RU2481418C1 - Method of producing rhenium methylate solutions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: electrochemical stripping of rhenium in the disclosed method is carried out with anode polarisation and at constant current potential parameters in anhydrous methyl alcohol which contains lithium chloride LiCl as an electroconductive additive, content of which is determined based on the amount needed to ensure sufficient conductivity of the electrolyte. The cathode used is an inert electrode and the fixed anode potential value E≤3.50±0.001, which enables to obtain a product of a defined composition which has the formula Re₄O_6-y(OCH₃)_12+y, where 0≤y≤ 4.

EFFECT: low temperature of the rhenium stripping process, high output and purity of the product.

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Description

The invention relates to the field of chemistry and technology of rhenium, in particular the electrochemical method for producing rhenium methylates, which can be used as precursors for the production of rhenium alloys with other refractory metals, ultrafine (> 100 nm) and nanoscale (<100 nm) powders of functional materials based on rhenium (metallic rhenium, rhenium (IV) and (VI) oxides), which have found their application in cross-condensation and reductive dehydration of alcohols in order to obtain motor fuels and / or additives to them.

Alkox technology is promising for the production at low temperatures (<500 ÷ 900 ° C) of materials (individual oxides, their solid solutions, complex oxides, metals, alloys) with increased phase and chemical uniformity and adjustable particle size distribution, as well as ultrafine and nanoscale materials .

The known method [Druce JGF Ethoxides and isopropoxides of manganese and rhenium // J. of the Chemical Society. 1937. P.1407-1408] obtaining rhenium ethylate Re (OEt) ₃ by reacting Re ₃ Cl _{9 of} 1.46 g in ether with an alcoholic solution of NaOEt (0.34 g of Na; 30 s.p. EtOH). Upon evaporation, rhenium ethoxide remained in the residue.

Significant disadvantages of the method are the complexity, the need to use sophisticated equipment, the complexity of automation of the process, obtaining the starting compounds is an independent synthesis task.

The known method [Kovsman EP et al. A method for producing titanium alkoxides, published / RF Patent No. 2079503] for producing titanium alkoxides (titanium tetrabutoxide (TBT) and tetraisopropoxide) by electrochemical dissolution of an anode of titanium in an electrolyte containing alkanol (butanol or isopropanol) and lithium chloride at current density 2-6 a / dm ² with the circulation of the electrolyte, the return of lithium chloride and an alkanol in the desired product and isolating the process, characterized in that the anode is made of titanium-metal and the process is carried out at a flow rate of the electrolyte in mezhelektro gap SG is not less than 5 cm / s. The disadvantage is the occurrence of secondary chemical reactions with products of electrochemical oxidation.

The closest technical solution is the method [Scheglov P.A. Mono-, bi- and trimetallic oxoalkoxy derivatives of rhenium (synthesis, properties and application). Disser. for a job. Ph.D. sciences. - M .: MITT them. MV Lomonosov, 2002, 139 pp.] Synthesis of Re ₄ O ₂ (OMe) ₁₆ and Re ₄ O ₆ (OMe) _{12 by the} electrochemical method. Anodic dissolution of rhenium in MeOH medium (Me is a methyl group) was carried out in the presence of a LiCl background electrolyte (0.025 mol / L) both without separation of the cathode and anode spaces, and with their separation through a porous glass membrane. The process was conducted at 18 ÷ 20 ° C. The current efficiency was 62 and 79%.

The main disadvantage of this method is the instability of obtaining synthesis products.

The technical result of the invention consists in lowering the temperature of the process, increasing the yield of the product, obtaining a product not contaminated with chlorine, since the content of the electrically conductive additive is significantly reduced, the technological flexibility of the process and relatively low costs.

The technical result is achieved by the electrochemical method, which consists in the anodic dissolution of rhenium in anhydrous methyl alcohol in the presence of an electrically conductive additive, characterized in that the dissolution of rhenium is carried out at a fixed value of the anode potential E≤3,50 ± 0,01, which provides a product of a certain composition, corresponding the general formula Re ₄ O ₆ -y (OCH ₃ ) _{12 + y} , where 0≤y≤4.

