CS273031B1 - High-temperature method of double manganese-cobalt cyclo-tetraphosphates preparation - Google Patents

Abstract

The invention is based on the calcination of the initial mixture composed of compounds of the manganous and cobaltous type of dihydrogen phosphates, or mixtures of phosphoric acid with manganese or cobalt hydrogen-phosphates or phosphates, or with manganese or cobalt oxides, hydroxides or carbonates in a quantity corresponding to the molar ratio Mn/Co = (2-x)/x and P2O5/(Mn+Co) equal to 0.95 to l.l to temperatures higher than 950 degrees C, when melting occurs. By intensive cooling this is transformed into a vitreous intermediate product, which, by repeated heating to a temperature of at least 500 degrees C and lower than 950 degrees C, re-crystallises causing the occurrence of micro-crystals of manganese-cobalt double cyclo-tetraphosphates.

Description

The present invention relates to a high temperature process for the preparation of double manganese-cobalt (II) cyclo-tetraphosphates. Double manganese-cobalt (II) cyclo-tetraphosphates ο-Μπ ₂ _ _χ Οο _χ Ρ ₄ Ο ^ ₂ , ^x (θ *

2) are compounds of the condensed phosphate type with a cyclic anion formed by four interconnected tetrahedra (PO ₄ ). They are mndrofialium compounds with high thermal and chemical stability with crystal structure in monoclinic system. The present invention discloses these compounds as novel substances and proposes a method for their synthesis based on the thermal treatment of a mixture of manganese and cobaltic oxide, hydroxide, carbonate or hydroxide-carbonate and phosphoric acid, using only temperatures where the products do not yet melt, ie up to 950 ° C. The method is advantageous from an energy and technological point of view, but sometimes it is necessary to prepare products with regular particles formed by well-developed microcrystals ^ε- ^ ^η 2-χθ ^ο χ ^Ρ 4θ12 'are more preferred for some applications; for example, the use of products for experimental research work for preparative purposes as well as for some agrochemical and pigmentary uses.

Preparation of Product with the above particle properties and higher purity provides for the invention high-temperature process for preparing double cyclo tetrapolyphosphate manganese cobalt, formula ^{C "Mn} 2-x ^As x ^P 4 ° i2 * ^{1 <Cle x} (°> ²⁾ 'wherein characterized in that the starting mixture consisting, on the one hand, of dihydrogen phosphates, hydrogen phosphates, manganese and cobalt phosphates or manganese oxide oxide, hydroxide or carbonate, and cobalt oxide oxide, hydroxide, carbonate or hydroxide, in such quantities that the molar ratio Μη / Co corresponds to (2-x) x) and, on the other hand, from phosphoric acid in such an amount that the phosphoric anions are molar in relation to the divalent cations. a P20g / (Mn + + Co) ratio of 0.95 to 1.1, preferably 1 to 1.01, is heated, preferably such that the heating rate is less than 20 ° C / min and the water vapor pressure in the space calcination is from 40 to 100 kPa, to a temperature of greater than 950 ° C, preferably greater than 10,000 ° C, when the previously formed intermediates thaw and then the melt is quenched, preferably by pouring into water or a cold plate of inert material, form a further intermediate product in the form of a homogeneous amorphous matrix glass which is further, preferably, after crushing again heated to a temperature of at least 500 ° C and lower than 950 ° C, preferably to a temperature higher than G50 ^D C and lower than 800 ° C where recrystallization of the intermediate takes place together with the rearrangement of the tetrahedra (PO4) in the anion to form double manganato-cobalt (II) cyclo-tetraphosphates, which is preferably ultimately pulverized to a fine-grained microcrystalline nature.

