Coral reef-shaped bifunctional catalyst for preparing green hydrogen through biomass gasification and synchronously decarbonizing as well as preparation method and application of coral reef-shaped bifunctional catalyst

Abstract

The invention provides a coral reef-shaped bifunctional catalyst for preparing green hydrogen through biomass gasification and synchronously decarbonizing and a preparation method of the coral reef-shaped bifunctional catalyst, and belongs to the field of biomass high-value utilization. The activity and the stability of the catalyst are improved by regulating and controlling the mutual matching of the active phase and the carrier through the falling position of the active metal; the coral reef-shaped bifunctional catalyst is directionally constructed, and a confinement environment required by bond breaking and CO2 conversion is provided by utilizing the unique spatial configuration of the carrier. The catalyst utilizes a green hydrogen production active center to directionally break bonds in a thermochemical conversion process, so that the content of green hydrogen in synthesis gas is increased; cO2 in the synthesis gas is absorbed and converted by using a decarburization active center, and the content of CO2 at an outlet of the reactor is reduced. The bifunctional catalyst prepared by the invention has relatively high activity and cycling stability, two reaction processes (bond breaking, decarbonylation and water gas shift reaction) are coupled to realize preparation of high-H2 / CO (3.84) synthesis gas through biomass thermochemical conversion, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation and high-value utilization of biomass, and specifically relates to a coral reef-like bifunctional catalyst for biomass gasification to produce green hydrogen with simultaneous decarbonization and a preparation method thereof, and also relates to the application of the above-mentioned coral reef-like bifunctional catalyst in the preparation of bio-based hydrogen-rich synthesis gas. Background Art

[0002] Hydrogen energy is a zero-carbon, clean and efficient energy source. At present, direct reforming of fossil fuels is the main way to supply hydrogen, accounting for about 96% of the global hydrogen source and 98.5% of the domestic hydrogen source. The huge fossil fuel hydrogen production industry has produced at least 300 million tons of carbon emissions and faces huge pressure for low-carbon transformation. Biomass is the only renewable carbon source on the earth. my country's biomass resource potential is equivalent to 1 billion tons of standard coal, and it has great potential for large-scale green hydrogen production. The total amount of biomass resources that can be utilized in my country each year is about 460 million tons of standard coal. In addition to 40% used as feed, fertilizer and industrial raw materials, about 60% has not been effectively utilized. Therefore, producing hydrogen with biomass as raw material has become an important way to alleviate the energy crisis.

[0003] Pyrolysis is an important method for biomass resource utilization, which converts biomass into hydrogen-rich gas products through high temperature. However, the high oxygen and water content of biomass leads to the high concentration of CO in the pyrolysis syngas. 2 High content, green hydrogen yield and H 2 / CO is low. Current research mainly focuses on improving the hydrogen yield in synthesis gas by developing reactors and optimizing reaction conditions, but the hydrogen production efficiency has not been significantly improved. Compared with pyrolysis, catalytic pyrolysis has the advantages of short reaction time and high hydrogen yield, obvious technical advantages and broad industrialization prospects.

[0004] Although catalytic pyrolysis technology can improve hydrogen production efficiency, there are still many key issues, especially the development of catalysts suitable for large-scale application, good activity, and high hydrogen selectivity. Current research has found that precious metal catalysts have high catalytic activity, but their high price limits large-scale application; non-precious metal (alkali metals, alkaline earth metals and transition metals) catalysts are deactivated by carbon deposition during the thermochemical conversion process, resulting in low hydrogen production efficiency and high tar content.

[0005] Based on this, starting from the characteristics of the products of biomass thermochemical conversion, in order to realize the thermochemical conversion of biomass to produce high-purity green hydrogen, it is necessary to construct a catalyst with two types of active centers: low cost, good stability, high activity, easy regeneration, resistance to carbon deposition, and coupled hydrogen production and decarbonization. Summary of the invention

[0006] One of the objectives of the present invention is to provide a preparation method of a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneously decarbonize, which has low cost, good stability, high activity, easy regeneration, anti-coking property, and couples two types of active centers for hydrogen production and decarbonization.

[0007] Another objective of the present invention is to provide a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneously decarbonize, which has low cost, good stability, high activity, easy regeneration, anti-coking property, and couples two types of active centers for hydrogen production and decarbonization.

