Preparation of initiator for preparing triangular silver nanometer base epoxy ethane catalyst and application thereof
By controlling the morphology of silver-based ethylene oxide catalysts using initiators with specific compositions, triangular silver nanoparticles were prepared, solving the problems of insufficient catalyst activity and selectivity in existing technologies and achieving more efficient catalytic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI REZEL KEHUA ENG DESIGN CO LTD
- Filing Date
- 2024-01-23
- Publication Date
- 2026-06-23
AI Technical Summary
In the existing technology, the preparation of triangular nanosilver-based ethylene oxide catalysts has not been able to effectively control the morphology of silver, resulting in insufficient catalytic activity and selectivity.
By using an initiator with a specific composition as the impregnation solution mother liquor system for a silver-based ethylene oxide catalyst, and by controlling the uniform dispersion and morphology of silver on the support, a catalyst with a triangular nano-silver morphology was prepared, thereby increasing the contact area between the nano-silver and the reactants.
The catalytic activity and selectivity of the triangular nano-silver-based ethylene oxide catalyst were improved, making it suitable for the partial oxidation of ethylene to produce ethylene oxide.
Abstract
Description
Technical Field
[0001] This application relates to the field of ethylene oxide catalyst preparation technology, and in particular to an initiator for preparing triangular nano-silver-based ethylene oxide catalysts and its application. Background Technology
[0002] Ethylene oxide (EO), as the simplest cyclic ether, is a crucial product in the ethylene industry. Its unique cyclic structure allows it to be used in the production of various fine chemicals, including ethylene glycol, synthetic detergents, nonionic surfactants, antifreeze, emulsifiers, and ethylene glycol derivatives. It is also used in the production of plasticizers, lubricants, rubber, and plastics. It has wide applications in numerous fields such as laundry and dyeing, electronics, pharmaceuticals, pesticides, textiles, papermaking, automotive, and oil extraction and refining.
[0003] The partial oxidation of ethylene to ethylene oxide is one of the most important processes in modern chemical industry. Ethylene oxide synthesis methods are divided into chlorohydrin methods and oxidation methods, with the oxidation method further divided into air oxidation and oxygen oxidation. Currently, the main catalysts used in the partial oxidation of ethylene to ethylene oxide are silver. Although extensive research has been conducted on the preparation of triangular nano-silver and silver-based ethylene oxide catalysts, and the technology is relatively mature, there are few reports on the preparation of ethylene oxide catalysts by controlling the specific morphology of silver. Summary of the Invention
[0004] To address the aforementioned problems, this application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts and its application. By using this initiator with a specific composition as the mother liquor system for impregnating the silver-based ethylene oxide catalyst, morphology control is applied to the silver-based ethylene oxide catalyst. After uniformly dispersing silver on a support, the morphology is controlled during synthesis to prepare silver-based ethylene oxide catalysts with triangular nano-silver morphology. This achieves the preparation of nano-silver catalysts with controllable morphology, increases the contact area between the nano-silver and the reactants, and thereby improves the catalytic performance of the triangular nano-silver-based ethylene oxide catalyst, such as catalytic activity and selectivity.
[0005] In a first aspect, this application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts, wherein the initiator comprises the following components by weight percentage:
[0006] Water 5-20 wt%, polyvinylpyrrolidone 0.1-20 wt%, n-alkane alcohol 65-85 wt%, and ethanol 1-20 wt%;
[0007] The n-alkane alcohol is at least one of C3 to C6 n-alkane alcohols.
[0008] Further, by weight percentage, the initiator comprises the following components:
[0009] Water 10-15 wt%, polyvinylpyrrolidone 0.1-5 wt%, n-alkane alcohol 68-75 wt%, and ethanol 5-15 wt%.
[0010] Secondly, this application provides the use of the initiator described in any one of the first aspects in the preparation of triangular nano-silver-based ethylene oxide catalysts.
