CA1062201A - Preparation and use of thallium palladate as cover layer of metal anodes - Google Patents
Preparation and use of thallium palladate as cover layer of metal anodesInfo
- Publication number
- CA1062201A CA1062201A CA295,395A CA295395A CA1062201A CA 1062201 A CA1062201 A CA 1062201A CA 295395 A CA295395 A CA 295395A CA 1062201 A CA1062201 A CA 1062201A
- Authority
- CA
- Canada
- Prior art keywords
- thallium
- cover layer
- palladate
- anode
- metal anodes
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Electrolytic Production Of Metals (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
ABSTRACT
A process for the production of thallium palladate (T1Pd3O4) a cardinal red face centred cubic crystalline compound when pure and if stoichiometric composition, in which thallic oxide is reacted with palladium monoxide at a temperature in the range 500-600°C. The thallic oxide May be derived from thallous nitrate and the palladium monoxide may be mixed either with the thallous nitrate or added after formation of the thallic oxide. Thallium palladate is useful as an electrochemically active cover layer for metal anodes.
A process for the production of thallium palladate (T1Pd3O4) a cardinal red face centred cubic crystalline compound when pure and if stoichiometric composition, in which thallic oxide is reacted with palladium monoxide at a temperature in the range 500-600°C. The thallic oxide May be derived from thallous nitrate and the palladium monoxide may be mixed either with the thallous nitrate or added after formation of the thallic oxide. Thallium palladate is useful as an electrochemically active cover layer for metal anodes.
Description
~062Z0~
This application is a division of Canadian Application Serial No.
212,232 filed October 24, 1974.
The present invention relates to the preparation of thallium palladate and the use thereof as a new electrochemical active substance for the cover layer of metal anodes.
Certain patents and patent applications, e.g. German Democratic Republic Patent 55,323, German Democratic Republic Patent No. 77,963, German Published Application No. 1,671,422, German Published Application 1,917,040, ~erman Published Application 1,813,944, German Published Application No. 1,962,860, and German Published Application No. 2,200,500 disclose metal anodes containing cover layers of the most varying composition in order to eliminate the drawbacksof the anode carrier members of passivatable metal, such as titanium, tantalum, zirconium, niobium, etc.
Most of the above substances, however, suggested for application as cover layer or as essential component thereof have unfortunately turned out to be disadvantageous, because their electrical conductivity and/or their chemical and;- electrochemical stability is not satisfactory or, respectively, a number of the suggested substances cannot at all or not very easily be applied to the anode carrier member without adversely affecting the requirements made respecting a cover layer. The methods used for applying a cover layer to an anode are well known to those skilled in the art and details thereof can be obtained from, for example, U.S. Patents 3,645,862; 3,632,498; 3,663,280; 3,711,397; 3,773,554 and 3,804,740, German Patents 2,304,380 and 2,328,417.
Whereas, for example, alkaline earth palladates such as CaPd304, ; SrPd304 and NaPd304 have already been synthesized in pure crystalline form, pre-paration and adequate characterization of TlPd304 has heretofore been impossible.
It is therefore an object underlying the invention to develop a prepar-ation and adequate characterization of a new electrochemically active substance : for the cover layer of metal anodes.
It is a further object of the invention to make the new electrochemic-'' ~ - 1 -. . .
,, - : -: . :
. , . : -iO6ZZOl ~`'y active substance adaptable for the use as cover layer of metal anodes. It is moreover a speclfic ob~ect to be solved by the invention to prepare and use thallium palladate, which is a cardinal-red crystalline compound of the general formula TlPd304, for the cover layer of metal anodes, which thallium palladate - has favourable electrochemical and electrical properties as active material for coating metal anodes.
- By one aspect of this invention, specifically claimed in this division-al application, there is provided an anode for electrochemical processes provided with an electrochemically-active cover layer comprising thallium palladate.
