrothermally crystallize at 160°C for 24 hours.

[0086] S4: The obtained product was centrifuged at 10,000 rpm, then washed with deionized water, and the centrifugation and washing were repeated 5 times until the sample was neutral. It was then dried at 80°C for 12 h, and finally calcined in a muffle furnace at 550°C for 6 h to obtain the TS-1 molecular sieve of this embodiment.

[0087] Example 4:

[0088] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that the amount of L-lysine added is changed to 2.79g.

[0089] Example 5:

[0090] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that the amount of L-lysine added is changed to 3.30g.

[0091] Example 6:

[0092] This embodiment provides a TS-1 molecular sieve, prepared according to the same method as in Example 1, except that the amount of tetrapropylammonium hydroxide aqueous solution added is changed to 36.68g.

[0093] Example 7:

[0094] This embodiment provides a TS-1 molecular sieve, prepared by the same method as in Example 1, except that the amount of tetrapropylammonium hydroxide aqueous solution added is changed to 55.03g.

[0095] Example 8:

[0096] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that the amount of tetrabutyl titanate added is changed to 1.19g.

[0097] Example 9:

[0098] This embodiment provides a TS-1 molecular sieve, prepared by the same method as in Example 1, except that the amount of tetrabutyl titanate added is changed to 2.78g.

[0099] Example 10:

[0100] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the crystallization time is changed to 12h.

[0101] Example 11:

[0102] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the crystallization time is changed to 36h.

[0103] Example 12:

[0104] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the crystallization time is changed to 48h.

[0105] Example 13:

[0106] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the crystallization temperature is changed to 170℃.

[0107] Example 14:

[0108] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the crystallization temperature is changed to 180℃.

[0109] Example 15:

[0110] This embodiment provides a TS-1 molecular sieve, and the preparation method is the same as in Example 1, except that the calcination temperature is changed to 500℃.

[0111] Example 16:

[0112] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that L-lysine is replaced with glycine.

[0113] Example 17:

[0114] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that L-lysine is replaced with alanine.

[0115] Example 18:

[0116] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that L-lysine is replaced with glutamic acid.

[0117] Example 19:

[0118] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that L-lysine is replaced with leucine.

[0119] Example 20:

[0120] This embodiment provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that 2.14g L-lysine is replaced with 1.07g L-lysine and 1.07g glycine.

[0121] Example 21:

[0122] This embodiment provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that 2.14g L-lysine is replaced with 1.07g L-lysine and 1.07g alanine.

[0123] Example 22:

[0124] This embodiment provides a TS-1 molecular sieve, prepared by the same method as in Example 1, except that 2.14g L-lysine is replaced with 1.07g L-lysine and 1.07g glutamic acid.

[0125] Example 23:

[0126] This embodiment provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that 2.14g L-lysine is replaced with 1.07g L-lysine and 1.07g leucine.

[0127] Comparative Example 1:

[0128] This embodiment provides a TS-1 molecular sieve, which is prepared in accordance with the method in Example 1, except that the amount of L-lysine added is changed to 5.62g.

[0129] Comparative Example 2:

[0130] This comparative example provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that L-lysine is not added.

[0131] Comparative Example 3:

[0132] This comparative example provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that L-lysine is replaced with tryptophan.

[0133] Comparative Example 4:

[0134] This comparative example provides a TS-1 molecular sieve, prepared according to the method in Example 1, except that L-lysine is replaced with histidine.

[0135] The present invention further applies the TS-1 molecular sieves prepared in Examples 1-23 and Comparative Examples 1-4 to the hydroxylation reaction of phenol and evaluates their activity. The specific application process is as follows:

[0136] In a 250 mL three-necked flask, 12.5 g of phenol, 25.0 g of methanol, and 0.625 g of TS-1 molecular sieve were added sequentially. Stirring was started and the temperature was raised to 80 °C. Then, 3.74 g of hydrogen peroxide (30 wt%) was added dropwise over 20 minutes. After the addition was complete, the reaction was allowed to continue for 8 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered, and a sample was taken for analysis.

[0137] The mass concentration of compounds in the reaction system was accurately measured using the area normalization method. The formulas for calculating the conversion rate of phenol, ortho-selectivity, para-selectivity, and hydrogen peroxide utilization are as follows:

[0138]

[0139]

[0140] Where A0 is the peak area of ​​phenol, A1 is the peak area of ​​catechol, A2 is the peak area of ​​hydroquinone, C0, C1, and C2 are the corresponding relative correction factors, X is the conversion rate of phenol, and Sortho and Spara are the selectivity of catechol and hydroquinone, respectively.

[0141]

[0142] The results of catalytic hydroxylation of phenol using the above-mentioned TS-1 molecular sieve are shown in Table 1 below.

[0143] Table 1. Phenol hydroxylation performance of TS-1 molecular sieve

[0144]

[0145]

[0146] Based on the data analysis of the above comparative examples and embodiments, the following conclusions are drawn:

[0147] (1) Comparative Examples 1-23 and 2-4 show that the TS-1 molecular sieve prepared with the addition of aliphatic amino acids exhibits a significant performance improvement in the phenol hydroxylation reaction. Compared with TS-1 molecular sieves without added amino acids or with added non-aliphatic amino acids, the phenol conversion rate increased by 40.4%-53.2%, the para-selectivity increased by 18.4%-20.8%, and the hydrogen peroxide utilization rate increased by 29.4%-39.2%. Among these, the effect of adding only L-lysine was the most significant. After adding L-lysine, it coordinates with the Ti precursor to form a stable Ti-(L-lysine) complex. During crystallization, these complexes can provide stable TiO6 species, and the species remains stable during calcination. This coordination also improves the effective utilization rate of the Ti precursor, allowing more Ti content to be introduced into the TS-1 molecular sieve, thereby improving the phenol conversion rate. In addition, the introduction of L-lysine enhances the shape-selective catalytic effect of the microporous system, resulting in an effective improvement in the selectivity of the para-product.

