Polymer halogenation process with catalyst recovery

Abstract

The present invention relates to a method for recovering antimony catalysts wherein the formation of insoluble solids is reduced.

1 ) A method for recovering antimony halide catalysts comprising:
 adding, to a mixture comprising: (i) aqueous hydrochloric acid, (ii) soluble antimony values, and (iii) at least one antimony value insoluble in the aqueous hydrochloric acid, aqueous hydrobromic acid, gaseous hydrobromic acid, or mixtures thereof in an amount effective at converting at least a portion of the insoluble antimony values into at least one antimony value that is soluble in the aqueous hydrochloric acid, wherein the at least one insoluble antimony value is selected from (i) antimony (IV) oxide, (ii) antimony (V) oxide, (iii) other antimony oxides, (iv) oxyhalide compounds, and mixtures of (i)-(iv).   
     
     
         2 ) The method according to  claim 1  wherein said at least one antimony value insoluble in the aqueous hydrochloric acid is antimony (IV) oxide, antimony (V) oxide, and mixtures thereof. 
     
     
         3 ) The method according to  claim 2  wherein at least a portion of the antimony (IV) oxide, antimony (V) oxide, and mixtures thereof are reduced to antimony (III) oxides, halides, oxyhalides, and mixtures thereof. 
     
     
         4 ) The method according to  claim 1  wherein said effective amount of aqueous hydrobromic acid is about 0.1 to about 5 moles of hydrobromic acid per mole of antimony present in the solution. 
     
     
         5 ) The method according to  claim 1  wherein said effective amount of aqueous hydrobromic acid is about 2.0 to about 3.0 moles of hydrobromic acid per mole of antimony present in the solution.