Composite catalyst, method for preparing the same, and method for preparing combustible gas

Abstract

The present application belongs to the field of combustible gas, and particularly relates to a composite catalyst, a preparation method thereof, and a method for preparing combustible gas. The preparation method of the composite catalyst comprises the following steps: dissolving humic acid in deionized water to obtain a humic acid aqueous solution, then adjusting the humic acid aqueous solution to be acidic, and finally adding ammonium bicarbonate, zinc chloride and aluminum nitrate into the humic acid aqueous solution and reacting for a period of time at a certain temperature to obtain a solution of the composite catalyst. The method for preparing combustible gas comprises the following steps: dissolving the above-mentioned solution of the composite catalyst in methanol to obtain a mixture, and gasifying the methanol reforming gas into combustible gas. After the composite catalyst aqueous solution and the methanol are mixed, the composite catalyst can be taken away by gasification while performing catalysis in the methanol reforming process, so that the problem of carbon deposition in the equipment is avoided, the efficient catalysis of the equipment is ensured, and the maintenance cost in the later period is reduced.

Description

Technical Field

[0001] This invention belongs to the field of combustible gas, specifically relating to a composite catalyst and its preparation method, and a method for preparing combustible gas. Background Technology

[0002] Methanol, as a liquid fuel, has a series of advantages such as high volumetric energy density, wide availability, low price, low storage and transportation costs, and safety and reliability.

[0003] Using methanol as a supplementary fuel holds promise for alleviating energy shortages caused by the heavy use of natural gas. However, the direct combustion calorific value of liquid methanol is relatively low. The calorific value of methanol is approximately 4650 kcal per kilogram, while that of natural gas is between 8000 and 9000 kcal per cubic meter. Studies have shown that methanol, under specific pressure and temperature, undergoes a reforming reaction after flowing through a catalyst bed loaded with a specific catalyst, producing combustible gases such as hydrogen, carbon monoxide, methane, ethane, and dimethyl ether, as well as non-combustible carbon dioxide. For example, Chinese invention patent CN117046480A discloses a methanol reforming hydrogen production catalyst and its preparation and hydrogen production method. This involves dissolving copper, zinc, aluminum, cerium, zirconium, and complexed carbon sources in deionized water and stirring until homogeneous. The resulting gel is then dried to obtain a precursor, which is subsequently calcined to obtain a solid powder. The solid powder is then mixed with a binder and extruded to obtain a cylindrical preform. Finally, the cylindrical preform is subjected to hydrogen reduction treatment to obtain the methanol reforming hydrogen production catalyst. For example, Chinese invention patent CN115518654A discloses a high-efficiency, high-selectivity, and high-stability methanol reforming hydrogen production catalyst and its preparation process, relating to the field of methanol steam reforming hydrogen production catalysts. It addresses the problems of low hydrogen production efficiency of industrial Cu-Zn-Al catalysts and high energy consumption and poor hydrogen selectivity of precious metal catalysts. The catalyst includes CuO, ZnO, Al2O3, Pt, or Pd. Therefore, reforming methanol into clean-burning hydrogen has become one of the main research and application directions.

[0004] To meet the demand for pure hydrogen in fuel cells and other applications, the mixed gas produced by industrial methanol reforming needs to be separated into high-purity hydrogen through pressure swing adsorption (PSA). However, from the perspective of industrial fuel use, there are two problems with the maximization of resource utilization in the methanol "reformation to hydrogen production-purification" process: 1) Other combustible gases in the reformed gas are not used downstream, resulting in a waste of combustible materials; 2) The carbon dioxide in the reformed gas is not further converted into combustible carbon monoxide.

