Preparation and Application of Anionic Nano-Silica Hydrosol

Abstract

The present invention relates to the preparation and application of an anionic nano-silica sol. The structural formula of the anionic nano-silica therein is shown in Formula (1): The nano-silica particles with this structure have great application potential in the field of nano-materials. The preparation method of the present invention is simple, easy to operate, the reaction conditions are mild and easy to control, and the reaction solvent is water, which conforms to the concept of green chemistry.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterial preparation and oilfield applications, and particularly relates to the preparation of an anionic nano-silica sol and its applications in scale prevention and tertiary oil recovery in oilfields. Background Art

[0002] Nanostructures based on silicon dioxide nanoparticles have been widely used in fields such as optoelectronic devices, MEMS devices, photonic crystals, and chemical / biological sensors. Various techniques such as electrostatic assembly, colloidal epitaxy, convective self-assembly, surface tension-mediated physical adsorption, and external electric fields have been used to direct the assembly on the surface of nanoparticles. In recent years, covalent interactions have been used to combine nanoparticles with some organic molecules to prepare functionalized nanoparticles, which requires the screening of nanoparticles and organic molecules so that the assembled functional nanoparticles have active groups. For example, amino and carboxyl groups have attracted people's attention due to their good activity. Among them, the surface modification method is a common method for obtaining active groups on the surface of nano-silica particles. At present, most of the literature on surface modification is based on the modification of nano-silica particles with silane coupling agents to graft organic functional groups on the silicon surface, such as amino, vinyl, pyridine, etc. Among them, the amino group has received great attention due to its wide application in biomedicine, but there are relatively few literature reports on carboxylic acid-functionalized nano-silica particles. In fact, carboxylic acid-functionalized nano-silica also has considerable potential. For example, it has broad application prospects in aspects such as biopharmacy, fingerprint visualization, surfactants, enzyme immobilization carriers, scale prevention, and tertiary oil recovery in oilfields.

[0003] Silica raw materials are easily available and inexpensive. Because its surface is rich in a large number of hydroxyl groups, the silica particles themselves have strong hydrophilicity. In addition, the hydroxyl groups on the surface of nano-silica particles are easily interacted with the silanol groups in the hydrolyzed organosilane coupling agent, so that different types of functional groups can be grafted on the silica surface through chemical modification, which is an ideal raw material for preparing anionic nano-silica. Generally, the following methods are used to prepare carboxylic acid-functionalized nano-silica particles: trichlorocyanethylsilane (TCES), polymer coatings (epoxy resin, isocyanate, polybutylene succinate, polypyrrole), glutaric anhydride or succinic anhydride are selected as the carboxylic acid source on the silicon surface, and then carboxylic acid-functionalized silica particles are obtained through different methods. For example, in the organic phase, with Using relatively monodisperse silica nanoparticles prepared by a method as raw materials, and 3-aminopropyltriethoxysilane (APTES) as a modifier, amino groups are introduced onto the silicon surface through silanization. Then, the amino-functionalized silica is added to a DMF solution of succinic anhydride. The amino groups on the silicon surface cause the ring-opening of succinic anhydride to form carboxyl groups, thereby preparing carboxyl-functionalized silica nanoparticles (Yanqing An., Journal of Colloid and Interface Science 311 (2007), 507 - 513). Using commercial amorphous silicon powder as raw materials, iminodiacetic acid (PMIDA) which is soluble in water and each molecule contains two carboxyl groups is selected as the carboxylic acid source, and anionic silica nanoparticles are prepared by a simple water-based one-pot method (Peter Majewski., Applied Surface Science 257 (2011), 9282 - 9286). Also, using mesoporous silicon wafers as raw materials, bis(triethoxysilyl)benzene (BTEB) is added to obtain mesoporous phenylsilicon wafers. Then, using triblock copolymer P123 and KCl as additives, sodium carboxyethylsilanetriol (CES) is added, and carboxylic acid-functionalized mesoporous silica nanoparticles are obtained through the co-condensation of BTEB and CES (Hao-Yiang Wu., Chem. Eur. J. 2013, 19, 6358 - 6367). In addition, using CTAB as a structure template agent, under alkaline catalysis, tetraethyl orthosilicate (TEOS) is used as a precursor, and monodisperse silica microspheres are prepared by the sol-gel method. Then, cyanoethyltriethoxysilane is added to graft -CN onto the silicon surface. Finally, -CN is hydrolyzed into -COOH under acidic conditions, thereby preparing anionic silica nanoparticles. However, when preparing anionic nano-silica by the above methods, some need to first prepare silica raw materials, some need to add corresponding additives, structure template agents, etc. Especially when using succinic anhydride as the carboxylic acid source, although it can easily convert amino groups into carboxyl groups without high temperature or adding a catalyst, the organic reagent DMF is used in the experiment, and its removal process makes the whole preparation more complicated, with higher costs and environmental risks; at the same time, the particle size of anionic nano-silica particles prepared by some methods is relatively large, and there may be problems with relatively large particle sizes in practical applications. Summary of the Invention

