BINDERLESS ADSORBENT FOR SEPARATION OF A GASEOUS STREAM

Abstract

A binderless zeolite adsorbent for separation of oxygen from a gaseous stream. The adsorbent is a blend of a lithium exchanged zeolite 13X, a lithium exchanged low silica zeolite X zeolite, and halloysite clay. Also disclosed is a process of making the binderless zeolite adsorbent. Further disclosed is a process for production of oxygen from a gaseous stream utilizing the binderless zeolite adsorbent.

Claims

1. A binderless adsorbent for separation of a gaseous stream comprising a blend of a lithium exchanged zeolite 13X (Li13X), a lithium exchanged low silica X zeolite (LiLSX), and halloysite clay, wherein the Li13X comprises from about 5 to about 20% of the adsorbent, wherein the LiLSX comprises from an 80 to about 90% of the adsorbent, and wherein the halloysite clay comprises from about 0.1% to 5.0% of the adsorbent, and wherein the adsorbent has a bulk density of at least about 640 g/L, as measured according to DIN/ISO 787.

2. The binderless adsorbent for separation of a gaseous stream of claim 1 wherein the adsorbent exhibits a median pore diameter greater than or equal to 5 microns, a percentage of pores less than 0.1 micron lower than 6.0 percent, and a pore diffusivity (D.sub.r), based on nitrogen pore diffusivity, as described in U.S. Pat. No. 6,500,234 B2 and 6,790,260 B2, greater than 5.0×10.sup.−6 m.sup.2/s.

3. The binderless adsorbent for separation of a gaseous stream of claim 1 wherein the adsorbent exhibits a crush strength greater than 8 N/mm.

4. The binderless adsorbent of claim 1 wherein the adsorbent has a hysteresis factor of at least about 0.6, as measured by the Hg porosimetry method described in U.S. Pat. No. 9,486,732 B2.

5. The binderless adsorbent of claim 1 wherein the adsorbent has a median pore diameter greater than or equal to 5 microns and a hysteresis factor of at least about 0.6, as measured by the Hg porosimetry method described in U.S. Pat. No. 9,486,732 B2.

6. A process of making an adsorbent for separation of a gaseous stream comprising the following steps: providing a low silica X zeolite; mixing said zeolite with a halloysite clay to form a mixture, wherein said halloysite clay comprises from about 5% to about 20% of the mixture; forming shaped products from said mixture; calcining said shaped products; caustically treating said calcined shaped products to convert at least a portion of said halloysite clay to a 13X zeolite; and lithium exchanging the LSX and 13X zeolite of said shaped products to produce the adsorbent.

7. The binderless adsorbent of claim 6 wherein the halloysite clay has a tubular shape with a length from about 0.5-2.0 micron and a diameter of about 50-100 nm.

8. The process of claim 6 wherein halloysite clay comprises from about 0.1 to about 5% of the adsorbent.

9. The process of claim 6 wherein a hydroxide is used for caustically treating the shaped products comprising sodium hydroxide and potassium hydroxide.

10. The process of claim 6 wherein a hydroxide is used for caustically treating the shaped products comprises substantially sodium hydroxide.

11. The process of claim 6 wherein the adsorbent exhibits a median pore diameter greater than or equal to 5 microns, a percentage of pores less than 0.1 micron lower than 6.0 percent, and a pore diffusivity (D.sub.p), based on nitrogen pore diffusivity as described in U.S. Pat. Nos. 6,500,234 B2 and 6,790,260, greater than 5.0×10.sup.−6 m.sup.2/s.

12. The process of claim 6 wherein the adsorbent exhibits a crush strength greater than 8 N/mm.

13. The process of claim 6 wherein from about 60 to about 95% of the halloysite clay is converted into zeolite 13X.

14. The process of claim 6 wherein the adsorbent has a crush strength greater than 8 N/mm, a median pore diameter greater than or equal to 5 microns, and a hysteresis factor of at least about 0.6, as measured by the Hg porosimetry method described in U.S. Pat. No. 9,486,732 B2.

15. The process of claim 6 wherein the low silica X zeolite and the 13X zeolite are lithium exchanged at least about 95%.

16. A process for the production of concentrated oxygen from a gaseous stream utilizing the binderless adsorbent of claim 1.

