DE670384C - Manufacture of alkali and alkaline earth metaphosphates - Google Patents

Description

Manufacture of alkali and alkaline earth metaphosphates For manufacture of alkali and alkaline earth metaphosphates, the corresponding primary ones have so far been asked for Orthophosphate heated, giving off crystal and constitution water the associated metaphosphates arise. The production presupposes the presence The orthophosphoric acid precedes pure salts, which in turn are based on aqueous orthophosphoric acid and a carbonate or hydroxide must be obtained.

In order to eliminate the aqueous phosphoric acid, one has already proposed that both ortho- and met, aphosphaite be prepared by reacting in-an phosphorus pentoxide as vapor or solid in the presence or absence of water vapor with alkali compounds by reacting the constituents : either introduced in molten salts or, as with the alkaline earth compounds P. 05, as steam in a rotary kiln over the solid substances. has directed. These modes of manufacture have several disadvantages. Alkali compounds only melt at very high temperatures, which is a. requires a considerable amount of heat. In addition, the alkali compounds evaporate noticeably at these temperatures. In addition, there are considerable demands on the building materials for the melting vessels. Operation is subject to frequent malfunctions because the inlet pipes for the phosphorus phosphorus and water vapor wear out, melt away and even clog. In order to counteract this problem, the alkali compounds have already been dusted in hot pentoxide gases and the reaction can be carried out in the gas phase. However, all of these processes, including those in which the pentoxide gases and the water vapor were only passed over the solid bases, have the following inherent: the serious disadvantage that the process cannot be controlled because phosphorus pentoxide is even larger, Amounts than the stoichiometric ratio, @ corresponds, is added, so that uniform end products, in particular i'vleta.phosphate, are not achieved.

You can also:, also meta, phosphat.e by saturating metaphosphoric acid Prepare in aqueous solution or in melt flow.

It has been shown that by heating a mixture one can calculate Quantities of solid, dry phosphorus pentoxide and a dry alkali, alkaline earth or earth metal compound in an oxidizing flame readily to form uniform metaphosphates the base in question arrives. The mixing can expediently in an all-silky closed Ball mill or: made other closed on all sides "-earth. It is important to lock the mixer to keep water away. With old presence of water., the phosphorus pentoxide quickly changes into a smeary state, the mixing. of the two dry, powdery reagents.

The base-supplying substances used in the present process are salts such acids into consideration, which in the heat by phosphoric acid or by phosphorus pentoxide be driven out. Because almost all acids in the heat in the presence of phosphoric acid escape, practically all four bonds of the metals mentioned come into consideration. First and foremost one will of course carbonates, bicarbonates, chlorides, or nitrates Use sulfates.

The heating temperature can vary with the new process 5oo and iooo "lie, depending on the type of metal compounds used and the Of course the desired metaphosphate. In general, compounds of the Alkalis lighter than the corresponding alkaline earth compounds and carbonates easier: than compounds with other anions. The use of an oxidizing 1'lamme or the anives °, meaning of oxygen may be necessary because the phosphorus pentoxide for the transition into the anion of the metaphosphoric acid oxygen required, as can be seen from the following formula, which is set up as an example 2NaC1 P.O5 - O = 2NaP0 .; i Cl .. In the practical implementation one fills z. B. that dry, powdery mixture: from phosphorus pentoxide and alkali compound from the Mixing device in a crucible or a melting vessel, and heated to the desired Temperature, with the acid anhydride escaping, the desired metaphosphere develop.

As was further found, it is not necessary with this procedure, To continuously heat the melting vessel from the outside, namely the reaction proceeds like this strongly exothermic, so that in most cases an initiation of the mixture is sufficient, to let the reaction run away. That once, brought to response temp: erature The mixture then reacts independently with the formation of metaphosphate. That's enough it z. B., the mixture in the still hot annealing furnace from the previous batch insert in which the reaction takes place without renewed @ external heat supply accomplishes. The initiation of the reaction mixture can also be initiated by a Jet flame, which only causes local heating or overheating, take place. Most surprising, however, is that the reaction can also be achieved by applying a A drop of water can be introduced onto the powdery, dry mixture. By the :: - #; Carrying a drop of water: heats up @z. B. the -at room temperature existing mixture by several ioo ', which in most cases is a start. and The reaction is sufficient.

Should be due to special circumstances, such as the small size of the reaction batch and heat radiation losses, the resulting temperature in the reaction mixture complete course of the reaction or to achieve the desired metaphosphate -not sufficient, a short reheating can of course be carried out by; external, Heat supply @ take place.