[0004] In order to at least partially solve the technical problems existing in the prior art, the specific embodiments of the present invention provide an anionic nano-silica, the preparation process of which is simple, low-cost, and in line with the concept of green chemistry, and the particle size of the anionic nano-silica particles is less than 100 nm.

[0005] As an aspect of the present invention, it relates to an anionic nano-silica, the structural schematic is as follows:

[0006]

[0007] In at least one possible specific embodiment, the above anionic nano-silica exists in the state of nanoparticles.

[0008] As another aspect of the present invention, it relates to an anionic nano-silica hydrosol.

[0009] As yet another aspect of the present invention, it relates to a method for preparing the above hydrosol, including: (1) under aqueous phase conditions, modifying a nano-silica hydrosol with a silane coupling agent containing an amino group to obtain a silica hydrosol grafted with an amino group on the silica surface; (2) adding an acid anhydride for reaction to obtain an anionic nano-silica hydrosol.

[0010] In at least one possible specific embodiment, the reaction temperature in step (1) is 35 - 45 °C.

[0011] In at least one possible specific embodiment, in step (1), the addition amount of the silane coupling agent containing an amino group is 4% - 10% of the mass of the silica, preferably 8% - 10%.

[0012] In at least one possible embodiment, the silane coupling agent containing an amino group is a silane coupling agent containing a C1 - C3 alkyl chain. Specifically, for example, it can be one or a combination of γ-aminopropyltriethoxysilane (KH550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602), 3-aminopropylmethyldiethoxysilane (APDES).

[0013] In at least one possible specific embodiment, in step (2), the acid anhydride, specifically, for example, can be one or a combination of succinic anhydride, glutaric anhydride, maleic anhydride.

[0014] In at least one possible embodiment, the dosage of the acid anhydride is 5 - 10% of the mass of the silica.

[0015] In at least one possible specific embodiment, in step (1), the pH of the nano-silica hydrosol is 6 - 9, and the concentration is 20 - 30%.

[0016] As yet another aspect of the present invention, it relates to the application of the above anionic nano-silica hydrosol in scale prevention and tertiary oil recovery in oilfields.

[0017] In the preparation method of the anionic nano-silica hydrosol provided by the present invention, after the nano-silica hydrosol is modified with an amino-group-containing silane coupling agent, the amino group grafted on the silicon surface reacts with succinic anhydride to obtain the anionic nano-silica hydrosol.

[0018] In the preparation method of an anionic nano-silica hydrosol provided by the present invention, a commercial nano-silica hydrosol is used as the raw material, and the particle size of the nano-silica particles is <100 nm. Since a commercial nano-silica hydrosol is used, on the one hand, the preparation process of preparing nano-scale silica sol by the conventional sol-gel method is simplified, and on the other hand, time is saved, making the preparation process simpler.

[0019] First, under aqueous conditions, the present invention uses an amino-group-containing silane coupling agent to modify the nano-silica hydrosol, grafting an amino group on the surface of the silica. Then, an appropriate amount of succinic anhydride is added to the amino-functionalized nano-silica hydrosol. Through the reaction between the amino group and succinic anhydride, the ring-opening of succinic anhydride occurs, and the nano-silica particles are transformed from amino-functionalization to carboxyl-functionalization, thereby preparing the anionic nano-silica hydrosol.

[0020] The modification of the nano-silica hydrosol with the amino-group-containing silane coupling agent is carried out under mild aqueous conditions, using a simple water-based environment, with a simple process, low cost, and being green and non-toxic.

[0021] The present invention provides a preparation method of an anionic nano-silica hydrosol. The nano-silica hydrosol is modified with an amino-group-containing silane coupling agent, and then succinic anhydride is used as the carboxylic acid source to prepare the anionic nano-silica hydrosol. Its modification step is carried out in the aqueous phase, and no additional reagents, catalysts, etc. are required during the preparation process. The reaction between the amino group grafted on the silica surface and the added succinic anhydride is the key to preparing the anionic nano-silica hydrosol.

