METHOD FOR THE ADSORPTIVE SEPARATION OF ETHYLENE AND ETHANE USING ULTRAMICROPOROUS METAL-ORGANIC FRAMEWORK

Abstract

The present invention provides a method for the adsorptive separation of C.sub.2H.sub.4 and C.sub.2H.sub.6 using ultramicroporous metal-organic framework material, comprising the following steps that (1) C.sub.2H.sub.4/C.sub.2H.sub.6 mixture is contacted with the ultramicroporous metal-organic framework material; (2) C.sub.2H.sub.4 is preferentially adsorbed and the separation of C.sub.2H.sub.4/C.sub.2H.sub.6 is realized. The described “ultramicroporous metal-organic framework material” has a formula of [M.sub.3L.sub.3A].sub.∞, wherein M represents the metal cation being any one of Cu.sup.2+, Zn.sup.2+, Co.sup.2+, and Ni.sup.2+; L represents the organic linker being any one of 1,2,4-triazole and its derivatives; A represents the oxygen-containing inorganic anion being any one of PO.sub.4.sup.3− and VO.sub.4.sup.3−. The class of ultramicroporous metal-organic frameworks has optimal pore size and pore chemistry, exhibiting both higher uptake capacity and faster adsorption rate for C.sub.2H.sub.4 as compared to C.sub.2H.sub.6, thus C.sub.2H.sub.4 can be preferentially adsorbed by these metal-organic frameworks with high selectivity, and high-purity C.sub.2H.sub.4 can be separated from C.sub.2H.sub.4/C.sub.2H.sub.6 mixtures efficiently.

Claims

1. A method for adsorptive separation of ethylene and ethane using ultramicroporous metal-organic framework material as an adsorbent, comprises the following steps: contacting C.sub.2H.sub.4/C.sub.2H.sub.6 mixture with the ultramicroporous metal-organic framework; adsorbing C.sub.2H.sub.4 from the mixture to separate C.sub.2H.sub.4/C.sub.2H.sub.6; wherein the ultramicroporous metal-organic framework material has a formula of [M.sub.3L.sub.3A].sub.∞; wherein M is metal cations, L is organic linkers, and A is oxygen-containing inorganic anions, in which the organic ligand is 1,2,4-triazole and its derivatives having a formula of: ##STR00005## R is one of H, CH.sub.3, NH.sub.2, SH, F, Cl, and Br; wherein the metal cation is one of Cu.sup.2+, Zn.sup.2+, Co.sup.2+, and Ni.sup.2+; wherein the oxygen-containing inorganic anion is one of PO.sub.4.sup.3− and VO.sub.4.sup.3−.

2. The adsorptive separation method according to claim 1, wherein the ultramicroporous metal-organic framework material has one-dimensional straight pore channels with a periodically expanded and contracted cross-section, wherein the minimum pore size is in the range of 3.0˜4.2 Å, and the pore surface is decorated by high-density oxygen-containing inorganic anions.

3. The adsorptive separation method according to claim 1, wherein the ultramicroporous metal-organic framework material is made by following method, wherein the precursors of metal cations, organic linkers, and oxygen-containing inorganic anions are mixed with water/alcohol solution in alkaline condition, then heated under certain temperatures; wherein the precursors of organic likers and metal cations are in a mole ratio of 1:1˜50:1; wherein the precursors of organic linker and oxygen-containing inorganic anions are in a mole ratio of 1:1˜50:1; wherein the temperature is in the range of 65˜210° C.

4. The adsorptive separation method according to claim 1, wherein the oxygen-containing inorganic anion is PO.sub.4.sup.3−, the metal cation is Zn.sup.2+, and the organic linker is 3-methyl-1,2,4-triazole.

5. The adsorptive separation method according to claim 1, wherein the oxygen-containing inorganic anion is PO.sub.4.sup.3−, the metal cation is Zn.sup.2+, and the organic linker is 3-amino-1,2,4-triazole.

