Modified titanium-silicalite molecular sieve and preparation method therefor, and epoxidation catalyst and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of catalytic chemistry. Disclosed are a modified titanium-silicalite molecular sieve and a preparation method therefor, and an epoxidation catalyst and a preparation method therefor and a use thereof. In the modified titanium-silicalite molecular sieve, in the 29Si NMR spectrum, the ratio of the characteristic peak area of the modified titanium-silicalite molecular sieve near -113 ppm to that near -103 ppm is greater than 35; and in the 1H NMR spectrum, the ratio of the titanium hydroxyl peak area of the modified titanium-silicalite molecular sieve near 3.5 ppm to that near 2.1 ppm is greater than or equal to 1. The epoxidation catalyst comprises a support and a noble metal component loaded on the support, wherein the support is the modified titanium-silicalite molecular sieve provided by the present invention. By using the epoxidation catalyst comprising the modified titanium-silicalite molecular sieve of the present invention to prepare propylene oxide (PO), a high propylene conversion rate and high PO selectivity can be obtained, and both the hydrogen efficiency and the PO generation rate are significantly high.

Description

Modified titanium-silicon molecular sieves and their preparation methods, epoxidation catalysts and their preparation methods and applications

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411443054.5, filed on October 16, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of catalytic chemistry, specifically to a modified titanium-silicon molecular sieve and its preparation method, and an epoxidation catalyst and its preparation method and application. Background Technology

[0004] Propylene oxide (PO) is the third largest propylene derivative and an important basic organic chemical raw material, mainly used in the production of polyethers and polyurethanes, which are widely used in construction, aerospace, and daily life. Mature PO production processes include the chlorohydrin process and the co-oxidation process; however, these two methods suffer from severe environmental pollution and economic benefits constrained by the supply and demand of byproducts, leading to their gradual market obsolescence. Liquid-phase epoxidation, due to its green, environmentally friendly, clean, and efficient nature, is developing into an emerging process for PO production, with HPPO and CHPPO processes being typical examples. However, both of these liquid-phase processes require large-scale peroxide production units on-site, significantly limiting process layout. Therefore, in recent years, researchers have developed a new route for in-situ synthesis of hydrogen peroxide under a hydrogen and oxygen atmosphere, followed by propylene oxidation, to produce PO in a "one-step" process. This allows for more flexible industrial layout and meets the demands for clean, efficient, green, and low-carbon development.

[0005] Existing methods for the direct gas-phase preparation of PO utilize catalysts supported on titanium-silicon molecular sieves and noble metal nanoparticles. In these catalysts, titanium atoms on the titanium-silicon molecular sieves can combine with peroxides to form Ti-OOH active centers. The noble metal nanoparticles possess catalytic properties for hydrogen dissociation and oxygen activation, thus enabling the epoxidation of propylene to PO. However, the PO selectivity of existing titanium-silicon molecular sieve-supported noble metal nanoparticle catalysts is relatively low. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low PO selectivity in existing titanium-silicon molecular sieve-supported noble metal nanoparticle catalysts, and to provide a modified titanium-silicon molecular sieve, its preparation method, an epoxidation catalyst, its preparation method, and its application. Using the epoxidation catalyst incorporating the modified titanium-silicon molecular sieve of this invention to prepare propylene oxide can achieve high propylene conversion and high PO selectivity.

[0007] To achieve the above objectives, the present invention provides, in one aspect, a modified titanium-silicon molecular sieve, in...29 In the Si NMR spectrum, the ratio of the characteristic peak area of ​​the modified titanium-silicon molecular sieve near -113 ppm to the characteristic peak area near -103 ppm is >35; 1 In the H NMR spectrum, the ratio of the area of ​​the titanium hydroxyl peak near 3.5 ppm to the area of ​​the silanol nest characteristic peak near 2.1 ppm of the modified titanium silicate molecular sieve is ≥1.

[0008] The second aspect of the present invention provides a method for preparing modified titanium-silicon molecular sieves, the method comprising: silanizing the titanium-silicon molecular sieve with a silanizing agent, and then modifying the silanized titanium-silicon molecular sieve with an organoammonium as shown in formula (I), wherein the silanizing agent is at least one selected from hexamethyldisilazane, bis(trimethylsilylmethyl)sulfide, tri(isopropylthio)silane and (phenylthio)trimethylsilane;

[0009] In formula (I), at least one of R1, R2, R3, and R4 is a C10-C30 alkyl group or a C3-C18 cyclic hydrocarbon group, X - For OH - Cl - or Br - .

[0010] A third aspect of the present invention provides a modified titanium-silicon molecular sieve prepared by the above method.

[0011] A fourth aspect of the present invention provides an epoxidation catalyst comprising a support and a noble metal component supported on the support, wherein the support is a modified titanium-silicon molecular sieve provided by the present invention.

[0012] The fifth aspect of the present invention provides a method for preparing an epoxidation catalyst, the method comprising: preparing a modified titanium-silicon molecular sieve according to the method of the present invention, and then loading a noble metal component onto the modified titanium-silicon molecular sieve.

[0013] The sixth aspect of the present invention provides an epoxidation catalyst prepared by the above method.

