Titanium silical molecular sieve, its preparation method and application
By using specific organosilicon compounds and microwave heating in the preparation of titanium-silicon molecular sieves, the problems of catalytic activity and selectivity caused by non-framework titanium were solved, and a highly efficient catalytic propylene epoxidation reaction was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-27
- Publication Date
- 2026-05-29
AI Technical Summary
Titanium-silicon molecular sieves prepared by traditional hydrothermal synthesis methods are prone to the formation of non-framework titanium, resulting in poor selectivity and activity in catalytic reactions.
A titanium-silicon molecular sieve with almost all titanium atoms inserted into the molecular sieve framework was prepared by treating the titanium-silicon precursor with a specific organosilicon compound and crystallizing it by microwave heating.
It improves the selectivity and catalytic activity of titanium-silicon molecular sieves in catalytic reactions. When applied to the catalytic propylene epoxidation reaction, the hydrogen peroxide conversion rate is ≥88% and the propylene oxide selectivity is >90%.
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Figure CN122102153A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of inorganic chemistry and catalytic chemistry, specifically to a titanium-silicon molecular sieve, its preparation method, and its applications. Background Technology
[0002] Titanium atoms replace a small number of silicon atoms in all-silicon molecular sieves, forming catalytically active centers and resulting in titanium-silicon molecular sieves with a regular topology. In the selective oxidation of hydrocarbons using hydrogen peroxide as an oxidant, titanium-silicon molecular sieves exhibit unparalleled advantages as catalysts compared to conventional methods, such as mild reaction conditions, high atom utilization, and environmentally friendly, pollution-free processes, demonstrating promising industrial application prospects and remaining a focus of research. Currently, Ti-containing heteroatom molecular sieves, represented by TS-1 molecular sieves, have been successfully applied in industrial production processes such as propylene liquid-phase epoxidation and cyclohexanone ammoxidation.
[0003] The titanium atoms in the framework of titanium-silicon molecular sieves possess empty orbitals, which can accept lone pairs of electrons from hydrogen and oxygen atoms in peroxide to form Ti-OOH active centers, thereby catalyzing the oxidation of hydrocarbons. The framework titanium atoms, as active centers, play a crucial catalytic role. However, due to the relatively large size of titanium atoms, their insertion into the molecular sieve framework can cause distortion and deformation of the framework structure. Therefore, during the hydrothermal crystallization synthesis of titanium-silicon molecular sieves, some titanium atoms often fail to successfully insert into the framework structure and aggregate as titanium dioxide. Since titanium dioxide often exists as a side reaction catalytic center, its formation must be minimized during the synthesis of titanium-silicon molecular sieves, instead promoting the complete insertion of titanium atoms into the framework structure. However, conventional hydrothermal synthesis methods often result in the formation of non-framework titanium atoms in the prepared titanium-silicon molecular sieves, leading to a decrease in reaction selectivity and activity, significantly impacting the reaction efficiency. Summary of the Invention
[0004] The purpose of this invention is to overcome the problem that titanium-silicon molecular sieves prepared by traditional hydrothermal synthesis methods are prone to the presence of non-framework titanium, resulting in poor selectivity and activity of the catalytic reactions of titanium-silicon molecular sieves. This invention provides a titanium-silicon molecular sieve, its preparation method, and its applications.
[0005] To achieve the above objectives, the present invention provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps:
[0006] (1) A silicon source, an alkaline template agent, a titanium source and water are mixed to obtain a titanium silicon precursor;
[0007] (2) The titanium silicon precursor is mixed with the organosilicon compound shown in formula (I) to obtain a mixture;
[0008] (3) The mixture is microwave heated to crystallize it, the solid is separated from the crystallized product, and then dried and calcined;
[0009]
[0010] Where i is any integer from 1 to 10; n is any integer from 0 to 10; R1, R2, and R3 are each independently selected from methyl, ethyl, propyl, butyl, or pentyl.
