Activated high purity magnesium oxide and its manufacturing method

Abstract

The present invention relates to a chemical technology, namely, to an activated high-purity magnesium oxide and a method for producing the same. Activated high-purity magnesium oxide (including surface-treated magnesium oxide) has a specific surface area of ​​BET 70 to 200 m 2 / g, mean particle size (d50) determined by laser diffraction method is 10 microns or less, iodine activity ranges from 70 to 200 mg J / g MgO, citric acid activity is within 40 seconds, and pore volume is 3.2 × 10 -2 cm 3 / g〜10.2×10 -2 cm 3 / g range; 10% of the particles have a diameter of 2 microns or less, 90% of the particles have a diameter of 30 microns or less, the mass fraction of residue on a 150 micron sieve is 1% or less, the mass fraction of residue on a 45 micron sieve is 2% or less, the mass fraction of chloride is 0.1% or less, the mass fraction of calcium is 0.1% or less, the mass fraction of materials insoluble in hydrochloric acid is 0.05% or less, the mass fraction of iron is 0.005% or less, the mass fractions of each of the impurities Ti, Co, Mo, V, Sb, and Ba cations are 1 ppm or less, and Pb, Cd, As, and Hg are 0.1 ppm or less. A method for producing activated high-purity magnesium oxide, including surface-treated ones, comprises calcining magnesium hydroxide obtained by interacting a magnesium salt solution with an alkaline agent. The magnesium hydroxide crystals are produced by a continuous process in which the magnesium hydroxide crystals are separated and isolated between each other in the presence of liquid oil product seed crystals, with all zones at a temperature of 40°C or higher, the residence time of the magnesium hydroxide crystal suspension in each separation zone at least 20 minutes, and the molar ratio of magnesium hydroxide, alkali agent, and magnesium chloride ions (OH- / Mg++) being within the range of (1.9 / 2.1):1. The activated high-purity magnesium oxide produced by this process has high activity and chemical purity, enabling its use as a filler for rubber, adhesives, plastics, and polymers; a stabilizer in the production of chloroprene rubber; and an additive for refining organic solvents in the pharmaceutical, drug, and food industries, as well as in the production of magnesia cement and other magnesium-containing materials.

Description

[Technology Field]

[0001] This invention relates to a chemical technology, namely, active high-purity magnesium oxide and a method for producing the same. [Background technology]

[0002] Magnesium oxide is used in the manufacture of refractory materials, electrical engineering, the pulp and paper industry, construction, rubber, and periclase.

[0003] The production of activated magnesium oxide is based on the thermal decomposition of naturally derived and synthetic magnesium compounds: magnesium carbonate, basic magnesium carbonate, magnesium hydroxide, and magnesium chloride [MEPozin Technology of mineral salts (fertilizers, pesticides, industrial salts, oxides and acids), pI, L.: Khimiya, 1974, 792p.; Mark A. Shand. The Chemistry and technology of magnesia. Wiley-Interscience, 2006].

[0004] Magnesium oxide produced by the thermal destruction of natural raw materials contains a considerable amount of impurities present in the natural materials. Synthetic magnesium oxide produced from purified reagents is characterized by its high chemical purity.

[0005] It is known that magnesium oxide can undergo slight calcination, solidification, ignition, and melting depending on the calcination temperature of the raw materials. Therefore, in terms of activity, magnesium oxide can be active (light) or inactive (heavy) [MEPozin Technology of mineral salts (fertilizers, pesticides, industrial salts, oxides and acids), pI, L.: Khimiya, 1974, 792 p.; Mark A. Shand. The Chemistry and technology of magnesia. Wiley-Interscience, 2006].

[0006] Activated magnesium oxide is used as a filler in rubber, adhesives, plastic materials, and polymers; as a stabilizer in the manufacture of chloroprene rubber; as a catalyst; in the manufacture of high-grade ceramics and specialty glass (lenses for photographic, cinematic, and astronomical purposes); in the pharmaceutical, drug, and food industries; in the manufacture of magnesia cement and other magnesium-containing materials; and as a curing agent for organic solvents.

[0007] One of the most important indicators of active magnesium oxide is its high reactivity. The activity of magnesium oxide can be described using properties such as specific surface area, iodine absorption value, citrate reactivity, acetate reactivity, and typical reactivity.

[0008] It should be noted that chemical purity is extremely important in several applications of activated magnesium oxide, including pharmaceutics, pharmacopoeias, the food industry, and the manufacture of advanced ceramics, specialty glass, and catalysts.

