CS274188B1 - Method of cobalt-zinc double cyclo-tetra-phosphates' high-temperature preparation - Google Patents

Abstract

The invention is based on the calcination of the initial mixture composed of compounds of the cobaltous and zincous type of dihydrogen phosphates, or mixtures of phosphoric acid with cobalt or zinc hydrogen phosphates or phosphates, or with cobalt or zinc oxides, hydroxides or carbonates in a quantity corresponding to the molar ratio Co/Zn = (2-x)/x and P2O5/(Co+Zn) equal to 0.98 to 1.10 to temperatures higher than 800 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 800 degrees C, re-crystallises causing the occurrence of microcrystals of zinc-cobalt double cyclo-tetraphosphates.

Description

CS 274 188 Bl

The invention relates to a high-temperature process for the preparation of cobalt-zinc cobalt double-phosphate phosphates.

Double cobaltaphosphate cobaltnaphosphate ^c 2 ^Co 2-x ^ ⁿ x ^P 4 ^ 12 * ^x

2) are compounds of the condensed phosphate type β cyclic anion / consisting of four interconnected tetrahedra (PO ^), these are colored compounds with high thermal and chemical stability and with crystal structure in a monoclinic system. They are known in the art for their synthesis, which is based on the thermal treatment of a mixture of cobalt oxide, hydroxide, carbonate or hydroxide-carbonate and zinc oxide, hydroxide or carbonate and phosphoric acid, using only temperatures that do not yet melt. ie, up to 800 ° C. The method is advantageous from the energy and technological terms' but sometimes I need to prepare products with regular particles formed by the well developed microcrystals ο-Οο ₂ _ _{χ 2η χ} ^P 4 · 12 ° which are advantageous for some uses; for example, the use of products for experimental research work; for preparative purposes as well as for some agrochemical and pigmentary uses.

According to the invention, the high temperature process for the preparation of cobalt-zinc cobalt double zinc phosphates of the formula ο-Οο ₂ _ _χ Ζη _χ Ρ ₄ 0 ^ ₂ enables the preparation of product 8 with the above-mentioned particle properties and higher purity; wherein xe (Oj 2) characterized by ee; that the starting mixture comprises, on the one hand, dihydrogen phosphates; hydrogen phosphates, phosphates or oxides or carbonates of cobalt and zinc (possibly also carbonate carbonates in such amounts) that the molar ratio Co / Zn corresponds to (2-x) / xa Firstly phosphorus cyealines in such amount / that phosphate anions are divalent to divalent cations in a mixture in a molar ratio of P ₂ O _g / (Co + 2n) equal to 0/98 to 1/10 / preferably 1 to 1.02; is heated, preferably ^one such; wherein the heating rate is less than 25 ° C / min and the water vapor pressure in the calcination space Js 40 to 100 kPa / to a temperature higher than 800 ° C, preferably higher than 1060 ° C, whereby the previously formed intermediates melt and then melt quenched, preferably by pouring into water or a cold plate of inert material, to form another intermediate product in the form of a homogeneous amorphous mass of glassy character which is longer / preferably after grinding; reheated to a temperature of at least 500 ° C and below 800 ° C; preferably to a temperature of greater than 650 ° C and less than 750 ° C; wherein recrystallization of the intermediate occurs along with the rearrangement of the tetraeders (PO ₄ ) in the anions; to form double cobalt tetra-zinc phosphate, which is preferably still ultimately pulverized to form fine-grained particles of microcrystalline nature.

