Catalyst with propylene gas phase epoxidation function, preparation method thereof and application

Abstract

The present invention relates to the technical field of propylene epoxidation, and discloses a catalyst with propylene gas-phase epoxidation function, a preparation method thereof and an application. The catalyst comprises a carrier and an active component supported on the carrier, the carrier is titanium silicalite molecular sieve, and based on the total amount of titanium element in the titanium silicalite molecular sieve, the content of non-framework titanium is not higher than 11% by weight. The preparation method of the catalyst of the present invention comprises loading the active component on the carrier. The present invention also provides a method for propylene gas-phase epoxidation reaction, which comprises: contacting propylene, hydrogen and oxygen with the catalyst, wherein the catalyst is the above-mentioned catalyst. When the catalyst of the present invention is used for propylene gas-phase epoxidation, the propylene conversion rate is high and the selectivity of propylene oxide is high.

Description

Technical Field

[0001] The present invention relates to the technical field of propylene epoxidation, and particularly to a catalyst with the function of gas-phase propylene epoxidation, a preparation method thereof, and an application thereof. Background Art

[0002] Propylene oxide (PO), as the third largest organic chemical product among propylene derivatives after polypropylene and acrylonitrile in terms of production volume, is widely used in the preparation of derivatives such as polyurethane and polyester resins. At present, the main methods for producing PO in industry are the chlorohydrin method, the co-oxidation method, and gas-phase propylene epoxidation. However, the chlorohydrin method has a large corrosion to equipment, produces a large amount of wastewater and chlorine-containing by-products during the production process, and does not meet the requirements of today's green environmental protection. And the economy of the co-oxidation method is restricted by a large amount of by-products. Gas-phase propylene epoxidation has obvious advantages. In the coexistence of H2 and O2, the gas-phase propylene epoxidation reaction can directly catalyze propylene to produce propylene oxide, and the by-product is usually only water, which is a process-simple, green and cheap propylene oxide production process.

[0003] The catalysts for gas-phase propylene epoxidation usually use metals (Cu, Ag, and Au) as active components to load on titanium silicalite molecular sieves. The traditional catalysts for gas-phase propylene epoxidation are prone to deactivation, mainly because the propylene oxide produced during the catalytic process will undergo a ring-opening polymerization side reaction on adjacent acidic Ti sites, and the oligomers and polymers generated cover the active centers of the catalyst, hindering the continuous progress of the epoxidation reaction. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of low propylene conversion rate in the gas-phase propylene epoxidation existing in the prior art, and to provide a catalyst with the function of gas-phase propylene epoxidation, a preparation method thereof, and an application thereof.

[0005] It is well known to those skilled in the art that the mesopore diameter of the titanium silicalite molecular sieve synthesized from a titanium source, a silicon source, and a mesoporous template agent after one crystallization and one calcination is in the range of 2-3 nm. However, the inventor found during the research process that recrystallizing the titanium silicalite molecular sieve seeds with an alkaline solution of the mesoporous template agent can not only rearrange the non-framework titanium in the titanium silicalite molecular sieve seeds to form framework titanium, but also form mesoporous cavities with a pore diameter in the range of 10-45 nm after calcination. When the titanium silicalite molecular sieve with mesoporous cavities in the range of 10-45 nm is used for gas-phase propylene epoxidation, the propylene conversion rate is high and the service life is long.

[0006] In the present invention, "non-framework titanium" refers to titanium atoms not in the framework, which exist in the form of TiO2; "framework titanium" refers to titanium atoms in the framework, and the titanium atoms with a coordination number of 4.

[0007] To achieve the above object, a first aspect of the present invention provides a catalyst with propylene gas-phase epoxidation function. The catalyst includes a carrier and an active component supported on the carrier. The carrier is a titanium silicalite molecular sieve. Based on the total amount of titanium elements in the titanium silicalite molecular sieve, the content of non-framework titanium is not higher than 11% by weight.

[0008] A second aspect of the present invention provides a method for preparing a catalyst with propylene gas-phase epoxidation function. The method includes supporting an active component on a carrier. Among them, the carrier is a titanium silicalite molecular sieve. Based on the total amount of titanium elements in the titanium silicalite molecular sieve, the content of non-framework titanium is less than 11% by weight.

[0009] A third aspect of the present invention provides a catalyst prepared by the above method.

[0010] A third aspect of the present invention provides a method for propylene gas-phase epoxidation reaction. The method includes contacting propylene, hydrogen, and oxygen with a catalyst. Among them, the catalyst is the above-mentioned catalyst.

[0011] Compared with the propylene liquid-phase epoxidation reaction, the gas-phase propylene epoxidation reaction does not use hydrogen peroxide and can directly use hydrogen and oxygen as raw materials to prepare propylene oxide, simplifying the process flow.

