Preparation method for producing hydrogen and nano carbon material by pressurizing and catalytic cracking of methane

Abstract

The invention relates to a preparation method of hydrogen and a nano-carbon material, in particular to a preparation method of hydrogen and a nano-carbon material by pressurized catalytic cracking of methane, which comprises the steps of pressurized purification of methane gas, pressurized catalytic cracking of methane and pressurized hydrogen separation. Airflow with certain pressure from the pressurized catalytic cracking reactor provides driving force required by the hydrogen separator for separating hydrogen, so that hydrogen and unconverted methane can be separated, and high-purity hydrogen is generated. The method disclosed by the invention is carried out under a pressurization condition, so that the treatment capacity of the reactor and the space-time yield of hydrogen and the nano carbon material can be greatly improved, and the production cost is greatly reduced, so that the maximization of economic benefits can be realized. The method is not only suitable for pressurized catalytic cracking of methane resources such as natural gas and liquefied natural gas to co-produce hydrogen and nano carbon materials, but also can be used for pressurized catalytic cracking of biological methane derived from biomass anaerobic fermentation to produce green hydrogen and green carbon materials, and has a wide application range.

Description

Technical Field

[0001] The invention relates to a method for preparing hydrogen and nano-carbon materials, in particular to a method for preparing hydrogen and nano-carbon materials by pressurized catalytic cracking of methane. Background Art

[0002] Clean and efficient utilization of fossil energy has become an important development direction in the transformation of energy structure. As one of the cleanest fossil energy sources, clean and efficient utilization of methane is regarded as one of the key technologies with good development prospects in energy transformation and has received widespread attention.

[0003] Methane reforming hydrogen production technology is one of the main industrial hydrogen production technologies in the world. This technology is based on the reforming reaction of methane with water vapor under high temperature, high pressure and catalyst conditions, but this technology has problems such as large investment, high energy consumption, high wastewater discharge and greenhouse gas emissions.

[0004] Compared with the methane reforming hydrogen production process, the methane cracking hydrogen production process has the advantage of not directly producing CO2. The H2 produced by the methane catalytic hydrogen production process is of high purity and has the potential to produce a variety of high-value carbon materials, such as amorphous carbon black to highly specialized graphene, carbon nanotubes and fibers, which can be widely used in rubber, batteries, chips and other fields. These high-value-added carbon materials can also generate considerable economic benefits, thereby shortening the investment payback time of process equipment. Methane cracking co-production of hydrogen and nanocarbon technology has been recognized as one of the most economically competitive CH4 utilization technologies in the future.

[0005] Compared with the simple high-temperature (above 1000 degrees) methane thermal cracking hydrogen production technology, the methane catalytic cracking hydrogen production process uses a catalyst, so it can be carried out under medium-high temperature conditions below 900 degrees, with lower energy consumption. However, the nano-carbon materials generated by the catalytic cracking of methane adhere to the metal particles, which will quickly deactivate the catalyst during the reaction, thereby reducing the methane single-pass conversion rate and the yield of hydrogen and nano-carbon materials.

[0006] At present, the invention patent with the announcement number CN118437343A has been published in China: a molten alloy catalyst for methane cracking to produce hydrogen and its preparation method and use, using one or more of Cu, Ni, Fe and Mo as catalytic metals, and one or more of Sn, Ga, Zn, Pb, Bi and In as metal additives, and reducing and passivating the composite metal oxide prepared by the melting method in a specific gas atmosphere for a long time to obtain a molten alloy catalyst for methane cracking to produce hydrogen. Although this alloy catalyst has a long life, its raw material cost is high and the preparation process is relatively complicated, so it is difficult to be widely used in industry.

[0007] There is also an invention patent with the announcement number CN117430084A: A method for preparing hydrogen by catalytic cracking of methane, using ore, zeolite, gravel, soil, smelting waste residue, slag, waste concrete, waste bricks, slag and waste metal containing metal elements such as aluminum, cobalt, nickel, copper, zinc and molybdenum as raw materials, and preparing a catalyst for preparing hydrogen by catalytic cracking of methane through ball milling, tableting and screening. Although this process can realize the cheap preparation and mass production of the catalyst, the heavy metal components therein will cause environmental pollution during the use of nano-carbon materials, so it is also difficult to obtain industrial application.

[0008] There is also an invention patent with publication number CN116251537A: a device for preparing metal-carbon materials by methane cracking method and its preparation method, using foamed metal washed with ethanol and strong acid as a catalyst for methane cracking reaction. This catalyst preparation process uses strong acid, which will produce a certain amount of acidic wastewater that needs to be treated, so it is difficult to obtain a relatively cheap catalyst for industrial application.

