Method for treating organic waste material and a catalyst/cocatalyst composition useful therefor

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Drawing sheet — no readable text.

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metals and/or platinum group metal oxides or mixtures

METHOD FOR TREATING ORGANIC WASTE having at least one valve-metal component, such as MATERAL AND A CATALYST/COCATALYST titanium, hafnium, zirconium, niobium, tantalum, and COMPOSITION USEFUL THEREFOR tungsten, in a process for electrolytically generating oxygen. The invention of U.S. Pat. No. 4,457,824 is an

FIELD OF THE INVENTION improvement on the same method. In these two patents, This invention relates to the use of a catalyst compo the catalysts are in the electrodes, and thus are not sition, comprising an electrocatalyst and a homogene available in solution for homogenous oxidation of any ous cocatalyst, for the electrochemical gasification of dissolved organics. Oxidation of organic materials using organic waste material in an electrolyte. 0 catalytic electrodes is not shown or suggested. CROSS-REFERENCE TO RELATED U.S. Pat. No. 4,105,755 concerns reacting an ash-con APPLICATION taining carbonaceous material, optionally an organic waste material, with a halogen, to form a halogen acid,

A related application entitled "A method for hydro 15 and then decomposing the halogen acid to halogen gen production and metal winning, and a catalyst (recycled) and hydrogen. The halogen acid is prefera Mcocatalyst composition useful therefor' is being filed bly decomposed electrolytically if this step of the reac concurrently herewith, and the specification thereof is tion takes place as a separate step from the initial reac incorporated herein by reference. tion of the ash-containing carbonaceous material and BACKGROUND OF THE INVENTION halogen.

Carbonaceous materials are oxidized when suspended SUMMARY OF THE INVENTION in an electrolyte containing a reversible or quasireversi An object of the present invention is to provide an ble electrocatalyst and a homogeneous cocatalyst. The electrocatalytic reactor system in which organic waste electrocatalyst is regenerated in an electrochemical cell material is oxidized using a catalyst/cocatalyst combi through which a direct current is passed. The reduced 25 nation in an electrolyte in an electrochemical cell. The electrocatalyst is reoxidized at the anode. over-all reactions in the anode half-cell and in the cath U.S. Pat. No. 4,412,893 concerns electrolyzing cati ode half-cell in aqueous acidic solutions are: ons at a cathode of an electrolytic cell, wherein anolyte contains ferrous ion as a reducing agent. The electroly sis is conducted while the anolyte is agitated or while 30 Anode: C -- 2H2O catalyst

the anode moves with respect to the anolyte, providing relative motion between the anode and the anolyte, promoting contact of the anode with the ferrous ion Cathode: 2H + 2e -GH2 despite their mutual electrostatic repulsion. A static relationship between the cathode and the catholyte is 35 The process employs one of several electrocatalysts required. The concentration of the ferrous ion is in the together with one of several homogeneous cocatalysts range from 0.5 to 10 grams per liter. to improve the organic oxidation rate and to lower the U.S. Pat. No. 4,389,288 relates to electrochemical gasification of carbonaceous material by anodic oxida activation material, energy for the oxidiation of the organic waste tion in an aqueous acidic electrolyte to produce oxides 40 Another object of the invention is to provide a of carbon at the anode and hydrogen at the cathode of method of using a catalyst/cocatalyst composition for an electrolytic cell using an iron catalyst.

U.S. Pat. No. 4,268,363 provides for electrochemical the treatment of organic waste material. A further ob gasification of carbonaceous materials by anodic oxida ject of the invention is to provide an electrolyte compo sition comprising organic waste material, a conductive tion, producing oxides of carbon at the anode and hy 45 electrolyte, catalyst and cocatalyst. drogen or metallic elements at the cathode of an elec There are several distinct aspects of this invention: trolytic cell. Carbonaceous materials may also be hy (a) a catalyst/cocatalyst composition, drogenated at the cathode by electrochemical reactions (b) use of (a) in a method of electrolytically treating during which carbonaceous material may also be anodi cally reacted within the anode compartment of an elec 50 organic waste material, (c) use of (a) to reduce potential and thus energy trolytic cell. Typical examples of metals produced at the cathode include chromium, manganese, cobalt, cally, required to gasify organic waste material electrochemi nickel, copper, indium, and tellurium. (d) an electrolyte composition comprising (a), and According to U.S. Pat. No. 4,341,608, hydrogen is produced from an electrolytic cell system by oxidizing 55 (e) a reaction medium composition comprising or a biomass product using a process of depolarizing the ganic waste material in (d).

anode of an aqueous electrolytic cell. Particular catalyst Component (a) is an indispensable subcombination of systems are not disclosed. each of the other aspects of the invention. The disper U.S. Pat. No. 4,279,710 presents an electrochemical sion of (a) throughout the electrolyte composition im method and associated apparatus for gasification of 60 parts homogeneity to the distribution of the cocatalyst carbonaceous materials to carbon dioxide with the at and of the catalyst.