[0011] Thirdly, this application provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, the method comprising the following steps:
[0012] A first aqueous solution containing a silver source was obtained;
[0013] A second aqueous solution containing an alkali metal auxiliary agent was obtained;
[0014] A third aqueous solution containing rare earth metal additives was obtained;
[0015] The initiator for preparing the triangular nano-silver-based ethylene oxide catalyst as described in any one of the first aspects is obtained;
[0016] The first aqueous solution was immersed in a porous alumina carrier to obtain a first mixed system;
[0017] The second aqueous solution and the third aqueous solution are added to the first mixed system for a second soaking to obtain the second mixed system;
[0018] The initiator was added to the second mixture to react, and then evaporated until the porous alumina support showed no excess water, thus obtaining a precursor containing triangular nano-silver.
[0019] The triangular silver nanoparticle precursor was aged, dried, and calcined to obtain the triangular silver nanoparticle-based ethylene oxide catalyst.
[0020] Furthermore, based on the total weight of the triangular nano-silver-based ethylene oxide catalyst, the silver content in the triangular nano-silver-based ethylene oxide catalyst is 15-30 wt%, the alkali metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01-0.2 wt%, and the rare earth metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01-1 wt%.
[0021] Furthermore, the silver source includes silver nitrate, the alkali metal auxiliaries contain at least one element from Group IA, and the rare earth metal auxiliaries contain at least one element from Groups IIIB to VIIB.
[0022] Furthermore, the performance parameters of the porous alumina carrier include: specific surface area less than 3 μm. 2 / g, α-Al2O3 support with a porosity greater than 45%, an Al2O3 content greater than 98%, a strength greater than 80N, and a shape of Raschig ring, five-hole column or seven-hole column.
[0023] Furthermore, the weight ratio of the silver source to the initiator is 1:(6-10).
[0024] Fourthly, this application provides a triangular nano-silver-based ethylene oxide catalyst, which is prepared by the preparation method described in any one of the third aspects.
[0025] Fifthly, this application provides the application of the triangular nano-silver-based ethylene oxide catalyst described in the fourth aspect in the production of ethylene oxide.
[0026] Compared with the prior art, the technical solutions provided in this application have at least the following advantages:
[0027] This application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts and its application. By using this initiator with a specific composition as the mother liquor system for impregnating the silver-based ethylene oxide catalyst, morphology control is applied to the silver-based ethylene oxide catalyst. After uniformly dispersing silver on a support, the morphology is controlled during synthesis to prepare a silver-based ethylene oxide catalyst with a triangular nano-silver morphology. This achieves the preparation of a controllable morphology nano-silver catalyst, increases the contact area between the nano-silver and the reactants, and thereby improves the catalytic performance of the triangular nano-silver-based ethylene oxide catalyst, such as catalytic activity and selectivity. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.
[0030] In a first aspect, this application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts, wherein the initiator comprises the following components by weight percentage:
[0031] Water 5-20 wt%, polyvinylpyrrolidone 0.1-20 wt%, n-alkane alcohol 65-85 wt%, and ethanol 1-20 wt%;
[0032] The n-alkane alcohol is at least one of C3 to C6 n-alkane alcohols.
[0033] This application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts and its application. By using this initiator with a specific composition as the mother liquor system for impregnating the silver-based ethylene oxide catalyst, morphology control is applied to the silver-based ethylene oxide catalyst. After uniformly dispersing silver on a support, the morphology is controlled during synthesis to prepare a silver-based ethylene oxide catalyst with a triangular nano-silver morphology. This achieves the preparation of a controllable morphology nano-silver catalyst, increases the contact area between the nano-silver and the reactants, and thereby improves the catalytic performance of the triangular nano-silver-based ethylene oxide catalyst, such as catalytic activity and selectivity.
[0034] In some specific embodiments, the weight percentage of water may be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, etc.
[0035] In some specific embodiments, the weight percentage of the polyvinylpyrrolidone (PVP) may be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, etc.
[0036] In some specific embodiments, the weight percentage of the n-alkane alcohol may be 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, etc.
[0037] In some specific embodiments, the weight percentage of ethanol may be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, etc.
[0038] Preferably, the initiator comprises the following components by weight percentage:
[0039] Water 10-15 wt%, polyvinylpyrrolidone 0.1-5 wt%, n-alkane alcohol 68-75 wt%, and ethanol 5-15 wt%.
