DE102008023649A1 - Purification of phosphorus-containing acid comprises mixing a first aqueous phase comprising a phosphorus-containing acid with a second phase comprising an organic solvent, separating the phases and isolating the second phase - Google Patents

Abstract

Purification of phosphorus-containing acid, comprises: (a) mixing a first aqueous phase comprising a phosphorus-containing acid with a second phase comprising at least one organic solvent to form an aqueous two-phase system; (b) separating the phases by centrifugation; and (c) isolating the second phase, which contains the phosphorus-containing acid.

Description

The The invention relates to a process for the purification of phosphoric acid or mixtures with phosphoric acid by extraction by means of Centrifuges.

phosphoric acid is one of the most important inorganic acids, in particular in large-scale processes. Phosphoric acid is for example, in the manufacture of fertilizers, preservatives (E338 acidity regulator) and / or rust transducers. Further, phosphoric acid is used as a mordant during polishing used by metal surfaces.

The Production of phosphoric acid is energy and material consuming. For economic and ecological reasons Therefore, the recycling of used phosphoric acid is desirable. Furthermore, it is also desirable, Rohphosphorsäure, which made from apatite and sulfuric acid, continues to grow clean.

For the purification of phosphoric acid, liquid / liquid extraction processes are known. The DE 197 03 884 describes a process for the liquid / liquid extraction of wet-process phosphoric acid with mixtures of alcohols, ethers and / or ketones in a mixer-settler process. In the mixer-settler process, two substantially immiscible liquids are filled into a mixer and stirred vigorously. Subsequently, the intensively mixed liquids are passed into a separator, also called settler. This is where the phases separate.

One Disadvantage of the mixer Settler procedure is however that very large Facilities are needed and the process is time consuming is.

task The present invention is a cleaning method for To provide phosphorus-containing acids which are fast and feasible with a low expenditure on equipment is.

• a) Mischen einer ersten wässerigen Phase, umfassend eine Phosphorhaltige Säure, mit einer zweiten Phase, umfassend mindestens ein organisches Lösungsmittel, wobei die erste und zweite Phase ein flüssiges Zweiphasensystem bilden,
• b) Separieren der Phasen durch Zentrifugation und
• c) Isolieren der zweiten Phase, welche die Phosphor-haltige Säure und das organische Lösungsmittel umfasst.

This object is achieved by the provision of a process for the purification of phosphorus-containing acid, comprising the steps:

• a) mixing a first aqueous phase comprising a phosphorus-containing acid with a second phase comprising at least one organic solvent, wherein the first and second phases form a liquid two-phase system,
• b) separating the phases by centrifugation and
• c) isolating the second phase comprising the phosphorus-containing acid and the organic solvent.

The inventive method allows an extraction in smaller plants in contrast to the conventional one Mixer-settler process, which requires very large plants.

After mixing, the first and second phases form a two-phase system, which is preferably an emulsion. In emulsions, at least two immiscible liquids which form two phases are preferably dispersed together. The one liquid preferably forms the dispersant for the other liquid, which is distributed in the form of fine droplets. The droplet diameter is preferably in the range of 10 ^-2 to 10 ^-6 cm. After centrifugation in step b), the first and second phases form two phases.

at In one embodiment, the phosphorus-containing Acid to ortho-phosphoric acid, phosphoric acid, Phosphinic acid, hypodiphosphonic acid, diphosphonic acid, Hypodiphosphoric acid and / or diphosphoric acid. Ortho-phosphoric acid is particularly preferred, which is hereafter Also referred to as phosphoric acid.

at an embodiment is in the step a) phosphoric acid used to Rohphosphorsäure or used phosphoric acid. The used phosphoric acid is preferably from the dye production, preferably from the quinacridone production, and / or it is used Phosphoric acid, which is used as the pickling acid of metal surfaces or as an etchant, for example for offset plates and / or semiconductors. The used phosphoric acid can also come from the textile industry, for example from dyeing, Softening and / or shrinking.

The Rohphosphorsäure can, for example, in the wet process getting produced. For this purpose, raw phosphate, preferably apatite, with acid, preferably sulfuric acid, decomposed. Thereafter, the resulting calcium sulfate and hexafluorosilicic acid separated from the generated phosphoric acid. These manufactured so Rohphosphorsäure can then by the inventive Procedures are easily and efficiently further purified.

The term "pickling acid" in the sense of the invention is to be understood as meaning that the surface of a workpiece or the entire workpiece is treated with pickling acids, for example for passivation, preservation, polishing, cleaning, smoothing of the surface and / or protection. As Beizsäuren phosphoric acid, sulfuric acid, nitric acid and / or hydrofluoric acid can be used. In one embodiment, phosphoric acid or a mixture of phosphoric acid and sulfuric acid is used as the phosphorus-containing acid. In particular, when polishing metallic bodies, before preferably when polishing aluminum and / or stainless steel, these pickling acids can be used.

at An embodiment is called phosphorus-containing acid a mixture of phosphoric acid and another acid, For example, sulfuric acid used. Preferably it is pickling acid. The concentration of phosphorus-containing acid in the first aqueous phase is preferably from 60 to 80 wt .-%, based on the total weight of the first phase.

