Transition metal-alkaline earth metal-FAU molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a transition metal-alkaline earth metal-FAU molecular sieve as well as a preparation method and application thereof, and relates to the technical field of adsorption separation of zeolite molecular sieves. The transition metal-alkaline earth metal-FAU molecular sieve is synthesized by taking a commercial Na-FAU molecular sieve as a raw material through the steps of ion exchange, high-temperature calcination and the like. 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 so as to realize deep purification of ethylene. The method for separating the acetylene-ethylene mixture and capturing the low-concentration acetylene by using the transition metal-alkaline earth metal-FAU molecular sieve is simple and convenient, the adsorbent is low in cost, and the method has a relatively strong industrial popularization prospect.

Description

Technical Field

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

[0002] As an important industrial raw material, ethylene is widely used in polymers, textiles, pesticides and other fields. In the polymer preparation process, the purity of ethylene monomer raw materials is very important. The presence of trace acetylene will have a huge impact on the properties and characteristics of the polymer, such as poisoning and deactivation of polymerization catalysts, and preventing the polymerization reaction. According to the national standard GB / T 7715-2014, the purity of first-class ethylene is required to be no less than 99.9%, and the purity of superior ethylene is required to be no 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 similar, it is difficult to remove trace acetylene from ethylene. Common methods for removing trace acetylene from ethylene include: catalytic hydrogenation, solvent absorption and adsorption. The catalytic hydrogenation method mainly uses precious metal catalysts such as silver or palladium to react acetylene with hydrogen under high temperature and high pressure to convert acetylene into ethylene. Although this method can convert acetylene into ethylene and improve the yield of ethylene, it is relatively expensive due to the need to use precious metal catalysts. 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 regeneration, which 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, regeneration and low cost. Therefore, it is expected to be a better solution for deep purification of ethylene and removal of trace acetylene impurities, and has a very broad industrial prospect.

[0004] Na-FAU (including X-type and Y-type) molecular sieves have been widely used in industry with low cost. However, the current Na-FAU molecular sieves have poor acetylene adsorption effect. The dynamic adsorption capacity of acetylene is generally low, and the adsorption capacity is even lower under low concentration acetylene / ethylene mixed gas conditions. At the same time, the ethylene / acetylene separation selectivity is poor, which is not conducive to the deep purification of ethylene, and the ethylene yield is low. Existing modified molecular sieves usually only use a single metal salt solution to carry out ion exchange treatment with Na-FAU molecular sieves. Related literature research shows that a single alkaline earth metal ion (Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+) can effectively improve the local electric field inside the Na-FAU molecular sieve, thereby increasing the adsorption of hydrocarbon compounds, but this will lead to the enhancement of the adsorption capacity of ethylene / acetylene, thus the selectivity of the separation of the two is not improved much; single transition metal ions (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, in order to ensure the capture effect of acetylene, it is necessary to ensure that more transition metal ions are exchanged to Na-FAU, which leads to the need for higher concentration and larger amount of transition metal salt solution, which is more expensive. Summary of the invention

[0005] In order to solve the above problems, the present invention prepares a transition metal-alkaline earth metal-FAU (M1-M2-FAU) molecular sieve, comprehensively considers the effects of alkaline earth metal ions and transition metal ions on Na-FAU and acetylene capture, adopts a reasonable exchange sequence, introduces alkaline earth metal ions and transition metal ions into Na-FAU, so that the two can play a synergistic role, achieve both efficient acetylene capture and deep purification of ethylene, achieve deep purification of ethylene and capture of trace acetylene, and reduce the amount of transition metal salt solution used.

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

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

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

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: In a first aspect, the present invention provides a method for preparing a transition metal-alkaline earth metal-FAU molecular sieve, comprising the following steps: (1) placing Na-FAU zeolite in a salt solution of an alkaline earth metal M2 to perform ion exchange, and filtering, washing and drying the obtained product to obtain a first material; (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 to perform ion exchange, and filtering, washing and drying the obtained product to obtain a third material; (4) calcining the third material at high temperature to obtain a transition metal-alkaline earth metal-FAU molecular sieve.