[0011] Preferably, in step (3), the microwave heating conditions include: a temperature of 50-200℃ and a time of 0.5-10h.
[0012] Preferably, step (1) specifically includes: mixing and stirring the silicon source, alkaline template agent and water, adding the titanium source during the stirring process, continuing to stir, and then performing alcohol removal treatment.
[0013] Preferably, the conditions for the alcohol removal treatment include: a temperature of 30-100℃ and a time of 2-10h.
[0014] Preferably, in step (1), the silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, silica gel, silica fume and silica sol.
[0015] Preferably, the alkaline template agent is selected from one or more of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines;
[0016] Preferably, the titanium source is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.
[0017] Preferably, in step (1), the silicon source is SiO2, and the molar ratio of the silicon source, alkaline template agent and water is 1:0.05-0.4:5-40;
[0018] Preferably, in step (1), the silicon source is SiO2 and the titanium source is TiO2, and the molar ratio of the silicon source and the titanium source is 1:0.001-0.04.
[0019] Preferably, the molar ratio of the organosilicon compound and the silicon source shown in formula (I) is 0.01-0.3:1.
[0020] Preferably, the organosilicon compound is one or more of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).
[0021]
[0022] Preferably, in step (3), the drying conditions include: a temperature of 40 to 200°C and a time of 0.5 to 24 hours.
[0023] Preferably, in step (3), the calcination conditions include: a temperature of 400-800℃ and a time of 1-15h.
[0024] A second aspect of the present invention provides a titanium-silicon molecular sieve prepared by the method described above.
[0025] Preferably, no TiO2 characteristic peak located at 320±10nm is observed.
[0026] The third aspect of the present invention provides the application of the titanium-silicon molecular sieve described above in the catalytic propylene epoxidation reaction.
[0027] In the preparation method provided by the present invention, a titanium-silicon molecular sieve with extremely low non-framework titanium content is obtained by treating the titanium-silicon precursor with a specific organosilicon compound and using microwave heating synthesis conditions. This improves the selectivity and catalytic activity of the titanium-silicon molecular sieve catalytic reaction, giving it high selectivity and high catalytic activity.
[0028] The titanium-silicon molecular sieve prepared by the method provided in this invention, when applied to the catalytic propylene epoxidation reaction, exhibits a hydrogen peroxide conversion rate of ≥88% and a propylene oxide selectivity of >90%. Attached Figure Description
[0029] Figure 1 This is the UV-Vis spectrum of the titanium-silicon molecular sieve prepared in Example 1 of this invention;
[0030] Figure 2 This is the XPS spectrum of the titanium-silicon molecular sieve prepared in Example 1 of this invention;
[0031] Figure 3 The UV-Vis spectrum of the titanium-silicon molecular sieve prepared in Comparative Example 1 is shown.
[0032] Figure 4 The XPS spectrum of the titanium-silicon molecular sieve prepared in Comparative Example 1 is shown below.
[0033] Figure 5 This is the UV-Vis spectrum of the titanium-silicon molecular sieve prepared in Comparative Example 2. Detailed Implementation
[0034] 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.
[0035] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0036] This invention provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps:
[0037] (1) A silicon source, an alkaline template agent, a titanium source and water are mixed to obtain a titanium silicon precursor;
[0038] (2) The titanium silicon precursor is mixed with the organosilicon compound shown in formula (I) to obtain a mixture;
[0039] (3) The mixture is microwave heated to crystallize it, the solid is separated from the crystallized product, and then dried and calcined;
[0040]
[0041] Where i is any integer from 1 to 10, and n is any integer from 0 to 10; R1, R2, and R3 are each independently selected from methyl, ethyl, propyl, butyl, or pentyl.
[0042] Conventional hydrothermal synthesis methods often result in the formation of non-framework titanium in titanium-silicon molecular sieves, especially when the titanium content is high. However, this invention utilizes specific organosilicon compounds to treat the titanium-silicon precursor and employs microwave heating for crystallization. This allows for the production of titanium-silicon molecular sieves where almost all titanium atoms are inserted into the molecular sieve framework, resulting in excellent catalytic performance. Furthermore, even with a high titanium content (titanium source / silicon source molar ratio ≥ 0.020), titanium-silicon molecular sieves with almost entirely inserted titanium atoms can still be produced.