[0012] Compared with the gas-phase propylene epoxidation reaction in the prior art, when the catalyst of the present invention is used for gas-phase propylene epoxidation, the propylene conversion rate is high. Description of the Drawings

[0013] Figure 1 SEM image of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0014] Figure 2 SEM image of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0015] Figure 3 TEM image of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0016] Figure 4 TEM image of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0017] Figure 5 XRD spectrum of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0018] Figure 6 UV-Vis spectrum of the titanium silicalite molecular sieve prepared in Preparation Example 1;

[0019] Figure 7 SEM image of the titanium silicalite molecular sieve prepared in Comparative Preparation Example 1;

[0020] Figure 8 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Comparative Preparation Example 1;

[0021] Figure 9 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Preparation Example 7;

[0022] Figure 10 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Preparation Example 8;

[0023] Figure 11 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Comparative Preparation Example 3;

[0024] Figure 12 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Preparation Example 10;

[0025] Figure 13 It is the transmission electron microscope (TEM) image of the titanium silicalite molecular sieve prepared in Preparation Example 11. Detailed implementation manners

[0026] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0027] In the present invention, unless otherwise stated, "titanium-silicon ratio" means the molar ratio between titanium element and silicon element.

[0028] The first aspect of the present invention provides a catalyst with propylene gas-phase epoxidation function. The catalyst includes a carrier and an active component supported on the carrier. The carrier is a titanium silicalite molecular sieve. Based on the total amount of titanium element in the titanium silicalite molecular sieve, the content of non-framework titanium is not higher than 11% by weight. Preferably, the content of non-framework titanium is not higher than 0.01% by weight.

[0029] The test method for the content of "non-framework titanium" is to pickle the titanium silicalite molecular sieve seeds or the titanium silicalite molecular sieve with a nitric acid solution (mass fraction of 10 wt%). The reduced mass of the titanium silicalite molecular sieve seeds or the titanium silicalite molecular sieve is the mass of non-framework titanium.

[0030] According to the present invention, preferably, the particle size of the titanium silicalite molecular sieve is 80 - 150 nm, the specific surface area is 320 - 500 m 2 / g, the pore volume of mesopores is 0.18 - 0.35 cm 3 / g, and the pore volume of micropores is 0.15 - 0.21 cm 3 / g. The pore volume of the mesopores refers to the total pore volume of pores with pore diameters in the range of 2 - 50 nm. The pore volume of the micropores refers to the total pore volume of pores with pore diameters less than 2 nm.

[0031] According to the present invention, preferably, the titanium silicalite molecular sieve has a microporous-mesoporous hierarchical pore structure. More preferably, the titanium silicalite molecular sieve has micropores with pore diameters in the range of 0.4 - 0.8 nm, and the titanium silicalite molecular sieve has a first mesopore and a second mesopore.

[0032] According to the present invention, preferably, the first mesopore has a pore diameter in the range of 2 - 3 nm, and the second mesopore has a pore diameter in the range of 10 - 45 nm.

[0033] According to the present invention, preferably, the titanium-silicon ratio in the titanium silicalite molecular sieve is 1:25 - 200.

[0034] According to the present invention, preferably, the active component includes Group IB metals.

[0035] According to the present invention, preferably, relative to 100 g of the titanium silicalite molecular sieve, the content of the active component in terms of metal element is 0.1 - 2 g, preferably 0.5 - 1 g.

[0036] According to the present invention, preferably, the active component is at least one of Cu, Ag, and Au.

[0037] The second aspect of the present invention provides a method for preparing a catalyst with propylene gas-phase epoxidation function, which includes loading an active component on a support; wherein, the support is a titanium silicalite molecular sieve, and based on the total amount of titanium elements in the titanium silicalite molecular sieve, the content of non-framework titanium is less than 11 wt%, preferably, the content of non-framework titanium is not higher than 0.01 wt%.

[0038] According to the present invention, preferably, the particle size of the titanium silicalite molecular sieve is 80 - 150 nm, the specific surface area is 320 - 500 m 2 / g, the pore volume of the mesopores is 0.18 - 0.35 cm 3 / g, and the pore volume of the micropores is 0.15 - 0.21 cm 3 / g.

[0039] According to the present invention, preferably, the titanium silicalite molecular sieve has a microporous-mesoporous hierarchical pore structure. More preferably, the titanium silicalite molecular sieve has micropores with pore diameters in the range of 0.4 - 0.8 nm, and the titanium silicalite molecular sieve has a first mesopore and a second mesopore.

[0040] According to the present invention, preferably, the first mesopore has a pore diameter in the range of 2 - 3 nm, and the second mesopore has a pore diameter in the range of 10 - 45 nm.

[0041] According to the present invention, preferably, the titanium-silicon ratio in the titanium-silicon molecular sieve is 1:25 - 200.

[0042] According to the present invention, preferably, the active component includes Group IB metals.

[0043] According to the present invention, preferably, relative to 100 g of the titanium-silicon molecular sieve, the amount of the active component used is such that the content of the active component in the resulting catalyst, calculated as the metal element, is 0.1 - 2 g, preferably 0.5 - 1 g.

[0044] According to the present invention, preferably, the active component is at least one of Cu, Ag, and Au.

[0045] According to the present invention, preferably, the loading method includes: immersing the carrier in a solution of the active component precursor, followed by drying and calcination. More preferably, the conditions for immersing the carrier include: the immersion temperature is 0 - 50 °C, and the immersion time is 0.5 - 5 h; the conditions for drying include: the temperature is 15 - 40 °C, and the time is 24 - 48 h; the conditions for calcination include: the temperature is 250 - 350 °C, and the time is 4 - 6 h.

