Catalyst for hydrogen production by reforming tar steam as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for hydrogen production through tar steam reforming and a preparation method and application thereof. The catalyst comprises a cobalt-magnesium-aluminum composite spinel carrier and an active component loaded on the cobalt-magnesium-aluminum composite spinel carrier, the active component comprises nickel and at least one metal additive selected from iron, zirconium and ruthenium. The preparation method mainly comprises the following steps: preparing the carrier by adopting a coprecipitation method, loading the active component by adopting an impregnation method, and drying and reducing to obtain the final catalyst. The catalyst is used for tar component steam reforming hydrogen production reaction, especially for treating raw materials containing phenol and water vapor at 600-700 DEG C, tar conversion can be efficiently catalyzed, product gas rich in hydrogen can be generated, hydrogen selectivity is high, and almost no methane is generated. The catalyst has the advantages of high activity, good stability, strong carbon deposition resistance and the like, and is suitable for purification and high-value utilization of biomass pyrolysis tar.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and relates to a catalyst for hydrogen production from tar steam reforming, its preparation method and application. Background Technology

[0002] With the continued growth of global energy demand and the increasing severity of environmental problems, the energy structure relying on traditional fossil fuels urgently needs transformation. Developing clean and renewable energy sources such as solar, wind, biomass, and hydrogen energy has become an important strategic measure to achieve diversified energy supply and green sustainable development. As a major agricultural country, my country possesses abundant agricultural and forestry biomass resources, which are inexpensive and highly renewable. Converting biomass into high-value energy through appropriate and reasonable technological means can not only meet some of the clean energy demand but also serve as an effective way to achieve the resource utilization and high-value utilization of agricultural and forestry waste.

[0003] In biomass thermochemical conversion technologies (such as gasification and pyrolysis), large organic molecules in the feedstock undergo incomplete decomposition and repolymerization at high temperatures, generating a viscous, brownish-black liquid byproduct: tar. Tar has a complex composition, mainly including monocyclic aromatic hydrocarbons such as benzene and toluene, oxygen-containing compounds such as phenols, furans, and ketones, and small amounts of polycyclic aromatic hydrocarbons. Tar readily combines with moisture through condensation, exhibiting corrosive and toxic properties. It not only clogs and corrodes downstream pipelines and equipment, leading to decreased system efficiency and increased maintenance costs, but also causes environmental pollution and harms human health. Therefore, the efficient removal and conversion of tar is one of the key bottlenecks that must be addressed for the large-scale, commercial application of biomass thermochemical utilization technology.

[0004] Currently, tar treatment methods mainly fall into three categories: first, reducing its formation at the source through raw material pretreatment or optimized reaction conditions; second, in-situ removal within the reactor via catalytic reforming or thermal cracking; and third, subsequent purification treatment of the produced gas. Among these, catalytic steam reforming, as a highly efficient off-furnace treatment technology, can convert large molecular organic compounds in tar into hydrogen gas. Syngas components such as carbon monoxide (CO) can not only achieve deep removal of tar, but also obtain high-value-added energy products, which has significant economic benefits and environmental value.

[0005] Among numerous catalytic steam reforming catalysts, nickel (Ni)-based catalysts have been widely studied and applied due to their relatively low cost and high activity in breaking C-C and CH bonds. However, traditional nickel-based catalysts still have several prominent drawbacks in practical applications: First, to achieve high tar conversion rates, high reaction temperatures (usually above 750℃) are typically required, resulting in huge energy consumption; second, under harsh reaction conditions, the catalyst surface is easily deactivated due to carbon deposition, leading to insufficient stability and lifespan; third, a considerable proportion of methane is often generated in the reaction products. This not only reduces the selectivity and yield of the target product hydrogen, but also requires an additional reforming step to convert methane, increasing process complexity. How to develop catalysts that maintain high catalytic activity, excellent resistance to carbon deposition, and high hydrogen selectivity while significantly reducing reaction temperature remains a significant challenge in this field.

[0006] Therefore, developing a novel, efficient, stable, and low-temperature active tar steam reforming hydrogen production catalyst is of great significance for reducing energy consumption in biomass conversion processes, extending catalyst lifespan, improving hydrogen yield and purity, and thus promoting the development of organic solid waste resource utilization and renewable energy technologies. Summary of the Invention

[0007] The present invention aims to at least partially solve one of the technical problems existing in the prior art. To this end, the present invention proposes a catalyst for hydrogen production from tar steam reforming, its preparation method and application.

[0008] According to one aspect of the present invention, a catalyst is provided, comprising a cobalt-magnesium-aluminum composite spinel support and an active component supported on the support; the active component comprises nickel and at least one metal additive selected from iron, zirconium, and ruthenium.

[0009] Preferably, in the active component, the molar ratio of nickel to the metal additive is 10:(4~20).

[0010] Preferably, based on the total mass of the catalyst, the nickel loading is 2.0 wt% to 20.0 wt%, and the metal additive loading is 0.5 wt% to 10.0 wt%.

[0011] Preferably, the metal additive is iron.

[0012] Preferably, in the cobalt-magnesium-aluminum composite spinel carrier, the molar ratio of cobalt, magnesium, and aluminum is 1:1:4.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned catalyst is provided, comprising the following steps: S1, preparing the cobalt-magnesium-aluminum composite spinel support by co-precipitation method; S2, loading the active component onto the support by impregnation method, followed by drying and reduction treatment to obtain the catalyst.

[0014] Preferably, step S1 includes: S11, dissolving a cobalt source, a magnesium source, an aluminum source, and an organic chelating agent in water to prepare solution A; wherein, , , The molar ratio of the organic chelating agent to the organic chelating agent is 1:1:(1~4). The molar ratio is (1~6):1; S12, dissolve sodium carbonate and sodium hydroxide in water to prepare solution B; dissolve sodium hydroxide in water to prepare solution C; wherein, solution B and solution C contain... sum and The molar ratio is 4~8, in solution B and The molar ratio is 0.2~5; S13, solution A and solution B are added dropwise to solution C to carry out a co-precipitation reaction to obtain a precipitate; S14, the precipitate is filtered, washed, dried and calcined in sequence to obtain the cobalt magnesium aluminum composite spinel carrier.

