Electrochemical cell for the oxidation of organic compounds, and electrocatalytic oxidation process

Abstract

An electrochemical cell comprising a negative electrode, a solid electrolyte which conducts oxygen ions, and a positive electrode comprising zeolites, mordenites, silicates, phosphates or mixed-metal oxides having a pore size of less than 200 nm can be used in a process for partially oxidizing organic compounds, for example alkanes, olefins or aromatic compounds.

What is claimed as new and is intended to be secured by Letters Patent is:  
     
         1 . An electrochemical cell comprising a negative electrode, a solid electrolyte which conducts oxygen ions, a positive electrode comprising a positive electrode material comprising at least one material selected from the group consisting of a zeolite, a mordenite, a silicate, a phosphate, and a mixed-metal oxide, and a power source connected to the positive and negative electrode, wherein said positive electrode material has a pore size of less than 200 nm.  
     
     
         2 . The electrochemical cell of  claim 1 , wherein the positive electrode material is a coating.  
     
     
         3 . The electrochemical cell of  claim 1 , wherein the negative electrode and positive electrode are disposed on opposing surfaces of the solid electrolyte.  
     
     
         4 . The electrochemical cell of  claim 1 , wherein the positive electrode material comprises a compound of formula IV 
       (El 2 O e ) α (Fe 2 O 3 ) β SiO 2   (IV) 
       wherein 
 El=an element from group IA, IIA, IIIA, IVA or VA or IIIB, IVB, VB, VIB, VIIB or VIII of the Periodic Table of the Elements  
 α=from 0 to 0.1,  
 β=from 0 to 0.1,  
 with the proviso that α and β are not simultaneously 0.  
 
     
     
         5 . The electrochemical cell of  claim 1 , wherein the pore size of the positive electrode material is less than 20 nm.  
     
     
         6 . The electrochemical cell of  claim 1 , wherein the solid electrolyte which conducts oxygen ions comprises cerium oxide (CeO 2 ) or cerium oxide (CeO 2 ) stabilized with at least one compound selected from the group consisting of lanthanum oxide (La 2 O 3 ), yttrium oxide (Y 2 O 3 ), ytterbium oxide (Yb 2 O 3 ) and gadolinium oxide (Gd 2 O 3 ).  
     
     
         7 . The electrochemical cell of  claim 1 , wherein the solid electrolyte which conducts oxygen ions comprises zirconium oxide (ZrO 2 ) or zirconium oxide (ZrO 2 ) stabilized with at least one compound selected from the group consisting of calcium oxide (CaO), scandium oxide (Sc 2 O 3 ), yttrium oxide (Y 2 O 3 ) and ytterbium oxide (Yb 2 O 3 ).  
     
     
         8 . The electrochemical cell of  claim 1 , wherein the solid electrolyte which conducts oxygen ions comprises a metal or metal oxide.  
     
     
         9 . The electrochemical cell of  claim 1 , wherein the solid electrolyte which conducts oxygen ions comprises a perovskite of formula II 
       Ln a X 1   b X 2   c X 3   d O e   (II) 
       wherein 
 Ln=La Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu  
 X 1 =Ca, Sr, Ba and/or Mg  
 X 2 =Ga, Al, Mn, Ti, Nb, Y, W and/or Zr  
 X 3 =Fe, Co, Ni and/or Cu  
 a=0.1 to 0.9,  
 b=0.1 to 0.9,  
 c=0 to 0.9,  
 d=0 to 0.9  
 with the proviso that a+b=0.3 to 1.5.  
 
     
     
         10 . The electrochemical cell of  claim 1 , wherein the solid electrolyte which conducts oxygen ions comprises a pyrochloro compound of formula III 
       (Ln f X 4   g ) 2 (X 5   h X 6   i ) 2 O k   (III) 
       wherein 
 Ln=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu  
 X 4 =Na, Mg, Ca and/or Sr,  
 X 5 =Ti, Nb, Ta and/or Zr,  
 X 6 =Fe, Al, Sc, Ga and/or Y,  
 f=0.2 to 1.2,  
 g=0 to 0.8,  
 h=0.2 to 1.2,  
 i=0 to 0.8.  
 
     
     
         11 . An electrochemical cell of  claim 1 , wherein the positive electrode material comprises a mixed oxide of formula V 
       A l B m X 7   n X 8   o X 9   p X 10   q X 11   r X 12   s O t   (V) 
       wherein 
 A and B are an element from Group IA, IIA and/or VA and/or Group IVB, VB, VIB, VIIB, or VIII of the Periodic Table of the Elements  
 X 7 =V, Nb, Cr, W, Ta, Ga and/or Ce  
 X 8 =Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and/or Ba,  
 X 9 =La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Au, Pd and/or Pt,  
 X 10 =Fe, Co, Ni and/or Zn,  
 X 11 =Sn,Pb,Sb and/or Te,  
 X 12 =Ti, Zr, Si and/or Al, where  
 l=0.001 to 30,  
 m=0.001 to 20,  
 n=0 to 15,  
 o=0.001 to 10,  
 p=0 to 10,  
 q=0to 40,  
 r=0 to 10, and  
 s=0 to 80, with the proviso that l+m is ≧0.01 and l+o is ≧0.005.  
 
