WO2014043648A2

WO2014043648A2 - Heterocycle catalyzed electrochemical process

Info

Publication number: WO2014043648A2
Application number: PCT/US2013/060000
Authority: WO
Inventors: Narayanappa Sivasankar; Emily Barton Cole; Rishi Parajuli; Andrew B. Bocarsly
Original assignee: Liquid Light, Inc.
Priority date: 2012-09-14
Filing date: 2013-09-16
Publication date: 2014-03-20
Also published as: WO2014043648A3

Abstract

A method for heterocycle catalyzed electrochemical reduction of a carbonyl compound is disclosed. The method generally includes steps (A) to (C). Step (A) may introduce the carbonyl compound into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell. The divided electrochemical cell may include an anode in a first cell compartment and a cathode in a second cell compartment. The cathode generally reduces the carbonyl compound to at least one aldehyde compound. Step (B) may vary which of the aldehyde compounds is produced by adjusting one or more of (i) a cathode material, (ii) the electrolyte, (iii) the heterocycle catalyst, (iv) a pH level and (v) an electrical potential. Step (C) may separate the aldehyde compounds from the solution.

Description

HETEROCYCLE CATALYZED ELECTROCHEMICAL PROCESS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001 ] This application claims the benefit of U.S. Patent Application Ser. No. 14/028,322 filed September 16, 2013, pending, which in turn claims the benefit of U.S. Provisional Application Ser. No. 61 /701 , 167 filed September 14, 2012. This application also claims the benefit of U.S. Patent Application Ser. No. 12/846,011 filed July 29, 2010, pending, which in turn claims the benefit of U.S. Provisional Application Ser. No. 61 /315,564, filed Mar. 19, 2010 and U.S. Provisional Application Ser. No. 61 /315,710, filed Mar. 19, 2010. Each of the above-listed applications is hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] The present invention relates to electrochemical processing generally and, more particularly, to a method and /or apparatus for implementing a heterocycle catalyzed electrochemical process.

BACKGROUND OF THE INVENTION

[0003] Alcohols and organic chemicals with hydroxyl and carbonyl functional groups are important to industrial processes and the production of light alcohol fuels. At present, several different processes are used for production of alcohols. Most alcohols are produced from oil or natural gas, while some including ethanol and pentanol are produced biologically. Hydroxyl groups are often introduced to organic molecules via catalytic hydrogenation of aldehydes or acid catalyzed

l hydration of alkenes. Some specific examples include methanol, which is produced by catalytic conversion of synthesis gas at high temperature and pressure. Ethanol is produced by acid catalyzed hydration of ethylene or by various microorganisms via fermentation of sugars.

[0004] Two major processes exist for propanol production. Acid catalyzed hydration of propylene is performed, resulting in a mixture of both isopropanol and n-propanol. Another process to make n-propanol is hydroformylation of ethylene to propionaldehyde followed by catalytic hydrogenation of propionaldehyde to n- propanol. N-butanol is produced in a manner similar to that of n-propanol. Propylene is converted to butyraldehyde via hydroformylation. The butyraldehyde is then catalytically hydrogenated to n-butanol. Sec-butanol is produced in a manner similar to ethanol, by the acid catalyzed hydration of 1 -butene or 2- butene. Isomers of pentanol are primarily produced by the distillation of fusel oil. Fusel oil is a product of some biological fermentation processes. Hexanol and higher order alcohols are commonly produced by oligomerization of ethylene, which results in a mix of different products separated via distillation.

[0005] At present, many different techniques are currently used to create other organic products. Biological processes, such as fermentation of sugars, produce ethanol or fusel oil. The Fischer-Tropsch process is used for conversion of synthesis gases to organic molecules. Hydroformylation of alkenes is followed by catalytic hydrogenation to alcohols or alkanes. Polymerization of alkenes results in organic products. Electrochemical hydrodimerization of alkenes, notably the Monsanto process, produces adiponitrile.

[0006] Existing electrochemical and photochemical processes/systems have one or more of the following problems that prevent commercialization on a large scale. Selectively producing some alcohols, notably isopropanol, butanol, pentanol, and higher order alcohols is difficult. Selectively reducing carboxyl or carbonyl groups is also difficult without undesirable side reactions such as hydrogenation of aromatic molecules or heterocycles. Many existing processes, notably the Fischer- Tropsch process, make multiple products that are subsequently separated. Production of some aldehydes and alcohols requires the use of multi-step reactions that collectively have low energy efficiency. Likewise, hydrodimerization without a catalyst can be very inefficient. Existing reaction pathways use high heat, high temperature and/or highly acid environments. The heat conditions result in the use of expensive materials for the reactors. Many existing processes, both thermally and electrochemically driven, also use alkenes as a starting material.

SUMMARY OF THE PREFERRED EMBODIMENTS

[0007] The present invention comprises a method for heterocycle catalyzed electrochemical reduction of a carbonyl compound. The method generally includes steps (A) to (C). Step (A) may introduce the carbonyl compound into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell. The divided electrochemical cell may include an anode in a first cell compartment and a cathode in a second cell compartment. The cathode generally reduces the carbonyl compound to at least one aldehyde compound. Step (B) may vary which of the aldehyde compounds is produced by adjusting one or more of (i) a cathode material, (ii) the electrolyte, (iii) the heterocycle catalyst, (iv) a pH level and (v) an electrical potential. Step (C) may separate the aldehyde compounds from the solution.

[0008] The objects, features and advantages of the present invention include providing a method and /or apparatus for implementing a heterocycle catalyzed electrochemical process that may (i) reduce carboxylic acid groups to aldehydes, (ii) reduce aldehydes to alcohols, (iii) reduce keto groups to hydroxyl groups, (iv) support heterocycle catalyzed electrochemical processing at a commercial level, (v) operate at atmospheric pressure, (vi) operate at ambient temperature, (vii) use water as a solvent, (viii) process at a mild pH, (ix) selectively electrohydrodimerize carbonyl-containing compounds to a variety of organic chemicals and /or (x) provide stable processing over time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other objects, features and advantages of the present invention will be apparent from the following detailed description and the appended claims and drawings in which:

[0010] FIG. 1 is a block diagram of a system in accordance with a preferred embodiment of the present invention;

[001 1 ] FIG. 2 is a diagram illustrating reductions of two-carbon and higher starting materials;

[0012] FIG. 3 are formulae of example hydrodimerization reactions;

[0013] FIG. 4 is a table illustrating relative product yields for different cathode material, catalyst and cathode potential combinations;

[0014] FIG. 5 is a formula of an aromatic heterocyclic amine catalyst;

[0015] FIGS. 6-8 are formulae of substituted or unsubstituted aromatic 5-member heterocyclic amines or 6-member heterocyclic amines;

[0016] FIG. 9-10 are flow diagrams of an example methods used in electrochemical examples and photochemical examples; [0017] FIG. 1 1 is a diagram of the use of oxalic acid and its use as an intermediate for the production of a variety of chemical compounds.

