FR2513662A1 - PROCESS FOR THE CATALYZED ELECTROCHEMICAL GASIFICATION OF CARBON MATERIALS TO THE ANODE OF AN ELECTROLYSIS CELL - Google Patents

Abstract

THE INVENTION RELATES TO THE FIELD OF ELECTROLYSIS. IT CONCERNS THE USE OF AN IRON CATALYST TO CATALYZE THE ELECTROCHEMICAL GASING REACTION OF CARBON MATERIALS BY ANODIC OXIDATION IN AN AQUEOUS ACID ELECTROLYTE TO PRODUCE CARBON OXIDES AT THE ANODE OF AN ELECTROLYTIC CELL. APPLICATION TO THE TREATMENT OF MANY CARBON MATERIALS SUCH AS VARIOUS TYPES OF COALS, WOOD, BIOMASSES, GADOUES, ETC.

Description

The present invention relates to the use of

  iron catalyst in the electronic gasification of

  carbonaceous material in an aqueous acidic electrolyte. It is known in the prior art that

  that carbonaceous materials are mixed with an elec-

  aqueous acid trolyte in an electrochemical cell in which a direct current is passed, they react electrochemically by oxidizing the carbonaceous material to carbon oxides at the anode The electrochemical oxidation of the carbonaceous material to the anode takes place

  whatever the nature of the simulated cathodic reaction

  which, for example, may be the production of hydro-

  metal electroplating, the hydrogenation of unsaturated organic compounds or any other process of electrochemical reduction, any other process which may take place at the cathode, as well as in any other compartment of the electrolytic cell other than at the anode, and that would generally be known to the man of

art.

  U.S. Patent No. 4,268,363 teaches the electrochemical gasification of carbonaceous materials by anodic oxidation, which produces oxides of carbon at the anode and hydrogen, metal elements or the hydrogenation of carbon at the anode. the

  cathode of an electrolytic cell.

  U.S. Patent 4,279,710 discloses electrochemical oxidation.

  of carbonaceous materials at the anode and the concomi-

  hydrogen at the cathode as well as the production of electrical energy by the use of said hydrogen

  as fuel of a fuel cell.

  The patent of the United States of America

  No. 4,226,683 teaches the process for producing hydro-

  gene by reaction of carbon or carbon powder with the hot water retained in the form of water at a pressure higher than the atmospheric pressure The pressure is regulated by the use of an inert dielectric liquid which washes the electrodes and which, by doing so, depolarizes them

by absorption of gases.

  U.S. Patent No. 4,233,132 teaches a method in which electrodes are immersed in oil which forms a layer in particular.

  above a quantity of water When passing a cou-

  between the electrodes, the water is thus exposed to electrodecomposition Hydrogen gas is collected in the enclosed space above the oil-water layers and

  oxygen is supposed to react with the constituents

in the oil layer.

  As recognized in the aforementioned U.S. Patent No. 4,226,683, the main problem with the use of this principle for the industrial production of hydrogen has been slow

  electrochemical reaction rate of coal or carbon

  and water It has now been discovered that when

  iron was added to an aqueous acid electrolyte containing

  carbon-based material, preferably iron at +3 valence, it catalyzed the reaction rate and contributed

  to obtain a more complete oxidation in terms of

  identifies the electrochemical oxidation of the carbonaceous material at the anode, thus making such processes feasible

  from the commercial point of view as a means of

  industrial hydrogen or as a method of obtaining by electrolysis. As indicated above, it is well known that a carbonaceous material such as coal can

  be oxidized at the anode of an electrochemical cell

  holding an aqueous acid electrolyte at the same time as carbon oxides are produced at the anode and that this anodic half-cell reaction can be used

  together with the cathodic reactions of half

  cell such as the electrodeposition of a metal M to

  from an aqueous solution of its ions m or the

  For example, in the case of electro-

  deposition of a metal, by concentrating the attention on the carbon contained in the carbon and by representing it with C, this anodic reaction can be reproduced according to the stoichiometry: C (s) + 2H 20 (1) -> CO 2 ( g) + 4H + + 4e () together with the simultaneous cathodic reaction Mm + me -4M (II) The overall reaction, i.e. the sum of equations (I) and (II) / -au where om = 1 - 7 is the following: C (s) + 2H 20 (1) + 4M +> CO 2 (g) + 4M + 4H (III)

