Process for the preparation of vanillin

Abstract

The present invention relates to a process for preparing vanillin, comprising an electrolysis of an aqueous, alkaline lignin-comprising suspension or solution, wherein, as anode material, a base alloy is used which is selected among Co-base alloys, Fe-base alloys, Cu-base alloys and Ni-base alloys.

1 . A process for preparing vanillin, said process comprising an electrolysis of an aqueous, alkaline lignin-comprising suspension or solution, wherein, as anode material, a base alloy is used which is selected from Co-base alloys, Fe-base alloys, Cu-base alloys, or Ni-base alloys. 
     
     
         2 . The process according to  claim 1 , wherein, as anode material, a base alloy is used which is selected from Co-base alloys, Fe-base alloys, or Ni-base alloys, wherein
 (1) the Ni-base alloy comprises:
 a1) 50 to 95% by weight of Ni and 
 b1) 5 to 50% by weight of at least one further alloy component, selected from Cu, Fe, Co, Mn, Cr, Mo, V, Nb, Ti, Si, Al, C, or S; 
   (2) the Co-base alloy substantially:
 a2) 50 to 95% by weight of Co and 
 b2) 5 to 50% by weight of at least one further alloy component, selected from Cu, Fe, Ni, Mn, Cr, Mo, W, V, Nb, Ti, Si, P, or C; and 
   (3) the Fe-base alloy substantially comprises:
 a3) 50 to 95% by weight of Co and 
 b3) 5 to 50% by weight of at least one further alloy component, selected from Cu, Co, Ni, Mn, Cr, Mo, W, V, Nb, Ti, Si, P, S or C. 
   
     
     
         3 . The process according to  claim 2 , wherein the base alloy is selected from
 1.1 Ni-base alloys that comprise 5 to 35% by weight of Cu,   1.2 Ni-base alloys that comprise 5 to 40% by weight of Cr,   1.3 Ni-base alloys that comprise 5 to 35% by weight of Mo,   2.1 Co-base alloys that comprise 5 to 40% by weight of Cr, or   3.1 high-alloy chromium-comprising stainless steels.   
     
     
         4 . The process according to  claim 1 , wherein the anode material is selected from a Cu-base alloy that comprises
 a4) 50 to 95% by weight of Cu and   b4) 5 to 50% by weight of at least one further alloy component selected from Ag, Pb, Ni, or Zn.   
     
     
         5 . The process according to  claim 4 , wherein the base alloy is selected from nickel silver and cupronickel. 
     
     
         6 . The process according to  claim 1 , wherein the anode is a grid, expanded metal or metal plate. 
     
     
         7 . The process according to  claim 1 , wherein, in the electrolysis, as cathode an electrode comprising an electrode material is used, said electrode material selected from nickel, Ni-base alloys, Co-base alloys, Fe-base alloys, Cu-base alloys, silver, Ag-base alloys, RuO x TiO x -mixed oxides, platinized titanium, platinum, graphite, or carbon. 
     
     
         8 . The process according to  claim 1 , in which the electrolysis is carried out at a current density in a range from 1 to 100 mA/cm 2 . 
     
     
         9 . The process according to any one of the preceding claims  claim 1 , in which the electrolysis is carried out at a temperature in a range from 10 to 100° C. 
     
     
         10 . The process according to  claim 1 , wherein the aqueous, alkaline lignin-comprising suspension or solution has a pH of at least 10. 
     
     
         11 . The process according to  claim 1 , wherein, as aqueous lignin-comprising suspension or solution, an aqueous lignin-comprising stream from paperstock, pulp ,or cellulose preparation is used. 
     
     
         12 . The process according to  claim 1 , wherein the aqueous, alkaline lignin-comprising suspension or solution is prepared by dissolving or suspending at least one lignin-comprising material in aqueous alkaline, wherein the lignin-comprising material is selected from lignin from black liquor, kraft lignin, lignin sulfonate, alkali lignin, organosolv lignin and corresponding residues from the paper industry, pulp, or cellulose preparation. 
     
     
         13 . The process according to  claim 1 , wherein the aqueous, alkaline lignin-comprising suspension or solution is selected from
 (a) an aqueous suspension or solution which is prepared by dissolving or suspending oxidized lignin in aqueous alkali, wherein oxidized lignin was obtained by oxidation of an aqueous, alkaline lignin-comprising suspension or solution, or   (b) an aqueous suspension or solution which is prepared by depleting vanillin from an aqueous reaction mixture, wherein the reaction mixture was obtained by oxidation of an aqueous, alkaline lignin-comprising suspension or solution.   
     
     
         15 . The process according to  claim 1 , wherein the aqueous, lignin-comprising suspension or solution comprises 0.5 to 30% by weight of lignin or a derivative of lignin, based on the total weight of the aqueous, lignin-comprising suspension or solution. 
     
     
         16 . The process according to  claim 1 , wherein the vanillin formed in the electrolysis is continuously removed from the aqueous, lignin-comprising solution or suspension.