DETAILED DESCRIPTION

[0018] Some embodiments of the present invention relate to heterocycle catalyzed reduction of keto groups to hydroxyl groups, carboxylic acids to more reduced carboxylic acids, carboxylic acids to aldehydes and /or aldehydes to alcohols. Some embodiments generally relate to hydrodimerization of carbonyl compounds. The methods generally include electrochemically and /or photoelectrochemically reducing in an aqueous, electrolyte-supported divided electrochemical cell that includes an anode (e.g., an inert conductive counter electrode) in a cell compartment and a conductive, or p-type semiconductor, working cathode electrode in another cell compartment. A catalyst may be included to help produce a reduced product. The reactants may be continuously introduced into the cathode electrolyte solution to saturate the solution.

[0019] For electrochemical reductions, the electrode may be a suitable conductive electrode, such as Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys (e.g., brass and bronze), Ga, Hg, In, Mo, Nb, Ni, Ni alloys, Ni--Fe alloys, Sn, Sn alloys, Ti, V, W, Zn, stainless steel (SS), austenitic steel, ferritic steel, duplex steel martensitic steel, Nichrome, elgiloy (e.g., Co--Ni--Cr), degenerately doped p-Si, degenerately doped p-Si:As and degenerately doped p-Si:B. Other conductive electrodes may be implemented to meet the criteria of a particular application. For photoelectrochemical reductions, the electrode may be a p-type semiconductor, such as p-GaAs, p-GaP, p-lnN, p- InP, p-CdTe, p-GalnP.sub.2 and p-Si. Other semiconductor electrodes may be implemented to meet the criteria of a particular application.

[0020] Before any embodiments of the invention are explained in detail, it is to be understood that the embodiments may not be limited in application per the details of the structure or the function as set forth in the following descriptions or illustrated in the figures of the drawing. Different embodiments may be capable of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of terms such as "including," "comprising," or "having" and variations thereof herein are generally meant to encompass the item listed thereafter and equivalents thereof as well as additional items. Further, unless otherwise noted, technical terms may be used according to conventional usage.

[0021 ] In the following description of methods, process steps may be carried out over a range of temperatures (e.g., approximately 10. degree. C. (Celsius) to 50. degree. C.) and a range of pressures (e.g., approximately 1 to 10 atmospheres) unless otherwise specified. Numerical ranges recited herein generally include all values from the lower value to the upper value (e.g., all possible combinations of numerical values between the lowest value and the highest value enumerated are considered expressly stated). For example, if a concentration range or beneficial effect range is stated as 1% to 50%, it is intended that values such as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expressly enumerated. The above may be simple examples of what is specifically intended.

[0022] Referring to FIG. 1 , a block diagram of a system 100 is shown in accordance with a preferred embodiment of the present invention. The system (or apparatus) 100 generally comprises a cell (or container) 102, a liquid source 104, a power source 106, a reactant source 108, an extractor 110 and an extractor 1 12. A product may be presented from the extractor 110. An output gas may be presented from the extractor 1 12. Another output gas may be presented from the cell 102.

[0023] The cell 102 may be implemented as a divided cell. The divided cell may be a divided electrochemical cell and/or a divided photochemical cell. The cell 102 is generally operational to reduce carbonyl compounds and /or carboxyl group compounds (e.g., reactants) to aldehyde, alcohols, hydroxyl groups and/or organic products containing keto groups. The reactants may also be reduced to methanol, ethanol, propanol, pentanol, hexanol and septanol. The cell 102 may also be operational to hydrodimerize carbonyl compounds to butanone (methyl ethyl ketone), butanol, octanone and/or octanol. The carbonyl compounds may include, but are not limited to, aldehydes and carboxylic acids. The reactions generally takes place by introducing the reactants into an aqueous solution of an electrolyte in the cell 102. A cathode in the cell 102 may hydrodimerize and/or reduce the reactants into one or more organic compounds.

[0024] The cell 102 generally comprises two or more compartments (or chambers) 1 14a- 1 14b, a separator (or membrane) 1 16, an anode 118 and a cathode 120. The anode 1 18 may be disposed in a given compartment (e.g., 1 14a). The cathode 120 may be disposed in another compartment (e.g., 1 14b) on an opposite side of the separator 116 as the anode 1 18. An aqueous solution 122 may fill both compartments 114a- 114b. A catalyst 124 may be added to the compartment 1 14b containing the cathode 120.

[0025] The liquid source 104 may implement a water source. The liquid source 104 may be operational to provide pure water to the cell 102.

[0026] The power source 106 may implement a variable voltage source. The source 106 may be operational to generate an electrical potential between the anode 118 and the cathode 120. The electrical potential may be a DC voltage.

[0027] The reactant source 108 may implement a keto group, carbonyl compound, carboxyl group compound and/or aldehyde source. The source 108 is generally operational to provide the reactants to the cell 102. In some embodiments, the reactants are introduced directly into the compartment 1 14b containing the cathode 120. [0028] The extractor 1 10 may implement an organic product extractor. The extractor 1 10 is generally operational to extract (separate) organic products (e.g., acetaldehyde, acetone, butanone, 2-butanol, n-butanol, ethanol, glyoxal, glyoxylic acid, methanol, octanone, octanol, oxalic acid, propanol, propioin and the like) from the electrolyte 122. The extracted organic products may be presented through a port 126 of the system 100 for subsequent storage and/or consumption by other devices and /or processes.

[0029] The extractor 1 12 may implement an oxygen extractor. The extractor 112 is generally operational to extract oxygen (e.g., O.sub.2) byproducts created by the reactions. The extracted oxygen may be presented through a port 128 of the system 100 for subsequent storage and /or consumption by other devices and /or processes. Any other excess gases (e.g., hydrogen) created by the reactions may be vented from the cell 102 via a port 130.

[0030] In the process described, water may be oxidized (or split) to protons and oxygen at the anode 1 18 while organic molecules containing a carbonyl or carboxyl group are hydrodimerized and sometimes reduced at the cathode 120. The electrolyte 122 in the cell 102 may use water as a solvent with any salts that are water soluble and with a heterocycle catalyst 124. The catalysts 124 may include, but are not limited to, azoles, imidazoles, indoles, pyridine, pyrrole, thiazole and furan. Examples of the heterocyclic compounds catalysts 124 may be pyridine, imidazole, pyrrole, thiazole, furan, thiophene and the substituted heterocycles such as amino-thiazole and benzimidazole. Cathode materials generally include any conductor. Any anode material may be used. The overall process is generally driven by the power source 106. Combinations of cathodes 120, electrolytes 122, introduction of the carbonyl or carboxyl group to the cell 102, pH levels and electric potential from the power source 106 may be used to control the reaction products of the cell 102. Organic products resulting from the reactions may include, but are not limited to, alcohols, aldehydes, organic molecules containing hydroxyl groups and /or organic products containing keto groups.

