METHOD FOR SEPARATING C8 AROMATIC HYDROCARBON ISOMER MIXTURE

Abstract

The present invention discloses a method of separating C8 aromatic hydrocarbon isomers. The anion-pillared metal-organic framework materials with a pore diameter of 5-10 Å is used as adsorbents to achieve selective adsorption and separation of C8 aromatic hydrocarbon isomers by contacting the C8 aromatic hydrocarbon isomers with the adsorbents; the anion-pillared microporous materials are porous materials formed by metal ion M, inorganic anion A and organic ligand L through coordination bonds, with the general formula of [MAL.sub.2].sub.n, where n>4 and n is an integer; the descried “metal ion M” is Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+; the descried “inorganic anion A” is SiF.sub.6.sup.2−, NbOF.sub.5.sup.2−, TaF.sub.7.sup.2−, ZrF.sub.6.sup.2−, TiF.sub.6.sup.2−, GeF.sub.6.sup.2−, SO.sub.3CF.sub.3.sup.−, NbF.sub.6.sup.−; the descried “organic ligand L” is selected from any of the following:

##STR00001##

Claims

1. A method for separating C8 aromatic hydrocarbon isomers, comprising the steps of using anion-pillared metal-organic framework materials as adsorbents, contacting the adsorbents with C8 aromatic hydrocarbon isomers, thus achieving selective adsorption and separation of a mixture of C8 aromatic hydrocarbon isomers; wherein, the anion-pillared microporous materials are porous materials formed by metal ion M, inorganic anion A and organic ligand L through coordination bonds, with the general formula of [MAL.sub.2].sub.n, where n>4 and n is an integer; wherein the metal ion M is Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+; wherein the inorganic anion A is SiF.sub.6.sup.2−, NbOF.sub.5.sup.2−, TaF.sub.7.sup.2−, ZrF.sub.6.sup.2−, TiF.sub.6.sup.2−, GeF.sub.6.sup.2−, SO.sub.3CF.sub.3.sup.−, NbF.sub.6.sup.−; wherein the organic ligand L″ is selected from any of the following: ##STR00004##

2. The method according to claim 1, wherein the pore size of the anion-pillared metal-organic framework materials disclosed herein is 5-10 Å.

3. The method according to claim 1, wherein the metal ion M is Ni.sup.2+ or Cu.sup.2+, the inorganic anion A is NbOF.sub.5.sup.2−, SiF.sub.6.sup.2− or TiF.sub.6.sup.2−, and the organic ligand L is 4,4′-bipyridine.

4. The method according to claim 1, wherein the mixture of C8 aromatic isomers is gaseous and/or liquid, which contains at least two of p-xylene, m-xylene, o-xylene and ethylbenzene.

5. The method according to claim 1, wherein the contact mode of the descried adsorbent and the C8 aromatic isomer mixture is any one of fixed-bed adsorption and simulated moving bed adsorption.

6. The method according to claim 5, wherein the adsorption temperature is 20-250° C., and the adsorption pressure is 0.1-5 bar.

7. The method according to claim 5, wherein the contact method is fixed-bed adsorption, which specifically comprises the following steps: 1) introducing the mixture of C8 aromatic isomers into a fixed-bed adsorption column, wherein strongly adsorbed C8 components are adsorbed on the adsorbent, and the specific C8 components that are not adsorbed or had low adsorption capacity are first penetrated to obtain the specific C8 components; 2) after the breakthrough and adsorption of the specific C8 components are completed, desorbing the strongly adsorbed C8 components from the adsorbent by means of decompression desorption, heating desorption, desorber desorption or inert gas purging to obtain them.

8. The method according to claim 7, wherein the desorption temperature is 20-250° C.

9. The method according to claim 7, wherein the described specific C8 component is p-xylene, and the mass percent purity is greater than 99.9%.

10. A method of selective adsorption and separation of C8 aromatic hydrocarbon isomers comprising the step of using anion-pillared microporous materials in contact with the C8 aromatic hydrocarbon isomers, wherein the anion-pillared microporous materials are porous materials formed by metal ion M, inorganic anion A and organic ligand L through coordination bonds, with the general formula of [MAL.sub.2].sub.n, where n>4 and n is an integer; wherein the metal ion M″ is Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+O; wherein the inorganic anion A is SiF.sub.6.sup.2−, NbOF.sub.5.sup.2−, TaF.sub.7.sup.2−, ZrF.sub.6.sup.2−, TiF.sub.6.sup.2−, GeF.sub.6.sup.2−, SO.sub.3CF.sub.3.sup.−, NbF.sub.6.sup.−; wherein the organic ligand L is selected from any of the following: ##STR00005##

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows the adsorption isotherms of p-xylene, m-xylene, o-xylene and ethylbenzene at 60° C. (333K) for the anion-pillared microporous material obtained in the example 1.

[0038] FIG. 2 shows the breakthrough curves obtained in the example 2.

[0039] FIG. 3 shows the adsorption isotherms of p-xylene, m-xylene, o-xylene and ethylbenzene at 60° C. (333K) for the anion-pillared microporous material obtained in the example 4.

[0040] FIG. 4 shows the breakthrough curves obtained in the example 5.

