GB2171398A - Cupric oxychloride - Google Patents

Abstract

A process for producing cupric oxychloride comprises treating metallic copper with sodium hypochlorite or calcium hypochlorite in an aqueous medium at a pH of 3 to 7 and, preferably, at a temperature of 40 to 80 DEG C. Chlorine or hydrochloric acid may be present.

Description

SPECIFICATION Process for producing cupric oxychloride The present invention relates to copper-containing inorganic compounds and, more particularly, to a process for producing cupric oxychloride. Cupric oxychloride is the active principle of fungicidal preparations which are widely employed in agriculture for controlling diseases of fruit and vegetable plants.

It is known to make cupric oxychloride by treating metallic copper with chlorine to form copper chloride and then treating the latter with chalk. (In Coll. "Inorganic Insecticides, Fungicides and Zoocides", Goskhimizdat Publishers, Moscow, 1960, pp. 133-145). In this process, granular metallic copper is dissolved by chlorine in a hydrochloric acid medium to form a concentrated solution of cupric chloride containing cuprous chloride as an impurity. The cuprous chloride is converted into cupric chloride by additional chlorination. The solution of cupric chloride, free from monovalent copper, is reacted with a suspension of chalkto give a suspension of cupric oxychloride in an aqueous solution of calcium chloride.This reaction can be represented by the following equation: 4CuCl2+3CaCO3+4H2O 3Cu(OH)2 CuCI2 H20+3CaCI2+3CO2 The cupric oxychloride is separated from the solution of calcium chloride by settling, filtration, water washing of the residue and is finally dried.

This process is multi-staged, necessitates sophisticated equipment, involves a large consumption of metal for the manufacture of the necessary process equipment, and does not guarantee the preparation of a finely divided product. A considerable volume of a copper-containing solution of calcium chloride is formed in the process, which necessitates the consumption of power for evaporating the solution and gives rise to the problem of finding a use for this by-product.

Many attempts have been made to improve the above-described process, in particular, by replacing chlorine with other oxidizing agents, such as oxygen-containing gases.

Another known process for producing cupric oxychloride (U.S.Patent No. 3,202,478) comprises three stages: (i) a concentrated solution of cupric chloride is first obtained by dissolving previously prepared cupric oxychloride in a 30% solution of hydrochloric acid; (ii) metallic copper is then introduced into the cupric chloride solution and cold air is bubbled through the resulting heterogeneous system for 1-2 hours; and (iii) a small amount of a basic catalyst, such as sodium hydroxide, ammonium carbonate or urea, is added and air heated to the temperature of 80"C is passed through this system for 3-5 hours.

This process, although avoiding the use of chlorine and chalk, is of a discontinuous and multi-staged character and is only of a low efficiency.

USSR Inventor's Certificate No. 367056 describes a process which comprises oxidising metallic copper with chlorine in the presence of an alkali or alkaline earth metal chloride, oxidising the resulting complex salt of monovalent copper with atmospheric oxygen at a temperature of from 20 to 90"C under a superatmospheric pressure of about 0.5 atm in order to reduce the rate of chlorine consumption.

This is also a multi-staged process which requires high rates of power consumption and results in the formation of a considerable amount of by-products.

In another process for producing cupric oxychloride (British Patent 1,374,078) metallic copper is air in a hydrochloric acid medium at a pH of 7-8, followed by separation of the solid product from the mother liquor and drying the separated product. Like the previously described processes, this process is complicated, multi-staged, gives only a low yield of the desired product and produces a large amount of waste products.

There is, therefore, an urgent need for an effective process for the production of cupric oxychloride which would be simple to perform and would enable a final product of better quality and a reduced proportion of non-useful production wastes, to be obtained.

We have now developed an improved process for the preparation of cupric oxychloride which, according to the invention, comprises treating metallic copper with sodium hypochlorite or calcium hypochlorite in an aqueous medium at a pH of from 3 to 7.

To control a pH within the above-specified range, acids or acidic gases can be used, but to ensure optimum quality of the final product, it is preferred to use hydrochloric acid or chlorine.

The process may be carried out under normal pressure and at a temperature which is preferably from 20 to 90"C and more preferably from 40 to 80"C.

The process according to the invention provides the following advantages over the prior art.

The process may be carried out in a single stage which substantially simplifies the process and reduces the equipment cost and energy consumption of the process; The oxidizing agents used, sodium hypochlorite and calcium hypochlorite, are readily availabie and inexpensive products; solutions of them are frequently obtained as effluents from the production of chlorine and the use of such effluents enables reactant costs to be reduced; The process can be operated to produce a stable, finely divided product with a particle size of from 1 to 3 Fm; The process, although in a preferred embodiment contemplating the use of chlorine, enables the consumption of chloride to be considerably reduced as compared with prior art processes; Environmental pollution is substantially reduced by the use, as oxidizing agents, of solutions of sodium hypochlorite or calciumhypochlorite which are effluents from the production of chlorine.

A preferred procedure for carrying out the process according to the invention will now be described in greater detail.