[0031 ] In some nonaqueous embodiments, the solvent may include methanol, acetonitrile, dimethylformamide, N-methylpyrrolidone, diethyl carbonate, dimethyl carbonate, dimethylsulfoxide, dipolar-aprotic solvents, and/or other nonaqueous solvents. The electrolytes generally include tetraalkyl ammonium salts and a heterocyclic catalyst. In a system containing nonaqueous catholyte and aqueous anolyte, the products generally include all of the products seen in aqueous systems with higher yields.

[0032] Experiments were conducted in one, two and three-compartment electrochemical cells 102 with a platinum anode 1 18 and Saturated Calomel Electrode (SCE) as the reference electrode. The experiments were generally conducted at ambient temperature and pressure. Reactants were introduced into the cells during the experiments. A potentiostat or DC power supply 106 provides the electrical energy to drive the process. Cell potentials ranged from 1.5 volts to 4 volts, depending on the cathode material. Half cell potentials at the cathode ranged from -1 volt to -2 volts relative to the SCE, depending on the cathode material used. Products from the experiments were analyzed using gas chromatography and a spectrometer.

[0033] Referring to FIG. 2, a diagram illustrating reductions of two-carbon and higher starting materials is shown. Complex molecules, such as oxalic acid (a carboxylic acid) may be reduced to simpler acids, such as glyoxylic acid (a C2 carboxylic acid). The glyoxylic acid may be further reduced to glyoxal (a dialdehyde). Furthermore, the glyoxal may be reduced to acetaldehyde (an aldehyde). The acetaldehyde is reducible to ethanol (a primary alcohol). Other aldehydes may include, but are not limited to, formaldehyde, butanal, benzaldehyde, aliphatic aldehydes, aromatic aldehydes, heteroaromatic aldehydes, and heterocyclic aldehydes. Other alcohols may include, but are not limited to, methanol, ethanol, 2-butanol, 1 -butanol, 1 -propanol, 2-propanol, alkyl alcohols, alkyl diols and polyols, aromatic alcohols, and heterocyclic alcohols, and heteroaromatic alcohols, and propioin. The process is controlled to get a desired product by using combinations of specific conductive cathodes, catalysts, electrolytes, surface morphology of the electrodes, pH levels and/or introduction of reactants relative to the cathode. Faradaic yields for the products generally range from less than 1% to more than 90% with the remainder generally being hydrogen.

[0034] Referring to FIG. 3, formulae of example hydrodimerization reactions are shown. Formula (1 ) generally illustrates a hydrodimerization of two acetaldehyde molecules (e.g., C.sub.2H.sub.40) into a butanone molecule (e.g., C.sub.4H.sub.80) and half of an oxygen (e.g., O.sub.2) molecule. Formula (2) may illustrate a hydrodimerization of two acetaldehyde molecules and two hydrogen ions (e.g., H.sup.+) into a butanol molecule (e.g., C.sub.4H.sub.90H) and half of an oxygen molecule. Formula (3) may show a hydrodimerization of two butyric acid molecules (e.g., C. sub.4H. sub.80. sub.2) and two hydrogen ions into an octanol molecule (e.g., C. sub.8H. sub.180) and one and a half oxygen molecules. Formula (4) generally illustrates a hydrodimerization of two butyric acid molecules into a 2- octanone molecule (e.g., C. sub.8H. sub.160) and one and a half oxygen molecules.

[0035] Referring to FIG. 4, a table illustrating relative product yields for different cathode material, catalyst and cathode potential combinations are shown. Lower pH generally favors reduction of a carbonyl group without dimerization, for instance, the reduction of formic acid to methanol. Aldehydes may be more likely to reduce to alcohols without dimerization. Carboxylic acids and dialdehydes may be more likely to dimerize, with the exception of formic acid. Faradaic yields generally improve with more negative cathodic potential, particularly for dimerization. Any N-containing heterocycle may be used as a catalyst. 4,4' bipyridine was generally found to be an effective catalyst. Conversion rates generally improve with catalyst concentrations in excess of 50 millimolar (mM). [0036] Referring to FIG. 5, a formula of an aromatic heterocyclic amine catalyst is shown. The ring structure may be an aromatic 5- member heterocyclic ring or 6- member heterocyclic ring with at least one ring nitrogen and is optionally substituted at one or more ring positions other than nitrogen with R. L may be C or N. R1 may be H. R2 may be H if L is N or R2 is R if L is C. R is an optional substitutent on any ring carbon and may be independently selected from H, a straight chain or branched chain lower alkyl, hydroxyl, amino, pyridyl, or two R's taken together with the ring carbons bonded thereto are a fused six-member aryl ring and n=0 to 4.

[0037] Referring to FIGS. 6-8, formulae of substituted or unsubstituted aromatic 5- member heterocyclic amines or 6-member heterocyclic amines are shown. Referring to FIG. 6, R3 may be H. R4, R5, R7 and R8 are generally independently H, straight chain or branched chain lower alkyl, hydroxyl, amino, or taken together are a fused six-member aryl ring. R6 may be H, straight chain or branched chain lower alkyl, hydroxyl, amino or pyridyl.

[0038] Referring to FIG. 7, one of L1 , L2 and L3 may be N, while the other L's may be C. R9 may be H. If L1 is N, R10 may be H. If L2 is N, R1 1 may be H. If L3 is N, R12 may be H. If L1 , L2 or L3 is C, then R10, R11 , R12, R13 and R14 may be independently selected from straight chain or branched chain lower alkyl, hydroxyl, amino, or pyridyl.

[0039] Referring to FIG. 8, R15 and R16 may be H. R17, R18 and R19 are generally independently selected from straight chain or branched chain lower alkyl, hydroxyl, amino, or pyridyl.