[0040] In some specific embodiments, the preparation method of the initiator provided by the present invention includes the following steps: water, polyvinylpyrrolidone, n-alkanol and ethanol are added to a container in sequence and stirred and mixed under a temperature of 30 to 50°C and continuous stirring.
[0041] Secondly, this application provides the use of the initiator described in any one of the first aspects in the preparation of triangular nano-silver-based ethylene oxide catalysts.
[0042] Compared with traditional silver-based ethylene oxide catalysts, this invention uses a mixed mother liquor (i.e., the initiator described in any of the first aspects) as an initiator in the preparation process, so that silver is uniformly dispersed on the support and the morphology is controlled to be triangular nano-silver to prepare a silver-based ethylene oxide catalyst. At the same time, the catalyst has good activity and excellent selectivity, and is suitable for actual factory production.
[0043] Thirdly, this application provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, the method comprising the following steps:
[0044] A first aqueous solution containing a silver source was obtained;
[0045] A second aqueous solution containing an alkali metal auxiliary agent was obtained;
[0046] A third aqueous solution containing rare earth metal additives was obtained;
[0047] The initiator for preparing the triangular nano-silver-based ethylene oxide catalyst as described in any one of the first aspects is obtained;
[0048] The first aqueous solution was immersed in a porous alumina carrier to obtain a first mixed system;
[0049] The second aqueous solution and the third aqueous solution are added to the first mixed system for a second soaking to obtain the second mixed system;
[0050] The initiator was added to the second mixture to react, and then evaporated until the porous alumina support showed no excess water, thus obtaining a precursor containing triangular nano-silver.
[0051] The triangular silver nanoparticle precursor was aged, dried, and calcined to obtain the triangular silver nanoparticle-based ethylene oxide catalyst.
[0052] The invention uses a mixed mother liquor (i.e., the initiator described in any of the first aspects) as an initiator in the preparation process, so that silver is uniformly dispersed on the support and the morphology is controlled to be triangular nano-silver to prepare a silver-based ethylene oxide catalyst. At the same time, the catalyst has good activity and excellent selectivity, and is suitable for actual factory production.
[0053] In some specific embodiments, the triangular nano-silver precursor is aged at room temperature for 2–12 h, dried at 60–80 °C for 2–4 h, and finally calcined at 150–300 °C for 0.5–3 h in a flowing air atmosphere to obtain a triangular nano-silver-based ethylene oxide catalyst.
[0054] As one embodiment of this application, based on the total weight of the triangular nano-silver-based ethylene oxide catalyst, the silver content in the triangular nano-silver-based ethylene oxide catalyst is 15-30 wt%, the alkali metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01-0.2 wt%, and the rare earth metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01-1 wt%.
[0055] When using the preparation method provided by this invention, the obtained triangular nano-silver-based ethylene oxide catalyst comprises:
[0056] i. Porous alumina carrier;
[0057] ii. Silver, an active component, one or more alkali additives, and rare earth additives loaded on the porous alumina support;
[0058] The porous alumina is characterized by having a specific surface area of less than 3 μm. 2 / g, α-Al₂O₃ support with a porosity greater than 45%, an Al₂O₃ content greater than 98%, and a strength greater than 80N, wherein the support shape is Raschig ring, five-pore column, or seven-pore column, preferably with a specific surface area less than 1m². 2 / g, with a porosity greater than 55% and a strength greater than 100N, and an α-Al2O3 support in the shape of a seven-hole column;
[0059] Based on the total mass of the silver-based catalyst, the silver active component mentioned above is silver nitrate, wherein the silver content is 15-30 wt%, preferably 18-25 wt%.
[0060] Based on the total mass of the silver-based catalyst, the aforementioned alkali metal promoter is one or more of Group IA, with a content of 0.01–0.2 wt%, preferably 0.05–0.1 wt%.
[0061] Based on the total mass of the silver-based catalyst, the rare earth metals mentioned above are one or more from groups IIIB to VIIB, with a content of 0.01 to 1 wt%, preferably 0.05 to 0.5 wt%.
[0062] In one embodiment of this application, the weight ratio of the silver source to the initiator is 1:(6-10).
