Composite catalyst for preparing furan from furfural and preparation method of composite catalyst
The composite catalyst prepared by combining chitosan and phytic acid solved the problems of short catalyst life and low product purity, achieving efficient furfural conversion and furan selectivity, and improving catalyst stability and product purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI PUCHENG WANDE SCI & TECH
- Filing Date
- 2026-04-08
- Publication Date
- 2026-05-12
AI Technical Summary
In existing furfural gas-phase decarbonylation processes, the catalyst life is short and the catalytic activity declines rapidly, resulting in poor production continuity and low product purity and selectivity. This is mainly due to carbon deposition deactivation and metal particle sintering problems.
A high-strength hydrogel was formed by chitosan and phytic acid, which combined with nickel, cerium and ruthenium ions. The composite catalyst was prepared by freeze drying and low-temperature calcination to form a stable NC three-dimensional network and polycrystalline pyrophosphate, which enhanced the metal-support anchoring effect and inhibited carbon deposition and sintering.
The stability and activity of the catalyst were improved, with furfural conversion reaching 89.7%-96.2% and furan selectivity reaching 92.5%. The performance remained good after 500 hours of continuous operation, and the furan purity reached 99.94%.
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Figure CN122006779A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of catalyst technology, and more specifically, to a composite catalyst for preparing furan using furfural and a method thereof. Background Technology
[0002] Furfural, as a highly promising biomass-derived platform compound, has important applications in the catalytic decarbonylation of furans for the conversion of agricultural waste into high-value-added fine chemical products (such as polytetrahydrofuran and pharmaceutical intermediates). The global demand for furans is substantial and increases annually; however, existing gas-phase decarbonylation processes generally face the problem of short catalyst lifetimes during continuous operation. This directly leads to production line shutdowns due to declining catalyst conversion and selectivity, severely impacting production continuity and resulting in significant equipment depreciation and energy losses.
[0003] Currently, the gas-phase decarbonylation of furfural mainly relies on two types of catalysts: one is noble metal catalysts such as palladium (Pd), which, although possessing high initial activity, are extremely expensive and sensitive to impurity poisoning; the other is transition metal catalysts represented by nickel (Ni), often using alumina or phosphate as supports. Due to the thermal stability and tunable acid-base properties of phosphate supports, the latter type of catalyst has become the main direction for replacing noble metal routes. However, existing phosphate-based nickel catalysts have encountered bottlenecks in practical applications: the furfural conversion rate drops sharply after 50 to 100 hours of operation, specifically manifested as a rapid increase in catalyst bed pressure drop, a significant increase in the proportion of byproducts (such as methylfuran and polymers) in the reaction products, and a substantial decrease in product purity.
[0004] The main reason for the above problems lies in the loss of control of two coupled microscopic mechanisms: one is carbon deposition and deactivation; the surface of traditional phosphate supports is rich in P-OH bonds, and these Brønsted acidic sites have a strong chemical adsorption capacity for electron-rich furan rings, leading to deep polymerization of furan and intermediate products on the catalyst surface, generating coated amorphous carbon; the other is sintering of active sites; under reaction temperatures of 250℃ to 400℃ and local exothermic polarization conditions, the strong metal-support interaction between nickel nanoparticles formed by physical loading or simple co-precipitation and the phosphate substrate is insufficient, causing the high-surface-energy nickel atoms to undergo Ostwald ripening, gradually agglomerating into large particles and drastically losing catalytic active area. Therefore, it is urgent to develop a composite catalyst with a strong metal-support anchoring effect to reduce carbon deposition and sintering problems in the furfural decarbonylation process, improve the catalyst's catalytic performance, and increase the purity of the catalytic reaction products. Summary of the Invention
[0005] To improve catalyst performance and increase the purity of catalytic reaction products, this application provides a composite catalyst for preparing furan using furfural and a method thereof.
