Preparation method of Au (M < + >) / Ti-MWW catalyst modified by alkali metal cations and application of Au (M < + >) / Ti-MWW catalyst in selective oxidation reaction of propylene

Abstract

The invention belongs to the technical field of industrial catalysis, and mainly relates to preparation of a high-activity and high-stability gold supported catalyst and application of the high-activity and high-stability gold supported catalyst to propylene epoxidation reaction in a hydrogen-oxygen system. A Ti-MWW molecular sieve with a special confinement structure is adopted as a carrier, the Au (M < + >) / Ti-MWW composite catalytic material is prepared through a cation modification method in the gold loading process, the Au (M < + >) / Ti-MWW composite catalytic material is used in the reaction for preparing epoxypropane through propylene gas-phase epoxidation, and the catalytic activity and catalytic stability of the Au (M < + >) / Ti-MWW composite catalytic material are greatly improved. The conversion rate of the catalyst in propylene gas-phase epoxidation reaches 5% or above, the selectivity of epoxypropane reaches 90% or above, and the service life is 200 hours or above. The catalyst provided by the invention is simple in preparation process, solves the key bottleneck problems of low activity, low selectivity, poor stability and the like of the gold supported / titanium silicalite molecular sieve catalyst prepared in the prior art, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial catalysis, and mainly relates to the preparation of a highly active and highly stable gold-loaded catalyst and its use in the propylene epoxidation reaction of a hydrogen-oxygen system. The present invention provides a Ti-MWW molecular sieve with a special confinement structure as a carrier, and by using a cation modification method during the process of loading gold, an Au(M + ) / Ti-MWW composite catalytic material is prepared and used in the reaction of gas-phase epoxidation of propylene to prepare propylene oxide, greatly improving its catalytic activity and catalytic stability. The conversion rate of this catalyst in the gas-phase epoxidation of propylene reaches more than 5%, the selectivity of propylene oxide is more than 90%, and the service life is more than 200 hours. The catalyst preparation process provided by the present invention is simple, solves the key bottleneck problems such as low activity, low selectivity and poor stability of the gold-loaded / titanium silicate molecular sieve catalyst prepared by the prior art, and is suitable for large-scale industrial production. Background Art

[0002] Propylene oxide is the second largest derivative of propylene. It has a broad market and large demand, and is widely used in industries such as furniture, household appliances, automobiles, and coatings, which is closely related to our lives. At present, there are mainly three production processes for propylene oxide in industry: the chlorohydrin method, the co-oxidation method, and the direct oxidation method of hydrogen peroxide. A large amount of halogen-containing waste liquid will be generated during the production process of the chlorohydrin method, seriously polluting the environment. The economic benefits of the co-oxidation method are greatly restricted by co-products. The oxidant hydrogen peroxide in the direct oxidation method of hydrogen peroxide is expensive and the cost is high. Directly using hydrogen, oxygen and propylene as raw materials can greatly reduce the cost, and the only by-product of this reaction is water, which is very friendly to the environment.

[0003] In 1998, Japanese scientist Haruta (J. Catal., 1998, 178, 566 - 575) and his colleagues loaded gold on TiO₂ and found that it could directly catalyze the selective oxidation of propylene to prepare propylene oxide in a hydrogen-oxygen system. Although the selectivity of propylene oxide was above 95%, the conversion rate of propylene was only 1 - 2%, and its stability was poor, with a lifespan of less than 10 hours. Subsequently, numerous titanium-containing supports were used in the preparation of propylene gas-phase epoxidation catalysts, such as Au / TS-1 (Ind. Eng. Chem. Res., 1999, 38, 884 - 891), Au / Ti-MCM-41 (Appl. Catal. A-Gen., 2000, 190, 43 - 50), Au / Ti-SBA-15 (J. Catal., 2008, 259, 43 - 53), Au / Ti-MCM-48 (J. Catal., 2002, 209, 331 - 340), Au / TS-2 (AICHE J., 2020, 66, e16815), etc. However, most current catalysts have problems such as poor low-temperature activity and poor high-temperature stability in gas-phase propylene epoxidation, which restricts the practical application of this process.

