DD206363A1 - METHOD FOR PRODUCING PURE PHOSPHORIC ACID - Google Patents

Abstract

THE INVENTION CONCERNS A METHOD FOR PRODUCING PURE PHOSPHOROUS ACID FROM THE PHOSPHOROUS (III) OXIDE P BOTTOM 4 O BELOW 6 AND WATER IN SOLUBLE SOLUBLE P BOTTOM 4 O BELOW 6: H BOTTOM 2 O <EQUAL TO 1: 6.5 UNDER INERT GASATE MUSPHAERE. THE OBJECT AND OBJECT OF THE INVENTION IS TO IMPROVE THE ECONOMY IN THE MANUFACTURE OF PHOSPHORIC ACID AND TO SIMPLIFY THE TECHNOLOGY OF THESE PROCESSES. IT HAS BEEN FOUND THAT, IN ADDITION OF ACTIVE COAL, PREFERABLY OF AN ACTIVE CARBON AT TEMPERATURES> 5OO DEGREES C, IN PARTICULAR OF ACTIVATED CARBON TREATED BY AIR, THE PHOSPHORUS (III) OXIDEO P DOWN4 O BELOW 6 AND WATER AT RECOURING SPEEDS OF APPROX. 100-300 RPM AT TEMPERATURES <120 DEG C, PREFERABLY 50-70 DEG C, AND THE SEPARATION OF THE ELEMENT TARPHOSPHERE AS A CARBON PHOSPHORUS WATER SOLIDS ADDUCTIVE EVEN AT TEMPERATURES. AT 45 DEGREE C BY FILTRATION AND THE RESPONSE SOLUTION WILL BE WORKED UP IN A KNOWN WAY.

Description

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Method for dissolving: pure phosphorous acid Field of application of the invention

The present invention relates to a method of producing pure phosphorous acid (H-PO_) from the phosphorus (III) oxide P _£ Og and water. H-PCU is needed for the production of many technically used P-organo compounds,

Characteristic of the known technical solutions

Numerous display variants are known which emanate from PCI. The reaction of the PCI with water is highly exothermic, it will u, a, large amounts of hydrogen chloride, which together with the PCI used to lead to significant corrosion phenomena developed. To obtain chlorine-free or very low-chlorine products, high technical expenses are necessary

Chlorine-free H-PO- is obtained in the hydrolysis of the trivalent P compound P ^ O, -. However, certain reaction conditions must be maintained in order to obtain H-PO of high purity in good space-time yields.

shallow THORPE and TUTTOST (J. Chem. Soc. 57 (1890), 545) is the reaction of the P., O ₁ - with hot water for illustration

T Ό

tion of H-, PO- unsuitable, because in the highly exothermic reaction H-PO ^, Slementarphosphor, phosphine and Phosphorsuboxide arise as by-products. With cold water,

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Used in large excess, a quantitative implementation is only after 18 h. The reaction of phosphorus (III) -oside dissolved in senzol with water is likewise unsuitable, since only very dilute aqueous solutions are obtained with a reaction time of 2 hours and additionally the use of a combustible organic solvent is required.

Pure H-PO, in high space-time yields can be obtained when according to WP.80 * 891 from 25.08.1969 water and

P, Or in a continuous process in molar ratio-4 o

nis> 6:. 1 under a protective gas atmosphere at temperatures between 0 and 50 ⁰ C and intensive stirring (ca, 2000 U / min) are reacted in aqueous, supersaturated H-POo solutions The Bach parts of this method order that at these high rotational speeds expensive and very prone to failure Stirrer, a re- latively complex control system for temperature control in this highly exothermic reaction and a narrow temperature range <45 ⁰ C for filtering the coming of the P, Qr Slementaruhosnhors from the supersaturated aqueous H-PO ~ solution, without it already comes to crystallization, are required.