[0009] As mentioned above, the current development of methane catalytic cracking hydrogen production technology in China is mainly focused on the direction of catalyst preparation technology. The catalyst performance test examples listed in the existing public patents are all carried out under normal pressure. There are no implementation cases of methane pressurized catalytic cracking and the development of pressurized catalytic cracking hydrogen production processes. The practical application of methane catalytic cracking hydrogen production technology not only needs to consider the maximization of catalyst performance and efficiency, but also needs to pursue the maximization of the economic benefits of the entire process including operating units such as raw gas purification and product hydrogen separation. These problems have not yet been paid attention to and solved in practical applications, which has also limited the large-scale commercialization of methane cracking co-production of hydrogen and nano-carbon material technology. Summary of the invention

[0010] The purpose of the present invention is to provide a method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure. The present invention increases the raw gas processing capacity of the reactor by multiples by increasing the reaction pressure, thereby promoting the heat and material transfer efficiency in the reactor, thereby greatly improving the macro cracking rate of methane and the space-time yield (absolute yield) of hydrogen and nano-carbon materials. At the same time, the pressure of the pressurized product gas flow is used as a driving force to achieve efficient separation of hydrogen and methane that does not participate in the reaction and hydrogen purification. The economic benefits of the methane cracking co-production of hydrogen and nano-carbon materials process, which includes raw methane gas purification, methane catalytic cracking and hydrogen separation, are maximized, rather than only considering the efficiency maximization of the methane cracking reactor.

[0011] The present invention adopts the following technical solutions: A method for preparing hydrogen and nano-carbon materials by pressurized catalytic cracking of methane, comprising a pressurized purification or separation zone (or pressurized zone) for raw methane gas, a pressurized catalytic cracking reaction zone (pressurized cracking reactor) and a pressurized separation and purification zone (hydrogen separator) for gaseous product hydrogen.

[0012] The methane raw gas is sequentially subjected to three processes of raw methane gas pressurization and purification, pressurized catalytic cracking reaction and hydrogen separation and purification to achieve efficient utilization of methane and faster output rate of hydrogen and nano-carbon materials.

[0013] The pressurized purification of the raw methane gas is to purify the volume concentration of methane in the methane raw gas to 50-100%; The pressure purification is to separate and purify the methane in the raw gas by increasing the pressure, so that the subsequent methane pressure catalytic cracking can be carried out efficiently; The pressurized catalytic cracking reaction is to perform pressurized catalytic cracking of the purified methane in a reactor, and the methane undergoes cracking reaction under high temperature and catalyst to generate hydrogen (H2) and nano-carbon materials; the hydrogen separation and purification is to separate the hydrogen after the pressurized catalytic cracking reaction and the unconverted methane gas under pressurized conditions, and transport the methane that does not participate in the reaction to the inlet end of the pressurized catalytic cracking reactor, and obtain high-purity hydrogen at the same time; The combination of the above three processes achieves efficient conversion of methane and greatly improves the space-time yield (yield) of hydrogen and nanocarbon materials.

[0014] The main technical elements of the process for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure are to control the temperature and pressure of the methane cracking reaction. The reaction temperature affects the methane conversion rate, and the reaction pressure affects the raw gas processing capacity of the reactor and the time-space yield of the product. The two work together to control the yield of the methane pressurized catalytic cracking reaction product and achieve efficient conversion of methane.

[0015] The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure, wherein the pressurization refers to increasing the pressure of the raw gas entering the process system (including a methane pressurized separation purifier, a catalytic cracking reactor and a hydrogen separator) to 0.1MPa-1MPa, preferably 0.2MPa-0.8MPa, and most preferably 0.4MPa-0.6MPa.

[0016] In the method for preparing hydrogen and nano-carbon materials by pressurized catalytic cracking of methane, the temperature in the pressurized catalytic cracking reactor is 700-850°C, preferably 720-820°C, and most preferably 730-760°C.

[0017] The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure, wherein the methane raw gas is a mixture of methane and other gases with a methane volume concentration of 50% or more; other gases include but are not limited to hydrogen, carbon monoxide, nitrogen, carbon dioxide, hydrogen sulfide and siloxane, etc.; wherein the volume concentration of carbon dioxide in the methane raw gas is less than 10%, the volume concentration of hydrogen sulfide is less than 1000ppm, and the volume concentration of siloxane is less than 500ppm. The raw methane gas composition preferably has a methane volume concentration of 80%-100%, preferably a methane volume concentration of 0%-5% of carbon dioxide, preferably a hydrogen sulfide volume concentration of less than 200ppm, and preferably a siloxane volume concentration of less than 100ppm.