[0009] Lead mass fraction up to 10 ppm, particle content exceeding 8 μm in maximum diameter (laser diffraction method) 5% by volume, specific surface area 1–50 m² measured by BET method. 2 The document states that the magnesium oxide used as a food additive has a concentration in the range of / g and a citric acid reactivity of 80 to 450 seconds [Japanese Patent Publication No. 2003-33159, published in 2003]. The example shows the chemical purity of the generated magnesium oxide determined by inductively coupled plasma spectroscopy (ICP). The mass fractions of impurities were lead (Pb) 0.3 to 1.4 ppm, chromium (Cr) 2 ppm (maximum), cadmium (Cd) 0.2 to 2.4 ppm, and copper (Cu) 0.1 to 0.2 ppm. However, the specific surface area and citric acid reactivity values ​​indicate that the magnesium oxide is not active.

[0010] Specific surface area of ​​10-200 m 2A method for activated magnesium oxide is known, having a secondary particle diameter d50 in the range of 0.1 to 1.5 μm and d90 up to 3.0 μm [European Patent No. 0370728, published in 1989], in which magnesium chloride or magnesium nitrate is used, and the formula Mg(OH) 2-x A x Magnesium oxychloride is produced in the form mH2O. In the formula, A represents Cl or NO3, x is a numerical value from 0 to 0.2, and m is an integer from 0 to 6. The mother liquor of the resulting product, containing the obtained product, is further heated at positive pressure or atmospheric pressure and a temperature of 50 to 200°C. The drawback of this method is that it produces a pseudo-amorphous deposit of magnesium oxide in the first step, and its suspension is a viscous, jelly-like substance that is difficult to stir. Achieving uniformity of reaction mass requires special stirring equipment and high stirring speeds, and when this method is used on an industrial scale, the complexity and cost of the technology increase.

[0011] Furthermore, a method for producing activated magnesium oxide by washing either magnesium oxide or magnesium hydroxide produced by thermal splitting with water, and then drying and calcining it at a temperature of 300-500°C is also known [U.S. Patent No. 3800032, published in 1974]. The washing consists of the following steps: a) dispersing magnesium hydroxide or magnesium oxide in water at a temperature of 80-100°C to form a turbid liquid with a turbidity density of 5-20%; b) vigorously stirring the turbid liquid at a temperature of 80-110°C for 5-60 minutes by introducing steam into the turbid liquid; and c) separating the magnesium hydroxide or magnesium oxide from the turbid liquid. The magnesium oxide mentioned in the examples has high activity - the iodine absorption number is 136-192 mg I equivalents / 100 g MgO. However, the inventors have not shown the chemical purity of the produced magnesium oxide, its particle size distribution, and other parameters.

[0012] The inventors [Patent No. 5037066, published in 2012] found that the specific surface area BET is 10 to 200 m². 2Magnesium hydroxide powder in the range of / g is heated and calcined, and then passed through a 0.25mm sieve at a maximum pressure of 300Pa and a temperature of 250-550°C for 1-10 hours, resulting in a specific surface area BET of 230-500m². 2 The concentration is in the range of / g, and it produces activated magnesium oxide with over 80% passing through a 0.25mm sieve. The drawback of this method is the complex equipment used to calcine the magnesium hydroxide under vacuum. The resulting magnesium oxide has a fairly large particle size, and the chemical purity of the product has not been demonstrated.

[0013] In this invention [Patent No. 3563269, published in 2004; Patent No. 3980569, published in 2007; Patent No. 3939102, published in 2007], the product of low-lead-content magnesium oxide produced by calcining magnesium oxide is generated at a temperature of 700 to 1300°C in the presence of a halogen source, which is a halide or halogen gas, through interaction with seawater and calcium hydroxide-containing lead or lead compounds. The lead content of the magnesium oxide is 2 × 10⁻⁶ -7 The generated magnesium oxide, at a concentration of mol / l, is intended for use as an additive in fertilizers, food products, pharmaceuticals, cosmetics, and other products. Unfortunately, the inventors have not provided any information on the active properties of the generated magnesium oxide, such as its specific surface area or iodine absorption number, or its particle size distribution.

[0014] The closest example is the invention adopted as a prototype [International Publication No. 2014 / 155764, published in 2014], in which magnesium oxide particles have a specific surface area BET of 143-200 m². 2The range is / g, the average particle size by laser diffraction method is at most 5 μm, and the maximum residue of the 5 μm sieve after sieving with a 45 μm sieve is 0.1% by weight. The method for producing magnesium oxide particles includes the following steps: interacting a water-soluble magnesium salt containing an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkaline earth metal hydroxide, or an aqueous solution of ammonia, seawater or brine with the product of a dispersion in a liquid; introducing the liquid containing the dispersion one or more times with the reactant of the seed crystal at a temperature in the range of 1 to 100 °C, or subjecting it to hydrothermal treatment at a temperature of 100 to 200 °C to produce a starting material for calcination, and calcining the starting material at a temperature in the range of 350 to 900 °C. In the shown example, when synthesizing magnesium hydroxide, a very excessive magnesium chloride (molar ratio Mg +2 / OH - , 1 / 1.8) is shown, and as a result, a cake with a high content of MgCl2 is produced. Therefore, the amount of water for washing magnesium hydroxide free of chloride increases, and magnesium oxide with an increased chloride content is produced. Since the inventors have not shown the chemical purity of the obtained product, it is impossible to evaluate its usefulness in the main active magnesium oxide applications.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0016]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0017] For some applications, such as using magnesium oxide in the pharmaceutical industry, when using magnesium oxide as a precursor for producing magnesium-containing compounds, it is necessary to prepare a magnesium oxide aqueous suspension. However, magnesium oxide aqueous suspensions often have a gelled or creamy consistency, which complicates stirring, pumping, and dosing.