[0005] If, during the methanol reforming process, the carbon dioxide in the reforming products can be simultaneously catalytically converted into carbon monoxide, the proportion of combustible material will be significantly increased. Therefore, considering the maximization of resource utilization and the convenience of using combustible gas, using the methanol reformed mixture directly as fuel without purification will help reduce economic costs and achieve the "dual carbon" goal. For example, Chinese invention patent CN 115092886B discloses a method for preparing a methanol-to-gas mixture and the catalyst used, specifically disclosing a composite catalyst GO-NH prepared by reacting graphene oxide with ammonium chloride and aluminum trichloride to produce a methanol-soluble form. x -AlCl y The calorific value of the combustible gas after reforming methanol with this composite catalyst at certain temperature and pressure is higher than that of direct methanol combustion. However, from an economic and technical perspective, the aforementioned disclosed invention patent still has the following problems:

[0006] 1) The preparation process of graphene oxide is costly and does not easily meet the industrial requirements for low-cost combustible gas.

[0007] 2) The composite catalyst lacks the participation of zinc salt, making it unable to further convert non-flammable carbon dioxide into combustible carbon monoxide.

[0008] Therefore, developing a low-cost composite catalyst that contains ammonium, zinc, and aluminum salts and is soluble in methanol, and in which methanol containing such a composite catalyst can be reformed to produce a combustible gas with a higher calorific value than methanol without purification, is an urgent problem to be solved. Summary of the Invention

[0009] Purpose of the invention: In order to overcome the problems of high raw material price of catalysts and lack of catalytic components in existing technologies to convert non-flammable carbon dioxide into combustible carbon monoxide, this invention discloses a composite catalyst and its preparation method, as well as a method for preparing combustible gas.

[0010] Technical solution: A composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0011]

[0012] in:

[0013] 0 < x ≤ 2, x is preferably 1 or 2;

[0014] 0 < y ≤ 2, where y is preferably 1 or 2;

[0015] 0 < z ≤ 2, and z is preferably 0.5, 1, 1.5, or 2.

[0016] The preparation method of the above composite catalyst includes the following steps:

[0017] Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of composite catalyst.

[0018] The composite catalyst is prepared by any one of the methods described above.

[0019] The method for preparing combustible gas involves dissolving the above-mentioned composite catalyst solution in methanol to obtain a mixture, and then reforming and gasifying the methanol into combustible gas.

[0020] In this invention, when the pH value is controlled between 6.3 and 6.7, the carboxylic acid functional groups on humic acid not only ensure the weak acidity of the composite catalyst, but also allow it to dissolve well in water and methanol due to the abundance of carboxyl and hydroxyl functional groups on the surface of humic acid. At the same time, the carboxyl functional groups on humic acid also provide reaction sites for nitrogen, zinc and aluminum in ammonium bicarbonate, zinc chloride and aluminum nitrate.

[0021] Key Invention Points: This invention uses humic acid, which is less expensive, as a raw material. By adding ammonium bicarbonate, zinc chloride, and aluminum nitrate, a composite catalyst HA-Nx-Zny-Alz is obtained. The composite catalyst disclosed in this invention not only reduces raw material costs but also promotes the conversion of carbon dioxide to carbon monoxide during methanol reforming.

[0022] Beneficial Effects: The composite catalyst and its preparation method disclosed in this invention, as well as the method for preparing combustible gas, have the following beneficial effects:

[0023] 1. The proportion of carbon dioxide and the proportion of carbon monoxide in the combustible gas prepared by methanol reforming using the composite catalyst of the present invention are reduced and increased, which ultimately increases the proportion of carbon elements in methanol converted into combustibles, thereby making the calorific value of the mixed gas prepared by the composite catalyst of the present invention higher than that of methanol alone.

[0024] 2. Replacing graphene with humic acid, which is cheaper, reduces the preparation cost of the composite catalyst.

[0025] 3. When the composite catalyst aqueous solution of the present invention is mixed with methanol, the composite catalyst can be vaporized and carried away during the methanol reforming process, ensuring that the equipment will not produce carbon deposits, guaranteeing the high efficiency of the equipment and reducing the later maintenance costs.

