A method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro chemical technology

Abstract

The present invention discloses a method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology. After the coal-based solid waste is crushed and screened, it is loaded and filled in a first micro-reactor, and an acid leaching solution is introduced for acid leaching. After the reaction is completed, it is washed to obtain the acid leaching residue of the coal-based solid waste. An alkali solution is introduced into the first micro-reactor for alkali washing, and a silicon-removed leaching solution is obtained at the outlet of the first micro-reactor. The silicon-removed leaching solution and a template agent are mixed through a second micro-reactor and then reacted with an acid solution / acid gas in a third micro-reactor, followed by solid-liquid separation, drying, and calcination to obtain the silicon-based micro-nano materials; or the silicon-removed leaching solution and the acid solution / acid gas are introduced into the second micro-reactor for reaction, followed by solid-liquid separation and drying to obtain the silicon-based micro-nano materials. The present invention makes full use of the abundant silica in the coal-based solid waste, uses it as a silicon source to prepare high-value-added silicon-based micro-nano materials, greatly reduces the synthesis cost of the silicon-based micro-nano materials, and improves the economic utilization value of the coal-based solid waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste solid recycling and utilization, and particularly relates to a method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology. Background Art

[0002] As one of the main energy sources in the world, coal occupies an extremely important position, and China is the largest coal producer and consumer in the world. As an important strategic resource, coal is mainly used in fields such as power generation, coking, and coal chemical industry, and a large amount of coal-based solid waste such as fly ash, coal gangue, and coal gasification slag is generated during the process. The long-term stacking of coal-based solid waste not only occupies a large amount of land, but also causes serious pollution to the ecological environment such as the atmosphere, water body, and soil. Therefore, comprehensively promoting the resource utilization of coal-based solid waste is an important way to realize the sustainable development of the coal-electricity-chemical industry. At present, the utilization of coal-based solid waste is more used for medium- and low-value utilization ways such as building materials and structural backfilling. In order to improve the added value of products and broaden the utilization ways of coal-based solid waste, it is necessary to further develop relevant high-value utilization technologies. Fly ash, coal gangue, coal gasification slag, etc. are typical aluminosilicate solid wastes and contain abundant silicon dioxide (SiO₂), so they can be used as silicon sources to prepare silicon-based micro-nano materials with high added value.

[0003] CN101993084A discloses a method for preparing silicon dioxide and alumina from fly ash. The method uses fly ash, sodium carbonate, and calcium oxide as raw materials, and alkali dissolves in a high-temperature reaction system to obtain sodium silicate solution, calcium carbonate, and desiliconized fly ash solid. Among them, silicon dioxide is obtained by carbonation of sodium silicate with carbon dioxide, and calcium carbonate and desiliconized fly ash solid are further used to prepare alumina.

[0004] CN114988426A discloses an alkali melting-hydrothermal preparation method of coal gangue-based molecular sieve: coal gangue powder and sodium hydroxide are mixed and ground and then calcined to obtain alkali-melted coal gangue; the alkali-melted coal gangue, sodium aluminate, and water are mixed and stirred evenly, and then a molecular sieve crude product is obtained through hydrothermal reaction. After the molecular sieve crude product is filtered, washed, and dried in sequence, a coal gangue-based molecular sieve is obtained.

[0005] CN112266000A discloses a method for preparing molecular sieve from coal gasification slag: the coal gasification slag is pretreated and then hydrothermally reacted with sodium hydroxide, and then the obtained filtrate is mixed with the template agent tetrapropylammonium hydroxide for crystallization reaction, and the crystallization product is subjected to solid-liquid separation, drying, and calcination to obtain a molecular sieve product.

[0006] Among the many developed methods for synthesizing high-value-added silicon-based materials from coal-based solid wastes, traditional equipment has a serious scale-up effect, resulting in difficulties in large-scale application and poor reproducibility between batches. For silicon-based micro-nano materials, the size distribution, yield, and size reproducibility between batches of particle synthesis are very important parameters in particle synthesis evaluation. The traditional macro reaction system process needs to go through the step-by-step scale-up from laboratory research and development, small-scale trials, pilot-scale trials to industrialization, which requires a long time of research and development and a large amount of human and material resources. Moreover, traditional equipment is difficult to provide uniform fluid mixing and transfer conditions, and it is also difficult to effectively control the flow rate, temperature, and reactant concentration distribution in the reaction system. At the same time, there is a serious equipment scale-up effect, which will seriously affect the controllability and accuracy of materials in the large-scale preparation process. The prepared micro-nano powder has problems such as agglomeration and difficult morphology control, and the reproducibility of particles obtained between batches is poor. From a chemical engineering perspective, to achieve the controllable preparation of high-value-added materials from coal-based solid wastes, it is necessary to develop efficient, controllable, and easily scalable preparation methods to ensure a uniform and controllable reaction environment during the material preparation process.

