Preparation method and application of catalyst for co-production of green hydrogen and aromatic hydrocarbon from biomass

Abstract

The invention provides a preparation method of a catalyst for co-production of green hydrogen and aromatic hydrocarbon from biomass, which comprises the following steps: placing a biomass raw material in an inert atmosphere, and calcining to obtain biochar; carrying out acid modification and alkali modification on the biochar in sequence to obtain an activated biochar carrier; placing the activated charcoal carrier, an iron-containing active phase precursor and a calcium and nickel-containing accelerator precursor in water, fully mixing, drying, calcining, and grinding to obtain the catalyst. The invention also provides application of the catalyst in co-production of green hydrogen and aromatic hydrocarbon from biomass, and a waste catalyst recycling method. The catalyst constructed through carrier pretreatment, active phase regulation and control and the accelerant has high adaptability to hydrogen production through biomass pyrolysis volatile component reforming and aromatic hydrocarbon BTX. In addition, the waste catalyst is used for adsorbing organic pollutants in organic wastewater, secondary utilization of the waste catalyst is achieved, waste is treated with waste, and the method has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical fields of catalyst preparation and biomass thermal conversion, and particularly relates to a preparation method of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass, and also relates to the application of the above catalyst and the recycling process. Background Art

[0002] With the improvement of global environmental protection awareness and the increase in energy demand, it is an irresistible trend to use renewable energy to replace traditional fossil fuels. From the perspective of elemental composition, biomass is the only carbon-containing and renewable resource on the earth and has the potential to produce hydrogen on a large scale. From the structure, biomass contains rich active groups such as aromatic rings, aliphatic and aromatic hydroxyl groups, and quinone groups, and is a natural "hydrocarbon pool".

[0003] Catalytic pyrolysis is an important way for biomass to co-produce aromatic hydrocarbons (BTX) and green hydrogen in one step. Volatiles are produced by high-temperature pyrolysis of biomass as raw materials, and then catalytically reformed into green hydrogen and BTX by a catalyst. Therefore, the catalyst is the key to the directional and efficient conversion of biomass into target products. The catalyst consists of a supported active phase and a promoter. Current research has found that the HZSM-5 support has uniform pores and is difficult to match the wide molecular weight distribution of volatiles produced by biomass pyrolysis, resulting in low hydrogen production efficiency by reforming; noble metals have good activity and high selectivity for target products, however, their high price limits large-scale applications; transition metals have become common catalysts for the directional production of green hydrogen and BTX by biomass catalytic pyrolysis due to the same outermost electron structure as noble metals. However, due to the influence of mass transfer resistance, oxygen-containing macromolecular compounds in pyrolysis volatiles are prone to coking on the catalyst, resulting in rapid deactivation of the catalyst and limiting the conversion of biomass into target products; in addition, the activity of transition metals is not high, which affects the cracking and reforming efficiency of volatiles on the catalyst surface, resulting in low yields of green hydrogen and BTX. At the same time, the waste catalyst obtained after biomass catalytic pyrolysis contains a certain amount of metal species. If directly treated as solid waste, it not only increases the post-treatment cost, cannot achieve continuous production, but also causes huge waste of resources and environmental pollution.

[0004] Based on this, in order to improve the yields of target products green hydrogen and BTX, it is urgent to directionally construct a catalyst with low cost, high activity and breakthrough of the influence of mass transfer resistance. In addition, developing a green and efficient waste catalyst recycling process to reduce resource waste and improve metal utilization rate is of great significance to the biomass thermal conversion industry for producing green hydrogen and BTX. Summary of the Invention

[0005] One object of the present invention is to provide a preparation method of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass.

[0006] The second object of the present invention is to provide an application of a catalyst for the co-production of green hydrogen and aromatic hydrocarbons from biomass and a recycling and reuse process.

[0007] The technical solution adopted by the present invention to achieve one of the objectives is: to provide a method for preparing a catalyst for co-production of green hydrogen and aromatic hydrocarbons from biomass, comprising the following steps: S1, placing the biomass raw material under an inert atmosphere and performing a first calcination treatment to obtain biochar; S2, successively subjecting the biochar to acid modification and alkali modification, washing and drying, to obtain an activated biochar carrier; S3. The activated biochar carrier, the iron-containing active phase precursor, and the promoter precursor containing calcium and nickel are placed in water and fully mixed, dried, subjected to a second calcination treatment, and ground to obtain a catalyst.