Means for Solving the Problems

[0018] The object of the present invention is to produce high-purity magnesium oxide having the following: specific surface area (BET) of 70 to 200 m 2 / g, preferably 130 to 180 m 2 / g, average particle diameter (d50) by laser diffraction method of at most 10 μm, preferably at most 8 μm, iodine absorption value in the range of 70 to 200 mgI / g MgO, porosity of 3.2×10 -2 cm 3 / g to 10.2×10 -2 cm 3 / g, maximum citric acid reactivity 40 seconds, maximum particle size 2 μm for 10% of particle size, maximum particle size 30 μm for 90% of particle size, maximum mass fraction of residue on a 150 μm sieve 1%, mass fraction of residue on a 45 μm sieve 2% or less, maximum mass fraction of chloride 0.1%, maximum mass fraction of calcium 0.1%, maximum mass fraction of substances insoluble in hydrochloric acid 0.05%, maximum mass fraction of iron 0.005%, mass fraction of each of the cation impurities Ti, Co, Mo, V, Sb, Ba 1 ppm or less, maximum of 0.1 ppm of Pb, Cd, As, Hg, preferably, maximum mass fraction of carbonate 1% by weight, and maximum kinematic viscosity of aqueous suspension 30 cP.

[0019] The target set is achieved by calcining magnesium hydroxide produced by the reaction of a magnesium salt solution and an alkaline agent, thereby producing activated, high-purity magnesium oxide, possibly surface-treated. Magnesium hydroxide crystals are produced by a sequential process separated and isolated from each other, including a seed crystal processing zone, a magnesium hydroxide crystal formation and growth zone, and a crystal accumulation and aggregation zone, while an aqueous solution of magnesium chloride and a magnesium hydroxide seed crystal suspension in an amount of 1-80% of the total weight of the supplied initial reagents is supplied to the seed crystal processing zone, along with the processed hydroxide seed crystal suspension from the previous zone and an alkaline agent in a molar ratio within the range of (1.9 / 2.1):1. - :Mg ++ The suspension from the previous zone is directed towards the primary crystal formation and growth zone, and the suspension from the previous zone is directed towards the crystal accumulation and aggregation zone. A temperature of 40°C or higher is maintained in all zones, and the residence time of the magnesium hydroxide crystal suspension in each isolation zone is 20 minutes or more. [Modes for carrying out the invention]

[0020] It is well known that the filtration and precipitation properties of precipitates depend on temperature, exposure time, pH of the medium, molar ratio of reactants, concentration of reactants, and inoculation of precipitate [Wasserman, IMC Chemical sedimentation from solutions]. It should be noted that the principles that have been most studied and proven effective for diluted solutions have been found not to be applicable to concentrated solutions. At the same time, by using highly mineralized brine containing more than 200 g / l of magnesium chloride in the technical process without prior dilution, the capacity of the reactor and tank equipment can be reduced, thereby improving the technical and economic parameters of the process. Therefore, in order to obtain suspensions with improved precipitation and filtration properties, it is necessary to select and carefully observe the technical parameters of the process.

[0021] To obtain magnesium hydroxide precipitate in crystalline form, the temperature in the initial reagent addition zone and the precipitate holding zone must be maintained above 40°C. This makes it possible to avoid even localized centers of precipitate formation in a pseudo-amorphous form, which is a gel-like viscous substance that is difficult to mix. Next, to obtain a suspension with improved precipitation and filtration properties, it is necessary to ensure crystal growth and aggregation of primary magnesium hydroxide particles. This is promoted by a sufficient residence time, during which secondary particle expansion occurs as the particles adhere to blocks and aggregate, making seed-containing crystals with the desired properties available. Crystal formation is induced according to specific types and accumulations, thereby improving the precipitate structure. Treating seed crystals with a magnesium salt solution, which is the initial reagent, promotes the subsequent addition of an alkaline agent, which is also an initial reagent, nucleation of primary crystals on their surfaces, formation according to a given type, and subsequent crystal expansion. A key element of these processes is to stir slowly so as not to break the resulting particle blocks and aggregates.

