RU2069182C1 - Method of complex oxides production - Google Patents

Abstract

FIELD: method of complex oxides production is used in chemical and petrochemical industries. SUBSTANCE: aim is to exercise synthesis in conditions of partial contact of reaction mixture with surrounding gas medium, that allows to carry out synthesis under partial pressures different from conditions in outside gas medium. Aim is achieved due to the fact, that reaction mixture is in crucible closed by lid and dipped in crucible of bigger size. Smaller crucible inside bigger crucible is buried with layer of finely dispersed inert substance ( building sand, aluminum, magnesium etc oxides). EFFECT: improved process. 2 cl

Description

 The invention relates to methods for the synthesis of compounds that are not resistant to the surrounding external gas environment. Known methods for producing such compounds in vacuum [1] in an inert atmosphere [2] in hermetically sealed installations with a controlled concentration of the corresponding gases [3] under conditions of comprehensive compression of the sample [4] in sealed ampoules [5] from an inert material (quartz, platinum, gold, etc.). An essential feature of all these widely known methods is that the synthesis is carried out in closed systems, and therefore the compositions of the generating phases are completely dependent at a given temperature on the partial pressures of the corresponding gases. If these pressures are artificially set using special devices, then the equilibrium pressures of these gases over the reaction mixture coincide with the set ones (analogues 1 3). If this is not done, then the equilibrium pressures are determined by the compositions of the initial reaction mixtures (4, 5). All these methods are quite complex and require the creation of special installations (1 4) or are associated with the use of expensive metals (4, 5) and the need to perform hot work. In addition, in the synthesis of compounds that decompose under the influence of the surrounding gas environment, in particular the air atmosphere, reagents are often used that, when heated, emit water vapor and other volatile components that increase the total pressure in the system, which can lead to the explosion of an ampoule or installation with one side and interfere with the formation of the resulting substances on the other hand.

 Closest to the proposed is a method according to which complex oxides are obtained by reacting the starting components taken in a stoichiometric ratio when heated using a screening layer of an inert substance.

 The purpose of the invention is the simplification and reduction of the complexity of the method.

 This goal is achieved in that in the proposed method for producing complex oxides with a high content of alkaline or alkaline earth metals, the crucible with the initial mixture is closed with a lid, placed in another crucible of a larger volume and the latter is filled with a chemically inert finely divided substance. The synthesis is carried out by conventional ceramic technology, i.e. maintaining the reaction mixture at a suitable temperature with periodic grinding it.

 A significant difference of the proposed method is that in order to simplify the method and reduce its complexity for the synthesis of oxosalts in order to avoid the interaction of the reaction mixture with carbon dioxide of air, the synthesis is carried out under a layer of finely dispersed inert substance, which can be, in particular, easily accessible building sand. Another significant difference of the method is the absence of the need to use complex plants using vacuum or artificial gas mixtures for synthesis, as well as to seal the reaction mixture in glass, quartz or metal ampoules.

The proposed method is not applicable if the purpose of the synthesis is to obtain compounds whose elements are in lower oxidation states that are unstable in the atmosphere of air. This is due to the fact that the partial pressure of oxygen in the air (0.21 atm) is much greater than the partial pressure of carbon dioxide (0.0003 atm), as a result of which the screening layer of an inert substance cannot retain oxygen, but does not allow carbon dioxide to pass through. In addition, the molecules of the latter and in their volume are slightly larger than oxygen molecules. Experimentally, this is confirmed, for example, by the fact that Ba ₄ V ₂ O ₉ at 800 ^° C interacts with carbon dioxide and gives a mixture of orthovanadate and barium carbonate according to X-ray powder diffraction data, while barium carbonate is not formed under a layer of building sand. On the other hand, powdered metallic copper both in air and under a layer of building sand with a thickness of 10 cm is completely oxidized to divalent copper oxide.

 Example 1

Stoichiometric amounts of 4.5878 g of Li ₂ O ₂ and 3.9995 g of TiO ₂ are taken, triturated, the mixture is placed in an alundum crucible, closed with an alundum lid and placed in a larger corundum crucible. Pour the latter with building sand or powdered alumina and incubate at 700 ^o C for 8 hours. Then, the alundum crucible is removed, the reaction mixture is ground in a mortar, it is again placed in the alundum crucible, the lid is covered with a crucible, the alundum crucible is placed in corundum, it is covered with building sand (or alumina) and it is kept for 16 hours at 700 ^o C. After that, from the alundum crucible about 6.9 g of Li ₄ TiO ₄ are recovered. When carrying out this synthesis in an atmosphere of air, only a mixture of orthotitanate, methanitanate and lithium carbonate can be obtained.

 Example 2

Take 1.53334 g of BaO and 6.4190 g of Ba ₃ V ₂ O ₈ and proceed further as in Example 1. About 7.9 g of Ba ₄ V ₂ O _{9 are} obtained.

 Example 3

1.6734 g of BaCO ₃ and 6.4190 g of B ₃ V ₂ O _{8 are} taken and proceed further as in Example 1. After the experiment, a mixture of the starting components is obtained. The reason for this result is that barium carbonate is selected for the synthesis, which at 700 ^° C is very stable and does not interact with barium orthovanadate.

 Example 4

Take 3.3868 g BaO ₂ and 5.3992 g Ba ₃ TiO ₅ and proceed further as in example 1, with the difference that the heating is carried out at 950 ^o C. Receive about 8.4 g Ba ₅ TiO ₇ , which in air conditions cannot be obtained due to its interaction at a given temperature with air carbon dioxide to form Ba ₃ TiO ₅ and barium carbonate, and at temperatures below the decomposition temperature of BaO ₂ (i.e. 800 ^o C) a mixture of Ba ₃ TiO is formed ₅ and BaO ₂ .

Ba ₅ TiO ₇ in this work was obtained for the first time.

 The main advantage of the proposed method is the relative ease of synthesis of compounds of this class. Another advantage is the possibility of using for the synthesis of certain metal salts and hydrates, which, when decomposed, emit corresponding gases that can break an ampoule or spoil the oil in a vacuum pump if the ampoule or vacuum method is used.

Claims (1)

 A method of producing complex oxides containing alkaline and alkaline earth metals by reacting the starting components in a stoichiometric ratio by heating using a shielding layer of an inert substance, characterized in that a finely dispersed substance is used as a shielding layer, with which a crucible with a lid is filled with initial components installed in a similar crucible of a larger size.