SU899464A1 - Process for producing silicon disulphide - Google Patents

Description

(54) METHOD FOR OBTAINING SILICON DISLIPHIDE

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This invention relates to preparative inorganic chemistry and concerns methods for producing silicon disulfide, which is used as a source material for a volatile silicon compound and as a starting material for the synthesis of silicon-organic compounds.

The synthesis of silicon disulfide from elements in an evacuated ampoule, developed by Malatesta, according to which silicon and sulfur are mixed in a powder state with a small amount of BaOj (as a catalyst), is known. Synthesis is carried out at 750 ° C, followed by purification of the product by vacuum sublimapia, yield 75% 11.

The closest in technical essence and the achieved result is the method of Alvarez-Tostado and Harlow, according to which 1 mole of silicon is ground in a mortar with 2; 5 mole of sulfur and mixed with pyrex glass wool. Synthesis is carried out in a flask ampoule at 900-lOOCfC.

After termination of the reaction, the excess sulfur is distilled off, and the resulting product is distilled off.

unreacted silicon, glycolate and silicon disulfide are subjected to multiple vacuum sublimation in another ampoule. The yield of pure product is 80% 12.

The disadvantages of the method are:

1. The low yield of the finished product, which is explained by the impossibility of complete homogenization of the starting materials with glass wool, this leads to the formation of a cake, which is a mixture of sulfur, silicon, silicon disulfide and glass wool. In addition, all further manipulated lines cleaning is associated with grinding and transferring the reaction product into special ampoules for vacuum sublimation, which leads to additional losses of silicon disulfide as a result of its hydrolysis with moisture in the air.