Particularly preferred phosphoric acid used is a phosphoric acid which has been used in the pickling of aluminum plates. The aluminum plates are then used, for example, as reflector plates in lamp production. This pickling acid preferably comprises:
40 to 50 wt .-%, preferably 43 to 47 wt .-%, phosphoric acid,
25 to 35 wt .-%, preferably 28 to 33 wt .-%, sulfuric acid, and
1 to 2% by weight of dissolved aluminum,
based on the total weight of the pickling acid.

Further can also use crude phosphoric acid in the first phase become. Preferably, the crude phosphoric acid has a concentration from 60 to 80 wt .-%, based on the first phase. Because the concentration the Rohphosphorsäure in the wet chemical production is lower, the wet-chemically produced Phosphoric acid are then concentrated.

at an embodiment of the invention Process, the first phase comprises phosphoric acid and sulfuric acid. The proportion of sulfuric acid in the first phase is preferably 15 to 35 wt .-%, based on the total weight of the first Phase. The proportion of phosphoric acid in the first phase is preferably 45 to 65 wt .-%, based on the Total weight of the first phase. The phase separation can by the Presence of sulfuric acid are accelerated.

at In one embodiment, the centrifugation is in step b) from 500 to 250,000 g, preferably from 50,000 to 200,000 g, carried out.

The Centrifugation can be carried out batchwise or continuously become. Under discontinuous centrifugation, centrifugation is too understand in which the first and second phases in a vessel without Entry and exit takes place. In the case of discontinuous centrifugation Steps b) and c) form two separate steps. In the continuous Centrifugation steps b) and c) form a step. Under continuous centrifugation is to be understood, for example, that the centrifugation takes place in a flow centrifuge. For example, the centrifuge from Westfalia has proven to be suitable Separator GmbH (Oelde, Germany) of the type 1-02-525, TC 75, TC100, TC150 and / or TC300 proven.

Preferably is the discontinuous centrifugation in step b) for 5 min until 30 min, preferably 10 min to 15 min performed. at continuous centrifugation in a flow centrifuge a certain adjustment time is needed until the Phase separation sets. The adjustment time is preferably 5 minutes to 30 minutes, preferably 10 minutes to 15 minutes.

at one embodiment is the organic solvent from the group consisting of phosphorus oxides with organic radicals, Phosphoric acid esters, in particular tri-n-butyl phosphate, and mixtures thereof.

bevorzugt. R₁, R₂ und R₃ können jeweils unabhängig voneinander gleich oder verschiedene Alkyl- und/oder Alkoxy-Gruppen sein. Die Alkyl- oder Alkoxygruppen können 1 bis 10, vorzugsweise 3 bis 8, weiter bevorzugt 3 bis 5, Kohlenstoffatome aufweisen.For the phosphorus oxides with organic radicals and / or phosphoric acid esters, the structure is:

prefers. R ₁ , R ₂ and R ₃ may each independently be the same or different alkyl and / or alkoxy groups. The alkyl or alkoxy groups may have 1 to 10, preferably 3 to 8, more preferably 3 to 5, carbon atoms.

For example may be tripropyl phosphate, dibutyl-butyl phosphonate (DBBP), Butyl dibutyl phosphinate, tributylphosphine oxide, trioctylphosphine oxide and / or triisobutyl phosphate. In the above indicated phosphorus oxides, the alkyl radicals Substituted by propyl, pentyl, hexyl, heptyl, and / or butyl radicals become.

Especially Preference is given to using tri-n-butyl phosphate.

Preferably the proportion of the first aqueous phase 10 to 90 wt .-%, more preferably 50 to 60 wt .-%, based on the total weight of the first phase and the second phase.

The Mixing in step a) can be accomplished by dynamic mixing or static Mixing to be done.

At the Dynamic mixing becomes a mechanical element, for example a stirrer in which liquid moves. This movement leads to the formation of an emulsion of the two liquid phases. At the static mixing are the liquid phases to be mixed, for example, via fins and webs, in partial flows split, diverted and merged again. The mixing can here by laminar flow by diffusion and / or be carried out by turbulence in turbulent flow. As static Mixer, for example, a SMX mixer is suitable.

Preferably Centrifuges are used in centrifugation, in which in particular the chambers in which the liquids be centrifuged, made of a corrosion-resistant material consist. Here, stainless steel has proven to be suitable. For example could Cr / Ni / Mo steel and / or duplex steel used become. Alloy 904L 1.4539 and Hastelloy G30 from Haynes International Inc. have proven to be suitable materials.

at In one embodiment, for centrifugation, a flow centrifuge, preferably a plate centrifuge used. The centrifuge can 40 to 150 plates included. The angle of inclination of the plates is preferably up to 40 ° relative to the base area. Through the use of flow centrifuges, the Inventive process operated continuously become.

Preferably the diameter of the centrifuge rotor is 10 to 80 cm, more preferably 50 to 70 cm. In one embodiment can in a continuous centrifugation process 80 to 3000 l / h, preferably 90 to 1000 l / h, liquid mixture, comprising the first and second phases, to be separated.