[0004] The method of loading gold on titanium-containing supports plays a crucial role in the activity, selectivity, and stability of propylene gas-phase epoxidation catalysts. Currently, the main method of loading gold on titanium-containing supports is the deposition-precipitation method. In addition, there are also methods such as inorganic salt impregnation and low-temperature freeze-drying. Among them, the selection of precipitants and preparation conditions will have a significant impact on the activity of the catalyst. For example, Patent CN109928942A discloses a catalytic material modified with a bimetallic promoter (a mixture of alkali metal salts and carbonates as a precipitant) for gas-phase propylene epoxidation. Although this method improves the catalytic activity, the evaluation of the catalyst's stability is only 15 hours, making it difficult to evaluate the long-term stability of the catalyst. Patent CN111822044A discloses a method of impregnating and modifying an Au / TS-1 catalyst with alkali metal carbonate for gas-phase propylene epoxidation. Although this preparation method can significantly improve the activity and stability of the catalyst, the selectivity will decrease with the increase of reaction time, only about 80%. Patent CN116212948A discloses a method of introducing group ⅣB oxides into Au / TS1 for modification and its application in propylene gas-phase epoxidation. This method reduces the catalytic temperature, improves the hydrogen efficiency and the selectivity of propylene oxide, but does not evaluate the stability. Currently, there are still bottlenecks in the preparation of catalysts with high activity, high propylene oxide selectivity (90%), and high stability (>100 hours), which severely restricts their industrial application.

[0005] The Ti-containing support is an important factor in this catalyst, which will affect the deposition position and loading amount of gold, and directly determines whether propylene can be selectively oxidized to propylene oxide. In addition to TS-1, which has been the most widely studied, Ti-MWW zeolite shows much higher catalytic activity than TS-1 zeolite in the liquid-phase epoxidation of olefins. Ti-MWW zeolite is a titanium silicate zeolite with a MWW-type topological structure (MWW is the structure code given by the International Zeolite Association to zeolites with such structures, and its specific structure is shown below). For example, Patent CN1709574A discloses a preparation method and application of a boron-containing titanium silicate zeolite with a MWW structure, indicating its ultra-high catalytic activity and selectivity in various reactions such as olefin epoxidation. In addition, Ti-MWW zeolite has a special configuration completely different from other titanium silicate zeolites. A large number of supercages in its crystal and bowl-shaped cavities on the surface can both serve as the confined space for loading gold species, which can improve the catalytic stability after gold loading. However, in the reaction of gas-phase epoxidation of propylene to propylene oxide, Wu Peng et al. (Pure Appl. Chem., 2012, 84, 561-578) used the traditional deposition-precipitation method (NaOH as the precipitating agent) to load gold on Ti-MWW zeolite for gas-phase propylene epoxidation. However, the propylene conversion was only 0.5-2%, and the selectivity was <80%, and it deactivated severely within 6 hours. This may be due to the acidity brought by a large number of silanol groups on the surface of Ti-MWW zeolite, which is unfavorable for this reaction, and the traditional deposition-precipitation method using NaOH as the precipitating agent cannot effectively neutralize the acidity of the support Ti-MWW zeolite and the gold content deposited on the support is too low.

[0006] In summary, although the direct use of hydrogen, oxygen, and propylene as raw materials for the propylene selective oxidation reaction is advanced in the technical route, the catalytic materials obtained by the existing preparation technologies are far lower than the actual application standards in terms of activity and stability. This is mainly due to the fact that the titanium silicate zeolite support is difficult to provide a confined environment that can stabilize gold species and the acidity of the support itself. Therefore, innovation must be made in the construction of the confined environment for loading gold in the titanium silicate zeolite and the method of acid property modulation. This patent uses Ti-MWW zeolite with a special cage-like confined structure as the support, develops a new preparation method for loading gold, and realizes the modulation of the acid properties of the zeolite during the gold loading process, solving the bottleneck problem of poor catalytic activity and stability of the Au / Ti-MWW catalyst in the propylene selective oxidation reaction.