6. The adsorptive separation method according to claim 1, wherein the volume ratio of C.sub.2H.sub.4 and C.sub.2H.sub.6 is in the range of 1:99˜99:1.

7. The adsorptive separation method according to claim 1, wherein C.sub.2H.sub.4/C.sub.2H.sub.6 mixture contacting with the ultramicroporous metal-organic framework material by any one of fixed-bed adsorptive separation, fluidized-bed adsorptive adsorption, and moving-bed adsorptive.

8. The adsorptive separation method according to claim 1 wherein the separation of C.sub.2H.sub.4 and C.sub.2H.sub.6 is implemented by a fixed-bed adsorptive separation, which comprises the following steps: (1) under set adsorption temperature and pressure, the ethylene and ethane mixture entering the fixed bed adsorption column filled with ultramicroporous metal organic frame material at a set flow rate, and the ethane component preferentially penetrating the bed, ethane being obtained directly from the outlet of the adsorption column; (2) enriching the ethylene component in the bed, and after the ethylene component penetrating, obtaining the ethylene gas through desorption.

9. The adsorptive separation method according to claim 8, wherein the temperature for the adsorption process is in the range of −50˜100° C., and the pressure is in the range of 0˜10 bar.

10. The adsorptive separation method according to claim 8, wherein the temperature for the desorption process is in the range of 25˜450° C., and the pressure is in the range of 0˜1 bar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 shows the powder X-ray diffraction pattern of the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0036] FIG. 2 shows the thermal gravimetric analysis curve of the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0037] FIG. 3 shows the adsorption isotherms of C.sub.2H.sub.4 and C.sub.2H.sub.6 at 298 K on the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0038] FIG. 4 shows the time-dependent adsorption curves of C.sub.2H.sub.4 and C.sub.2H.sub.6 at 298 K and 0.4 bar on the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0039] FIG. 5 shows the adsorption isotherms of C.sub.2H.sub.4 and C.sub.2H.sub.6 at 273 K on the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0040] FIG. 6 shows the time-dependent adsorption curves of C.sub.2H.sub.4 and C.sub.2H.sub.6 at 273 K and 0.4 bar on the ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0041] FIG. 7 shows the C.sub.2H.sub.4 adsorption isotherms at 298 K on water/air treated Zn-Atz-PO.sub.4 synthesized in exampled 1.

[0042] FIG. 8 shows the breakthrough curves of the ethylene/ethane mixed gas (volume ratio 50:50) obtained in example 3.

[0043] FIG. 9 shows the structure of the ultramicroporous metal-organic framework described in the present invention (wherein a and b are from two different angles).

SPECIFIC EMBODIMENTS OF THE INVENTION

Example 1

[0044] The method described in the literature (Angewandte Chemie, 2012, 124(8): 1862-1865.) was used to synthesize the ultra-microporous metal organic frame material Zn-Atz-PO.sub.4 by using phosphoric acid, Zn(OH).sub.2.2ZnCO.sub.3 and 3-amino-1,2,4-triazole as raw materials. The powder X-ray diffraction pattern of Zn-Atz-PO.sub.4 is shown in FIG. 1, which agrees well with the literature report. The narrowest part of the material pore size is 3.8 Å. The thermal gravimetric analysis curve of Zn-Atz-PO.sub.4 is presented in FIG. 2, which suggests a high thermal decomposition temperature of nearly 420° C.

[0045] The adsorption isotherms and time-dependent adsorption profiles of C.sub.2H.sub.4 and C.sub.2H.sub.6 on Zn-Atz-PO.sub.4 were collected at 273 K and 298 K as can be seen from FIG. 3-6. The results indicate that the metal-organic framework simultaneously presents higher equilibrium uptake capacity and faster adsorption rate for C.sub.2H.sub.4 in contrast to C.sub.2H.sub.6. Under 273 K, the thermodynamic selectivity and kinetic selectivity (C.sub.2H.sub.4/C.sub.2H.sub.6) of Zn-Atz-PO.sub.4 is calculated to be 4 and 27, respectively, leading to an excellent equilibrium-kinetics combined selectivity of 20, exceeding ITQ-55 (˜6), the best material for kinetic separation of ethylene and ethane.