[0046] According to a particularly preferred embodiment of the present invention, the process of loading the active component onto the carrier includes: placing the carrier in an aqueous solution of the active component precursor, adjusting the pH value to 6 - 8, immersing at 0 - 50 °C for 0.5 - 5 h, drying at 15 - 40 °C for 24 - 48 h, and calcining at 250 - 350 °C for 4 - 6 h to obtain the catalyst of the present invention. Among them, the active component precursor is a water-soluble salt containing the active component, for example, chloroauric acid, copper chloride, silver nitrate, preferably chloroauric acid; relative to 100 g of the carrier, the amount of chloroauric acid used is 0.86 - 3.45 g.

[0047] According to the present invention, preferably, the method for preparing the carrier includes the following steps:

[0048] (1) Contacting a titanium source, a silicon source, and a microporous template agent, then aging for 1 - 24 h, crystallizing at 150 - 200 °C for 24 - 72 h, and then calcining at 480 - 600 °C for 3 - 8 h to obtain titanium-silicon molecular sieve seeds, wherein the molar ratio of the titanium source, the silicon source, and the microporous template agent is 1:25 - 200:100 - 200, the amount of the titanium source is calculated as Ti, and the amount of the silicon source is calculated as Si;

[0049] (2) Mix the prepared titanium silicalite seeds with a solution containing a mesoporous template agent and an alkali, crystallize at 100 - 150 °C for 24 - 72 h, and then calcine at 480 - 600 °C for 5 - 10 h to obtain a micro-mesoporous composite silicon-titanium molecular sieve TS-1. Among them, the mass ratio of the titanium silicalite seeds, the mesoporous template agent, and the alkali is 1:0.1 - 0.5:50 - 100.

[0050] According to the present invention, the silicon source can be a substance commonly used in the art that can provide silicon elements. Preferably, the silicon source is a silicate ester, and more preferably at least one of tetraethyl orthosilicate, methyl orthosilicate, and ethyl orthosilicate.

[0051] According to the present invention, the titanium source can be a substance commonly used in the art that can provide titanium elements. Preferably, the titanium source is a titanium source containing an alkoxy group, and more preferably tetrabutyl titanate.

[0052] According to the present invention, preferably, the microporous template agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0053] According to the present invention, preferably, the mesoporous template agent is a quaternary ammonium salt, and more preferably at least one of cetyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, decyltrimethylammonium bromide, and octyltrimethylammonium bromide.

[0054] According to the present invention, preferably, the alkali is at least one of ammonia, alkali metal hydroxides, and organic amines, and further preferably at least one of ammonia, sodium hydroxide, potassium hydroxide, urea, and ethylenediamine.

[0055] According to the method for preparing titanium silicalite seeds of the present invention, the crystallization equipment is not particularly limited. Preferably, the crystallization equipment is an autoclave.

[0056] According to the method for preparing titanium silicalite seeds of the present invention, preferably, before calcining the crystallization product, it further includes first washing and first drying. The number of first washing times is 3 - 5 times, and distilled water or deionized water can be used for washing; the temperature of the first drying is 90 - 120 °C, and the time is 12 - 24 h.

[0057] According to the method for preparing titanium silicalite seeds of the present invention, the calcination atmosphere is not particularly limited and can be at least one of an air atmosphere, a nitrogen atmosphere, and a helium atmosphere. Further preferably, the calcination is carried out in an air atmosphere.

[0058] According to the present invention, the titanium silicalite seeds described in step (1) can be prepared according to the conventional methods of titanium silicalite in the art, and the present invention does not particularly limit this. For example, the method disclosed in patent CN107265474A can be referred to for preparation.

[0059] According to a preferred embodiment, the titanium silicalite seeds are prepared by the following method: mixing a titanium source and isopropanol to obtain solution A, mixing a silicon source and a microporous template agent to obtain solution B, adding solution B to solution A at a rate of 0.01 mL / min, and then aging, crystallizing, and calcining to obtain the titanium silicalite seeds.

[0060] According to the present invention, there is no particular limitation on the preparation method of the solution containing the mesoporous template agent and the base. Preferably, the solution containing the mesoporous template agent and the base is obtained by mixing the mesoporous template agent and an aqueous solution of the base.

[0061] According to the present invention, the aqueous solution of the base can be obtained by purchase or can be prepared by itself according to the mass concentration.

[0062] According to the present invention, preferably, the mass fraction of the aqueous solution of the base is 20 - 30 wt%.

[0063] According to the present invention, in step (2), preferably, before calcining the crystallization product, it further includes second washing and second drying. The number of second washings is 3 - 5 times, and distilled water or deionized water can be used for washing; the temperature of the second drying is 90 - 120 °C, and the time is 12 - 24 h.

[0064] According to the present invention, in order to further promote the formation of a mesoporous structure in the titanium silicalite. Preferably, the crystallization temperature in step (1) is higher than the crystallization temperature in step (2). Further preferably, the crystallization temperature in step (1) is 40 - 50 °C higher than the crystallization temperature in step (2).