[0007] Summary of the Invention

[0008] In view of the deficiencies in the prior art, this patent discloses a catalyst for the gas-phase epoxidation of propylene to propylene oxide in a hydrogen and oxygen system and its preparation method. The present invention uses a titanium silicate molecular sieve with a special cage-confined environment of MWW topological structure as a carrier (i.e., Ti-MWW molecular sieve), which provides more space for the deposition of gold and increases the gold loading amount (>0.2 wt%). During the process of loading gold species, the acidity of the Ti-MWW carrier is effectively inhibited by the method of alkali metal cation modification. The conversion rate of this catalyst in the gas-phase epoxidation of propylene reaches more than 5%, the selectivity of propylene oxide is more than 90%, and the service life is 200 hours or more. Compared with the previously disclosed catalytic materials, the present invention solves the key bottleneck problems such as low activity, low selectivity, and poor stability of the gold-loaded / titanium silicate molecular sieve catalysts prepared by the prior art.

[0009] The technical solution provided by the present invention is as follows:

[0010] A preparation method of a propylene epoxidation catalyst in a hydrogen-oxygen system, comprising the following steps:

[0011] (1) Preparation of MWW-type titanium silicate molecular sieve catalyst: Add a silicon source, a titanium source, boric acid, an organic template agent, potassium carbonate, and water in a certain proportion into a polytetrafluoroethylene inner liner, crystallize under high temperature and dynamic conditions, and after washing, filtering, drying, pickling, and calcination, a Ti-MWW molecular sieve catalyst is prepared.

[0012] (2) Modification of Ti-MWW molecular sieve with alkali metal cations and loading of gold (2.1) Loading of gold after modification with alkali metal cations first: Mix Ti-MWW and an aqueous solution of alkali metal nitrate, adjust the pH with an alkali solution of the same alkali metal ion for ion exchange, wash, and dry to obtain a catalyst precursor modified with cations. Mix the above modified catalyst precursor and an aqueous solution of chloroauric acid, add the same alkali metal carbonate as a precipitant, stir for a period of time, filter by suction, and dry in vacuum to obtain an Au(M + ) / Ti-MWW catalyst, M + represents the type of alkali metal cation.

[0013] (2.2) Simultaneous modification of alkali metal cations and loading of gold: Add Ti-MWW molecular sieve into an aqueous solution of chloroauric acid, add an alkali metal carbonate solution, stir, filter, wash, and dry in vacuum to obtain an Au(M + ) / Ti-MWW catalyst, M + represents the type of alkali metal cation.

[0014] Further, in step (1), the silicon source is one of silica aerosol and silica liquid sol, the titanium source is one of tetrabutyl titanate (TBOT) and hexafluorotitanic acid, and the template agent (abbreviated as OSDA) is one or more of hexamethyleneimine (HMI), piperidine (PI), and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH). The molar composition range of the synthesis gel is: SiO2:TBOT:OSDA:K2CO3:H3BO3:H2O = 1:(0.015 - 0.05):(0.01 - 0.045):(0.1 - 1.5):(0 - 1.34):(15 - 45).

[0015] Further, in step (2), the nitrate is an alkali metal nitrate (CsNO3, NaNO3, KNO3), the alkali solution is an aqueous solution of an alkali metal hydroxide (CsOH, NaOH, KOH), and the carbonate is an alkali metal carbonate (Cs2CO3, Na2CO3, K2CO3).

[0016] Further, in step (2), during cation modification, the pH range of the solution is adjusted to 4 - 9. The content of gold in the chloroauric acid aqueous solution is 0.01 g / mL, and the feeding amount of gold is 0.01 - 5 wt.% of the catalyst. The molar ratio of the carbonate feeding amount to gold is 2 - 10.