[0046] The obtained Zn-Atz-PO.sub.4 material was exposed to air (25° C., relative humidity 70%) for 60 days or soak in water for 48 hours. Then the material was analyzed by X-ray diffraction, and the adsorption isotherm of ethylene on the material at 298 K was measured again. The results were shown in FIG. 1 and FIG. 7. The results showed that the Zn-Atz-PO.sub.4 material exposed to water and air environment for a long time can still maintain a complete crystal structure, and compared with the newly synthesized sample, the ethylene adsorption capacity does not decrease significantly, indicating that Zn-Atz-PO.sub.4 has excellent stability.

Example 2

[0047] CoCO.sub.3, Na.sub.3VO.sub.4, and 3-chloro-1H-1,2,4-triazole with a mass ratio of 1:1:4 were firstly poured into an aqueous solution comprising H.sub.2O and ethanol in volume ratio of 1:1, followed by adjusting the pH of the resulting mixture to 8.5 using hydrochloric acid. After that, the mixture was placed in an oven under 120° C. for 48 hours, then after reaction, the mixture was cooled to room temperature naturally. The precipitation was further collected by filtration and washed with methanol. Last, the product was heated at 100° C. under high vacuum for 12 hours to obtain the ultramicroporous metal-organic framework Co-Cltz-VO.sub.4.

[0048] The as-synthesized ultramicroporous metal-organic framework Co-Cltz-VO.sub.4 was packed into a fixed-bed sorption column with a length of 5 cm. Then, breakthrough experiment was carried out by introducing C.sub.2H.sub.4/C.sub.2H.sub.6 mixture (90:10, v/v) into the column under 298 K and 8 bar with a flow rate of 2 mL min.sup.−1. The slow-diffusing C.sub.2H.sub.6 component flowed out of the column firstly, and high-purity C.sub.2H.sub.6 (99.99%) can be directly obtained from the outlet. The flow of C.sub.2H.sub.4/C.sub.2H.sub.6 gas mixture was turned off upon C.sub.2H.sub.4 broke through the column. After that, the column was purged with 5 mL of He, then the column pressure was reduced to less than 0.2 bar, so that C.sub.2H.sub.4 with a high purity of 95% can be released from the column and the regeneration of Co-Cltz-VO.sub.4 can be achieved.

Example 3

[0049] The ultramicroporous metal-organic framework Zn-Atz-PO.sub.4 synthesized in example 1 was packed into a fixed-bed sorption column with a length of 5 cm, and breakthrough experiment was then carried out under 273 K and 1 bar by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6 mixture (50:50, v/v) into the column with a rate of 0.5 mL min.sup.−1. As can be seen from the obtained breakthrough curves presented in FIG. 8, high-purity C.sub.2H.sub.6 (99.999%) flowed out of the column quickly after 27 min, while C.sub.2H.sub.4 was continuously adsorbed by Zn-Atz-PO.sub.4 until its breakthrough point of 70 min. After that, the C.sub.2H.sub.4/C.sub.2H.sub.6 gas flow was turned off. The column was further purged with 5 mL of high-purity C.sub.2H.sub.4 produced in exampled 2, followed by decreasing the column pressure to <0.05 bar and heating the column to 65° C., so that C.sub.2H.sub.4 with a high purity of 99% can be released from the column and the regeneration of Zn-Atz-PO.sub.4 can be realized.

