Process for producing pure ammonium perrhenate

Abstract

The present invention provides an ammonium perrhenate containing less than 5 ppm of potassium.

What is claimed is: 
     
         1 . An ammonium perrhenate containing less than 5 ppm of potassium. 
     
     
         2 . The ammonium perrhenate as recited in  claim 1 , wherein the ammonium perrhenate contains less than 1 ppm of potassium. 
     
     
         3 . The ammonium perrhenate as recited in  claim 1 , wherein the ammonium perrhenate is prepared by a process comprising:
 producing a first aqueous suspension containing an ammonium perrhenate;   adding a stoichiometric amount of a nitric acid to the first aqueous suspension so as to produce a second suspension;   introducing the second suspension into a cathode space of an electrolysis cell, wherein the electrolysis cell is divided by a cation-exchange membrane into the cathode space and an anode space;   cathodically reducing the nitric acid to a nitrous acid in the cathode space by applying an electric potential;   reacting the nitrous acid with ammonium ions of the ammonium perrhenate so as to form an aqueous perrhenic acid;   removing potassium ions from the aqueous perrhenic acid; and   adding at least a stoichiometric amount of ammonia to the aqueous perrhenic acid so as to produce the pure ammonium perrhenate.   
     
     
         4 . A method of using an ammonium perrhenate containing less than 5 ppm of potassium as a precursor for the preparation of at least one of a pure rhenium compound and a pure rhenium metal for use in a superalloy, the method comprising:
 providing an ammonium perrhenate containing less than 5 ppm of potassium;   introducing the ammonium perrhenate as a precursor in the least one of a rhenium compound and a rhenium metal so as to produce the at least one of a pure rhenium compound and a pure rhenium metal; and   applying the at least one of a pure rhenium compound and a pure rhenium metal as an alloying metal in the superalloy.   
     
     
         5 . The method as recited in  claim 4 , wherein the ammonium perrhenate contains less than 1 ppm of potassium. 
     
     
         6 . A method of using an ammonium perrhenate containing less than 5 ppm of potassium as a precursor for the preparation of at least one of a pure rhenium compound and a pure rhenium metal to coat a rotary X-ray anode, the method comprising:
 providing an ammonium perrhenate containing less than 5 ppm of potassium;   introducing the ammonium perrhenate as a precursor in the least one of a rhenium compound and a rhenium metal so as to produce the at least one of a pure rhenium compound and a pure rhenium metal;   providing an X-ray anode; and   coating the X-ray anode with the at least one of the pure rhenium compound and the pure rhenium metal.   
     
     
         7 . The method as recited in  claim 6 , wherein the ammonium perrhenate contains less than 1 ppm of potassium.