[0017] The present invention also provides the application of the above catalyst in the gas-phase epoxidation of propylene in a hydrogen-oxygen system. The gas-phase epoxidation of propylene is carried out in a fixed bed, the reaction pressure is 0.1 - 2 MPa, the reaction temperature is 130 - 250 °C, the reaction gas composition is C3H6:H2:O2:Ar = 0.1 - 1:1:1:7.9 - 1 (volume ratio), the space velocity is 4000 - 18000 mL / (h·g cat ), and the reaction tail gas is detected and analyzed by gas chromatography.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention uses Ti-MWW molecular sieve with a special supercage structure as the carrier for gold loading, which provides more effective confinement space for the deposition of gold and can increase the gold loading amount (>0.2 wt%). The present invention modifies the MWW-type titanium-silicon molecular sieve carrier with alkali metal cations, which can effectively inhibit the acidity of the carrier. It has excellent performance in the propylene epoxidation in a hydrogen-oxygen system, with a propylene conversion rate higher than 5%, a selectivity for propylene oxide higher than 90%, and a catalytic stability ≥ 200 hours, solving the problems of poor stability, poor selectivity, and low activity of the gold-based catalysts prepared by the prior art. Description of the Drawings

[0020] Figure 1Catalytic activity and stability data graph for Comparative Example 1 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0021] Figure 2 Catalytic activity and stability data graph for Comparative Example 2 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0022] Figure 3 Catalytic activity and stability data graph for Example 1 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0023] Figure 4 Catalytic activity and stability data graph for Example 2 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0024] Figure 5 Catalytic activity and stability data graph for Example 3 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0025] Figure 6 Catalytic activity and stability data graph for Example 4 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0026] Figure 7 Catalytic activity and stability data graph for Example 5 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0027] Figure 8 Catalytic activity and stability data graph for Example 6 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0028] Figure 9 Catalytic activity and stability data graph for Example 7 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: ethanal, PO: propylene oxide).

[0029] Figure 10 Catalytic activity and stability data graph for Example 8 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0030] Figure 11 Catalytic activity and stability data graph for Example 9 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0031] Figure 12 Catalytic activity and stability data graph for Example 10 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0032] Figure 13 Catalytic activity and stability data graph for Example 11 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0033] Figure 14 Catalytic activity and stability data graph for Example 12 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0034] Figure 15 Catalytic activity and stability data graph for Example 13 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0035] Figure 16 Catalytic activity and stability data graph for Example 14 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0036] Figure 17 Catalytic activity and stability data graph for Example 15 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0037] Figure 18 Catalytic activity and stability data graph for Example 16 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0038] Figure 19 Catalytic activity and stability data graph for Example 17 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0039] Figure 20 Catalytic activity and stability data graph for Example 18 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0040] Figure 21 Catalytic activity and stability data graph for Example 19 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0041] Figure 22 Catalytic activity and stability data graph for Example 20 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide).

[0042] Figure 23 Catalytic activity and stability data graph for Example 21 (Acrolein: acrolein, acetone: acetone, propanal: propanal, ethanal: acetaldehyde, PO: propylene oxide). Detailed implementation mode

[0043] Comparative Example 1

[0044] Preparation of Ti-MWW support: Synthesis was carried out according to the molar ratio of feedstock SiO2:TBOT:TMAdaOH:HMI:K2CO3:H2O = 1:0.03:0.01:0.3:0.035:43. The specific operation was as follows: 20.3 g of deionized water was added to a polytetrafluoroethylene inner liner, then 7.3 g of an aqueous solution of 25 wt% N,N,N-trimethyladamantylammonium hydroxide (TMAdaOH, Leyan) was added, followed by 0.16 g of potassium carbonate (K2CO3, Sinopharm Chemical Reagent) and 1 g of hexamethyleneimine (HMI, Aladdin). Then, 0.4 g of tetrabutyl titanate (TBOT, Lingfeng Chemical) was added, and the mixture was stirred at room temperature for 2 hours to hydrolyze the titanium source. Next, 2 g of fumed silica (CAB-O-SIL M5) was added, and the mixture was stirred for 1 hour to dissolve the silicon source. The polytetrafluoroethylene inner liner containing the gel was placed in a kettle for crystallization at 150 °C for 5 days. The obtained crystallized molecular sieve was filtered, washed, and dried to obtain a molecular sieve powder. The obtained Ti-MWW molecular sieve precursor was mixed with a 2 M HNO3 solution and pickled under reflux conditions for 18 hours, then filtered, washed with deionized water until neutral, and dried, followed by calcination in an air atmosphere at 550 °C for 6 hours. A Ti-MWW sample with a silicon-titanium ratio (Si / Ti) of 26 was obtained by testing with an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0045] Take 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL, add 20 mL of deionized water for dilution, heat to 70 °C, then add 0.3 g of the above Ti-MWW, and adjust the pH to 7 by dropwise adding a 0.1 M NaOH solution. After stirring at 70 °C for 1 hour, filter, wash, and dry at room temperature under vacuum to obtain Au / Ti-MWW-1.

