DD205413B1 - PROCESS FOR PREPARING AMMONIUM TRIOXALATOFERRATE (III) TRIYDRATE - Google Patents

Description

Field of application of the invention

The invention relates to a process for the preparation of ammonium trioxalatoferrate (III) trihydrate from iron oxide yellow, oxalic acid dihydrate and ammonia solution.

Characteristic of the known technical solutions

It is known and u. a. by A. Rosenheim, Z. anorg. Ch. 11 (1896) 216, described that ammonium trioxalatoferrate (III) trihydrate can be prepared by incorporating iron (III) hydroxide gel into a hot ammonium hydrogen oxalate solution. This process only leads to dissolution when freshly precipitated iron (III) hydroxide gel is used, whereas aged iron (III) hydroxide gel is sparingly soluble.

Furthermore, before the crystallization of ammonium trioxalatoferrate (III) trihydrate, iron (III) hydroxide precipitates since the composition of the solution differs from that of the salt. The reaction must also be carried out under exclusion of air. The procedure for the preparation and purification of iron (III) hydroxide gel is cumbersome and very time consuming.

It is also known, and by T. Wada, Japanese Patent Publications Japan 8910 ('57), Oct. 19, ref. CA. 52 (1958) P 13206a and Japan 8911 ('57), Oct. 19, ref. C.A. 52 (1958) P13205 i, as well as in the working instruction Fo. A80 (1956) of VEB Laboratory Chemistry Apolda described that ammonium trioxalatoferrate (III) trihydrate can be prepared from ferrous oxalate dihydrate, ammonia solution, ammonium oxalate monohydrate and oxalic acid dihydrate. The iron (II) oxalate dihydrate is oxidized by the addition of 30% hydrogen peroxide solution. As intermediates, depending on the reaction conditions, iron (III) hydroxide, basic iron (III) oxalates, basic ammonium iron (III) oxalates and, with incomplete oxidation, ammonium iron (II) oxalate.

However, part of the oxalic acid is oxidized by hydrogen peroxide. This proportion is always different and probably depends on the feed rate and the mixing of the suspension. As a result, the hydrogen peroxide consumption is significantly higher than the theoretical consumption.

In this process, it is necessary to cool the reaction mixture well. Under certain circumstances, a thick, gelatinous pulp forms for a short time, which has an adverse effect on heat dissipation and reaction in large stirred tanks.

It is further known and described in the working procedure A249 of VEB Laborchemie Apolda that ammonium trioxalatoferrate (III) trihydrate can be prepared by dissolving iron oxide yellow in boiling oxalic acid solution and then adding ammonia solution.

Iron (II) compounds are oxidized by the addition of concentrated nitric acid to iron (III) salts. There is a risk of uncontrolled reactions, which result in a foaming of the boiler and the formation of significant amounts of nitrous gases result.

The dissolution of iron oxide yellow in boiling oxalic acid solution is very slow and incomplete. Due to the incomplete dissolution process, ammonium oxalate monohydrate precipitates as an undesired by-product in different amounts after the addition of ammonia solution. It is generally known that iron oxide yellow (a-FeOOH) dissolves well only in hydrochloric acid.

Object of the invention

The object of the invention is to design the process for preparing ammonium trioxalatoferrate (III) trihydrate from iron oxide yellow, oxalic acid dihydrate and ammonia solution in such a way that it can be operated with high space-time yield, high material economy and technical safety.

Explanation of the essence of the invention

The object of the invention is to achieve a process by which the reaction of iron oxide yellow takes place completely and in a short time and the by-product ammonium oxalate monohydrate can be used as the starting material for new reactions. In order to exclude spontaneous side reactions, should be worked without the addition of oxidants.

It has surprisingly been found that iron oxide yellow in a boiling solution containing the components of oxalic acid and ammonia in a molar ratio of 1.06 to 2, preferably 1.07 to 1.08, in 0.5 to 2 hours completely dissolves.

The excess oxalic acid is neutralized after completion of the dissolution with ammonia solution and the resulting Ammoniumoxalatmonohydrat together with Oxalsäuredihydrat in a molar ratio of 1 to 1.12 to 3, preferably 1 to 1.15 to 1.16, used for new approaches.

Under these reaction conditions, the addition of oxidants is not necessary.

The reaction proceeds according to the following reaction scheme:

O,

^{3 H} 2 ^C 2 ° 4 (aq.) ^{+ Б 1 TH} 3 (aq.) -

(HH) C 0 + 3 HC 0 .2 E 0 75 - 80 ° С _д

2PeO (OH), _{s #)} ^w * bi K ₂ ^ ₂ U ₄ ^

(Aq.)

+ 2H ₂ O

10 "G" r ™ ν (aq.) * ~ ^{2 (i} 'V.