[0026] 4. The combustible gas prepared by the present invention does not require additional equipment such as separation and purification, and can be directly used for industrial combustion. The combustion products are carbon dioxide and water, without other pollutants, which improves the convenience of using methanol as fuel. Detailed Implementation

[0027] The specific embodiments of the present invention are described in detail below.

[0028] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0033] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0034] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0035] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0036] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0037] In this invention, the combustible gas components were tested using a gas chromatograph, model GC-9560-HS, with standards for hydrogen, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, propane, isopropane, isobutane, and dimethyl ether as references.

[0038] In this invention, the calorific value of the prepared combustible gas is measured using a calorimeter with water as the medium. That is, according to the law of conservation of energy, it is assumed that during steady-state combustion, all the heat released by the combustion of the gas is absorbed by the water.

[0039] Under steady-state, complete combustion conditions, the energy conservation equation is:

[0040] Physical heat carried in by air + Physical heat carried in by fuel gas + Chemical heat carried in fuel gas = Heat absorbed by cooling water + Heat loss from flue gas + Heat dissipation loss

[0041] If the exhaust gas temperature is controlled to be close to the ambient temperature, then:

[0042] Physical heat carried in by air + physical heat carried in by fuel gas ≈ flue gas heat loss

[0043] The calorimeter is equipped with an insulation layer, which makes its heat loss to the environment close to zero.

[0044] In this way, the chemical heat of the gas (i.e., the calorific value of combustion) is equal to the heat absorbed by the cooling water.

[0045] The synthetic route of this invention is as follows:

[0046]

[0047] A composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0048]

[0049] in:

[0050] 0 < x ≤ 2, x is preferably 1 or 2;

[0051] 0 < y ≤ 2, where y is preferably 1 or 2;

[0052] 0 < z ≤ 2, and z is preferably 0.5, 1, 1.5, or 2.

[0053] The preparation method of the above composite catalyst includes the following steps:

[0054] Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of composite catalyst.

[0055] Furthermore, the pH value of the humic acid aqueous solution is controlled between 6.3 and 6.7.

[0056] Further, the mass ratio of the humic acid, ammonium bicarbonate, zinc chloride, aluminum nitrate and the deionized water is (0.5-1):(0.2-0.4):(0.2-0.4):(0.2-0.4):1000.

[0057] Furthermore, the reaction temperature is room temperature, and the reaction time is at least 2 hours, preferably 2-4 hours.

[0058] The composite catalyst is prepared by any one of the methods described above.

[0059] The method for preparing combustible gas involves dissolving the above-mentioned composite catalyst solution in methanol to obtain a mixture, and then reforming and gasifying the methanol into combustible gas.

[0060] Furthermore, the combustible gas is composed of one or more of hydrogen, carbon monoxide, methane, ethane, isopropane, and dimethyl ether.

[0061] Furthermore, the reaction temperature of the reforming gasification is controlled at at least 290°C, preferably 290-350°C, and the reaction pressure is controlled at at least 0.5 MPa, preferably 0.5 MPa-3 MPa.

[0062] Furthermore, the mass ratio of the composite catalyst solution to the methanol is (1-2):1000.

[0063] Furthermore, the calorific value of the mixed fuel gas prepared from each kilogram of the composite catalyst solution in a methanol mixture is 6800 kcal to 7050 kcal.

[0064] In one embodiment

[0065] A composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0066]

[0067] x is 1; y is 1; z is 0.5.

[0068] The preparation method of the above composite catalyst includes the following steps:

[0069] Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of composite catalyst.

[0070] Furthermore, the pH value of the humic acid aqueous solution is controlled at 6.3.

[0071] Furthermore, the mass ratio of the humic acid, ammonium bicarbonate, zinc chloride, aluminum nitrate, and deionized water is 0.5:0.2:0.2:0.2:1000.

[0072] Furthermore, the reaction temperature was room temperature, and the reaction time was 2 hours.

[0073] The composite catalyst is prepared by any one of the methods described above.