Instead of thallic oxide, thallous nitrate can be used as the starting material: it decomposes to thallic oxide at temperatures above about 350C. In this case the palladium monoxide can either be mixed with the thallous nitrate or can be added after the thallic oxide has been formed. The reactions involved are summarized by the equations:
~` 350C
This application is a division of Canadian Application Serial No.
212,232 filed October 24, 1974.
The present invention relates to the preparation of thallium palladate and the use thereof as a new electrochemical active substance for the cover layer of metal anodes.
Certain patents and patent applications, e.g. German Democratic Republic Patent 55,323, German Democratic Republic Patent No. 77,963, German Published Application No. 1,671,422, German Published Application 1,917,040, ~erman Published Application 1,813,944, German Published Application No. 1,962,860, and German Published Application No. 2,200,500 disclose metal anodes containing cover layers of the most varying composition in order to eliminate the drawbacksof the anode carrier members of passivatable metal, such as titanium, tantalum, zirconium, niobium, etc.
Most of the above substances, however, suggested for application as cover layer or as essential component thereof have unfortunately turned out to be disadvantageous, because their electrical conductivity and/or their chemical and;- electrochemical stability is not satisfactory or, respectively, a number of the suggested substances cannot at all or not very easily be applied to the anode carrier member without adversely affecting the requirements made respecting a cover layer. The methods used for applying a cover layer to an anode are well known to those skilled in the art and details thereof can be obtained from, for example, U.S. Patents 3,645,862; 3,632,498; 3,663,280; 3,711,397; 3,773,554 and 3,804,740, German Patents 2,304,380 and 2,328,417.
Whereas, for example, alkaline earth palladates such as CaPd304, ; SrPd304 and NaPd304 have already been synthesized in pure crystalline form, pre-paration and adequate characterization of TlPd304 has heretofore been impossible.
It is therefore an object underlying the invention to develop a prepar-ation and adequate characterization of a new electrochemically active substance : for the cover layer of metal anodes.
It is a further object of the invention to make the new electrochemic-'' ~ - 1 -. . .
,, - : -: . :
. , . : -iO6ZZOl ~`'y active substance adaptable for the use as cover layer of metal anodes. It is moreover a speclfic ob~ect to be solved by the invention to prepare and use thallium palladate, which is a cardinal-red crystalline compound of the general formula TlPd304, for the cover layer of metal anodes, which thallium palladate - has favourable electrochemical and electrical properties as active material for coating metal anodes.
- By one aspect of this invention, specifically claimed in this division-al application, there is provided an anode for electrochemical processes provided with an electrochemically-active cover layer comprising thallium palladate.
Instead of thallic oxide, thallous nitrate can be used as the starting material: it decomposes to thallic oxide at temperatures above about 350C. In this case the palladium monoxide can either be mixed with the thallous nitrate or can be added after the thallic oxide has been formed. The reactions involved are summarized by the equations:
~` 350C
2 TlN03 ~ T1203 + NO + N02 T123 --~ T120 + 2 ~ 2 + T120 + 6 PdO > 2 TlPd304 Any thallium oxides present in the product thus obtained can be removed by sublimation at a temperature of about 650 C and any palladium present can be removed by boiling with aqua regia.
Below an example for the preparation of the above new electrochemically active substance is given.
Example 1 Mol PdO is intimately mixed with 4 to 5 Mol of TlN03 and is slowly heated to 500 - 600 C in sintered corundum trays. In this connection, by decomposition of the thallium nitrates above 300 C the cubic T1203 results in jet-black crystals which react with PdO starting from 500 C. Excess T1203 is removed by sublimation at 650 C; and excess palladium is removed by boiling with aqua regia. The cardinal-red :'' '~.
. ~
.. i ~:. -.. - , - : . : :
~ . , - - - - : . . . - :
:. ~ ... . . .- :.: - . : :
~: ' : ~ ::' : -. ~ ' ::::-: :'' -':: : .. : :~ . ::: .. :,.. : :: .. - :- -106ZZ0~
r~action product accordlng to guiniex photos cont~ins no further impurities.
