Preparation method for preparing catalyst by using red mud and application of catalyst

Abstract

The application provides a preparation method of a catalyst by using red mud and application of the catalyst, and the preparation method comprises the following steps: S1, red mud is calcined and then crushed to obtain a red mud carrier; and S2, the red mud carrier and an active metal precursor are placed in an H2O2 solution for soaking and modification to obtain the catalyst. In the catalyst preparation process, the original low-valence metal in the catalyst composition is oxidized into a high-valence metal due to the presence of the H2O2 solution, so that the catalytic gasification efficiency of the catalyst is improved. The addition sequence is preferably that the metal oxide is added first and then the metal salt is added, so that the catalyst substances are uniformly mixed, and the best effect of the catalyst is ensured.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling, specifically relating to a method for preparing catalysts using red mud and the application of the catalysts. Background Technology

[0002] Red mud is a solid waste generated during the alumina industrial production process. In 2020, China's total alumina production reached 73.132 million tons. Approximately 1.0 to 1.8 tons of red mud are generated for every ton of alumina produced. As the amount of red mud accumulated increases, the waste of resources and the pollution to the environment become more and more serious. The comprehensive utilization rate of red mud in my country is only 4%. The main components of red mud are iron oxide, alumina, calcium oxide, titanium oxide, sodium oxide, and silicon dioxide. Iron oxide is an environmentally friendly, inexpensive, and highly active catalyst component. Alumina has the advantages of high melting point and large specific surface area, and can be used as a catalyst carrier.

[0003] Underground coal gasification enables in-situ gasification and conversion of underground coal seams, generating gaseous compounds that are easy to transport and utilize. It is particularly suitable for situations where coal geological conditions are unfavorable, and conventional mining is neither economical nor safe. Underground gasification effectively solves these problems. Underground catalytic coal gasification technology is a catalytic thermal conversion process that achieves in-situ controlled pyrolysis, gasification, and combustion of coal in underground coal seams under the action of a catalyst, generating high-quality coal gas rich in hydrogen and methane. Underground catalytic gasification technology can effectively increase the hydrogen and methane content in the coal gas, thus offering advantages such as high safety, low investment, high efficiency, low pollution, and good economic benefits.

[0004] Currently, commonly used catalysts for coal catalytic gasification reactions mainly include alkali metal catalysts, alkaline earth metal catalysts, and transition metal catalysts. Based on the composition of the active components, they can be divided into monoprotic catalysts and composite catalysts. Multiprotic composite catalysts exhibit higher gasification efficiency, higher carbon conversion rate, and methane selectivity, showing promising industrialization prospects. However, the high price, low recovery rate, and potential secondary pollution of alkaline catalysts hinder the industrialization of coal catalytic gasification. Furthermore, due to the unique characteristics of underground coal gasification sites, catalysts used in underground gasification must not only meet the requirements of strong coal adaptability and high activity, but also, since catalysts are not recyclable, possess abundant and inexpensive raw material sources.

[0005] Patent CN201710141373.4 discloses a method for preparing a waste coal gasification catalyst using red mud. The method involves adding a certain amount of barium salt as a stabilizer to high-grade vanadium-containing material, converting V₂O₅ to 2BaO·V₂O₅ through high-temperature calcination, and then mixing this with a certain amount of red mud to obtain a mixture. Ferric oxide from the red mud is used as a promoter, and the mixture is ground to 100 mesh to obtain the waste coal gasification catalyst. This method results in high catalyst production costs. The main purpose of this catalyst is to improve coal combustion efficiency and achieve coal saving.

[0006] Patent CN201510215285.5 discloses a supported red mud composite catalyst for coal catalytic gasification and its preparation method. The catalyst-active components are loaded onto red mud treated by sintering to produce alumina. The active components of the catalyst are alkali metal elements and calcium and iron minerals in the red mud that can be partially converted into catalyst-active components. This method requires drying and roasting to prepare the catalyst, resulting in complex preparation and transportation processes, which is not conducive to thorough mixing of the catalyst and coal, leading to low catalytic gasification efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a catalyst using red mud. This catalyst is suitable for underground catalytic gasification of coal and solves the problems of slow reaction and low effective gas composition in current underground coal gasification processes.

[0008] To achieve the above objectives, the present invention provides a method for preparing a catalyst using red mud, comprising the following steps:

[0009] S1, Red mud is roasted and then crushed to obtain a red mud carrier;

[0010] S2, red mud support and active metal precursor are soaked in H2O2 solution for modification to obtain catalyst.

