A titanium-silicate molecular sieve catalyst, its preparation method and application

Abstract

The present invention provides a titanium silicalite molecular sieve catalyst, a preparation method thereof, and an application thereof. The R 1121 / R 800 of the titanium silicalite molecular sieve catalyst is 0.1 to 4, where R 1121 is the maximum absorption peak intensity at around 1121 cm ‑1 in the ultraviolet-Raman spectrum of the titanium silicalite molecular sieve catalyst, and R 800 is the maximum absorption peak intensity at around 800 cm ‑1 in the ultraviolet-Raman spectrum of the titanium silicalite molecular sieve catalyst; the most probable pore diameter of the titanium silicalite molecular sieve catalyst is 15 to 36 nm. The titanium silicalite molecular sieve catalyst of the present invention has a high framework titanium content and an appropriate most probable pore diameter, and has high raw material conversion rate and product selectivity. The preparation method of the titanium silicalite molecular sieve catalyst of the present invention includes two hydrothermal crystallizations, and after the first hydrothermal crystallization is completed, there is no need to perform operations such as solid-liquid separation, drying, and calcination on the material after the first hydrothermal crystallization, which not only simplifies the process flow for preparing the titanium silicalite molecular sieve catalyst, but also can regulate the realization of the most probable pore diameter by controlling parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve preparation, and particularly relates to a titanium silicate molecular sieve catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The titanium silicate molecular sieve catalyst TS-1 is a Pentasil type heteroatom molecular sieve containing framework titanium atoms. In addition to maintaining the topological structure of the original MFI molecular sieve, the titanium atoms in TS-1 are evenly distributed in the framework to form framework Si-O-Ti bonds with special properties, which makes the TS-1 molecular sieve have both catalytic oxidation activity and shape-selective catalytic performance.

[0003] Since the synthesis method of TS-1 was first disclosed (USP4410501) in 1981, the hydrothermal synthesis method of TS-1 has developed into two systems. One is to use tetrapropylammonium hydroxide (TPAOH) as a template to synthesize the titanium silicate molecular sieve catalyst, also known as the classical system; the other is to use inexpensive tetrapropylammonium bromide as a template to synthesize TS-1, which is called the inexpensive system; in addition, there are also various methods such as isomorphous substitution. Although there are various synthesis methods, due to the fact that the Ti-O bond in the TS-1 structure is longer than the Si-O bond, it is difficult for titanium atoms to enter the framework during synthesis. Therefore, the TS-1 synthesized by the existing methods will produce non-framework titanium. Non-framework titanium itself does not have catalytic oxidation activity and will also cause a large amount of decomposition of hydrogen peroxide, thereby reducing the catalytic performance of TS-1; further considering that it is difficult to control the content of non-framework titanium during the synthesis process, this results in poor stability and catalytic performance of the titanium silicate molecular sieve catalyst product, restricting the industrial application of TS-1. In addition, it should also be noted that in order to prepare a highly active titanium silicate molecular sieve catalyst, the synthesized molecular sieve raw powder needs to be subjected to acid-base modification or rearrangement crystallization in industrial production, which makes the preparation process of the TS-1 molecular sieve longer, increases the production cost, and also generates a large amount of wastewater, restricting the improvement of production capacity. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention discloses a titanium silicate molecular sieve catalyst, a preparation method thereof, and an application thereof. The titanium silicate molecular sieve catalyst has a high framework titanium content and an appropriate most probable pore diameter, and the preparation process flow is relatively simpler than the prior art. The titanium silicate molecular sieve catalyst has high raw material conversion rate and product selectivity in the reaction of epoxidizing propylene to produce propylene oxide.

[0005] On the one hand, the present invention discloses a titanium silicate molecular sieve catalyst, and the R of the titanium silicate molecular sieve catalyst 1121 / R 800 is 0.1 to 4, and R 1121 is the 1121 cm in the ultraviolet-Raman spectrum of the titanium silicate molecular sieve catalyst -1The intensity of the maximum absorption peak at the vicinity, R 800 is the intensity of the maximum absorption peak at the vicinity of 800 cm -1 in the ultraviolet-Raman spectrum of the titanium silicalite molecular sieve catalyst; the most probable pore diameter of the titanium silicalite molecular sieve catalyst is 15-36 nm.