[0010] The following is a detailed description: The Na-FAU (faujasite) zeolite of step (1) includes at least one of a Na-X molecular sieve having a silicon-aluminum ratio of 1.0 and a Na-Y molecular sieve having a silicon-aluminum ratio of 2.6.

[0011] The alkaline earth metal M2 in step (1) includes at least one of magnesium, calcium, strontium and barium.

[0012] The salt solution of the alkaline earth metal M2 in step (1) may be at least one of a nitrate solution, an acetate solution and a chloride solution of the alkaline earth metal M2.

[0013] Preferably, the mass volume ratio of the Na-FAU zeolite to the alkaline earth metal M2 salt solution in step (1) is 1-5 g:100-500 ml (preferably 2.5 g:125 ml); the concentration of the alkaline earth metal M2 salt solution is 0.01-1 mol / L (preferably 0.2 mol / L).

[0014] Preferably, the ion exchange in step (1) is carried out in a water bath at 25-90°C (preferably 70°C) for 1-24 h (preferably 4 h).

[0015] Preferably, the calcination temperature of step (2) is 300-800°C (preferably 550°C), and the calcination time is 2-12 h (preferably 6 h).

[0016] The transition metal M1 in step (3) includes at least one of cobalt and nickel.

[0017] The salt solution of the transition metal M1 in step (3) may be at least one of a nitrate solution, an acetate solution and a chloride solution of the transition metal M1.

[0018] Preferably, the mass volume ratio of the second material in step (3) to the salt solution of the transition metal M1 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).

[0019] Preferably, the ion exchange in step (3) is carried out in a water bath at 25-90°C (preferably 70°C) for 1-24 h (preferably 4 h).

[0020] Preferably, the calcination temperature of step (4) is 300-800°C (preferably 550°C), and the calcination time is 2-12 h (preferably 6 h).

[0021] The present invention uses commercial molecular sieve Na-FAU molecular sieve as raw material, performs ion exchange with alkaline earth metal and transition metal ions in sequence, and prepares transition metal-alkaline earth metal-FAU (M1-M2-FAU) molecular sieve after sufficient calcination in each step.

[0022] In a second aspect, the present invention provides a transition metal-alkaline earth metal-FAU molecular sieve prepared by the above preparation method, wherein the transition metal and the alkaline earth metal are loaded on a FAU molecular sieve carrier.

[0023] In a third aspect, the present invention provides an application of the above transition metal-alkaline earth metal-FAU molecular sieve in selectively adsorbing trace acetylene in ethylene.

[0024] The application comprises the following steps: (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) The gas in the separation column is maintained under certain conditions, and the changes in the gas composition at the outlet of the separation column are detected by a directly connected gas chromatograph to calculate the elution time and dynamic adsorption amount of acetylene on the transition metal-alkaline earth metal-FAU molecular sieve.

[0025] Preferably, in step (a), the inert gas is at least one of helium, nitrogen and argon; and the pretreatment comprises treating at 100-400° C. (preferably 300° C.) for 0.5-2 h (preferably 1 h).

[0026] Preferably, in step (b), the acetylene content in the mixed gas is 0.01%-5%, and the ethylene content is 95%-99.99%.

[0027] Preferably, in step (c), the gas in the separation column is maintained under the following conditions: operating temperature is 0-50°C (preferably 25°C), total gas pressure is 0.1-10 bar (preferably 1 bar), and total gas flow rate is 1-100 mL / min (preferably 10 mL / min).

[0028] Technical effects: 1. The present invention realizes efficient separation of acetylene and ethylene mixture, and the adsorbent transition metal-alkaline earth metal-FAU molecular sieve used has simple synthesis steps, low cost and potential industrial application value.