[0065] According to the present invention, in step (2), there is no particular limitation on the calcination atmosphere, and it can be at least one of an air atmosphere, a nitrogen atmosphere, and a helium atmosphere. Further preferably, the calcination is carried out in an air atmosphere.

[0066] The third aspect of the present invention provides a catalyst prepared by the above method.

[0067] The third aspect of the present invention provides a method for the gas-phase epoxidation of propylene, which includes: contacting propylene, hydrogen, and oxygen with a catalyst, wherein the catalyst is the above-mentioned catalyst.

[0068] According to the present invention, preferably, the conditions of the contact include: the volume ratio of propylene, hydrogen, oxygen and nitrogen is 1: 1-3: 1-3: 5-10, and the total volume space velocity of propylene, hydrogen and oxygen is 10,000-20,000 h -1 , the pressure is 0.1-1 MPa, and the temperature is 150-250 °C.

[0069] The present invention will be described in detail below through preparation examples. In the following preparation examples,

[0070] "Room temperature" refers to "25 °C".

[0071] The pore structure and specific surface area of the silico-titanium molecular sieve were characterized by BET. The instrument used for the BET test was the ASAP2020 model of Micromeritics, USA. The pore structure test method was as follows: Take a certain amount of sample, about 0.10 g, and degas it under vacuum conditions of 200 °C and 1 mmHg for 6 hours, and measure the nitrogen adsorption and desorption curves of the sample in liquid nitrogen (-196 °C); then use NLDFT to calculate the pore size and distribution of the mesopores in the pore size distribution. The test method for the specific surface area was as follows: Take a certain amount of sample, about 0.10 g, evacuate it at 30 °C for 10 h, and the vacuum degree <6.67×10 2 Pa, and then use the adsorption line data in the BET equation to calculate the specific surface area of the sample.

[0072] The crystal structure of the silico-titanium molecular sieve was characterized by XRD. The instrument used for the XRD test was the D / Max2550VB / PC type X-ray diffractometer of Rigaku Corporation. The test conditions were: the incident light source was a Cu target, K α rays, the tube current was 100 mA, the tube voltage was 40 kV, and the scanning rate was 12 scanning rate 40; before the test, the powder sample was pressed into a sheet on the sample holder and then tested.

[0073] The internal mesopore distribution of the silico-titanium molecular sieve was characterized by TEM. The instrument used for the TEM test was the JEM 2100F model of JEOL, Japan. The test conditions were: the acceleration voltage was 200 kV, the point resolution of the instrument was 0.23 nm, and the line resolution was 0.14 nm. Before the test, the sample was crushed and ground to 300 meshes and placed in ethanol to form a suspension. After ultrasonic dispersion at room temperature for 5-10 min, the upper suspension was sucked with a dropper and dropped on a copper grid. After the ethanol evaporated, HRTEM (high-resolution transmission electron microscopy) characterization was carried out.

[0074] The morphology and particle size of the silico-titanium molecular sieve were characterized by SEM. The instrument used for the SEM test was the JSM360LVJOEL model, and the test voltage was 20 kV.

[0075] The carbon deposition content of the catalyst was tested by thermogravimetry (TGA), and the instrument used was a Perkin-Elmer Pyris1 thermogravimetric analyzer from Perkin-Elmer Company in the United States;

[0076] The coordination state of titanium in the titanium silicalite molecular sieve was characterized by an ultraviolet-visible spectrophotometer. The instrument model used was a Shimadzu UV-2700 ultraviolet spectrophotometer from Japan. The test conditions were: the detection wavelength range λ = 200 - 700 nm, and BaSO4 was used as the reference. The ultraviolet-visible diffuse reflection spectrum discriminates the coordination state of heteroatoms by comparing the transfer absorption of framework heteroatoms and their corresponding oxide electrons. Among them, the characteristic peak at a wavelength of 220 nm corresponds to tetracoordinated framework Ti, and the characteristic peak at a wavelength of 330 nm corresponds to non-framework Ti.

[0077] The mass fraction of ammonia water was 25 wt%.

[0078] The titanium-silicon ratio in the titanium silicalite molecular sieve was measured by an elemental analyzer (ICP).

[0079] Preparation Example 1

[0080] (1) Take 3.6 g of isopropanol and mix it evenly with 0.368 g of tetrabutyl titanate to obtain Solution A. Take 27.9 g of tetrapropylammonium hydroxide and place it in a beaker, add 22.58 g of tetraethyl orthosilicate and 6.93 g of H2O, stir for 30 min to obtain Solution B, add Solution B to Solution A at a rate of 0.01 mL / min, stir for 3 h to obtain a mixed solution C, then age it at room temperature for 3 h, and then raise the temperature to 90 °C at a heating rate of 5 °C / min. Remove the alcohol at 90 °C for 12 h until a transparent gel liquid is obtained. Put the transparent gel liquid into an autoclave, crystallize it at 170 °C for 36 h, take it out and wash it with water 3 times, then dry it at 100 °C for 15 h, and then calcine it in an air atmosphere at 550 °C for 6 h to obtain titanium silicalite TS-1 seeds.

