JPH03150383A - Filter press type bipolar electrolyzer - Google Patents

Abstract

PURPOSE:To prevent active dissolution of the face of titanium opposite to the flow hole of an electrolyte and to stably operate electrolysis for a long period of time by coating a platinum-contg. film on the liquid contact part except the part coated with anodic active substance on the anodic surface of an electrode plate. CONSTITUTION:In a bipolar electrolyzer, a film contg. 10-60mol.% platinum and 40-90mol.% at least one kind of oxide of Ti, Zr, Nb, Ta and Sn is coated on the liquid contact part except the part coated by anodic active substance on the anodic surfaces of plural electrode plates. Thereby a filter press type bipolar electrolyzer is obtained which is capable of preventing active dissolution of the face of titanium and of being stably operated for a long time. A halogen- contg. soln. is utilized as an electrolyte and this electrolyzer is utilized to obtain the aimed substance such as hypohalogenite and halogenate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a filter press type bipolar electrolytic cell, which is particularly suitable for producing hypohalites or halogenates by non-diaphragm electrolysis of halogen-containing solutions. Regarding a filter press type bipolar electrolytic cell.

(Prior art) Conventionally, monopolar electrolyzers have been used to produce halogenates, hypohalites, etc., but recently, filter press type bipolar electrolyzers have been used. I started. Although the single-pole type has a simple electrolytic cell structure, it is larger and requires a larger installation area, and due to the high current and low voltage, the rectifier is expensive and requires a thick busbar, and the through flow rate is also large. There are many.

On the other hand, the filter press type bipolar type is easy to make compact, the rectifier has a small current and high voltage, it is extremely inexpensive, the electrical connection is simple, and the flow rate passing through is small.
It has many advantages such as improved current efficiency.

As a specific example of this filter press type bipolar electrolytic cell, as disclosed in Japanese Patent Publication No. 59-24192, a plurality of bipolar electrode plates having electrolyte flow holes and a frame-shaped slot are alternately laminated. An anode plate and a cathode plate with electrolyte flow holes and current terminals are placed on both ends of the plate, and a supply plate with an electrolyte inlet and a discharge plate with an electrolyte outlet are placed on both ends, and end plates are placed on both sides. , and tighten them together with through bolts to form a bipolar electrolytic cell.

By the way, in the bipolar electrolytic cell, current flows not only on the cathode surface facing the anode surface but also on the cathode surface that is one space apart through the electrolyte flow hole, which is a leakage current peculiar to the so-called bipolar electrolytic cell. Therefore, the anode active material is not applied over the entire surface of the anode surface of the electrode plate used, but is applied to the central part of the electrode plate away from the electrolyte flow holes, thereby minimizing leakage current.

Therefore, there will be a part on the anode surface of the electrode plate where the electrode plate base and the electrolyte come into contact, but the potential of the surface facing the electrolyte flow hole is extremely lower than that of the part covered with the anode active material. As a result, titanium, which is the material of the electrode plate, is actively dissolved. To prevent this, octopus is conventionally used with hypohalite,
Corrosion-resistant polyvinyl chloride resin or polyethylene sheets or thin plates were attached to objects such as halogenates using adhesives, but the manufacturing process was complicated, and when used for a long period of time, the adhesives became wet and the electrolyte solution may invade and cause pitting in the electrode plate base material, and the electrode plate may have to be replaced even though the electrode active material remains.

(Problems to be Solved by the Invention) The present invention provides a filter press type bipolar electrolytic cell that prevents active dissolution of the titanium surface facing the electrolyte flow hole, thereby stably kneading electrolysis for a long period of time. It is about providing.

(Means for Solving the Problems) As a result of the inventors' earnest efforts to find a method for preventing active dissolution of the titanium surface facing the electrolyte distribution hole, the present inventors found that The present invention has been achieved by overcoming the above problems by applying a platinum-containing coating with low electrochemical activity to the titanium surface.

That is, the present invention provides a bipolar electrolytic cell in which a target product is manufactured by flowing an electrolyte through an electrolytic chamber configured by alternately stacking a plurality of electrode plates having electrolyte distribution holes and a plurality of frame shapes with a sket. , 10-60 mol % of platinum and Ti
, Zr, Nb, Ta, and Sn oxides.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail based on the drawings regarding the case where a solution containing 7% densities is used as an electrolytic solution. 1 and 2, two bipolar electrode plates 2 are provided with electrolyte flow holes 1 at the upper and lower ends of one side, and an anode plate is provided with electrolyte flow holes 1 and current terminals 14 at the lower end of one side. 3. A cathode plate 7 with electrolyte flow holes 1 and current terminals 14 provided at the upper and lower ends of one side, and frame-shaped sketches 4 cut out from the center of three sheets alternately stacked one on top of the other, and an electrolyte at the lower end of one side. It is sandwiched between the supply plate 5 to which the inlet piping 12 is attached and the discharge plate 5 to which the electrolyte outlet piping 13 is attached to the upper and lower ends of one side to form three electrolysis chambers 6, and furthermore, through-bolt holes 10 and 3 are formed. An end plate 8 having a hole 11 for electrolyte piping at the lower end of the upper side, and a hole 11 for electrolyte piping and a hole 10 for a through bolt at the upper and lower ends of one side are applied to both ends, and a through bolt 9 is placed on both ends. and then tighten them all together to form a bipolar electrolytic cell.