[0011] Before firing the red mud, it can be filtered to remove impurities, mainly large, hard-to-break materials such as stones and branches.

[0012] The method for preparing catalysts using red mud according to the present invention, wherein the red mud is roasted in step S1, the main purpose of which is to convert low-valence metal oxides into high-valence metal oxides. The roasting temperature and time are not specifically limited and can be appropriately adjusted according to the specific type of red mud, as long as the above purpose can be achieved. Preferably, the red mud is roasted at 600-800℃ for 2-3 hours. The particle size of the crushed red mud carrier is not specifically limited and can be conventionally adjusted according to the application scenario of the catalyst. Preferably, the particle size is less than 300 micrometers.

[0013] The preparation method for catalysts using red mud according to the present invention, in step S2, soaking the red mud support in H2O2 solution aims to oxidize the low-valence metals in the red mud using hydrogen peroxide, thereby oxidizing the low-valence metals to high-valence metals. The concentration, amount, and soaking time of the H2O2 solution are not specifically limited, as long as the oxidation effect is achieved. Preferably, the mass concentration of the H2O2 solution is 1-5%, and the soaking time is 2-4 hours. In step S2 of the preparation method for catalysts using red mud according to the present invention, the type of active metal is not specifically limited and can be selected according to the specific application of the catalyst. Preferably, the active metal includes one or more of transition metals, alkali metals, and alkaline earth metals.

[0014] The method for preparing a catalyst using red mud according to the present invention comprises the following: the transition metal is iron and / or manganese, the alkali metal is potassium and / or sodium, and the alkaline earth metal is calcium and / or magnesium.

[0015] In the method for preparing catalysts using red mud according to the present invention, in step S2, transition metals are introduced by adding transition metal oxides; alkaline earth metals are introduced by adding alkaline earth metal oxides or alkaline earth metal salts; and alkali metals are introduced by adding alkali metal salts.

[0016] The method for preparing catalysts using red mud according to the present invention, in step S2, uses an active metal precursor that is a commonly used active metal-containing substance in catalyst preparation, preferably an active metal salt and / or an active metal oxide. The type of active metal salt is not specifically limited and can be nitrate, carbonate, or sulfate, preferably nitrate or carbonate. When using sulfate, SO2 is generated during the high-temperature reaction, affecting the composition of the syngas and increasing the subsequent desulfurization cost. In this invention, when the red mud support and active metal precursor are soaked and modified in H2O2 solution, the red mud support, active metal salt, and / or active metal oxide can be added to the H2O2 solution simultaneously or in batches. When adding in batches, the order of addition is not important; for example, the red mud support can be soaked in H2O2 solution first, and then the active metal salt and / or active metal oxide can be added, either simultaneously or in batches; or the red mud support and active metal salt can be soaked in H2O2 solution simultaneously first, and then the active metal oxide can be added. In this invention, it is preferable to add the active metal oxide first and then the active metal salt, as this order of addition can improve the catalytic effect of the catalyst.

[0017] The preparation method of catalyst using red mud described in this invention does not impose special limitations on the amounts of hydrogen peroxide, red mud, and active metal. These amounts can be adjusted according to the specific application scenario of the catalyst. Preferably, the mass ratio of hydrogen peroxide to red mud is 2:1 to 1:2, and the mass ratio of active metal oxide and active metal salt to red mud is 1:1 to 1:20, wherein the mass ratio of active metal oxide to active metal salt is 10:1 to 1:1.

[0018] The method for preparing a catalyst using red mud according to the present invention includes a transition metal oxide in the active metal oxide, wherein the content of the transition metal oxide is 1-20% of the total mass of the catalyst.

[0019] The present invention also provides an application of the above-mentioned catalyst in underground coal gasification, wherein the reaction pressure is 0-4.0 MPa, the temperature is 600-1000℃, and the gasifying agent is air or oxygen, preferably oxygen.

[0020] The beneficial effects of this invention are:

[0021] In the catalyst preparation process of this invention, the strong oxidizing property of H2O2 solution is utilized to oxidize the original low-valence metals in the catalyst components to high-valence metals, thereby improving the catalytic gasification efficiency of the catalyst. Adding the metal oxide first, followed by the metal salt, promotes uniform mixing of the catalyst components and ensures optimal catalyst performance.

[0022] This catalyst can be used in underground catalytic gasification of coal to improve carbon conversion rate and the effective composition of underground gasified coal gas. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the pressurized fixed-bed reactor used for catalyst performance evaluation experiments in this invention.