[0006] In the above technical solution, the titanium silicalite molecular sieve catalyst of the present invention has a high framework titanium content and an appropriate most probable pore diameter. Combining the examples and the comparative examples, it can be seen that the titanium silicalite molecular sieve catalyst of the present invention is suitable for catalytic propylene epoxidation reaction and has high raw material conversion rate and product selectivity.

[0007] Further, the R 1121 / R 800 of the titanium silicalite molecular sieve catalyst is 0.1, and the most probable pore diameter is 35.

[0008] Further, the R 1121 / R 800 of the titanium silicalite molecular sieve catalyst is 3.5, and the most probable pore diameter is 17.

[0009] Another aspect of the present invention discloses a preparation method of a titanium silicalite molecular sieve catalyst, which method includes two hydrothermal crystallizations; a first silicon source and a titanium source are subjected to a first hydrothermal crystallization in an aqueous solution of a first template agent; after the first hydrothermal crystallization is completed, a pressure relief operation is carried out, and then a second silicon source, a second template agent and an organic amine are added for a second hydrothermal crystallization to obtain a secondary hydrothermal crystallization mixture.

[0010] It should be noted that the preparation process of the titanium silicalite molecular sieve catalyst of the present invention is carried out in a reaction kettle. The present invention does not limit the reaction kettle used. The broad understanding of the reaction kettle used in the present invention is a container for physical or chemical reactions. Through the structural design and parameter configuration of the container, the heating, evaporation, cooling and mixing functions of low and high speeds required by the process are realized. Those of ordinary skill in the art can select a suitable reaction kettle through non-creative labor, and the technical solutions formed therefrom are all within the protection scope of the present invention.

[0011] In the above technical solution, there is no need to carry out operations such as solid-liquid separation, drying, roasting, etc. on the material after the first hydrothermal crystallization, and the second silicon source, the second template agent and the organic amine can be directly added to the reaction kettle for the second hydrothermal crystallization. Thus, not only the process flow of preparing the titanium silicalite molecular sieve catalyst is simplified, but also the realization of the most probable pore diameter can be regulated by controlling parameters.

[0012] Further, in the first hydrothermal crystallization, the molar ratio of Si in the first silicon source, Ti in the titanium source, the first template agent and water is 1:(0.01-0.5):(0.03-0.6):(1-100), and the preferred molar ratio is 1:(0.1-0.5):(0.2-0.6):(60-80).

[0013] Furthermore, in order to promote full reaction, the first hydrothermal crystallization further includes adding the first silicon source and titanium source to an aqueous solution of a template agent and then stirring, with the stirring time being 0.5 h to 24 h and the stirring temperature being 0 to 60°C.

[0014] Furthermore, the temperature of the first hydrothermal crystallization is 100 to 300°C and the time is 10 to 100 h.

[0015] Furthermore, the gas discharged during the pressure relief operation is condensed to obtain a condensate, and the mass of the condensate accounts for 5% to 50% of the total weight of the material after the first hydrothermal crystallization is completed; preferably 10% to 49%.

[0016] In the above technical solution, the water content in the material after the first hydrothermal crystallization is relatively large, resulting in a relatively low concentration of the newly added second template agent during the second hydrothermal crystallization, thereby further leading to low reaction efficiency; moreover, the high water content also increases the time for the subsequent solid-liquid separation operation of the secondary hydrothermal crystallization mixture and is also prone to cause material loss. In addition, the condensate mainly includes water and substances produced by the decomposition of the first template agent during the first hydrothermal crystallization process; the substances produced by the decomposition of the first template agent not only affect the quality of the finished titanium-silicon molecular sieve catalyst but also float on the upper layer of the reaction material and adhere to the surface of the reaction kettle during the subsequent crystallization process, affecting the crystallization efficiency and increasing the cleaning difficulty of the reaction kettle. Therefore, the present invention sets a pressure relief operation after the first hydrothermal crystallization is completed, which not only facilitates the subsequent second hydrothermal crystallization, reduces the subsequent treatment difficulty, but also improves the quality of the titanium-silicon molecular sieve catalyst and the overall preparation efficiency, and reduces the equipment cleaning difficulty.