[0074] The method for preparing combustible gas involves dissolving the above-mentioned composite catalyst solution in methanol to obtain a mixture, and then reforming and gasifying the methanol into combustible gas.

[0075] Furthermore, the combustible gas is composed of one or more of hydrogen, carbon monoxide, methane, ethane, isopropane, and dimethyl ether.

[0076] Furthermore, the reaction temperature of the reforming gasification is controlled at 290°C, and the reaction pressure is controlled at 3 MPa.

[0077] Furthermore, the mass ratio of the composite catalyst solution to the methanol is 1:1000.

[0078] Furthermore, the calorific value of the mixed fuel gas prepared from each kilogram of the composite catalyst solution in a methanol mixture is 6800 kcal to 7050 kcal.

[0079] In another embodiment

[0080] A composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0081]

[0082] x is 2; y is 2; z is 2.

[0083] The preparation method of the above composite catalyst includes the following steps:

[0084] Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of composite catalyst.

[0085] Furthermore, the pH value of the humic acid aqueous solution is controlled at 6.7.

[0086] Furthermore, the mass ratio of the humic acid, ammonium bicarbonate, zinc chloride, aluminum nitrate, and deionized water is 1:0.4:0.4:0.4:1000.

[0087] Furthermore, the reaction temperature was room temperature and the reaction time was 4 hours.

[0088] The composite catalyst is prepared by any one of the methods described above.

[0089] The method for preparing combustible gas involves dissolving the above-mentioned composite catalyst solution in methanol to obtain a mixture, and then reforming and gasifying the methanol into combustible gas.

[0090] Furthermore, the combustible gas is composed of one or more of hydrogen, carbon monoxide, methane, ethane, isopropane, and dimethyl ether.

[0091] Furthermore, the reaction temperature of the reforming gasification is controlled at 350°C, and the reaction pressure is controlled at 0.5 MPa.

[0092] Furthermore, the mass ratio of the composite catalyst solution to the methanol is 2:1000.

[0093] Furthermore, the calorific value of the mixed fuel gas prepared from each kilogram of the composite catalyst solution in a methanol mixture is 6800 kcal to 7050 kcal.

[0094] In yet another embodiment:

[0095] A composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0096]

[0097] x is 1; y is 1; z is 1.

[0098] In another embodiment, a composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0099]

[0100] x is 1; y is 1; z is 1.5.

[0101] In another embodiment, a composite catalyst, named HA-Nx-Zny-Alz, has the following structural formula:

[0102]

[0103] x is 0.1; y is 0.1; z is 0.1.

[0104] The preparation method of the above composite catalyst includes the following steps:

[0105] Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of composite catalyst.

[0106] Furthermore, the pH value of the humic acid aqueous solution is controlled at 6.5.

[0107] Furthermore, the mass ratio of the humic acid, ammonium bicarbonate, zinc chloride, aluminum nitrate, and deionized water is 0.75:0.3:0.3:0.3:1000.

[0108] Furthermore, the reaction temperature was room temperature, and the reaction time was 3 hours.

[0109] The composite catalyst is prepared by any one of the methods described above.

[0110] The method for preparing combustible gas involves dissolving the above-mentioned composite catalyst solution in methanol to obtain a mixture, and then reforming and gasifying the methanol into combustible gas.

[0111] Furthermore, the combustible gas is composed of one or more of hydrogen, carbon monoxide, methane, ethane, isopropane, and dimethyl ether.

[0112] Furthermore, the reaction temperature of the reforming gasification is controlled at 330°C, and the reaction pressure is controlled at 1 MPa.

[0113] Furthermore, the mass ratio of the composite catalyst solution to the methanol is 1.5:1000.

[0114] Furthermore, the calorific value of the mixed fuel gas prepared from each kilogram of the composite catalyst solution in a methanol mixture is 6800 kcal to 7050 kcal.

