Monodisperse nanocarbonates and methods of making and using the same

Abstract

The application relates to the technical field of nanomaterials, and discloses monodisperse nanometer carbonate and a preparation method and application thereof. The method for preparing the monodisperse nanometer carbonate comprises the following steps: (1) performing acid-base neutralization reaction on a calcium source and / or a magnesium source and a surfactant in the presence of an organic solvent; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid; (2) mixing water with the product obtained through the acid-base neutralization reaction in step (1); (3) performing first carbonization reaction on the mixture obtained through step (2) and a carbon source a; (4) performing second carbonization reaction on the product obtained through the first carbonization reaction and a carbon source b; wherein the carbon source a is different from the carbon source b. The monodisperse nanometer carbonate particles disclosed by the application are small in particle size, 1-5 nm in size, small in particle size, uniform in particle size distribution, monodisperse, and good in dispersity.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a monodisperse nanocarbonate, its preparation method, and its application. Background Technology

[0002] Nano-carbonates, such as nano-calcium carbonate and nano-magnesium carbonate, have low cost, abundant raw material sources, excellent biocompatibility, and acid-soluble properties, and are widely used in medical materials, oilfield chemicals, and oil additives. For example, CN118304473A discloses an antibacterial and osteogenic implant and its preparation method, which prepares a nano-magnesium carbonate coating that can effectively control magnesium release and promote osteogenic differentiation of osteogenic cells by magnesium ions. CN114940893A discloses a thickening nano-calcium carbonate oil displacement agent that can emulsify crude oil and water to form a W / O emulsion, which can block dominant channels, thereby increasing the crude oil sweep volume in low-permeability areas and ultimately achieving the goal of improving oil recovery.

[0003] The existing methods for preparing nano-carbonates mainly include carbonation and metathesis. Carbonation involves passing CO2 gas into a suspension of metal oxides or metal hydroxides to prepare nano-carbonates. For example, CN117776246A discloses a nano-calcium carbonate microcrystalline dispersion system and its preparation method, using calcium hydroxide or calcium oxide and passing CO2 gas to prepare nano-calcium carbonate with a preferred particle size of 100-200 nm. Metathesis involves mixing a metal salt solution and a soluble carbonate solution to precipitate nano-carbonates. For example, CN102583481A discloses a reverse microemulsion method for preparing spherical nano-calcium carbonate particles of different sizes, using calcium chloride and sodium carbonate to prepare nano-calcium carbonate with a particle size of 10-100 nm. However, although the nano-carbonates obtained by the above preparation method have small primary particle size, the high surface energy associated with the small size makes their dispersion stability poor, and they are prone to agglomeration. They are difficult to disperse stably in liquid media. When used as medical materials, nanofluid oil displacement agents, or oil additives, they tend to precipitate before storage, before pumping, or after injection into the formation, which in turn affects their application performance.

[0004] To address the aggregation problem of nano-carbonates, current technologies employ surfactant modification of the nanoparticle surface to disperse nano-calcium carbonate in a liquid medium, maintaining stability. For example, CN115897285A discloses a transparent aqueous dispersion of nano-calcium carbonate and its preparation method, producing nano-calcium carbonate particles with a diameter of 5-100 nm that can be stably dispersed in an aqueous phase for 30 days. CN116082859A discloses a transparent liquid dispersion of monodispersed nano-calcium carbonate in an organic reagent and its preparation method, producing nano-calcium carbonate with a minimum one-dimensional size of 10 nm that can be stable in organic solvents for several months. However, there is still no nano-calcium carbonate with a particle size smaller than 5 nm, excellent dispersion performance, and the ability to be stably dispersed in a liquid medium for more than a year to meet various application requirements.

[0005] In summary, there is an urgent need for a low-cost, simple preparation method for preparing nano-carbonates with small particle size, uniform size, and good modification, which can stably disperse them in a liquid medium. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of large particle size and poor dispersibility of nano-carbonates in liquid media in the prior art, and to provide a monodisperse nano-carbonate, its preparation method and application.

[0007] The inventors of this invention have discovered that by first reacting a calcium source and / or magnesium source with an organic acid, and then carrying out a stepwise carbonation reaction using two different carbon sources in the presence of an aqueous phase and an organic phase, the particle size of the carbonate can be reduced and the dispersibility of the carbonate in a liquid medium can be improved. To achieve the above objectives, a first aspect of this invention provides a method for preparing monodisperse nano-carbonates, the method comprising the following steps:

[0008] (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid;

[0009] (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1);

[0010] (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a;

[0011] (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction;

[0012] Wherein, carbon source a is different from carbon source b.

[0013] A second aspect of the present invention provides a monodisperse nano carbonate prepared by the method described above.

[0014] A third aspect of the present invention provides a monodisperse nano carbonate comprising carbonate particles and a surfactant coated on the surface of the carbonate particles, wherein the surfactant is an organic acid and the carbonate is calcium carbonate and / or magnesium carbonate.

[0015] A fourth aspect of the present invention provides a monodisperse nano carbonate dispersion comprising a liquid phase medium and the aforementioned monodisperse nano carbonate dispersed in the liquid phase medium.

[0016] The fifth aspect of the present invention provides a method for preparing a monodisperse nano carbonate dispersion, the method comprising: mixing the monodisperse nano carbonate described above with a liquid medium.

[0017] The sixth aspect of this invention provides a method for preparing a monodisperse nano-carbonate dispersion, the method comprising the following steps:

[0018] (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid;

[0019] (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1);

[0020] (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a;

[0021] (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction;

[0022] (5) The product obtained from the second carbonization reaction is subjected to solid-liquid separation to obtain a liquid phase containing nano carbonates, and then some organic solvents in the liquid phase containing nano carbonates are removed.

[0023] Wherein, carbon source a is different from carbon source b.

[0024] The seventh aspect of the present invention provides a monodisperse nano carbonate dispersion prepared by the method described above.

[0025] The eighth aspect of the present invention provides the application of the above-described monodisperse nano carbonates and / or the above-described monodisperse nano carbonate dispersions in medical materials, food additives and oil additives.

[0026] Through the above technical solution, the present invention achieves the following beneficial effects:

[0027] (1) The monodisperse nano carbonate particles of the present invention are easily dispersed in low polarity liquid solvents and have a high solid content, which can reach 1-60 wt%.

[0028] (2) The monodisperse nano carbonate particles of the present invention have small particle size, ranging from 1 to 5 nm. They have small particle size, uniform particle size distribution, monodispersity, and good dispersibility.

[0029] (3) The monodisperse nano carbonate liquid phase dispersion of the present invention has good transparency, high purity, and high stability. It remains transparent and without sedimentation after standing for ≥24 months.

[0030] (4) The preparation method of the monodisperse nano carbonate of the present invention is simple, easy to operate, has low equipment requirements, and low production cost.

[0031] (5) The monodisperse nano carbonate of the present invention has good oil washing efficiency when used in the preparation of oil additives. Attached Figure Description

[0032] Figure 1 Electron micrograph of the monodisperse nano-calcium carbonate dispersion prepared in Example 1;

[0033] Figure 2 The particle size distribution of the monodisperse nano-calcium carbonate dispersion prepared in Example 1 is shown in the figure.

[0034] Figure 3 This is a thermogravimetric analysis (TGA) diagram of the monodisperse nano-calcium carbonate dispersion from Example 1.

[0035] Figure 4-5 The image shows the XRD pattern of the monodisperse nano-calcium carbonate dispersion of Example 1.

