Abstract:
A method of converting methane to methanol at low temperatures utilizes a reactor including an anode, a cathode, a membrane separator between the anode and cathode, a metal oxide catalyst at the anode and a hydrogen recovery catalyst at the cathode. The method can convert methane to methanol at as rate exceeding the theoretical Faradaic rate due to the contribution of an electrochemical reaction occurring in tandem with a Faradaic reaction.

Description:
This invention was made with government support under DE-AR0000307 awarded by the United States Department of Energy. The government has certain rights in the invention. 
    
    
     FIELD OF INVENTION 
     The present invention is directed to an improved method of converting methane to methanol. The method utilizes inorganic metal oxide cation intermediates as catalysts to oxidize methane to methanol at temperatures not greater than about 160° C. and suitably at room temperature. 
     BACKGROUND OF THE INVENTION 
     A Faradaic reaction is a heterogeneous charge-transfer reaction occurring at the surface of an electrode. Faradaic reactions are typically a defining feature of electrochemical cells. The production of methanol has conventionally been accomplished using a high temperature Fischer-Tropsch process operating at temperatures of about 150-300° C., typically using a transition metal catalyst. The Fischer-Tropsch process involves a collection of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons, including methane, methanol and various alkanes and alkanes. Thus, the production or methanol using this technique requires not only careful selection of the reactants, process conditions and catalysts to favor methanol conversion, but also the ability to separate methanol from the other reaction products. 
     Methanol can also be made from methane using a series of three reactions known as steam reforming, water shift, and synthesis performed sequentially as follows:
 