  In the case of copper, for example, electro-

  deposition of copper-assisted copper would take

form: -

  C (s) + 2 H 20 (g) + 2 Cu 2 + C 2 (g) + 2 Cu (s) + 4 H + In the case of hydrogen production, considering the carbon contained in coal and in the representative

  by C, this anodic reaction can be reproduced according to

  stoichiometry: C (s) + 2H 20 (1) -2C O 2 (g) + 4H + 4EE O = 0.21 volt (IV) together with simultaneous cathodic reaction 4H + 4e 2 H 2 g) E = 0.0 volts (V) The net reaction, ie the sum of equations (IV) and (V), is as follows: 2 H 20 () + C (s) -0 i C 02 (g) + 2 H 2 (g) EO = 0.21 volts (VI) In these equations, the letters (g), (s) and (1) symbolize, respectively, the gaseous, solid states and

  The equations (I) and (IV), that is the reaction

  between coal and water, caused by the application of

  potential for an electrochemical cell

  as appropriate, constitute what is considered

  the electrochemical gasification of coal in the

  vets of the United States of America N 4 268 363 and N 4 279 710 cited above.

  A problem related to these methods of the prior art

  is the relatively low reaction rate and the incomplete combustion of the material

carbon at the anode.

  It has been discovered that the addition of a sufficient amount of iron at the elemental valence level + 2 or + 3 or their mixtures to the carbonaceous material undergoing oxidation in an aqueous acidic electrolyte at the anode

  increased the reaction rate of the oxidation process

  The iron catalyst contributes to the fulfillment

  oxidation of the carbonaceous material and increases the quantity

  current generated at the anode by a given working voltage.

  The advantageous carbonaceous materials to be used

  In accordance with the present invention, a wide variety of materials such as fatty charcoal, carbonization products of coal, lignite, peat, active carbons, coke, carbon blacks,

  carbon, graphite; wood or other ligno

  cellulosic products including forest products such as wood waste, wood chips, sawdust

  wood, wood powder, bark, chips, agglomerates

  mounts of wood; including various biomassic materials such as terrestrial or marine plant products or their residues after further processing, such as herbs, various cutting products, cultivated plants and their wastes, coffee grounds, leaves, straw, ensiled products, pods, pods, stems, shelling products, stalks and

  residues such as animal manure; slushes

  coming from municipal treatment plants and plastics or wastes or residues formed in

  the production of plastics such as polyethylene

  Thus, it can be seen that virtually any combustible or waste material, be it liquid such as a gaseous oil such as methane or another hydrocarbon or a carbon-containing waste material, is exception of CO 2,

  constitutes a suitable source of carbonaceous

  to be used in accordance with the invention.

  The particular apparatus used to conduct the electrolytic oxidation of carbonaceous materials is not critical. In the process of the present invention practically the same apparatus and techniques as those used in the present invention can be used. 2t 13662

  electrolytic deposition of metals and in the decomposition

  electrolytic treatment of water as well as those

  ueCj 1 dabn C The L evr S ues at L-5 'Us du -il Lrqu.

  No. 4,268,363, No. 4,279,710, No. 4,226,683 and No. 4,233,132 above. Any choice of suitable modifications in the use of the materials and / or the technique is entirely within the competence of the man of the art. art in the field

  to which the present invention is directed.

  The cells described in the aforementioned U.S. Patent Nos. 4,268,363 and 4,279,710, involving the use of aqueous acidic electrolytes, the choice of anodic and cathodic materials and the optional but preferred use of membranes. to maintain the carbonaceous material on the side of the anode, are

most appreciated.

  Although the electrode materials described in U.S. Patents No. 4,268,363

  and N 4,279,710 cited above may be used

  In the process of the invention, particularly good anodic materials comprise a mixture of Ru O 2 / Ti O 2 on a Ti substrate and a mixture of Ir O 2 / Ti O 2 on a formed substrate. of

  Ti, these anodes being both available in the

  commerce. Acidic aqueous electrolytes that can be

  advantageously have a p H less than 3 and

  take strong acid solutions such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc. Although temperatures can be used from a value above the freezing point of

  water temperatures of approximately 25 to 350 C are

  The temperatures of 120 to 300 C are preferred, particularly

  When using carbonaceous materials such as coal at temperatures below 140 ° C, the reactivity of solid carbonaceous materials such as

  coal is constantly decreasing as the oxidation

  This decrease in reactivity is

"1543662

  presumably due to the accumulation of oxides at

  In the face of the coal, which hinders the maintenance of the coal at temperatures of about 1400 ° C. and higher, the reaction of the coal is maintained and no noticeable diminution is observed. Since the maintenance of the reaction in the liquid phase is desired, it is of course necessary that at high temperatures the reaction be conducted at a high pressure.