[0008] A further objective of the present invention is to provide an application of the coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneously decarbonize in the production of bio-based hydrogen-rich syngas.

[0009] The technical solution adopted by the present invention to achieve the first objective is as follows: providing a preparation method of a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneously decarbonize, comprising the following steps: S1. The alumina support is subjected to acid leaching, calcination, and grinding to obtain an activated alumina support; magnesium oxide is subjected to calcination and grinding to obtain activated magnesium oxide. S2. The activated alumina support and the activated magnesium oxide are mixed to obtain a composite support. S3. The composite support, the iron active phase precursor, and the nickel active phase precursor are placed in water and fully mixed, and after drying, they are subjected to calcination and grinding to obtain a coral reef-shaped bifunctional catalyst.

[0010] The general idea and invention principle of the present invention are as follows: Aiming at the deficiencies of existing catalysts in the production of bio-based hydrogen-rich syngas, the preparation method provided by the present invention constructs a coral reef-shaped bifunctional catalyst, which realizes the continuous and efficient production of high-H 2 / CO syngas from biomass by means of two types of active centers for hydrogen production and decarbonization in the catalyst.

[0011] The composite support of the present invention adopts a dual-support mode formed by "activated alumina support + activated magnesium oxide". Among them, the alumina support is activated by calcination and acid leaching, has a special regular tetrahedral structure and abundant oxygen vacancies, and the active metals iron and nickel are anchored on the oxygen vacancies of the activated alumina support as the active centers for hydrogen production. The metal anchoring makes the catalyst structure more stable. After five cycles and regenerations, the catalyst can still maintain the special coral reef-like morphology and maintain high catalytic activity. At the same time, the activated magnesium oxide support serves as a decarbonization center. In the application of catalytic preparation of hydrogen-rich syngas, by taking one oxygen atom from CO 2 to form a MgO(O) intermediate, thereby realizing the deoxygenation of carbon dioxide (MgO + CO 2→MgO(O) + CO). Compared with other decarbonization materials (such as CaO), activated magnesium oxide basically does not undergo carbonation reactions during the decarbonization process. During multiple cycles, it always maintains its original morphological structure and high activity, and has excellent cycle stability.

[0012] Starting from the preparation method, the preparation method of the catalyst provided by the present invention has the advantages of simple process, mild conditions, relatively cheap precursors and solvents, short cycle, and low equipment requirements; starting from the characteristics of the catalyst itself, the catalyst has the characteristics of low active metal loading, good dispersion, and stable structure. At the same time, the active phase of the catalyst is a transition metal, and compared with noble metal catalysts, the production cost is low; starting from the function, the catalyst has the advantages of high hydrogen production and decarbonization activity, easy regeneration, and anti-coking.

[0013] Further, in step S1, the alumina support is γ-Al 2 O 3 ; compared with other supports, γ-Al 2 O 3 has higher activity in biomass catalytic conversion. The acid leaching is carried out using a nitric acid solution with a concentration of 0.1 - 2 mol / L, and the acid leaching time is 2 - 4 h; the calcination temperature of the alumina support is 600 - 900 °C, and the time is 2 - 4 h. The calcination is carried out in an inert atmosphere.

[0014] Further, in step S1, the calcination temperature of magnesium oxide is 700 - 900 °C, and the time is 1.5 - 3.5 h. The calcination is carried out in an inert atmosphere.

[0015] Further, in step S2, in the composite support, the mass ratio of the activated alumina support to the activated magnesium oxide is 1:4 - 4:1. In the composite support provided by the present invention, the structure of alumina itself is relatively stable, but its activity is generally average. In order to make full use of the spatial configuration of alumina to load active metals, the mass ratio of the alumina support to the magnesium oxide support is set within the above range. Preferably, in the composite support, the mass ratio of the activated alumina support to the activated magnesium oxide is 1:1 - 1:4. Under this condition, the composite support not only has special morphology and structural features that provide oxygen vacancies, but also has sufficient decarbonization active centers.

[0016] Further, in step S3, the active phase precursor of iron includes soluble iron salts, and the active phase precursor of nickel includes soluble nickel salts. Among them, the soluble iron salts include one or a combination of ferric nitrate, ferric chloride, and ferric sulfate; the soluble nickel salts include one or a combination of nickel chloride, nickel sulfate, and nickel acetate.