[0022] A technical embodiment of the above process is the continuous formation of magnesium hydroxide in a reactor cascade, with reaction zones separated according to their functional purposes. In a first reactor, the seed crystals are processed, with a suspension of seed crystals and a magnesium salt solution being simultaneously distributed in the presence of a liquid petroleum product; in a second reactor, the processed seed crystals and a magnesium salt solution containing an alkaline agent, representing a suspension of magnesium hydroxide crystals in a sodium chloride solution, are simultaneously added to the reaction mass, resulting in the formation of primary magnesium hydroxide particles in crystalline form; in subsequent reactors, the maturation, accumulation, and aggregation of secondary particles occur on the already formed magnesium hydroxide crystals. The reaction mass from the last reactor, containing magnesium hydroxide crystals with the necessary filtering and precipitation properties, acts as a seeding agent.

[0023] Three to five reactors are required within the designated cascade of the continuous reactor, which is sufficient to provide separate functional zones.

[0024] The residence time in each separation zone is at least 20 minutes, preferably 20 minutes to 2 hours, depending on the concentration of the reactants and the selected temperature (it must not be below 40°C). If the residence time in the separation zone is less than 20 minutes, the required filtration and precipitation properties of the resulting suspension cannot be reliably obtained, and if the residence time exceeds 2 hours, it is economically inefficient.

[0025] As water-soluble magnesium salts, synthetic or naturally occurring magnesium chloride solutions are used. For example, bischofite solutions, which may be pre-purified by known methods from heavy metals and / or iron, and / or sulfates, and / or boron, and / or bromine, and / or other undesirable impurities.

[0026] The aggregates of magnesium hydroxide crystals obtained by the proposed method provide efficient filtration and precipitation properties, and contribute to obtaining magnesium oxide with an increased particle size distribution. To further break down the aggregates, a liquid petroleum product, such as a product of direct and / or vacuum petroleum refining, is added to the magnesium chloride solution. This product has an initial boiling point of 150°C or higher, a final boiling point of 400°C or lower, a density in the range of 750–880 kg / m³, and is present in an amount of 0.0001–0.01% by weight. Examples of liquid petroleum products include diesel fuel, low-viscosity marine fuel, kerosene, and similar petroleum products.

[0027] The liquid petroleum product is absorbed by magnesium hydroxide seed crystals, forming a thin film in the seed crystal treatment zone. Subsequently, during the calcination of the magnesium hydroxide crystal aggregates in the calcination furnace, boiling and evaporation of the liquid petroleum product occur at temperatures ranging from 150 to 400°C. This leads to the rupture and destruction of secondary particle aggregates, thereby facilitating grinding and reducing the size of the secondary particles of the resulting activated high-purity magnesium oxide. The vaporized liquid petroleum product is decomposed into CO2 and H2O in the calcination furnace.

[0028] The addition of liquid petroleum products to a magnesium chloride solution, and the production method proposed, contributes to the formation of active, high-purity magnesium oxide particles, resulting in gel-like and cream-like viscosities. Furthermore, it is possible to obtain a reduced-viscosity aqueous suspension without complicating stirring, pumping, and adding processes.

[0029] As an alkaline agent, a solution of alkali metal hydroxide, such as sodium hydroxide solution, is used.

[0030] Alkaline agent ions vs. magnesium chloride OH - :Mg ++It is preferable that the molar ratio of (1,9 / 2,1):1 or less. An increase in excess chloride leads to contamination of the resulting magnesium hydroxide with magnesium chloride, necessitates an increase in the volume of water used for washing, and increases the mass fraction of chloride in the resulting magnesium oxide. An increase in the excess amount of alkaline agent leads to the formation of a finely dispersed precipitate of magnesium hydroxide that is difficult to filter, resulting in a decrease in process efficiency.

[0031] The experimentally determined effective mixing rate that provides sufficient contact area for the phases without disrupting the aggregates of the formed particles is in the range of 20–300 rpm.

[0032] A suspension of magnesium hydroxide crystals prepared in the mother liquor is used as a seed. The seed is supplied to the first functional zone in an amount of 1–80% of the total mass of the initial reagent supplied.

[0033] After the crystal accumulation and aggregation zone, the magnesium hydroxide crystals can be subjected to hydrothermal recrystallization at temperatures ranging from 120 to 220°C, pressures ranging from 0.1 to 2.3 MPa, and durations of 1 to 24 hours. Hydrothermal recrystallization of magnesium hydroxide crystals facilitates more effective washing of magnesium hydroxide crystals from chlorides, as well as a reduction in the size of secondary magnesium hydroxide particles.