[0024] Figure 2 This is a process flow diagram of the method for preparing catalysts using red mud according to the present invention. Detailed Implementation

[0025] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0026] (1) Source of raw materials:

[0027] The carriers are red mud from Chinalco Shanxi Branch (SX) and Shandong Branch (SD), and their specific composition is shown in the table below:

[0028]

[0029] Other raw materials

[0030]

[0031]

[0032] (2) Evaluation and analysis methods:

[0033] The evaluation test was conducted on a pressurized fixed bed (the device structure is as follows). Figure 1 As shown in the figure, the experimental process mainly consists of the following three steps:

[0034] (1) The coal sample was loaded into a fixed-bed reactor that could simulate underground gasification, and the air in the reactor was replaced with N2 and pressurized.

[0035] (2) Turn on the electric furnace and heat the reactor in N2 atmosphere. After the reactor temperature reaches the set value, stabilize it for 5 minutes.

[0036] (3) The catalyst is injected into the fixed-bed reactor using a mud pump;

[0037] (4) Introduce the reaction gas and start recording the gas flow rate and gas composition.

[0038] The tail gas first passes through an electronic flow meter to record its volumetric flow rate online. After passing through the electronic flow meter, the composition of the gas is automatically measured using a micro gas chromatograph (INFICON 3000).

[0039] Evaluation devices such as Figure 1 As shown.

[0040] Example 1

[0041] Process flow as follows Figure 2 As shown.

[0042] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 600℃ for 2 hours. Then it was crushed and screened to obtain red mud carrier with a particle size of less than 300 micrometers. 200g of red mud (SX) carrier was weighed out for later use.

[0043] Prepare 150g of H2O2 solution with a concentration of 4%, put the red mud carrier into the solution, and stir and soak for 3 hours;

[0044] Weigh out 40g of calcium oxide, 20g of magnesium oxide and 20g of ferric oxide, dissolve them in the carrier solution, stir and soak for 3 hours to make the metal oxides and red mud solution evenly mixed.

[0045] Weigh 20g of potassium carbonate and 20g of sodium carbonate, dissolve them in the carrier solution, stir and soak for 4 hours to obtain the underground coal gasification catalyst.

[0046] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Shenmu bituminous coal, the reaction pressure was 1.0 MPa, the reaction temperature was 900℃, and the gasifying agent was air. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 36.12%, and the lower calorific value of the coal gas was 1236 kcal / Nm³. 3 .

[0047] Example 2

[0048] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 700℃ for 3 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SX) carriers were weighed out for later use.

[0049] Prepare a 3% H2O2 solution (400g total), add the red mud carrier to the solution, and stir and soak for 2 hours.

[0050] Weigh 5g of calcium oxide, dissolve it in the carrier solution, stir and soak for 3 hours to make the metal oxide and red mud solution evenly mixed;

[0051] Weigh 5g of potassium carbonate, dissolve it in the carrier solution, stir and soak for 3 hours to obtain the underground coal gasification catalyst.

[0052] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Shenmu bituminous coal, the reaction pressure was 2.0 MPa, the reaction temperature was 850℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 89.04%, and the lower calorific value of the coal gas was 2698 kcal / Nm³. 3 .

[0053] Example 3

[0054] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 600℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0055] Prepare 150g of H2O2 solution with a concentration of 4%, put the red mud carrier into the solution, and stir and soak for 3 hours;

[0056] Weigh out 50g of calcium oxide and 50g of manganese dioxide, dissolve them in the carrier solution, stir and soak for 3 hours to make the metal oxides and red mud solution evenly mixed;

[0057] Weigh 50g of potassium carbonate and 50g of sodium carbonate, dissolve them in the carrier solution, stir and soak for 4 hours to obtain the underground coal gasification catalyst.

[0058] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Shenmu bituminous coal, the reaction pressure was 1.0 MPa, the reaction temperature was 900℃, and the gasifying agent was air. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 37.23%, and the lower calorific value of the coal gas was 1252 kcal / Nm³. 3 .

[0059] Example 4

[0060] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 700℃ for 3 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0061] Prepare 100g of 3% H2O2 solution, put the red mud carrier into the solution, and stir and soak for 2 hours;

[0062] Weigh out 30g of calcium oxide and 70g of manganese dioxide, dissolve them in the carrier solution, stir and soak for 3 hours to make the metal oxides and red mud solution evenly mixed;

[0063] Weigh 10g of potassium carbonate, dissolve it in the carrier solution, stir and soak for 3 hours to obtain the underground coal gasification catalyst.

