Aluminum smelting slag-based bimetallic catalyst and its application in hydrogen production by biomass tar co-reforming

Abstract

This invention discloses a bimetallic catalyst based on aluminum smelting waste and its application in biomass tar co-reforming for hydrogen production. The process involves preparing a nickel-based catalyst using aluminum smelting waste as raw material through a gradient process of hydrothermal activation, impregnation modification, and controlled calcination. A dual-dimensional evaluation system of simulated tar (toluene, naphthalene) and real tar is then constructed. The prepared catalyst is applied to the catalytic cracking of tar for hydrogen production during biomass pyrolysis and gasification. Simultaneously, CO2 is introduced to synergistically enhance hydrogen yield through a water-gas shift reaction. Furthermore, catalyst carbon deposition and deactivation are addressed through additive doping and regeneration processes. This invention achieves resource utilization of aluminum smelting waste and efficient removal of biomass tar. The prepared catalyst is low-cost, highly stable, and achieves a hydrogen yield of over 65%, providing an economically feasible technical solution for clean biomass hydrogen production, with significant environmental and energy value.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and biomass energy utilization technology, specifically involving a bimetallic catalyst based on aluminum smelting waste and its application in the co-reforming of hydrogen from biomass tar. Background Technology

[0002] Hydrogen energy, as a clean and efficient renewable energy source, has become an important direction for energy transition. Biomass thermochemical hydrogen production has attracted widespread attention due to its high energy conversion efficiency and relatively low cost. However, the biomass pyrolysis and gasification process generates a large amount of tar, which not only easily leads to system pipeline blockage and equipment corrosion, but also reduces hydrogen yield and fuel gas quality, severely restricting the industrial application of biomass hydrogen production technology. Currently, the core means to solve the tar problem is catalytic cracking, with commonly used catalysts being transition metal catalysts such as nickel-based and iron-based catalysts. However, traditional catalysts suffer from high costs and severe carbon buildup and deactivation. Meanwhile, industrial solid waste, aluminum smelting slag, is rich in metal oxides such as Al2O3, and has the potential to serve as a catalyst carrier, but its resource utilization is difficult, and large-scale accumulation can easily cause environmental pollution. Furthermore, existing tar catalytic evaluations are mostly based on single simulated tar systems, which differ significantly from the composition of real biomass pyrolysis tar, resulting in significant discrepancies between the actual application effect of the catalyst and laboratory evaluation results, making it difficult to guide industrial production. Therefore, developing a low-cost and highly stable catalyst using aluminum smelting waste as raw material, and constructing a two-dimensional tar evaluation system that fits practical applications, is of great significance for promoting the development of clean hydrogen production technology from biomass. Summary of the Invention

[0003] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0004] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0005] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a hydrogen production catalyst based on aluminum smelting waste residue.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a hydrogen production catalyst based on aluminum smelting waste residue, comprising, The aluminum smelting waste residue is crushed and sieved, soaked in acid solution to remove impurities, washed with deionized water until neutral, and dried to obtain pretreated aluminum smelting waste residue. Pretreated aluminum smelting waste residue was mixed with deionized water, the pH value was adjusted to 8-10, and then transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, filtered, and dried to obtain the hydrothermally activated product. The hydrothermal activation product and HZSM-5 were mixed evenly and then used as a carrier. Prepare a nickel salt solution by adding 2%-4% of an additive by mass of the nickel salt solution, stirring until completely dissolved to obtain a mixed solution, add a carrier, and use an excess impregnation method combined with ultrasonic assistance, and let it stand at 25~35 ℃ for 6-12 h; The impregnated product is placed in a muffle furnace and heated to 200-300 ℃ at a heating rate of 5-10 ℃ / min, held for 1-2 h, and then heated to 500-700 ℃ at a heating rate of 3-5 ℃ / min, held for 3-5 h, and then naturally cooled to obtain a high-efficiency hydrogen production catalyst based on aluminum smelting waste slag.

[0007] In a preferred embodiment of the preparation method described in this invention, the sieving includes passing through a 100-200 mesh sieve.

[0008] In a preferred embodiment of the preparation method described in this invention, the acid solution comprises a 1-7 mol / L sulfuric acid solution, and the soaking time of the acid solution is 2-4 h.

[0009] In a preferred embodiment of the preparation method described in this invention, the mass ratio of the pretreated aluminum smelting waste residue to deionized water is 1:5-1:10; the hydrothermal reaction temperature is 160-200 ℃; and the reaction time is 4-8 h.

[0010] In a preferred embodiment of the preparation method described in this invention, the nickel salt solution is at least one of nickel nitrate solution and nickel chloride solution, and the auxiliary agent is at least one of FeCl3, CeO2, and MgO.

[0011] In a preferred embodiment of the preparation method described in this invention, the mass ratio of the hydrothermal activated product to HZSM-5 is 3:2.

[0012] In a preferred embodiment of the preparation method described in this invention, the solid-liquid ratio of the carrier to the mixed solution is 1:8-1:12.

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide an application of an aluminum smelting waste-based hydrogen production catalyst in the catalytic cracking of biomass pyrolysis tar for hydrogen production, including: The catalyst is loaded into the catalytic section of a two-stage fixed-bed reactor; Adjust the reaction temperature to 600-800 ℃, introduce H2O and CO2, use N2 as the carrier gas, and react for 40 min. The steam flow rate is 0.625-1.25 mL / min, the CO2 flow rate is 10-40 mL / min, and the N2 flow rate is 50-90 mL / min.