[0115] Example 1

[0116] 1. Preparation of aqueous solution of composite catalyst

[0117] Add 0.6 g of humic acid to 1000 mL of deionized water to obtain an aqueous solution of humic acid. Adjust the pH of the aqueous solution of humic acid to 6.3, and then add 0.35 g of ammonium bicarbonate, 0.3 g of zinc chloride, and 0.3 g of aluminum nitrate to it. Stir well to obtain an aqueous solution of a catalyst, numbered 1#, formed by the reaction of nitrogen in ammonium bicarbonate, zinc in zinc chloride, aluminum in aluminum nitrate, and carboxyl functional groups on humic acid.

[0118] 2. Evaluation of catalysts

[0119] One gram of the prepared composite catalyst aqueous solution (numbered 1#) was added to one kilogram of methanol (industrial grade, ≥98.5 wt%) and stirred until homogeneous. The methanol mixture containing the composite catalyst was then passed through a stainless steel tank at 320 degrees Celsius under a pressure of 0.5 MPa. The mixed gas was collected at the tank outlet for gas chromatography analysis and calorific value analysis. The results are shown in Table 1. It is noted that one kilogram of methanol containing the composite catalyst can reform 2 cubic meters of mixed gas. The calorific value is expressed as per kilogram of methanol containing the composite catalyst.

[0120] Example 2

[0121] 1. Preparation of aqueous solution of composite catalyst

[0122] 0.6 g of humic acid was added to 1000 mL of deionized water to obtain an aqueous solution of humic acid. The pH of the aqueous solution of humic acid was adjusted to 6.5. Then, 0.3 g of ammonium bicarbonate, 0.3 g of zinc chloride, and 0.3 g of aluminum nitrate were added to it and stirred evenly to obtain an aqueous solution of composite catalyst No. 2, which was formed by the reaction of nitrogen in ammonium bicarbonate, zinc in zinc chloride, aluminum in aluminum nitrate, and carboxyl functional groups on humic acid.

[0123] 2. Evaluation of catalysts

[0124] 1.5 g of the prepared composite catalyst aqueous solution (numbered 2#) was added to 1 kg of methanol (industrial grade, ≥98.5 wt%) and stirred until homogeneous. The methanol mixture containing the composite catalyst was then passed through a stainless steel tank at 310°C under a pressure of 1 MPa. The mixed gas was collected at the outlet for gas chromatography analysis and calorific value analysis. The results are shown in Table 2. It is noted that each kilogram of methanol containing the composite catalyst can reform 2 cubic meters of mixed gas. The calorific value is expressed as per kilogram of methanol containing the composite catalyst.

[0125] Example 3

[0126] 1. Preparation of aqueous solution of composite catalyst

[0127] Add 0.75 g of humic acid to 1000 mL of deionized water to obtain an aqueous solution of humic acid. Adjust the pH of the aqueous solution of humic acid to 6.7, and then add 0.3 g of ammonium bicarbonate, 0.3 g of zinc chloride, and 0.3 g of aluminum nitrate to it. Stir well to obtain an aqueous solution of composite catalyst No. 3, which is formed by the reaction of nitrogen in ammonium bicarbonate, zinc in zinc chloride, aluminum in aluminum nitrate, and carboxyl functional groups on humic acid.

[0128] 2. Evaluation of catalysts

[0129] 1.2 g of the prepared composite catalyst aqueous solution (numbered 3#) was added to 1 kg of methanol (industrial grade, ≥98.5 wt%) and stirred until homogeneous. The methanol mixture containing the composite catalyst was then passed through a stainless steel tank at 290°C under a pressure of 2 MPa. The mixed gas was collected at the outlet for gas chromatography analysis and calorific value analysis. The results are shown in Table 3. It is noted that each kilogram of methanol containing the composite catalyst can reform 2 cubic meters of mixed gas. The calorific value is expressed as per kilogram of methanol containing the composite catalyst.