[0017] Further, in step S3, in the iron active phase precursor and the nickel active phase precursor, the molar ratio of iron element to nickel element is 1:3 - 3:1. During the preparation of the catalyst, through the calcination treatment in step S3, the active components iron and nickel will combine to form an alloy. Among them, iron itself has weak activity, and if the content is too much, it will agglomerate and cause the catalyst to deactivate; while nickel has high activity but is easily deactivated due to poisoning. Through a large number of research and explorations in the present invention, combined with the design and research of different molar ratios, it is found that within the above range, both iron and nickel can maintain good activity. Preferably, when the molar ratio of iron and nickel elements is 1:1, Fe 0.64 Ni 0.36 alloy phase is more likely to form and better catalytic activity is obtained.

[0018] Further, in step S3, the mixing is carried out under the stirring condition with a rotation speed of 600 - 900 r / min, the mixing temperature is 60 - 100 °C, and the time is 2 - 3 h; the calcination is carried out in an inert atmosphere, the calcination temperature is 700 - 900 °C, and the time is 3 - 4 h.

[0019] The technical solution adopted by the present invention to achieve the second object is: to provide a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneous decarbonization, which is prepared by the preparation method according to the first object of the present invention.

[0020] The coral reef-shaped bifunctional catalyst includes a γ-Al 2 O 3 support with a regular tetrahedron structure and an active MgO support for decarbonization; the active metals iron and nickel are anchored on the oxygen vacancies of the γ-Al 2 O 3 support, and the loading amounts of the active metals iron and nickel relative to the total weight of the catalyst are 8 wt.% - 10 wt.%.

[0021] The technical solution adopted by the present invention to achieve the third object is to provide an application of the coral reef-shaped bifunctional catalyst according to the second object of the present invention in the production of bio-based hydrogen-rich syngas.

[0022] Further, the application includes: mixing the dried biomass raw material and the coral reef-shaped bifunctional catalyst in a certain proportion, using water as the gasifying agent, and carrying out a pyrolysis reaction to obtain hydrogen-rich syngas; in the hydrogen-rich syngas, the molar ratio of H 2 to CO is 2 - 4.

[0023] Further, in the application, the mass ratio of the dried biomass raw material to the coral reef-shaped bifunctional catalyst is 1:0.1 - 1.5; the biomass raw material includes one or more combinations of wheat straw, corn straw, rice straw, and bagasse.

[0024] Further, in the pyrolysis reaction, the reaction temperature is 400 - 700 °C; the reforming heater temperature is 600 - 900 °C. The pyrolysis heater uses a three-stage tubular furnace, and its heating temperatures from top to bottom are 750 - 900 °C, 650 - 800 °C, and 500 - 700 °C respectively; the injection amount of the gasifying agent water and the mass ratio of the biomass raw material is 1.6 - 9.8 mg / g.

[0025] Preferably, before the reaction, the bed velocity of the carrier gas (nitrogen) passing through the catalyst is 0.04 - 0.30 m / min, and during the reaction process, it is set to 0.02 - 0.13 m / min; the flow rate of the gasifying agent water is maintained at 0.08 - 0.48 mL / min, and the corresponding nitrogen flow rate is 0.04 - 0.30 m / min.

[0026] In some preferred embodiments, in the coral reef-shaped bifunctional catalyst, the mass ratio of the active γ-Al 2 O 3 support to the active MgO support is 1:4, the loading amounts of the active metals iron and nickel relative to the total weight of the catalyst are 9 wt.%, and the elemental molar ratio of iron and nickel is 1:1. In the application of producing bio-based hydrogen-rich syngas, this catalyst couples two processes of bond breaking, decarbonylation, and water-gas shift to achieve a molar ratio of H 2 to CO in the hydrogen-rich syngas of 3.84.

[0027] Further, the application also includes: the deactivated catalyst after use is subjected to combustion treatment to obtain a regenerated catalyst. The temperature of the combustion treatment is 600 - 800 °C, and the time is 30 - 80 min. Through the combustion treatment, the carbon deposition on the catalyst surface can be removed, making it regain its activity, and thus realizing regeneration.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and synchronous decarbonization provided by the present invention adopts an impregnation-high temperature calcination method. By regulating the mutual matching of the active phase and the support through metal deposition, a coral reef-shaped catalyst is constructed directionally. This preparation method has a simple process, mild conditions, relatively inexpensive precursors and solvents, a short preparation cycle, and common equipment, and can be mass-produced.