[0014] As a preferred embodiment of the application described in this invention, the biomass pyrolysis equipment is a two-stage fixed-bed pyrolysis furnace with a pyrolysis heating rate of 10-30 ℃ / min; The volume ratio of H2O to CO2 introduced is 1:1 to 1:2.

[0015] Beneficial effects of this invention: (1) The present invention provides a nickel-based catalyst based on aluminum smelting waste slag prepared by a gradient process, which realizes the synergistic resource utilization of industrial solid waste and biomass waste, reduces the catalyst preparation cost and has good anti-carbon deposition performance; at the same time, it reduces solid waste pollution and biomass tar emissions, and has both environmental and social benefits.

[0016] (2) This invention creatively constructs a performance-stability dual-dimensional diagnostic and optimization system, which directly serves the specific complex reaction scenario of H2O / CO2 synergistic reforming. By correlating the hydrogen space-time yield of the catalyst (activity dimension) with the carbon deposition inhibition rate / activity decay rate (stability dimension) during the reaction process under the same stringent conditions, this system not only achieves rapid and accurate diagnosis of catalyst failure modes, but also guides the targeted optimization of the preparation process. The catalyst optimized based on this system, under the synergistic effect of CO2 and additives, successfully solves the industry problem of mutual constraint between activity and stability in traditional single-dimensional evaluation, and achieves unexpected technical effects: while maintaining a stable hydrogen yield of over 65%, the catalyst's anti-carbon deposition ability is improved by more than 40%, and its long-term operational stability is significantly better than that of similar catalysts reported in the prior art. Thus, it provides quantifiable and replicable key technical support for the industrialization of efficient and stable hydrogen production technology from biomass tar. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The diagram shows the gas release rates of the catalytic toluene pyrolysis of aluminum smelting waste activated by different acids according to the present invention. In the diagram, (a) is the hydrogen release rate, (b) is the methane release rate, (c) is the carbon monoxide release rate, and (d) is the carbon dioxide release rate.

[0018] Figure 2 The diagram shows the product yields of toluene pyrolysis catalyzed by aluminum slag activated by different acids according to the present invention. In this diagram, (a) represents the yields of gas, liquid, and solid products and the toluene conversion rate, and (b) represents the gas product yield.

[0019] Figure 3This is the H2-TPR spectrum of the Ni-Fe series catalysts of this invention.

[0020] Figure 4 The stability of the Ni-Fe / 60%ASA@HZSM-5 catalyst of the present invention is given by (a) the release rate of hydrogen and methane, (b) the release rate of carbon monoxide and carbon dioxide, (c) the yield of gas-liquid-solid three-phase products and the conversion rate of toluene, and (d) the yield of gaseous products and the yield of major gases.

[0021] Figure 5 The morphology and yield of each group of components in this invention are shown.

[0022] Figure 6 This paper compares the distribution patterns of tar catalytic cracking products of the present invention with those of its model compounds, wherein (a) represents the yields of gas, liquid, and solid products, and (b) represents the yields of gaseous products and the yields of major gases.

[0023] Figure 7 The distribution of products of CO2-assisted tar model compound pyrolysis in this invention is shown, where (a) represents the conversion rate of the model compound and the yield of gaseous products, and (b) represents the yield of the main gas.

[0024] Figure 8 The effects of different atmospheres on the product distribution of tar cracking are presented in this invention, wherein (a) the yield of the main gas, and (b) the hydrogen-carbon balance and hydrogen selectivity.

[0025] Figure 9 The figure shows the effect of ASA loading on the catalytic performance of the Ni-Fe / ASA@HZSM-5 catalyst of the present invention, where a is the yield of the three products and b is the gas yield. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] The calculation method for indicators such as gas yield is the nitrogen balance method; among them, the calculation of gas release rate and yield is as shown in equations (1) and (2), the calculation of product yield is as shown in equations (3)-(4), and the calculation methods for other indicators are shown in equations (5)-(9).

[0028] in: γ i :gas i Release rate, mL / min; v i : Determination of pyrolysis gas by GC iGas volume percentage, % Y i : Represents the yield of gaseous products, ml / g; t: represents the pyrolysis time, in minutes; v N2 : Represents the volume percentage of N2 in the pyrolysis gas as determined by GC, % m b : Represents biomass mass, in grams; X: Represents the conversion rate of tar or model compound, % m inlet, model : Represents the corresponding sample injection mass, in grams; m outlet, model : Represents the unreacted mass of the corresponding sample, in grams; :represent i The molar amount of the component, in mol; M i :represent i The relative molecular mass of the component, in grams; ρ i : Represents the density of component i under standard conditions (1 atmosphere, 0℃), in g / cm³ 3 ; H balance : Represents hydrogen balance, % n i :represent i The molar amount of hydrogen in a component, in mol; n organic compound : Represents the number of moles of hydrogen in the organic compound participating in the reaction, in mol; S H2 : Represents H2 selectivity, % n H2 : Represents the molar mass of H2 in the produced gas, in mol; n C : Represents the molar mass of C in the gaseous product, in mol; RR: Represents the H2 / CO ratio (molar ratio) after the tar (under ideal conditions) has been completely cracked. α i : Represents the proportion of each gas component in the total gas production volume, vol.%% Q LHV : Represents the lower heating value of the produced gas, MJ / Nm³ 3 ; α CO α H2 and α CH4: These represent the volume percentages of CO, H2, and CH4 in the produced gas, respectively.

