Metal-organic framework for adsorptive separation of acetylene/ethylene mixture and preparation method therefor

Abstract

The present invention provides a metal-organic framework material for the adsorptive separation of acetylene/ethylene mixture and preparation method therefor. The metal-organic framework material is named TJE-2 with a chemical formula of [Ni(pyc)(apyz)].sub.n, wherein, Ni represents nickel as a metal center, pyc represents the organic ligand 1H-pyrazole-4-carboxylic acid, and apyz represents the organic ligand 2-aminopyrazine. The preparation method is as follows: thoroughly dissolving pyc, apyz and Ni(NO.sub.3).sub.2.Math.6H.sub.2O, transferring the mixture to a pressure-resistant closed container for heating reaction, followed by solvent exchange and activation to obtain a homogeneous powder material. The ultra-microporous metal-organic framework material prepared by the present invention features a significantly high C.sub.2H.sub.2 adsorption capacity, good selectivity, and low raw material costs, and therefore can realize C.sub.2H.sub.2/C.sub.2H.sub.4 separation at lower costs.

Claims

1. A metal-organic framework material for adsorptive separation of acetylene/ethylene mixture, wherein the metal-organic framework material is named TJE-2 with a chemical formula of [Ni(pyc).sub.3(apyz).sub.2].sub.n, wherein Ni represents nickel as a metal center, pyc represents an organic ligand 1H-pyrazole-4-carboxylic acid (structural formula: ##STR00003## and apyz represents an organic ligand 2-aminopyrazine (structural formula: ##STR00004## and wherein the metal-organic framework material is 6-coordinated without forming open metal sites, each metal center being coordinated with: one N atom from a first 1H-pyrazole-4-carboyxlic acid ligand, one N atom from a second 1H-pyrazole-4-carboyxlic acid ligand, two O atoms from a third 1H-pyrazole-4-carboyxlic acid ligand, one N atom from a first 2-aminopyrazine ligand, and one N atom from a second 2-aminopyrazine ligand.

2. The metal-organic framework material according to claim 1, wherein the metal-organic framework material TJE-2 has ultra-microporous periodic one-dimensional channels, wherein the pore diameter of the channels is 4.3-6, and wherein electronegative oxygen atoms, pyrazine rings and amino groups are distributed on the channel surface.

3. A method for preparing the metal-organic framework material according to claim 1, comprising the following steps: S1: dissolving the organic ligands 1H-pyrazole-4-carboxylic acid and 2-aminopyrazine in an organic solvent under stirring, and then adding and dissolving Ni(NO.sub.3).sub.2.Math.6H.sub.2O into the organic solvent by stirring or ultrasonic vibration to obtain a mixture comprising the organic ligands and Ni(NO.sub.3).sub.2.Math.6H.sub.2O dissolved in the organic solvent; S2: transferring the mixture obtained in step S1 to a pressure-resistant closed container, and heating the mixture to 80-100° C. for 24-48 h; S3: cooling the heated mixture to room temperature, obtaining a homogeneous powder material from the cooled mixture by filtration, and then solvent-exchanging the powder material with methanol; S4: filtrating the solvent-exchanged powder material and then heating the filtrated solvent-exchanged powder material under vacuum at 80-100° C. for 24-48 h to completely remove solvent molecules in the channels, thereby obtaining the metal-organic framework material.

4. The method according to claim 3, wherein the molar ratio of the organic ligand 1H-pyrazole-4-carboxylic acid, the organic ligand 2-aminopyrazine, and Ni(NO.sub.3).sub.2.Math.6H.sub.2O is 1:1-2:1-5 in step S1.

5. The method according to claim 3, wherein the organic solvent is composed of methanol and N,N-dimethylformamide, and the volume ratio of methanol to N,N-dimethylformamide in the organic solvent is 1:0.5-2 in step S1.

6. The method according to claim 3, wherein the closed container in step S2 is a closed glass reaction bottle with a polytetrafluoroethylene mat or a polytetrafluoroethylene-lined reaction kettle.

7. The method according to claim 3, wherein the solvent exchange is performed for not less than 4 days and not less than 8 times in step S3.