[0034] Hot water recrystallization can be performed in the reaction mother liquor at a wide range of reagent concentrations, and the preferred magnesium hydroxide content is in the range of 2 to 10% by weight.

[0035] The separation of magnesium hydroxide crystals from the mother liquor is carried out by any known method, such as filtering the resulting suspension or precipitate, and then filtering out the thickened portion.

[0036] Washing of magnesium hydroxide crystals from chloride is carried out by any known method, such as washing the filter residue and / or repelling the residue and subsequent filtration. To increase washing efficiency, an aqueous sodium hydroxide solution with a mass fraction of 0.01–0.50% is used as the washing solution.

[0037] Washing of magnesium hydroxide crystals is carried out in one or two stages: In the first stage, the magnesium hydroxide crystals are washed using a filter with demineralized water and / or alkaline water representing an aqueous solution of sodium hydroxide with a mass fraction of 0.01–0.50%. In the second stage, the magnesium hydroxide crystals are dispersed in an aqueous medium. This includes demineralized water and / or alkaline water representing an aqueous solution of sodium hydroxide with a mass fraction of 0.01–0.50% and a mass ratio of water medium / magnesium hydroxide in the range of (5 / 30):1, thereby forming a suspension of magnesium hydroxide, which is then filtered.

[0038] To obtain magnesium oxide, washed magnesium hydroxide crystals are calcined in a furnace at a temperature in the range of 300–700°C and then crushed. Calcination of magnesium hydroxide crystals is carried out periodically or continuously.

[0039] The resulting highly purified active magnesium oxide has a specific surface area BET of 70–200 m². 2 / g, average particle size (d50) ≤ 10 μm as determined by laser diffraction, iodine activity in the range of 70–200 mg I / g MgO, citrate activity within 40 seconds, pore volume 3.2 × 10⁻⁶ -3 cm 3 / g ~ 10.2 × 10 -2 cm 3The range of / g is as follows: 10% of the particles have a diameter of 2 μm or less, 90% of the particles have a diameter of 30 μm or less, the mass fraction of the residue on a 150 μm sieve is 1% or less, the mass fraction of the residue on a 45 μm sieve is 2% or less, the mass fraction of chloride is 0.1% or less, the mass fraction of calcium is 0.1% or less, the mass fraction of substances insoluble in hydrochloric acid is 0.05% or less, the mass fraction of iron is 0.005% or less, the mass fraction of each impurity (Ti, Co, Mo, V, Sb, Ba cations) is 1 ppm or less, and Pb, Cd, As, and Hg are 0.1 ppm or less.

[0040] The specified magnesium oxide has a mass fraction of 1% or less of carbonate and a mass fraction of 2 ppm or less of manganese (Mn).

[0041] The specified magnesium oxide has a kinematic viscosity of 30 cP or less in its aqueous suspension, which allows for the production of a reduced-viscosity aqueous suspension, potentially simplifying the technical aspects of mixing, pumping, and loading.

[0042] The highly purified active magnesium oxide obtained by the above method can be modified with one or more surface treatment agents and / or binding silane agents. Compounds selected from the group of saturated and unsaturated fatty acids containing 8 to 20 carbon atoms, or their alkali metal salts and / or mixtures thereof, can be used as surface treatment agents. Examples of such compounds include stearic acid, oleic acid, lauric acid, palmitic acid, behenic acid, myristic acid, and tall oil fatty acids.

[0043] Compounds and / or mixtures thereof selected from the group of organically functional trialkoxysilanes, such as alkyltriethoxysilanes, alkyltrimethoxysilanes, alkenyltriethoxysilanes, alkenyltrimethoxysilanes, and aminosilanes, are used as silane binders. Examples of such compounds include methyltriethoxysilane, octyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-methacrylateoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, glycidoxypropyltrimethoxysilane, aminopropyltriethoxysilane, and aminopropyltrimethoxysilane.

[0044] It is preferable to use a surface treatment agent in an amount ranging from 0.1% to 5.0% by weight, calculated using magnesium oxide.

[0045] Surface treatment is carried out by any known method, such as the suspension method or the dry method.

[0046] The highly active magnesium oxide obtained by the proposed method possesses adjustable activity and particle size distribution and high chemical purity, making it suitable for use in the pharmaceutical, drug, and food industries, as well as in the manufacture of catalysts, specialty ceramics, specialty glass, rubber, adhesives, plastic ingots, polymer fillers, stabilizers in the production of chloroprene rubber, and as a purification additive for organic solvents in the production of magnesia cement and other magnesium-containing materials.