[0043] In some implementations, the conditions for microwave heating in step (3) include: a temperature of 50-200°C and a time of 0.5-10h.
[0044] In some embodiments, the microwave heating conditions in step (3) further include: power 100-150W / 100mL material volume.
[0045] In a preferred embodiment, in step (3), the microwave heating conditions include: a temperature of 50-150°C and a time of 0.5-8h. Under the above microwave heating conditions, the content of non-framework titanium in the obtained titanium-silicon molecular sieve is lower.
[0046] In some embodiments, step (1) specifically includes: mixing and stirring a silicon source, an alkaline template agent and water, adding a titanium source during the stirring process, continuing to stir, and then performing an alcohol removal treatment.
[0047] Further, step (1) includes: mixing silicon source, alkaline template agent and water, and stirring at room temperature for 0.1-2 hours. During the stirring of the above mixture, titanium source is added and stirred for 0.5-6 hours to obtain a transparent solution, and the transparent solution is subjected to alcohol removal treatment.
[0048] Preferably, in step (1), after adding the titanium source, the stirring time is 0.5-5h.
[0049] The present invention does not impose any particular limitation on the specific selection of the silicon source in step (1), and it can be a conventional silicon source in the art. In some embodiments, the silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, silica gel, silica fume, and silica sol.
[0050] In this invention, the alkaline template agent may be selected from one or more of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines. Preferably, the alkaline template agent is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.
[0051] The present invention does not limit the specific selection of the titanium source, which can be a conventional titanium source in the art, such as an organic titanium source and / or an inorganic titanium source. In some preferred embodiments, the titanium source is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.
[0052] In some embodiments, in step (1), the molar ratio of the silicon source, the alkaline template agent, and water is 1:0.05-0.4:5-40, preferably 1:0.1-0.3:5-25, wherein the silicon source is SiO2, and the alkaline template agent is N when it contains nitrogen, and OH when it does not contain nitrogen. - count.
[0053] In some embodiments, the silicon source is SiO2, the titanium source is TiO2, and the molar ratio of the silicon source to the titanium source is 1:0.001-0.04, preferably 1:0.005-0.03.
[0054] In some embodiments, the molar ratio of the organosilicon compound and the silicon source shown in formula (I) is 0.01-0.3:1, preferably 0.01-0.2:1. By controlling the ratio of the organosilicon compound and the silicon source within the above range (especially the preferred range), the catalytic activity and selectivity of the prepared titanium-silicon molecular sieve are improved.
[0055] In the method described in this invention, step (1) refers to removing alcohol generated from the hydrolysis of silicon and titanium sources from a transparent solution. Specifically, it refers to removing alcohol from the reaction system by azeotropic distillation, and replenishing the water lost during azeotropic distillation to achieve the specified material ratio. In some embodiments, the conditions for the alcohol removal treatment include: a temperature of 30-100°C and a time of 2-10 hours.
[0056] In a preferred embodiment, the reaction temperature for the alcohol removal treatment is 40-90°C, and the reaction time is 4-10 h.
[0057] In the method described in this invention, in the organosilicon compound represented by formula (I), i is any integer from 1 to 10, that is, the number of methylene groups between Si and O is 1 to 10, preferably, i is any integer from 1 to 5.
[0058] In the method described in this invention, in the organosilicon compound represented by formula (I), n is any integer from 0 to 10, that is, the number of methylene groups between the epoxy group and O is 0 to 10. Preferably, i is any integer from 0 to 5. Wherein, i and n can be the same or different.
[0059] In the method described in this invention, R1, R2, and R3 are each independently selected from methyl, ethyl, propyl, butyl, or pentyl, wherein R1, R2, and R3 may be the same or different, and are preferably the same.
