LT6284B - Anhydrous calcium silicate production method and thus obtained anhydrous calciun silicate - Google Patents

Abstract

The present invention relates to the one-step hydrothermal synthesis method of anhydrous calcium silicate - kilchoanite (Ca3Si2O7). Invention refers to hydrothermal synthesis conditions and to chemical nature of raw materials, indicators of purity, activity and composition of mixtures which determine anhydrous calcium silicate formation.

Description

FIELD OF THE INVENTION The invention relates to methods for producing inorganic materials, namely methods for obtaining anhydrous calcium silicates. More particularly, the present invention relates to the manufacture of anhydrous calcium silicate - kilocoanite (Ca3S2207) by single-stage hydrothermal synthesis. Techniques of Invention by Ivan

The main compounds of the anhydrous calcium silicate group are volastonite, belita and alita. They are widely used not only in the production of binding materials, but also in many other industries.

Monocalcium Silicate - Volastonite (CaSiOs) is used in the ceramics, glass, cement, paint, paper and plastics industries. Due to its unique properties - biocompatibility with the human body, volastonite is widely used in medicine, especially in the manufacture of implants [Lin K, et al., Study of the mechanical property and in vitro biocompatibility of CaSi03 ceramics. Ceram Int 2005; 31: 323-6; Sreekanth Chakradhar RP et al. Solution combustion derived nanocrystalline macroporous vvollastonite ceramics. Mater Chem Phys 2006; 95: 169-75; Carrodeguas RG et al. J Biomed Mater Res 2007; 83A: 484-95; Lin K et al. A simple method to synthesize single-crystalline p-wollastonite nanowires. J Cryst Grovvth 2007; 300: 267-71; Wang H et al. Synthesis and microvvave dielectric properties of the CaSi03 nanopovvder by the sol-gel process. Ceram Int 2008; 34: 1405-8; Long L et al. Preparation and properties of CaSiO3 / Zr02 (3Y) in nanocomposites. J Eur Ceram Soc 2008; 28: 2883-7 et al. ].

Other anhydrous calcium silicates are dicalcium silicate (Ca2SiO4) - belite and tricalcium silicate (CasSiOs) - alita.

Belitas and Alitas are the most widely used in the binder industry. These calcium silicates have a unique feature: hydrating, t. y. water-reactive products combine fine and coarse aggregates (sand, gravel, crushed stone) into the monolith. Bonding materials made on this basis are used for the production of concrete, construction mortars, joining of building components and others.

Unlike calcium hydrosilicates, known methods of production of anhydrous calcium silicates are complex, costly, associated with high CO2 emissions because of the need for heat treatment at 600-1450 ° C.

To summarize the production methods of anhydrous calcium silicates, three main methods can be distinguished.

First: Production of calcium silicates by solid phase sintering: treatment / combustion of homogenous mixture of starting materials at high temperature (1100-1450 ° C). This is a major drawback of this method.

Volastonite is formed at a temperature of 1100 ° C, where the composition of the starting components corresponds to the molar ratio CaO / SiO2 = 1 [Ibanez A, Penas JMG, Sandoval F. Solid state reaction for producing vollollastonite. Ceram Bull 1990; 69: 374-8.]. Belitas is formed at 1350 ° C, when the composition of the original components corresponds to the molar ratio CaO / SiO2 = 2. This method of production of belitol is very complicated not only because of the high temperature, but also because of the rapid cooling necessary to obtain the proper belite variety, The use of additives allows to reduce the temperature of the formation of belite to 1150 ° C [A. K. Chatterjee, Future Technological Options: Part II, Cem. Concr. Res., 26 [8] 1227-37 (1996); L. Kriskova et al., "Influence of mechanical and chemical activation on the hydraulic properties of gamma dicalcium silicate" Cem. Concr. Res., 55 [1] 59-68 (2014)]. The alloy is formed at 1450 ° C when the composition of the starting components corresponds to the molar ratio: CaO / SiO2 = 3 [H. F. W. Taylor, Cement Chemistry. ISBN 0126839026. London. 1964, Vol. 1.].

