GB2097775A

GB2097775A - Production of aluminium or magnesium phosphide

Info

Publication number: GB2097775A
Application number: GB8212058A
Authority: GB
Original assignee: Degesch GmbH; Deutsche Gesellschaft fuer Schadingbekampfung GmbH
Current assignee: Degesch GmbH; Deutsche Gesellschaft fuer Schadingbekampfung GmbH
Priority date: 1981-05-02
Filing date: 1982-04-26
Publication date: 1982-11-10
Also published as: FR2504908A2; MX157403A; BR8202525A; DE3117393C2; FI821507L; CA1182273A; NO821427L; NO156084C; AU549936B2; ES511837A0; SE8202737L; ATA169382A; ES8304518A2; AT394843B; NO156084B; JPS582210A; DK157911B; AU8316082A; FI821507A0; IT1156465B

Abstract

The phosphide of aluminium or magnesium is produced by reacting the finely divided metal or an alloy of the two metals with yellow phosphorus at a temperature from 300 to 600 DEG C in an inert gas atmosphere and in the presence of a catalytically effective amount of water, the element chlorine, bromine, or iodine or a compound of such element with phosphorus, sulphur, hydrogen, ammonium, zinc, or the metal being reacted. Both the yellow phosphorus in liquid form and the finely divided metal are slowly fed into the reaction vessel.

Description

SPECIFICATION Method for the production of aluminium or magnesium phosphide The present invention relates to a process for the production of aluminium or magnesium phosphide.

Our prior British patent application No.

2062602A relates to a process for the production of the phophides of aluminium or magnesium in which the finely divided metal or an alloy of the two metals is reacted with yellow phosporus at a temperature from 300 to 600"C in an inert gas atmosphere and in the presence of, as a catalyst, water, or the element chlorine, bromine or iodine, or a compound of such element, with phosporus, sulphur, hydrogen, zinc, or the metal being reacted, or an ammonium halide.

According to a particularly preferred process, the finely divided or gritty metal is first intimately mixed with the catalyst. The mixture is heated to the reaction temperature of from 300 to 600"C in a suitable reactor where it is capable of being enclosed in an inert gas atmosphere, for example, under nitrogen at normal pressure. When the desired reaction temperature is reached liquid yellow phosporus is added at such a speed that the heat of reaction liberated is led off without problem and the temperature can be maintained in the range from 300 to 600"C .

It has now been found that the process of the application referred to above can be carried out even more safely, can be more readily controlled and above all can be carried out partially or even full continuously if the finely divided metal is also slowly added to the reaction vessel.

The present invention provides a process for preparing the phosphide of aluminium or magnesium which comprises reacting the finely divided metal or an alloy of the two metals with liquid yellow phosporus at a temperature from 300 to 600 C in an inert gas atmosphere and in the presence of, a catalyst, water, the element chlorine, bromine or iodine or a compound of such element with phosphorus, sulphur, hydrogen, zinc or the metal being reacted, or an ammonium halide, both the liquid phosphorus and the finely divided metal being introduced into the reaction by being slowly added to the reaction vessel.

If the process of the invention is carried out in a substantially cylindrical reaction vessel, which is heated from below the bottom then four different zones are clearly formed which, from top to bottom, can be descirbed as follows: Zone 1: In this uppermost zone only gas exists, namely a mixture of the inert gas employed and phosphorus vapour. Even in the most extreme case a maximum temperature of only about 200"C is reached in this zone. The vapour pressure of the phosphorus is relatively small so that the gas mixture consists chiefly of the inert gas employed.

Zone 2: This is the vaporization zone of the yellow phosphorus. In this zone temperatures prevail which are slightly above the boiling point of the yellow phosphorus. In this zone also only gas is present, which consists for the most part of phosphorus vapour.

Zone 3: In this zone the uppermost layer of the container filling is located which is the true reaction zone in which phosphorus vapour comes in contact with the finely divided metal and the already formed phosphide. In this zone, which is at the reaction temperature of 300 to 600"C, the strongly exothermic reaction between the phosphorus vapour and the finely divided metal takes place. Since the phosphorus vapour reacts very quickly with the metal, it does not penetrate very deeply into the container filling but only to a depth of about 10 to 1 5 cm. Therefore within the container filling, in the direction from the top downwards, the gas phase very rapidly has a reduced phosphorus vapour content.

Zone 2: In the lowermost zone the gas phase consists substantially only of inert gas because the phophorus vapour does not penetrate to this depth. The solid material consists substantially only of the phoshide formed and contains perhaps small amounts of unreacted metal. A slight excess of metal makes certain that the phosphide formed is free of phosporus.

