Titanium silicalite supported gold catalysts, processes for their preparation and use

Abstract

The application relates to the technical field of inorganic chemistry and catalytic chemistry, and discloses a titanium-silicon molecular sieve supported gold catalyst and a preparation method and application thereof. The method comprises the following steps: (1) mixing a silicon source, an alkaline template agent, a titanium source and water to obtain a titanium-silicon sol; (2) contacting a special organosilicon compound with a gold-containing compound to obtain a gold-containing complex; (3) mixing the gold-containing complex with the titanium-silicon sol and crystallizing, separating a solid from a crystallization product, and then performing calcination. The functional silanization agent and the gold complex are used to treat a titanium-silicon sol precursor, Au can be directionally loaded in the mesopore channels of the hierarchical pore titanium-silicon molecular sieve, the gold loading amount of the prepared titanium-silicon molecular sieve supported gold catalyst can be effectively improved, and the activity of the catalyst is improved.

Description

Technical Field

[0001] This invention relates to the fields of inorganic chemistry and catalytic chemistry, specifically to a gold catalyst supported on a titanium-silicon molecular sieve, its preparation method, and its application. Background Technology

[0002] Propylene oxide, as an important organic chemical raw material, is mainly used to produce downstream products such as polyether, propylene glycol and nonionic surfactants. Its derivative, polyurethane, can be used for sound insulation, packaging, thermal insulation and other applications, widely meeting the needs of industries such as construction, aviation and medicine, and is closely related to people's lives.

[0003] Currently, the direct oxidation of propylene oxide using air (or oxygen) is a gas-solid two-phase reaction, which is easy to operate, the products are easily separated, it is highly economical, and the process is green and environmentally friendly, aligning with the trend of green development in the propylene oxide industry. However, the gas-phase epoxidation process is still in the experimental stage, the technology is not yet mature, and there are no production enterprises using the direct oxidation method using air (or oxygen). To date, there has been substantial progress in laboratory research on the gas-phase epoxidation of propylene catalyzed by gold catalysts supported on titanium-silicon molecular sieves.

[0004] In recent years, researchers have primarily employed the deposition-precipitation (DP) method to prepare gold catalysts supported on titanium-silicon molecular sieves. During Au loading using the DP method, chloroauric acid gradually hydrolyzes and deposits on the support as an alkaline precipitant is added. However, the DP method can only deposit a small amount of Au species onto the support. The precipitant, solution pH, and support properties all significantly influence the Au loading. In particular, the Au loading is limited when the solution pH is high, the support Ti content is low, or the titanium-silicon molecular sieve is highly hydrophobic. Therefore, optimizing the preparation method of Au-supported catalysts on titanium-silicon molecular sieves has a significant impact on catalyst synthesis and its catalytic performance in the gas-phase epoxidation of propylene. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low gold loading in the bulk phase of titanium-silicon molecular sieves and poor catalytic activity in existing titanium-silicon molecular sieve-supported gold catalysts. This invention provides a titanium-silicon molecular sieve-supported gold catalyst, its preparation method, and its application. The method involves treating the titanium-silicon sol precursor with a functionalized silanizing reagent and a gold complex, which can directionally load Au into the mesoporous channels of the hierarchical titanium-silicon molecular sieve, thereby effectively improving the catalytic activity of the catalyst.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a gold catalyst supported on a titanium-silicon molecular sieve, the method comprising the following steps:

[0007] (1) Mix silicon source, alkaline template agent, titanium source and water to obtain titanium silica sol;

[0008] (2) The organosilicon compound shown in formula (I) is contacted with a gold-containing compound to obtain a gold-containing complex;

[0009] (3) The gold complex is mixed with the titanium silica sol and crystallized using microwave heating. The solid is separated from the crystallization product and then calcined.

[0010]

[0011] Where i is an integer from 1 to 6; R1, R2 and R3 are each independently C1-C6 alkyl groups; R4 and R5 are each independently hydrogen or C1-C6 alkyl groups; R6 is -SH, -NHR7 or -NH2; R7 is a C1-C6 alkyl group.