[0148] (2) Comparison of Comparative Example 1 and Examples 2-5 reveals that the improvement in phenol conversion rate is related to the amount of L-lysine added. With increasing L-lysine addition, the content of hexacoordinate titanium species in the TS-1 molecular sieve increases, leading to improved phenol conversion. However, when the amount of L-lysine added exceeds a certain threshold, it leads to the formation of TiO2, which in turn causes the ineffective decomposition of hydrogen peroxide, hindering the hydroxylation reaction of phenol. The optimal addition amount was determined to be a molar ratio of L-lysine to tetraethyl silicate (calculated as SiO2) of 0.065:1.

[0149] (3) It can be seen from Examples 1 and 6-9 that the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate (calculated as SiO2) and the molar ratio of tetrabutyl titanate to tetraethyl silicate (calculated as SiO2) both have a certain influence on the activity of TS-1 molecular sieve. When the molar ratio of tetrapropylammonium hydroxide to tetraethyl silicate (calculated as SiO2) reaches 0.28:1 and the molar ratio of tetrabutyl titanate to tetraethyl silicate (calculated as SiO2) reaches 0.025:1, TS-1 molecular sieve has excellent catalytic performance.

[0150] (4) Comparing Examples 1 and 10-15, it can be found that crystallization times of 12-48 h all exhibit good catalytic activity, with the optimal crystallization time being 24 h. Crystallization temperatures of 160-180 °C all exhibit good catalytic activity, with the optimal crystallization temperature being 160 °C. Calcination temperatures of 500-600 °C have little effect on the catalyst's catalytic activity.

[0151] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing TS-1 molecular sieve, characterized in that, The method comprises the following steps: S1: tetraethyl orthosilicate is added into an aqueous solution of tetrapropylammonium hydroxide and stirred uniformly, and then tetrabutyl titanate alcohol solution is added and stirred to obtain a mixed solution; S2: amino acid is added into the mixed solution of S1 and stirred to obtain a pretreated solution; the amino acid is an aliphatic amino acid; S3: the pretreated solution obtained in S2 is placed in a high-pressure reaction kettle for hydrothermal crystallization to obtain a crystallization product; S4: the crystallization product obtained in S3 is centrifuged and washed with water until neutral, and then dried and calcined to obtain the TS-1 molecular sieve.

2. The method of making TS-1 zeolite of claim 1, wherein, In step S1, the molar ratio of tetrapropylammonium hydroxide in the aqueous solution of tetrapropylammonium hydroxide, tetrabutyl titanate in the tetrabutyl titanate alcohol solution and tetraethyl orthosilicate calculated in terms of SiO2 is (0.2-0.3):(0.015-0.035):1; the stirring speed is 500 rpm-800 rpm, and the stirring time is 2-3 h.

3. The method of making TS-1 zeolite of claim 1, wherein, In step S1, the concentration of the aqueous solution of tetrapropylammonium hydroxide is 20%wt-50%wt, and the concentration of the tetrabutyl titanate alcohol solution is 10%wt-20%wt; the alcohol solvent used in the tetrabutyl titanate alcohol solution includes any one or both of ethanol or isopropyl alcohol.

4. The method of making TS-1 zeolite of claim 1, wherein, In step S2, the amino acid is selected from any one or more of aliphatic neutral amino acids, aliphatic acidic amino acids or aliphatic basic amino acids; the aliphatic amino acid is selected from any one or more of L-lysine, glycine, alanine, glutamic acid or leucine.

5. The method of making TS-1 zeolite of claim 1, wherein, In step S2, the molar ratio of the amino acid to tetraethyl orthosilicate calculated in terms of SiO2 is (0.025-0.1):1; the stirring time is 1-2 h, and the stirring speed is 500 rpm-800 rpm.

6. The method of making TS-1 zeolite of claim 1, wherein, In step S3, the hydrothermal crystallization is performed at 110-180 ℃ for 12-48 h.

7. The method of making TS-1 zeolite of claim 1, wherein, In step S4, the calcination is performed at 500-600 ℃ for 5-6 h in an air atmosphere.

8. TS-1 molecular sieve prepared according to the preparation process of any one of claims 1 to 7, characterized in that, The TS-1 molecular sieve has a particle size of 80-100 nm and contains six-coordinated titanium species.

9. Use of TS-1 molecular sieve prepared according to the preparation method of any one of claims 1-7 in a phenol hydroxylation reaction, characterized in that, The TS-1 molecular sieve is used as a catalyst for a phenol hydroxylation reaction, and the application process comprises the following steps: After the TS-1 molecular sieve, phenol and solvent are mixed, the mixture is heated to 60-80 ℃ under stirring, then hydrogen peroxide is added dropwise, after the dropwise addition is completed, the temperature is maintained for continuous reaction for 6-8 h, after the reaction is completed, the temperature is cooled to room temperature, and then filtration is performed, and sampling analysis is performed.

10. Use according to claim 9, characterized in that, The mass ratio of the TS-1 molecular sieve to phenol is (0.05-0.1):1, the mass ratio of the solvent to phenol is (2-4):1, and the mass ratio of hydrogen peroxide to phenol is (0.25-0.35):

1. The solvent includes any one or more of methanol, ethanol, water or acetone; and the concentration of hydrogen peroxide is 30-50 wt%.

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