8. The method according to claim 3, wherein the suction filtration processes in steps S3 and S4 are conducted in a glass sand core suction filtration device or a Buchner funnel equipped with an organic phase filter membrane with a pore size of 0.2-0.8 μm.

9. A method for adsorptive separation of acetylene/ethylene mixture using the metal-organic framework material according to claim 1, comprising the following steps: A1: loading the metal-organic framework material in a fixed bed adsorption column with an inner diameter of 6-10 mm, and then introducing a C.sub.2H.sub.2/C.sub.2H.sub.4 mixture at a flow rate of 2-10 mL/min at ambient temperature and pressure; A2: allowing the metal-organic framework material to adsorb and capture the C.sub.2H.sub.2, thus separating C.sub.2H.sub.2 from C.sub.2H.sub.4, and obtaining a C.sub.2H.sub.4 gas with a purity of >99.9% from an exit of the adsorption column; A3: after the metal-organic framework material reaches an uptake capacity, achieving regeneration of the metal-organic framework material by desorption under vacuum for 2-8 h or by heating and purging with inert gas.

10. The method for adsorptive separation of an acetylene/ethylene mixture according to claim 9, wherein the volume ratio of acetylene and ethylene in the C.sub.2H.sub.2/C.sub.2H.sub.4 mixture is 1:99 to 99:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To describe the technical solutions in the embodiments and prior art solutions of the present invention more clearly, the following is a brief description of the drawings that need to be used in the description of the embodiments or prior art. The drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained from these drawings without creative labor for those of ordinary skill in the art.

(2) FIG. 1 is a schematic diagram showing the spatial structure of TJE-2 (where a and b are views observed from two different perspectives).

(3) FIG. 2 shows the powder X-ray diffraction pattern for TJE-2 prepared in Example 1.

(4) FIG. 3 shows the thermogravimetric curves of TJE-2 prepared in Example 1.

(5) FIG. 4 shows sorption isotherms of TJE-2 prepared in Example 1 for C.sub.2H.sub.2 and C.sub.2H.sub.4 at 298 K.

(6) FIG. 5 shows the IAST selectivity of TJE-2 prepared in Example 1 for C.sub.2H.sub.2/C.sub.2H.sub.4 mixture with the ratio of 50:50 and 1:99 at 298 K.

(7) FIG. 6 shows a breakthrough curve of TJE-2 prepared in Example 1 for a C.sub.2H.sub.2/C.sub.2H.sub.4 mixture (with a volume ratio of 50:50) at 298 K.

(8) FIG. 7 shows the powder X-ray diffraction pattern for TJE-2 prepared in Example 2 and after soaking in water.

(9) FIG. 8 shows the powder X-ray diffraction pattern for the scale-up synthesized TJE-2 in Example 3.

DETAILED DESCRIPTION

(10) The following describes the present invention in detail concerning the accompanying drawings and examples. Apparently, the embodiments described are merely some rather than all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the protection scope of the present invention.

EXAMPLE 1

(11) 112 mg of 1H-pyrazole-4-carboxylic acid (pyc) and 95 mg of 2-aminopyrazine (apyz) were weighed and dissolved in 30 mL of MeOH/DMF (i.e., a mixture of methanol and N,N-dimethylformamide, with a volume ratio of 1:1). Then, 290 mg of nickel nitrate hexahydrate was added and thoroughly dissolved by ultrasonic vibration. The mixture was transferred to a 50 mL sealed glass reaction vial, heated to 80° C., and reacted for 24 h. After cooling, the reaction solution was filtered using a glass sand core suction filtration device equipped with an organic phase filter membrane with a pore size of 0.22 μm, and then solvent-exchanged with methanol for 5 days. The solvent was changed twice a day, and 30 mL of fresh methanol was used each time. At last, the powder sample obtained from suction filtration was heated to 80° C. and dried for 24 h in a vacuum oven to obtain activated TJE-2.

(12) The spatial structure of TJE-2 is shown in FIG. 1. The powder X-ray diffraction results were consistent with the simulated result (FIG. 2). The thermogravimetric curves of the material before and after activated (FIG. 3) show that the material has been fully activated.

