Preparation method of high-purity carbon microspheres based on reverse emulsion gel-carbonization process

Abstract

The invention belongs to the technical field of carbon material preparation, and particularly relates to a preparation method of high-purity carbon microspheres based on a reverse emulsion gel-carbonization process, which comprises the following steps: (1) preparing a water phase; (2) preparing an oil phase; (3) preparing a water-in-oil emulsion; (4) preparing a sugar carbon microsphere precursor; (5) preparing carbon microspheres; according to the preparation method of the high-purity carbon microspheres based on the reverse emulsion gel-carbonization process, a high-purity water-soluble carbohydrate is used as a carbon source, water-phase emulsion droplets are subjected to gel solidification, dehydration and pre-carbonization of gel droplets are completed in an oil phase, and then high-temperature carbonization is performed, so that the carbon yield in the carbohydrate is close to the theoretical carbon content; meanwhile, the reverse emulsion gel method is simple in process, and carbon microspheres with different sizes and good sphericity and high carbon yield can be produced on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon material preparation, and in particular relates to a method for preparing high-purity carbon microspheres based on a reverse emulsion gel-carbonization process. Background Art

[0002] Among the many carbon materials with different forms and unique functions, carbon microspheres have attracted extensive attention from researchers due to their advantages such as regular structure and morphology, high thermal conductivity, good heat resistance, and stable physical and chemical properties. They have great application value in many fields such as electromagnetism, biology, physics, chemistry, and materials science. At present, carbon microspheres have been used in many fields such as lithium-ion battery electrode materials, electrochemical capacitor electrode materials, hollow spherical material production templates, adsorption materials, fuel cell catalyst carriers, hydrogen storage materials, and additives for functional materials, and have formed a certain market scale. Therefore, the preparation and research of carbon microspheres is of great significance.

[0003] Except for the preparation of carbon microspheres with mesophase pitch, the carbon yields prepared by CVD and hydrothermal methods are insufficient, and the liquid phase method is not suitable for large-scale rapid production.

[0004] Therefore, how to overcome the insufficient carbon yield in large-scale production of carbon microspheres is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the invention

[0006] The embodiments of the present disclosure at least provide a method for preparing high-purity carbon microspheres based on a reverse emulsion gel-carbonization process.

[0007] In a first aspect, the embodiments of the present disclosure provide a method for preparing high-purity carbon microspheres based on a reverse emulsion gel-carbonization process, comprising: (1) preparing an aqueous phase, namely, adding a water-soluble sugar substance, a gelling agent and an initiator to deionized water respectively, stirring and heating to dissolve the deionized water to obtain an aqueous phase; (2) preparing an oil phase, namely, adding a surfactant to the oil, stirring and heating to dissolve the deionized water to obtain an oil phase; (3) preparing an oil-in-water emulsion, namely, adding the aqueous phase to the oil phase, and emulsifying the oil-in-water emulsion to obtain the oil-in-water emulsion; (4) preparing a sugar-carbon microsphere precursor, namely, stirring and heating to solidify the water phase in the oil-in-water emulsion by emulsion gelation, and then gradually heating to complete a low-temperature pyrolysis pre-carbonization treatment, and after cooling, degreasing, washing and drying to obtain a sugar-carbon microsphere precursor; (5) preparing carbon microspheres, namely, subjecting the sugar-carbon microsphere precursor to a high-temperature carbonization treatment to obtain carbon microspheres.

[0008] In an optional embodiment, the water-soluble sugar substance includes any one or more combinations of water-soluble sucrose, glucose, fructose and maltose; and the added amount of the water-soluble sugar substance is 50%-200% of the weight of the deionized water.

[0009] In an optional embodiment, the gelling agent is a crosslinking agent of acrylamide monomer and N,N'-methylenebisacrylamide, and the weight ratio of the two is 20-50:1; and the amount of the gelling agent added is 15%-30% of the weight of the deionized water.