[0007] The microchemical technology developed since the 1990s has provided a new way to solve the mass transfer and mixing of this kind of fast reaction, and its application in the field of material preparation also shows obvious advantages. Compared with the traditional macro reaction system, the microreactor has a series of unique advantages, including small reaction volume, low cost, simple operation, low energy consumption, precise regulation of reaction material ratio / temperature / time, high specific surface area, short residence time, automatic mixing reaction, rapid screening of experimental conditions, few by-products, high safety, easy scalability, and high heat / mass transfer rate. The microchemical technology has realized the intensification, miniaturization, and greening of chemical processes, and is considered to be one of the new important directions in the development of chemical engineering disciplines. These unique advantages also make the microchemical technology have great application potential in constructing a system for preparing silicon-based micro-nano materials from coal-based solid wastes. Summary of the Invention

[0008] To overcome the problems in the prior art, the purpose of the present invention is to provide a method for preparing silicon-based micro-nano materials from coal-based solid wastes based on microchemical technology. Using coal-based solid wastes such as fly ash, coal gangue, and coal gasification slag as raw materials, based on a microreactor, high-throughput, controllable, and rapid synthesis of silicon-based micro-nano materials is realized. While solving solid waste, high-value-added materials are prepared, and the resource utilization efficiency of coal-based solid wastes is improved.

[0009] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0010] A method for preparing silicon-based micro-nano materials from coal-based solid wastes based on microchemical technology, comprising the following steps:

[0011] Crush and screen the coal-based solid waste, then load and fill it in the first microreactor, and introduce an acid leaching solution for acid leaching. After the reaction is completed, wash it to obtain the acid leaching residue of the coal-based solid waste.

[0012] Introduce an alkali solution into the first microreactor for alkali washing, and obtain a desiliconized leaching solution at the outlet of the first microreactor.

[0013] Mix the desiliconized leaching solution and the template agent through the second microreactor, then introduce them together with an acid solution / acid gas into the third microreactor for reaction. Carry out solid-liquid separation, drying and calcination on the reaction product to obtain the silicon-based micro-nano material; or introduce the desiliconized leaching solution and the acid solution / acid gas into the second microreactor for reaction, carry out solid-liquid separation and drying on the reaction product to obtain the silicon-based micro-nano material.

[0014] Furthermore, the coal-based solid waste is fly ash, coal gangue or coal gasification slag.

[0015] Furthermore, the acid leaching solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid; the concentration of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid is 0.1 - 12 mol / L, the concentration of acetic acid is 0.1 - 6 mol / L, the temperature of acid leaching is 20 - 100 °C, and the time of acid leaching is 0.1 - 48 h.

[0016] Furthermore, the alkali solution is one or two of sodium hydroxide solution and potassium hydroxide solution; the mass fraction of the alkali solution is 1% - 50%, the temperature of alkali washing is 20 - 100 °C, and the time of alkali washing is 0.1 - 48 h.

[0017] Furthermore, the acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid with a concentration of 0.01 - 1 mol / L; the acid gas is one or more of CO2, HCl, SO2, SO3, NO2, Cl2, Br2 and H2S.

[0018] Furthermore, the template agent is one or more of tetrapropylammonium hydroxide, cetyltrimethylammonium bromide, cetyltriethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinylpyrrolidone, tetrapropylammonium bromide, n-propylamine and n-butylamine.

[0019] Furthermore, when mixing the desiliconized leaching solution and the template agent through the first microreactor and then introducing them together with the acid solution / acid gas into the second microreactor for reaction, the molar ratio of SiO2 to the template agent in the desiliconized leaching solution is 1:0.01 - 10.

[0020] Furthermore, when mixing the desiliconized leaching solution and the template agent through the second microreactor and then introducing them together with the acid solution / acid gas into the third microreactor for reaction, the reaction time is 30 s - 100 min, and the reaction temperature is 20 - 120 °C.

[0021] The desilication leaching solution and the acid solution / gas are introduced into the second microreactor, and the reaction time is 30 s to 100 min, and the reaction temperature is 20 to 120 °C.

[0022] Furthermore, the microreactor includes a microchannel, and the microchannel is spiral, serpentine, annular, serrated, rectangular or irregular, and the cross-section of the microchannel is circular, rectangular, trapezoidal, rhombic or irregular.