[0012] Preferably, in step (1), the process of preparing the titanium silica sol includes: first mixing the silicon source, the alkaline template agent and water, then adding the titanium source to the resulting mixture under stirring to obtain a transparent solution, and then heating the transparent solution to remove alcohol.

[0013] Preferably, the conditions for heating to remove alcohol include: a temperature of 30-90°C and a time of 2-10 hours.

[0014] Preferably, in step (1), the silicon source is selected from at least one 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 at least one of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines.

[0016] Preferably, the titanium source is selected from at least one of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.

[0017] Preferably, in step (1), the molar ratio of the alkaline template agent, the water, the titanium source and the silicon source is (0.05-0.4):(5-40):(0.001-0.04):1.

[0018] Preferably, in step (2), the conditions for contacting the organosilicon compound with the gold-containing compound include: a temperature of 10-60°C and a time of 0.5-24h.

[0019] Preferably, in step (2), the molar ratio of the gold-containing compound to the organosilicon compound is 1:1-10.

[0020] Preferably, the organosilicon compound is at least one of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).

[0021]

[0022] Preferably, the gold-containing compound is at least one selected from chloroauric acid, gold acetate, sodium gold thiosulfate, and sodium tetrachloroaurate.

[0023] Preferably, in step (3), the crystallization conditions include: a temperature of 50-200℃ and a time of 0.5-10h.

[0024] Preferably, in step (3), the molar ratio of the gold complex to the titanium silica sol (calculated as silicon) is 0.01-0.3:1.

[0025] Preferably, in step (3), the calcination conditions include: a temperature of 400-800℃ and a time of 1-15h.

[0026] A second aspect of the present invention provides a gold catalyst supported on a titanium-silicon molecular sieve prepared by the method described above.

[0027] A third aspect of the present invention provides the application of the gold catalyst supported on the titanium-silicon molecular sieve described above in the catalytic gas-phase epoxidation reaction of propylene.

[0028] The method for preparing the gold-supported titanium-silicon molecular sieve catalyst of the present invention involves treating the titanium-silicon sol precursor with a functionalized silanizing agent and a gold complex, which enables Au to be directionally loaded into the mesoporous channels of the hierarchical titanium-silicon molecular sieve. Compared with the prior art, this method can effectively increase the gold loading of the prepared gold-supported titanium-silicon molecular sieve catalyst, thereby improving the catalytic activity of the catalyst.

[0029] The titanium-silicon molecular sieve-supported gold catalyst described in this invention exhibits excellent catalytic activity when applied to the gas-phase epoxidation reaction of propylene. Specifically, the propylene conversion rate is above 4%, and the propylene oxide selectivity is above 80%. Attached Figure Description

[0030] Figure 1 This is a TEM image of the gold catalyst Cat-1 supported on the titanium-silicon molecular sieve prepared in Example 1;

[0031] Figure 2 This is a TEM image of the gold catalyst D-Cat-1 supported on the titanium-silicon molecular sieve prepared in Comparative Example 1. Detailed Implementation

[0032] 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.

[0033] 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.

[0034] The preparation method of the gold catalyst supported on titanium-silicon molecular sieves according to the present invention includes the following steps:

[0035] (1) Mix silicon source, alkaline template agent, titanium source and water to obtain titanium silica sol;

[0036] (2) The organosilicon compound shown in formula (I) is contacted with a gold-containing compound to obtain a gold-containing complex;

[0037] (3) The gold complex is mixed with the titanium silica sol and crystallized using microwave heating. The solid is separated from the crystallization product and then calcined.

[0038]

[0039] Where i is an integer from 1 to 6; R1, R2 and R3 are each independently C1-C6 alkyl groups; R4 and R5 are each independently hydrogen or C1-C6 alkyl groups; R6 is -SH, -NHR7 or -NH2; R7 is a C1-C6 alkyl group.

