Background
Silica is a tasteless, nontoxic and pollution-free non-metallic material, is widely applied in many fields such as ceramics, electronics, metallurgy and machinery, and has important functions in chemical fields such as catalysis, medicine and coating due to the characteristics of excellent chemical stability, thermal stability, biocompatibility and the like, so that the silica is widely researched. The dimension, size and morphology (especially micro/nano scale) of the silicon dioxide material have great influence on the performance of the silicon dioxide material, and the silicon dioxide material with a unique morphology structure is concerned with the expansion of the application field and the improvement of the performance requirement.
The silica structures reported so far include spherical, rod-like, fibrous, flower-like, mushroom-like, chain-like, and the like; however, when the low-dimensional material is used as a catalyst or a catalyst carrier, the small size of the material can cause difficult separation and recovery (particularly liquid-solid reaction), and the large size can cause the problems of slow internal diffusion speed and the like; in addition, the structural material is easy to agglomerate, most fillers used as rubber materials are poor in compatibility with polymers, surface modification is needed, and otherwise ideal composite material performance is difficult to achieve.
Disclosure of Invention
The invention aims to provide a method for preparing silicon dioxide with a three-dimensional ball chain structure aiming at the defects in the prior art. According to the method, on the basis of a synthesis system consisting of ethyl orthosilicate and a water-alcohol mixture, a silane coupling agent KH570 is added, parameters such as a water-alcohol ratio, the dosage of a surfactant and a stirring speed are adjusted, so that silicon dioxide with a three-dimensional spherical chain structure is synthesized, and the size of a material sphere can be adjusted within a certain scale range. The silicon dioxide material synthesized by the invention has a three-dimensional framework structure, can effectively improve or solve the problems in the prior art, and the size of the sphere is controllable within a certain range.
The technical scheme of the invention is as follows:
a method for preparing three-dimensional spherical chain structure silicon dioxide comprises the following steps:
(1) mixing absolute ethyl alcohol and distilled water, adding a surfactant CTAB, dissolving, sequentially adding Tetraethoxysilane (TEOS) and ammonia water under stirring, and finally dropwise adding gamma-methacryloxypropyltrimethoxysilane (KH570) to obtain a white suspension;
wherein, the volume ratio of absolute ethyl alcohol: distilled water: ethyl orthosilicate: ammonia water: gamma-methacryloxypropyltrimethoxysilane (gamma-methacryloxypropyltrimethoxysilane) (50-150): 50-150: 1-4: 2-5: 0.5-2.5; adding 0.20-2.00g of surfactant CTAB into every 50-150 ml of absolute ethyl alcohol;
(2) reacting the white suspension obtained in the step (1) for 1-6h at 25-50 ℃ under the stirring condition, separating, washing and drying the product, and roasting at 450-700 ℃ for 5-8 h to obtain the final product, namely the three-dimensional spherical chain silicon dioxide.
The stirring speed in the step (1) and the step (2) is 200-1000 rpm.
The temperature rise rate of the roasting at the temperature of 450-700 ℃ in the step (2) is 1-5 ℃/min.
The advantages and the achieved beneficial effects of the invention are as follows:
1. the method has the advantages of simple process, mild reaction conditions and strong controllability; after being roasted at high temperature, the spherical silicon dioxide still can keep good appearance and has good thermal stability; meanwhile, a large number of silicon hydroxyl groups exist on the surface of the prepared silicon dioxide (the infrared characterization result of figure 5 is 3400 cm)-1And 960cm-1The infrared peak at the wave number is the characteristic absorption peak of the silicon hydroxyl group), thereby providing convenience for the later application and modification of the material in different fields and having very high potential application value.
2. The spherical chain-shaped silicon dioxide material prepared by the invention has a three-dimensional structure (shown in SEM pictures in attached figures 1-3 in detail), the prepared material is used as a catalyst or a catalyst carrier, and the ultra-large space among the spherical chain structures provides convenience for the diffusion of reactants and products, so that the influence of internal diffusion is favorably eliminated; in addition, the oversized size of the three-dimensional structure is more beneficial to the separation of the catalyst; the sphere size of the material can be adjusted within a certain range, so that convenience and possibility are provided for meeting the structural requirements of different fields of application, for example, the material can be used as an inorganic template agent to synthesize porous materials with different pore diameters.
3. The spherical chain silicon dioxide material prepared by the invention can be directly used without roasting treatment, and the chain part in the material contains a large amount of organic chains, so that the compatibility between the material and a polymer can be effectively improved, and the bonding force between the material and the polymer is improved, thereby endowing the composite material with special functions.
Detailed Description
The present invention is illustrated below by examples, which are described only for further explaining and explaining the present invention in detail, but the scope of the present invention is not limited to the following examples, and the insubstantial modifications and adaptations made by those skilled in the art based on the contents of the present invention still belong to the scope of the present invention.
Example 1:
uniformly mixing 75mL of absolute ethyl alcohol and 125mL of distilled water, adding 0.400g of CTAB surfactant, sequentially dropwise adding 1.75mL of tetraethoxysilane under the stirring of 400rpm, stirring for 5min, then dropwise adding 2.5mL of ammonia water for 3min, stirring for 10min, converting the solution into milk white, finally adding 0.75mL of KH570 into 3min, continuously stirring at room temperature for reaction for 3h, separating, washing and drying the sample overnight, heating to 600 ℃ at the speed of 1 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional spherical chain structure.