[0014] The seventh aspect of the present invention provides a method for preparing propylene oxide, the method comprising: reacting hydrogen, oxygen and propylene in the presence of the epoxidation catalyst described above.

[0015] In the modified titanium-silicon molecular sieve described in this invention, the silanol content is reduced to a level lower than that of titanium hydroxyl groups, and the titanium hydroxyl groups are protected, facilitating subsequent loading of noble metal components. Furthermore, according to the epoxidation catalyst described in this invention, loading noble metal components reduces the titanium hydroxyl content, resulting in lower silanol and titanium hydroxyl content in the epoxidation catalyst. Therefore, using the epoxidation catalyst of this invention to prepare propylene oxide can achieve higher propylene conversion and higher PO selectivity, with significantly higher hydrogen efficiency and propylene oxide formation rate. Attached Figure Description

[0016] Figure 1 shows the modified titanium-silicon molecular sieves prepared in Example 1 and Comparative Example 1. 29 Si NMR spectrum;

[0017] Figure 2 shows the modified titanium-silicon molecular sieves prepared in Example 1 and Comparative Example 1. 1 H NMR spectrum;

[0018] Figure 3 shows the epoxidation catalysts prepared in Example 10 and Comparative Example 4. 29 Si NMR spectrum;

[0019] Figure 4 shows the epoxidation catalysts prepared in Example 10 and Comparative Example 4. 1 H NMR spectrum. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] In this invention, 1 The 1H NMR spectra were obtained using a Bruker AVANCE III 500MHz spectrometer, with the following parameters: Larmor frequency of 500.57MHz, MAS rotation rate of 14kHz, 4mm triple resonance probe, 4.0μs π / 2 pulse length, and 5s cycle delay. Samples were dehydrated before testing: at <10... -3 Under a pressure of Pa, the temperature is increased from room temperature to the final target temperature (673K) at a rate of 1K / min, held for at least 10 hours, and finally cooled to ambient temperature.

[0022] In this invention, 29 The Si NMR spectrum was measured using a Bruker Avance III 500MHz instrument with a 7mm WVT dual resonance probe, a resonance frequency of 99.28MHz, and a spectral width of 400ppm.

[0023] In this invention, the thermal weight loss rate is detected by a TA SDT Q600 synchronous differential thermal analyzer. During the test, 150-200 mg of sample is taken in air atmosphere, the test temperature range is 50-800℃, the heating rate is 10℃ / min, and a programmed temperature rise test is performed.

[0024] According to the modified titanium-silicon molecular sieve described in this invention, in 29 In the Si NMR spectrum, the ratio of the characteristic peak area near -113 ppm to the characteristic peak area near -103 ppm of the modified titanium-silicon molecular sieve is >35, preferably 40-80, and more preferably 55-70. This parameter indicates that the modified titanium-silicon molecular sieve has a very low silanol content. In this invention, "near -113 ppm" refers to -113 ppm ± 2 ppm; "near -103 ppm" refers to -103 ppm ± 2 ppm.

[0025] According to the modified titanium-silicon molecular sieve described in this invention, in 1 In the H NMR spectrum, the ratio of the area of ​​the titanium hydroxyl peak near 3.5 ppm to the area of ​​the characteristic peak of the silanol nest near 2.1 ppm in the modified titanium-silicon molecular sieve is ≥1, preferably 1.1-10, and more preferably 1.15-8. This parameter indicates that the content of silanols in the modified titanium-silicon molecular sieve is less than that of titanium hydroxyls. In this invention, "near 3.5 ppm" refers to 3.5 ppm ± 0.2 ppm; "near 2.1 ppm" refers to 2.1 ppm ± 0.1 ppm.

[0026] In the modified titanium-silicon molecular sieve of the present invention, the molar ratio of titanium to silicon can be 0.001-0.04:1, preferably 0.005-0.025:1.

[0027] According to the modified titanium-silicon molecular sieve described in this invention, in 1 In the 1H NMR spectrum, the sum of the characteristic peak areas of alkyl hydrogens in the range of 0-1.5 ppm accounts for less than 10% of the total peak area, preferably less than 5%, and more preferably less than 1%.

[0028] According to the modified titanium-silicon molecular sieve of the present invention, thermogravimetric analysis revealed that the thermal weight loss rate of the modified titanium-silicon molecular sieve is <1%, preferably <0.8%, and more preferably <0.5%.

[0029] The method for preparing the modified titanium-silicon molecular sieve of the present invention includes: silanizing the titanium-silicon molecular sieve with a silanizing agent, and then modifying the silanized titanium-silicon molecular sieve with an organic ammonium as shown in formula (I), wherein the silanizing agent is at least one selected from hexamethyldisilazane, bis(trimethylsilylmethyl) sulfide, tris(isopropylthio)silane, and (phenylthio)trimethylsilane.

[0030] In formula (I), at least one of R1, R2, R3, and R4 is a C10-C30 alkyl group or a C3-C18 cyclic hydrocarbon group, X - For OH - Cl - or Br - .

[0031] In the preparation method of the modified titanium-silicon molecular sieve, the silanization process may include: contacting the titanium-silicon molecular sieve with a mixed gas containing a silanizing agent for reaction.

