A method for synthesizing a catalyst for underground coal gasification

Abstract

The application discloses a synthesis method of a coal underground gasification catalyst, which comprises the following steps: placing a basic solution and a modified coupling agent in a first evaporation chamber, and heating to generate a first hot solution; spraying the first hot solution into a first reaction chamber, and reacting with alumina placed in the first reaction chamber to obtain a first product; separating the first product by using a cyclone separation device arranged at the tail end of the first reaction chamber to obtain a sample, and placing the sample in a second reaction chamber; placing a silicon oxide precursor, an alumina precursor, a nano calcium carbonate solution, a coupling agent and a curing agent in a second evaporation chamber, and heating to generate a second hot solution; spraying the second hot solution into the second reaction chamber, and reacting with the sample to obtain a second product; and separating the second product by using a cyclone separation device arranged at the tail end of the second reaction chamber to obtain the catalyst. According to the application, the catalyst with improved reaction activity can be synthesized in an environment-friendly way with low cost and easy construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal underground gasification development and yield increase, and particularly relates to a synthesis method and device of a coal underground gasification catalyst. BACKGROUND

[0002] Coal is one of the most abundant and widely distributed energy mineral resources in the world. China, as a coal power, is rich in coal resources, but the distribution is uneven. In China, the coal reserves suitable for open-pit mining are relatively small, accounting for only about 7% of the total reserves, and the deep and ultra-deep coal seam mining operation is extremely difficult, which poses a challenge to the utilization of China's coal resources. In 1888, Russian chemist Mendeleev proposed the development method of coal underground gasification. Underground coal gasification (UCG) is a process of controlled combustion of coal underground to produce combustible gas through thermal and chemical effects of coal. Since 1958, China has begun to conduct coal underground gasification test work under natural conditions. After more than 20 years of exploration, pilot tests have been conducted in more than ten mining areas such as Xuzhou, Shandong, Tangshan, Hebi, Feicheng, and Xinwen, laying a rich experience foundation for the development of coal underground gasification in China.

[0003] In the early development of UCG technology, air-water vapor was used as a gasification agent to produce synthesis gas. In 1976, the United States first injected oxygen-water vapor as a gasification agent to produce crude gas at Hoe Creek, and the heat value of synthesis gas can be as high as 9.78 MJ / m 3 , which is about 3 times the heat value of crude gas produced under air-water vapor conditions. Since then, the "oxygen-water vapor" or "oxygen-enriched (O2 volume fraction > 23.5%) -water vapor" gasification agent system has been used to date.

[0004] Different from the ground coal gasification catalyst, the coal underground gasification catalyst needs to meet the requirements of easy injection, safe transportation, environment-friendly, underground abandonment and the like. The specific requirements are as follows: 1. Easy injection. Under the condition of the original coal underground gasification engineering facility layout, no additional land area is increased. Under the field operation environment, the catalyst particles are injected with water, that is, mixed and matched; 2. Safe transportation. The coal underground gasification catalyst needs to be transported to the target gasification area through the vertical injection well and the horizontal well before reaching the target coal seam. The conventional coal gasification catalyst has certain metal corrosivity, which is easy to corrode the pipeline during the pipeline transportation, causing equipment loss. Therefore, the pH value of the catalyst in the injection process is required to be neutral to avoid corroding the pipeline; 3. Environment-friendly and underground abandonment. The catalyst particles are transported to the target coal seam in the underground with water, the produced raw coal gas is collected from the production well site, and the solid particles of the catalyst after reaction are retained in the stratum. Therefore, the coal underground catalyst system is required to not pollute and damage the stratum environment. The present application is based on the above problems. SUMMARY

[0005] The present application aims to provide a synthesis method and device of a coal underground gasification catalyst to solve the above technical problems. In order to achieve the above purpose, the present application provides the following technical solutions:

[0006] The present application provides a synthesis method of a coal underground gasification catalyst, comprising:

[0007] The alkaline solution and the modified coupling agent are placed in the first evaporation chamber and heated to generate a first hot solution;

[0008] The first hot solution is sprayed into the first reaction chamber and reacts with the alumina placed in the first reaction chamber to obtain a first product;

[0009] The first product is separated by the cyclone separation device arranged at the tail end of the first reaction chamber to obtain a sample, and the sample is placed in the second reaction chamber;

[0010] The silicon oxide precursor, the alumina precursor, the nano calcium carbonate solution, the coupling agent and the curing agent are placed in the second evaporation chamber and heated to generate a second hot solution;

[0011] The second hot solution is sprayed into the second reaction chamber and reacts with the sample to obtain a second product;

[0012] The second product is separated by the cyclone separation device arranged at the tail end of the second reaction chamber to obtain the catalyst.

