Silver catalyst suitable for high airspeed condition and one-step impregnation preparation method

Abstract

The invention discloses a silver catalyst suitable for a high airspeed condition and a one-step impregnation preparation method thereof, and belongs to the technical field of catalyst preparation. The applicable airspeed range of the silver catalyst prepared by the method is 5000-7000h <-1 >, the temperature is 227-260 DEG C, the silver content is 18-22wt%, the silver catalyst only needs one impregnation step after the catalyst impregnation liquid and the impregnation process are optimized, the obtained silver catalyst is suitable for high airspeed, the silver content in the catalyst is reduced, and the silver content in the catalyst is reduced. And the selectivity of the catalyst product is further improved. The catalyst can directly oxidize ethylene to produce ethylene oxide, the silver content is 18-22 wt%, the catalyst can be prepared by adopting a one-step impregnation method, the preparation steps are simplified, and the cost of the catalyst is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a silver catalyst suitable for high space velocity conditions and a one-step impregnation preparation method thereof. Background Art

[0002] Ethane present in natural gas is primarily used to produce ethylene, a cornerstone of the petrochemical industry. Ethylene oxide (EO) is a downstream derivative of ethylene, second only to polyethylene. It is primarily used in the production of chemical raw materials such as ethylene glycol and polyether monomers, and is a key chemical product today. Ethylene oxide is also a crucial chemical intermediate that can be further converted into consumer products such as antifreeze, pharmaceuticals, detergents, and plastics, offering broad development and utilization prospects.

[0003] Industrially, ethylene oxide is produced through gas-phase selective ethylene oxidation (ethylene epoxidation), typically carried out in a fixed-bed tubular reactor using a silver catalyst supported on an α-Al₂O₃ catalyst at a temperature of 230–270°C and a pressure of 1–3 MPa. Ethylene oxide selectivity is the most important parameter determining the performance of silver catalysts. The selective epoxidation of ethylene to ethylene oxide is accompanied by two highly thermodynamically favorable side reactions: complete combustion of ethylene (ΔH = -1327 kJ / mol) and combustion of ethylene oxide (ΔH = -1223 kJ / mol). These side reactions pose significant challenges to achieving high ethylene oxide selectivity. Therefore, the use of catalysts with high EO selectivity can significantly reduce the production cost of ethylene oxide.

[0004] Prior art US2014 / 0179516A1 discloses a catalyst for ethylene oxide epoxidation, the main active component of which is Ag, and contains various alkali metal additives such as cesium and rhenium. Compared with the single-loaded Ag catalyst, the EO selectivity of this catalyst is greatly improved. Patent US4766105 discloses a silver catalyst with the main active component being Ag, and also containing various alkaline earth metal additives such as tungsten, which further improves the selectivity of ethylene oxide. However, the above two technologies have high efficiency when the space velocity is higher than 5000h -1 Under these conditions, the performance of the catalyst is relatively general.

[0005] The type and content of additives in silver catalysts significantly influence catalyst performance. The matching relationship between silver content and additive content significantly influences the catalyst's ethylene oxide selectivity and yield, and is of great research significance and practical value. Summary of the Invention

[0006] The purpose of the present invention is to provide a one-step impregnation preparation method for a silver catalyst suitable for high space velocity conditions. The silver catalyst prepared by the method has an applicable space velocity range of 5000 to 7000 h -1, temperature is 227-260°C, and silver content is 18-22wt%. After optimizing the catalyst impregnation liquid and impregnation process, the silver catalyst only requires one impregnation step. Not only is the obtained silver catalyst suitable for high space velocity, but it also reduces the silver content in the catalyst, further improving the selectivity of the catalyst product.

[0007] The present invention is achieved through the following technical solutions:

[0008] A silver catalyst suitable for high space velocity conditions, wherein the applicable space velocity range of the silver catalyst is 5000 to 7000 h -1 , the temperature is 227~260℃, and the silver content is 18~22wt%.

[0009] A one-step impregnation preparation method for a silver catalyst suitable for high space velocity conditions comprises the following steps:

[0010] S1, mixing an amine organic compound, a silver compound, an additive and deionized water to obtain a catalyst impregnation solution;

[0011] S2, immersing the support into the catalyst impregnation solution of S1 for static impregnation, then removing and draining to obtain a silver catalyst precursor;

[0012] S3. activating the silver catalyst precursor at high temperature in an air atmosphere to obtain a silver catalyst.

[0013] Preferably, the mass ratio of the amine organic compound, the silver compound, the auxiliary agent and the deionized water is 61g:95-100g:0.8-1.3g:30g.

[0014] Preferably, the amine organic compound is composed of ethylenediamine and ethanolamine in a mass ratio of 45g:16g;

[0015] The silver compound is silver oxalate;

[0016] The additives are composed of alkali metal and alkaline earth metal additives and other metal oxide additives;

[0017] The total amount of the alkali metal and alkaline earth metal additives accounts for 800 to 1500 ppmw of the total amount of the silver catalyst;

[0018] The total amount of the other metal oxide additives accounts for 500 to 800 ppmw of the total amount of the silver catalyst.