[0015] According to another aspect of the present invention, a method for producing hydrogen by steam reforming tar components is provided, comprising the following steps: loading the above-mentioned catalyst into a reactor; heating the reactor to a reaction temperature under a carrier gas atmosphere; and introducing a feedstock containing tar components and water into the catalyst bed to carry out a steam reforming reaction to obtain a product gas rich in hydrogen.

[0016] Preferably, the tar component is phenol.

[0017] Preferably, in the raw materials, the molar ratio of water to carbon atoms in the tar component (S / C) is 10~20; and the reaction temperature is 600~700℃.

[0018] This invention constructs bimetallic active sites for nickel and specific metal additives (iron, zirconium, ruthenium) on a cobalt-magnesium-aluminum composite spinel support. The synergistic effect between the metals effectively optimizes the chemical properties of these active sites, significantly enhancing their ability to break C-C bonds in tar macromolecules. Compared to traditional single nickel-based catalysts, this catalyst achieves highly efficient conversion of typical tar components (such as phenol) at a lower reaction temperature of 600-700℃, with a maximum phenol conversion rate of 88.7%, effectively reducing system energy consumption.

[0019] The catalyst of this invention exhibits excellent product directivity in steam reforming reactions. The gaseous products generated by the reaction have a high hydrogen content and do not produce methane. This feature allows for the subsequent acquisition of high-purity hydrogen or hydrogen-rich syngas simply through carbon dioxide capture, simplifying the product separation and purification process and improving the overall economic efficiency of the process.

[0020] The catalyst provided by this invention exhibits excellent structural stability and resistance to deactivation during long-term operation. In a continuous stability test lasting up to 70 hours, the catalyst activity decayed slowly, without any rapid deactivation. This is mainly attributed to the stable structure of the composite spinel support and its strong interaction with the bimetallic active component, which effectively inhibits the sintering of the active metal and the formation of surface carbon, thus extending the catalyst's lifespan.

[0021] The catalyst preparation method of this invention (coprecipitation combined with impregnation method) is mature, with clear steps and controllable conditions, which is conducive to the large-scale preparation of the catalyst and lays a technical foundation for its practical application in the field of biomass tar purification and high-value utilization. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0023] Figure 1 This is a comparison chart of the catalytic performance of different catalysts provided in the embodiments of the present invention in the steam reforming reaction of phenol, a typical tar component.

[0024] Figure 2 It is provided according to the embodiments of the present invention. Figure showing the results of the stability test (lifetime experiment) of the catalyst in the phenol steam reforming reaction. Detailed Implementation

[0025] The following examples are provided to help those skilled in the art better understand the present invention. It should be noted that the following examples are not intended to limit the scope of protection claimed by the present invention, but are merely illustrative. Unless otherwise specified, the raw materials, reagents, or devices mentioned in the following examples are commercially available or obtained through known existing methods.

[0026] Example 1

[0027] This embodiment provides a composite catalyst for hydrogen production from steam reforming of typical tar components. The preparation method of phenol and its application in the steam reforming reaction are described in detail below:

[0028] (1) Preparation of cobalt-magnesium-aluminum composite spinel carrier

[0029] The support was prepared by coprecipitation method, and 2.91 g of cobalt nitrate hexahydrate ( ), 2.56g magnesium nitrate hexahydrate ( ), 15.00 g aluminum nitrate nonahydrate ( ) and 5.76 g citric acid ( ), together with , are dissolved in 50 mL of deionized water, and thoroughly mixed to prepare solution A. Among them, , , , The molar ratio with citric acid is approximately 1:1:4:4.

[0030] Preparation of solution B: Dissolve a certain amount of sodium carbonate and sodium hydroxide in deionized water to make the molar ratio of OH⁻ to Al³⁺ in the solution 4~8. and The molar ratio is 0.2~5.

[0031] Preparation of solution C: Dissolve a certain amount of sodium hydroxide in deionized water.

[0032] Under continuous stirring, solution A and solution B were slowly added dropwise to solution C using a constant flow pump. The co-precipitation reaction was carried out in an oil bath at 80°C, and stirring was continued for 12 hours until a complete precipitate was formed.

[0033] The obtained precipitate was filtered, and the filter cake was repeatedly washed with hot deionized water at 60-80℃ until the pH of the washing solution reached 7-8. Then, the filter cake was dried in a forced-air drying oven at 75℃ for 12 hours. The dried solid was ground into powder, transferred to a muffle furnace, and calcined at 750℃ for 4 hours in air. After calcination, it was naturally cooled to room temperature to obtain cobalt-magnesium-aluminum composite spinel. Carrier.

[0034] (2) Loading of active components and preparation of catalysts

[0035] The active metal component was loaded onto the above-mentioned support using an equal-volume impregnation method. 0.25 g of nickel nitrate hexahydrate (…) was weighed out. ) and 0.15 g ferric nitrate nonahydrate ( They were dissolved together in an appropriate amount of 50 wt% methanol aqueous solution to prepare a total metal salt solution.

[0036] Weigh 1.00 g of the cobalt-magnesium-aluminum composite spinel carrier obtained in step (1) and place it in a container. Add the prepared metal salt solution dropwise to the carrier to ensure uniform impregnation. After stirring and impregnating at room temperature for 12 hours, transfer the mixture to a 75°C forced-air drying oven and dry for 12 hours to remove the solvent.

[0037] The dried solid precursor was placed in a tube furnace and reduced under a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 600 °C at a rate of 10 °C / min and held at 600 °C for 2 hours. After reduction, the precursor was cooled to room temperature under hydrogen protection to obtain the target catalyst. .

