Preparation method of Ni-based / dolomite catalyst for preparing synthesis gas through biomass gasification
By pretreating the dolomite support and loading Ni species with high dispersion, combined with precise reduction conditions, a high-performance Ni-based/dolomite catalyst was constructed. This solved the problems of reduced active sites and carbon deposition in traditional catalysts at high temperatures, achieving efficient tar conversion and a long-life catalyst, thus promoting the industrial application of biomass gasification technology.
Patent Information
- Application Number
- CN202511717937.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-02-13
AI Technical Summary
Traditional Ni-based catalysts are prone to reduced active sites and carbon deposition in harsh gasification reaction environments, leading to a decline in catalytic performance. Furthermore, the original dolomite support has a low specific surface area and underdeveloped pore structure, making it difficult to fully exert the synergistic catalytic effect.
A high-specific-surface-area composite oxide support was formed by high-temperature calcination and atmosphere control of dolomite support. Ni species were loaded by ultrasonic-assisted impregnation, and stable metal-support interaction was formed by precisely controlling H2 reduction conditions, thus constructing a high-performance Ni-based/dolomite catalyst.
It achieves high tar conversion rate, good syngas selectivity, and long catalyst life, solves the problems of catalyst activity and stability, and enhances the industrial application potential of biomass gasification technology.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomass-based syngas production technology, specifically referring to a method for preparing and operating a Ni-based / dolomite catalyst for biomass gasification to produce syngas. Background Technology
[0002] Syngas, a core chemical feedstock primarily composed of CO and H2, is widely used in modern energy and chemical processes such as Fischer-Tropsch synthesis, methanol synthesis, and hydrogen production. my country's energy structure—rich in coal, poor in oil, and lacking in natural gas—means that coal-based gasification for syngas production remains dominant, but this process has high carbon emission intensity and faces severe environmental pressure. Biomass energy, as a renewable and carbon-neutral green resource, is considered a crucial pathway to achieving a low-carbon transformation of chemical processes through gasification technology. This technology not only effectively treats agricultural waste but also converts biomass into high-value-added chemicals, which is of great significance for building a green circular economy system.
[0003] However, the industrial application of biomass gasification technology still faces core challenges. The large amount of tar byproducts generated during gasification not only clogs and corrodes downstream equipment but also covers catalyst active sites, leading to rapid catalyst deactivation. Tar has become a major bottleneck restricting the development of biomass gasification technology. Among numerous tar removal methods, catalytic cracking is widely recognized as the most promising technology route because it can directly convert tar into the target product, syngas, achieving efficient utilization of energy and materials.
[0004] In catalytic material systems, Ni-based catalysts have become the most widely studied tar cracking catalysts due to their excellent activity in breaking C-C and CH bonds and their relatively low cost. However, traditional Ni-based catalysts (such as Ni / Al2O3 and Ni / SiO2) face two major problems in the harsh gasification reaction environment: sintering of active components and carbon deposition. Under high-temperature conditions of 700-900 °C, Ni nanoparticles are prone to migration and aggregation, leading to a reduction in active sites and a decrease in catalytic performance. Secondly, severe carbon deposition occurs. The strong adsorption of intermediates such as olefins and aromatics on the Ni surface easily triggers deep dehydrogenation reactions, forming amorphous carbon or graphitic carbon covering the active centers; at the same time, side reactions such as the Budoal reaction and methane cracking can also induce filamentous carbon growth, causing catalyst pore blockage and structural damage.
[0005] To overcome these limitations, researchers have actively explored the optimization of the catalyst support. Natural dolomite (CaMg(CO3)2) has attracted attention due to its wide availability, low price, and certain catalytic activity. The CaO-MgO mixed oxides generated from its high-temperature decomposition exhibit good thermal stability and surface alkaline sites, promoting tar cracking and inhibiting carbon deposition. However, pristine dolomite suffers from low specific surface area and underdeveloped pore structure, limiting its ability to disperse and anchor Ni active components, thus hindering the full realization of synergistic catalytic effects.