[0029] (2) The coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and synchronous decarbonization prepared by the present invention uses a composite support composed of an active alumina support and an active magnesia support, and has double active centers for producing green hydrogen and decarbonization. Among them, by using the active center for producing green hydrogen, bond breaking is directed during the thermochemical conversion process to increase the content of green hydrogen in the syngas; by using the decarbonization active center of the catalyst, CO in the syngas is absorbed and converted 2 , reducing CO at the reactor outlet 2Content. In addition, the unique spatial configuration of the carrier provides a confined environment required for bond breaking and CO 2 conversion. The coral reef-like bifunctional catalyst prepared in the present invention has the characteristics of low active metal loading, good dispersion, and good structural stability. The active phase of this catalyst is a transition metal, and compared with noble metal catalysts, the production cost is low.

[0030] (3) The bifunctional catalyst prepared in the present invention has a special coral reef-like morphology. This coral reef-like bifunctional catalyst exhibits excellent performance in the process of biomass thermochemical conversion to produce hydrogen-rich syngas, and has the characteristics of good catalytic activity, high stability, and strong anti-coking ability. When this coral reef-like bifunctional catalyst is used for biomass thermochemical conversion, through the coupling of two processes of green hydrogen production by chemical bond breaking, decarbonylation, and water gas shift, high H 2 / CO (molar ratio of 3.84) syngas is prepared directionally, realizing the high-value utilization of biomass resources, and having broad popularization and application prospects. Description of the Drawings

[0031] Figure 1 is a schematic flow chart of a preparation method of a coral reef-like bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneous decarbonization provided by an embodiment of the present invention; Figure 2 is the surface electron microscope scanning image of the 3Fe1Ni / 1MgO4Al 2 O 3 catalyst prepared in Example 1; among them, a-b are SEM images; c is a TEM image; Figure 3 is the gas product distribution diagram in the syngas prepared in the application of the catalyst prepared in Example 1; among them, a is the gas product distribution with different amounts of gasifying agent (H 2 O) injection; b is the comparison diagram of H 2 / CO of fresh catalyst, recycled and regenerated; Figure 4 is the gas product distribution diagram (without adding gasifying agent) under different active phase and carrier ratio conditions in Examples 1-9; Figure 5 is the real-time gas distribution curve in the syngas under the action of the catalyst provided in Example 1 (without adding gasifying agent); Figure 6 is the real-time gas distribution curve in the syngas under the action of the catalyst provided in Example 8 (without adding gasifying agent); Figure 7 is the gas product distribution and catalyst crystal type after cycling and regeneration of the catalyst provided in Example 8 under the action of the gasifying agent; among them, a is the gas product distribution after 5 cycles and regeneration of the catalyst; b is the catalyst crystal type after 5 cycles and regeneration; Figure 81Fe1Ni / 4MgO1Al prepared in Example 8 2 O 3 EDX-mapping diagram of the catalyst; Figure 9 1Fe1Ni / 4MgO1Al prepared in Example 8 2 O 3 EPR analysis diagram of the catalyst; Figure 10 1Fe1Ni / 4MgO1Al prepared in Example 8 2 O 3 SEM-EDX analysis diagram of the catalyst. Detailed implementation manners

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0033] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0034] The embodiment of the present invention provides a preparation method of a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneous decarbonization. The process schematic diagram is as Figure 1 shown, and includes the following steps: Step 1: The alumina support is subjected to acid leaching, calcination and grinding to obtain an activated alumina support; magnesium oxide is subjected to calcination and grinding to obtain activated magnesium oxide; wherein, the alumina support adopts γ-Al 2 O 3 ; The acid leaching uses a nitric acid solution with a concentration of 0.1-2 mol / L, and the acid leaching time is 2-4 h; the calcination temperature of the alumina support is 600-900 °C, and the time is 2-4 h. The calcination temperature of magnesium oxide is 700-900 °C, and the time is 1.5-3.5 h; the calcination is carried out in an inert atmosphere.