[0038] (3) Catalyst performance evaluation

[0039] The catalyst prepared above was applied to the phenol steam reforming hydrogen production reaction to evaluate its catalytic performance. 0.2 g of catalyst was weighed and uniformly mixed with 0.8 g of quartz sand, then packed into the isothermal zone of a fixed-bed reactor and fixed at both ends with quartz wool. Before the reaction, high-purity nitrogen gas at a rate of 25 mL / min was introduced as a carrier gas to purge the reaction system for 30 minutes. Subsequently, under continuous nitrogen carrier gas supply, the reactor was heated to 650 °C at a heating rate of 10 °C / min. After the temperature stabilized, a 5.5% (w / w) aqueous solution of phenol (the carbon molar ratio of water to phenol, S / C, is approximately 16.7) was continuously introduced into the reactor via a syringe pump at a rate controlled at 0.35 mL / min. The gaseous products generated by the reaction were condensed and dehydrated, collected using a gas bag, and their composition was analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD).

[0040] The test results show that at a reaction temperature of 650℃, the catalyst prepared in this example has a phenol conversion rate of 78.74% and a hydrogen yield of 76.98%, demonstrating good catalytic activity.

[0041] Example 2

[0042] This embodiment provides a composite catalyst for hydrogen production from steam reforming of typical tar components. Preparation method and performance evaluation of ).

[0043] Catalyst preparation

[0044] (1) Preparation of cobalt-magnesium-aluminum composite spinel carrier

[0045] The support was synthesized using a coprecipitation method. First, 2.91 grams of cobalt nitrate hexahydrate (… ), 2.56 grams of magnesium nitrate hexahydrate ( ), 15.00 grams of aluminum nitrate nonahydrate ( ) and 5.76 grams of citric acid ( ), together dissolved in 50 ml of deionized water, and stirred thoroughly to form a homogeneous and transparent solution A. Among them, , , The molar ratio of citric acid to citric acid is controlled at approximately 1:1:4:4.

[0046] Subsequently, an alkaline precipitant solution was prepared: appropriate amounts of sodium carbonate and sodium hydroxide were dissolved in deionized water to prepare solution B, and the concentration of the precipitant was controlled. and The molar ratio is 4~8. and The molar ratio is 0.2~5; in addition, an appropriate amount of sodium hydroxide is dissolved in deionized water to prepare solution C.

[0047] With continuous stirring, solution A and solution B were slowly added dropwise to solution C using a constant flow pump. The co-precipitation reaction was carried out in an oil bath at 80°C, and the mixture was stirred continuously for 12 hours to ensure complete precipitation.

[0048] After the reaction, the resulting suspension was filtered, and the filter cake was repeatedly washed with hot deionized water at 60-80°C until the pH of the washing solution was 7-8. The washed filter cake was then dried in a forced-air drying oven at 75°C for 12 hours. The dried solid was ground into powder and placed in a muffle furnace, where it was calcined at 750°C for 4 hours in air. After calcination, the powder was allowed to cool naturally to room temperature to obtain cobalt-magnesium-aluminum composite spinel. Carrier powder.

[0049] (2) Loading of active components and activation of catalyst

[0050] The active metal was loaded using an equal-volume impregnation method. 0.25 g of nickel nitrate hexahydrate (…) was weighed out. ) and 0.37 g of ferric nitrate nonahydrate ( The total metal salt impregnation solution is prepared by dissolving the metal salts together in an appropriate amount of 50 wt% methanol aqueous solution.

[0051] Weigh 1.00 g of the carrier powder prepared in the above steps and place it in a container. Add the prepared impregnation solution dropwise to the carrier, ensuring uniform wetting, and then stir continuously at room temperature for 12 hours.

[0052] The impregnated material was transferred to a 75°C forced-air drying oven and dried for 12 hours to completely remove the solvent. The dried precursor was then placed in a tube furnace and subjected to programmed temperature reduction under a hydrogen atmosphere. The reduction program was as follows: the temperature was increased from room temperature to 600°C at a rate of 10°C / min, and then maintained at 600°C for 2 hours. After reduction, the material was cooled to room temperature under hydrogen protection to obtain the target catalyst. .

[0053] Catalyst performance testing

[0054] The prepared catalyst was applied to the steam reforming reaction of phenol to evaluate its activity and stability. In a fixed-bed reactor, 0.2 g of catalyst (uniformly mixed with 0.8 g of silica sand) was charged, and the reaction temperature was set at 650 °C. High-purity nitrogen was used as the carrier gas at a flow rate of 25 mL / min. The reactant was a 5.5% (w / w) aqueous solution of phenol (the carbon molar ratio of water to phenol, S / C, was approximately 16.7), continuously fed via a syringe pump at a rate of 0.35 mL / min. The gaseous products after the reaction were condensed to remove water, and their composition was analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD).

[0055] The catalyst prepared in this embodiment achieved an initial conversion rate of 88.7% for phenol and a hydrogen yield of 82.78% at a reaction temperature of 650°C. To investigate the catalyst's stability, a continuous reaction test was conducted for up to 70 hours. The results showed that after 70 hours of reaction, the phenol conversion rate remained at 78.58%, and the hydrogen yield was 68.39%, demonstrating excellent catalytic activity and long-term operational stability.

[0056] Example 3

[0057] This embodiment provides a composite catalyst for hydrogen production from steam reforming of typical tar components. Preparation method of phenol and its application in phenol steam reforming reaction.

[0058] Catalyst preparation

[0059] (1) Cobalt-magnesium-aluminum composite spinel Preparation of carrier

[0060] The support was synthesized using a coprecipitation method. 2.91 g of cobalt nitrate hexahydrate (…) was accurately weighed. ), 2.56 grams of magnesium nitrate hexahydrate ( ), 15.00 grams of aluminum nitrate nonahydrate ( ) and 5.76 grams of citric acid ( ), and together they are dissolved in 50 ml of deionized water and magnetically stirred until completely dissolved to form solution A.

