A transition metal-alkaline earth metal-FAU molecular sieve, its preparation method and application

Abstract

The present invention discloses a transition metal-alkaline earth metal-FAU molecular sieve, a preparation method thereof and an application thereof, and relates to the technical field of adsorption separation of zeolite molecular sieves. The transition metal-alkaline earth metal-FAU molecular sieve uses a commercial Na-FAU molecular sieve as a raw material and is synthesized through steps such as ion exchange and high-temperature calcination. The prepared transition metal-alkaline earth metal-FAU molecular sieve has a strong local electric field and has an extremely strong adsorption and capture effect on acetylene. The transition metal-alkaline earth metal-FAU molecular sieve can selectively adsorb acetylene from an acetylene-ethylene mixture to achieve deep purification of ethylene. The method for separating the acetylene-ethylene mixture and capturing low-concentration acetylene by using the transition metal-alkaline earth metal-FAU molecular sieve is simple, the cost of the adsorbent is low, and it has strong industrial popularization prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption separation of zeolite molecular sieves, and particularly to the preparation of a transition metal-alkaline earth metal-FAU (M1-M2-FAU) molecular sieve with strong capture ability for acetylene, and its application in purifying ethylene in an acetylene / ethylene mixture. Background Art

[0002] Ethylene, as an important industrial raw material, is widely used in fields such as polymers, textiles, and pesticides. In the polymer preparation process, the purity of ethylene monomer raw materials is very important. The presence of trace amounts of acetylene will have a huge impact on the properties and characteristics of polymers, such as causing the polymerization reaction catalyst to be poisoned and inactivated, and preventing the polymerization reaction from proceeding. According to the national standard GB / T 7715-2014, the purity requirement for first-class ethylene is not less than 99.9%, and the purity requirement for premium ethylene is not less than 99.95%. Therefore, the deep purification of ethylene and the removal of trace acetylene impurities are particularly important.

[0003] Since the physical and chemical properties of ethylene and acetylene are very close, it is difficult to remove trace amounts of acetylene from ethylene. Commonly used methods for removing trace amounts of acetylene from ethylene include: catalytic hydrogenation method, solvent absorption method, and adsorption method. The catalytic hydrogenation method mainly uses noble metal catalysts such as silver or palladium to react acetylene with hydrogen under high temperature and pressure to convert acetylene into ethylene. Although this method can convert acetylene into ethylene and improve the yield of ethylene, due to the use of noble metal catalysts, the cost is relatively high. The solvent absorption method mainly uses absorbents such as N-methylpyrrolidone to selectively absorb acetylene in ethylene. Although this method has high selectivity, it requires the use of a large amount of toxic solvents, and the solvent has poor regenerability and is not conducive to recycling. The adsorption method uses adsorbents such as molecular sieves to selectively adsorb acetylene in ethylene. This method has high selectivity, large adsorption capacity, can be regenerated, and has low cost. Therefore, it is expected to be a better solution for the deep purification of ethylene and the removal of trace acetylene impurities, and has a very broad industrial prospect.

[0004] Na-FAU (including type X and type Y) molecular sieves have been widely used in industry and have low cost. However, the current Na-FAU molecular sieves have poor adsorption effect on acetylene, and the dynamic adsorption capacity of acetylene is generally low, and the adsorption capacity is even lower under the condition of low-concentration acetylene / ethylene mixed gas; at the same time, the ethylene / acetylene separation selectivity is poor, which is not conducive to the deep purification of ethylene, and the yield of ethylene is low. Existing modified molecular sieves usually only use a single metal salt solution to perform ion exchange treatment with Na-FAU molecular sieves. Relevant literature studies have shown that single alkaline earth metal ions (Mg 2+ 、Ca 2+ 、Sr 2+ and Ba 2+)(It) can effectively improve the local electric field inside the Na-FAU molecular sieve, thereby increasing the adsorption amount of hydrocarbon compounds. However, this will enhance the adsorption capacity of both ethylene and acetylene, resulting in a relatively low improvement in the selectivity for separating the two; a single transition metal ion (Co 2+ , Ni 2+ and Cu 2 + etc.) can complex with the carbon-carbon triple bond in acetylene, which helps to capture acetylene through chemical bonding. At the same time, to ensure the capture effect of acetylene, it is necessary to ensure that a relatively large amount of transition metal ions are exchanged onto Na-FAU, which leads to the need for a transition metal salt solution with a relatively high concentration and large dosage, resulting in a high cost. Summary of the Invention