[0019] The selection of the above-mentioned additives improves the selectivity and yield of the catalyst for ethylene oxide under high space velocity conditions.

[0020] Preferably, the metal elements in the alkali metal and alkaline earth metal additives include one or more of lithium, sodium, potassium, cesium, rubidium, barium, and strontium;

[0021] The metal elements in the other metal oxide additives include one or more of rhenium, molybdenum, tungsten, cobalt, and nickel.

[0022] Preferably, the metal elements in the alkali metal and alkaline earth metal additives include one or more of lithium, potassium, cesium, and strontium;

[0023] The metal elements in the other metal oxide additives include one or more of rhenium, molybdenum and tungsten.

[0024] Preferably, the carrier is an α-alumina carrier with an average strength greater than 100N / particle and a specific surface area of ​​1-2m 2 / g, water absorption rate is greater than 50%.

[0025] Preferably, in S2, the static immersion time is 2 to 3 hours.

[0026] Preferably, in S3, the high-temperature activation temperature is 350-500° C., and the activation time is 3-15 minutes.

[0027] The high temperature activation can promote the formation of silver nanoparticles.

[0028] Compared with the prior art, the present invention has at least the following technical effects:

[0029] The present invention provides a one-step impregnation preparation method for a silver catalyst suitable for high space velocity conditions. The silver catalyst prepared by the method has an applicable space velocity range of 5000 to 7000 h -1 , temperature is 227-260°C, and silver content is 18-22wt%. After optimizing the catalyst impregnation liquid and impregnation process, the silver catalyst only requires one impregnation step. Not only is the obtained silver catalyst suitable for high space velocity, but it also reduces the silver content in the catalyst, further improving the selectivity of the catalyst product.

[0030] In the silver catalyst suitable for use under high space velocity conditions, an amine organic compound, a silver compound, an additive and deionized water are mixed to obtain a catalyst impregnation solution. The optimized combination not only reduces the number of catalyst impregnation steps but also further reduces the production cost of the catalyst. Specifically, by reducing the silver content of the catalyst, adjusting the content and ratio of alkali metal and alkaline earth metal additives, and adding other metal oxide additives, the selectivity of the catalyst is significantly improved, thereby achieving high performance of the catalyst operating under high space velocity conditions.

[0031] The catalyst prepared by the one-step impregnation preparation method of the silver catalyst suitable for high space velocity conditions can be used to directly oxidize ethylene to produce ethylene oxide. The silver content is 18-22 wt.%. The catalyst can be prepared by the one-step impregnation method, thereby simplifying the preparation steps and reducing the catalyst cost. DETAILED DESCRIPTION

[0032] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0033] Example 1:

[0034] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 100 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0035] S2. Dissolve 0.34 g of cesium sulfate, 0.31 g of lithium nitrate, 0.22 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0036] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0037] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation at an air flow rate of 1 / 2 h for 7 minutes at a temperature of 300° C.

[0038] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-Z-1.

[0039] Example 2:

[0040] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 95 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0041] S2. Dissolve 0.34 g of cesium sulfate, 0.16 g of lithium nitrate, 0.04 g of potassium nitrate, 0.22 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0042] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0043] S4, put the silver catalyst precursor into the activation furnace, at 30m3 The silver catalyst was obtained by activation at an air flow rate of 1 / 2 h for 7 minutes at a temperature of 300° C.

[0044] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-Z-2.

[0045] Example 3:

[0046] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 98 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0047] S2. Dissolve 0.34 g of cesium sulfate, 0.08 g of potassium nitrate, 0.22 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0048] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0049] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation at an air flow rate of 1 / 2 h for 7 minutes at a temperature of 300° C.

[0050] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-Z-3.

[0051] Example 4:

[0052] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 100 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0053] S2. Dissolve 0.34 g of cesium sulfate, 0.31 g of lithium nitrate, and 0.22 g of strontium acetate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0054] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0055] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation at an air flow rate of 1 / 2 h for 7 minutes at a temperature of 300° C.

[0056] The silver content in the silver catalyst is 20 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-Z-4.

[0057] Comparative Example 1:

[0058] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 105 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0059] S2. Dissolve 0.68 g of cesium sulfate, 0.62 g of lithium nitrate, 0.44 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0060] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0061] S4. Place the silver catalyst precursor into an activation furnace and activate it for 7 minutes at an air flow rate of 30 m3 / h and a temperature of 300°C to obtain a silver catalyst.

[0062] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 2400 ppmw, which is recorded as Ag-F-1.

[0063] Comparative Example 2:

[0064] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 98 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0065] S2. Dissolve 0.38 g of cesium sulfate, 0.22 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0066] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0067] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation at an air flow rate of 1 / 2 h for 7 minutes at a temperature of 300° C.

[0068] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-F-2.

[0069] Comparative Example 3:

[0070] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 100 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0071] S2. Dissolve 0.34 g of cesium sulfate, 0.08 g of potassium nitrate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate, and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0072] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0073] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation for 7 minutes at an air flow rate of 1 / 2 h and a temperature of 300° C.

[0074] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 1200 ppmw, which is recorded as Ag-F-3.