[0060] In a preferred embodiment, the organosilicon compound is one or more of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).
[0061]
[0062] In some embodiments, step (2) specifically includes: adding the organosilicon compound of formula (I) to the titanium silicon precursor and stirring at room temperature for 0-24 hours; preferably, the stirring time at room temperature is 0.5-10 hours.
[0063] In some embodiments, in step (3), the solid is separated from the crystallized product by filtration.
[0064] In some embodiments, in step (3), the crystallized product is washed before separating the solid from the crystallized product. In one specific embodiment, the washing conditions include: a temperature of 20-50°C, mixing or rinsing with water, the amount of water generally being 1-20 times the mass of the crystallized product.
[0065] In some embodiments, the drying conditions in step (3) include: a drying temperature of 40 to 200°C, preferably 100 to 200°C; and a drying time of 0.5 to 24 hours, preferably 1 to 5 hours.
[0066] In some embodiments, in step (3), the calcination temperature is 400-800℃, preferably 500-600℃.
[0067] In some embodiments, the roasting time in step (3) is 1-15 hours, preferably 4-8 hours.
[0068] The present invention also proposes a titanium-silicon molecular sieve prepared by the method described above.
[0069] In some embodiments, the ultraviolet spectrum of the titanium-silicon molecular sieve does not show the characteristic TiO2 peak at 320±10nm, indicating that almost all the titanium atoms fed in are inserted into the molecular sieve framework.
[0070] In a specific embodiment, the ultraviolet spectrum of the titanium-silicon molecular sieve has only characteristic peaks located at 215±10nm and optionally 280±10nm, where the 215 peak represents tetracoordinated Ti atoms and the 280 peak represents pentacoordinated and hexacoordinated Ti atoms.
[0071] In some embodiments, when the ultraviolet spectrum of the titanium-silicon molecular sieve has characteristic peaks at 215±10nm and 280±10nm, the ratio of their peak areas is >1.5. The above ultraviolet spectrum results indicate that the Ti atoms in the titanium-silicon molecular sieve are still mainly in tetracoordinate form, while some Ti atoms exist in pentacoordinate and hexacoordinate forms.
[0072] The titanium-silicon molecular sieve described in this invention is widely used in chemical production processes. It exhibits excellent catalytic effects in catalyzing hydrocarbon oxidation and epoxidation reactions, such as phenol hydroxylation, propylene liquid-phase epoxidation, and cyclohexanone ammoniumization.
[0073] Furthermore, this invention also proposes the application of the titanium-silicon molecular sieve described above in the catalytic propylene epoxidation reaction, especially its role in the catalytic liquid-phase epoxidation reaction of propylene.
[0074] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.
[0075] In the following examples and comparative examples, room temperature refers to 20±5℃.
[0076] Example 1
[0077] This embodiment is used to illustrate the titanium-silicon molecular sieve and its preparation method according to the present invention.
[0078] (1) The three substances, tetramethyl silicate, tetrapropylammonium hydroxide and water, were mixed in a molar ratio of 1:0.15:15 and stirred at room temperature. During the stirring of the above mixture, tetraethyl titanate was added in proportion and stirred for 2.5 h to obtain a transparent solution, wherein the molar ratio of tetramethyl silicate and tetraethyl titanate was 1:0.025. The transparent solution was placed on a magnetic stirrer and heated to 60°C for 7 h to remove alcohol and obtain titanium silicon precursor.
[0079] (2) Add the organosilicon compound of formula (I-1) to the titanium silicon precursor and stir at room temperature for 3 h to obtain a mixture, wherein the molar ratio of the organosilicon compound of formula (I-1) to tetramethyl silicate is 0.15:1.
[0080] (3) The above mixture was placed in a microwave heating device and heated to 120°C for hydrothermal crystallization for 5 hours. The microwave power was 150W / 100mL of material volume. The reacted material was rinsed with water and filtered at room temperature, then dried at 120°C for 2 hours, and then calcined at 550°C for 6 hours to obtain titanium silicon molecular sieve denoted as A1.