[0040] In some embodiments, the process of preparing the titanium silica sol in step (1) includes: first mixing a silicon source, an alkaline template agent, and water; then adding a titanium source to the resulting mixture under stirring to obtain a transparent solution; and finally heating the transparent solution to remove alcohol. In these embodiments, when the titanium silica sol is prepared according to the above steps, the titanium silica molecular sieve prepared from the titanium silica sol has a better pore structure.

[0041] In a preferred embodiment, the process of preparing the titanium silica sol in step (1) further includes: first mixing the silicon source, alkaline template agent and water and stirring for 0.1-2 hours, then adding the titanium source to the resulting mixture while stirring and continuing to stir for 0.5-6 hours to obtain a colorless and transparent solution.

[0042] In a preferred embodiment, the conditions for heating to remove alcohol include: a temperature of 30-90°C, more preferably 50-70°C, and a time of 2-10 hours, more preferably 6-8 hours. In these preferred embodiments, when the conditions for heating to remove alcohol are within the above ranges (especially the preferred ranges), the removal of alcohol from the titanium silica sol is more thorough.

[0043] In some embodiments, the process of preparing the titanium silica sol includes: first mixing and stirring a silicon source, an alkaline template agent, and water for 0.1-2 hours; then adding a titanium source to the resulting mixture while stirring and continuing to stir for 0.5-6 hours to obtain a colorless and transparent solution; and then heating the transparent solution to remove alcohol, wherein the conditions for heating to remove alcohol include a temperature of 30-90°C and a time of 0.5-6 hours. When step (1) is performed according to this embodiment, the prepared titanium silica molecular sieve has a good pore structure.

[0044] In this invention, the silicon source may be selected from at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, silica gel, silica fume, and silica sol, with ethyl orthosilicate being the most preferred.

[0045] In this invention, the basic template agent can be selected from at least one of quaternary ammonium bases, aliphatic amines, and aliphatic alkanolamines. The quaternary ammonium base can be at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. The aliphatic amine can be at least one of dodecylamine, methylalkylamine, 2-ethylhexylamine, and hexadecylamine. The aliphatic alkanolamine can be at least one of fatty acyl diethanolamine, ethanolamine, diethanolamine, and N-phenylethanolamine. Preferably, the basic template agent is at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, with tetrapropylammonium hydroxide being the most preferred.

[0046] In this invention, the titanium source may be selected from at least one of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate, with tetraethyl titanate being the most preferred.

[0047] When the silicon source, the alkaline template agent, and the titanium source are selected from the above-mentioned substances (especially preferred substances), the titanium-silicon molecular sieve prepared from the above-mentioned raw materials has a better pore structure.

[0048] In the method described in this invention, in step (1), the alkaline template agent is calculated as nitrogen (when containing nitrogen) or as OH... -The molar ratio of the alkaline template agent, water, titanium source (calculated as TiO2), and silicon source (calculated as SiO2) can be (0.05-0.4):(5-40):(0.001-0.04):1, preferably (0.1-0.3):(5-25):(0.005-0.025):1, and more preferably (0.2-0.3):(5-10):(0.005-0.025):1. In these embodiments, when the molar ratio of the alkaline template agent, water, titanium source, and silicon source is within the above range (especially the preferred range), the titanium-silicon molecular sieve prepared from the above raw materials has a better pore structure.

[0049] In the method described in this invention, in step (2), the conditions for contacting the organosilicon compound with the gold-containing compound may further include: a temperature of 10-60°C, preferably 20-50°C; and a time of 0.5-24 h, preferably 1-10 h. In these embodiments, when the conditions for contacting the organosilicon compound with the gold-containing compound are within the above-mentioned ranges (especially the preferred ranges), the coordination efficiency of the organosilicon compound and the gold-containing compound is higher during contact.

[0050] In the method described in this invention, in step (2), the molar ratio of the organosilicon compound to the gold-containing compound can be 1-10:1, preferably 1-8:1. In this invention, when the molar ratio of the gold-containing compound to the organosilicon compound is within the above range (especially the preferred range), the coordination efficiency of the organosilicon compound and the gold-containing compound is higher upon contact.