0.2 to 40 M Pa are satisfactory.

  It has also been found that the addition of

  The solid iron carbon-based catalyst maintained coal activity at temperatures below 1200 C for a longer time, compared with systems not containing the iron catalyst. Also, the catalytic effects of the iron catalyst are

  more pronounced at high temperatures.

  Although iron can be used in its elemental form, preference is given to iron at its +2 valence and its +3 valence, that is to say the iron being, respectively, in the ferrous state and in the ferric state We particularly appreciate the use of iron

  valence + 3 Thus, it is possible to use inor-

  iron oxides such as iron oxides, iron carbonate, iron silicates, iron sulphide, iron oxide, iron hydroxide, iron halides, iron sulphate, nitrate of iron iron, etc. Also, various salts and organic complexes of iron such as salts of carboxylic acids, for example iron acetates, iron citrates, iron formates, iron glyconates, etc., can be used. iron cyanide, iron chelates such as chelates formed with diketones such as 2,4-pentanedione, iron complex of ethylenediaminetetraacetic acid, iron oxalates, and the like. Although the iron catalyst can be used at a concentration up to the saturation point in the aqueous electrolyte, the preferred range of iron catalyst proportions is from 0.04 to 0.5 M and especially 0.05 to 0.1 M. Although some carbonaceous materials such as coal may contain iron as an impurity, a catalyst containing iron from an external source is generally required to increase the reaction rate. at least initially up to levels acceptable for commercial use It is conceivable to generate the iron catalyst in situ by oxidation of a sufficient amount of iron-containing coal so as to generate an effective amount of

  iron catalyst in the electrolyte.

  Naturally, essential carbonaceous materials

  iron-free, such as card black

  require the addition of an iron catalyst

from an external source.

  Thus, according to one embodiment of the present invention, a sufficient amount of iron catalyst is added from an external source to cover the preferred molar range of catalysts, namely from 0.04 to 0.5M. second embodiment, an effective amount of iron catalyst can be generated

  in situ by oxidation of a sufficient quantity of

  good iron container, albeit initially at a speed

  lower, to cover the preferred range of the catalyst.

  The generated catalyst must then be freed of coal and it must be able to operate in the same way

  an iron catalyst brought from outside -

  In a third embodiment, the association between an externally introduced iron catalyst and an in situ generated iron catalyst can be used to cover the preferred molar range of catalyst, i.e. 04 to 0.5 M. The concentration or quantity of carbonaceous material present in the electrolyte may vary over a wide range depending on whether it is a liquid, a solid or a gas and according to the diameter of the particles;

  however, the recommended range is from about 0.1 to 0.7 g / ml.

  As in the case described in the aforementioned U.S. Patent No. 4,268,363, it is possible

  to obtain electrolysis, electroplating or electro-

  deposition any element that can be reduced to the cathode

  from an aqueous solution at the same time as the oxy-

  Anodic electrochemical dation of a carbonaceous material.

  Examples of metal elements often deposited in practice from an aqueous electrolyte include Cr, Mn, Co, Ni, Pb, Cu, Sn, Zn, Ga, Hg, Cd, Ir, Au, Ag, Os, Rh , Ru, Ir, Pd and Pt The metallic elements are

  preferably Cu, Zn, Ag, Ni and Pb.

  The invention is illustrated by the examples

  following, given in a non-limitative manner.

Example 1

  Copper plating was conducted under constant tension in a membrane cell "Nafion" (registered trademark), catholyte and anolyte solutions

being pumped.

  In this first test, the anolyte did not contain added coal or iron and was pumped into an external circuit.

  by pumping in a circuit similar to that of the anolyte.

  The aqueous electrolyte consisted of 0.5 M H 2 SO 4, the cathode also containing 0.5 M Cu SO 4. The total volume was 500 ml; the temperature line was made at 950 ° C and 120 ° C; the anode, with a surface area of 55 cm 2, was titanium coated with iridium oxide / titanium dioxide (TIR);

  the cathode was a copper foil.