tendant formation of fuels or high-energy intermediates, The benefits derived from use of the catalyst such as hydrogen or light hydrocarbons, and produc /cocatalyst are many. The process for treating organic tion of electric power. No particular catalyst systems waste material significantly reduces the amount of are disclosed. 65 solids electrochemically, producing gaseous products In U.S. Pat. No. 4,311,569, an improved catalytic and some residue; it minimizes the amount of waste anode of a ternary platinum group reduced metal oxide material which must be dumped or otherwise disposed is used alone or in combination with platinum group of. Likewise, an increase in reaction rates using the

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catalyst/cocatalyst combination (a) provides energy volved in the oxidation forms spontaneously when the saving economy. homogeneous cocatalyst is added to an electrolyte con taining dissolved or suspended organic compounds

BRIEF DESCRIPTION OF THE DRAWINGS which have functional groups or bonds capable of inter FIG. 1 is a vertical sectional view of an electrochemi acting with the cocatalyst. The relative weight ratios cal cell useful for practicing the invention. vary with the type of organic compound, the type of FIG. 2 is a cross-sectional view taken on the plane cocatalyst and the electrocatalyst. Preferred ranges of 2-2 of the cell of FIG. 1. proportions for each component are relatively large FIG. 3 is a vertical sectional view of apparatus in amounts of organic material (an activity for the organic which the organic reaction area and electrochemical O of 1 or more), a great concentration of the electrocata cell are separated. lyst (activity of 0.1 to 1.0 or more) and a smaller concen

DETAILED DESCRIPTION OF THE

tration of the cocatalyst compound (activity of 0.01 to

INVENTION

0.001 or less). The ETC is formed in an electrolyte which solvates the catalysts and at a temperature of 0

In the process of the invention organic waste material 15 C. or higher with an organic material with functionali is oxidized in an electrolytic cell. The reaction at the ties which can interact with the cocatalyst, and in the anode is a mediated, or electrocatalytic, reaction in absence of any interfering conditions, such as species which the oxidized form of a reversible redox couple, which tie up or precipitate the catalysts. The species produced at the anode, subsequently oxidizes carbon of which precipitate the catalysts are those which form the organic waste material. The products of the carbon 20 insoluble salts with the catalysts, such as (for the metals) oxidiation are carbon oxides and the reduced form of hydroxide, silicate, sulfide, high concentrations of sul the redox couple, which is reoxidized at the anode. The fate or high concentrations of phosphate, and (for bro process described herein employs one of several elec mine) silver cation, gold cation or mercury cation. Spe trocatalysts along with one of several homogeneous cies or substances which tie up the catalysts include cocatalysts to improve the organic oxidation rate and to 25 highly absorptive inert materials such as clay or acti lower the activation energy required for the oxidiation vated carbon, or compounds with which the catalysts of the organic material. Obtained data show that the react irreversibly, such as the reaction of bromine with mechanism of the organic oxidation is changed by the an organic compound to form bromoform or tetra homogeneous cocatalyst, which apparently forms an bronomethane.

electron transfer complex involving the electrocatalyst. 30 The electrocatalyst is obtained as pure catalyst, from This results in improvement in reaction rate and/or various salts or compounds of the electrocatalyst, or lowering of activation energies. from impurities in the organic material. The electron transfer complex must exit at least mo The solutions usually used in the catalytic system mentarily to account for increased oxidation rates and dissolve many metal oxides, sulfides, many metal salts, lowered activation energies of the reactions taking 35 etc. If any of these compounds exist as impurities in the place. It is postulated that the oxidation mechanism organic waste used in the reactor, they will be leached involves a short-lived coordination complex between out by the solution. Iron is one of the most common the organic compound and the homogeneous cocata metals found in sewage sludge, manure and many other lyst, such as that of platinum ions or palladium ions and biological wastes, and so can supply part or all of the the double bonds of organic compounds, e.g., Ziese's electrocatalyst once leached from the organic material. salt anion, the trichloro(ethylene)platinate (II) ion, Bromine or iodine, found in sufficient quantity in some which is stable in aqueous solution. Similar platinum waste materials, particularly brominated or iodinated organic double-bond complexes are apparently formed organics, can supply the necessary electrocatalyst con in catalyst mixtures of this invention. The standard centration. The electrocatalyst is usually added to the potential of the iron (II)/iron (III) redox couple in 1.OM 45 electrolyte, as there is not enough normally found in sulfuric acid is -0.69 V. The standard potential of plati waste materials to develop the desired reaction rate, but num (IV)/platinum (II) redox couple in 1.0M sulfuric some waste materials supply their own electrocatalyst, acid is also approximately --0.69 V. Thus, the platinum e.g. when leachable iron, bromine or iodine is present in (II) species is in equilibrium with the platinum (IV) sufficient quantity in the waste material. It is doubtful species, iron (III) and iron (II), and can be considered to 50 that any waste material will contain sufficient quantities be complexed for at least short periods of time to or of copper, nickel, platinum, vanadium, etc., to supply ganic double bonds or other appropriate functionality their own cocatalyst as well, but such is not precluded. on the organic compounds. The increase in reaction rate Whether the electrocatalyst and cocatalyst are added as produced by platinum, palladium, rhodium and ruthe metals, metal salts, etc., or leached from the organic nium is due to the fact that the homogeneous cocatalyst 55 waste material does not affect the nature of the process /organic complexes are more long-lived than the elec described herein. The catalyst materials are identified trocatalyst/organic complexes and thus are more effi by chemical analysis of the waste material to determine cient at transferring electrons. Lowered activation ener catalyst content (if any), and by chemical analysis of the gies are accounted for by the lower activation energy electrolyte solution (after it has been thoroughly mixed necessary for formulation of the organic compound with the waste and allowed to stand for, e.g., from 24 to homogeneous cocatalyst complex. The required supply 72 hours).