[0013] Optionally, the alkaline solution is an alkali metal solution or an alkaline earth metal solution.

[0014] Optionally, the alkali metal solution comprises one or more of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium hydroxide solution, potassium carbonate solution, potassium bicarbonate solution, calcium hydroxide solution, calcium bicarbonate solution, and low-concentration calcium carbonate solution.

[0015] Optionally, the modified coupling agent is a mixture of a metal coupling agent, an organic solvent, a surfactant, and a pH regulator.

[0016] Optionally, the metal coupling agent comprises one or both of aluminum zirconium coupling agent and aluminate coupling agent, the organic solvent comprises one or more of ethanol, isopropyl alcohol, ethyl acetate, methanol, and acetone, the surfactant comprises one or more of polyoxyethylene fatty alcohol ether, fatty acid monoglyceride, glycerol monostearate, and polysorbate, and the pH regulator comprises one or more of sorbic acid, citric acid, hydrochloric acid, and acetic acid.

[0017] Optionally, the solution concentration of the alkali metal solution or the alkaline earth metal solution is 0.5-10 mol / L.

[0018] Optionally, the temperature of the first evaporation chamber is 100-150°C.

[0019] Optionally, the aluminum oxide comprises one of α-Al2O3, β-Al2O3, and γ-Al2O3.

[0020] Optionally, the temperature of the first reaction chamber is 100-300°C.

[0021] Optionally, the nozzle orifice plate pore size in the first evaporation chamber is 200-900 nm.

[0022] Optionally, the second product is separated by a cyclone separation device arranged at the tail end of the second reaction chamber to obtain the catalyst, comprising:

[0023] The second product is separated by a cyclone separation device arranged at the tail end of the second reaction chamber to obtain an initial sample meeting the particle size requirement.

[0024] The initial sample is subjected to drying treatment to obtain the sample.

[0025] Optionally, the drying treatment condition is to place the sample in a drying oven at 200-300°C and to perform constant-temperature drying for 10-24 h.

[0026] Optionally, the temperature of the second reaction chamber is 100-200°C.

[0027] Optionally, the nozzle orifice plate pore size in the second evaporation chamber is 50-150 nm.

[0028] Optionally, the silicon oxide precursor includes one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, tetraethyl orthosilicate, methyltrioxysilane, and vinyltriethoxysilane.

[0029] Optionally, the aluminum oxide precursor includes one or more of aluminum sec-butoxide, aluminum nitrate, and aluminum ammonium carbonate.

[0030] Optionally, the solution concentration of the nano calcium carbonate solution is 5-30 mol / L.

[0031] Optionally, the coupling agent includes one or more of aluminum zirconium coupling agent, aluminate coupling agent, aluminum zirconium coupling agent, 3-glycidyloxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane.

[0032] Optionally, the curing agent includes one or more of ammonia, a blend of propionic ester and ethanol, trimethylolpropane, and ethylenediamine.

[0033] The present application also provides a device for synthesizing a coal underground gasification catalyst, including:

[0034] A first hot solution generating unit is configured to place a basic solution and a modified coupling agent in a first evaporation chamber and heat to generate a first hot solution;

[0035] A first reaction chamber reaction unit is configured to spray the first hot solution into a first reaction chamber and react with aluminum oxide placed in the first reaction chamber to obtain a first product;

[0036] A sample obtaining unit is configured to separate the first product by a cyclone separation device arranged at the tail end of the first reaction chamber, obtain a sample, and place the sample in a second reaction chamber;

[0037] A second hot solution generating unit is configured to place silicon oxide precursor, aluminum oxide precursor, nano calcium carbonate solution, coupling agent, and curing agent in a second evaporation chamber and heat to generate a second hot solution;

[0038] A second reaction chamber reaction unit is configured to spray the second hot solution into a second reaction chamber and react with the sample to obtain a second product;

[0039] A catalyst obtaining unit is configured to separate the second product by a cyclone separation device arranged at the tail end of the second reaction chamber to obtain the catalyst.