[0036] Figure 6 A photograph of the monodisperse nano-calcium carbonate dispersion of Example 1;

[0037] Figure 7 This is a photograph of the monodisperse nano-calcium carbonate solid obtained in step (6) of Example 2;

[0038] Figure 8 Thermogravimetric analysis diagram of the monodisperse nano-calcium carbonate white oil phase dispersion of Example 2;

[0039] Figure 9 A photograph of the monodisperse nano-calcium carbonate white oil phase dispersion of Example 2;

[0040] Figure 10 A photograph of the monodisperse nano-calcium carbonate white oil phase dispersion of Example 2 used in heavy oil;

[0041] Figure 11 A photograph of the monodisperse nano-calcium carbonate toluene phase dispersion of Example 3;

[0042] Figure 12 A photograph of the monodisperse nano-magnesium carbonate toluene phase dispersion of Example 4;

[0043] Figure 13 This is an electron microscope image of the monodisperse nano-calcium carbonate dispersion of Example 7;

[0044] Figure 14 The particle size distribution of the monodisperse nano-calcium carbonate dispersion in Example 7 is shown in the figure.

[0045] Figure 15 Photograph of the monodisperse nano-carbonate dispersion of Comparative Example 1.

[0046] Figure 16 The image shows an electron microscope image of the nano-calcium carbonate dispersion of Comparative Example 4.

[0047] Figure 17 The particle size distribution of the nano-calcium carbonate dispersion in Comparative Example 4 is shown in the figure.

[0048] Figure 18 Electron micrograph of the nano-calcium carbonate dispersion of Comparative Example 5.

[0049] Figure 19 The particle size distribution of the nano-calcium carbonate dispersion in Comparative Example 5 is shown in the figure.

[0050] Figure 20 The image shows the XRD pattern of the solid obtained by centrifugation in Comparative Example 6. Detailed Implementation

[0051] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0052] The first aspect of this invention provides a method for preparing monodisperse nano-carbonates, the method comprising the following steps:

[0053] (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid;

[0054] (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1);

[0055] (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a;

[0056] (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction;

[0057] Wherein, carbon source a is different from carbon source b.

[0058] According to the present invention, preferably, the organic solvent includes a low-polarity solvent and / or a water-soluble organic solvent.

[0059] According to the present invention, preferably, the low-polarity solvent includes at least one of benzene, toluene, chlorobenzene, petroleum ether, petroleum ether, petroleum ether, pentane, isopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, cycloheptane, cyclopentane, naphtha, diesel, kerosene, gasoline, white oil, peanut oil, castor oil, hydrogenated castor oil, fish oil, coconut oil, olive oil, corn oil, soybean oil, sunflower seed oil, juniper berry oil, stigmata oil, dill oil, perilla leaf oil, cinnamon oil, flaxseed oil, avocado oil, bay leaf oil, behenicol, peppermint oil, camphor oil, eucalyptus oil, clove basil oil, clove stem and leaf oil, paraffin wax, ceresin wax, beeswax, vitex oil, toad oil, burn oil, patchouli oil, rhododendron oil, star anise oil, turpentine oil, tea oil, turmeric oil, and heavy oil.

[0060] According to the present invention, preferably, the water-soluble organic solvent includes at least one of a monohydric alcohol (e.g., methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, benzyl alcohol), a dihydric alcohol (e.g., at least one of 1,2-butanediol, 1,3-butanediol, neopentanediol), a trihydric alcohol (e.g., glycerol), a tetrahydric alcohol (e.g., pentaerythritol and / or dipentaerythritol), trimethylolpropane, tetrahydrofuran, dichloromethane, chloroform, and tetrachloromethane.

[0061] According to the present invention, preferably, the calcium source includes an inorganic alkaline calcium source and / or an organic alkaline calcium source; more preferably, it is at least one of the following: seashell, limestone, marble, gypsum, apatite, calcium oxide, calcium hydroxide, calcium formate, calcium acetate (e.g., calcium acetate monohydrate), calcium propionate, calcium pyruvate, calcium stearate, calcium alginate, calcium citrate, DL-calcium tartrate (e.g., DL-calcium tartrate tetrahydrate), L-calcium ascorbate (e.g., L-calcium ascorbate dihydrate), calcium acetylacetone, calcium methacrylate, calcium lactate (e.g., calcium lactate hydrate), calcium neodecanoate, calcium palmitate, calcium gluconate, and calcium malate.

[0062] According to the present invention, preferably, the magnesium source includes an inorganic alkaline magnesium source and / or an organic magnesium-based calcium source; more preferably, it is at least one selected from magnesium oxide, magnesium hydroxide, magnesium formate, magnesium acetate, magnesium propionate, magnesium pyruvate, magnesium stearate, magnesium alginate, magnesium citrate, magnesium tartrate, magnesium antiascorbate, magnesium acetylacetonate, magnesium methacrylate, magnesium lactate, magnesium neodecanoate, magnesium palmitate, magnesium gluconate, and magnesium malate.

[0063] In this invention, the calcium source and / or magnesium source can be a calcium source and / or magnesium source with water of crystallization, or a calcium source and / or magnesium source without water of crystallization.

[0064] When the prepared nano-carbonate is used in medical materials, the purity of the calcium source and / or magnesium source and surfactant is food grade; when the prepared nano-carbonate is used in oilfield chemicals and oil additives, the purity of the calcium source and / or magnesium source and surfactant is industrial grade.

[0065] In this invention, in step (1), a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with an organic acid to generate organic calcium and / or organic magnesium, which exist in the organic phase of the reaction system in the form of micelles.

[0066] Preferably, the calcium source and / or includes a substance with water-absorbing properties, such as calcium oxide, magnesium oxide, gypsum, etc. When the calcium source and / or includes a substance with water-absorbing properties, it can promote the acid-base neutralization reaction.

[0067] According to the present invention, preferably, the surfactant is an aliphatic organic carboxylic acid, an aromatic organic carboxylic acid, an aliphatic organic sulfonic acid, or an aromatic organic sulfonic acid; more preferably, the surfactant includes at least one of butyric acid, succinic acid, valeric acid, glutaric acid, hexanoic acid, adipic acid, heptanoic acid, pimelic acid, octanoic acid, octanoic acid, nonanoic acid, azelaic acid, decanoic acid, sebacic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, linoleic acid, eicosenoic acid, benzoic acid, sorbic acid, ferulic acid, alginic acid, mandelic acid, salicylic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, hexadecylbenzene sulfonic acid, and dinonylnaphthalene sulfonic acid.

[0068] According to the present invention, preferably, based on the total weight of the organic solvent, surfactant, calcium source and / or magnesium source, the concentration of the calcium source and / or magnesium source is 0.1-30 wt%, preferably 0.5-30 wt%, the concentration of the surfactant is 0.1-60 wt%, preferably 0.5-50 wt%, and the concentration of the water-soluble organic solvent is 10-80 wt%, preferably 10-75 wt%.

[0069] In this invention, the total weight of the organic solvent, surfactant, calcium source and / or magnesium source is used as a basis, and the concentration of the calcium source and / or magnesium source can be 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, or any two of the above.

[0070] In this invention, based on the total weight of the organic solvent, surfactant, calcium source and / or magnesium source, the concentration of the surfactant can be 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 40wt%, 50wt%, 60wt%, or any two of the above.

[0071] In this invention, based on the total weight of the organic solvent, surfactant, calcium source and / or magnesium source, the concentration of the water-soluble organic solvent can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or any two of the above.

[0072] According to the present invention, preferably, the conditions for the acid-base neutralization reaction include: a temperature of 20-100℃, preferably 25-95℃, and a time of 5min-15h, preferably 5min-12h.

[0073] According to the present invention, preferably, in step (2), the volume ratio of water to the product obtained by the acid-base neutralization reaction in step (1) is 0.0002-5:1, more preferably 0.001-3:1, and even more preferably 0.001-0.08:1.