[0047] The following analytical methods were used to analyze magnesium oxide. -Specific surface area BET and pore volume were determined using the high-speed surface area and pore size analyzer "Nova2200e" (Quantachrome Instruments, USA). - The particle size distribution was determined by laser diffraction using a Malvern MasterSizer-2000E device (Malvern Limited, UK) equipped with a Scirocco 2000 module. - Iodine activity (unit: mg I / g MgO) was determined by iodine titration in a carbon tetrachloride medium. -Citric acid activity (in seconds) was determined by adding a 0.4N citrate solution containing phenolphthalein indicator to water containing a magnesium oxide suspension at 29±2°C, and measuring the time it took for the color to appear crimson. -Cl - Chloride and SO4 2- The mass fraction of sulfate was determined by optical turbidimetry. - The mass fraction of substances insoluble in hydrochloric acid was determined by gravimetric analysis in accordance with GOST 4526 "Reagents. Magnesium Oxide". The mass fraction of the residue on the -150 μm sieve was determined by dry sieving using a brush. The mass fraction of the residue on the -45 μm sieve was determined by wet sieving under a water flow; The mass fractions of Fe, Ca, Pb, Cd, As, Hg, Ti, Co, Mo, V, Sb, Ba, and Mn impurities were determined by atomic emission spectrometry using inductively coupled plasma with the "Optima8000" device (PerkinElmer, USA). -CO3 2 - The mass fraction of carbonate was determined by the neutralization method. - Kinematic viscosity was measured using a Brookfield viscometer. Magnesium oxide (50g) was suspended in water (400ml) at room temperature for 1 hour, and the kinematic viscosity of the resulting suspension was measured. The proposed method for producing highly purified activated magnesium oxide is illustrated by the following examples. [Examples]

[0048] The magnesium hydroxide crystal production process is carried out in continuous mode during setup, consisting of a cascade of three reactors equipped with anchor-type stirrers with a rotational speed of 37. The operating capacity of the reactors is 120 dm³. 3 In all reactors of the cascade, a temperature of 50-60°C is maintained.

[0049] A Bischofite solution, pre-washed from heavy metals and iron, is continuously supplied to the first reactor of the cascade. The Bischofite solution has a mass fraction of magnesium chloride of 31.6%, a mass fraction of diesel fuel of 0.001%, a flow rate of 24.8 kg / h, and a seed flow rate of 38.5 kg / h. The seed is a suspension of finished crystals from the last reactor of the cascade.

[0050] A suspension of magnesium hydroxide seed crystals treated with bischofite solution enters the second reactor from the first reactor of the cascade. Simultaneously, a sodium hydroxide solution with a mass fraction of 9.3% and a flow rate of 70.7 kg / h is supplied to the second reactor of the cascade. The resulting suspension of magnesium hydroxide crystals is then transferred from the second reactor containing the formed suspension to the third reactor of the cascade. The residence time in the reactor cascade is 1 hour.

[0051] Magnesium hydroxide crystals are filtered and washed with alkaline water, which is a 0.05% sodium hydroxide aqueous solution. After adjusting the mass ratio of alkaline water to magnesium hydroxide to 10 / 1 using a filter, the crystals are dispersed in alkaline water. This is an aqueous solution of sodium hydroxide with a mass fraction of 0.01% and a mass ratio of alkaline water to magnesium hydroxide equal to 20 / 1, forming a suspension of magnesium hydroxide, which is then filtered.

[0052] After the final cleaning, the magnesium hydroxide crystals are heated in a furnace at a rate of 10°C / min, calcined at a temperature of 600°C for 2 hours, and then crushed with a hammer mill to obtain activated high-purity magnesium oxide.

[0053] The properties of the obtained magnesium oxide are shown in Tables 1 and 2. [Examples]

[0054] The production of magnesium oxide is the same as in Example 1, except that a low-viscosity Bischofite solution of marine fuel with a mass fraction of 0.0002% is supplied. A sodium hydroxide solution with a mass fraction of 9.3% and a flow rate of 71.1 kg / h is supplied to the second reactor of the cascade, and the mixture is washed with demineralized water using a filter at a demineralized water / magnesium hydroxide mass ratio equal to 1 / 6. After filter washing, the magnesium hydroxide crystals are dispersed in demineralized water and filtered.

[0055] The magnesium hydroxide cake is baked at 450°C.

[0056] The properties of the obtained magnesium oxide are shown in Tables 1 and 2. [Examples]

[0057] The production of magnesium oxide is carried out in the same manner as in Example 1, except that a bischofite solution purified from heavy metals, iron, and sulfates with a low viscosity mass fraction of 0.0002% of marine fuel is supplied. The magnesium hydroxide suspension from the third reactor of the cascade is directed to hydrothermal recrystallization at a temperature of 170°C and a pressure of 0.6 MPa for 2 hours. Washing of the magnesium hydroxide crystals is performed by filtration, with an alkaline water / magnesium hydroxide mass ratio of 6 / 1, and no dispersion of crystals is performed.