[0029] 2. The M1-M2-FAU molecular sieve prepared in the present invention exhibits a strong acetylene adsorption capacity in the acetylene / ethylene dynamic penetration experiment, and the purification effect of ethylene is significantly improved.

[0030] 3. The present invention has mild operating conditions for preparing M1-M2-FAU molecular sieves, simple operating equipment, and can achieve the removal of trace acetylene and deep purification of ethylene at room temperature and pressure.

[0031] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the adsorption isotherm of acetylene and ethylene on Ni-Ba-Y molecular sieve at 25 ℃.

[0033] Figure 2 This is the dynamic breakthrough curve of Ni-Ba-Y separating acetylene and ethylene mixture (ethylene 99%, acetylene 1%) at 25 °C and 1 bar.

[0034] Figure 3 This is the dynamic breakthrough curve of Ni-Ba-X separating acetylene and ethylene mixture (ethylene 99%, acetylene 1%) at 25 °C and 1 bar.

[0035] Figure 4 This is the dynamic breakthrough curve of Ni-Ba-Y separating acetylene and ethylene mixture (ethylene 99.5%, acetylene 0.5%) at 25 °C and 1 bar.

[0036] Figure 5 This is the dynamic breakthrough curve of Co-Ba-Y separating acetylene and ethylene mixture (ethylene 99.5%, acetylene 0.5%) at 25 °C and 1 bar.

[0037] Figure 6 This is the dynamic breakthrough curve of Ni-Ca-Y separating acetylene and ethylene mixture (ethylene 99.5%, acetylene 0.5%) at 25 °C and 1 bar.

[0038] Figure 7 This is the dynamic breakthrough curve of Ni-Ba-Y separating acetylene and ethylene mixture (ethylene 99.8%, acetylene 0.2%) at 25 °C and 1 bar.

[0039] Figure 8 It is the dynamic breakthrough curve of Ni-Ba-Y for separation of acetylene and ethylene mixture (ethylene 99.9%, acetylene 1000 ppm) at 25 °C and 1 bar.

[0040] Fig. 9This is the dynamic breakthrough curve of Ni / Ba-Y for separation of acetylene and ethylene mixture (ethylene 99%, acetylene 1%) at 25 °C and 1 bar.

[0041] Fig.10 This is the dynamic breakthrough curve of Ba-Ni-Y separating acetylene and ethylene mixture (ethylene 99%, acetylene 1%) at 25 °C and 1 bar.

[0042] Fig.11 It is a schematic diagram of the homemade column separation device. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.

[0044] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0045] Na-X and Na-Y molecular sieves were purchased from the catalyst factory of Nankai University, alkaline earth metal salts and transition metal salts were purchased from Tianjin Jiangtian Chemical Technology Co., Ltd., and deionized water was prepared by the laboratory ultrapure water machine. The dynamic adsorption of acetylene and the ethylene yield were determined by the following formula: Calculation of acetylene dynamic adsorption:

[0046] Where: q is the dynamic adsorption amount 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 =24.5cm 3 / mmol; t is the time for acetylene adsorption saturation, min; c is the molar concentration of acetylene during adsorption, mol / m 3 ; c 0 is the initial molar concentration of acetylene in the mixed gas, mol / m 3 .

[0047] Calculation of ethylene yield:

[0048] Where: Pis 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 elution time of ethylene, min; t 2 is the elution time of acetylene, min; c is the molar concentration of ethylene during adsorption, mol / m 3 ; c 0 is the initial molar concentration of ethylene in the mixed gas, mol / m 3 .