[0040] Suitably, the concentration of aromatic heterocyclic amine catalysts is about 10 mM to 1 M. Concentrations of the electrolyte may be about 0.1 M to 1 M. The electrolyte may be suitably a salt, such as KCl, NaNO.sub.3, Na.sub.2SO.sub.4, NaCl, NaF, NaClO.sub.4, KClO.sub.4, K.sub.2Si0.sub.3, or CaCl.sub.2 at a concentration of about 0.5 M. Other electrolytes may include, but are not limited to, all group 1 cations (e.g., H, Li, Na, K, Rb and Cs) except Francium (Fr), Ca, ammonium cations, alkylammonium cations and alkyl amines. Additional electrolytes may include, but are not limited to, all group 17 anions (e.g., F, CI, Br, I and At), borates, carbonates, nitrates, nitrites, perchlorates, phosphates, polyphosphates, silicates and sulfates. Na generally performs as well as K with regard to best practices, so NaCl may be exchanged with KCl. NaF may perform about as well as NaCl, so NaF may be exchanged for NaCl or KCl in many cases. Larger anions tend to change the chemistry and favor different products. For instance, sulfate may favor polymer or methanol production while CI may favor products such as acetone. The pH of the solution is generally maintained at about pH 3 to 8, suitably about 4.7 to 5.6.

[0041 ] Some embodiments of the present invention may be further explained by the following examples, which should not be construed by way of limiting the scope of the invention.

Example 1

General Electrochemical Methods

[0042] Chemicals and materials. All chemicals used were >98% purity and used as received from the vendor (e.g., Aldrich), without further purification. Either deionized or high purity water (Nanopure, Barnstead) was used to prepare the aqueous electrolyte solutions.

[0043] Electrochemical system. An electrochemical system was composed of a standard two-compartment electrolysis cell 102 to separate the anode 1 18 and cathode 120 reactions. The compartments were separated by a porous glass frit or other ion conducting bridge 1 16. A 0.5 M KCl (Electro Migration Dispersion (EMD)>99%) was generally used as the supporting electrolyte 122. A concentration of the desired aromatic heterocyclic amine, such as pyridine, pyridine derivatives, bipyridine, imidazole and imidazole derivatives, of between about 1 mM to 1 M was used.

[0044] Referring to FIG. 9, a flow diagram of an example method 140 used in the electrochemical examples is shown. The method (or process) 140 generally comprises a step (or block) 142, a step (or block) 144, a step (or block) 146, a step (or block) 148 and a step (or block) 150. The method 140 may be implemented using the system 100.

[0045] In the step 142, the electrodes 1 18 and 120 may be activated where appropriate. Introduction of the reactants into the cell 102 may be performed in the step 144. Electrolysis of the reactants into organic products may occur during step 146. In the step 148, the organic products may be separated from the electrolyte. Analysis of the reduction products may be performed in the step 150.

[0046] The working electrode was a steel electrode of a known area. Before and during all electrolysis, the reactants were continuously introduced into the electrolyte to saturate the solution. The resulting pH of the solution was maintained at about pH 3 to pH 8.

Example 2

General Photoelectrochemical Methods

[0047] Chemicals and materials. All chemicals used were analytical grade or higher. Either deionized or high purity water (Nanopure, Barnstead) was used to prepare the aqueous electrolyte solutions. [0048] Photoelectrochemical system. The photoelectrochemical system was composed of a Pyrex three-necked flask containing 0.5 M KCl as supporting electrolyte and a 1 mM to 1 M catalyst (e.g., 10 mM pyridine or pyridine derivative). The photocathode was a single crystal p-type semiconductor etched for approximately 1 to 2 minutes in a bath of concentrated HNO.sub.3:HCl, 2: 1 v/v prior to use. An ohmic contact was made to the back of the freshly etched crystal using an indium/zinc (2 wt. % Zn) solder. The contact was connected to an external lead with conducting silver epoxy (Epoxy Technology H31 ) covered in glass tubing and insulated using an epoxy cement (Loctite 0151 Hysol) to expose only the front face of the semiconductor to solution. All potentials were referenced against a saturated calomel electrode (Accumet). During all electrolysis, the reactants were continuously introduced to the electrolyte to saturate the solution. The resulting pH of the solution was maintained at about pH 3 to 8 (e.g., pH 5.2).

[0049] Referring to FIG. 10, a flow diagram of an example method 160 used in the photochemical examples is shown. The method (or process) 160 generally comprises a step (or block) 162, a step (or block) 164, a step (or block) 166, a step (or block) 168 and a step (or block) 170. The method 160 may be implemented using the system 100.

[0050] In the step 162, the photoelectrode may be activated. Introduction of the reactants into the cell 102 may be performed in the step 164. Electrolysis of the reactants into organic products may occur during step 166. In the step 168, the organic products may be separated from the electrolyte. Analysis of the reduction products may be performed in the step 170.

[0051 ] Light sources. Four different light sources were used for the illumination of the p-type semiconductor electrode. For initial electrolysis experiments, a Hg--Xe arc lamp (USHIO UXM 200H) was used in a lamp housing (PTI Model A- 1010) and powered by a PTI LTS-200 power supply. Similarly, a Xe arc lamp (USHIO UXL 151 H) was used in the same housing in conjunction with a PTI monochromator to illuminate the electrode at various specific wavelengths.

[0052] A fiber optic spectrometer (Ocean Optics S2000) or a silicon photodetector (Newport 818-SL silicon detector) was used to measure the relative resulting power emitted through the monochromator. The flatband potential was obtained by measurements of the open circuit photovoltage during various irradiation intensities using the 200 watt (W) Hg--Xe lamp (3 W/cm. sup.2-23 W/cm.sup.2). The photovoltage was observed to saturate at intensities above approximately 6 W/cm.sup.2.

[0053] For quantum yield determinations, electrolysis was performed under illumination by two different light-emitting diodes (LEDs). A blue LED (Luxeon V Dental Blue, Future Electronics) with a luminous output of 500 milliwatt (mW)+/- 50 mW at 465 nanometers (nm) and a 20 nm full width at half maximum (FWHM) was driven at to a maximum rated current of 700 mA using a Xitanium Driver (Advance Transformer Company). A Fraen collimating lens (Future Electronics) was used to direct the output light. The resultant power density that reached the window of the photoelectrochemical cell was determined to be 42 mW/cm.sup.2, measured using a Scientech 364 thermopile power meter and silicon photodetector. The measured power density was assumed to be greater than the actual power density observed at the semiconductor face due to luminous intensity loss through the solution layer between the wall of the photoelectrochemical cell and the electrode.

Example 3

Analysis of Products of Electrolysis

[0054] Electrochemical experiments were generally performed using a CH Instruments potentiostat or a DC power supply with current logger to run bulk electrolysis experiments. The CH Instruments potentiostat was generally used for cyclic voltammetry. Electrolysis was run under potentiostatic conditions from approximately 6 hours to 30 hours until a relatively similar amount of charge was passed for each run.