[0005] To solve the above problems, the present invention prepares a transition metal-alkaline earth metal-FAU (M1-M2-FAU) molecular sieve. By comprehensively considering the effects of alkaline earth metal ions and transition metal ions on Na-FAU and acetylene capture, and adopting a reasonable exchange sequence, alkaline earth metal ions and transition metal ions are introduced into Na-FAU, expecting them to play a synergistic role to achieve both efficient capture of acetylene and deep purification of ethylene, realizing the deep purification of ethylene and the capture of trace acetylene, while reducing the dosage of the transition metal salt solution.

[0006] One object of the present invention is to provide a preparation method of a transition metal-alkaline earth metal-FAU molecular sieve.

[0007] Another object of the present invention is to provide a transition metal-alkaline earth metal-FAU molecular sieve prepared by the above preparation method.

[0008] A third object of the present invention is to provide an application of a transition metal-alkaline earth metal-FAU molecular sieve in selectively adsorbing acetylene in ethylene.

[0009] To achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a preparation method of a transition metal-alkaline earth metal-FAU molecular sieve, including the following steps:

[0011] (1) Put the Na-FAU zeolite into a salt solution of alkaline earth metal M2 for ion exchange, filter, wash and dry the obtained product to obtain a first material;

[0012] (2) Calcinate the first material at a high temperature to obtain a second material;

[0013] (3) Put the second material into a salt solution of transition metal M1 for ion exchange, filter, wash and dry the obtained product to obtain a third material;

[0014] (4) Calcinate the third material at high temperature to obtain a transition metal-alkaline earth metal-FAU molecular sieve.

[0015] The following is a detailed description:

[0016] The Na-FAU (faujasite) zeolite in step (1) includes at least one of a Na-X molecular sieve with a silica-alumina ratio of 1.0 and a Na-Y molecular sieve with a silica-alumina ratio of 2.6.

[0017] The alkaline earth metal M2 in step (1) includes at least one of magnesium, calcium, strontium, and barium.

[0018] The salt solution of the alkaline earth metal M2 in step (1) can be at least one of a nitrate solution, an acetate, and a chloride of the alkaline earth metal M2.

[0019] Preferably, the mass-volume ratio of the Na-FAU zeolite to the salt solution of the alkaline earth metal M2 in step (1) is 1-5 g: 100-500 ml (preferably 2.5 g: 125 ml); the concentration of the salt solution of the alkaline earth metal M2 is 0.01-1 mol / L (preferably 0.2 mol / L).

[0020] Preferably, the ion exchange in step (1) is carried out under a water bath condition of 25-90 °C (preferably 70 °C), and the ion exchange is carried out for 1-24 h (preferably 4 h).

[0021] Preferably, the calcination temperature in step (2) is 300-800 °C (preferably 550 °C), and the calcination time is 2-12 h (preferably 6 h).

[0022] The transition metal M1 in step (3) includes at least one of cobalt and nickel.

[0023] The salt solution of the transition metal M1 in step (3) can be at least one of a nitrate solution, an acetate, and a chloride of the transition metal M1.

[0024] Preferably, the mass-volume ratio of the second material to the salt solution of the transition metal M1 in step (3) is 1-5 g: 100-500 ml (preferably 1.25 g: 125 ml); the concentration of the salt solution of the transition metal M1 is 0.001-0.1 mol / L (preferably 0.05 mol / L).

[0025] Preferably, the ion exchange in step (3) is carried out under a water bath condition of 25-90 °C (preferably 70 °C), and the ion exchange is carried out for 1-24 h (preferably 4 h).

[0026] Preferably, the calcination temperature in step (4) is 300 - 800 °C (preferably 550 °C), and the calcination time is 2 - 12 h (preferably 6 h).

[0027] In the present invention, commercial zeolite Na-FAU zeolite is used as the raw material. After ion exchange with alkaline earth metal and transition metal ions successively and sufficient calcination in each step, transition metal-alkaline earth metal-FAU (M1-M2-FAU) zeolite is prepared.

[0028] In the second aspect, the present invention provides a transition metal-alkaline earth metal-FAU zeolite, which is prepared by the above preparation method, and the transition metal and alkaline earth metal are loaded on the FAU zeolite support.

[0029] In the third aspect, the present invention provides an application of the above transition metal-alkaline earth metal-FAU zeolite in selectively adsorbing trace acetylene in ethylene.

[0030] The application includes the following steps:

[0031] (a) Weigh 0.50 g of transition metal-alkaline earth metal-FAU zeolite and add it to the separation column, and pretreat it with an inert gas;

[0032] (b) After cooling to room temperature, introduce a mixed gas containing ethylene and acetylene;

[0033] (c) Maintain the gas in the separation column under certain conditions, detect the change of the gas composition at the outlet of the separation column through a directly connected gas chromatograph, and calculate the elution time and dynamic adsorption capacity of acetylene on the transition metal-alkaline earth metal-FAU zeolite.

[0034] Preferably, in step (a), the inert gas is at least one of helium, nitrogen, and argon; the pretreatment includes treating at 100 - 400 °C (preferably 300 °C) for 0.5 - 2 h (preferably 1 h).

[0035] Preferably, in step (b), the content of acetylene in the mixed gas is 0.01% - 5%, and the content of ethylene is 95% - 99.99%.

[0036] Preferably, in step (c), maintain the gas in the separation column under the following conditions: the operating temperature is 0 - 50 °C (preferably 25 °C), the total gas pressure is 0.1 - 10 bar (preferably 1 bar), and the total gas flow rate is 1 - 100 mL / min (preferably 10 mL / min).

[0037] Technical effects:

[0038] 1. The present invention realizes the efficient separation of acetylene and ethylene mixtures, and the adsorbent transition metal-alkaline earth metal-FAU zeolite used has simple synthesis steps and low cost, having potential industrial application value.

[0039] 2. The M1-M2-FAU zeolite prepared by the present invention shows strong acetylene adsorption capacity in the acetylene / ethylene dynamic breakthrough experiment, and the purification effect of ethylene is significantly improved.

[0040] 3. The preparation of the M1-M2-FAU zeolite of the present invention has mild operating conditions and simple operating equipment, and the removal of trace acetylene and the deep purification of ethylene can be realized under normal temperature and pressure.

[0041] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art or the summary of the invention or the following examples. Description of the Drawings

[0042] Figure 1 are the acetylene and ethylene adsorption isotherms of Ni-Ba-Y zeolite at 25 °C.

[0043] Figure 2 is the dynamic breakthrough curve of separating the acetylene and ethylene mixture (99% ethylene, 1% acetylene) by Ni-Ba-Y at 25 °C and 1 bar.

[0044] Figure 3 is the dynamic breakthrough curve of separating the acetylene and ethylene mixture (99% ethylene, 1% acetylene) by Ni-Ba-X at 25 °C and 1 bar.

[0045] Figure 4 is the dynamic breakthrough curve of separating the acetylene and ethylene mixture (99.5% ethylene, 0.5% acetylene) by Ni-Ba-Y at 25 °C and 1 bar.

[0046] Figure 5 is the dynamic breakthrough curve of separating the acetylene and ethylene mixture (99.5% ethylene, 0.5% acetylene) by Co-Ba-Y at 25 °C and 1 bar.

[0047] Figure 6 is the dynamic breakthrough curve of separating the acetylene and ethylene mixture (99.5% ethylene, 0.5% acetylene) by Ni-Ca-Y at 25 °C and 1 bar.

[0048] Figure 7It is the dynamic breakthrough curve of the Ni-Ba-Y for separating the acetylene and ethylene mixture (99.8% ethylene and 0.2% acetylene) at 25 °C and 1 bar.

[0049] Figure 8 It is the dynamic breakthrough curve of the Ni-Ba-Y for separating the acetylene and ethylene mixture (99.9% ethylene and 1000 ppm acetylene) at 25 °C and 1 bar.

[0050] Figure 9 It is the dynamic breakthrough curve of the Ni / Ba-Y for separating the acetylene and ethylene mixture (99% ethylene and 1% acetylene) at 25 °C and 1 bar.

[0051] Figure 10 It is the dynamic breakthrough curve of the Ba-Ni-Y for separating the acetylene and ethylene mixture (99% ethylene and 1% acetylene) at 25 °C and 1 bar.

[0052] Figure 11 It is the schematic diagram of the self-made column separation device. Detailed implementation mode

[0053] The present invention will be further described below in conjunction with the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection required by the present invention.

