A method of separating propyne and propadiene

Abstract

The application discloses a method for separating propyne and propadiene, which comprises the following steps: contacting mixed gas containing propyne and propadiene with a metal organic framework material having special window active sites, and selectively adsorbing propyne in the mixed gas by the metal organic framework material, so as to realize the separation of propadiene and propyne; the metal organic framework material is formed by coordinating a six-coordinated divalent metal cation Cu 2+ with a tridentate nitrogen-containing ligand L to form a cage structure, and then bridging a high-coordination-number divalent inorganic anion ZrF6 2‑ to form a structure having special window active sites; the molecular formula of the metal organic framework material is (CuZrF6)3L4, wherein the tridentate nitrogen-containing ligand L is tris(4-pyridyl)amine. The method can separate propyne and propadiene mixed gas with high capacity and high selectivity, the adsorbent is easy to regenerate, and the hydrothermal stability is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical separation technology, and particularly relates to a method for separating propyne and propadiene. BACKGROUND

[0002] Propadiene (CH2=C=CH2) as the simplest diene compound is an important raw material for organic synthesis. Propadiene can be used as a chiral synthon to participate in cycloaddition reaction to prepare cyclobutane or trimethylene cyclohexane derivatives; it can also be combined with cheap and environmentally friendly silane to replace stoichiometric number of allyl metal reagent, which is necessary for most enantioselective ketone allylation reactions. In addition, the dimer prepared from propadiene (unsaturated four-membered ring hydrocarbon) is also a widely used intermediate, which can be used to produce many high-value-added products. At present, propadiene is prepared by chemical synthesis, which has problems such as low yield, high energy consumption and many by-products, so it is urgent to develop an alternative method for producing propadiene. Petroleum cracking is the largest process for producing low-carbon hydrocarbons in the world, with more than 500 million tons of raw materials converted annually. Propadiene is one of the by-products, accounting for 0.3-0.6wt% of the total output and 6mol% of the C3 crude distillate. However, propadiene and propyne usually exist in the form of mixed gas, and the molecular shape, size and boiling point of the two are very close, so there is currently no effective technology to separate them in industry. The mixture containing propadiene is usually processed into fuel for direct combustion in industry, causing a lot of waste. Therefore, it is urgent to develop a new separation technology to realize the efficient separation of propyne / propadiene.

[0003] Physical adsorption is a relatively energy-efficient separation technology, but the current traditional adsorbent materials such as molecular sieves and activated carbon are difficult to accurately identify propyne and propadiene molecules, so they cannot effectively separate the two gases. Metal-organic framework materials (MOFs) are a class of organic-inorganic hybrid materials with intramolecular pores formed by self-assembly of organic ligands and metal ions or clusters through coordination bonds, which have the advantages of large specific surface area, fine-tunable pore size and pore environment, and have potential application prospects in the field of gas adsorption and separation. Since the molecular shape and size of propadiene and propyne are similar, it is difficult to separate the two by molecular sieving or kinetic separation, and only by introducing adsorption sites with specific recognition of propyne or propadiene molecules into porous materials and constructing specific pore environment can propyne / propadiene separation be realized. Currently, MOFs with open metal sites are the best materials for propyne / propadiene separation. For example, the propyne adsorption capacity of HKUST-1 reaches 191.97 cm 3 / cm 3 at 50kPa, but the propyne / propadiene selectivity is only 3.46. NKMOF-1-Ni has the highest propyne / propadiene separation selectivity (4.83) at present, but the propyne adsorption capacity is only 64 cm3 / g, (Nat. Commun, 2021, 12, 5768). It can be seen that although open metal site MOFs can achieve propadiene purification, the game effect between selectivity and adsorption capacity cannot be overcome at present.