[0006] Firstly, the preparation method of the composite catalyst for furan using furfural in this application adopts the following technical solution: A method for preparing a composite catalyst for furan using furfural includes the following steps: 1) Mix chitosan and glacial acetic acid evenly in water, then add soluble nickel salt, soluble cerium salt, and soluble ruthenium salt, and mix to react; 2) Add phytic acid solution dropwise to the system after the reaction in step 1), mix well, then adjust the pH to 6.2-6.7 with potassium hydroxide solution, let it stand and age to obtain hydrogel; 3) Freeze the hydrogel obtained in step 2) with liquid nitrogen, and then freeze-dry it to obtain an aerogel; 4) The aerogel obtained in step 3) is kept at 420-460℃ for 2.5-3.5h under a protective atmosphere, and then kept at 530-580℃ for 3-5h under a hydrogen-containing atmosphere to obtain the final product.
[0007] This application introduces chitosan and phytic acid. Chitosan contains abundant amino and hydroxyl groups, while phytic acid contains six phosphate groups, enabling acid-base neutralization and multiple hydrogen bond cross-linking to form a high-strength macromolecular hydrogel. During gelation, nickel, cerium, and potassium ions from the added salt are uniformly locked within the molecular-level network. During pre-calcination under an inert atmosphere, the carbon skeleton of chitosan and phytic acid is carbonized in situ, forming a nitrogen-doped carbon (NC) three-dimensional network with good thermal conductivity and Lewis basicity. Phosphate groups condense within the spatial confinement of the carbon network, generating nanoscale polycrystalline pyrophosphate. The basicity of this in-situ grown NC network neutralizes the P-OH acidic sites on the phosphate surface, cutting off the pathway for furan polymerization into coke. Since nickel ions are extremely stable in the pure pyrophosphate lattice, conventional hydrogen reduction requires temperatures above 700°C, which can cause pore collapse. This application couples trace amounts of ruthenium with highly reactive cerium. With the introduction of Ru atoms, hydrogen can be dissociated into active hydrogen (atoms) at a temperature of 450°C. These active hydrogen atoms target and reduce neighboring nickel ions through the carbon network and lattice defects. Simultaneously, Ce ions form a large amount of Ce in the phosphate lattice. 3+ / Ce 4+Redox pairs rapidly transfer electrons from oxygen vacancies to Ni clusters, enhancing the anchoring force of Ni-P bonds. During freezing, the growth and sublimation of ice crystals create larger pores in the gel, providing high-speed mass transfer channels for subsequent gas-phase large-molecule furfural. After subsequent carbonization and reduction, a stable three-phase interface is formed, firmly fixing the nickel and significantly improving the metal-support anchoring effect, thereby enhancing the performance of the composite catalyst.
[0008] In step 1), the mass ratio of chitosan to glacial acetic acid is 4-5:1.5-2.5.
[0009] In step 1), the chitosan and glacial acetic acid are mixed evenly in water by adding the chitosan to the aqueous solution of glacial acetic acid and stirring for 1-3 hours. Preferably, the stirring speed is 400-600 rpm.
[0010] In step 1), the soluble nickel salt is any one of nickel nitrate, nickel chloride, and nickel acetate. Preferably, in step 1), the soluble nickel salt is any one of nickel nitrate hexahydrate, nickel chloride hexahydrate, and nickel acetate tetrahydrate.
[0011] In step 1), the soluble cerium salt is any one of cerium nitrate, cerium chloride, and cerium acetate. Preferably, in step 1), the soluble cerium salt is any one of cerium nitrate hexahydrate, cerium chloride heptahydrate, and cerium acetate.
[0012] In step 1), the soluble ruthenium salt is any one of ruthenium nitrate, ruthenium chloride, and ruthenium acetate. Preferably, in step 1), the soluble ruthenium salt is ruthenium chloride trihydrate.
[0013] Since many factors affect the solubility of ruthenium salts, this application selected the aforementioned ruthenium salt with relatively good solubility to better promote the reaction of metal ions and form a homogeneous reaction system. More preferably, ruthenium chloride trihydrate is selected as the soluble ruthenium salt, which has better solubility in the above system.
[0014] In step 1), the mass ratio of soluble nickel salt to soluble cerium salt is 7-18:3-9. Preferably, the mass ratio of soluble nickel salt to soluble cerium salt in step 1) is 12-15:4-5.
[0015] In step 1), the mass ratio of soluble nickel salt to soluble ruthenium salt is 7-18:0.02-0.08. Preferably, the mass ratio of soluble nickel salt to soluble ruthenium salt in step 1) is 12-15:0.04-0.06.