[0017] Furthermore, in the second hydrothermal crystallization, the molar ratio of the second silicon source, the second template agent, the organic amine, and water is 1:(0.01 to 0.5):(0.03 to 0.6):(1 to 100).

[0018] Furthermore, in order to promote full reaction, the second hydrothermal crystallization further includes stirring after adding the second silicon source, the second template agent, and the organic amine, with the stirring time being 0.5 h to 24 h and the stirring temperature being 0 to 60°C.

[0019] Furthermore, the temperature of the second hydrothermal crystallization is 100 to 300°C, the time is 10 to 100 h, and preferably 60 to 100 h.

[0020] The first silicon source and the second silicon source are each independently selected from one or more of inorganic silicon or organosilicon grease; the inorganic silicon includes silica sol, silicon dioxide, and white carbon black; the general formula of the organosilicon grease is Si(OR1)4, where R1 is an alkyl substituent having 1 to 6 carbon atoms.

[0021] Further, the titanium source is one or more of inorganic titanium sources or organic titanates; the inorganic titanium includes titanium tetrachloride and titanium sulfate; the general formula of the organic titanate is Ti(OR 2 )4, where R 2 is an alkyl substituent having 2 to 6 carbon atoms.

[0022] Further, the first template agent is one or more of quaternary ammonium bases or quaternary ammonium salts; the quaternary ammonium bases include tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, and tetrabutylammonium hydroxide; the quaternary ammonium salts include tetrapropylammonium bromide, tetrapropylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride.

[0023] Further, the second template agent is a quaternary ammonium salt; the quaternary ammonium salts include one or more of tetrapropylammonium bromide, tetrapropylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride.

[0024] Further, the organic amine is one or more of aliphatic amine compounds, alkanolamine compounds, or aromatic amine compounds; the aliphatic amine compounds include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, n-butylamine, isobutylamine, tert-butylamine, sec-butylamine, butanediamine, diisobutylamine, pentylamine, isopentylamine, sec-pentylamine, cyclopentylamine, propylamine, dipropylamine, tripropylamine, isopropylamine, diisopropylamine; the alkanolamine compounds include monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, butyldiethanolamine; the aromatic amine compounds include aniline, toluidine, phenylenediamine.

[0025] Further, the above technical solution further includes solid-liquid separation of the secondary hydrothermal crystallization mixture to obtain a solid phase, and drying and baking the solid phase.

[0026] Furthermore, the drying is carried out at a temperature of 50 to 200 °C. In the present invention, the drying time is not limited. Those skilled in the art can set a suitable solid-phase drying time in combination with the calcination operation as needed. In some working conditions, the drying operation is not required, and the separated solid phase can be directly calcined; the calcination is carried out at a temperature of 350 to 700 °C, and the calcination time is 1 to 8 h.

[0027] Another aspect of the present invention discloses the application of the above titanium silicalite catalyst or the titanium silicalite catalyst prepared by the above preparation method in the propylene epoxidation reaction; further, the propylene epoxidation reaction is a reaction for preparing propylene oxide by propylene epoxidation.

[0028] Compared with the prior art, the titanium silicalite molecular sieve catalyst of the present invention has a high framework titanium content and an appropriate most probable pore diameter, is suitable for the propylene epoxidation reaction, and has high raw material conversion rate and product selectivity. In the preparation method of the titanium silicalite molecular sieve catalyst of the present invention, pressure relief operation is carried out after the first hydrothermal crystallization is completed, and then without performing operations such as solid-liquid separation, drying, and roasting on the material after the first hydrothermal crystallization, the second silicon source, the second template agent, and organic amine can be directly added for the second hydrothermal crystallization, which not only simplifies the process flow of preparing the titanium silicalite molecular sieve catalyst, but also can regulate the realization of the most probable pore diameter by controlling parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0030] Figure 1 It is the electron microscope morphology diagram of the titanium silicalite molecular sieve catalyst prepared in Example 6;

[0031] Figure 2 It is the ultraviolet-Raman spectrum diagram of the titanium silicalite molecular sieve catalyst prepared in Example 3;

[0032] Figure 3 It is the comparison diagram of the mesopore sizes of the titanium silicalite molecular sieve catalysts prepared in Example 6 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] For the convenience of understanding the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods used are all conventional methods unless otherwise specified.