[0004] In contrast, MOFs with large pore volume but lack of obvious active sites, such as UiO-66 and UiO-67, have basically the same adsorption capacity for propyne and propadiene, and can be considered as having no separation effect. MOFs with multiple fluorine anion active sites, such as SIFSIX-2-Cu-i, SIFSIX-3-Ni and ZU-62, can efficiently separate acetylene / ethylene and propyne / propylene, but have basically the same adsorption capacity for propyne and propadiene, only with some difference at low pressure, so they cannot achieve the purpose of purifying propadiene from equimolar propyne / propadiene gas (Nat. Commun, 2021, 12, 5768).

[0005] The patent specification with publication number CN1109420479A discloses a method for preparing an ionic hybrid porous material capable of being used for propyne / propadiene / propylene adsorption separation. This material can only realize the co-adsorption of trace amounts of propyne and propadiene to purify propylene, but cannot separate propyne and propadiene which are more similar in structure, properties and size.

[0006] The patent specification with publication number CN114534441A discloses a method for one-step deep removal of alkyne and propadiene from complex cracking gas by using ionic hybrid ultra-microporous material. The material involved in this method can only adsorb propyne and propadiene simultaneously, and cannot separate propyne and propadiene.

[0007] The patent specification with publication number CN114177890A discloses a kind of preparation can be used for propyne / propylene, acetylene / ethylene separation column cage type metal organic framework material.This kind of material is not involved in propyne and allomycin separation, as listed above many prior art, the person skilled in the art cannot obviously expect that propyne / propylene separation material can be directly transferred to propyne / allomycin separation, propyne, allomycin may be simultaneously adsorbed, because propyne and allomycin separation is more difficult.The person skilled in the art will not think that propyne / propylene and propyne / allomycin are similar separation systems, because one is to overcome the technical problem of propyne and propylene adsorption capacity difference, and the other is to overcome the technical problem of propyne and allomycin adsorption capacity difference, the two adsorption capacity differences are not comparable, so in the art, it is completely different two separation systems, based on this, the person skilled in the art cannot know whether this kind of column cage type MOFs capable of propyne / propylene separation can distinguish the adsorption capacity difference between propyne and allomycin.In addition, the same author reported in the international journal Angew.Chem.Int.Ed, 2022, 61, e202200946 that the mechanism of column cage type metal organic framework ZNU-2 separating propyne / propylene with TiF6 2-

[0008] In summary, although acetylene / ethylene, propyne / propylene and propyne / allomycin separation can be achieved by selectively adsorbing alkyne to separate mixed gas, propyne / allomycin is more similar in molecular shape, size or property, and the ratio of propyne / allomycin in the mixed gas is close to that of acetylene / ethylene, propyne / propylene, which is significantly different from the application environment of removing trace alkyne (<1%) in the separation of acetylene / ethylene, propyne / propylene, so the separation difficulty is obviously higher. Fundamentally, a material that can achieve good propyne / propylene adsorption separation cannot be deduced to achieve good propyne / allomycin separation. And so far, there has been no clear report of a good porous material that can achieve high selectivity and high capacity propyne / allomycin separation.

[0009] Based on a large number of experimental results, the present application unexpectedly found that by using ZrF6 2- ​The anion-constructed CuZrF6-TPA can capture propyne through a special window action site, and is different from the action mechanism of columnar cage MOFs such as ZNU-2, so that the CuZrF6-TPA exhibits significant differences in adsorption of propyne and propadiene, has the highest propyne / propadiene selectivity and extremely high propyne adsorption capacity so far, and thus can effectively realize efficient separation of propyne / propadiene. SUMMARY

[0010] The application provides a method for separating propyne and propadiene.

[0011] The specific technical scheme is as follows:

[0012] A method for separating propyne and propadiene, which comprises: contacting a mixed gas containing propyne and propadiene with a metal organic framework material having a special window action site, so that the metal organic framework material selectively adsorbs propyne in the mixed gas, and separation of propadiene and propyne is realized.