[0074] According to the present invention, preferably, in step (2), the mixing conditions include: a temperature of 20-100℃, preferably 25-95℃; and a time of 5min-15h, preferably 5min-12h.

[0075] In this invention, the mixing order in step (2) is not limited. The mixing method between water and the product obtained from the acid-base neutralization reaction in step (1) can be: adding water to the product obtained from the acid-base neutralization reaction in step (1) at a certain flow rate; or adding the product obtained from the acid-base neutralization reaction in step (1) to water at a certain flow rate. When water is added to the product obtained from the acid-base neutralization reaction in step (1) at a certain flow rate, the flow rate of water relative to each mole of calcium source and / or magnesium source can be 0.1-12000 mL / min. When the product obtained from the acid-base neutralization reaction in step (1) is added to water at a certain flow rate, the flow rate of the product obtained from the acid-base neutralization reaction in step (1) can be 0.1-12000 mL / min.

[0076] The inventors of this invention speculate that the reason why this invention can obtain small-particle-size monodisperse nano-carbonate particles may be that: adding water in step (2) can form water-in-oil nanomicelles in the reaction system, allowing the first and second carbonation reactions to occur sequentially in the water-in-oil aqueous phase, thus promoting the first and second carbonation reactions to obtain small-particle-size nano-carbonates and achieving monodispersity of the nano-carbonates in the liquid solvent. Furthermore, adding water in step (2) can also convert water-absorbing substances in the reaction system into non-water-absorbing substances, avoiding interference with the subsequent formation of water-in-oil nanomicelles.

[0077] According to the present invention, preferably, carbon source a and carbon source b are each independently selected from at least one of water-soluble carbonates, water-soluble bicarbonates, basic magnesium carbonate, magnesium hydroxide carbonate, carbon dioxide, and compressed air; preferably, carbon source a and carbon source b are each independently selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, tetramethylammonium bicarbonate, trimethylammonium bicarbonate, triethylammonium bicarbonate, basic magnesium carbonate, magnesium hydroxide carbonate, carbon dioxide, and compressed air. Carbon source a and carbon source b may also be independently selected from hydrates of the above-mentioned solid carbon sources, such as potassium carbonate 1,5-hydrate.

[0078] In this invention, carbon source a and carbon source b can provide carbonate ions for the carbonation process, so that calcium ions can be converted into calcium carbonate and magnesium ions can be converted into magnesium carbonate.

[0079] In this invention, carbon source a in step (3) can be added to the mixture obtained in step (2) in solid form or introduced into the mixture obtained in step (2) in gas form. The method of adding carbon source a can be reasonably selected according to the form of the carbon source. Similarly, carbon source b in step (4) can be added to the product of the first carbonization reaction in solid form or introduced into the product of the first carbonization reaction in gas form.

[0080] According to the present invention, preferably, when the carbon source a is a solid, the molar ratio of the carbon source a to the calcium source and / or magnesium source is 0.001-0.3:1, more preferably 0.01-0.2:1. When the amount of carbon source a is limited to the above range, the uniformity of the particle size morphology of nano-carbonates can be further improved.

[0081] According to the present invention, preferably, when the carbon source a is a gas, the flow rate of the carbon source a is 1-2000 mL / min relative to each mole of calcium source and / or magnesium source, and the aeration time is 0.01-6 h.

[0082] According to the present invention, preferably, when the carbon source b is a solid, the molar ratio of the carbon source b to the calcium source and / or magnesium source is 0.002-0.7:1.

[0083] According to the present invention, preferably, when the carbon source b is a gas, the flow rate of the carbon source b is 2-5000 mL / min relative to each mole of calcium source and / or magnesium source, and the aeration time is 0.01-6 h. When the amount of carbon source b is limited to the above range in the present invention, the uniformity of the nano-carbonate particle size morphology can be further improved.

[0084] In this invention, when the carbon source is gas, the ventilation method can be one or more of the following: normal pressure circulating ventilation, normal pressure non-circulating ventilation, and pressure-holding continuous ventilation; wherein the pressure of the pressure-holding continuous ventilation is 20 kPa-4 MPa.

[0085] According to the present invention, preferably, the conditions for the first carbonization reaction and the second carbonization reaction each independently include: a temperature of 20-210°C, preferably 25-180°C, and a time of 0.01-12h, preferably 0.01-10h.

[0086] According to the present invention, preferably, during the first carbonization reaction and the second carbonization reaction, the reaction system is kept at a certain stirring rate to ensure that the carbon source and the reaction liquid are fully mixed. The stirring rate can be 200-1500 r / min.

[0087] According to the present invention, preferably, the method further includes: (5) performing solid-liquid separation on the product obtained from the second carbonization reaction to obtain a liquid phase containing nano-carbonates, and then removing the solvent from the liquid phase containing nano-carbonates.

[0088] In this invention, the solid-liquid separation method described in step (5) is not particularly limited and can be a solid-liquid separation method commonly used in the art, such as: letting the liquid stand and then pouring it out, centrifugation, filtration (vacuum filtration or pressure filtration, ultrafiltration, nanofiltration) at least one of the following.

[0089] According to the present invention, preferably, step (5) further includes: washing the solid obtained by solid-liquid separation, then mixing the washing liquid with a liquid phase containing nano carbonate, and then removing the solvent.

[0090] In this invention, the method of solid washing in step (5) is not particularly limited and can be any washing method commonly used in the art, such as soaking, rinsing, filtration (vacuum filtration or pressure filtration, ultrafiltration, nanofiltration), dialysis, centrifugation, or at least one of these. The number of washing cycles can be 1-10. The solvent used for washing can be selected from one or more of the following substances: water, methanol, ethanol, acetone, n-pentane, isopentane, cyclopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, cycloheptane, n-octane, isooctane, 3-methyloctane, petroleum ether (30-60℃), petroleum ether (60-90℃), petroleum ether (90-120℃), tetrahydrofuran, benzofuran, benzene, toluene, phenylacetic acid ester, chlorobenzene, dichloromethane, trichloromethane, tetrachloromethane.

[0091] The solid produced in step (5) may be due to a side reaction that occurred during the second carbonization reaction, producing calcium carbonate or magnesium carbonate that is coated on the outer layer of the carbon or magnesium source, and the particles are relatively large.

[0092] In step (5), the solvent removal method is selected from one or more of the following: freeze drying, vacuum drying, atmospheric pressure evaporation, rotary vacuum evaporation, forced air drying, infrared irradiation, and spray drying. The number of drying cycles can be 1-10. Under normal circumstances, all solvents in the liquid phase can be removed to obtain nano-carbonate solids; alternatively, some solvents in the liquid phase can be removed (partial solvents usually refer to solvents with a boiling point below 120℃ under atmospheric pressure) to directly obtain monodisperse nano-carbonate dispersions.

[0093] When the prepared nano-carbonate is used in medical materials, the amount of solvent residue to be removed complies with the "National Food Safety Standard for the Use of Food Additives".

[0094] A second aspect of the present invention provides a monodisperse nano carbonate prepared by the method described above.

[0095] A third aspect of the present invention provides a monodisperse nano carbonate comprising carbonate particles and a surfactant coated on the surface of the carbonate particles, wherein the surfactant is an organic acid and the carbonate is calcium carbonate and / or magnesium carbonate.

[0096] According to the present invention, preferably, the types of organic acids are as described in the first aspect, and will not be repeated here.

[0097] According to the present invention, preferably, the average particle size of the carbonate particles is 1-5 nm.

[0098] According to the present invention, preferably, the surfactant content is 5-50 wt%, based on the total weight of the carbonate particles and the surfactant.