The obtained product has no change of the silicon dioxide sphere before and after roasting, which shows that the product has good stability; the morphology of the three-dimensional spherical chain structure sample before and after roasting is shown in a scanning electron microscope photo of figure 1, and the diameter of the sphere is 700 nm; the XRD characterization results shown in FIG. 4 indicate that the prepared sample is a pure silicon dioxide material; FIG. 5 shows the infrared spectra before and after sample calcination, wherein 1086cm-1And 805cm-1Absorption peaks at wave numbers indicate that a large amount of Si-O-Si framework structures are formed in the material; 1721cm-1A new absorption peak appears at 2927cm, which is the stretching vibration absorption peak of the C ═ O group in the silane coupling agent KH570-1And 2854cm-1Is out ofnow-CH3The antisymmetric and symmetric stretching vibration absorption peaks indicate that the sample contains a large amount of organic functional groups.
Example 2:
uniformly mixing 65mL of absolute ethyl alcohol and 125mL of distilled water, adding 0.400g of CTAB surfactant, sequentially dropwise adding 1.75mL of tetraethoxysilane under the stirring of 400rpm, stirring for 5min, then dropwise adding 2.5mL of ammonia water for 3min, stirring for half an hour, converting the solution into milk white, finally adding 0.75mL of KH570 into 3min, continuously stirring at room temperature for reaction for 3h, separating, washing, drying overnight, heating to 600 ℃ at the speed of 1 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional spherical chain structure. The silica spheres before and after calcination were unchanged, and the scanning electron micrograph of the calcined sample is shown in FIG. 2, with sphere diameters of 300 nm.
Example 3:
uniformly mixing 75mL of absolute ethyl alcohol and 125mL of distilled water, adding 0.400g of CTAB surfactant, sequentially adding 1.75mL of tetraethoxysilane under the stirring of 400rpm, stirring for 5min, dropwise adding 2.5mL of ammonia water for 3min, stirring for 10min, converting the solution into milk white, finally adding 1.75mL of KH570 into 7min, stirring at room temperature for 3h, separating, washing, drying overnight, heating to 600 ℃ at the speed of 1 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional spherical chain structure. The silica spheres before and after calcination were unchanged, and the scanning electron micrograph of the calcined sample is shown in FIG. 3, with a sphere diameter of 600 nm.
Example 4:
uniformly mixing 75mL of absolute ethyl alcohol and 125mL of distilled water, adding 1.200g of a surfactant CTAB, sequentially adding 3.5mL of tetraethoxysilane under the stirring of 400rpm, using for 10min, dropwise adding 2.5mL of ammonia water for 3min, stirring for half an hour, converting the solution into milk white, finally adding 1.5mL of KH570 into 6min, continuously stirring at room temperature for reaction for 5h, separating and washing a sample, drying overnight, heating to 500 ℃ at the speed of 5 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional sphere chain structure, wherein the silicon dioxide spheres are unchanged before and after roasting, and the diameter of the spheres is 300 nm.
Example 5:
uniformly mixing 75mL of absolute ethyl alcohol and 125mL of distilled water, adding 0.800g of CTAB surfactant, sequentially adding 3.5mL of ethyl orthosilicate while stirring at 800rpm, using for 10min, dropwise adding 2.5mL of ammonia water for 3min, stirring for half an hour, converting the solution into milk white, finally adding 1.5mL of KH570, continuously stirring at room temperature for reaction for 5h, separating and washing a sample, drying overnight, heating to 500 ℃ at the speed of 5 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional spherical chain structure, wherein the silicon dioxide spheres are unchanged before and after roasting, and the diameter of the spheres is 200 nm.
Example 6:
uniformly mixing 75mL of absolute ethyl alcohol and 125mL of distilled water, adding 0.400g of CTAB surfactant, sequentially adding 1.75mL of tetraethoxysilane under the stirring of 400rpm, using for 5min, dropwise adding 5mL of ammonia water for 6min, stirring for 10min, converting the solution into milk white, finally adding 0.75mL of KH570, continuously stirring at room temperature for reaction for 1h, separating and washing a sample, drying overnight, heating to 500 ℃ at the speed of 1 ℃/min, and roasting for 6h to obtain the silicon dioxide with the three-dimensional spherical chain structure, wherein the silicon dioxide spheres are unchanged before and after roasting, and the diameter of the spheres is 700 nm.
In conclusion, the sphere diameter of the silica with the spherical chain structure reported by the method can be regulated and controlled within the range of 200-700nm by regulating parameters such as stirring speed, alcohol-water ratio in the system, dosage of the surfactant and the like. The stirring speed is increased to be beneficial to the dispersion of the tetraethoxysilane in a synthesis system, so that the emulsion droplets formed by the tetraethoxysilane in the system are smaller as the stirring speed is higher, and the finally prepared spheres are smaller; the more the surfactant is, the easier the protective layer is formed on the surface of the ethyl orthosilicate liquid drop, so that the liquid drops are effectively prevented from colliding, polymerizing and growing, and the formation of smaller spherical particles after hydrolysis is ensured; the surface tension of the alcohol-water ratio increasing system is reduced, and the larger the formed emulsion liquid drop is, the larger the diameter of the sphere prepared by hydrolysis is.
The invention is not the best known technology.