The second is the production of starting compounds by herbal gel and the resulting product burning to form calcium silicates. During this production calcium silicates are formed at lower temperatures. The initial soluble calcium and silicon components (eg calcium nitrate and S1O2 gel) in the required amounts (the composition of the initial mixture must correspond to the molar ratio of calcium silicate) are dissolved in liquid, usually in an aqueous medium and thoroughly mixed. The excess solvent is removed by drying and the resulting gel is burned to form calcium silicate. For example, using ammonium nitrate and citric acid supplements for herb production, Volastonite can be formed after 2 hours of burning at 650 ° C [X. Huang, J. Chang, Synthesis of Nanocrystalline Proliferation Povvders by Citrate-Nitrate Gelion Method, Materials Chemistry and Physics 115 [1] 1-4 (2009)]. After 1 hour of burning at 750 ° C, belitis is formed. The belts produced in this way have a large surface area (Sbet: 7.43-12.94 m2 / g) [A. K. Chatterjee, Future Technological Options: Part II, Cem. Concr. Res., 26 [8] 1227-37 (1996)]. After 12 hours of combustion at 1350 ° C, an aldit is formed [H. Zhen, et al., Synthesis of C3S by sol-gel and its features, Journal of the University of Technology-Mater25 [1] 138-141 (2010)]. The main disadvantage of this production method is the high price of the original low-dispersive materials.

Third: the production of calcium silicates in a two-way way. This method of production consists of two steps: hydrothermal synthesis and dehydration of the resulting calcium hydrosilicates i.e. heat treatment of intermediate products to form a target calcium silicate.

Most often, the hydrothermal synthesis without stirring the suspension is carried out in a reactor-autoclave at a temperature of 100 ° to 250 ° C in a saturated water vapor atmosphere, and at a pressure of about 1-40 bar, at 8-14 or. Conventional products of this synthesis are calcium hydrosilicates. y. silicic acid salts, and their general formula is expressed as the ratio of their constituent components: xCa0-ySiO2-pH20 (where: x, y, p is the number of moles).

During the production of Volastonite, hydrothermal synthesis is carried out at a temperature of 100-200 ° C and the decomposition of the intermediate product takes place at a temperature of 900 to 1000 ° C. The temperature of the hydrothermal synthesis directly influences the temperature of the second stage, ie. y. the temperature at which belitis is formed. As a result, the processing temperature of the products varies over wide ranges: when hydrothermal synthesis is carried out at 100 ° C, the belts are formed by heat treatment of the intermediate compounds at 800 to 1300 ° C, and when hydrothermal synthesis is carried out at 200 to 250 ° C, the intermediate product decomposes at 600 ° C C, during which belitis is formed (see AK Chatterjee, supra). It should be noted that alite is not produced in this way.

The said production processes, one of which is hydrothermal synthesis, have both positive and negative aspects. Advantages of this method of production: hydrothermal synthesis allows the use of different starting materials (CaO, Ca (OH) 2, amorphous S1O2, quartz, various industrial wastes: volatile ash, granite atoms, etc.) that are put together in the right quantities to match molar ratio of calcium silicate. By changing the conditions of hydrothermal treatment: temperature, pressure, duration can be controlled by the microstructure of the surface of calcium silicates, the specific surface area, the size of the dominant pores and their distribution by radius, the size and shape of the crystals and the stability at low or high temperatures and other properties.

Disadvantage: The aqueous suspensions obtained by hydrothermal synthesis must be diluted, granulated, burned at high temperature and crushed.

The international application VV02007 / 017142 (publ. 2007) discloses the technology of manufacturing of binding materials for belts. CaO and S1O2-containing raw materials are added to the initial mixture during the production of said binders, when the Ca / Si molar ratio varies from 2.5: 1 to 1.5: 1 and a certain amount of α-C2SH for crystallization centers formation (here the calcium silicate classification continues) and Marking by: Raimundas Šiaučiūnas, Kęstutis Baltakys “Calcium Hydrosilicates: Synthesis, Properties and Usage of Filosilicate Group Compounds” KTU, Technologija, Kaunas, 2010).

The initial mixture is then hydrothermally treated at a temperature of 100-300 ° C to give a-C2SH during this process. After hydrothermal synthesis, the products obtained after burning in the temperature range of 500-1000 ° and after cooling, form a belite which has no H-0 bond, and its crystal spatial structure consists of isolated silicate tetrahedrons (Q °).