[0055] Gas Chromatography. Electrolysis samples were analyzed using a gas chromatograph (HP 5890 GC) equipped with a FID detector. Removal of the supporting electrolyte salt was first achieved with an Amberlite IRN-150 ion exchange resin (cleaned prior to use to ensure no organic artifacts by stirring in a 0.1% v/v aqueous solution of Triton X-100, reduced (Aldrich), filtered and rinsed with a copious amount of water, and vacuum dried below the maximum temperature of the resin (approximately 60. degree. C.) before the sample was directly injected into the GC which housed a DB-Wax column (Agilent Technologies, 60 m, 1 micrometer (.mu.m) film thickness). Approximately 1 gram of resin was used to remove the salt from 1 milliliter (mL) of the sample. The injector temperature was held at 200. degree. C, the oven temperature maintained at 120. degree. C, and the detector temperature at 200. degree. C.

[0056] Spectrophotometry. The presence of formaldehyde was also determined by the chromotropic acid assay. Briefly, a solution of 0.3 g of 4,5- dihydroxynaphthalene-2,7-disulfonic acid, disodium salt dihydrate (Aldrich) was dissolved in 10 mL deionized water before diluting to 100 mL with concentrated sulfuric acid. For formaldehyde, an aliquot of 1.5 mL was then added to 0.5 mL of the sample. The presence of formaldehyde (absorbency at 577 nm) was detected against a standard curve using an HP 8453 UV-Vis spectrometer. For formic acid, a 0.5 mL aliquot of sample was first reduced with an approximately 100 mg piece of Mg wire and 0.5 mL concentrated hydrochloric acid (added slowly in aliquots over a 10 minute period) to convert to formaldehyde before following the chromotropic acid assay as described above. [0057] Nuclear Magnetic Resonance. NMR spectra of electrolyte volumes after bulk electrolysis were also obtained using an automated Bruker Ultrashield.TM. 500 Plus spectrometer with an excitation sculpting pulse technique for water suppression. Data processing was achieved using MestReNova software.

[0058] Selective hydrodimerization of carbonyl-containing organic molecules, such as aldehydes and carboxylic acids, may be performed in the cell 102. For instance, some two-carbon molecules such as an acetaldehyde may be hydrodimerized into butanone (methyl ethyl ketone) or butanol. Similarly, a carboxylic acid such as butyric acid may be hydrodimerized to octanone or octanol.

[0059] Selective reduction of carboxylic acids to aldehydes and /or alcohols and the reduction of aldehydes to alcohols may also be performed in the cell 102. Other carbonyl groups, such as ketones, may also be reduced to hydroxyl groups. The selectivity of the process generally maximizes efficiency and ease of product extraction relative to existing processes used for organic chemical production. Some embodiments do not operate at high temperatures, high pressures or high acidity. Biologically-produced chemicals with carbonyl groups may be converted to environmentally-friendly alcohol fuels, thereby reducing greenhouse gas emissions. Conversion of small molecules to longer-chain molecules, generally reduces the costs of upgrading small molecules into high value products. A variety of C2, C4, C6, C8 organic molecules may be produced.

[0060] Some embodiments of the present invention generally provide for new cathode materials and new electrolyte materials. Specific combinations of the cathode materials, the electrolytes and the catalysts may be used to get a desired organic product. Process conditions may be controlled to maximize conversion efficiency and selectivity. Cell parameters may be selected to minimize unproductive side reactions like H.sub.2 evolution from water electrolysis. Choice of specific configurations of heterocyclic amine catalysts with engineered functional groups may be utilized in the system 100 to achieve high faradaic rates. Process conditions described above may facilitate long life (e.g., improved stability), electrode and cell cycling and product recovery.

[0061 ] Cathode, catalyst and electrolyte combinations may be used to selectively electrohydrodimerize carbonyl-containing compounds to a variety of valuable organic chemicals. The cathode, catalyst and electrolyte combinations may also be used to selectively reduce carbonyl groups, including aldehydes, to alcohols and carboxylic acids to aldehydes and /or alcohols. The relative low cost and abundance of the combinations disclosed above generally opens the possibility of commercialization. The processes described may operate at atmospheric pressure, ambient temperature, uses water as a solvent and features mild pH (e.g., generally greater than pH 4). The features generally mean that abundant, low-cost materials may be used to build plants incorporating some embodiments of the present invention. Furthermore, the process may be stable over time.

[0062] In an electrochemical system with fixed cathodes, the electrolyte and/or catalyst may be altered to change the organic product mix. The cathodes may be swapped out in a modular electrochemical system to change the organic product mix. In a hybrid photoelectrochemical system, the cathode or anode may be a photovoltaic material. Plant operating in conjunction with biological production of simple carbonyl-containing chemicals such as acetaldehyde, lactic acid, citric acid, etc. may include the system 100 to convert the chemicals into other useful organic compounds. Biologically produced chemicals may be converted into longer chain chemicals and products such fuels, solvents and the like.

[0063] In an embodiment of the disclosure, a method for electrochemically converting a two-carbon chemical to a more reduced two-carbon chemical where the two-carbon starting chemical could be derived from the electrochemical reduction of carbon dioxide in a separate reactor. In particular, a method for converting glyoxal to glycolaldehyde and converting oxalic acid to acetic acid is disclosed. Advantageously, the method may include electrochemical conversion may include of a lower value chemical to a higher value chemical. This process may have an economical advantage considering the cost of production. Additionally, the process may include electrochemical conversion of a smaller market chemical to a larger market chemical.

[0064] It is contemplated that a method for electrochemical conversion may include a two-step process allows for better energy efficiency. For example, first, a 2e^" reduction of carbon dioxide may produce oxalic acid in the first electrochemical cell. Secondly, oxalic acid may be converted in a second electrochemical cell to acetic acid, a 6e^" reduction. By converting oxalic acid to acetic acid rather than direct carbon dioxide to acetic acid, ideal catalytic conditions may be selected for each reduction step. This may be kinetically easier than completing a single 8e^" reduction from carbon dioxide. 0065] EXAMPLE 4. Experiments were conducted in a two comparment glass electrochemical cell with a salt bridge separating the working and counter compartments. Aqueous solutions were prepared using 0.5M KCl and 33mM of glyoxal with and without 10mM of pyridine at pH of about 5.2. The working electrode was indium foil that was polished with 5μΜ alumina then swabbed with acetone and finally rinsed with Dl water. A commerically available counter electrode (Telpro) was employed as was an SCE reference electrode. Constant potential electrolyses at -1 .46V vs. SCE were run for 5.75 hrs under stirred conditions. Products were analyzed by NMR, GC, and IC.

[0066] In general, an addition of homogenous pyridine catalyst increased the observed FY for the products listed of acetaldehyde, glycolaldehyde, ethanol, and acetic acid with trace oxalic acid. However, using just an indium electrode with no additional homogenous catalyst also yields the same products. Table 1 :Faradaic efficiencies for glyxol reduction using In cathode with and without catalyst.

