ZEOLITE ADSORBENT MATERIAL, METHOD OF PREPARATION AND USE FOR NON-CRYOGENIC SEPARATION OF INDUSTRIAL GASES

Abstract

Provided is a zeolitic adsorbent material. The material is based on LSX zeolite crystals the particle size distribution of which is characterized by a peak width (2) in a range from 6.0 to 20.0, limits included, for a number average diameter (d50) in a range from 0.5 m to 20.0 m. The material has an Si/Al atomic ratio comprised in a range from 1.00 to 1.15, limits included. The lithium content of the material, expressed by weight of Li.sub.2O, is in a range from 9% to 12% by weight relative to the total weight of the material. The material has a non-zeolitic phase (NZP) content such that 0<NZP8% by weight relative to the total weight of the material.

Claims

1. Zeolitic adsorbent material: based on LSX zeolite crystals the particle size distribution of which is characterised by a peak width (2) comprised in a range from 6.0 to 20.0, limits included, for a number average diameter (d.sub.50) comprised in a range from 0.5 m to 20.0 m, with an Si/Al atomic ratio comprised in a range from 1.00 to 1.15, limits included, the lithium content of which, expressed by weight of Li.sub.2O, is comprised in a range from 9% to 12% by weight relative to the total weight of the zeolitic adsorbent material, and with a non-zeolitic phase (NZP) content such that 0<NZP8% by weight relative to the total weight of the zeolitic adsorbent material.

2. Material according to claim 1, for which the particle size distribution is a Gaussian distribution with a peak width (2) comprised in a range from 8.0 to 18.0, limits included.

3. Material according to claim 1, in which the number-average diameter (d.sub.50) of the LSX zeolite crystals is comprised in a range from 1.0 m to 15.0 m.

4. Material according to claim 1, in which the amount of non-zeolitic phase (NZP) is 0.5%NZP4% by weight relative to the total weight of the zeolitic adsorbent material.

5. Material according to claim 1, which is in the form of beads with a volume mean diameter of between 0.05 mm and 5 mm, limits included.

6. Material according to claim 1, having an apparent density comprised in a range from 0.58 kg/m.sup.3 to 0.80 kg/m.sup.3.

7. Method for preparing the zeolitic adsorbent material according to claim 1, comprising the following steps: a/ agglomerating LSX zeolite crystals with an agglomerating binder and a silica source, followed by shaping, drying and calcining of the agglomerated crystals, b/ zeolitising the binder by the action of a basic alkaline solution, c/ replacing the major part of the cations at the exchangeable sites of the product obtained in step b/ by lithium cations, followed by washing and drying of the product thus treated, and d/ optional drying, and activating the zeolitic adsorbent material obtained.

8. Method according to claim 7, in which, at the end of step a/, the amount by weight of LSX zeolite crystals is comprised in a range from 75% to 90% by weight relative to the total weight of said product obtained at the end of step a/ and the amount of zeolitisable clay is comprised in a range from 5% to 25% by weight relative to the total weight of said product obtained at the end of step a/.

9. Method according to claim 7, in which the silica source is added in an amount such that it represents, at the end of step a/, from 0.1% to 10% by weight, relative to the total weight of said product obtained at the end of step a/.

10. Method according to claim 7, in which the agglomerating binder contains at least 80% by weight of zeolitisable clay(s), said zeolitisable clays belonging to the class of kaolinites, halloysites, nacrites, dickites, kaolins and/or metakaolins.

11. Method according to claim 1, in which the lithium exchange is carried out such that the lithium content (expressed as lithium oxide Li.sub.2O) of the zeolitic adsorbent material of the invention is between 9% and 12% by weight relative to the total weight of the zeolitic adsorbent material.

12. Use of the material according to claim 1 as nitrogen-adsorbent material for the separation of the gases in air and as nitrogen-adsorbent and/or carbon monoxide-adsorbent material for the purification of hydrogen.

13. Use according to claim 12 in PSA, VPSA or VSA adsorption methods for N.sub.2/O.sub.2 separation in industrial gases, and for N.sub.2/O.sub.2 separation in apparatus for producing medical oxygen.

14. Consumable cartridge of zeolitic adsorbent, comprising at least one zeolitic adsorbent material according to any of claim 1.

15. Oxygen concentrator for respiratory assistance, which is transportable, mobile, comprising at least one zeolitic adsorbent material according to claim 1.

Description

EXAMPLE 1 (COMPARATIVE): PREPARATION OF A ZEOLITIC ADSORBENT MATERIAL WITH LSX CRYSTALS OF 2=1.2 and of d.SUB.50.=1.3 m, According to FR2925478

[0099] In the following example, the masses given are expressed as calcined equivalents.

[0100] A homogeneous mixture is prepared, consisting of 1700 g of LSX zeolite crystals of 2=1.2 and of d.sub.50=1.3 m, as described in FR2925478, with a shear rate of 135 s.sup.1, 300 g of Charentes kaolinite, and an amount of water such that the loss on ignition of the paste before shaping is 39%. The paste thus prepared is used on a granulator plate to produce beads of agglomerated zeolitic adsorbent material.

[0101] The beads obtained are selected by sieving in order to recover beads with a diameter comprised in a range from 0.3 mm to 0.8 mm and a volume-average diameter of 0.50 mm.

[0102] The beads are dried overnight in a ventilated oven at 80 C. They are subsequently calcined at 550 C. for two hours under a flow of decarbonated dry air.