[0054] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0055] Both Na-X and Na-Y molecular sieves are purchased from the Catalyst Factory of Nankai University. Alkaline earth metal salts and transition metal salts are all purchased from Tianjin Jiangtian Chemical Technology Co., Ltd. Deionized water is prepared by a laboratory ultrapure water machine. The dynamic acetylene adsorption capacity and ethylene yield are determined by the following formulas:

[0056] Calculation of dynamic acetylene adsorption capacity:

[0057]

[0058] In the formula: q is the dynamic acetylene adsorption capacity, mmol / g; V is the total flow rate of the mixed gas, cm 3 / min; m is the mass of the adsorbent, g; is the mole fraction of acetylene in the mixed gas; v is the standard gas constant at 25 °C and 1 bar, v = 24.5 cm 3 / mmol; tis the time for acetylene adsorption saturation, min; c is the molar concentration of acetylene during the adsorption process, mol / m 3 ; c 0 is the initial molar concentration of acetylene in the mixed gas, mol / m 3 .

[0059] Calculation of ethylene yield:

[0060]

[0061] In the formula: P is the yield of acetylene, mmol / g; V is the total flow rate of the mixed gas, cm 3 / min; m is the mass of the adsorbent, g; is the mole fraction of acetylene in the mixed gas; v is the standard gas constant at 25 °C and 1 bar, v = 24.5 cm 3 / mmol; t 1 is the effluent time of ethylene, min; t 2 is the effluent time of acetylene, min; c is the molar concentration of ethylene during the adsorption process, mol / m 3 ; c 0 is the initial molar concentration of ethylene in the mixed gas, mol / m 3 .

[0062] Example 1

[0063] Ni-Ba-Y zeolite was prepared by the ion exchange method. Specifically, 2.5 g of commercial Na-Y zeolite (silica-alumina ratio of 2.6) was added to 125 mL of an aqueous Ba(NO3)2 solution with a concentration of 0.2 mol / L, and stirred for 4 hours using a magnetic stirrer under the condition of water bath heating at 70 °C. It was filtered by suction and washed with deionized water until there was no barium ion in the filtrate, and the filter cake was dried in a forced-air drying oven at 90 °C. The dried solid was placed in a muffle furnace, heated from room temperature to 550 °C, then calcined for 6 h, exchanged 1 - 2 times, and finally Ba-Y zeolite with an exchange degree greater than 95% was obtained. 1.25 g of Ba-Y zeolite was added to 125 mL of an aqueous Ni(NO3)2 solution with a concentration of 0.05 mol / L, and stirred for 4 h using a magnetic stirrer under the condition of water bath heating at 70 °C. It was filtered by suction and washed with deionized water until there was no nickel ion in the filtrate, and the filter cake was dried and then placed in a muffle furnace, heated from room temperature to 550 °C and calcined for 6 h to obtain Ni-Ba-Y zeolite.

[0064] The adsorption isotherms of ethylene and acetylene on the Ni-Ba-Y molecular sieve prepared in Example 1 were measured using a Belsorp PM2-1560 physical adsorption analyzer, and the results are as Figure 1 shown.

[0065] The molecular sieve prepared in Example 1 was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device (as Figure 11 shown). The specific operation was as follows: 0.5 g of the Ni-Ba-Y sample was loaded into the sample cell of the self-made separation column, and the sample was pretreated by purging with helium at a temperature of 300 °C for 1 hour. After the pretreatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content 99%, acetylene content 1%) was passed into the separation column. The total gas flow rate was 10 mL / min, at 25 °C and 1 bar. A gas chromatograph was connected to the gas outlet of the separation column to monitor the composition of the outlet gas in real time online. The test results are as Figure 2 shown. The breakthrough time of acetylene was 64 minutes, the dynamic adsorption capacity of Ni-Ba-Y for acetylene was 0.394 mmol / g, and the yield of ethylene was 51.7 mmol / g.