Starting with 33mM Glyoxal 0.5M KCl with and without catalyst

[0067] EXAMPLE 5. Experiments were conducted in a three chambered air-tight glass cell with separated cathode and anode chambers. The cathode chamber contained an aqueous solution of 0.5M KCl and 33mM of oxalic acid with 10mM of 2,6- Lutidene. The anode solution contained water with 0.1667M K₂S0₄. The working electrode was ss-304 foil, that was polished with 5μΜ alumina then swabbed with acetone and was rinsed with and sonicated in Dl water for 2 minutes and finally rinsed with Dl water. A commerically available counter electrode (Telpro) was employed as was an SCE reference electrode. Constant potential electrolyses at -0.43V vs. SCE were run for 24 hrs under stirred conditions. Prior to electrolysis, the electrochemical cell was purged with Ar for 30 minutes to get rid of the dissolved gaseous that might undergo electroreduction under our experimental conditions. The electrolyses were performed at pH 2.77 to be between the two pKa's of oxalic acid so that only one of the carboxylic acid groups was protonated. This is to protect one carboxylic acid group during the electroreduction so that oxalic acid reduction will stop at acetic acid as the highest possible reduced product instead of acetaldehyde, ethanol, ethane, and ethylene. Products were analyzed on by IC Dionex (ICS 5000) and GC-MS (Agilent 5975C).

Table 2:Faradaic efficiencies for oxalic acid reduction to two carbon products using ss-304 cathode with 2,6 Lutdiene as a catalyst. Electrolysis Cathode Potential(V) Catalyst

FY(%)

Glycolic Acetic

A ss-304 -0.43 2,6- 5.09 4.79

Lutdiene

B ss-304 -0.43 2,6 3.70 2.47

Lutdiene

[0068] It is contemplated that Example 4 and 5 highlight conditions for starting with two starting materials and converting to two different two-carbon products. However, a range of starting two-carbon intermediates may be used to produce other two-carbon products. Oxalic acid could be a starting material for the production of glyoxlic acid, glyoxal, glycolic acid, glycolaldehyde, acetic acid, acetaldehyde, ethylene glycol, ethanol, ethane, or ethylene, or mixes thereof. Glyoxylic acid could be a starting material for the production of glyoxal, glycolic acid, glycolaldehyde, acetic acid, acetaldehyde, ethylene glycol, ethanol, ethane, or ethylene, or mixes thereof. Glycolic acid and glyoxal could be starting materials for the production of glycolaldehyde, acetic acid, acetaldehyde, ethylene glycol, ethanol, ethane, or ethylene, or mixes thereof. Acetic acid could be a starting material for the production of acetaldehyde, ethylene glycol, ethanol, ethane, or ethylene, or mixes thereof. Acetaldehyde and ethylene glycol could be starting materials for the production of ethanol, ethane, and ethylene. Ethanol could be a starting material for the production of ethane and ethylene. Ethane could be a starting material for the production of ethylene. Glyoxal to glycolaldehyde and oxalic acid to acetic acid are preferred. In some embodiments of the invention, it is contemplated that the concentration of the starting material could range from 1 mM to 70 wt% of an aqueous or non-aqueous mixture. [0069] It is anticipated that a wide range of electrode materials could serve as the cathode material for the method such as In, Sn, C, Pb, Cd, Zn, Bi, Ag, Au, Ni, Co, Pt, Pd, Fe, Cr, and their alloys, stainless steels, and n-type semiconductor materials. The various electrochemical reductions may occur in a pH range of 1 -9. pH is an important parameter in controlling the reaction product. The reduction of the carboxylic acids to various products must occur at acidic pH's where the carboxylic acid is in the acid form. For the reduction of oxalic acid to glyoxylic acid, acetic acid, and glycolic acid, the operating pH must be in between the two pKa's of oxalic acid to protect one side of the molecule from reduction. The electrolyte is at least one of a H, Li, Na, K, Rb, Cs, Ca, ammonium, alkylammonium, or tetraalkylammonium cation and at least one of a F, CI, Br, I, alkyl amine, borate, carbonate, nitrite, nitrate, phophate, polyphosphate, perchlorate, silicate, sulfate anion.

[0071 ] A homogenous catalyst may be one or more of adenine, amines containing sulfur, amines containing oxygen, azoles, benzimidazoles, bipyridines, furan, imidazoles, pyridines, quinolines, pyrroles, lutidines, thiazoles. Pyridine and 2,6- lutidine are preferred.

[0072] It is contemplated from Example 4 that glyoxal may be electrochemically reduced to glycolaldeyde and other products at an indium electrode with and without a homogenous catalyst, where the addition of the homogenous catalyst increases the FY and where glyoxal is the preferred starting material for making glycolaldehyde. It is contemplated from Example 5 that oxalic acid can be electrochemically reduced to glycolic acid and acetic acid at a stainless steel cathode, such as stainless steel 304 cathode, with a homogeneous catalyst, such as 2,6 lutidine as the homogenous catalyst at a pH of 2.77 where oxalic acid is the preferred starting material.

[0073] In another embodiment of the disclosure, electrochemical reduction of oxalic acid in batch reactors with various cathode materials was studied. The best faradaic yields (FY) for the production of glycolic and glyoxylic acids were 60% and 75%, respectively, for the direct reduction of oxalic acid. A FY of 95% was also achieved for the reduction of glyoxylic acid to glycolic acid. Mono-Ethylene Glycol (MEG) was observed with Cd cathode in trace amounts.

[0074] It is contemplated that an oxalate salt may be synthesized with high yield directly from the electrochemical reduction of carbon dioxide in non-aqueous solvent. The acid form, oxalic acid, has many industrial uses and may be used as an intermediate for the production of a large variety of chemical compounds such as glyoxylic acid, glyoxylate, glycolic acid, glycolyate, glyoxal, glycolaldehyde, ethylene glycol, acetic acid, acetaldehyde as shown in FIG. 1 1 . It is contemplated that oxalic electrochemical reduction may convert oxalic acid into other chemicals, including but not limited to: glycolic acid, glycoaldehyde, acetic acid, and /or mono ethylene glycol.

[0075] To obtain a reproducible surface, the cathode electrode materials were cleaned. In a typical experiment, about 2 cm2 metal pieces were cut from bulk metal and polished with alumina powder (0.3μηη), rinsed with deionized water, and degreased with acetone. A polished electrode was then sonicated for 2 minutes in deionized water. Prior to use, cleaned electrodes were dried by pressing between clean kimwipes.