[0006] To address the aforementioned issues, this study proposes a solution for constructing high-performance Ni-based / dolomite catalysts through an innovative preparation process. The core of this approach lies in: firstly, pretreating the dolomite support by controlling its pore structure and surface properties through high-temperature calcination and atmosphere regulation; subsequently, employing ultrasonic-assisted impregnation to achieve high dispersion and loading of Ni species; and finally, establishing stable metal-support interactions through precise control of reduction conditions. This method aims to simultaneously solve key issues such as catalyst activity, stability, and anti-coking performance, providing technical support for the industrial application of biomass gasification technology. Preliminary studies show that this catalyst exhibits significant advantages in tar conversion rate, syngas selectivity, and service life, demonstrating promising application prospects.
[0007] Based on the above conclusions, researching a method for preparing a supported Ni-based / dolomite catalyst will show great promise and advantages in the process of biomass gasification to syngas. Summary of the Invention
[0008] In order to overcome some of the problems mentioned in the background above, the present invention provides a method for preparing a Ni-based / dolomite catalyst for biomass gasification to syngas, so as to at least partially solve the above problems.
[0009] According to the technical solution of the present invention, a method for preparing a Ni-based / dolomite catalyst for biomass gasification to syngas is provided, comprising the following steps:
[0010] S1. Pretreatment of dolomite: The crushed and screened natural dolomite raw material is heat-treated in a nitrogen atmosphere through a two-stage temperature control program. The first stage is a medium-temperature calcination for initial activation and decomposition. After the intermediate heat preservation, it is transferred to the second stage of high-temperature calcination for crystal phase reconstruction and pore development. Then, it is subjected to programmed cooling, atmosphere protection cooling and dry environment physical stabilization treatment to obtain the pretreated dolomite carrier.
[0011] S2. Ni impregnation loading: Ni metal impregnation solution is prepared by dissolving nickel nitrate hexahydrate in deionized water and adding complexing agent as nickel source, and then impregnating and loading Ni species with the pretreated dolomite carrier in equal volume. After drying and calcination, Ni(NO3)2 is converted into Ni2O3 to obtain Ni2O3 and dolomite composite material.
[0012] S3. H2 reduction activation: The Ni2O3 and dolomite composite material was subjected to a programmed temperature reduction reaction in a fixed-bed reactor using a hydrogen-nitrogen mixture as the reducing atmosphere. The heating rate was controlled at 3℃ / min and maintained at 500℃ for 4h. Subsequently, the mixture was switched to 1% O2 / N2 mixture for 2h passivation treatment to obtain a Ni-based / dolomite catalyst with metallic Ni as the active center.
[0013] Preferably, in step S1, the crushing and screening mesh of the natural dolomite raw material is 100-150 mesh.
[0014] Preferably, the two-stage temperature control procedure in step S1 is as follows:
[0015] The first stage involves raising the temperature to 500~700℃ at a rate of 10℃ / min and holding it at that temperature for 1 hour.
[0016] The second stage involves increasing the temperature to 700~900℃ at a rate of 10℃ / min and holding it at that temperature for 3 hours.
[0017] Preferably, in step S1, before the two-stage temperature-controlled calcination, an acid washing step is also included: using a 0.5~1.5mol / L HCl solution, stirring at 60~80℃ for 1~2h to remove impurities.
[0018] Preferably, in step S2, the complexing agent is citric acid, and Ni 2+ The molar ratio with citric acid is 1:0.3 to 1:0.5.
[0019] Preferably, the equal-volume impregnation conditions in step S2 are as follows: the liquid-to-solid ratio of the pretreated dolomite carrier to the Ni metal impregnation solution is 1.5~2.5 ml / g, the impregnation temperature is 50℃, and the impregnation time is 2h.
[0020] Preferably, the drying and calcination process in step S2 includes: first, segmented drying at 80~120℃, followed by step calcination in air atmosphere, wherein the step calcination is carried out at 300~450℃ for 1 hour, and then at 400~600℃ for 2~4 hours.
[0021] Preferably, in step S2, the mass percentage of Ni2O3 in the Ni2O3 and dolomite composite material is 20%~30%.
[0022] Preferably, in step S3, the volume fraction of H2 in the hydrogen-nitrogen mixture is 5% to 15%.
[0023] On the other hand, the present invention also provides an application of the Ni / dolomite catalyst prepared by the preparation method in the biomass gasification to syngas production. 0.5~1.0 g of the catalyst is loaded into a reactor and the gasification reaction is carried out under the conditions of a reaction temperature of 700~850℃ and a water vapor to biomass mass ratio of 0.5~1.5:1.