[0075] Comparative Example 4:

[0076] S1. Weigh 45 g of ethylenediamine and 16 g of ethanolamine and mix them. Add 100 g of silver oxalate to the mixed solution in a cold water bath and continue stirring until the solution is clear.

[0077] S2. Dissolve 0.28 g of cesium sulfate, 0.16 g of lithium nitrate, 0.15 g of strontium acetate, 0.07 g of ammonium metatungstate, 0.23 g of ammonium perrhenate and 0.06 g of ammonium molybdate in 30 g of water, and then add the solution to the clear solution to obtain a catalyst impregnation solution.

[0078] S3. Weigh 50 g of the carrier and put it into the catalyst impregnation solution. Let it stand for more than 2 hours. Take out the impregnated carrier and drain it to obtain a silver catalyst precursor.

[0079] S4, put the silver catalyst precursor into the activation furnace, at 30m 3 The silver catalyst was obtained by activation for 7 minutes at an air flow rate of 1 / 2 h and a temperature of 300° C.

[0080] The silver content in the silver catalyst is 15 wt %, and the proportion of alkali metal and alkaline earth metal additives is 900 ppmw, which is recorded as Ag-F-4.

[0081] Catalyst evaluation experiment:

[0082] A fixed bed reactor was used to evaluate the performance of the silver catalyst prepared in the present invention.

[0083] The catalyst evaluation pressure was 2.0 MPa and the volume space velocity was 6000 h -1 The reaction temperature is 230° C. The reaction inlet gas composition includes 30 mol% ethylene, 6 mol% oxygen, less than 0.2 mol% carbon dioxide, 0.5-5 ppm ethyl chloride, and nitrogen as the balance gas.

[0084] After the measurement results were corrected for volume shrinkage, the selectivity (S) was calculated according to the following formula:

[0085] S=ΔEO / (ΔEO+0.5*ΔCO2)*100%

[0086] Where ΔEO is the concentration difference of ethylene oxide in the reactor inlet and outlet gases, and ΔCO2 is the concentration difference of carbon dioxide in the reactor inlet and outlet gases.

[0087] Table 1 Silver catalyst performance test results

[0088]

[0089] Note: If the ethylene oxide yield does not meet the requirements, the selectivity and ethylene single-pass conversion will not be calculated and will be indicated by “-”.

[0090] Conclusion: In the above evaluation experiments, the ethylene feed concentration was 30 mol% and the oxygen feed concentration was 6 mol%, and the ethylene oxide yield could reach 2.4-2.6 mol%, which is lower than the actual application conditions of 35 mol% ethylene concentration and 7.5 mol% oxygen concentration in industrial plants. This shows that the catalyst has a high space-time yield and excellent performance, and has good application prospects in actual ethylene oxide production plants.

[0091] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A silver catalyst suitable for use under high space velocity conditions, characterized in that: The applicable space velocity range of the silver catalyst is 5000~7000h -1 , the temperature is 227~260℃, and the silver content is 18~22wt%.

2. A one-step impregnation preparation method for a silver catalyst suitable for high space velocity conditions as claimed in claim 1, characterized in that: The steps include: S1, mixing an amine organic compound, a silver compound, an additive and deionized water to obtain a catalyst impregnation solution; S2, immersing the support into the catalyst impregnation solution of S1 for static impregnation, then removing and draining to obtain a silver catalyst precursor; S3. activating the silver catalyst precursor at high temperature in an air atmosphere to obtain a silver catalyst.

3. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 2, characterized in that: The mass ratio of the amine organic compound, the silver compound, the auxiliary agent and the deionized water is 61g:95-100g:0.8-1.3g:30g.

4. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 3, characterized in that: The amine organic compound is composed of ethylenediamine and ethanolamine in a mass ratio of 45g:16g; The silver compound is silver oxalate; The additives are composed of alkali metal and alkaline earth metal additives and other metal oxide additives; The total amount of the alkali metal and alkaline earth metal additives accounts for 800 to 1500 ppmw of the total amount of the silver catalyst; the total amount of the other metal oxide additives accounts for 500 to 800 ppmw of the total amount of the silver catalyst.

5. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 4, characterized in that: The metal elements in the alkali metal and alkaline earth metal additives include one or more of lithium, sodium, potassium, cesium, rubidium, barium, and strontium; The metal elements in the other metal oxide additives include one or more of rhenium, molybdenum, tungsten, cobalt, and nickel.

6. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 5, characterized in that: The metal elements in the alkali metal and alkaline earth metal additives include one or more of lithium, potassium, cesium, and strontium; The metal elements in the other metal oxide additives include one or more of rhenium, molybdenum and tungsten.

7. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 2, characterized in that: The carrier is an α-alumina carrier with an average strength greater than 100N / particle and a specific surface area of ​​1-2m 2 / g, water absorption rate is greater than 50%.

8. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 2, characterized in that: In the step S2, the static immersion time is 2 to 3 hours.

9. The one-step impregnation preparation method of a silver catalyst suitable for high space velocity conditions according to claim 2, characterized in that: In the above-mentioned S3, the high temperature activation temperature is 350-500° C. and the activation time is 3-15 minutes.

Images