A series of patents [US5750038, publ. 1998; VVO2013 / 189573, publ. 2013; et al., describes methods for producing calcium silicate-containing materials which carry out a hydrothermal reaction, but necessarily carry out an additional thermal treatment (combustion) step for the target product as mentioned above.

The publications on anhydrous calcium silicate - kilocoanite (Ca3Si207) are not many and all point to a complicated, multi-stage production method that is unattractive both ecologically and economically. In addition, many sources only emphasize the peculiarities of the crystalline structure of the kilocoanite.

Japanese Patent JPH0465010, published in 1984, mentions a process for the production of kilocoanite by treating an aqueous suspension of primary oxide components (molar ratio Ca / Si 1.3 - 1.8: 1) under hydrothermal reaction conditions at 160-250 ° C in a saturated water vapor environment. However, the stoichiometry of the initial blend has a significant effect on the mineral composition of the products, and therefore the unclear or pure (> 95%) kilchoanite can be formed in mixtures whose molar ratio does not correspond to the chemical composition of said compound. Since the duration of isothermal retention is unclear, it is difficult to judge / estimate the chemical composition and formation and stability conditions of the kilocoanite in the specified temperature range.

In addition, authors' research has shown that calcium silicates at temperatures below 175 ° C do not even form 72 hours of isothermal retention in mixtures with a molar ratio of Ca / Si ranging from 1.5 to 1.75: 1.

Therefore, obtaining anhydrous calcium silicate (for example, kilocoanite) in a stable and pure form without additional combustion at elevated temperatures is a serious technical problem.

As a result of the research, it was unexpectedly found that by hydrothermal synthesis not only conventional calcium hydrosilicates but also anhydrous calcium silicates could be obtained.

Accordingly, it is an object of the present invention to provide anhydrous calcium silicate kilocoanite by one-stage hydrothermal synthesis. Another object of the invention is to obtain a target product having a purity of 96% or greater. In order to achieve these goals, it was important to find the conditions under which the recrystallization of intermediate hydrothermal products into the target product is possible.

The present invention provides conditions for hydrothermal synthesis (temperature and duration of isothermal retention, water / solid ratio, temperature increase / cooling rate, magnitude of overpressure), and chemical nature, purity, activity rates of the raw materials, and composition of the mixtures to form anhydrous calcium silicates. Summary of the Invention The present invention provides a novel process for the preparation of anhydrous calcium silicates having a Ca / Si molar ratio of 1.16 to 1.6: 1 under hydrothermal conditions.

Its main difference is that it performs at least 24 hours of isothermal maintenance.

Another important feature of the new method is that hydrothermal synthesis is carried out under pressure of saturated water vapor, with an overpressure of about 10 bar before synthesis.

More specifically, the proposed process for producing anhydrous calcium silicates comprises the following operations: preparing an aqueous suspension of a starting mixture having a Ca0 / SiO2 molar ratio of 1.5-1.75: 1, wherein the ratio of water to solids is about 10: 1; the suspension is placed in an autoclave at a pressure of about 10 bar, and hydrothermal synthesis comprising a temperature increase gradually to 190-210 ° C over about 2 or. and isothermal retention at said temperature optimally 48-72 or at a pressure of 24 to 30 bar.

In an optimal embodiment of the method, prior to preparation of the aqueous suspension, said initial mixture wherein the specific surface of the compound containing the calcium oxide component is Sic. is about 1673 m2 / kg and CaO isvas 98.7%, and the silicon oxide-containing compound has a specific surface Sic. about 1309 m2 / kg and 5.19%, additional homogenizing.

The compound containing the calcium oxide component of the initial mixture is selected from the group consisting of calcium oxide, calcium hydroxide and calcium carbonate, and the silicon oxide component compound is amorphous silica.

For anhydrous calcium silicate kilchoanite, the molar ratio of the initial mixture of CaO / SiO2 is 1.5: 1, the isothermal retention time is optimally 48 or. and temperature 200 ° C.

