HU194146B - Process for recovering red phosphorus applied during the preparation of ethyl iodide from alcohol and iodine in the presence of red phosphorus - Google Patents

Abstract

Ethyl-iodide is prepd. from ethyl-alcohol and iodine with an excess 10-40 pref. 18 vol.% red phosphorous. The raw product is stirred with aq. sodiumhydrogen sulphite. The distillation residue of the reaction is reacted with this soln. for the regeneration of red phosphorous.

Description

This application relates to a commercially applicable red phosphorus recovery process for the preparation of ethyl iodide.

Ethyl iodide is used in the manufacture of important industrial raw materials, pharmaceuticals, pesticides and other chemicals. There are several methods for preparing it in the literature. Chemische Berichte can be prepared from diethyl sulfate and potassium iodide as described in Volume 38, p. 2327, or by reaction of ethyl alcohol with phosphorus pentajodide as described in Volume 87, p. However, the process for direct preparation of ethyl alcohol and elemental iodine is more preferred. Such as Organic Synthesis II. 399-39, which is carried out by reaction of ethanol with elemental iodine in the presence of yellow and red phosphorus. The process is described in detail for methyl iodide but it is mentioned that ethyl iodide can be prepared in the same way.

The main disadvantage of the process is that the application of the method requires special equipment even in the order of kg and although the yield calculated for iodine is good, the amount of phosphorus used is very high. Apart from economic reasons, this excess is also harmful for environmental reasons, and the description does not provide any solution.

Mercury treatment is recommended for the purification of the product obtained, but it is quite dangerous because it produces extremely toxic ethylmercuric iodide, especially when exposed to light. (Organic Synthesis Volume II, p. 403, p. 13)

The reaction equation of the process is as follows:

C ₂ H ₅ OH + 3 I ₂ > 2 P = 6 C ₂ H _s í + 2 Η ₃ ΡΟ ₃

In a preferred embodiment of the process, ethyl alcohol and red phosphorus are reacted with elemental iodine. The reaction mixture is heated to reflux and the resulting product is distilled off with excess ethyl alcohol. Ethyl alcohol is removed from the distillate by washing with water and the residue is stirred with aqueous sodium bisulfite solution. The resulting ethyl iodide was 99.7% pure and stable. The aqueous sodium bisulfite base is added to the evaporation residue to give a red phosphorus precipitate which can be reused.

The reaction can be carried out using either anhydrous or 96% ethyl alcohol. A minimum of 2.3 to 3.2 moles of ethanol per mole of iodine is required to produce a minimum loss of iodine of ca. 5 t%. From an industrial point of view, it is preferable to conduct the reaction using 3-3.2 moles of ethanol. Thus, it can be achieved that the iodine can be added to the ethyl alcohol red phosphorus suspension at a much faster rate compared to the methods described in the literature. Of course, about 90% by weight of the excess ethyl alcohol can be recovered from the aqueous mother liquor formed during the processing of the reaction mixture.

For safety and accident prevention reasons, only red phosphorus is used, preferably in an amount of 15-25% by weight, preferably 20% by weight, based on the theoretical amount of phosphorus, to achieve a 95% yield of iodine ethyl iodide.

According to our surprising experimental experience, which forms the basis of the present invention, a portion of the reported amount of phosphorus intake can be recovered in a simple manner.

The amount of phosphorus recovered can be further increased and the quality of ethyl iodide is improved by mixing the product obtained after washing with water with an aqueous sodium bisulfite solution and reacting this sodium bisulfite solution with the evaporation residue, as it is also removed from the ethyl iodide. phosphorus compounds distilled with it.

From the resulting mixture, the recovered red phosphorus can be recovered by filtration and reused without further purification and drying, in an amount of 40-50% by weight.

Surprisingly, only 65-70% by weight of the phosphorus actually reacted, and 30-35% by weight of the phosphorus reacted by the process according to the invention, can be recovered by the simple methods mentioned above. The mother liquor remaining after phosphorus removal does not contain any toxic substances and is therefore not polluting.

The procedure is illustrated by the following example without limiting the scope of the invention to the example.

Example

Into a 1250 L apparatus, 480 L (370 kg) of anhydrous ethyl alcohol and 60 kg of red phosphorus are weighed. While stirring at room temperature, 600 kg of iodine was added in 30 kg portions over 1 hour. During the addition, the temperature was kept below 50 ° C. At the end of the addition, the working opening of the reflux condenser is closed and the contents boiled for 2 hours. By the end of the second hour, the internal temperature has dropped from an initial 80 ° C to 72 ° C. This indicates the completion of the reaction. The apparatus is set up for distillation and, until an internal temperature of 98 ° C is reached, approx. 300 l of distillate are collected. The distilled alcohol-ethyl iodide mixture was stirred with 300 L of water. After separation, the aqueous phase is combined with the distillation residue, and the ethyl iodide phase is mixed with 12 kg of sodium bisulfite in 50 kg of aqueous solution. The ethyl iodide phase should be colorless. Otherwise, mix again with a new portion of sodium bisulfite solution. The separated sodium bisulfite solution was combined with the distillation residue, which already contained the aqueous phase, and stirred at room temperature for half an hour, then the precipitated red phosphorus was filtered off, washed with water (30 L) and reused without drying. Weight: 40 kg of wet phosphorus (27 kg based on test drying) is recovered, which is 45% of the initial phosphorus intake. The ethyl iodide separated from the sodium bisulfite wash is dried over anhydrous sodium sulfate or calcium chloride.

99.7% ethyl iodide KF vC content: 0.05%.

From the aqueous mother liquor obtained after phosphorus filtration, 140 l (110.6 kg) of 96% ethanol are recovered by distillation and can be recycled to the next production.

Yield: 81%.

Claims (2)

CLAIMS 1. A process for recovering red phosphorus from ethyl iodide production from ethanol and iodine, comprising reacting ethyl iodide, which is distilled from the mixture, and washed with water with 1-10 wt.% Sodium bi-21 by weight of iodine added, the phosphorus precipitated is filtered off. A process according to claim 1, wherein the aqueous solution contains 20% by weight sodium bisulfite. 194.146 sulfate - 15-25% aqueous solution is mixed, the sodium bisulfite solution is separated and the sodium bisulfite solution is distilled at room temperature without drawing