[0076] Electrolysis was performed using an Arbin MSTAT 167563 Potentiostat (Arbin Instruments) at constant potentials. Unless otherwise noted, all electrolysis was carried out in a three chambered glass cell with separated cathode and anode chambers. For the electrolysis that involved a mercury cathode, a two chambered electrochemical set up was used, with a glass frit separated cathode chamber. An insulated copper wire was used to establish the connection between the liquid mercury on the cathode and the potentiostat. Various forms of carbon were tested for the anode compatibility.

[0077] Glycolic and glyoxylic quantitation was performed by Ion Chromatography (IC). Other anolytes were quantified by NMR. Analytical samples for NMR were prepared as such: 800uL of sample, 100uL of D₂0, and 100uL of 1000ppm acetone in H20. They were run for H1 using solvent suppression. Quantitation was based on relative peak areas using response factors calculated from prepared standard mixes.

[0078] The experimental results obtained from several experiments may be categorized based on the major products obtained, or the results obtained from pure metal cathodes vs. alloys. The electrolyte seems to have negligible effect on the products obtained. The temperature effect on the product is observed on a cadmium (Cd) electrode. At room temperature, Cd makes glyoxylic acid as the major product (Table 3), whereas glycolic acid is the major product obtained from the Bi at elevated temperature (Table 4). Also, Cd as well as Hg cathodes lead to the formation of trace amount of highly reduced product, mono ethylene glycol (MEG) (Table 5). Bi may be utilized as an electrode for the production of glycolic as well. Pb may be used as a cathode for glyoxylic acid production. Table 6 shows experimental results obtained with various metal alloys. All Pb based alloys, as well as Gallinstin, reduced oxalic acid to glyoxylic acid with some glycolic byproduct.

[0079] To study electrochemical reduction, a set of experiments were conducted starting with glycolic acid, glyoxylic acid, and glycol aldehyde as starting reactants. As seen in Table 3, some cathodes were able to reduce glycolic acid to further reduced products, such as glycolaldehyde and acetic acid (GL167, GL172, GL176 and GL177).

[0082] Enhanced catalytic activities on alloy surfaces may result from the increased adsorption of the reactant due to distinct binding properties and extra stabilization of the transition state on the alloy as compared to the corresponding transition state on the monometallic catalyst surface. Table 3. Systems producing Glyoxalate

Table 4 Systems producing Glycolate

*Cathodes that made more reduced products

a 0.065% EG, ^b 0 .17% EG, ^c 0.19%EG; 4.98% glycolaldehyde, ^d 0.23% EG

Table 5 EC reduction of oxalic acid or glycolic acid

Table 6. Experimental results obtained by the electrochemical reduction of oxalic acid on metal alloys cathodes

Galinstan 0.5M HBr 7.5%Ox -1.6 RT 33.5 21.5

[0084] While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention.

Claims

CLAIMS What is claimed is:

1 . A method for heterocycle catalyzed electrochemical reduction of a carbonyl compound, comprising the steps of:

(A) introducing said carbonyl compound into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell, wherein (i) said divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said carbonyl compound to at least one aldehyde compound;

(B) varying which of said aldehyde compounds is produced by adjusting one or more of (i) a cathode material, (ii) said electrolyte, (iii) said heterocycle catalyst, (iv) a pH level and (v) an electrical potential; and

(C) separating said aldehyde compounds from said solution.

2. The method according to claim 1 , wherein said cathode material is at least one of Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys, Ga, Hg, In, Mo, Nb, Ni, Ni alloys, Ni-Fe alloys, Sn, Sn alloys, Ti, V, W, Zn, elgiloy, Nichrome, austenitic steel, duplex steel, ferritic steel, martensitic steel, stainless steel, degenerately doped p-Si, degenerately doped p-Si:As and degenerately doped p-Si:B.

3. The method according to claim 1 , wherein said electrolyte is at least one of Na₂S0₄ , KCl, NaN0₃ , NaCl, NaF, NaCl0₄ , KC10₄ , K₂Si0₃ , CaCl₂ , a H cation, a Li cation, a Na cation, a K cation, a Rb cation, a Cs cation, a Ca cation, an ammonium cation, an alkylammonium cation, a F anion, a CI anion, a Br anion, an I anion, an At anion, an alkyl amine, borates, carbonates, nitrites, nitrates, phosphates, polyphosphates, perchlorates, silicates, sulfates, and a tetraalkyl ammonium salt.

4. The method according to claim 1 , wherein said heterocycle catalyst is one or more of amino-thiazole, aromatic heterocyclic amines with an aromatic 5- member heterocyclic ring, aromatic heterocyclic amines with 6-member heterocyclic ring, azoles, benzimidazole, bipyridines, furan, imidazoles, imidazole related species with at least one five-member ring, indoles, pyridines, pyridine related species with at least one six-member ring, pyrrole, thiophene and t hi azoles.

5. The method according to claim 1 , wherein said pH level ranges from approximately 3 to approximately 8.

6. The method according to claim 1 , wherein said electrical potential ranges from approximately -1 volt to approximately -2 volts.

7. The method according to claim 1 , wherein said aldehyde compounds comprise one or more of benzaldehyde, butanal, formaldehyde and glyoxal.

8. A method for heterocycle catalyzed electrochemical reduction of an aldehyde compound, comprising the steps of: (A) introducing said aldehyde compound into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell, wherein (i) said divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said aldehyde compound to at least one alcohol; (B) varying which of said alcohols is produced by adjusting one or more of (i) a cathode material, (ii) said electrolyte, (iii) said heterocycle catalyst, (iv) a pH level and (v) an electrical potential; and (C) separating said alcohol from said solution.

9. The method according to claim 8, wherein said cathode material is at least one of Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys, Ga, Hg, In, Mo, Nb, Ni, Ni alloys, Ni--Fe alloys, Sn, Sn alloys, Ti, V, W, Zn, elgiloy, Nichrome, austenitic steel, duplex steel, ferritic steel, martensitic steel, stainless steel, degenerately doped p-Si, degenerately doped p-Si:As and degenerately doped p-Si:B.

10. The method according to claim 8, wherein said electrolyte is at least one of Na.sub.2SO.sub.4, KCl, NaNO.sub.3, NaCl, NaF, NaCIO, KClO.sub.4, K.sub.2Si0.sub.3, CaCl.sub.2, a H cation, a Li cation, a Na cation, a K cation, a Rb cation, a Cs cation, a Ca cation, an ammonium cation, an alkylammonium cation, a F anion, a CI anion, a Br anion, an I anion, an At anion, an alkyl amine, borates, carbonates, nitrites, nitrates, phosphates, polyphosphates, perchlorates, silicates, sulfates, and a tetraalkyl ammonium salt.