[0063] The purpose of controlling the weight ratio of the silver source and the initiator to be 1:(6-10), preferably 1:9, in this application is to regulate the particle size range of silver nanoparticles and the forming ratio of triangular silver nanoparticles. The adverse effect of an excessively large weight ratio of the silver source and the initiator is that the silver nanoparticles are too small, resulting in low initial catalyst activity. The adverse effect of an excessively small ratio is that the silver nanoparticles are too large, leading to reduced activity.
[0064] Fourthly, this application provides a triangular nano-silver-based ethylene oxide catalyst, which is prepared by the preparation method described in any one of the third aspects.
[0065] The triangular nano-silver-based ethylene oxide catalyst provided by this invention should have an average crushing strength greater than 70N and exhibit good activity and excellent selectivity.
[0066] Fifthly, this application provides the application of the triangular nano-silver-based ethylene oxide catalyst described in the fourth aspect in the production of ethylene oxide.
[0067] The triangular nano-silver-based ethylene oxide catalyst provided by this invention has an average crushing strength greater than 70N and exhibits good activity and excellent selectivity, and can be widely used in the partial oxidation of ethylene to produce ethylene oxide.
[0068] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.
[0069] The silver catalyst of this invention is suitable for the production process of ethylene oxidation to ethylene oxide. In the embodiments, the elemental content in the catalyst was determined by X-ray fluorescence spectrometry, and the specific surface area, pore capacity, and distribution of the catalyst were determined by a combination of nitrogen adsorption and mercury porosimetry; the composition analysis of the raw materials and reaction products was performed by gas chromatography, and the mechanical strength of the catalyst was determined by a pressure measuring instrument.
[0070] The catalysts in the following examples were prepared based on 1 kg of catalyst.
[0071] Example 1
[0072] This example provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, including the following steps:
[0073] 850g of self-made seven-hole column α-Al2O3 support was added to the reaction vessel and pretreated at 70°C under a negative pressure of 10mmHg. The purpose of this pretreatment was to remove the moisture adsorbed by the support at room temperature. The pretreatment lasted for 2 hours.
[0074] Accurately weigh 236.24 g of silver nitrate and dissolve it in 1 L of water for later use; prepare 0.01 mol / L aqueous solutions of cesium nitrate and ammonium perrhenate separately, weigh 1.949 g of cesium nitrate and dissolve it in 1 L of water, and weigh 2.682 g of ammonium perrhenate and dissolve it in 1 L of water for later use; prepare a mother liquor system by mixing water, PVP, n-pentanol, and ethanol in a mass ratio of 10:1:79:10. The order of addition is as follows: add ethanol to water, stir evenly, add n-pentanol, continue stirring, and finally add PVP. After stirring, let it stand for 1 h to obtain the initiator for preparing triangular nano-silver-based ethylene oxide catalyst for later use.
[0075] Add 1L of prepared silver nitrate solution to the pretreated carrier for immersion for 2 hours at a speed of 50r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10mmHg to remove some of the water.
[0076] First, add 37.5 mL of 0.01 mol / L cesium nitrate to the reaction vessel, then add 26.8 mL of 0.01 mol / L ammonium perrhenate solution, and continue soaking for 2 hours at a rotation speed of 50 r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10 mmHg to remove some of the water.
[0077] Add the prepared mixed mother liquor system, add 750g of mixed solution at a mass ratio of 1:5 with silver, soak for 2 hours at normal pressure and temperature, then raise the temperature to 80℃ and the pressure to 10mmHg, remove the excess solution, and take out the catalyst precursor impregnated with the support.
[0078] The above precursors were aged at room temperature for 2–8 hours and then dried at 60°C for 2 hours.
[0079] The above catalyst precursor was placed in a flowing air atmosphere and calcined at 220°C for 15 min to obtain a triangular nano-silver-based catalyst, denoted as S1. The physicochemical properties of the catalyst are shown in Table 1 below.
[0080] Example 2
[0081] This example provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, which differs from Example 1 in that the contents of silver, rhenium, and cesium are different, and the proportions of the components in the mother liquor system are also different; specifically, it includes the following steps:
[0082] 820g of a self-made seven-hole column α-Al2O3 support was added to the reaction vessel, and the support was pretreated at 70°C under a negative pressure of 10mmHg for 4h.