[0040] Technical effects and advantages of the present application:

[0041] This invention provides a method for synthesizing a coal underground gasification catalyst, comprising: placing an alkaline solution and a modified coupling agent in a first evaporation chamber and heating to generate a first hot solution; spraying the first hot solution into a first reaction chamber and reacting it with alumina placed in the first reaction chamber to obtain a first product; separating the first product using a cyclone separator located at the tail end of the first reaction chamber to obtain a sample, and placing the sample in a second reaction chamber; placing a silica precursor, an alumina precursor, a nano-calcium carbonate solution, a coupling agent, and a curing agent in a second evaporation chamber and heating to generate a second hot solution; spraying the second hot solution into a second reaction chamber and reacting it with the sample to obtain a second product; and separating the second product using a cyclone separator located at the tail end of the second reaction chamber to obtain the catalyst. This invention allows for the synthesis of a catalyst with improved reactivity in a low-cost, easy-to-construct, and environmentally friendly manner.

[0042] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0043] Figure 1 A flowchart of a method for synthesizing catalysts for underground coal gasification;

[0044] Figure 2 This is a structural diagram of the reaction equipment;

[0045] Figure 3 This is a schematic diagram of the particle size distribution in the embodiment;

[0046] Figure 4 This is a schematic diagram showing the release ratio of active sites at different temperatures in the embodiments;

[0047] Figure 5 This is a schematic diagram of the TG curve in the embodiment;

[0048] Figure 5-1 This is a schematic diagram of the DSC curve in the embodiment;

[0049] Figure 6 This is a flowchart of a coal underground gasification catalyst synthesis unit. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] To address the shortcomings of existing technologies, this invention discloses a method for synthesizing a coal underground gasification catalyst, comprising: placing an alkaline solution and a modified coupling agent in a first evaporation chamber and heating to generate a first hot solution; spraying the first hot solution into a first reaction chamber and reacting it with alumina placed in the first reaction chamber to obtain a first product; separating the first product using a cyclone separator located at the tail end of the first reaction chamber to obtain a sample, and placing the sample in a second reaction chamber; placing a silica precursor, an alumina precursor, a nano-calcium carbonate solution, a coupling agent, and a curing agent in a second evaporation chamber and heating to generate a second hot solution; spraying the second hot solution into a second reaction chamber and reacting it with the sample to obtain a second product; and separating the second product using a cyclone separator located at the tail end of the second reaction chamber to obtain the catalyst. This invention allows for the synthesis of a catalyst with improved reactivity in a low-cost, easy-to-construct, and environmentally friendly manner.

[0052] To better explain the present invention, the concept of the present invention will be described in detail below.

[0053] This invention focuses on the reactivity modification of gasifying agents involved in underground coal gasification reactions. The material involves a synthesis process for a suspended core-shell structured catalytic material. This material has nanoscale particle size and consists of an inert shell and an active core. Regarding the release of activity, the catalyst incorporates nanoscale catalytic particles with a core-shell structure into water. The inert shell allows the release of the active core particles at different temperature gradients (200–500°C) by adjusting the formulation ratio. Regarding pipeline corrosion resistance, the material remains inert below 200°C due to the heat-resistant shell, preventing corrosion at the injection wellhead and in the delivery pipeline. Regarding on-site availability, the material is available in both nanoscale powder and liquid suspension states, allowing for immediate mixing, preparation, and injection on-site without delay, simplifying operation and requiring minimal space. Furthermore, the injection of this underground coal gasification catalyst can significantly improve underground coal gasification efficiency, enhance CO selectivity, and reduce CO2 production, providing effective technical support for cleaner underground coal gasification production.

[0054] The following combination Figure 1 and Figure 2 The preparation of the catalyst is described in detail. Among other things, Figure 2In the diagram, ① is the evaporation chamber, ② is the spray gun, ③ is the orifice plate, ④ is the reaction chamber, and ⑤ is the cyclone separator.

