Tin-titanium-silicon molecular sieve supported gold nanoparticle catalyst, preparation method and method for gas phase epoxidation of propylene
By loading gold nanoparticle catalysts onto titanium silica molecular sieves and controlling their composition and particle size, the problems of low propylene conversion and propylene oxide selectivity of existing catalysts were solved, and a highly efficient gas-phase propylene epoxidation reaction was achieved.
Patent Information
- Application Number
- CN202310374783.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-10
- Publication Date
- 2026-05-15
- Estimated Expiration
- 2043-04-10
AI Technical Summary
Existing titanium-silicon molecular sieve-supported metal catalysts do not achieve high propylene conversion and propylene oxide selectivity in the gas-phase propylene epoxidation reaction.
A gold nanoparticle catalyst was prepared by using a tin-titanium-silicon molecular sieve as a support and loading it onto the catalyst. The content of gold nanoparticles, the molar ratio of titanium to silicon and the molar ratio of tin to silicon were controlled to ensure that the proportion of 0-valent Au in the catalyst was higher than 90% and the particle size of gold nanoparticles was less than 5 nm.
It significantly improves propylene conversion and propylene oxide selectivity. The catalyst can achieve a propylene conversion of 10-16% and a propylene oxide selectivity of 85-95% in the gas-phase propylene epoxidation reaction.
Smart Images
Figure CN118767986B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of inorganic chemistry and catalytic chemistry, specifically to a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst and its preparation method, and a method for the gas-phase epoxidation of propylene. Background Technology
[0002] Propylene oxide, also known as propylene oxide or methyl ethylene oxide, has the chemical formula C3H6O and is an important propylene derivative. Propylene oxide has a low boiling point, is flammable, and is miscible with ethanol and diethyl ether.
[0003] Currently, the industrial production of propylene oxide mainly employs the chlorohydrin process, co-oxidation process, and direct hydrogen peroxide oxidation (HPPO). The chlorohydrin process requires toxic chlorine gas and generates a large amount of calcium chloride waste during production; the economic benefits of the co-oxidation process are heavily influenced by co-products. The HPPO process, however, is relatively simple and environmentally friendly. The HPPO process uses titanium-silicon molecular sieves as catalysts and hydrogen peroxide as an oxidant. Hydrogen peroxide, as one of the main reactants, is used in large quantities; however, due to cost and transportation limitations, the HPPO process typically requires a dedicated hydrogen peroxide production unit. To further optimize the process layout, hydrogen peroxide production is integrated into the epoxidation process, where propylene directly reacts with hydrogen and oxygen under the action of a catalyst. To achieve in-situ synthesis of hydrogen peroxide from hydrogen and oxygen, another metal active center needs to be loaded onto the existing titanium-silicon molecular sieve support. Research has found that metals such as Au, Ag, and Pd, and their alloys, can all serve as active centers for catalyzing hydrogen peroxide generation.
[0004] However, the catalysts obtained by supporting metals on titanium-silicon molecular sieves in the existing technology do not have high propylene conversion or propylene oxide selectivity in the propylene gas-phase epoxidation reaction. Therefore, there is an urgent need to provide a propylene epoxidation catalyst with high propylene conversion and high propylene oxide selectivity in the propylene gas-phase epoxidation reaction. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of low propylene conversion and propylene oxide selectivity in the gas-phase propylene epoxidation reaction of existing propylene epoxidation catalysts, and to provide a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst, its preparation method, and a method for gas-phase propylene epoxidation. The tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst provided by this invention significantly improves the propylene conversion rate and exhibits high propylene oxide selectivity in the gas-phase propylene epoxidation reaction.
[0006] To achieve the above objectives, a first aspect of the present invention provides a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst, the catalyst comprising a tin-titanium-silicon molecular sieve and gold nanoparticles supported on the tin-titanium-silicon molecular sieve; wherein, based on the total weight of the catalyst, the content of the gold nanoparticles is 0.01-1% by weight, preferably 0.04-0.8% by weight; wherein, based on Au element, the proportion of 0-valent Au in the gold nanoparticles is >90%, as determined by XPS detection and calculation; wherein, in the catalyst, the molar ratio of titanium to silicon is 0.005-0.04:1, and the molar ratio of tin to silicon is 0.005-0.04:1.
[0007] Preferably, in the catalyst, the gold nanoparticles have a particle size of <5nm, and more preferably <3nm.
[0008] Preferably, the tin-titanium-silicon molecular sieve is selected from one or more of the following types: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve.
[0009] A second aspect of the present invention provides a method for preparing the gold nanoparticle catalyst supported on the tin-titanium-silicon molecular sieve described in the first aspect, the method comprising the following steps:
[0010] S1. Mix the tin-titanium-silicon molecular sieve with an aqueous solution containing a gold compound, and then adjust the pH of the resulting mixture to alkaline. The amount of the aqueous solution containing the gold compound, calculated as Au, is 0.05-5% by weight of the amount of the tin-titanium-silicon molecular sieve.
[0011] S2. The product obtained in step S1 is subjected to solid-liquid separation, and the resulting solid product is activated.