[0034] It should be noted that the relative terms such as "first time" and "second time" in this embodiment are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components. The features defined with "first time" and "second time" may explicitly or implicitly include one or more of such features.

[0035] Example 1

[0036] This example is carried out in a reaction kettle and includes the following operations:

[0037] (1) Mix methyl orthosilicate and titanium tetrachloride, and then add the mixture to an aqueous solution of tetramethylammonium hydroxide and stir well. The stirring temperature is 0 °C and the stirring time is 24 h to obtain a hydrolysis solution of the silicon source and titanium source. The molar ratio of Si, Ti, tetramethylammonium hydroxide and water is 1:0.01:0.03:1. Subsequently, carry out the first hydrothermal crystallization at 150 °C, and the hydrothermal crystallization time is 96 h.

[0038] (2) After the first hydrothermal crystallization is completed, release the pressure of the reaction kettle. Subsequently, add silica sol, tetrapropylammonium bromide, n-butylamine and water and stir. The stirring temperature is 0 °C and the stirring time is 24 h. Among them, the molar ratio of silica sol, tetrapropylammonium bromide, n-butylamine and water is 1:0.01:0.03:1. Carry out the second hydrothermal crystallization at 100 °C, and the hydrothermal crystallization time is 100 h to obtain a secondary hydrothermal crystallization mixture. Among them, the mass of the condensate obtained after condensing the output gas after pressure release accounts for 5% of the total amount of the material after the first hydrothermal crystallization is completed.

[0039] (3) After the second hydrothermal crystallization is completed, carry out solid-liquid separation to obtain a solid phase. Dry the obtained solid phase at 50 °C, and then calcine it at 700 °C for 1 h to obtain titanium silicalite catalyst A1.

[0040] Example 2

[0041] The preparation process of the titanium silicalite catalyst in this example is the same as the steps shown in Example 1, but:

[0042] In step (1), the first silicon source, titanium source and first template agent are tetraethyl orthosilicate, titanium sulfate and tetrapropylammonium hydroxide respectively. The stirring temperature is 60 °C and the stirring time is 0.5 h. Among them, the molar ratio of Si:Ti:tetrapropylammonium hydroxide:water is 1:0.5:0.6:100. The temperature of the first hydrothermal crystallization is 100 °C and the time is 100 h.

[0043] In step (2), after pressure release, the second silicon source, second template agent and organic amine added are silica sol, tetrapropylammonium bromide and diethanolamine. The stirring temperature is 30 °C and the stirring time is 15 h. Among them, the molar ratio of silica sol, tetrapropylammonium bromide, diethanolamine and water is 1:0.5:0.6:100. The temperature of the second hydrothermal crystallization is 300 °C and the time is 10 h. The mass of the condensate accounts for 50% of the total amount of the material after the first hydrothermal crystallization is completed.

[0044] In step (3), after the second hydrothermal crystallization is completed, carry out solid-liquid separation to obtain a solid phase. Dry the obtained solid phase at 200 °C, and then calcine it at 350 °C for 8 h to obtain titanium silicalite catalyst A2.

[0045] Example 3

[0046] The preparation process of the titanium silicalite molecular sieve catalyst in this example is the same as the steps shown in Example 1, but:

[0047] In step (1), the first silicon source, titanium source, and first template agent are tetraethyl orthosilicate, titanium sulfate, and tetrapropylammonium hydroxide respectively. The stirring temperature is 20°C, and the stirring time is 12 h. Among them, the molar ratio of Si, Ti, tetrapropylammonium hydroxide, and water is 1:0.2:0.05:1. The temperature of the first hydrothermal crystallization is 300°C, and the time is 10 h.