Description

EXAMPLES

Inventive Example 1

[0053] A low silica zeolite X (2.0 silica/alumina ratio) is mixed with a halloysite clay in a ratio of about 85/15 zeolite to clay. This mixture is then formed into spheres and calcined. These calcined particles are then introduced to a hot (˜90 C) sodium hydroxide solution for several hours to convert the clay into 13X zeolite. The particles are then washed with water to remove excess caustic, and then the particles undergo a lithium ion exchange to at least about 95%. The quantity of the lithium exchanged low silica zeolite X is 85%, the quantity of the lithium exchanged zeolite 13X is 12%, and the quantity of the residual halloysite clay is 3%.

Comparative Sample 1 (C-1)

[0054] A shaped adsorbent containing lithium exchanged low silica X zeolite with an attapulgite binder, as described in columns 3-8 of U.S. Pat. No. 7,300,899.

Comparative Sample 2 (C-2)

[0055] A binderless adsorbent, as described in columns 8 and 9 of U.S. Pat. No. 6,425,940 B1.

Comparative Sample 3 (C-3)

[0056] A shaped adsorbent containing lithium exchanged low silica X zeolite with a silica-based binder, as described in example 2 of U.S. Pat. No. 9,486,732 B2.

Comparative Sample 4 (C-4)

[0057] A binderless shaped adsorbent obtained from Tosoh, which contains LiLSX with a commercial name of NSA-700.

Comparative Sample 5 (C-5)

[0058] A binderless shaped adsorbent obtained from Hanchang, which contains LiLSX.

[0059] In the following Table 1, characteristics of Inventive Example 1 are compared with adsorbents of Comparative Samples C-1, C-2, C-3, C-4, and C-5.

TABLE-US-00001 TABLE 1 Physical Parameters of Inventive Sample I-1 in comparison with Comparative Samples C-1, C-2, C-3, C-4, and C-5 Median Tapped Pore Pore Bulk Crushing Hysteresis Pore Small Sample Diameter.sup.1 Density.sup.2 Strength.sup.3 Factor.sup.4 Diffusivity.sup.5 Pore %.sup.6 I-1 0.6 660 11 0.7 6.46E−6 4.7 C-1 0.3 610 5.6 0.4 4.02E−6 22.0 C-2 0.9 0.2 9.1 C-3 0.5 620 4.8 0.8 4.99E−6 6.4 C-4 0.5 680 6.7 0.4 3.35E−6 11.8 C-5 0.4 611 5.1 0.6 4.79E−6 12.6 .sup.1microns .sup.2g/L .sup.3N/mm .sup.4See description of pore hysteresis factor in U.S. Pat. No. 9,486,732 B2 .sup.5Pore diffusivity(D.sub.p), as described in U.S. Pat. No. 6,500,234 B2 and U.S. Pat. No. 6,790,260 B2. .sup.6pores less than 0.1 micron per mercury porosimetry analysis.

[0060] From the data in Table 1, it is evident that the inventive adsorbent composition containing a combination of LiX and Li13X with residual halloysite clay has the best combination of both physical characteristics and pore structure, including median pore diameter, lower percentage of pores that are less than 0.1 μm, improved hysteresis factor and higher pore diffusivity. Notwithstanding these improved characteristics, the inventive composition also contained a higher tapped bulk density and greater crushing strength than the comparative examples.

[0061] While a conventional composition with high density and crush strength traditionally meant a composition with reduced mass transfer or pore diffusivity (D.sub.p), surprisingly, the inventive composition exhibited higher pore diffusivity (D.sub.p) than the comparative compositions. The inventive composition also showed a diffusion rate within the particles that was surprisingly fast, even though the composition had high density and crush strength. Nitrogen uptake rates for the inventive composition was also surprisingly fast in comparison to the other compositions.

[0062] The inventive binderless adsorbent is particularly useful for separation of gaseous streams, such as for recovery of concentrated oxygen gas through selective adsorption of nitrogen in air. When oxygen in air is concentrated using PSA, VPSA, or TSA methods, the operation involves a series of steps including an adsorption step, in which a packed layer of a binderless zeolitic material is contacted with air for the selective adsorption of nitrogen. Concentrated oxygen is then collected from an outlet of the packed bed. Further processing of the gaseous material is conventional.

[0063] The adsorbent of this invention is particularly effective for air separation by the PSA/VPSA/TSA method. When air is separated by the PSA/VPSA/TSA method, the amount and yield of concentrated oxygen gas is high and the adsorbent exhibits good physical characteristics for long life.

[0064] The foregoing detailed description is provided for understanding and does not provide any limitation on the scope of the claims. Modification to the invention will be obvious to those skilled in the art upon a review of the disclosure without departing from the scope of the impended claims.