[0012] Preferably, in the tin-titanium-silicon molecular sieve, the molar ratio of titanium to silicon is 0.005-0.04:1, and the molar ratio of tin to silicon is 0.005-0.04:1.
[0013] Preferably, the tin-titanium-silicon molecular sieve is selected from one or more of the following types: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve.
[0014] Preferably, the aqueous solution containing the gold compound is selected from one or more of aqueous solutions of chloroauric acid, cesium chloroaurate, and potassium chloroaurate.
[0015] Preferably, in step S1, the concentration of the aqueous solution containing the gold compound is 0.0001-0.1 mol / L, more preferably 0.0005-0.05 mol / L, and even more preferably 0.005-0.05 mol / L.
[0016] Preferably, in step S1, the amount of the aqueous solution containing the gold compound, calculated as Au, is 0.1-5% by weight of the amount of the tin-titanium-silicon molecular sieve.
[0017] Preferably, in step S1, the pH value of the mixture is adjusted to 7-10, more preferably 7-9.
[0018] Preferably, in step S1, the pH adjuster used to adjust the pH value of the mixture is an alkaline solution.
[0019] Preferably, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, cesium hydroxide solution, urea solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate solution, cesium carbonate solution, and cesium bicarbonate solution.
[0020] Preferably, in step S2, the activation conditions include: a temperature of 150-300°C and a time of 1-5 hours.
[0021] A third aspect of the present invention provides a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst prepared by the method described in the second aspect above.
[0022] A fourth aspect of the present invention provides a method for the gas-phase epoxidation of propylene, the method comprising: reacting hydrogen, oxygen and propylene in the presence of a protective gas and a catalyst to obtain propylene oxide; wherein the catalyst is the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst described in the first aspect or the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst described in the third aspect.
[0023] Preferably, the reaction conditions include a volume flow rate ratio of hydrogen, oxygen, and propylene of 0.5-2:0.5-2:1.
[0024] Preferably, the volumetric flow rate ratio of propylene to protective gas is 1:1-10.
[0025] Preferably, the reaction conditions include: a temperature of 100-250°C and a pressure of 0.1-0.7 MPa.
[0026] Preferably, the reaction conditions include: a temperature of 120-220°C and a pressure of 0.1-0.5 MPa.
[0027] The gold nanoparticle catalyst supported on tin-titanium-silicon molecular sieve provided by this invention uses tin-titanium-silicon molecular sieve as a support. The proportion of 0-valent gold nanoparticles in the catalyst is >90%, and the catalyst contains a specific ratio of titanium to silicon, a specific ratio of tin to silicon, and a specific amount of gold nanoparticles. The catalyst with these characteristics has high catalytic activity in the gas-phase epoxidation reaction of propylene, and the propylene conversion rate can be increased to 10-16%, and the propylene oxide selectivity can reach 85-95%. Attached Figure Description
[0028] Figure 1 These are the XPS spectra of the catalysts prepared in Example 1 and Comparative Example 2;
[0029] Figure 2 This is a high-angle annular dark-field scanning transmission electron microscope image of the catalyst prepared in Example 1. Detailed Implementation
[0030] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0031] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0032] The first aspect of the present invention provides a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst, the catalyst comprising a tin-titanium-silicon molecular sieve and gold nanoparticles supported on the tin-titanium-silicon molecular sieve.
[0033] In this invention, tin-titanium-silicon molecular sieves are used as a carrier to load gold nanoparticles, which can improve the propylene conversion rate in the propylene epoxidation reaction. The inventors discovered that Sn and Ti additives jointly provide electrons to Au, resulting in more electron-rich Au. 0 The active sites effectively promote the rate-determining step of in-situ synthesis of H2O2 from hydrogen and oxygen, resulting in a high propylene conversion rate when applied to the gas-phase epoxidation reaction of propylene.
[0034] According to the present invention, the content of gold nanoparticles, the molar ratio of titanium to silicon, and the molar ratio of tin to silicon in the catalyst all have a significant impact on improving the propylene conversion and propylene oxide selectivity during the catalytic gas-phase epoxidation reaction of propylene. Specifically, based on the total weight of the catalyst, the content of gold nanoparticles can be 0.01-1% by weight, preferably 0.04-0.8% by weight. Furthermore, the molar ratio of titanium to silicon in the catalyst can be 0.005-0.04:1, and the molar ratio of tin to silicon can be 0.005-0.04:1.
[0035] In this invention, the content of gold nanoparticles in the catalyst was determined by ICP. The molar ratios of titanium and silicon, and tin and silicon, were detected and calculated using X-ray fluorescence spectrometry. The instrument used was a Rigaku Denki Corporation ZSM Primus II X-ray fluorescence spectrometer with a rhodium target, an excitation voltage of 40 kV, and an excitation current of 250 mA.
[0036] The inventors discovered that in-situ generation of H₂O₂ is crucial in the gas-phase epoxidation reaction of propylene. The transfer of negative charge from Au atoms to adsorbed O₂ favors the in-situ generation of H₂O₂. Therefore, Au nanoparticles possessing a higher negative charge are beneficial to the reaction; that is, Au in its zero-valence state is more favorable for the gas-phase epoxidation reaction of propylene.
