Process for the separation of organic nitrosonium and/or hydroxylamine compounds by means of cation exchange resins and recovery and oxidation processes based thereon

Abstract

A process for the separation of a secondary organic nitrosonium compound and/or a secondary organic hydroxylamine compound from an acidic aqueous medium containing them in dissolved form, includes the step of bringing into contact said acidic aqueous medium with a cation exchange resin. The process is used in a process for the recovery of secondary organic nitroxy compounds from an aqueous medium containing the nitroxy compound and oxidation processes for hydroxy compounds.

1 . Process for the separation of a secondary organic nitrosonium compound and/or a secondary organic hydroxylamine compound from an acidic aqueous medium containing them in dissolved form, said process comprising the step of bringing into contact said acidic aqueous medium with a cation exchange resin.  
     
     
         2 . Process according to  claim 1 , wherein the acidic aqueous medium contains an organic nitrosonium and a protonated organic hydroxylamine compound.  
     
     
         3 . Process according to  claim 2 , wherein the organic nitrosonium and hydroxylamine compounds are obtained by disproportionating a secondary organic nitroxy compound.  
     
     
         4 . Process according to  claim 1 , wherein the acidic aqueous medium containing the organic nitrosonium and/or hydroxylamine compound is obtained from a reaction mixture obtained by oxidizing a hydroxy compound in the presence of a secondary organic nitroxy compound and/or the corresponding nitrosonium ion.  
     
     
         5 . Process according to  claim 3 , wherein the organic nitroxy compound has the following formula (V):  
       
         
           
           
               
               
           
         
       
       where n=0 or 1 and where the methylene groups of the ring may carry one or more substituents selected from alkyl, alkoxy, aryl, aryloxy, amino, amido, oxo, cyano, hydroxy, carboxyl, phosphonooxy, maleimido, isothiocyanato, alkyloxy, fluorophosphinyloxy, substituted or unsubstituted benzoyloxy.  
     
     
         6 . Process according to  claim 1 , wherein the step of contacting involves passing the aqueous medium over a column filled with a cation exchange resin.  
     
     
         7 . Process according to  claim 1 , wherein the cation exchange resin has sulfonate and/or carboxylate anchor groups.  
     
     
         8 . Process according to  claim 1 , wherein the organic nitrosonium and/or hydroxylamine compounds are recovered from the cation exchange resin by washing or eluting the resin with an aqueous acid solution or an aqueous solution of a metal salt.  
     
     
         9 . Process according to  claim 8 , wherein the eluted aqueous medium contains organic nitrosonium and hydroxylamine, preferably in equimolar amounts and is neutralized to form the corresponding nitroxy compound.  
     
     
         10 . Process according to  claim 8 , wherein the eluted aqueous medium contains at least the hydroxylamine which is oxidized to the corresponding nitrosonium compound.  
     
     
         11 . Process according to  claim 4 , wherein the organic nitroxy compound has the following formula (V):  
       
         
           
           
               
               
           
         
       
       where n=0 or 1 and where the methylene groups of the ring may carry one or more substituents selected from alkyl, alkoxy, aryl, aryloxy, amino, amido, oxo, cyano, hydroxy, carboxyl, phosphonooxy, maleimido, isothiocyanato, alkyloxy, fluorophosphinyloxy, substituted or unsubstituted benzoyloxy.  
     
     
         12 . Process for the recovery of secondary organic nitroxy compounds from an aqueous medium comprising said nitroxy compound, said process comprising the steps of: 
 (a) acidifying the aqueous medium to disproportionate the nitroxy compound to obtain a mixture of the corresponding protonated hydroxylamine compound and nitrosonium compound,    (b) contacting the mixture of protonated hydroxylamine compound and nitrosonium compound with a cation exchange resin to retain said mixture,    (c) eluting the cation exchange resin with an aqueous solution of an acid or a metal salt in order to remove the hydroxylamine and nitrosonium compounds from the cation exchange resin, and    (d) neutralizing the resulting purified mixture of hydroxylamine and nitrosonium compounds to form the nitroxy compound.    
     
     
         13 . Process according to  claim 12 , wherein the aqueous medium comprising said nitroxy compound was obtained from reaction mixture obtainable by oxidizing a hydroxy compound in the presence of a secondary organic nitroxy compound and/or the corresponding nitrosonium ion.  
     
     
         14 . Process according to  claim 12 , wherein the organic nitroxy compound has the following formula (V):  
       
         
           
           
               
               
           
         
       
       where n=0 or 1 and where the methylene groups of the ring may carry one or more substituents selected from alkyl, alkoxy, aryl, aryloxy, amino, amido, oxo, cyano, hydroxy, carboxyl, phosphonooxy, maleimido, isothiocyanato, alkyloxy, fluorophosphinyloxy, substituted or unsubstituted benzoyloxy.  
     
     
         15 . Process according to  claim 12 , wherein step (b) involves passing the aqueous medium over a column filled with a cation exchange resin.  
     
     
         16 . Process according to  claim 12 , wherein the cation exchange resin has sulfonate and/or carboxylate anchor groups.  
     
     
         17 . Process for the oxidation of a hydroxy compound, said process comprising the steps of: 
 (i) oxidizing a hydroxy compound in an aqueous medium in the presence of a secondary organic nitroxy compound and a primary oxidant,    (ii) optionally, acidifying the resulting reaction mixture to disproportionate unreacted nitroxy compound to the corresponding protonated hydroxylamine and nitrosonium ion followed by recovering the nitroxy compound according to steps (a) to (d) of  claim 12 , and    (iii) recycling the nitroxy compound recovered thereby to step (i).    
     
     
         18 . Process for the oxidation of a hydroxy compound in the presence of an organic nitrosonium compound comprising the steps of: 
 (i′) oxidizing in an aqueous medium a hydroxy compound in the presence of a secondary organic nitrosonium compound while the nitrosonium ion compound is reduced to the corresponding protonated hydroxylamine,    (ii′) optionally, acidifying the resulting oxidation mixture, followed by separating unreacted nitrosonium compound, if present, and hydroxylamine formed, according to the process of  claim 1  which comprises contacting them with a cation exchange resin,    (iii′) eluting the unreacted nitroxy compound, if present, and the protonated hydroxylamine from the resin,    (iv′) adding a primary oxidant in order to convert the protonated hydroxylamine compound to the corresponding nitrosonium compound, and    (v′) recycling the nitrosonium compound to step (i′).    
     
     
         19 . Process according to  claim 18 , wherein the cation exchange resins have sulfonate and/or carboxylate anchor groups, and the organic nitrosonium and/or hydroxylamine compounds are recovered from the cation exchange resin by washing or eluting the resin with an aqueous acid solution or an aqueous solution of a metal salt.  
     
     
         20 . Process according to  claim 17 , wherein the hydroxy compound to be oxidized is cellulose present in cellulosic pulp.  
     
     
         21 . Process according to  claim 20 , wherein the oxidation is conducted in the absence of chlorine-containing oxidants.  
     
     
         22 . Process according to  claim 18 , wherein the hydroxy compound to be oxidized is cellulose present in cellulosic pulp.