[0023] Furthermore, the size range of the microchannel is 100 μm to 10 mm, and the material of the microchannel is polymer, silicon wafer, metal, glass or ceramic.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention uses a microreactor, which can realize rapid mixing of reagents, temperature control and precise spatio-temporal manipulation during the reaction. By adjusting the flow rate of the materials, flexible control of the dosage of the reaction materials and the reaction time can be achieved. Through the microchannel structure design combined with fluid flow regulation, a uniform concentration distribution is maintained to ensure the uniformity and consistency of the growth conditions. The micro-nano particle synthesis is carried out by using microchemical technology, and the mixing is controlled and uniform. The method for preparing silicon-based micro-nano materials from coal-based solid waste provided by the present invention is relatively easy to scale up due to the characteristics of the microreactor. According to the integrated idea, the equipment size can be appropriately enlarged based on the parallel increase in the number of microchannels and the similar behavior of fluid mechanics, and finally the amplification effect is minimized to ensure the large-scale controllable preparation of materials. It provides a preparation method with simple process, strong operation controllability, stable production performance and easy amplification for preparing silicon-based micro-nano materials from coal-based solid waste, and is suitable for industrial production.

[0026] Furthermore, the method for preparing silicon-based micro-nano materials from coal-based solid waste of the present invention makes full use of the rich silica in coal-based solid waste such as fly ash, coal gangue and coal gasification slag as the silicon source, reduces the synthesis cost of high-value-added silicon-based micro-nano materials, improves the economic utilization value of coal-based solid waste, and effectively promotes the resource utilization of coal-based solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a synthesis flow chart of the silicon-based micro-nano materials of the present invention.

[0028] Figure 2 It is a schematic diagram of the microchannel structure of the microreactor; among them, (a) is spiral, (b) is serpentine, (c) is annular, (d) is serrated, and (e) is rectangular;

[0029] Figure 3 It is an enlarged schematic diagram of the microreactor;

[0030] Figure 4TEM image of the silica micro-nano particle sample in Example 1.

[0031] Figure 5 TEM image of the mesoporous silica particle sample in Example 2

[0032] In the figure, 1 is the first liquid storage tank, 2 is the first heat exchanger, 3 is the first microfluidic pump, 4 is the first microreactor, 5 is the second microfluidic pump, 6 is the first valve, 7 is the second liquid storage tank, 8 is the second heat exchanger, 9 is the third microfluidic pump, 10 is the second microreactor, 11 is the third liquid storage tank, 12 is the third heat exchanger, 13 is the fourth microfluidic pump, 14 is the second valve, 15 is the third valve, 16 is the filter, 17 is the dryer, and 18 is the third microreactor. Detailed implementation manners

[0033] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0034] See Figure 1 , the device for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology adopted by the present invention includes a first liquid storage tank 1, a first heat exchanger 2, a first microfluidic pump 3, a first microreactor 4, a second microfluidic pump 5, a first valve 6, a second liquid storage tank 7, a second heat exchanger 8, a third microfluidic pump 9, a second microreactor 10, a third liquid storage tank 11, a third heat exchanger 12, a fourth microfluidic pump 13, a second valve 14, a third valve 15, a filter 16, a dryer 17 and a third reactor 18. Among them, the outlet of the first liquid storage tank 1 is connected to the inlet of the first microreactor 4 through the first heat exchanger 2 and the first microfluidic pump 3, the outlet of the first microreactor 4 is connected to the inlet of the second microreactor 10 through the second microfluidic pump 5, and the first outlet of the second microreactor 10 is connected to the second liquid storage tank 7 through the third microfluidic pump 9 and the second heat exchanger 8; the second outlet of the second microreactor 10 is divided into two paths, one path is connected to the dryer 17 through the third valve 15 and the filter 16, and the other path is connected to the inlet of the third reactor 18 through the second valve 14. The first outlet of the third reactor 18 is connected to the filter 16, and the second outlet of the third reactor 18 is connected to the third liquid storage tank 11 through the fourth microfluidic pump 13 and the third heat exchanger 12.

[0035] See Figure 1 , a method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology of the present invention includes the following steps:

[0036] (1) Pre-treating the coal-based solid waste: crushing the coal-based solid waste through a 200-300 mesh sieve, then loading the coal-based solid waste into the first microreactor channel, and allowing a certain concentration of acid to be controlled by a microfluidic pump to pass into the first microreactor after preheating. The reaction temperature is controlled by an external heat exchanger. The coal-based solid waste is fully contacted with the acid to react, and the first microfluidic pump 3, the second microfluidic pump 5 and the first valve 6 are jointly regulated to allow part of the acid to be recycled, thereby achieving full utilization. After the reaction is completed, the acid is replaced with water, which is passed into the microreactor by the microfluidic pump for washing to obtain coal-based solid waste acid leaching residue. At the same time, the obtained acid washing waste liquid can be used for the recovery and utilization of aluminum resources in coal gasification ash residue;

[0037] The coal-based solid waste includes fly ash, coal gangue and coal gasification slag.

[0038] The acid solution is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid. Preferably, the concentration of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid is 0.1-12 mol / L, the concentration of acetic acid is 0.1-6 mol / L, the reaction temperature is 20-100°C, and the reaction time is 0.1-48h.