[0032] During the silanization process, the mixed gas containing the silanizing agent may contain 0.01-1 vol% of the silanizing agent and 99-99.99 vol% of the protective gas. Preferably, the mixed gas containing the silanizing agent contains 0.1-0.8 vol% of the silanizing agent and 99.2-99.9 vol% of the protective gas. More preferably, the mixed gas containing the silanizing agent contains 0.4-0.6 vol% of the silanizing agent and 99.4-99.6 vol% of the protective gas. The protective gas may be nitrogen or an inert gas (such as argon).

[0033] During the silanization process, the conditions for the contact reaction may include: a temperature of 170-250℃, preferably 180-220℃; and a time of 0.5-2h, preferably 0.8-1.5h.

[0034] During the silanization process, the titanium-silicon molecular sieve can be any type of molecular sieve well known in the art. In a specific embodiment, the titanium-silicon molecular sieve is selected from at least one of TS-1 molecular sieve, TS-2 molecular sieve, Ti-Beta molecular sieve, and Ti-MWW molecular sieve. The molar ratio of titanium to silicon in the titanium-silicon molecular sieve can be 0.005-0.04:1, preferably 0.005-0.03:1.

[0035] In the preparation method of the modified titanium-silicon molecular sieve, the organic ammonium has the structural formula shown in formula (I).

[0036] In formula (I), at least one of R1, R2, R3, and R4 is a C10-C30 alkyl group or a C3-C18 cyclic hydrocarbon group, X - For OH - Cl - or Br - In a preferred embodiment, one, two, or three of R1, R2, R3, and R4 are selected from alkyl groups of C12-C28, aryl groups of C6-C12, and cycloalkyl groups of C6-10, and the remaining groups are alkyl groups of C1-C3.

[0037] In this invention, examples of C12-C28 alkyl groups may be selected from, but are not limited to, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, dodecyl, tetradecyl, hexadecyl, and octadecyl.

[0038] In this invention, examples of C6-C12 aryl groups may be selected from, but are not limited to, phenyl, benzyl, and tolyl.

[0039] In this invention, examples of C6-10 cycloalkyl groups may be selected from, but are not limited to, cyclohexyl, cyclopropyl, and adamantyl.

[0040] In this invention, examples of C1-C3 alkyl groups can be methyl, ethyl, or propyl.

[0041] In some embodiments, in the organic ammonium shown in formula (I), any one of R1, R2, R3 and R4 is a C12-C28 alkyl group, and the other three are C1-C3 alkyl groups. Examples of this embodiment include docosyltrimethylammonium chloride, octadecyltrimethylammonium chloride, etc.

[0042] In other embodiments, in the organic ammonium shown in formula (I), any two of R1, R2, R3 and R4 are C12-C28 alkyl groups, and the other two are C1-C3 alkyl groups. Examples of this embodiment include dodecyl dimethyl ammonium chloride, dimethyl di(octadecyl) ammonium bromide, etc.

[0043] In other embodiments, in the organic ammonium shown in formula (I), any three of R1, R2, R3 and R4 are C12-C28 alkyl groups, and the remaining one is a C1-C3 alkyl group. For example, methyltris(dodecyl)ammonium chloride is used as an example of this embodiment.

[0044] In other embodiments, in the organic ammonium shown in formula (I), any one of R1, R2, R3 and R4 is a C6-10 cycloalkyl group, and the other three are C1-C3 alkyl groups. As an example of this embodiment, cyclohexyltrimethylammonium chloride is an example.

[0045] In other embodiments, in the organic ammonium shown in formula (I), one of R1, R2, R3 and R4 is a C6-C12 aryl group, one is a C12-C28 alkyl group, and the remaining two are C1-C3 alkyl groups. As an example of this embodiment, benzyldodecyldimethylammonium chloride is used.

[0046] More preferably, the organic ammonium is at least one selected from the following: dodecyl dimethyl ammonium chloride, methyl tri(dodecyl) ammonium chloride, docosyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, cyclohexyl trimethyl ammonium chloride, dimethyl di(octadecyl) ammonium bromide, and benzyl dodecyl dimethyl ammonium chloride.

[0047] In the preparation method of the modified titanium-silicon molecular sieve, the process of modifying the silanized titanium-silicon molecular sieve with organic ammonium may include: mixing the silanized titanium-silicon molecular sieve, the organic ammonium and water to react, separating the resulting reaction product into solid and liquid phases, and then drying and calcining the separated solid.

[0048] During the modification process, the molar ratio of the titanium-silicon molecular sieve (calculated as SiO2) to the organic ammonium can be 1:0.001-0.5, preferably 1:0.001-0.2.

[0049] During the modification process, the conditions for the mixed reaction may include: a temperature of 100-250℃, preferably 180-220℃; and a time of 0.5-24h, preferably 8-15h.

[0050] During the modification process, the drying conditions may include: a temperature of 100-150℃ and a time of 1-5 hours.

[0051] During the modification process, the calcination conditions may include: a temperature of 450-650℃ and a time of 4-10h.