[0049] Example 1 Ni-Ba-Y molecular sieve was prepared by ion exchange method. The specific operation was as follows: 2.5 g of commercial Na-Y molecular sieve (silicon-aluminum ratio of 2.6) was added to 125 mL of 0.2 mol / L Ba(NO 3 ) 2 The aqueous solution was stirred with a magnetic stirrer for 4 hours under 70 °C water bath heating conditions. It was filtered and washed with deionized water until the filtrate was free of barium ions, and the filter cake was dried in a 90 °C forced air drying oven. 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 a Ba-Y molecular sieve with an exchange degree greater than 95% was obtained. 1.25 g of Ba-Y molecular sieve was added to 125 mL of Ni(NO 3 ) 2 The aqueous solution was stirred with a magnetic stirrer for 4 h under the condition of 70 °C water bath heating. It was filtered and washed with deionized water until the filtrate was free of nickel ions. The filter cake was dried and placed in a muffle furnace and calcined from room temperature to 550 °C for 6 h to obtain Ni-Ba-Y molecular sieve.

[0050] The adsorption isotherms of ethylene and acetylene by the Ni-Ba-Y molecular sieve prepared in Example 1 were measured using a Bester PM2-1560 physical adsorption instrument. The results are as follows: Figure 1 shown.

[0051] A self-made column separation device (such as Fig.11(As shown in the figure) The molecular sieve prepared in Example 1 was applied to the ethylene / acetylene penetration experiment. The specific operation was to load 0.5 g of Ni-Ba-Y sample into the sample pool of the homemade separation column, and pre-treat the sample with helium purge at 300 °C for 1 hour. After the pre-treatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content of 99%, acetylene content of 1%) was passed into the separation column, and the total gas flow rate was 10 mL / min, 25 °C, and 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are shown in FIG. Figure 2 The elution time of acetylene was 64 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.394 mmol / g, and the yield of ethylene was 51.7 mmol / g.

[0052] Example 2 The same preparation method as in Example 1 was used to replace the Y-type molecular sieve with the X-type molecular sieve. 3 ) 2 Solution and Ni(NO 3 ) 2 The solution was subjected to ion exchange successively to obtain Ni-Ba-X molecular sieve. The Ni-Ba-X molecular sieve synthesized in the above steps was applied to the ethylene / acetylene penetration experiment using a homemade column separation device. The specific operation is as follows: 0.5 g of Ni-Ba-X sample was loaded into the sample pool of the homemade separation column, and the sample was pretreated with helium purge at 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 passed into the sample. The total gas flow rate was 10 mL / min, 25°C, 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are as follows: Figure 3 The elution time of acetylene was 20.0 min, the dynamic adsorption amount of acetylene by Ni-Ba-X was 0.133 mmol / g, and the yield of ethylene was 16.2 mmol / g.

[0053] Example 3 A Ni-Ba-Y molecular sieve was prepared by a preparation method basically the same as that in Example 1. The Ni-Ba-Y molecular sieve synthesized in the above steps was applied to the ethylene / acetylene penetration experiment using a homemade column separation device. The specific operation is as follows: 0.5 g of Ni-Ba-Y sample was loaded into the sample pool of the homemade separation column, and the sample was pretreated with helium purge at 300°C for 1 hour. After the pretreatment was completed and the sample was cooled 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. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are as follows: Figure 4 The elution time of acetylene was 118 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.349 mmol / g, and the yield of ethylene was 95.8 mmol / g.

[0054] Example 4 Using the same preparation method as in Example 1, Ba(NO 3 ) 2 The solution was replaced with Ca(NO 3 ) 2 solution to obtain Ni-Ca-Y molecular sieve. The Ni-Ca-Y molecular sieve synthesized in the above steps was applied to the ethylene / acetylene breakthrough experiment using a homemade column separation device. The specific operation is as follows: 0.5 g of Ni-Ca-Y sample was loaded into the sample pool of the homemade separation column, and the sample was pretreated with helium purge at 300°C for 1 hour. After the pretreatment was completed and cooled to room temperature, a mixed gas of ethylene and acetylene (ethylene content of 99.5%, acetylene content of 0.5%) was passed into the sample. The total gas flow rate was 10 mL / min, 25°C, 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are as follows: Figure 5 The elution time of acetylene was 51 minutes, the dynamic adsorption amount of acetylene by Ni-Ca-Y was 0.131 mmol / g, and the yield of ethylene was 41.4 mmol / g.