[0081] (2) Take 1.4 g of cetyltrimethylammonium bromide, add it to 260 g of ammonia water and stir for 30 min to obtain Solution D. Put 4 g of titanium silicalite TS-1 seeds into Solution D and stir for 3 h. Put Solution D and the seeds into an autoclave, crystallize it at 130 °C for 48 h, take it out and wash it with water 5 times, then dry it at 100 °C for 15 h, and then calcine it in an air atmosphere at 550 °C for 6 h to obtain micro-mesoporous composite titanium silicalite TS-1. The test results are shown in Table 1 and Table 2.

[0082] The morphology and particle size of the micro-mesoporous composite titanium silicalite TS-1 prepared in Preparation Example 1 were observed by SEM, and the results are as Figure 1 and Figure 2As shown, it can be seen from the figure that the morphology of the micro-mesoporous composite silico-titanium molecular sieve TS-1 is blackberry-like, with small protrusions covering the surface, and the particle size is between 80 - 150 nm.

[0083] The internal mesopore distribution of the micro-mesoporous composite silico-titanium molecular sieve TS-1 prepared in Preparation Example 1 was observed by TEM, and the results are as Figure 3 and Figure 4 shown. It can be seen from the figure that the micro-mesoporous composite silico-titanium molecular sieve TS-1 has mesopores with pore diameters in the range of 10 - 45 nm inside the crystal.

[0084] The crystal form of the micro-mesoporous composite silico-titanium molecular sieve TS-1 prepared in Preparation Example 1 was observed by XRD, and the results are as Figure 5 shown. It can be seen from the figure that characteristic diffraction peaks of the MFI structure appear near 2θ of 7.96°, 8.83°, 23.18°, 23.99°, and 24.45°, proving that the silico-titanium molecular sieve prepared in Preparation Example 1 has the MFI structure.

[0085] The existence form of titanium in the micro-mesoporous composite silico-titanium molecular sieve TS-1 prepared in Preparation Example 1 was observed by UV-Vis, and the results are as Figure 6 shown. It can be seen from the figure that only the characteristic peak with a wavelength of 220 nm appears, indicating that all the titanium in the micro-mesoporous composite silico-titanium molecular sieve TS-1 exists in the form of framework Ti.

[0086] Preparation Example 2

[0087] (1) 3.6 g of isopropanol was mixed evenly with 0.368 g of tetrabutyl titanate to obtain solution A. 32.65 g of tetrapropylammonium hydroxide was placed in a beaker, 30.21 g of tetraethyl orthosilicate and 9.05 g of H2O were added, and stirred for 30 min to obtain solution B. Solution B was added to A at a rate of 0.01 mL / min, and stirred for 3 h to obtain a mixed solution C. It was aged at room temperature for 7 h, then heated to 90 °C at a heating rate of 6 °C / min, and the alcohol was removed at 90 °C for 12 h until a transparent gel liquid was obtained. The transparent gel liquid was put into an autoclave, crystallized at 160 °C for 50 h, taken out and washed with water 3 times, then dried at 100 °C for 15 h, and calcined in air atmosphere at 500 °C for 8 h to obtain the silico-titanium molecular sieve TS-1 seed crystals.

[0088] (2) 1.6 g of cetyltrimethylammonium bromide was added to 300 g of ammonia water and stirred for 30 min to obtain solution D. 4 g of the silico-titanium molecular sieve TS-1 seed crystals were put into solution D and stirred for 3 h. Solution D and the seed crystals were put into an autoclave, crystallized at 120 °C for 60 h, taken out and washed with water 5 times, then dried at 100 °C for 15 h, and calcined in air atmosphere at 500 °C for 8 h to obtain the micro-mesoporous composite silico-titanium molecular sieve TS-1. The test results are shown in Table 1 and Table 2. The XRD characterization results are the same asFigure 5 Similar, which will not be shown here.

[0089] Preparation Example 3

[0090] (1) Take 3.6 g of isopropanol and mix it evenly with 0.368 g of tetrabutyl titanate to obtain Solution A. Take 37.25 g of tetrapropylammonium hydroxide and place it in a beaker, add 33.79 g of tetraethyl orthosilicate and 10.12 g of H2O, stir for 30 min to obtain Solution B, add Solution B to A at a rate of 0.01 mL / min, stir for 3 h to obtain a mixed solution C. Age at room temperature for 10 h, then heat up to 90 °C at a heating rate of 6 °C / min, and remove alcohol at 90 °C for 12 h until a transparent gel liquid is obtained. Put the transparent gel liquid into an autoclave, crystallize at 180 °C for 30 h, take it out and wash it with water 3 times, then dry it at 100 °C for 15 h, and then calcine it in an air atmosphere at 580 °C for 5 h to obtain the TS-1 seed crystal of silicotitanium molecular sieve.