[0022] The present invention provides a preparation method of an anionic nano-silica hydrosol. The modification step of the nano-silica particles in the hydrosol and the preparation process of the anionic nano-silica particles both occur on the surface of a single silica particle. The degree of modification of the nano-silica hydrosol with the amino-group-containing silane coupling agent at the initial stage determines the conversion rate of the carboxyl group on the silicon surface in the later stage. At the same time, the grafting rate of the amino group on the silicon surface can be regulated by changing the concentration of the nano-silica hydrosol and the dosage of the amino-group-containing silane coupling agent;

[0023] The present invention provides a preparation method of an anionic nano-silica hydrosol. The reason for choosing an amino-group-containing silane coupling agent to modify the nano-silica hydrosol is that the amino group is chemically stable in the aqueous phase.

[0024] The present invention provides a method for preparing an anionic nano-silica hydrosol. The present invention uses a commercial nano-silica hydrosol as a raw material, which not only simplifies the preparation process of the nano-silica hydrosol, makes the preparation process simple, but also saves time and has relatively low costs.

[0025] The present invention provides a method for preparing an anionic nano-silica hydrosol. The nano-silica particles of this structure have great application potential in the field of nano-materials. The preparation method of the present invention is simple, easy to operate, the reaction conditions are mild and easy to control, and the reaction solvent is water, which conforms to the concept of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0027] Figure 1 is a schematic structural diagram of the anionic nano-silica particles prepared in Example 1 of the present invention.

[0028] Figure 2 is an infrared spectrum diagram of the anionic nano-silica particles before and after anion modification involved in Example 3 of the present invention, as well as the nano-silica particles in Comparative Examples 5 and 6.

[0029] Figure 3 is a nuclear magnetic resonance carbon spectrum diagram of the anionic nano-silica particles before and after anion modification involved in Example 3 of the present invention.

[0030] Figure 4 is a particle size distribution diagram of the anionic nano-silica particles before and after anion modification involved in Examples 1-4 of the present invention.

[0031] Figure 5 is a particle size distribution diagram of the anionic nano-silica particles before and after anion modification involved in Example 5 of the present invention.

[0032] Figure 6 is a particle size distribution diagram of the anionic nano-silica particles before and after anion modification involved in Example 6 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0034] Example 1

[0035] The present invention provides a method for preparing an anionic nano-silica hydrosol, which is obtained through the following steps:

[0036] Step 1: Under aqueous conditions, add 40 g of nano-silica hydrosol (mass fraction of SiO2 is 30%, pH = 8) into a reaction flask, then add γ-aminopropyltriethoxysilane (KH550), and control its addition amount to be 4% of the mass of silica in the hydrosol. Stir well in a water bath at 35 °C for 4 h, and finally place it at room temperature for 3 d to obtain a nano-silica hydrosol grafted with amino groups on the silica surface.

[0037] Step 2: First, weigh 1.2 g of succinic anhydride and dissolve it in 60 mL of deionized water, then mix it with the aminated nano-silica hydrosol in Step 1 respectively, and stir well at room temperature for 24 h to obtain an anionic nano-silica hydrosol with a particle size of <100 nm.

[0038] Example 2

[0039] The present invention provides a method for preparing an anionic nano-silica hydrosol, which is obtained through the following steps:

[0040] Step 1: Under aqueous conditions, add 40 g of nano-silica hydrosol (mass fraction of SiO2 is 25%, pH = 8.5) into a reaction flask, then add N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602), and control its addition amount to be 10% of the mass of silica in the hydrosol. Stir well in a water bath at 40 °C for 4 h, and finally place it at room temperature for 3 d to obtain a nano-silica hydrosol grafted with amino groups on the silica surface.

[0041] Step 2: First, weigh 0.6 g of succinic anhydride and dissolve it in 60 mL of deionized water, then mix it with the aminated nano-silica hydrosol in Step 1, and stir well at room temperature for 24 h to obtain an anionic nano-silica hydrosol with a particle size of <100 nm.

[0042] Example 3

[0043] The present invention provides a method for preparing an anionic nano-silica hydrosol, which is obtained through the following steps:

[0044] Step 1: Under aqueous conditions, add 40 g of nano-silica sol (mass fraction of SiO2 is 20%, pH = 6.5) into a reaction flask, then add γ-aminopropyltriethoxysilane (KH550), and control its addition amount to be 8% of the mass of silica in the sol. Stir well in a water bath at 40 °C for 4 h, and finally leave it at room temperature for 3 d to obtain a nano-silica sol with amino groups grafted on the silica surface.