The analysis of this compound is complicated insofar as TlPd304 is well soluble only in hydrobromic acid, however, the presence of bromide ions is disturbing in the course of the analysis by the formation of the TlBr that is difficult to dissolYe and PdBr2, Thus, it was necessary to boil the hydrobromic acid solution of the TlPd304 with a few drops of elementary bromine in order to bring the TlBr which always precipitates in smaller amounts in solution as TlBr3; subsequently to quantitatively expel bromine by boiling with concentrated HN03 and, since the oxidizing - -properties of the nitric acid also adversely affect the applied precipi-tation with organic reagents, to fume them off with sulphuric acid. The : . ~
gravimetric determination of the thallium was conducted by precipitation ~-` with thionalide. Palladium is precipitated with dimethylglyoxime.
` content of Tl content of Pd calculated 34.8% 54.3%
test results 344 69%% 54 6%
34-9% 54.5%
. TlPd304 is readily soluble, with decomposition, in constantly boiling hydrobromic acid, is moderately soluble in aqua regia and per-;~ 20 chloric acid, is difficult to dissolve in sulphuric acid, nitric acid, ; formic acid and alkaline solvent. Above ~50C TlPd304 is decomposed into - elementary palladium and T1203. The pyknometric density was found to be 8.99 g/cm3 and is well concurring with the X-ray density of 8.83 g/cm3.
The radiographic evaluation for TlPd304 resulted in a cubic elementary cell:
.. .. .
lattice constant a = 9.596 + 0.002 A
~ volume of the element- V = 883.68 A3 ary cell Ez . . .
- number of formula Z = 8 units
Below an example for the preparation of the above new electrochemically active substance is given.
Example 1 Mol PdO is intimately mixed with 4 to 5 Mol of TlN03 and is slowly heated to 500 - 600 C in sintered corundum trays. In this connection, by decomposition of the thallium nitrates above 300 C the cubic T1203 results in jet-black crystals which react with PdO starting from 500 C. Excess T1203 is removed by sublimation at 650 C; and excess palladium is removed by boiling with aqua regia. The cardinal-red :'' '~.
. ~
.. i ~:. -.. - , - : . : :
~ . , - - - - : . . . - :
:. ~ ... . . .- :.: - . : :
~: ' : ~ ::' : -. ~ ' ::::-: :'' -':: : .. : :~ . ::: .. :,.. : :: .. - :- -106ZZ0~
r~action product accordlng to guiniex photos cont~ins no further impurities.
The analysis of this compound is complicated insofar as TlPd304 is well soluble only in hydrobromic acid, however, the presence of bromide ions is disturbing in the course of the analysis by the formation of the TlBr that is difficult to dissolYe and PdBr2, Thus, it was necessary to boil the hydrobromic acid solution of the TlPd304 with a few drops of elementary bromine in order to bring the TlBr which always precipitates in smaller amounts in solution as TlBr3; subsequently to quantitatively expel bromine by boiling with concentrated HN03 and, since the oxidizing - -properties of the nitric acid also adversely affect the applied precipi-tation with organic reagents, to fume them off with sulphuric acid. The : . ~
gravimetric determination of the thallium was conducted by precipitation ~-` with thionalide. Palladium is precipitated with dimethylglyoxime.
` content of Tl content of Pd calculated 34.8% 54.3%
test results 344 69%% 54 6%
34-9% 54.5%
. TlPd304 is readily soluble, with decomposition, in constantly boiling hydrobromic acid, is moderately soluble in aqua regia and per-;~ 20 chloric acid, is difficult to dissolve in sulphuric acid, nitric acid, ; formic acid and alkaline solvent. Above ~50C TlPd304 is decomposed into - elementary palladium and T1203. The pyknometric density was found to be 8.99 g/cm3 and is well concurring with the X-ray density of 8.83 g/cm3.
The radiographic evaluation for TlPd304 resulted in a cubic elementary cell:
.. .. .
lattice constant a = 9.596 + 0.002 A
~ volume of the element- V = 883.68 A3 ary cell Ez . . .