[0048] In step (2), the second silicon source, second template agent, and organic amine added after pressure relief are methyl orthosilicate, tetrapropylammonium bromide, and aniline. The stirring temperature is 20°C, and the stirring time is 12 h. Among them, the molar ratio of methyl orthosilicate, tetrapropylammonium bromide, aniline, and water is 1:0.4:0.5:80. The temperature of the second hydrothermal crystallization is 150°C, and the time is 72 h. The mass of the condensate accounts for 40% of the total amount of the material after the first hydrothermal crystallization is completed.

[0049] In step (3), after the second hydrothermal crystallization is completed, solid-liquid separation is carried out to obtain a solid phase. The obtained solid phase is dried at a temperature of 50°C, and then calcined at a temperature of 700°C for 1 h to obtain the titanium silicalite molecular sieve catalyst A3. The ultraviolet-Raman spectrum of A3 is as Figure 2 shown.

[0050] Example 4

[0051] The preparation process of the titanium silicalite molecular sieve catalyst in this example is the same as the steps shown in Example 1, but:

[0052] In step (1), the first silicon source, titanium source, and first template agent are propyl orthosilicate, methyl titanate, and tetrabutylammonium hydroxide respectively. The stirring temperature is 40°C, and the stirring time is 24 h. Among them, the molar ratio of Si, Ti, tetrabutylammonium hydroxide, and water is 1:0.4:0.05:1. The temperature of the first hydrothermal crystallization is 100°C, and the time is 72 h.

[0053] In step (2), the second silicon source, second template agent, and organic amine added after pressure relief are butyl orthosilicate, tetrapropylammonium chloride, and tri-n-propylamine. The stirring temperature is 60°C, and the stirring time is 0.5 h. Among them, the molar ratio of butyl orthosilicate, tetrapropylammonium chloride, tri-n-propylamine, and water is 1:0.1:0.5:100. The temperature of the second hydrothermal crystallization is 170°C, and the time is 100 h. The mass of the condensate accounts for 5% of the total amount of the material after the first hydrothermal crystallization is completed.

[0054] In step (3), after the second hydrothermal crystallization, solid-liquid separation is carried out to obtain a solid phase; the obtained solid phase is dried at a temperature of 50 °C, and then calcined at a temperature of 700 °C for 1 h to obtain titanium silicalite catalyst A4.

[0055] Example 5

[0056] The preparation process of the titanium silicalite catalyst in this example is the same as the steps shown in Example 1, but:

[0057] In step (1), the first silicon source, titanium source, and first template agent are tetraethyl orthosilicate, tetrabutyl titanate, and tetramethylammonium hydroxide, respectively. The stirring temperature is 10 °C, and the stirring time is 12 h. Among them, the molar ratio of Si, Ti, tetramethylammonium hydroxide, and water is 1:0.5:0.6:80. The temperature of the first hydrothermal crystallization is 150 °C, and the time is 96 h.

[0058] In step (2), after pressure relief, the second silicon source, second template agent, and organic amine added are tetraethyl orthosilicate, tetrapropylammonium bromide, aniline + triethylamine. The stirring temperature is 40 °C, and the stirring time is 12 h. Among them, the molar ratio of tetraethyl orthosilicate, tetrapropylammonium bromide, aniline + triethylamine, and water is 1:0.5:0.6:100. The temperature of the second hydrothermal crystallization is 200 °C, and the time is 60 h. The mass of the condensate accounts for 5% of the total amount of the material after the first hydrothermal crystallization is completed.

[0059] In step (3), after the second hydrothermal crystallization, solid-liquid separation is carried out to obtain a solid phase; the obtained solid phase is dried at a temperature of 100 °C, and then calcined at a temperature of 600 °C for 4 h to obtain titanium silicalite catalyst A5.

