CS266700B1 - Process for the preparation of cobalt-nickel nickel double cyclo-phosphates - Google Patents

Abstract

The method consists in calcining a mixture of oxide, hydroxide, carbonate or hydroxide-carbonate of cobalt and nickel in an amount corresponding to the molar ratio Co/Ni => (2-x)/ and phosphoric acid in an amount corresponding to the ratio PgOjj/CCo+Ni) equal to 0.96 to 1.2·, with the heating rate being less than 35 °C/min, to a temperature of 250 to 1060 °C and the vapor pressure in the calcination space being higher than 20 kPa.

Description

The invention relates to a process for the preparation of double cobalt nickel cyclotriphosphates.

Double cobalt-nickel cyclotriphosphates are represented by the formula 2 ' ^{where x} ranges from values approaching zero to values approaching two. These compounds are characterized by high thermal and chemical stability and intense color. So far, the only mentioned method of preparation of these substances consists in their crystallization from a cooling melt containing in the required amounts phosphate anions together with cobalt and nickel cations. However, this process for the preparation of double cobalt nickel cyclophosphates is particularly suitable for preparative laboratory purposes. It is thus possible to prepare very pure products, but this method is only slightly suitable for wider technological use. with constant reheating) cool, the technological implementation of this method is also complicated by the need to ensure a dry atmosphere or vacuum in the melt space.

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These disadvantages are overcome by the process for the preparation of double cobalt-nickel ^{cyclophosphates of the formula c} '" ^Go 2 ~ x ííi x ^ř 4 ⁰ 12 ^{and where x} are in the range from values approaching zero to values approaching two, according to the invention. that the cobalt oxide, hydroxide, carbonate or hydroxide-carbonate, together with the nickel oxide, hydroxide, carbonate or hydroxide in the ratio Co / Ni corresponding to the molar relationship (2-x) / x, is calcined with phosphoric acid in the starting mixture , wherein the amount of phosphate anions to divalent cations corresponds to a molar ratio of P2O2 / (Go + Ni) of 0.96 to 1.2 /, preferably 1 to 1.03, the starting mixture being prepared by converting to cobalt and the nickel compound is treated with phosphoric acid, and preferably a concentration of 30 to 90 wt. % H 2 PO 2 ^{and the} starting mixture is preferably left to react freely for at least 2 hours (preferably with stirring and then started heating at a rate of less than 35 ° C / min _; preferably at a rate of 1 to 10 ° C / min, to a temperature of 250-1060 ° C, _of preferably at 350 to 750 ° C, wherein in the calcination chamber is water vapor tension higher than 20 kPa, preferably 60-100 kPa.

The mutual ratio of cobalt and nickel compounds in the starting mixture is chosen according to the requirement for the content of cobalt and nickel cations in the product. The content of nickel cations (x) can range from values approaching zero to values approaching two. A value of zero or two cannot be used, because then it would not be a double product, but a pure dicobalt cyclotriphosphate c ~ Co ₂ P ^ 0 ₁₂ , resp. o Pure dinicelium cycloetaphosphate c-Ni 2 P 2 O 2. The amount of phosphoric acid in the starting mixture, expressed by the molar ratio P ₂ O 2 / (Co + Ni), would be most suitable to use exactly according to the stoichiometry (i.e. said ratio equal to one) in the case of processing completely pure raw materials. However, according to the purity of the phosphoric acid used (the content of metal ions in it) and the purity of the cobalt and nickel raw materials (metal impurities), the ratio must be adjusted.

- 3,266,700 in the stated range of 0.96 to 1.2, with a small excess (1 to 1.03) of phosphate anions being more advantageous than their significant deficiency compared to stoichiometry. The concentration of phosphoric acid is from the point of view of controlling condensation reactions. , and thus the yield and purity of the product more advantageous lower; however, this lower concentration in turn causes an increase in the energy requirements for the evaporation of the excess water and increases the volume of the starting mixture, which in addition has the character of a slurry. Its calcination then presents technical problems compared to the calcination of a mixture of a smaller volume, which would be in the form of a solid or pasty which is formed if a phosphoric acid concentration in the stated preferred range of 30 to 90 wt. %. Allowing the mixture containing phosphate, cobalt and nickel ions to react spontaneously for at least 2 hours before calcination is advantageous for the initial reaction of the starting cobalt and nickel compound with phosphoric acid to take place sufficiently; this is a neutralization reaction using hydroxides, or in particular the decomposition reactions of carbonates, since the carbon dioxide released and the swelling of the mixture caused by it would complicate the calcination itself. Therefore, it is also advantageous to stir the reacting starting mixture. The heating of the mixture at a rate of less than 30 ° C / min is chosen so that the individual dehydration and condensation reactions successively taking place in the mixture can proceed as slowly as possible at (or near) the temperatures at which they occur, and thus in the highest yields. . Otherwise, the intermediates would be undesirably cleaved to release the phosphorus component, which would then condense separately to polyphosphoric acids, thereby contaminating the main product and reducing its yield. When choosing a very low heating rate, it is again necessary to take into account the disproportionate extension of the product preparation time, and thus a certain increase in material and energy requirements. In addition, in this case it will be more difficult to maintain a sufficient water vapor pressure in the space of the calcined mixture, and thus to prevent the possible cleavage of the intermediates. The lower required limit of the calcination temperature (250 ° C) is given by the temperature of the gradual formation of the first particles of double cyclone.