[0045] Step 2: First, weigh 0.7 g of succinic anhydride and dissolve it in 60 mL of deionized water, then mix it with the amino-functionalized nano-silica sol obtained in Step 1, and stir well at room temperature for 24 h to obtain an anionic nano-silica sol with a particle size of <100 nm.

[0046] Example 4

[0047] The present invention provides a method for preparing an anionic nano-silica sol, which is obtained through the following steps:

[0048] Step 1: Under aqueous conditions, add 40 g of nano-silica sol (mass fraction of SiO2 is 30%, pH = 7.5) into a reaction flask, then add γ-aminopropyltriethoxysilane (KH550), and control its addition amount to be 6% of the mass of silica in the sol. Stir well in a water bath at 40 °C for 4 h, and finally leave it at room temperature for 3 d to obtain a nano-silica sol with amino groups grafted on the silica surface.

[0049] Step 2: First, weigh 1.1 g of glutaric anhydride and dissolve it in 60 mL of deionized water, then mix it with the amino-functionalized nano-silica sol obtained in Step 1, and stir well at room temperature for 24 h to obtain an anionic nano-silica sol with a particle size of <100 nm.

[0050] In the above examples, the present invention successfully prepared an anionic nano-silica sol, wherein the particle size of the anionic nano-silica particles is <100 nm, and the structural schematic diagram is as Figure 1 shown. Since the preparation method directly uses commercial nano-silica sol as the raw material, the preparation process is simpler and the cost is lower. In addition, because the amino group is chemically stable in the aqueous phase and is easy to react with succinic anhydride, it plays an important role in the preparation of the anionic nano-silica sol.

[0051] Example 5

[0052] To prove the successful preparation of the anionic nano-silica sol, a control experiment was carried out, and the steps are as follows:

[0053] Weigh 1.2 g of succinic anhydride and dissolve it in 60 mL of deionized water. Then mix the aqueous solution of succinic anhydride with 40 g of unmodified nano-silica sol (mass fraction of SiO₂ is 30%, pH = 8), and stir well at room temperature for 24 h. The test results of particle size distribution show that in addition to the particle distribution between <100 nm, there is also particle distribution between 100 - 1000 nm.

[0054] Example 6

[0055] To prove the successful preparation of anionic nano-silica sol, a control experiment was carried out, and the steps are as follows:

[0056] Weigh 1.2 g of succinic anhydride and dissolve it in 60 mL of deionized water. Then, using the one-pot method, add 8% γ-aminopropyltriethoxysilane (KH550) and the aqueous solution of succinic anhydride to 40 g of nano-silica sol (mass fraction of SiO₂ is 30%, pH = 8), stir well at room temperature for 24 h. The test results of particle size distribution show that in addition to the particle distribution between <100 nm, there is also particle distribution between 100 - 1000 nm.

[0057] Application Example 1

[0058] Measure Ca in the anionic nano-silica sol obtained in Example 1 according to the method of SYT5673-2020 "General Technical Conditions for Scale Inhibitors for Oilfields" at a concentration of 50 mg / L. 2+ The scale inhibition rate of calcium carbonate scale in an aqueous solution with a Ca concentration of 132 mg / L is 97.8%.

[0059] Application Example 2

[0060] Core with a gas permeability of 0.8 mD is saturated with kerosene at 60 °C, then 20 times the pore volume of water is injected, and the cumulative oil production is measured. Then continue to inject 20 times the pore volume of the anionic nano-silica sol obtained in Example 4 with a concentration of 0.1%, and measure the additional cumulative oil production. Then put the core into an oven and remove water at a constant temperature of 100 °C, and weigh the core after water removal. Remove oil by thermal decomposition at 400 °C and weigh the dry core. It is calculated that the oil displacement recovery rate using the anionic nano-silica sol obtained in Example 4 is increased by 3.5 percentage points.

[0061] The anionic nano-silica sample synthesized in Example 3 above was characterized:

[0062] (1) Infrared spectroscopy characterization (FTIR)

[0063] Take a small amount of the sample and mix it with an appropriate amount of KBr in an agate mortar, grind it, use a tablet press to press it into a transparent thin film, and use an infrared spectrometer (Bruker Tensor 27, Germany) to perform infrared characterization on the unmodified nano-silica (unmodified SiO2) and anionic nano-silica (SiO2-COOH) samples respectively. The scanning range is 4000 cm -1 ~400 cm -1 -1. As a control, infrared characterization was also performed on the samples in Examples 5 and 6, and the results are as Figure 2 shown.

