Anodes for the Electrolytic Production of Nitrogen Trifluoride and Fluorine

Abstract

A process and an anode for the production of nitrogen trifluoride or fluorine where the anode in the electrolytic cell is made primarily from mesocarbon microbeads. The mesocarbon microbead anodes minimize the production of CF 4 and improve the purity of the nitrogen trifluoride or fluorine gas produced. Additionally, the anodes may be molded, instead of extruded or machined, providing for improved dimensional and mechanical integrity of the anode.

1 . A process of producing nitrogen trifluoride or fluorine comprising:
 performing electrolysis of an electrolyte by using an electrolytic anode comprising primarily mesophase carbon to obtain nitrogen trifluoride or fluorine.   
     
     
         2 . The process according to  claim 1 , wherein the mesophase carbon comprises mesocarbon microbeads. 
     
     
         3 . The process according to  claim 2 , wherein the mesocarbon microbeads are isostatically pressed mesocarbon microbeads. 
     
     
         4 . The process according to  claim 2 , wherein the mesocarbon microbeads have an average particle size of about 1-5 microns. 
     
     
         5 . The process according to  claim 2 , wherein the mesocarbon microbeads are not graphitized. 
     
     
         6 . The process according to  claim 1 , wherein the anode comprises:
 at least 40% mesophase carbon; and   optionally, up to 10% of a stabilizing aid.   
     
     
         7 . The process according to  claim 1 , wherein the anode has a density of 1.7 g/cm 3  or higher. 
     
     
         8 . The process according to  claim 1 , wherein the anode consists of molded and self-sintered mesocarbon microbeads and optionally a sintering aid. 
     
     
         9 . The process according to  claim 1 , wherein the anode has an active area up to about 70,000 cm 2 . 
     
     
         10 . The process according to  claim 1 , wherein the process produces less than 100 Ppm of CF 4  in pure nitrogen trifluoride or fluorine. 
     
     
         11 . The process according to  claim 1 , wherein the process produces nitrogen trifluoride or fluorine with a selectivity of 70% or greater. 
     
     
         12 . The process according to  claim 1 , wherein the process produces nitrogen trifluoride or fluorine with a selectivity of 80% or greater. 
     
     
         13 . The process according to  claim 1 , wherein nitrogen trifluoride is produced and the electrolyte is a ternary electrolyte composition comprising HF, NH 4 F, and KF. 
     
     
         14 . The process according to  claim 13 , wherein the ternary electrolyte composition comprises 35-45 wt % HF, 15-25 wt % NH 4 F, and 40-45 wt % KF. 
     
     
         15 . The process according to  claim 1 , wherein fluorine is produced and the electrolyte is a binary electrolyte composition comprising HF and KF. 
     
     
         16 . The process according to  claim 1 , wherein nitrogen trifluoride is produced and the electrolyte is electrolyzed at a temperature of about 120-140° C. 
     
     
         17 . The process according to  claim 1 , wherein fluorine is produced and the electrolyte is electrolyzed at a temperature of about 80-90° C. 
     
     
         18 . The process according to  claim 1 , wherein the process is operated at a current density of about 70-250 mA/cm 2 . 
     
     
         19 . The process according to  claim 1 , wherein nitrogen trifluoride is produced and the process is operated at a current density of about 100-250 mA/cm 2 . 
     
     
         20 . The process according to  claim 1 , wherein fluorine is produced and the process is operated at a current density of about 120-250 mA/cm 2 . 
     
     
         21 . An electrolytic cell for producing nitrogen trifluoride or fluorine comprising:
 an anode comprising mesocarbon microbeads;   a cathode; and   an electrolyte composition comprising HF, optionally KF, and optionally NH 4 F,   wherein the electrolytic cell is operated to produce nitrogen trifluoride or fluorine.   
     
     
         22 . The electrolytic cell according to  claim 21 , wherein the anode consists of self-sintered isostatically pressed mesocarbon microbeads and optionally a sintering aid. 
     
     
         23 . The electrolytic cell according to  claim 21 , where the anode exhibits retained wettability without the addition of a wetting agent. 
     
     
         24 . The electrolytic cell according to  claim 21  wherein the mesocarbon microbeads are not graphitized. 
     
     
         25 . An anode comprising mesocarbon microbeads that are ungraphitized. 
     
     
         26 . The anode of  claim 25  further comprising an anode current connection.