[0016] In step 1), the mass ratio of chitosan to soluble nickel salt is 4-5:7-18. Preferably, the mass ratio of chitosan to soluble nickel salt in step 1) is 4-5:12-15.
[0017] The temperature during the mixing reaction in step 1) is 40-50℃. The mixing reaction time is 50-70 min. The stirring speed during the mixing reaction is 500-720 rpm.
[0018] In step 2), the phytic acid solution has a mass fraction of 40%–60%. Preferably, the phytic acid solution has a mass fraction of 45%–55%.
[0019] To ensure that phytic acid-induced supramolecular crosslinking and gelation proceeds slowly and stably, phytic acid should be added dropwise, and its mass fraction should not be too high to guarantee uniform gelation. The mass fraction of the phytic acid solution should also not be too low; otherwise, introducing too much solvent will affect the gelation process.
[0020] In step 2), the amount of phytic acid solution used is 18-25 mL of phytic acid solution for every 7-18 g of soluble nickel salt.
[0021] In step 2), the phytic acid solution is added at a rate of 1-3 mL / min.
[0022] In step 2), the concentration of the potassium hydroxide solution is 1-2 mol / L. The potassium hydroxide solution is added dropwise at a rate of 1-2 mL / min.
[0023] Adjusting the pH with potassium hydroxide solution can introduce potassium ions. These potassium ions work synergistically with the in-situ generated nitrogen-doped carbon network structure to neutralize strong acid sites to the greatest extent and reduce carbon buildup.
[0024] The aging time in step 2) is 20-30 hours.
[0025] In step 3), the time for liquid nitrogen freezing and solidification is 2-3 hours.
[0026] Liquid nitrogen freeze-curing can utilize crystal growth to construct large-pore channels. Liquid nitrogen freezing temperatures are lower, and the freezing time should not be too long; it is sufficient to form large-pore channels to avoid overgrowth, which could lead to a decrease in specific surface area or pore wall strength. Preferably, liquid nitrogen freezing involves placing the aged hydrogel into a mold with a copper plate at the bottom, and then directly contacting the copper plate with the liquid nitrogen surface for unidirectional freeze-curing.
[0027] In step 3), the temperature for vacuum freeze-drying is -60 to 70°C. The vacuum degree for vacuum freeze-drying is 5 to 50 Pa. Preferably, the vacuum degree for vacuum freeze-drying is 5 to 20 Pa.
[0028] In step 3), the vacuum freeze-drying time is 70-80 hours.
[0029] In step 4), the protective atmosphere is either argon or nitrogen. The flow rate of the protective atmosphere is 100-150 mL / min.
[0030] In step 4), the hydrogen-containing atmosphere is a mixture of hydrogen and argon. The volume ratio of hydrogen to argon is 1-2:8-9.
[0031] Secondly, the composite catalyst for preparing furan using furfural in this application adopts the following technical solution: A method for preparing a composite catalyst for preparing furan using furfural, obtained by the above-described preparation method.
[0032] This application has at least the following beneficial effects: The preparation method described in this application involves first protonating and dissolving chitosan, then adding metal ions, with the noble metal ions assisting in the initial coordination with the amino and hydroxyl groups on the chitosan molecular chain. Phytic acid is then added to induce supramolecular cross-linking and gelation, forming macroporous channels during freezing. Sintering at low temperature completes the construction of the carbon network and the pyrophosphate phase transition, resulting in a highly tough metal-support interface anchoring structure. The prepared composite catalyst has a large specific surface area, reaching 215.8 m². 2 The catalyst exhibits a high conversion rate (89.7%-96.2%) in the production of furfural to furan, with a furan selectivity of 92.5%. Furthermore, after 500 hours of continuous operation, the catalytic performance remains excellent, with only a slight decrease in conversion rate. The composite catalyst of this application produces furan with a final purity of 99.94% in the furfural-to-furan production. Attached Figure Description
[0033] Figure 1 This is a gas chromatogram of furan prepared from furfural using the catalyst prepared in Example 1 of this application. Detailed Implementation
[0034] The present application will be further described in detail below with reference to the embodiments.
[0035] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.