Another object of the invention is an anhydrous calcium silicate obtained by the proposed process, which is a kilo-anhyde Ca3Si207 having a purity of 96%, preferably not less than 98%. The present invention provides a product in a crystalline form having infrared peaks at 435; 495; 516; 583; 710; 896; 930; 977; 1045; 1200 cm ~ 1 and / or typical diffraction peaks of X-ray diffraction at 2 Θ: 0.57; 0.508; 0.464; 0.427; 0.417; 0.397; 0.375; 0.367; 0.355; 0.337; 0.309; 0.305; 0.294; 0.2881; 0.286; 0.277; 0.275; 0.267; 0.254; 0.248; 0.247; 0.242; 0.236; 0.235; 0.226; 0.221; 0.217; 0.214; 0.209; 0.206; 0.204; 0.199; 0.197; 0.195; 0.19; 0.187; 0.187; 0.184; 0.181; 0.18 nm. Its infrared spectrum is shown in FIG. 6 and / or powder diffraction X-ray is shown in FIG. 5a.

BRIEF DESCRIPTION OF THE DRAWINGS The essence of the invention is illustrated by figures depicting:

FIG. 1 - X-ray diffraction analysis (a) of the fusion product and simultaneous thermal analysis (b): thermogravimetry (1 cr.), Differential scanning calorimetry (2 cr.) Curves with a molar C / S ratio of 1.5 and synthesis 200 ° Duration C at 16 or. Here: c - C-S-H (l); a - 0C2S hydrate; k - calcium carbonate, b - C-S-H (II).

Fig. 2 is an IR adsorption curve for a synthesis product at a temperature of 200 ° C for 16 hours.

FIG. 3 - X-ray diffraction analysis (a) and simultaneous thermal analysis (b) of fusion product: thermogravimetry (1 cr.), Differential scanning calorimetry (2 cr.) Curves with molar C / S ratio of 1.5 and fusion 200 ° Duration C at 24 or. Here: c - C-S-H (l); d - kilchoanite; k - calcium carbonate.

FIG. 4 - IR product adsorption curve for synthesis time at 200 ° C for 24 hours.

FIG. 5 - X-ray diffraction diffraction analysis (a) differential scanning calorimetry (b) curves when the molar C / S ratio of the mixture is 1.5 and the duration of fusion at 200 ° C is 48 or. Here: d -chilocyanite; k - calcium carbonate.

FIG. 6 - IR adsorption curve for synthesis time at 200 ° C for 48 hours.

FIG. 7 - X-ray diffraction analysis curve for synthesis product with a molar C / S ratio of 1.5 and a duration of 72 for fusion at 200 ° C. Here: d - kilchoanite; k - calcium carbonate; F - CeSs.

FIG. 8 - X-ray diffraction analysis curve for the fusion product with a C / S ratio of 1.75 and a duration of fusion at 200 ° C of 48 or. Here: c - C-S-H (l); a - C1-C2S hydrate; d - kilchoanite; k - calcium carbonate.

FIG. 9 is the IR adsorption curve of the synthesis product at 48 ° C for 48 hours.

FIG. 10 - X-ray diffraction curve for the fusion product with a C / S ratio of 1.75 and a fusion time of 200 ° C at 72 ° C. Here: d - kilchoanite; k - calcium carbonate; F - CeSs.

FIG. 11 is the IR adsorption curve of the synthesis product at a temperature of 200 ° C for 72 hours.

FIG. 12 - X-ray diffraction diffraction analysis (a) and simultaneous thermal analysis (b) of fusion product: thermogravimetry (1 cr.), Differential scanning calorimetry (2 cr.) Curves with molar C / S ratio of 1.5 and synthesis 175 ° C duration 72 or. Here: c - C-S-H (l); a - α-C2S hydrate; k - calcium carbonate, b - C-S-H (II).

FIG. 13 - X-ray diffraction analysis curve for the fusion product with a C / S ratio of 1.5 and a duration of 72 at 190 ° C. Here: d - kilchoanite; F - CsSs; s - scout (not marked in previous pictures).

FIG. 14 - X-ray diffraction analysis curve for the fusion product with a C / S ratio of 1.75 and a duration of 72 at 190 ° C. Here: d - kilchoanite; F - CeS ^ s - Scouting.

FIG. 15 - X-ray diffraction analysis curve for the fusion product with a C / S ratio of 1.5 and a duration of 72 ° C at 210 ° C. Here: d - kilchoanite; F - CeSs; x - xsonotlite; s - Scouting.