[0055] Nanoscale alumina was placed in the first reaction chamber. An alkali metal or alkaline earth metal solution (concentration 0.5–10 mol / L) and a modified coupling agent were placed in the first evaporation chamber and heated to 100–150°C. An inert gas was used as a carrier gas to carry the hot solution into the first reaction chamber for gas-phase coupling with the alumina. The temperature of the first reaction chamber was controlled between 100 and 300°C. During the evaporation process, the blower was kept running continuously, and the inert gas flow rate was controlled at 0.1 × 10⁻⁶. -6 ~0.3×10 -6 m 3 / s. The orifice diameter of the spray gun in the first evaporation chamber is controlled between 200 and 900 nm. A cyclone separator is installed at the tail end of the first reaction chamber to separate fine powder particles of different particle sizes. Select a suitable fine powder sample according to the requirements and place it in a drying oven at 200-300℃ for 10-24 hours.

[0056] Among them, nano-sized alumina includes one of α-Al2O3, β-Al2O3, and γ-Al2O3.

[0057] Alkali metal solutions include one or more of the following: sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium hydroxide solution, potassium carbonate solution, potassium bicarbonate solution, calcium hydroxide solution, calcium bicarbonate solution, and low-concentration calcium carbonate solution.

[0058] Among them, metal coupling agents include one or two of aluminum-zirconium coupling agents and aluminate coupling agents.

[0059] The organic solvents include one or more of ethanol, isopropanol, ethyl acetate, methanol, and acetone.

[0060] Among them, surfactants include one or more of the following: polyoxyethylene fatty alcohol ethers, fatty acid monoglycerides, glyceryl monostearate, polysorbate (Tween type) HLB (Hydrophile-Lipophile Balance Number, also known as water-oil ratio) 9 to 12.

[0061] The pH adjuster includes one or more of sorbic acid, citric acid, hydrochloric acid, and acetic acid. The pH of the mixed solution remains stable in the range of 5 to 6.8.

[0062] The modified coupling agent is a stable solution composed of a metal coupling agent, an organic solvent, a surfactant, and a pH adjuster, with the following mass fractions: 10-40% metal coupling agent, 40-60% organic solvent, 2-15% surfactant, and the amount of pH adjuster is based on the pH of the mixed solution.

[0063] The inert gas includes one of N2 and Ar.

[0064] The silica precursor, alumina precursor, nano-calcium carbonate solution, coupling agent, and curing agent are placed in the second evaporation chamber. The dried fine powder is then placed in the second reaction chamber. The mixture is heated to 100–200°C, and an inert gas is continuously introduced. The inert gas flow rate is controlled at 0.1 × 10⁻⁶. -5 ~0.2×10 -5 m 3 / s. The orifice diameter of the spray gun in the second evaporation chamber is controlled between 50 and 150 nm. A cyclone separator is installed at the tail end of the second reaction chamber to collect fine powder particles of different particle sizes, and then place them in a drying oven at 200–300℃ for 10–24 h.

[0065] Among them, the alumina precursor includes one or more of aluminum sec-butoxide, aluminum nitrate, and ammonium aluminum carbonate.

[0066] The silicon oxide precursor includes one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane tetraethyl orthosilicate, methyltrioxysilane, and vinyltriethoxysilane.

[0067] The molar concentration of the nano-calcium carbonate solution is 5–30 mol / L.

[0068] The coupling agent includes one or more of the following: aluminum zirconium coupling agent, aluminate coupling agent, aluminum zirconium coupling agent, 3-glycidyl etheroxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane.

[0069] The curing agent includes one or more of ammonia, a blend of propionate and ethanol, trimethylolpropane, and ethylenediamine.

[0070] The proportions of silica precursor, alumina precursor, nano-calcium carbonate solution, coupling agent, and curing agent, by mass fraction, are as follows: silica precursor 10%–40%, alumina precursor 10–40%, nano-calcium carbonate solution 2–40%, coupling agent 0.2–5%, and curing agent 1–10%.

[0071] To better explain this application, specific embodiments are described below.