of oxidizing electrons can be derived from direct reduc The homogeneous cocatalyst is optionally obtained tion of the cocatalyst, followed by reoxidation by the from pure cocatalyst metal, from various salts or com electrocatalyst, or by formation of a short-lived elec pounds of the cocatalyst, or from impurities in the or trocatalyst/cocatalyst/organic complex in which the 65 ganic material. The homogeneous cocatalyst is dis cocatalyst compound acts as a bridge to transfer an solved in or homogeneously distributed throughout the electron from the organic compound to the electrocata catalyst solution. This is advantageous in that it elimi lyst. Thus, the electron transfer complex (ETC) in nates one heterogeneous step in the process of transfer

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of electrons from the electrocatalyst and in that the cocatalyst providing an appropriate reaction rate is cocatalyst is available to the entire surface of any solid from 0.0001M to 0.1M. The preferred range is from organic particles immersed in the catalyst solution. The 0.001M to 0.01 M. The preferred ranges provide econ cocatalyst is homogeneous with the electrocatalyst so omy of operation.

lution, it is a single ion complex (not an admixture), and Anode materials used in the invention are, for exam the homogeneity of the cocatalyst is very critical to the ple, platinum, platinum-clad titanium, graphite, reticu increased reaction rates observed. lated vitreous carbon or platinum plated reticulated The employed electrolyte is any solution in which the vitreous carbon. Suitable anode materials are those electrocatalyst and cocatalyst are soluble at least in materials which do not corrode in the electrolyte and at reduced form, but is typically a solution of a strong 10 which the electrode-catalyst redox pair is reversible or mineral acid, such as hydrochloric acid, phosphoric quasi-reversible.

acid or sulfuric acid. The acid solution provides a solu Suitable cathode materials are, for example, nickel bilizing medium for the catalyst composition. The sys mesh or platinum or platinum plated reticulated vitre tem is satisfactorily operated at various temperatures, ous carbon. Other suitable cathode materials are materi depending on the catalyst combination and the organic 15 als which do not corrode in the electrolyte. source; temperatures from 70' C. to 200 C. are typical. The electrolyte is, for example, phosphoric or sulfu However, temperatures from 0 C. to 500' C. or more ric acid in concentrations varying from 1M to 6M, or may be used. potassium sulfate at 0.2M. Other useful electrolytes are The principle advantage of the process is that it ef those which possess the necessary conductivity, dis fects the oxidation (without burning, standard chemical 20 solve at least the reduced form of the catalyst, and do oxidation or biological digestion) of most organic mate not interfere with or poison the catalyst. The electrolyte rials directly to simple compounds. Chemical analysis of is made by diluting concentrated sulfuric acid, phos gaseous products and anolyte solutions after oxidation phoric acid or potassium sulfate crystals with water of indicates that the process is clean and efficient, leaving reasonable purity, e.g. distilled water, deionized water little residue. The organic waste/electrocatalyst/homo 25 or tap water.

geneous cocatalyst combination acts as a depolarizing The electrolyte solution optionally has many differ agent to reduce the potential applied at the anode. ent compositions. Various other acids which are suit Examples of organic waste material or biomass suit able electrolytes are perchloric acid, hydrochloric acid, able for practicing the invention are woody wastes, hydrobromic acid, hydroiodic acid, nitric acid, boric cattle manure, garbage, sewage sludge, various indus 30 acid, hydrofluoric acid, or any other strong acid which trial chemical wastes, food and fiber processing by-pro is not irreversibly degraded in the system. There are a ducts or waste, or any organic material which has a variety of salts which are suitable electrolytes, includ positive cost of disposal. ing sodium or potassium chloride, bromide or iodide, Examples of catalyst compositions useful for practic iron chloride, bromide or iodide, sodium or potassium ing the invention are various combinations of metal ion 35 postassium phosphate, sodium sulfate, any of the alkali complexes and/or oxidizing halogens. The complexes metal fluorides, any of the alkali or alkaline-earth ni vary and depend upon the composition of the solution trates or perchlorates, iron nitrate, iron percholorate, and the nature of the organic waste material. Non-limit any of the soluble borate salts, any of the soluble alumi ing examples of electrocatalysts are cerium (4--) ion num or ammonium salts and any other electrolyte salt complex, iron (3-) ion complex, bromine and iodine. or salt mixture which is not irreversibly degraded in the Non-limiting examples of homogeneous cocatalysts are system. The important attributes of the electrolyte are platinum (4--) ion complex, ruthenium (3--) ion com that it is able to solvate at least the reduced form of the lex, rhodium (3+) ion complex, nickel (2+) ion com electrocatalyst, that it provides a low-resistivity me plex, cobalt (2+) ion complex, palladium (2+) ion com dium between the electrodes and that it does not de plex, copper (2+) ion complex and vanadium (5+) 45 grade in the oxidation system.