[0039] The washing process includes washing the coal-based solid waste acid leaching residue with water until the pH value of the outlet solution is 6.0 to 8.0.

[0040] (2) After the treatment in step (1), the coal-based solid waste acid leaching residue is obtained, and a certain concentration of alkali solution is controlled by the first microflow pump to be introduced into the first microreactor 4 after preheating. The reaction temperature is controlled by an external heat exchanger to make the coal-based solid waste acid leaching residue and the alkali solution fully contact and react. The obtained alkali leaching solution is the desiliconization leaching solution, and the first microflow pump 3, the second microflow pump 5 and the first valve 6 are jointly regulated to make part of the alkali solution recycled, thereby achieving full utilization of the alkali solution;

[0041] The alkali solution is one or a combination of sodium hydroxide solution and potassium hydroxide solution. Preferably, the mass fraction of the alkali solution is 1% to 50%, the reaction temperature is 20 to 100° C., and the reaction time is 0.1 to 48 hours.

[0042] (3) the desiliconized leachate obtained in step (2) is mixed with other reagents required for synthesis (the reagents include acid solution / gas and template agent), and the flow rate of each stream of materials is controlled by a microflow pump, so that the preheated reagents enter the microreactor synchronously at a set flow rate to react, and the reaction temperature is controlled by an external heat exchanger, and a reaction product is obtained from the outlet of the microreactor;

[0043] When the desiliconized leachate is mixed only with the acid solution / acid gas, the desiliconized leachate and the acid solution / gas are simultaneously introduced into the second microreactor for reaction, and a reaction product 1 is obtained from the outlet.

[0044] The acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid with a concentration of 0.01 - 1 mol / L; the acid gas is one or more of CO2, HCl, SO2, SO3, NO2, Cl2, Br2 and H2S.

[0045] When the desiliconized leaching solution is successively mixed with the template agent and the acid solution / gas, the desiliconized leaching solution and the template agent are first introduced into the second microreactor for full and complete mixing, and then the obtained mixed material and the acid solution / acid gas are synchronously introduced into the third microreactor 18 for reaction, and the reaction product 2 is obtained at the outlet.

[0046] The template agent is one or more combinations of tetrapropylammonium hydroxide (TPAOH), cetyltrimethylammonium bromide (CTAB), cetyltriethylammonium bromide (CTEAB), sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), tetrapropylammonium bromide (TPABr), n-propylamine and n-butylamine.

[0047] The molar ratio of SiO2 to the template agent in the desiliconized leaching solution is 1:0.01 - 10.

[0048] The reaction time in the microreactor is 30 s - 100 min, and the reaction temperature is 20 - 120 °C. The set flow rate of the microfluidic pump is 0.5 - 500 mL / min.

[0049] See Figure 2 In (a), (b), (c), (d) and (e), the microreactor includes a microchannel, and the microchannel includes but is not limited to spiral, serpentine, annular, zigzag, rectangular, irregular shapes, etc. The cross-section of the channel includes but is not limited to circular, rectangular, trapezoidal, rhombic, irregular shapes, etc. The size range of the microchannel is 100 μm - 10 mm. The material of the microreactor is selected from polymers (such as polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), ABS, polydimethylsiloxane (PDMS), etc.), silicon wafers, metals (such as stainless steel, titanium alloy, zirconium alloy, Hastelloy carbon steel, etc.), glass or ceramics.

[0050] See Figure 3 In the present invention, the microreactor realizes enhanced mixing through spiral, serpentine, annular, zigzag, rectangular channels, etc., flexibly controls the residence time of the reactants by controlling the channel length and the feed flow rate, and multiple microreactors can be stacked. Based on the idea of number magnification combined with fluid behavior similarity magnification, the microreaction equipment can be scaled up and thus move towards industrial applications.

[0051] (4) The reaction product 1 obtained in step (3) is subjected to solid-liquid separation and drying to obtain a silica micro-nano material. The reaction product 2 is subjected to solid-liquid separation and drying, and further calcined at high temperature to remove the template agent to obtain a mesoporous silica material.

[0052] The calcination temperature is 400-900°C, the calcination time is 3-10h, and the heating rate is 0.5-3°C / min.

[0053] The application of silicon-based micro-nano materials prepared according to the method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology in the present invention, specifically, the prepared nano silica particles, micron silica particles and mesoporous silica particles can be used for nanofluid preparation, metal ion adsorption, drug loading and other applications.