[0037] In this invention, to improve the catalytic activity of the catalyst in the gas-phase epoxidation reaction of propylene and to increase the propylene conversion and propylene oxide selectivity, the catalyst needs to have a high proportion of 0-valent Au. Specifically, based on elemental Au, the proportion of 0-valent Au in the gold nanoparticles is >90%, as determined by XPS detection and calculation.
[0038] According to the present invention, XPS characterization yields 0-valent Au(Au) 0 The characteristic peaks are centered at 83-84 eV; XPS peak analysis using XPS software showed that the area of the 0-valent Au peak was >90% of the total peak area. XPS measurements were performed on a Thermo Fisher Scientific ESCALab 250 X-ray photoelectron spectrometer, using monochromatic Al Kα X-rays at an energy of 1486.6 eV and a power of 150 W; the narrow scan passthrough energy was 30 eV; and the baseline vacuum during analysis was approximately 6.5 × 10⁻⁶. - 8 Pa.
[0039] Studies have found that the particle size of gold nanoparticles has a significant impact on improving the catalytic effect of the catalyst in this invention. To further enhance the catalytic activity of the catalyst in the gas-phase epoxidation of propylene, and to improve propylene conversion and propylene oxide selectivity, preferably, the particle size of the gold nanoparticles in the catalyst is <5 nm, more preferably <3 nm. The particle size of the gold nanoparticles was observed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).
[0040] According to the present invention, the type of tin-titanium-silicon molecular sieve is not limited, as long as it is a molecular sieve containing silicon, titanium, tin and oxygen.
[0041] In this invention, the tin-titanium-silicon molecular sieve may be selected from one or more of the following: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal structure tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve, preferably MFI type tin-titanium-silicon molecular sieve.
[0042] According to the present invention, the tin-titanium-silicon molecular sieve has an absorption peak at 200-300 nm in the UV-Vis spectrum, that is, the tin-titanium-silicon molecular sieve contains framework Ti atoms or Sn atoms.
[0043] According to the present invention, in a preferred embodiment, at least a portion of the crystal grains of the tin-titanium-silicon molecular sieve have a void structure.
[0044] A second aspect of the present invention provides a method for preparing the gold nanoparticle catalyst supported on the tin-titanium-silicon molecular sieve described in the first aspect, the method comprising the following steps:
[0045] S1. Mix the tin-titanium-silicon molecular sieve with an aqueous solution containing a gold compound, and then adjust the pH of the resulting mixture to be alkaline.
[0046] S2. The product obtained in step S1 is subjected to solid-liquid separation, and the resulting solid product is activated.
[0047] In this invention, tin-titanium-silicon molecular sieve is used as a carrier, and Au is loaded by deposition precipitation method to obtain the tin-titanium-silicon molecular sieve-loaded gold nanoparticle catalyst described in this invention. This method is simple and easy to operate.
[0048] In this invention, excessive amounts of gold compound can lead to the aggregation of gold nanoparticles, triggering side reactions during the gas-phase epoxidation of propylene and reducing the selectivity of propylene oxide. Conversely, insufficient amounts of gold compound can reduce the catalytic activity of the prepared catalyst. Therefore, it is necessary to control the amount of gold compound to ensure that an appropriate amount of gold nanoparticles are loaded onto the tin-titanium-silicon molecular sieve. Specifically, in this invention, the amount of the aqueous solution containing the gold compound, calculated as Au, is 0.05-5% by weight of the amount of the tin-titanium-silicon molecular sieve, preferably 0.1-5% by weight, for example, 0.1% by weight, 0.5% by weight, 1% by weight, 1.5% by weight, 2% by weight, 2.5% by weight, 3% by weight, 3.5% by weight, 4% by weight, 4.5% by weight, or 5% by weight.
[0049] According to the present invention, in order to further improve the catalytic activity and selectivity of the prepared catalyst, preferably, the molar ratio of titanium to silicon in the tin-titanium-silicon molecular sieve can be 0.005-0.04:1, and the molar ratio of tin to silicon can be 0.005-0.04:1.
[0050] According to the present invention, the type of tin-titanium-silicon molecular sieve is not limited, as long as it is a molecular sieve containing silicon, titanium, tin and oxygen.
[0051] In this invention, the tin-titanium-silicon molecular sieve may be selected from one or more of the following: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal structure tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve, preferably MFI type tin-titanium-silicon molecular sieve.
[0052] According to the present invention, the tin-titanium-silicon molecular sieve has an absorption peak at 200-300 nm in the UV-Vis spectrum, that is, the tin-titanium-silicon molecular sieve contains framework Ti atoms or Sn atoms.
[0053] In some preferred embodiments, at least a portion of the crystal grains of the tin-titanium-silicon molecular sieve have a void structure.
[0054] According to the present invention, the tin-titanium-silicon molecular sieve can be obtained commercially, prepared according to the methods in the prior art, or prepared by oneself; preferably, the tin-titanium-silicon molecular sieve can be prepared according to the method disclosed in Chinese patent application CN114105158A.