[0052] In this invention, because the titanium content of the titanium-silicon molecular sieve is inherently low, the content of titanium hydroxyl groups on the titanium-silicon molecular sieve is typically low, and significantly lower than the content of silanol groups. After modifying the titanium-silicon molecular sieve according to the method described in this invention, the content of silanol groups is reduced to a level lower than that of titanium hydroxyl groups, and the titanium hydroxyl groups are protected and not reduced during the modification process, facilitating the subsequent loading of noble metal components. Therefore, the modified titanium-silicon molecular sieve prepared according to the method has a lower hydroxyl content, particularly a lower silanol content, and the silanol content is lower than the titanium hydroxyl content.

[0053] The modified titanium-silicon molecular sieve prepared according to the method described in this invention, in 1 In the 1H NMR spectrum, the sum of the characteristic peak areas of alkyl hydrogens in the range of 0-1.5 ppm accounts for less than 10% of the total peak area, preferably less than 5%, and more preferably less than 1%. This parameter indicates that the modified titanium-silicon molecular sieve has been treated with an organic base (i.e., the organic ammonium shown in formula (I)) to essentially eliminate the silane groups introduced on the molecular sieve by the silanizing reagent used in the silanization process, thereby effectively exposing Ti-OH.

[0054] The modified titanium-silicon molecular sieve prepared according to the method of the present invention, by thermogravimetric analysis, showed that the thermal weight loss rate of the modified titanium-silicon molecular sieve was <1%, preferably <0.8%, and more preferably <0.5%. This parameter further indicates that the modified titanium-silicon molecular sieve, through organic base treatment, has essentially eliminated the silane groups introduced on the molecular sieve by the silanizing reagent used in the silanization process.

[0055] The epoxidation catalyst of the present invention contains a support and a noble metal component supported on the support, wherein the support is the modified titanium-silicon molecular sieve described above.

[0056] In the epoxidation catalyst of the present invention, based on the total weight of the epoxidation catalyst, the content of the noble metal component, calculated as metal element, is 0.01-1 wt%, preferably 0.04-0.95 wt%, more preferably 0.05-0.6 wt%, specifically, for example, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, or 0.6 wt%.

[0057] According to the epoxidation catalyst described in this invention, in 29 In the Si NMR spectrum, the ratio of the characteristic peak area near -113 ppm to the characteristic peak area near -103 ppm of the epoxidation catalyst is >35, preferably 40-80, and more preferably 55-70. This parameter indicates that the epoxidation catalyst contains very few silanol groups. In this invention, "near -113 ppm" refers to -113 ppm ± 2 ppm; "near -103 ppm" refers to -103 ppm ± 2 ppm.

[0058] According to the epoxidation catalyst described in this invention, in 1 In the 1H NMR spectrum, the ratio of the area of ​​the titanium hydroxyl peak near 3.5 ppm to the area of ​​the characteristic peak of the silanol nest near 2.1 ppm in the epoxidation catalyst is <1, preferably 0.1-0.99, more preferably 0.14-0.99. This parameter indicates that the content of titanium hydroxyl groups in the epoxidation catalyst is lower than that of silanol groups. In this invention, "near 3.5 ppm" refers to 3.5 ppm ± 0.2 ppm; "near 2.1 ppm" refers to 2.1 ppm ± 0.1 ppm.

[0059] It is evident that loading noble metal components significantly reduces the content of titanium hydroxyl groups, resulting in very low contents of both silanol and titanium hydroxyl groups in the final epoxidation catalyst.

[0060] According to the epoxidation catalyst described in this invention, in 1In the 1H NMR spectrum, the sum of the characteristic peak areas of alkyl hydrogens in the range of 0-1.5 ppm accounts for less than 10% of the total peak area, preferably less than 5%, and more preferably less than 1%.

[0061] According to the epoxidation catalyst of the present invention, thermogravimetric analysis revealed that the thermal weight loss rate of the epoxidation catalyst is <1%, preferably <0.8%, and more preferably <0.5%.

[0062] In the epoxidation catalyst of the present invention, preferably, the noble metal in the noble metal component is at least one of gold, palladium and platinum.

[0063] The preparation method of the epoxidation catalyst of the present invention includes: preparing a modified titanium-silicon molecular sieve according to the method described above, and then loading a noble metal component onto the modified titanium-silicon molecular sieve.

[0064] In the preparation method of the epoxidation catalyst, the process of loading noble metal components onto the modified titanium-silicon molecular sieve can be carried out by deposition precipitation. Preferably, the specific process of loading noble metal components onto the modified titanium-silicon molecular sieve includes: mixing the modified titanium-silicon molecular sieve with an aqueous solution of a noble metal precursor, adjusting the pH of the resulting mixture to alkaline and reacting it, performing solid-liquid separation on the mixture obtained after the reaction, and activating the separated solid.

[0065] The noble metal precursor may be at least one of chloroauric acid, palladium chloride, chloroplatinic acid, gold acetate, palladium sulfate, and sodium hexachloroplatinate.

[0066] The concentration of the aqueous solution of the noble metal precursor can be 0.001-0.1 mol / L, preferably 0.005-0.05 mol / L.