DETAILED DESCRIPTION OF THE INVENTION According to the present inventors, the general scheme of formation of anhydrous calcium silicates according to the present invention is as follows:

where: A is a compound having a CaO component, Wcao > 95%, a compound having a B-S1O2 component, Wsio2 > 95%.

In the manufacture of anhydrous calcium silicates according to the present invention, raw materials such as calcium oxide and amorphous SiO 2 nhteO are stored in raw material bunkers. The required quantities of material weighed from the bunkers of these bunkers are delivered to a periodic propeller mixer, which is filled with the required volume of water from the tank. Mixed starting materials are pumped to the autoclave. The synthesized material is transferred to an intermediate reservoir where the pump is used to drain the excess water and is supplied to the dryer to remove the remaining moisture.

More specifically, the kilocoanite was obtained in one step using calcium oxide prepared from the reagent Ca (OH) 2 (additionally burned at 500-550 ° C, ground and sieved through a sieve). Specific surface of prepared calcium oxide

Spav. = 1673 m2 / kg; CaOiadvas = 98.7%. Silicon oxide SiCte-nteO (used amorphous silica with a purity of at least 98%) was also ground and sieved. Prepared Silicon Oxide Spav. = 1309 m2 / kg; damage - 5.19%. From these compounds, a starting mixture having a molar ratio of Ca to SiO 2 of 1.5-1.75 was prepared. This initial mixture was homogenized, for example, by a homogenisation device or analogously, and filled with distilled water to give a ratio of water to solids in V / K equal to 10. Details of the fusion conditions are given in the examples below. The invention is illustrated by the following examples. This information is provided for illustrative purposes and is not intended to limit the scope of the invention. Example 1

Starting Raw Materials: Calcium Oxide prepared from Reagent Ca (OH) 2, additionally burned for 1 hour at 550 ° C, ground at a speed of 30 s 600 rpm in a vibrating disc mill and sieved through a sieve with mesh size of 80 µm. Specific Surface Spav. = 1673 m2 / kg; CaOiadvas = 98.7%; SiCte-n ^ O reagent, min. 2.5 min at 850 rpm, ground in a vibrating disk mill and sieved through a sieve with mesh size of 80 µm. Spav. = 1309 m2 / kg; damage - 5.19%.

In the preparation of the initial mixtures, the required quantities of components were poured into sealed plastic containers and three porcelain grinding bodies (homogenizing quality) were added. The mixtures were homogenized for 45 min (49 rpm) with a material homogenizer.

The composition of the initial mixture corresponded to the molar ratio CaO / SiO2 = 1.5. The homogenized starting mixture was filled with distilled water to give a ratio of water to solids V / K equal to 10. The synthesis was carried out without mixing the suspension in 25 ml PTFE vessels placed in an autoclave Parr Instruments (Germany) at 200 ° C saturated water vapor temperature. and isothermal retention time of 16 or. 200 ° C temperature was reached within 2 or. The synthesis products were flushed with acetone to less carbonise, dried at 50 ° C for 24 hours and passed through a sieve with mesh size of 80 µm.

Product characteristics are given in 1.1 -1.3. Table 1.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 1.2

Characteristics of the product's main adsorption bands

Table 1.3

Product thermal effects characteristics

From 1.1 -1.3 tables and FIG. The data presented in Figures 1 and 2 show that no calcium silicates are formed in the production conditions described in Example 1. Example 2

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the duration of isothermal maintenance is 24 hours.

Product characteristics are presented in Tables 2.1 - 2.3. Table 2.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 2.2

Characteristics of the product's main adsorption bands

Table 2.3

Product thermal effects characteristics

Tables 2.1 to 2.3 and Fig. The data presented in Figures 3 and 4 show that the biphasic calcium hydrosilicates formed in the production conditions described in Example 2 are unstable and start to crystallize into a target product of kilchoanite in an amount not exceeding 10%. Example 3

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the duration of isothermal maintenance is 48 hours.