[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0025] This invention utilizes a "calcination-carbonation" pretreatment process to not only remove crystal water and impurities from dolomite but also reconstruct its pore structure, forming a composite carrier with high specific surface area and suitable alkalinity. This carrier can efficiently disperse Ni species, and its alkaline sites can neutralize the acidic carbon deposit precursors generated during the cracking reaction, thus inhibiting tar formation and carbon deposition at the source.
[0026] This invention employs an ultrasonic-assisted equal-volume impregnation method, utilizing the ultrasonic cavitation effect to strongly promote the diffusion and adsorption of Ni precursor solution within the mesopores of a support, achieving a high degree of dispersion of Ni species at the atomic / nanoscale. The resulting NiO particles are small in size and uniformly distributed, laying the foundation for subsequent reduction to generate high-density, highly active metallic Ni centers;
[0027] This invention, by precisely controlling the temperature and time of H2 reduction, effectively promotes strong metal-support interactions between Ni nanoparticles and the pretreated dolomite support (especially the MgO phase) while gently reducing NiO to metallic Ni. This strong interaction, like a "pinning effect," greatly inhibits the migration and sintering of Ni particles under high-temperature reaction conditions, enabling the catalyst to maintain excellent activity and structural stability during long-term operation.
[0028] This invention optimizes the biomass gasification reaction pathway through the synergistic effect of a modified support and highly dispersed Ni active sites: the Ni centers are responsible for the efficient breaking of C-C and CH bonds, promoting the cracking and reforming of tar macromolecules; the basic sites on the support preferentially adsorb and activate CO2 and H2O molecules, promptly removing reaction intermediates through dry reforming and steam reforming reactions, and converting carbon deposits into CO and H2. This synergistic mechanism enables the catalyst to maintain a high syngas yield (>1.35 L / g biomass) and an ideal H2 / CO ratio (1.5-2.0) while reducing the tar content of the outlet gas to below 3 g / Nm³, and significantly extending the catalyst's single-pass lifetime to over 120 h. Detailed Implementation
[0029] The technical solutions in the embodiments are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.
[0030] This invention provides a method for preparing a Ni-based / dolomite catalyst for biomass gasification to syngas, comprising the following steps:
[0031] S1. Pretreatment of dolomite: Natural dolomite is crushed, ground, and sieved to obtain 60-100 mesh particles. It is then calcined in air at 800-950 ℃ for 2-4 h to fully decompose it into active CaO-MgO composite oxides. Subsequently, partial carbonation is carried out in CO2 atmosphere at 600-700 ℃ for 1-2 h, with the CO2 flow rate controlled at 100-200 mL / min, to form a CaO-MgO-CO2 composite carrier with abundant mesopores and a stable structure.
[0032] S2. Ni impregnation loading: Using nickel nitrate hexahydrate as the Ni source, a Ni metal impregnation solution was prepared according to the equal volume impregnation method, wherein the Ni loading amount was 5-15 wt% of the carrier mass; the impregnation solution was added dropwise to the pretreated dolomite carrier prepared in S1 above, and ultrasonically impregnated at 60℃ for 1-2 h; after impregnation, the sample was placed in an oven at 100-120℃ for 6-12 h to dry, and then calcined in air at 500-600℃ for 3-5 h to obtain Ni2O3 / dolomite composite material;
[0033] S3. H2 reduction and activation: The Ni2O3 / dolomite composite material prepared in S2 was placed in a tube furnace and reduced at 500-700℃ for 2-4 h in an H2 atmosphere. The H2 flow rate was controlled at 50-100 mL / min to fully reduce Ni2O3 to metallic Ni with high catalytic activity, and finally Ni / dolomite catalyst was obtained.
[0034] In a further embodiment of this example, the preferred conditions for the high-temperature calcination in step S1 are: calcination temperature of 850-900℃ and calcination time of 3 h.
[0035] In a further embodiment of this example, the preferred conditions for the partial carbonation treatment in step S1 are: treatment temperature 650℃, CO2 flow rate 150 mL / min, and treatment time 1.5 h.
[0036] In a further embodiment of this example, in step S2, the preferred loading of Ni is 8-12 wt%.