[0054] Example 1

[0055] Take 10g of coal gangue and crush it through a 200-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10mm. After heating 6mol / L hydrochloric acid solution to 80°C through a heat exchanger, pass it into the first microreactor 4. The flow rate is controlled to be 1mL / min by the first microflow pump 3 to realize the continuous flow pickling reaction of coal gangue in the microchannel. After reacting for 10 minutes, replace the solution at the inlet with water, and then pass it into the first microreactor 4 at a flow rate of 1mL / min until the pH value of the solution at the outlet is 7. Then replace the solution at the inlet with a sodium hydroxide solution with a mass fraction of 30%, preheat it to 80°C through the first heat exchanger 2, and pass it into the first microreactor 4 at a flow rate of 1mL / min. After reacting for 10 minutes, the desiliconized leachate of coal gangue can be obtained at the outlet of the first microreactor 4.

[0056] The microchannel size of the second microreactor 10 is selected to be 800 μm, the second microfluidic pump 5 is adjusted to allow the desiliconized leachate to flow into the second microreactor 10 at a flow rate of 1 mL / min, and the third microfluidic pump 9 is adjusted to allow the 0.1 mol / L hydrochloric acid solution to flow into the second microreactor 10 at a flow rate of 1 mL / min, the desiliconized leachate and the hydrochloric acid solution flow into the second microreactor 10 at the same time, and after being fully mixed and reacted at room temperature for 1 min, a suspension is obtained. The obtained suspension is filtered to obtain a silicic acid precipitate, and after drying in a thermostat at 80°C, a silicon dioxide powder is obtained.

[0057] Example 2

[0058] Take 10 g of coal gasification ash residue, crush it and sieve it through a 200-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. After heating the 4 mol / L nitric acid solution to 70 °C through a heat exchanger, introduce it into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 1.5 mL / min, and the continuous-flow pickling reaction of the coal gasification ash residue is realized in the microchannel. After reacting for 15 min, replace the solution at the inlet with water and introduce it into the first microreactor 4 at a flow rate of 1.5 mL / min until the pH value of the solution at the outlet is 7. Then replace the solution at the inlet with a potassium hydroxide solution with a mass fraction of 30%, preheat it to 70 °C through the first heat exchanger 2 and introduce it into the first microreactor 4 at a flow rate of 1.5 mL / min. After reacting for 15 min, the silicon-removed leaching solution of the coal gasification ash residue can be obtained at the outlet of the first microreactor 4.

[0059] Select the microchannel sizes of the second microreactor 10 and the third microreactor 18 to be 500 μm. Adjust the second microfluidic pump 5 and the third microfluidic pump 9 so that the silicon-removed leaching solution and the template agent CTAB solution are introduced into the second microreactor 10 at a flow rate of 1.5 mL / min at the same time. The molar ratio of SiO2 to the template agent in the silicon-removed leaching solution is 1:0.01. After being fully and evenly mixed in the second microreactor 10, the mixed material is obtained at the outlet of the second microreactor 10. Adjust the fourth microfluidic pump 13 so that the nitric acid solution enters the third microreactor 18 at a flow rate of 3 mL / min synchronously with the mixed material. After being fully mixed and reacting at room temperature for 2 min, a suspension is obtained. Filter the suspension to collect the solid matter, dry it in an incubator at 80 °C and then calcine it at 600 °C to obtain the mesoporous silica powder.

[0060] Example 3

[0061] Take 10 g of coal gasification ash residue, crush it and sieve it through a 250-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. After heating the 7 mol / L acetic acid solution to 90 °C through a heat exchanger, introduce it into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 2 mL / min, and the continuous-flow pickling reaction of the coal gasification ash residue is realized in the microchannel of the first microreactor 4. After reacting for 20 min, replace the solution at the inlet with water until the pH value of the solution at the outlet is 7. Then replace the solution at the inlet with a sodium hydroxide solution with a mass fraction of 20%, preheat it to 90 °C through the first heat exchanger 2 and introduce it into the first microreactor 4 at a flow rate of 2 mL / min. After reacting for 20 min, the silicon-removed leaching solution of the coal gasification ash residue can be obtained at the outlet of the first microreactor 4.

[0062] The microchannel size of the second microreactor 10 was selected to be 600 μm. The second microfluidic pump 5 was adjusted so that the desilication leaching solution was introduced into the second microreactor 10 at a flow rate of 2 mL / min. CO2 gas was simultaneously introduced into the second microreactor 10 by adjusting the pressure controller. After sufficient mixing and reaction at room temperature for 2 min, a suspension was obtained. The obtained suspension was filtered by suction to obtain a silicic acid precipitate, which was dried in an incubator at 90 °C to obtain silica powder.