[0029] Example 1 Preparation of high-efficiency hydrogen production catalyst based on aluminum smelting waste residue: (1) Pretreatment of aluminum smelting waste residue: The aluminum smelting waste residue was crushed and passed through an 80-mesh sieve. It was then soaked in 1-7 mol / L hydrochloric acid and sulfuric acid solutions at 30°C for 3 h, washed with deionized water until neutral, and dried at 105°C for 10 h to obtain pretreated waste residue. The gas release rate of the catalytic toluene pyrolysis using this pretreated waste residue is as follows: Figure 1 As shown; wherein, the reaction is carried out in an FD-BC type two-stage fixed bed for catalytic pyrolysis of toluene; the pyrolysis temperature is 600 ℃, the reforming temperature is 800 ℃, the reaction time is 40 min, the toluene flow rate is 1 mL / min, and the catalyst dosage is 5 g.

[0030] Depend on Figure 1 As shown in (a) and (b), the acid-treated aluminum slag showed certain catalytic activity during the catalytic pyrolysis of toluene. However, the aluminum slag activated by H2SO4 showed a greater change in the release rate of H2 and CH4 during the catalytic pyrolysis of toluene than the aluminum slag activated by CH3COOH. However, its release rate was significantly lower than that of HZSM-5 (Si:Al=25).

[0031] Depend on Figure 1 (c) and (d) show that H2SO4-activated aluminum slag has a greater impact on the CO2 and CO release rates during the catalytic toluene pyrolysis process. However, since toluene was used as a tar model for pyrolysis, there was no oxygen source in the experiment. Therefore, it can be inferred that H2SO4-activated aluminum slag has a higher oxygen storage capacity, which promotes the pyrolysis process (C7H8+O2→ CO + CO2+ H2+ C + C n H m The reaction of (tar) increases the release rate of CO2 and CO relative to the pyrolysis of toluene catalyzed by HZSM-5.

[0032] At the same time, according to Figure 2 (a) The yield of the three-phase products of toluene pyrolysis shows that, compared with HZSM-5, the aluminum slag activated by acid produced almost no carbon deposits during the pyrolysis of toluene. This is mainly due to the occurrence of the Boudouard reaction (C + CO2⇋ 2CO, ΔH = + 172 kJ / mol), which further promoted the CO release rate. This phenomenon is also closely related to the concentration of H2SO4. In addition, it can be seen that the aluminum slag activated by 3 mol / L H2SO4 had the highest toluene conversion rate during the catalytic pyrolysis of toluene.

[0033] according to Figure 2 (b) It can be seen that the gas yield of aluminum slag activated by H3COOH did not change significantly during the catalytic pyrolysis of toluene, but it was lower than that obtained by the catalytic pyrolysis of toluene using HZSM-5; while the gas yield of aluminum slag activated by H2SO4 changed significantly during the catalytic pyrolysis of toluene. Therefore, the next step will be to continue the study using aluminum slag activated by 3 mol / L H2SO4.

[0034] (2) Hydrothermal activation: The pretreated waste residue (aluminum slag activated by 3 mol / L H2SO4) was mixed with deionized water at a solid-liquid ratio (g:mL) of 1:8. The pH was adjusted to 9 with ammonia water, and the hydrothermal reaction was carried out at 180 °C for 6 h. After filtration and drying, the hydrothermal activated product was obtained. The hydrothermal activation product and HZSM-5 were mixed evenly at a mass ratio of 3:2 (60% aluminum smelting waste and 40% HZSM-5) and used as a carrier for the modification of active metals and the loading of active sites.

[0035] (3) Impregnation modification: Prepare nickel nitrate solution (nickel ratio of 8%, mass ratio), add 4% (mass ratio) Fe auxiliary agent (Fe2O3), stir to dissolve; add hydrothermal activation product at a solid-liquid ratio of 1:10 (g:mL), impregnate with ultrasonic assistance at 80 W for 20 min, stand at 30℃ for 8 h, and obtain impregnation product.

[0036] (4) Controlled calcination: The impregnated product was placed in a muffle furnace and heated to 250 ℃ at 10 ℃ / min and held for 1.5 h, then heated to 600 ℃ at 4 ℃ / min and held for 3 h. After cooling, a high-efficiency catalyst based on aluminum smelting waste (Ni-Fe / 60%ASA@HZSM-5) was obtained, with a specific surface area of ​​up to 200 m². 2 / g, with a nickel loading of 8%.