[0061] Preparation of alkaline coprecipitant: Dissolve appropriate amounts of sodium carbonate and sodium hydroxide in deionized water to prepare solution B, controlling the concentration of... The total concentration to the molar ratio of Al³⁺ in the solution is 4~8. and The molar ratio is 0.2~5; a sodium hydroxide solution C of a certain concentration is also prepared.

[0062] With continuous stirring, solutions A and B were slowly added dropwise to a reactor containing solution C using a constant flow pump. The co-precipitation reaction was carried out under an oil bath at 80°C. After the addition was completed, stirring was continued for 12 hours to allow the precipitate to age completely.

[0063] After the reaction, the resulting slurry was filtered, and the filter cake was repeatedly washed with hot deionized water at 60-80℃ until the pH of the washing liquid reached 7-8. The washed filter cake was then dried in a 75℃ forced-air drying oven for 12 hours. The dried solid was ground into powder, placed in a muffle furnace, and heated to 750℃ at a rate of 5℃ / min under air atmosphere, and calcined at this temperature for 4 hours. After calcination, it was naturally cooled to room temperature to obtain cobalt-magnesium-aluminum composite spinel carrier powder.

[0064] (2) Active component loading and catalyst reduction

[0065] The active metals nickel and iron were loaded using an equal-volume impregnation method. 0.25 g of nickel nitrate hexahydrate (…) was accurately weighed. ) and 0.73 g of ferric nitrate nonahydrate ( The total metal salt impregnation solution was prepared by dissolving the metal salts together in an appropriate amount of 50 wt% methanol-water mixed solvent.

[0066] Weigh 1.00 g of the product prepared in the above steps. The carrier powder was placed in a crucible. The prepared mixed metal salt impregnation solution was added dropwise to the carrier, with constant stirring to ensure uniform impregnation. The mixture was then allowed to age at room temperature for 12 hours.

[0067] The impregnated and aged material was transferred to a 75°C forced-air drying oven and dried for 12 hours to completely remove the solvent. The dried catalyst precursor was then transferred to a tubular reduction furnace for programmed temperature reduction under a pure hydrogen atmosphere (flow rate 50 mL / min). The reduction program was set as follows: increasing the temperature from room temperature to 600°C at a rate of 10°C / min, and maintaining this temperature at 600°C for 2 hours. After reduction, the material was cooled to room temperature under hydrogen protection to obtain the final catalyst product, denoted as […]. .

[0068] Catalyst performance evaluation

[0069] The performance of the prepared catalyst in phenol vapor reforming for hydrogen production was evaluated using a fixed-bed microreactor. 0.20 g of the catalyst (20-40 mesh) was weighed and uniformly mixed with 0.80 g of quartz sand (20-40 mesh), then packed into the isothermal zone of a reaction tube and secured at both ends with quartz wool. Before the reaction, the system was purged with high-purity nitrogen at a flow rate of 50 mL / min for 30 minutes. Subsequently, the reactor was heated to 650 °C and stabilized under a nitrogen carrier gas atmosphere at a heating rate of 10 °C / min. A 5.5% (w / w) aqueous solution of phenol (with a carbon molar ratio of water to phenol of approximately 16.7) was continuously injected into the preheating vaporization section using a syringe pump at a rate controlled at 0.35 mL / min. After removing liquid water by condensation in an ice-water bath, the gaseous products were collected periodically using a gas bag, and their composition was analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD).

[0070] Under reaction conditions of 650℃, normal pressure, and S / C≈16.7, the product prepared in this example... The performance of the phenol steam reforming reaction on the catalyst is as follows: phenol conversion rate 81.55%; hydrogen yield 75.81%. Test results show that the catalyst exhibits good steam reforming activity and hydrogen production selectivity for phenol, a typical tar model compound, under the stated conditions.

[0071] Example 4

[0072] This embodiment provides a catalyst using zirconium (Zr) as a metal promoter. Preparation method of ) and its performance evaluation in phenol steam reforming hydrogen production reaction.

[0073] Preparation of chemical agents

[0074] (1) Cobalt-magnesium-aluminum composite spinel Preparation of carrier

[0075] The support was prepared using a coprecipitation method. The specific steps were as follows: 2.91 grams of cobalt nitrate hexahydrate (… ), 2.56 grams of magnesium nitrate hexahydrate ( ) and 15.00 grams of aluminum nitrate nonahydrate ( ) as the metal source, and 5.76 grams of citric acid were added at the same time. As an organic chelating agent, the above substances were dissolved together in 50 ml of deionized water and magnetically stirred to form a homogeneous and transparent mixed salt solution, denoted as solution A.

[0076] Preparation of alkaline precipitant: Dissolve the calculated amounts of sodium carbonate and sodium hydroxide in deionized water to obtain solution B. Control the total concentration of OH⁻ ions in solution B to be similar to that in solution A. The molar ratio is 4~8. and The molar ratio is 0.2~5; a sodium hydroxide solution C of a certain concentration is also prepared.

[0077] Under constant temperature of 80℃ and continuous stirring, solutions A and B were slowly added dropwise together to a reaction vessel containing solution C using a dual-channel constant flow pump to carry out a co-precipitation reaction. After the addition was complete, the mixture was stirred and aged in an 80℃ oil bath for 12 hours.

[0078] After the reaction, the resulting slurry was vacuum filtered, and the filter cake was repeatedly washed with hot deionized water at 60-80℃ until the pH of the washing liquid reached 7-8. The filter cake was transferred to a forced-air drying oven and dried at 75℃ for 12 hours. The dried solid blocks were ground into powder, placed in a muffle furnace, and heated to 750℃ at a programmed heating rate of 5℃ / min under air atmosphere, and calcined at this temperature for 4 hours. After natural cooling, the desired cobalt-magnesium-aluminum composite spinel carrier powder was obtained.