Example 4

[0050] After Zn-Atz-PO.sub.4 was regenerated as described example 3, breakthrough experiment was again carried out on the same fixed bed by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6/N.sub.2 mixture (90:5:5, v/v/v) into the column under 273 K and 2 bar with a rate 1.0 mL min.sup.−1. Upon the experiment started, N.sub.2 flowed out of the column immediately due to steric effect. Next, C.sub.2H.sub.6 also broke through and high-purity C.sub.2H.sub.6 (>95%) can be directly obtained from the outlet. After C.sub.2H.sub.4 penetrated the column, the C.sub.2H.sub.4/C.sub.2H.sub.6/N.sub.2 flow was turned off. The column was further purged with 10 mL of high-purity C.sub.2H.sub.4 produced in example 2, and then the column pressure was reduced to <0.02 bar, so that C.sub.2H.sub.4 adsorbed in the fixed bed with a high purity of 98% can be released and the regeneration of Zn-Atz-PO.sub.4 can be accomplished.

Example 5

[0051] Zn(OH)2.2ZnCO.sub.3, 3-methyl-1H-1,2,4-triazole, and phosphoric acid (85% water solution) with a mass ratio of 1:4:0.35 were poured into an aqueous solution comprising H.sub.2O and of ethanol in volume ratio of 1:1, followed by adjusting the pH of the resulting mixture to 7.5 using aqueous ammonia. After that, the mixture was placed in an oven under 180° C. for 48 hours, then cooled to room temperature naturally. The precipitation was further collected by filtration and washed with methanol. Last, the product was heated at 100° C. under high vacuum for 12 hours to obtain the ultramicroporous metal-organic framework Zn-Ctz-PO.sub.4.

[0052] The adsorption isotherms of C.sub.2H.sub.4 and C.sub.2H.sub.6 on the resultant Zn-Ctz-PO.sub.4 were measured at 298 K. Under a pressure of 1 bar, the equilibrium uptake capacity of C.sub.2H.sub.4 can be 1.5 mmol g.sup.−1, equivalent to three times that of C.sub.2H.sub.6 (0.5 mmol g.sup.−1).

Example 6

[0053] 2NiCO.sub.3.3Ni(OH).sub.2, 1H-1,2,4-triazole and phosphoric acid (85% water solution) with a mass ratio of 1:4:0.35 were poured into an aqueous solution comprising H.sub.2O and ethanol in volume ratio of 1:1, followed by adjusting the pH of the resulting mixture to 7.5 using aqueous ammonia. After that, the mixture was placed in an oven under 180° C. for 72 hours, then cooled to room temperature naturally. The precipitation was further collected by filtration and washed with methanol. Last, the product was heated at 100° C. under high vacuum for 12 hours to obtain the metal-organic framework Ni-Tz-PO.sub.4.

[0054] The as-synthesized Ni-Tz-PO.sub.4 was packed into a fixed-bed sorption column with a length of 5 cm, and then breakthrough experiment was carried out by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6 mixture (85:15, v/v) into the column under 263 K and 10 bar with a rate of 2 mL min.sup.−1. During this period, high-purity C.sub.2H.sub.6 (99.999%) can be directly harvested from the outlet of the column. After C.sub.2H.sub.4 broke through, the flow of C.sub.2H.sub.4/C.sub.2H.sub.6 mixture was turned off. The column was heated to 100° C. with the pressure reduced to less than 1 bar, so that the adsorbed C.sub.2H.sub.4 component with a purity of >93% can be released from the column. The recovery rate of C.sub.2H.sub.4 can be 75%.

Example 7

[0055] Cu.sub.2(OH).sub.2CO.sub.3, 3-bromo-1H-1,2,4-triazole and phosphoric acid with a mass ratio of 1:4:0.4 were poured into an aqueous solution comprising 2 mL of H.sub.2O and 2 mL of butanol, followed by adjusting the pH of the resulting mixture to 7.5 using aqueous ammonia. After that, the mixture was placed in an oven under 180° C. for 48 hours, then cooled to room temperature naturally. The precipitation was further collected by filtration and washed with methanol. Last, the product was heated at 100° C. under high vacuum for 12 hours to obtain the ultramicroporous metal-organic framework Cu-Brtz-PO.sub.4.