[0010] In an optional embodiment, the initiator includes any one of persulfate and water-soluble azo initiator; and the added amount of the initiator is 0.2%-0.6% of the weight of the deionized water.

[0011] In an optional embodiment, the oil includes any one of vegetable oil and mineral oil.

[0012] In an optional embodiment, the hydrophile-lipophile balance value of the surfactant is 4-7; and the amount of the surfactant added is 2%-6% of the weight of the oil.

[0013] In an optional embodiment, the emulsification treatment is specifically to add the water phase to the oil phase and then use a shear emulsifier to stir at high speed to obtain an oil-in-water emulsion; wherein the weight ratio of the water phase to the oil phase is 10-30:100, the stirring rate is 100-300r / s, and the shear emulsification time is 5-20min.

[0014] In an optional embodiment, the step (4) of preparing the sugar-carbon microsphere precursor specifically includes placing the container containing the oil-in-water emulsion in an oil bath heating magnetic stirrer, heating to 60-80°C while stirring and maintaining for 3-5 hours to allow the water phase to undergo emulsion gel solidification, then heating to 200-220°C at a rate of 10-30°C / h and maintaining for 0.5-1h to complete partial dehydration of the gel droplets and low-temperature pyrolysis pre-carbonization treatment, cooling and deoiling by centrifugation or filtration, and then washing and drying with gasoline and anhydrous ethanol, respectively, to obtain the sugar-carbon microsphere precursor.

[0015] In an optional embodiment, the step (5) of preparing carbon microspheres specifically includes placing the sugar-carbon microsphere precursor in a ceramic or graphite crucible and keeping it at 800-1200° C. for 1-2 hours under the protection of an inert gas.

[0016] In a second aspect, the embodiments of the present disclosure further provide high-purity carbon microspheres obtained by the preparation method as described above, wherein the carbon yield of the high-purity carbon microspheres is not less than 88%.

[0017] The beneficial effect of the present invention is that the preparation method of high-purity carbon microspheres based on the reverse emulsion gel-carbonization process uses high-purity water-soluble sugar substances as carbon sources, solidifies the water phase emulsion droplets and completes dehydration and pre-carbonization of the gel droplets in the oil phase, and then high-temperature carbonization can make the carbon yield in the sugar substance close to its theoretical carbon content. At the same time, the reverse emulsion gel method is simple and can mass-produce carbon microspheres of different sizes with good sphericity and high carbon yield.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a SEM morphology of the glucose carbon microsphere precursor after 220°C pre-carbonization treatment provided in the embodiment of the present disclosure;

[0022] Figure 2 This is a SEM morphology of glucose carbon microspheres after carbonization treatment at 800°C provided in an embodiment of the present disclosure;

[0023] Figure 3 This is a SEM morphology of the sucrose carbon microsphere precursor after 200°C pre-carbonization treatment provided in the embodiment of the present disclosure;

[0024] Figure 4 This is a SEM morphology of sucrose carbon microspheres after carbonization treatment at 1200°C provided in an embodiment of the present disclosure;

[0025] Figure 5 This is an enlarged SEM morphology of sucrose carbon microspheres after carbonization treatment at 1200°C provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Therefore, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, so that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like are used to "serve as an example, instance, or illustration." Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. On the contrary, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0028] Herein, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." modify the entire list of elements when following a list of elements, rather than modifying individual elements in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0029] The terms used herein are only used to describe specific exemplary configurations and are not intended to be limited. As used herein, the singular articles "one", "an" and "the" may also be intended to include plural forms, unless it is clearly indicated above that this is not the case. The terms "comprise", "include" and "have" are inclusive, and therefore specify the presence of features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof. The method steps, processes and operations described herein should not be interpreted as necessarily requiring them to be performed in the specific order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0030] Carbon microspheres were first discovered in the 1960s. Scientists accidentally discovered that a small amount of optically anisotropic spheres were generated in the vitrine during the study of coal coking. The spheres grew and fused to form a mosaic structure, which was the precursor of mesocarbon microspheres. In 1972, Honda and Yamada first produced micron-sized mesocarbon microbeads (MCMB) by separating asphalt.