[0046] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube, and in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), the temperature was raised to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 1 shown. The product conversion rate, selectivity, and stability data can be calculated according to the gas chromatogram, as shown in Table 1 below

[0047] Table 1

[0048]

[0049] Comparative Example 2

[0050] Using TS-1 zeolite (with an Si / Ti ratio of 30) as the carrier, 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL was taken, diluted with 9 mL of deionized water, 0.3 g of TS-1 zeolite was added to the above aqueous solution of chloroauric acid, and then 0.91 mL of an aqueous solution of Cs2CO3 with a concentration of 1 M was added. After stirring at 25 °C for 5 hours, filtration, washing, and vacuum drying at room temperature were carried out to obtain Au / TS-1.

[0051] The evaluation of the catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube, and in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), it was heated to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 2 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 2 below:

[0052] Table 2

[0053]

[0054] Example 1

[0055] The preparation process of Ti-MWW in Comparative Example 1 was repeated.

[0056] 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL was taken, diluted with 9 mL of deionized water, 0.3 g of Ti-MWW was added to the above aqueous solution of chloroauric acid, and then 0.91 mL of a Cs2CO3 solution with a concentration of 1 M was added. After stirring at 25 °C for 5 hours, filtration, washing, and vacuum drying at room temperature were carried out to obtain Au(Cs + ) / Ti-MWW-2.

[0057] The evaluation of the catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube, and in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), it was heated to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 3 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 3 below:

[0058] Table 3

[0059]

[0060] Example 2

[0061] Prepare Ti-MWW according to the feeding gel ratio SiO2:TBOT:TMAdaOH:HMI:K2CO3:H2O = 1:0.01:0.01:0.3:0.035:43, and repeat the preparation process in Comparative Example 1. A Ti-MWW sample with a silicon-titanium ratio (Si / Ti) of 80 was obtained by testing with an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0062] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, add 0.3 g of Ti-MWW to the above chloroauric acid aqueous solution, then add 0.91 mL of 1 M Cs2CO3 solution, stir at 25 °C for 5 hours, then filter, wash, and dry in vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-3.

[0063] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube, and in the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), it was heated to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 4 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 4 below

[0064] Table 4

[0065]

[0066] Example 3

[0067] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0068] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, add 0.3 g of Ti-MWW to the above chloroauric acid aqueous solution, then add 0.91 mL of 1 M K2CO3 solution, stir at 25 °C for 5 hours, then filter, wash, and dry in vacuum at room temperature to obtain Au(K + ) / Ti-MWW-4.

[0069] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube, and in the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), it was heated to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 5As shown, the product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 5 below:

[0070] Table 5

[0071]

[0072] Example 4

[0073] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0074] Take 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW, and then add 0.91 mL of 1 M Na2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry under vacuum at room temperature to obtain Au(Na + ) / Ti-MWW-5.

[0075] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min) for 150 minutes. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 6 shown. The product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 6 below:

[0076] Table 6

[0077]

[0078] Example 5

[0079] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0080] Take 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW, and then add 0.76 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-6.

[0081] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as followsFigure 7 As shown, the product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 7 below:

[0082] Table 7

[0083]

[0084] Example 6

[0085] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0086] Take 3 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW, and then add 1.07 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry in vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-7.

[0087] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 8 As shown, the product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 8 below:

[0088] Table 8

[0089]

[0090] Example 7

[0091] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0092] Take 2 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW, and then add 0.61 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry in vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-8.

[0093] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as followsFigure 9 As shown, the product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 9 below:

[0094] Table 9

[0095]

[0096] Example 8

[0097] Repeat the preparation process of Ti-MWW in Comparative Example 1.

[0098] Take 4 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW, and then add 1.21 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-9.