In the high-temperature process for the preparation of double-manganese-cobalt-manganese-cobalt phosphate, it is possible to start from raw materials in which the phosphorus ions content of the respective bivalent cations expressed as a molar ratio P ₂ Og / (Co + Mn) to 1.1, preferably 1 to 1.01. It is therefore possible to start from a mixture of dihydrophosphates (hydrates or anhydrides) or of a mixture of hydrogen phosphates or phosphates (tertiary) (again in hydrate or anhydride form) with phosphoric acid. However, phosphate-type feedstocks are less suitable for wider technological use because they require a pre-preparation which is not in itself a simple operation, so that it is more suitable only for the preparation of smaller amounts of c-Mn _{2 x x} Co, P ₄ O _{4 products.} in pure form. For technological applications such as the synthesis of double cyclo-tetraphosphates for pigmentary or agrochemical purposes, it is preferable to start with mixtures of oxides or hydroxides or carbonates of manganese and cobalt (in this case also hydroxide-carbonate) with phosphoric acid. The acid can be used at any concentration, however, it is to be understood that dilute acid is preferable for the effective reaction of the starting mixture, whereas higher concentration acid is preferable in terms of energy requirements for evaporating the aging water from the acid. The acid concentration should therefore be selected individually according to the reactivity of the starting manganese and cobalt compounds and the energy potential of the manufacturer. When using acid. · I

CS 273 031 B1 at high concentrations may, at high heating rates, create the risk of separate condensation of phosphoric acid to higher polyphosphoric acids and even at high temperatures even to phosphorous pentoxide, which may then volatilize from the mixture and thereby adversely affect the phosphate anions / divalent cation ratio calcine and melt respectively. The first condensed phosphate-type intermediate produced during the calcination is a double dihydrogen diphosphate at temperatures of about 200 ° C.

This, at temperatures of about 100 DEG to 200 DEG C., is then converted to a product which, to a greater or lesser extent, corresponds to double cyclotetraphosphates. In order to maximize the proportion of double cyclo-tetraphosphates, which are also an intermediate in this phase and to minimize the risk of separate condensation of the phosphorous component and hence its volatilization losses, it is advantageous to conduct a heating rate of less than 20 ° C / min. vapor in the calcinate space of at least 40 kPa is advantageous for preventing the formation of undesirable by-products, in particular preventing the cleavage and separate condensation of the phosphorus component. The water vapor present in the individual condensation reaction slows down the formation of the intermediates somewhat, allowing them to be more quantitatively avoiding the formation of undesired non-porous crusts on the surface of the particles in the calcined mixture, which would prevent the dehydration reactions from occurring. The final calcination temperature at this stage of the preparation of the product of the invention must be greater than 950 ° C because this is the lowest temperature at which some intermediates melt; due to the requirement of rapid melting of the calcine which may also contain other starting substances, it is preferable to select a temperature higher, i.e. above 1060 ° C. The intermediate melts non-congruently, with the disintegration of the tetraphosphate cycles and the coupling of the resulting short phosphate chains into long chains, to which the presence of at least trace amounts of water vapor in the melt area also contributes. Thereafter, the melt should be quenched, preferably by pouring it into water or a cold plate of inert material (metal or ceramic).

This produces a further intermediate product which is a homogeneous amorphous mass of glassy character, containing anions in the form of long chains. The piece of glass thus obtained, after cooling and eventual drying, is preferably ground dry and reheated to recrystallize the intermediate to rearrange the tetrahedron (PO4) in the anion to form the microcrystals of double manganese-cobalt manganese-cobaltate cyclo-tetraphosphates, ^{c M n} 2 -x ^CD x ^P 4 ° 12 (0; 2)). This releases small amounts of chemically bound water in the glassy intermediate. Therefore, it is easier to conduct the process of thermal recrystallization if the glassy intermediate is dry-ground beforehand. The lower temperature of this reheat is 500 ° C and corresponds to the lowest recrystallization temperature of the manganese-cobalt intermediates. While this temperature can only be achieved, because the recrystallization process is exothermic and once it starts, it continues to run spontaneously, however, the preferred temperature range for recrystallization is higher than 650 ° C and lower than 800 ° C, where recrystallization of the glassy intermediate always occurs. at any heating rate and any consistency of the intermediate (powdered, lumpy or completely compact) and there is no risk of melting the final product, which, due to its non-congruity, would again lead to the formation of a glassy intermediate. Thus, in the recrystallization, it is not possible to exceed the limit of 950 ° C, which corresponds to the lowest melting point of the double products, namely the melting point of c-Mn _{2 x x} Co _x P 2 O ₄ , when x approaches zero. I _<the final product - double cyclo-tetraphosphate manganese cobalt -, allowed to cool, preferably still crushed (milling, grinding) regular fine particles mikrokrystalickóho character. If the glass product was ground before recrystallization, the final comminution of the products is very easy.