[0058] The magnesium hydroxide cake is baked at 450°C.

[0059] The properties of the obtained magnesium oxide are shown in Tables 1 and 2. [Examples]

[0060] Magnesium oxide is obtained in the same manner as in Example 3, except that after washing, magnesium hydroxide crystals are dispersed in alkaline water. This is an aqueous sodium hydroxide solution with a mass fraction of 0.05% and a mass ratio of alkaline water / magnesium hydroxide equal to 20 / 1, forming a magnesium hydroxide suspension, which is then filtered.

[0061] The magnesium hydroxide cake is baked at 450°C.

[0062] The properties of the obtained magnesium oxide are shown in Tables 1 and 2.

[0063] Comparative Examples 361.5 kg of 9.2% mass fraction sodium hydroxide solution in a working volume of 500 dm³ 3 Add to the reactor and add 118.5 kg of Bischof stone solution containing a mass fraction of 33.46% magnesium chloride. The reaction mixture is stirred for 2 hours at 20-30°C. Next, the magnesium hydroxide crystals are filtered using a filter and washed with desalinated water in which the mass ratio of alkaline water to magnesium hydroxide is equal to 10 / 1. The magnesium hydroxide crystals are heated in a furnace at a rate of 10°C / min and calcined at a temperature of 600°C for 2 hours, then crushed in a hammer mill to obtain magnesium oxide.

[0064] The properties of the obtained magnesium oxide are shown in Table 1.

[0065] Examples of surface treatment Add 200 g of magnesium oxide obtained as described in Example 3 to a Henschel mixer, supply 7 g of stearic acid thereto, and stir the mixture at 80°C for 100 to 20 minutes. Surface-treated magnesium oxide is obtained in which the mass fraction of stearic acid is equal to 3.5%.

[0066] The above embodiments are illustrative and illustrate the essence of the present invention, and do not limit the field of the claimed invention.

[0067] The examples shown demonstrate that the proposed manufacturing method can yield highly purified active magnesium oxide with adjustable activity, chemical purity, and particle size distribution.

[0068] [Table 1]

[0069] [Table 2]

Claims

1. Specific surface area BET70~200m 2 / g, an average particle size (d50) of 10 μm or less as determined by laser diffraction, an iodine activity in the range of 70 to 200 mg J / g MgO, a citric acid activity of 40 seconds or less, and a pore volume of 3.2 × 10 -2 cm 3 / g〜10.2×10 -2 cm 3 / g range; 10% of the particles have a diameter of 2 μm or less, 90% of the particles have a diameter of 30 μm or less, the mass fraction of the residue on a 150 μm sieve is 1% or less, the mass fraction of the residue on a 45 μm sieve is 2% or less, the mass fraction of chloride is 0.1% or less, the mass fraction of calcium is 0.1% or less, the mass fraction of substances insoluble in hydrochloric acid is 0.05% or less, the mass fraction of iron is 0.005% or less, and the mass fractions of each of the impurities Ti, Co, Mo, V, Sb, and Ba cations are 1 ppm or less, and each of Pb, Cd, As, and Hg is 0.1 ppm or less.

2. 130-180m 2 2. The active high-purity magnesium oxide according to claim 1, characterized in that it has a specific surface area BET in the range of / g.

3. 2. The activated high purity magnesium oxide of claim 1, characterized in that it has an average particle size (d50) determined by laser diffraction method that is less than or equal to 2 microns.

4. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of chlorides that is less than or equal to 0.02% by weight.

5. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of calcium that is less than or equal to 0.05% by weight.

6. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of carbonates that is less than or equal to 1% by weight.

7. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of sulfates that is less than or equal to 0.01% by weight.

8. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of iron (Fe) that is less than or equal to 0.003% by weight.

9. 2. The activated high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of manganese Mn that is less than or equal to 2 ppm.

10. 2. Active high-purity magnesium oxide according to claim 1, characterized in that it has a mass of residue on a 150 micron sieve of less than 0.05%.

11. 2. Activated high-purity magnesium oxide according to claim 1, characterized in that it has a mass fraction of residue on a 45 micron sieve of less than or equal to 0.1%.

12. 2. The active high-purity magnesium oxide according to claim 1, characterized in that it has a kinematic viscosity of its aqueous suspension of 30 cP or less.

13. Activated high-purity magnesium oxide according to claim 1, characterized by a surface treatment with one or more silane coupling agents or one or more surface treatment agents, wherein the one or more silane coupling agents are selected from organofunctional trialkoxysilane groups, such as alkyltriethoxysilane, alkyltrimethoxysilane, alkenyltriethoxysilane, alkenyltrimethoxysilane, etc., and the one or more surface treatment agents are selected from saturated and unsaturated fatty acid groups, containing 8 to 20 carbon atoms, and including stearic acid, oleic acid, palmitic acid, behenic acid, myristic acid, tall oil fatty acid, and / or their alkali and / or alkaline earth metal salts, and / or mixtures thereof, in an amount of 0.1 to 5.0% of the magnesium oxide mass.