[0013] The metal organic framework material is formed by coordination of a six-coordinated divalent metal cation Cu 2+ and a tridentate nitrogen-containing ligand L to form a cage structure, and then bridged by a high-coordination-number divalent inorganic anion ZrF6 2- to form a structure having a special window action site.

[0014] The molecular formula of the metal organic framework material is (CuZrF6)3L4, wherein the tridentate nitrogen-containing ligand L is tris(4-pyridyl)amine.

[0015] The metal organic framework material having the special window action site can be synthesized by at least one of well-known co-precipitation method, interfacial diffusion method, and solvothermal method.

[0016] Propyne and propadiene are both linear molecules, and the molecular sizes are highly close, so it is difficult to separate the two by molecular sieving or kinetic mechanism. Only by introducing an adsorption site having specific recognition of propyne or propadiene molecules into a porous material, and constructing a specific pore environment, can the separation of propyne / propadiene be realized.

[0017] The metal organic framework material containing the specific anion in the application has a large number of regularly arranged negatively charged ZrF6 2- polyfluoride anion functional groups on the surface, and the negatively charged anion forms a special electrostatic environment in the limited space of the metal organic framework material with the specific structure, can selectively recognize and adsorb propyne molecules from the mixed gas containing propyne and propadiene, and the metal organic framework material of the application further has a special window action site which can accurately capture propyne molecules in the propyne / propadiene mixed gas, so as to realize separation of the propyne / propadiene mixed gas.

[0018] The inventors have found that the metal-organic framework material containing ZrF6 2- The metal-organic framework material containing ZrF6 2- The polyfluoride anion can form a regular arrangement structure on the pore surface, so that the special electrostatic environment is formed in the limited space of the pore channel of the material with the specific structure. On the one hand, the ZrF6 2- The introduction of the polyfluoride anion can enhance the selective recognition of propyne in the propyne / allene mixed system, and on the other hand, the material has a special window effect site, which can enhance the adsorption of propyne in the propyne / allene mixed gas, thereby improving the separation selectivity of propyne / allene. The above two characteristics are indispensable, and only when both exist can the purpose of effectively separating propyne and allene required by the present application be achieved.

[0019] The metal-organic framework material containing ZrF6 2- The metal-organic framework material containing ZrF6

[0020] In the mixed gas containing propyne and allene, the molar content of propyne can be between 10% and 90%, based on 100% of the total molar amount of propyne and allene.

[0021] Further, in the mixed gas containing propyne and allene, the molar content of propyne can be 50% to 90%, based on 100% of the total molar amount of propyne and allene.

[0022] The mixed gas containing propyne and allene is contacted with the metal-organic framework material having a special window effect site in any one or a combination of fixed bed adsorption, fluidized bed adsorption, and moving bed adsorption.

[0023] In a preferred example, the contacting of the mixed gas containing propyne and allene with the metal-organic framework material having a special window effect site is in the form of fixed bed adsorption, which can specifically include: under a set adsorption temperature and pressure, the mixed gas containing propyne and allene enters a fixed bed adsorption column filled with the metal-organic framework material at a set flow rate, and the allene component preferentially penetrates the bed layer, and high-purity allene gas is directly obtained from the outlet of the adsorption column.

[0024] The metal organic framework material can reach a high adsorption capacity of propyne gas in a propyne / propadiene mixed system in a certain temperature range. The adsorption temperature can be 0-40℃.

[0025] The adsorption pressure can be 0.5-10 atm.

[0026] After the metal organic framework material selectively adsorbs propyne in the mixed gas to realize the separation of propadiene and propyne, the propyne can be desorbed to realize the regeneration of the metal organic framework material under the conditions of a temperature of 30-100℃ and a pressure of 0-1 atm. In the present application, the physical force between the metal organic framework material and the gas molecules is easy to desorb and regenerate, and the conditions are mild.

