DE19702814A1 - Recovering iodine from iodo-aromatic compounds - Google Patents

Abstract

Recovery of iodine from iodo-aromatics (I) in acid solution is carried out in presence of a reducing agent (II) at 100-140 deg C, optionally followed by oxidation with hydrogen peroxide, chlorine or hypochlorite and sublimation of the liberated iodine. The reaction with (II) may be carried out in a pressure reactor at 100-140 (preferably 130) deg C. (I) are iodine-containing X-ray contrast media or their intermediates. The process comprises reacting (I) in dilute or concentrated hydrochloric acid in presence of sodium bisulphite, sulphur dioxide or hypophosphorous acid or its salts, at 100-140 (preferably 130) deg C in a pressure reactor.

Description

The invention relates to a process for recovering iodine from aromatic iodines in dilute or concentrated acidic solution in the presence of a reducing agent at temperatures of 100 ° C to 140 ° C, preferably 130 ° C in the pressure reactor optionally subsequent oxidation and subsequent sublimation of the released iodine.

The following disposal methods are known from the prior art:

• 1. Total combustion with loss of iodine.
• 2. discharge into the sewage treatment plant; Disadvantages are the high AOX load and the Loss of iodine.
• 3. Cleavage with concentrated sulfuric acid at approx. 100 ° C. This procedure is uneconomical and has not disposed of products from the stages of Iopromide and iotrolan synthesis suitable.
• 4. Hydrogenation in alkaline solution (DE 42 36 724 A1; WO 94/10083) is an expensive one Method that is also not suitable for all wastes containing iodine.
• 5. Oxidation with ozone or hydrogen peroxide under UV radiation. A uneconomical process for the disposal of large quantities.
• 6. Reduction using dithionite, aluminum, zinc, tin or silicon in alkaline or acidic solution.

The invention solves the problem of disposal of iodine-containing products within X-ray contrast media production as a cheap, universally applicable process with decomposition of the iodine aromatics, the iodine being recovered in pure form can be.

The invention includes a method for the disposal of aromatic iodines in acidic Solution in the presence of a reducing agent and subsequent sublimation of the released iodine; specifically a process for iodine recovery Iodinated aromatics in dilute or concentrated acidic solution in the presence of a Reducing agents at temperatures from 100 ° C to 140 ° C, preferably at 130 ° C, if appropriate in the pressure reactor, if appropriate subsequent oxidation by means of Hydrogen peroxide, chlorine or hypochlorite and subsequent sublimation of the released iodine. The pressure to be used is below 10 bar, in particular below 5 bar, usually in the range 2-3 bar.  

More specifically, a process in which iodine-containing x-ray contrast agents and their intermediates (e.g. iopromide, jopamidol, iodamic acid, Johexol, AT acid, TAMIP monoamide) in dilute or concentrated hydrochloric acid in the presence of sodium bisulfite, sulfur dioxide, dithionite, rongalite, phosphorous or hypophosphorous acid or its salts at temperatures from 100 ° C to 140 ° C, preferably 130 ° C are implemented in the pressure reactor.

The process has the following advantages:

• 1. Complete deiodination without the use of catalysts such as palladium Coal. Therefore no problems with catalyst poisons and with the separation and Recovery of expensive precious metal catalysts.
• 2. Very high concentrations (<300 g / liter) can be used. Even poorly soluble compounds can be implemented as a suspension.
• 3. There is no need for complex enrichment of the iodine aromatics. A mother liquor containing 1.5% iodine aromatics is also complete deodable.
• 4. Also only incomplete according to the sulfuric acid process mentioned Deodable iodoaromatics are produced using the process described here implemented quickly and completely.
• 5. The deiodinated aromatics can be added by adding the required amount Sodium hydroxide solution is almost completely precipitated and incinerated. This reduces the wastewater pollution caused by COD (chemical oxygen demand) significantly reduced.
• 6. Water is the only solvent. Environmental pollution from organic So there are no solvents.
• 7. It is possible to control the reaction by suitable dosage of the reducing agent to drive in such a way that elemental iodine is formed and therefore in the hydrogenation process additional reaction stage required for iodine extraction can be omitted.
• 8. Because of the cheap raw materials, the short reaction time and the high possible reactant concentration is a very inexpensive process.

The following new method shows in laboratory tests with TAMIP monoamide (5-amino 2,4,6-triiodoisophthalic acid mono- (2,3-dihydroxy-propyl) -amide), TIP-diamide chloride (5-methoxyacetylamino-2,4,6-triiodoisophthalic acid (2,3-dihydroxypropyl) amide chloride) and iopromide promising results:

example 1 (Iopromide)

Dissolve 79.1 g iopromide and suspend in
120 ml conc. Hydrochloric acid + 40 ml water,
Heat to 100 ° C and slowly with
14.25 g sodium disulfite, dissolved in 35 ml water
drop.

The expected amount of iodine forms in the reaction mixture over the course of about 6 hours. This sublimates out of the reaction mixture and can be deposited for isolation.
Yield: 36.2 g iodine = 95% of theory Th.