Aim of the invention

The aim of the present invention is to provide an economically advantageous process of pure H-PO- from the chlorine-free P (III) compound P ^ Og and water *

Essence of the invention;

The invention is based on the object, the implementation of P ^ Og. and water under technologically simple conditions. ·

It has been found that with the addition of 0.05 to 1% by weight of activated carbon, based on the reacted amount of α, O,

¹ T o

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preferably one at temperatures> 500 C, in particular with access of air treated activated carbon, phosphorus (III) oxide and water in the molar ratio P ^ Og: H ^ O ^ * 1: .6.5 at stirring speeds of ca, 100-300 U / min and at temperatures of <120 ⁰ C, preferably 50 to 70 ⁰ C are reacted so that in the aqueous activated carbon suspension as long P ^ Qg is added until the heat of reaction liberated temperatures of <120 C arise and further supply of P ^ Og and optionally also water and activated carbon to the Η-, ΡΟ- supersaturated solution at temperatures of preferably 50 to 70 C, the separation of the elemental phosphorus as a carbon-phosphorus V / asser solid adduct even at temperatures> 45 ⁰ C by filtration and the reaction solution is worked up in a manner known per se. The P inserted ^ Og is purified only by separation of the lifting products, it can be for example, B, according to 79,280 to produce the WP from 12.06 ^ 1969 abtrennen- of the resulting by-products by filtration * contains This used P ₄ Or still best in mte proportions on. P ^ and P (III, Y) oxides.

The surprisingly positive effect of the activated carbon with respect to a low-decomposition or non-free plydrolysis process is obtained with the aid of the data given in Example 1,

According to. WP 80,891 is for a unique reaction course according to equation 1

P ₄ O ₆ + 6H ₂ O 4 H ₃ PO ₃ (1)

To create a large surface area in P.Or hydrolysis, the use of very high speed stirrers is required. If you work with only relatively slow-moving agitators, as used in the invention, so you do not achieve sufficient surface enlargement, P ^ Og settles as a liquid below the Wasserschicht- "The once started implementation with V / asser then runs so extremely that a large part of the

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action approach is thrown out of the container and the already observed by THOEPE and TUTTOU lifting reactions take place,

The action of the activated carbon can be understood in various ways. The donor-acceptor interaction between the active, possibly acidic centers of the char and the hydrophobic substance P. 0, - can increase the surface area as well as the favorable polarity ratios create advantageous attack of the water, so that the necessary for a low-decomposition "or -freie hydrolysis process sufficient amount of water to the

P.Or molecules as well as their fast reaction with-4 b

given to each other * If such conditions are not met, the most varied reactions of tebenes occur, as well as the rearrangement of the metastable phosphorus (III) oxide at room temperature into the thermodynamically favored decomposition products.

Also, when using the activated carbon is observed, if appropriate with the addition of P, Og (at temperatures> 25 ⁰ C) primarily its deposition as a liquid below the aqueous phase, onset When compared to Example 1 more quickly; Hydrolysis causes the according to the reaction according to equation 1 released amount of heat Temperaturstiege to about 120 C without in comparison to a procedure "according to Wp 80.891 (using the same P ^ Og starting material) z, B * significantly higher P (T) - Shares arise.

The use of the activated carbon permits also a better separation of the from the P ^ 0 _r coming yellow phosphorus .. The latter forms together with water and the component carbon at temperatures> 45 ⁰ G, ie above the P. melting point, a Feststoffaddukt, in which the elementary phosphorus is firmly bound

 According to the procedure according to WP 80,891 you have the

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Filtration of the precipitated yellow phosphorus at temperatures <45 ° C. In particular, at temperatures of $ 25 ⁰ C, however, crystallization of the H-PO from the supersaturated solution can very easily take place, so that only a very narrow temperature range and careful work are required or required. According to this procedure, the filtration can be carried out at temperatures> 50 C. Furthermore, the elemental phosphorus is present in this solid adduct in a better filterable form »

The process of H-PO production can also be operated continuously. The reaction components V ₄ Or,

4b '

Water and charcoal are metered under the conditions already mentioned above to the aqueous H-PO solution, expediently to a H-PO-supersaturated solution, and the reaction solution is introduced, for example. over a band filter. Very pure H-PO- obtained therefrom according to known methods or limited to the removal of excess water, z.l, in a spray tower. The advantage of the invention is that with the help of small additions of activated carbon pure H-PO from PiO and water under technologically simple

can be produced

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embodiments

The invention will be explained in more detail by the following examples.