[0083] Accurately weigh 283.5 g of silver nitrate and dissolve it in 1 L of water for later use; prepare 0.01 mol / L aqueous solutions of cesium nitrate and ammonium perrhenate separately, weigh 1.949 g of cesium nitrate and dissolve it in 1 L of water, and weigh 2.682 g of ammonium perrhenate and dissolve it in 1 L of water for later use; prepare the stock solution system by mixing water:PVP:n-pentanol:ethanol in a mass ratio of 10:2:50:38, adding the solutions in the same order as in Example 1, stirring and letting stand for 1 hour for later use;
[0084] Add 1L of prepared silver nitrate solution to the pretreated carrier for immersion for 2 hours at a speed of 50r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10mmHg to remove some of the water.
[0085] First, add 37.5 mL of 0.01 mol / L cesium nitrate to the reaction vessel, then add 16.1 mL of 0.01 mol / L ammonium perrhenate solution, and continue soaking for 2 hours at a rotation speed of 50 r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10 mmHg to remove some of the water.
[0086] Add the prepared mixed mother liquor system, add 360g of mixed solution at a mass ratio of 1:2 with silver, soak for 2 hours at normal pressure and temperature, then raise the temperature to 80℃ and the pressure to 10mmHg, remove the excess solution, and take out the catalyst precursor impregnated with the carrier.
[0087] The above precursors were aged at room temperature for 2–8 hours and then dried at 70°C for 4 hours.
[0088] The above catalyst precursor was placed in a flowing air atmosphere and calcined at 230°C for 15 min to obtain a triangular nano-silver-based catalyst, denoted as S2.
[0089] Example 3
[0090] This example provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, which differs from Example 1 in that cesium and rhenium are not added for modification during the preparation process; specifically, it includes the following steps:
[0091] 850g of a self-made seven-hole column α-Al2O3 support was added to the reaction vessel and pretreated at 65°C under a negative pressure of 10mmHg for 3h.
[0092] Accurately weigh 236.24 g of silver nitrate and dissolve it in 1 L of water for later use; prepare the initiator by mixing the mother liquor system according to the mass ratio of water:PVP:n-pentanol:ethanol of 10:2:75:13. The order of addition is as follows: add ethanol to water and stir well, then add n-pentanol and continue stirring, and finally add PVP. After stirring, let it stand for 2 hours for later use.
[0093] Add silver nitrate solution to the initiator stock solution and stir at 45°C for 2 hours to ensure thorough mixing.
[0094] Add the above-mixed mother liquor to the reaction vessel and soak for 1 hour at room temperature and pressure;
[0095] The temperature was raised to 75℃, the pressure was 10 mmHg, the rotation speed was 60 r / min, and the reaction was carried out for 3 h. The excess liquid in the solution was removed to obtain the catalyst precursor.
[0096] The above precursors were aged at room temperature for 2–8 hours and then dried at 70°C for 4 hours.
[0097] The above catalyst precursor was placed in a flowing air atmosphere and calcined at 240°C for 10 min to obtain a triangular nano-silver-based catalyst, denoted as S3.
[0098] Example 4
[0099] This example provides a method for preparing a triangular nano-silver-based ethylene oxide catalyst, which differs from Example 1 in that the alcohol used in the initiator is selected from n-butanol, n-pentanol, and ethanol, and the remaining steps are also different; specifically, it includes the following steps:
[0100] 800g of a self-made seven-hole column α-Al2O3 support was added to the reaction vessel, and the support was pretreated at 80℃ under a negative pressure of 10mmHg for 1h.
[0101] Accurately weigh 341.99 g of silver nitrate and dissolve it in 2 L of water for later use; prepare 0.01 mol / L aqueous solutions of cesium nitrate and ammonium perrhenate separately, weigh 1.949 g of cesium nitrate and dissolve it in 1 L of water, and weigh 2.682 g of ammonium perrhenate and dissolve it in 1 L of water for later use; prepare the initiator by mixing a mother liquor system with water: n-butanol: n-pentanol: ethanol: PVP in a mass ratio of 10:27:50:10:3.
[0102] Add 2L of prepared silver nitrate solution to the pretreated carrier for immersion for 1 hour at a speed of 50r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10mmHg to remove some of the water.
