Method for preparing 2, 5-dimethylfuran through hydrogenation of 5-hydroxymethylfurfural by using CuPd / C catalyst

Abstract

The invention provides a continuous flow preparation method of a CuPd / C catalyst. The method is simple and efficient, and one-step and continuous production can be realized. The method has the core advantages that multi-phase flow is ordered, the mixing efficiency is high, reaction parameters are accurate and adjustable, the repeatability and the automation degree are remarkably superior to those of a traditional impregnation method, and the problems that the traditional method is long in time consumption, low in selectivity, high in operation dependency, uneven in mixing and the like are effectively solved. In addition, catalyst synthesis conditions are screened, and optimal preparation conditions are determined. According to the CuPd / C catalyst prepared by the method, the conversion rate of 2, 5-dimethylfuran prepared from 5-hydroxymethylfurfural can reach 100%, and the selectivity of 2, 5-dimethylfuran can reach 97.5%. Compared with a CuPd / C catalyst prepared by an impregnation method, the yield of 2, 5-dimethylfuran is improved by more than 34.5%, and is superior to most reported catalysts at present. And mechanical operation can avoid personal errors, so that the result is easier to repeat, and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy catalysis and continuous flow preparation technology, specifically relating to a method for preparing a CuPd / C catalyst for the hydrogenation of 5-hydroxymethylfurfural, a biomass derivative, to 2,5-dimethylfuran. The catalyst uses activated carbon as a support, Pd as the main active component, and Cu as a metal promoter. By controlling the catalyst preparation method, a continuous flow preparation method is used to improve the production efficiency of the CuPd / C catalyst. This catalyst can effectively catalyze the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran. Furthermore, the continuous flow preparation method is highly efficient and simple, allowing for continuous mass production, reducing human error, and has significant application value. Background Technology

[0002] A continuous flow reactor (CFR) is a novel reaction apparatus in which reactions occur within channels with inner diameters ranging from a few micrometers to a few millimeters. In chemical engineering, micro-continuous flow devices offer unique control over critical reaction parameters due to their small size. Continuous flow reactors offer numerous advantages, including high mass and heat transfer efficiency, precise control of reaction temperature, pressure, and time, and easier integration and automation, thus improving reaction efficiency and attracting widespread attention.

[0003] Lignocellulosic biomass is an abundant and renewable carbon resource that holds promise for replacing traditional non-renewable fossil resources in chemical and fuel production, thereby reducing heavy dependence on fossil resources and mitigating related environmental impacts. Lignin, cellulose, and hemicellulose are all derived from lignocellulosic biomass, and they can depolymerize into various platform compounds, which can be further upgraded into high-value chemicals and fuels.

[0004] 5-Hydroxymethylfurfural (HMF) is an important biomass-derived intermediate with broad application potential. Converting HMF to 2,5-dimethylfuran (DMF) is a crucial pathway to realizing its high-value utilization. DMF possesses advantages such as low volatility, high octane number, high energy density, and immiscibility with water, making it a highly efficient and promising fossil fuel alternative. Therefore, developing efficient catalysts to facilitate this reaction is particularly important. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a CuPd / C catalyst for the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran. Using a continuous flow method, a highly active catalyst is simply and efficiently prepared by screening the metal ratio, solution mixing method, stabilizer dosage, and reducing agent dosage. Under reaction conditions of 130 °C and 2 MPa hydrogen pressure, the conversion rate of 5-hydroxymethylfurfural can reach 100%, and the selectivity for 2,5-dimethylfuran is 97.5%. Furthermore, this method allows for the one-step preparation of a highly active catalyst, simplifies the reaction steps, saves reaction time, and significantly improves production efficiency through continuous production.

[0006] To solve the technical problem of this invention, the proposed technical solution is: a method for preparing a CuPd / C catalyst for the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran, comprising the following steps:

[0007] The continuous flow device consists of a raw material unit, a feed conveying unit, a reactor unit, and a collection unit; the feed conveying unit is a peristaltic pump; the reactor unit consists of a temperature control device and a spiral reaction pipeline.

[0008] (1) Preparation of metal precursor solution: Measure 400 mL of deionized water into a beaker, add an appropriate amount of polyvinylpyrrolidone (PVP), and then take 1000 μL (Cu precursor) and 559.8 μL (Pd precursor) to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0009] (2) Preparation of reducing agent solution: Measure 400 mL of ice-cold deionized water into a beaker, and then take an appropriate amount of sodium borohydride to prepare an ice-cold sodium borohydride aqueous solution.