[0055] In some preferred embodiments, the method for preparing the tin-titanium-silicon molecular sieve includes:
[0056] (1) A first mixture is obtained by mixing an organosilicon source, an organic base, a solvent, a tin source, a titanium source, and an alkaline template agent; wherein the organic base is tetrapropylammonium hydroxide or tetrabutylammonium hydroxide; the molar ratio of the organosilicon source, the organic base, the solvent, the tin source, and the titanium source is 1:(0.05-0.6):(10-30):(0.005-0.04):(0.005-0.04), the organosilicon source is calculated as SiO2, the tin source is calculated as SnO2, and the titanium source is calculated as TiO2; the molar ratio of the tin source to the alkaline template agent is 1:(1-10), and the tin source is calculated as anion;
[0057] (2) The first mixture is heated at 30-80°C for 2-10 hours to obtain the second mixture;
[0058] (3) The second mixture is subjected to a hydrothermal reaction at 120-200℃ for 2-7 days to obtain a third mixture;
[0059] (4) Remove the solid from the third mixture and dry and calcine it.
[0060] In this invention, the aqueous solution containing the gold compound can be any aqueous solution well known to those skilled in the art. Preferably, the aqueous solution containing the gold compound is selected from one or more of aqueous solutions of chloroauric acid, cesium chloroaurate, and potassium chloroaurate.
[0061] This invention does not impose any particular restrictions on the method of mixing the tin-titanium-silicon molecular sieve with the aqueous solution of the gold-containing compound. Preferably, the mixing of the tin-titanium-silicon molecular sieve with the aqueous solution of the gold-containing compound can be achieved by stirring at room temperature. Similarly, adjusting the pH of the resulting mixture to alkaline can also be achieved by stirring at room temperature.
[0062] In a preferred embodiment, the process of mixing the tin-titanium-silicon molecular sieve with the aqueous solution of the gold compound can be as follows: first, the gold compound is prepared into an aqueous solution with water, and then the tin-titanium-silicon molecular sieve is mixed with the aqueous solution of the gold compound to obtain a mixture. Unless otherwise specified herein, room temperature refers to 20-30°C.
[0063] To further improve the catalytic performance of the catalyst and increase the propylene conversion and propylene oxide selectivity, under preferred conditions, in step S1, the concentration of the aqueous solution containing the gold compound can be 0.0001-0.1 mol / L, preferably 0.0005-0.05 mol / L, more preferably 0.005-0.05 mol / L, for example 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.035 mol / L, 0.04 mol / L, 0.045 mol / L, or 0.05 mol / L.
[0064] In some preferred embodiments, in step S1, the pH value corresponding to the alkalinity can be 7-10, preferably 7-9, for example 7, 7.5, 8, 8.5, or 9. Specifically, according to the present invention, after adjusting the pH value of the obtained mixture to alkalinity, the resulting product is a suspension.
[0065] In this invention, specifically, the pH adjuster used to adjust the pH value of the mixture is an alkaline solution. There are no specific limitations on the type and concentration of the alkaline solution, as long as it can adjust the pH value of the mixture to a specific alkalinity. Preferably, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, cesium hydroxide solution, urea solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate solution, cesium carbonate solution, and cesium bicarbonate solution.
[0066] In this invention, the solid-liquid separation of the product obtained in step S1 can be performed using various solid-liquid separation methods well-known to those skilled in the art, as long as the solid product and the liquid can be separated. Preferably, the solid-liquid separation method is filtration or centrifugation.
[0067] In some preferred embodiments of the present invention, in order to improve the catalytic performance of the catalyst and further improve the propylene conversion and propylene oxide selectivity, the activation conditions in step S2 include: a temperature of 150-300°C, for example, 150°C, 180°C, 200°C, 220°C, 250°C, 280°C, or 300°C; and a time of 1-5 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours. In a preferred embodiment, the activation process includes: calcination at 150-300°C for 1-5 hours in an air atmosphere.
[0068] A third aspect of the present invention provides a tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst prepared by the method described in the second aspect above.
[0069] In some preferred embodiments of the present invention, the catalyst comprises a tin-titanium-silicon molecular sieve and gold nanoparticles supported on the tin-titanium-silicon molecular sieve; wherein, based on the total weight of the catalyst, the content of the gold nanoparticles is 0.01-1% by weight, preferably 0.04-0.8% by weight; wherein, based on Au element, the proportion of 0-valent Au in the gold nanoparticles is >90%, as determined by XPS detection and calculation; wherein, in the catalyst, the molar ratio of titanium to silicon is 0.005-0.04:1, and the molar ratio of tin to silicon is 0.005-0.04:1.
[0070] To improve the catalytic performance of the catalyst, in the catalyst of the present invention, preferably, the particle size of the gold nanoparticles is <5nm, and more preferably <3nm.
[0071] According to the present invention, the type of tin-titanium-silicon molecular sieve is not limited, as long as it is a molecular sieve containing silicon, titanium, tin and oxygen.