[0099] A fourth aspect of the present invention provides a monodisperse nano carbonate dispersion comprising a liquid phase medium and the aforementioned monodisperse nano carbonate dispersed in the liquid phase medium.

[0100] According to the present invention, preferably, the carbonate content in the dispersion is 1-60 wt%. The carbonate content in the dispersion may be 1.5-60 wt%, or 2-60 wt%, or 5-60 wt%, or 10-60 wt%, or 20-60 wt%, or 30-60 wt%, or 40-60 wt%, or 50-60 wt%, or 5-50 wt%, or 5-45 wt%, or 5-40 wt%, or 5-35 wt%, or 5-30 wt%, or 5-25 wt%, or 10-20 wt%, or 10-15 wt%, or 15-55 wt%, or 20-50 wt%, or 25-40 wt%.

[0101] According to the present invention, preferably, the liquid medium includes benzene, toluene, xylene, chlorobenzene, petroleum ether (30-60°C), petroleum ether (60-90°C), petroleum ether (90-120°C), pentane, isopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, cycloheptane, cyclopentane, naphtha, diesel, kerosene, gasoline, white oil, peanut oil, castor oil, hydrogenated castor oil, polyoxyethylene castor oil (e.g., polyoxyethylene (35) castor oil), polyoxyethylene hydrogenated castor oil (e.g., polyoxyethylene (40) hydrogenated castor oil, polyoxyethylene (60) hydrogenated castor oil), fish oil, coconut oil, olive oil, palm oil, corn oil, soybean oil, sunflower seed oil, juniper berry oil, stigmata oil, dill oil, perilla leaf oil, and cinnamon. Oil, linseed oil, avocado oil, bay leaf oil, glyceryl behenate, peppermint oil, camphor oil, eucalyptus oil, clove basil oil, clove stem and leaf oil, methyl oleate, methylated vegetable oil, epoxidized vegetable oil, paraffin wax, ceresin wax, beeswax, petrolatum, vitex oil, toad oil, burn oil, patchouli oil, rhododendron oil, star anise oil, turpentine oil, tea oil, turmeric oil, turmeric oil, tung oil, linseed oil, heavy oil, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, benzyl alcohol, 1,2-butanediol, 1,3-butanediol, glycerol, neopentyl glycol, pentaerythritol, dipentaerythritol, trimethylolpropane, tetrahydrofuran, dichloromethane, chloroform, tetrachloromethane, ethyl acetate, butyl acetate, acetone.

[0102] The fifth aspect of the present invention provides a method for preparing a monodisperse nano carbonate dispersion, the method comprising: mixing the monodisperse nano carbonate described above with a liquid medium.

[0103] According to the present invention, preferably, the liquid medium is as described in the fourth aspect, and will not be repeated here.

[0104] The sixth aspect of this invention provides a method for preparing a monodisperse nano-carbonate dispersion, the method comprising the following steps:

[0105] (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid;

[0106] (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1);

[0107] (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a;

[0108] (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction;

[0109] (5) The product obtained from the second carbonization reaction is subjected to solid-liquid separation to obtain a liquid phase containing nano carbonates, and then some organic solvents in the liquid phase containing nano carbonates are removed.

[0110] Wherein, carbon source a is different from carbon source b.

[0111] According to the present invention, preferably, the types and amounts of the organic solvent, calcium source, magnesium source, surfactant, carbon source a, carbon source b, etc., and the reaction conditions of each step are as described in the first aspect, and will not be repeated here.

[0112] The seventh aspect of the present invention provides a monodisperse nano carbonate dispersion prepared by the method described above.

[0113] The eighth aspect of the present invention provides the application of the above-described monodisperse nano carbonates and / or the above-described monodisperse nano carbonate dispersions in the fields of medical materials, food additives, oil additives and catalysis.

[0114] According to the present invention, preferably, as a pharmaceutical preparation, an easily absorbed and highly stable calcium supplement is provided; as an oilfield chemical, a carbonate-based nano-displacement agent is provided to improve the recovery rate of low-permeability oil reservoirs; and as an oil additive, a carbonate-based lubricating oil additive is provided to improve the base value of lubricating oil.

[0115] The present invention will be described in detail below through embodiments. In the following embodiments,

[0116] The method for calculating the average particle size is as follows: Randomly select 100 calcium carbonate particles from the electron microscope image, count the particle size of the 100 calcium carbonate particles, and then calculate the average particle size of the 100 calcium carbonate particles.

[0117] Example 1

[0118] This embodiment illustrates the preparation method of monodisperse nano carbonate dispersions.

[0119] (1) Mix water-soluble organic solvent (40.2g n-propanol and 79.5g dichloromethane) and low-polarity solvent (18g food-grade fish oil), then add calcium source (12g food-grade calcium hydroxide and 0.75g food-grade calcium oxide) and surfactant (13g food-grade oleic acid) to carry out acid-base neutralization reaction. The reaction temperature is 35℃ and the reaction time is 4h.

[0120] (2) Add water droplets to the product of the acid-base neutralization reaction in step (1). The flow rate of water is 28.5 mL / min relative to each mole of calcium source. The temperature of the droplets is 35°C. After the droplets are added, the mixing time at this temperature is 20 min and the stirring rate is 500 r / min. The volume ratio of water to the product of the acid-base neutralization reaction in step (1) is 0.002:1.

[0121] (3) Add carbon source a (sodium bicarbonate) to the product obtained in step (2) to carry out the first carbonization reaction; the conditions for the first carbonization reaction include: temperature of 75℃, time of 50min, and stirring rate of 500r / min; wherein the molar ratio of carbon source a to calcium source is 0.0136:1.

[0122] (4) Carbon source b (carbon dioxide gas) is introduced into the product of the first carbonization reaction to carry out the second carbonization reaction; wherein, relative to each mole of calcium source, the carbon dioxide gas flow rate is 3400 mL / min, the gas flow mode is atmospheric pressure non-circulating gas flow, and the gas flow time is 90 min; the conditions for the second carbonization reaction include: reaction temperature of 35℃, reaction time of 6 h, and stirring rate of 500 r / min.

[0123] (5) After the reaction solution obtained from the second carbonization reaction is allowed to stand, the upper liquid is separated; and the lower solid is washed with water 5 times and with dichloromethane 5 times by soaking. The upper liquid and the dichloromethane washing solution contain carbonates.

[0124] (6) The upper liquid obtained in step (5) is mixed with dichloromethane washing liquid, and the solvent with a boiling point below 120°C under normal pressure is removed by vacuum drying (in this example, all solvents except fish oil, namely water, dichloromethane, and n-propanol). After drying once, a monodisperse nano carbonate dispersion is obtained.

[0125] Transmission electron microscopy (TEM) image of the monodisperse nano-calcium carbonate dispersion prepared in Example 1 is shown below. Figure 1 As shown, 100 calcium carbonate particles were randomly selected from the electron microscope image, and their particle sizes were counted, resulting in the following... Figure 2 The statistical chart shown. (From...) Figure 1 It can be seen that the prepared nano-calcium carbonate particles have uniform size and morphology, are monodisperse, and have good dispersibility. Figure 2It can be concluded that the average particle size of the nano-calcium carbonate particles is 3.1 nm, and the particle size distribution is uniform.