[0010] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced at a flow rate of 10 mL / min; another stream of the 400 mL sodium borohydride aqueous solution prepared in step (2) with ice water is introduced at a flow rate of 10 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 40 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0011] (4) Carrier pretreatment: Take an appropriate amount of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0012] (5) Nanoparticle loading: Liquid is introduced into two pipelines at the same time. One pipeline introduces CuPd nanoparticles prepared in step (3) at a flow rate of 16 mL / min, and the other pipeline introduces activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The liquid is collected through a three-way valve and the loaded activated carbon slurry is collected in a beaker.

[0013] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0014] (7) Add the reaction raw material 5-hydroxymethylfurfural, solvent and CuPd / C catalyst from step (6) to a high-pressure reactor equipped with a thermal conductivity detector, and carry out the hydrogenation of 5-hydroxymethylfurfural to prepare 2,5-dimethylfuran under stirring; the amount of catalyst used is 35 mg; the initial hydrogen pressure is 2 MPa; the reaction temperature is 100-170 ℃; the solvent is isopropanol; after the reaction, the catalyst and the reaction solution are separated by centrifugation.

[0015] The CuPd / C catalyst was used to catalyze the preparation of 2,5-dimethylfuran from 5-hydroxymethylfurfural, achieving a 100% conversion of 5-hydroxymethylfurfural and a 97.5% selectivity for 2,5-dimethylfuran.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention provides a continuous flow preparation method for CuPd bimetallic catalysts. Compared with the impregnation method, which is time-consuming, depends on the operator's skill, and is prone to uneven mixing, this method is simpler, more efficient, and can be produced in one step and continuously. The prepared particles have small particle size, narrow particle size distribution, and good dispersion, avoiding human error problems such as operator skill and uneven mixing. This method is simple and efficient.

[0018] This invention provides a continuous flow method for preparing CuPd / C catalysts. This method is simple, efficient, and allows for one-step, continuous production. It features ordered and controllable multiphase flow, high mixing efficiency, precise control of reaction parameters, good reaction repeatability, and a high degree of integration and automation. It effectively solves the problems of time-consuming preparation, low selectivity, reliance on operator experience, and uneven mixing inherent in traditional impregnation methods. Furthermore, this method screened the amounts of stabilizer and reducing agent, as well as the liquid flow rate within the continuous flow apparatus, to determine the optimal conditions for preparing CuPd / C catalysts. The CuPd / C catalyst prepared by this method achieves 100% conversion of 5-hydroxymethylfurfural to 2,5-dimethylfuran, with a selectivity of 97.5%. The yield of 2,5-dimethylfuran is more than 34.5% higher than that prepared by the impregnation method, surpassing most reported catalysts. Mechanized operation avoids human error, makes results more reproducible, and improves production efficiency. Attached Figure Description

[0019] Figure 1 Schematic diagram of an apparatus for preparing CuPd / C catalysts using a continuous flow method.

[0020] Figure 2 Pathway diagram for the preparation of 2,5-dimethylfuran from 5-hydroxymethylfurfural

[0021] Figure 3 TEM images and particle size distribution of CuPd / C catalyst (3Cu0.8Pd) prepared by continuous flow method

[0022] Figure 4 TEM images and particle size distribution of CuPd / C catalyst (3Cu0.8Pd) prepared by impregnation method.

[0023] Figure 5 XRD pattern of CuPd / C catalyst (3Cu0.8Pd) prepared by continuous flow method

[0024] Figure 6 Effect of different reaction temperatures on the yield of the target product 2,5-dimethylfuran Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific examples. These embodiments are only for illustrating the present invention, but the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] Continuous flow device Figure 1It consists of raw material units (A, B), a feed conveying unit C, a first reactor unit D, and a collection unit E. Raw material unit A: metal precursor solution; Raw material unit B: reducing agent solution and ice-water bath; Feed conveying unit C: flow peristaltic pump; First reactor unit D: temperature control device and spiral reaction pipeline (fixed by pipeline supports). Collection unit E: CuPd nanoparticle solution;

[0028] It also includes raw material unit F: activated carbon slurry; second reactor unit: temperature control device and spiral reaction pipeline (fixed with pipeline support); collection unit G: CuPd / C solution.