[0063] Example 4

[0064] 10 g of fly ash was taken and pulverized through a 200-mesh sieve. The microchannel size of the first microreactor 4 was selected to be 5 mm. The 3 mol / L phosphoric acid solution was heated to 90 °C by a heat exchanger and then introduced into the first microreactor 4. The flow rate was controlled by the first microfluidic pump 3 to be 2.5 mL / min, and continuous-flow pickling reaction of fly ash was realized in the microchannel. After reacting for 40 min, the solution at the inlet was replaced with water, which was introduced into the first microreactor 4 at a flow rate of 2.5 mL / min until the pH value of the solution at the outlet was 7. Then the solution at the inlet was replaced with a 20% potassium hydroxide solution by mass fraction, which was preheated to 90 °C by the first heat exchanger 2 and then introduced into the first microreactor 4 at a flow rate of 2.5 mL / min. After reacting for 40 min, the desilication leaching solution of fly ash could be obtained at the outlet of the first microreactor 4.

[0065] The microchannel sizes of the second microreactor 10 and the third microreactor 18 were selected to be 1 mm. The second microfluidic pump 5 and the third microfluidic pump 9 were adjusted so that the desilication leaching solution and the template agent TPAOH solution were simultaneously introduced into the second microreactor 10 at a flow rate of 2.5 mL / min. The molar ratio of SiO2 to the template agent in the desilication leaching solution was 1:10. After sufficient and uniform mixing in the second microreactor 10, a mixed material was obtained. Bromine gas was simultaneously introduced into the third microreactor 18 with the mixed material by adjusting the pressure controller. After sufficient mixing and reaction at room temperature for 2 min, a suspension was obtained. The suspension was filtered by suction to collect the solid matter, which was dried in an incubator at 80 °C and then calcined at 700 °C for 5 h to obtain mesoporous silica powder.

[0066] Example 5

[0067] Take 10 g of fly ash, crush it and sieve it through a 300-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. After heating the 6 mol / L acetic acid solution to 20 °C through a heat exchanger, introduce it into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 1 mL / min, and the continuous-flow pickling reaction of coal gangue is realized in the microchannel. After reacting for 120 min, replace the solution at the inlet with water, and then introduce it into the first microreactor 4 at a flow rate of 1 mL / min until the pH value of the solution at the outlet is 6. Then replace the solution at the inlet with a 1% sodium hydroxide solution, preheat it to 100 °C through the first heat exchanger 2, and introduce it into the first microreactor 4 at a flow rate of 1 mL / min. After reacting for 120 min, the desilication leaching solution of coal gangue can be obtained at the outlet of the first microreactor 4.

[0068] Select the microchannel size of the second microreactor 10 to be 8 mm. Adjust the second microfluidic pump 5 to make the desilication leaching solution flow into the second microreactor 10 at a flow rate of 1 mL / min. By adjusting the third microfluidic pump 9, make the 0.01 mol / L sulfuric acid solution flow into the second microreactor 10 at a flow rate of 0.5 mL / min. The desilication leaching solution and the hydrochloric acid solution flow into the second microreactor 10 simultaneously. After sufficient mixing and reacting at 20 °C for 100 min, a suspension is obtained. Filter the obtained suspension to obtain the silica precipitate. After drying in an oven at 80 °C, silica powder can be obtained.

[0069] Example 6

[0070] Take 10 g of coal gasification slag, crush it and sieve it through a 230-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. After heating the 12 mol / L nitric acid solution to 100 °C through a heat exchanger, introduce it into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 1 mL / min, and the continuous-flow pickling reaction of coal gangue is realized in the microchannel. After reacting for 1 min, replace the solution at the inlet with water, and then introduce it into the first microreactor 4 at a flow rate of 1 mL / min until the pH value of the solution at the outlet is 8. Then replace the solution at the inlet with a 10% sodium hydroxide solution, preheat it to 20 °C through the first heat exchanger 2, and introduce it into the first microreactor 4 at a flow rate of 1 mL / min. After reacting for 120 min, the desilication leaching solution of coal gangue can be obtained at the outlet of the first microreactor 4.

[0071] Select the microchannel size of the second microreactor 10 to be 800 μm. Adjust the second microfluidic pump 5 to make the desilication leaching solution flow into the second microreactor 10 at a flow rate of 1 mL / min. By adjusting the pressure controller, introduce sulfur dioxide gas into the second microreactor 10 synchronously with the mixed materials. After sufficient mixing and reacting at 120 °C for 30 s, a suspension is obtained. Filter the obtained suspension to obtain the silica precipitate. After drying in an oven at 80 °C, silica powder can be obtained.

[0072] Example 7

[0073] Take 10 g of coal gangue, crush it and sieve it through a 270-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. A mixed solution of 10 mol / L phosphoric acid solution and 12 mol / L nitric acid solution with a volume ratio of 1:1 is heated to 40 °C through a heat exchanger and then introduced into the first microreactor 4 at a flow rate of 20 mL / min. The flow rate is controlled by the first microfluidic pump 3 to be 1 mL / min, and the continuous-flow pickling reaction of coal gangue is realized in the microchannel. After reacting for 80 min, the solution at the inlet is replaced with water, and then introduced into the first microreactor 4 at a flow rate of 1 mL / min until the pH value of the solution at the outlet is 6. Then the solution at the inlet is replaced with a 50% sodium hydroxide solution by mass, preheated to 40 °C through the first heat exchanger 2, and then introduced into the first microreactor 4 at a flow rate of 1 mL / min. After reacting for 0.1 h, the desilication leaching solution of coal gangue can be obtained at the outlet of the first microreactor 4.