[0018] In the method for preparing hydrogen and nano-carbon materials by pressurized catalytic cracking of methane, the pressurized catalytic cracking reactor is selected from, for example, but not limited to, moving bed, rotating bed or molten liquid metal bed and other reactors.

[0019] The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure, wherein the catalyst used for the catalytic cracking reaction of methane under pressure includes but is not limited to iron-based catalysts, iron-copper-based catalysts, iron-palladium-based catalysts, preferably iron-supported catalysts.

[0020] The method for preparing hydrogen and nano-carbon materials by pressurized catalytic cracking of methane, the reducing gas used in the catalyst activation process in the initial stage of the pressurized catalytic cracking reaction of methane includes but is not limited to methane (CH4), a mixed gas of methane and hydrogen, etc., preferably a mixed gas of hydrogen and methane with a hydrogen volume concentration of less than 10%, and most preferably a mixed gas of hydrogen and methane with a hydrogen volume concentration of less than 2%.

[0021] The present invention has the following beneficial effects: First, the process is simple. Increasing the pressure can double the raw gas processing capacity of the methane catalytic cracking reactor, and also promote the heat and material transfer efficiency in the reactor, thereby significantly improving the macroscopic reaction rate of methane catalytic cracking. Second, increasing the pressure can significantly increase the space-time yield of hydrogen and nanocarbon materials in a single methane catalytic cracking reactor and reduce the investment cost of process equipment; Third, increasing the pressure can greatly improve the methane purification efficiency and hydrogen separation efficiency of the raw gas, thereby greatly improving the economic efficiency of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are partial embodiments of the present invention.

[0023] Figure 1 This is a process for producing hydrogen and nano-carbon materials by pressurizing and catalytically cracking methane using methane feed gas containing carbon dioxide, hydrogen sulfide, etc. in an embodiment of the present invention; Figure 2 This is a process diagram of producing hydrogen and nano-carbon materials by pressurizing methane in an embodiment of the present invention; Figure 3 is a curve showing the change of methane conversion rate over reaction time in Example 2 of the present invention; Figure 4 The curve showing the change of methane conversion rate with reaction time in Example 3 of the present invention; Figure 5 The curve showing the change of methane conversion rate with reaction time in Example 4 of the present invention; Figure 6 This is a curve showing the change of methane conversion rate over reaction time in Example 5 of the present invention; Figure 7 This is the TG graph of the product nanocarbon material of Example 5 of the present invention; Figure 8 This is the SEM image of the product nanocarbon material of Example 5 of the present invention.

[0024] Reference numerals in the figure: methane raw gas storage tank 1, methane pressurized separation device 2, methane pressurized catalytic cracking reaction device 3, pressurized hydrogen separation device 4, hydrogen storage tank 5, CO2 and other gas storage tower hydrogen storage tank 6, nano-carbon material storage tank 7. DETAILED DESCRIPTION

[0025] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows: Example 1

[0026] This embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane. Figure 2 As shown, it includes a methane raw gas storage tank 1, a methane pressurized separation device 2, a methane pressurized catalytic cracking reaction device 3, a pressurized hydrogen separation device 4, a hydrogen storage tank 5, a CO2 and other gas storage tower hydrogen storage tank 6, and a nano-carbon material storage tank 7. Example 2

[0027] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 720° C., the reaction pressure is 0.1 MPa, the weight of the iron-supported catalyst is 0.2 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0028] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the output of nano-carbon materials finally obtained by cracking is 3.1g. Example 3

[0029] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 720° C., the reaction pressure is 0.2 MPa, the weight of the iron-supported catalyst is 0.2 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0030] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 8.5 g. Example 4

[0031] In the embodiment, the volume concentration of methane in the raw material gas is 99.99%, the reaction temperature is 740° C., the reaction pressure is 0.4 MPa, the weight of the iron-supported catalyst is 0.2 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0032] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 12.7 g. Example 5

[0033] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 720° C., the reaction pressure is 0.4 MPa, the weight of the iron-supported catalyst is 0.2 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0034] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 11.8 g. Example 6

[0035] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 720° C., the reaction pressure is 0.6 MPa, the weight of the iron-supported catalyst is 0.2 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0036] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 13.3 g. Example 7

[0037] In the embodiment, the volume concentration of methane in the raw gas is 100%, the reaction temperature is 740° C., the reaction pressure is 0.4 MPa, the weight of the iron-supported catalyst is 0.4 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0038] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 22.8 g. Example 8

[0039] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 760° C., the reaction pressure is 0.6 MPa, the weight of the iron-supported catalyst is 0.4 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0040] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 22.6 g. Example 9

[0041] In the embodiment, the volume concentration of methane in the raw gas is 99.99%, the reaction temperature is 760° C., the reaction pressure is 0.6 MPa, the weight of the iron-supported catalyst is 0.6 g, and the weight percentage of iron oxide in the iron-supported catalyst is 80%.