oxide complex. The catalyst solutions are made by dis The operating potential of the system is dependent on solving the halogen, metal, and/or soluble metal salt in the electrocatalyst and the electrolyte. The electrolyte, an electrolyte solution. Useful combinations of electro because of its relatively high concentration, generally catalyst and homogeneous cocatalyst include: determines the form of the electrocatalyst complex (if iron with platinum+ (urea, wood cellulose, ma 50 any), and can shift the redox potential of the electrocat nure and/or fat) alyst by several tenths of volts. For iron (3-) in 1M iront with vanadium (sewage sludge) phosphoric acid, the standard redox potential is -0.49 bromine with ruthenium3+ (urea, wood cellulose volt, and the cell anode is operated at any potential from and/or fat) --0.5 to -- 1.5 volts or more, versus the normal hydro bromine with vanadium- (wood cellulose and/or 55 gen electrode (NHE).

manure) The normal hydrogen electrode (NHE) is an imagi iron- with cobalt2+ (wood cellulose and/or ma nary electrode at which the H/H2 redox reaction is nure) perfectly reversible, and which is suspended in solution iodine with ruthenium3+ (urea) where the activity of the hydrogen cation is 1.0 and iron3+ with palladium2+ (fat) where hydrogen gas at 1.0 atmosphere (activity = 1.0) is bromine with palladium2+ (fat) bubbled over the electrode surface. The potential of this iron3+ with nickel2+ (manure0 electrode is defined to be 0.000 V, and is the standard of In practicing the invention, an electrolyte, an electro reference for redox potentials of other species. In prac catalyst and a homogenous oxidation cocatalyst are tice, the electrode is approximated by a piece of planti combined for oxidizing organic waste material. 65 nized platinum (platinum covered with platinum black) The range of electrocatalyst concentration providing in an acid solution of H activity 1.0, while hydrogen a suitable reaction rate is from 0.01M up to 100 percent. gas at 1.0 atmosphere is bubbled over the surface (H2 The preferred range is 0.1M up to 1.0M. The range of activity - 1.0).

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The preferred operating range for iron (3+) in phos trodes are planar. The separator is, optionally, an ion phoric acid is +0.5 to +0.8 volt. For iron (3+) in 1.M specific membrane or any semipermeable barrier. sulfuric acid, the standard redox potential is -0.69 volt, Suitable ion-specific membranes include cation and the cell anode is suitably operated at any potential specific membranes, for example, Ionics 61 CZL-386 from --0.70 to -- 1.5 volts or more, versus the NHE. (manufactured by Ionics, Inc.) and Nafion 423 (manu The preferred potential range at the anode for iron (3+) factured by DuPont). The semi-permeable membrane is, in sulfuric acid solution is -0.7 to -- 1.0 volt. For bro e.g., a microporous plastic, sintered (fritted) glass, a gel, mine, the standard redox potential is +1.087 volts, and such as agar, or any other material which restricts fluid the cell anode is effectively operated at any potential flow and does not allow intimate mixing of the anolyte from -1.0 to -- 1.5 volts or more, versus the NHE. O and catholyte. The Ionics 61 CZA-386 membrane is a Preferred potential range for bromine is from + 1.0 to modacrylic fiber-backed cation-transfer membrane. -- 1.2 volts versus the NHE. For iodine, the standard Either an ion-specific or a semi-permeable membrane redox potential is approximately --0.47 volt, and the may be used, but the use of ion-specific membranes cell anode is operated at any potential from +0.5 to leads to higher electrochemical cell efficiency since -- 1.5 volts or more, versus the NHE. The preferred 15 they strongly limit the diffusion of the electrocatalyst potential range for iodine is from +0.50 to +0.70 volt. between the catholyte and the anolyte. Semipermeable Referring now to the Figures, FIG. 1 shows an elec membranes are generally less expensive but do not pro trochemical cell 2 suitable for practicing the invention. vide as much of a barrier to electrocatalyst diffusion, Tank 4 contains electrolyte 5 in which anode 6 and thus lowering the efficiency of the electrochemical cell stirrer 10 are immersed. Electrolyte 5 is an electrolyte 20 in comparison with a cell using an ion-specific mem containing electrocatalyst and homogeneous cocatalyst brane.