[0067] In a preferred embodiment, the amount of the noble metal precursor, calculated as metal element, is 0.05-6 parts by weight relative to 100 parts by weight of the modified titanium-silicon molecular sieve, more preferably 0.2-5 parts by weight, and even more preferably 0.25-3 parts by weight. By adjusting the amounts of the modified titanium-silicon molecular sieve and the noble metal precursor, the content of the noble metal component in the prepared epoxidation catalyst is made to be in the range of 0.01-1% by weight, preferably in the range of 0.05-0.6% by weight.

[0068] In a preferred embodiment, the pH of the mixture of the modified titanium silicate molecular sieve and the aqueous solution of the noble metal precursor is adjusted to 7-9.

[0069] In this invention, the pH adjuster used for adjustment may be selected from at least one of sodium hydroxide, potassium hydroxide, cesium hydroxide, urea, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, and cesium bicarbonate.

[0070] During the loading of noble metal components, the reaction can be carried out at room temperature for 15-48 hours.

[0071] During the loading of noble metal components, the solid-liquid separation process can be carried out in accordance with solid-liquid separation methods well known to those skilled in the art, such as filtration, centrifugation, etc.

[0072] During the loading of noble metal components, the activation conditions may include: a temperature of 150-300℃ and a time of 1-5h.

[0073] The present invention also provides an epoxidation catalyst prepared by the above method. This epoxidation catalyst has a significantly lower hydroxyl content; specifically, the content of both silanol and titanium hydroxyl groups in the epoxidation catalyst is very low, and the content of titanium hydroxyl groups is even lower than that of silanol.

[0074] The epoxidation catalyst prepared according to the method described in this invention, in... 1 In the 1H NMR spectrum, the sum of the characteristic peak areas of alkyl hydrogens in the range of 0-1.5 ppm accounts for less than 10% of the total peak area, preferably less than 5%, and more preferably less than 1%. This parameter indicates that the epoxidation catalyst is substantially free of silane groups introduced by silanization treatment.

[0075] The epoxidation catalyst prepared according to the method of the present invention exhibits a thermal weight loss rate of <1%, preferably <0.8%, and more preferably <0.5%, as revealed by thermogravimetric analysis. This parameter further indicates that the epoxidation catalyst is substantially free of silane groups introduced by silanization treatment.

[0076] The present invention also provides a method for preparing propylene oxide, the method comprising: reacting hydrogen, oxygen and propylene in the presence of the epoxidation catalyst described above.

[0077] In this invention, the preparation method of propylene oxide can be carried out in a continuous operation mode. Specifically, after the epoxidation catalyst is loaded into the reactor, a mixture of hydrogen, oxygen, propylene, and a protective gas is continuously added to carry out the reaction. The volumetric flow rate ratio of hydrogen, oxygen, and propylene can be 0.5-2:0.5-2:1. The volumetric flow rate ratio of propylene to the protective gas can be 1:1-10.

[0078] In the method for preparing propylene oxide, the reaction conditions may include: a temperature of 100-250°C, preferably 120-200°C; and a pressure of 0.1-0.7 MPa, preferably 0.1-0.5 MPa. In this invention, pressure refers to absolute pressure.

[0079] In the method for preparing propylene oxide, the protective gas can be nitrogen and / or an inert gas (such as argon).

[0080] In the method for preparing propylene oxide, the separation of the reaction product from the epoxidation catalyst can be adjusted according to the catalyst morphology and actual needs. For example, when the epoxidation catalyst is in powder form, the product can be separated and the catalyst can be recovered and reused through sedimentation, filtration, centrifugation, evaporation, membrane separation, etc.; when the epoxidation catalyst is in the form of a molded catalyst, the molded catalyst can be loaded into a fixed-bed reactor, and the catalyst can be recovered after the reaction is completed.

[0081] In this invention, by using the epoxidation catalyst provided by this invention, a significantly higher propylene conversion rate and propylene oxide selectivity can be obtained in the preparation process of propylene oxide.

[0082] The modified titanium-silicon molecular sieve, its preparation method, and the epoxidation catalyst, its preparation method, and their applications are further illustrated below through examples. These examples are implemented based on the technical solutions of this invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this invention is not limited to the following examples.

[0083] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0084] Example 1

[0085] 20g of titanium silicate molecular sieve was placed in a tubular reactor, and a mixture of hexamethyldisiloxane and nitrogen was introduced at 200℃ (wherein the concentration of hexamethyldisiloxane was 0.5% by volume). The gas flow rate of the mixture was 35mL / min, and the treatment was continued for 1h.

[0086] The silanized titanium-silicon molecular sieve sample was placed in a reaction vessel. An organic ammonium aqueous solution was prepared according to the ratio of n(titanium-silicon molecular sieve, calculated as SiO2):n(benzyldodecyldimethylammonium chloride):n(water) = 1:0.1:20, and then added to the reaction vessel. The mixture of titanium-silicon molecular sieve and organic ammonium aqueous solution was placed in a sealed reaction vessel and reacted at 200℃ for 10 h. The resulting suspension was then filtered, and the separated solid was dried at 120℃ for 2 h, and then calcined at 550℃ for 6 h to obtain modified titanium-silicon molecular sieve A1. The material ratio is shown in Table 1, and the product characterization is shown in Table 2.