The essence of the proposed method is as follows. An electrolyte is placed in the electrochemical cell, which is dehydrated methyl alcohol with a conductive additive (LiCl) dissolved in it and pre-dried. The concentration of LiCl is determined on the basis of the amount necessary to ensure sufficient conductivity, usually 0.03-0.08 mol / L. An inert electrode is used as the cathode, and metallic rhenium is used as the anode. The dissolution of rhenium is carried out at a fixed value of the potential of the anode, which determines the course of the anode reaction of interest, which allows to obtain a product of a certain composition Re ₄ O _6-y (OCH ₃ ) _{12 + y} , where 0≤y≤4 (Figure 2). The potential of the anode is determined using polarization and depolarization curves obtained using an electrochemical research and technological complex (EHK-1012, IP Tetran LLC) using a non-compensation method for measuring potential [RF patent No. 2106620 of 04/26/96].

It has been established that the literature does not describe the influence of the electrode potential on the production of rhenium oxomethylates of a certain composition.

Example 1. Anodic dissolution of metallic rhenium in methyl alcohol with the addition of LiCl 0.05-0.06 mol / L was carried out in a two-chamber flow cell made of fluoroplastic (Figure 1), with a total volume of 100 ml. Cell chambers are separated by MK-40 cation-exchange membrane. The electrolyte flow at a given speed in the installation is provided by a peristaltic pump.

Using polarization and depolarization curves obtained using EHK-1012, technological parameters were selected: the dissolution potential of rhenium E = 2.91 V, the accuracy of maintaining the potential ΔE = ± 0.01 V, temperature - 20-25 ° C, flow rate - 0.4 l / h The selected parameters ensure the occurrence of a single reaction at the anode at the maximum possible speed and productivity of the process, limited by the technical characteristics of EHK-1012.

At the end of the experiment, analyzes of samples of electrolyte solutions were carried out using IR spectroscopy, EPR spectroscopy; The rhenium concentration in anolyte and catholyte was determined by the photometric method.

The products of electrochemical synthesis in methyl alcohol in the presence of an electrically conductive additive at a potential of E = 2.91 ± 0.01 V are the rhenium complex (VI) Re ₄ O ₆ (OCH ₃ ) ₁₂ , where one terminal oxoligand per rhenium atom (Re bond = O).

Example 2. Anodic dissolution of metallic rhenium in methanol with the addition of LiCl 0.05-0.06 mol / L was carried out in a two-chamber flow cell made of fluoroplastic (Figure 1).

With technological parameters: the rhenium dissolution potential is E ≤ 2.91 ± 0.01 V, the temperature is 20-25 ° C, the flow rate is 0.4 l / h. The product of electrochemical synthesis in methyl alcohol is the rhenium complex (VI) Re ₄ O ₆ (OCH ₃ ) ₁₂ analogously to example 1.

Example 3. The anodic dissolution of metallic rhenium in methanol with the addition of LiCl 0.05-0.06 mol / L was carried out in a two-chamber flow cell made of fluoroplastic (Figure 1) with technological parameters: the dissolution potential of rhenium E = 3.50 V, the accuracy of maintenance potential ΔЕ = ± 0.01 V, temperature - 20-25 ° С, flow rate - 0.4 l / h. The product of electrochemical synthesis in methyl alcohol is the complex Re ₄ O ₂ (OCH ₃ ) ₁₆ (V), in which terminal oxoligands.

Thus, from the description of examples and results, it follows that the proposed method allows for the implementation of controlled electrochemical synthesis of rhenium methylates. Setting fixed electrochemical parameters makes it possible to obtain reproducible results of anodic dissolution.

Explanations for the figures.

Figure 1 - Electrochemical cell for the synthesis of alkoxysilane:

1 - cell body;

2 - current supply to the titanium cathode;

3 - current supply to the anode (Re);

4 - membrane MK-40;

5 - fitting.

Figure 2 - Structure of Re ₄ O ₆ (OCH ₃ ) ₁₂ .

Claims (1)

The method of producing rhenium oxometylates by the electrochemical method, which consists in the anodic dissolution of rhenium in anhydrous methyl alcohol in the presence of an electrically conductive additive, characterized in that the dissolution of rhenium is carried out at a fixed value of the anode potential E ≤ 3.50 ± 0.001, to obtain a product of a certain composition, corresponding to the formula Re ₄ O _6-y (OCH ₃ ) _{12 + y} , where 0≤y≤4.

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