-cobalt-nickel tetraphosphates. The upper limit of the calcination temperature range (1060 ° C) is related to the thermal stability of the double cobalt-nickel cyclophosphates, which can already melt uncongruently at this temperature. The preferred calcination temperature in the range of 350 DEG to 750 DEG C. is due to the fact that the double cyclo-tetraphosphates are formed at a temperature above 350 DEG C. with sufficient velocity and initially forming amorphous products are converted into microcrystals. The upper limit of this preferred temperature range (750 DEG C.) is then given by the fact that at this temperature the reactions of the formation of double cyclo-tetraphosphates have already taken place (if the preferred heating rates have been used), even at higher water vapor tensions in the calcination space. Maintaining a water vapor pressure in the calcined mixture space of more than 20 kPa is necessary to prevent the formation of undesired condensation by-products and to prevent the cleavage and separate condensation of the phosphorus component. The presence of water vapor slows down the individual condensation reactions somewhat, allows them to proceed more quantitatively and also prevents the formation of undesired non-porous crusts on the surface of the calcined mixture particles, which would prevent the quantitative course of dehydration reactions. It is advantageous to keep the water vapor pressure above 60 kPa, when its action in this direction is sufficient. The upper limit for the advantageous water vapor pressure in the space of the calcined mixture of 100 kPa - is given mainly by the need for increased construction, material and energy requirements for the calcination equipment and calcination line, when using higher pressures than atmospheric pressure. ^w _av £ _c increased inhibition of condensation and dehydration reactions due to a water vapor pressure of 100 kPa would again disproportionately prolong the preparation time tu,

The essence of the process according to the invention further lies in the fact that the product is treated after calcination with hydrochloric, sulfuric, nitric or phosphoric acid, preferably by weight concentration of 0.5 to 10%. This operation is performed ev

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- 5 266 700 as purification of the product obtained in its need in pure form. residues of the starting mixture, which thus go into solution. Double cobalt nickel nickel cyclophosphates resist the action of these acids. If the double cobalt-nickel cyclophosphates are prepared for technological use and in particular if they have been prepared under the conditions according to the invention mentioned as preferred, this purification does not need to be carried out.

The process allows the preparation of double cobalt-nickel cyclophosphates under technologically feasible conditions, with sufficient yield and with sufficient product purity. It also allows the use of lower quality raw materials - dilute and less pure phosphoric acid and less pure cobalt and nickel compounds. Under the conditions of preparation of the product according to the invention, it is advantageous to prepare almost pure double cobalt-nickel cyclophosphates. If less pure products are obtained, they can be purified by the process according to the invention.

The following are examples of the preparation of double cobalt nickel cyclophosphates by the process of the invention.

Example 1

100 g of cobalt carbonate (containing 49% Co) and 101.7 g of nickel carbonate (containing 18% Ni) were mixed with 506 g of phosphoric acid at a concentration of 65% by weight and allowed to react spontaneously with occasional stirring for 8 hours. The mixture was then heated at 450 ° C / min to 450 ° C for 1 h at this temperature. The water vapor pressure in the calcined mixture space was maintained at 85 to 95 kPa. 380 g of product were obtained, which contained 94% of double cobalt nickel cyclophosphate of the formula o-CoNiP ^ O ^ ·

- 6 Example 2 ^{266 700}

100 g of cobalt hydroxide (containing 57% of Co) and 35.05 g of nickel hydroxide (containing 54% of Ni) were carefully mixed with 300 g of phosphoric acid at a concentration of 85% by weight of H 2 PO 2 and left under occasional stirring for 5 h to react spontaneously. The mixture was then heated at 500 ° C / min to 500 ° C for 1 h at this temperature. The water vapor pressure in the quenched mixture space was maintained at 75 to 85 kPa. 292 g of product were obtained, which was further purified by leaching with hydrochloric acid at a concentration of 4 wt. % HCl. After washing with water and drying at 110 ° C, 285 g of product containing 98% of c-Go ^ ^ Νίθ ^ Ρ ^ Ο ^ ·

Claims (2)

OBJECT OF THE INVENTION 266 700 1. A process for the preparation of double cobalt-nickel cyclophosphates of the formula ° “θ ° 2-.χ ^ χ ^ 4θΐ 2 * ^x can range from values approaching zero to values approaching two, characterized in that the oxide , cobalt hydroxide, carbonate or hydroxide-carbonate together with nickel oxide, hydroxide, carbonate or hydroxide-carbonate in a Co / Ni ratio corresponding to the molar ratio (2-x) / x, are calcined with phosphoric acid in the starting mixture, where the amounts of phosphate of anions to divalent cations corresponds to a molar ratio PgO 2 (ACo + Ni) of 0.96 to 1.2.8, preferably 1 to 1.03, the starting mixture being prepared by treating the cobalt and nickel compounds with phosphoric acid. , preferably a concentration of 30 to 90 wt. % ^{and the} starting mixture is preferably left to react freely for at least 2 hours, preferably with stirring, and then heated at a rate of less than 35 ° C / min ₍ preferably at a rate of 1 to 10 ° C / min ₎ to a temperature of 250 to 1060 ° C, with preferably to a temperature of 350 to 750 ° C, wherein the water vapor pressure in the calcination space is higher than 20 kPa, preferably 60 to 100 kPa. 2. A process according to claim 1, characterized in that the product, after calcination, is treated with hydrochloric, sulfuric, nitric or phosphoric acid ₍ preferably a concentration of 0.5 to 10% by weight). Price: 2.40 CZK Printed by Moravské tiskařské závody, center 100, Studentská tř.5, OLOMOUC