Example 1 (comparative example)

In a closed stirrer vessel with cooling jacket provided with stirrer, gas (inlet and outlet) pipe and overpressure protection (rupture disk), 117 parts by weight of water are initially charged and placed under an inert gas atmosphere (H ₀ ).

at Rührge.schwindigkeiten of 250 U / min at a jacket temperature of 50 - 60 ⁰ C P. Q _r added. From the ent.

α. ο

- 6 -.

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corresponding to the molar ratio P-Og: HpO = 1: 6.5 weighed P.Og amount of 220 parts by weight were added after 15 min ca 3/ 3/4, as the hydrolysis reaction with the deposited below the water layer liquid P. Og phase began. The temperature in the reaction vessel rapidly increased to values> 120 ^° C. The reaction was so vigorous that the bursting disk broke and a portion of the reaction mixture was spun into a downstream safety vessel. In the outgoing gas stream phosphine could be detected. The remaining gate of all colored by phosphorus suboxide orange-brown colored reaction solution was analyzed and contained, inter alia, an ELPO-- or ELPO ^ share of 19.8% and 9.8 SS.

Example 2

In the Rührwerksgefäß analogously to Example 1 parts by water and 0.22 parts by weight of an approximately 1 h treated at 1000 ⁰ g of active carbon are added 117, submitted. The 0.22 parts by weight correspond to 0.1 %, based on the used

P.Or amount of 220 parts by weight. ? "0, - was at a 4 ο 4 ο

Stirring rate of 250 U / min and room temperature (about 25 ⁰ C) was added dropwise until a rise in temperature up to 112 G occurred by the onset of hydrolysis. After supplying the cooling medium, the remaining main amount of P ^ O, - was added at temperatures of about 70 C. The reaction was completed after 15 minutes, based on the time of the beginning of the P ^ Cv addition. The solution was filtered at 50 ⁰ C and had thereafter · following composition: P (ILI) = 36.8%, P (V) = 0.16%, Έ, = <0.0002%. The supersaturated solution was crystallized, the H 2 PO 4 crystals separated by centrifugation. The (III) value of this purified acid was 37.7 %, which corresponds to a purity of> 99 %.

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Example 3

To 100 parts by weight of an aqueous phosphorous acid (about 90% H-PO., This corresponds to a Einsatzmol-, ratio P ^ Og: BLO = 1: 8) are in a reaction vessel under Hp atmosphere at temperatures of 60-80 ⁰ C and while stirring (revolution speed 150 U / min) in one minute continuously 4.4 parts by weight of P.Og, 2.88 parts by weight of water and 0.05 parts by weight of the example 2 already mentioned activated carbon and in the same time unit about 7.28 parts by weight of the resulting .Reaktionslösung continuously withdrawn and then filtered. The clear solution gave the following analytical values: P (III) = 33.99 %, P '(V) = 0.18%, P = < 0.0002%. From the solution, an IL ₁ PO was obtained with a purity of> 99% by crystallization.

Claims (3)

Erf ύ Ι * Erf Erf Erf Erf Erf Erf Erf Erf 1. A process for the preparation of pure phosphorous acid from phosphorus (III) oxide and water in the molar ratio P.Og: H ₂ O = 1: 6.5 under an inert gas atmosphere, characterized in that when activated carbon is added, preferably a Temperatures> 500 C, in particular under treatment of air treated activated carbon, the phosphorus (III) P- ₄ Og and water at stirring speeds of .ca. 100-300 U / min at temperatures < 120 ⁰ G, preferably 50 to 70 ⁰ C is reacted and the separation of the elemental phosphorus as a carbon-Phospbor-water-solid. Adduct is also carried out at temperatures.,> 45 ⁰ C by filtration and the reaction solution is worked up in a conventional manner * · 2 · Process for the preparation of pure phosphorous acid according to item 1, characterized in that the activated carbon is presented as an aqueous activated carbon suspension ^ and P ^ Og is added at room temperature until the temperature rises to> 50 ⁰ G by the liberated 'heat of reaction' and the further supply of P ₄ -OgJ optionally also water and activated carbon to the H-JPO_ supersaturated solution at temperatures of 50 to 70 ⁰ C, 3. Process for the preparation of pure phosphorous acid • according to point 1, characterized -gekennzeichnet that the zuge-. activated carbon content was 0.05 to 1 * 0 parts by weight based on the P ^ Or amount.