[0055] Example 5 Using the same preparation method as in Example 1, Ni(NO 3 ) 2 The solution was replaced by Co(NO 3 ) 2solution to obtain Co-Ba-Y molecular sieve. The Co-Ba-Y molecular sieve synthesized in the above steps was applied to the ethylene / acetylene breakthrough experiment using a homemade column separation device. The specific operation is as follows: 0.5 g of Co-Ba-Y sample was loaded into the sample pool of the homemade separation column, and the sample was pretreated with helium purge at 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 99.5%, acetylene content was 0.5%) was passed into the sample. The total gas flow rate was 10 mL / min, 25°C, 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are as follows: Figure 6 The elution time of acetylene was 40 minutes, the dynamic adsorption amount of acetylene by Co-Ba-Y was 0.204 mmol / g, and the yield of ethylene was 32.5 mmol / g.

[0056] Example 8 A Ni-Ba-Y molecular sieve was prepared by a preparation method basically the same as that in Example 1. The Ni-Ba-Y molecular sieve synthesized in the above steps was applied to the ethylene / acetylene penetration experiment using a homemade column separation device. The specific operation is as follows: 0.5 g of Ni-Ba-Y sample was loaded into the sample pool of the homemade separation column, and the sample was pretreated with helium purge at 300 °C for 1 hour. After the pretreatment was completed and the temperature was cooled to room temperature, a mixed gas of ethylene and acetylene (ethylene content was 99.8%, acetylene content was 0.2%) was passed into the sample. The total gas flow rate was 10 mL / min, 25 °C, 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are as follows: Figure 7 The elution time of acetylene was 300 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.323 mmol / g, and the yield of ethylene was 244.4 mmol / g.

[0057] Example 9 The molecular sieve prepared in Example 1 was applied to the ethylene / acetylene penetration experiment using a homemade 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 homemade separation column, and the sample was pretreated with helium purge at 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 of 99.9%, acetylene content of 1000 ppm) was passed into the separation column, with a total gas flow rate of 10 mL / min, 25 °C, and 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are shown in FIG. Figure 8The elution time of acetylene was 680 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.323 mmol / g, and the yield of ethylene was 554.5 mmol / g.

[0058] Comparative Example 1 Ba-Y and Ni-Y molecular sieves were prepared by ion exchange method. The specific operation was as follows: 2.5 g of commercial Na-Y molecular sieve (silicon-aluminum ratio of 2.6) was added to 125 mL of 0.2 mol / L Ba(NO 3 ) 2 The aqueous solution was stirred with a magnetic stirrer for 4 hours under 70 °C water bath heating conditions. It was filtered and washed with deionized water until the filtrate was free of barium ions, and the filter cake was dried in a 90 °C forced air drying oven. 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 obtained a Ba-Y molecular sieve with an exchange degree greater than 95%. On the other hand, 1.25 g of commercial Na-Y molecular sieve (silicon-aluminum ratio of 2.6) was added to 125 mL of Ni(NO) with a concentration of 0.05 mol / L 3 ) 2 In aqueous solution, stir with a magnetic stirrer for 4 h under 70 °C water bath heating conditions. Filter and wash with deionized water until the filtrate is free of nickel ions. After drying, the filter cake is placed in a muffle furnace and calcined from room temperature to 550 °C for 6 h to obtain Ni-Y molecular sieve. The obtained Ba-Y molecular sieve and Ni-Y molecular sieve are evenly ground in a mortar in the same ratio (Ba / Ni=2 / 1 (molar ratio)), which is recorded as Ni / Ba-Y molecular sieve.

[0059] The molecular sieve prepared in Comparative Example 1 was applied to the ethylene / acetylene penetration experiment using a homemade column separation device. The specific operation was to load 0.5 g of Ni / Ba-Y sample into the sample pool of the homemade separation column, and pre-treat the sample with helium purge at 300 °C for 1 hour. After the pre-treatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content of 99% and acetylene content of 1%) was passed into the separation column, with a total gas flow of 10 mL / min, 25 °C, and 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are shown in Figure 2. Fig. 9 The elution time of acetylene was 32 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.216 mmol / g, and the yield of ethylene was 12.9 mmol / g.

[0060] Comparative Example 2 The Ni was first exchanged by ion exchange method. 2+ After exchange Ba 2+The specific operation is to add 2.5 g of commercial Na-Y molecular sieve (silicon-aluminum ratio of 2.6) into 125 mL of 0.05 mol / L Ni(NO 3 ) 2 The aqueous solution was stirred with a magnetic stirrer for 4 hours under 70 °C water bath heating conditions. It was filtered and washed with deionized water until the filtrate was free of nickel ions, and the filter cake was dried in a 90 °C forced air drying oven. 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 obtained Ni-Y molecular sieve. 1.25 g Ni-Y molecular sieve was added to 125 mL of Ba(NO 3 ) 2 The aqueous solution was stirred with a magnetic stirrer for 4 h under the condition of 70 °C water bath heating. It was filtered and washed with deionized water until the filtrate was free of nickel ions. The filter cake was dried and placed in a muffle furnace and calcined from room temperature to 550 °C for 6 h, which was recorded as Ba-Ni-Y molecular sieve.

[0061] The molecular sieve prepared in Comparative Example 2 was applied to the ethylene / acetylene penetration experiment using a homemade column separation device. The specific operation was to load 0.5 g of Ba-Ni-Y sample into the sample pool of the homemade separation column, and pre-treat the sample with helium purge at 300 °C for 1 hour. After the pre-treatment was completed and the temperature dropped to room temperature, a mixed gas of ethylene and acetylene (ethylene content of 99% and acetylene content of 1%) was passed into the separation column, with a total gas flow of 10 mL / min, 25 °C, and 1 bar. The gas outlet of the separation column was connected to a gas chromatograph to monitor the composition of the outlet gas online in real time. The test results are shown in Figure 2. Fig.10 The elution time of acetylene was 9.3 minutes, the dynamic adsorption amount of acetylene by Ni-Ba-Y was 0.095 mmol / g, and the yield of ethylene was 3.8 mmol / g.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; 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, characterized in that: The following steps are involved: (1) placing Na-FAU zeolite in a salt solution of an alkaline earth metal M2 to perform ion exchange, and filtering, washing and drying the obtained product to obtain a first material; (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 to perform ion exchange, and filtering, washing and drying the obtained product to obtain a third material; (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 alkaline earth metal M2 in step (1) includes at least one of magnesium, calcium, strontium and barium; The mass volume ratio of the Na-FAU zeolite to the alkaline earth metal M2 salt solution in step (1) is 1-5 g:100-500 ml; the concentration of the alkaline earth metal M2 salt solution is 0.01-1 mol / L.

3. 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.

4. 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.

5. The preparation method according to claim 1, characterized in that: The transition metal M1 in step (3) includes at least one of cobalt and nickel; The mass volume ratio of the second material in step (3) to the salt solution of the transition metal M1 is 1-5 g:100-500 ml; the concentration of the salt solution of the transition metal M1 is 0.001-0.1 mol / L.

6. 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.

7. 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.

8. 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 7, wherein the transition metal and the alkaline earth metal are loaded on the FAU molecular sieve.

9. Use of the transition metal-alkaline earth metal-FAU molecular sieve according to claim 8 in selectively adsorbing trace acetylene in ethylene.

10. The use according to claim 9, 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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