[0051] In the organosilicon compound shown in formula (I), i is an integer from 1 to 6, specifically, for example, 1, 2, 3, 4, 5 or 6.

[0052] In the organosilicon compound shown in formula (I), R1, R2, and R3 may be the same or different, but are preferably the same. As a specific example, R1, R2, and R3 are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or pentyl.

[0053] In the organosilicon compound shown in formula (I), as an example, R4 and R5 are each independently selected from hydrogen, methyl, ethyl, n-propyl, or isopropyl, with hydrogen or methyl being the most preferred. R4 and R5 may be the same or different, but are preferably the same.

[0054] In the organosilicon compound shown in formula (I), when R6 is -NHR7, R7 can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or pentyl, preferably methyl or ethyl.

[0055] In a preferred embodiment, the organosilicon compound is at least one of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).

[0056]

[0057] In this invention, the gold-containing compound can be at least one of chloroauric acid, gold acetate, sodium gold thiosulfate, and sodium tetrachloroaurate, with chloroauric acid being the most preferred.

[0058] In the method described in this invention, the process of mixing the gold complex with the titanium silica sol in step (3) may further include: adding the gold complex to the titanium silica sol under stirring and continuing to stir for 0-24 hours, preferably 0.5-10 hours.

[0059] In the method described in this invention, the crystallization conditions in step (3) may include: a temperature of 50-200℃, preferably 100-180℃; and a time of 0.5-10h, preferably 2-8h. In this invention, when the crystallization conditions are within the above range (especially the preferred range), the gold active site loading in the titanium-silicon molecular sieve-supported gold catalyst prepared according to this invention is higher.

[0060] In the method described in this invention, in step (3), the molar ratio of the gold complex to the titanium silica sol (based on silicon element) is 0.01-0.3:1, preferably 0.05-0.2:1. In this invention, when the molar ratio of the raw materials is within the above range (especially the preferred range), the gold active sites in the prepared titanium silica molecular sieve-supported gold catalyst of this invention are higher.

[0061] In the method described in this invention, in step (3), the loading of gold element in the mixture obtained by mixing the gold complex with the titanium silica sol is 0.05%-0.5wt%, preferably 0.05%-0.2wt%. In these embodiments, when the loading of gold element is within the above range (especially the preferred range), the prepared titanium silica molecular sieve-supported gold catalyst has better catalytic activity.

[0062] In the method described in this invention, step (3) may further include: washing and filtering the crystallized product, and then placing the separated solid product into an oven to dry.

[0063] In a preferred embodiment, the washing process may further include rinsing or soaking the crystallized product with water, wherein the volume ratio of water to the crystallized product is 1-20:1.

[0064] In a preferred embodiment, the drying conditions may include: a temperature of 40-150°C, preferably 100-140°C; and a time of 1-15 hours, preferably 1-5 hours.

[0065] In the method described in this invention, the calcination conditions in step (3) may include: a temperature of 400-800℃, preferably 400-600℃; and a time of 1-15h, preferably 4-8h.

[0066] In some embodiments, the process of preparing the gold-supported titanium-silicon molecular sieve catalyst includes: adding the gold-containing complex to the titanium-silicon sol under stirring and continuing stirring for 0-24 hours; then placing the resulting mixture in a microwave heater and crystallizing it at 50-200°C for 0.5-10 hours; washing and filtering the crystallized product with water; then placing the separated solid product in an oven and drying it at 40-150°C for 0.5-24 hours; and finally calcining it at 400-800°C for 1-15 hours. When step (3) is carried out according to this embodiment, the gold-supported titanium-silicon molecular sieve catalyst prepared has a good pore structure and a high gold active site loading.