The process according to the invention further comprises treating the product after calcination with hydrochloric, sulfuric, nitric or phosphoric acid, preferably by mass, of a concentration of 0.5 to 10%. This operation is carried out as an eventual purification of the obtained products in their pure form, for example for analytical or preparative purposes. The action of these acids removes all unwanted by-products and any residual starting material which is then dissolved. Double manganese-cobalt (II) cyclo-tetraphosphates resist the action of these acids.

Advantages of the process according to the invention are the high yield and high purity of the products, flight ³ . CS 273 031 The blue can also be cleaned by leaching. Another advantage is the microcrystalline fine-grained character of the product particles, which are regular and very well developed on the surface. Axes are therefore suitable for some special applications.

Examples of use of the process according to the invention are given below.

Example 1

Mixture of 100 g manganese dibasic phosphate (47% Ρ ₂ θ ₅ ,% ^Μπ ) ^{and 102,8} g dicalcium phosphate dibasic (45,8% PgOg,% ^C °) ^with P ° 2 ^U · ² * · 9 phosphoric acid . the concentration of 80% HgPO4 was calcined at a rate of 10 ° C / min while maintaining the water vapor pressure in the calcitate space up to a temperature of 500 ° C higher than 85 kPa at a temperature of 1100 ° C. The resulting melt was quenched by pouring into water. The glassy intermediate obtained was separated, dried and dry ground. It was then heated to 550 ° C and, after cooling, triturated. The product contained 97.6% of double manganato-cobalt manganese-cobalt phosphate dibasic, of the formula c-MnCoP2O4, to give 285 g; it was in the form of regular fine micro-crystals.

Example 2

A mixture of 100 g of manganese carbonate (47% Mn) and 34.3 g of cobalt carbonate (49% Co) together with 456 g of phosphoric acid. the concentration of 50% HgPO4 was calcined at a rate of 5 ° C / min while maintaining the water vapor pressure in the calcitate space up to a temperature of 550 ° C higher than 80 kPa at a temperature of 1080 ° C. The resulting melt was quenched by pouring onto a corundum plate. The cooled glassy intermediate was dry milled and then heated to 670 ° C and then triturated after cooling. 240 g of product were obtained, which contained more than 97.2% of double manganese-cobalt manganese-cobaltate cyclo-tetraphosphates of the formula c-Mn · _{5 5} θ 5 5 ^P 4 ° 12 ⁱⁿ microcrystalline fine-grained form.

Claims (2)

The first high-temperature process for preparing double-cyclo tetrapolyphosphate manganese cobalt-Μπ formula ο ₂ _ _{χ Οο χ Ρ} 0 ₄ ^ _2, ^x (0 «2), characterized in that a starting mixture comprising both of dihydrogen phosphate, hydrogen phosphate, phosphate manganese and cobalt oxide or manganese oxide, oxide or hydroxide and cobalt oxide oxide, hydroxide, carbonate or carbonate in such amounts that the molar ratio Μπ / Co corresponds to (2-x) / x and, on the other hand, phosphoric acid in such an amount that phosphorus anions they are heated to divalent cations in the mixture in a molar ratio of PgOg (1 Mn + Co) of 0.95 to 1.1, preferably 1 to 1.01, preferably such that the heating rate is less than 20 ^D C / min and the water vapor pressure in the calcitate space is 40 to 100 kPa, to a temperature higher than 950 ° C, preferably higher than 1060 ° C, when the previously formed intermediates thaw and m is melt quenched, preferably by pouring into water, or the cold plate of an inert material to produce the next product in the form of a homogeneous amorphous matrix glass which is further, preferably, after crushing again heated to a temperature of at least 500 ^D C and lower over 950 ° C, preferably above 650 ° C and below 800 ° C, whereby recrystallization of the intermediate together with the rearrangement of the tetraethers (O 2) in the anion occurs to form double manganato-cobalt (II) cyclo-tetraphosphates, which eventually more preferably, they are comminuted into finely divided particles of microcrystalline nature. 2. 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.