(13) Sorption isotherms of activated TJE-2 for C.sub.2H.sub.2 and C.sub.2H.sub.4 at 298 K were measured, as shown in FIG. 4. The adsorption capacity of TJE-2 for C.sub.2H.sub.2 (81.1 cm.sup.3.Math.g.sup.−1) was significantly higher than that for C.sub.2H.sub.4 (49.2 cm.sup.3.Math.g.sup.−1). As calculated using the ideal adsorbed solution theory (IAST), the ideal adsorption selectivities of TJE-2 for C.sub.2H.sub.2/C.sub.2H.sub.4 with a ratio of 50:50 and 1:99 at 298 K were 13.3 and 16.0, respectively (FIG. 5), indicating that TJE-2 has the adsorptive separation ability for C.sub.2H.sub.2/C.sub.2H.sub.4.

(14) 0.8 g of the activated TJE-2 material was loaded into an 8 mm fixed bed adsorption column for fixed bed penetration experiments. At 298 K and 1 bar, a C.sub.2H.sub.2/C.sub.2H.sub.4 mixture with a volume ratio of 50:50 was introduced at a total flow rate of 10 mL/min. C.sub.2H.sub.4 gas with a purity of >99.9% was obtained directly from the outlet of the adsorption column

(15) (FIG. 6). After the adsorption of C.sub.2H.sub.2 is saturated, the adsorption column was purged with helium at 80° C. to achieve the desorption of C.sub.2H.sub.2 and the recycling of TJE-2.

EXAMPLE 2

(16) 112 mg of 1H-pyrazole-4-carboxylic acid (pyc) and 190 mg of 2-aminopyrazine (apyz) were weighed and dissolved in 30 mL of MeOH/DMF (with a volume ratio of 1:2). Then, 1.45 g of nickel nitrate hexahydrate was added and thoroughly dissolved by ultrasonic vibration. The mixture was transferred to a 50 mL closed polytetrafluoroethylene reactor, heated to 90° C., and reacted for 36 h. After cooling, the reaction solution was filtered using a Buchner funnel equipped with an organic phase filter membrane with a pore size of 0.6 μm, and then solvent-exchanged with methanol for 4 days. The solvent was changed twice a day, and 30 mL of fresh methanol was used each time. The resulting solution after suction filtration was heated to 90° C. for 36 h in a vacuum oven to obtain activated TJE-2.

(17) 0.2 g of the activated TJE-2 material was soaked in 20 mL of water. After 10 days, the material was dried at 100° C. for 24 h under vacuum. The results of powder X-ray diffraction for the material remained unchanged throughout the process and were consistent with the simulated result, indicating that TJE-2 has excellent water stability (FIG. 7).

EXAMPLE 3

(18) Example 3 provides a scale-up synthesis with gram-scale yield. 3.36 g of 1H-pyrazole-4-carboxylic acid (pyc) and 2.85 g of 2-aminopyrazine (apyz) were weighed and dissolved in 800 mL of MeOH/DMF (with a volume ratio of 1:0.5). Then, 17.4 g of nickel nitrate hexahydrate was added and thoroughly dissolved by ultrasonic vibration. The mixture was transferred to a 1 L closed glass reaction bottle, heated to 100° C., and reacted for 48 h. After cooling, the reaction solution was filtered using a glass sand core suction filtration device equipped with an organic phase filter membrane with a pore size of 0.8 μm, and then solvent-exchanged with methanol for 5 days. The solvent was changed three times a day, and 100 mL of fresh methanol was used each time. The resulting solution after suction filtration was heated to 100° C. for 48 h in a vacuum oven to obtain activated TJE-2. The mass of the activated material was weighed to be 6.85 g, and the yield (calculated based on the ligand pyc) was 86.5%.

(19) The material was analyzed using powder X-ray diffraction, and the results were consistent with the simulated result (FIG. 8), proving that the scaled-up synthesis was successful.

(20) The foregoing embodiments are used only to illustrate the technical solutions of the present invention, but not to limit it. Although the present invention has been described in detail concerning the foregoing embodiments, it should be understood by those of ordinary skill in the art that 1) it is still possible to modify the technical solutions in the above embodiments or to replace some or all of the technical features with equivalent modifications or replacements; 2) these modifications or replacements do not make the essence of the corresponding technical solutions out of the scope of the present invention.