[0103] After cooling, 100 g of these (agglomerated) beads are immersed in 750 mL of aqueous sodium hydroxide solution with a concentration of 100 g/L.sup.1, at a temperature set at 98 C. The system is held at temperature with gentle stirring for three hours. The agglomerates are then washed with water until the final pH of the wash water is close to 10.

[0104] Next, five successive exchanges are carried out using 1 M lithium chloride solutions, in a proportion of 20 ml/g.sup.1 of solid. Each exchange is continued for four hours at 100 C., and intermediate washes are carried out, thus making it possible to remove the excess salt at each step. In the final step, four washes are carried out at ambient temperature, in a proportion of 20 ml/g.sup.1.

[0105] The beads are dried overnight in a ventilated oven at 80 C. They are subsequently activated at 550 C. for two hours under a blanket of decarbonated dry air.

[0106] The lithium oxide Li.sub.2O content, determined by ICP-AES, is 10.6% by weight relative to the total weight of the zeolitic adsorbent material. The volume-average diameter of the beads is 0.50 mm. The mechanical bulk crushing strength of the beads of lithium-exchanged LSX zeolite is 1.4 MPa, the apparent density is 0.58 kg/m.sup.3, the Si/Al ratio of the zeolitic material is 1.02, and the NZP is 3%

[0107] The mass adsorption capacity at 25 C. under 1 bar is 24.7 Ncm.sup.3 g.sup.1.

EXAMPLE 2 (ACCORDING TO THE INVENTION): PREPARATION OF A ZEOLITIC ADSORBENT MATERIAL WITH LSX CRYSTALS OF 2=11.6 AND OF D.SUB.50.=5.6 M

[0108] A homogeneous mixture is prepared consisting of 1700 g of LSX zeolite crystals of 2=11.6 and of d.sub.50=5.6 m, as described in FR2925478 but with a shear rate of 5 s.sup.1, 300 g of Charentes kaolinite, 40 g (as calcined equivalents) of colloidal silica sold under the name Klebosol 30, and an amount of water such that the loss on ignition of the paste before shaping is 39%.

[0109] The zeolitic adsorbent material is subsequently prepared according to the protocol described in example 1.

[0110] The lithium oxide Li.sub.2O content, determined by ICP-AES, is 10.7% by weight relative to the total weight of the zeolitic adsorbent material. The volume-average diameter of the beads is 0.50 mm. The mechanical bulk crushing strength (BCS) of the beads of lithium-exchanged LSX zeolite is 2.6 MPa, the apparent density is 0.63 kg/m.sup.3, the Si/Al ratio of the zeolitic material is 1.03, and the NZP is 2.7%.

[0111] The mass adsorption capacity at 25 C. under 1 bar is 27 Ncm.sup.3 g-1.

EXAMPLE 3: N.SUB.2./O.SUB.2 .SEPARATION TESTS ON A FIXED BED OF ADSORBENT WITH PRESSURE SWING ADSORPTION (PSA)

[0112] An N.sub.2/O.sub.2 separation test is carried out by adsorption in a single column in accordance with the principle presented in Adsorbent particle size effects in the separation of air by rapid pressure swing adsorption, by E. Alpay et al., Chemical Engineering Science, 49(18), 3059-3075, (1994).

[0113] FIG. 1 describes the assembly produced. A column (1) of internal diameter equal to 27.5 mm and of internal height equal to 600 mm, filled with zeolitic adsorbent material (2), is intermittently fed with dry air (3) by means of a valve (4). The time for feeding the column (1) with the flow (3) is called adsorption time. When the column (1) is not fed with dry air, the flow (3) is discharged into the atmosphere by the valve (5). The zeolitic adsorbent material preferentially adsorbs nitrogen, such that an oxygen-enriched air leaves the column via the check valve (6), and moves to a buffering tank (7). A regulating valve (8) continuously delivers the gas at the outlet (9) at a constant flow rate fixed at 1 NL/min.sup.1.

[0114] When the column (1) is not fed, i.e., when the valve (4) is closed and the valve (5) is open, the column (1) is depressurised by the valve (10) to the atmosphere (11), for a period called the desorption time. The adsorption and desorption phases follow on from one another. The durations of these phases are fixed from one cycle to the next and they are adjustable. Table 1 shows the respective state of the valves according to the adsorption and desorption phases.

TABLE-US-00001 TABLE 1 Adsorption phase Desorption phase Valve (4) open Valve (4) closed Valve (5) closed Valve (5) open Valve (10) closed Valve (10) open

[0115] When the column (1) is not fed, i.e., when the valve (4) is closed and the valve (5) is open, the column (1) is depressurised by the valve (10) to the atmosphere (11), for a period called the desorption time. The adsorption and desorption phases follow on from one another. The durations of these phases are fixed from one cycle to the next and they are adjustable. Table 1 shows the respective state of the valves according to the adsorption and desorption phases.

[0116] The tests are carried out in succession with the zeolitic adsorbent materials in example 1 and example 2. The column is loaded at constant volume, with respectively 219 g and 228.5 g of adsorbent materials. The pressure at the inlet is set at 280 kPa relative.

[0117] The flow rate at the outlet is set at 1 NL/min.sup.1. The adsorption time is set at 1 s. The adsorption time varies from 2 s to 4.5 s.

[0118] The oxygen concentration at the outlet (9) is measured using a Servomex 570A oxygen analyser.

[0119] FIG. 2 shows the oxygen content of the flow produced at the outlet (9) according to the desorption time set for the materials in example 1 and example 2. The material in example 2 proves to be much more effective in terms of oxygen content of the gas produced than the solid in example 1.