[0066] Example 2

[0067] Using a preparation method basically the same as that in Example 1, the Y-type molecular sieve was replaced with an X-type molecular sieve, and ion exchange was carried out successively with Ba(NO3)2 solution and Ni(NO3)2 solution to prepare Ni-Ba-X molecular sieve. The Ni-Ba-X molecular sieve synthesized in the above steps was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation was as follows: 0.5 g of the Ni-Ba-X sample was loaded into the sample cell of the self-made separation column, and the sample was pretreated by purging with helium at a temperature of 300 °C for 1 hour. After the pretreatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content 99%, acetylene content 1%) was passed into the sample. The total gas flow rate was 10 mL / min, at 25 °C and 1 bar. A gas chromatograph was connected to the gas outlet of the separation column to monitor the composition of the outlet gas in real time online. The test results are as Figure 3 shown. The breakthrough time of acetylene was 20.0 minutes, the dynamic adsorption capacity of Ni-Ba-X for acetylene was 0.133 mmol / g, and the yield of ethylene was 16.2 mmol / g.

[0068] Example 3

[0069] Using a preparation method basically the same as that in Example 1, Ni-Ba-Y zeolite was prepared. The Ni-Ba-Y zeolite synthesized in the above steps was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation was as follows: 0.5 g of the Ni-Ba-Y sample was loaded into the sample pool of the self-made separation column, and the sample was pretreated by purging with helium at a temperature of 300 °C for 1 hour. After the pretreatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content was 99.5%, acetylene content was 0.5%) was passed into the sample, the total gas flow rate was 10 mL / min, 25 °C, 1 bar, and a gas chromatograph was connected to the gas outlet of the separation column to online and real-time monitor the composition of the outlet gas. The test results were as Figure 4 shown. The breakthrough time of acetylene was 118 minutes, the dynamic adsorption capacity of Ni-Ba-Y for acetylene was 0.349 mmol / g, and the yield of ethylene was 95.8 mmol / g.

[0070] Example 4

[0071] Using a preparation method basically the same as that in Example 1, the Ba(NO3)2 solution was replaced with a Ca(NO3)2 solution to prepare Ni-Ca-Y zeolite. The Ni-Ca-Y zeolite synthesized in the above steps was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation was as follows: 0.5 g of the Ni-Ca-Y sample was loaded into the sample pool of the self-made separation column, and the sample was pretreated by purging with helium at a temperature of 300 °C for 1 hour. After the pretreatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content was 99.5%, acetylene content was 0.5%) was passed into the sample, the total gas flow rate was 10 mL / min, 25 °C, 1 bar, and a gas chromatograph was connected to the gas outlet of the separation column to online and real-time monitor the composition of the outlet gas. The test results were as Figure 5 shown. The breakthrough time of acetylene was 51 minutes, the dynamic adsorption capacity of Ni-Ca-Y for acetylene was 0.131 mmol / g, and the yield of ethylene was 41.4 mmol / g.

[0072] Example 5

[0073] Using a preparation method substantially the same as that in Example 1, replace the Ni(NO3)2 solution with a Co(NO3)2 solution to obtain Co-Ba-Y molecular sieve. Apply the Co-Ba-Y molecular sieve synthesized in the above step to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation is as follows: Load 0.5 g of the Co-Ba-Y sample into the sample pool of the self-made separation column, pretreat the sample with helium purge at a temperature of 300 °C for 1 hour. After the pretreatment is completed and the temperature drops to room temperature, introduce a mixed gas of ethylene and acetylene (ethylene content is 99.5%, acetylene content is 0.5%) into the sample, the total gas flow rate is 10 mL / min, 25 °C, 1 bar. Connect a gas chromatograph to the gas outlet of the separation column to online real-time monitor the composition of the outlet gas, and the test results are as Figure 6 shown. The breakthrough time of acetylene is 40 minutes, the dynamic adsorption capacity of Co-Ba-Y for acetylene is 0.204 mmol / g, and the yield of ethylene is 32.5 mmol / g.

[0074] Example 8

[0075] Using a preparation method substantially the same as that in Example 1, obtain Ni-Ba-Y molecular sieve. Apply the Ni-Ba-Y molecular sieve synthesized in the above step to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation is as follows: Load 0.5 g of the Ni-Ba-Y sample into the sample pool of the self-made separation column, pretreat the sample with helium purge at a temperature of 300 °C for 1 hour. After the pretreatment is completed and the temperature drops to room temperature, introduce a mixed gas of ethylene and acetylene (ethylene content is 99.8%, acetylene content is 0.2%) into the sample, the total gas flow rate is 10 mL / min, 25 °C, 1 bar. Connect a gas chromatograph to the gas outlet of the separation column to online real-time monitor the composition of the outlet gas, and the test results are as Figure 7 shown. The breakthrough time of acetylene is 300 minutes, the dynamic adsorption capacity of Ni-Ba-Y for acetylene is 0.323 mmol / g, and the yield of ethylene is 244.4 mmol / g.

[0076] Example 9

[0077] Apply the molecular sieve prepared in Example 1 to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation is as follows: Load 0.5 g of the Ni-Ba-Y sample into the sample pool of the self-made separation column, pretreat the sample with helium purge at a temperature of 300 °C for 1 hour. After the pretreatment is completed and the temperature drops to room temperature, introduce a mixed gas of ethylene and acetylene (ethylene content is 99.9%, acetylene content is 1000 ppm) into the separation column, the total gas flow rate is 10 mL / min, 25 °C, 1 bar. Connect a gas chromatograph to the gas outlet of the separation column to online real-time monitor the composition of the outlet gas, and the test results are asFigure 8 As shown, the effluent time of acetylene is 680 minutes, the dynamic adsorption capacity of Ni-Ba-Y for acetylene is 0.323 mmol / g, and the yield of ethylene is 554.5 mmol / g.

[0078] Comparative Example 1

[0079] Ba-Y and Ni-Y molecular sieves were respectively prepared by the ion exchange method. The specific operation was as follows: 2.5 g of commercial Na-Y molecular sieve (silica-alumina ratio of 2.6) was added to 125 mL of an aqueous Ba(NO3)2 solution with a concentration of 0.2 mol / L, and stirred with a magnetic stirrer for 4 hours under the condition of water bath heating at 70 °C. It was filtered by suction and washed with deionized water until there was no barium ion in the filtrate, and the filter cake was dried in a blast drying oven at 90 °C. The dried solid was placed in a muffle furnace, heated from room temperature to 550 °C, and then calcined for 6 h, exchanged 1 - 2 times, and finally Ba-Y molecular sieve with an exchange degree greater than 95% was obtained. On the other hand, 1.25 g of commercial Na-Y molecular sieve (silica-alumina ratio of 2.6) was added to 125 mL of an aqueous Ni(NO3)2 solution with a concentration of 0.05 mol / L, and stirred with a magnetic stirrer for 4 h under the condition of water bath heating at 70 °C. It was filtered by suction and washed with deionized water until there was no nickel ion in the filtrate, and the filter cake was dried and then placed in a muffle furnace, heated from room temperature to 550 °C and calcined for 6 h to obtain Ni-Y molecular sieve. The obtained Ba-Y molecular sieve and Ni-Y molecular sieve were ground evenly in a mortar at an equal ratio (Ba / Ni = 2 / 1 (molar ratio)), denoted as Ni / Ba-Y molecular sieve.

[0080] The molecular sieve prepared in Comparative Example 1 was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation was as follows: 0.5 g of Ni / Ba-Y sample was loaded into the sample pool of the self-made separation column, and the sample was pretreated by purging with helium at a temperature of 300 °C for 1 hour. After the pretreatment was completed and cooled to room temperature, a mixed gas of ethylene and acetylene (ethylene content was 99%, acetylene content was 1%) was introduced into the separation column, the total gas flow rate was 10 mL / min, 25 °C, 1 bar. A gas chromatograph was connected to the gas outlet of the separation column to online real-time monitor the composition of the outlet gas, and the test results were as Figure 9 shown. The effluent time of acetylene was 32 minutes, the dynamic adsorption capacity of Ni-Ba-Y for acetylene was 0.216 mmol / g, and the yield of ethylene was 12.9 mmol / g.

[0081] Comparative Example 2

[0082] Prepare by ion exchange method, first exchange Ni 2+ and then exchange Ba 2+Samples were prepared as follows: 2.5 g of commercial Na-Y zeolite (with a silica-alumina ratio of 2.6) was added to 125 mL of an aqueous Ni(NO3)2 solution with a concentration of 0.05 mol / L. The mixture was stirred for 4 hours using a magnetic stirrer under water bath heating at 70 °C. It was then filtered by suction and washed with deionized water until no nickel ions were detected in the filtrate. The filter cake was dried in a forced-air drying oven at 90 °C. The dried solid was placed in a muffle furnace, heated from room temperature to 550 °C, and then calcined for 6 hours. This exchange process was repeated 1 - 2 times, and finally, Ni-Y zeolite was obtained. 1.25 g of Ni-Y zeolite was added to 125 mL of an aqueous Ba(NO3)2 solution with a concentration of 0.2 mol / L. The mixture was stirred for 4 hours using a magnetic stirrer under water bath heating at 70 °C. It was then filtered by suction and washed with deionized water until no nickel ions were detected in the filtrate. The filter cake was dried and then placed in a muffle furnace, heated from room temperature to 550 °C and calcined for 6 hours, denoted as Ba-Ni-Y zeolite.