[0037] In a further embodiment of this example, the preferred conditions for ultrasonic impregnation in step S2 are: ultrasonic impregnation at 60 °C for 1.5 h at a liquid-solid ratio of carrier: impregnation liquid = 1 g: 1 ml.
[0038] In a further embodiment of this example, the preferred conditions for H2 reduction in step S3 are: reduction temperature 550-650 ℃ and reduction time 3 h.
[0039] A second objective of this invention is to provide an application of the Ni-based / dolomite catalyst, wherein 0.5-1.0 g of the Ni-based / dolomite catalyst is packed into a fixed-bed reactor, and a biomass gasification reaction is carried out under conditions of a gasification temperature of 700-850 °C and a steam-to-biomass mass ratio of 1-2.
[0040] Example 1
[0041] A method for preparing a Ni-based / dolomite catalyst for biomass gasification to syngas was disclosed, and the effect of adjusting the Ni loading on catalyst performance was investigated. While keeping the support pretreatment and reduction conditions constant, the Ni loading was adjusted to 8 wt% to explore the optimizing effect of moderately reducing the metal loading on the dispersion of active sites and catalyst stability.
[0042] The preparation method includes the following steps:
[0043] S1: Dolomite Pretreatment: Weigh 20.00 g of natural dolomite (60-80 mesh) and place it in a 100 mL alumina crucible. Place the crucible in a muffle furnace with an air atmosphere (flow rate 300 mL / min). Increase the temperature of the muffle furnace from room temperature to 900℃ at a heating rate of 5℃ / min and maintain the temperature at this temperature for 3 h. After calcination, allow it to cool naturally to room temperature to obtain a white, loose CaO-MgO composite oxide. Subsequently, take 10.00 g of the calcined sample, load it into a quartz boat, and transfer it to a tube furnace. Under a CO2 atmosphere (flow rate 150 mL / min), heat the sample to 650℃ at a rate of 3℃ / min and perform partial carbonation treatment at this temperature for 1.5 h. After treatment, cool the sample to below 200℃ under a CO2 atmosphere and remove it to obtain a pretreated dolomite carrier with a rich mesoporous structure.
[0044] S2: Ni Impregnation Loading: Accurately weigh 3.81 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, analytical grade), dissolve it in 10 mL of deionized water, and stir magnetically for 10 min until completely dissolved to prepare a Ni metal impregnation solution; weigh 10.00 g of the pretreated dolomite support obtained in step S1 and place it in a 50 mL beaker; add the Ni metal impregnation solution dropwise to the support at a rate of approximately 0.2 mL / time using a pipette, and continuously stir with a glass rod to ensure uniform impregnation; after the addition is complete, seal the beaker and place it in a 60℃ ultrasonic cleaner (power 300 W, frequency 40 kHz) for ultrasonic impregnation for 1.5 h; then transfer the slurry to a 120℃ forced-air drying oven and dry for 12 h; finally, calcine the dried sample in a muffle furnace at 550℃ for 4 h (heating rate 2 ℃ / min) to obtain the Ni2O3 / dolomite composite material;
[0045] S3: H2 reduction and activation: Weigh 2.00 g of the Ni2O3 / dolomite composite material obtained in step S2, spread it evenly in a quartz boat, and then put it into the constant temperature zone of a tube furnace; first, purge with N2 (flow rate 100 mL / min) for 30 min to remove air, and then switch the N2 to an H2 / N2 mixture (H2 volume fraction 10%, total flow rate 80 mL / min); heat to 600℃ at a rate of 3 ℃ / min, and reduce at this temperature for 3 h; after the reduction is completed, cool the reactor to room temperature under an H2 / N2 atmosphere, switch to pure N2 protection, take out the catalyst sample and seal it for storage, and the final Ni / dolomite catalyst is obtained.
[0046] Example 2
[0047] A method for preparing a Ni / dolomite-based catalyst for biomass gasification to syngas was disclosed, focusing on the effect of higher Ni loading on catalyst performance. Under the same preparation process, the Ni loading was increased to 12 wt% to explore the feasibility of further enhancing catalytic activity by increasing the number of active sites while maintaining dispersion.