together with the organic waste material. Anode 6 and Other operating limitations are principally imposed cathode 8 are separated by an ion specific or semi by the materials used in construction of the reactor permeable membrane 12. Anode 6 is connected to lead system. The system may be built of very inert, strong, 14 and cathode 8 is connected to lead 16. Leads 14 and 25 expensive materials, such as quartz-lined steel, and op 16 are connected to a source of electric current (not erated at relatively high temperatures (100' to 500 C. shown). Gases generated in the cathode compartment or more) or it may be made from inexpensive materials, are removed through conduit 18, and gases generated in such as polypropylene or polyethylene and ordinary the anode compartment are removed through conduit gallss, and operated at temperatures of 20 C. to 120° C. 20. FIG. 2 is a top view of the electrochemical cell 2, 30 Electrode materials must not corrode at the operating showing circular anode 6, circular cathode 8 and anode temperature of the electrochemical cell. Another limita electrolyte solution 5 containing the electrolyte, elec tion is the necessity to operate below the critical tem trocatalyst and homogeneous cocatalyst, together with perature of the electrolyte solution being used. the organic waste material. Ion specific or semi-permea Elevated temperatures are used when oxidizing a ble membrane 12 is shown as a circular separator be 35 refractory organic compound, such as lignin, chitin or a tween the anode and cathode compartments. FIG. 3 saturated aliphatic hydrocarbon; or when excess heat shows tank 30 which contains a mixture 32 of electro energy is available at low cost and a lower redox poten lyte, electrocatalyst, homogeneous cocatalyst and or tial electrocatalyst (for example, iron in phosphoric ganic waste material resting on optional filter screen 34. acid, or iodine) can be used to reduce electrical costs. Organic waste material is reacted with electrolyte and 40 When a lower-potential electrocatalyst has an unac catalyst combination in tank 30, and electrolyte solution ceptable reaction rate at, e.g., 70 C., it is not precluded 35 flows through exit 36 via pump 38 to electrochemical from oxidizing the organic compound at an adequate cell 40, which contains electrolyte solution 35 in which rate at, e.g. 250 C. The pressure in the system may vary anode 42 is immersed. Anode 42 and cathode 43 are and is dependent on the nature of the electrolyte and the separated by ion specific or semi-permeable membrane 45 electrocatalyst. A concentrated sulfuric acid solution separator 44. Anode 42 is connected to lead 46, and does not reach one atmosphere (14.7 psia) vapor pres cathode 43 is connected to lead 48. Leads 46 and 48 are sure until 330 C, and concentrated phosphoric acid has connected to a source of electric current (not shown). a similar low pressure at elevated temperature. The Gases generated at the cathode are led off at exit 50. reaction may be run in molten salt electrolyte at ele Solution from the anode compartment is returned by 50 vated temperatures with no significant overpressure in conduit 52 to tank 30 for reuse. Gases generated in tank the reactor.

30 are withdrawn therefrom through conduit 54. Waste Potential applied to the anode is kept as low as possi material in tank 30 is mixed with catalyst solution by ble to maximize the energy efficiency of the system. An precolation, spraying, stirring, density gradient or other increase in temperature increases the reaction rate and method. Catalyst which is reduced in tank 30 is reoxi 55 reduces the necessary size of the reactor for oxidizing a dized in electrochemical cell 40 before being returned given amount of organic waste material in applications to tank 30, where space is at a premium or rapid oxidation is de The electrocatalyst is regenerated from the reduced sired. Operating the anode at a higher potential drives form by oxidation at the anode. There may be some the reaction more quickly but is of limited utility be reoxidation of reduced cocatalyst at the anode, but this 60 yond about 0.2 to 0.3 volt more (positive) than the elec is minimal compared with the reoxidation of the elec trocatalyst redox potential. The acidity of the electro trocatalyst since the cocatalyst is largely not consumed. lyte solution normally used affects the reaction rate by The electrochemical cells shown in FIGS. 1 to 3 are aiding in the decomposition of the organic waste com non-limiting examples of the invention. The electro pounds due to dehydration and other acid catalyzed chemical cell may be configured as a cylinder, a sphere 65 reactions. With woody organic waste material greater or other appropriate shape. The anode compartment is acid concentrations are particularly effective in increas alternatively the inner compartment, the outer compart ing the electrocatalytic oxidation reaction rate, due to ment, or either compartment in a cell in which the elec breakdown of the cellulose chains.

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For oxidative degradation of organic waste material, creased using the combination of electrocatalyst and catalyst and reactor conditions are chosen to insure homogeneous cocatalyst of the invention. maximum conversion of the organic waste to an easily In practicing the invention, the mechanism of organic disposable form. Strong acid solutions (6M or more) oxidation is changed by addition of the homogeneous and active catalysts are selected. Useful combinations 5 cocatalyst to the electrocatalyst and by formation of an for oxidative degradation include: electron transfer complex involving the electrocatalyst, 0.2M iron (3+)/0.001M platinum (4-)/fats, wood homogeneous cocatalyst and the organic waste mate cellulose or sewage sludge/6M hydrochloric acid; rial. The electron transfer complex has not been charac 0.01M bromine/0.001M ruthenium (3+)/urea fats or terized but its presence is demonstrated by the reduced wood cellulose/6M sulfuric acid; O activation energies and/or increased reaction rates in 0.01M bromine/001M vanadium (5+)/wood cellu the presence of homogeneous cocatalyst as opposed to lose or manure/6M sulfuric acid; use of the electrocatalyst alone, as shown in Table I. 0.01M iron (3+)/0.01M vanadium (5+)/sewage The use of the combination of electrocatalyst and ho sludge/6M hydrochloric or sulfuric acid; and mogeneous cocatalyst of the invention results in an cerium (4--)/platinum (4--)/fats, wood cellulose and 15 increase in reaction rate and a decrease in activation many other organics/6M sulfuric or hydrochloric acid. energies.

