CS267050B1 - Method of double manganese-nickel cyclo-tetraphospates preparation - Google Patents

Abstract

The solution lies in the calcination of the mixture manganese oxide, hydroxide or carbonate and nickel in the corresponding amount molar ratio Μη / Ni = = (2-x) / x and phosphoric acid in amount corresponding to P205 / (Mn + Ni) equal to 0.965 to 1.25? taking heating rate is less than 40 ° C / min at a temperature of 260 to 950 ° C and in space calcination, the water vapor pressure is higher than 20 kPa.

Description

The present invention relates to a process for the preparation of double cyclo-tetraphosphates of manganese (II) manganese.

Double manganato-nickel cyclo-tetraphosphates are represented by the formula c-Mn _{2 x} Ni _x P ₄ 0 ₁₂ > ^where * can range from near to zero up to two. These compounds are characterized by high thermal and chemical stability and intensive coloring. The only method so far disclosed is to crystallize them from a cooling melt containing phosphate anions in the necessary amounts together with ananganate and nickel cations. However, this process for the preparation of double manganato-nickel cyclo-tetraphosphates is particularly suitable for preparative laboratory purposes. Thus, very pure products can be prepared, but this method is not suitable for wider technological applications. In fact, this method requires high energy requirements, since it is not necessary to transfer the starting mixture to the melt at high temperatures, and it must then be allowed to cool in a controlled manner (under continuous heating). Technological implementation of this method is also complicated by the necessity of providing a dry atmosphere or vacuum in the melt space.

The above mentioned drawbacks are eliminated by a process for the preparation of double manganato-nickel cyclo-tetraphosphates of the formula ο-Μη _{2 - χ} Νΐ _χ Ρ 0 ^ ^ ^ _>> kde kde kde kde kde kde kde kde by calcining manganese oxide, hydroxide or carbonate together with nickel oxide, hydroxide, carbonate or hydroxide-carbonate in a Μη / Ni ratio corresponding to the (2-x) / x molar ratio, to calcine with phosphoric acid in the starting mixture, wherein the amount of phosphate anions to divalent cations corresponds to a molar ratio of PgO (1 / NH 3 + Ni) of 0.965 to 1.25, preferably 1 to 1.04, the starting mixture being prepared by treating the manganese and nickel compounds with phosphoric acid, preferably a concentration of 30 to 90 wt. And the starting mixture is preferably allowed to continue to react for at least 2 hours, preferably with stirring, and then heated at a rate of less than 40 ° C / min, and preferably at a rate of 1 to 10 ° C / min, to a temperature of 260 to 950 ° C, preferably to 380 to 700 ° C, wherein the water vapor pressure in the calcination space is higher than 20 kPa, preferably 60 to 100 kPa.

The ratio of the manganese and nickel compounds in the starting mixture is chosen according to the requirement for the content of manganese and nickel cations in the product. The content of nickel cations (x) can range from values close to zero to values close to two. A value of zero or two cannot be used, since it would not be a double product, but pure cyclotetaphosphates - c-MnjP ^ O ^ and c-N ^ P ^ O ^ ,,. The amount of phosphoric acid in the starting mixture, expressed as a molar ratio of P10 / CMn + Ni), would be best to use exactly by stoichiometry (i.e., said ratio equal to one) when processing completely pure raw materials. However, according to the purity of the phosphoric acid used (the content of the metal ions therein) and the purity of the manganese and nickel raw materials (metal admixtures), the ratio should be adjusted within the stated range of 0.965 to 1.25. to 1.04) than their significant deficiency compared to atechiometry. The concentration of phosphoric acid is lower in terms of control of the condensation reactions and hence the yield and purity of the product; however, this lower concentration causes in turn an increase in the energy requirement for the evaporation of excess water and increases the volume of the starting mixture, which moreover has the character of a slurry. Its calcination then presents technical problems over the calcination of a smaller volume mixture which would be in the form of a solid or pasty, which would arise if a phosphoric acid concentration of said preferred