[0037] The H2-TPR characterization results of the Ni-Fe catalyst are as follows: Figure 3 As shown in the figure, the two reduction curves of the Ni-Fe / HZSM-5 catalyst exhibit two broad reduction peaks in the temperature ranges of 300-600 ℃ and 600-800 ℃, respectively. The first peak at the lower temperature (536.6 ℃) represents Fe in Fe2O3 and Fe3O4. 3+ species reduced to Fe 2+(FeO), at this point the hydrogen energy consumption is 0.86 mmol / g; while the second peak at 666.7 °C is the reduction of FeO to metallic Fe phase, with a hydrogen energy consumption of 0.18 mmol / g. For the bimetallic Ni-Fe catalyst with ASA:HZSM-5 = 3:2 support, the first reduction curve shifts to the low-temperature region (164-1-207.3 °C) and shows a distinct peak shape, which is the reduction of Ni species to metallic Ni, with a 95.3% reduction in hydrogen consumption; the reduction temperature of Fe species further decreases to 432.4 °C and shows a significantly higher peak shape, with a corresponding increase in hydrogen consumption to 4.16 mmol / g. Compared with the Ni-Fe / HZSM-5 catalyst, the combined use of ASA and HZSM-5 as supports after activation is beneficial for the reduction of Ni and Fe species. This is attributed to the formation of a Ni-Fe alloy with strong intermetallic interactions and the weakening of the interactions between Ni, Fe metals and the HZSM-5 support. In particular, the Ni-Fe / 60%ASA@HZSM-5 catalyst exhibited the lowest hydrogen consumption at lower temperatures, indicating that the appropriate ratio of ASA:HZSM-5 support of 3:2 enabled it to generate more metal centers under mild conditions, thereby improving the reduction capacity of iron species and increasing the activity and stability of the Ni-Fe / 60%ASA@HZSM-5 catalyst.

[0038] The effect of the number of cycles on the catalyst activity was investigated by pyrolyzing Ni-Fe / 60%ASA@HZSM-5 catalyst at 800℃ and a flow rate of 1 ml / min for 40 min. The results are as follows: Figure 4 See Table 1.

[0039] Table 1

[0040] Table 1 shows the mass changes of the catalyst after reaction and regeneration. Each regeneration resulted in a higher catalyst mass than the original mass, indicating that the catalyst was collected relatively completely each time with minimal loss, making the data usable. In particular, after the fourth regeneration, the catalyst mass increased by 0.429 g compared to the original. This increase in mass is due to permanent carbon deposition, which cannot be eliminated by calcination and will cause permanent deactivation of some active sites on the catalyst. This non-calcinable carbon deposition is the main reason for the deterioration of catalyst activity and stability. Compared to the Ni-Fe / HZSM-5 catalyst, this significantly improves the carbon deposition content and demonstrates better anti-carbon deposition performance.

[0041] Combination Figure 4 (a) and Figure 4(b) It can be seen that with the increase of the number of cycles, the main gas release rate shows the same trend but exhibits a significant decreasing trend; furthermore, based on the toluene conversion rate, the toluene conversion rate does not change much in the four-cycle experiment, but the gas and liquid yields gradually decrease while the solid yield gradually increases. This indicates that with the increase of the number of cycles, the catalyst activity shows a certain decreasing trend, which is also due to... Figure 4 (c) and Figure 4 (d) As can be seen, overall, the Ni-Fe / 60%ASA@HZ-5 catalyst exhibits better catalytic activity. The partial replacement of HZSM-5 molecular sieves by ASA and its synergistic use as a support demonstrates better catalytic activity and stability.

[0042] Example 2: Application of catalysts in a two-dimensional evaluation system (1) Simulated tar system: First, based on the typical chemical structure characteristics and elemental composition of tar, benzene (C6H6, AR), toluene (C7H8, AR) and 1-methylnaphthalene (C 11 H 10 AR (C4H8O, AR) represents the main monocyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons with methyl side chains, and bicyclic aromatic hydrocarbons in tar, respectively; and tetrahydrofuran (C4H8O, AR), acetic acid (CH3COOH, AR), and n-heptanol (C7H4H8O, AR) are also mentioned. 16 O and AR represent heterocyclic compounds, aliphatic carboxylic acids, and oxygen-containing compounds, respectively, which are present in small amounts in tar components and have little impact on their catalytic cracking; cyclohexane (C6H) 12 AR) and n-heptane (C7H) 16 AR is a representative model compound of aliphatic alkane in tar.

[0043] Secondly, based on the content and composition characteristics of carbon, hydrogen, and oxygen elements in biomass tar, as well as the chemical formulas of representative model compounds, the proportions of representative model components in the composite model compounds were estimated. Among them, Model 1-1 (toluene: 1-methylnaphthalene: tetrahydrofuran: cyclohexane: n-heptane: acetic acid: benzene, with a mass ratio of 48:19:22:2:2:2:2) is a model compound covering all components of biomass tar, and Model 1-2 (toluene: 1-methylnaphthalene: tetrahydrofuran: n-heptol, with a mass ratio of 59:28:12:1) is a model compound including the main components of biomass tar.

[0044] Therefore, Model 1-1 and Model 1-2 were used as model compounds for the study of catalytic cracking mechanism of tar.

[0045] (2) Real tar system: Before the pyrolysis test, the sample tube containing the biomass sample was placed in the quartz glass reactor; N2 was introduced to check the airtightness of the device and to act as a protective gas. The flow rate of N2 was controlled at 90 mL / min using a rotor flow meter, and the temperature was increased to the set temperature at a rate of 10 °C / min. Starting from 200 °C, a gas sample passing through the cooling system was collected every 5 min, and the components and contents of the mixed gas were analyzed by gas chromatography (GC).

[0046] After the reaction, the increase in weight of the sample vial was the solid mass; after cooling, the liquid weight was measured to obtain the tar mass. The tar was extracted using CH2Cl2 as the extractant, and then separated into aliphatic (AL), aromatic (AR), ester (ES), complex aromatic oxygenated compounds (OC), and asphaltenes using a combination of distillation and column chromatography. The morphologies of the four groups are as follows: Figure 5 As shown, analysis of small amounts of different group components of tar fractions on GC-MS revealed that ES had the highest yield (46.96%) and consisted of furans (6.83%), phenols (76.94%), benzylamine (11.27%), alcohols (4.96%), and other oxygen-containing compounds with molecular weights between 98 and 225 Da; OC (22.58%) consisted of compounds with molecular weights between 258 and 455 Da; AR (16.46%) consisted of 1-4 ring aromatic hydrocarbons and oxygen-containing compounds with molecular weights between 128 and 312 Da; and AL consisted of alkanes and alkenes with molecular weights between 150 and 310 Da.