[0074] Select the microchannel size of the second microreactor 10 to be 800 μm. Adjust the second microfluidic pump 5 to make the desilication leaching solution flow into the second microreactor 10 at a flow rate of 500 mL / min. By adjusting the third microfluidic pump 9, a mixed solution of 0.05 mol / L phosphoric acid solution and 0.01 mol / L nitric acid solution with a volume ratio of 1:1 is introduced into the second microreactor 10 at a flow rate of 20 mL / min. After sufficient mixing and reacting at 50 °C for 70 min, a suspension is obtained. The obtained suspension is filtered by suction to obtain silica precipitate. After drying in an oven at 80 °C, silicon dioxide powder can be obtained.

[0075] Example 8

[0076] Take 10 g of coal gasification ash residue, crush it and sieve it through a 200-mesh sieve. Select the microchannel size of the first microreactor 4 to be 10 mm. 4 mol / L nitric acid solution is heated to 70 °C through a heat exchanger and then introduced into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 1.5 mL / min, and the continuous-flow pickling reaction of coal gasification ash residue is realized in the microchannel. After reacting for 15 min, the solution at the inlet is replaced with water and introduced into the first microreactor 4 at a flow rate of 1.5 mL / min until the pH value of the solution at the outlet is 7. Then the solution at the inlet is replaced with a 30% sodium hydroxide solution by mass, preheated to 70 °C through the first heat exchanger 2, and then introduced into the first microreactor 4 at a flow rate of 1.5 mL / min. After reacting for 48 h, the desilication leaching solution of coal gasification ash residue can be obtained at the outlet of the first microreactor 4.

[0077] The microchannel sizes of the second microreactor 10 and the third microreactor 18 are selected to be 500 μm. Adjust the second microfluidic pump 5 and the third microfluidic pump 9 so that the desilication leaching solution and the templating agent (a mixed solution of CTEAB solution and SDBS solution, where the mass ratio of CTEAB to SDBS is 1:1) are simultaneously introduced into the second microreactor 10 at a flow rate of 1.5 mL / min. The molar ratio of SiO₂ to the templating agent in the desilication leaching solution is 1:5. After sufficient and uniform mixing in the second microreactor 10, a mixed material is obtained at the outlet of the second microreactor 10. Nitrogen dioxide gas is introduced into the third microreactor 18 synchronously with the mixed material by adjusting the pressure controller. After sufficient mixing and reacting at 100 °C for 10 min, a suspension is obtained. The suspension is filtered by suction to collect the solid, dried in an incubator at 80 °C, and then calcined at 400 °C for 10 h to obtain mesoporous silica powder.

[0078] Example 9

[0079] Take 10 g of coal gasification ash residue, crush it and pass it through a 200-mesh sieve. Select the microchannel size of the first microreactor 4 to be 3 mm. The 4 mol / L nitric acid solution is heated to 70 °C by a heat exchanger and then introduced into the first microreactor 4. The flow rate is controlled by the first microfluidic pump 3 to be 1.5 mL / min, and continuous-flow pickling reaction of the coal gasification ash residue is realized in the microchannel. After reacting for 15 min, the solution at the inlet is replaced with water and introduced into the first microreactor 4 at a flow rate of 1.5 mL / min until the pH value of the solution at the outlet is 7. Then the solution at the inlet is replaced with a 30% potassium hydroxide solution by mass, preheated to 70 °C by the first heat exchanger 2, and then introduced into the first microreactor 4 at a flow rate of 1.5 mL / min. After reacting for 15 min, the desilication leaching solution of the coal gasification ash residue can be obtained at the outlet of the first microreactor 4.

[0080] The microchannel sizes of the second microreactor 10 and the third microreactor 18 are selected to be 500 μm. Adjust the second microfluidic pump 5 and the third microfluidic pump 9 so that the desilication leaching solution and the templating agent (a mixed solution of SDS solution, PVP solution and TPABr solution, where the mass ratio of SDS, PVP to TPABr is 1:1:1) are simultaneously introduced into the second microreactor 10 at a flow rate of 1.5 mL / min. The molar ratio of SiO₂ to the templating agent in the desilication leaching solution is 1:3. After sufficient and uniform mixing in the second microreactor 10, a mixed material is obtained at the outlet of the second microreactor 10. Hydrogen sulfide gas is introduced into the third microreactor 18 synchronously with the mixed material by adjusting the pressure controller. After sufficient mixing and reacting at 20 °C for 120 min, a suspension is obtained. The suspension is filtered by suction to collect the solid, dried in an incubator at 80 °C, and then calcined at 900 °C for 3 h to obtain mesoporous silica powder.

