Method for separating C8 aromatic hydrocarbon isomer mixture

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 2 ] n , where n>4 and n is an integer;

wherein the metal ion M is Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ ;

wherein the inorganic anion A is SiF 6 2− , NbOF 5 2− , TaF 7 2− , ZrF 6 2− , TiF 6 2− , GeF 6 2− , SO 3 CF 3 − , NbF 6 − ;

wherein the organic ligand L is selected from any of the following:

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 2+ or Cu 2+ , the inorganic anion A is NbOF 5 2− , SiF 6 2− or TiF 6 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 2 ] n , where n>4 and n is an integer;

wherein the metal ion M″ is Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ 0;

wherein the inorganic anion A is SiF 6 2− , NbOF 5 2− , TaF 7 2− , ZrF 6 2− , TiF 6 2− , GeF 6 2− , SO 3 CF 3 − , NbF 6 − ;

wherein the organic ligand L is selected from any of the following: