CS266697B1 - A high temperature process for preparing underwater manganese zinc cyclotetraphosphates - Google Patents

Abstract

The solution consists in calcining the starting mixture consisting of manganese and zinc compounds of the dihydrogen phosphate type, or a mixture of phosphoric acid with hydrogen phosphates or manganese and zinc phosphates or with manganese and zinc oxides, hydroxides or carbonates in amounts corresponding to the molar ratio of raN/Zn = (2-x)/x and P20s/(Mn+Zn) equal to 0.97 to 1.25, to temperatures higher than 800 °C, when a melt is formed. This is converted by rapid cooling into a glassy intermediate product, which is recrystallized by reheating to a temperature of at least " 480 °C and lower than 800 °C to form microcrystals of double zinc-manganate cyclotetraphosphates.

Description

The present invention relates to a high temperature process for the preparation of double manganatosine zinc cyclopetraphosphates.

Double manganese-zinc cyclo-tetraphosphates ο-Μη _2βΗχ Ζη _χ Ρ _ζ | 0 ₁ 2, where x é (Oj 2) are compounds of the condensed phosphate type with a cyclic anion formed by four interconnected tetrahedra (P0 ^) <This is a light pink compounds with high thermal and chemical stability with a crystal structure in a monoclinic system. The present invention discloses these compounds as novel substances and further proposes a process for their synthesis which is based on the heat treatment of a mixture of manganese and zinc oxide, hydroxide or carbonate and phosphoric acid, only temperatures when they are not yet melting can be used. products - ie up to 800 ° 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 o-Mng microcrystals. .

According to the invention, the preparation of a product with the above-mentioned particle properties and higher purity is made possible by a high-temperature process for the preparation of double manganese-zinc cyclophosphates, of the formula c-Mng ^ Zn ^ P ^ O ₁₂ , where x £ (0; 2), characterized in that starting mixture consisting on the one hand 'χ ^ χ ^ θΐζ * · by the axis P ^ by some uses more advantageous - 2 -

266,697 from dihydrogenphosphates, hydrogenphosphoronates, phosphates or oxides, hydroxides or carbonates of manganese and zeanitrate in such amounts that the molar ratio Mn / Zn corresponds to (2-x) / x and on the one hand from phosphoric acid in such an amount that the phosphorus anions are divalent to divalent. cations in the mixture in a molar ratio Ρ Ο ^ ^ / ζΜη Ζη +) value equal to from 0.97 to 1.25, preferably 1 ^ 1.05 ^ _of heated, preferably such that the heating rate is less than J0 ° C / min and the water vapor pressure in the quenching space is 40 to 100 kPa, to a temperature higher than 800 ° C, preferably higher than 950 ° C, when the previously formed intermediates are removed and then the melt is rapidly cooled, 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 _from, preferably after milling / reheated to a temperature of at least 480 ° C and lower than 800 ° C, preferably to a temperature higher than 600 ° C and lower than 750 ° C when recrystallization of the intermediate occurs together with the rearrangement of tetrahedra (PO 2) in the anion, to form double manganese-zinc cyclo-tetraphosphate, which is preferably finally comminuted into fine-grained microcrystalline particles ·

In the high-temperature process for the preparation of double manganese-zinc cyclo-tetraphosphates, it is possible to start from raw materials in which the content of phosphorus anions of the respective divalent cations is expressed by a molar ratio Ρ ₂₀ $ / / (Mn + Zn) equal to one, or is close to one 0.97 It is therefore possible to start from a mixture of dihydrogen phosphates (hydrates or anhydrides) or from a mixture of hydrogen phosphate or phosphates (tertiary) (again in hydrate or anhydride form) with phosphoric acid. However, phosphate-type starting materials are less suitable for wider technological use because they require pre-preparation, which is not in itself a simple operation, so it is more suitable only for the preparation of smaller quantities of c-Mug ^ Zn ^^ O ^ _{2 products} in completely pure form. · For technological use it is more advantageous to start from mixtures of oxides - 3 -

266 697 or manganese and zinc hydroxides or carbonates with phosphoric acid. The acid can be used in any concentration, but it must be taken into account and that from the point of view of efficient reaction of the starting mixture the dilute acid is more preferred, while from the point of view of energy requirements for evaporation of diluting water it is more suitable acid higher concentration. The reactivity of the starting manganese and zinc compounds and according to the energy possibilities of the potential manufacturer. thus adversely affecting the mutual ratio of phosphate anions and divalent cations in the kaleinate or melt. The first condensed phosphate-type intermediate formed during calcination is double dihydrogen diphosphate at temperatures of about 200 ° C. In order to minimize the proportion of double cyclophosphophosphates, which are also intermediates in this phase, and to minimize the risk of condensation of the phosphorus component itself, and thus its volatile losses, it is advantageous to conduct the heating at a rate of less than 30 ° C. min in the presence of water vapor and a tension of 40 to 100 kPa. The astonishing of a water vapor pressure in the calcine space of at least 40 kPa is advantageous for preventing the formation of undesired by-products, in particular preventing cleavage and separate condensation of the phosphorus component. The presence of water vapor slows down the individual condensation reactions somewhat to the formation of intermediates, allows their more quantitative course; it also prevents the formation of undesired non-porous crusts on the surface of the particles in the calcined mixture, which would prevent the course of dehydration reactions. The final calcination temperature at this stage of the preparation of the product according to the invention must be higher than 800 ° C, as this is the lowest temperature at which some

- 4 266 697 ré the relevant intermediates are kept secret; Due to the requirement for rapid and reliable melting of the calcine, which may contain 1 Other high melting substances, it is advantageous to choose a higher temperature, i.e. above 950 ° C. The intermediate melts non-congruently, with the decomposition of the tetraphosphate cycles and the joining of the formed short phosphate chains into long chains, to which the presence of at least trace amounts of water vapor in the melt space also contributes. The melt must then be quenched, preferably by pouring into water or on a cold plate of inert material (metal or ceramic). This produces the next product which is homogeneous amorphous mass glassy comprising anions in the form of long strings ^»T portion and the piece glassy solid after cooling and if necessary, drying is preferably ground to dryness and again heated so as to recrystallize the intermediate to rearrangement of the tetrahedra (PO 2) in the anion, to form microcrystals of double manganese-zinc cyclophosphates, of formula c-to ^ ^ Zn ^^ O. ^ ^{6 2} ^ · small amounts of chemically bound water are released in the glassy intermediate. Therefore, it is easier to guide the thermal recrystallization process if the glassy intermediate is dry ground beforehand. The lower temperature limit of this reheating is 480 ° C and corresponds to the lowest recrystallization temperature of the manganese-zinc intermediates. Although this temperature only needs to be reached, because the recrystallization process is exothermic and once it starts, it continues to run spontaneously, but the preferred temperature range for recrystallization is temperatures higher than 600 ° C and lower than 750 ° C, where recrystallization of the glassy intermediate always heating rate and any consistency of the intermediate product (powder, lump or completely compact) without the risk of melting of the final product, which, due to its non-congruent nature, would again lead to the formation of a glassy intermediate product. It is therefore not possible to exceed the limit of 800 ° C during recrystallization, which corresponds to the lowest melting point of the double products, namely the melting point ο-Μη _2-χ Ζη _χ Ρ ^ 0 ₁₂ , when it finally approaches two. The final products - · double manganate-zinc cyclophosphates - are preferably further ground (by grinding, trituration) into regular, fine-grained microcrystalline particles after cooling. * If the glassy product has been ground before recrystallization, the final grinding of the products is very easy

The essence of the process according to the invention further consists in that the product after treatment is treated with hydrochloric, sulfuric, nitric or phosphoric acid, preferably with a weight concentration of 0.5 to 10%. completely pure form, eg for analytical or preparative purposes

