Electrochemical method for manufacturing methyl ethyl ketone

Abstract

It is provided a process for the preparation of methyl ethyl ketone by electroreduction of acetoin in aqueous media using a high hydrogen overvoltage cathode made of lead, the process comprising the steps of a) forming a solution by mixing acetoin with an aqueous medium and a supporting electrolyte soluble in such a medium, and b) electrolyzing said solution continuously or discontinuously in an electrochemical reactor by applying a voltage between an anode and the cathode using a direct current power supply at a current density from 500 to 5000 A/m2.

1 . A process for the preparation of methyl ethyl ketone (MEK) by electroreduction of acetoin in aqueous media using a cathode made of lead, the process comprising the steps of:
 a) forming a solution by mixing acetoin with an aqueous medium and a supporting electrolyte soluble in such a medium, and   b) electrolyzing said solution continuously or discontinuously in an electrochemical reactor by applying a voltage between an anode and the cathode using a direct current power supply at a current density from 500 to 5000 A/m 2 .   
     
     
         2 . The process according to  claim 1 , wherein the process is carried out in the absence of a hydrogenation catalyst which is a catalyst which is capable of catalysing the reduction by hydrogen of a group susceptible of being reduced in a bulk catholyte. 
     
     
         3 . (canceled) 
     
     
         4 . The process according to  claim 1 , wherein the cathode made of lead is lead as a flat sheet or deposited in a porous support such as a carbon felt, and carbon foam. 
     
     
         5 . The process according to  claim 1 , wherein the anode is selected from carbon steel, platinum supported on titanium, and iridium-based dimensionally stable anodes in non-porous flat form and as perforated materials such as nets, metal meshes, lamellae, shaped webs and grids. 
     
     
         6 . The process according to  claim 1 , wherein the aqueous medium comprises 100 wt % water or a mixture of water with a fully or partially water-miscible non-electroactive solvent in which the amount of water is from 50 to 99 wt %, particularly from 70 to 99 wt %, more particularly from 85 to 99 wt %. 
     
     
         7 . The process according to  claim 1 , wherein the electrochemical reactor is an undivided reactor. 
     
     
         8 . The process according to  claim 1 , wherein the supporting electrolyte forming a solution with acetoin is selected from the group comprising ammonium and alkaline and alkaline earth metal salts of inorganic acids, and ammonium quaternary salts, and mixtures thereof, and the supporting electrolytes for anolyte in divided cells are non-oxidizable inorganic acids. 
     
     
         9 . The process according to  claim 8 , wherein supporting electrolyte forming a solution with acetoin is in an amount from 0.1 to 20 wt %, particularly from 1 to 15 wt %, and more particularly from 5 to 10 wt %, based on the total mass of the solution. 
     
     
         10 . The process according to  claim 1 , wherein the solution formed by mixing acetoin with an aqueous medium and a supporting electrolyte soluble in such a medium has a pH from 2.5 and 7, particularly from 3 to 7, and more particularly from 4 to 7. 
     
     
         11 . The process according to  claim 1 , wherein for electroreducing acetoin to MEK, an amount of electricity from 50% and 125% of the theoretical one for obtaining a 100% conversion of acetoin assuming a current efficiency of 100%, more particularly from 55% to 100%, and most particularly from 60% to 75%, is circulated. 
     
     
         12 . The process according to  claim 1 , wherein electroreduction is carried out at a temperature from 10° C. to 70° C., particularly room temperature. 
     
     
         13 . The process according to  claim 1 , wherein the MEK is continuously removed from the aqueous medium by vacuum evaporation. 
     
     
         14 . The process according to  claim 1 , wherein the MEK is continuously removed from the aqueous medium by liquid-liquid extraction using a water-insoluble inert solvent. 
     
     
         15 . The process according to  claim 1 , which is carried out:
 i) in one electrochemical reactor; or   ii) in at least two electrochemical reactors connected in series in such a way that the solution, comprising a mixture of unreacted acetoin, MEK, an aqueous medium, and a supporting electrolyte soluble in such a medium, resulting from one electrochemical reactor feeds the subsequent one.   
     
     
         16 . The process according to  claim 2 , wherein the cathode material is lead as a flat sheet or deposited in a porous support such as a carbon felt, and carbon foam. 
     
     
         17 . The process according to  claim 16 , wherein the aqueous medium comprises 100 wt % water or a mixture of water with a fully or partially water-miscible non-electroactive solvent in which the amount of water is from 50 to 99 wt %, particularly from 70 to 99 wt %, more particularly from 85 to 99 wt %. 
     
     
         18 . The process according to  claim 17 , wherein the electrochemical reactor is an undivided reactor. 
     
     
         19 . The process according to  claim 18 , wherein the supporting electrolyte forming a solution with acetoin is selected from the group comprising ammonium and alkaline and alkaline earth metal salts of inorganic acids, and ammonium quaternary salts, and mixtures thereof, and the supporting electrolytes for anolyte in divided cells are non-oxidizable inorganic acids. 
     
     
         20 . The process according to  claim 19 , wherein the amount of the supporting electrolyte forming a solution with acetoin is from 0.1 to 20 wt %, particularly from 1 to 15 wt %, and more particularly from 5 to 10 wt %, based on the total mass of the solution. 
     
     
         21 . The process according to  claim 20 , wherein the solution formed by mixing acetoin with an aqueous medium and a supporting electrolyte soluble in such a medium has a pH from 2.5 and 7, particularly from 3 to 7, and more particularly from 4 to 7.