950 cc 1200 C

  Potential of Intensity Potential of Intensity the cell (V) (m A> the cell (V> (m A)

1.25 370 1.22 600

1.00 9 1.00 35

Example 2

  The equipment and conditions were the same as in Example 1, except that the pumped anolyte contained 0.5 g / cm 3 of carbon.

_ 3662

  (WOW 3932) The results were as follows,

___ 95 O C

  Cell potential (V) 0.40 0.60 1.00

Example 3

Intensity (m A)

1200 C

  Cell Intensity Potential (V) (m A)

0.40 170

0.60 520

1.00 627

  In the third experiment, the conditions and the apparatus were the same as in Example 2, except that the anolyte had been made 0.04 M in Fe 3 + by the addition of Fe 2 (504) 3 o The results were as follows: CC Potential of Intensity Potential of Intensity cell (V) (m A) cell (V) (m A)

0.40 180 0.40 370

0.60 530 0.60 1140

1.00 620 0.65 1310

  At 120 ° C, the concentration of Fe 3 + was increased to 0.1 M, all other conditions and apparatus

remaining constant.

  The results were as follows: Cell potential (V) 0.35 0.40 0, 60 C Intensity (m A)

Example 4

  The electroproduction of hydrogen was conducted at constant voltage in a cell equipped with a membrane "Nafion" (registered trademark), catholyte solutions and

  of anolyte being stirred with magnetic stirrers.

  The aqueous electrolyte consisted of 0.5 M H 2 SO 4 for both catholyte and anolyte solutions. The total volume of the cell was 500 ml; the temperature was 180 C; the anode, with an area of 98 cm 2, consisted of titanium coated with iridium oxide / titanium dioxide; the cathode was in platinum The first test was conducted without the addition of charcoal to the anolyte Results:

1800 C

  Cell potential (V) 1.00 1.30 1.70 Intensity (A) 0.05 0.15 1.00

Example 5

  The apparatus and conditions were the same as in Example 1, except that the anolyte contained 0.17 g / c S 2. coal (WOW 3932) or coke

(El Segundo)

Cell potential (V) 1.00 1.30

Example 6

  Carbon Cc Intensity (A) Cell Potential (V)

0.48 1.00

1.50 1.30

oke Intensity (A) 0.21 0.79

  Conditions and equipment have been identified

  to those of Example 2, with the difference that the anolyte

  was made 0.07 M in Fe 3 + by the addition of Fe 2 (504) 3.

  Cl Cell Potential (V) 1.00 1.30 harb Intensity (A> 1.09 3.16 Coke Cell Potential (V) 1.00 1.30 Intensity (A> 1.24 3.17 1 1

Claims (3)

  1 Improved process for electronic gasification   chemical composition of carbonaceous material in an aqueous acid electrolyte by anodic oxidation to produce carbon oxides at the anode of an electrolytic cell, characterized   in that the improvement consists in adding to the elec-   trolyte containing the carbonaceous material, iron at its elemental degree of +2 or +3 valency, or mixtures of these valence degrees, in an amount sufficient to increase   the oxidation rate of the carbonaceous material at the anode.   2 Improved electrified gasification process   chemical composition of carbonaceous material according to claim 1 in an aqueous acid electrolyte by anodic oxidation   to produce carbon oxides at the anode and hydro-   gene at the cathode, comprising the steps of introducing carbonaceous materials and said electrolyte into a cathode and anode electrolytic cell and applying an electromotive force between said electrodes, so that said carbonaceous materials react at the anode and that hydrogen is produced at the cathode of the cell   electrolytic system, characterized in that   consists in adding to the electrolyte containing the carbonaceous material iron at its elemental degree of valence + 2 or + 3, or mixtures of these degrees of valence, in an amount sufficient to increase the rate of oxidation of the carbonaceous material at the anode.   3 Advanced method of electrified gasification   chemical composition of carbonaceous material according to claim 1 in an aqueous acid electrolyte by anodic oxidation to produce oxides of carbon at the anode and for   obtaining by electrolysis of a metallic element   firing an electrolyte containing a metal component   as a cationic component, comprising the steps of introducing   producing carbonaceous material and said electrolyte in an electrolytic cell having a cathode and anode and applying an electromotive force to said   electrodes, said carbonaceous materials reacting to the anode   of and the metal component being deposited at the cathode,