Metallic copper in the form of granules is charged into a column and a dilute solution of hydrochloric acid or chlorine is introduced at the top of the column. The effluent solution from the column is delivered to a receiving vessel and recycled therefrom to the column by means of a pump. In this manner a closed circuit for the solution stream is formed. The initial pH of the circulating solution is from 1 to 3.

After the formation of the above-mentioned cycle, an aqueous solution of sodium hypochlorite or calcium hypochlorite is introduced into the bottom zone of the column to obtain pH of the reaction medium of 3 to 4.

The solution temperature is maintained at from 40 to 80"C. Under these conditions, intensive oxidation of copper occurs with the formation of seeds of cupric oxychloride which, upon achieving pH of 4 to 7, grow into crystals of cupric oxychloride. The process is then continued at a pH of 4 to 7 which is maintained by the addition of the above-mentioned components, sodium or calcium hypochlorite and the hydrochloric acid or chlorine solution as the acidifying agent. The oxidation of copper with the formation of the desired product can be represented by the following overall equations: 4Cu+4NaClO+2HCl +3H2O 3Cu(OH)2 CuCI2-H2O+4NaCI 4Cu +2Ca(C10)2+2HCI +3H2Oo3Cu (OH)2- CuC12-H2O +2CaCI2 4Cu+3NaClO+Cl2+4H2O3Cu(OH)2CuCI2H2O+3NaCl These reactions can only proceed at a pH within the range of from 3 to 7.Within this range sodium or calcium hypochlorite and the acidifying agent are in the form of the effective oxidizing agent, that is hypochlorous acid: HCl+NaCIOo HCIO+NaC[ Cl2+H2Oo HCI+HCIO The above-specified pH range is responsible for the existence of cupric oxychloride in aqueous solution.

At a pH of less than 3, hypochlorites and chlorine exist in the form of dissolved chlorine having a lower oxidizing potential than hypochlorous acid, while at a pH above 7, chlorine is combined with sodium hydroxide or calcium hydroxide and forms sodium or calcium hypochlorite which has an even lower oxidizing potential as compared with hypochlorous acid. At a pH below 3, cupric oxychloride passes into solution as cupric chloride, while at a pH above 7 cupric oxychloride converts into cupric oxide which is undesirable.

Under these conditions the process can be carried out either continuously or discontinuously. The resulting suspension is settled, filtered, and the precipitate is washed with water to remove water-soluble sodium or calcium chloride. The washed cupric oxychloride has a paste-like consistence and can be used for the preparation of a paste-like fungicide.

To obtain a dry product, the resulting paste is dried, suitably at a temperature of from 90 to 1000C to a moisture content of not more than 2% by weight In this case a finely divided powder of a light green colour with a bluish shade is obtained which corresponds to the formula: Cu(OH)2-CuCI2-nH2O, where n = O to 3.

The copper content of the product is 51 +2%, the content of water-soluble chlorides is not more than 0.8% by weight; particle size, 80% of particles with a size of 1 to 3 m and 20% of particles with a size of 3 to 20clam; stability of a 0.5% aqueous suspension is not less than 80%. The product of the above-specified quality is normally obtained in a yield of not less than 98%.

The high quality of the product and the high yield thereof just mentioned can be obtained by strictly observing the above-mentioned process conditions, namely: pH within the range of from 3 to 7 and temperature within the range of from 40 to 80"C. Faiiure to maintain the above-specified pH range results in a reduced yield and impaired quality of the desired product It is possible, though undesirable, to carry out the process at a temperature below 40"C, but at such temperatures the reaction rate is undesirably reduced; if temperatures above 80"C are used, the desired product tends to crystallise in the column which is also undesirable.

Cupric oxychloride produced by the process according to the present invention is very finely subdivided and has a good miscibility with water and the ability to form stable suspensions. Because of these properties, its fungicidal properties are superior to those of known preparations such as Bordeaux mixture and "Microcope8, a fungicide of U.S. origin.

As already mentioned, the product can be obtained in a paste-like form. The use of such a paste avoids the problem of dusting of the material; in certain circumstances this can be an important advantage.

In order that the invention may be more fully understood, the following examples are given by way of illustration only: Example 1 400 g of metallic copper granules and 400 ml of a 1.8% solution of hydrochloric acid were charged into a column. The solution leaving the column was passed to a receiving vessel and then recycled into the column by means of a pump, thus effecting circulation of the solution. The pH of the recycled solution was 1-2. 95ml of an aqueous solution of sodium hypochlorite containing 10.4 g of active chlorine were then continuously charged into the bottom section of the column.

When pH of 3 to 4 was established, seeds of cupric oxychloride of a light green colour were formed which grew into crystals of the desired product upon achieving a pH of 5 to 7. The temperature of the suspension of these crystals was maintained at about 80"C. The process was carried out in a single stage and could be carried out continuously under the above-described conditions. To this end, solutions of sodium hypochlorite and of hydrochloric acid were continuously and simultaneously charged into the column in the above-specified amounts. A portion of the suspension of cupric oxychloride was continuously withdrawn from the receiving vessel in an amount equivalent to the amount of the supplied reactions, that is about 400 ml of the suspension.