[0047] (3) Catalytic cracking to produce hydrogen: The reaction was carried out in an FD-BC type two-stage fixed bed reactor with a catalyst loading of 5 g, a reaction temperature of 800 ℃, a tar and model material flow rate of 0.6 mL / min, an H2O vapor flow rate of 1.25 mL / min, a CO2 flow rate of 40 mL / min, a N2 carrier gas flow rate of 90 mL / min, and a reaction time of 40 min. The experiment included a catalytic tar cracking reaction and a product analysis. Each time, the catalyst was placed in the second section of a fixed-bed reactor, and nitrogen (protective gas) was continuously introduced for 30 minutes to remove air from the pipeline and ensure an inert atmosphere. The primary fixed bed was heated to 600 °C at a heating rate of 20 °C / min, while the secondary fixed bed was simultaneously heated to 800 °C. Tar and its model material were injected into a gasifier via a constant-flow dual-plunger pump for gasification, and then fed into the primary fixed-bed reactor for pyrolysis and gasification. The gas underwent cracking and reforming in a fixed secondary reactor. The reaction products were sequentially condensed through a condensation system containing ice salt and ice water. The liquid phase in the gas was then removed through a drying pipeline to remove moisture, ensuring that only gaseous substances were collected as the final product.

[0048] (5) Results Analysis: A comparative analysis was conducted on the catalytic cracking processes of real tar and its composite model compounds. Figure 6 The product distribution and gas yield of tar and its model compound (Model 1-1) cracked at 800℃ are shown. Figure 6 (a) It can be seen that, compared with tar cracking, the yield of gaseous products after cracking of tar model compounds increased by 36.50%, while the yields of liquid and solid products decreased by 73.86% and 69.45%, respectively; indicating that under the same catalyst, the cracking of tar model compounds reduced the probability of polymerization and carbon deposition reactions, and tended to produce gas through cracking.

[0049] Depend on Figure 6 (b) It can be seen that the H2 yield in the gas produced by the catalytic cracking of the tar model compound reached a maximum of 159.27 mL / g. -model compound Secondly, the CH4 yield (88.58 mL / g) -model compound CO yield ranked third (17.59 mL / g). -model compound ), yielding 269.62 mL / g -model compound The total gas yield was increased by 10.17%, H2 yield increased by about 2 times, CH4 yield increased by about 6.77%, and CO2 yield decreased by 69.03% compared with tar cracking. This indicates that the probability of carbon deposit gasification reaction during the catalytic cracking of tar model compounds is relatively high.

[0050] In the simulated tar system Figure 7 The conversion rate and gaseous product distribution of catalytic cracking in Model 1-2 are shown. Figure 7 It can be seen that the conversion rate of Model 1-2 decreased by 4.93% under CO2 assistance. This is because the catalytic cracking of the model compound is an endothermic reaction. When CO2 passes through the catalyst bed along with the carrier gas and the vapor of the model compound, it carries away a certain amount of heat, resulting in insufficient reaction temperature in the reactor and a decrease in the cracking rate of the tar model compound. However, the conversion rates of H and C in the gas both increased, indicating that the decrease in cracking rate led to a decrease in coke deposition rate, while the gas production rate increased accordingly. The CO yield increased to 20.49%, indicating that CO2 mainly promoted the coke gasification reaction and improved the catalyst's resistance to coke deposition. Therefore, CO2 has a good promoting effect on the cracking of tar model compounds, and the various indicators are shown in Table 2.

[0051] Table 2. Indicators of tar model compound pyrolysis under CO2-assisted gas-phase conditions.

[0052] In a real tar system, the effects of different atmospheres (N2, N2 / CO2, N2 / CO2 / H2O, N2 / H2O) on the catalytic cracking behavior of tar were investigated at a pyrolysis temperature of 600 ℃ and a reforming temperature of 800 ℃. The results are as follows: Figure 8 .Depend on Figure 8 It can be seen that under N2 atmosphere, the yields of H2, CH4, and CO were the lowest, at 55.25 mL / g. -biomass 56.39 mL / g -biomass 54.27 mL / g -biomass Under an N2 / CO2 atmosphere, the yields of H2, CH4, and CO increased by 12.80%, 25.20%, and 43.16%, respectively, resulting in a higher hydrogen balance (40.72%), and the calorific value of the fuel gas was 19.91 MJ / m³. 3 However, it reduced the H2 / CO and S ratios. H2 This indicates that the introduction of CO2 reacts with free carbon to form CO, suggesting that CO2 preserves the pore structure of the catalyst and increases its graphitization. Compared to the N2 / CO2 atmosphere, the H2 yield and S2 yield are higher under the N2 / H2O atmosphere. H2 The yields increased significantly by 20.85% and 4.74%, respectively, while the yields of CH4 and CO decreased by 13.31% and 8.25%, respectively; the calorific value of the fuel gas was 17.12 MJ / m³. 3 Compared to the N2 atmosphere, the calorific value decreased by 5.55%, indicating that the water vapor atmosphere suppressed C4 formation, favoring the reaction towards H2 production and providing a hydrogen source for H2 generation. Under the N2 / CO2 / H2O atmosphere, the total gas yield significantly increased to 267.34 mL / g. -biomass The proportions of H2, CH4, and CO were 33.44%, 32.16%, and 34.40%, respectively. The yields of H2 and CO reached their maximum under all atmospheres, also achieving the largest H, C, and S balances. H2 .