[0008] The overall idea and inventive principle of the present invention are as follows: Biomass has a natural pore structure, and the pore structure is retained after pyrolysis into carbon, which is a cheap and readily available porous structure carrier. However, the volatile matter with a wide molecular weight distribution produced by biomass pyrolysis leads to low reforming hydrogen production efficiency. At the same time, due to the influence of mass transfer resistance, the oxygen-containing macromolecular compound catalyst in the pyrolysis volatile matter is prone to coking, resulting in rapid deactivation of the catalyst, limiting the conversion of biomass to target products. In response to the above problems, the preparation method of the catalyst provided in this application mainly makes the following two improvements: On the one hand, in terms of the treatment of the biochar carrier, the present invention successively performs acid modification and alkali modification on the biochar that has undergone the first calcination treatment, and pre-adjusts the biochar surface and pores in an all-round and multi-level manner through the acid-base coupling technology to obtain a biochar carrier with a high specific surface area and uneven sizes. The biochar carrier prepared by the present invention solves the problem that the HZSM-5 carrier has a single pore and a uniform structure that is difficult to match the volatile components produced by biomass pyrolysis, which are of various types and have a wide molecular weight distribution.

[0009] On the other hand, the present invention uses activated biochar carriers to load iron-containing active phases and promoters containing calcium and nickel to prepare catalysts. Among them, the biochar is modified by acid and alkali to increase the surface pores, improve the surface structural characteristics, make it more conducive to the dispersion of the active phase, avoid the agglomeration of the active phase, and ensure the effective performance of the catalytic activity. The active phase iron is conducive to the breaking of chemical bonds, and the calcium and nickel in the promoter can prevent the active phase from excessively agglomerating and coking. These improvements not only make the catalyst prepared by the present invention show good tar reforming performance (the selectivity of BTX reaches 100%), but also the used catalyst shows efficient adsorption capacity when treating phenol in wastewater, reducing the treatment cost of solid waste and environmental pollution, and realizing resource utilization through the recycling and reuse route of waste treatment.

[0010] Further, in step S1, the biomass raw material includes one or a combination of wheat straw, corn straw, rice straw, and bagasse; the temperature of the first calcination treatment is 850 - 950 °C, and the time is 2.5 - 3.5 h.

[0011] Further, in step S2, the acid modification uses a hydrochloric acid solution with a concentration of 0.05 - 0.4 mol / L; the alkali modification uses a potassium hydroxide solution with a concentration of 0.1 - 0.4 mol / L. Among them, both the acid modification and the alkali modification of the biochar are carried out by soaking under continuous stirring conditions, and the soaking times for acid modification and alkali modification are 12 - 36 h respectively. Preferably, the concentrations of both the hydrochloric acid solution and the potassium hydroxide solution are 0.2 mol / L.

[0012] Further, in step S2, after washing the alkali - modified biochar until the filtrate is neutral, it is soaked in a dilute acid with a concentration of 0.05 - 0.1 mol / L for 8 - 24 h, and then subsequent operations are carried out. In the present invention, by performing acid leaching on the alkali - modified biochar, the residual K in the biochar pores is removed + , avoiding the influence of residual potassium ions on subsequent biomass pyrolysis reforming experiments. Preferably, the dilute acid uses an aqueous solution of hydrochloric acid.

[0013] Further, in step S3, the iron - containing active phase precursor is a soluble iron salt, and the promoter precursors containing calcium and nickel are composed of a soluble calcium salt and a soluble nickel salt. Among them, the soluble iron salts include one or a combination of iron nitrate, iron chloride, and iron sulfate; the soluble calcium salts include one or a combination of calcium nitrate, calcium chloride, and calcium acetate; the soluble nickel salts include one or a combination of nickel chloride, nickel sulfate, and nickel acetate.

[0014] Further, in step S3, in the catalyst, relative to the weight of the activated biochar carrier, the loading amount of the active phase iron is 2 wt.% - 10 wt.%; the loading amounts of the promoters calcium and nickel are 0.2 wt.% - 2 wt.%.

[0015] Preferably, in the catalyst, the loading amount of the active phase iron is 1 wt.% - 10 wt.%, the loading amount of the calcium promoter is 0.2 wt.% - 2.0 wt.%, and the loading amount of the nickel promoter is 0.1 wt.% - 1.0 wt.%.