[0056] The as-synthesized Cu-Brtz-PO.sub.4 was shaped into 1˜2 mm pellets by extruding, which were then packed into a fluidized-bed sorption column. Breakthrough experiment was carried out by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6 mixture (10:90, v/v) into the column under 313 K and 5 bar with a rate of 2 mL min.sup.−1. During this period, high-purity C.sub.2H.sub.6 (99.99%) can be directly obtained from the outlet of the sorption column. After C.sub.2H.sub.4 broke through, the flow of C.sub.2H.sub.4/C.sub.2H.sub.6 mixture was turned off. The column was purged with 10 mL of high-purity C.sub.2H.sub.4 produced in example 2, followed by reducing the column pressure to less than 0.1 bar, so that the adsorbed C.sub.2H.sub.4 component with a purity of >95% can be released from the adsorbent.

Example 8

[0057] Zn(OH).sub.2.2ZnCO.sub.3, 3-fluoro-1H-1,2,4-triazole and phosphoric acid (85% water solution) with a mass ratio of 1:4:0.35 were poured into an aqueous solution comprising H.sub.2O and methanol in volume ratio of 1:1, followed by adjusting the pH of the resulting mixture to 7.5 using aqueous ammonia. After that, the mixture was placed in an oven under 180° C. for 48 hours, then cooled to room temperature naturally. The precipitation was further collected by filtration and washed with methanol. Last, the product was heated at 100° C. under high vacuum for 12 hours to obtain the ultramicroporous metal-organic framework Zn-Ftz-PO.sub.4. The as-synthesized Zn-Ftz-PO.sub.4 was shaped into 1˜2 mm pellets by extruding, which were then packed into a moving-bed sorption column. Breakthrough experiment was conducted under 273 K and 4 bar by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6/CH.sub.4 mixture (90:5:5, v/v/v) into the column with a rate of 4 mL min.sup.−1. After C.sub.2H.sub.4 eventually penetrated the sorption column, the C.sub.2H.sub.4/C.sub.2H.sub.6/CH.sub.4 flow was turned off. Then, high-purity C.sub.2H.sub.4 (>95%) can be leased from the metal-organic framework by heating the column to 100° C., and the regeneration of Zn-Ftz-PO.sub.4 can be realized at the same time.

Example 9

[0058] Zn(OH).sub.2.2ZnCO.sub.3, 3-mercapto-1,2,4-triazole and phosphoric acid (85% aqueous solution) in a mass ratio of 1:4:0.35 were added into a 1:1 volume ratio of water/methanol mixed solvent and stirred evenly in the medium, and ammonia water was added to adjust the pH of the reaction solution to 7.5, and then the mixture was placed in an oven at 180° C. for 48 hours. After the reaction, the obtained solid product was collected by suction filtration, washed with methanol several times, and the sample was activated at 100° C. in a vacuum environment for 12 hours to obtain the metal organic framework material Zn-Stz-PO.sub.4.

[0059] The as-synthesized Zn-Stz-PO.sub.4 was packed into a fixed-bed sorption column with a length of 5 cm, and breakthrough experiment was carried under 323 K and 2 bar by introducing a flow of C.sub.2H.sub.4/C.sub.2H.sub.6/CO.sub.2 mixture (90:9:1, v/v/v) into the column with a rate of 1 mL min.sup.−1. During this period, high-purity C.sub.2H.sub.6 (99.9%) can be continuously harvested from the outlet of the column. After C.sub.2H.sub.4 eventually broke through, the flow of C.sub.2H.sub.4/C.sub.2H.sub.6/CO.sub.2 mixture was turned off. The column was purged with 5 mL of high-purity C.sub.2H.sub.4 produced in example 2, followed by reducing the column pressure to less than 0.05 bar, so that the adsorbed C.sub.2H.sub.4 with a purity of (97%) can be released from the bed, and the regeneration of Zn-Stz-PO.sub.4 can be realized.

[0060] Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Although only the selected embodiments have been chosen to illustrate the present invention, the all involved change or modification without departing from the scope of the invention as defined in the appended claims are covered in this invention.