Formation of tungsten monocarbide from a molten tungstate-halide phase by gas sparging

Abstract

Tungsten monocarbide is prepared by sparging a molten composition comprising an alkali metal halide and an oxygen compound of tungsten with a gas comprising a gaseous hydrocarbon, particularly methane.

We claim: 
     
       1. A process for preparation of tungsten monocarbide comprising: (a) providing a molten composition comprising an alkali metal halide and an oxygen compound of tungsten;   (b) sparging said composition with a gas comprising a gaseous hydrocarbon which is selected from the group consisting of natural gas, methane, ethane, acetylene, propane, butane, mixtures thereof, and admixtures of these gases with H 2  or CO, at a temperature of about 900° to 1100° C. for a sufficient time for the tungsten compound to be substantially converted to tungsten carbide; and   (c) decanting the molten halide from the tungsten carbide product.   
     
     
       2. The process of claim 1 wherein the alkali metal halide is sodium chloride. 
     
     
       3. The process of claim 1 in which the oxygen compound of tungsten is tungstic oxide, an alkali metal tungstate, or ammonium tungstate. 
     
     
       4. The process of claim 3 in which the tungsten compound is sodium tungstate. 
     
     
       5. The process of claim 1 in which the gaseous hydrocarbon is methane or natural gas. 
     
     
       6. The process of claim 1 in which the tungsten carbide product is cooled and purified by water leaching. 
     
     
       7. The process of claim 1 in which the molten composition consists essentially of a mixture of sodium chloride and sodium tungstate. 
     
     
       8. The process of claim 7 in which the NaCl-Na 2  WO 4  mixture is prepared by forming a melt comprising a tungsten ore concentrate, sodium chloride and sodium silicate, whereby the tungsten concentrates in the sodium chloride phase. 
     
     
       9. The process of claim 8 in which the tungsten ore is scheelite or wolframite. .Iadd. 
     
     
       10.  The process of claim 1, wherein a reductant is included in the molten composition. .Iaddend. .Iadd.11. The process of claim 10, wherein the reductant is selected from the group consisting of powdered charcoal, coke breeze and calcium carbide. .Iaddend.