[0016] More preferably, the total loading amount of the active phase and the promoter in the catalyst is 5 wt.% - 10 wt.%, and the weight ratio of iron, calcium, and nickel is 30 - 60:10 - 20:5 - 10.

[0017] Further, in step S3, the temperature of the second calcination treatment is 750 - 850 °C, and the time is 1.5 - 2.5 h. Preferably, the temperature of the first calcination treatment is 900 °C, the time is 3 h, the temperature of the second calcination treatment is 800 °C, and the time is 2 h. In the present invention, the biochar is calcined twice successively. A stable biochar support is obtained through the first calcination treatment, and the loading of metal active components is achieved through the second calcination treatment.

[0018] The technical solution adopted by the present invention to achieve the second object is: to provide an application of a catalyst for biomass co-production of green hydrogen and aromatic hydrocarbons prepared by the preparation method according to the first object of the present invention.

[0019] The application includes: mixing a biomass raw material with the catalyst according to a weight ratio of 1:0.1 - 1.5, and performing a catalytic pyrolysis reaction under an inert atmosphere. The temperature of the pyrolysis section is 600 - 900 °C, the temperature of the reforming section is 400 - 700 °C, and the time is 20 - 60 min to obtain hydrogen-rich syngas and aromatic hydrocarbons.

[0020] In some preferred embodiments, the biomass raw material is wheat straw, the weight ratio of wheat straw to the catalyst is 1:1, the catalytic pyrolysis reaction is carried out in a nitrogen environment, the temperature of the pyrolysis section is 800 °C, the temperature of the reforming section is 600 °C, and the time is 40 min.

[0021] Further, the application further includes recycling and reuse: using the catalyst after the catalytic pyrolysis reaction to adsorb and treat organic pollutants in wastewater.

[0022] The present invention uses the catalyst after the catalytic pyrolysis reaction for the treatment of organic pollutants in wastewater, and based on the actions of hydrogen bonds, van der Waals forces, metal charge attraction, etc., realizes the efficient adsorption of organic pollutants. By performing acid-base combined modification on the biochar support of the catalyst, the present invention enables the catalyst to have more confined spaces beneficial for adsorption, provides more adsorption sites, and avoids reaching the adsorption saturation state prematurely. In addition, a certain structure remains in the catalyst (waste catalyst) after the catalytic pyrolysis reaction of the present invention, which is beneficial for the adsorption of organic pollutants. At the same time, after the waste catalyst is used in pyrolysis catalysis, there are still some amorphous carbon deposits on its surface, which can provide hydrogen bonds beneficial for the adsorption of organic pollution. Therefore, when treating wastewater containing organic pollutants, the waste catalyst exhibits better adsorption performance than the fresh catalyst.

[0023] Preferably, the organic pollutant in the wastewater is phenol, the concentration of phenol in the wastewater is 1000 - 3000 mg / L, the weight ratio of the dosage of the catalyst to phenol is 0.2 - 10:1, the temperature of the adsorption treatment is 20 - 30 °C, and the time of the adsorption treatment is 12 - 48 h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a preparation method of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass. By means of acid-base coupling technology, the surface and pores of biochar are pre-adjusted comprehensively and multi-levelly to obtain a biochar carrier with a high specific surface area and uneven sizes, solving the problems that the pores of the HZSM-5 carrier are single and the structure is uniform, making it difficult to match the various and wide molecular weight distribution of volatiles generated by biomass pyrolysis.

[0025] (2) The catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass prepared by the present invention uses the activated biochar carrier to load an iron-containing active phase and promoters containing calcium and nickel. Among them, the biochar is modified by acid-base combination to increase the surface pores, improve the surface structure characteristics, making it more conducive to the dispersion of the active phase, avoiding the agglomeration of the active phase, and ensuring the effective exertion of the catalytic activity; the active phase iron is beneficial to the breaking of chemical bonds, and calcium and nickel in the promoters can prevent the over-agglomeration and coking of the active phase.

[0026] (3) The catalyst prepared by the present invention for co-producing green hydrogen and aromatic hydrocarbons from biomass shows good tar reforming performance (the selectivity of BTX reaches 100%). At the same time, the used waste catalyst shows high adsorption capacity when treating organic pollutants in wastewater, reducing the treatment cost of solid waste and environmental pollution, improving the system economy, reflecting the concept of treating waste with waste, and having good application prospects. Description of the Drawings

[0027] Figure 1 It is a schematic process flow diagram of a preparation method, application, and recycling of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass provided by an embodiment of the present invention. Detailed Embodiments

[0028] Next, the technical solutions of the present invention will be described clearly and completely in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of 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 shall fall within the protection scope of the present invention.