CH 4 +H 2 O→CO+3H 2  
 
CO+H 2 O→CO 2 +H 2  
 
2H 2 +CO→CH 3 OH
 
     Because the foregoing process requires three separate reactions to occur in sequence, significant amounts of by-products can again be formed which require separation from the methanol product. Also, the high reaction temperatures require significant amounts of energy input. There is a need or desire for an efficient, relatively low temperature process of manufacturing methanol directly from methane. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a high efficiency method of converting methane to methanol at temperatures less than about 160° C., suitably room temperature (25° C.) which avoids the need for a high temperature Fischer-Tropsch process. The method includes the step of providing a reactor including an anode, a cathode, a membrane, separator between the anode and cathode. A metal oxide catalyst is provided at the anode, and water or an aqueous solution is provided at the cathode. Methane is fed to the anode, and is converted to methanol and electrons in the presence of the metal oxide catalyst at the anode. The electrons are conducted to the cathode, where they transform at least some of the water to hydrogen gas and hydroxide ions. The hydroxide ions are transferred through the membrane separator to the anode, where they cause regeneration of the metal oxide catalyst. Methanol is recovered from the reactor at the anode, and hydrogen gas can be recovered at the cathode. 
     Because the reactor operates at low temperature, the energy input required to produce methanol from methane is less than would be required using a conventional Fischer-Tropsch process. Moreover, the method of the invention produces methanol at a production rate that exceeds the theoretical production rate of a purely Faradaic reaction. This is because the reactor is believed to produce methanol using both a Faradaic and a non-Faradic reaction, with the production rate being the sum of the rates for both reactions. The result is a relatively low-cost, low energy, efficient and easy to use method of converting methane to methanol. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates an electrochemical reactor used to practice the method of the invention. 
         FIG. 2  is a graph comparing methanol signal and methane, carbon dioxide and oxygen signals, all as a function of cell voltage, according to reactor experiments as described in the Examples. 
         FIG. 3  is a graph comparing methanol signal to current density and cell voltage, according to reactor experiments described in the Examples. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a reactor  10  is provided including an anode  12 , a cathode  14 , and a membrane separator  16  between the anode and cathode which can be an electrolyte membrane, and which has an anode side  18  and a cathode side  20 . A metal oxide catalyst is disposed on the anode side  18 , suitably on an anode electrode  22 . A hydrogen recovery catalyst is disposed on the cathode side  20 , suitably on a cathode electrode  24 . A power supply  26  is connected to the anode  12  and cathode  14  of reactor  10  and can be set at various levels of voltage to generate an electric current flowing from the anode  12  to the cathode  14 . 
     The anode electrode  22  can include an inert base material formed of carbon felt or cloth, fluoroethylene polymer (e.g., Teflon), nickel foam, anion exchange resin, or a combination thereof. The base material is coated with a metal oxide, or a combination of one or more metal oxides, that serve as catalysts. Suitable metal oxide catalysts include without limitation oxides and hydroxides of nickel, cobalt, copper, silver, platinum, gold, cerium, lead, iron, manganese, zinc, and combinations thereof. Specific examples include without limitation nickel hydroxide iron hydroxide, zinc hydroxide, manganese hydroxide, cobalt hydroxide, cobalt oxide, silver oxide platinum oxide, cerium oxide, zinc oxide, manganese oxide, iron oxide, and combinations thereof. 
     The cathode electrode  24  can include a base material formed of graphite or another inert material, or a combination thereof. The base material is coated with as metal that serves as a hydrogen recovery catalyst. Suitable metals include without limitation platinum. Group VIII metals of the Periodic Table of Elements (iron, ruthenium, osmium), and combinations thereof. 
     The membrane separator  16  can be an electrolyte membrane, and can be a porous polymer material that contains an electrolyte. Other suitable membranes include ion conductive materials that have low water transport. It is desirable to restrict the transport of water from the cathode to the anode, because excessive water in the anode dilutes the methanol product. Particularly suitable electrolyte membranes include anionic exchange membranes formed from alkaline ionomers, available from Tokuyama Corporation under the product name NEOSEPTA®. These membranes have high permselectivity to facilitate permeation of specific anions, low electric resistance, low diffusion of liquids, and high mechanical strength. Other examples of anionic exchange membranes include porous membranes sold by Freudenberg under the product name 700/30K, microporous membranes sold by Celgard under the product name CELGARD® 3400, and microporous membranes sold by Daramic under the product name DARAMIC® DP-34.14. Cationic exchange membranes can also be employed in the membrane separator  16 . Cationic exchange membranes include without limitation proton exchange membranes formed of sulfonated tetratluoroethylene-based fluoropolymer copolymer, available from Aldrich Chemical Co. under the product name NAFION®. 
     The anode  12  and cathode  14  also include outer plates  28  and  30  which, in order to facilitate a stable process and long useful life of the reactor  10 , are designed to be substantially free of corrosion and leakage. The plates  28  and  30  can be formed of a graphite which has been electroplated with nickel to seal the pores in the graphite to prevent any leakage or corrosion. The plates  28  and  30  can alternatively include a graphite layer and a second, protective metal alloy layer that has been sealed to the graphite layer. 
     During use of the reactor  10 , methane is fed to the anode  12  via inlet stream  32  and is converted to methanol in the presence of the metal oxide catalyst. The chemical reactions at the anode may vary depending on the specific metal oxide catalyst and whether the environment is basic or acidic. In each case, the methane is oxidized to methanol and the metal oxide catalyst is converted to a non-catalytic state. 
     For example, the metal oxide catalyst can be a divalent metal hydroxide having the formula M 1 (OH 2 ), such as β-nickel hydroxide, Ni(OH) 2 . In this case, the following chemical reactions would occur together at the anode, in a basic environment, and at room temperature without requiring added heat.
 
M 1 (OH) 2 +OH − →M 1 O + +H 2 O+ e   − 
 
M 1 O + +OH − +CH 4 →CH 3 OH+OH − +M 1   + 
 
M 1 ++½O 2 →M 1 O + 
 
M 1 O + +OH − →M 1 O + OH − 
 
     The net chemical reaction at the anode, which is the sum of the individual reactions, yields a converted (non-catalytic) metal hydroxide, methanol, water, and free electrons.
 