- number of formula Z = 8 units
- 3 -- . --: . ' ' , : ~
~: .
~ ~ : :' :
~06ZZ01 X-ray denslty Ro 5.11 oz/cu.ln.
From the crystal lattice plane statistic the extinction conditions resulted:
hKl : h + k = 2n-1 k + 1 = 2n-1 (h + l)= 2n-1 On the basis of these extinction conditions, the space groups Fm3m-0h5, F432-0 , F45m - Td Fm3 Th3 and F23-T come into consideration for TlPd304 The raster-electromicroscopic examination resulted in the presence of partially twinned octahedrons.
Viewing the results in combination, they confirm the presence of a cubic face-centered structure.
- If one now applies the TlPd304 to alloyed or unalloyed metal anode base members together with co-adhesives using any one of the many known processes therefor, the electrolyses of NACl-, KCl, chlorate- and HCl-solutions can be conducted, as well as of course other electrochemical processes.
A satisfactory electrochemical effectiveness is ensured even when only 20% thallium palladate is present in the cover layer of an anode. In permanent operation (10.000 A/m2) a thus coated metal-anode worked well over a period of time of 12 months without showing an alteration of the electrical properties as current yield, cell voltage, or electrochemical activity, such as chlorine deposition, resistance of the cover layer against wear.
i~
:
.. ....... .. . ~
. . ~
~: .
~ ~ : :' :
~06ZZ01 X-ray denslty Ro 5.11 oz/cu.ln.
From the crystal lattice plane statistic the extinction conditions resulted:
hKl : h + k = 2n-1 k + 1 = 2n-1 (h + l)= 2n-1 On the basis of these extinction conditions, the space groups Fm3m-0h5, F432-0 , F45m - Td Fm3 Th3 and F23-T come into consideration for TlPd304 The raster-electromicroscopic examination resulted in the presence of partially twinned octahedrons.
Viewing the results in combination, they confirm the presence of a cubic face-centered structure.
- If one now applies the TlPd304 to alloyed or unalloyed metal anode base members together with co-adhesives using any one of the many known processes therefor, the electrolyses of NACl-, KCl, chlorate- and HCl-solutions can be conducted, as well as of course other electrochemical processes.
A satisfactory electrochemical effectiveness is ensured even when only 20% thallium palladate is present in the cover layer of an anode. In permanent operation (10.000 A/m2) a thus coated metal-anode worked well over a period of time of 12 months without showing an alteration of the electrical properties as current yield, cell voltage, or electrochemical activity, such as chlorine deposition, resistance of the cover layer against wear.
i~
:
.. ....... .. . ~
. . ~
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An anode for electrochemical processes provided with an electro-chemically-active cover layer comprising thallium palladate.
2. An anode as claimed in claim 1 wherein said cover layer con-sists essentially of thallium palladate.
3. An anode as claimed in claim 1 or 2 wherein said cover layer is applied to a metal base anode member.
4. An anode as claimed in claim 1 wherein said cover layer comprises at least 20 percent thallium palladate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,395A CA1062201A (en) | 1973-10-27 | 1978-01-20 | Preparation and use of thallium palladate as cover layer of metal anodes |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2353995A DE2353995C3 (en) | 1973-10-27 | 1973-10-27 | Crystalline TL Pd3 O4 and its uses |
| CA212,232A CA1047229A (en) | 1973-10-27 | 1974-10-24 | Preparation and use of thallium palladate as cover layer of metal anodes |
| CA295,395A CA1062201A (en) | 1973-10-27 | 1978-01-20 | Preparation and use of thallium palladate as cover layer of metal anodes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062201A true CA1062201A (en) | 1979-09-11 |
Family
ID=27163678
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,395A Expired CA1062201A (en) | 1973-10-27 | 1978-01-20 | Preparation and use of thallium palladate as cover layer of metal anodes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1062201A (en) |
-
1978
- 1978-01-20 CA CA295,395A patent/CA1062201A/en not_active Expired
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