The inventive method allows smaller amounts of phosphoric acid in a short time easy purify.

With The process of the invention can phosphorus-containing Acid can be freed of impurities by extraction. The extraction comprises the process steps a) to c). At this Extraction, the phosphorus-containing acid goes out of the first aqueous phase in the organic solvent (second Phase) and part of the phosphorus-containing acid as well as the impurities remain in the first aqueous Phase. This aqueous first phase can also be used as a raffinate be designated.

To the isolation of the first phase in step c), which phosphorus-containing Acid as well as the impurities, this raffinate can be subjected again to steps a), b) and c). This process can be repeated 2 to 3 times. Alternatively, in step c) also be isolated the second phase.

• d) Mischen mit einem wässerigen Lösungsmittel, vorzugsweise Wasser,
• e) Separieren der Phasen durch Zentrifugation und
• f) Isolieren der wässerigen Phase, welche die gereinigte Phosphorhaltige Säure enthält,

unterworfen werden.Furthermore, the second phase isolated in step c), which comprises the purified phosphorus-containing acid and the at least one organic solvent, can be used for the further steps

• d) mixing with an aqueous solvent, preferably water,
• e) Separating the phases by centrifugation and
• f) isolating the aqueous phase containing the purified phosphorus acid,

be subjected.

This This process can also be called reextraction. This is the purified phosphorus-containing acid as an aqueous Solution and the organic solvent, which is preferably substantially free of phosphorus-containing acid is, gets back.

The Steps d) to f) can be repeated 2 to 3 times. In the case of discontinuous centrifugation, the steps e) and f) two separate steps. In continuous centrifugation Steps e) and f) form a step.

Further may after the last step f) possibly in the phosphoric acid contained sulfuric acid precipitated by the addition of calcium oxide become.

at Reextraktion are preferably 10 to 90 wt .-%, more preferably 20 to 30 wt .-%, organic solvent, which with the phosphorus-containing acid is loaded with 90 to 10 wt .-%, more preferably from 70 to 80% by weight of aqueous solvent, preferably water, based on the total weight of organic Solvent and aqueous solvent, re-extracted.

The purified by the method according to the invention For example, phosphoric acid can be used in fertilizer production be used.

By The following example is intended to explain the invention in more detail but in no way be limited.

example

1000 kg of pickling acid (77 wt .-% acidity based on the total weight of the solution, wherein the acid content to 60 wt .-% of phosphoric acid and 40 wt .-% of sulfuric acid, based on the total weight of phosphoric acid and sulfuric acid) were with 818 kg of acid-free tributyl-n-phosphate extracted (mixing ratio Wt% -55% / wt-45%, based on the total weight of the extraction mixture). For this purpose, the components were continuously mixed thoroughly in a static mixer with about 100 l / h flow from Sulzer Chemtech AG and then separated in a centrifuge Westfalia Separator GmbH type 1-02-525 at 80,000 g. Subsequently, the phosphoric acid and sulfuric acid were reextracted from the thereby obtained with phosphoric acid and sulfuric acid loaded tributyl-n-phosphate phase (about 1100 kg) with 3.8 t of water. This step was carried out analogously to the first extraction step. There were obtained 4.2 t of purified dilute phosphoric acid / sulfuric acid.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 19703884 [0004]

Claims (10)

Process for the purification of phosphorus-containing Acid, comprising the steps a) mixing a first aqueous phase comprising a phosphorus-containing acid, with a second phase comprising at least one organic solvent, wherein the first and second phases are a liquid two-phase system form, b) separating the phases by centrifugation and c) Isolate the second phase containing the phosphorus-containing acid includes. The method of claim 1, wherein the Phosphorus-containing acid is phosphoric acid. The method of claim 2, wherein the Phosphoric acid to Rohphosphorsäure, prepared from apatite to used phosphoric acid from the quinacridone production and / or used phosphoric acid used for pickling Metal surfaces is used is. Method according to one of the preceding claims, wherein the organic solvent is tri-n-butyl phosphate is. Method according to one of the preceding claims, wherein in step a) the proportion of the first phase is 10 to 90% by weight, based on the total weight of the first and second phase. Method according to one of the preceding claims, wherein the first phase isolated in step c) which residues of the Phosphorus-containing acid and impurities, again the steps a, b) and c) is subjected. Method according to one of the preceding claims, wherein the second phase isolated in step c) which is the purified one Phosphorus-containing acid and the organic solvent includes, the further steps d) mixing with an aqueous Solvent, in particular water, e) Separate the phases by centrifugation and f) isolate the aqueous Phase containing the purified phosphorus acid, subject becomes. Method according to one of the preceding claims, wherein the centrifugation in step b) with 500 to 250,000 g, preferably continuously, is performed. Method according to one of the preceding claims, wherein the centrifugation in step b) discontinuously for 5 min 30 min is performed. Method according to one of the preceding claims, wherein during centrifugation a flow centrifuge, preferably a plate centrifuge is used.