M 1 (OH) 2 +CH 4 +3OH − →M 1 O + OH − +CH 3 OH+2H 2 O+3 e   − 
 
     The foregoing net chemical reaction is Faradaic because of the generation of electrons. Additionally, a non-Faradaic electrochemical reaction occurs in the anode due to the electric current supplied to the reactor. The oxygen supplied to this reaction is the trace oxygen present in the anode from the inlet stream  32 . 
     
       
                 
         
             
             
         
      
     
     The non-Faradaic electrochemical reaction causes the total methanol production rate to exceed the theoretical maximum production rate from the Faradaic reaction using the metal oxide catalyst. For example, the methanol conversion rate may exceed the theoretical Faradic rate by at least about 10% or at least about 25%, or at least about 50% or more. The theoretical Faradaic production rate of methanol using the metal oxide catalyst is about 0.75 ml/A·min. Yet the total methanol production rate from the reactor  10 , using a 1.4 volt power supply, has been up to about 1.20 ml/A·min, representing a surprising 60 percent improvement. 
     The methanol is recovered from the anode  12  of reactor  10  via the outlet stream  34 , which also includes some unreacted methane. The methanol and methane are then separated, and the unreacted methane is recycled back to the inlet stream  32  via the recycle stream  38 . The methanol product is recovered from the combined stream  34  via product stream  36 . Because of the dual (Faradaic and non-Faradaic) reactions occurring in the anode  12 , the conversion rate of methane to methanol can be quite high. The outlet stream  34  may contain at least about 10% by weight methanol and not More than about 60% by weight methane balanced by water vapor (30%), suitably at least about 40% by weight methanol and not more than about 20% by weight methane balanced by water vapor (40%). The methane gas works both as a carrier gas and a reactant. 
     The free electrons generated at the anode  12  are conducted to the cathode  14 . Water or an aqueous solution is fed to the cathode  14  via inlet  40 , typically as a basic or acidic solution. When an acidic solution is used at the cathode, a bipolar membrane separator  16  is used. The bipolar membrane separator contains an acidic polymer electrolyte overlapped on a basic polymer electrolyte. The basic polymer electrolyte faces the anode and the acidic polymer electrolyte faces the cathode. In the embodiment shown, a 25% w/w potassium hydroxide solution having a pH of about 14 or greater is fed to the cathode  14  via inlet  40 . The free electrons interact with the water in the presence of the hydrogen evolution catalyst to generate hydroxide ions and hydrogen gas, the latter of which exits the cathode through outlet  42  and can be recovered for various uses. The hydroxide ions are then transferred through the membrane separator  16  back to the anode  12 , where they react with and regenerate the used metal oxide catalyst. 
     The following chemical reactions typically occur at the cathode  14 , where M 2  is the hydrogen recovery catalyst, platinum or a Group VIII metal.
 
M 2 +H 2 O+ e   − →M 2 H+OH − 
 
M 2 H→M 2 +½H 2  
 
     As indicated, the hydrogen recovery catalyst M 2  is self-regenerating. The net chemical reaction at the cathode  14 , which is the sum of the foregoing reactions, converts the water to hydroxide ions and hydrogen.
 
H 2 O+ e   − →OH − +½H 2  
 
     The overall sum of the Faradaic reactions occurring in the anode  12  and cathode  14  is the hydrolysis of methane.
 
CH 4 +H 2 O→CH 3 OH+H 2  
 
     The reactor  10 , and the foregoing chemical reactions in the anode  12  and cathode  14 , can occur at a temperature less than about 160° C., or less than about 100° C. or less than about 50° C., or at ambient temperature (about 25° C.). As shown above, the overall reaction uses only methane and water to produce methanol and hydrogen gas. The other reactants are used only to form intermediate compounds, and are continuously regenerated. 
     EXAMPLES 
     Examples 1-27 
     Using a reactor  10  designed as shown in  FIG. 1 , experiments were performed using various configurations for the anode electrode (including different metal oxide catalysts) and for the membrane separator. In each experiment, the cathode electrode was graphite coated with platinum. The hydrogen recovery catalyst (platinum) was constant. The reactor  10  had an area of about 30 cm 2  for the anode plate, the cathode plate and the membrane separator. 
     In the following Examples 1-27, the following acronyms or abbreviations are used. 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 FEP: 
                 Fluoroethylene polymer available from Delaware 
               
               
                   
                 Specialty Distribution, LLC under the product name 
               
               
                   
                 DuPont TEFLON ® FEP, TE-9568. 
               