[0099] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 10 As shown, the product conversion rate, selectivity, and stability data can be calculated from the gas chromatogram, as shown in Table 10 below:

[0100] Table 10

[0101]

[0102] Example 9

[0103] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, and then gradually add 0.1 M CsOH to adjust the pH = 7. Stir at room temperature for 16 hours for cation modification, then filter, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-1 sample.

[0104] Take 3 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-1 sample, and then add 0.91 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-10.

[0105] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 11 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 11 below:

[0106] Table 11

[0107]

[0108] Example 10

[0109] Repeat the preparation process of Ti-MWW in Comparative Example 1. 0.3 g of the above Ti-MWW was mixed with 15 mL of 0.1 M KNO3, and then 0.1 M KOH was added dropwise to adjust the pH = 7. Stir at room temperature for 16 hours for cation modification, then filter by suction, wash with a large amount of water, and dry to obtain the modified Ti-MWW-K sample.

[0110] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-K sample, and then add 0.91 mL of 1 M K2CO3 solution. Stir at 25 °C for 5 hours, then filter by suction, wash, and dry under vacuum at room temperature to obtain Au(K + ) / Ti-MWW-11.

[0111] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 12 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 12 below:

[0112] Table 12

[0113]

[0114] Example 11

[0115] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M NaNO3, then slowly add 0.1 M NaOH dropwise to adjust the pH to 7. Stir at room temperature for 16 hours for cation modification, then filter by suction, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Na sample.

[0116] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Na sample, and then add 0.91 mL of 1 M Na2CO3 solution. Stir at 25 °C for 5 hours, then filter by suction, wash, and dry under vacuum at room temperature to obtain Au(Na + ) / Ti-MWW-12.

[0117] The catalyst activity evaluation was carried out in a fixed bed. Load 0.15 g of the above catalyst into a quartz tube, and under the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), heat up to 180 °C. Analyze the above-obtained product by gas chromatography (Agilent 8890, FID), and its catalytic data are as follows Figure 13 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 13 below:

[0118] Table 13

[0119]

[0120] Example 12

[0121] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, then slowly add 0.1 M CsOH dropwise to adjust the pH to 9. Stir at room temperature for 16 hours for cation modification, then filter by suction, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-2 sample.

[0122] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-2 sample, and then add 0.91 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter by suction, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-13.

[0123] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 14 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 14 below:

[0124] Table 14

[0125]

[0126] Example 13

[0127] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, then gradually add 0.1 M CsOH to adjust the pH to 5, stir at room temperature for 16 hours for cation modification, then filter by suction, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-3 sample.

[0128] Take 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-3 sample, and then add 0.91 mL of 1 M Cs2CO3 solution. After stirring at 25 °C for 5 hours, filter by suction, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-14.

[0129] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 15 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 15 below:

[0130] Table 15

[0131]

[0132] Example 14

[0133] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, then slowly add 0.1 M CsOH dropwise to adjust the pH to 7. Stir at room temperature for 16 hours for cation modification. Subsequently, perform suction filtration, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-4 sample.

[0134] Take 2 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-4 sample, and then add 0.61 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then perform suction filtration, wash, and dry under vacuum at room temperature to prepare Au(Cs + ) / Ti-MWW-15.

[0135] The catalyst activity evaluation was carried out in a fixed bed. Load 0.15 g of the above catalyst into a quartz tube, and under the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), heat up to 180 °C. Analyze the above-obtained product by gas chromatography (Agilent 8890, FID), and its catalytic data is as follows Figure 16 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 16 below:

[0136] Table 16

[0137]

[0138] Example 15

[0139] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, then slowly add 0.1 M CsOH dropwise to adjust the pH to 7. Stir at room temperature for 16 hours for cation modification. Subsequently, perform suction filtration, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-5 sample.

[0140] Take 4 mL of an aqueous chloroauric acid solution with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-5 sample, and then add 1.21 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then perform suction filtration, wash, and dry under vacuum at room temperature to prepare Au(Cs + ) / Ti-MWW-16.