[0029] 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.

[0030] The embodiments of the present invention provide a preparation method of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass, including the following steps: Step 1: placing the biomass raw material under an inert atmosphere and performing a first calcination treatment to obtain biochar; wherein the biomass raw material includes a combination of one or more of wheat straw, corn straw, rice straw, and sugarcane bagasse; the temperature of the first calcination treatment is 850-950°C and the time is 2.5-3.5h.

[0031] Step 2: The biochar is subjected to acid modification and alkali modification in turn, and after washing and drying, an activated biochar carrier is obtained; wherein the acid-modified solution adopts a hydrochloric acid solution with a concentration of 0.05-0.4 mol / L; the alkali modification adopts a potassium hydroxide solution with a concentration of 0.1-0.4 mol / L; after washing the alkali-modified biochar until the filtrate is neutral, it is placed in a dilute hydrochloric acid with a concentration of 0.05-0.1 mol / L and immersed for 8-24 hours, and then subsequent operations are carried out.

[0032] Step 3: The activated biochar carrier, the iron-containing active phase precursor, and the promoter precursor containing calcium and nickel are placed in water and fully mixed, dried, calcined for the second time, and ground to obtain a catalyst; wherein the iron-containing active phase precursor is a soluble iron salt, and the promoter is composed of a soluble calcium salt and a soluble nickel salt; in the catalyst, the loading amount of active phase iron is 2wt.%-10wt.%; and the loading amount of promoter calcium and nickel is 0.2wt.%-2wt.%. The temperature of the second calcination treatment is 750-850℃, and the time is 1.5-2.5h.

[0033] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0034] The main experimental conditions and parameters involved in the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0035] Table 1

[0036] Example 1 This embodiment provides a method for preparing a catalyst for co-production of green hydrogen and aromatic hydrocarbons from biomass, and its flow diagram is as follows: Figure 1 As shown, the following steps are included: Step 1: Weigh 20 g of wheat straw and heat it at 900 °C and N 2 The biochar was obtained by calcining under atmosphere for 3 h; Step 2: Weigh 15 g of biochar into a beaker, then add 50 mL of 0.2 M HCl to modify the biochar and continue stirring for 24 h. Then wash repeatedly with a large amount of deionized water until the filtrate is added with AgNO 3Without white precipitate; then add 50 mL of 0.2 M KOH for modification. After stirring for 24 h, rinse with a large amount of deionized water until the filtrate is neutral. Finally, soak the filter residue in dilute hydrochloric acid (0.1 M) for 12 h to ensure the removal of residual K in the biochar pores + , and then filter immediately. Wash the filter residue with a large amount of deionized water until the filtrate is neutral, and dry it at 100 - 120 °C to obtain the activated carbon support; Step 3: Weigh 3.6071 g, 0.8838 g, and 0.3946 g of Fe(NO 3 ) 3 ·9H 2 O, Ca(NO 3 ) 2 ·4H 2 O, and Ni(NO 3 ) 2 ·6H 2 O respectively, dissolve them by stirring in 50 mL of deionized water to obtain a solution containing active phases and promoters. Then add 10 g of pre-activated biochar to the solution, stir well for 1 h, and then impregnate it in a water bath at 80 °C until the liquid completely evaporates. Immediately place it in an oven at 105 °C and dry for 24 h. Collect the solid material, grind it, and calcine it at 800 °C in an N 2 atmosphere for 2 h. After the product cools down, grind and sieve it to obtain the biochar-based Fe-Ni-Ca catalyst modified by acid-base combination, denoted as Fe-Ni-Ca / 0.2HKC).

[0037] Example 2 The difference between this example and Example 1 is that in Step 3, iron, calcium, and nickel are fed according to the loadings of 1 wt.%, 0.2 wt.%, and 0.1 wt.% respectively. The remaining operations and experimental conditions remain unchanged, and the biochar-based Fe-Ni-Ca catalyst modified by acid-base combination is prepared.