[0072] In some preferred embodiments, the tin-titanium-silicon molecular sieve may be selected from one or more of the following: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal structure tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve, with MFI type tin-titanium-silicon molecular sieve being preferred.
[0073] The catalyst prepared by the method of the present invention can be applied to the catalytic gas-phase epoxidation reaction of propylene, and the propylene conversion rate can reach 10-16%, and the propylene oxide selectivity can reach 85-95%.
[0074] A fourth aspect of the present invention provides a method for the gas-phase epoxidation of propylene, the method comprising: reacting hydrogen, oxygen and propylene in the presence of a protective gas and a catalyst to obtain propylene oxide; wherein the catalyst is the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst described in the first aspect or the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst described in the third aspect.
[0075] According to the present invention, under preferred conditions, the reaction conditions include a volume flow rate ratio of hydrogen, oxygen and propylene of 0.5-2:0.5-2:1.
[0076] More preferably, the volumetric flow rate ratio of propylene to the protective gas is 1:1-10. In this invention, the protective gas is nitrogen and / or an inert gas.
[0077] In some preferred embodiments of the present invention, the reaction conditions further include: a temperature of 100-250°C and a pressure of 0.1-0.7 MPa; more preferably, the temperature is 120-200°C and the pressure is 0.1-0.5 MPa.
[0078] In this invention, the method for gas-phase epoxidation of propylene can be carried out in a continuous operation mode. Specifically, after the catalyst is loaded into the reactor, a mixture of hydrogen, oxygen, propylene and protective gas is continuously added to carry out the reaction.
[0079] The present invention does not have special requirements for the morphology of the catalyst. The catalyst can be gold nanoparticle powder supported on tin-titanium-silicon molecular sieve, or it can be further loaded onto a support for use. Those skilled in the art can select the catalyst according to the type of reactor.
[0080] In this invention, the separation of propylene gas-phase epoxidation products from the catalyst can be adjusted according to the morphology of the catalyst and actual needs. For example, when the catalyst is gold nanoparticle powder supported on tin-titanium-silicon molecular sieve, the product separation and catalyst recycling can be achieved by sedimentation, filtration, centrifugation, evaporation, membrane separation, etc. When the catalyst is gold nanoparticle supported on tin-titanium-silicon molecular sieve (shaped catalyst), the shaped catalyst can be packed into a fixed-bed reactor, and the catalyst can be recovered after the reaction is completed.
[0081] The present invention will be described in detail below through examples, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, all raw materials used in the following examples are chemically pure reagents.
[0082] The tin-titanium-silicon molecular sieves used in the examples are all tin-titanium-silicon molecular sieves with MFI type structure, and are prepared according to the method disclosed in CN114105158A.
[0083] In this invention:
[0084] The content of gold nanoparticles was measured by inductively coupled plasma (ICP).
[0085] The particle size of the gold nanoparticles was observed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).
[0086] The contents of tin, silicon and titanium were analyzed by X-ray fluorescence spectroscopy using a Rigaku Denki Corporation ZSM Primus II X-ray fluorescence spectrometer. The test conditions were a rhodium target, an excitation voltage of 40 kV and an excitation current of 250 mA.
[0087] The proportion of Au in the catalyst at zero valence was determined and calculated using XPS. XPS measurements were performed on a Thermo Fisher Scientific ESCALab 250 X-ray photoelectron spectrometer with a monochromatic Al Kα X-ray excitation source of 1486.6 eV and a power of 150 W; the narrow scan passthrough energy was 30 eV; and the baseline vacuum during analysis was approximately 6.5 × 10⁻⁶. - 8 Pa.
[0088] Preparation Examples 1-5 and Preparation Comparative Examples 1-2 are used to illustrate the preparation process of molecular sieves.
[0089] Preparation Example 1
[0090] The method described in Example 1 of Chinese patent application CN114105158A was used to prepare an MFI-type tin-titanium-silicon molecular sieve, denoted as Sn-Ti-MFI-1.
[0091] Preparation Example 2
[0092] The method described in Example 12 of Chinese patent application CN114105158A was used to prepare an MFI-type tin-titanium-silicon molecular sieve, which was designated as Sn-Ti-MFI-2.
[0093] Preparation Example 3
[0094] The method described in Example 13 of Chinese patent application CN114105158A was used to prepare an MFI-type tin-titanium-silicon molecular sieve, denoted as Sn-Ti-MFI-3.
[0095] Preparation Example 4
[0096] MFI-type tin-titanium-silicon molecular sieves were prepared according to the method of Preparation Example 1, except that the molar ratio of tetrabutyl titanate to tetraethyl orthosilicate was 0.01:1, resulting in MFI-type tin-titanium-silicon molecular sieves, denoted as Sn-Ti-MFI-4.
[0097] Preparation Example 5
[0098] MFI-type tin-titanium-silicon molecular sieves were prepared according to the method of Preparation Example 1, except that the molar ratio of tetrabutyl titanate to tetraethyl orthosilicate was 0.03:1, resulting in MFI-type tin-titanium-silicon molecular sieves, denoted as Sn-Ti-MFI-5.