[0130] Table 1. Composition and calorific value of the mixed gas prepared in Example 1

[0131]

[0132] Table 2. Composition and calorific value of the mixed gas prepared in Example 2

[0133]

[0134] Table 3. Composition and calorific value of the mixed gas prepared in Example 3

[0135]

[0136]

[0137] The composite catalyst prepared in this invention uses humic acid as a complexing support, and ammonium salt, zinc salt, and aluminum salt are complexed onto humic acid to obtain a composite catalyst. As shown in Tables 1-3, the composite catalyst, after dissolving in methanol, can reformat and gasify methanol at 290-350°C and a pressure of 0.5-3 MPa. The gasification products include combustible gases such as hydrogen, carbon monoxide, methane, ethane, propane, and dimethyl ether. The calorific value of the mixed gas produced per kilogram of methanol containing this composite catalyst reaches 6800-7050 kcal, higher than the 4650 kcal calorific value of pure methanol.

[0138] Comparative tests and experimental data between the present invention and existing technologies

[0139] The humic acid used in this invention has a market price of about 10 yuan per kilogram, while the graphene oxide used in the prior art has a market price of tens of yuan per gram.

[0140] The combustible gas prepared by this invention contains between 2.14% and 3.12% carbon dioxide and between 22.25% and 24.35% carbon monoxide. In contrast, the combustible gas prepared by prior art [published invention patent "A method for preparing mixed gas from methanol and the catalyst used" (authorization announcement number: CN 115092886 B)] contains between 4.23% and 5.28% carbon dioxide and between 19.11% and 22.28% carbon monoxide. Therefore, by simultaneously introducing zinc salt into the catalyst, this invention can reduce the proportion of non-combustible carbon dioxide and increase the proportion of combustible carbon monoxide in the combustible gas.

[0141] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A composite catalyst, characterized in that, Its structural formula is as follows: in: 0 < x ≤ 2, x is preferably 1 or 2; 0 < y ≤ 2, where y is preferably 1 or 2; 0 < z ≤ 2, and z is preferably 0.5, 1, 1.5, or 2.

2. A method for preparing the composite catalyst according to claim 1, characterized in that, The steps are as follows: Humic acid is dissolved in deionized water to obtain an aqueous solution of humic acid. The aqueous solution of humic acid is then adjusted to acidity. Finally, ammonium bicarbonate, zinc chloride, and aluminum nitrate are added to the aqueous solution of humic acid and reacted at a certain temperature for a period of time to obtain a solution of the composite catalyst.

3. The method for preparing a composite catalyst as described in claim 2, characterized in that, The pH value of the humic acid aqueous solution is controlled between 6.3 and 6.

7.

4. The method for preparing a composite catalyst as described in claim 2, characterized in that, The mass ratio of humic acid, ammonium bicarbonate, zinc chloride, aluminum nitrate to deionized water is (0.5-1):(0.2-0.4):(0.2-0.4):(0.2-0.4):1000.

5. The method for preparing a composite catalyst as described in claim 2, characterized in that, The reaction temperature is room temperature, and the reaction time is at least 2 hours, preferably 2-4 hours.

6. A composite catalyst, prepared by the method described in any one of claims 2-5.

7. A method for preparing combustible gas, characterized in that, The composite catalyst of claim 1 or 6 is dissolved in methanol to obtain a mixture, and the methanol is reformed and gasified into a combustible gas.

8. The method for preparing combustible gas as described in claim 7, characterized in that, The combustible gas is composed of one or more of hydrogen, carbon monoxide, methane, ethane, isopropane, and dimethyl ether.

9. The method for preparing combustible gas as described in claim 7, characterized in that, The reaction temperature of the reforming gasification is controlled at at least 290°C, preferably 290-350°C, and the reaction pressure is controlled at at least 0.5 MPa, preferably 0.5 MPa-3 MPa.

10. The method for preparing combustible gas as described in claim 7, characterized in that, The mass ratio of the composite catalyst solution to the methanol is (1-2):1000.

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