[0126] Figure 3 The thermogravimetric analysis (TGA) chart shows the monodisperse nano-calcium carbonate dispersion of Example 1. The weight loss at 30-320℃ (28.5 wt%) is the solvent fish oil, the weight loss at 320-550℃ (34.3 wt%) is the surfactant oleic acid, and the weight loss at 520-850℃ (15.8 wt%) is carbon dioxide from the calcium carbonate. The remaining 21.4 wt% is calcium oxide. The calcium carbonate content was calculated based on the carbon dioxide content using the formula: carbon dioxide mass fraction × M. 碳酸钙 / M 二氧化碳 =15.8wt% × 100 / 44 = 35.9wt%; the calculated calcium carbonate content in the monodisperse nano-calcium carbonate dispersion is 35.9wt%. The purity of calcium carbonate is calculated based on the content of calcium carbonate, carbon dioxide, and calcium oxide in the dispersion. The formula for calculating calcium carbonate purity is: calcium carbonate content / (carbon dioxide content + calcium oxide content) × 100%; the calculated calcium carbonate purity is 96.5wt%. The yield of calcium carbonate is calculated using the formula: amount of calcium carbonate in the monodisperse nano-calcium carbonate dispersion / amount of calcium source × 100%; the calculated calcium carbonate yield is 86%.

[0127] Add 2 times the volume of acetone to the nano-calcium carbonate fish oil phase dispersion obtained in Example 1 to cause the nano-calcium carbonate particles originally dispersed in the system to flocculate and precipitate. Separate the precipitate by centrifugation, wash it twice with acetone by centrifugation, and dry it at 60°C for 3 hours to obtain nano-calcium carbonate solid. Figure 4 The image shows the XRD pattern of nano-calcium carbonate. Analysis of the image reveals that the nano-calcium carbonate particles have an amorphous structure. Figure 5 The image shows the XRD pattern of solid nano-calcium carbonate after calcination at 400℃ for 3 hours. Analysis of the image shows that the main component of the generated nanoparticles is calcium carbonate.

[0128] Figure 6 The image shows a photograph of the monodisperse nano-calcium carbonate dispersion from Example 1. The photograph demonstrates that the dispersion exhibits good monodispersity. Furthermore, observation after standing for ≥24 months reveals high stability; the dispersion remains transparent and shows no sedimentation.

[0129] The monodisperse nano-calcium carbonate dispersion prepared in Example 1 consists of nano-calcium carbonate, surface-grafted oleic acid (which, according to GB 2760-2024 National Food Safety Standard for the Use of Food Additives, is a permitted natural flavoring for food) and solvent fish oil, with content conforming to the National Food Safety Standard for the Use of Food Additives. It can be used as a calcium supplement, a nutritional supplement for the prevention and treatment of calcium deficiency, and promotes healthy teeth and bones.

[0130] Example 2

[0131] This embodiment illustrates the preparation method of monodisperse nano carbonate dispersions.

[0132] (1) A water-soluble organic solvent (53.4g tetrahydrofuran) and a low-polarity solvent (75.1g cyclopentane) were mixed, and then a calcium source (15.6g calcium oxide) and a surfactant (3g dodecylbenzenesulfonic acid) were added to carry out an acid-base neutralization reaction. The reaction temperature was 35℃ and the reaction time was 4h.

[0133] (2) Water is added dropwise to the product of the acid-base neutralization reaction in step (1). The flow rate of water is 36 mL / min relative to each mole of calcium source. The temperature of the dropwise addition is 95°C. After the dropwise addition is completed, the mixing time at this temperature is 9 h, and the stirring rate is 300 r / min. The volume ratio of water to the product of the acid-base neutralization reaction in step (1) is 0.0625:1.

[0134] (3) Add carbon source a (potassium carbonate and potassium bicarbonate in a weight ratio of 0.1:1) to the product obtained in step (2) to carry out the first carbonization reaction; the conditions for the first carbonization reaction include: temperature of 95℃, time of 2h, and stirring rate of 300r / min; wherein the molar ratio of carbon source a to calcium source is 0.1:1.

[0135] (4) Carbon source b (carbon dioxide gas) is introduced into the product of the first carbonization reaction to carry out the second carbonization reaction; relative to each mole of calcium source, the carbon dioxide gas flow rate is 36 mL / min, the gas introduction method is continuous gas introduction under pressure, the pressure is 500 kPa, and the gas introduction time is 3 h; the conditions for the second carbonization reaction include: the reaction temperature is 95 °C, the reaction time is 10 min, and the stirring rate is 300 r / min.

[0136] (5) The reaction solution obtained from the second carbonization reaction was centrifuged to separate liquid I; the separated solid was then washed three times with water, three times with ethanol, and three times with cyclopentane by centrifugation. Liquid I and the cyclopentane washing liquid contained carbonates.

[0137] (6) After mixing liquid I and the liquid washed with cyclopentane, the solvent with a boiling point below 120°C under normal pressure (in this example, water, cyclopentane, tetrahydrofuran and a small amount of residual ethanol) is removed by rotary evaporation. After drying once, transparent monodisperse nano calcium carbonate solid is obtained.

[0138] Figure 7The image shows a physical picture of the monodisperse nano-calcium carbonate solid obtained in step (6) of Example 2. As can be seen from the image, due to the small particle size and monodispersity of the obtained calcium carbonate, the nano-calcium carbonate solid is also transparent. The monodisperse nano-calcium carbonate solid obtained in step (6) of Example 2 was mixed with white oil to obtain a monodisperse nano-calcium carbonate white oil phase dispersion. The monodisperse nano-calcium carbonate white oil phase dispersion was tested by transmission electron microscopy and found that the average particle size of the nano-calcium carbonate particles was 4 nm, the particle size distribution was uniform, and it had good monodispersity.

[0139] Figure 8 The thermogravimetric analysis (TGA) chart of the monodisperse nano-calcium carbonate white oil phase dispersion in Example 2 shows that the weight loss at 30-350℃ (30 wt%) is the solvent white oil, the weight loss at 320-500℃ (15.3 wt%) is the surfactant dodecylbenzenesulfonic acid, and the weight loss at 520-850℃ (23.2 wt%) is carbon dioxide from the calcium carbonate, leaving 31.5 wt% calcium oxide. The calcium carbonate content was calculated based on the carbon dioxide content: the formula is carbon dioxide mass fraction × M. 碳酸钙 / M 二氧化碳 = 23.2wt% × 100 / 44 = 52.7wt%; the calculated calcium carbonate content in the monodisperse nano-calcium carbonate dispersion is 52.7wt%. The purity of calcium carbonate is calculated based on the content of calcium carbonate, carbon dioxide, and calcium oxide in the dispersion. The formula for calculating calcium carbonate purity is: calcium carbonate content / (carbon dioxide content + calcium oxide content) × 100%; the calculated calcium carbonate purity is 96.3wt%. The yield of calcium carbonate is calculated using the formula: amount of calcium carbonate in the monodisperse nano-calcium carbonate dispersion / amount of calcium source × 100%; the calculated calcium carbonate yield is 80%.

[0140] Figure 9 The image shows a photograph of the monodisperse nano-calcium carbonate white oil phase dispersion of Example 2. As can be seen from the photograph, the dispersion has good transparency. At the same time, when the dispersion is left to stand, it shows high stability and remains transparent without sedimentation even after standing for ≥24 months.

[0141] The monodisperse nano-calcium carbonate white oil phase dispersion obtained in Example 2 has an alkalinity (TBN) of 550 mg KOH / g. The alkalinity determination method is SH / T0251-1993 (perchloric acid titration method). It can be used as a high alkalinity lubricating oil, which can effectively neutralize harmful inorganic and organic acids generated during the use of fuel and lubricating oil, slow down the oil oxidation process, reduce engine corrosion and wear, and extend the service life of oil and engine.