[0041] FIG. 5 shows the breakthrough curves obtained in the example 6.

[0042] FIG. 6 shows the breakthrough curves obtained in the example 7.

[0043] FIG. 7 shows the regeneration curves of the breakthrough experiments on adsorbent ZU-61 in the example 8;

[0044] FIG. 8 shows the cycling breakthrough curves obtained in the example 9.

[0045] FIG. 9 shows the crystal structure diagram of the anion-pillared microporous material obtained in example 4 after adsorption of p-xylene.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The present invention would be further explained below in conjunction with the drawings and specific embodiments. And these embodiments are provided for illustration only, not for the purpose of limiting the invention as defined by the appended claims and their equivalents. For unrecited specific conditions of the operation methods in the following examples, it is usually in accordance to the normal conditions, or the conditions recommended by the manufacturer.

Example 1

[0047] An ethylene glycol solution of 4,4′-bipyridylacetylene was mixed with an aqueous solution of 0.27 g Cu(BF.sub.4).sub.2.xH.sub.2O and 0.20 g (NH.sub.4).sub.2SiF.sub.6 under stirring and then heated at 60-70° C. for 1-12 hours. The obtained SIFSIX-1-Cu was further filtered and then washed with methanol. After vacuum activation at 25-80° C. for 2-6 hours, the activated SIFSIX-1-Cu material obtained.

[0048] The adsorption isotherms of p-xylene isomers and ethylbenzene at 60° C. (333K) for SIFSIX-1-Cu are shown in FIG. 1.

Example 2

[0049] The SIFSIX-1-Cu prepared in example 1 was loaded into a 50 mm long column, then the p-xylene, m-xylene, o-xylene and ethylbenzene (1/1/1/1, mass ratio) mixture obtained through nitrogen bubbling was introduced into the column at 20-40 mL/min with an operating temperature of 60° C. The breakthrough curve is shown in FIG. 2, and high-purity p-xylene can be obtained from the effluent gas.

Example 3

[0050] The ternary p-xylene, m-xylene and o-xylene (1/1/1, mass ratio) gas mixture obtained through nitrogen bubbling was introduced into the column of example 2 at 20-40 mL/min with an operating temperature of 60° C. High-purity p-xylene (over 99.9%, mass percentage) can be obtained from the effluent gas.

Example 4

[0051] An ethylene glycol solution of 4,4′-bipyridylacetylene was mixed with an aqueous solution of NiNbOF.sub.5 under stirring and then heated at 60-70° C. for 1-12 hours. The obtained ZU-61 was further filtered and then washed with methanol. After vacuum activation at 25-150° C. for 2-8 hours, the activated ZU-61 material obtained.

[0052] The adsorption isotherms of p-xylene isomers and ethylbenzene at 60° C. for ZU-61 material are shown in FIG. 3.

Example 5

[0053] The ZU-61 prepared in example 4 was loaded into a 50 mm long column, then the p-xylene, m-xylene, o-xylene and ethylbenzene (1/1/1/1, mass ratio) mixture obtained through nitrogen bubbling was introduced into the column at 20-40 mL/min with an operating temperature of 60° C., and high-purity p-xylene can be obtained from the effluent gas. The adsorbed column was purged by N.sub.2 flow for 15 hours and then could be reused. The breakthrough curve shown in FIG. 4 demonstrates that this material can realize the separation of the above-mentioned C8-aromatics.

Example 6

[0054] The ternary p-xylene, m-xylene and o-xylene (1/1/1, mass ratio) gas mixture obtained through nitrogen bubbling was introduced into the column illustrated in the example 5 at 20-40 mL/min with an operating temperature of 60° C. As shown in FIG. 5, high-purity p-xylene (over 99.9%, mass percentage) can be obtained from the effluent gas.

Example 7

[0055] The ternary p-xylene, m-xylene and o-xylene (1/1/1, mass ratio) gas mixture obtained through nitrogen bubbling was introduced into the column illustrated in the Example 5 at 20-40 mL/min with an operating temperature of 120° C. As shown in FIG. 6, high-purity p-xylene (over 99.9%, mass percentage) can be obtained from the effluent gas.

Example 8

[0056] The ternary p-xylene, m-xylene and o-xylene (1/1/1, mass ratio) gas mixture obtained through nitrogen bubbling was introduced into the column illustrated in the example 5 at 20-40 mL/min with an operating temperature of 120° C. High-purity p-xylene (over 99.9%, mass percentage) can be obtained from the effluent gas. The adsorbed column was purged by N.sub.2 flow for 6-15 hours and then could be reused. The regeneration curves of sample are shown in FIG. 7.

Example 9

[0057] The ternary p-xylene, m-xylene and o-xylene (1/1/1, mass ratio) gas mixture obtained through nitrogen bubbling was introduced into the column illustrated in the example 5 at 20-40 mL/min with an operating temperature of 120° C. High-purity p-xylene (over 99.9%, mass percentage) can be obtained from the effluent gas. The adsorbed column was purged by N.sub.2 flow for 6-15 hours and then could be reused. The cycle curves of sample shown in FIG. 8 demonstrate the stability of the material.

[0058] 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.