[0072] Example 1

[0073] The preparation method of the nanoscale core-shell structured catalyst in this example includes the following steps:

[0074] α-Al₂O₃ was placed in a reaction chamber. A sodium bicarbonate solution (2.4 mol / L) and a modified coupling agent were placed in an evaporation chamber and heated to 100–150 °C. Ar was used as a carrier gas to carry the hot solution into the reaction chamber for gas-phase coupling with α-Al₂O₃. The reaction chamber temperature was controlled at 150 °C, and the blower was kept running continuously during the evaporation process. The inert gas flow rate was controlled at 0.2 × 10⁻⁶. - 6 m 3 / s. The orifice diameter range of the spray gun plate in the evaporation chamber is controlled within 500nm. A cyclone separator is installed at the tail end of the reaction chamber to separate fine powder particles of the same particle size range. Select a fine powder sample with a suitable particle size range according to the requirements and place it in a 200℃ drying oven for constant temperature drying for 24h.

[0075] The modified coupling agent is composed of 40% aluminum zirconium coupling agent, 40% isopropanol, 20% polysorbate, and citric acid mixed at 30°C, with the pH controlled at 6.5.

[0076] By weight, 35% octamethylcyclotetrasiloxane, 35% aluminate coupling agent, 15% nano-calcium carbonate solution (20 mol / L), 8% (3-(2,3-epoxypropoxy)propyltriethoxysilane), 5% propionate, and 2% ethanol were placed in an evaporation chamber. The dried fine powder was then placed in a reaction chamber and heated to 100°C while continuously introducing inert gas. The inert gas flow rate was controlled at 0.1 × 10⁻⁶. -5 m 3 / s. The aperture range of the spray gun orifice plate in the evaporation chamber is controlled within 50nm. A cyclone separator is installed at the tail end of the reaction chamber to collect fine powder particles of different particle sizes, and then place them in a drying oven at 200℃ for 24h.

[0077] Example 2

[0078] The preparation method of the nanoscale core-shell structured catalyst in this example includes the following steps:

[0079] β-Al₂O₃ was placed in a reaction chamber. A sodium bicarbonate solution (10 mol / L) and a modified coupling agent were placed in an evaporation chamber and heated to 150°C. N₂ was used as a carrier gas to carry the hot solution into the reaction chamber for gas-phase coupling with β-Al₂O₃. The reaction chamber temperature was controlled at 100°C, and the blower was kept running continuously during the evaporation process. The inert gas flow rate was controlled at 0.3 × 10⁻⁶. -6 m 3 / s. The orifice diameter range of the spray gun plate in the evaporation chamber is controlled within 600nm. A cyclone separator is installed at the tail end of the reaction chamber to separate fine powder particles of the same particle size range. Select a fine powder sample with a suitable particle size range according to the requirements and place it in a 200℃ drying oven for constant temperature drying for 10h.

[0080] The modified coupling agent is composed of 40% aluminate coupling agent, 45% ethanol, 15% polysorbate, and citric acid mixed at 30°C, with the pH controlled at 5.7.

[0081] By weight, 25% methyltrioxysilane, 35% aluminum nitrate, 25% nano-calcium carbonate solution (25 mol / L), 5% vinyltriethoxysilane, and 5% ammonia were placed in an evaporation chamber. The dried fine powder was then placed in a reaction chamber and heated to 250°C while continuously introducing inert gas. The inert gas flow rate was controlled at 0.15 × 10⁻⁶. -5 m 3 / s. The aperture range of the spray gun orifice plate in the evaporation chamber is controlled within 80nm. A cyclone separator is installed at the tail end of the reaction chamber to collect fine powder particles of different particle sizes, which are then placed in a 200℃ drying oven and dried for 12h.

[0082] Example 3

[0083] The preparation method of the nanoscale core-shell structured catalyst in this example includes the following steps:

[0084] γ-Al₂O₃ was placed in a reaction chamber, and a potassium carbonate solution (5 mol / L) and a modified coupling agent were placed in an evaporation chamber and heated to 120°C. The hot solution was then injected into the reaction chamber using N₂ as a carrier gas for gas-phase coupling with γ-Al₂O₃. The reaction chamber temperature was controlled at 200°C, and the blower was kept running continuously during the evaporation process. The inert gas flow rate was controlled at 0.25 × 10⁻⁶. -6 m 3 / s. The orifice diameter range of the spray gun plate in the evaporation chamber is controlled within 400nm. A cyclone separator is installed at the tail end of the reaction chamber to separate fine powder particles of the same particle size range. Select a fine powder sample with a suitable particle size range according to the requirements and place it in a 200℃ drying oven for constant temperature drying for 10h.