[0087] Examples 2-9

[0088] Modified titanium-silicon molecular sieves were prepared according to the method of Example 1. The proportions and synthesis conditions are shown in Table 1. Other conditions are the same as in Preparation Example 1. Modified titanium-silicon molecular sieves A2 to A9 were prepared respectively. The product characterization is shown in Table 2.

[0089] Comparative Example 1

[0090] Commercially purchased TS-1 molecular sieves, without processing, are called titanium-silicon molecular sieve D1.

[0091] Among them, the titanium-silicon molecular sieves of Example 1 and Comparative Example 1 29 The Si NMR spectrum is shown in Figure 1.

[0092] Comparative Example 2

[0093] 1.0 g of TS-1 powder was added to a mixed solution consisting of 1.5 g of hexadecyltrimethylammonium bromide, 210 mL of H2O, 100 mL of ethanol, 2.4 mL of ammonia, and 30 mL of diethyl ether. After sonication for 10 minutes and stirring for 30 minutes at 25 °C, 1.5 mL of tetraethyl silicate was added dropwise to the solution. The resulting mixture was stirred at 25 °C for 6 hours. The final product was centrifuged, washed, dried at 100 °C for 12 hours, and finally calcined at 550 °C for 6 hours to obtain modified titanium silicate molecular sieve D2.

[0094] Comparative Example 3

[0095] 10 g of TS-1 molecular sieve was mixed with 4.8 g of a 28 wt% tetraethylammonium hydroxide solution. The mixture was then placed in a polytetrafluoroethylene liner on a support, and 2 ml of water was added under the support. The mixture was reacted in a sealed autoclave at 145 °C for 12 h. After treatment, the sample was dried and calcined to obtain modified titanium-silicon molecular sieve D3.

[0096] Comparative Example 4

[0097] 20g of titanium-silicon molecular sieve was placed in a tubular reactor, and a mixed gas of hexamethyldisiloxane and nitrogen (the concentration of hexamethyldisiloxane was 0.5% by volume) was introduced at 200℃. The gas flow rate of the mixed gas was 35mL / min, and the treatment was continued for 1h to obtain modified titanium-silicon molecular sieve D4. The material ratio is shown in Table 1, and the product characterization is shown in Table 2.

[0098] Comparative Example 5

[0099] Titanium silicate molecular sieves were placed in a reactor. An organic ammonium aqueous solution was prepared according to the ratio of n(titanium silicate molecular sieve, calculated as SiO2):n(benzyldodecyldimethylammonium chloride):n(water) = 1:0.1:20, and then added to the reactor. The mixture of titanium silicate molecular sieves and organic ammonium aqueous solution was placed in a sealed reactor and reacted at 200℃ for 10 h. The resulting suspension was then filtered, and the separated solid was dried at 120℃ for 2 h, and then calcined at 550℃ for 6 h to obtain modified titanium silicate molecular sieve D5. The material ratios are shown in Table 1, and the product characterization is shown in Table 2.

[0100] Comparative Example 6

[0101] Modified titanium-silicon molecular sieves were prepared according to the method in Example 1, except that trimethylchlorosilane was used instead of hexamethyldisiloxane for silanization treatment with the same molar amount, and the modified titanium-silicon molecular sieve D6 was finally obtained. The material ratio is shown in Table 1 and the product characterization is shown in Table 2.

[0102] Comparative Example 7

[0103] Titanium silicate molecular sieves were placed in a reactor, and an organic ammonium aqueous solution was prepared according to the ratio of n(titanium silicate molecular sieve, calculated as SiO2):n(benzyldodecyldimethylammonium chloride):n(water) = 1:0.1:20. This solution was then added to the reactor. The mixture of titanium silicate molecular sieves and the organic ammonium aqueous solution was placed in a sealed reactor and reacted at 200°C for 10 hours. The resulting suspension was then filtered, and the separated solid was dried at 120°C for 2 hours, followed by calcination at 550°C for 6 hours to obtain the organic ammonium-modified titanium silicate molecular sieve.

[0104] 20g of organoammonium-modified titanium-silicon molecular sieve was placed in a tubular reactor. A mixed gas of hexamethyldisiloxane and nitrogen (with hexamethyldisiloxane concentration of 0.5% by volume) was introduced at 200℃ at a gas velocity of 35mL / min for 1 hour to obtain modified titanium-silicon molecular sieve D7. The material ratio is shown in Table 1, and the product characterization is shown in Table 2.

[0105] Table 1 Note: The molar ratio of modified materials refers to the molar ratio of titanium silicon molecular sieve, organic ammonium and water.

[0106] Table 2 Note: ① is in 29 The ratio of the characteristic peak area of ​​the modified titanium-silicon molecular sieve at -113 ppm to that at -103 ppm in the Si NMR spectrum; ② is in 1 The percentage of the area of ​​the titanium hydroxyl peak at 3.5 ppm in the modified titanium silicate molecular sieve in the total peak area; ③ is in 1The percentage of the area of ​​the characteristic peak of the silanol nest at 2.1 ppm in the modified titanium-silicon molecular sieve in the 1H NMR spectrum; ④ is in 1 The ratio of the area of ​​the titanium hydroxyl peak at 3.5 ppm to the area of ​​the silanol nest characteristic peak at 2.1 ppm in the 1H NMR spectrum of the modified titanium silicate molecular sieve. 1 The total peak area in the H NMR spectrum is equal to the peak area of ​​1.7 ppm + the peak area of ​​2.1 ppm + the peak area of ​​3.5 ppm.