Deodorization is more economical and more universally applicable at elevated temperature under pressure:

Example 2 (Iopromide + H ₃ PO ₂ , 130 ° C, 2 h)

33 g (0.0417 mol) iopromide (contains 15.9 g iodine = 0.1250 mol)
21 ml (0.2440 mol) hydrochloric acid conc.
8.7 g hypophosphorous acid 50% (stoichiometric: 8.27 g = 0.0626 mol)
with water
Fill up with 100 ml.
Heat to 130 ° C in an autoclave.
Exothermic reaction: at bath temperatures of 140 ° C the internal temperature at 3 bar was 139 ° C
As the reaction progressed, the pressure rose to 3.9 bar at 130 ° C. IT.
→ AOX: 756 mg / L
→ After adding sodium hydroxide solution, vigorous precipitation at pH 3.

Example 3 (TAMIP diacetate + H ₃ PO ₂ , 130 ° C, 2 h)

29.9 g (0.0417 mol) of TAMIP diacetate (contains 15.9 iodine = 0.1250 mol)
21 ml (0.2440 mol) conc. Hydrochloric acid,
8.7 g hypophosphorous acid 50% (stoichiometric: 8.27 g = 0.0626 mol)
with water
Fill up with 100 ml.
Heat to 130 ° C in an autoclave.
→ Temperature rise: IT = MT = 135 ° C

Example 4 (TIP diamide chloride + H ₃ PO ₂ , 130 ° C, 2 h)

33.6 g (0.0417 mol) TAMIP monoamide (contains 15.9 g iodine = 0.1250 mol)
21 ml (0.2440 mol) hydrochloric acid conc.
8.7 g hypophosphorous acid 50% (stoichiometric: 8.27 g = 0.0626 mol)
with water
Fill up with 100 ml.
Heat to 130 ° C in an autoclave.
TIP diamide chloride dissolves at around 105 ° C. No discernible exotherm.
Slow pressure increase as with iopromide (up to approx.3.9 bar).

Example 5 (Methyl tetrachloride + H ₃ PO ₂ , 130 ° C, 2 h)

26.8 g (0.0209 mol) methyl tetrachloride (contains 15.9 g iodine = 0.1250 mol)
21 mol (0.2440 mol) hydrochloric acid conc.
8.7 hypophosphorous acid 50% (stoichiometric: 8.27 g = 0.0626 mol)
with water
Fill up with 100 ml.
Heat to 130 ° C in an autoclave.

Example 6 (Iotrolan + H ₃ PO ₂ , 130 ° C, 2 h)

33.9 g (0.5 × 0.0417 mol) iopromide (contains 15.9 g iodine = 0.1250 mol)
21 ml (0.2440 ml) hydrochloric acid conc.
8.7 hypophosphorous acid 50% (stoichiometric: 8.27 g = 0.0626 mol)
with water
Fill up with 100 ml.
Heat to 130 ° C in an autoclave.

Example 7 (TAMIP monoamide raw mother liquor)

100 ml TAMIP mono amide mother liquor (contains approx. 15 g / L aromatic iodine and 6% HCl) and 0.8 ml hypophosphorous acid 50%, are in the autoclave for 2 hours Heat 130 ° C. According to HPLC, all known ones are present in the mother liquor Iodine aromatics have been completely deodized. The reaction product is the halogen-free one Aminoisophthalic acid. The iodine can be removed from the reaction by conventional methods mixture can be obtained.

Other iodine-containing wastes can be added to the TAMIP monoamide raw mother liquor will. This makes the disposal of the iodoaromatics at the same time Recovery of elemental iodine economically.

Example 8 (with iodine recovery)

182 ml of raw TAMIP mother liquor (4.5 iodide in the form of aromatic iodine), 11.8 ml of distillation bottoms (2.7 g iodine in the form of aromatic iodine) and 8 g of sodium bisulfite solution (40%) are within 1-2 hours heated to 130 ° C (pressure rise to 2 bar);
Heated at 130 ° C for 2 hours,
let cool to 25 ° C within 2-3 hours,
adjust to pH 3 with approx. 40 g sodium hydroxide solution (50%), the aminoisophthalic acid precipitates, the precipitate is filtered off,
the iodide-containing filtrate is mixed with 20 g of hydrochloric acid (36%);
9.1 g of hydrogen peroxide solution (17%) are added and a redox potential of 450 mV is set and the precipitated iodine is filtered off.
Yield: 8.0 g = 97% of theory. Theory,
the iodine can be sublimed for further purification.

Claims (3)

1. Process for the recovery of iodine from aromatic iodines in acid solution in Presence of a reducing agent at temperatures from 100 ° C to 140 ° C, optionally subsequent oxidation using hydrogen peroxide, chlorine or Hypochloride and, if necessary, subsequent sublimation of the released Iodine. 2. Process for the recovery of iodine from aromatic iodines in acidic solution Presence of a reducing agent at temperatures from 100 ° C to 140 ° C, preferably 130 ° C in the pressure reactor, optionally subsequent oxidation using hydrogen peroxide, chlorine or hypochlorite and optionally Subsequent sublimation of the released iodine. 3. The method according to claim 1, wherein as iodine aromatics containing iodine X-ray contrast media and their intermediates in diluted or concentrated hydrochloric acid in the presence of sodium bisulfite, sulfur dioxide or hypophosphorous acid or its salts at temperatures from 100 ° C to 140 ° C, optionally at 130 ° C in the pressure reactor.