[0085] The modified coupling agent is composed of 30% aluminate coupling agent, 55% methanol, 15% polyoxyethylene fatty alcohol ether, and hydrochloric acid mixed at 30°C, with the pH controlled at 6.

[0086] By weight, 25% octamethylcyclotetrasiloxane, 25% ammonium aluminum nitrate, 38% nano-calcium carbonate solution (20 mol / L), 5% 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, and 7% ethylenediamine were placed in an evaporation chamber. The dried fine powder was then placed in a reaction chamber and heated to 100°C while continuously introducing inert gas. The inert gas flow rate was controlled at 0.1 × 10⁻⁶. -5 m 3 / s. The aperture range of the spray gun orifice plate in the evaporation chamber is controlled within 50nm. A cyclone separator is installed at the tail end of the reaction chamber to collect fine powder particles of different particle sizes, and then place them in a drying oven at 200℃ for 12h.

[0087] Example 4

[0088] The preparation method of the nanoscale core-shell structured catalyst in this example includes the following steps:

[0089] α-Al₂O₃ was placed in a reaction chamber. A sodium bicarbonate solution (8 mol / L) and a modified coupling agent were placed in an evaporation chamber and heated to 150°C. N₂ was used as a carrier gas to carry the hot solution into the reaction chamber for gas-phase coupling with α-Al₂O₃. The reaction chamber temperature was controlled at 200°C. During the evaporation process, the blower remained continuously operating, and the inert gas flow rate was controlled at 0.3 × 10⁻⁶. -6 m³ / s. The orifice diameter of the spray gun plate in the evaporation chamber is controlled within 600 nm. A cyclone separator is installed at the tail end of the reaction chamber to separate fine powder particles of the same size range. Fine powder samples with a suitable particle size range are selected according to requirements and placed in a 300℃ drying oven for 15 hours.

[0090] The modified coupling agent is composed of 30% aluminum zirconium coupling agent, 55% ethanol, 15% polyoxyethylene fatty alcohol ether, and citric acid mixed at 30°C, with the pH controlled at 6.5.

[0091] By weight, 35% vinyltriethoxysilane, 35% aluminum butoxide, 20% nano-calcium carbonate solution (20 mol / L), 5% 3-glycidyl etheroxypropyltrimethoxysilane, and 5% trimethylolpropane were placed in an evaporation chamber. The dried fine powder was then placed in a reaction chamber and heated to 150°C while continuously introducing Ar inert gas. The inert gas flow rate was controlled at 0.2 × 10⁻⁶. -5 m 3 / s. The orifice diameter range of the spray gun plate in the evaporation chamber is controlled within 50nm. A cyclone separator is installed at the tail end of the reaction chamber to collect fine powder particles of different particle sizes, and then place them in a drying oven at 250℃ for 16h.

[0092] The following tests demonstrate this, firstly, the particle size and distribution.

[0093] Information about particle diffusion velocity can be obtained from dynamic light scattering, and then the hydrodynamic radius can be obtained through the Stokes-Einstein equation.

[0094]

[0095] Where d(h) is the hydrodynamic diameter; k B η is Boltzmann constant; T is absolute temperature; η is viscosity; D is diffusion coefficient.

[0096] In this invention, the shell thickness is adjusted by varying the ratio of the core suspension to SiO2. With a consistent amount of core suspension, the core suspension / SiO2 ratios in examples NHK-① to NHK-④ are 1.9, 0.1, 1.2, and 0.5, respectively, arranged from smallest to largest as follows: NHK-② < NHK-④ < NHK-③ < NHK-①. Dynamic light scattering test results show the mechanical radii and their distribution range (e.g., ...) of examples NHK-① to NHK-④. Figure 3 The nm diameters (as shown in Table 1) are 200–600 nm, 400–900 nm, 100–600 nm, and 300–800 nm, respectively. The test results indicate that the particles in the embodiments of this invention are all nanoscale, and the ratio of the core suspension to SiO2 is inversely proportional to the shell thickness, which is consistent with the inventive design concept.

[0097] Table 1 Particle size distribution of the examples

[0098] Example Particle size range / nm NHK-1 200～600 NHK-2 400～900 NHK-3 100～600 NHK-4 300～800

[0099] Secondly, the release characteristics of the active center were tested.