[0079] (2) Loading of active components and activation of catalyst

[0080] The active metallic nickel and the additive zirconium were loaded using an equal-volume impregnation method. 0.25 g of nickel nitrate hexahydrate (… ) and 0.094 g zirconium nitrate pentahydrate ( The metal salts were dissolved together in an appropriate amount of 50 wt% methanol aqueous solution, and ultrasonically assisted to completely dissolve them, thus preparing a clear mixed metal salt impregnation solution.

[0081] Accurately weigh 1.00 g of the above-prepared... The carrier powder was placed in a crucible. The prepared nickel-zirconium mixed impregnation solution was added dropwise to the carrier, and the crucible was gently shaken continuously to ensure uniform impregnation. The mixture was then allowed to age at room temperature for 12 hours.

[0082] The impregnated and aged wet material was placed in a 75°C forced-air drying oven and dried for 12 hours to completely remove solvent and moisture. The dried catalyst precursor was then transferred to a tube furnace for reduction activation under a pure hydrogen atmosphere (flow rate of 50 mL / min). The reduction procedure was as follows: the temperature was increased from room temperature to 600°C at a rate of 10°C / min and held at 600°C for 2 hours. After reduction, the material was cooled to room temperature under a hydrogen atmosphere to obtain the final catalyst product, denoted as […]. .

[0083] Catalyst performance evaluation

[0084] The performance of the catalyst in phenol vapor reforming was evaluated using a fixed-bed microreactor. 0.20 g (20-40 mesh) of the prepared catalyst was weighed and uniformly mixed with 0.80 g of silica sand of the same particle size. The mixture was then packed into the isothermal zone of the reaction tube and secured at both ends with silica wool. Before the reaction began, the reaction system was purged with high-purity nitrogen at a flow rate of 50 mL / min for 30 minutes. Subsequently, the carrier gas was switched to high-purity nitrogen at a flow rate of 25 mL / min, and the reactor was heated to the target temperature of 650 °C at a heating rate of 10 °C / min and stabilized. A 5.5% (w / w) aqueous solution of phenol (with a carbon molar ratio of water to phenol of approximately 16.7) was continuously injected into the vaporization section of the system using a precision injection pump at a feed rate of 0.35 mL / min. After the reaction, the outflowing gas is condensed in an ice-water trap to remove entrained moisture and unreacted organic matter. It is then collected in a gas bag with timed sampling and analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD).

[0085] Under standard test conditions of reaction temperature 650℃, atmospheric pressure, water-to-carbon ratio S / C≈16.7, and nitrogen carrier gas, the product prepared in this example... The phenol steam reforming reaction exhibited the following performance on the catalyst: phenol conversion rate 76.2%; hydrogen yield 71.14%. Test results indicate that the nickel-based bimetallic catalyst prepared using zirconium (Zr) as a metal promoter demonstrates certain catalytic activity and hydrogen selectivity for the phenol steam reforming hydrogen production reaction in the reaction system described in this invention.

[0086] Example 5

[0087] This embodiment provides a catalyst using the noble metal ruthenium (Ru) as a metal promoter. Preparation method of ) and its performance evaluation in phenol steam reforming hydrogen production reaction.

[0088] Catalyst preparation

[0089] (1) Cobalt-magnesium-aluminum composite spinel Preparation of carrier

[0090] The support was prepared using a coprecipitation method. 2.91 g of cobalt nitrate hexahydrate (…) was accurately weighed. ), 2.56 grams of magnesium nitrate hexahydrate ( ) and 15.00 grams of aluminum nitrate nonahydrate ( ) as the metal source, and added 5.76 grams of citric acid ( As an organic chelating agent, the above materials were dissolved together in 50 ml of deionized water and magnetically stirred to form a homogeneous and transparent mixed salt solution, labeled as solution A.

[0091] Preparation of alkaline coprecipitant: Dissolve the calculated amounts of sodium carbonate and sodium hydroxide in deionized water to prepare solution B, ensuring that... Total ion concentration and solution A The molar ratio is 4~8. and The molar ratio is 0.2~5; at the same time, a sodium hydroxide solution C of a certain concentration is prepared.

[0092] Under constant temperature oil bath conditions of 80℃ and continuous stirring, solutions A and B were simultaneously and slowly added dropwise to a reactor containing solution C using a constant flow pump to carry out a co-precipitation reaction. After the addition was complete, stirring and aging continued at 80℃ for 12 hours.

[0093] After the reaction, the resulting precipitate slurry was vacuum filtered, and the filter cake was thoroughly washed with hot deionized water at 60-80℃ until the pH of the washing liquid reached 7-8. The filter cake was placed in a forced-air drying oven and dried at 75℃ for 12 hours. The dried solid was ground into powder, transferred to a muffle furnace, and calcined at 750℃ in air at a programmed heating rate of 5℃ / min for 4 hours. After natural cooling, cobalt-magnesium-aluminum composite spinel carrier powder was obtained.

[0094] (2) Active component loading and catalyst reduction

[0095] The active metal nickel and the noble metal additive ruthenium were loaded using an equal-volume impregnation method. First, 0.25 grams of nickel nitrate hexahydrate (… The nickel and ruthenium were dissolved in an appropriate amount of 50 wt% methanol aqueous solution. Then, 1.0 mL of ruthenium trichloride (RuCl3) aqueous solution with a concentration of 0.02 g / mL was added to the solution, and the mixture was magnetically stirred to ensure thorough mixing, thus preparing a clear mixed impregnation solution containing nickel and ruthenium.

[0096] Accurately weigh 1.00 gram of the product prepared in the above steps. Carrier powder. The prepared nickel-ruthenium mixed impregnation solution was added dropwise to the carrier, with slight agitation during the process to ensure uniform impregnation. It was then allowed to age at room temperature for 12 hours.