     
     
         12 . The electrochemical cell of  claim 1 , wherein the positive electrode further comprises a mixture of the solid electrolyte which conducts oxygen ions and the positive electrode material.  
     
     
         13 . The electrochemical cell of  claim 1 , wherein the positive electrode further comprises a mixture of an electrically conductive metal and the positive electrode material.  
     
     
         14 . The electrochemical cell of  claim 1 , wherein a metal foil having a maximum thickness of 200 μm is disposed between the solid electrolyte which conducts oxygen ions and the positive electrode.  
     
     
         15 . The electrochemical cell of  claim 14 , wherein the metal foil comprises at least one metal selected from the group consisting of Cu, Au, Ag, Pt, Pd and Ir.  
     
     
         16 . The electrochemical cell of  claim 1 , wherein the negative electrode comprises a metal.  
     
     
         17 . The electrochemical cell of  claim 1 , wherein the negative electrode comprises at least one metal selected from the group consisting of Cu, Au, Ag, Pt, Pd, and Ir.  
     
     
         18 . The electrochemical cell of  claim 1 , wherein the negative electrode comprises one or more metal oxides or a metal mixed oxide.  
     
     
         19 . The electrochemical cell of  claim 1 , wherein the negative electrode comprises a perovskite of the general formula I 
       La u X 13   v X 14   w X 15   x X 16   y O 3±z   (I) wherein    X 13 =Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu,    X 14 =Ca, Sr, Ba and/or Mg,    X 15 =Mn, Fe, Ti, Ga, Mn and/or Zr,    X 16 =Co, Ni, Cu, Al an d/or Cr    u=0 to 0.2,    v=0 to 1.0,    w=0.01 to 0.8,    with the proviso that u+v+w is ≦1.5, and    x=0.2 to 1.3,    y=0 to 0.9,    with the proviso that x+y is ≧0.3.    
     
     
         20 . A process for the selective oxidation of an organic compound in an electrochemical cell, comprising: 
 passing the organic compound over the surface of a positive electrode comprising a positive electrode material comprising at least one material selected from the group consisting of a zeolite, a mordenite, a silicate, a phosphate, and a mixed-metal oxide having a pore size of less than 200 nm, thereby partially oxidizing the organic compound,    passing an oxygen- or N 2 O-containing gas over a negative electrode,    wherein a solid electrolyte which conducts oxygen ions is disposed between the positive and negative electrodes, and the positive and negative electrodes are connected to a power source.    
     
     
         21 . The process of  claim 20 , wherein the positive electrode material comprises a compound of formula IV 
       (El 2 O e ) α (Fe 2 O 3 ) β SiO 2   (IV) 
       wherein 
 El=an element from group IA, IIA, IIIA, IVA or VA or IIIB, IVB, VB, VIB, VIIB or VIII of the Periodic Table of the Elements  
 α=from 0 to 0.1  
 β=from 0 to 0.1,  
 with the proviso that α and β are not simultaneously 0.  
 
     
     
         22 . The process of  claim 20 , wherein the pore size of the positive electrode material is less than 20 nm.  
     
     
         23 . The process of  claim 20 , wherein the solid electrolyte which conducts oxygen ions comprises cerium oxide (CeO 2 ) or cerium oxide (CeO 2 ) stabilized with at least one stabilizer selected from the group consisting of lanthanum oxide (La 2 O 3 ), yttrium oxide (Y 2 O 3 ), ytterbium oxide (Yb 2 O 3 ) and gadolinium oxide (Gd 2 O 3 ).  
     
     
         24 . The process of  claim 20 , wherein the solid electrolyte which conducts oxygen ions comprises zirconium oxide (ZrO 2 ) or zirconium oxide (ZrO 2 ) stabilized with at least one stabilizer selected from the group consisting of calcium oxide (CaO), scandium oxide (Sc 2 O 3 ), yttrium oxide (Y 2 O 3 ) and ytterbium oxide (Yb 2 O 3 ).  
     
     
         25 . The process of  claim 20 , wherein the solid electrolyte which conducts oxygen ions comprises a metal or metal oxide.  
     