[0031] In the early stage, the raw material for preparing carbon microspheres was mainly mesophase pitch. The raw material pitch was used to obtain mesophase pitch through thermal polycondensation, and then the mesophase pitch microspheres were separated, and then the carbon microspheres were obtained after pre-oxidation and carbonization. Esumi K et al. obtained carbon microspheres with a C / H ratio of 2.314 and a diameter of 2 to 15um after thermal polycondensation of coal tar pitch (Esumi K, Nishina S, Sakurada S, et al. Formation of mesophase spheres from a coal tar pitch up on heating and subsequent cooling. Carbon, 1987, 25 (6): 821). The polycondensation method has simple conditions, easy operation, and is easy to realize industrial continuous production, but there are problems such as too wide ball diameter distribution, uneven shape and size, and low yield. Despite this, the polycondensation method is still the main method for modern industrial production of carbon microspheres.

[0032] In recent years, researchers from all over the world have gradually studied the use of non-asphalt raw materials to prepare carbon microspheres, and successfully synthesized carbon sphere materials with different particle sizes and structures through different methods, which has greatly enriched the research field of carbon materials. Among them, the most studied methods are the preparation of carbon microspheres using chemical vapor deposition (CVD) and solvent (water) thermal methods.

[0033] CVD method is to utilize chemically active compounds containing unsaturated chemical bonds, such as gases such as acetylene, benzene, ethylene, styrene and toluene as raw materials, and to form elementary particles by chemical reaction in gas phase by controlling parameters such as reaction temperature, air pressure and air flow rate, and to form carbon microspheres through two stages of nucleation and growth. Wang et al. utilize CH4 as raw material, and utilize CVD to obtain carbon microspheres with a particle size of 210nm under the condition of dioxide as catalyst (Wang ZL, Kang ZC. Pairing of pentagonal and heptagonal carbon rings in the growth of nanosize carbonspheres synthesized by a mixed-valent oxide catalytic carbonization process. J Chem Phys, 1996, 100 (45): 5163). Wang et al. prepared carbon microspheres with a particle size of 2 μm using synthetic naphthalene isotropic pitch at 420°C in a nitrogen atmosphere (Wang YG, Chang YC, Ishida S, et al. Stabilization and carbonization properties of mesocarbon microbeads (MCMB) prepared from a synthetic naphthalene isotropic pitch. Carbon, 1999, 37 (6): 969). Serp et al. prepared carbon microspheres with a particle size of 100 to 300 nm using a mixture of H2 and CH4 under high-temperature metal catalysis (Ph Serp, R Feurer, Ph Kalck, et al. A chemical vapor deposition process for the production of carbon nanospheres. Carbon, 2001, 39 (4): 621). Since CVD synthesis requires a high temperature gradient, the synthesized particles are large and easy to agglomerate, plasma CVD technology was developed based on CVD. Qiu et al. used coal as raw material and nickel as catalyst to synthesize carbon microspheres of 10 to 20 μm in arc plasma (Jieshan Oiu, Yongfeng Li, Yunping Wang, et al. A novel form of carbon micro-balls from coal. Carbon, 2003, 41(4): 767).Pocsik et al. used benzene vapor to ionize under a pulsed electric field and then deposited to obtain carbon microspheres of 100 to 200 nm (Pocsik I, Veres M, Fule M, et al. Carbon nano-particles prepared by ion-clustering in plasma. Vacuum, 2003, 71 (1-2): 171). The CVD method has a high degree of graphitization and good stability, and is currently one of the commonly used methods for preparing carbon microspheres. However, this method has high requirements for equipment and high process costs, especially its carbon recovery rate (gas utilization rate) is low and the output is small.