[0091] (2) Take 1.2 g of cetyltrimethylammonium bromide, add it to 340 g of ammonia water and stir for 30 min to obtain Solution D. Put 4 g of the TS-1 seed crystal of silicotitanium molecular sieve into Solution D and stir for 3 h. Put Solution D and the seed crystal into an autoclave, crystallize at 140 °C for 30 h, take it out and wash it with water 5 times, then dry it at 100 °C for 15 h, and then calcine it in an air atmosphere at 580 °C for 5 h to obtain the micro-mesoporous composite TS-1 of silicotitanium molecular sieve. The test results are shown in Table 1 and Table 2. The XRD characterization results are Figure 5 Similar, which will not be shown here.

[0092] Preparation Example 4

[0093] (1) Take 3.6 g of isopropanol and mix it evenly with 0.368 g of tetrabutyl titanate to obtain Solution A. Take 22 g of tetrapropylammonium hydroxide and place it in a beaker, add 18.04 g of tetraethyl orthosilicate and 5.42 g of H2O, stir for 30 min to obtain Solution B, add Solution B to A at a rate of 0.01 mL / min, stir for 3 h to obtain a mixed solution C. Age at room temperature for 24 h, then heat up to 90 °C at a heating rate of 6 °C / min, and remove alcohol at 90 °C for 12 h until a transparent gel liquid is obtained. Put the transparent gel liquid into an autoclave, crystallize at 150 °C for 72 h, take it out and wash it with water 3 times, then dry it at 100 °C for 15 h, and then calcine it in an air atmosphere at 600 °C for 3 h to obtain the TS-1 seed crystal of silicotitanium molecular sieve.

[0094] (2) Take 0.4 g of cetyltrimethylammonium bromide, add it to 400 g of ammonia water and stir for 30 min to obtain solution D. Take 4 g of titanium silicalite TS-1 seeds and put them into solution D and stir for 3 h. Put solution D and the seeds into an autoclave, crystallize at 100 °C for 72 h, take out and wash with water 5 times, then dry at 100 °C for 15 h, and then calcine in air atmosphere at 600 °C for 5 h to obtain micro-mesoporous composite titanium silicalite TS-1. The test results are shown in Table 1 and Table 2. The XRD characterization results are similar to Figure 5 and are not shown here again.

[0095] Preparation Example 5

[0096] (1) Take 3.6 g of isopropanol and 0.368 g of tetrabutyl titanate and mix them evenly to obtain solution A. Take 43.96 g of tetrapropylammonium hydroxide in a beaker, add 45.05 g of tetraethyl orthosilicate and 13.51 g of H2O, stir for 30 min to obtain solution B, add solution B to A at a rate of 0.01 mL / min, stir for 3 h to obtain a mixed solution C. Age at room temperature for 1 h, then heat up to 90 °C at a heating rate of 6 °C / min, and remove alcohol at 90 °C for 12 h until a transparent gel liquid is obtained. Put the transparent gel liquid into an autoclave, crystallize at 200 °C for 24 h, take out and wash with water 3 times, then dry at 100 °C for 15 h, and then calcine in air atmosphere at 480 °C for 8 h to obtain titanium silicalite TS-1 seeds.

[0097] (2) Take 2 g of cetyltrimethylammonium bromide, add it to 200 g of ammonia water and stir for 30 min to obtain solution D. Take 4 g of titanium silicalite TS-1 seeds and put them into solution D and stir for 3 h. Put solution D and the seeds into an autoclave, crystallize at 150 °C for 24 h, take out and wash with water 5 times, then dry at 100 °C for 15 h, and then calcine in air atmosphere at 480 °C for 8 h to obtain micro-mesoporous composite titanium silicalite TS-1. The test results are shown in Table 1 and Table 2. The XRD characterization results are similar to Figure 5 and are not shown here again.

[0098] Preparation Example 6

[0099] Prepare the molecular sieve according to the method of Preparation Example 1, except that in step (2), the amount of cetyltrimethylammonium bromide used is 4 g and the amount of ammonia water used is 500 g. The test results are shown in Table 1 and Table 2.

[0100] Preparation Example 7

[0101] Prepare the molecular sieve according to the method of Preparation Example 1, except that in step (2), the crystallization conditions include: temperature is 250 °C and time is 12 h. The test results are shown in Table 1 and Table 2. Observe the internal pore distribution of the molecular sieve prepared in Preparation Example 7 by TEM, and the results are asFigure 9 As shown, it can be seen from the figure that there are no obvious mesopores in the molecular sieve.

[0102] Preparation Example 8

[0103] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), tetrapropylammonium hydroxide was used instead of cetyltrimethylammonium bromide. The test results are shown in Tables 1 and 2. The internal pore distribution of the molecular sieve prepared in Preparation Example 8 was observed by TEM, and the results are as Figure 10 shown. It can be seen from the figure that hollow molecular sieves appear in the molecular sieve.

[0104] Preparation Example 9

[0105] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), ammonia water was replaced by calcium hydroxide. The test results are shown in Tables 1 and 2.

[0106] Preparation Example 10

[0107] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), dodecyltrimethylammonium bromide was used instead of cetyltrimethylammonium bromide. The test results are shown in Tables 1 and 2. The internal pore distribution of the molecular sieve prepared in Preparation Example 10 was observed by TEM, and the results are as Figure 12 shown. It can be seen from the figure that the microporous and mesoporous composite silicotitanate molecular sieve TS-1 crystals have mesopores with pore diameters in the range of 20 - 30 nm inside.