[0097] The impregnated and aged material was placed in a 75°C forced-air drying oven and dried for 12 hours to completely remove the solvent. The dried catalyst precursor was then placed in a tubular reduction furnace and activated under a pure hydrogen atmosphere (flow rate 50 mL / min). The reduction procedure was as follows: the temperature was increased from room temperature to 600°C at a rate of 10°C / min, and then maintained at 600°C for 2 hours. After the reduction process, the material was cooled to room temperature under hydrogen protection to obtain the final catalyst product, denoted as […]. .

[0098] Catalyst performance evaluation

[0099] The performance of the catalyst in phenol vapor reforming for hydrogen production was evaluated in a fixed-bed microreactor. 0.20 g (20-40 mesh) of the catalyst prepared above was weighed and mixed uniformly with 0.80 g of quartz sand of the same particle size. The mixture was then packed into the isothermal zone of the reaction tube and fixed at both ends with quartz wool.

[0100] Before the reaction began, the reaction system was purged with high-purity nitrogen at a flow rate of 50 mL / min for 30 minutes. Subsequently, the carrier gas was stabilized at a flow rate of 25 mL / min with high-purity nitrogen, and the reactor was heated to the target temperature of 650°C at a heating rate of 10°C / min. A 5.5% (w / w) aqueous solution of phenol (with a carbon molar ratio of approximately 16.7 for water to phenol) was continuously injected into the vaporization section of the system using a precision syringe pump at a rate controlled at 0.35 mL / min. The gaseous products after the reaction were condensed in an ice-water bath to remove moisture, collected periodically using a gas bag, and their composition was analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD).

[0101] Under the standard evaluation conditions of a reaction temperature of 650°C, atmospheric pressure, a water-to-carbon ratio (S / C) of approximately 16.7, and nitrogen as the carrier gas, the product prepared in this example... The performance of the phenol steam reforming reaction on the catalyst is as follows: phenol conversion rate is 78.96%; hydrogen yield is 73.06%. Test results show that the nickel-based bimetallic catalyst prepared with ruthenium (Ru) as a promoter exhibits good catalytic activity and hydrogen production selectivity for the phenol steam reforming hydrogen production reaction in the reaction system described in this invention.

[0102] Comparative Example 1

[0103] This comparative example provides a catalyst that does not contain metal additives and uses nickel as the sole active component. The preparation method of ) and its performance evaluation in the phenol steam reforming hydrogen production reaction are used for comparison with the foregoing embodiments of the present invention.

[0104] Preparation of chemical agents

[0105] (1) Cobalt-magnesium-aluminum composite spinel Preparation of carrier

[0106] The carrier preparation method is the same as that described in Example 1 of this invention. That is, a co-precipitation method is used, employing the same mass of cobalt nitrate, magnesium nitrate, aluminum nitrate, and citric acid (respectively...). , , , Solution A was prepared, and a sodium carbonate / sodium hydroxide mixed solution (solution B) and a sodium hydroxide solution (solution C) were used as precipitants. The mixture was co-precipitated in an oil bath at 80°C with stirring, filtered, washed with hot deionized water at 60-80°C (to pH 7-8), dried at 75°C for 12 hours, ground, and then calcined at 750°C in air for 4 hours to obtain the final product. Carrier powder.

[0107] (2) Loading of active components and activation of catalyst

[0108] The method employs equal-volume impregnation, loading only active metallic nickel without adding any metal additives. Weigh 0.25 g of nickel nitrate hexahydrate (… Dissolve it in an appropriate amount of 50 wt% methanol aqueous solution to prepare a single metal salt impregnation solution.

[0109] Weigh 1.00 g of the above-prepared Carrier powder. Nickel nitrate impregnation solution was added dropwise to the carrier, and the mixture was stirred at room temperature for 12 hours to ensure uniform impregnation. The material was then dried at 75°C for 12 hours. The dried precursor was placed in a tube furnace and subjected to programmed temperature reduction under a hydrogen atmosphere (flow rate 50 mL / min), under the same conditions as in the example: the temperature was increased from room temperature to 600°C at a rate of 10°C / min, and then isothermal reduction was performed at 600°C for 2 hours. After reduction, the catalyst was cooled to room temperature under hydrogen protection to obtain a single nickel-based catalyst, denoted as […]. .

[0110] Catalyst performance testing

[0111] The catalyst performance testing conditions were kept consistent with those of the embodiments of the present invention to ensure comparability of results: 0.2 g of catalyst (mixed with quartz sand) was loaded into a fixed-bed reactor, and a steam reforming reaction was carried out at 650°C with nitrogen gas at a rate of 25 mL / min and 5.5 wt% phenol aqueous solution (inlet rate of 0.35 mL / min). The composition of the product gas was analyzed by gas chromatography.

[0112] Under identical reaction conditions of 650 °C, the single nickel-based catalyst prepared in this comparative example ( The performance data are as follows: phenol conversion rate is 75.89%; hydrogen yield is 75.70%.

[0113] Comparative Example 2

[0114] This comparative example provides a catalyst that does not contain active nickel and uses iron (Fe) as the sole active component. The preparation method of the bimetallic active component and its performance evaluation in the phenol steam reforming hydrogen production reaction are used to further compare and illustrate the synergistic effect of the bimetallic active component in this invention.

[0115] Catalyst preparation

[0116] (1) Cobalt-magnesium-aluminum composite spinel Preparation of carrier

[0117] The preparation process of the carrier is the same as in all embodiments of the present invention and Comparative Example 1. Specifically, a co-precipitation method was used, with 2.91 g of cobalt nitrate, 2.56 g of magnesium nitrate, and 15.00 g of aluminum nitrate as metal sources, and 5.76 g of citric acid as a chelating agent, to prepare solution A. A sodium carbonate / sodium hydroxide mixture (solution B) and a sodium hydroxide solution (solution C) were used as precipitants. The mixture was co-precipitated in an oil bath at 80°C with stirring, filtered, washed with hot deionized water at 60-80°C (to pH=7-8), dried at 75°C for 12 hours, and then calcined at 750°C for 4 hours in air atmosphere to obtain... Carrier powder.