[0036] The phytic acid solution used in the following examples has a mass fraction of 50% and a density of approximately 1.4 g / mL.
[0037] Example 1 The preparation method of the composite catalyst for furan preparation using furfural in this embodiment includes the following steps: 1) Slowly add 4.5g of chitosan powder to a mixed solution containing 2.0mL of glacial acetic acid and 100.0mL of deionized water, and stir continuously at 500rpm for 120min at room temperature (25℃) until a light yellow viscous liquid is formed. 2) Add 14.5g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 4.3g of cerium nitrate hexahydrate and 0.05g of ruthenium chloride to 50.0mL of deionized water, stir to dissolve, and obtain a mixture; add the mixture to the pale yellow viscous liquid obtained in step 1), and stir at 600rpm for 60min at 40℃ to allow the metal ions to fully coordinate with the amino and hydroxyl groups on the chitosan molecular chain. 3) While maintaining a stirring speed of 600 rpm, 20.0 mL of 50% phytic acid aqueous solution was added dropwise at a rate of 2.0 mL / min to the system after the reaction in step 2), so that the phosphate groups of phytic acid could interact with the protonated chitosan amino groups through electrostatic and hydrogen bonding. After the addition was complete, stirring was continued for 30 min, and the system was transformed into a dark green gel. 4) Slowly add a 1.0 mol / L KOH solution to the gel obtained in step 3) at a rate of 1.0 mL / min, while monitoring with a precision pH meter. Stop adding the solution when the pH of the system stabilizes at 6.5 (this process consumes about 35.0 mL of KOH solution); then let it stand for 24 hours to allow potassium ions to penetrate evenly and stabilize the molecular network. 5) The aged hydrogel from step 4) was frozen and solidified with liquid nitrogen for 120 min, and then transferred to a vacuum freeze dryer for sublimation drying at a cold trap temperature of -65℃ and a vacuum degree of 10 Pa for 72 h to obtain a light green sponge-like aerogel with vertically oriented channels. 6) The aerogel obtained in step 5) was placed in a tube furnace and heated: First stage: high-purity argon gas (flow rate of 100 mL / min) was introduced, and the temperature was increased to 450℃ at a heating rate of 2.0℃ / min and held for 180 min; Second stage: the atmosphere was switched to a H2 / Ar mixture with a volume ratio of 1:9 (flow rate maintained at 100 mL / min), and the temperature was increased to 550℃ at a heating rate of 1.0℃ / min and held for 240 min. Then, it was naturally cooled to room temperature under argon protection, crushed, and sieved to obtain a blackish-gray porous composite catalyst with a metallic luster.
[0038] Example 2 The preparation method of the composite catalyst for furan preparation using furfural in this embodiment includes the following steps: 1) Slowly add 3.5g of chitosan powder to a mixed solution containing 2.0mL of glacial acetic acid and 100.0mL of deionized water, and stir continuously at 500rpm for 120min at room temperature (25℃) until a light yellow viscous liquid is formed. 2) Add 7.3g nickel nitrate hexahydrate, 8.7g cerium nitrate hexahydrate and 0.031g ruthenium chloride to 80.0mL of deionized water, stir to dissolve, and obtain a mixture; add the mixture to the pale yellow viscous liquid obtained in step 1), and stir at 500rpm for 60min at 45℃.
[0039] Everything else is the same as in Example 1.
[0040] Example 3 The preparation method of the composite catalyst for furan preparation using furfural in this embodiment includes the following steps: 1) Slowly add 4.5g of chitosan powder to a mixed solution containing 2.0mL of glacial acetic acid and 100.0mL of deionized water, and stir continuously at 500rpm for 120min at room temperature (25℃) until a light yellow viscous liquid is formed. 2) Add 14.5g nickel nitrate hexahydrate, 4.3g cerium nitrate hexahydrate and 0.05g ruthenium chloride to 50.0mL of deionized water, stir to dissolve, and obtain a mixture; add the mixture to the pale yellow viscous liquid obtained in step 1), and stir at 600rpm for 60min at 40℃. 3) While maintaining a stirring speed of 600 rpm, 20.0 mL of 50% phytic acid aqueous solution was added dropwise at a rate of 2.0 mL / min to the system after the reaction in step 2), so that the phosphate groups of phytic acid could interact with the protonated chitosan amino groups through electrostatic and hydrogen bonding. After the addition was complete, stirring was continued for 30 min, and the system was transformed into a dark green gel. 4) Slowly add 1.0 mol / L ammonia solution to the gel obtained in step 3) at a rate of 1.0 mL / min, while monitoring with a precision pH meter, until the pH of the system stabilizes at 6.5 and then stop adding the solution; then let it stand for 24 hours to age.