The formation of the four zones within the reaction vessel described above makes possible a particularly simple and completely safe form of the process of the invention. According to this form of the process, the liquid yellow phosphorus is continuously added into the upper part of the reaction vessel, i.e. into the gas space above the container filling, where it can be vapourized without hindrance.

It is especially advantageous if the entrance for the liquid phosphorus is located entirely in the upper part of the reaction vessel, i.e. in the above-mentioned zone 1. It is possible to also add the finely divided metal in the upper part of the reaction vessel. In this case, however, the rapid and vigorous reaction with the phosphorus vapour already present in high concentration makes necessary the use of special closing off devices for the entrance in order to prevent the phosphorus vapour from penetrating into the conveying device for the finely divided metal. For this reason it is more advantageous to continuously add the finely divided metal into the lower part of the reaction vessel, i.e. so that the entrance is in the region of the container filling. This can occur in the above-mentioned zone 3, which is the true reaction zone.It is then suitable to provide at about the height of the entrance for the metal a stirrer whose conveying elements move the container packing along the peri phery of the container and thus provide for a uniform distribution of the freshly added metal in th reaction zone. However, it is still more advantageous if the addition of the finely divided metal takes place in the lowest part of the reaction vessel, i.e. in the above-mentioned zone 4. In this case it is suitable to provide a stirrer whose conveying eiements move the container packing along the periphery of the container and simultaneously provide for a thorough mixing vertically.

It is possible in the manner described to continuously add equivalent amounts of finely divided metal, which contains the catalyst mixed therein, and liquid yellow phosphorus into the reaction vessel and during the reaction to withdraw from the lowest part of the reaction vessel (the above-mentioned zone 4) the phosphide formed, which is free from unreacted phosphorus. The withdrawal takes place through an opening at the bottom of the reaction vessel. It can be carried out as desired continuously or batchwise. In continuous withdrawal the product is dishcharged in an amount corresponding exactly to the metal and phosphorus added. However, it is also just as possible to let the product slowly build up in the lowermost zone in the reaction vessel (the above-mentioned zone 4) and then to discharge the phsophide formed batchwise.

However, in this case care must be taken that only material which contains no unreacted phosphorus is actually discharged from zone 4, and not, for example, also material from the reaction zone, which can happen through weight control.

If the finely divided metal-as described above-is fed into the lower part of the reaction vessel, i.e. in the above-mentioned zone 3 or zone 4, then a conventional screw conveyer is sufficient as the feeding device, because the solid, gritty container filling serves at the same time as a closing off device.

Should the process of the invention be started in an empty reaction vessel, it is therefore suitable to introduce first only finely divided metal until the entrance for the metal is covered, and only then to begin the slow addition of the liquid phosphorus. However it is still more advantageous if the reaction vessel is first filled with the corresponding phosphide produced earlier until it is above the entrance for the metal, and then addition of the liquid phosphorus and the finely divided metal is commenced simultaneously.

The process of the invention is illustrated in more detail in the following examples. Unless otherwise stated all percentages are by weight.

Example I The reaction vessel was a cylindrical container having a diameter of about 80 cm and a height of about 100 cm which was provided with a stirrer, a cooling system, temperature probes at various heights, an inlet line for inert gas and an outlet line for waste gas. The bottom of the container was provided on the outside with a gas burner capable of heating it to a temperature up to 500"C. A supply vessel for liquid phosphorus was connected to the reaction vessel, the supply vessel having a pump which permitted as desired, circulation of the liquid yellow phosphorus in the supply vessel or feed into the reaction vessel. A supply vessel for the finely divided metal to be reacted having a conveying device for adding the metal into the reaction vessel was also connected to the reaction vessel.At the bottom of the reaction vessel a small opening was located provided with a locking off device for discharge of product. For reasons of safety the reaction vessel was provided with a rupture disc to counter any possible increase in pressure. The reaction vessel was rinsed before and after the reaction with nitrogen, during the reaction the reaction mixture was covered with argon. The waste gas was led off over a water receiver habing a glass fibre filter and a subsequent activated carbon filter.

Before the beginning of the reaction 50 kg of magnesium phosphide from an earlier production run were placed in the reaction vessel, a mixture of 200 kg of magnesium and 0.8 Kg of iodine were placed in the metal supply vessel, and the liquid phosphorus was circuiated in the supply vessel. The reaction vessel was then heated at the bottom to 300'C. 10 kg of magnesium were then fed into the reaction vessel and the feeding in of liquid phosphorus was commenced with a speed of 0.4 to 1 kg per minute. Simultaneously more magnesium was also added. The heat of reaction caused the temperature to increase in the lower part of the reaction vessel to 550'C.

Addition of the phosphorus and the magnesium was then so regulated that the temperature was maintained at 550"C and the weight ratio between phosphorus and magnesium was around 0.85:1. After about 180 kg of magnesium phosphide had formed in the reaction vessel 100 kg of product were discharged through the withdrawal opening over a period of 10 minutes whilst continuously adding further phosphorus and magnesium.