[0038] Example 3 The difference between this example and Example 1 is that in Step 3, iron, calcium, and nickel are fed according to the loadings of 10 wt.%, 2 wt.%, and 1 wt.% respectively. The remaining operations and experimental conditions remain unchanged, and the biochar-based Fe-Ni-Ca catalyst modified by acid-base combination is prepared.

[0039] Example 4 This example provides a preparation method of a catalyst for the co-production of green hydrogen and aromatic hydrocarbons from biomass. The process schematic diagram is as Figure 1 shown, and it includes the following steps: Step 1: Weigh 20 g of wheat straw, and at 900 °C, N 2Calcined in an atmosphere for 3 h to obtain biochar; Step 2: Weigh 15 g of biochar and place it in a beaker. Then add 50 mL of 0.05 M HCl to modify the biochar, and continuously stir for 36 h. Then wash it repeatedly with a large amount of deionized water until no white precipitate appears when AgNO 3 is added to the filtrate; immediately add 50 mL of 0.1 M KOH for modification. After stirring for 36 h, rinse it with a large amount of deionized water until the filtrate is neutral. Finally, soak the filter residue in dilute hydrochloric acid (0.05 M) for 24 h to ensure the removal of residual K + in the pores of the biochar, and then filter it immediately. Wash the filter residue with a large amount of deionized water until the filtrate is neutral, and dry it at 100 - 120 °C to obtain the activated carbon support; Step 3: Weigh 3.6071 g, 0.8838 g, 0.3946 g of Fe(NO 3 ) 3 ·9H 2 O, Ca(NO 3 ) 2 ·4H 2 O and Ni(NO 3 ) 2 ·6H 2 O respectively, dissolve them in 50 mL of deionized water with stirring to obtain a solution containing active phases and promoters. Then add 10 g of pre-activated biochar to the solution, stir well for 1 h, and then impregnate it in a water bath at 80 °C until the liquid is completely evaporated. Immediately place it in an oven at 105 °C and dry for 24 h. Collect the solid substance, grind it, and calcine it at 800 °C in an N 2 atmosphere for 2 h. After the product is cooled, grind it and sieve it to obtain the biochar-based Fe-Ni-Ca catalyst modified by acid-base combination, denoted as Fe-Ni-Ca / 0.05H0.1KC).

[0040] Example 5 This example provides a preparation method of a catalyst for co-producing green hydrogen and aromatic hydrocarbons from biomass, and its process schematic diagram is as Figure 1 shown, including the following steps: Step 1: Weigh 20 g of wheat straw, and calcine it at 900 °C in an N 2 atmosphere for 3 h to obtain biochar; Step 2: Weigh 15 g of biochar and place it in a beaker. Then add 50 mL of 0.4 M HCl to modify the biochar, and continuously stir for 12 h. Then wash it repeatedly with a large amount of deionized water until no white precipitate appears when AgNO 3There is no white precipitate; then 50 mL of 0.4 M KOH is added for modification. After stirring for 12 h, it is rinsed with a large amount of deionized water until the filtrate is neutral. Finally, the filter residue is soaked in dilute hydrochloric acid (0.1 M) for 8 h to ensure the removal of residual K in the pores of the biochar. + , and then filtration is carried out immediately. The filter residue is washed with a large amount of deionized water until the filtrate is neutral, and then dried at 100 - 120 °C to obtain the activated carbon support; Step 3: Weigh 3.6071 g, 0.8838 g, and 0.3946 g of Fe(NO 3 ) 3 ·9H 2 O, Ca(NO 3 ) 2 ·4H 2 O, and Ni(NO 3 ) 2 ·6H 2 O respectively, and stir and dissolve them in 50 mL of deionized water to obtain a solution containing the active phase and the promoter. Subsequently, 10 g of pre-activated biochar is added to the solution. After stirring for 1 h, it is fully impregnated in a water bath at 80 °C until the liquid is completely volatilized. Then, it is placed in an oven at 105 °C and dried for 24 h. The solid substance is collected, ground, and calcined at 800 °C in an N 2 atmosphere for 2 h. After the product is cooled, it is ground and sieved to obtain the biochar-based Fe-Ni-Ca catalyst modified by acid-base combination, denoted as Fe-Ni-Ca / 0.4H0.4KC).

