JPS6241174B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the oxidation of primary thallium compounds to secondary thallium compounds. Oxythallation reactions are well known and detailed in the literature. These reactions involve the addition of inorganic thallium salts to unsaturated organic substances such as olefins, acetylenes, ketones or aldehydes. US Patent No.
No. 3,641,067, Kruse discloses the use of thallium carboxylates, such as thallium acetate, to oxidize olefins in acid solutions to the corresponding epoxides. In order to put this process into practical use, an economical method for oxidizing thallium() to thallium() must allow recycling of the valence of thallium. MacLean et al., in US Pat. No. 3,479,262, propose the electrolytic oxidation of an acid solution of thallium sulfate ( ) to thallium sulfate ( ) and the use of the resulting acid solution for olefin oxidation. The use of molecular oxygen is described in U.S. Pat. No. 3,399,956;
Proposed in Nos. 4115419 and 4192814. When using molecular oxygen, it is generally necessary to use additional catalysts and promoters, and from the viewpoint of economy, it is necessary to use high pressure oxygen. Moreover, high alloy equipment is usually required in molecular oxygen processes due to the use of acidic media in the presence of oxygen. U.S. Pat. Nos. 4,115,419 and 4,115,421 disclose the use of organic hydroperoxides in the oxidation of acidic solutions of thallium ( ) to (acidic solutions of) thallium () and the further use of group noble metal compounds as catalysts. It suggests that there is a sex.
Organic hydroperoxide processes have the disadvantages of expensive noble metal catalysts and the problem of disposal of organic by-products produced from hydroperoxides. US Pat. No. 4,226,790 suggests the use of organic peracids for the oxidation of thallium () to thallium (). This process not only has the disadvantage of producing undesirable by-products, namely carboxylic acids, which need to be recovered, but also the extremely expensive ruthenium or manganese, which needs to be separated from the (reaction) solution. It also has the disadvantage of using catalysts such as 〓〓〓〓
In U.S. Pat. No. 3,436,409, Hill et al. propose that thallium can be regenerated by known techniques, such as chemically, such as by reaction with molecular oxygen, hydrogen peroxide, and the like, or by electrolytic methods. Says. However, Hill et al. do not disclose how hydrogen peroxide can be utilized for this purpose. This mention that hydrogen peroxide oxidizes thallium () to thallium () is probably from Zeit.Anorg.Chem., No. 48.
Based on the text by Rabe, Vol. 427-440 (1906). The reaction between elemental thallium and its compounds using hydrogen peroxide was first described by Schonbein in 1864, who showed that hydrogen peroxide first oxidized thallium oxide to higher oxides and then converted it to higher oxides. Rabe said he observed that it reduced to produce oxygen and reacted with higher oxides, releasing that oxygen. Rabe has shown that thallium oxide, thiocholate brown, can be produced in strongly alkaline solutions using a 100% excess of hydrogen peroxide.
found out. The reaction yield based on thallium is 4
% potassium hydroxide solution (PH13.8) was 98%; 2-1/2% potassium hydroxide solution (PH10.3)
In this case, the thallium yield dropped to 81%. Perhaps the extremely low solubility of thallium hydroxide ( ^10-53 solubility product) explains the ability of hydrogen peroxide to oxidize thallium (2) to thallium (2) at a pH of 10 or higher. 1982 12
In US Patent Application No. 447368, co-filed by Lance R. Byers on May 6th, it was found that the reaction rate of hydrogen peroxide is dependent on pH. Dipersulfate ion, also known as peroxodisulfate ion, is known as a strong oxidizing agent that works by a different mechanism than hydrogen peroxide. The reaction mechanism is explained by Kimura et al., “Oxidation reaction of Tl() to Tl() by peroxodisulfate ion: Reaction rate and mechanism in aqueous solution, Part 1”, Bull.Chem.Soc., Japan, Vol. 53. (1980)
It has been reported in The reaction in 0.01M perchloric acid (PH2) is very slow, and thallium () is produced in 149 hours.
Kimura et al. report that the reaction is a chain reaction in which the initial step is the formation of two sulfuric acid (salt) free radicals by thermal decomposition of dipersulfate ions. Unlike both persulfate ion and hydrogen peroxide, monopersulfate (peroxo-sulfate) ion is widely used.