[0100] The aqueous solution of the core active center involved in this invention has an alkaline pH, and the shell design aims to prevent pipe corrosion due to leakage of the core active center during pipeline transportation. This test examined the release ratio of the active component in four embodiments, NHK-① to NHK-④, at different temperatures. The test results showed that no active center release was observed in embodiments NHK-① to NHK-④ at 250℃, indicating high shell stability. Figure 4 As shown, with increasing temperature, the shell begins to rupture and release active centers. At a fixed temperature, the release ratio of active centers decreases with increasing shell thickness. The test results indicate that at 200℃, this core-shell material exhibits stable temperature resistance, and the outer shell effectively suppresses the overflow of the core material. Furthermore, by adjusting the SiO2 intake, the release rate of the active agent in the core-shell material within the temperature range of 300–700℃ can be effectively controlled. In practical engineering applications, based on the on-site process requirements of underground coal gasification, one or more process combinations can be selected to regulate the release ratio of the active agent at a constant temperature, thereby achieving process control during underground coal gasification, optimizing the composition of the crude coal gas, and improving its calorific value.

[0101] Finally, the core catalytic activity was tested.

[0102] Examples NHK-① to NHK-④ underwent artificial shell-breaking treatment. Using inert particles as a reference sample, the carbon conversion rate of the five types of samples was tested using a thermogravimetric analyzer. The experimental conditions were: heating to 120℃ at a rate of 15℃ / min under N2 atmosphere, holding for 15 min, then heating to 900℃, stabilizing for 10 min, and then switching to CO2. The test results showed that the core-shell catalyst involved in this invention can significantly increase the reaction sites in coal gasification and improve the carbon conversion rate, such as... Figure 5 and Figure 5-1 As shown in Table 2, indoor coal gasification experiments demonstrate that, compared to the inert reference sample, the introduction of the catalyst in the embodiments of this invention significantly reduces the CO2 component concentration while improving CO selectivity.

[0103] Table 2 CO selectivity and CO2 yield in the examples

[0104] CO selectivity / % CO2 component concentration / vol.% Inert particles 17 43 NHK-1 45 27 NHK-2 27 32 NHK-3 35 17 NHK-4 29 31

[0105] In summary, this catalyst uses near-well water resources as a solvent medium and is suspended in a solvent. It uses a core-shell structured active catalyst material as the active center. By adjusting the melting temperature range of the shell structure through molecular design, the active component is selectively released, thereby significantly improving the gasification reaction efficiency and the selectivity of effective components in the underground confined environment. The specific effects are as follows: 1. The particle size of the core-shell structured catalyst involved in this invention can be controlled within the range of 100-900 nm, allowing for immediate mixing, preparation, and injection with injected water. On-site preparation is convenient and quick, and the underground gasifying agent injection process can achieve thorough mixing with underground coal along with steam; 2. The solid active particles involved in this invention are coated with an inert shell layer, with a melting temperature higher than 200℃. After mixing with water, they form a neutral aqueous solution, eliminating the risk of pipeline corrosion; 3. The solid active center involved in this invention has low cost and is environmentally friendly. After release, it directly contacts the coal, significantly reducing the activation energy of the reaction between the coal surface and the gasifying agent and the effective component CO, thereby improving the reaction activity. CO selectivity can be increased by 10-28% under catalyst-free conditions, and the CO2 component concentration in the crude coal gas is reduced by 11-26%.

[0106] This invention also provides a device for synthesizing underground coal gasification catalysts, such as... Figure 6 As shown. Since this device part corresponds to the method described above, it will not be described in detail here. If anything is unclear, please refer to the description of the method above.

[0107] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synthesizing a coal underground gasification catalyst, characterized in that, include: An alkaline solution and a modified coupling agent are placed in a first evaporation chamber and heated to generate a first hot solution; The first hot solution is sprayed into the first reaction chamber and reacted with the alumina placed in the first reaction chamber to obtain the first product; The first product is separated by a cyclone separator located at the tail end of the first reaction chamber to obtain a sample, which is then placed in the second reaction chamber. The silica precursor, alumina precursor, nano-calcium carbonate solution, coupling agent and curing agent are placed in the second evaporation chamber and heated to generate a second hot solution; The second hot solution is sprayed into the second reaction chamber and reacted with the sample to obtain the second product; The catalyst is obtained by separating the second product using a cyclone separator located at the tail end of the second reaction chamber.