[0041] Example 6 The difference between this example and Example 1 is that in Step 1, the calcination temperature is 850 °C and the time is 3.5 h; in Step 3, the calcination temperature is 750 °C and the time is 2.5 h. The rest of the operations and experimental conditions remain unchanged, and a biochar-based Fe-Ni-Ca catalyst modified by acid-base combination is prepared.

[0042] Example 7 The difference between this example and Example 1 is that in Step 1, the calcination temperature is 950 °C and the time is 2.5 h; in Step 3, the calcination temperature is 850 °C and the time is 1.5 h. The rest of the operations and experimental conditions remain unchanged, and a biochar-based Fe-Ni-Ca catalyst modified by acid-base combination is prepared.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that: the step of activating the biochar with hydrochloric acid and potassium hydroxide in Step 2 is removed, and the biochar prepared in Step 1 is directly used to load the active phase and the promoter, and the loading amount and other conditions are the same as those in Example 1. The prepared catalyst is denoted as Fe-Ni-Ca / C.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: In Step 2, only hydrochloric acid was used to activate and modify the biochar (hydrochloric acid concentrations were 0.1 mol / L, 0.2 mol / L, and 0.3 mol / L respectively), and the subsequent alkali modification step was removed; in Step 3, the acid-modified biochar was loaded with the active phase and the promoter, and the loading amount and other conditions were kept the same as those in Example 1. The prepared catalysts were denoted as Fe-Ni-Ca / 0.1HC, Fe-Ni-Ca / 0.2HC, and Fe-Ni-Ca / 0.3HC respectively.

[0045] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: In Step 2, only KOH solution was used to activate and modify the biochar (KOH concentrations were 0.1 mol / L, 0.2 mol / L, and 0.3 mol / L respectively), and the previous acid modification operation was omitted. In Step 3, the alkali-modified biochar was loaded with the active phase and the promoter, and the loading amount and other conditions were kept the same as those in Example 1. The prepared catalysts were denoted as Fe-Ni-Ca / 0.1KC, Fe-Ni-Ca / 0.2KC, and Fe-Ni-Ca / 0.3KC.

[0046] Application Example 1 The catalysts prepared in Example 1, 4, and 5 of the present invention and Comparative Examples 1-3 were respectively used for the production of hydrogen-rich syngas by biomass thermal conversion, including the following process: Step 1: The weight ratio of wheat straw to the carbon-based catalyst was 1:1. 1.0 g of wheat straw with a particle size of 40 mesh and 1.0 g of biochar-based Fe-Ni-Ca catalyst were weighed, and a biomass catalytic pyrolysis experiment was carried out in a fixed-bed reactor.

[0047] Step 2: After installing the reactor and checking the airtightness, a certain amount of inert gas (N 2 ) was introduced to displace the air in the reactor until there was no oxygen in the outlet gas of the reactor. The temperature controller was adjusted, and the heating button was pressed to start heating the reactor. After the temperature in the reactor reached the target temperature (800 °C for the pyrolysis section and 600 °C for the reforming section), the catalyst and the raw material were pushed into the reactor for rapid catalytic pyrolysis for 40 min. The outlet of the reactor was connected to a three-stage condensation device and a gas drying and purification device.

[0048] Step 3: The liquid in the condenser was filtered with a microporous filter membrane, and the types of compounds were detected and determined by GC / MS. The product content in the liquid is shown in Table 2; the gas components in the syngas were measured by a flue gas analyzer and GC, and the yields of each component in the syngas are shown in Table 3.

[0049] Table 2

[0050] From Table 2, we can see that In each embodiment and comparative example, gas chromatography / mass spectrometry (GC / MS) of the liquid in the condensation bottle after the reaction detected only two products: benzene and toluene; and quantitative analysis showed that the benzene selectivity in embodiments 1, 4 and 5 was not less than 87.23%, and in embodiment 1, the selectivity of benzene in the liquid was as high as 98.44%.