[0048] The preparation method includes the following steps:
[0049] S1: Dolomite Pretreatment: Weigh 20.00 g of natural dolomite (60-80 mesh) and place it in a 100 mL alumina crucible. Place the crucible in a muffle furnace with an air atmosphere (flow rate 300 mL / min). Increase the temperature of the muffle furnace from room temperature to 900℃ at a heating rate of 5℃ / min and maintain the temperature at this temperature for 3 h. After calcination, allow it to cool naturally to room temperature to obtain a white, loose CaO-MgO composite oxide. Subsequently, take 10.00 g of the calcined sample, load it into a quartz boat, and transfer it to a tube furnace. Under a CO2 atmosphere (flow rate 150 mL / min), heat the sample to 650℃ at a rate of 3℃ / min and perform partial carbonation treatment at this temperature for 1.5 h. After treatment, cool the sample to below 200℃ under a CO2 atmosphere and remove it to obtain a pretreated dolomite carrier with a rich mesoporous structure.
[0050] S2: Ni Impregnation Loading: Accurately weigh 5.71 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, analytical grade), dissolve it in 10 mL of deionized water, and stir magnetically for 10 min until completely dissolved to prepare a Ni metal impregnation solution; weigh 10.00 g of the pretreated dolomite support obtained in step S1 and place it in a 50 mL beaker; add the Ni metal impregnation solution dropwise to the support at a rate of approximately 0.2 mL / time using a pipette, and continuously stir with a glass rod to ensure uniform impregnation; after the addition is complete, seal the beaker and place it in a 60℃ ultrasonic cleaner (power 300 W, frequency 40 kHz) for ultrasonic impregnation for 1.5 h; then transfer the slurry to a 120℃ forced-air drying oven for drying for 12 h; finally, calcine the dried sample in a muffle furnace at 550℃ for 4 h (heating rate 2 ℃ / min) to obtain the NiO / dolomite composite material;
[0051] S3: H2 reduction and activation: Weigh 2.00 g of the NiO / dolomite composite material obtained in step S2, spread it evenly in a quartz boat, and then put it into the constant temperature zone of a tube furnace; first, purge with N2 (flow rate 100 mL / min) for 30 min to remove air, then switch the N2 to an H2 / N2 mixture (H2 volume fraction 10%, total flow rate 80 mL / min); heat to 600℃ at a rate of 3 ℃ / min, and reduce at this temperature for 3 h; after the reduction is completed, cool the reactor to room temperature under an H2 / N2 atmosphere, switch to pure N2 protection, take out the catalyst sample and seal it for storage, thus obtaining the final Ni / dolomite catalyst.
[0052] Example 3
[0053] A method for preparing a Ni / dolomite-based catalyst for biomass gasification to syngas was disclosed, focusing on the effect of reduction temperature on the formation of Ni active sites. While keeping other preparation parameters constant, the H2 reduction temperature was adjusted to 550℃ to explore the regulatory effect of relatively mild reduction conditions on the formation of Ni particles of suitable size and the enhancement of metal-support interactions.
[0054] The preparation method includes the following steps:
[0055] S1: Dolomite Pretreatment: Weigh 20.00 g of natural dolomite (60-80 mesh) and place it in a 100 mL alumina crucible. Place the crucible in a muffle furnace with an air atmosphere (flow rate 300 mL / min). Increase the temperature of the muffle furnace from room temperature to 900℃ at a heating rate of 5℃ / min and maintain the temperature at this temperature for 3 h. After calcination, allow it to cool naturally to room temperature to obtain a white, loose CaO-MgO composite oxide. Subsequently, take 10.00 g of the calcined sample, load it into a quartz boat, and transfer it to a tube furnace. Under a CO2 atmosphere (flow rate 150 mL / min), heat the sample to 650℃ at a rate of 3℃ / min and perform partial carbonation treatment at this temperature for 1.5 h. After treatment, cool the sample to below 200℃ under a CO2 atmosphere and remove it to obtain a pretreated dolomite carrier with a rich mesoporous structure.