[0041] Everything else is the same as in Example 1.
[0042] Example 4 The preparation method of the composite catalyst for furan preparation using furfural in this embodiment includes the following steps: 1) Slowly add 4.5g of chitosan powder to a mixed solution containing 2.0mL of glacial acetic acid and 100.0mL of deionized water, and stir continuously at 500rpm for 120min at room temperature (25℃) until a light yellow viscous liquid is formed. 2) Add 14.5g nickel nitrate hexahydrate, 4.3g lanthanum nitrate hexahydrate and 0.05g ruthenium chloride to 50.0mL of deionized water and stir to dissolve to obtain a mixture; add the mixture to the pale yellow viscous liquid obtained in step 1) and stir at 600rpm for 60min at 40℃.
[0043] Everything else is the same as in Example 1.
[0044] Example 5 The difference between this embodiment and Embodiment 1 is that step 5) is: The aged hydrogel from step 4) was placed in a vacuum drying oven and dried at 80°C and a vacuum of 0.08 MPa for 24 hours to achieve constant weight. Everything else is the same as in Example 1.
[0045] Example 6 The difference between this embodiment and Embodiment 1 is that step 6) is: The aerogel obtained in step 5) was placed in a tube furnace and heated: First stage: high-purity argon gas (flow rate of 100 mL / min) was introduced, and the temperature was increased to 450℃ at a heating rate of 2.0℃ / min and held for 180 min; Second stage: the atmosphere was switched to a H2 / Ar mixture with a volume ratio of 1:9 (flow rate maintained at 100 mL / min), and the temperature was increased to 700℃ at a heating rate of 5.0℃ / min and held for 240 min, and then naturally cooled to room temperature under argon protection.
[0046] Everything else is the same as in Example 1.
[0047] Comparative Example 1 The preparation method of the composite catalyst for furan preparation using furfural in this embodiment includes the following steps: 1) Add 14.5g nickel nitrate hexahydrate, 4.3g cerium nitrate hexahydrate and 0.05g ruthenium chloride to 50.0mL of deionized water, stir to dissolve, and obtain a mixture; stir the mixture at 600rpm for 60min at 40℃. 2) While maintaining a stirring speed of 600 rpm, add 20.0 mL of 50% phytic acid aqueous solution at a dropping rate of 2.0 mL / min to the system in step 1); after the addition is complete, continue stirring for 30 min. 3) Slowly add a 1.0 mol / L KOH solution to the system obtained in step 2) at a rate of 1.0 mL / min, while monitoring with a precision pH meter, until the pH of the system stabilizes at 6.5 and then stop adding the solution (this process consumes approximately 35.0 mL of KOH solution); then let it stand for 24 hours to age. 4) The aged gel from step 3) was frozen and solidified with liquid nitrogen for 120 min, and then transferred to a vacuum freeze dryer for sublimation drying at a cold trap temperature of -65℃ and a vacuum degree of 10 Pa for 72 h to obtain an aerogel. 5) Place the aerogel obtained in step 4) in a tube furnace and heat it: First stage: introduce high-purity argon gas (flow rate of 100 mL / min), heat to 450℃ at a heating rate of 2.0℃ / min, and hold for 180 min; Second stage: switch the atmosphere to a H2 / Ar mixture with a volume ratio of 1:9 (flow rate maintained at 100 mL / min), heat to 550℃ at a heating rate of 1.0℃ / min, hold for 240 min, and then cool naturally to room temperature under argon protection.
[0048] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: Step 2) is as follows: Add 14.5g of nickel nitrate hexahydrate and 4.3g of cerium nitrate hexahydrate to 50.0mL of deionized water, stir to dissolve, and obtain a mixed solution; add the mixed solution to the pale yellow viscous liquid obtained in step 1), and stir at 600rpm for 60min at 40℃.