[0081] Example 2
[0082] Titanium-silicon molecular sieve material, denoted as A2, was prepared according to the method in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0083] Example 3
[0084] Titanium-silicon molecular sieve material, denoted as A3, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0085] Example 4
[0086] Titanium-silicon molecular sieve material, denoted as A4, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0087] Example 5
[0088] Titanium-silicon molecular sieve material, denoted as A5, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0089] Example 6
[0090] Titanium-silicon molecular sieve material, denoted as A6, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0091] Example 7
[0092] Titanium-silicon molecular sieve material, denoted as A7, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0093] Example 8
[0094] Titanium-silicon molecular sieve material, denoted as A8, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0095] Example 9
[0096] Titanium-silicon molecular sieve material, denoted as A9, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0097] Example 10
[0098] Titanium-silicon molecular sieve material, denoted as A10, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0099] Example 11
[0100] Titanium-silicon molecular sieve material, denoted as A11, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0101] Example 12
[0102] Titanium-silicon molecular sieve material, denoted as A12, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0103] Example 13
[0104] Titanium-silicon molecular sieve material, denoted as A13, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0105] Example 14
[0106] Titanium-silicon molecular sieve material, denoted as A14, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0107] Example 15
[0108] Titanium-silicon molecular sieve material, denoted as A15, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0109] Example 16
[0110] Titanium-silicon molecular sieve material, denoted as A16, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0111] Example 17
[0112] Titanium-silicon molecular sieve material, denoted as A17, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0113] Example 18
[0114] Titanium-silicon molecular sieve material, denoted as A18, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0115] Example 19
[0116] Titanium-silicon molecular sieve material, denoted as A19, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0117] Example 20
[0118] Titanium-silicon molecular sieve material, denoted as A20, was prepared according to the method described in Example 1. Its proportions and synthesis conditions are shown in Table 1.
[0119] The proportions and synthesis conditions of each embodiment are shown in Table 1 below. In Table 1, the ratio of raw materials refers to the molar ratio, the stirring time of titanium ester refers to the stirring time after adding the titanium source in step (1), and the stirring time of compound refers to the stirring time after adding the organosilicon compound in step (2).
[0120]
[0121] Comparative Example 1
[0122] This comparative example illustrates a conventional TS-1 molecular sieve and its preparation method, which includes the following steps:
[0123] Mix 22.5g tetraethyl silicate, 7.0g tetrapropylammonium hydroxide and 59.8g deionized water evenly and hydrolyze at 60℃ for 1.0h. Then, under vigorous stirring, slowly add a solution of 1.1g tetrabutyl titanate and 5.0g isopropanol to the above solution. Stir the mixture at 75℃ for 3h to obtain a clear and transparent colloid. Transfer the colloid to a stainless steel sealed reactor and crystallize at 170℃ for 72h to obtain conventional TS-1 molecular sieve.
[0124] Comparative Example 2
[0125] The method described in Example 1 was implemented, except that in step (2), no organosilicon compound with the structure shown in formula (I-1) was added.
[0126] Specifically, the method includes the following steps:
[0127] (1) The three substances, tetramethyl silicate, tetrapropylammonium hydroxide and water, were mixed in a molar ratio of 1:0.15:15 and stirred at room temperature. During the stirring of the mixture, tetraethyl titanate was added in proportion and stirred for 2.5 h to obtain a transparent solution, wherein the molar ratio of tetramethyl silicate and tetraethyl titanate was 1:0.025. The transparent solution was placed on a magnetic stirrer and heated to 60°C for 7 h to remove alcohol and obtain a titanium silicon precursor.
[0128] (2) The above titanium silicon precursor was placed in a microwave heating device and heated to 120°C for hydrothermal crystallization for 5 hours. The reacted material was rinsed with water and filtered, then dried at 120°C for 2 hours, and then calcined at 550°C for 6 hours to obtain titanium silicon molecular sieve.