In the high-temperature process for the preparation of cobalt-zinc cobalt double-zinc phosphates, one can start from euroses, where the phosphorus anion content of the respective divalent cations, expressed as a molar ratio P ₂ O _g / (Co + Zn) 98 to 1.10 and preferably 1 to 1/02. It is therefore possible to start with at least 3 dihydrogen phosphates (hydrates or anhydrides) or mixtures 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 applications; because I require preparation in advance which is not a simple operation; so it is more suitable only for the preparation of smaller quantities of products ο-Οο ₂ _ _χ 2η _χ Ρ ₄₀ 0 ^ ₂ in completely pure form. For technological applications, it is preferable to start from a mixture of oxides / hydroxides or cobalt hydroxide or carbonate or carbonates and zinc oxides, hydroxides or carbonates 8. The acid can be used at any concentration (however, it is to be understood that dilute acid is more effective for reacting the starting mixture), whereas higher acid concentration is preferable for the energy requirement of evaporating dilution water from the acid. The acid concentration should therefore be selected individually according to the reactivity of the cobalt and zinc starting materials and according to the energy possibilities of the possible manufacturer. The use of high concentration acid at high heating rates may create a risk of separate condensation of phosphoric acid to higher polyphosphoric acid

However, at high temperatures even up to phosphorus pentoxide, which can then volatilize from the mixture and thus adversely affect the mutual ratio of phosphate anions and divalent cations in the calcinate or melt respectively. The first condensed phosphate type intermediate; which is produced during the quenching process is a double dihydrogen diphosphate; at temperatures of about 200 ° C. This then passes to the product at temperatures of about 100 to 200 ° C higher; which, for the most part or less, corresponds to the double cyclotetraphosphate. Order the proportion of double cyclo-tetrafosphates; which is also an intermediate at this stage, and to minimize the risk of separate condensation of the phosphorous layer and thus its possible loss of volatility, it is advantageous to conduct a heating rate of less than 25 ° C / min. up to 100 kPa. Maintaining a water vapor pressure in the calcinate space of at least 40 kPa is advantageous for preventing the formation of undesirable by-products, in particular preventing cleavage and separate condensation of the phosphorus component. The water vapor present in the individual condensation reaction slows down the formation of intermediates somewhat, ”allows their more quantitative course; it also prevents the formation of undesirable nonporous crusts on the surface of the particles in the calcined composition, which would prevent the dehydration reaction from occurring. The final calcination temperature at this stage of the preparation of the product according to the invention must be higher than 800 ° C. because it is the lowest temperature when some intermediates melt; due to the requirement for rapid melting of the calcine; which may also contain other above-mentioned substances, it is preferable to select a higher temperature; i.e., 1,060 ° C. The intermediate melts non-congruently, ”with the disintegration of the tetrafosphate cycles and the coupling of the resulting short phosphate chains into long chains ^1, which is also due to the presence of at least trace amounts of water vapor in the melt area. Thereafter, the melt needs to be quenched, preferably by pouring it into water or onto a cold plate of inert material (metal or ceramic). This affords another intermediate; which is a homogeneous amorphous mass of vitreous nature, containing long-chain anions. The thus obtained piece of vitreous mass, after cooling and eventual drying, is preferably ground in a dry manner and reheated again; in order to recrystallization of intermediates for the rearrangement of tetrahedrons (PO ^) in the anion to form the microcrystals of the double-cyclo tetrapolyphosphate cobalt-zinc formula _{ο-0θ2_} χ Ζη χ ^P 4 ° 12 S * £ (0j 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 limit of this reheat is 500 ° C and corresponds to the lowest recrystallization temperature of the cobalt-zinc intermediates. This temperature can only be achieved because the recrystallization process is very rapid and as soon as you start running, but the preferred temperature range for recrystallization is higher than 650 ° C and lower than 750 ° C / when recrystallization of the glassy intermediate occurs at any time the heating rate and any consistency of the intermediate (powdered, lump or completely compact) and there is no risk of melting the final product (which, due to its non-congruence), would again lead to the formation of a glassy intermediate. You can not therefore exceed the recrystallization at 800 ° C / which corresponds to the lowest melting point binary products, namely a melting point ^{c Co} 2-x ^Zn x ^P 4 ° i2 'dy ^ x - * 2. The final products - cobalt-zinc double-cyclo-tetraphosphate-double-cycles - after cooling 8 are advantageously comminuted (grinding, comminuting) to regular fine-grained particles of microcrystalline nature. If the glass product was ground before crystallization, the final comminution of the products is very easy.