               
                 A3: 
                 Anion exchange resin available from Tokuyama 
               
               
                   
                 Corp. under the product name A3. 
               
               
                 Carbon Cloth: 
                 Available from Zoltek, under the product name 
               
               
                   
                 PANEX ® 30. 
               
               
                 Carbon Felt: 
                 Available from SQL Carbon under the product 
               
               
                   
                 name SIGRATHERM ®. 
               
               
                 Tokuyama Membrane: 
                 Anion exchange membrane composition with 
               
               
                   
                 quaternary ammonium group, available from 
               
               
                   
                 Tokuyama Corp. under the product name AEM 
               
               
                   
                 A201. 
               
               
                 Ni foam: 
                 Available from international Nickel Company 
               
               
                   
                 (“INCO”) under the product name INCOFOAM ®. 
               
               
                 Daramic membrane: 
                 Anionic exchange membrane available from 
               
               
                   
                 Daramic under the product name DARAMICV DP- 
               
               
                   
                 34.14. 
               
               
                 Vilene separator: 
                 Anionic exchange membrane available from 
               
               
                   
                 Freudenberg Nonwovens, LP under the product 
               
               
                   
                 name FV-4365K. 
               
               
                 NAFION ® 112 
                 Sulfonated tetrafluoroethylene cationic exchange 
               
               
                   
                 membrane, available from Aldrich Chemical Co. 
               
               
                 CG 135: 
                 Polypropylene membrane available from Celgard. 
               
               
                   
               
             
          
         
       
     
     In each experiment, the reactor was supplied with a current of 8 mA/cm 2  (based on 1.48 volts) for at least six hours. Methane was fed to the anode at a rate of 1 ml/min., and aqueous potassium hydroxide (25% w/v) was fed to the cathode at a rate of 0-10. The product stream exiting the anode was analyzed using gas chromatography. In order to calibrate the instrument, various solutions of methanol ranging in concentration from 1 to 5 moles were prepared, each in an aqueous solution of 25% w/v potassium hydroxide. A plot of GC signal (mV) versus molar concentration of methanol was prepared for use as a calibration curve. 
     The results are summarized in Table 1. The column entitled “observations” indicates the combinations of anode electrode configuration and catalyst, and separator membrane, that resulted in large methanol peaks as an indicator of good methane to methanol conversions. In general, the catalyst combinations of Ni(OH) 2  with CoO and CeO 2 , as well as Ni(OH) 2  with CeO 2 , resulted in the largest methanol peaks in the product stream using various materials for the membrane separator. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Example 
                 Anode 
                 Membrane 
                 Cathode 
                 Observations 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Ni(OH)2/CoO(9:1)/FEP/A3 
                 Daramic 
                 Pt/C 
                 methanol peak small 
               
               
                   
                 [73:20:7] painted on Carbon 
                   
                   
                 hump 
               
               
                   
                 Cloth 
               
               
                 2 
                 Ni(OH)2/CoO(9:1)/FEP/A3 
                 Vilene 
                 Pt/C 
                 too much solution 
               
               
                   
                 [73:20:7] painted on Carbon 
                 separator 
                   
                 cross over, no 
               
               
                   
                 Cloth 
                   
                   
                 methanol peak, lots 
               
               
                   
                   
                   
                   
                 of O2 peak 
               
               
                 3 
                 Ni(OH)2/CoO(9:1)/FEP/A3 
                 Hexane 
                 Pt/C 
                 methanol peak not 
               
               
                   
                 [73:20:7] sprayed on Carbon 
                 washed 
                   
                 significant 
               
               
                   
                 Felt 
                 Daramic 
               
               
                 4 
                 Ni(OH)2/CoO(9:1)/FEP/A3 
                 sprayed on 
                 Pt/C 
                 methanol peak not 
               
               
                   
                 [73:20:7] Tokuyama 
                   
                   
                 significant 
               
               
                   
                 membrane, 3.6 mg/cm2(cat) 
               
               
                 5 
                 Ni(OH)2/(Ag/C)(9:1)/A3/FEP 
                 Tokuyama 
                 Pt/C 
                 flow rate very small. 
               