[0083] The zeolite prepared in Comparative Example 2 was applied to the ethylene / acetylene breakthrough experiment using a self-made column separation device. The specific operation was as follows: 0.5 g of the Ba-Ni-Y sample was loaded into the sample cell of the self-made separation column. The sample was pretreated by purging with helium at 300 °C for 1 hour. After the pretreatment ended and the temperature dropped to room temperature, a mixture of ethylene and acetylene (ethylene content: 99%, acetylene content: 1%) was introduced into the separation column. The total gas flow rate was 10 mL / min, at 25 °C and 1 bar. A gas chromatograph was connected to the gas outlet of the separation column to on-line and real-time monitor the composition of the outlet gas. The test results are as Figure 10 shown. The breakthrough time of acetylene was 9.3 minutes. The dynamic adsorption capacity of Ni-Ba-Y for acetylene was 0.095 mmol / g, and the yield of ethylene was 3.8 mmol / g.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: within the scope of the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a transition metal-alkaline earth metal-FAU molecular sieve for selectively adsorbing acetylene in ethylene, characterized in that: The following steps are involved: (1) placing Na-FAU zeolite in a salt solution of an alkaline earth metal M2, performing ion exchange, and filtering, washing, and drying the obtained product to obtain a first material; the alkaline earth metal M2 includes at least one of magnesium, calcium, strontium, and barium; the mass volume ratio of the Na-FAU zeolite to the salt solution of the alkaline earth metal M2 is 1-5 g: 100-500 ml; and the concentration of the salt solution of the alkaline earth metal M2 is 0.01-1 mol / L; (2) calcining the first material at high temperature to obtain a second material; (3) placing the second material into a salt solution of transition metal M1, performing ion exchange, filtering the obtained product, washing and drying to obtain a third material; the transition metal M1 includes at least one of cobalt and nickel; the mass volume ratio of the second material to the salt solution of transition metal M1 is 1-5 g: 100-500 ml; the concentration of the salt solution of transition metal M1 is 0.001-0.1 mol / L; (4) calcining the third material at high temperature to obtain a transition metal-alkaline earth metal-FAU molecular sieve.

2. The preparation method according to claim 1, characterized in that: The ion exchange in step (1) is carried out in a water bath at 25-90°C for 1-24 hours.

3. The preparation method according to claim 1, characterized in that: The calcination temperature of step (2) is 300-800°C, and the calcination time is 2-12 h.

4. The preparation method according to claim 1, characterized in that: The ion exchange in step (3) is carried out in a water bath at 25-90°C for 1-24 h.

5. The preparation method according to claim 1, characterized in that: The calcination temperature of step (4) is 300-800°C, and the calcination time is 2-12 h.

6. A transition metal-alkaline earth metal-FAU molecular sieve, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1 to 5, wherein the transition metal and the alkaline earth metal are loaded on the FAU molecular sieve.

7. Use of the transition metal-alkaline earth metal-FAU molecular sieve according to claim 6 in the selective adsorption of acetylene in ethylene.

8. The use according to claim 7, characterized in that: The following steps are involved: (a) Weigh 0.50 g of transition metal-alkaline earth metal-FAU molecular sieve and add it to the separation column, and pre-treat it with inert gas; (b) after cooling to room temperature, introducing a mixed gas containing ethylene and acetylene; (c) maintaining the gas in the separation column under certain conditions, detecting the change in the gas composition at the outlet of the separation column by a directly connected gas chromatograph, and calculating the elution time and dynamic adsorption amount of acetylene on the transition metal-alkaline earth metal-FAU molecular sieve; In step (a), the inert gas is at least one of helium, nitrogen and argon; the pretreatment comprises treating at 100-400°C for 0.5-2 h; In step (b), the acetylene content in the mixed gas is 0.01%-5%, and the ethylene content is 95%-99.99%; In step (c), the gas in the separation column is maintained under the following conditions: operating temperature of 0-50°C, total gas pressure of 0.1-10 bar, and total gas flow rate of 1-100 mL / min.

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