[0034] The preparation of carbon microspheres by solvent (hydrothermal) method has attracted wide attention in recent years. This method uses sugar substances or resin substances as raw materials, and prepares carbon microspheres by controlling the raw material concentration, reaction temperature, time, pressure and pH value. Chen CY et al. used glucose as raw material and synthesized monodispersed colloidal carbon microspheres (colloidal carbon spheres CCS) with a diameter range of 160-400nm by a two-step hydrothermal method. The size consistency is very good. When the glucose concentration is 0.1-0.4M, the size standard deviation of the synthesized colloidal carbon microspheres is only 8% (Chen CY, Sun XD, Jiang XC, et al. A two-stepshydrothermal synthesis approach to monodispersed colloidal carbon spheres [J]. Nanoscale Resolution Letters, 2009, (49): 971-976). Min Li et al. used glucose as raw material and prepared carbon spheres with good sphericity and rich oxygen functional groups on the surface (Oxygen-rich CSs) by a simple one-step hydrothermal method. Under the optimal hydrothermal process conditions (180-230℃ / 3-4h), the size of ~800nm, smooth surface, good consistency of carbon microspheres (Min Li, Wei Li, and Shouxin Liu. Control of the morphology and chemical properties of carbon spheres prepared from glucose by a hydrothermal method. J. Mater. Res. Vol. 27, No. 8, Apr 28, 2012). Wei Jing et al. used glucose, fructose, sucrose, and xylose as raw materials to synthesize carbon microspheres rich in oxygen functional groups on the surface by hydrothermal carbonization (200℃ / 24h), with a diameter of about 1um. Experiments show that due to the formation of intermediates (organic acids) during the reaction process, the carbon yield of sugar substances is very low, less than 30% of its theoretical carbon content (Wei Jing, Chu Yun, Jiang Guomin et al.: Preparation of carbon microspheres by hydrothermal carbonization [J], Functional Materials, 2014, 45 (S2): 136-139). Liu Jianjun used formaldehyde and urea as raw materials and formic acid as catalyst to prepare urea-formaldehyde resin microspheres with good dispersibility and sphericity by hydrothermal method (130℃ / 1h), and obtained carbon microspheres with a diameter of 1-2um after carbonization treatment at 800℃. (Liu Jianjun. Preparation and electrochemical performance of urea-formaldehyde resin-based carbon microspheres [J]. China Chemical Trade, 2015 (28), 170-171) In general, the above hydrothermal method for preparing carbon microspheres generally has low production efficiency (the solution concentration is very low).

[0035] The liquid phase method refers to a type of preparation method in which the initial phase of the reaction system is mainly liquid. The main method for preparing carbon microspheres by the liquid phase method is the suspension emulsion method. This method requires the reaction carbon source to be dissolved in the internal phase and insoluble in the external phase, and requires a suitable emulsifier to form a stable and good emulsified system. For traditional carbon source mesophases such as asphalt, resin and sugar, a certain emulsified system can be formed by finding the corresponding external phase, internal phase and emulsifier. Kodama et al. first proposed the use of an emulsification method to prepare carbon microspheres (Kodama M, Fujirua T, Esumi K, et al. Preparation of meso-carbon microbeads with a narrow size distribution, Carbon, 1988, 26 (4): 595). The method grinds quinoline-soluble mesophase pitch to 200-325 mesh and then suspends it in silicone oil (2g / 150ml), heats and blows nitrogen to stir to form an emulsion, and maintains it at a temperature near the softening point of the mesophase pitch (290℃~310℃) for a certain time (10~60min) to form a microsphere dispersion. After cooling, it is washed with benzene, dried, and carbonized to obtain carbon microspheres. By grading the mesophase pitch grinding powder, relatively uniform carbon microspheres with an average diameter of about 30um are obtained. The process of preparing carbon spheres by emulsion method using resin as a carbon source is similar to that of mesophase pitch. These methods require relatively expensive raw materials, have high requirements for equipment and thermally stable media, have complicated processes, and have very low production efficiency. In addition, the use of soluble sugars as carbon sources can easily form a variety of stable emulsified systems, but the uncontrollable foaming of sugar substances limits their wide application. In general, the above hydrothermal method for preparing carbon microspheres generally has low production efficiency (very low solution concentration). Problems include high equipment requirements (high temperature reaction equipment required) and uncontrollable foaming.

[0036] The defects existing in the above solutions are the results obtained by the inventor after practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the present disclosure for the above problems below should be the contributions made by the inventor to the present disclosure during the disclosure process.

[0037] The disclosed embodiment provides a method for preparing high-purity carbon microspheres based on a reverse emulsion gel-carbonization process, comprising: (1) preparing an aqueous phase, namely, adding a water-soluble sugar substance, a gelling agent and an initiator to deionized water, respectively, stirring and heating to dissolve until clarified to obtain an aqueous phase; (2) preparing an oil phase, namely, adding a surfactant to the oil, stirring and heating to dissolve until clarified to obtain an oil phase; (3) preparing an oil-in-water emulsion, namely, adding the aqueous phase to the oil phase, emulsifying the oil-in-water emulsion; (4) preparing a sugar-carbon microsphere precursor, namely, stirring and heating to solidify the water phase in the oil-in-water emulsion by emulsion gelation, then gradually heating to complete a low-temperature pyrolysis pre-carbonization treatment, cooling, degreasing, washing and drying to obtain a sugar-carbon microsphere precursor; (5) preparing carbon microspheres, namely, subjecting the sugar-carbon microsphere precursor to a high-temperature carbonization treatment to obtain carbon microspheres.

[0038] In some embodiments, specifically, the water-soluble sugar substance includes a combination of any one or more of water-soluble sucrose, glucose, fructose and maltose; and the added amount of the water-soluble sugar substance is 50%-200% of the weight of the deionized water, preferably 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190% and 200%.

[0039] In some embodiments, specifically, the gelling agent is a crosslinking agent of acrylamide monomer and N,N'-methylenebisacrylamide, and the weight ratio of the two is 20-50:1, preferably 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1; and the amount of the gelling agent added is 15%-30% of the weight of the deionized water, preferably 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, 30%.

[0040] In some embodiments, specifically, the initiator includes any one of a persulfate and a water-soluble azo initiator, the persulfate is preferably ammonium persulfate, and the water-soluble azo initiator is preferably water-soluble azobisisobutylamidine hydrochloride (V50); and the added amount of the initiator is 0.2%-0.6% of the weight of the deionized water.

[0041] In some embodiments, specifically, the oil includes any one of vegetable oil and mineral oil, the vegetable oil includes rapeseed oil, peanut oil, soybean oil, sunflower oil, olive oil, and the mineral oil includes motor oil, white oil, and silicone oil.

[0042] In some embodiments, specifically, the hydrophile-lipophile balance (HLB) of the surfactant is 4-7, preferably HLB = 4.0, 4.3, 4.7, 5.0, 5.3, 5.6, 6.0, 6.5, 7.0; and the amount of the surfactant added is 2%-6% of the weight of the oil, preferably 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%.

[0043] In some embodiments, specifically, the emulsification treatment is specifically to add the water phase to the oil phase and then use a shear emulsifier to stir at high speed to obtain an oil-in-water emulsion; wherein the weight ratio of the water phase to the oil phase is 10-30:100, preferably 10:100, 15:100, 20:100, 25:100, 30:100, the stirring rate is 100-300r / s, preferably 100r / s, 150r / s, 200r / s, 250r / s, 300r / s, and the shear emulsification time is 5-20min, preferably 5min, 8min, 12min, 15min, 20min.

[0044] In some embodiments, specifically, the step (4) of preparing the sugar-carbon microsphere precursor specifically includes placing the container containing the oil-in-water emulsion in an oil bath heating magnetic stirrer, heating to 60-80°C while stirring and maintaining for 1-5h to allow the water phase to undergo emulsion gel solidification, preferably 60°C / 4h, 60°C / 3h, 70°C / 3h, 70°C / 2h, 80°C / 2h, 80°C / 1h, and then heating to 200-220°C at a rate of 10-30°C / h and maintaining for 0.5-1h to complete partial dehydration of the gel droplets and low-temperature pyrolysis pre-carbonization treatment, cooling and deoiling by centrifugation or filtration, and then washing and drying with gasoline and anhydrous ethanol, respectively, to obtain the sugar-carbon microsphere precursor.

[0045] In some embodiments, optionally, heating to 200-220°C and maintaining for 0.5-1h can be that after heating to 100°C, the dehydration and pyrolysis pre-carbonization treatment of the emulsion droplets are completed with the procedure of 100°C / 3h→110°C / 1h→120°C / 1h→130°C / 1h→140°C / 1h→150°C / 1h→160°C / 1h→170°C / 1h→180°C / 1h→200°C / 1h→220°C / 1h; after heating to 100°C, the dehydration and pyrolysis pre-carbonization treatment of the emulsion droplets are completed with the procedure of 100°C / 2h→120°C / 2h→140°C / 2h→160°C / 2h→180°C / 2h→200°C / 2h.

[0046] In some embodiments, specifically, the step (5) of preparing carbon microspheres specifically includes placing a sugar-carbon microsphere precursor in a ceramic or graphite crucible, and keeping it at 800-1200°C for 1-2h under the protection of an inert gas, preferably 800°C / 1h, 800°C / 1.5h, 800°C / 2h, 850°C / 1h, 850°C / 1.5h, 850°C / 2h, 900°C / 1h, 900°C / 1.5h, 900°C / 2h, 1000°C / 1h, 1000°C / 1.5h, 1000°C / 2h, 1200°C / 1h, 1200°C / 1.5h, 1200°C / 2h.

[0047] The disclosed embodiment also provides a high-purity carbon microsphere, which is obtained by the preparation method as described above, and the carbon yield of the high-purity carbon microsphere is not less than 88%.

[0048] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0049] Example 1

[0050] Weigh 80g analytical pure anhydrous glucose and 40g deionized water, heat to 60℃ to dissolve, cool to room temperature, add 10g acrylamide, 0.3g N,N'-methylenebisacrylamide, 0.5g azobisisobutylamidine hydrochloride (V50), stir magnetically to dissolve and let stand to clarify as the water phase; weigh 400g white oil and put it in a 800ml beaker, add 19.0g Span 80 and 1g Tween 80 mixed surfactant as the oil phase; weigh 100g The aqueous phase solution was added to the oil phase, and stirred at a speed of 250r / s for 15 minutes using a shear emulsifier to obtain a milky white oil-in-water emulsion; the beaker was placed in an oil bath heating magnetic stirrer, the temperature was raised to 80°C and stirred for 6 hours to solidify the aqueous phase emulsion gel; then the temperature was raised to 100°C while stirring, and the temperature was adjusted from 100°C / 3h→110°C / 1h→120°C / 1h→130°C / 1h→140°C / 1h→150°C / 1h→160°C / 1h→170°C / 1h→

[0051] The emulsion was dehydrated and pre-carbonized by pyrolysis at 180°C / 1h→200°C / 1h→220°C / 1h. After cooling to room temperature, the emulsion was degreased by a centrifugal dryer, washed with gasoline and centrifuged twice, washed with anhydrous ethanol and filtered once, and finally placed in an oven at 100°C / 2h to obtain 46.2 g of brown-black glucose carbon microsphere precursor. The SEM morphology is shown in FIG. Figure 1 As shown; 30g of glucose carbon microsphere precursor was weighed and put into a graphite crucible, and carbonized at 800℃ for 2h under argon protection to obtain 14.8g of carbon microspheres. It can be calculated that the carbon yield reaches more than 93% of the theoretical carbon content of glucose, and its SEM morphology is as follows Figure 2 As shown, the size distribution of the obtained carbon spheres is uniform, and the average particle size is about 1 μm.

[0052] Example 2

[0053] Weigh 10g analytical pure sucrose, 2g acrylamide, 0.1g N,N'-methylenebisacrylamide, 0.25g ammonium persulfate, add to 8g deionized water, stir magnetically to dissolve and let stand to clarify as the water phase; weigh 40g soybean oil in a 100ml beaker, add 2g Span 60 surfactant, heat to 60℃ and stir to dissolve as the oil phase; add the water phase solution to the oil phase, stir at 100r / s for 8 minutes with a shear emulsifier to obtain a milky yellow oil-in-water emulsion; put the beaker into an oil bath and heat with a magnetic stirrer. The mixture was heated to 80°C and stirred for 4 h to solidify the aqueous phase emulsion gel; then the mixture was heated to 100°C and the emulsion was dehydrated and pyrolyzed for pre-carbonization at a procedure of 100°C / 2h→120°C / 2h→140°C / 2h→160°C / 2h→180°C / 2h→200°C / 2h; after cooling to room temperature, the mixture was filtered with filter paper to remove oil, and then washed and filtered twice with gasoline, and once with anhydrous ethanol, and finally placed in an oven at 100°C / 2h to obtain 8.52 g of brown sucrose carbon microsphere precursor. Its SEM morphology is shown in the figure. Figure 3 As shown; 3.5g of sucrose carbon microsphere precursor was weighed and placed in an alumina ceramic crucible, and carbonized at 1200℃ for 1h under nitrogen protection to obtain 1.58g of carbon microspheres. It can be calculated that the carbon yield reaches more than 91% of the theoretical carbon content of glucose, and its SEM morphology is as shown Figure 4 As shown, the size distribution of the obtained carbon spheres is relatively uniform, with particle sizes ranging from 0.2 μm to 2 μm, and an average particle size of about 0.5 μm.

[0054] Example 3

[0055] Weigh 10g analytically pure sucrose, 10g analytically pure glucose monohydrate, 4g acrylamide, 0.1g N,N'-methylenebisacrylamide, and 0.5g ammonium persulfate, add them into 15g deionized water, dissolve them by magnetic stirring, and let them stand to clarify as the water phase; weigh 160g silicone oil into a 250ml beaker, add 4g Span 60 surfactant, heat to 60℃ and stir as the oil phase; add the aqueous phase solution into the oil phase, stir with a shear emulsifier at a speed of 150r / s for 10 minutes to obtain a white oil-in-water emulsion; put the beaker into an oil bath heating magnetic stirrer, heat to 70℃ and stir for 4h to solidify the aqueous phase emulsion gel; then heat to 100℃ and stir at 100 ℃ / 3h→120℃ / 1h→140℃ / 1h→160℃ / 1h→180℃ / 1h→200℃ / 1h→220℃ / 1h program to complete the dehydration and pyrolysis pre-carbonization treatment of the emulsion droplets; after cooling to room temperature, use a centrifugal dryer to remove oil, then wash with gasoline and centrifuge and dry twice, wash with anhydrous ethanol and filter once, and finally place in an oven at 100℃ / 2h to obtain 15.52g of brown sugar carbon microsphere precursor; weigh 6g of sugar carbon microsphere precursor and put it into an alumina ceramic crucible, carbonize it at 1000℃ for 2h under nitrogen protection conditions to obtain 2.79g of carbon microspheres. Calculation shows that the carbon yield reaches more than 88% of the theoretical carbon content of glucose.