[0053] Therefore, CO2 reduces the H2 / CO ratio of the fuel gas, increasing its calorific value; water vapor increases the H2 / CO ratio and hydrogen selectivity, decreasing its calorific value. However, the positive effect of CO2 on the calorific value of the fuel gas and the negative effect of water vapor on its calorific value achieve a synergistic effect, resulting in a calorific value of 19.52 MJ / m³. 3 The calorific value of the gas was determined; the negative effect of CO2 on the H2 / CO ratio of the gas and the positive effect of H2O on the H2 / CO ratio of the gas achieved a synergistic effect. Therefore, CO2 and H2O play an important role in improving gas quality.

[0054] In summary, in the field of biomass energy utilization, this catalyst can be directly embedded in the pyrolysis and gasification system of agricultural and forestry waste (corn stalks, forestry pruning branches, etc.). It converts polycyclic aromatic hydrocarbon tar (a pollutant difficult to treat in traditional processes) generated during the catalytic cracking process into high-purity hydrogen (volume fraction ≥65%), while simultaneously reducing tar emissions by over 90%, thus solving the "secondary pollution" problem in biomass hydrogen production at its source. Regarding the co-processing of industrial solid waste, the catalyst uses aluminum smelting waste slag as the core raw material (accounting for ≥60%). Each ton of catalyst prepared can dispose of 3-5 tons of industrial solid waste, significantly reducing soil heavy metal pollution and dust pollution caused by waste slag accumulation, achieving a circular economy model of "treating waste with waste." The CO2 introduced during the reaction not only acts as a reaction aid to increase hydrogen yield but also fixes CO2 in industrial exhaust gas, contributing to the achievement of carbon emission reduction targets.

[0055] This invention provides a method for preparing and applying a high-efficiency hydrogen production catalyst based on aluminum smelting waste residue under a dual-dimensional evaluation system for biomass pyrolysis tar. Through a complete and optimized technical path of acid washing-basic hydrothermal activation-nickel / auxiliary co-impregnation-specific calcination, it is directionally converted into a high-efficiency hydrogen production catalyst. The technological breakthroughs and unexpected technical effects are mainly reflected in the following three aspects: (1) Raw material innovation and performance breakthrough: A qualitative change from waste to high-efficiency catalyst has been achieved.

[0056] In existing technologies, the preparation of nickel-based catalysts using pure chemicals or conventional supports (such as Al2O3, SiO2) is the mainstream approach. Although there are reports of using waste residue, its catalytic performance (such as hydrogen production rate and stability) is usually far lower than that of commercial catalysts. This invention, through an original process, enables the hydrogen production activity of aluminum smelting waste residue-based catalysts to reach the level of some commercial nickel-based catalysts. Through the specific process of this invention, aluminum smelting waste residue is not a inferior substitute, but can become a high-performance catalyst precursor.

[0057] (2) Existing technologies mostly treat waste residue by simple acid washing or direct calcination. Acid washing mainly removes impurities, but may leave a dense skeleton with low specific surface area. In this invention, hydrothermal activation under alkaline pH is introduced after acid washing. This step realizes the reconstruction of microstructure and creates active surface, thereby significantly improving the catalyst's anti-sintering ability and long-term operational stability.

[0058] (3) Process synergy effect: The catalytic performance optimization achieved a "1+1>2" effect. The process of this invention is an organic whole. The optimized surface properties of the hydrothermally activated carrier have a synergistic effect with the subsequent nickel co-impregnation and two-stage calcination process, which effectively inhibits the loss of active nickel and the formation of carbon deposits during the reaction. This synergistic performance improvement achieved through a specific process chain cannot be achieved by simply copying existing technology segments.

[0059] (4) This invention introduces both H2O (steam) and CO2 simultaneously, instead of traditional steam reforming or simple CO2 reforming. This constructs a composite reaction system that combines steam reforming (SMR), dry reforming (DRM), and reverse water-gas shift (RWGS) reactions. It is specifically designed to treat biomass pyrolysis tar, a difficult-to-process raw material with extremely complex composition (containing phenols, polycyclic aromatic hydrocarbons, etc.) and prone to coking. In the prior art, there are two main pathways for biomass tar to produce hydrogen: one is to introduce steam to mainly promote tar cracking and methane reforming, but this easily leads to carbon deposition on the catalyst surface (Boudouard reaction: 2CO → C + CO2) and has limited ability to convert heavy aromatic hydrocarbons; the other is to use CO2 as a mild oxidant, which helps to eliminate carbon deposits (C + CO2 → 2CO), but the reaction is endothermic and energy-intensive, and CO2 has a weak initial cracking activation ability for tar macromolecules. The prior art usually regards these two reactions as alternative or competitive pathways, because simple mixing may lead to ineffective competitive adsorption or reaction pathway conflicts. Therefore, there is a lack of technical guidance on using H2O and CO2 as a pair of synergistic co-reactants and matching them with specific catalysts and precise process parameters to systematically solve the contradiction between cracking efficiency and anti-carbon deposition in tar conversion.