[0067] The gold-supported titanium-silicon molecular sieve catalyst prepared by the method described in this invention possesses a good mesoporous structure. In this catalyst, the gold active sites are directionally loaded within the hierarchical mesoporous channels of the titanium-silicon molecular sieve, exhibiting excellent catalytic activity. This gold-supported titanium-silicon molecular sieve catalyst can be widely applied in chemical production processes, demonstrating excellent catalytic effects in the gas-phase oxidation and epoxidation of hydrocarbons, such as the gas-phase epoxidation of propylene. In a preferred embodiment, when the gold nanoparticle catalyst supported on the titanium-silicon molecular sieve is applied to the catalytic gas-phase epoxidation of propylene, the propylene conversion rate is above 4%, and the propylene oxide selectivity is above 80%.

[0068] The following examples further illustrate the titanium-silicon molecular sieve-supported gold catalyst, its preparation method, and its application according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0069] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples are commercially available.

[0070] Unless otherwise specified, all other reagents used in the following examples and comparative examples are commercially available products.

[0071] Example 1

[0072] (1) Tetraethyl orthosilicate, tetrapropylammonium hydroxide and water are mixed in a molar ratio of 1:0.25:15. The resulting mixture is stirred at room temperature. During the stirring process, tetraethyl titanate is added to the mixture and stirring is continued for 2.5 h to obtain a transparent solution. The molar ratio of tetraethyl orthosilicate to tetraethyl titanate is 1:0.01. The transparent solution is placed on a magnetic stirrer and heated to 60°C and kept at a constant temperature for 7 h to remove alcohol and obtain titanium silicate sol.

[0073] (2) The organosilicon compound with the structure shown in formula (I-1) was mixed with chloroauric acid and reacted at 25°C for 2 h to obtain a gold-containing complex;

[0074] (3) The gold-containing complex is added to the titanium silicate sol, and the resulting mixture is stirred at room temperature for 3 hours. The molar ratio of the gold-containing complex to the tetraethyl orthosilicate is 0.15:1 (based on gold element). The mixture is placed in a microwave heating device, heated to 120°C and hydrothermally crystallized for 5 hours. The hydrothermally crystallized material is washed with water, filtered, and the separated solid product is dried at 120°C for 2 hours. The dried solid product is then placed in a tube furnace and calcined at 550°C for 6 hours to obtain the titanium silicate molecular sieve-supported gold catalyst of the present invention, designated as Cat-1.

[0075] Example 2

[0076] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), the molar ratio of tetraethyl orthosilicate, tetrapropylammonium hydroxide and water is 1:0.05:15, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is called Cat-2.

[0077] Example 3

[0078] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), the molar ratio of tetraethyl orthosilicate, tetrapropylammonium hydroxide and water is 1:0.40:40, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is called Cat-3.

[0079] Example 4

[0080] This embodiment is carried out according to the method described in Example 1, except that in step (1), the molar ratio of tetraethyl orthosilicate and tetraethyl titanate is 1:0.001, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is designated as Cat-4.

[0081] Example 5

[0082] This embodiment is carried out according to the method described in Example 1, except that in step (1), the molar ratio of tetraethyl orthosilicate and tetraethyl titanate is 1:0.04, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is designated as Cat-5.

[0083] Example 6

[0084] This embodiment is implemented according to the method described in Example 1. The difference is that in step (1), tetraethyl titanate is added to the mixture during the stirring process and stirring is continued for 0.5 h to obtain titanium silica sol, and the titanium silica molecular sieve supported gold catalyst of the present invention is prepared, which is named Cat-6.

[0085] Example 7

[0086] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), tetraethyl titanate is added to the mixture during the stirring process and stirring is continued for 6 hours to obtain titanium silica sol, and the titanium silica molecular sieve supported gold catalyst of the present invention is prepared, which is named Cat-7.

[0087] Example 8

[0088] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), the transparent solution is placed on a magnetic stirrer and heated to 90°C and kept at a constant temperature for 3 hours to remove alcohol, thereby obtaining titanium silica sol and preparing the titanium silica molecular sieve supported gold catalyst of the present invention, designated as Cat-8.