[0118] (2) Loading of active components and activation of catalyst

[0119] An equal-volume impregnation method was used, with only iron as the single active metal and no nickel. 0.37 g of ferric nitrate nonahydrate (…) was weighed out. The iron salt was dissolved in a suitable amount of 50 wt% methanol aqueous solution to prepare a single iron salt impregnation solution. 1.00 g of the above carrier powder was weighed, and the iron salt impregnation solution was added dropwise to the carrier. The mixture was stirred at room temperature for 12 hours to ensure thorough impregnation. The material was then dried in a 75°C forced-air drying oven for 12 hours.

[0120] The dried sample was placed in a tube furnace and activated under the same reduction conditions as in the example: the temperature was increased to 600°C at a rate of 10°C / min under a hydrogen atmosphere (flow rate 50 mL / min), and maintained at this temperature for 2 hours. After reduction, the sample was cooled to room temperature under hydrogen protection to obtain a catalyst containing only the iron active component, denoted as […]. .

[0121] Catalyst performance evaluation

[0122] To ensure a fair comparison, the catalyst performance was evaluated under the exact same reaction conditions as in all previous examples and Comparative Example 1: reaction temperature 650°C, 0.2 g of catalyst mixed with quartz sand packed in a fixed bed, nitrogen gas at a flow rate of 25 mL / min, and a 5.5 wt% phenol aqueous solution (injection rate 0.35 mL / min). The product gas was condensed and analyzed by gas chromatography, and the phenol conversion and hydrogen yield were calculated.

[0123] Under standard test conditions, the single iron-based catalyst prepared in this comparative example ( The performance of the product is as follows: phenol conversion rate is 76.00%; hydrogen yield is 68.12%.

[0124] Example Effect Analysis and Discussion

[0125] Based on the performance test data of the catalysts prepared in Examples 1-5 and Comparative Examples 1-2, the structure-activity relationship and stability of the catalysts of the present invention are analyzed and discussed as follows:

[0126] Effect of active component constitution on catalytic performance

[0127] To systematically investigate the effect of the composition of active components on the vapor reforming performance of phenol, under the same support... Catalysts with different compositions were prepared and tested at similar total active metal loadings. The key performance indicators for catalytic activity—phenol conversion and hydrogen yield—were calculated using the following formulas:

[0128]

[0129] (1) The influence of the type of metal additive

[0130] Comparing Examples 1 (5Ni-2Fe), 4 (5Ni-2Zr), and 5 (5Ni-2Ru), it is evident that under conditions of the same nickel loading and similar additive metal loading, the addition of different types of metal additives has a significant impact on catalytic activity. For example... Figure 1 As shown, at a reaction temperature of 650°C, the catalyst with iron as an auxiliary agent (Example 1) exhibited the highest relative phenol conversion (78.74%) and hydrogen yield (76.98%), which was superior to catalysts with zirconium (Example 4, conversion 76.2%, hydrogen yield 71.14%) or ruthenium (Example 5, conversion 78.96%, hydrogen yield 73.06%) as auxiliary agents. This indicates that in the catalyst system described in this invention, iron (Fe), as a highly efficient and economical auxiliary agent, exhibits a superior synergistic catalytic effect when forming bimetallic active sites with nickel.

[0131] (2) Effect of iron additive dosage

[0132] By comparing Example 1 (5Ni-2Fe), Example 2 (5Ni-5Fe), Example 3 (5Ni-10Fe) with Comparative Example 1 (5Ni, no Fe) and Comparative Example 2 (5Fe, no Ni), the key role of the amount of iron (Fe) added and the nickel-iron bimetallic combination can be clearly observed. Figure 1As shown, compared to a single nickel catalyst (Comparative Example 1, conversion rate 75.89%) or a single iron catalyst (Comparative Example 2, conversion rate 76.00%), the catalytic activity was generally improved after introducing an iron promoter to form a Ni-Fe bimetallic system. In particular, the catalytic performance was optimal when the molar ratio of nickel to iron was close to 1:1 (e.g., 5Ni-5Fe in Example 2), with a phenol conversion rate as high as 88.7% and a hydrogen yield of 82.78%. However, when the iron content was further increased to 10Fe (Example 3), the catalytic activity decreased (conversion rate 81.55%), indicating that there is an optimal nickel-iron ratio. Excessive iron may cover some of the nickel active sites or change the electronic structure and dispersion state of the bimetallic particles, thereby affecting its catalytic efficiency.

[0133] Based on the above analysis, the product prepared in Example 2... The catalyst exhibits the highest activity for hydrogen production from phenol steam reforming.

[0134] Catalyst stability evaluation

[0135] For the best performing catalyst (Example 2) A continuous reaction stability test was conducted for up to 70 hours. The results are as follows: Figure 2 As shown, during the 70-hour test period, the phenol conversion rate of the catalyst remained in the high range of 70-90%, and the hydrogen yield remained stable between 60-80%. Although the activity decreased slightly after long-term operation (conversion rate was 78.58% and hydrogen yield was 68.39% after 70 hours), the overall fluctuations were gentle, and no sharp deactivation was observed.

[0136] Furthermore, the composition of the gaseous products remained stable throughout the stability test, consisting mainly of hydrogen ( ) and carbon dioxide ( It consists of a small amount of carbon monoxide (CO), and methane was never detected. The generation of hydrogen is highly advantageous for the selectivity of the target product hydrogen and subsequent hydrogen purification processes, as it avoids the consumption of hydrogen by the methanation side reaction, allowing for the removal of hydrogen through adsorption and other methods. High-purity hydrogen or hydrogen-rich syngas can then be obtained. This result fully demonstrates that the catalyst of the present invention not only has excellent initial activity, but also good resistance to carbon deposition and long-term operational stability.