[0129] Comparative Example 3
[0130] The method described in Example 1 is implemented, except that in step (2), the organosilicon compound with the structure shown in formula (I-1) is replaced with the compound shown in formula (II);
[0131]
[0132] Test Example 1
[0133] The titanium-silicon molecular sieve samples prepared in Example 1 and Comparative Examples 1-2 were characterized. The UV-Vis spectra of the samples were obtained using an Agilent Cary 300 UV spectrophotometer with a wavelength interval of 3 nm and a scanning range of 190-800 nm. The X-ray diffraction patterns (XPS) were obtained using an ESCALab250 X-ray photoelectron spectrometer. The detection results for Example 1 are as follows... Figure 1 (UV-Vis spectrum) and Figure 2 As shown in the XPS spectrum, the detection results of Comparative Example 1 are as follows: Figure 3 (UV-Vis spectrum) and Figure 4 As shown in the XPS spectrum, the UV detection results of Comparative Example 2 are as follows: Figure 5 As shown.
[0134] Depend on Figure 1 It can be seen that the titanium-silicon molecular sieve prepared in Example 1 contains only the framework four-coordinated Ti characteristic peak located at 210 nm; from Figure 2 It can be seen that the titanium-silicon molecular sieve prepared in Example 1 contains only the framework four-coordinate Ti characteristic peak located near 459 eV.
[0135] Depend on Figure 3 It can be seen that the titanium-silicon molecular sieve prepared in Comparative Example 1 contains, in addition to the characteristic peaks of framework four-coordinate Ti at 210 nm and five- and six-coordinate Ti at 280 nm, a TiO2 characteristic peak near 320 nm; Figure 4 It can be seen that the titanium-silicon molecular sieve prepared in Comparative Example 1 contains not only the characteristic peak of framework four-coordinate Ti located near 459 eV, but also the characteristic peak of TiO2 located near 458.5 eV.
[0136] Depend on Figure 5 It can be seen that the titanium-silicon molecular sieve prepared in Comparative Example 2 contains a TiO2 characteristic peak located near 320 nm.
[0137] Test Example 2
[0138] This test example illustrates the reaction effects of the sample provided in the embodiments of this invention and the sample prepared in the comparative example for the liquid-phase epoxidation of propylene to prepare propylene oxide (HPPO). All reagents used in this test example are 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; the analytical column used was an HP-5 capillary column with a flame ionization detector. Component concentrations were quantified using the external standard method. First, the peak areas of each component were measured, and the component concentrations were obtained from the standard working curve to calculate each index.
[0139] In the test example, the hydrogen peroxide conversion rate and propylene oxide selectivity were calculated according to the following formulas:
[0140] Hydrogen peroxide conversion rate % = (1 - number of moles of hydrogen peroxide remaining after reaction / number of moles of hydrogen peroxide added before reaction) * 100%;
[0141] propylene oxide selectivity % = number of moles of propylene oxide after reaction / (number of moles of propylene added before reaction - number of moles of propylene remaining after reaction) * 100%;
[0142] Propylene, hydrogen peroxide, and methanol were introduced into a fixed-bed reactor containing the samples prepared in Examples 1-20 and the comparative examples, with a molar ratio of propylene, hydrogen peroxide, and methanol of 1:1:10; the reaction temperature was 40°C, and the liquid hourly space velocity was 0.1-7 h⁻¹. -1 Samples were taken for chromatographic analysis, and the reaction results are shown in Table 2.
[0143] Table 2
[0144]
[0145]
[0146] As can be seen from the results in Table 2, when the titanium-silicon molecular sieve prepared in the embodiments of the present invention is applied to the catalytic propylene epoxidation reaction, the hydrogen peroxide conversion rate is ≥88% and the propylene oxide selectivity is >90%, indicating that the titanium-silicon molecular sieve prepared by the method provided by the present invention has high selectivity and catalytic activity in the catalytic reaction.