               
                   
                 [70:5:25] on Ni foam (KOH 
                 (KOH 
                   
                 at 80° C. significant 
               
               
                   
                 soaked), 50 mg/cm2(cat) 
                 soaked) 
                   
                 methanol peak 
               
               
                 6 
                 Ni(OH)2/Pt(9:1)/A3/FEP 
                 Tokuyama 
                 Pt/C 
               
               
                   
                 [70:5:25] on Ni foam (KOH 
                 (KOH 
               
               
                   
                 soaked), 46 mg/cm2(cat) 
                 soaked) 
               
               
                 7 
                 Ni(OH)2/Ag/C/PbO 
                 Tokuyama 
                 Pt/C 
               
               
                   
                 (60:5:5)/A3/FEP [70:5:25] on 
                 (KOH 
               
               
                   
                 Ni foam, 49 mg/cm2(cat) 
                 soaked) 
               
               
                 8 
                 Ni(OH)2/Ag/C/CeO2(90:5:5)/ 
                 Tokuyama 
                 Pt/C 
                 methanol peak very 
               
               
                   
                 A3/FEP [70:5:25], 49 mg/cm2 
                 (KOH 
                   
                 good (small CO2 
               
               
                   
                 (cat) 
                 soaked) 
                   
                 peak, O2 peak big) at 
               
               
                   
                   
                   
                   
                 1.48V, 76° C. 
               
               
                 9 
                 Ni(OH)2/ Ag/C (1:1)/A3/FEP 
                 Tokuyama 
                 Pt/C 
                 methanol peak very 
               
               
                   
                 [70:5:25] sprayed on Ni foam, 
                 (KOH 
                   
                 good (small CO2 
               
               
                   
                 40 mg/cm2(cat) 
                 soaked) 
                   
                 peak, O2 peak big) at 
               
               
                   
                   
                   
                   
                 1.48V, 76° C., MeOH 
               
               
                   
                   
                   
                   
                 peak not as high as 
               
               
                   
                   
                   
                   
                 Ni(OH)2/Ag/C/CeO2 
               
               
                 10 
                 Ni(OH)2/ Ag2O (1:1)/A3/FEP 
                 Tokuyama 
                 Pt/C 
                 this is to study 
               
               
                   
                 [70:5:25] sprayed on Ni foam, 
                 (KOH 
                   
                 carbon content effect 
               
               
                   
                 55 mg/cm2(cat) 
                 soaked) 
               
               
                 11 
                   Ni(OH)2/Ag/C/CeO2 (83:5:10)/ 
                 Tokuyama 
                 Pt/C 
                 this is to study CeO2 
               
               
                   
                 A3/FEP [70:5:25] sprayed on 
                 (KOH 
                   
                 content effect 
               
               
                   
                 Ni foam 54 mg/cm2(cat) 
                 soaked) 
               
               
                 12 
                 
                   Ni(OH)2/CoO(9:1)Ag/C/CeO2 
                 
                 Catalyst 
                 Pt/C 
                 this is to study 
               
               
                   
                 (90:5:5)/A3/FEP [70:5:25] 
                 sprayed 
                   
                 catalyst contact with 
               
               
                   
                 sprayed on Ni foam 
                 Tokuyama 
                   
                 membrane 
               
               
                   
                 47 mg/cm2(cat) 
                 membrane 
               
               
                   
                 
                   Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 
               
               
                   
                 (90:5:5)/A3/FEP [70:5:25] 
               