It has been found that it is effective in oxidizing thallium ( ) to thallium ( ) over a pH range and with high conversion efficiency. For those skilled in the art, for example U.S. Pat. No. 4,049,786
Monopersulfate ions can be supplied either by a preferred method such as reacting hydrogen peroxide with sulfuric acid to form monopersulfuric acid (Carrow's acid) as taught in No. 1, or by using a monopersulfate salt. is obvious. The conversion rate of thallium ( ) to thallium ( ) using dipersulfate ions is almost quantitative at pH 15, and drops below 50% at pH 5 or lower. With monopersulfate ions, conversion is essentially quantitative even down to pH 1, where monopersulfate rapidly hydrolyzes to hydrogen peroxide and sulfuric acid. Oxidation of thallium ( ) by monopersulfate ions does not require a catalyst. Preferred embodiments of the method will become clear to those skilled in the art from the following non-limiting examples. Example 1 10 mmol of thallium (), or 2.524 g
of Tl ₂ SO ₄ was dissolved in 100 ml of water. 18M sulfuric acid and
The PH was adjusted and maintained at the desired value using 10M potassium hydroxide. A stoichiometric amount of Caro's acid (monopersulfuric acid) was added. The conversion to thallium () was then measured. The results are shown in Table 1. Tl()% and Tl()% in Table 1 indicate residual Tl()% and generated Tl()%, respectively, based on the number of moles of Tl() added at the beginning of the experiment. For example, in Experiment 1 in Table 1, for the initially added Tl() [10 mmol as mentioned above],
After 20.0 hours, 20.6 mol% [2.06 mmol] of Tl() remained, meaning that 79.4 mol% [7.94 mmol] of Tl() was produced. The same applies below. In experiments 2 and 3, it was not opened to the atmosphere, but connected to a gas reservoir, eliminating the possibility of oxidation of thallium by oxygen from the atmosphere. In other experiments (Experiment 1 and Experiments 4-10), reactions were carried out in contact with air (open to the atmosphere). Experiments 1 to 3 are experiments outside the scope of the present invention (PH 0.95). As mentioned above, at pH below 1, monopersulfuric acid rapidly hydrolyzes into hydrogen peroxide and sulfuric acid. It is known that hydrogen peroxide is easily decomposed due to the presence of heavy metals and other causes. Experiments 1 to 3 were all PH
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0.95 (However, as mentioned above, there is a difference between Experiment 1 and Experiments 2 and 3 regarding the presence or absence of contact with air), Tl()% and Tl()
There are significant differences in the percentages. This means that Tl at PH0.95
This means that the oxidation reaction of ()→Tl() results in widely varying experimental results due to various factors that are difficult to control (decomposition of monopersulfuric acid, further decomposition of generated hydrogen peroxide, etc.). Experiment 1 (Experiments 4 to 10)
), but the residual (unconverted) Tl()% is very high (20.6%). Experiments 4 to 10 are experiments within the scope of the present invention. Experiment 6 (PH4.50) had some residual Tl()% (9.4%)
However, in other experiments Tl
() Remaining % is zero or very small. This shows that the oxidation reaction of Tl()→Tl() according to the present invention proceeds almost quantitatively (or at a very high conversion rate) over a wide PH range, almost independently of the PH. This is in contrast to the significant PH dependence in the case of the comparative example (using dipersulfate) described below. Comparative example 1 10 mmol thallium (), 2.524 g
Tl ₂ SO ₄ was dissolved in 100 ml of water. 18M sulfuric acid and 10M
The pH was adjusted and maintained at the desired value using sodium hydroxide. A stoichiometric amount of 2.282 g of ammonium dipersulfate was added. After 4 hours, thallium ()
The conversion (rate) to was measured. The results are shown in Table 2. In addition, Tl()% and Tl()% in Table 2
has the same meaning as described for Table 1 in Example 1. In the even-numbered experiments, the flask was connected to a gas bottle without being exposed to the atmosphere to eliminate the possibility of oxidation of thallium ( ) to thallium ( ) by oxygen in the air. In the odd-numbered experiments, reactions were carried out in contact with air (open to the atmosphere).
As is clear from the results in Table 2, in the experiments at PH2, exposure to the atmosphere had a severe negative effect on the oxidation of Tl()→Tl(), and this tendency was also observed in the experiments at PH15; It's not terrible.
In experiments with pH 5 to 12, there was almost no effect of opening to the atmosphere, but even if there was, it was very small. Comparing the results in Table 2 with those in Table 1, we can see that the conversion rate of the Tl() → Tl() oxidation reaction with dipersulfate is very strongly affected by pH (very low at low pH). It will be appreciated that this is in contrast to the result of the oxidation reaction of Tl() → Tl() with monopersulfate in that only the conversion rate is obtained).

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Claims (1)

[Claims] 1. A method for oxidizing thallium () to thallium () in an aqueous solution, which comprises adjusting the pH of the thallium () aqueous solution to between PH2 and 15, and adding a monopersulfate compound thereto.