[0089] Example 9

[0090] This embodiment is implemented according to the method described in Example 1. The difference is that in step (1), the transparent solution is placed on a magnetic stirrer and heated to 30°C and kept at a constant temperature for 10 hours to remove alcohol, thereby obtaining titanium silica sol and preparing the titanium silica molecular sieve supported gold catalyst of the present invention, designated as Cat-9.

[0091] Example 10

[0092] This embodiment is carried out according to the method described in Example 1, except that in step (1), the tetraethyl orthosilicate is replaced with tetramethyl orthosilicate and the tetraethyl titanate is replaced with tetrabutyl titanate to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, designated as Cat-10.

[0093] Example 11

[0094] This embodiment is carried out according to the method described in Example 1, except that in step (1), the tetraethyl orthosilicate is replaced with tetrapropyl orthosilicate and the tetraethyl titanate is replaced with titanium sulfate to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, named Cat-11.

[0095] Example 12

[0096] This embodiment is carried out according to the method described in Example 1, except that in step (1), the tetraethyl orthosilicate is replaced with tetrabutyl orthosilicate, the tetraethyl titanate is replaced with tetrabutyl titanate, and the tetrapropylammonium hydroxide is replaced with tetrabutylammonium hydroxide to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, named Cat-12.

[0097] Example 13

[0098] This embodiment is carried out according to the method described in Example 1. The difference is that in step (2), the organosilicon compound with the structure shown in formula (I-1) is replaced with the organosilicon compound with the structure shown in formula (I-2) to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is named Cat-13.

[0099] Example 14

[0100] This embodiment is carried out according to the method described in Example 1. The difference is that in step (2), the organosilicon compound with the structure shown in formula (I-1) is replaced with the organosilicon compound with the structure shown in formula (I-3) to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is named Cat-14.

[0101] Example 15

[0102] This embodiment is carried out according to the method described in Example 1. The difference is that in step (3), the molar ratio of the gold complex to the tetraethyl orthosilicate, calculated as silicon, is 0.01:1, and the gold catalyst supported on the titanium-silicon molecular sieve of the present invention is prepared as Cat-15.

[0103] Example 16

[0104] This embodiment is carried out according to the method described in Example 1. The difference is that in step (3), the molar ratio of the gold complex to the tetraethyl orthosilicate, calculated as silicon, is 0.3:1, and the gold catalyst supported on the titanium-silicon molecular sieve of the present invention is prepared as Cat-16.

[0105] Example 17

[0106] This embodiment is carried out according to the method described in Example 1. The difference is that in step (3), the gold complex is added to the titanium silica sol, and the resulting mixture is stirred at room temperature for 1 hour to prepare the titanium silica molecular sieve supported gold catalyst of the present invention, which is named Cat-17.

[0107] Example 18

[0108] This embodiment is carried out according to the method described in Example 1. The difference is that in step (3), the gold complex is added to the titanium silica sol, and the resulting mixture is stirred at room temperature for 24 hours to prepare the titanium silica molecular sieve supported gold catalyst of the present invention, which is named Cat-18.

[0109] Example 19

[0110] This embodiment is implemented according to the method described in Embodiment 1. The difference is that in step (3), the mixed system is placed in a microwave heating device, heated to 50°C and hydrothermally crystallized for 0.5 h to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is designated as Cat-19.

[0111] Example 20

[0112] This embodiment is implemented according to the method described in Embodiment 1. The difference is that in step (3), the mixed system is placed in a microwave heating device, heated to 200°C and hydrothermally crystallized for 10 hours to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is named Cat-20.

[0113] Example 21

[0114] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), the molar ratio of tetraethyl orthosilicate, tetrapropylammonium hydroxide and water is 1:0.03:45, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is named Cat-21.

[0115] Example 22

[0116] This embodiment is carried out according to the method described in Example 1, except that in step (1), the molar ratio of tetraethyl orthosilicate and tetraethyl titanate is 1:0.045, and the titanium-silicon molecular sieve supported gold catalyst of the present invention is prepared, which is named Cat-22.