[0064] In the infrared spectrum of unmodified nano-silica, the symmetric stretching vibration and bending vibration absorption peaks of Si-OH on the silica surface and -OH in physically adsorbed water are at 3460 cm -1 and 1642 cm -1 -1. At 1112 cm -1 -1, 803 cm -1 -1 and 470 cm -1 -1, they are respectively attributed to the asymmetric stretching vibration, symmetric stretching vibration and bending vibration absorption peaks of Si-O-Si. After anionic modification, in the infrared spectrum of SiO2-COOH, two new absorption peaks appear at 1557 cm -11 and 1730 cm -1 -1, which are the characteristic absorption peaks of amide bonds and C=O in carboxylic acids respectively. The absorption peak at 2990 - 2830 cm -1 -1 is the asymmetric stretching vibration and symmetric stretching vibration peaks of C-H in KH550 and succinic anhydride. The two are connected by an amide bond, resulting in the overlap of the characteristic absorption peaks of methylene. In addition, the infrared spectrum of the control experiment shows that except for the characteristic peaks of silica and the C-H absorption peak at 2990 - 2830 cm -1 -1, no characteristic absorption peaks of carboxyl or amide appear.

[0065] (2) Nuclear magnetic resonance characterization (NMR)

[0066] Use a VARIAN III 600 MHz nuclear magnetic resonance spectrometer (NMR) from Bruker Company, Germany, with TMS as the internal standard, to perform 13 13C NMR characterization on the anionic nano-silica particles (SiO2-COOH) sample in Example 3, and the results are as Figure 3 shown.

[0067] After anionic modification, 13New absorption peaks appeared in the ¹³C NMR spectrum. The peak at 185 ppm was attributed to the carbon signal peak in -COOH, and the peak at 37 ppm was the carbon signal peak in alkanes. Since succinic anhydride and KH550 were linked by an amide bond, the alkyl chain was lengthened. Therefore, the signal peak at this position was the result of the overlap of -CH₂- in both. Combining with the infrared spectrum proved that anionic nano-silica hydrosol was successfully prepared.

[0068] (3) Dynamic Light Scattering Particle Sizer (DLS)

[0069] The size and distribution of nano-silica particles before and after anionic modification were analyzed by DLS (Malvern Instrument Zetasizer Nano ZS90), and the results are as Figure 4 shown.

[0070] After anionic modification of the nano-silica hydrosol, the particle size increased, such as from 22 nm to about 30 nm, and the particle size distribution was narrow, showing good monodispersity.

[0071] Figure 5 and Figure 6 corresponded to the particle size test results of Example 5 and Example 6 respectively. There were many large particle size particles between 100 - 1000 nm in the samples prepared by Example 5 or Example 6. This was mainly because under the conditions of Example 5 or Example 6, the unmodified nano-silica hydrosol could not react with the modifier, and at the same time, the modifier would cause aggregation between the particles of the unmodified nano-silica hydrosol, resulting in many large particle size particles.

[0072] The specific embodiments described above further detailed the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anionic nano-silica, characterized in that, The structural formula is as shown in formula (1): （1）。 2. The anionic nano-silica according to claim 1, characterized in that, The anionic nano-silica exists in the state of nano-particles.

3. An anionic nano-silica hydrosol, characterized in that, The hydrosol comprises the anionic nano-silica according to any one of claims 1 or 2.

4. A method for preparing an anionic nano-silica hydrosol, characterized in that, Comprising: (1) Under aqueous phase conditions, modifying the nano-silica hydrosol with a silane coupling agent containing an amino group to obtain a silica hydrosol grafted with an amino group on the silica surface; (2) Adding an acid anhydride for reaction to obtain an anionic nano-silica hydrosol; The silane coupling agent containing an amino group is selected from γ-aminopropyltriethoxysilane or N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane; The acid anhydride is selected from succinic anhydride or glutaric anhydride.

5. The method according to claim 4, wherein The reaction temperature of step (1) is 35 - 45 °C.

6. The method according to claim 4, characterized in that In step (1), the addition amount of the silane coupling agent containing an amino group is 4% - 10% of the mass of the silica.

7. The method according to claim 6, wherein In step (1), the addition amount of the silane coupling agent containing an amino group is 8% - 10% of the mass of the silica.

8. The method according to claim 4, characterized in that The dosage of the acid anhydride is 5 - 10% of the mass of the silica.

9. Application of the anionic nano-silica hydrosol prepared by the method according to any one of claims 4 - 8 in the fields of scale prevention and tertiary oil recovery in oilfields.

Images