^{3 H} 2 ° (s.)

Pe (G ₀ OJ

The technical economic effects are due to the fact that the inventive method can be carried out with high yield and good quality in a short reaction time and most effective material use, as by the reaction of the invention, the well-known slow and incomplete dissolution of iron oxide yellow (a-FeOOH) in different Solvents, with the exception of hydrochloric acid, significantly faster and complete. The by-produced ammonium oxalate monohydrate is used as starting material. The process according to the invention can be used both on a laboratory scale and in an industrial scale, with ammonium trioxalatoferrate (III) trihydrate being obtained in good yield and quality as a crystalline, light green product, regardless of the reaction volume

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

embodiments

In a 2000 liter stirred tank with steam heating, 225 kg of oxalic acid dihydrate are dissolved in 1000 liters of 35 ° C warm, distilled water. At this temperature the solution is neutralized with 25% ammonia solution, ie a pH of 7.5 is set. Subsequently, 260 kg of oxalic acid dihydrate are added and the solution is heated to 75 ° C-80 ° C. To the reaction solution, 106 kg of iron oxide yellow are added. Now is heated to boiling temperature and worked under the greatest possible exclusion of light. After 1-2 hours, the yellow iron oxide has completely dissolved and the solution is colored dark green. The solution is allowed to cool to 50 ⁰ C and neutralized the excess oxalic acid with 25% ammonia solution. In this case, a pH of 6.0 to 6.3 is set.

The solution is filtered and then concentrated to a density of 1.17 to 1.18 g · cm ^"3 at 95 ⁰ C. The solution is cooled in a vacuum crystallizer at 15 ° C. The precipitated Ammoniumoxalatmonohydrat is separated by centrifugation from the solution. This is used for formulations according to Example 2. The remaining solution is concentrated to a density of 1.36 g · cm ^-3 at 95 ° C. The pH of the solution is, if necessary, adjusted with 25% strength ammonia solution to 6.0-6.3 and the solution in a vacuum crystallizer at 10 ⁰ C cooled

 By centrifugation, the crystal pulp is separated into crystals and mother liquor. Yield: approx. 400kg without mother liquor.

Example 2:

In a 2000-liter stirred tank with steam heating 255kg Ammoniumoxalatmonohydrat 1 000 liters of 50 ⁰ C are dissolved warm distilled water. The pH of the solution is readjusted to 7.5 with 25% ammonia solution and then 260 kg of oxalic acid dihydrate are added to the solution. Now, the solution is heated to 75 ° C-80 ° C and enters 106 kg of iron oxide yellow. The solution is heated to boiling with exclusion of light. After 1-2 hours, the dissolution of iron oxide yellow is completed. The further procedure is as described in Example 1. Yield: approx. 400kg without mother liquor.

Example 3:

In an omlml Erlenmeyer flask, 29.8 g of oxalic acid dihydrate are dissolved in 150 ml of distilled water while heating to 35 ° C. and stirring. The solution is neutralized with 25% ammonia solution, ie adjusted to a pH of 7.5. If one adds 34.5 g of oxalic acid dihydrate to the solution and heated to 80 ⁰ C.

Then 14 g of iron oxide yellow are added and the solution is heated to boiling with exclusion of light. During the reaction phase, the liquid level is kept constant by adding distilled water. After about 1.5 hours, the yellow iron oxide has completely dissolved. It is now the pH with 25% ammonia solution to 6.0 to 6.3, filtered, the dark green solution, concentrated under exclusion of light to a density of 1.18g · cm " ³ at 95 ⁰ C and then cooled 15 ° C from. the precipitated Ammoniumoxalatmonohydrat is filtered off. the remaining solution is concentrated under exclusion of light to a density of 1.36 g · cm cjiä "" ³ at 95 ⁰ C and the pH adjusted to 6.0-6.3. It is slowly cooled to 10 ^° C., the precipitated crystals are filtered off with suction and washed with a little cold ethanol. Yield: 50 g.

Claims (4)

claims: A process for the preparation of ammonium trioxalatoferrate (III) trihydrate from iron oxide yellow, oxalic acid dihydrate and ammonia solution, characterized in that iron oxide yellow is reacted with a boiling solution of oxalic acid and ammonia in a molar ratio of 1.06 to 2: 1. 2. The method according to item 1, characterized in that the molar ratio of oxalic acid and ammonia in the boiling solution is 1.07-1.08: 1. 3. The method according to item 1, characterized in that the resulting in the reaction by-product Ammoniumoxalatmonohydrat with oxalic acid dihydrate in a molar ratio of 1: 1.12 to 3 is used as the starting material. 4. The method according to item 3, characterized in that ammonium oxalate monohydrate and oxalic acid dihydrate in a molar ratio of 1: 1.15 to 1.16 is used.