[0035] Step 2: The activated alumina support and the activated magnesium oxide are mixed according to a mass ratio of 1:4-4:1 to obtain a composite support.

[0036] Step 3: Place the composite support, the iron active phase precursor, and the nickel active phase precursor in water and mix them thoroughly. After drying, calcine and grind them to obtain a coral reef-shaped bifunctional catalyst. Among them, the iron active phase precursor includes a soluble iron salt, and the nickel active phase precursor includes a soluble nickel salt; in the iron active phase precursor and the nickel active phase precursor, the molar ratio of iron element to nickel element is 1:3 - 3:1; the mixing is carried out under stirring conditions with a rotation speed of 600 - 900 r / min, the mixing temperature is 60 - 100 °C, and the time is 2 - 3 h; the calcination is carried out in an inert atmosphere, the calcination temperature is 700 - 900 °C, and the time is 3 - 4 h.

[0037] A coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneous decarbonization prepared in an embodiment of the present invention includes a γ-Al 2 O 3 support with a regular tetrahedron structure and an active MgO support for decarbonization; active metals iron and nickel are anchored on the oxygen vacancies of the γ-Al 2 O 3 support, and the loading amounts of active metals iron and nickel relative to the total weight of the catalyst are 8 wt.% - 10 wt.%.

[0038] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the present invention.

[0039] In each embodiment of the present invention, for the convenience of comparison, the total weight of the composite support is controlled to be 1 g, the total weight of active metals iron and nickel is 0.1 g, and the loading amounts of active metals iron and nickel relative to the total weight of the catalyst are 9 wt.%. The specific composition of the composite support and the contents of active metals iron and nickel are shown in Table 1.

[0040] Table 1

[0041] Example 1 This example provides a preparation method of a coral reef-shaped bifunctional catalyst for biomass gasification to produce green hydrogen and simultaneous decarbonization, including the following steps: Step 1: Stir 10 g of γ-Al 2 O 3 in 1 mol / L HNO 3 solution for 3 hours, then rinse with deionized water until neutral, dry in an oven at 105 °C, and calcine in an N 2 (99.99%) atmosphere at 900 °C for 3 h with a flow rate of 50 mL / min to obtain an activated γ-Al 2 O 3 support; place the MgO powder in an N 2 atmosphere and calcine at 800 °C for 2.5 h to obtain an activated magnesium oxide support.

[0042] Step 2: Take 0.8 g of activated γ-Al 2 O 3 support and 0.2 g of activated MgO and mix them to obtain 1 g of composite support.

[0043] Step 3: Select Ni(NO 3 ) 2 •6H 2 O and Fe(NO 3 ) 3 •9H 2 O as catalyst precursors. Dissolve 0.5244 g of Fe(NO 3 ) 3 •9H 2 O and 0.1250 g of Ni(NO 3 ) 2 •6H 2 O in 10 mL of deionized water, stir well, and after complete dissolution, add it to 1 g of the composite support. Stir the suspension continuously at 60 °C for 2 hours, then transfer it to an oven at 105 °C until the water is completely evaporated. After the product is dried, calcine it in a nitrogen atmosphere at 800 °C for 3 hours, and grind it to obtain a light yellow 3Fe1Ni / 1MgO4Al 2 O 3 catalyst. The SEM and TEM images of the catalyst are as shown in Figure 2 shown.

[0044] Examples 2 - 9 The preparation methods and processes of Examples 2 - 9 are basically the same as those of Example 1, except that Examples 2 - 9 prepare the catalysts according to the composition and dosage of the composite support and the content of the active metal shown in Table 1 respectively.

[0045] Application Examples (I) Catalytic activity test of the catalyst This application example examines the application performance of the catalysts prepared in each example in the production of bio-based hydrogen-rich syngas. The specific test method is as follows: Use the catalyst for the thermal conversion of biomass to hydrogen-rich syngas, including the following process: Prepare 1.0 g of wheat straw with a particle size of 60 - 80 mesh and 1.0 g of the catalyst prepared in each example according to the mass ratio of biomass raw material to coral reef-like catalyst of 1:1. The application experiment is carried out in a three-stage fixed-bed reactor. First, install the reaction device, check the airtightness of the equipment, and continuously blow N 2There is no oxygen up to the gas outlet. Then, adjust the temperature controller panel to heat the reactor to the required temperature. The temperature of the upper section is 600 °C, and the pyrolysis temperature of the lower section is 800 °C. After the set temperature is reached, the gasifying agent at 4.8 mg / g (0.24 mL / min) is introduced into the reactor together with the carrier gas (N 2 ) at a bed velocity of 0.11 m / min (200 mL / min).