[0099] Preparation of Comparative Example 1
[0100] The preparation method for TS-1 titanium-silicon molecular sieve is as follows:
[0101] Approximately 3 / 4 of a tetrapropylammonium hydroxide (TPAOH, 20%, purchased from Aldrich, USA) solution was added to a tetraethyl orthosilicate (TEOS) solution to obtain a liquid mixture with a pH of approximately 13. Then, under vigorous stirring, the required amount of anhydrous isopropanol solution of tetrabutyl titanate [Ti(OBu)4] was added dropwise to the resulting liquid mixture. After stirring for 15 minutes, a clear liquid was obtained. Finally, the remaining TPAOH was slowly added to the clear liquid, and the mixture was stirred at 348-353 K for approximately 3 hours to obtain a product with a chemical composition of 0. A sol of 0.3TiO2:SiO2:0.36TPA:35H2O was prepared and crystallized at 443K for 3 days. The resulting solid was then filtered, washed with distilled water, dried at 373K for 5 hours, and calcined at 823K for 10 hours to obtain a molecular sieve sample. The amount of TEOS was 42g, TPAOH was 73g, Ti(OBu)4 was 2g, anhydrous isopropanol was 10g, and water was 68g, resulting in TS-1 titanium-silicon molecular sieve, denoted as TS-1.
[0102] Preparation of Comparative Example 2
[0103] The method for preparing Sn-MFI molecular sieves is as follows:
[0104] Tin tetrachloride pentahydrate (SnCl4·5H2O) was dissolved in water. This aqueous solution was added to tetraethyl orthosilicate (TEOS) and stirred. While stirring, tetrapropylammonium hydroxide (TPAOH, 20% aqueous solution) and water were added, and stirring continued for 30 minutes to obtain a clear liquid with a chemical composition of 0.03SnO2:SiO2:0.45TPA:35H2O. The liquid was then crystallized at 433K for 2 days. The resulting solid was filtered, washed with distilled water, dried at 393K for 5 hours, and then calcined at 823K for 10 hours to obtain a molecular sieve sample. The sample contained 15.31 g of TEOS, 33.67 g of TPAOH, and SnCl4·5H2O. 4.5 The amount of H2O used is 0.38g, and the amount of water used is 39.64g, to obtain Sn-MFI molecular sieve, denoted as Sn-MFI.
[0105] Table 1
[0106]
[0107]
[0108] Examples 1-8 and Comparative Examples 1-4 are used to illustrate the preparation process of the catalyst.
[0109] Example 1
[0110] The Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve from Preparation Example 1 was mixed with an aqueous chloroauric acid solution to obtain a mixture, wherein the concentration of the aqueous chloroauric acid solution was 0.03 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve. Then, sodium hydroxide solution was added to adjust the pH of the resulting mixture to 7.7 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 200°C for 2 hours to obtain a catalyst.
[0111] Example 2
[0112] The Sn-Ti-MFI-2 tin-titanium-silicon molecular sieve from Preparation Example 2 was mixed with an aqueous chloroauric acid solution to obtain a mixture. The concentration of the aqueous chloroauric acid solution was 0.05 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-2 tin-titanium-silicon molecular sieve. Then, potassium hydroxide solution was added to adjust the pH of the mixture to 8.1 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 150°C for 3 hours to obtain a catalyst.
[0113] Example 3
[0114] The Sn-Ti-MFI-3 tin-titanium-silicon molecular sieve from Preparation Example 3 was mixed with an aqueous chloroauric acid solution to obtain a mixture, wherein the concentration of the aqueous chloroauric acid solution was 0.08 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-3 tin-titanium-silicon molecular sieve. Then, cesium hydroxide solution was added to adjust the pH of the obtained mixture to 8.5 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 120°C for 4 hours to obtain a catalyst.
[0115] Example 4
[0116] The Sn-Ti-MFI-4 tin-titanium-silicon molecular sieve from Preparation Example 4 was mixed with an aqueous chloroauric acid solution to obtain a mixture. The concentration of the aqueous chloroauric acid solution was 0.005 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-4 tin-titanium-silicon molecular sieve. Then, urea solution was added to adjust the pH of the mixture to 7.1 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 220°C for 1.5 h to obtain a catalyst.
[0117] Example 5
[0118] The Sn-Ti-MFI-5 tin-titanium-silicon molecular sieve from Preparation Example 5 was mixed with an aqueous chloroauric acid solution to obtain a mixture, wherein the concentration of the aqueous chloroauric acid solution was 0.008 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-5 tin-titanium-silicon molecular sieve. Then, sodium carbonate solution was added to adjust the pH of the resulting mixture to 7.4 to obtain a second suspension. The second suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 250°C for 1 hour to obtain a catalyst.
[0119] Example 6
[0120] The Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve from Preparation Example 1 was mixed with an aqueous chloroauric acid solution to obtain a mixture, wherein the concentration of the aqueous chloroauric acid solution was 0.01 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 0.1% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve. Then, sodium bicarbonate solution was added to adjust the pH of the resulting mixture to 7.5 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 200°C for 2.5 h to obtain a catalyst.