[0056] S2: Ni Impregnation Loading: Accurately weigh 4.76 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, analytical grade), dissolve it in 10 mL of deionized water, and stir magnetically for 10 min until completely dissolved to prepare a Ni metal impregnation solution; weigh 10.00 g of the pretreated dolomite support obtained in step S1 and place it in a 50 mL beaker; add the Ni metal impregnation solution dropwise to the support at a rate of approximately 0.2 mL / time using a pipette, and continuously stir with a glass rod to ensure uniform impregnation; after the addition is complete, seal the beaker and place it in a 60℃ ultrasonic cleaner (power 300 W, frequency 40 kHz) for ultrasonic impregnation for 1.5 h; then transfer the slurry to a 120℃ forced-air drying oven for drying for 12 h; finally, calcine the dried sample in a muffle furnace at 550℃ for 4 h (heating rate 2 ℃ / min) to obtain the NiO / dolomite composite material;
[0057] S3: H2 reduction and activation: Weigh 2.00 g of the NiO / dolomite composite material obtained in step S2, spread it evenly in a quartz boat, and then put it into the constant temperature zone of a tube furnace; first, purge with N2 (flow rate 100 mL / min) for 30 min to remove air, then switch the N2 to an H2 / N2 mixture (H2 volume fraction 10%, total flow rate 80 mL / min); heat to 550℃ at a rate of 3 ℃ / min, and reduce at this temperature for 3 h; after the reduction is completed, cool the reactor to room temperature under an H2 / N2 atmosphere, switch to pure N2 protection, take out the catalyst sample and seal it for storage, thus obtaining the final Ni / dolomite catalyst.
[0058] Example 4
[0059] A method for preparing a Ni / dolomite-based catalyst for biomass gasification to syngas was proposed, focusing on the effect of calcination temperature during support pretreatment. While keeping the Ni loading (10 wt%) and reduction conditions (600℃) constant, the dolomite calcination temperature was adjusted to 850℃ to investigate the key role of pretreatment temperature in the formation of the support pore structure and the regulation of surface properties.
[0060] The preparation method includes the following steps:
[0061] S1: Dolomite Pretreatment: Weigh 20.00 g of natural dolomite (60-80 mesh) and place it in a 100 mL alumina crucible. Place the crucible in a muffle furnace with an air atmosphere (flow rate 300 mL / min). Increase the temperature of the muffle furnace from room temperature to 850℃ at a heating rate of 5℃ / min and maintain the temperature at this temperature for 3 h. After calcination, allow it to cool naturally to room temperature to obtain a white, loose CaO-MgO composite oxide. Subsequently, take 10.00 g of the calcined sample, load it into a quartz boat, and transfer it to a tube furnace. Under a CO2 atmosphere (flow rate 150 mL / min), heat the sample to 650℃ at a rate of 3℃ / min and perform partial carbonation treatment at this temperature for 1.5 h. After treatment, cool the sample to below 200℃ under a CO2 atmosphere and remove it to obtain a pretreated dolomite carrier with a rich mesoporous structure.
[0062] S2: Ni Impregnation Loading: Accurately weigh 4.76 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, analytical grade), dissolve it in 10 mL of deionized water, and stir magnetically for 10 min until completely dissolved to prepare a Ni metal impregnation solution; weigh 10.00 g of the pretreated dolomite support obtained in step S1 and place it in a 50 mL beaker; add the Ni metal impregnation solution dropwise to the support at a rate of approximately 0.2 mL / time using a pipette, and continuously stir with a glass rod to ensure uniform impregnation; after the addition is complete, seal the beaker and place it in a 60℃ ultrasonic cleaner (power 300 W, frequency 40 kHz) for ultrasonic impregnation for 1.5 h; then transfer the slurry to a 120℃ forced-air drying oven and dry for 12 h; finally, calcine the dried sample in a muffle furnace at 550℃ for 4 h (heating rate 2 ℃ / min) to obtain the Ni2O3 / dolomite composite material;
[0063] S3: H2 reduction and activation: Weigh 2.00 g of the Ni2O3 / dolomite composite material obtained in step S2, spread it evenly in a quartz boat, and then put it into the constant temperature zone of a tube furnace; first, purge with N2 (flow rate 100 mL / min) for 30 min to remove air, and then switch the N2 to an H2 / N2 mixture (H2 volume fraction 10%, total flow rate 80 mL / min); heat to 600℃ at a rate of 3 ℃ / min, and reduce at this temperature for 3 h; after the reduction is completed, cool the reactor to room temperature under an H2 / N2 atmosphere, switch to pure N2 protection, take out the catalyst sample and seal it for storage, and the final Ni / dolomite catalyst is obtained.