[0060] (6) This invention discovers and proves that in the specific aluminum smelting waste-based Ni-Fe bimetallic catalyst and H2O / CO2 co-feed system of this invention, the role of CO2 undergoes a qualitative leap. Experimental data shows that its role far exceeds the commonly known weak promotion or end-of-pipe carbon removal. Instead, through synergy with the unique active sites of the catalyst, it significantly promotes the initial activation and ring-opening of tar macromolecules (especially polycyclic aromatic hydrocarbons) in the early and middle stages of the reaction, thereby deeply coupling with the H2O pathway. This synergistically increases the tar conversion rate from about 85% under pure steam conditions to nearly 99%, and increases the hydrogen yield by more than 30%. This enhancement of the mechanism and effect of CO2 action caused by the specific catalyst and reaction environment completely exceeds the expectations of common knowledge in the field and constitutes the substantial feature of this invention.

[0061] The core concept of this invention lies in intelligently guiding H2O and CO2 to perform their respective functions and form a virtuous cycle on the catalyst surface through catalyst characteristics (specific components and structures derived from waste residue) and precisely controlled operating conditions (temperature, flow rate ratio). Water vapor primarily plays a strong cracking role, efficiently breaking CH and CC bonds in tar to generate small-molecule hydrocarbons and H2, which is the main contributing step in hydrogen production. CO2 mainly acts as an in-situ carbon remover and syngas regulator. On the one hand, it promptly removes intermediate carbon species generated by H2O cracking through dry reforming and reverse water-gas shift reaction, greatly inhibiting the formation and accumulation of carbon deposits. On the other hand, it participates in the reaction to regulate the H2 / CO ratio in the products. For the aluminum smelting waste residue-based catalyst prepared by this invention, under specific conditions of 600-800 °C, H2O to CO2 flow rate ratio of 1:1 to 1:2, and N2 carrier gas dilution, the above two reactions achieve dynamic equilibrium and perfect synergy. This produces the following unexpected effects, as evidenced by experimental data: (1) Significant synergistic improvement in hydrogen yield and tar conversion rate: At 750℃, using the H2O and CO2 co-feed mode, compared with the mode of using only equivalent H2O or only equivalent CO2, the tar conversion rate increased by nearly 20% from H2O and CO2 alone, and the hydrogen yield increased by more than 30%-60%, achieving a synergistic effect of 1+1>2.

[0062] (2) Revolutionary improvement in catalyst stability: After 40 min of reaction, under H2O and CO2 co-feed conditions, the amount of carbon deposits on the catalyst was reduced by more than 60% compared with the single steam condition, and the carbon deposits were more amorphous carbon that is easy to gasify, rather than graphite carbon that leads to deactivation; in long-term tests (>10 h), the activity decay rate of the catalyst under co-feed mode was much lower than that under any single atmosphere mode.

[0063] (3) Product controllability and process intensification: By adjusting the H2O / CO2 ratio, the H2 / CO ratio in the outlet syngas can be actively controlled within a certain range, making it more flexible to adapt to different needs such as downstream Fischer-Tropsch synthesis or methanol synthesis. This online adjustability is not available in single-atmosphere reactions.

[0064] In summary, this invention, using H2O and CO2 as co-reactants for catalytic hydrogen production from biomass tar, is the first to design and validate a composite reaction system and precise process parameters that enable H2O and CO2 to complement each other and synergistically enhance their effects, specifically targeting the characteristics of aluminum smelting waste-based catalysts. This invention successfully solves the industry challenge of balancing tar conversion rate and catalyst stability under traditional single-atmosphere conditions, achieving unexpected technical benefits such as significantly improved hydrogen yield and greatly enhanced catalyst resistance to carbon buildup.

[0065] In existing technologies, the development of catalysts for biomass tar reforming typically employs single-dimensional evaluation criteria, such as total hydrogen yield or tar conversion rate. This evaluation method cannot diagnose the causes of deactivation and provides poor guidance for complex reaction systems. Therefore, the technical problem this application aims to solve is to provide an evaluation and optimization method specifically designed to guide the development of high-performance catalysts suitable for H2O / CO2 co-reforming systems. To address this problem, this application creatively proposes a core evaluation system consisting of the following two interrelated and indispensable dimensions: Activity dimension (dimension one): hydrogen space-time yield (or instantaneous hydrogen production rate under specific conditions). This dimension directly quantifies the ability of a catalyst to efficiently crack and reform tar molecules to generate hydrogen in an H2O / CO2 coexisting atmosphere. Stability dimension (dimension two): the carbon deposition inhibition rate or activity decay rate under H2O / CO2 atmosphere within a specific reaction time; this dimension specifically quantifies the catalyst's ability to resist graphitization and carbon deposition caused by excessive dehydrogenation of intermediates in the presence of CO2.

[0066] The tests in both dimensions must be conducted under identical specific reaction conditions (temperature, H2O / CO2 ratio, etc.) protected by this application.

[0067] This dual-dimensional evaluation system brings technical benefits far exceeding those of general testing methods: by examining both dimensions simultaneously, the failure modes of catalysts can be quickly diagnosed. If dimension one is low and dimension two is high, it indicates that there are insufficient cracking active centers, and the loading or dispersion of active components should be optimized. If dimension one is high and dimension two is low, it indicates that although the initial activity is good, the anti-carbon deposition structure is poor, and the metal-support interaction should be strengthened or the additives should be adjusted.

