Zeolite adsorbent based on mesoporous zeolite
View Patent ↗The present invention relates to a zeolite adsorbent having an external surface area of between 20 m 2 ·g −1 and 70 m 2 ·g −1 , a mesopore volume (V meso ) of less than or equal to 0.20 cm 3 ·g −1 , and a content of non-zeolite phase (NZP) of less than or equal to 6%, and in which at least one of its dimensions is greater than or equal to 30 μm. The invention also relates to the process for preparing said zeolite materials in agglomerated form and to the uses thereof for gas-phase or liquid-phase separation operations.
1. A mesoporous zeolite adsorbent having the following characteristics when the zeolite adsorbent is in its sodium-exchanged form:
an external surface area, measured by nitrogen adsorption, of between 20 m 2 ·g −1 and 70 m 2 ·g −1 , limits included,
a mesopore volume (V meso ) such that 0<V meso ≤0.20 cm 3 ·g −1 , measured by nitrogen adsorption,
a content of non-zeolite phase (NZP) such that 0≤NZP 6%, by weight relative to the total weight of the adsorbent, and
at least one dimension which is greater than or equal to 30 μm.
2. A zeolite adsorbent according to claim 1 , having exchangeable cationic sites occupied by one or more ions of groups IA, IIA, IIIA and IIIB of the periodic table of elements, trivalent ions of the elements of the lanthanide series, zinc(II) ion, copper(II) ion, chromium(III) ion, iron(III) ion, ammonium ion, hydronium ion or mixtures of two or more of them, in any proportions.
3. A zeolite adsorbent according to claim 1 , having exchangeable cationic sites occupied by one or more ions selected from the group consisting of hydronium, lithium, sodium, potassium, cesium, magnesium, calcium, strontium, barium, praseodymium and lanthanum, and mixtures of two or more of them in any proportions.
4. A zeolite adsorbent according to claim 1 , having, in its sodium-exchanged form, a bulk density of between 0.4 g·cm −3 and 1.0 g·cm −3 limits included, said bulk density being measured as described in standard DIN 8948/7.6.
5. A zeolite adsorbent according to claim 1 , comprising at least one mesoporous zeolite selected from the group consisting of mesoporous zeolites of LTA, EMT and FAU structure with an Si/Al atomic ratio of between 1 and 5.
6. A zeolite adsorbent according to claim 5 , in which said at least one mesoporous zeolite is in the form of crystals of which the number-average diameter, measured with a scanning electron microscope (SEM) is less than 20 μm, limits included.
7. A zeolite adsorbent according to claim 1 , in which the crystals of the zeolite(s) are agglomerated with a binder comprising a zeolitizable clay alone or as a mixture with one or more other zeolitizable or non-zeolitizable clays.
8. A zeolite adsorbent according to claim 1 , in which the crystals of the zeolite(s) are agglomerated with a binder comprising a clay selected from the group consisting of kaolins, kaolinites, nacrites, dickites, halloysites, attapulgites, sepiolites, montmorillonites, bentonites, illites and metakaolins, and mixtures of two or more of them in any proportions.
9. A zeolite adsorbent according to claim 1 , having:
a bulk crushing strength (BCS) measured according to standard ASTM 7084-04 of between 1.0 MPa and 3.5 MPa, for a material with a mean volume diameter (D50), or a length (largest dimension when the material is not spherical), of less than 1 mm, limit excluded,
a grain crushing strength, measured according to standards ASTM D 4179 (2011) and ASTM D 6175 (2013), of between 1.5 daN and 30 daN, for a material with a mean volume diameter (D50), or a length (largest dimension when the material is not spherical), of greater than or equal to 1 mm, limit included.
10. A process for preparing a zeolite adsorbent according to claim 1 , comprising at least the steps of:
a) agglomerating crystals of at least one mesoporous zeolite with a number-average diameter of between 0.1 pm and 20 μm, with an Si/Al atomic ratio of between 1 and 1.4, limits included, and with a mesoporous external surface area, defined by the t-plot method, of between 40 m 2 ·g −1 and 400 m 2 ·g −1 , limits included, with at least one agglomeration binder, optionally one or more additives, and also with an amount of water which allows the shaping of the zeolite adsorbent, thereby obtaining agglomerates;
b) drying the agglomerates at a temperature of between 50° C. and 150° C.;
c) calcining the agglomerates obtained in step b), at a temperature above 150° C., for a few hours;
d) zeolitizing at least one part of the agglomeration binder by bringing the agglomerates obtained in step c) into contact with an alkaline aqueous solution, optionally in the presence of at least one structuring agent;
e) optionally, removing the structuring agent optionally present;
f) optionally cation exchange(s) of the agglomerates obtained in step c) or in step d) by bringing the agglomerates into contact with a solution of at least one alkali metal or alkaline-earth metal salt;
g) then washing and drying of the agglomerates obtained in step d) or e) under the conditions described in step b), and
h) producing the zeolite adsorbent by activating the agglomerates obtained in step f) under the conditions described in step c).
11. A process according to claim 10 , wherein step d) is carried out in the presence of at least one structuring agent.
12. A process according to claim 11 , wherein the structuring agent is [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride.
13. A process according to claim 10 , wherein step a) is carried out in the presence of at least one additive which comprises a source of silica.
14. A process comprising using at least one zeolite adsorbent according to claim 1 , wherein the process is selected from the group consisting of gas-phase and liquid-phase separation operations.
15. A zeolite adsorbent according to claim 1 , wherein the external surface area, measured by nitrogen adsorption, is between 40 m 2 ·g −1 and 60 m 2 ·g −1 , limits included.
16. A zeolite adsorbent according to claim 1 , wherein the mesopore volume (V meso ) is such that 0<V meso ≤0.10 cm 3 ·g −1 , measured by nitrogen adsorption.
17. A zeolite adsorbent according to claim 1 , wherein the content of non-zeolite phase (NZP) is such that 3%≤NZP≤6%, by weight relative to the total weight of said adsorbent.
18. A zeolite adsorbent according to claim 1 , having at least one dimension which is greater than or equal to 80 μm.
19. A zeolite adsorbent according to claim 1 , having, in its sodium-exchanged form, a bulk density of between 0.5 g·cm −3 and 0.9 g·cm −3 limits included, said bulk density being measured as described in standard DIN 8948/7.6.
20. A zeolite adsorbent according to claim 1 , comprising at least one mesoporous zeolite selected from the group consisting of mesoporous zeolites of FAU structure of type X, MSX and LSX.
21. A zeolite adsorbent according to claim 1 , which is in its sodium-exchanged form.
22. A zeolite adsorbent according to claim 21 , which has a degree of sodium ion exchange of greater than 95%.
23. A zeolite adsorbent according to claim 1 , which has an external surface area as measured by the t-plot method of 40 m 2 ·g −1 and 400 m 2 ·g −1 .
24. The process according to claim 13 , wherein the source of silica comprises at least one member selected from the group consisting of colloidal silica, diatomaceous earths, perlites, fly ash, and sand.
25. A separation process comprising contacting a gas phase or a liquid phase with a zeolite adsorbent according to claim 1 .