[0027] The method provided by the present application can selectively adsorb propyne from a propyne / propadiene mixed gas with high capacity, purify propadiene, and regenerate the adsorbent easily, and has good hydrothermal stability.

[0028] As a general inventive concept, the present application also provides the use of the metal organic framework material with a special window active site in the separation of propyne and propadiene. The metal organic framework material selectively adsorbs propyne in the mixed gas containing propyne and propadiene after being contacted with the mixed gas, to realize the separation of propadiene and propyne.

[0029] The separation selectivity of the metal organic framework material for a mixed gas of propyne and propadiene with a molar ratio of 1:1 is 6.03 at 298K and 100kPa.

[0030] The separation potential of the metal organic framework material for a mixed gas of propyne and propadiene with a molar ratio of 1:1 is 5.72mmol propadiene / cm 3 Metal organic framework material

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1. On the one hand, the metal organic framework material containing ZrF6 2- anions has a large number of regularly arranged ZrF6 2- polyfluoride anion functional groups. Such anions form a special electrostatic environment in the space-limited pores of the specific structure of the MOF material in the present application, and can capture propyne from a propyne / propadiene mixed gas with high capacity and high selectivity. On the other hand, the metal organic framework material containing ZrF6 2- anions has a special window active site, which can enhance the adsorption of propyne and thus improve the separation selectivity of propyne / propadiene. The combination of the two aspects can achieve the technical effect of efficiently separating propyne and propadiene required by the present application.

[0033] 2. The metal organic framework material containing ZrF62- The anionic metal-organic framework material is easy to desorb and regenerate, has great advantages compared to traditional chemical absorbents, and can reduce the energy consumption of material regeneration. Meanwhile, the material can be regenerated and reused.

[0034] 3. The metal-organic framework material with special window active sites has excellent hydrothermal stability and also shows excellent cycle stability, and the excellent stability also shows that the metal-organic framework material with special window active sites has potential application value in industry. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a window diagram in the crystal structure of CuZrF6-TPA;

[0036] Figure 2 is a single-component adsorption isotherm diagram of propyne and propadiene of CuZrF6-TPA in Example 4 at 298K, 0-100kPa;

[0037] Figure 3 is a single-component adsorption isotherm diagram of propyne and propadiene of CuZrF6-TPA in Example 4 at 278K and 308K, 0-100kPa;

[0038] Figure 4 is an IAST separation selectivity diagram of CuZrF6-TPA and other metal-organic framework materials for separating equimolar propyne / propadiene at 298K, 0-100kPa in Example 5;

[0039] Figure 5 is a comparison diagram of propyne adsorption amount (50kPa) of CuZrF6-TPA and other metal-organic framework materials and propyne / propadiene separation selectivity at 298K in Example 4 and Example 5;

[0040] Figure 6 is an adsorption heat curve diagram of CuZrF6-TPA for propyne and propadiene in Example 6;

[0041] Figure 7 is an in-situ single crystal diagram of CuZrF6-TPA after loading propyne gas. DETAILED DESCRIPTION

[0042] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0043] Example 1

[0044] Dissolve 16.8 mg of CuZrF6·3H2O in 10 mL of water (solution A), then dissolve 10 mg of tris(4-pyridyl)amine (TPA) in 10 mL of methanol (solution B), and then prepare 20 mL of methanol / water (volume ratio 1 / 1) buffer solution. Finally, add 1 mL of solution A, 2 mL of buffer solution, and 1 mL of solution B to a 5 mL test tube. Seal the test tube and let it stand at room temperature for a week to obtain blue crystals of CuZrF6-TPA, which is the metal-organic framework material with a special window action site of the present invention. After crystal analysis, it was found that the structure of CuZrF6-TPA is as follows: Figure 1 Unless otherwise specified, subsequent tests and characterizations all used the CuZrF6-TPA prepared by the method of this example.