The withdrawal opening was then closed again. After about 1 80 kg of magnesium phoshide had formed again this was again discharged and subsequently the entire process was again repeated. After using up the supply of 200 kg of magnesium the addition of phosphorus was stopped. The product still located in the reaction vessel was again heated briefly and discharged. Including the magnesium phosphide present in the reaction vessel in the course of 5 hours 41 5 kg of, product having a magnesium phosphide content of 92% were discharged.

Example 2 The reaction vessel described in Example 1 contained a mixture of 100 kg of magnesium and 0.3 kg of iodine, the supply vessel for the metal contained a mixture of a further 1 50 kg of magnesium and 0.5 kg of iodine. The reaction vessel was then heated at the bottom to 300"C. Phosphorus was then added at such a speed that the temperature in the lower part of the reaction vessel slowly increased 550"C. Through control of the addition of phosphorus this temperature was maintained until altogether 82 kg of phosphorus was used.Magnesium and phosphorus were then simultaneously added in a weight ratio of 1:0.83 at such a velocity that the temperature in the lower part of the reaction vessel continuously remained between 500 and 550"C. At the same time product was continuously discharged through the withdrawal opening in such an amount that it exactly corresponded to the amount of magnesium and phosphorous added, i.e. a total of 1 50 kg of magnesium and 1 23 kg of phosphorus. Finally the product still remaining in the reaction vessel was heated again briefly and further discharged continuously. The yield in all amounted to 450 kg with an average content of magnesium phosphide of 90%.

Example 3 The reaction vessel described in Example 1 contained a.mixture of 50 kg of a gritty aluminium-magnesium alloy having a magnesium content of 5% and 0.2 kg of iodine. The supply vessel for the metal contained a mixture of a further 200 kg of the alloy mentioned and 0.6 kg of iodine. The reaction vessel was then heated at the bottom to 450"C. Addition of the phosphorus was first added with a relatively greater speed, in order to compensate for the excess of alloy present, until an overall weight ratio of phosphorus to alloy of 1.1:1 was reacted, Heating was continued until a temperature of 500"C was reached in the lower part of the reaction vessel. Subsequently more phosphorus and alloy were added in a weight ratio of 1.1:1 until the reaction vessel contained about 200 kg of product.From this point on product was continuously discharged through the withdrawal opening at the same velocity as phosphorus and alloy were added. The addition was so adjusted that the temperature did not exceed 550"C. After use of the entire alloy the addition of the phosphorus was stopped, the heating set in operation and the remainder of the product continuously further discharged. In all 520 kg of gritty product was obtained with a phosphide content of 90% of theory.

Example 4 The reaction vessel described in Example 1 contained 1 30 kg of aluminium phosphide from an earlier production run, the supply vessel for the metal contained a mixture of 250 kg of aluminium and 1 kg of iodine. The reaction vessel was then heated at the bottom to 480"C and 20 kg of aluminium were introduced. Aluminium and phosphorus were then simultaneously added and after a temperature of 500"C had been reached heating was stopped. Initially phosphorus was added more quickly to compensate for the excess of metal present, after which aluminium and phosphorus were added in a constant weight ratio of 1:1.1 at such a velocity that a temperature of 570"C was not exceeded. After a total of 230 kg of product had accumulated in the reaction vessel 1 30 kg of product was discharged with continued addition of aluminium and phosphorus. This process was repeated until 250 kg of aluminium had been used up. In all 501 kg of product discharged with an aluminium phosphide content of 95%, around a further 1 55 kg being left in the reaction vessel as a heel for the next product.

Claims

1. A process for preparing the phoshide of aluminium or magnesium which comprises reacting the finely divided metal or an alloy of the two metals with liquid yellow phosphorus at a temperature from 300 to 600"C in an inert gas atmosphere and in the presence of, as catalyst, water, the element chlorine, bromine or iodine or a compound of such element with phosphorus, sulphur, hydrogen, zinc, or the metal being reacted, or an ammonium halide, both the liquid phosphorus and the finely divided metal being introduced into the reaction by being slowly added to the reaction vessel.

2. A process as claimed in claim 1, wherein the reaction vessel contains solid reaction mixture or reaction product and the liquid yellow phophorus is fed into the upper part of the reaction vessel above the solids.

3. A process according to claim 1 or 2, wherein the finely divided metal is fed into the lower part of the reaction vessel where the reaction vessel contains reaction mixture or reaction product.

4. A process for preparing the phosphide of aluminium or magnesium substantially as described with particular reference to any of the examples.

5. Aluminium or magnesium phosphide when prepared by a process as claimed in any of claims 1 to 4.