[0060] Example 6

[0061] The preparation process of the titanium silicalite catalyst in this example is the same as the steps shown in Example 1, but:

[0062] In step (1), the first silicon source, titanium source, and first template agent are silicon source, titanium source, and tetrapropylammonium hydroxide, respectively. The stirring temperature is 20 °C, and the stirring time is 6 h. Among them, the molar ratio of Si, Ti, tetrapropylammonium hydroxide, and water is 1:0.1:0.2:60. The temperature of the first hydrothermal crystallization is 150 °C, and the time is 96 h.

[0063] In step (2), the second silicon source, the second template and the organic amine added after the pressure release are tetraethyl orthosilicate, tetrapropyl ammonium bromide, n-butylamine + triethanolamine, and the stirring time temperature is 20°C and the stirring time is 6 hours. Among them, the molar ratio of tetraethyl orthosilicate, tetrapropyl ammonium bromide, n-butylamine + triethanolamine and water is 1:0.5:0.6:100. The temperature of the second hydrothermal crystallization is 100°C and the time is 100 hours. The mass of the condensate accounts for 25% of the total amount of the material after the first hydrothermal crystallization is completed.

[0064] In step (3), after the second hydrothermal crystallization is completed, solid-liquid separation is performed to obtain a solid phase; the obtained solid phase is dried at 50°C, and then calcined at 700°C for 1h to obtain titanium silicon molecular sieve catalyst A6. The electron microscope morphology of A6 is shown in Figure 1 shown.

[0065] Comparative Example 1

[0066] The preparation process of this comparative example is carried out in a reactor and comprises the following steps:

[0067] (1) A silicon source and a titanium source are mixed and added to an aqueous solution of tetrabutylammonium hydroxide and stirred thoroughly, wherein the molar ratio of Si:Ti:tetrapropylammonium hydroxide:water is 1:0.4:0.05:1; the mixed solution is subjected to hydrothermal crystallization in a reactor at a temperature of 100°C for 96 hours.

[0068] (2) After the crystallization, solid-liquid separation was performed to obtain a solid phase, which was then dried at 50°C and subsequently calcined at 700°C for 1 h to obtain the titanium silicate molecular sieve catalyst B1. Figure 3 shown.

[0069] Comparative Example 2

[0070] The preparation process of this comparative example is the same as that of comparative example 1, except that:

[0071] In step (1), the silicon source, titanium source and template are tetraethyl orthosilicate, titanium sulfate and tetrapropylammonium hydroxide, and the molar ratio of tetraethyl orthosilicate, titanium sulfate, tetrapropylammonium hydroxide and water is 1:0.5:0.6:100. The temperature of hydrothermal crystallization is 200°C and the time is 24h.

[0072] In step (2), after the crystallization is completed, solid-liquid separation is performed to obtain a solid phase, which is then dried at 200° C. and subsequently calcined at 550° C. for 8 h to obtain the titanium silicon molecular sieve catalyst B2.

[0073] Test Example 1-8

[0074] In order to further verify the catalytic performance of the titanium silicalite molecular sieve catalyst of the present invention, a test example of propylene epoxidation to propylene oxide was set up to evaluate the performance of the titanium silicalite molecular sieve catalysts prepared in Examples 1-6 and Comparative Examples 1-2.

[0075] It should be noted that before the test, the titanium silicalite molecular sieve catalyst needs to be pretreated, that is: the titanium silicalite molecular sieve catalysts prepared in Examples 1-6 or Comparative Examples 1-2, silica sol, and water are mixed in a certain proportion and then kneaded, and then put into an extruder and extruded; after extrusion, it is dried and calcined to obtain a shaped titanium silicalite molecular sieve catalyst.

[0076] The specific test process includes adding 20 g of the pretreated shaped titanium silicalite molecular sieve catalyst to a fixed-bed reactor, heating to 40-50 °C, and the reaction pressure is 2 MPaG; introducing raw materials methanol, propylene, and hydrogen peroxide, and the molar ratio of the three is 9:2:1, and the mass space velocity is 0.1-1 h -1 ; after gas-liquid separation of the reaction products, the liquid phase is collected for chromatographic analysis.