The advantages of the process according to the invention are the high yield and high purity of the products, which can be further purified by leaching. They are therefore suitable for some more special applications®

The following are examples of the use of the method according to the invention®

Example 1

A mixture of 100 g of manganese hydrogen phosphate (47% P ₂ ° 5 »36.4% Mn) and 107 g of zinc hydrogen phosphate (44% ^P 2 ° 5 '0.5% ^Zn ) together with 328 g of phosphoric acid by weight 40 *% The calcine was treated at a rate of 15 DEG C./min while maintaining the water vapor pressure in the calcinate space up to a temperature of 450 DEG C. higher than 85 kPa, to a temperature of 970 DEG C. The resulting melt was quenched by pouring into water. The glassy intermediate obtained was separated, dried and ground

- 6 266 697 drought. It was then heated to 650 ° C and triturated after cooling. The product contained 95% of double manganese-zinc cyclophosphate of the formula c-MhZnP 2 O ₁₂ to give 301 g; was in the form of regular fine microcrystals.

Example 2

A mixture of 100 g of manganese carbonate (47% Mn) and 36.6 g of zinc carbonate (51% Zn) together with 376 g of phosphoric acid with a concentration of 60% H 2 PO 2 was calcined at a rate of 10 ° C / min while the water pressure was steam in the calcine space is kept up to a temperature of 500 ° C higher than 80 kPa, to a temperature of 1000 C. The resulting melt was rapidly cooled by pouring onto a corundum plate. The cooled glassy intermediate was dry ground and then heated to 600 ° C and triturated after cooling. 253 g of product were obtained, which contained more than 97% of double manganese-zinc cyclophosphates of the formula c-Mn 2 O 3 P 2 O ₁₂ in microcrystalline fine-grained form.

Example 3

A mixture of 50 g of manganese oxide (containing 77% by weight) and 382 g of zinc hydroxide slurry (containing 36% of Zn) together with 694 g of phosphoric acid with a concentration of 80 wt. % H The resulting melt was quenched by pouring into water. The resulting glassy intermediate was separated, dried and dry milled. It was then heated to 700 ° C. 645 g of product were thus obtained, which contained 93.5% of double manganese-zinc cyclophosphates of the formula c-Μηθ ^ Zn ^ ⁱⁿ microcrystalline form.

Claims (2)

OBJECT OF THE INVENTION. 266 697 The first high-temperature process for preparing double-cycle -tetraíosfoiOcnemů manganese-zinc formula 2 ° ≤ ^η-η χ χ ^ ^ 4θ12 'where x β (0, 2), characterized in that a starting mixture comprising both of dihydrogen phosphate, hydrogen phosphate, phosphate or oxides, hydroxides or carbonates of manganese and zinc in such amounts that the molar ratio Mn / Zn corresponds to the relationship (2-x) / x and on the one hand from phosphoric acid in such an amount that the phosphorus anions are in a molar ratio of P2 O 2 to the divalent cations in the mixture. / (Mn + Zn) equal to 0.97 to 1.25 _z , preferably 1 to 1.05 _; is preferably heated so that the heating rate is less than 30 ° C / min and the water vapor pressure in the calcine space is 40 to 100 kPa, to a temperature higher than 800 θΟ, β preferably higher than 950 ° C, when the previously formed intermediates melt and then the melt is quenched, preferably by pouring into water or on a cold plate of inert material, to give a further intermediate in the form of a homogeneous amorphous glassy mass which is further preferably reheated to at least 480 ° C and below 800 ° C, preferably to a temperature higher than 600 ° C and lower than 750 ° C, when recrystallization of the intermediate takes place together with rearrangement of tetrahedra (PO 2) in the anion to form double manganese-zinc cyclophosphates, which is finally still preferred. ground into the form of fine-grained particles of microcrystalline character. 2. The process according to claim 1, characterized in that the product after treatment is treated with hydrochloric, sulfuric, nitric or phosphoric acid, preferably a concentration of 0.5 to 10% by weight.