[0081] In the present invention, the micro-chemical technology is applied to the synthesis of high-value-added silicon-based micro-nano materials from coal-based solid wastes. In a micro-reaction device, the fluid behavior can be precisely regulated, the reaction conditions can be accurately controlled, the efficient transfer and reaction can be promoted to realize process intensification, providing a good platform for the controllable preparation of high-performance micro-nano materials, and enabling the prepared silicon-based materials to have uniform morphology, narrow size distribution, and good dispersibility.

[0082] Since the micro-chemical technology basically has no scale-up effect, compared with traditional reactors that need to go through stages such as small-scale experiments and pilot-scale experiments for step-by-step empirical scale-up, microreactors can be scaled up based on the parallel increase in the number of microchannels and the similar behavior of fluid mechanics. This integrated concept can achieve the consistency of the reaction environment in a single channel during industrial large-scale production with the conditions of a single channel in the laboratory, without the scale-up problems of traditional reactors, greatly reducing the input of human, material, and time costs in the early R & D process, and shortening the time from the laboratory to the market for products.

[0083] Due to the small-scale characteristics of the micro-chemical technology, the equipment size is significantly reduced, and the occupied volume is significantly smaller than that of traditional chemical equipment. During the actual production process, it also has the advantages of rapid start-up and shutdown, flexible production, and distributed mobile production, etc.

[0084] The above is only an illustration of the best embodiments of the present invention, but it should not be construed as a limitation of the claims. The present invention is not limited to the above embodiments, and its specific structure allows for changes. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

Claims

1. A method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology, characterized in that, It includes the following steps: Crush and screen the coal-based solid waste, then load and fill it into the first microreactor, introduce an acid leaching solution for acid leaching, wash it after the reaction is completed to obtain the acid leached residue of the coal-based solid waste; Introduce an alkali solution into the first microreactor for alkali washing, and obtain a desilication leaching solution at the outlet of the first microreactor; Mix the desilication leaching solution with a template agent through a second microreactor, then introduce the mixture and an acid solution / acid gas into a third microreactor for reaction, perform solid-liquid separation, drying and calcination on the reaction product to obtain a silicon-based micro-nano material; or introduce the desilication leaching solution and an acid solution / acid gas into a second microreactor for reaction, perform solid-liquid separation and drying on the reaction product to obtain a silicon-based micro-nano material; The coal-based solid waste is fly ash, coal gangue or coal gasification slag; The microreactor includes a microchannel, the microchannel is spiral, serpentine, annular, serrated, rectangular or irregular, and the cross-section of the microchannel is circular, rectangular, trapezoidal, rhombic or irregular.

2. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, characterized in that, The acid leaching solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid; the concentration of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid is 0.1 - 12 mol / L, the concentration of acetic acid is 0.1 - 6 mol / L, the temperature of acid leaching is 20 - 100 °C, and the time of acid leaching is 0.1 - 48 h.

3. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, characterized in that The alkali solution is one or two of sodium hydroxide solution and potassium hydroxide solution; the mass fraction of the alkali solution is 1% - 50%, the temperature of alkali washing is 20 - 100 °C, and the time of alkali washing is 0.1 - 48 h.

4. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, characterized in that, The acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid with a concentration of 0.01 - 1 mol / L; the acid gas is one or more of CO2, HCl, SO2, SO3, NO2, Cl2, Br2 and H2S.

5. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, characterized in that, The template agent is one or more of tetrapropylammonium hydroxide, cetyltrimethylammonium bromide, cetyltriethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinylpyrrolidone, tetrapropylammonium bromide, n-propylamine and n-butylamine.

6. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro chemical technology according to claim 1, characterized in that, When mixing the desilication leaching solution with a template agent through a first microreactor and then introducing the mixture and an acid solution / acid gas into a second microreactor for reaction, the molar ratio of SiO2 to the template agent in the desilication leaching solution is 1:0.01 - 10.

7. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, wherein The reaction time for mixing the desilication leaching solution with a template agent through a second microreactor and then introducing the mixture and an acid solution / acid gas into a third microreactor for reaction is 30 s - 100 min, and the reaction temperature is 20 - 120 °C; The reaction time for introducing the desilication leaching solution and an acid solution / acid gas into a second microreactor for reaction is 30 s - 100 min, and the reaction temperature is 20 - 120 °C.

8. The method for preparing silicon-based micro-nano materials from coal-based solid waste based on micro-chemical technology according to claim 1, characterized in that The size range of the microchannel is 100 μm - 10 mm, and the material of the microchannel is polymer, silicon wafer, metal, glass or ceramic.

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