[0042] The present embodiment provides a process for producing hydrogen and nano-carbon materials by pressurizing methane, including methane gas pressurization, methane catalytic cracking and hydrogen separation; wherein, methane gas pressurization and methane catalytic cracking reactions are both carried out in a tubular fixed bed, and catalyst activation and pressurized catalytic cracking reactions are completed in a methane atmosphere; the methane conversion rate when the reaction is completed is 20%, and the final yield of nano-carbon materials is 32.5 g.

[0043] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0044] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0045] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0046] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure, characterized in that: The methane raw gas of the method is sequentially subjected to three steps of pressurized separation and purification, pressurized catalytic cracking reaction and pressurized hydrogen separation to achieve efficient conversion of methane and efficient output of hydrogen and nano-carbon materials; The preparation process includes the following: (1) The methane concentration of the methane raw gas under pressure is 50-100% by volume. The methane in the raw gas is separated and purified by increasing the pressure, so that the subsequent methane pressure catalytic cracking can be carried out efficiently. (2) Pressurized catalytic cracking reaction: The pressurized purified methane is subjected to pressurized catalytic cracking in the reactor. Under the action of high temperature and catalyst, methane undergoes cracking reaction to generate hydrogen (H2) and nano-carbon materials. (3) Pressurized hydrogen separation and purification is to separate the gas after the pressurized catalytic cracking reaction, separate the methane that does not participate in the reaction from the product gas flow and transport it back to the inlet of the pressurized catalytic cracking reactor to mix with the methane gas from the pressurized purification separator, and obtain high-purity hydrogen at the same time; the combination of the above three processes can achieve efficient conversion and utilization of methane, greatly improve the time and space yield of hydrogen and nano-carbon materials, that is, the output of hydrogen and nano-carbon materials per unit time and unit reactor volume.

2. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The pressurization is to increase the pressure of the raw gas entering the process system to a specific pressure, which ranges from 0.1 MPa to 1.0 MPa, preferably 0.2 MPa to 0.8 MPa, and most preferably 0.4 MPa to 0.6 MPa.

3. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The temperature in the pressurized catalytic cracking reactor is 700-850°C, preferably 720-820°C, most preferably 730-760°C.

4. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The methane raw gas is a mixture of methane and other gases with a methane volume concentration of 50% or more; other gases include but are not limited to hydrogen, carbon monoxide, nitrogen, carbon dioxide, hydrogen sulfide and siloxane; wherein the volume concentration of carbon dioxide in the methane raw gas is less than 10%, the volume concentration of hydrogen sulfide is less than 1000ppm, and the volume concentration of siloxane is less than 500ppm; the raw methane gas composition preferably has a methane volume concentration of 80%-100%, preferably a methane volume concentration of 0%-5% of carbon dioxide, preferably a hydrogen sulfide volume concentration of less than 200ppm, and preferably a siloxane volume concentration of less than 100ppm.

5. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The pressurized catalytic cracking reactor can be selected including but not limited to a moving bed, a rotating bed or a molten liquid metal bed reactor.

6. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The catalyst in the methane pressure catalytic cracking reaction includes but is not limited to an iron-based catalyst, an iron-copper-based catalyst, an iron-palladium-based catalyst, and is preferably an iron-supported catalyst.

7. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 6, characterized in that: The iron-supported catalyst has an iron oxide (Fe2O3) weight content of 20-95%, preferably an iron oxide (Fe2O3) weight content of 60-95%, and most preferably an iron oxide (Fe2O3) weight content of 80-95%.

8. The method for preparing hydrogen and nano-carbon materials by catalytic cracking of methane under pressure according to claim 1, characterized in that: The reducing gas used in the initial catalyst activation process of the methane pressurized catalytic cracking reaction includes but is not limited to methane (CH4), a mixed gas of methane and hydrogen, preferably a mixed gas of hydrogen and methane with a hydrogen volume concentration of less than 10%, and most preferably a mixed gas of hydrogen and methane with a hydrogen volume concentration of less than 2%.

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