[0077] The reaction products are titrated for the residual hydrogen peroxide by the national standard method, and the conversion rate of the raw material hydrogen peroxide and the selectivity of the product propylene oxide are calculated. The specific calculation methods are as follows:

[0078] Hydrogen peroxide conversion rate = (the amount of hydrogen peroxide added - the amount of remaining hydrogen peroxide) / the amount of hydrogen peroxide added × 100%;

[0079] Propylene oxide selectivity = the amount of propylene consumed to convert into propylene oxide / the amount of converted propylene × 100%.

[0080] In addition, the above 8 molecular sieves were also measured by ultraviolet-Raman spectroscopy, and the most probable pore diameters of each molecular sieve were measured by a physical adsorption instrument. The test results are shown in Table 1, Figure 2 and Figure 3 .

[0081] Table 1

[0082]

[0083]

[0084] It can be verified from Table 1 that the titanium silicalite molecular sieve catalysts shown in Examples 1-6 have appropriate most probable pore diameters, and the ultraviolet-Raman spectroscopy test results R 1121 / R 800 are between 0.1 and 4, indicating a relatively high framework titanium content. The test examples using the titanium silicalite molecular sieve catalysts shown in Examples 1-6 have high raw material conversion rates and product selectivities.

[0085] It should be noted that the above content is a further detailed description of the present invention in combination with specific implementation manners, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions; the dimensional data of this embodiment does not necessarily limit the technical solution, but only shows one specific working condition. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple improvements and refinements can still be made, and all should be regarded as belonging to the scope of protection of the present invention.

Claims

1. A titanium silicalite molecular sieve catalyst, characterized in that, The R of the titanium silicalite molecular sieve catalyst 1121 / R 800 is 0.1 to 4, and R 1121 is the maximum absorption peak intensity at around 1121 cm -1 in the ultraviolet-Raman spectrum of the titanium silicalite molecular sieve catalyst, and R 800 is the maximum absorption peak intensity at around 800 cm -1 in the ultraviolet-Raman spectrum of the titanium silicalite molecular sieve catalyst; the most probable pore diameter of the titanium silicalite molecular sieve catalyst is 15 to 36 nm; The preparation method of the titanium-silicate molecular sieve catalyst includes two hydrothermal crystallization steps; the first silicon source and titanium source are subjected to the first hydrothermal crystallization in an aqueous solution of the first template agent; after the first hydrothermal crystallization is completed, a pressure relief operation is carried out, and then the second silicon source, the second template agent and an organic amine are added for the second hydrothermal crystallization to obtain a secondary hydrothermal crystallization mixture; it also includes performing solid-liquid separation on the secondary hydrothermal crystallization mixture to obtain a solid phase, and drying and calcining the solid phase.

2. The titanium-silicon molecular sieve catalyst according to claim 1, wherein The R of the titanium silicalite molecular sieve catalyst 1121 / R 800 is 0.1, and the most probable pore diameter is 35.

3. The titanium silicalite molecular sieve catalyst according to claim 1, characterized in that, The R of the titanium silicalite molecular sieve catalyst 1121 / R 800 is 3.5, and the most probable pore diameter is 17.

4. A method for preparing a titanium-silicate molecular sieve catalyst, characterized in that, It includes two hydrothermal crystallizations; the first silicon source and titanium source are subjected to the first hydrothermal crystallization in an aqueous solution of the first template agent; after the first hydrothermal crystallization is completed, a pressure relief operation is carried out, and then the second silicon source, the second template agent and an organic amine are added for the second hydrothermal crystallization to obtain a secondary hydrothermal crystallization mixture; it also includes solid-liquid separation of the secondary hydrothermal crystallization mixture to obtain a solid phase, and drying and calcining the solid phase; the R of the titanium-silicon molecular sieve catalyst 1121 / R 800 is 0.1 to 4, and R 1121 is the maximum absorption peak intensity at around 1121 cm -1 in the ultraviolet-Raman spectrum of the titanium-silicon molecular sieve catalyst, and R 800 is the maximum absorption peak intensity at around 800 cm -1 in the ultraviolet-Raman spectrum of the titanium-silicon molecular sieve catalyst; the most probable pore diameter of the titanium-silicon molecular sieve catalyst is 15 to 36 nm.