[0103] First, add 22.5 mL of 0.01 mol / L cesium nitrate to the reaction vessel, then add 26.8 mL of 0.01 mol / L ammonium perrhenate solution, and continue soaking for 2 hours at a rotation speed of 50 r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10 mmHg to remove some of the water.
[0104] Add the prepared mixed mother liquor system, add 800g of mixed solution at a mass ratio of 1:4 with silver, soak for 2 hours at normal pressure and temperature, then raise the temperature to 80℃ and the pressure to 10mmHg, remove the excess solution, and take out the catalyst precursor impregnated with the carrier.
[0105] The above precursors were aged at room temperature for 2–8 hours and then dried at 65°C for 2 hours.
[0106] The above catalyst precursor was placed in a flowing air atmosphere and calcined at 240°C for 10 min to obtain a triangular nano-silver-based catalyst, denoted as S4.
[0107] Comparative Example 1
[0108] This comparative example does not use an initiator during preparation to compare the formation of nano-silver. The detailed steps are as follows:
[0109] 850g of a self-made seven-hole column α-Al2O3 support was added to the reaction vessel and pretreated at 70°C under a negative pressure of 10mmHg for 2h.
[0110] Accurately weigh 236.24 g of silver nitrate and dissolve it in 1 L of water for later use; prepare 0.01 mol / L aqueous solutions of cesium nitrate and ammonium perrhenate separately, weigh 1.949 g of cesium nitrate and dissolve it in 1 L of water, and weigh 2.682 g of ammonium perrhenate and dissolve it in 1 L of water for later use;
[0111] Add 1L of prepared silver nitrate solution to the pretreated carrier for immersion for 2 hours at a speed of 50r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10mmHg to remove some of the water.
[0112] First, add 37.5 mL of 0.01 mol / L cesium nitrate to the reaction vessel, then add 26.8 mL of 0.01 mol / L ammonium perrhenate solution, and continue soaking for 2 hours at a rotation speed of 50 r / min, a temperature of 45 degrees Celsius, and a negative pressure of 10 mmHg to remove some of the water.
[0113] The above precursors were aged at room temperature for 2–8 hours and then dried at 60°C for 2 hours.
[0114] The above catalyst precursor was placed in a flowing air atmosphere and calcined at 250°C for 10 min to obtain a nano-silver-based catalyst, denoted as D1.
[0115] Comparative Example 2
[0116] The difference in this comparative example is that a mixed mother liquor system for initiating the formation of triangular silver nanoparticles was added to the basis of comparative example 1. n-Butanol was used instead of n-pentanol, and the mass ratio was water:n-butanol:ethanol:PVP = 20:65:10:5. The preparation order was to first mix water with the two alcohols and then add PVP. The remaining steps were the same as in comparative example 1. The resulting catalyst was denoted as D2.
[0117] Test case
[0118] The physical properties of the catalysts obtained in the examples and comparative examples are shown in Table 1. Performance evaluations were also conducted on each catalyst. The evaluation method included the following steps: the catalysts obtained in the examples and comparative examples were ground to 60–100 mesh particles; the catalyst loading mass was 2 g, with inert ceramic balls placed on top (bottom); ensuring the catalyst was not carried away during the reaction; and placing the catalyst in the constant temperature zone of the reactor; the evaluation conditions were: reaction pressure 0.1–3.5 MPa, reaction temperature 180–280 °C, and space velocity 5000–10000 h⁻¹. -1 The raw material gas composition was: 28% ethylene; 7% oxygen; 2% carbon dioxide; with nitrogen as the stabilizer. The evaluation results are shown in Table 2 below.
[0119] Table 1
[0120] catalyst Strength (N) <![CDATA[Al2O3(%)]]> <![CDATA[Ag2O(%)]]> Cs (ppm) Re(ppm) S1 91 83.77 16.13 473 461 S2 86 81.57 19.34 509 288 S3 97 83.56 16.41 / / S4 79 79.33 21.49 502 278 D1 103 83.99 15.92 489 505 D2 98 83.91 16.02 505 511
[0121] Table 2
[0122] project reaction temperature Selectivity (%) S1 225 82.3 S2 229 83.2 S3 219 78.6 S4 226 84.4 D1 230 75.3 D2 230 82.5
[0123] In Table 2 above, the selectivity of the silver catalyst in S1 to S4 is higher than that of the comparative catalyst D1. Furthermore, the selectivity of the D2 catalyst prepared after the introduction of the initiator is significantly improved. Therefore, the silver catalyst of the present invention has good catalytic performance and the selectivity of ethylene oxide products is also significantly improved.