[0064] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Shenmu bituminous coal, the reaction pressure was 2.0 MPa, the reaction temperature was 850℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 92.05%, and the lower calorific value of the coal gas was 2753 kcal / Nm³. 3 .

[0065] Example 5

[0066] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 750℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SX) carriers were weighed out for later use.

[0067] Prepare a 3% H2O2 solution (150g total), add the red mud carrier to the solution, and stir and soak for 2 hours.

[0068] Weigh 10g of calcium oxide, dissolve it in the carrier solution, stir and soak for 4 hours to make the metal oxide and red mud solution evenly mixed;

[0069] 10g of sodium carbonate was weighed, dissolved in the carrier solution, and stirred and soaked for 5 hours to obtain the underground coal gasification catalyst.

[0070] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Holingol lignite, the reaction pressure was 2.5 MPa, the reaction temperature was 600℃, and the gasifying agent was air. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 38.48%, and the lower calorific value of the coal gas was 1523 kcal / Nm³. 3 .

[0071] Example 6

[0072] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 800℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SX) carriers were weighed out for later use.

[0073] Prepare a 3% H2O2 solution (200g total), add the red mud carrier to the solution, and stir and soak for 4 hours.

[0074] Weigh out 30g of calcium oxide and 20g of ferric oxide, dissolve them in the carrier solution, stir and soak for 5 hours to make the metal oxide and red mud solution evenly mixed;

[0075] Weigh 10g of potassium carbonate and 10g of sodium carbonate, dissolve them in the carrier solution, stir and soak for 5 hours to obtain the underground coal gasification catalyst.

[0076] The prepared coal underground gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Jincheng lignite-free coal, the reaction pressure was 4.0 MPa, the reaction temperature was 1000℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 83.95%, and the lower calorific value of the coal gas was 2542 kcal / Nm³. 3 .

[0077] Example 7

[0078] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 750℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0079] Prepare a 3% H2O2 solution (300g total), add the red mud carrier to the solution, and stir and soak for 2 hours.

[0080] Weigh out 20g of calcium oxide and 30g of manganese dioxide, dissolve them in the carrier solution, stir and soak for 4 hours to make the metal oxides and red mud solution evenly mixed;

[0081] 10g of sodium carbonate was weighed, dissolved in the carrier solution, and stirred and soaked for 4 hours to obtain the underground coal gasification catalyst.

[0082] The prepared underground coal gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Holingol lignite, the reaction pressure was 2.5 MPa, the reaction temperature was 750℃, and the gasifying agent was air. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 40.59%, and the lower calorific value of the coal gas was 1550 kcal / Nm³. 3 .

[0083] Example 8

[0084] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 800℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0085] Prepare a 3% H2O2 solution (200g total), add the red mud carrier to the solution, and stir and soak for 4 hours.

[0086] Weigh out 30g of calcium oxide, 20g of magnesium oxide, 20g of manganese dioxide and 30g of ferric oxide, dissolve them in the carrier solution, stir and soak for 5 hours to make the metal oxides and red mud solution evenly mixed;

[0087] Weigh 30g of potassium carbonate and 20g of sodium carbonate, dissolve them in a carrier solution, stir and soak for 5 hours to obtain the underground coal gasification catalyst.

[0088] The prepared coal underground gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Jincheng lignite-free coal, the reaction pressure was 3.5 MPa, the reaction temperature was 900℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 84.15%, and the lower calorific value of the coal gas was 2564 kcal / Nm³. 3 .

[0089] Example 9

[0090] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 800℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0091] Prepare a 3% H2O2 solution (200g total), add the red mud carrier to the solution, and stir and soak for 4 hours.

[0092] Weigh out 30g of potassium carbonate and 20g of sodium carbonate, dissolve them in the carrier solution, stir and soak for 5 hours to make the metal salt and red mud solution evenly mixed.

[0093] Weigh out 30g of calcium oxide, 20g of magnesium oxide, 20g of manganese dioxide and 30g of ferric oxide, dissolve them in a carrier solution, stir and soak for 5 hours to obtain the underground coal gasification catalyst.

[0094] The prepared coal underground gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Jincheng lignite-free coal, the reaction pressure was 3.5 MPa, the reaction temperature was 900℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 78.25%, and the lower calorific value of the coal gas was 2315 kcal / Nm³. 3 .