     
         26 . The process of  claim 20 , wherein the solid electrolyte which conducts oxygen ions comprises a perovskite of formula II 
       Ln a X 1   b X 2   c X 3   d O e   (II) 
       wherein 
 Ln=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu  
 X 1 =Ca, Sr, Ba and/or Mg  
 X 2 =Ga, Al, Mn, Ti, Nb, Y, W and/or Zr  
 X 3 =Fe, Co, Ni and/or Cu  
 a=0.1 to 0.9,  
 b=0.1 to 0.9,  
 c=0 to 0.9,  
 d=0 to 0.9  
 with the proviso that a+b=0.3 to 1.5.  
 
     
     
         27 . The process of  claim 20 , wherein the solid electrolyte which conducts oxygen ions is a pyrochloro compound of formula III 
       (Ln f X 4   g ) 2 (X 5   h X 6   i ) 2 O k   (III) 
       wherein 
 Ln=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu  
 X 4 =Na, Mg, Ca and/or Sr,  
 X 5 =Ti, Nb, Ta and/or Zr,  
 X 6 =Fe, Al, Sc, Ga and/or Y,  
 f=0.2to 1.2,  
 g=0 to 0.8,  
 h=0.2 to 1.2,  
 i=0 to 0.8.  
 
     
     
         28 . The process of  claim 20 , wherein the positive electrode material comprises a mixed oxide of formula V 
       A l B m X 7   n X 8   o X 9   p X 10   q X 11   r X 12   s O t   (V) 
       wherein 
 A and B are an element from Group IA, IIA and/or VA and/or Group IVB, VB, VIB, VIIB, or VIII of the Periodic Table of the Elements  
 X 7 =V, Nb, Cr, W, Ta, Ga and/or Ce  
 X 8 =Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and/or Ba,  
 X 9 =La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Au, Pd and/or Pt,  
 X 10 =Fe, Co, Ni and/or Zn,  
 X 11 =Sn,Pb,Sb and/or Te,  
 X 12 =Ti, Zr, Si and/or Al, where  
 l=0.001 to 30,  
 m=0.001 to 20,  
 n=0 to 15,  
 o=0.001 to 10,  
 p=0 to 10  
 q=0 to 40  
 r=0 to 10 and  
 s=0 to 80, with the proviso that l+m is ≧0.01 and l+o is ≧0.005.  
 
     
     
         29 . The process of  claim 20 , wherein the positive electrode further comprises a mixture of the solid electrolyte which conducts oxygen ions and the positive electrode material.  
     
     
         30 . The process of  claim 20 , wherein the positive electrode further comprises a mixture of an electrically conductive metal and the positive electrode material.  
     
     
         31 . The process of  claim 20 , wherein a metal foil having a maximum thickness of 200 μm is disposed between the solid electrolyte which conducts oxygen ions and the positive electrode.  
     
     
         32 . The process of  claim 31 , wherein the metal foil comprises at least one metal selected from the group consisting of Cu, Au, Ag, Pt, Pd and Ir.  
     
     
         33 . The process of  claim 20 , wherein the negative electrode comprises a metal.  
     
     
         34 . The process of  claim 20 , wherein the negative electrode comprises at least one metal selected from the group consisting of Cu, Au, Ag, Pt, Pd, and Ir.  
     
     
         35 . The process of  claim 20 , wherein the negative electrode comprises one or more metal oxides or a mixed metal oxide.  
     
     
         36 . The process of  claim 20 , wherein the negative electrode comprises a perovskite of formula I 
       La u X 13   v X 14   w X 15   x X 16   y O 3±z   (I) 
       wherein 
 X 13 =Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu,  
 X 14 =Ca, Sr, Ba and/or Mg,  
 X 15 =Mn, Fe, Ti, Ga, Mn and/or Zr,  
 X 16 =Co, Ni, Cu, Al and/or Cr  
 u=0 to 1.2,  
 v=0 to 1.0  
 w=0.01 to 0.8,  
 with the proviso that u+v+w is ≦1.5  
 x=0.2 to 1.3,  
 y=0 to 0.9,  
 with the proviso that x+y is ≧0.3.  
 
     
     
         37 . An electrochemical cell comprising a negative electrode means, a positive electrode means, an electrolyte means capable of conducting oxygen ions therebetween, and means for applying a voltage to the positive and negative electrode means.  
     
     
         38 . A process for the selective oxidation of an organic compound in an electrochemical cell, comprising: 
 passing the organic compound over the surface of a positive electrode comprising a positive electrode material, whereby the organic compound is partially oxidized,    passing an oxygen- or N 2 O-containing gas over a negative electrode, whereby the oxygen or N 2 O is converted to oxygen ions,    wherein the oxygen ions are conducted in an ion conductive means disposed between the positive and negative electrodes, and the positive and negative electrodes are connected to a means for applying a voltage to the positive and negative electrode.