[0045] Example 2

[0046] In a 50 mL round-bottom flask, 322.8 mg (1.0 mmol) of CuZrF6·3H2O was dissolved in 14 mL of water. In a separate 50 mL round-bottom flask, 331.05 mg (1.3 mmol) of tris(4-pyridyl)amine was dissolved in 30 mL of methanol. The methanol solution was added dropwise to the aqueous solution and stirred at 80°C for 72 hours to produce a blue solid precipitate, which was filtered and washed with methanol. The solid was then immersed in anhydrous methanol, with the anhydrous methanol replaced every six hours for a total of three or more replacements to remove water molecules from the material's pores, resulting in the metal-organic framework CuZrF6-TPA with specific window sites.

[0047] Example 3

[0048] About 100 mg of CuZrF6-TPA material obtained in Example 1 was placed in an adsorption tube. After vacuuming at room temperature for two hours, it was activated by vacuuming at 120°C for 10 hours. Then, in a liquid nitrogen bath, the activated sample was subjected to a 77K nitrogen adsorption-desorption test using an adsorption instrument. The BET specific surface area, pore volume and pore size distribution of the material can be calculated based on the nitrogen adsorption isotherm.

[0049] Example 4

[0050] Under the conditions of 278K, 298K and 308K, the CuZrF6-TPA sample activated in Example 3 was subjected to single-component gas adsorption experiments of propyne and propadiene using an adsorption instrument, and its single-component gas adsorption curve was measured as follows: Figure 2 and Figure 3 Specifically, at 298K and 50kPa, the propyne adsorption capacity of CuZrF6-TPA can reach 177.4cm 3 / cm 3 , the adsorption capacity of propadiene is 147.5cm3 cm 3 The propyne adsorption capacity of CuZrF6-TPA at 50 kPa was then compared with other MOF materials, and the results are shown in Figure 5 .

[0051] Example 5

[0052] The single-component propyne or propadiene gas adsorption isotherms of CuZrF6-TPA were fitted using the two-site Langmuir-Freundlich (with temperature factor) model, and then the parameters obtained by fitting were used to calculate the propyne / propadiene (50 / 50 v / v) separation selectivity of CuZrF6-TPA at 298 K, 100 kPa to be 6.03 using the ideal solution adsorption theory (IAST), indicating that CuZrF6-TPA can realize the separation of equimolar propyne / propadiene. The selectivity curve is shown in Figure 4 , and then the propyne / propadiene (50 / 50 v / v) separation selectivity of CuZrF6-TPA at 298 K, 100 kPa was compared with other MOF materials, and the results are shown in Figure 5 .

[0053] Example 6

[0054] The adsorption heat curve of CuZrF6-TPA was calculated using the parameters obtained by fitting in Example 5 and the Clausius-Clapeyron equation. Under zero loading, the adsorption heat of CuZrF6-TPA for propyne and propadiene was 47 kJ / mol and 42 kJ / mol, respectively. The adsorption heat curve is shown in Figure 6 .

[0055] Example 7

[0056] The CuZrF6-TPA material obtained in Example 2 was ground into fine powder of uniform size, loaded into an adsorption column with an inner diameter of 0.5 cm and a length of 5 cm, activated at 100°C for 10 hours, and at room temperature 25°C, propyne / propadiene mixed gas (50 / 50 v / v) was passed into the adsorption column at 2 mL / min. It was observed that propadiene gas came out first, and after a certain time, propyne gas came out.

[0057] Example 8

[0058] In-situ single crystal test was performed on the CuZrF6-TPA crystals loaded with propyne in Example 4, and after analysis, it was found that the adsorption site of the propyne molecule was located at the window of CuZrF6-TPA. The in-situ single crystal test results are shown in Figure 7 .

[0059] Table 1 demonstrates the comparison of CuZrF6-TPA with other existing MOF materials for 50 kPa propyne uptake, propyne / propadiene (50 / 50 v / v) IAST separation selectivity, propyne heat of adsorption, and propyne / propadiene (50 / 50 v / v) separation potential (i.e. maximum propadiene production per volume of material theoretically achievable for 50 / 50 v / v propyne / propadiene mixed gas separation based on material static adsorption data).