The discharged suspension was filtered, the residue was washed to remove water-soluble chlorides, dried, at a temperature of 90-100 C to a moisture content of not more than 2%. The yield of dry product was 20 g., that is 97% of theory. 10 g of metallic copper was consumed in the reaction. The final product contained 51% of copper. The product had the following particle size: 80% of particles 1-3 m, 12% of particles 4-10 ijm, 8% 11-20 Fm. The stability of a 0.5% suspension was 96%. The chloride content of the washed product was 0.7%.

The washing waters containing 100 g/l of sodium chloride and 5 mg/l of cupric ions were delivered, after purification, to electrolysis to produce chlorine and caustic soda. The process of this Example is, therefore, waste-free.

Example 2 400 g of copper granules and 400 ml of a 1.8% solution of hydrochloric acid were charged into a column.

The solution leaving the column was passed to a receiving vessel and pumped back into the column, thus ensuring recycling of the solution. Its pH was 1-2. 140 ml of an aqueous solution of calcium hypochlorite containing 15.4 g of active chlorine were then continuously introduced into the lower section of the column over a period of 2-3 hours.

When pH of 3.0-3.5 was reached, seeds of cupric oxychloride were formed which grew as the pH increased to 5-6 into crystals of the desired product. The suspension of crystals was maintained at a temperature of about 40"C. The process was carried out in a single stage and could be conducted under these conditions in a continuous manner. To this end, the calcium hypochlorite solution and the hydrochloric acid solution were charged into the column continuously and simultaneously in the above-specified amounts. A portion of the suspension of cupric oxychloride was continuously discharged from the receiving vessel in an amount equivalent to the amount of the supplied reactants, that is about 530 ml of the suspension.

The discharged suspension was filtered, the residue was washed to remove water-soluble chlorides, and dried at a temperature of 90-100 C to a moisture content of note more than 2%. The yield of the dry product was 23.5 g, that is 98.0% of the theoretical. 12 g of metallic copper were consumed in the reaction. The final product contained 50.6% of copper. The product particle size was as follows: 70% of particles 1 to 3m, 25% 5-10 Fm, 5% - 10-20 im. The chloride content of the washed product was 0.8%. Th stability of a 0.5% aqueous suspension was 86%. The washing waters containing 10mg/l of copper ions and 100 g/l of calcium chloride were sent to evaporation.

Example 3 100 g of metallic copper granules and 200 ml of water. Water effluent from the column was passed to a receiving vessel and recycled to the column by means of a pump.

One litre of pure chlorine vapour was supplied to the bottom zone of the column. Upon saturation of the water in the column, with chlorine, the resulting recycled solution contained 8 g/l of dissolved chlorine and 50 g/l of cupric chlorate; the pH of the recycled solution was 1.5. 100 ml of an aqueous solution of sodium hypochlorite containing 10 g of active chlorine were then continuously introduced into the bottom zone of the column over a period of 2-3 hours.

When a pH of 3.0-4.0 was reached, seeds of cupric oxychloride of a light green colour were formed which grew, at a pH of 5-7, into crystals of the desired product. The crystal suspension was maintained at a temperature of about 60 C.

The process was carried out in one stage and could be continuously carried out under the above-specified conditions. To this end, sodium hypochlorite and chlorine were continuously and simultaneously introduced into the column in the above-specified amounts. A portion of the suspension of cupric oxychloride was continuously discharged from the receiving vessel in an amount equivalent to that of the supplied reactants, that is about 200 ml of the suspension.

The discharged suspension was filtered, the residue was washed to remove water-soluble chlorides, and then dried at a temperature of from 90 to 100 C to a moisture content of not more than 2%. The yield of dry product was 19.8 g, or 98.5% of the theoretical.

10 g of metallic copper were consumed in the reaction. The final product contained 50.8% of copper. The content of water-soluble chlorides was 0.6%. The product had the following particle size distribution: 70% of particles 1 to 3 ym, 25% - 5 to 10 m, 5% 10 to 20 yam. The chloride content of the washed product was 0.8%.

The stability of a 0.5% aqueous suspension of the product was 86%. The washing waters containing 10 mg/l of copper ions and 150 g/l of sodium chloride, were sent to evaporation.

Claims (6)

1. A process for the preparation of cupric oxychloride, which comprises treating metallic copper with sodium hypochlorite or calcium hypochlorite in an aqueous medium at a pH of from 3 to 7.

2. A process according to claim 1, in which the treatment is carried out in the presence of chlorine.

3. A procese according to claim 1 or 2, in which the treatment is carried out in the presence of hydrochloric acid.

4. A process according to any of claims 1 to 3, in which the treatment is carried out at a temperature of from 40 to 80"C.

5. A process for the preparation of cupric oxychloride substantially as herein described in any of the Examples.

6. Cupric oxychloride when made by the process claimed in any of the preceding claims.