[0051] Aromatic hydrocarbons such as benzene are important chemical raw materials and are widely used in the fields of industry, medicine, and chemical industry. At present, the production of benzene at home and abroad mainly relies on fossil resources such as petroleum, which is usually obtained by hydrogenating, reforming, converting and separating petroleum with catalysts. Fossil resources are non-renewable and emit greenhouse gases during their use, prompting people to look for new ways to produce benzene. Biomass, as a renewable resource, is carbon neutral and has large reserves. At present, the utilization of biomass is mainly to degrade biomass into small molecular compounds such as sugars, sugar alcohols, low-carbon alkanes, CO, H by pyrolysis, enzymolysis and hydrolysis. 2 and CO 2 Etc., and then use them. Pyrolysis technology, biomass is pyrolyzed at high temperature into bio-based synthesis gas components, and then contacted with catalysts such as molecular sieves to produce aromatics. The process steps are simple, but the catalyst deactivates quickly and needs to be continuously regenerated. In addition, liquid phase reforming technology converts sugar into reformed oil rich in C5 and C6 alcohols, aldehydes and ketones, and converts it into a fuel of gasoline components. This process achieves the purpose of degrading biomass and produces C5 and C6 oxygen-containing compounds. It has certain downstream development potential, but the reformed oil has a complex composition. If it is to be converted into useful chemicals such as BTX, it still needs to be converted, and the energy consumption is high. Compared with the existing methods, the present invention uses cheap catalysts to convert biomass into green hydrogen in a one-step method, and at the same time, highly selectively co-produces aromatic hydrocarbons such as benzene. It has certain technical advantages and also provides an important reference for new routes for high-value utilization of biomass.

[0052] Table 3

[0053] As can be seen from Table 3, the modification method of the catalyst carrier has a great influence on the distribution of the reforming products of the volatile matter of biomass pyrolysis. From the results of Comparative Examples 2 and 3, the base modification alone has an inhibitory effect on the selectivity of hydrogen, while the acid-modified carrier alone promotes the formation of hydrogen. Compared with the acid-base modification alone, Examples 1, 4 and 5 use a combined acid-base modification method to activate the biochar carrier, and the prepared catalyst has a higher hydrogen yield, among which the hydrogen production rate of Example 1 is the highest at 465.58 mL / g, which shows that the present invention adopts a combined acid-base modification method and optimizes the concentration of acid and base, which is conducive to further improving the hydrogen selectivity during catalytic application.

[0054] Application Example 2 This application example examines the adsorption performance of the catalyst (waste catalyst) after pyrolysis catalysis in Application Example 1 for the organic pollutant phenol in wastewater, in order to realize the recycling and reuse of the waste catalyst. The specific method is as follows: Step 1: Prepare a phenol solution with a concentration of 2000 mg / L in a volumetric flask; weigh 0.1 g of the waste catalyst and place it in a conical flask, add 50 mL of the prepared phenol solution, and shake the conical flask to ensure that the waste catalyst is completely immersed in the phenol solution. Seal the conical flask and place it in a shaker, shake it at 25 °C for 24 h to ensure adsorption saturation.

[0055] Step 2: Pour out the liquid in the conical flask, perform suction filtration, and place the filtrate in a cuvette for analysis with a UV spectrophotometer to obtain the amount of phenol adsorbed.

[0056] The adsorption amounts of phenol before and after using the catalysts prepared in Examples 1, 4, and 5 and Comparative Examples 2 and 3 are shown in Table 4 (where, S- represents the waste catalyst).

[0057] Table 4

[0058] As can be seen from Table 4, The adsorption capacities of the waste catalysts of Example 1, Comparative Example 2 (0.2HC), and Comparative Example 3 (0.2KC) for phenol are 323.29 mg / g, 295.97 mg / g, and 314.64 mg / g respectively, all of which are superior to high-quality commercial activated carbon. This indicates that the waste catalyst has certain advantages in adsorbing organic pollutants in wastewater.

[0059] Compared with Comparative Examples 2 and 3, the waste catalyst of Example 1 has the highest phenol adsorption amount of 323.29 mg / g, even superior to the fresh catalyst Fe-Ni-Ca / 0.2HKC. This phenomenon indicates that, on the one hand, through the combined acid-base modification of the catalyst biochar carrier in the present invention, the catalyst has more confined spaces beneficial for adsorption, provides more adsorption sites, and avoids reaching the adsorption saturation state prematurely; on the other hand, the waste catalyst that has experienced the pyrolysis catalysis reaction not only retains a certain pore structure beneficial for the adsorption of organic pollutants, but also there are some amorphous carbon deposits on the surface of the used waste catalyst, which can provide hydrogen bonds beneficial for the adsorption of organic pollutants, making it show better adsorption performance than the fresh catalyst when treating wastewater containing organic pollutants.

[0060] In addition, by comparing the test results of Example 1 with those of Examples 4 and 5, it can be seen that Example 1 can significantly improve the adsorption amount of the waste catalyst for phenol by optimizing the concentrations of acid and base in the combined acid-base modification.