TABLE I

Organic Electrocatalyst Homogeneous Cocatalyst Electrolyte Rate (sec) (kcal/mole) wood cellulose iron (III) One 6. MH2SO4 G 50' C. 1.4 x 10-6 12. wood cellulose iron (III) cobalt(II) 6. MH2SO4 G 50' C. 4.1 x 10-6 11.3 wood cellulose iron (III) platinum (IV) 6. MH2SO4 G 50' C. 3.6 x 106 8. beef fat iron (III) de 1.0 MH2SO4 G. 20' C. <1 x 10-9 beef fat iron (III) platinum (IV) 1.0 MHSo4 G. 20' C. 4.7 x 10-7 4.5 beeffat iron (III) palladium (II) 1.0 M HCl G20 C. 2.2 x 10-6 3. iron (III) Oe 1.0 MH2SO4 G20 C. 4 x 109 w ea iron (III) ruthenium (III) 1.0 MH2So G20 C. 2.2 x 10-8 rea iron (III) platinum (IV) 1.0 MH2So4 G. 20' C. 1.2 x 10-6 4.8 3. iodine ce 1.0 MH2SO4 G. 20' C. <1 x 10-9 WOOD 3. iodine ruthenium (III) 1.0 MH2SO4 G20 C. 5. x 10-9 O 3. bromine Ole 1.0 MH2SO4 G20 C. 2.0 x 10-5 2 bromine ruthenium (III) 1.0 MH2SO4. G. 20' C. 2.6 x 10- 8.6 cellulose bromine Oe 0.2 MK2SO4 G. 20" C. 1.6 x 10-6 w cellulose bromine platinum (IV) 0.2 MK2SO4 (a 20' C. 2.9 x 10-6 O cellulose bromine rhodium (III) 0.2 MK2SO4 G. 20' C. 8.6 x 10-6 O cellulose bromine ruthenium (III) 0.2 MK2So G20 C. 1.7 x 10-5 2. cellulose bromine One 6.0 MH2SO4 G 50' C. 1.6 x 10-5 10.6 cellulose bromine vanadium (V) 6.0 MHSo4 G. 20' C. 4.7 x 10-5 1.4 cellulose ce vanadium (V) 6.0 MHSo4 G. 20" C. <1. x 10-6 are fat bromine tole 0.2 MK2SO4 G. 20" C. 1.9 x 10-6 w fat bromine palladium (II) 0.2 MK2So4 G. 20' C. 2.9 x 10-6 fat bromine ruthenium (III) 0.2 MK2SO4 G. 20' C. 9.3 x 10-6 11. cattle manure iron (III) ore 6.0 MH2SO4 G 50° C. 4.0 x 10-7 12.3 cattle manure iron (IIE) platinum (IV) 6.0 MH2SO4 G 50' C. 1.1 x 10-6 cattle manure iron (III) cobalt(II) 6.0 MH2SO4 (a 50' C. 1.2 x 10-6 8.0 cattle manure iron (III) nickel (II) 6.0 MH2SO4 g 50'C. 8.0 x 10-7 cattle manure bromine One 6.0 MH2SO4 G 50' C. 7.6 x 10-6 0.0 cattle nanure bromine vanadium (V) 6.0 MH2SO4 G 50 C. 1.1 x 10-5 5.1 sewage sludge iron (III) O 6.0 MH2SO4 (a 50 C. 1.2 x 10-6 18.7 sewage sludge iron (III) vanadium (V) 6.0 MH2SO4 G 50° C. 3.8 x 10-6 13.3

The temperature of the reactor should preferably be examplesThe invention is further illustrated by the following maintained at 100 C. or more for most applications, but in which all parts and percentages are by for some materials, such as urea, a lower reaction tem SO weight unless otherwise indicated. These non-limiting perature is suitable. The cathode material is suitably examples are illustrative of certain embodiments de platinum, nickel or nickel-plated carbon as well as a the signed to teach those skilled in the art how to practice variety of other metals or electrode materials with rela invention and represent the best mode contemplated tively low electrochemical overpotentials. The anode for carrying out the invention.