[0108] Preparation Example 11

[0109] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), octyltrimethylammonium bromide was used instead of cetyltrimethylammonium bromide. The test results are shown in Tables 1 and 2. The internal pore distribution of the molecular sieve prepared in Preparation Example 11 was observed by TEM, and the results are as Figure 13 shown. It can be seen from the figure that the microporous and mesoporous composite silicotitanate molecular sieve TS-1 crystals have mesopores with pore diameters in the range of 5 - 10 nm inside.

[0110] Preparation Example 12

[0111] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (1), the amount of tetrabutyl titanate used was 0.736 g.

[0112] Comparative Preparation Example 1

[0113] The titanium silicalite TS-1 was synthesized by a conventional method described in the prior art (zeolites, 1992, vol.12943-12950). The specific process was as follows: First, 2 g of Tween 20 was mixed with 28.6 g of water and 22.6 g of the template tetrapropylammonium hydroxide and stirred for 1 h until it became clear; 40.5 g of the silicon source tetraethyl orthosilicate was slowly added to the above solution and stirring was maintained for 1 h until the solution became clear; a solution obtained by fully mixing 0.66 g of tetrabutyl titanate and 3.6 g of isopropanol was slowly added dropwise to the above mixed solution and stirred for 2 h, and then the alcohol was removed at 80 °C for 6 h. Finally, the mixture after alcohol removal was transferred into a crystallization kettle and crystallized at 180 °C for 40 h. After the crystallization, the sample was taken out, centrifuged, washed, and calcined in a muffle furnace at 550 °C for 6 h.

[0114] The morphology and particle size of the silicon-titanium molecular sieve prepared in Preparation Example 1 were observed and compared by SEM. The results were as Figure 7 shown. It can be seen from the figure that the morphology of the silicon-titanium molecular sieve is blackberry-like, with small protrusions covering the surface, and the particle size is between 100 - 500 nm.

[0115] The internal structure of the titanium silicalite TS-1 prepared in Preparation Example 1 was observed and compared by TEM. The results were as Figure 8 shown. It can be seen from the figure that the silicon-titanium molecular sieve does not have a mesoporous structure.

[0116] Comparative Preparation Example 2

[0117] The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), ammonia water was replaced with hydrochloric acid (mass fraction 25 wt%). The test results are shown in Table 1 and Table 2. Since hydrochloric acid dissolved all the seeds of the silicon-titanium molecular sieve TS-1, the generated molecular sieve did not have a crystal form.

[0118] Comparative Preparation Example 3

[0119] The molecular sieve was prepared according to the method of Preparation Example 1, except that the one-pot method was used to prepare the molecular sieve. 3.6 g of isopropanol, 0.368 g of tetrabutyl titanate, 27.9 g of tetrapropylammonium hydroxide, 22.58 g of tetraethyl orthosilicate, 6.9 g of H2O, 1.4 g of cetyltrimethylammonium bromide, and 260 g of ammonia water were directly mixed, aged at room temperature for 3 h, then heated to 90 °C at a heating rate of 5 °C / min, and the alcohol was removed at 90 °C for 12 h until a transparent gel liquid was obtained. The transparent gel liquid was placed in an autoclave and crystallized at 130 °C for 48 h. After taking out, washing, and drying, it was calcined in an air atmosphere at 550 °C for 6 h to obtain the silicon-titanium molecular sieve. The test results are shown in Table 1 and Table 2. The internal pore distribution of the molecular sieve prepared in Comparative Preparation Example 3 was observed and compared by TEM. The results were as Figure 11 shown. It can be seen from the figure that no mesoporous structure appears in the molecular sieve.

[0120] Table 1

[0121]

[0122] Table 2

[0123]

[0124] Example 1

[0125] Dissolve 0.86 g of chloroauric acid in 430 g of water to prepare a solution. Immerse 100 g of the carrier prepared in Preparation Example 1 in the aqueous solution of chloroauric acid, adjust the pH value to 7, immerse at 0 °C for 1 h, then dry at 25 °C for 48 h, and then calcine at 300 °C for 5 h to prepare a catalyst.

[0126] Example 2

[0127] Dissolve 0.86 g of chloroauric acid in 430 g of water to prepare a solution. Immerse 100 g of the carrier prepared in Preparation Example 2 in the aqueous solution of chloroauric acid, adjust the pH value to 7.5, immerse at 25 °C for 1 h, then dry at 25 °C for 48 h, and then calcine at 300 °C for 5 h to prepare a catalyst.

[0128] Example 3

[0129] Dissolve 0.86 g of chloroauric acid in 430 g of water to prepare a solution. Immerse 100 g of the carrier prepared in Preparation Example 3 in the aqueous solution of chloroauric acid, adjust the pH value to 7.5, immerse at 50 °C for 1 h, then dry at 100 °C for 48 h, and then calcine at 300 °C for 5 h to prepare a catalyst.

[0130] Example 4

[0131] Dissolve 1.38 g of chloroauric acid in 430 g of water to prepare a solution. Immerse 100 g of the carrier prepared in Preparation Example 4 in the aqueous solution of chloroauric acid, adjust the pH value to 6, immerse at 0 °C for 1 h, then dry at 25 °C for 48 h, and then calcine at 300 °C for 5 h to prepare a catalyst.