               
                   
                 sprayed on Tokuyama 
               
               
                   
                 membrane, 1.3 mg/cm2(cat) 
               
               
                 13 
                 Ni(OH)2/Ag/C/CeO2(90:5:5) 
                 Tokuyama 
                 Pt/C 
                 this is to prevent 
               
               
                   
                 A3/FEP [70:5:25] sprayed on 
                 (KOH 
                   
                 excess water on 
               
               
                   
                 hydrophobic Ni foam (teflon, 
                 soaked) 
                   
                 anode side, large 
               
               
                   
                 350 F.) 50 mg/cm2(cat) 
                   
                   
                 MeOH peak 
               
               
                 14 
                 Ni(OH)2/Ag/C/CeO2(90:5:5)/ 
                 Tokuyama 
                 Pt/C 
               
               
                   
                 A3/FEP [70:5:25] sprayed on 
                 (KOH 
               
               
                   
                 hydrophobic Ni foam (teflon, 
                 soaked) 
               
               
                   
                 350 F.) 50 mg/cm2(cat) 
               
               
                 15 
                 Ni(OH)2/Ag/C/CeO2(90:5:5)/ 
                 Tokuyama 
                 Pt/C 
                 this is to study more 
               
               
                   
                 A3/FEP [45:5:50] sprayed on 
                 (KOH 
                   
                 content of teflon on 
               
               
                   
                 hydrophobic Ni foam (teflon, 
                 soaked) 
                   
                 anode side. Current 
               
               
                   
                 350 F.) 60 mg/cm2(cat) 
                   
                   
                 density is small. 
               
               
                 16 
                 Ni(OH)2/Ag/C/CeCO2(90:5:5)/ 
                 Tokuyama 
                 Pt/C 
               
               
                   
                 A3/FEP [70:5:25] sprayed on 
                 (KOH 
               
               
                   
                 hydrophobic carbon cloth 
                 soaked) 
               
               
                   
                 44 mg/cm2(cat) 
               
               
                 17 
                 Ni(OH)2/CoO/ZnO/Ni 
                 Tokuyama 
                 Pt/C 
                 no MeOH found 
               
               
                   
                 (90:6:1:3)/FEP [93:7] sprayed 
                 (KOH 
               
               
                   
                 on hydrophobic carbon cloth 
                 soaked) 
               
               
                   
                 50 mg/cm2(cat), electrode heat 
               
               
                   
                 treated 360 F. 
               
               
                 18 
                 Ni(OH)2/Ag/C/CeO2(85:5:10)/ 
                 Daramic 
                 Pt/C 
                 MeOH peak found 
               
               
                   
                 A3/FEP [70:5:25] sprayed on 
               
               
                   
                 hydrophobic Ni Foam (teflon, 
               
               
                   
                 350 F.) 60 mg/cm2(cat) 
               
               
                 19 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 Daramic 
                 Pt/C 
                 MeOH peak found 
               
               
                   
                 (85:5:10)/A3/FEP [6O:20:2O] 
               
               
                   
                 sprayed on Daramic membrane, 
               
               
                   
                 hydrophobic carbon cloth as 
               
               
                   
                 backing. 
               
               
                 20 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 Daramic 
                 Pt/C 
                 big MeOH peak 
               
               
                   
                 (85:5:10)/A3/FEP [60:20:20] 
                   
                   
                 found 
               
               
                   
                 sprayed on Daramic membrane, 
               
               
                   
                 heat 62° C. for 3 h to get rid of 
               
               
                   
                 VOC, hydrophobic carbon 
               
               
                   
                 cloth as backing. 
               