[0117] Example 23

[0118] This embodiment is carried out according to the method described in Example 1. The difference is that in step (1), the transparent solution is placed on a magnetic stirrer and kept at a constant temperature of 25°C for 12 hours to remove alcohol, so as to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is named Cat-23.

[0119] Example 24

[0120] This embodiment is carried out according to the method described in Example 1. The difference is that in step (2), the organosilicon compound with the structure shown in formula (I-1) is replaced with an aqueous solution of 3-mercaptopropyltrimethoxysilane ligand to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is named Cat-24.

[0121] Example 25

[0122] This embodiment is implemented according to the method described in Example 1. The difference is that in step (3), the molar ratio of the gold complex to the tetraethyl orthosilicate is 0.4:1, and the gold catalyst supported on the titanium-silicon molecular sieve of the present invention is prepared as Cat-25.

[0123] Example 26

[0124] This embodiment is implemented according to the method described in Embodiment 1. The difference is that in step (3), the mixed system is placed in a microwave heating device and hydrothermally crystallized at 30°C for 0.5 h to prepare the titanium-silicon molecular sieve supported gold catalyst of the present invention, which is designated as Cat-26.

[0125] Comparative Example 1

[0126] (1) Mix 19.2g of tetraethyl silicate and 0.354g of tetraethyl titanate and stir at 35°C for 0.5h. Cool the resulting mixture to 0°C using an ice bath. Then add 20g of 40% tetrapropylammonium hydroxide aqueous solution dropwise to the mixture. Heat the mixture at 80°C for 4h to remove alcohol and obtain titanium silica sol.

[0127] (2) Add 0.387g of the organosilicon compound with the structure shown in formula (I-1) to the titanium silica sol, mix evenly, and then add 0.02-0.11g of chloroauric acid trihydrate dropwise to the resulting mixture. Heat the mixture to 80°C and keep it at that temperature for 4h. Then transfer it to a high-pressure reactor and crystallize it at 135°C for 80h to obtain a titanium silica molecular sieve supported gold catalyst, designated as D-Cat-1.

[0128] Comparative Example 2

[0129] This comparative example is carried out according to the method described in the example, except that in step (2), the organosilicon compound with the structure shown in formula (I-1) is replaced with vinyltrimethoxysilane to obtain a titanium silicon molecular sieve supported gold catalyst, denoted as D-Cat-2.

[0130] Test Example 1

[0131] In this test example, the morphology of the gold catalyst supported on the titanium-silicon molecular sieve prepared in Example 1 and Comparative Example 1 was characterized by TEM.

[0132] Depend on Figure 1 As can be seen, the gold catalyst Au nanoparticles supported on the titanium-silicon molecular sieve prepared in Example 1 were successfully loaded into the mesoporous channels of the titanium-silicon molecular sieve and the size was about 1 nm.

[0133] Depend on Figure 2 It can be seen that the gold catalyst Au nanoparticles supported on the titanium-silicon molecular sieve prepared in Comparative Example 1 all float on the surface of the molecular sieve and have a size > 2 nm.

[0134] Test Example 2

[0135] This test example illustrates the catalytic performance of the sample prepared in the embodiments and comparative examples of this invention in the gas-phase epoxidation reaction of propylene. 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, with a molecular sieve 5A and a PoraBOND U column, and FID and TCD detectors.

[0136] The titanium-silicon molecular sieve-supported gold catalysts Cat-1 to Cat-26 prepared in Examples 1-26 of the present invention and the titanium-silicon molecular sieve-supported gold catalyst D-Cat-1 prepared in Comparative Example 1 were respectively placed in a tubular reactor with an inner diameter of 8 mm. The reactor was heated to 180 °C in a N2 atmosphere, and then hydrogen, oxygen, and propylene were introduced into the tubular reactor to start the reaction. After 1 h of reaction, the product was analyzed online and the propylene conversion rate and propylene oxide selectivity were calculated. The amount of catalyst used was 0.4 g, the flow rates of hydrogen, oxygen, propylene, and nitrogen were 2, 2, 2, and 14 mL / min, respectively, and the reaction pressure was 0.1 MPa.