[0121] Example 7
[0122] The Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve from Preparation Example 1 was mixed with an aqueous chloroauric acid solution to obtain a mixture. The concentration of the aqueous chloroauric acid solution was 0.09 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 4.5% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve. Then, potassium bicarbonate solution was added to adjust the pH of the mixture to 7.8 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 180°C for 2 hours to obtain a catalyst.
[0123] Example 8
[0124] The Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve from Preparation Example 1 was mixed with an aqueous chloroauric acid solution to obtain a mixture, wherein the concentration of the aqueous chloroauric acid solution was 0.0008 mol / L, and the amount of the aqueous chloroauric acid solution, calculated as Au, was 2% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve. Then, potassium carbonate solution was added to adjust the pH of the resulting mixture to 7.1 to obtain a suspension. The suspension was then filtered, and the obtained filter residue was activated. The activation conditions included: air atmosphere and calcination at 200°C for 2 hours to obtain a catalyst.
[0125] Comparative Example 1
[0126] The method of Example 1 was carried out, except that the Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve in Preparation Example 1 was replaced with the TS-1 titanium-silicon molecular sieve in Comparative Example 1 to obtain the catalyst.
[0127] Comparative Example 2
[0128] The method of Example 1 was carried out, except that the Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve in Preparation Example 1 was replaced with the Sn-MFI tin-silicon molecular sieve in Comparative Example 2, and a catalyst was obtained.
[0129] Comparative Example 3
[0130] The method was carried out according to Example 1, except that the amount of chloroauric acid aqueous solution, calculated as Au, was 6% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve, and the catalyst was obtained.
[0131] Comparative Example 4
[0132] The method was carried out according to Example 1, except that the amount of chloroauric acid aqueous solution, calculated as Au, was 0.005% by weight of the amount of Sn-Ti-MFI-1 tin-titanium-silicon molecular sieve, and the catalyst was obtained.
[0133] Test Example 1
[0134] The Au content in the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 was tested, and the results are shown in Table 2. The test method was as follows: ASTM D5185 standard method, using Spike ACROSS inductively coupled plasma (ICP) assay.
[0135] XPS was used to detect the characteristic peak positions of Au in the catalysts prepared in Examples 1-8 and Comparative Examples 1-4, and the proportion of Au with zero valence was calculated. The results are shown in Table 2. The XPS spectra of the catalysts prepared in Example 1 and Comparative Example 2 are shown below. Figure 1 As shown.
[0136] The molar ratios of tin and silicon and titanium and silicon in the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 were analyzed and calculated using X-ray fluorescence spectroscopy, and the results are shown in Table 2.
[0137] The particle size of gold nanoparticles in the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 was observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and the results are shown in Table 2. A high-angle annular dark-field scanning transmission electron microscopy image of the catalyst prepared in Example 1 is shown below. Figure 2 As shown.
[0138] Table 2
[0139]
[0140] Test Example 2
[0141] This test example illustrates the reaction effect of the catalysts prepared in Examples 1-8 and Comparative Examples 1-4 of this invention in the gas-phase epoxidation reaction of propylene. All reagents used in this test example were commercially available chemically pure reagents. The concentrations of each substance after the reaction were quantitatively analyzed using gas chromatography. The instrument used was an Agilent 6890 gas chromatograph, with molecular sieve 5A and PoraBOND U columns, and FID and TCD detectors.
[0142] In the various embodiments and comparative examples:
[0143] Propylene conversion rate % = (moles of propylene in feedstock - moles of propylene in product) / moles of propylene in feedstock × 100%;
[0144] propylene oxide selectivity % = (number of moles of propylene oxide in the product / total number of moles of the product) × 100%.
[0145] The testing procedure was as follows: Catalyst samples prepared in the above examples and comparative examples were placed in a tubular reactor with an inner diameter of 8 mm. The reactor was then heated to 180 °C in a N2 atmosphere, and hydrogen, oxygen, and propylene were introduced to start the reaction. After 1 h of reaction, the products were analyzed online. The catalyst dosage was 0.4 g, and the flow rates of hydrogen, oxygen, propylene, and nitrogen were 2 mL / min, 2 mL / min, 2 mL / min, and 14 mL / min, respectively. The reaction pressure was 0.1 MPa. The catalytic reaction results are shown in Table 3.
[0146] Table 3
[0147] serial number propylene conversion rate / % propylene oxide selectivity / % Example 1 13.2 90.5 Example 2 12.8 90.6 Example 3 14.5 92.3 Example 4 11.6 91.4 Example 5 12.3 89.6 Example 6 10.3 94.3 Example 7 15.8 87.9 Example 8 13.1 89.1 Comparative Example 1 6.6 76.5 Comparative Example 2 4.1 65.2 Comparative Example 3 8.6 58.2 Comparative Example 4 1.8 86.5
[0148] As can be seen from Table 3, the propylene conversion rate of the catalyst provided in the embodiments of the present invention for the propylene gas-phase epoxidation reaction is significantly higher than that of the comparative example, and the propylene oxide selectivity of the catalyst provided in the embodiments of the present invention for the propylene gas-phase epoxidation reaction is also maintained at a high level.