5. The method for preparing a titanium silicalite molecular sieve catalyst according to claim 4, wherein, In the first hydrothermal crystallization, the molar ratio of Si in the first silicon source, Ti in the titanium source, the first template agent and water is 1: (0.01 to 0.5): (0.03 to 0.6): (1 to 100).

6. The preparation method according to claim 4, characterized in that, The first hydrothermal crystallization also includes stirring after adding the first silicon source and titanium source to the aqueous solution of the template agent, with the stirring time being 0.5 h to 24 h and the stirring temperature being 0 to 60 °C.

7. The preparation method according to claim 4, characterized in that, The temperature of the first hydrothermal crystallization is 100 to 300 °C, and the time is 10 to 100 h.

8. The preparation method according to claim 4, characterized in that, The gas discharged during the pressure relief operation is condensed to obtain a condensate, and the mass of the condensate accounts for 5% to 50% of the total weight of the materials after the first hydrothermal crystallization is completed.

9. The preparation method according to claim 4, characterized in that, In the second hydrothermal crystallization, the molar ratio of the second silicon source, the second template agent, the organic amine and water is 1: (0.01 to 0.5): (0.03 to 0.6): (1 to 100).

10. The preparation method according to claim 4, characterized in that, The second hydrothermal crystallization also includes stirring after adding the second silicon source, the second template agent and the organic amine, with the stirring time being 0.5 h to 24 h and the stirring temperature being 0 to 60 °C.

11. According to the preparation method described in claim 4, characterized in that, The temperature of the second hydrothermal crystallization is 100 to 300 °C, and the time is 10 to 100 h.

12. The preparation method according to claim 4, characterized in that, The first silicon source and the second silicon source are each independently selected from one or more of inorganic silicon or organosilicon grease; the inorganic silicon includes silica sol, silicon dioxide, and white carbon black; the general formula of the organosilicon grease is Si(OR 1 )4, where R 1 is an alkyl substituent having 1 to 6 carbon atoms.

13. The preparation method according to claim 4, characterized in that, The titanium source is one or more of an inorganic titanium source or an organic titanate; the inorganic titanium includes titanium tetrachloride and titanium sulfate; the general formula of the organic titanate is Ti(OR 2 )4, where R 2 is an alkyl substituent having 2 to 6 carbon atoms.

14. The preparation method according to claim 4, characterized in that, The first template agent is one or more of quaternary ammonium bases or quaternary ammonium salts; the quaternary ammonium bases include tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide and tetrabutylammonium hydroxide; the quaternary ammonium salts include tetrapropylammonium bromide, tetrapropylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium chloride.

15. The preparation method according to claim 4, characterized in that, The second template agent is a quaternary ammonium salt; the quaternary ammonium salts include one or more of tetrapropylammonium bromide, tetrapropylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium chloride.

16. The preparation method according to claim 4, characterized in that, The organic amine is one or more of aliphatic amine compounds, alkanolamine compounds or aromatic amine compounds; the aliphatic amine compounds include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, n-butylamine, isobutylamine, tert-butylamine, sec-butylamine, butanediamine, diisobutylamine, pentylamine, isopentylamine, sec-pentylamine, cyclopentylamine, propylamine, dipropylamine, tripropylamine, isopropylamine, diisopropylamine, tri-n-propylamine; the alkanolamine compounds include monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, butyldiethanolamine; the aromatic amine compounds include aniline, toluidine, phenylenediamine.

17. The preparation method according to claim 4, characterized in that, The drying is carried out at a temperature of 50 to 200 °C; the calcining is carried out at a temperature of 350 to 700 °C, and the calcining time is 1 to 8 h.

18. Use of the titanium silicalite molecular sieve catalyst according to any one of claims 1-3 or the titanium silicalite molecular sieve catalyst prepared by the preparation method according to any one of claims 4-17 in the propylene epoxidation reaction.

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