[0107] Example 10

[0108] The modified titanium-silicon molecular sieve A1 was mixed with a 0.05 mol / L aqueous solution of a noble metal precursor. The amount of the noble metal precursor, calculated as metal element, was 2.5 wt% of the modified titanium-silicon molecular sieve A1. Then, a pH adjuster was added to adjust the pH of the resulting mixture to 8.1. The reaction was carried out for 24 h. The resulting suspension was filtered, and the separated solid (i.e., filter residue) was activated at 200 °C for 2 h to obtain the epoxidation catalyst Cat-1. The material ratio is shown in Table 3, and the product characteristics are shown in Table 4.

[0109] Examples 11-22 and Comparative Examples 8-16

[0110] The epoxidation catalyst was prepared according to the method of Example 10. The material ratio and synthesis conditions are shown in Table 3. Other conditions are the same as in Example 10. Epoxidation catalysts Cat-2 to Cat-13 and Cat-D1 to Cat-D9 were prepared respectively. The product characteristics are shown in Table 4.

[0111] Table 3

[0112] Table 4 Note: ① is in 29 The ratio of the characteristic peak area of ​​the epoxidation catalyst at -113 ppm to the characteristic peak area at -103 ppm in the Si NMR spectrum; ② is in 1 The percentage of the total peak area of ​​the titanium hydroxyl peak at 3.5 ppm in the ¹H NMR spectrum of the epoxidized catalyst; ③ is in 1 The percentage of the total peak area of ​​the silanol nest characteristic peak at 2.1 ppm in the 1H NMR spectrum of the epoxidized catalyst; ④ is in 1 The ratio of the area of ​​the titanium hydroxyl peak at 3.5 ppm to the area of ​​the silanol nest characteristic peak at 2.1 ppm in the 1H NMR spectrum of the epoxidized catalyst.

[0113] Test case

[0114] This test example illustrates the reaction effect of the epoxidation catalyst samples prepared in the above examples and comparative examples in the gas-phase epoxidation reaction of propylene. All reagents used in this test example were commercially available chemically pure reagents. The concentrations of each substance after the reaction were quantitatively analyzed using gas chromatography. The instrument used was an Agilent 6890 gas chromatograph, with a molecular sieve 5A and a PoraBOND U column, and FID and TCD detectors.

[0115] The epoxidation catalyst samples prepared in the above examples and comparative examples were respectively loaded onto a tubular reactor with an inner diameter of 8 mm for evaluation. The catalyst dosage was 0.4 g, and the flow rates of hydrogen, oxygen, propylene, and nitrogen were 2 mL / min, 2 mL / min, 2 mL / min, and 14 mL / min, respectively. The reaction pressure was 0.1 MPa. After the catalyst was loaded into the reactor, the temperature was raised to 180 °C in a N2 atmosphere, and hydrogen, oxygen, and propylene were introduced to start the reaction. After 1 h of reaction, the products were analyzed online. The propylene conversion rate, propylene oxide selectivity, and hydrogen efficiency were calculated according to the following formulas, and the propylene oxide formation rate (i.e., PO formation rate) was detected. The results are shown in Table 5.

[0116] Propylene conversion rate % = (Moles of propylene in feedstock - Moles of propylene in product) / Moles of propylene in feedstock × 100%

[0117] Propylene oxide selectivity % = (Number of moles of propylene oxide in the product / Total number of moles of the product) × 100%

[0118] Hydrogen efficiency % = (Moles of propylene oxide in the product) / (Moles of hydrogen in the feedstock - Moles of hydrogen in the product) × 100%

[0119] Table 5

[0120] As shown in Table 5, the preparation of propylene oxide using the epoxidation catalyst of the present invention can achieve a high propylene conversion rate and a high PO selectivity, and the hydrogen efficiency and propylene oxide formation rate are both significantly higher.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified titanium silicalite zeolite characterized by, In 29 In the Si NMR spectrum, the ratio of the characteristic peak area of the modified titanium silicalite in the vicinity of -113 ppm to the characteristic peak area in the vicinity of -103 ppm is > 35; and 1 In the H NMR spectrum, the ratio of the titanium hydroxyl peak area of the modified titanium silicalite in the vicinity of 3.5 ppm to the silicon hydroxyl nest characteristic peak area in the vicinity of 2.1 ppm is ≥ 1.

2. The modified titanium silicalite zeolite of claim 1, wherein, In 29 The modified titanium silicalite has a ratio of the area of the characteristic peak in the Si NMR spectrum in the vicinity of -113 ppm to the area of the characteristic peak in the vicinity of -103 ppm of 40 to 80.

3. The modified titanium silicalite zeolite according to claim 1 or 2, characterized in that, In 1 The modified titanium silicalite has a ratio of the area of the titanium hydroxyl peak in the H NMR spectrum near 3.5 ppm to the area of the silicon hydroxyl nest characteristic peak near 2.1 ppm of 1.1 to 10.

