DD272315A1 - DIMENSION STABLE ANODE - Google Patents

Abstract

The invention relates to a dimensionally stable anode for electrochemical processes, in particular for the chloralkali electrolysis, in which an increase in the service life is achieved by applying an intermediate layer with a different composition on a Titangrundkoerper. The aim of the invention is a dimensionally stable anode conventional composition having a Titangrundkoerper and an electrochemically active layer on RuO2 / TiO2 or RuO2 / IrO2 / TiO2-based, in which by incorporating a noble metal-free intermediate layer of high electrical conductivity, the oxidation of Titangrundkoerpers both during preparation as also restricted during the electrolysis and thus the service life is increased. The dimensionally stable anode according to the invention, consisting of a titanium base body, an intermediate layer and an electrochemically active layer, is characterized in that the intermediate layer consists of TiNx.

Description

Field of application of the invention.

The invention relates to an anode for electrochemical · Prom ··, in particular for dl · chloroalkali electrolysis. The invention is applicable in the chemical industry.

Characteristic of the known 8tand ·· of the technology In the past 16 years, dimeniloniitablle anodes (OSA) have been available for the chlorinated allelic electrolyte

usual graphite anodes on a world scale. Above 8OH, the chlorine produced in the world today is produced with dimensionally stable anodes, this applies to both the diaphragm and you for the mercury · and

Membrane processes. Dimensionally Stable Anodes are made of a support metal, generally titanium, and one by thermal desiccation

prepared electrochemically active coating on Pt / Ir-Basls or ruthenium dioxide and titanium oxide in the appropriate

Motverhlltnis made under Zusatt further suitable substances. These anodes are therefore also called composite electrodes

designated.

(K.HASS, Chem.-Ing.-Techn.47 | 197S | 121; V.OE NORA, J.W. KÜHN OF BURQSDORFF, Chem. Ing. Tochn.4711975) 125; DDPS55323; DE-OS 1671422)

For the deactivation of RuO> / TiO | electrodes under the technical conditions of anodic chlorine evolution » _μ ^; ilen

both a barrier formation of titanium metal and an active layer is also known as corrosion of RuOi · η

Electrode surfaces play an essential role (S. TRASATTI and O. LODI In S.TRASATTI (ad) Electrodes of Conductive Metalic Oxides, Elsevier, Amsterdam 1981, Part B, pp. 621-626). Based on this, in the patent literature, in principle, there are basically Λιι ianton for increasing the stage yoke. For one thing, it tries to

by modifying the electrochemically active layer, lowering the corrosion rate of RuOj, and thus the

Increase lifetime (US 4005004, DE 2342M3, DE 2625820, DD 98620, PP? 19802). On the other hand, attempts are made by the incorporation of a so-called intermediate layer, the Sperrschlchtbildung at the phase boundary To delay titanium metal / oxide layer, thereby extending the life of the "cuen tu. As a principle possibility

in this case, the incorporation of precious metals such as Ag, Au, Ru or Pd (US-PS 4086157) or a precious metal-rich layer in

Comparison door outer RuOj / TIOj-Schlcht (DE 2815955) tu call. There are further proposals for the incorporation of noble metal oxides (Rh, Ir) directly into the oxide layer of the valve metal Electrode body, turn Example titanium (DD 153397). Although additional Edelmetollbeigaben in the intermediate layer cause excellent electrical conductivity and

increase dl · Stand of the anodes. On the other hand, a high precious metal content in the intermediate layer represents a significant economic disadvantage.

Other patents recommend the incorporation of thin layers of Niclttodel.iUalloxl / en to Belsplol SnO; (DE 2532553)

or anreduziertea and with predominantly höhorwertigon oxides doped titanium oxide (TiO ₄ -,) (DD-WP 220621). Although these intermediate layers, produced by thermal decomposition, restrict the formation of poorly soluble ions, they prolong the service life of the anodes. However, so that the Titanium Round Matorial is not tightly closed, so that no complete protection is guaranteed.

