Producing chlorine and hydrogen from hydrogen chloride by plasma process

• US 5,935,390 A
• Filed: 02/20/1997
• Issued: 08/10/1999
• Est. Priority Date: 02/29/1996
• Status: Expired due to Term

• Current Assignee: Plasma Plus, Inc., The Chemours Company FC, LLC (The Chemours Company)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.), Plasma Plus
• Inventors: Paskalov, George, Felix, Vinci Martinez
• Primary Examiner(s): Mayekar, Kishor
• Application Number:
  US08/804,159
• Time in Patent Office: 901 Days
• Field of Search: 204/164, 423/507
• US Class Current: 204/164
• CPC Class Codes: B01J 12/002 carried out in the plasma state generating or handling plasma H05H1/00
• CPC Class Codes: B01J 19/129 Radiofrequency
• CPC Class Codes: B01J 2219/00148 Radiofrequency
• CPC Class Codes: B01J 2219/0875 Gas
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: C01B 2203/0465 Composition of the impurity
• CPC Class Codes: C01B 3/04 by decomposition of inorganic compounds, e.g. ammonia C01B3/0005 takes precedence
• CPC Class Codes: C01B 3/506 at low temperatures
• CPC Class Codes: C01B 7/04 Preparation of chlorine from hydrogen chloride
• CPC Class Codes: H01J 37/32 Gas-filled discharge tubes heating by discharge H05B
• CPC Class Codes: H05H 1/2465 the plasma being activated by inductive coupling, e.g. using coiled electrodes
• CPC Class Codes: H05H 1/4697 using glow discharges
• CPC Class Codes: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

A process is disclosed for converting hydrogen chloride (HCl) to molecular chlorine (Cl₂) and molecular hydrogen (H₂), and more particularly to such process conducted in a plasma environment.

Claims

1. A process for producing hydrogen and chlorine from hydrogen chloride which comprises the steps of:

(i) generating a plasma by the use of a radio-frequency plasma generating means;

(ii) introducing HCl, accompanied by an inert non-oxygenated plasma-forming gas, into said plasma wherein said HCl is heated to a temperature in the range between 2000 degrees K and 6000 degrees K to convert at least a portion of the HCl into its constituents;

(iii) cooling the constituents to form a gas product mixture comprising H₂ and Cl₂ ; and

(iv) recovering said gas product mixture.

2. The process of claim 1 wherein said HCl is substantially anhydrous.

3. The process of claim 1 wherein said inert gas comprises at least one of Ar, He, Ne, Kr, Xe or their mixture combinations.

4. The process of claim 3 wherein said inert gas comprises Ar.

5. The process of claim 3 wherein said inert gas is present in an amount of from about 0.2 to about 2 parts by weight on the HCl introduced into the plasma.

6. The process of claim 1 wherein the plasma is generated by means of a radio-frequency induction plasma generator comprising an induction coil.

7. The process of claim 1 wherein the plasma is generated by means of a radio-frequency capacitive plasma generator comprising external ring electrodes.

8. The process of claim 1 wherein the plasma is generated by means of a radio-frequency induction-capacitive plasma generator comprising external ring electrodes and an induction coil.

9. The process of claim 1 or 8 wherein the plasma is generated in and contained in a cylindrical dielectric vessel comprising:

(i) a plasma-generating zone;

(ii) a cooling zone downstream of said plasma-generating zone adapted to cool the constituents and form the gas product mixture comprising H₂ and Cl₂ ; and

(iii) means for removing the gas product mixture from the vessel.

10. The process of claim 9 wherein the cooling zone comprises a jacketed section of said vessel in association with means for circulating cooling fluid through the jacketed section.

11. The process of claim 9 wherein at least the plasma-generating zone of the cylindrical dielectric vessel comprises at least one member selected from the group consisting of quartz, tantalum, niobium, alloys of Ta with Nb, Re, Os, Mo, Ir, or Ru, or alloys of Nb with Re, Os, Mo, Ir, or Ru.

12. The process of claim 9 wherein the vessel is in operative relationship with a means for detecting the presence of dissociated HCl generated in the plasma-generating zone.

13. The process of claim 9 wherein the vessel is in operative relationship with a means for detecting the presence of molecular H₂ and molecular Cl₂ in the gas product mixture formed therein.

14. The process of claim 1 or 2 further comprises the step of separating the recovered gas product mixture into a fraction comprising molecular H₂ and a fraction comprising molecular Cl₂.

15. The process of claim 14 wherein the separation is effected by condensing the gas product mixture to form a liquid or solid condensate fraction comprising Cl₂ and a gas fraction comprising H₂, and separating the fractions.

16. The process of claim 14 wherein the Cl₂ component of the gas product mixture is separated by contacting the mixture with a chemical means that is effective to remove Cl₂ and is inert to H₂, and the H₂ component is separated from the chemical means and recovered.

17. The process of claim 14 wherein said separating comprises at least one of

a) passing said gas product mixture through a membrane;

b) condensing said gas product mixture; and

c) contacting said gas product mixture with an adsorbent.