               
                 21 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 Daramic 
                 Pt/C 
                 big MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                   
                   
                 found 
               
               
                   
                 [50:20:30] sprayed on Daramic 
               
               
                   
                 membrane, hydrophobic carbon 
               
               
                   
                 cloth as backing 
               
               
                 22 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 KOH 
                 Pt/C 
                 big MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                 Nafion 112 
                   
                 found 
               
               
                   
                 [50:20:30] sprayed on 
               
               
                   
                 hydrophobic carbon cloth, 
               
               
                   
                 43 mg/cm2 
               
               
                 23 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 CG35 
                 Pt/C 
                 big MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                 (1 layer) 
                   
                 found, too much 
               
               
                   
                 [50:20:30] sprayed on 
                   
                   
                 KOH solution 
               
               
                   
                 hydrophobic carbon cloth, 
                   
                   
                 crossover from 
               
               
                   
                 43 mg/cm2 
                   
                   
                 cathode to anode 
               
               
                 24 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 CG35 
                 Pt/C 
                 found MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                 (2 layer) 
               
               
                   
                 [50:20:30] sprayed on 
               
               
                   
                 hydrophobic carbon cloth, 
               
               
                   
                 43 mg/cm2 
               
               
                 25 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 CG35 
                 Pt/C 
                 found MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                 (2 layer) 
               
               
                   
                 [50:20:30] sprayed on 
               
               
                   
                 hydrophobic carbon cloth, 
               
               
                   
                 5 mg/cm2, hot press 
               
               
                   
                 200 F./4000 lb/ 5 min 
               
               
                 26 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 CG35 
                 Pt/C 
                 found MeOH peak 
               
               
                   
                 (85:5:10)/KOH Nafion/FEP 
                 (1 layer) 
               
               
                   
                 [50:20:30] sprayed on 
               
               
                   
                 hydrophobic carbon cloth, 
               
               
                   
                 5 mg/cm2, hot press 
               
               
                   
                 200 F./4000 lb/5 min 
               
               
                 27 
                 Ni(OH)2/CoO(9:1)/Ag/C/CeO2 
                 CG35 
                 Pt/C 
                 this is to study anode 
               
               
                   
                 (85:5:10)/FEP [70:30] sprayed 
                 (2 layer) 
                   
                 without Nafion 
               
               
                   
                 on hydrophobic carbon cloth, 
               
               
                   
                 5 mg/cm2, hot press 
               
               
                   
                 200 F./4000 lb/5 min 
               
               
                   
               
             
          
         
       
     
     Examples 28-33 
     For Examples 28-33, a small reactor was used having an area of about 30 cm 2  for the anode and cathode and the membrane separator. The membrane separator was an anionic electrolyte membrane sold by Tokuyama (Japan) under the product name AEM A201. The metal oxide catalyst present at the anode was nickel hydroxide, Ni(OH) 2 , coated onto a graphite cloth sold by Zoltek under the product name PANEX® 30. The hydrogen recovery catalyst present at the cathode was platinum metal, coated onto a layer of graphite. 
     The current to the reactor was varied using a cell voltage of 1.30 volts (Example 28), 1.35 volts (Example 29), 1.40 volts (Example 30), 1.43 volts (Example 31), 1.45 volts (Example 32) and 1.50 volts (Example 33). Methane was fed to the anode at a constant rate of 1 ml/min. Aqueous potassium hydroxide (25% w/v) was fed to the cathode at a constant rate of 10 ml/min. For each change in voltage, the reactor was allowed to reach steady state, requiring a time period of at least 3 min. 
     The methanol signal at the exit stream from the anode was measured using gas chromatography, as described above. The signals for methane, carbon dioxide and oxygen were also measured and recorded. The results are plotted in  FIG. 2 . As shown, the methanol signal (indicative of methane to methanol conversion) increased substantially as the cell voltage was increased, while the methane signal fell. The oxygen signal increased very slowly with voltage and did not spike. The carbon dioxide signal increased very slowly at voltages up to 1.45 volts, then spiked at 1.5 volts. 
       FIG. 3  is a plot comparing methanol signal and current density as a function of increasing voltage. Overall, the methanol signal increased proportionally to the current density between 1.30 and 1.50 volts. However, the methanol signal increased faster than current density at intermediate voltages. 
     While the embodiments of the invention described herein are presently preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated by the appended claims, and all changes that fall within the meaning and range of equivalents are intended to be embraced therein.