For a MnOj-coated titanium anode, a TiN intermediate layer has been proposed (OB-PS 1527369). This was through

a chemical reaction, for example, of TiCl ₄ and NH ₁ on a titanium base plate at elevated temperatures (5C0'C to 700'C). In general, however, show manganese titanium anodes under the conditions of technical

Chloralkali electrolysis poor properties (H.Hofmann et al., Chem.Techn.3311981) 353), so that a large-scale Use for the Chlorprodukt'on is not possible. Another disadvantage of the anode described in British Patent Specification QB-PS 1527369 is the chemical reaction

to mention on the titanium surface produced at elevated temperatures TiN intermediate layer, due to this

Manufacturing conditions has no optimal barrier function against penetrating oxygen.

-2- 272 816

ZItIdM invention

According to the invention, for electrochemical celebrities, particularly for chloroalkali electrolysis, amine-stable dimenion-stable anode of conventional composition having a titanium base, an intermediate layer, and an electrochemically active layer on RuOiATIOf or RuOi / IrO / TIOi-Basls pass through a substantial increase of the stand ausieichnet, resulting in their application energy ·, precious metal · and Arbeitsieleinsparung.

Presentation of the essence of the invention The invention has the object iugrunde, a dlmenslonistablle anode, which is known from titan basic body, Interlayer and electrochemically active layer on RuO | / TiOi · or RuOi / lrOt / TiOi base consists tu develop at the

the intermediate layer, a precious metal fragment not known for these anodes, ensures a high electrical conductivity

Having composite rescue and allows a good Haftunq dei electrochemically active layer. Erfindungsgamäß this object is achieved in that the known, defatted and mechanically smoothed titanium basic grains

before application of an electrochemically active RuOj / TIOr or RuOj / lrOj / 1 IO | Layer with a TIN.Schlcht with χ »0.1 to 1.2 and a layer thickness of up to 100 pm, for example, with a TINo Schlcht is provided.

The Titannltridschicbt is erieugt by per se known reactive D. C. Plaimatronsputtem on Titanium body. In front

the actual coating, the titanium plate is gosputtered in a high vacuum with argon ions, so that there are no oxides on the body, which can have a negative effect on the resistance of the electrode. Another advantage of the reactive

Sputtering consists in the fact that by the choice of suitable process variables (kinetic energy, Stoßtahlverhlltnisse the Reaction partner, substrate temperature) the properties of TIN.-Schlcht like Hlrte, stoichiometric aggregate,

Spatula electrical resistance, roughness, porosity, layer thickness, etc. can be determined. Through this

Procedure: Is it possible for you to have good mutability for the pervading layer? The titanium nitride intermediate layer produced in this way is roughened, for example with hot aqua regia, to form a

good reason to create. Subsequently, a known Ru / Tl odor Ru / Ir / Ti preparation solution is applied, through which the electrochemically active layer is formed. The preparation of the preparation is applied several times to the etched TIN.-Schlcht. After leather coating, drying takes place at temperatures up to 100 ° C and then baking

Temperatures! Wipe 350 * C and COO'C. Very advantageous is the use of a preparation solution with a Precious metal content up to 40MoI-S. The dimensionally stable anode on the basis Ti, TiN ,, RuO ₁ ZTiOi or RuOjZIfO ₁ ATiO ₁ was so far not in this combination

known, it has the following advantages:

1. The intermediate layer according to the invention is both a noble metal-free and a highly conductive layer.

2. This intermediate layer protects the base metal during electrode production, where it is exposed to long-term temperatures between 3WC and 500'C, before oxidation.