CS 267 050 B1 range 30 to 9C wt. %. Allowing the mixture containing phosphate, manganese and nickel ions to react for at least 2 hours before calcination is advantageous for the initial reaction of the starting manganese and nickel compounds with phosphoric acid, i.e. the neutralization reaction using hydroxides, or especially the decomposition reaction of carbonates, carbon dioxide and the resulting leaking of the mixture would complicate the calcination itself. For this reason, stirring of the reacting starting mixture is also advantageous. The heating of the mixture at a rate of less than 4 ° C / min is chosen so that the individual dehydration and condensation reactions successively taking place in the mixture can proceed at or near the temperatures at which they occur at the slowest possible yield. Otherwise, unwanted cleavage of the intermediates would result in the release of the phosphorous component, which would then condense separately to polyphosphoric acids, thereby polluting the main product and reducing its yield. When selecting a very low heating rate, a disproportionate increase in product preparation time and hence a certain increase in material and energy requirements is to be expected. In addition, in this case it will be more difficult to maintain sufficient water spring pressure in the space of the calcined mixture and thereby prevent the possible breakdown of the intermediates. The lower limit of calcination temperature (260 ° C) required is given by the temperature of the gradual formation of the first particles of double-manganato-nickel double cyclo-tetraphosphate.

The upper limit of the calcination temperature range (950 ° C) is related to the thermal stability of double manganato-nickel manganese-nickel cyclo-tetraphosphates, some of which may already melt non-congruently. The preferred calcination temperature in the range of 380 to 700 ° C is given by the fact that double cyclo-tetraphosphates are formed at a temperature above 380 ° C at a sufficient rate and the amorphous products initially formed are converted to the microcrystals which are most suitable for their intended use. . The upper limit of this preferred temperature range (700 ° C) is given by the fact that at this temperature the double cyclo-tetraphosphate formation reactions have already taken place (if advantageous heating rates have been used), even at higher water vapor pressures in the calcined mixture space. more than 20 kPa is necessary to prevent the formation of undesired by-products of condensation and to prevent cleavage and separate condensation of the phosphorus component. The present water vapor slows down some condensation reactions somewhat, allows their more quantitative course and also prevents the formation of undesired non-porous crust on the surface of the calcined mixture particles, which would prevent the quantitative course of dehydration reactions. It is advantageous to maintain the pressure of the water spring above 60 kPa, when its action in this direction is sufficient. The upper limit for a suitable water vapor pressure in the space of the calcined mixture - 10C kPa - is given mainly by the necessity of increased constructional, material and energy requirements for the calcining plant and the calcination line, at higher pressures than atmospheric pressure. Moreover, increased braking of the condensation and dehydration reactions due to a water vapor pressure above 100 kPa would again disproportionately prolong the product preparation time.

Furthermore, the process according to the invention consists in treating the product after calcination with hydrochloric, sulfuric, nitric or phosphoric acid, preferably a concentration of 0.5 to 10% by weight. This operation is performed ev. as a purification of the obtained product in its pure form. The action of said acids removes all unwanted by-products and ev. residues of the starting mixture which thus pass into solution. Double manganese-nickel cyclo-tetraphosphates resist the action of these acids. If the double manganato-nickel cyclo-tetraphosphates are prepared for technological use, and in particular if they have been prepared under the preferred conditions of the invention, such purification is not required.

Claims (1)

The process makes it possible to prepare double manganetone nickel cyclo-tetrafosphorates under technologically feasible conditions, with a sufficient yield and with a sufficient purity of the product. It also allows the use of lower-quality raw materials - dilute and less pure phosphoric acid and less pure manganese and nickel compounds. Under the conditions of preparation of the product according to the invention which are preferred according to the invention, the near-double double manganato-nickel manganese-nickel cyclo-tetraphosphates can be prepared. If less pure products are obtained, they can be purified by the process according to the invention. Example 1 100 g of manganese carbonate (containing 47% Mn) and 104.6 g of nickel carbonate (and containing 48% Ni) were mixed with 565 g of phosphoric acid at a concentration of 60% H 2 PO 4 and allowed to react spontaneously with occasional stirring. The mixture was then heated at 5 ° C / min to 500 ° C for 1 h at this temperature. The water pressure in the space of the calcined mixture was maintained at 80 to 90 kPa. 376 g of product were obtained, which contained 95% of double manganetec-nickel cyclo-tetraphosphate c-MnNiP ₄ O _12> Example 2 100 g of manganese dioxide (containing 77% Mn) and 50.8 g of nickel hydroxide carbonate (containing 54% Ni) were carefully mixed with 493 g of 75% phosphoric acid. % H3PO4 ^and allowed to react spontaneously with occasional stirring for 3 h. The mixture was then heated at 10 ° C / min to 430 ° C for 2 hours at this temperature. The water vapor pressure in the space of the calcined mixture was maintained at 90-100 kPa. 412 g of product were obtained, which was further purified by leaching with 3% hydrochloric acid. % HCl. After washing with water and drying at 120 ° C, 399 g of product with 98.5% content were obtained.