[0095] Comparative Example 1

[0096] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 800℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SX) carriers were weighed out for later use.

[0097] Place the red mud carrier in 200g of deionized water and stir to soak for 4 hours;

[0098] Weigh out 30g of calcium oxide and 20g of ferric oxide, dissolve them in the carrier solution, stir and soak for 5 hours to make the metal oxide and red mud solution evenly mixed;

[0099] Weigh 10g of potassium carbonate and 10g of sodium carbonate, dissolve them in the carrier solution, stir and soak for 5 hours to obtain the underground coal gasification catalyst.

[0100] The prepared coal underground gasification catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Jincheng lignite-free coal, the reaction pressure was 4.0 MPa, the reaction temperature was 1000℃, and the gasifying agent was oxygen. The experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 75.53%, and the lower calorific value of the coal gas was 2272 kcal / Nm³. 3 .

[0101] Comparative Example 2

[0102] Impurities were removed by filtering the red mud waste residue, the moisture was evaporated by drying, and it was calcined at 750℃ for 2 hours. After crushing and screening, red mud carriers with a particle size of less than 300 micrometers were finally obtained. 200g of red mud (SD) carriers were weighed out for later use.

[0103] Place the red mud carrier in 300g of deionized water and stir to soak for 2 hours;

[0104] Weigh out 20g of calcium oxide and 30g of manganese dioxide, dissolve them in the carrier solution, stir and soak for 4 hours to make the metal oxides and red mud solution evenly mixed;

[0105] 10g of sodium carbonate was dissolved in a carrier solution and stirred for 4 hours to prepare the underground coal gasification catalyst. The prepared catalyst was injected into a fixed-bed reactor simulating underground gasification conditions using a mud pump. The coal type was Holingol lignite, the reaction pressure was 2.5 MPa, the reaction temperature was 750℃, and the gasifying agent was air. Experimental results showed that the effective gas (CO+H2+CH4) content in the coal gas was 35.07%, and the lower calorific value of the coal gas was 1346 kcal / Nm³. 3 .

[0106] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a catalyst using red mud, characterized in that, Includes the following steps: S1, Red mud is roasted and then crushed to obtain a red mud carrier; S2, red mud support and active metal precursor are soaked and modified in H2O2 solution to obtain catalyst; In step S2, the red mud carrier is first soaked in H2O2 solution, and then the active metal precursor is added.

2. The method for preparing a catalyst using red mud according to claim 1, characterized in that, In step S1, the red mud is roasted at 600~800℃ for 2~3 hours, and the particle size of the crushed red mud carrier is less than 300 micrometers.

3. The method for preparing a catalyst using red mud according to claim 1, characterized in that, In step S2, the mass concentration of the H2O2 solution is 1-5%, and the soaking time is 2-4 hours.

4. The method for preparing a catalyst using red mud according to claim 1, characterized in that, In step S2, the active metal includes one or more of transition metals, alkali metals, and alkaline earth metals.

5. The method for preparing a catalyst using red mud according to claim 4, characterized in that, The transition metal is iron and / or manganese, the alkali metal is potassium and / or sodium, and the alkaline earth metal is calcium and / or magnesium.

6. The method for preparing a catalyst using red mud according to claim 4, characterized in that, In step S2, transition metals are introduced by adding transition metal oxides; alkaline earth metals are introduced by adding alkaline earth metal oxides or alkaline earth metal salts; and alkali metals are introduced by adding alkali metal salts.

7. The method for preparing a catalyst using red mud according to claim 6, characterized in that, In step S2, the active metal oxide is added first, followed by the active metal salt.

8. The method for preparing a catalyst using red mud according to claim 1, characterized in that, The mass ratio of hydrogen peroxide to red mud is 2:1 to 1:2, and the mass ratio of active metal oxides and active metal salts to red mud is 1:1 to 1:20, wherein the mass ratio of active metal oxides to active metal salts is 10:1 to 1:

1.

9. The method for preparing a catalyst using red mud according to claim 8, characterized in that, The active metal oxide includes transition metal oxides, and the content of transition metal oxides is 1-20% of the total mass of the catalyst.

10. The application of the catalyst according to any one of claims 1 to 9 in underground coal gasification, characterized in that, The reaction pressure is 0~4.0MPa, the temperature is 600~1000℃, and the vaporizing agent is air or oxygen.

11. The application of the catalyst according to claim 10 in underground coal gasification, characterized in that, The vaporizing agent is oxygen.

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