[0049] Everything else is the same as in Example 1.
[0050] Comparative Example 3 The difference between this comparative example and Comparative Example 2 is: Step 6) involves placing the aerogel obtained in step 5) in a tube furnace and heating it: First stage: High-purity argon gas (flow rate of 100 mL / min) is introduced, and the temperature is increased to 450℃ at a heating rate of 2.0℃ / min, and held for 180 min; Second stage: The atmosphere is switched to a H2 / Ar mixture with a volume ratio of 1:9 (flow rate maintained at 100 mL / min), and the temperature is held at 450℃ for 300 min, and then naturally cooled to room temperature under argon protection.
[0051] The rest are the same as in Comparative Example 2.
[0052] Test case Catalytic performance test: In a 2L hydrogenation reactor, add 10g of furfural, 1g of composite catalyst, 1g of cesium carbonate, and 60g of methanol in sequence. Then start stirring, purge with nitrogen three times, slowly raise the temperature to 195-200℃, maintain the pressure inside the reactor at about 2.5-3MPa, and maintain the temperature and pressure for 12 hours.
[0053] Then let it stand and cool down to about 100°C, then cool it down to about 40°C with water, then cool it down to below 10°C with zero-degree water, let it stand, and then quickly take samples for testing.
[0054] The above samples were subjected to gas chromatography detection, and the furfural conversion rate and furan selectivity were calculated, as shown in the table below.
[0055] Table 1. Catalyst detection data prepared in the examples and comparative examples.
[0056] As demonstrated in Examples 1-3 and Comparative Example 1, the catalyst of this application exhibits very high catalytic activity and selectivity. This is attributed to the coordination interaction between the metal ions in the metal salt and the amino and hydroxyl groups on the chitosan molecular chain, constructing an ordered metal dispersion structure that effectively inhibits the aggregation of active metal particles. In Example 3, ammonia was used instead of KOH. The absence of K ions may result in a large number of unneutralized polar P-OH bonds remaining in the phosphate lattice. The strong acid sites trigger severe ring-opening polymerization side reactions of furfural, leading to the blockage of pores by polymeric coke.
[0057] As shown in Examples 1 and 4, cerium and ruthenium in this application play a synergistic catalytic and structural regulation role when combined with metal salts, which can improve the conversion rate of furfural and the selectivity of the product furan. This indicates that the catalyst of this application has better active centers and electron transfer efficiency. In Example 4, replacing cerium with lanthanum resulted in a decrease in catalytic performance. Analysis suggests that this may be because the La ion has a fixed valence and cannot react with cerium like Ce. 3+ / Ce 4+ The redox pair provides sufficient dynamic oxygen vacancies, leading to the accumulation and poisoning of CO molecules generated from decarbonylation on the Ni surface, thus weakening the interfacial bonding.
[0058] As shown in Examples 1 and 5-6, this application employs a low-temperature liquid nitrogen freezing and freeze-drying process to obtain an aerogel support with a macroporous structure, which greatly improves the structural stability and active component dispersion effect of the catalyst during high-temperature calcination. Furthermore, the 550°C temperature setting is highly advantageous; excessively high or low temperatures can lead to the agglomeration of metal particles in the catalyst, affecting the catalytic effect. In Example 5, liquid nitrogen freezing and freeze-drying were not used; direct vacuum drying resulted in difficulty in forming macropores, material structure shrinkage, increased density, decreased specific surface area, and reduced pore volume, leading to a decrease in catalytic performance, including a decrease in furfural conversion and furan selectivity. In Example 6, the excessively high reduction temperature and rapid heating rate exceeded the thermodynamic stability limit of pyrophosphate, easily causing partial melting of the crystal structure and collapse of the carbon network. Ni clusters detached from the physical confinement interface underwent Ostwald ripening at high temperatures, resulting in sintering deactivation.
[0059] As shown in Comparative Examples 2-3, the use of ruthenium chloride as an anchoring agent for the support metal in this application enhances the interaction between the active metal particles and the support, inhibits the movement and aggregation of the active metal particles at high temperatures, and thus maintains the activity and stability of the catalyst. In Comparative Example 3, ruthenium chloride was not added, resulting in the loss of Ru's hydrogen dissociation ability. Reduction was performed at 450°C, but the activation process failed because pure hydrogen molecules have great difficulty directly attacking the Ni-OP bonds encapsulated in the deep lattice.