Product characteristics are presented in Tables 3.1 - 3.3. Table 3.1

Product mineral composition and diffraction angles 20, distances between atomic planes d and Miller index hkl

Table 3.2

Characteristics of the product's main adsorption bands

Table 3.3

Product thermal effects characteristics

The product obtained is a crystalline material, the chemical formula -Ca 6 (SiO 4) (Si 2 O 10); class - silicates; subclass - sorosilicates; color - white; gloss-matt; crystalline system - orthorhombic; hardness ~ 3; practically insoluble in water. In Tables 3.1 - 3.3 and Fig. Figures 5 and 6 show that kilchoanite with a purity of at least 96 percent was obtained. The purity of the target product can be increased to 98%, for example by eliminating its interaction with CO2 in ambient air during production. Example 4

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the duration of isothermal maintenance is 72 hours.

Product characteristics are presented in Table 4.1. Table 4.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

From Table 4.1 and FIG. Fig. 7 shows that kilchoanite is unstable and begins to recrystallize into related anhydrous calcium silicates. Example 5

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the composition of the initial mixture corresponded to the molar ratio Ca0 / SiO2 = 1.75, and the isothermal duration was 48 hours.

Product characteristics are presented in Tables 5.1 - 5.2 Table 5.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 5.2

Characteristics of the product's main adsorption bands

Tables 5.1 to 5.2 and Fig. The data presented in Figures 8 and 9 show that the target product, Kchoanite, with a purity of at least 50%, is formed together with the biphasic calcium hydrosilicate. Example 6

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the composition of the initial mixture corresponded to the molar ratio Ca0 / SiO2 = 1.75 and the isothermal retention time was 72 hours.

Product characteristics are presented in Tables 6.1 - 6.2 Table 6.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 6.2

Characteristics of the product's main adsorption bands

From Tables 6.1 to 6.2 and Fig. Data 10 and 11 show that the synthesis product is predominantly anhydrous calcium silicates: kilchoanite, CeSs, scout. Example 7

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the saturated water vapor temperature is 175 ° C and the isothermal retention time is 72 hours.

Product characteristics are presented in Tables 7.1 - 7.2 Table 7.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 7.2

Product thermal effects characteristics

From Tables 7.1 to 7.2 and Fig. The data presented in Figure 12 show that under the given production conditions anhydrous calcium silicates are not formed. Example 8

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that saturated water vapor temperature is 190 ° C and isothermal retention time is 72 hours.

Product characteristics are presented in Table 8.1 Table 8.1

Product mineral content and diffraction angles 29, distances between atomic planes d and Miller index hkl

From Table 8.1 and Fig. The data presented in Figure 13 show that under the conditions of production, calcium silicates are also formed after 72 or less. isothermal retention. Example 9

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the composition of the initial mixture corresponded to the molar ratio Ca0 / SiO2 = 1.75, saturated water vapor temperature 190 ° C, and isothermal retention time 72 hours.

Product characteristics are presented in Table 9.1. Table 9.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

Table 9.1 and Fig. The data presented in Figure 14 shows that under the conditions of production, calcium silicates are also formed after 72 or less. isothermal retention. Example 10

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the saturated water vapor temperature is 210 ° C and the isothermal retention time is 72 hours.

Product characteristics are presented in Table 10.1 in Table 10.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

From Table 10.1 and FIG. The data presented in Figure 15 show that the calcium silicates formed in the produced production conditions are unstable and start to regroup into the calcium hydrosilicate - xsonotlite. Example 11

Preparation of the initial mixture and hydrothermal synthesis are performed as described in Example 1.

The difference is that the composition of the initial mixture corresponded to the molar ratio Ca0 / SiO2 = 1.75, saturated water vapor temperature 210 ° C, and isothermal retention time 72 hours.

Product characteristics are presented in Table 11.1 in Table 11.1

Product mineral composition and diffraction angles 2Θ, distances between atomic planes d and Miller indexes hkl

From the data in Table 11.1, it appears that the calcium silicates that are formed under the given production conditions are unstable and start to regroup into calcium hydrosilicate - xsonotlite.

It was found that the preparation of the initial mixture and hydrothermal synthesis as described in Example 1, with saturated water vapor temperature of 220 ° C, and an isothermal retention time of up to 72 hours, independent of the composition of the initial mixture (Ca0 / SiO2 = 1.5; 1.75 ), the products contain calcium hydrosilicate - xsonotlite in combination with anhydrous calcium silicates - kilchoite and CeSs.