[0142] The monodisperse nano-calcium carbonate white oil phase dispersion obtained in Example 2 was used to prepare a viscoelastic and stable nano-displacement emulsion system. The emulsion preparation method was as follows: using the monodisperse nano-calcium carbonate white oil phase dispersion of Example 2 as the oil phase, an aqueous solution of the active functional polymer (partially hydrolyzed polyacrylamide) as the aqueous phase, and Span-80 and polyoxyethylene ether as surfactants, the oil phase, aqueous phase, and surfactants were mixed to obtain a viscoelastic and stable nano-displacement emulsion system; wherein, the weight of the oil phase was 30g, the weight of the aqueous phase was 35g, the content of the active functional polymer in the aqueous phase was 1000mg / L, and the weights of the surfactants Span-80 and polyoxyethylene ether were 5g each. The viscoelastic and stable nano-displacement emulsion system was added to crude oil, and the operation process was as follows. Figure 10 As shown, by Figure 10 It can be seen that when the viscoelastic stable nano-displacement emulsion system is added to crude oil, the crude oil is emulsified into micron-sized or smaller droplets, indicating that the viscoelastic stable nano-displacement emulsion system has the function of dispersing oil droplets.

[0143] As a control group, an oil displacement emulsion system without the addition of nano-calcium carbonate dispersion was prepared using an equal mass of white oil as the oil phase, with other parameters remaining unchanged. The oil washing efficiency of the oil displacement emulsions with and without the addition of nano-calcium carbonate dispersion was compared. Before oil washing, the oil displacement emulsions with and without the addition of nano-calcium carbonate dispersion were mixed with a solvent to obtain an oil washing agent. The oil washing agent formulation was as follows: the emulsion and solvent (mineralized water, mineralization of 60000 mg / L NaCl + 6000 mg / L CaCl2) were mixed at a ratio of 20000 mg emulsion to 1 L solvent to obtain the oil washing agent.

[0144] The test method for oil washing efficiency is as follows: (1) Preparation of oil sand: Crude oil is mixed with an equal mass of petroleum ether (boiling point 30-60℃) to obtain diluted crude oil. Quartz sand is mixed with diluted crude oil at a mass ratio of 8:1 and placed in a 50℃ constant temperature oven for aging for 24 hours. The beaker containing the above materials is placed on a water bath and heated to a temperature not exceeding 80℃. After the petroleum ether evaporates, the oil sand is aged for 36 hours. (2) The oil sand is washed with an oil washing agent prepared by adding / not adding nano calcium carbonate dispersion: m1 of oil sand is weighed and placed into an oil washing bottle. The above two oil washing agents are added respectively. After being kept at 50℃ for 24 hours, the oil sand is filtered and dried. The amount of dried oil sand washed out, m2, is read. The formula for calculating the oil washing efficiency is:

[0145] X s = (m1-m2) / km1×100%

[0146] In the formula: X s —Oil washing efficiency, %;

[0147] k – percentage of oil content in oil sands, %; in this experiment, k is 20%.

[0148] m1 — Mass of oil sand, g;

[0149] m2 — Mass of dry oil sand, in grams.

[0150] The oil washing efficiency of the washing agent without adding nano-calcium carbonate oil displacement emulsion was 69%, while that with the addition of nano-calcium carbonate oil displacement emulsion was 83%, showing a significant improvement in washing efficiency. Furthermore, the nano-oil displacement emulsion system has functions such as improving wettability, reducing interfacial tension, improving mobility ratio, and reducing structural separation pressure. The nano-calcium carbonate prepared in this embodiment has a small particle size and good dispersibility, making it easier to inject into the reservoir and migrate within the reservoir pores, thus being an effective tool for improving oil recovery in low-permeability reservoirs.

[0151] Example 3

[0152] The method of Example 2 was followed, except that the monodisperse nano-calcium carbonate solid obtained in step (6) of Example 2 was mixed with toluene at a weight ratio of 0.27:1 to obtain a monodisperse nano-calcium carbonate toluene phase dispersion. Thermogravimetric analysis showed that the content of nano-calcium carbonate in the dispersion was 20 wt%.

[0153] Figure 11 The image shows a photograph of the monodisperse nano-calcium carbonate toluene phase dispersion obtained in Example 3. The photograph demonstrates the high transparency of the dispersion. Transmission electron microscopy (TEM) analysis of the monodisperse nano-calcium carbonate toluene phase dispersion revealed that the average particle size of the nano-calcium carbonate particles was 4 nm, with a uniform particle size distribution, exhibiting good monodispersity. Furthermore, observation after static standing showed high stability; the dispersion remained transparent and showed no sedimentation even after ≥24 months of standing.

[0154] Example 4

[0155] This embodiment illustrates the preparation method of monodisperse nano carbonate dispersions.

[0156] (1) Mix water-soluble organic solvent (20g chloroform) and low-polarity solvent (90g petroleum ether (90-120℃) and 10g toluene), then add magnesium source (3.6g magnesium hydroxide and 1.1g magnesium stearate) and surfactant (2g stearic acid) to carry out acid-base neutralization reaction. The reaction temperature is 70℃ and the reaction time is 2h.

[0157] (2) Water is added dropwise to the product of the acid-base neutralization reaction in step (1). The flow rate of water is 31 mL / min relative to each mole of magnesium source. The temperature of the dropwise addition is 70°C. After the dropwise addition is completed, the mixing time at this temperature is 2 h, and the stirring rate is 500 r / min. The volume ratio of water to the product of the acid-base neutralization reaction in step (1) is 0.0135:1.

[0158] (3) Add carbon source a (ammonium bicarbonate) to the product obtained in step (2) to carry out the first carbonization reaction; the conditions for the first carbonization reaction include: reaction temperature of 70℃, reaction time of 1h, and stirring rate of 500r / min. Among them, the molar ratio of carbon source a to magnesium source is 0.187:1.

[0159] (4) Carbon source b (carbon dioxide) is introduced into the product of the first carbonization reaction to carry out the second carbonization reaction; the carbon dioxide gas flow rate is 310 mL / min relative to each mole of magnesium source, the pressure is continuously purged, the pressure is 500 kPa, and the purging time is 3 h; the conditions for the second carbonization reaction include: temperature of 70 °C, reaction time of 1 h, and stirring rate of 500 r / min.

[0160] (5) The reaction liquid obtained from the second carbonization reaction is separated into solid and liquid by centrifugation to obtain a liquid containing carbonate.

[0161] (6) The liquid obtained in step (5) is separated by rotary vacuum evaporation to remove the solvent with a boiling point below 120°C at normal pressure (in this example, water, chloroform, petroleum ether (90-120°C), toluene), and dried once to obtain monodisperse nano magnesium carbonate solid.

[0162] The monodisperse nano-magnesium carbonate solid prepared in step (6) of Example 4 was mixed with toluene at a weight ratio of 0.11:1 to obtain a monodisperse nano-magnesium carbonate toluene phase dispersion (see physical image). Figure 12 (As shown). Transmission electron microscopy (TEM) analysis of the monodisperse nano-magnesium carbonate in toluene phase revealed that the average particle size of the nano-magnesium carbonate particles was 3 nm, with uniform particle size distribution and good monodispersity. Furthermore, the dispersion exhibited high stability, remaining transparent and without sedimentation even after standing for ≥24 months. Thermogravimetric analysis showed that, based on the total weight of carbonate particles and surfactant, the surfactant content was 31 wt%; the nano-magnesium carbonate content in the dispersion was 20 wt%; and the magnesium carbonate purity was 95.7 wt%. The magnesium carbonate yield was 78%.

[0163] Example 5

[0164] The procedure was carried out according to Example 1, except that in step (4), the flow rate of carbon dioxide was 4500 mL / min relative to each mole of calcium source.