3. The lifetime of the electrode is substantially increased by the intermediate layer according to the invention.

The effect mentioned above is surprising in itself but also in its size, since the intermediate dip layer has a different structure than the electrochemically active layer. In contrast to the rutile structure of RuOj / TIO} · and RuOj / lrOj / TIOi active layer, TiN has sodium chloride id structure (Gmelin's Handbook of Inorganic Chemistry, Titan, Verlag Chemie, Weinheim 1951) - the good precompound between these two layers is therefore astonishing ,

Exemplary embodiments Example 1: The degreased and mechanically smoothed titanium basic body is sputtered in a high vacuum with argon ions and then

provided with a TiN.layer by D.C. Plasmaser sputtering. The production conditions are chosen so that an approximately 1 pm thick TINoj layer is applied.

The intermediate layer thus produced is etched for a few minutes with hot (80 ° C.) water. After dom rinse off the acid

becomes a known Ru / Ti-Präpa. applied ationalöiung, through which the electrochemically active layer is formed. The

The preparation solution is applied several times to the etched TiN.-layer. After joder coating takes place T'ocknuno at 80 * C and then a sminütipes branding at 4 WC. After application of the last single layer closes one

one-hour final performance at 45O'C.

Titanium is in the form of Ti (OC ₄ Hi) ₄ (titanium tetrabutylate) and ruthenium in the form of Ru (s), Clj

(Rutheniumtrisethylendiamintrichlorld) used in alcoholic solution. The preparation of Ru (en), Clj is carried out according to

DD-W? 157697. Since the Ru / Ti molar ratio is 30/70, the amount of precious metals applied is 13g RuO ₁ An '. The thus prepared anodes were used for the electrolysis of aqueous 4 molar sodium chloride solution (pH ·> 2.5). at

a current density of lOOmA / cm ¹ and a temperature of 26'C, the anodic overvoltage was 60 ... 7OmV. In the so-called sulfuric acid test (electrolysis in 2 NH] SO ₄ , 25'C, 0.5A / cm ') a service life of 34 hours was registered.

Example 2:

The degreased and mechanically smoothed Titanqrundkorper is sputtered in a high vacuum with argon ions and then provided by reactive DC Plasmatron sputtering with a TiN.-layer. The production conditions are chosen so that an about 1 mm thick TiN ₀ »- is applied. The thus prepared intermediate layer is with a few minutes

-3-272,316

helQem WC) Königswatter valid. According to the description of the invention, oil is applied to Ru / TIPr Iparatlonilöiung, by means of which the "t" ktroch nlich becomes active · 8chlcht auagablldat. Oil · Prolparatloniieaung is hlartu mahrmala on dl · galUte

TIN.-Schlcht applied. After leather B "Mühlchtung erfolgt" In · drying at MO and then a 2mlnutlgee branding at

42O ¹ C. After application of the method, use a final temperature of 430'C.

Titanium is prepared in toluene from Ti (OC ₄ Hf) ₄ (titanium tetrabutylate) and ruthenium in the form of RuCl ₁ .3H ₁ O (ruthenium (110-chlorofl-3-hydrotein)

divided into itopropanol. Oat Ru / Tl molar ratio is 26 / 7S, the amount of noble metal applied is 12.8g RuOi / m *.

The prepared anodes were classified by electrolytes into an adverse 4 molar sodium chloride solution (pH 2.8). at

a current density of 200mA / cm * and a temperature of 26'C, the anodic over-voltage was 70 ... 8OmV. in the

Schwelfeilureiteit wurnle a stand of 38 hours raglttriert.

Claims (2)

272 310 Claim: 1. Dimensional Stable Anode for electrochemical pretense, consisting of a titanium basic body, an intermediate layer and an electrochemically active layer on RuCVTIOi or RuCVIrO) / TiOfBasls, characterized in that the dlmenslonsstablle anode with a on the Agroninnen sputtered Tltangrundkörpor by per se known reactive DC · Plasmatron sputtering applied, consisting of TIN «with χ - 0.1 to 1.2 and roughened before application of the electrochemically active layer interlayer of Schlchtdicxo provided to a maximum of 100 microns Int. 2. Dlmensionsstablle anode according to claim 1, characterized in that the dimensionally stable anode · with an example of TIN _0. * Existing and roughened with hot aqua regia or hot Alklallauge roughened intermediate layer is provided.