material may be platinum, carbon, platinum-plated car 55 EXAMPLES bon, platinum-clad titanium or niobium, or any other Example 1 electrode material which does not corrode in the cata lyst solution and has a relatively low overpotential for A catalyst solution of 6.0M sulfuric acid containing the electrocatalyst oxidation. The operating potential at 0.2M iron (III) and 0.01M cobalt(II) is prepared by the anode is maintained at +0.5 to - 1.5 volts versus the 60 diluting 0.330 liter of concentrated sulfuric acid, 40 NHE. grams of iron (III) sulfate and 1.55 grams of cobalt(II) Table I, below, tabulates non-limiting examples of sulfate to 1 liter with water. The resulting solution is organic material, electrocatalyst, homogeneous cocata stirred to dissolve the salts thoroughly. A 600 ml por lyst, electrolyte, reaction rate, and activation energy, tion of this solution is then transferred to the anode particularly pointing out the advantageous effect when 65 half-cell of FIG. 1; a solution of 1.0M sulfuric acid is a homogeneous cocatalyst is used in combination with added to the cathode half-cell. These two solutions are an electrocatalyst contrasted with the use of the electro the anolyte and the catholyte, respectively. The anode catalyst alone. The reaction rate is significantly in is a platinum-clad titanium wire mesh formed into a

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cylindrical shape, and is totally immersed in the solu mine liquid and 0.21 grams of ruthenium (III) chloride tion. The cathode is a cylinder formed of fine nickel to one liter with water. A 600 ml portion of this solution wire mesh, and is also totally immersed in the solution. is transferred to the anode half-cell of FIG. 1, and a A Teflon (R)-coated stirring bar is used to agitate the solution of 0.5M sulfuric acid is added to the cathode solution in the anode half-cell. An Ionics 61 CZL-386 5 half-cell. The anode is a platinum-clad titanium wire cation-specific membrane is used to separate the two mesh formed into a cylindrical shape, and is totally half-cells. Approximately 6 grams of sawdust, or other immersed in the solution in the anode half-cell. The source of cellulose, is added to the anode half-cell, fol cathode is a cylinder formed of fine nickel wire mesh, lowing which the cell tank is sealed and heated to 70° C. and is totally immersed in the solution in the cathode A D.C. potential of approximately 1.0 V is applied O half-cell. A Telfon (E)-coated stirring bar is used to agi across the electrodes giving a current of approximately tate the solution in the anode half-cell, and an Ionics 61 16.8 milliamperes (Reaction rate constant=1.5X106 CZL-386 cation-specific membrane is used to separate sect-1, activation energy = 11 kcal/mole). The cell pres the two half-cells. Approximately 6 grams of fat is sure in this case is a little over one atmosphere. Analysis added to the anode half-cell, following which the cell of the gaseous products from the anode half-cell shows 15 tank is sealed and heated to 70° C. A D.C. potential of only carbon dioxide. The optimum size for a reactor approximately 1.25 V is applied across the electrode, under these conditions is an anode half-cell chamber of giving a resultant steady state current of approximately 4,000 to 16,000 liters (volume), assuming the cylindrical 15 milliamperes (Reaction rate constant=2.6X 10 shape of FIG. 1 with approximately 25% of the total sec, activation energy = 11 kcal/mole). Pure carbon volume occupied by the cellulosic material and the dioxide is produced in the anode half-cell at almost 100 reactor head space. percent efficiency.

Example 2 Further examples of systems operated at higher tem peratures are shown in Table II.

TABLE II

EXAMPLES OF SYSTEMS AT HIGHER TEMPERATURES

Electrolyte

Electrocatalyst Cocatalyst Medium Temperature Pressure 0.2 MIron (III) 0001 M Platinum (IV) 6 MH2SO4 100. C. <15 psia 0.2 MIron (III) 0.01 M Cobalt(II) H2SO4 330.C. - 15 psia 0.2 MIron (III) 0.01 MVanadium (V) H3PO4 200. C. < 15 psia

Bromine 0.01 MVanadium (V) HBr 225. C. ~2000 psia 0.2 MIron (III) 0.001 M Platinum (IV) AlCl3 200. C. ~40 psia

Bromine 0.001 M Ruthenium (III) 6 MH2SO4 10, C. - 30 psia

Iodine 0.01 M Copper (I) H2So 265." C, ~75 psia 0.2 M Cesium 0.001 M Palladium (II) 6 MNaCl 225. C. ~300 psia

The reactor tank of FIG. 3 is loaded with a supported bed of 500 grams of wood chips over filters of 1.0 mm and 0.25 mm Teflon (R) screen. A solution of 6.0M sulfu ric acid containing 0.2M iron (III) and 0.01M cobalt(II) 40 Variations and modifications may be effected within is prepared by diluting 3.3 liters of concentrated sulfuric the scope of the invention as described above, and as acid, 400 grams of iron (III) sulfate and 15.5 grams of defined in the appended claims. Throughout the disclo cobalt(II) sulfate to 10 liters with water. The solution is sure and claims all references to "homogeneous cocata agitated to dissolve the salts and then transferred into lyst' mean that the cocatalyst is substantially uniformly the reactor tank. The electrodes in the electrochemical 45 dispersed throughout the electrolyte. cell are a 20 pores/inch reticulated vitreous carbon What is claimed is:

(RVC) anode and a platinum-plated 20 pores/inch 1. A method for gasifying organic waste which com RVC cathode, separated by a Nafion (R) 423 cation prises:

specific membrane. A potential of 1.0 volt is applied combining organic waste material with electrolyte, across the electrodes. The reactor tank is sealed, and the 50 conducting an electrocatalytic reaction between the catalyst solution is pumped from the tank through the organic waste material and the electrolyte, and electrochemical cell and back into the tank. The reactor maintaining an electrochemical potential across an tank is heated to about 80 C., giving steady state cur anode and a cathode in an electrochemical cell rent levels of approximately 2.0 amperes. The reaction containing the electrolyte, tank volume is about twice the volume of the solution in 55 the electrolyte containing a catalyst combination of liters, and the reaction rate is about 1X 10-5 sec-1. (a) electrocatalyst and (b) homogeneous cocatalyst. Total reaction time is dependent on the flow rate. With 2. A method of claim 1 wherein the electrocatalyst is a flow rate of 4 liters/sec, a reaction tank volume of 20 a member selected from the group consisting of cerium liters and a tank loading of 500 grams wood chips, total (4--) complex, iron (3-) complex, bromine and iodine. reaction is achieved in about 46 hours. The electro 60 3. A method of claim 1 wherein the homogeneous chemical cell operates at 95-- percent efficiency and cocatalyst is a member selected from the group consist the biomass tank produces essentially pure carbon diox ing of platinum (4--) ion complex, ruthenium (3--) ion ide. complex, rhodium (3) ion complex, nickel (2--) ion Example 3 complex, cobalt (2-) ion complex, palladium (2--) ion 65 complex and vanadium (5+) oxide complex. S

A catalyst solution of 1.0x10-3M bromine (as Br2) 4. A method of claim 3 wherein the electrocatalyst is and 1.0X 10-3M ruthenium (III) is prepared by diluting a member selected from the group consisting of cerium 27.5 ml of concentrated sulfuric acid, 0.05 ml of bro (4-H) complex, iron (3--) complex, bromine and iodine.

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5. A method of claim 1 comprising admixing the 16. A method of claim 1 comprising treating the or organic waste material with the electrolyte and catalyst ganic waste material in the electrochemical cell. composition in the electrochemical cell. 17. A method of claim 1 wherein the catalyst combi 6. A method of claim 1 comprising separating the nation increases the reaction rate by an amount greater anode from the cathode in the electrochemical cell by 5 than that attributable to the additive effect of said elec interposing an ion-specific membrane therebetween. trocatalyst and said homogeneous cocatalyst, when 7. A method of claim 1 comprising separating the each is used alone.

anode from the cathode in the electrochemical cell by 18. A method of claim 1 wherein the catalyst compo interposing a semi-permeable membrane therebetween. sition decreases the activation energy of the reaction by 8. A method of claim 1 comprising treating the or 10 an amount greater than that attributable to the additive ganic waste material in a tank, circulating electrolyte effect of said electrocatalyst and said homogeneous solution containing the catalyst combination in reduced cocatalyst, when each is used alone. form to the electrochemical cell for reoxidation of the 19. A method of claim 6 wherein the ion-specific electrocatalyst and homogeneous cocatalyst, and recir membrane is a cation specific membrane. culating the electrolyte containing electrocatalyst and 15 20. A method of claim 9 wherein the ion-specific homogeneous cocatalyst to the tank for treating organic membrane is a cation specific membrane. waste material. 21. A process for gasifying organic waste which com 9. A method of claim 8 comprising separating the prises combining organic waste material with electro anode from the cathode in the electrochemical cell by lyte containing a catalyst combination comprising (a) an interposing an ion-specific membrane therebetween. 20 electrocatalyst and (b) a homogeneous cocatalyst, and 10. A method of claim 8 comprising separating the maintaining an electrochemical potential across an anode and the cathode in the electrochemical cell by anode and a cathode in an electrochemical cell contain interposing a semipermeable membrane therebetween. ing the electrolyte and the catalyst combination, the 11. A method of claim 8 comprising dissolving the process being effected at a reaction rate, at a given catalyst combination in its reduced form in the electro 25 temperature, which is attributable to the catalyst combi lyte solution. nation and which is greater than the sum of catalytic 12. A method of claim 1 which is carried out at O' C. effects of respective components of said catalyst combi to 500 C. nation.

13. A method of claim 1 wherein the anode is con 22. A process for gasifying organic waste which com structed of a material selected from the group consisting 30 prises combining organic waste material with electro of platinum, platinum-doped carbon, platinum-clad tita lyte containing a catalyst combination comprising (a) an nium, niobium, graphite, reticulated vitreous carbon electrocatalyst and (b) a homogeneous cocatalyst, and and platinum-plated reticulated vitreous carbon. maintaining an electrochemical potential across an 14. A method of claim 1 wherein the cathode is con anode and a cathode in an electrochemical cell contain structed of a material selected from the group consisting 35 ing the electrolyte and the catalyst combination, of platinum, platinum plated reticulated vitreous car wherein, at a givven temperature, obtained reaction bon, platinum-doped carbon, platinum-clad titanium, activation energy required to oxidize the organic waste niobium, nickel and nickel-doped carbon. material is decreased a greater amount by the catalyst 15. A method of claim 1 wherein the anode is main combination than by the combined catalytic effects of tained at an operating potential of -0.5 to -- 1.5 volts, each component of said catalyst combination. versus that of the normal hydrogen electrode.