[0056] In summary, the preparation method of high-purity carbon microspheres based on the reverse emulsion gel-carbonization process uses high-purity water-soluble sugar substances as the carbon source, solidifies the aqueous phase emulsion droplets and completes the dehydration and pre-carbonization of the gel droplets in the oil phase, and then high-temperature carbonization can make the carbon yield in the sugar substance close to its theoretical carbon content. At the same time, the reverse emulsion gel method is simple and can mass-produce carbon microspheres of different sizes with good sphericity and high carbon yield.

[0057] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing high-purity carbon microspheres based on an inverse emulsion gel-carbonization process, characterized in that: include: (1) preparing an aqueous phase, namely, adding a water-soluble sugar substance, a gelling agent and an initiator to deionized water respectively, stirring and heating to dissolve until the mixture is clear, thereby obtaining an aqueous phase; (2) preparing the oil phase, i.e. adding a surfactant to the oil, stirring and heating to dissolve until it becomes clear, thereby obtaining the oil phase; (3) preparing a water-in-oil emulsion, i.e., adding a water phase to an oil phase and performing an emulsification treatment to obtain a water-in-oil emulsion; (4) preparing a sugar-carbon microsphere precursor, that is, stirring and heating the water phase in the water-in-oil emulsion to solidify the droplet gel, then gradually heating the water phase to complete the low-temperature pyrolysis pre-carbonization treatment, cooling, degreasing, washing, and drying to obtain the sugar-carbon microsphere precursor; (5) Preparing carbon microspheres, namely subjecting the sugar-carbon microsphere precursor to high-temperature carbonization treatment to obtain carbon microspheres.

2. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The water-soluble sugar substances include any one or more combinations of water-soluble sucrose, glucose, fructose and maltose; and The amount of the water-soluble sugar substance added is 50%-200% of the weight of the deionized water.

3. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The gelling agent is a cross-linking agent of acrylamide monomer and N,N'-methylenebisacrylamide, and the weight ratio of the two is 20-50:1; and The added amount of the gelling agent is 15%-30% of the weight of the deionized water.

4. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The initiator includes any one of a persulfate and a water-soluble azo initiator; and The added amount of the initiator is 0.2%-0.6% of the weight of the deionized water.

5. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The oil includes any one of vegetable oil and mineral oil.

6. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The hydrophile-lipophile balance value of the surfactant is 4-7; and The surfactant is added in an amount of 2% to 6% by weight of the oil.

7. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The emulsification treatment specifically includes adding the water phase to the oil phase and then stirring at high speed with a shear emulsifier to obtain a water-in-oil emulsion; wherein The weight ratio of the water phase to the oil phase is 10-30:100, the stirring rate is 100-300 r / s, and the shear emulsification time is 5-20 min.

8. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The step (4) of preparing the sugar-carbon microsphere precursor specifically includes placing the container containing the water-in-oil emulsion in an oil bath heating magnetic stirrer, heating to 60-80°C while stirring and maintaining for 3-5 hours to allow the water phase to undergo emulsion droplet gelation solidification, then heating to 200-220°C at a rate of 10-30°C / h and maintaining for 0.5-1h to complete partial dehydration of the gel droplets and low-temperature pyrolysis pre-carbonization treatment, cooling and deoiling by centrifugation or filtration, and then washing and drying with gasoline and anhydrous ethanol, respectively, to obtain the sugar-carbon microsphere precursor.

9. The method for preparing high-purity carbon microspheres based on the inverse emulsion gel-carbonization process according to claim 1, characterized in that: The step (5) of preparing carbon microspheres specifically comprises placing the sugar-carbon microsphere precursor in a ceramic or graphite crucible and keeping the temperature at 800-1200° C. for 1-2 hours under the protection of an inert gas.

10. A high-purity carbon microsphere, characterized in that: The high-purity carbon microspheres are obtained by the preparation method according to any one of claims 1 to 9, and the carbon yield of the high-purity carbon microspheres is not less than 88%.

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