[0060] Purity test: Using the composite catalyst prepared in Example 1, furan was prepared by the above method. After the reaction vessel was cooled and allowed to stand, the pressure was released, a sample was taken, and the sample was distilled at atmospheric pressure. The fraction collected at 30-32℃ was analyzed by gas chromatography. The results are as follows. Figure 1 As shown in the figure (the values marked with retention times in the figure are 2.942, 3.340, 3.507, 5.250, and 5.548 from left to right).
[0061] As shown in the figure, a large chromatographic peak appeared at a retention time (RT) of 2.942 min, with a peak area accounting for as high as 99.94%. 2.942 min is a relatively early elution time. Considering the extremely low boiling point of furan (approximately 31.3 °C), it would elute very quickly in a conventional chromatographic column. Therefore, this main peak can be identified as furan. Between 3.3 and 5.5 min, there were four extremely small peaks, with a total area accounting for only about 0.053%. These may be trace amounts of byproducts (such as 2-methylfuran) or systemic impurities.
[0062] Based on the "area normalization method", the purity of furan in this sample can be calculated to be 99.94% (as shown in the table below), which is an extremely high purity product.
[0063] Table 2
[0064] Physicochemical performance testing: The specific surface area of the composite catalyst prepared in Example 1 was tested using the BET method, and the result was 215.8 m². 2 / g.
[0065] Continuous run test: Using the composite catalyst prepared in Example 1, furan was prepared by the above method. After 500 hours of continuous operation, the furfural conversion rate was tested to be 95.8%, maintaining a high conversion rate. Thermogravimetric analysis (TGA) was performed on the unloaded catalyst, and the carbon deposition was 0.8%.
[0066] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A method for preparing a composite catalyst for furan using furfural, characterized in that, Includes the following steps: 1) Mix chitosan and glacial acetic acid evenly in water, then add soluble nickel salt, soluble cerium salt, and soluble ruthenium salt, and mix to react; 2) Add phytic acid solution dropwise to the system after the reaction in step 1), mix well, then adjust the pH to 6.2-6.7 with potassium hydroxide solution, let it stand and age to obtain hydrogel; 3) Freeze the hydrogel obtained in step 2) with liquid nitrogen, and then freeze-dry it to obtain an aerogel; 4) The aerogel obtained in step 3) is kept at 420-460℃ for 2.5-3.5h under a protective atmosphere, and then kept at 530-580℃ for 3-5h under a hydrogen-containing atmosphere to obtain the final product.
2. The method for preparing a composite catalyst for furan using furfural according to claim 1, characterized in that, In step 1), the mass ratio of chitosan to glacial acetic acid is 4-5:1.5-2.
5.
3. The method for preparing a composite catalyst for furan using furfural according to claim 1, characterized in that, In step 1), the soluble ruthenium salt is any one of ruthenium nitrate, ruthenium chloride, or ruthenium acetate.
4. The method for preparing a composite catalyst for furan using furfural according to claim 3, characterized in that, In step 1), the soluble ruthenium salt is ruthenium chloride trihydrate.
5. The method for preparing a composite catalyst for furan using furfural according to claim 1, characterized in that, In step 1), the mass ratio of soluble nickel salt to soluble cerium salt is 7-18:3-9.
6. The method for preparing a composite catalyst for furan using furfural according to claim 5, characterized in that, In step 1), the mass ratio of soluble nickel salt to soluble ruthenium salt is 7-18:0.02-0.
08.
7. The method for preparing a composite catalyst for furan using furfural according to claim 1, characterized in that, In step 2), the phytic acid solution has a mass fraction of 40%-60%.
8. The method for preparing a composite catalyst for furan using furfural according to claim 1, characterized in that, In step 4), the hydrogen-containing atmosphere is a mixed gas atmosphere of hydrogen and argon, and the volume ratio of hydrogen to argon is 1-2:8-9.
9. A composite catalyst for preparing furan using furfural, prepared by the method according to any one of claims 1-7.