[0046] Place 1 g of the pre-prepared catalyst on the top, and put 1 g of biomass into a quartz crucible and fix it at the bottom. Then push the basket and the quartz crucible into the reactor, and the reaction time is 40 min. After the reaction is completed, turn on the cooling system, connect the gas on-line monitoring device to the dryer, and simultaneously detect the gas composition in the reactor. The gas composition is quantitatively analyzed by a gas analyzer.

[0047] The syngas production is calculated according to formula (1).

[0048] (1) where i represents different components in the syngas, such as H 2 , CO, CO 2 or CH 4 ; m represents the mass of the raw materials for each experiment; X i (mL / g) represents the real-time yield of the syngas; t represents the reactor time; Y i (mol / g) represents the total yield of the syngas.

[0049] H 2 / CO is an important index for evaluating the reactor effect, and it is calculated according to formula (2): (2) where C H2 , C CO (Vol. %) represents the volume concentration of H 2 , CO in the syngas.

[0050] Figures 3 - 6 Shows the content of each component in the syngas and H 2 / CO under the action of the catalysts prepared in Examples 1-9. Table 2 shows the yields of each combination in the syngas in the above application (without adding the gasifying agent, only the effects of the catalysts in bond breaking and decarbonylation in Process 1) for Examples 1-9 and the blank sample without adding the catalyst.

[0051] Table 2

[0052] From Table 2 and Figures 3 - 6 it can be seen that Compared with the blank sample, the application of the catalysts prepared in Examples 1-9 can significantly increase the total output of syngas, the hydrogen content in the syngas is significantly increased, and the carbon dioxide content is slightly decreased. At the same time, under the condition of the same carrier, when the molar ratio of the active components iron and nickel in the catalyst is controlled to be 1:1, the hydrogen production is the highest. Compared with other examples, in Example 8, when the iron-nickel molar ratio is controlled to be 1:1 and the mass ratio of the magnesium oxide carrier to the alumina carrier is 4:1, the carbon monoxide production is the highest, which indicates that the increase in the proportion of active magnesium oxide in the composite carrier is beneficial to reducing the carbon dioxide content in the syngas and increasing the carbon monoxide production, proving that the active magnesium oxide carrier can play a role in promoting the deoxidation of carbon dioxide.

[0053] In addition, Figure 3 (a) shows the gas product distribution under different steam injection amounts in the application of the catalyst prepared in Example 1. When the steam injection amount is 0.24 mL / min, the H 2 / CO molar ratio is 3.84.

[0054] (II) Catalyst cycle performance and regeneration performance tests The method for the cycle performance test is as follows: According to the method for the catalytic activity test of the catalyst in (I), after the reaction is completed, new biomass raw materials are put back for the catalyst cycle experiment, and the content of each component in the syngas is collected and tested. Such a cycle is carried out 5 times.

[0055] The method for the regeneration performance test is as follows: The catalyst after 5 cycles is taken out and placed in a quartz crucible, and then placed in a tube furnace. It is heated to 700 °C at a heating rate of 10 °C / min under normal pressure and in an air atmosphere, and the catalyst is regenerated at this temperature for 30 min. The regenerated catalyst is used for the biomass catalytic pyrolysis experiment, and the experimental process and gas detection method are the same as those in (I) the catalytic activity test of the catalyst.

[0056] Figure 7 Shows the cycle performance test results of the 1Fe1Ni / 4MgO1Al 2 O 3 catalyst prepared in Example 8. It can be seen from Figure 7 that after the catalyst prepared by the present invention undergoes five cycles and regeneration, it still maintains this special coral reef-like morphology, and the dual active centers remain unchanged. There is no carbide phase in the recycled catalyst, indicating that the catalyst has anti-coking performance. In addition, during the cycle and regeneration of the catalyst, the active magnesium oxide carrier is basically not carbonated during the catalytic reaction process ( Figure 7 XRD data does not show the diffraction peak of MgCO 3 ), which indicates that the active magnesium oxide takes CO 2One of the oxygen atoms forms an MgO(O) intermediate to achieve carbon dioxide deoxidation (MgO + CO 2 →MgO(O)+CO). Further, Figure 8 The edx-mapping diagram of