4. The modified titanium silicalite zeolite according to any one of claims 1 to 3, characterized in that The molar ratio of titanium to silicon in the modified titanium-silicon molecular sieve is 0.001-0.04:1, preferably 0.005-0.025:

1.

5. A process for the preparation of a modified titanium silicalite zeolite characterized by, The method comprises: subjecting the titanium silicalite molecular sieve to silanization treatment using a silanization agent, and then modifying the titanium silicalite molecular sieve subjected to the silanization treatment with an organic ammonium represented by formula (I), wherein the silanization agent is at least one of hexamethyldisilathiane, bis(trimethylsilylmethyl)sulfide, tris(isopropylthio)silane and (phenylthio)trimethylsilane. In formula (I), at least one of R1, R2, R3and R4is a C10-C30 alkyl group or a C3-C18 cycloalkyl group, X - is OH - , Cl - or Br - .

6. The method of claim 5, wherein, In formula (I), one, two or three of R1, R2, R3 and R4 are selected from alkyl groups of C12-C28, aryl groups of C6-C12 and cycloalkyl groups of C6-10, and the remaining groups are alkyl groups of C1-C3.

7. The method according to claim 5 or 6, characterized in that, The organic ammonium is at least one of the following: didodecyl dimethyl ammonium chloride, methyl tri(dodecyl) ammonium chloride, docosyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, cyclohexyl trimethyl ammonium chloride, dimethyl di(octadecyl) ammonium bromide, and benzyl dodecyl dimethyl ammonium chloride.

8. The method according to any one of claims 5-7, characterized in that, The silanization process includes: contacting the titanium-silicon molecular sieve with a mixed gas containing a silanizing agent for reaction; Preferably, the mixed gas contains 0.01-1 vol% of a silanizing agent and 99-99.99 vol% of a protective gas; Preferably, the reaction conditions include a temperature of 170-250°C and a time of 0.5-2 hours.

9. The method according to claim 5 or 8, characterized in that, The titanium-silicon molecular sieve is at least one of TS-1 molecular sieve, TS-2 molecular sieve, Ti-Beta molecular sieve and Ti-MWW molecular sieve.

10. The method according to any one of claims 5-9, characterized in that, The modification process includes: mixing and reacting the silanized titanium-silicon molecular sieve, the organic ammonium and water, separating the resulting reaction product into solid and liquid phases, and then drying and calcining the separated solid. Preferably, the molar ratio of the titanium-silicon molecular sieve (calculated as SiO2) to the organic ammonium is 1:0.001-0.5, more preferably 1:0.001-0.2; Preferably, the reaction conditions include: a temperature of 100-250°C and a time of 0.5-24 hours; Preferably, the calcination conditions include: a temperature of 450-650℃ and a time of 4-10h.

11. A modified titanium-silicon molecular sieve prepared by the method according to any one of claims 5-10.

12. An epoxidation catalyst comprising a support and a noble metal component supported on said support, characterized in that, The carrier is the modified titanium-silicon molecular sieve according to any one of claims 1-4 and 11.

13. The epoxidation catalyst of claim 12, wherein Based on the total weight of the epoxidation catalyst, the content of the noble metal component, calculated as metal element, is 0.01-1% by weight, preferably 0.05-0.6% by weight.

14. The epoxidation catalyst according to claim 12 or 13, characterized in that, In 29 In the Si NMR spectrum, the ratio of the area of the characteristic peak located near -113 ppm to the area of the characteristic peak located near -103 ppm is > 35, preferably 55-70.

15. The epoxidation catalyst according to any one of claims 12 to 14, characterized in that, In 1 The ratio of the area of the titanium hydroxyl peak in the H NMR spectrum, located near 3.5 ppm, to the area of the characteristic peak of silicon hydroxyl nests, located near 2.1 ppm, of the epoxidation catalyst is < 1, preferably 0.1 to 0.

99.

16. The epoxidation catalyst according to any one of claims 12 to 15, characterized in that, The precious metal in the precious metal component is at least one of gold, palladium and platinum.

17. A process for the preparation of an epoxidation catalyst, characterized in that The method includes: preparing a modified titanium-silicon molecular sieve according to any one of claims 5-10, and then loading a noble metal component onto the modified titanium-silicon molecular sieve.

18. The method of claim 17, wherein, The process of loading noble metal components onto the modified titanium-silicon molecular sieve is carried out by a deposition-precipitation method; Preferably, the amount of the noble metal precursor used, calculated as metal element, is 0.05-6 parts by weight, more preferably 0.2-5 parts by weight, relative to 100 parts by weight of the modified titanium-silicon molecular sieve. Preferably, the noble metal precursor is at least one selected from chloroauric acid, palladium chloride, chloroplatinic acid, gold acetate, palladium sulfate, and sodium hexachloroplatinate.

19. An epoxidation catalyst prepared by the method of claim 17 or 18.

20. A process for the preparation of propylene oxide, characterized by, The method includes reacting hydrogen, oxygen and propylene in the presence of the epoxidation catalyst of any one of claims 12-16 and 19.

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