[0132] Example 5

[0133] Dissolve 3.45 g of chloroauric acid in 430 g of water to prepare a solution. Immerse 100 g of the carrier prepared in Preparation Example 5 in the aqueous solution of chloroauric acid, adjust the pH value to 8, immerse at 0 °C for 1 h, then dry at 25 °C for 48 h, and then calcine at 300 °C for 5 h to prepare a catalyst.

[0134] Examples 6 - 12

[0135] Prepare the catalyst according to the method of Example 1, except that the carriers used are different, as shown in Table 3.

[0136] Test Example 3

[0137] The catalysts prepared in the above examples and comparative examples were used in the gas-phase propylene epoxidation reaction. The reaction conditions included: in a fixed-bed reactor, the volume ratio of propylene, hydrogen, oxygen, and nitrogen was 1:1:1:8, and the total volume space velocity of propylene, hydrogen, and oxygen was 15000 h -1 , the pressure was 0.1 MPa, the temperature was 200 °C, and the reaction time was 100 h. The reaction products were analyzed by on-line monitoring with a gas chromatograph, and the results are shown in Table 3. The propylene conversion and the selectivity of propylene oxide in Table 3 are the average values during the reaction time.

[0138] Table 3

[0139]

[0140]

[0141] It can be seen from the results in Table 3 that the catalyst prepared by the method of the present invention has a high conversion rate and a relatively high selectivity for propylene oxide.

[0142] Test Example 4

[0143] The carbon deposition amount of the catalyst after the reaction in Test Example 3 was characterized. The catalyst after the reaction was heated at a rate of 5 °C / min in a carrier gas (nitrogen) at 50 mL / min, and the carbon deposition amount was analyzed. The results are shown in Table 4.

[0144] Table 4

[0145]

[0146]

[0147] It can be seen from the results in Table 4 that the carbon deposition content of the catalyst prepared by the preferred method of the present invention is low, indicating that the catalyst of the present invention has a long service life while ensuring the conversion rate and selectivity.

[0148] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst with propylene gas-phase epoxidation function, characterized in that, The method includes loading an active component onto a support; wherein, the support is a titanium silicalite molecular sieve, and based on the total amount of titanium element in the titanium silicalite molecular sieve, the content of non-framework titanium is less than 11% by weight; The particle size of the titanium silicalite molecular sieve is 80 - 150 nm, the specific surface area is 320 - 500 m 2 / g, the pore volume of the mesopores is 0.18 - 0.35 cm 3 / g, the pore volume of the micropores is 0.15 - 0.21 cm 3 / g, and the titanium to silicon ratio in the titanium silicalite molecular sieve is 1:50 - 75; The preparation method of the support includes the following steps: (1) Contact a titanium source, a silicon source and a microporous template agent, then age for 1 - 24 h, crystallize at 150 - 200 °C for 24 - 72 h, and then calcine at 480 - 600 °C for 3 - 8 h to obtain titanium silicalite molecular sieve seeds, wherein, the molar ratio of the titanium source, the silicon source and the microporous template agent is 1:25 - 200:100 - 200, the amount of the titanium source is calculated as Ti, and the amount of the silicon source is calculated as Si; (2) Mix the prepared titanium silicalite molecular sieve seeds with a solution containing a mesoporous template agent and an alkali, crystallize at 100 - 150 °C for 24 - 72 h, and then calcine at 480 - 600 °C for 5 - 10 h to obtain a micro-mesoporous composite silicon-titanium molecular sieve TS-1, wherein, the mass ratio of the titanium silicalite molecular sieve seeds, the mesoporous template agent and the alkali is 1:0.1 - 0.5:50 - 100; The process of loading the active component onto the support includes: placing the support in an aqueous solution of an active component precursor, adjusting the pH value to 6 - 8, impregnating at 0 - 50 °C for 0.5 - 5 h, drying at 15 - 40 °C for 24 - 48 h, and calcining at 250 - 350 °C for 4 - 6 h.

2. The method according to claim 1, wherein The active component includes Group IB metals.

3. The method according to claim 1, wherein, Relative to 100 g of the titanium silicalite molecular sieve, the amount of the active component is such that in the resulting catalyst, the content of the active component calculated as the metal element is 0.1 - 2 g.

4. The method according to claim 1, wherein The active component is at least one of Cu, Ag and Au.

5. A catalyst prepared by the method according to any one of claims 1 - 4.

6. A method for the gas-phase epoxidation of propylene, characterized in that, The method includes: contacting propylene, hydrogen and oxygen with a catalyst, wherein, the catalyst is the catalyst according to any one of claims 1 - 5.

7. The method according to claim 6, wherein The conditions of the contact include: the volume ratio of propylene, hydrogen, oxygen and nitrogen is 1:1 - 3:1 - 3:5 - 10, and the total volume space velocity of propylene, hydrogen and oxygen is 10000 - 20000 h -1 , the pressure is 0.1 - 1 MPa, and the temperature is 150 - 250 °C.

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