[0057] Figure 9 also proves that magnesium oxide is not carbonated and exists in the form of magnesium oxide. Figure 10 And 2 O 3 show the EPR data and EDX images of the 1Fe1Ni / 4MgO1Al Figure 9 catalyst prepared in Example 8. From Figure 10 it can be seen that after the addition of the active phase, the peak representing oxygen vacancies disappears, indicating that part of the active metal is anchored on the oxygen vacancies. Compared with the loading of the active components on the surface and voids of the support during the preparation of other catalysts, in the present invention, with alumina as the support, by first calcining and then acid leaching and activating, the oxygen vacancies on the surface of the alumina support are increased, and the subsequently loaded active metal can be precisely and firmly anchored on the alumina skeleton through the oxygen vacancies, and is not easy to fall off and undergo drastic changes at high temperatures during high-temperature conditions, multiple cycles and regeneration, thereby maintaining better structural stability and cycle stability.

[0058] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent substitutions and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a coral reef-like bifunctional catalyst for biomass gasification to produce green hydrogen with simultaneous decarbonization, characterized in that: The following steps are involved: S1, the alumina carrier is acid-leached, calcined and ground to obtain an activated alumina carrier; the magnesium oxide is calcined and ground to obtain activated magnesium oxide; S2, mixing the activated alumina carrier with the activated magnesium oxide to obtain a composite carrier; S3. The composite carrier, the active phase precursor of iron and the active phase precursor of nickel are placed in water and fully mixed. After drying, the mixture is calcined and ground to obtain a coral reef-like bifunctional catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the alumina carrier is γ-Al2O3; the acid leaching uses a nitric acid solution with a concentration of 0.1-2 mol / L, and the acid leaching time is 2-4 hours; the alumina carrier is calcined at a temperature of 600-900°C for 2-4 hours, and the calcination is carried out under an inert atmosphere.

3. The preparation method according to claim 1, characterized in that: In step S1, the calcination temperature of magnesium oxide is 700-900° C., the time is 1.5-3.5 hours, and the calcination is carried out under an inert atmosphere.

4. The preparation method according to claim 1, characterized in that: In step S2, in the composite carrier, the mass ratio of the activated alumina carrier to the activated magnesium oxide is 1:4-4:

1.

5. The preparation method according to claim 1, characterized in that: In step S3, the active phase precursor of iron includes a soluble iron salt, and the active phase precursor of nickel includes a soluble nickel salt.

6. The preparation method according to claim 1, characterized in that: In step S3, in the active phase precursor of iron and the active phase precursor of nickel, the molar ratio of the iron element to the nickel element is 1:3-3:

1.

7. The preparation method according to claim 1, characterized in that: In step S3, the mixing is carried out at a stirring speed of 600-900 r / min, a mixing temperature of 60-100° C., and a time of 2-3 h; the calcination is carried out under an inert atmosphere, a calcination temperature of 700-900° C., and a time of 3-4 h.

8. A coral reef-like bifunctional catalyst for simultaneous decarbonization of biomass gasification to produce green hydrogen, prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The coral reef-like bifunctional catalyst includes a γ-Al2O3 carrier with a regular tetrahedral structure and an active MgO carrier for decarbonization; active metal iron and nickel are anchored on the oxygen vacancies of the γ-Al2O3 carrier, and the loading amount of the active metal iron and nickel relative to the total weight of the catalyst is 8wt.%-10wt.%.

9. The use of the coral reef-shaped bifunctional catalyst according to claim 8 in the production of bio-based hydrogen-rich synthesis gas, characterized in that: The dried biomass raw material is mixed with a coral reef-shaped bifunctional catalyst in a certain proportion, and water is used as a gasifying agent to carry out a pyrolysis reaction to obtain hydrogen-rich synthesis gas; in the hydrogen-rich synthesis gas, the molar ratio of H2 to CO is 2-4.

10. The use according to claim 9, characterized in that: The deactivated catalyst after use is treated by combustion to obtain a regenerated catalyst, and the combustion treatment temperature is 600-800°C and the time is 30-80 minutes.

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