[0149] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst, characterized in that, The catalyst comprises a tin-titanium-silicon molecular sieve and gold nanoparticles supported on the tin-titanium-silicon molecular sieve; wherein, based on the total weight of the catalyst, the content of the gold nanoparticles is 0.01-1% by weight; wherein, based on Au element, the proportion of 0-valent Au in the gold nanoparticles is >90%, as determined by XPS detection and calculation; wherein, in the catalyst, the molar ratio of titanium to silicon is 0.005-0.04:1, and the molar ratio of tin to silicon is 0.005-0.04:1; A method for preparing a gold nanoparticle-supported catalyst using a tin-titanium-silicon molecular sieve includes the following steps: S1. Mix the tin-titanium-silicon molecular sieve with an aqueous solution containing a gold compound, and then adjust the pH of the resulting mixture to alkaline. The amount of the aqueous solution containing the gold compound, calculated as Au, is 0.05-5% by weight of the amount of the tin-titanium-silicon molecular sieve. S2. The product obtained in step S1 is subjected to solid-liquid separation, and the obtained solid product is activated. The activation conditions include: temperature of 150-300℃ and time of 1-5h.
2. The catalyst according to claim 1, characterized in that, Based on the total weight of the catalyst, the content of the gold nanoparticles is 0.04-0.8% by weight.
3. The catalyst according to claim 1, characterized in that, In the catalyst, the gold nanoparticles have a particle size of <5 nm.
4. The catalyst according to claim 3, characterized in that, In the catalyst, the gold nanoparticles have a particle size of <3nm.
5. The catalyst according to claim 1, characterized in that, The tin-titanium-silicon molecular sieve is selected from one or more of the following types: MFI type tin-titanium-silicon molecular sieve, MEL type tin-titanium-silicon molecular sieve, BEA type tin-titanium-silicon molecular sieve, MWW type tin-titanium-silicon molecular sieve, MOR type tin-titanium-silicon molecular sieve, hexagonal tin-titanium-silicon molecular sieve, and USY type tin-titanium-silicon molecular sieve.
6. A method for preparing the gold nanoparticle catalyst supported on a tin-titanium-silicon molecular sieve according to any one of claims 1-5, characterized in that, The method includes the following steps: S1. Mix the tin-titanium-silicon molecular sieve with an aqueous solution containing a gold compound, and then adjust the pH of the resulting mixture to alkaline. The amount of the aqueous solution containing the gold compound, calculated as Au, is 0.05-5% by weight of the amount of the tin-titanium-silicon molecular sieve. S2. The product obtained in step S1 is subjected to solid-liquid separation, and the resulting solid product is activated.
7. The method according to claim 6, characterized in that, The gold-containing aqueous solution is selected from one or more of the following: aqueous solution of chloroauric acid, aqueous solution of cesium chloroaurate, and aqueous solution of potassium chloroaurate.
8. The method according to claim 6, characterized in that, In step S1, the concentration of the aqueous solution containing the gold compound is 0.0001-0.1 mol / L.
9. The method according to claim 8, characterized in that, In step S1, the concentration of the aqueous solution containing the gold compound is 0.0005-0.05 mol / L.
10. The method according to claim 6, characterized in that, In step S1, the amount of the aqueous solution containing the gold compound, calculated as Au, is 0.1-5% by weight of the amount of the tin-titanium-silicon molecular sieve.
11. The method according to claim 6, characterized in that, In step S1, the pH of the mixture is adjusted to 7-10.
12. The method according to claim 11, characterized in that, In step S1, the pH of the mixture is adjusted to 7-9.
13. The method according to claim 6, characterized in that, In step S1, the pH adjuster used to adjust the pH value of the mixture is an alkaline solution.
14. The method according to claim 13, characterized in that, In step S1, the alkaline solution is selected from one or more of the following: sodium hydroxide solution, potassium hydroxide solution, cesium hydroxide solution, urea solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate solution, cesium carbonate solution, and cesium bicarbonate solution.
15. A tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst prepared by the method according to any one of claims 6-14.
16. A method for the vapor-phase epoxidation of propylene, characterized in that, The method includes: reacting hydrogen, oxygen and propylene in the presence of a protective gas and a catalyst to obtain propylene oxide; The catalyst is the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst according to any one of claims 1-5 or the tin-titanium-silicon molecular sieve-supported gold nanoparticle catalyst according to claim 15.
17. The method according to claim 16, characterized in that, The reaction conditions include a volume flow rate ratio of hydrogen, oxygen, and propylene of 0.5-2:0.5-2:
1.
18. The method according to claim 17, characterized in that, The volumetric flow rate ratio of propylene to protective gas is 1:1-10.
19. The method according to claim 16, characterized in that, The reaction conditions include a temperature of 100-250℃ and a pressure of 0.1-0.7MPa.
20. The method according to claim 19, characterized in that, The reaction conditions include a temperature of 120-220℃ and a pressure of 0.1-0.5MPa.