[0147] A comparison of Examples 1-20 with Comparative Example 1 shows that the titanium-silicon molecular sieves prepared in Examples 1-20 exhibit better catalytic activity and selectivity. It is speculated that this may be because, during the preparation of the titanium-silicon molecular sieve, the rapid hydrolysis of titanium esters after alcohol removal initially polymerizes into Ti-O-Ti, resulting in the presence of non-framework titanium in the titanium-silicon molecular sieves prepared in the comparative example. In contrast, this invention, by adding a specific organosilicon compound and then generating molecular vibrations under microwave heating, causes the Ti-O-Ti bonds to break, which then bond with the added organosilicon compound and reconnect with the hydrolyzed Si-OH to form a molecular sieve framework. This results in the titanium-silicon molecular sieves being almost entirely free of non-framework titanium, thus improving their catalytic activity and selectivity.
[0148] Comparing Example 1 with Comparative Examples 2-3, it can be seen that the titanium-silicon molecular sieve prepared in Example 1 has better catalytic activity and selectivity. It is speculated that this invention may be due to the selection of specific organosilicon compounds, which can act as a bridge for the bonding between Si-OH and the depolymerized Ti-OH. Under the action of epoxy groups, the depolymerized Ti-OH is also connected to the molecular sieve framework, so that the titanium-silicon molecular sieve contains almost no non-framework titanium, thereby improving the catalytic activity and selectivity of the titanium-silicon molecular sieve.
[0149] 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 combinations of 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 method for preparing a titanium-silicon molecular sieve, characterized in that, The method includes the following steps: (1) A silicon source, an alkaline template agent, a titanium source and water are mixed to obtain a titanium silicon precursor; (2) The titanium silicon precursor is mixed with the organosilicon compound shown in formula (I) to obtain a mixture; (3) The mixture is microwave heated to crystallize it, the solid is separated from the crystallized product, and then dried and calcined; Where i is any integer from 1 to 10; n is any integer from 0 to 10; R1, R2, and R3 are each independently selected from methyl, ethyl, propyl, butyl, or pentyl.
2. The method according to claim 1, characterized in that, In step (3), the microwave heating conditions include: a temperature of 50-200℃ and a time of 0.5-10h.
3. The method according to claim 1, characterized in that, Step (1) specifically includes: mixing and stirring the silicon source, alkaline template agent and water, adding the titanium source during the stirring process, continuing to stir, and then performing alcohol removal treatment.
4. The method according to claim 3, characterized in that, The conditions for the alcohol removal treatment include: a temperature of 30-100℃ and a time of 2-10h.
5. The method according to claim 1 or 3, characterized in that, In step (1), the silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, silica gel, silica fume, and silica sol; and / or The alkaline template agent is selected from one or more of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines; and / or The titanium source is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.
6. The method according to any one of claims 1-5, characterized in that, In step (1), the silicon source is SiO2, and the molar ratio of the silicon source, alkaline template agent, and water is 1:0.05-0.4:5-40; and / or In step (1), the silicon source is SiO2 and the titanium source is TiO2, and the molar ratio of the silicon source and the titanium source is 1:0.001-0.
04.
7. The method according to any one of claims 1-6, characterized in that, The molar ratio of organosilicon compound to silicon source shown in formula (I) is 0.01-0.3:
1.
8. The method according to claim 1, characterized in that, The organosilicon compound is one or more of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).
9. The method according to claim 1, characterized in that, In step (3), the drying conditions include a temperature of 40 to 200°C and a time of 0.5 to 24 hours.
10. The method according to claim 1, characterized in that, In step (3), the calcination conditions include: a temperature of 400-800℃ and a time of 1-15h.
11. The titanium-silicon molecular sieve prepared by the method according to any one of claims 1-10.
12. The titanium-silicon molecular sieve according to claim 11, characterized in that, The ultraviolet spectrum of the titanium-silicon molecular sieve did not show the characteristic TiO2 peak located at 320±10nm.
13. The application of the titanium-silicon molecular sieve according to claim 11 or 12 in the catalytic propylene epoxidation reaction.