[0064] Comparative Example 1
[0065] A comparative catalyst preparation method was provided to investigate the effect of support pretreatment steps on catalyst performance. This comparative example used untreated natural dolomite as the support, with other preparation steps consistent with Example 1. Specifically, natural dolomite (60-80 mesh) was directly used as the support without high-temperature calcination or atmosphere protection pretreatment, followed by Ni impregnation loading (10 wt%) and H2 reduction activation (600°C) following the same steps as in Example 1. This comparative example clearly demonstrates the key contributions of the support pretreatment process to the formation of mesoporous structures, regulation of surface alkalinity, and enhancement of metal-support interactions, verifying its necessity in improving the catalyst's resistance to carbon deposition and stability.
[0066] Comparative Example 2
[0067] A comparative catalyst preparation method was provided to evaluate the effect of ultrasound-assisted impregnation on Ni dispersion. In this comparative example, conventional mechanical stirring impregnation was used instead of ultrasound-assisted impregnation in the Ni impregnation loading step, while other conditions remained identical to those in Example 1. Specifically, during the impregnation process, the Ni impregnation solution was dropwise added to the pretreated dolomite support, placed in a 60°C water bath, and mechanically stirred at 400 rpm for 1.5 h. Subsequent drying, calcination, and reduction steps remained unchanged. This comparative example aims to demonstrate the superiority of ultrasonic cavitation effect in achieving efficient diffusion and uniform dispersion of Ni species within the support pores, and to elucidate its crucial role in forming high-density, small-size Ni active centers.
[0068] Comparative Example 3
[0069] A comparative catalyst preparation method is presented to verify the importance of the H2 reduction activation step in generating active sites for metallic Ni. This comparative example omits the H2 reduction step, directly using the calcined Ni2O3 / dolomite composite material as the catalyst for performance testing. Specifically, after Ni impregnation and loading and calcination at 550℃, no subsequent H2 reduction treatment is performed; the resulting Ni2O3 / dolomite material is directly used for reaction evaluation. This comparative example, by comparing the catalytic behavior of metallic Ni and Ni2O3 in the reaction, clarifies the crucial role of H2 reduction activation in generating metallic Ni sites with high dehydrogenation and cracking activity, proving that this step is indispensable for obtaining high-performance catalysts.
[0070] The catalysts obtained in Examples 1-4 and Comparative Examples 1-3 were used in the biomass gasification to syngas reaction. The reaction was carried out in a fixed-bed reactor equipped with a quartz reaction tube (20 mm inner diameter). Specific reaction conditions were as follows: catalyst loading of 0.80 g (mixed with 20-mesh quartz sand at a volume ratio of 1:3), reaction temperature of 800℃, water vapor injected into the gasification chamber by a micro-injection pump to mix with the biomass, a water vapor to biomass mass ratio (S / B) of 1.5, a biomass feed rate of 0.20 g / min, and N2 as the carrier gas at a flow rate of 100 mL / min. After the reaction had stabilized for 1 hour, the product gas was quantitatively analyzed using online gas chromatography, and the tar content was determined using a cold trap-gravimetric method. The reaction was continued until catalyst deactivation (defined as a tar conversion rate below 90%) to assess its lifetime. The performance comparison results are shown in Table 1.
[0071] Table 1. Performance Comparison of Catalysts in Biomass Gasification Reactions
[0072] sample Syngas yield (L / g biomass) <![CDATA[H2 / CO ratio]]> Tar conversion rate (%) Catalyst lifetime (h) Example 1 1.45 1.82 98.5 125 Example 2 1.48 1.75 98.9 115 Example 3 1.42 1.83 97.2 120 Example 4 1.41 1.81 97.0 122 Comparative Example 1 1.15 1.55 89.3 68 Comparative Example 2 1.32 1.78 94.1 92 Comparative Example 3 1.05 1.50 85.6 45
[0073] In summary, the Ni-based / dolomite catalyst prepared by the claimed technical solution exhibits excellent activity and stability in the catalytic biomass gasification reaction. As shown in Table 1, Examples 1-4 show significant improvements in syngas yield, H2 / CO ratio, tar conversion rate, and catalyst lifetime compared to Comparative Examples 1-3. Among them, Example 1 (10 wt% Ni loading, 900℃ pretreatment, 600℃ reduction) demonstrates the best overall performance. Comparative Example 1 shows that the untreated natural dolomite support has a poor structure, resulting in poor Ni dispersion and weak resistance to carbon deposition. Comparative Example 2 illustrates that the traditional stirring impregnation method has slightly lower Ni dispersion uniformity than the ultrasonic-assisted method, affecting the number and efficiency of active sites. Comparative Example 3 directly proves the necessity of metallic Ni active centers for this reaction, and the catalytic performance of the Ni2O3 precursor is very limited. This fully demonstrates that this application has successfully constructed a Ni active center with high density, high stability and excellent anti-carbon deposition ability through a three-step strategy of "support pretreatment - Ni high dispersion loading - controllable reduction". The synergistic effect of support pretreatment and metal loading effectively improves the comprehensive performance of the catalyst, which is of great value for promoting the industrial application of biomass gasification technology.