[0060] Table 1

[0061]

[0062] It is to be understood that while the application has been described above with reference to particular embodiments, the application can be implemented differently. It is therefore desired that the present application be limited only as described in the appended claims.

Claims

1. A method of separating propyne and propadiene, characterized by, The mixed gas containing propyne and propadiene is contacted with a metal organic framework material with special window active sites, and the metal organic framework material selectively adsorbs propyne in the mixed gas, so that the separation of propadiene and propyne is realized. The metal organic framework material is formed by coordination of a hexacoordinated divalent metal cation Cu 2+ with a tridentate nitrogen-containing ligand L to form a cage structure, and then a high-coordination-number divalent inorganic anion ZrF6 2- bridging to form a structure with a special window function site; The molecular formula of the metal organic framework material is (CuZrF6)3L4, wherein the tridentate nitrogen-containing ligand L is tris(4-pyridyl)amine.

2. The method of separating propyne and propadiene of claim 1, wherein, In the mixed gas containing propyne and propadiene, the molar content of propyne is between 10% and 90%, based on 100% of the total molar amount of propyne and propadiene.

3. The method of separating propyne and propadiene of claim 2, wherein, In the mixed gas containing propyne and propadiene, the molar content of propyne is 50% to 90%, based on 100% of the total molar amount of propyne and propadiene.

4. The method of separating propyne and propadiene of claim 1, wherein, The mixed gas containing propyne and propadiene is contacted with a metal organic framework material with special window active sites, and the contact mode is any one or a combination of more than one of fixed bed adsorption, fluidized bed adsorption, and moving bed adsorption.

5. The method of separating propyne and propadiene of claim 4, wherein, The contact mode of the mixed gas containing propyne and propadiene with the metal organic framework material with special window active sites is fixed bed adsorption, which comprises: under a set adsorption temperature and pressure, the mixed gas containing propyne and propadiene enters a fixed bed adsorption column filled with the metal organic framework material at a set flow rate, and the propadiene component preferentially penetrates the bed layer, and high-purity propadiene gas is directly obtained from the outlet of the adsorption column.

6. The method of separating propyne and propadiene of claim 1, wherein, The adsorption temperature is 0-40°C.

7. The method of separating propyne and propadiene of claim 1, wherein, The adsorption pressure is 0.5-10 atm.

8. The method of separating propyne and propadiene of claim 1, wherein, After the metal organic framework material selectively adsorbs propyne in the mixed gas to realize the separation of propadiene and propyne, the propyne is desorbed at a temperature of 30-100°C and a pressure of 0-1 atm to regenerate the metal organic framework material.

9. Use of a metal-organic framework material having a special windowing site for the separation of propyne and propadiene, characterized in that, The metal organic framework material selectively adsorbs propyne in the mixed gas containing propyne and propadiene after being contacted with the mixed gas, so that the separation of propadiene and propyne is realized. The metal organic framework material is formed by coordination of a hexacoordinated divalent metal cation Cu 2+ with a tridentate nitrogen-containing ligand L to form a cage structure, and then a high-coordination-number divalent inorganic anion ZrF6 2- bridging to form a structure with a special window function site; The molecular formula of the metal organic framework material is (CuZrF6)3L4, wherein the tridentate nitrogen-containing ligand L is tris(4-pyridyl)amine.

10. Use according to claim 9, characterized in that, The separation selectivity of the metal organic framework material for a mixed gas of propyne and propadiene with a molar ratio of 1:1 at 298K and 100kPa is 6.

03. The separation potential of the metal organic framework material for a propyne and propadiene mixed gas of a molar ratio of 1 : 1 is 5.72 mmol propadiene / cm 3 Metal organic framework material.

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