[0141] The evaluation of the catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 17 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 17 below:

[0142] Table 17

[0143]

[0144] Example 16

[0145] Repeat the preparation process of Ti-MWW in Comparative Example 1. Mix 0.3 g of the above Ti-MWW with 15 mL of 0.1 M CsNO3, then gradually add 0.1 M CsOH to adjust the pH = 7, stir at room temperature for 16 hours for cation modification, then filter by suction, wash with a large amount of water, and dry to obtain the modified Ti-MWW-Cs-6 sample.

[0146] Take 3 mL of an aqueous solution of chloroauric acid with a concentration of 0.01 g / mL, add it to 9 mL of deionized water for dilution, then add 0.3 g of the above Ti-MWW-Cs-6 sample, and then add 0.76 mL of 1 M Cs2CO3 solution. Stir at 25 °C for 5 hours, then filter by suction, wash, and dry under vacuum at room temperature to obtain Au(Cs + ) / Ti-MWW-17.

[0147] The evaluation of the catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 18 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 18 below:

[0148] Table 18

[0149]

[0150] Example 17

[0151] Prepare boron-containing Ti-MWW according to the feeding gel ratio of SiO2:TBOT:H3BO3:PI:H2O = 1:0.03:1.3:1.4:43. The specific operation is as follows: Add 14.2 g of deionized water into a polytetrafluoroethylene inner liner, then add 5.0 g of piperidine (PI, Lingfeng Chemistry), and then add 0.5 g of tetrabutyl titanate (TBOT, Lingfeng Chemistry). Stir at room temperature for 2 hours to hydrolyze the titanium source. Then add 3.5 g of boric acid and stir for half an hour. Then add 2.5 g of fumed silica (CAB-O-SIL M5) and stir for 2 hours to dissolve the silicon source. Place the polytetrafluoroethylene inner liner containing the gel into the autoclave for crystallization, and crystallize dynamically at 170 °C for 7 days. Filter, wash, and dry the obtained crystallized molecular sieve to obtain molecular sieve powder. Mix the obtained Ti,B-MWW molecular sieve precursor with 2 M HNO3 solution, perform acid washing under reflux conditions for 18 hours, then filter, wash with deionized water until neutral, and dry, and then calcine in air at 550 °C for 6 hours. A boron-containing Ti-MWW sample with a silicon-titanium ratio (Si / Ti) of 30 is obtained by testing with an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0152] Take 3 mL of chloroauric acid aqueous solution with a concentration of 0.01 g / mL, add 9 mL of deionized water for dilution, add 0.3 g of Ti-MWW into the above chloroauric acid aqueous solution, and then add 0.91 mL of Cs2CO3 solution with a concentration of 1 M. Stir at 25 °C for 5 hours, then filter, wash, and dry at room temperature under vacuum to prepare Au(Cs + ) / Ti-MWW-1.

[0153] The catalyst activity evaluation is carried out in a fixed bed. Load 0.15 g of the above catalyst into a quartz tube, and under the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), heat up to 180 degrees. Analyze the above-obtained product by gas chromatography (Agilent 8890, FID), and its catalytic data are as shown in the appendix Figure 19 shown. According to the gas chromatogram, the product conversion rate, selectivity, and stability data can be calculated, as shown in Table 19 below:

[0154] Table 19

[0155]

[0156] Example 18

[0157] Repeat the preparation process of Au(Cs + ) / Ti-MWW-2 in Example 1.

[0158] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 2:2:2:14 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 20 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 20 below:

[0159] Table 20

[0160]

[0161] Example 19

[0162] Repeat the preparation process of Au(Cs + ) / Ti-MWW-2 in Example 1.

[0163] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 180 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:1:3.5:27 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 21 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 21 below:

[0164] Table 21

[0165]

[0166] Example 20

[0167] Repeat the preparation process of Au(Cs + ) / Ti-MWW-2 in Example 1.

[0168] The evaluation of catalyst activity was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube and heated to 160 °C in a reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min). The product obtained above was analyzed by gas chromatography (Agilent 8890, FID), and its catalytic data are as attached Figure 22 As shown, the product conversion rate, selectivity and stability data can be calculated according to the gas chromatogram, as shown in Table 22 below:

[0169] Table 22

[0170]

[0171] Example 20

[0172] Repeat the preparation process of Au(Cs + ) / Ti-MWW-2 in Example 1.