[0137] Verification of universality of bimetallic synergistic effect

[0138] Although the degree of catalytic performance improvement varies among different metal promoters, as shown in Examples 1, 4, and 5, all bimetallic catalysts with at least one metal promoter selected from iron, zirconium, and ruthenium exhibit significantly higher phenol conversion rates than single nickel catalysts (Comparative Example 1) or single iron catalysts (Comparative Example 2). For example, compared to a single nickel catalyst (conversion rate 75.89%), the addition of zirconium (Example 4, conversion rate 76.2%), ruthenium (Example 5, conversion rate 78.96%), or iron (Example 1, conversion rate 78.74%) all resulted in a clear performance improvement. This result demonstrates that in the catalyst system of the present invention, the bimetallic active center formed by nickel and a specific metal promoter is key to enhancing the activity of tar steam reforming.

[0139] In specific embodiments, the defined ranges for nickel loading (0.5 wt%~10 wt%) and metal additive loading (0.1 wt%~10 wt%) of the catalyst are determined based on precise calculations of the catalysts prepared in each embodiment and comparative example. The calculations follow conventional methods in the art, specifically calculating the mass fraction of active metal elements (Ni, Fe, Zr, Ru) based on the total mass of the final catalyst product. In each embodiment, the mass of the cobalt-magnesium-aluminum spinel support used for loading is 1.0 g. The active metals are derived from their corresponding salt solutions, which, after impregnation, drying, and reduction, convert the metal salts into elemental metals and load them onto the support. The total mass of the catalyst is the sum of the support mass and the mass of all active metal elements. Based on the mass and molecular weight of the metal salt reagents used, the theoretical mass of the active metal elements can be calculated, and the loading is then calculated using the following formula: Loading (wt%) = (Mass of active metal elements / Total mass of catalyst) × 100%. The specific calculation results are as follows.

[0140] Example 1 ( In this mixture, the nickel loading is approximately 4.71%, and the iron additive loading is approximately 1.94%.

[0141] Example 2 ( In this mixture, the nickel loading is approximately 4.58%, and the iron additive loading is approximately 4.64%.

[0142] Example 3 ( In this mixture, the nickel loading is approximately 4.38%, and the iron additive loading is approximately 8.76%.

[0143] Example 4 ( In this mixture, the nickel loading is approximately 4.71%, and the zirconium additive loading is approximately 1.87%.

[0144] Example 5 ( In this mixture, the nickel loading is approximately 4.76%, and the ruthenium additive loading is approximately 0.92%.

[0145] Comparative Example 1 ( In this sample, the nickel loading is approximately 4.80%.

[0146] Comparative Example 2 ( In this study, the iron load was approximately 4.86%.

[0147] As can be seen from the above, the actual nickel loading in the preferred embodiments of the present invention ranges from 4.38% to 4.80%, and the actual metal additive loading ranges from 0.92% to 8.76%. Based on the verification provided in the embodiments, those skilled in the art can reasonably conclude that, based on the total mass of the catalyst, the nickel loading is 2.0 wt% to 20.0 wt%. This lower limit considers the critical value of catalyst performance; too low a loading may lead to insufficient active sites, affecting the catalytic effect. This upper limit considers that excessively high nickel loading may lead to metal agglomeration, destruction of the support structure, and is uneconomical. The metal additive loading is 0.5 wt% to 10.0 wt%. This lower limit ensures that the additive can produce an observable synergistic effect; below this value, it may not effectively improve catalyst performance. This upper limit considers that excessively high additive loading may mask the nickel active sites.

[0148] 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 catalyst, characterized in that, It includes a cobalt-magnesium-aluminum composite spinel carrier and an active component loaded on the carrier; the active component includes nickel and at least one metal additive selected from iron, zirconium, and ruthenium.

2. The catalyst according to claim 1, characterized in that, In the active component, the molar ratio of nickel to the metal additive is 10:(4~20).

3. The catalyst according to claim 1 or 2, characterized in that, Based on the total mass of the catalyst, the nickel loading is 2.0 wt% to 20.0 wt%, and the metal additive loading is 0.5 wt% to 10.0 wt%.

4. The catalyst according to claim 1, characterized in that, The metallic additive is iron.

5. The catalyst according to claim 1, characterized in that, In the cobalt-magnesium-aluminum composite spinel carrier, the molar ratio of cobalt, magnesium, and aluminum is 1:1:

4.

6. A method for preparing the catalyst according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. The cobalt-magnesium-aluminum composite spinel support was prepared by co-precipitation method; S2. The active component is loaded onto the support by impregnation, and then dried and reduced to obtain the catalyst.

7. The preparation method according to claim 6, characterized in that, Step S1 includes: S11. Dissolve the cobalt source, magnesium source, aluminum source, and organic chelating agent in water to prepare solution A; wherein... , , The molar ratio of the organic chelating agent to the organic chelating agent is 1:1:(1~4). The molar ratio is (1~6):1; S12. Dissolve sodium carbonate and sodium hydroxide in water to prepare solution B; dissolve sodium hydroxide in water to prepare solution C; wherein, solution B and solution C contain... sum and The molar ratio is 4~8, in solution B and The molar ratio is 0.2~5; S13. Solution A and solution B are added dropwise to solution C to carry out a co-precipitation reaction, and a precipitate is obtained. S14. The precipitate is sequentially filtered, washed, dried and calcined to obtain the cobalt-magnesium-aluminum composite spinel carrier.

8. A method for producing hydrogen by steam reforming tar components, characterized in that, Includes the following steps: The reactor is filled with the catalyst according to any one of claims 1 to 5; Under a carrier gas atmosphere, the reactor is heated to the reaction temperature; A steam reforming reaction is carried out by introducing a feedstock containing tar components and water into the catalyst bed to obtain a product gas rich in hydrogen.

9. The method according to claim 8, characterized in that, The tar component is phenol.

10. The method according to claim 8, characterized in that, In the raw materials, the molar ratio of water to carbon atoms in the tar component (S / C) is 10~20; the reaction temperature is 600~700℃.

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