[0165] Thermogravimetric analysis showed that, based on the total weight of carbonate particles and surfactant, the surfactant content was 32.8 wt%; the content of nano-calcium carbonate in the dispersion was 17 wt%; and the purity of calcium carbonate was 96.2 wt%. The yield of calcium carbonate was 50%.

[0166] Transmission electron microscopy revealed that the average particle size of the nano-calcium carbonate particles was 4.2 nm. Furthermore, the dispersion exhibited high stability, remaining transparent and without sedimentation even after standing for ≥24 months.

[0167] Example 6

[0168] The method of Example 1 is followed, except that in step (2), the volume ratio of water to the product of the acid-base neutralization reaction in step (1) is 0.1:1.

[0169] Thermogravimetric analysis showed that, based on the total weight of carbonate particles and surfactant, the surfactant content was 33.5 wt%; the content of nano-calcium carbonate in the dispersion was 22.8 wt%; and the purity of calcium carbonate was 94.2 wt%. The yield of calcium carbonate was 55%.

[0170] Transmission electron microscopy revealed that the average particle size of the nano-calcium carbonate particles was 5 nm. Furthermore, the dispersion exhibited high stability, remaining transparent and without sedimentation even after standing for ≥24 months.

[0171] Example 7

[0172] The method of Example 1 is followed, except that in step (3), the molar ratio of carbon source a to calcium source is 0.0012:1.

[0173] Thermogravimetric analysis showed that, based on the total weight of carbonate particles and surfactant, the surfactant content was 36 wt%; the content of nano-calcium carbonate in the dispersion was 24 wt%; and the purity of calcium carbonate was 96.5 wt%. The yield of calcium carbonate was 58%.

[0174] The electron micrograph of the monodisperse nano-calcium carbonate dispersion prepared in Example 7 is shown below. Figure 13 As shown, by Figure 13 It can be seen that the prepared nano-calcium carbonate particles have relatively uniform morphology and good dispersibility. One hundred calcium carbonate particles were randomly selected from the electron microscope images, and their particle sizes were statistically analyzed, as shown below. Figure 14 The statistical chart shown. Figure 14 It can be concluded that the average particle size of the nano-calcium carbonate particles is 2.6 nm, and the particle size distribution is relatively uniform. Furthermore, the dispersion exhibits high stability, remaining transparent and without sedimentation even after standing for ≥24 months.

[0175] Comparative Example 1

[0176] The procedure was carried out according to Example 1, except that oleic acid was replaced with an equimolar amount of γ-methacryloyloxypropyltrimethoxysilane.

[0177] Figure 15The image shows a photograph of the monodisperse nano-carbonate dispersion prepared in Comparative Example 1. As can be seen from the image, the dispersion is a suspension, indicating that the method in Comparative Example 1 cannot achieve monodispersity of solid particles in a liquid medium. Furthermore, analysis of the solid particles in the suspension revealed no calcium carbonate, indicating that the method in Comparative Example 1 cannot prepare calcium carbonate.

[0178] Comparative Example 2

[0179] The procedure was carried out according to Example 3, except that calcium oxide was replaced with an equimolar amount of calcium chloride.

[0180] The dispersion prepared in Comparative Example 2 was a suspension, indicating that the method in Comparative Example 2 could not achieve monodispersity of calcium carbonate in a liquid medium.

[0181] Comparative Example 3

[0182] The method is carried out according to Example 1, except that the second carbonization process in step (4) is not included; and the molar ratio of carbon source a to calcium source in step (3) is 1:1.

[0183] In Comparative Example 3, after the reaction solution obtained from the carbonization reaction was allowed to stand, almost all the solid precipitated to the bottom, and the upper liquid contained almost no solid. This indicates that the solid prepared by the method in Comparative Example 3 cannot be dispersed in a liquid solvent.

[0184] Comparative Example 4

[0185] The method is carried out according to Example 1, except that the first carbonization process in step (3) is not included.

[0186] Transmission electron microscopy (TEM) image of the nano-calcium carbonate dispersion prepared in Comparative Example 4 is shown below. Figure 16 As shown, by Figure 16 It can be seen that the prepared nano-calcium carbonate particles have uneven morphology, with some large particles forming. One hundred calcium carbonate particles were randomly selected from the electron microscope images, and their particle sizes were statistically analyzed, resulting in the following... Figure 17 The statistical chart shown. Figure 17 It can be concluded that the average particle size of the nano-calcium carbonate particles is 13.5 nm.

[0187] Comparative Example 5

[0188] The method of Example 1 is followed, except that the first carbonization reaction in step (3) is not included. Carbon source a and carbon source b are added to the product obtained in step (2) at the same time, and then the carbonization reaction is carried out under the second carbonization conditions.

[0189] Transmission electron microscopy (TEM) image of the nano-calcium carbonate dispersion prepared in Comparative Example 5 is shown below. Figure 18 As shown, by Figure 18It can be seen that the prepared calcium carbonate particles have uneven morphology, and some strip-shaped particles are formed. One hundred calcium carbonate particles were randomly selected from the electron microscope images, and their particle sizes were counted, resulting in the following... Figure 19 The statistical chart shown. Figure 19 It can be concluded that the average particle size of the nano-calcium carbonate particles is 14.1 nm.

[0190] Comparative Example 6

[0191] The procedure was carried out according to Example 2, except that "dodecylbenzenesulfonic acid" was replaced with isomolar 1240903.

[0192] I97300BHY

[0193] "Ammonium dodecylbenzenesulfonate".

[0194] The reaction solution obtained from the second carbonization reaction in Comparative Example 6, after centrifugation, yielded liquid I, which contained almost no solids. This indicates that the solids prepared by the method in Comparative Example 6 cannot be dispersed in a liquid solvent. Furthermore, XRD analysis of the centrifuged solids yielded the following results: Figure 20 As shown, from Figure 20 The analysis shows that the main component of the calcium slag is Ca(OH)2, with no calcium carbonate present. Therefore, replacing the organic acid surfactant with an organic acid salt will not yield a nano-calcium carbonate dispersion, or even calcium carbonate at all.

[0195] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing monodisperse nano-carbonates, characterized in that, The method includes the following steps: (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid; (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1); (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a; (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction; Wherein, carbon source a is different from carbon source b.

2. The method according to claim 1, wherein, The organic solvents include low-polarity solvents and / or water-soluble organic solvents; Preferably, the low-polarity solvent includes at least one of benzene, toluene, chlorobenzene, petroleum ether, pentane, isopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, cycloheptane, cyclopentane, naphtha, diesel, kerosene, gasoline, white oil, peanut oil, castor oil, hydrogenated castor oil, fish oil, coconut oil, olive oil, corn oil, soybean oil, sunflower seed oil, juniper berry oil, stigmacandra glabra oil, dill oil, perilla leaf oil, cinnamon oil, flaxseed oil, avocado oil, bay leaf oil, behenicol, peppermint oil, camphor oil, eucalyptus oil, clove basil oil, clove stem and leaf oil, paraffin wax, ceresin wax, beeswax, vitex oil, toad oil, burn oil, patchouli oil, rhododendron oil, star anise oil, turpentine oil, tea oil, turmeric oil, and heavy oil. Preferably, the water-soluble organic solvent includes at least one selected from monohydric alcohol, dihydric alcohol, trihydric alcohol, tetrahydric alcohol, trimethylolpropane, tetrahydrofuran, dichloromethane, chloroform, and tetrachloromethane; And / or, the calcium source includes an inorganic alkaline calcium source and / or an organic alkaline calcium source; preferably at least one of the following: seashell, limestone, marble, gypsum, apatite, calcium oxide, calcium hydroxide, calcium formate, calcium acetate, calcium propionate, calcium pyruvate, calcium stearate, calcium alginate, calcium citrate, DL-calcium tartrate, L-calcium ascorbate, calcium acetylacetone, calcium methacrylate, calcium lactate, calcium neodecanoate, calcium palmitate, calcium gluconate, and calcium malate. And / or, the magnesium source includes an inorganic alkaline magnesium source and / or an organic magnesium-based calcium source; preferably at least one of magnesium oxide, magnesium hydroxide, magnesium formate, magnesium acetate, magnesium propionate, magnesium pyruvate, magnesium stearate, magnesium alginate, magnesium citrate, magnesium tartrate, magnesium antiascorbate, magnesium acetylacetonate, magnesium methacrylate, magnesium lactate, magnesium neodecanoate, magnesium palmitate, magnesium gluconate, and magnesium malate. And / or, the surfactant is an aliphatic organic carboxylic acid, an aromatic organic carboxylic acid, an aliphatic organic sulfonic acid, or an aromatic organic sulfonic acid; preferably, the surfactant includes at least one of butyric acid, succinic acid, valeric acid, glutaric acid, hexanoic acid, adipic acid, heptanoic acid, pimelic acid, octanoic acid, octanoic acid, nonanoic acid, azelaic acid, decanoic acid, sebacic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, linoleic acid, eicosenoic acid, benzoic acid, sorbic acid, ferulic acid, alginic acid, mandelic acid, salicylic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, hexadecylbenzene sulfonic acid, and dinonylnaphthalene sulfonic acid.