[0068] In summary, the dual-dimensional evaluation system described in this invention is specifically designed for optimizing catalysts in the complex new system of H2O / CO2 synergistic reforming. It can not only evaluate performance but also diagnose problems, guide process optimization, and predict long-term stability, directly leading to the achievement of the final catalyst product performance (hydrogen yield of over 65% and high stability). This system, together with the preparation method and application conditions of this invention, constitutes a complete technical solution. The preparation method determines the initial properties of the catalyst, the evaluation system guides its optimization, and the application conditions are the final manifestation of its performance.

[0069] The effect of ASA loading on the catalytic performance of Ni-Fe / ASA@HZSM-5 catalyst is shown in the figure. Figure 9 The synergistic factors of aluminum ash and HZSM-5 molecular sieve as co-supports for H2 and CO yields were 1.30 and 1.70, respectively, demonstrating a dual role in improving H2 and CO yields and achieving synergistic regulation of catalytic and thermal conversion effects. (Synergistic factor (...)) SF ) is one of the parameters used to quantify this synergistic effect. Typically, SF It can be defined as: In the equation, the effect of the actual mixture is the hydrogen production observed in the experiment. The expected effect of the mixture is the expected hydrogen production calculated based on the weighted average of the hydrogen production when using ASA and HZMS-5 as catalysts alone and the mixing ratio. If SF > 1, it means there is a synergistic effect; SF = 1, it means there is no synergistic effect; SF < 1, it means there is an antagonistic effect.

[0070] This invention achieves unexpected synergistic effects far exceeding those of single-metal catalysts by introducing a nickel-iron bimetallic support. Under identical support and preparation conditions, comparative experimental data show that the hydrogen yield of the bimetallic catalyst supported on 8% Ni and 4% Fe increases from 53.7% to 68.5% compared to the catalyst supported on 8% Ni alone. More importantly, the carbon deposition after the reaction decreases dramatically from 12.5 wt% to 3.8 wt%, and the activity decay rate improves from 25% to less than 5%. This not only demonstrates that the addition of Fe significantly enhances the inherent activity of Ni, but more importantly, it fundamentally changes the catalyst's anti-carbon deposition pathway, solving the industry problem of the incompatibility between activity and stability in nickel-based catalysts during tar reforming. This synergistic effect of "1+1>2" resulting from constructing bimetallic active centers in a specific ratio is something that those skilled in the art could not have foreseen based on the common knowledge of single metals, constituting a substantial breakthrough of this invention.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a bimetallic catalyst based on aluminum smelting waste, characterized in that: include, The aluminum smelting waste residue is crushed and sieved, soaked in acid solution to remove impurities, washed with deionized water until neutral, and dried to obtain pretreated aluminum smelting waste residue. Pretreated aluminum smelting waste residue was mixed with deionized water, the pH value was adjusted to 8-10, and then transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, filtered, and dried to obtain the hydrothermally activated product. The hydrothermal activation product and HZSM-5 were mixed evenly and then used as a carrier. Prepare a nickel salt solution by adding 2%-10% of an additive by mass of the nickel salt solution, stirring until completely dissolved to obtain a mixed solution, adding a carrier, and using an excess impregnation method combined with ultrasonic assistance, and letting it stand at 25~35 ℃ for 6-12 h. The impregnated product is placed in a muffle furnace and heated to 200-300 ℃ at a heating rate of 5-10 ℃ / min, held for 1-2 h, and then heated to 500-700 ℃ at a heating rate of 3-5 ℃ / min, held for 3-5 h, and then naturally cooled to obtain an aluminum smelting waste-based bimetallic catalyst.

2. The preparation method according to claim 1, characterized in that: The sieving includes passing through a 100-200 mesh sieve.

3. The preparation method according to claim 1, characterized in that: The acid solution comprises a 1-7 mol / L sulfuric acid solution, and the soaking time in the acid solution is 2-4 h.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the pretreated aluminum smelting waste residue to deionized water is 1:5-1:10; the hydrothermal reaction temperature is 160-200 ℃, and the reaction time is 4-8 h.

5. The preparation method according to claim 1, characterized in that: The nickel salt solution is at least one of nickel nitrate solution and nickel chloride solution, and the auxiliary agent is at least one of FeCl3, CeO2, and MgO.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the hydrothermal activation product to HZSM-5 is 3:

2.

7. The preparation method according to claim 1, characterized in that: The solid-liquid ratio of the carrier to the mixed solution is 1:8 to 1:

12.

8. The application of the aluminum smelting waste-based bimetallic catalyst prepared by any one of claims 1 to 7 in the co-reforming of hydrogen from biomass tar, characterized in that: include, The catalyst is loaded into the catalytic section of a two-stage fixed-bed reactor; Adjust the reaction temperature to 600-800 ℃, introduce H2O and CO2, use N2 as the carrier gas, and react for 40 min. The steam flow rate is 0.625-1.25 mL / min, the CO2 flow rate is 10-40 mL / min, and the N2 flow rate is 50-90 mL / min.

9. The application as described in claim 8, characterized in that: The biomass pyrolysis equipment is a two-stage fixed-bed pyrolysis furnace with a pyrolysis heating rate of 10-30 ℃ / min; The volume ratio of H2O to CO2 introduced is 1:1 to 1:2.

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