The halogen-containing solution is supplied through the electrolyte outlet port 12, and is electrolyzed while sequentially passing through each electrolytic chamber 6 in a horizontal meandering manner. 1, the electrolytic solution containing a large amount of generated gas that has separated upwardly in the electrolytic solution passes through the upper electrolytic solution flow hole 1 and is discharged from the electrolytic solution outlet pipe 13 as a hypohalite- or halide-containing solution.

The above-mentioned bipolar electrolytic cell is a basic structure for explaining the gist of the present invention in a simple manner, and is described in Japanese Patent Publication No. 59-24192 in order to increase the utilization rate of salt and realize high current efficiency. Appropriate steam removal means or heat exchange as seen in .

The platinum-containing coating used in the present invention was prepared as follows.
Ru. After degreasing the titanium surface, it is treated with hydrofluoric acid or oxalic acid, and a coating solution is applied thereon with a brush or the like. The coating solution is prepared by dissolving chloroplatinic acid, platinum tetrachloride, etc., flucoxide of a valve metal such as butyl titanate, tin chloride, etc. in an organic solvent such as isopropyl alcohol. After drying, it is placed in an electric furnace and heated in the atmosphere at a temperature of 450 to 609°C for 1G to 30 minutes. Coating and heating are repeated to obtain a coating of desired thickness.

The part to which the platinum-containing coating of the present invention is applied is the anode surface of the electrode plate, which is the part facing the electrolyte flow hole, but the liquid contact surface other than the part coated with the anode active material (the central part of the electrode plate) It will be more perfect if you apply it to everything.

Conventionally known positive electrode active materials are used in the bipolar electrolytic cell of the present invention, and platinum group metals and their oxides are generally applied by a pyrolysis method in the same manner as the platinum-containing coating described above. For example, a coating made of platinum palladium monoxide and ruthenium monoxide has a high chlorine generation efficiency and can produce highly concentrated sodium hypochlorite. Also, a platinum-iridium coating can produce sodium chlorate efficiently.

The thickness of the platinum-containing coating in the present invention should be adjusted so that the anode active material coating is consumed by electrolysis and disappears at the same time as the electrode reaches the end of its life. Usually, a coating of 15 to 20 g/m2 of platinum is preferable. It is.

(Function) 10 to 60 mol% of platinum in the present invention and T+,・2'
A platinum-containing coating consisting of 40-90 mol% of at least one selected from oxides of Nb%, Ta, and Sn is applied on a titanium plate, and this is used as an anode, and titanium, platinum, etc. are used as a cathode. When a constant voltage is applied in a saline solution of approximately 1% by weight, current flows smoothly immediately after loading, but only a weak current flows within just a few minutes. The origin of the present invention was the knowledge that the platinum-containing coating is electrochemically deactivated, and it is thought that the weak current flowing from the platinum-containing coating protects the titanium base that is the electrode plate.

(Example) Examples 1 to 4 As shown in Fig. 1 and Fig. 2, the thickness is 2mm.
Platinum 2 is placed in the center of the anode surface of the titanium electrode plate shown in
A mixture of 5% by weight of palladium oxide, 20% by weight of palladium oxide, and 55% by weight of ruthenium oxide was coated with a mixture of 30% by weight of titanium dioxide (metallic oxide 1
) was applied.

Table 1 \1 Electrode number I Platinum-containing coating ffi formation Presence or absence of pitting I Example 11 - SPt 40 mol % 1 No Tio - 60 mol % 1 〃 26 - 10 Pt 20 mol %
〃Tr02 go mol% #3111~tsl Pt 40 mol% 1〃1Ta
20,60 mol%1 416-20 Pi 40 mol%
〃8n0 = 60 mol% Mark electrode numbers 1 to 20 with a punch on one anode plate and 19 bipolar electrode plates, and
A coating consisting of 40 mol% of platinum and 60 mol% of titanium dioxide was applied to the part of the pond up to the slits (excluding the slit margin), and the following coatings were applied in the same manner as shown in Table 1.
A platinum-containing coating of 1120 g/w2 was applied to every 5 sheets up to the number.