3. The method according to claim 2, wherein, Based on the total weight of the organic solvent, surfactant, calcium source and / or magnesium source, the concentration of the calcium source and / or magnesium source is 0.1-30 wt%, preferably 0.5-30 wt%, the concentration of the surfactant is 0.1-60 wt%, preferably 0.5-50 wt%, and the concentration of the water-soluble organic solvent is 10-80 wt%, preferably 10-75 wt%. And / or, the conditions for the acid-base neutralization reaction include: a temperature of 20-100℃, preferably 25-95℃, and a time of 5min-15h, preferably 5min-12h.

4. The method according to claim 1, wherein, In step (2), the volume ratio of water to the product obtained from the acid-base neutralization reaction in step (1) is 0.0002-5:1, preferably 0.001-3:1; And / or, in step (2), the mixing conditions include: a temperature of 20-100℃, preferably 25-95℃; and a time of 5min-15h, preferably 5min-12h.

5. The method according to claim 1, wherein, The carbon source a and carbon source b are each independently selected from at least one of water-soluble carbonates, water-soluble bicarbonates, basic magnesium carbonate, magnesium hydroxide carbonate, carbon dioxide, and compressed air; preferably, the carbon source a and carbon source b are each independently selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, tetramethylammonium bicarbonate, trimethylammonium bicarbonate, triethylammonium bicarbonate, basic magnesium carbonate, magnesium hydroxide carbonate, carbon dioxide, and compressed air; And / or, when carbon source a is a solid, the molar ratio of carbon source a to calcium source and / or magnesium source is 0.001-0.3:1; And / or, when carbon source a is a gas, the flow rate of carbon source a is 1-2000 mL / min relative to each mole of calcium source and / or magnesium source, and the aeration time is 0.01-6 h; And / or, when the carbon source b is a solid, the molar ratio of the carbon source b to the calcium source and / or magnesium source is 0.002-0.7:1; And / or, when carbon source b is a gas, the flow rate of carbon source b is 2-5000 mL / min relative to each mole of calcium source and / or magnesium source, and the aeration time is 0.01-6 h; And / or, the conditions for the first carbonization reaction and the second carbonization reaction each independently include: a temperature of 20-210°C, preferably 25-180°C, and a time of 0.01-12h, preferably 0.01-10h.

6. The method according to claim 1, wherein, The method further includes: (5) separating the product obtained from the second carbonization reaction into a liquid phase containing nano carbonates and then removing the solvent from the liquid phase containing nano carbonates. Preferably, step (5) further includes: washing the solid obtained from solid-liquid separation, then mixing the washing liquid with a liquid phase containing nano-carbonate, and then removing the solvent.

7. Monodisperse nanocarbonates prepared by the method according to any one of claims 1-6.

8. A monodisperse nano-carbonate, characterized in that, The monodisperse nano carbonate comprises carbonate particles and a surfactant coated on the surface of the carbonate particles, wherein the surfactant is an organic acid and the carbonate is calcium carbonate and / or magnesium carbonate.

9. The monodisperse nano-carbonate according to claim 8, wherein, The average particle size of the carbonate particles is 1-5 nm; And / or, based on the total weight of carbonate particles and surfactant, the surfactant content is 5-50 wt%.

10. A monodisperse transparent dispersion of nano-carbonate, characterized in that, The dispersion comprises a liquid phase medium and a monodisperse nano carbonate as described in any one of claims 7-9 dispersed in the liquid phase medium.

11. The dispersion according to claim 10, wherein, The carbonate content in the dispersion is 1-60 wt%. And / or, the liquid medium includes benzene, toluene, xylene, chlorobenzene, petroleum ether, pentane, isopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, cycloheptane, cyclopentane, naphtha, diesel, kerosene, gasoline, white oil, peanut oil, castor oil, hydrogenated castor oil, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, fish oil, coconut oil, olive oil, palm oil, corn oil, soybean oil, sunflower seed oil, juniper berry oil, stigmacanzu oil, dill oil, perilla leaf oil, cinnamon oil, flaxseed oil, avocado oil, bay leaf oil, behenicol, peppermint oil, camphor oil, eucalyptus oil, clove basil oil, and more. At least one of the following: aromatic stem and leaf oil, methyl oleate, methylated vegetable oil, epoxidized vegetable oil, paraffin wax, ceresin wax, beeswax, petrolatum, vitex oil, toad oil, burn oil, patchouli oil, rhododendron oil, star anise oil, turpentine oil, tea oil, turmeric oil, turmeric oil, tung oil, linseed oil, heavy oil, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, benzyl alcohol, 1,2-butanediol, 1,3-butanediol, glycerol, neopentyl glycol, pentaerythritol, dipentaerythritol, trimethylolpropane, tetrahydrofuran, dichloromethane, chloroform, tetrachloromethane, ethyl acetate, butyl acetate, and acetone.

12. A method for preparing a monodisperse nano-carbonate transparent dispersion, characterized in that, The method includes: mixing the monodisperse nano-carbonate according to any one of claims 7-9 with a liquid medium; Preferably, the liquid medium is as described in claim 11.

13. A method for preparing a monodisperse nano-carbonate transparent dispersion, characterized in that, The method includes the following steps: (1) In the presence of an organic solvent, a calcium source and / or a magnesium source are subjected to an acid-base neutralization reaction with a surfactant; wherein the calcium source is an alkaline calcium source, the magnesium source is an alkaline magnesium source, and the surfactant is an organic acid; (2) Mix water with the product obtained from the acid-base neutralization reaction in step (1); (3) The mixture obtained in step (2) is subjected to a first carbonization reaction with carbon source a; (4) The product obtained from the first carbonization reaction is reacted with carbon source b to carry out a second carbonization reaction; (5) The product obtained from the second carbonization reaction is subjected to solid-liquid separation to obtain a liquid phase containing nano carbonates, and then some organic solvents in the liquid phase containing nano carbonates are removed. Wherein, carbon source a is different from carbon source b.

14. A monodisperse nanocarbonate dispersion prepared by the method of claim 12 or 13.

15. The use of the monodisperse nano carbonate according to any one of claims 7-9 and / or the monodisperse nano carbonate dispersion according to any one of claims 10, 11 and 14 in medical materials, food additives, oilfield chemicals and oil additives.

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