The specified properties enable continuous implementation of the process z. B. in a rotary kiln: In these the finished reaction mixtures, as usual, introduced at the cold end. As soon as the required initiation temperature is reached, the reaction takes place, and depending on the temperature setting At the h: eil'.en end of the furnace one can put any desired motaphosphate there Composition continuous: peel off. Here is only a very low level of heating des D @ i @ chofe'ns required. Here, too, it is useful to point i to a corresponding one Pay attention to the excess of fuel in the heating gases.

Example i A mixture of 1.12 kg produced in the ball mill Phosphorus pentoxide and. i, o6 kg of sodium carbonate is i11 a: heated to oo ° Enter the crucible with the H, izflame switched off. The reaction starts immediately. With the escape of carbonic acid, the mass carried in melts down without that additional heating would be necessary. A few minutes. after entering the Melt solidified by pouring it out. The obtained glassy transparent Product can be ground into powder. It is pure sodium hexametaphosphate.

Example 2 I "42 kg of phosphorus pentoxide are mixed with 1.7 kg of sodium chloride mixed in a ball mill. The mixture is made up in small proportions 8oo 'heated crucible, from which initially; small amounts of hydrogen chloride, Later, however, mainly chlorine-containing gases escape, with the mixture under Formation of a more or less coarsely sintered product melts down. Around To obtain pure hexametaphosphate, the product obtained is heated about 6 hours at 8oo ° and pours the obtained melt then from, wherein on cooling it solidifies to a colorless, transparent Cn glass, which turns out to be Sodium hexametaphosphate with a content of 0.3% chlorine proves.

Example 3 A mixture as given in Example i is obtained at room temperature wetted on the surface with a drop of water. It is best to give the drop of water into a recess made in the mixture. The temperature of the mass rises almost instantaneously to about 500 degrees, which causes the reaction to take place, which is already is practically over after 3 minutes. A porous, sintered mass is obtained, a mixture of different metaphosphate modifiers with a content of only o, o60; ö represents carbon dioxide. To convert the 'mixture into hexametaphosphate A short heating is sufficient: to about 65.0 °, whereby the sinter becomes colorless Glass melts together. Example q. One in a ball mill that is closed on all sides produced mixture of 1.42 kg of phosphorus pentoxide and i, oo kg of calcium carbonate : Partly put into a: heated crucible to the point of 100 ". The mixture melts with the release of carbonic acid. When the entry is complete, 1 is displayed; . S @ do @ nde i ooö 'heated and quenched the melt by pouring it out. She freezes into one colorless clear glass that is practically carbonic acid free and calcium metaphosphate represents.

The present method allows in a much simpler manner and with significantly less work than before. Metaphosphates any to produce the desired composition. By the fact that an evaporation of water omitted in the present process, there is a substantial saving in heating material achieved, quite apart from the fact that the reaction, as shown above, only at all very little, possibly no external heat supply at all required. In technical Regarding working in the absence of water, apart from that mentioned above Savings, still the advantage of being dry. Powder itself very easily completely Mix evenly, shovel and let transport. It is already known To produce phosporic acid-containing mixed fertilizers by adding calcium chloride finely ground wood waste or sawdust with the addition of phosphoric anhydride with a potassium-containing mineral, such as orthoclase or apatite, and mixes this mixture heated to bright red heat. The resulting distillation products of the wood, such as acetone, acetic acid and the like are collected separately. With this way of working so if reducing agents are worked with great effort, it is a development of metaphosphate is not possible. Incidentally, both contain the wood waste as well as the calcium chloride usually considerable amounts of water necessary for the formation of orthophosphoric acid from the phosphoric anhydride. Is according to the invention As explained above, it is essential to work in a moisture-proof environment and continue to use mainly oxidizing heating, since this is the only way to manufacture homogeneous, uniform metaphosphates of the desired composition succeeds.

Claims (2)

PATENT ANsrizLCHL: i. Process for the preparation of metaphosphates by heating phosphorus pentoxide .und a salt containing the corresponding base, e.g. B. alkali or alkaline earth salt, the anion of which is expelled in the heat by phosphorus pentoxide, optionally in the presence of oxygen, characterized in that one expediently generated in a ball mill or another mixer closed on all sides mixture of calculated amounts of solid., Dry phosphorus pentoxide and of a dry salt containing the desired base, preferably in continuous operation, in a rotary kiln, heated to temperatures between about 500 and 100 ° or, only to Berginn, heats the reaction from outside. 2. Procedure according to Claim i, characterized in that in the case of the use of basic salt ice initiation of the reaction mixture by applying small amounts of water individual places of the mixture takes place.