14. 1. A process for producing activated, possibly surface-treated, high-purity magnesium oxide by calcining magnesium hydroxide produced by the interaction of an aqueous magnesium salt solution with an alkaline agent, wherein magnesium hydroxide crystals are produced by a continuous process in which they are separated and isolated from each other in a seed crystal treatment zone, a magnesium hydroxide crystal formation and growth zone, and a crystal accumulation and aggregation zone, and further wherein an aqueous magnesium chloride solution and a magnesium hydroxide seed crystal suspension are fed to said seed crystal treatment zone in the presence of a liquid petroleum product in an amount of 1-80% of the total mass of the fed initial reagents, and the treated magnesium hydroxide crystal suspension from the previous zone and the alkaline agent in a molar ratio of OH to magnesium chloride ions are fed to said seed crystal treatment zone. - :Mg ++ wherein an alkaline agent having a ratio of 1.9 / 2.1:1 is fed to the crystal formation and growth zone, and the suspension from the previous zone is fed to the crystal accumulation and aggregation zone, the temperature in all zones being maintained at 40°C or higher, and the residence time of the magnesium hydroxide crystal suspension in each isolation zone is 20 minutes or longer.

15. 15. A method for producing activated high purity magnesium oxide according to claim 14, characterized in that an aqueous magnesium chloride solution of synthetic or natural origin is used, which has been previously cleaned from heavy metals and / or iron, and / or sulfates, and / or boron, and / or bromine, and / or other unintended impurities as the aqueous magnesium chloride solution.

16. 15. The method for producing activated high-purity magnesium oxide according to claim 14, wherein an aqueous sodium hydroxide solution is used as the alkaline agent.

17. Initial boiling point above 150°C, final boiling point below 400°C, in an amount of 0,0001 to 0,01% by weight, 750 to 880 kg / m 3 15. A method for producing activated high purity magnesium oxide according to claim 14, characterized in that a liquid petroleum product, being the product of direct and / or vacuum petroleum refining, having a density in the range of 0.1 to 0.5, is added to the magnesium chloride solution.

18. 15. A method for producing active high purity magnesium oxide according to claim 14, characterized in that after the crystal accumulation and aggregation zone, the magnesium hydroxide suspension is subjected to hydrothermal repeated crystallization of magnesium hydroxide particles within a temperature range of 120-220°C, a pressure range of 0.1-2.3 MPa, and a duration range of 1-24 hours.

19. 15. A method for producing activated high-purity magnesium oxide according to claim 14, characterized in that for washing the magnesium hydroxide crystals, demineralized water and / or alkaline water, which is an aqueous sodium hydroxide solution with a mass fraction in the range of 0.01 to 0.50%, is used.

20. 15. A method for producing active high-purity magnesium oxide according to claim 14, characterized in that the washing of magnesium hydroxide crystals is carried out in one or two stages, in which in the first stage, the magnesium hydroxide crystals are washed using a filter with demineralized water and / or alkaline water, an aqueous sodium hydroxide solution with a mass fraction ranging from 0.01 to 0.50%, and in the second stage, the magnesium hydroxide crystals are dispersed in an aqueous medium, comprising demineralized water and / or alkaline water, an aqueous sodium hydroxide solution with a mass fraction ranging from 0.01 to 0.50%, an aqueous medium / magnesium hydroxide mass ratio ranging from (5 / 30):1, thereby forming a magnesium hydroxide suspension, which is then filtered.

21. 15. The method for producing activated high purity magnesium oxide according to claim 14, characterized in that the washed magnesium hydroxide crystals are calcined in a calciner at a temperature ranging from 300 to 700°C.

22. 15. A method for producing activated high purity magnesium oxide according to claim 14, characterized by the magnesium oxide surface treatment with one or more silane coupling agents or one or more surface treatment agents, wherein the one or more silane coupling agents are selected from organofunctional trialkoxysilane groups, such as alkyltriethoxysilane, alkyltrimethoxysilane, alkenyltriethoxysilane, alkenyltrimethoxysilane, etc., and the one or more surface treatment agents are selected from saturated and unsaturated fatty acid groups, containing 8 to 20 carbon atoms, including stearic acid, oleic acid, palmitic acid, behenic acid, myristic acid, tall oil fatty acid, and / or their alkali and / or alkaline earth metal salts, and / or mixtures thereof, in an amount of 0.1 to 5.0% of the magnesium oxide mass.