1 1 . The method according to claim 8, wherein said heterocycle catalyst is one or more of amino-thiazole, aromatic heterocyclic amines with an aromatic 5- member heterocyclic ring, aromatic heterocyclic amines with 6-member heterocyclic ring, azoles, benzimidazole, bipyridines, furan, imidazoles, imidazole related species with at least one five-member ring, indoles, pyridines, pyridine related species with at least one six-member ring, pyrrole, thiophene and t hi azoles.

12. The method according to claim 8, wherein said alcohol comprises one or more of 2-butanol, n-butanol, ethanol, methanol, propanol and propioin.

13. The method according to claim 8, wherein said cathode further reduces a keto compound to at least one hydroxyl compound.

14. The method according to claim 8, wherein said reducing is performed at ambient temperature and ambient pressure.

15. The method according to claim 8, wherein a faradaic yield of said alcohol is at least 50 percent.

16. A method for heterocycle catalyzed hydrodimerization of carbonyl- containing molecules, comprising the steps of: (A) introducing said carbonyl- containing molecules into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell, wherein (i) said divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode hydrodimerizing said carbonyl-containing molecules into at least one organic product; (B) varying which of said organic products is produced by adjusting one or more of (i) a cathode material, (ii) said electrolyte, (iii) said heterocycle catalyst, (iv) a pH level and (v) an electrical potential; and (C) separating said organic products from said solution.

17. The method according to claim 16, wherein said electrolyte is at least one of Na.sub.2SO.sub.4, KCl, NaNO.sub.3, NaCl, NaF, NaClO.sub.4, KClO.sub.4, K.sub.2Si0.sub.3, CaCl.sub.2, a H cation, a L1 cation, a Na cation, a K cation, a Rb cation, a Cs cation, a Ca cation, an ammonium cation, an alkylammonium cation, a F anion, a CI anion, a Br anion, an I anion, an At anion, an alkyl amine, borates, carbonates, nitrites, nitrates, phosphates, polyphosphates, perchlorates, silicates, sulfates, and a tetraalkyl ammonium salt.

18. The method according to claim 16, wherein said heterocycle catalyst is one or more of amino-thiazole, aromatic heterocyclic amines with an aromatic 5- member heterocyclic ring, aromatic heterocyclic amines with 6-member heterocyclic ring, azoles, benzimidazole, bipyridines, furan, imidazoles, imidazole related species with at least one five-member ring, indoles, pyridines, pyridine related species with at least one six-member ring, pyrrole, thiophene and t hi azoles.

19. The method according to claim 16, wherein said organic products comprise one or more of butanone, butanol, octanone and octanol.

20. The method according to claim 16, wherein said carbonyl-containing molecules comprise one or more of acetaldehyde, butyric acid and lactic acid.

21 . A method for heterocycle catalyzed electrochemical reduction of a carbonyl compound, comprising the steps of:

(A) introducing a carboxylic acid into a solution of an electrolyte and a heterocycle catalyst in a divided electrochemical cell, wherein (i) said divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said carboxylic acid to at least one aldehyde compound;

(C) separating said aldehyde compounds from said solution.

22. The method according to claim 21 , wherein said cathode material is at least one of Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys, Ga, Hg, In, Mo, Nb, Ni, Ni alloys, Ni-Fe alloys, Sn, Sn alloys, Ti, V, W, Zn, elgiloy, Nichrome, austenitic steel, duplex steel, ferritic steel, martensitic steel, stainless steel, degenerately doped p-Si, degenerately doped p-Si:As and degenerately doped p-Si:B.

23. The method according to claim 21 , wherein said electrolyte is at least one of Na₂S0₄ , KCl, NaN0₃ , NaCl, NaF, NaCl0₄ , KC10₄ , K₂Si0₃ , CaCl₂ , a H cation, a Li cation, a Na cation, a K cation, a Rb cation, a Cs cation, a Ca cation, an ammonium cation, an alkylammonium cation, a F anion, a CI anion, a Br anion, an I anion, an At anion, an alkyl amine, borates, carbonates, nitrites, nitrates, phosphates, polyphosphates, perchlorates, silicates, sulfates, and a tetraalkyl ammonium salt.

24. The method according to claim 21 , wherein said heterocycle catalyst is one or more of amino-thiazole, aromatic heterocyclic amines with an aromatic 5- member heterocyclic ring, aromatic heterocyclic amines with 6-member heterocyclic ring, azoles, benzimidazole, bipyridines, furan, imidazoles, imidazole related species with at least one five-member ring, indoles, pyridines, pyridine related species with at least one six-member ring, pyrrole, thiophene and t hi azoles.

25. The method according to claim 21 , wherein said pH level ranges from approximately 3 to approximately 8.

26. The method according to claim 21 , wherein said electrical potential ranges from approximately -1 volt to approximately -2 volts.

27. The method according to claim 21 , wherein said aldehyde compounds comprise one or more of benzaldehyde, butanal, formaldehyde and glyoxal.

28. A method electrochemical reduction of a carbonyl compound, comprising the steps of:

(A) introducing a carbonyl compound into a solution of an electrolyte in a first divided electrochemical cell, wherein (i) said first divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said carbonyl compound to oxalic acid;

(B) separating the oxalic acid from the solution of said first divided electrochemical cell;

(C) introducing the oxalic acid into a solution of an electrolyte in a second divided electrochemical cell, wherein (i) said second divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said oxalic acid to acetic acid; and

(D) separating said acetic acid from said solution of said second divided electrochemical cell.

29. The method as claimed in claim 28, wherein the cathode of the second divided electrochemical cell is stainless steel.

30. The method as claimed in claim 29, wherein the solution of an electrolyte includes a homogeneous catalyst.

31 . The method as claimed in claim 30, wherein the homogeneous catalyst is 2,6 lutidine.

32. A method electrochemical reduction of a carbonyl compound, comprising the steps of:

(A) introducing a carbonyl compound into a solution of an electrolyte in a first divided electrochemical cell, wherein (i) said first divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said carbonyl compound to glyoxal;

(B) separating the glyoxal from the solution of said first divided electrochemical cell;

(C) introducing the glyoxal into a solution of an electrolyte in a second divided electrochemical cell, wherein (i) said second divided electrochemical cell comprises an anode in a first cell compartment and a cathode in a second cell compartment, (ii) said cathode reducing said glyoxal to glycolaldehyde;

(D) separating the glycolaldehyde from the solution of said second divided electrochemical cell.

33. The method as claimed in claim 32, wherein the cathode of the second divided electrochemical cell is indium.

34. The method as claimed in claim 33, wherein the solution of an electrolyte includes a homogeneous catalyst.