[0137] Propylene conversion rate % = (Moles of propylene in feedstock - Moles of propylene in product) / Moles of propylene in feedstock × 100%

[0138] Propylene oxide selectivity % = (Number of moles of propylene oxide in the product / Total number of moles of the product) × 100%

[0139] The results are shown in Table 2.

[0140] Table 2

[0141]

[0142]

[0143] As can be seen from the results in Table 1, when the method described in this invention is applied to the propylene gas-phase epoxidation reaction, the titanium-silicon molecular sieve-supported gold catalysts Cat-1 to Cat-26 prepared in Examples 1-26 have better catalytic activity than the catalyst D-Cat-1 prepared in Comparative Example 1. When applied to the propylene gas-phase epoxidation reaction, the propylene conversion rate is >4% and the propylene oxide selectivity is >88%. Furthermore, when the Cat-1 to Cat-20 prepared in Preferred Examples 1-20 are applied to the propylene gas-phase epoxidation reaction, the propylene conversion rate is >6% and the propylene oxide selectivity is >90%.

[0144] 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 gold catalyst supported on a titanium-silicon molecular sieve, characterized in that, The method includes the following steps: (1) Mix silicon source, alkaline template agent, titanium source and water to obtain titanium silica sol; (2) The organosilicon compound shown in formula (I) is contacted with a gold-containing compound to obtain a gold-containing complex; (3) The gold complex is mixed with the titanium silica sol and crystallized using microwave heating. The solid is separated from the crystallization product and then calcined. Where i is an integer from 1 to 6; R1, R2 and R3 are each independently C1-C6 alkyl groups; R4 and R5 are each independently hydrogen or C1-C6 alkyl groups; R6 is -SH, -NHR7 or -NH2; R7 is a C1-C6 alkyl group.

2. The method according to claim 1, characterized in that, In step (1), the process of preparing the titanium silica sol includes: first mixing the silicon source, the alkaline template agent and water, then adding the titanium source to the resulting mixture under stirring to obtain a transparent solution, and then heating the transparent solution to remove alcohol; Preferably, the conditions for heating to remove alcohol include: a temperature of 30-90°C and a time of 2-10 hours.

3. The method according to claim 1 or 2, characterized in that, In step (1), the silicon source is selected from at least one 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 at least one of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines; and / or The titanium source is selected from at least one of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.

4. The method according to claim 1 or 2, characterized in that, In step (1), the molar ratio of the alkaline template agent, the water, the titanium source and the silicon source is (0.05-0.4):(5-40):(0.001-0.04):

1.

5. The method according to claim 1, characterized in that, In step (2), the conditions for contacting the organosilicon compound with the gold-containing compound include: a temperature of 10-60°C and a time of 0.5-24h.

6. The method according to claim 1 or 5, characterized in that, In step (2), the molar ratio of the organosilicon compound to the gold-containing compound is 1-10:

1.

7. The method according to claim 1, 5, or 6, characterized in that, The organosilicon compound is at least one of the compounds shown in formula (I-1), formula (I-2), and formula (I-3).

8. The method according to claim 1, 5, or 6, characterized in that, The gold-containing compound is at least one of chloroauric acid, gold acetate, sodium gold thiosulfate, and sodium tetrachloroaurate.

9. The method according to claim 1, characterized in that, In step (3), the crystallization conditions include a temperature of 50-200℃ and a time of 0.5-10h.

10. The method according to claim 1, characterized in that, In step (3), the molar ratio of the gold complex to the titanium silica sol (calculated as silicon) is 0.01-0.3:

1.

11. 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.

12. A gold catalyst supported on a titanium-silicon molecular sieve prepared by the method according to any one of claims 1-9.

13. The application of the titanium-silicon molecular sieve-supported gold catalyst according to claim 12 in the catalytic gas-phase epoxidation reaction of propylene.

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