2. The method according to claim 1, characterized in that, The alkaline solution is an alkali metal solution or an alkaline earth metal solution.

3. The method according to claim 2, characterized in that, The alkali metal solution includes one or more of the following: sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium hydroxide solution, potassium carbonate solution, potassium bicarbonate solution, calcium hydroxide solution, calcium bicarbonate solution, and low-concentration calcium carbonate solution.

4. The method according to claim 1, characterized in that, The modified coupling agent is a mixture of a metal coupling agent, an organic solvent, a surfactant, and a pH adjuster. The metal coupling agent includes one or two of aluminum zirconium coupling agents and aluminate coupling agents; the organic solvent includes one or more of ethanol, isopropanol, ethyl acetate, methanol, and acetone; the surfactant includes one or more of polyoxyethylene fatty alcohol ethers, fatty acid monoglycerides, glyceryl monostearate, and polysorbate; and the pH adjuster includes one or more of sorbic acid, citric acid, hydrochloric acid, and acetic acid.

5. The method according to claim 2, characterized in that, The concentration of the alkali metal solution or the alkaline earth metal solution is 0.5–10 mol / L.

6. The method according to claim 1, characterized in that, The temperature of the first evaporation chamber is 100-150℃.

7. The method according to claim 1, characterized in that, The alumina includes one of α-Al2O3, β-Al2O3 and γ-Al2O3.

8. The method according to claim 1, characterized in that, The temperature of the first reaction chamber is 100–300°C.

9. The method according to claim 1, characterized in that, The nozzle orifice plate in the first evaporation chamber has a diameter of 200–900 nm.

10. The method according to claim 1, characterized in that, The step of separating the second product using a cyclone separator located at the tail end of the second reaction chamber to obtain the catalyst includes: The second product is separated by a cyclone separator located at the tail end of the second reaction chamber to obtain an initial sample that meets the particle size requirements. The initial sample is dried to obtain the final sample.

11. The method according to claim 10, characterized in that, The drying conditions are as follows: place the product in a drying oven at 200-300℃ and dry at a constant temperature for 10-24 hours.

12. The method according to claim 1, characterized in that, The temperature of the second reaction chamber is 100–200°C.

13. The method according to claim 1, characterized in that, The nozzle orifice plate in the second evaporation chamber has a diameter of 50–150 nm.

14. The method according to claim 1, characterized in that, The silicon oxide precursor includes one or more of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, tetraethyl orthosilicate, methyltrioxysilane, and vinyltriethoxysilane.

15. The method according to claim 1, characterized in that, The alumina precursor includes one or more of aluminum sec-butoxide, aluminum nitrate, and ammonium aluminum carbonate.

16. The method according to claim 1, characterized in that, The concentration of the nano-calcium carbonate solution is 5–30 mol / L.

17. The method according to claim 1, characterized in that, The coupling agent includes one or more of the following: aluminum zirconium coupling agent, aluminate coupling agent, aluminum zirconium coupling agent, 3-glycidyl etheroxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane.

18. The method according to claim 1, characterized in that, The curing agent includes one or more of ammonia, a blend of propionate and ethanol, trimethylolpropane, and ethylenediamine.

19. A synthesis apparatus for an underground coal gasification catalyst, characterized in that, include: A first hot solution generation unit is used to place an alkaline solution and a modified coupling agent in a first evaporation chamber and heat them to generate a first hot solution; The first reaction chamber reaction unit is used to spray the first hot solution into the first reaction chamber and react it with the alumina placed in the first reaction chamber to obtain the first product; A sample obtaining unit is used to separate the first product by means of a cyclone separator located at the tail end of the first reaction chamber to obtain a sample, and to place the sample in the second reaction chamber; The second hot solution generation unit is used to place the silicon oxide precursor, aluminum oxide precursor, nano-calcium carbonate solution, coupling agent and curing agent in the second evaporation chamber and heat them to generate the second hot solution; The second reaction chamber reaction unit is used to spray the second hot solution into the second reaction chamber and react it with the sample to obtain the second product; A catalyst obtaining unit is used to separate the second product by means of a cyclone separator located at the tail end of the second reaction chamber, thereby obtaining the catalyst.

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