Selective removal of nitrogen from natural gas by pressure swing adsorption

• US 6,197,092 B1
• Filed: 03/22/1999
• Issued: 03/06/2001
• Est. Priority Date: 03/22/1999
• Status: Expired due to Term

• Current Assignee: Engelhard Corporation (BASF SE)
• Original Assignee: Engelhard Corporation (BASF SE)
• Inventors: Kuznicki, Steven M., Dolan, William B., Butwell, Kenneth F.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US09/273,684
• Time in Patent Office: 715 Days
• Field of Search: 95/96--06, 951/30, 951/43, 959/01, 959/02, 951/14, 951/15
• US Class Current: 95/96
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/106 Silica or silicates
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2256/10 Nitrogen
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2258/06 Polluted air
• CPC Class Codes: B01D 2259/40052 Recycled product or process gas
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: Y02C 20/20 of methane
• CPC Class Codes: Y10S 95/902 Molecular sieve

Abstract

A pressure swing adsorption process for the separation of hydrogen from a mixture of the same with methane, utilizing two separate PSA stages, one containing a nitrogen selective crystalline zeolite, and the second containing a methane selective adsorbent.

Claims

1. A pressure swing adsorption (PSA) process for the separation of nitrogen from a mixture of the same with methane which comprises

(a) passing a feed stream comprising said mixture to a PSA unit containing a nitrogen selective adsorbent so as to preferentially adsorb nitrogen and produce a product stream enriched with methane and a low pressure waste stream rich in nitrogen desorbed from said adsorbent;

(b) recovering said product stream;

(c) subsequent to production of said low pressure waste stream, periodically heating said nitrogen selective adsorbent to drive off accumulated methane therefrom; and

(d) subsequent to step (c) cooling said nitrogen selective adsorbent.

2. The process of claim 1 wherein the nitrogen selective adsorbent of step (a) is a CTS-1 zeolite characterized as having a pore size of approximately 3-4 Å

units and a composition in terms of mol ratios of oxide as follows;

3. The process of claim 1 wherein the nitrogen selective zeolite of step (a) is barium exchanged ETS-4 wherein barium represents at least 30% of the exchangeable cations.

4. The process of claim 1 wherein said nitrogen selective adsorbent is heated with said low pressure waste stream.

5. The process of claim 1 further comprising;

d) compressing said low pressure waste stream to a higher pressure waste stream;

e) passing said higher pressure waste stream to a PSA unit containing a methane selective adsorbent so as to produce a product stream rich in nitrogen and a low pressure waste stream rich in methane.

6. The process of claim 5 wherein said nitrogen selective adsorbent is heated with said nitrogen-rich product stream.

7. The process of claim 1 wherein said product stream enriched with methane contains at least 90 mol % methane.