The process according to the invention is furthermore characterized in that the product, after calcination, is treated with hydrochloric acid, sulfuric acid; preferably a concentration of 0.5 to 10% by weight of nitrogen or phosphorus. This operation is carried out as a possible clean-up of the products obtained when they are needed, in a completely pure form; for example for analytical or preparative purposes. The action of said acids removes all unwanted by-products and any residues of the starting mixture; that will go into solution. Double cyclotetraphosphonates of cobalt-zinc phosphates resist the action of these acids.

CS 274 188 Bl

Advantages of the process according to the invention are the high yield and high purity of the products; which can still be cleaned by leaching. Yet another advantage is the microcrystalline particle size of the product particles; They are regular and superficially well developed.

□ are therefore suitable for some of the more specific uses.

Example 1

Mixture of 100 g cobalt dibasic phosphate (45/8% Ρ ₂ θς ^{38 38} % Co) and 104, 1 g zinc dibasic phosphate (44% ^P 2 ° s »40,5% Zn) together with 212 g phosphoric acid concentration by weight The 60% HgPO4 was calcined at a rate of 15 ° C / min while maintaining the water vapor pressure in the calcined space up to 500 ° C above 85 kPa, to a temperature of 1100 ° C. The resulting melt was quenched by pouring into water. The resulting glassy intermediate was separated, dried and dry ground. It was then heated to 650 ° C and, after cooling, triturated. The product contained 96/0% double cyclotetraphosphonates of cobalt-zinc phosphates of formula c-CoZnP 4 ° 12 and was obtained in the form of regular fine microcrystals 291 g.

Example 2

A mixture of 100 g of cobalt carbonate (49% Co) and 35/5 g of zinc carbonate (51% Zn) together with 436 g of phosphoric acid at a concentration of 50% HgPO4 was calcined at a rate of 10 ° C / min. The calcinate space was maintained at a temperature of less than 80 kPa / 1100 ° C up to 450 ° C. The resulting melt was quenched by pouring onto a corundum plate. The cooled glassy intermediate was dry ground and then heated to 700 [deg.] C. and triturated after cooling. Was obtained 249 g of product, "which contained more than would have 97/2% of double-cyclo tstrafosforečnanů cobalt-zinsčnatých vzorcs C-Co ^ Ζηθ ₅ '5 ^p 4 ° ⁱ² * ^{I <rokrystalické} Jsmnozrnné form.

SUMMARY OF THE INVENTION

Claims (2)

A process for the high temperature preparation of cobalt-zinc cobalt-zinc phosphate double cyclotrophosphates of the formula ^C 2 ^Co x- ^Zn x ^P 4 ° 12'd and X 6 (O 2), characterized in that the starting material is C? a mixture consisting of dihydroganophosphates; hydrogen phosphates / phosphates or oxides, cobalt and zinc hydroxides or carbonates and, optionally, cobalt hydroxide carbonates) in such amounts; that the molar Co / Zn ratio corresponds to (2-x) / x and, on the one hand, from phosphoric acid in such an amount that the phosphorus anions are 0/98 molar ratio P ₂ Og / (Co + Zn) to divalent cations in the mixture to 1/10; preferably 1 to 1.02 () is heated (preferably so; wherein the heating rate J is less than 25 ° C / rain and the water feathers in the calcine space are 40 to 100 kPa, to a temperature higher than 800 ° C / and preferably higher than 1060 ° C; whereby the previously formed intermediates melt and then melt quenched; and preferably poured into water or on a cold plate of inert material to form a further intermediate product in the form of a homogeneous amorphous glassy material which is preferably, after grinding, reheated to a temperature of at least 500 ° C and below 800 ° C. β preferably to a temperature of greater than 650 ° C and less than 750 ° C; when the intermediate of the intermediate is crystallized together with the rearrangement of the tetrasters (PO an) in the anion to form double cobalt-zinc phosphate phosphates, which is finally and advantageously pulverized to form a jam-like portion of microcrystalline character. 2. The method of item 1; characterized in that the product is calcined with hydrochloric acid; air, nitric or phosphorus, and preferably a concentration of 0.5 to 10% by weight.