2. Low purity of the product, which is explained by the presence of glass wool in the reaction mixture. In addition, in the case of vacuum sublimation, the interaction of the remaining P1 preprinted silicon with the Si + SiS reaction is used. - 2SiST 2SiS „aboutI 13Т15luiТV Formation of silicon monosulfide requires exactly repeated vacuum sublimation of the finished product. 3. Explosiveness of this synthesis, which is explained by the impossibility of completely homogenizing the initial reaction mixture. At a temperature of synthesis, namely 900-1000 C, the pressure of saturated sulfur vapor significantly exceeds 1 atm. and the reaction of silicon with sulfur occurs with the release of a large amount of heat, i.e., an uneven heating of the reaction mixture is possible. The purpose of the invention is to increase the yield of the finished product, increase the purity of the product and safe process management. The goal is achieved by the method of obtaining silicon disulfide, including the interaction of silicon and excess sulfur when heated in an evacuated ampoule, sublimation of the resulting product, followed by distillation of excess sulfur, and taking the silicon in the form of plates 250-400 C, and in the section containing silicon 900-1000 C, and the distillation of excess sulfur is carried out in the same ampoule (intermediate zone - deposition - 550-700C). The method of ampoule synthesis in vacuum using a two-section silica glass ampoule as a reaction vessel was selected, where silicon in the form of plates is placed on one edge of one section and sulfur (elementary in a special additional ampoule in another section of a reaction vessel.) The vacuum vessel and the evacuated tank are placed in a furnace with a temperature gradient in such a way that during the synthesis three zones are implemented: the zone — 250–400 С elemental sulfur, 9001000 С — the reaction zone and the deposition zone of the resulting The product is 550-700 C. The vapor of sulfur, diffused from one zone to another, reacts with the surface of silicon to form a disulfide, which is deposited in the space of a partial portion of the reaction vessel in the precipitation zone. Since the surface of silicon is small, since it is not powder but silicon wafers, the reaction proceeds slowly without much heating, and the total pressure in the system is determined by the pressure of the saturated sulfur vapor, the lowest temperature of the reaction vessel is 250-400 ° C, which gives several tens of mm Hg. Art. and is explosion proof. Synthesis and simultaneous refining of silicon disulphide takes place according to the method of diffusing the transfer of gaseous components in the CONDITIONS, but in the ampoule it is advisable to have a pressure lower than atla (t. Kin. Sulfur 444.6 C); At temperatures below 250 ° C, the vapor pressure of sulfur and the rate of its diffusion are such that its concentration in the silicon zone (900-1000 ° C) is insufficient and the process proceeds with the formation of the volatile silicon monosulfide product, which disproportionates on the silicon in the deposition zone and silicon disulfide and contaminates the resulting product. The temperature in the silicon zone 900- is chosen because the interaction of silicon with sulfur is violent with a large release of heat, so at a temperature of more than 1000 ° C a strong local heating of the silicon surface is possible, which will lead to the melting of the reaction product (melting point of silicon disulfide is 1090 ° C), and the appearance of a liquid phase on the silicon surface will cause the surface of the silicon to crust with a melt crust, which means that it will impede the delivery of sulfur to this surface, which will lead to a strong slowdown of the process. In addition, the molten silicon disulfide reacts with quartz to form a non-volatile mass, which leads to a decrease in the yield of the pure substance. After complete silicon sulfidation and sublimation of the product to the precipitation zone (815 h), the reaction vessel is removed from the furnace and excess sulfur is distilled off into the section where the ampoule with sulfur is placed. At the same time, the section of the reaction vessel with silicon disulfide is heated in a furnace up to AIA) C. And the rest is at room temperature or cooled with liquid nitrogen. After the sulfur has been distilled off, the reaction vessel is stirred at the transfer point. Thus, the resulting refined silicon disulfide remains in one ampoule and the sulfur residue in the other. The ampoule with the obtained substance is placed in a dry box, the substance is opened and sampled for chemical and X-ray phase analysis. Excess sulfur should be 5-10%. The proposed temperature range allows synthesis in soft amplifications, and when setting average temperatures, namely, in the sulfur zone of 325-75 ° C, in the silicon zone of 950-50 ° C, to conduct the process without the rigidity of thermostating. Example 1. In a two-sectional quartz reaction vessel, 2 g of KEF silicon — 0.5 in the form of plates and 4.3 g of sulfur of the OFS are placed in separate sections of the cell in a separate, specially prepared ampoule, evacuated, sealed, and heated in a furnace with a temperature gradient So. that sulfur is at 25Q ° C, silicon is 900 ° C, and the resulting silicon disulfide product sublimates into the intermediate deposition zone at 550-700 ° C. After the end of the process, after 8 hours, in the section where the sulfur was placed, its excess is distilled off and the reaction vessel is soldered in the place of overflow. The silicon yield is about 100%. The obtained substance is identified by chemical, X-ray phase and spectral analyzes, from which it follows that the composition of the obtained product corresponds to the formula of silicon disulfide Si82, found Si 30.6 + 0.3 wt.% (Theoretically 30.5), S 69.5 + 0.2 wt.% (theoretically 69.5), and the structure corresponds to the roman modification of SiS2, the content of trace impurities, wt.%: 1-1 (and 5, Ca; the remaining less than I-IOT, Example 2. In a two-section quartz reaction 2.5 g of KEF silicon — 0.5 in the form of plates and 5.5 g of sulfur of the OFS are placed in a separate section of the vessel in a separate, specially prepared ampoule, that sulfur is at 400 ° C., silicon is 1000 ° C, and the resulting product, silicon disulfide, is sublimated into an intermediate deposition zone at 550 ° C. After the process is over, after 15 hours, the section where the sulfur was placed is distilled off from the exchanger and the reaction vessel soldered at the transfer point. The silicon yield is approximately 100%. The obtained substance is identified by chemical, X-ray phase and spectral analyzes, which implies that the composition of the obtained product corresponds to the formula of silicon disulfide SiS found Si 30.5 + 0.2 wt.% (theoretically 30.5)., S 69.6 + 0.3 ne .% (Theoretical 69.5) and the orthorhombic structure corresponds modifications trace content, weight%: Mg 510 and L1;. 2, Ca; the rest is less. Thus, the proposed method allows to increase the yield of the finished product and bring it up to 100%, to increase the purity of disulfide silicon: due to the use of initial products of qualification of partial frequency mixture and the absence of by-products in the reaction, the finished product contains Minimal impurities. The entire workshop takes place in explosion-proof conditions.

Claims (2)

 The invention of the method for producing silicon disulfide, including the interaction of silicon and excess sulfur when heated in an evacuated ampoule, sublimating the product obtained, followed by stripping off excess sulfur, characterized in that, in order to increase the yield of the second product and increase its purity and also increase process safety, take in the form of plates and the interaction is carried out in a two-section vacuum ampoule in the temperature range in the section containing sulfur 250-400 С, and in the section containing silicon 900-ЮОО С, and The excess sulfur is given in the same ampoule. Sources of information taken into account in the examination 1.Z. Malatesta, bazzetta chimica I taliana. Chemical Abstracts, 1949, 43, 8, p. 2884. 2. US patent number 2589653, cl. 23-206, 1952.