[0124] In summary, this application provides an initiator for preparing triangular nano-silver-based ethylene oxide catalysts and its application. By using this initiator with a specific composition as the mother liquor system for the impregnation solution of the silver-based ethylene oxide catalyst, morphology control is applied to the silver-based ethylene oxide catalyst. After uniformly dispersing silver on the support, the morphology is controlled during synthesis to prepare a silver-based ethylene oxide catalyst with a triangular nano-silver morphology. This achieves the preparation of a controllable morphology nano-silver catalyst, increases the contact area between the nano-silver and the reactants, and thereby improves the catalytic performance of the triangular nano-silver-based ethylene oxide catalyst, such as catalytic activity and selectivity.
[0125] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.
[0126] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for preparing a triangular nano-silver-based ethylene oxide catalyst, characterized in that, Includes the following steps: A first aqueous solution containing a silver source was obtained; A second aqueous solution containing an alkali metal auxiliary agent was obtained; A third aqueous solution containing rare earth metal additives was obtained; Obtain the initiator; The first aqueous solution was immersed in a porous alumina carrier to obtain a first mixed system; The second aqueous solution and the third aqueous solution are added to the first mixed system for a second soaking to obtain the second mixed system; The initiator was added to the second mixture to react, and then evaporated until the porous alumina support showed no excess water, thus obtaining a precursor containing triangular nano-silver. The triangular silver nanoparticle precursor was aged, dried, and calcined to obtain the triangular silver nanoparticle-based ethylene oxide catalyst. The initiator comprises the following components by weight percentage: Water 5-20 wt%, polyvinylpyrrolidone 0.1-20 wt%, n-alkanol 65-85 wt%, and ethanol 1-20 wt%; The n-alkane alcohol is at least one of C3-C6 n-alkane alcohols.
2. The method for preparing the triangular nano-silver-based ethylene oxide catalyst according to claim 1, characterized in that, The initiator comprises the following components by weight percentage: Water 10-15 wt%, polyvinylpyrrolidone 0.1-5 wt%, n-alkanol 68-75 wt%, and ethanol 5-15 wt%.
3. The method for preparing the triangular nano-silver-based ethylene oxide catalyst according to claim 1, characterized in that, Based on the total weight of the triangular nano-silver-based ethylene oxide catalyst, the silver content in the triangular nano-silver-based ethylene oxide catalyst is 15~30wt%, the alkali metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01~0.2wt%, and the rare earth metal content in the triangular nano-silver-based ethylene oxide catalyst is 0.01~1wt%.
4. The method for preparing the triangular nano-silver-based ethylene oxide catalyst according to claim 1, characterized in that, The silver source includes silver nitrate, the alkali metal auxiliaries contain at least one alkali metal element from Group IA, and the rare earth metal auxiliaries contain at least one rare earth metal element from Groups IIIB to VIIB.
5. The method for preparing the triangular nano-silver-based ethylene oxide catalyst according to claim 1, characterized in that, The performance parameters of the porous alumina carrier include: specific surface area less than 3 μm. 2 / g, α-Al2O3 support with a porosity greater than 45%, an Al2O3 content greater than 98%, a strength greater than 80N, and a shape of Raschig ring, five-hole column or seven-hole column.
6. The method for preparing the triangular nano-silver-based ethylene oxide catalyst according to claim 1, characterized in that, The weight ratio of the silver source to the initiator is 1:(6~10).
7. A triangular nano-silver-based ethylene oxide catalyst, characterized in that, The triangular nano-silver-based ethylene oxide catalyst is prepared by the preparation method described in any one of claims 1-6.
8. The application of the triangular nano-silver-based ethylene oxide catalyst according to claim 7 in the production of ethylene oxide.