One coated anode plate, 19 bipolar electrode plates, one uncoated cathode plate, and 20 picture frame-shaped soft vinyl chloride plates are arranged in 20 chambers by stacking the sockets alternately. An electrode chamber was constructed, a supply plate and a discharge plate were placed on both sides, and both ends were sandwiched between two end plates, and a seawater electrolytic cell with an effective chlorine generation rate of 2.5 kg/h was loosened and erected. The external dimensions were 650 mm wide x 250 mm wide x 450 mm high.

This bipolar electrolytic cell was installed at a waterfront chemical factory in Okinawa Prefecture, and seawater was supplied to the bipolar electrolytic cell from the electrolyte inlet piping at a liquid volume of 60 Z/win, and a Q125A, 90 V DC current was applied to the rectifier. An electrolytic test was conducted.

As a result, the current efficiency is 90-97%, and the effective chlorine concentration is 80%.
High performance from 0 to 920ppa+ is shown, and the electrode life is S
It was the year. After the test, it was confirmed by fluorescence X-ray film thickness measurement that no pitting was observed on the electrodes, and that platinum remained in the platinum-containing coatings of all electrode plates.

Example 5 An electrolytic cell having the same structure as that used in Examples 1 to 4 (but using a fluorine gasket) was installed in a sodium chlorate manufacturing factory.

Anode coating: 70% by weight platinum, 30% by weight iridium oxide
The platinum-containing coating was the same as that used in Example 1.
A TiO□ coating was used.

Electrolytes containing 60 g/+2 sodium chlorate, 280 g/l sodium chloride, and Ig/l sodium dichromate were supplied at a flow rate of 501/min. As a result of conducting an electrolytic test by applying an electrolytic current of 155 A and 67 V, it was found that electrolysis was still continuing after three years, and no pitting traces were observed on the electrode surface.

Example 6 A humyl alcohol solution of chloroplatinic acid and chloroiridic acid was applied with a brush to the center of the anode surface of the two electrode plates used in Examples 1 to 4, and heated at 500°C for 30 minutes in an electric furnace. processed. This coating to firing process was repeated 7 times to coat 70% by weight of platinum and 30% by weight of iridium oxide (20g
/+a2) was prepared.

One electrode plate coated with 40 mol% of platinum and 160 mol% of dichloride oxide and 150 mol% of platinum and zirconium oxide are placed on the other parts of the anode-coated surface except for the sketches. One electrode plate coated with 50 mol % was prepared, and an electrolytic cell having three electrode chambers was constructed in the same manner as in Example 1.

An electrolytic solution consisting of 280 g/l of sodium bromide, 60 g/l of sodium bromate, and 1 g/l of sodium dichromate was supplied to this electrolytic cell, and sodium bromate was electrolytically produced at 70°C and 20 A/d+2. .

Six months later, when the electrolytic cell was disassembled and the electrode plates were inspected, no pitting was found and the platinum in the platinum-containing coating was hardly consumed.

(Effects of the Invention) According to the present invention, active dissolution of the titanium surface can be prevented by applying a platinum-containing coating, and it is no longer necessary to repair the active dissolution prevention method using a synthetic resin sheet, which was conventionally done every six months. A filter press type bipolar electrolytic cell was realized that can operate stably for a long period of time until the electrode active material reaches the end of its original life due to consumption of the electrode active material.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the basic structure of the bipolar electrolytic cell of the present invention, and FIG. 2 is a cross-sectional view taken along line A--A in FIG. 1. 1. Electrolyte distribution hole 2. Multipolar electrode plate 3. Anode plate 4. Frame-shaped socket 5. Supply plate 5
・・Drain plate 6・・Electrolysis chamber 7・・Cathode plate 8・・End plate 9・・Through bolt 10・・Through bolt hole 11・・Electrolyte distribution hole 12・・・Electrolyte solution inlet piping 13・・・Electrolyte solution outlet piping
14...Current terminal patent applicant Nippon Carlit Co., Ltd. No. 2m

Claims (1)

[Claims] 1. A filter press type that electrolytically manufactures a target product by flowing an electrolyte through an electrolytic chamber configured by alternately stacking a plurality of electrode plates having electrolyte distribution holes and a plurality of frame-shaped gaskets. In the bipolar electrolytic cell, 10 to 60 mol% of platinum and oxides of Ti, Zr, Nb, Ta, and Sn are added to the wetted parts other than the part coated with the anode active material on the anode surface of the electrode plate. A filter press type bipolar electrolytic cell characterized by being coated with a coating containing 40 to 90 mol% of at least one selected species. 2. The filter press type bipolar electrolytic cell according to claim 1, wherein the electrolytic solution is a halogen-containing solution and the target substance is a hypohalite or a halogen salt.