[0061] Furthermore, Table 5 shows the physical structure characteristics of the catalysts prepared in Examples 1, 4, and 5 and Comparative Examples 2 and 3 before and after use (where S- represents the spent catalyst).

[0062] Table 5

[0063] As can be seen from Table 5, Compared with Comparative Examples 2 and 3, the catalyst prepared by the combined acid-base modification method in Example 1 has a larger specific surface area, slightly higher pore volume, and larger average pore diameter, which can provide better catalytic performance and stability, making it have a higher hydrogen production and better selectivity in the application of pyrolytic catalytic biomass co-production of green hydrogen and aromatic hydrocarbons.

[0064] Furthermore, although the specific surface area and pore volume of the catalyst (spent catalyst) after the pyrolytic catalytic reaction decreased significantly compared with the fresh catalyst, the spent catalyst of Example 1 still had a higher specific surface area and pore volume compared with the spent catalysts of Comparative Examples 2 and 3. Therefore, it also showed more excellent adsorption performance when treating phenol-containing wastewater.

[0065] Comparing the test results of Example 1 with those of Examples 4 and 5, it can be seen that during the combined acid-base modification process, the control of the concentrations of acid and base will affect the physical structure characteristics of the catalyst before and after use: when the concentrations of acid and base are low, the modification is insufficient, which is not conducive to the formation of a large specific surface area and pore volume; while when the concentrations of the modified acid and base are high, it is easy to cause pore collapse, manifested as a relatively large average pore diameter, which will also affect the catalytic application effect of the catalyst and the adsorption performance of the spent catalyst for organic pollutants to a certain extent.

[0066] The above are only 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 able to realize that all 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 catalyst for co-production of green hydrogen and aromatic hydrocarbons from biomass, characterized in that: The following steps are involved: S1, placing the biomass raw material under an inert atmosphere and performing a first calcination treatment to obtain biochar; S2, successively subjecting the biochar to acid modification and alkali modification, washing and drying, to obtain an activated biochar carrier; S3. The activated biochar carrier, the iron-containing active phase precursor, and the promoter precursor containing calcium and nickel are placed in water and fully mixed, dried, subjected to a second calcination treatment, and ground to obtain a catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the biomass raw material includes one or more of wheat straw, corn straw, rice straw, and sugarcane bagasse; the temperature of the first calcination treatment is 850-950°C, and the time is 2.5-3.5h.

3. The preparation method according to claim 1, characterized in that In step S2, the acid modification uses a hydrochloric acid solution with a concentration of 0.05-0.4 mol / L; the alkali modification uses a potassium hydroxide solution with a concentration of 0.1-0.4 mol / L.

4. The preparation method according to claim 3, characterized in that: In step S2, the alkali-modified biochar is washed until the filtrate is neutral, and then immersed in a dilute acid with a concentration of 0.05-0.1 mol / L for 8-24 hours before performing subsequent operations.

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

6. The preparation method according to claim 1, characterized in that In step S3, in the catalyst, the loading amount of active phase iron is 2wt.%-10wt.%; the loading amount of promoter calcium and nickel is 0.2wt.%-2wt.%.

7. The preparation method according to claim 1, characterized in that: In step S3, the temperature of the second calcination treatment is 750-850°C and the time is 1.5-2.5h.

8. Use of a catalyst for co-production of green hydrogen and aromatic hydrocarbons from biomass prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The biomass raw material and the catalyst are mixed in a weight ratio of 1:0.1-1.5, and a catalytic pyrolysis reaction is carried out under an inert atmosphere, with a pyrolysis section temperature of 600-900°C, a reforming section temperature of 400-700°C, and a time of 20-60 minutes to obtain hydrogen-rich synthesis gas and aromatic hydrocarbons.

9. The use according to claim 8, characterized in that: The application also includes recycling and reuse: using the catalyst after the catalytic pyrolysis reaction to adsorb and treat organic pollutants in wastewater.

10. The use according to claim 9, characterized in that The organic pollutant in the wastewater is phenol, the concentration of phenol in the wastewater is 1000-3000 mg / L, the weight ratio of the catalyst addition amount to phenol is 0.2-10:1, the temperature of the adsorption treatment is 20-30°C, and the time of the adsorption treatment is 12-48h.

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