[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a Ni-based / dolomite catalyst for biomass gasification to syngas, characterized in that, Includes the following steps: S1. Pretreatment of dolomite: The crushed and screened natural dolomite raw material is heat-treated in a nitrogen atmosphere through a two-stage temperature control program. The first stage is a medium-temperature calcination for initial activation and decomposition. After the intermediate heat preservation, it is transferred to the second stage of high-temperature calcination for crystal phase reconstruction and pore development. Then, it is subjected to programmed cooling, atmosphere protection cooling and dry environment physical stabilization treatment to obtain the pretreated dolomite carrier. S2. Ni impregnation loading: Ni metal impregnation solution is prepared by dissolving nickel nitrate hexahydrate in deionized water and adding complexing agent as nickel source, and then impregnating and loading Ni species with the pretreated dolomite carrier in equal volume. After drying and calcination, Ni(NO3)2 is converted into Ni2O3 to obtain Ni2O3 and dolomite composite material. S3. H2 reduction activation: The Ni2O3 and dolomite composite material was subjected to a programmed temperature reduction reaction in a fixed-bed reactor using a hydrogen-nitrogen mixture as the reducing atmosphere. The heating rate was controlled at 3℃ / min and maintained at 500℃ for 4h. Subsequently, the mixture was switched to 1% O2 / N2 mixture for 2h passivation treatment to obtain a Ni-based / dolomite catalyst with metallic Ni as the active center.
2. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, In step S1, the crushing and screening mesh of the natural dolomite raw material is 100-150 mesh.
3. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, The two-stage temperature control procedure in step S1 is as follows: The first stage involves raising the temperature to 500~700℃ at a rate of 10℃ / min and holding it at that temperature for 1 hour. The second stage involves increasing the temperature to 700~900℃ at a rate of 10℃ / min and holding it at that temperature for 3 hours.
4. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, In step S1, before the two-stage temperature-controlled calcination, an acid washing step is also included: using a 0.5~1.5mol / L HCl solution, stirring at 60~80℃ for 1~2h to remove impurities.
5. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, In step S2, the complexing agent is citric acid, and Ni 2+ The molar ratio with citric acid is 1:0.3 to 1:0.
5.
6. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, The equal-volume impregnation conditions in step S2 are as follows: the liquid-to-solid ratio of the pretreated dolomite carrier to the Ni metal impregnation solution is 1.5~2.5 ml / g, the impregnation temperature is 50℃, and the impregnation time is 2h.
7. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, The drying and calcination process in step S2 includes: first, segmented drying at 80~120℃, followed by step calcination in air atmosphere, with step calcination being held at 300~450℃ for 1 hour, and then held at 400~600℃ for 2~4 hours.
8. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, In step S2, the mass percentage of Ni2O3 in the Ni2O3 and dolomite composite material is 20%~30%.
9. The method for preparing the Ni-based / dolomite catalyst for biomass gasification to syngas according to claim 1, characterized in that, In step S3, the volume fraction of H2 in the hydrogen-nitrogen mixture is 5% to 15%.
10. The application of a Ni / dolomite catalyst prepared by the method according to any one of claims 1-9 in biomass gasification to syngas, characterized in that, 0.5-1.0 g of the catalyst was loaded into the reactor and the gasification reaction was carried out at a reaction temperature of 700-850 °C and a steam-to-biomass mass ratio of 0.5-1.5:1.