[0173] The catalyst activity evaluation was carried out in a fixed bed. 0.15 g of the above catalyst was loaded into a quartz tube. In the reaction gas atmosphere (C3H6:H2:O2:Ar = 3.5:3.5:3.5:24.5 mL / min), it was pressurized to 1 Mpa and heated to 180 °C. The above-obtained product was analyzed by gas chromatography (Agilent 8890, FID). The catalytic data are as follows Figure 23 shown. According to the gas chromatogram, the product conversion rate, selectivity and stability data can be calculated, as shown in Table 23 below:

[0174] Table 23

[0175]

Claims

1. A method for preparing a propylene epoxidation catalyst in a hydrogen-oxygen system, characterized in that: The following steps are involved: (1) Preparation of MWW type titanium silicon molecular sieve catalyst: silicon source, titanium source, boric acid, organic template, potassium carbonate and water are added to a polytetrafluoroethylene liner in a certain proportion, and crystallized under high temperature dynamic conditions. After washing, filtering, drying, acid washing and calcination, a Ti-MWW molecular sieve catalyst is obtained; (2) Ti-MWW molecular sieve modified with alkali metal cations and loaded with gold; (2.1) Alkali metal cation modification followed by gold loading: Ti-MWW and an aqueous solution of alkali metal nitrate are mixed, the pH is adjusted with an alkaline hydroxide solution containing the same alkali metal ion, ion exchange is performed, washing is performed, and drying is performed to obtain a cation-modified catalyst precursor. The modified catalyst precursor is mixed with an aqueous solution of chloroauric acid, and the same alkali metal carbonate is added as a precipitant. After stirring for a period of time, the mixture is filtered and vacuum dried to obtain Au(M + ) / Ti-MWW catalyst, M + represents the type of alkali metal cation; (2.2) Alkali metal cation modification and gold loading are carried out simultaneously: Ti-MWW molecular sieve is added to chloroauric acid aqueous solution, alkali metal carbonate solution is added, stirred, filtered, washed, and vacuum dried to obtain Au (M + ) / Ti-MWW catalyst, M + Represents the type of alkali metal cation.

2. The method for preparing MWW titanium silicon molecular sieve according to claim 1, characterized in that: The silicon source is one of silica aerosol and silica liquid sol, the titanium source is one of tetrabutyl titanate (TBOT) and hexafluorotitanic acid, and the template agent (abbreviated as OSDA) is one or more of hexamethyleneimine (HMI), piperidine (PI), and N,N,N-trimethyladamantane ammonium hydroxide (TMAdaOH).

3. The method for preparing MWW titanium silicon molecular sieve according to claim 1, characterized in that: The molar composition range of the synthesized gel is: SiO2:TBOT:OSDA:K2CO3:H3BO3:H2O=1:(0.015~0.05):(0.01~0.045):(0.1-1.5):(0-1.34):(15-45).

4. The cationic modification method according to claim 1, characterized in that: In step (2), the nitrate is an alkali metal nitrate (CsNO3, NaNO3, KNO3), the alkaline solution is an alkali metal hydroxide aqueous solution (CsOH, NaOH, KOH), and the carbonate is an alkali metal carbonate (Cs2CO3, Na2CO3, K2CO3).

5. The cationic modification method according to claim 1, characterized in that: In step (2), during cation modification, the pH range of the solution is adjusted to 4-9; the gold content in the chloroauric acid aqueous solution is 0.01 g / mL, the amount of gold added is 0.01-5 wt.% of the catalyst; and the molar ratio of the carbonate addition amount to gold is 2-10.

6. The propylene gas phase reaction according to claim 1, characterized in that: The gas phase epoxidation of propylene is carried out in a fixed bed, the reaction pressure is 0.1-2 MPa, the reaction temperature is 130-250°C, the reaction gas composition is C3H6:H2:O2:Ar=0.1-1:1:1:7.9-1 (volume ratio), the space velocity is 4000-18000 mL / (h·g cat ), and the reaction tail gas was detected and analyzed by gas chromatography.

Images