The present invention provides conditions for hydrothermal synthesis (isothermal retention temperature and duration, water / solid ratio, temperature increase / cooling rate, magnitude of overpressure), and chemical nature, purity, activity, and composition of raw materials to form anhydrous calcium silicates, particularly chocoanite.

In summary, the proposed invention has the following main advantages over the prior art: 1) hydrothermal synthesis allows not only calcium hydrosilicates but also anhydrous calcium silicates; 2) allows the use of different starting materials for the synthesis of calcium silicates; 3) allows to obtain high purity kilchoanite and control its stability; 4) allows to control the microstructure of the surface of calcium silicates, the specific surface area, the size of the dominant pores and their distribution by radius; 5) reduce energy costs and cost / cost of production of anhydrous calcium silicates; 6) reduce CO2 emissions;

Industrial Applicability From the experimental data presented in Examples 1-8 of the present invention, it can be concluded that the anhydrous calcium silicate (s) of the invention can be effectively used in innovative production technologies of alternative binders, dyes, paper, plastics or medicine. The product can also be used as a carrier for chromatography, as a thermal insulating material, as a refractory coating or as a fireproof construction material.

Claims (8)

DEFINITION DEFINITION The process for the preparation of anhydrous calcium silicates having a Ca / Si molar ratio of 1.16 to 1.6: 1 under hydrothermal conditions, characterized in that the synthesis is carried out for at least 24 hours of isothermal retention. A process for the preparation of anhydrous calcium silicates according to claim 1, characterized in that the hydrothermal synthesis is carried out at a pressure of saturated water vapor, using an excess pressure of about 10 bar prior to synthesis. Process for the preparation of anhydrous calcium silicates according to any one of claims 1 to 2, comprising preparing an aqueous suspension of an initial mixture having a Ca0 / SiO2 molar ratio of 1.5-1.75: 1, wherein the ratio of water to solid is is about 10: 1; The suspension is placed in an autoclave at the initial pressure of about 10 bar and undergoes hydrothermal synthesis, comprising a temperature increase stepwise up to 190-210 ° C for about 2 hours, an isothermal retention at said temperature of optimally 48-72 or at a pressure of 24-30 ° C. bars. Process for the preparation of anhydrous calcium silicates according to any one of claims 1 to 3, characterized in that, before preparing the aqueous suspension, said initial mixture wherein the specific surface of the compound containing the calcium oxide component is acidic. is about 1673 m2 / kg and CaOidwave 98.7%, and the silicon oxide containing compound has a specific surface Sic. about 1309 m2 / kg and 5.19%, additional homogenizing. Process for the preparation of anhydrous calcium silicates according to any one of claims 1 to 4, characterized in that the compound containing the calcium oxide component of the initial mixture is selected from the group consisting of calcium oxide, calcium hydroxide and calcium carbonate, and the compound containing the silicon oxide component is amorphous silica. Process for preparing anhydrous calcium silicate according to any one of claims 1 to 5, characterized in that the molar ratio of Ca0 / SiO2 of the initial mixture is 1.5: 1, the isothermal retention time is 48 or. and temperature 200 ° C. Anhydrous calcium silicate obtained by the process according to any one of the preceding claims, characterized in that it is a kilocoanite Ca3Si207 having a purity of 96%, preferably not less than 98%. Anhydrous calcium silicate according to claim 7 in a crystalline form having infrared spectrum peaks at 435; 495; 516; 583; 710; 896; 930; 977; 1045; 1200 cnr1 and / or typical diffraction peaks of x-ray diffraction at 2Θ: 0.57; 0.508; 0.464; 0.427; 0.417; 0.397; 0.375; 0.367; 0.355; 0.337; 0.309; 0.305; 0.294; 0.2881; 0.286; 0.277; 0.275; 0.267; 0.254; 0.248; 0.247; 0.242; 0.236; 0.235; 0.226; 0.221; 0.217; 0.214; 0.209; 0.206; 0.204; 0.199; 0.197; 0.195; 0.19; 0.187; 0.187; 0.184; 0.181; 0.18 nm. Anhydrous calcium silicate in crystalline form according to claim 8, wherein the infrared spectrum is shown in FIG. 6 and / or powder diffraction X-ray is shown in FIG. 5a.