[0029] A method for preparing CuPd / C catalysts via a continuous flow process includes the following steps:

[0030] (1) Weigh 1 g of palladium nitrate dihydrate (Pd(NO3)2·2H2O) and dissolve it in 50 mL of deionized water to prepare a Pd precursor solution (Pd concentration 7.146 mg / mL) for later use. Weigh 4.065 g of copper chloride dihydrate (CuCl2·2H2O) and dissolve it in 100 mL of deionized water to prepare a Cu precursor solution (Cu concentration 15 mg / mL) for later use. Taking the preparation of 500 mg 3Cu0.8Pd / C catalyst as an example, the specific steps are as follows:

[0031] (2) Preparation of metal precursor solution: Measure 400 mL of deionized water into a beaker, add 19 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio of 1:1), and then take 1000 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0032] (3) Preparation of reducing agent solution: Measure 400 mL of ice-cold deionized water into a beaker, and then take 51.8 mg of sodium borohydride to prepare an ice-cold water solution of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1).

[0033] (4) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (2) is introduced, with a flow rate of 10 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (3) with ice water is introduced, with a flow rate of 10 mL / min. The solution is collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 40 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0034] (5) Carrier pretreatment: Take 481 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0035] (6) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 16 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded activated carbon slurry is collected in a beaker.

[0036] (7) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0037] The catalyst was named 3Cu0.8Pd / C.

[0038] In the preparation of CuPd / C nanoparticles, the continuous flow method exhibits a significant advantage over the impregnation method in particle size control: such as Figure 3 TEM images and particle size distribution diagrams of 3Cu0.8Pd / C catalyst nanoparticles prepared by the continuous flow method are shown. These indicate that the continuous flow method can synthesize 3Cu0.8Pd / C nanoparticles with a size of 3.41±0.38 nm, compared to the 4.3±0.66 nm particles prepared by the impregnation method (e.g., ...). Figure 4 As shown in the figure, its particle size is smaller and its distribution is narrower.

[0039] The actual metal loadings of Cu and Pd in ​​the catalyst were determined by ICP-OES, and the results are shown in Table 1. The actual loadings of the catalysts were close to the theoretical values, confirming the quantitative controllability of the continuous flow method in multi-metal systems. Furthermore, this method can still achieve uniform dispersion and fine control of nanoparticles even with a Pd loading as low as 0.8% (mass fraction). This advantage stems from the uniform mixing and high mass transfer efficiency of the reactants in the continuous flow system, which effectively controls the nucleation and growth processes, avoiding particle agglomeration or size deviations caused by localized concentration unevenness in the impregnation method. This provides a more reliable synthetic route for preparing highly dispersed, small-sized bimetallic nanoparticles, and the smaller particle size helps expose more active sites, giving the catalyst potential performance advantages in catalytic applications.

[0040] Example 2

[0041] (1) Preparation of metal precursor solution: Measure 170 mL of deionized water into a beaker, add 9 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio of 1:1), and then take 333.3 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0042] (2) Preparation of reducing agent solution: Measure 170 mL of ice-cold deionized water into a beaker, and then take 22 mg of sodium borohydride to prepare sodium borohydride ice-cold aqueous solution (the molar ratio of sodium borohydride to metal ions is 5:1).

[0043] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced, with a flow rate of 10 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (2) with ice water is introduced, with a flow rate of 10 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 17 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0044] (4) Carrier pretreatment: Take 491 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0045] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 7 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded catalyst slurry is collected in a beaker.

[0046] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0047] The catalyst was named 1Cu0.8Pd / C.

[0048] Example 3

[0049] (1) Preparation of metal precursor solution: Measure 285 mL of deionized water into a beaker, add 14 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio of 1:1), and then take 666.7 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0050] (2) Preparation of reducing agent solution: Measure 280 mL of ice-cold deionized water into a beaker, and then take 36.9 mg of sodium borohydride to prepare an ice-cold water solution of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1).

[0051] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced, with a flow rate of 10 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (2) with ice water is introduced, with a flow rate of 10 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 29 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0052] (4) Carrier pretreatment: Take 486 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0053] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 12 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded catalyst slurry is collected in a beaker.

[0054] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0055] The catalyst was named 2Cu0.8Pd / C.

[0056] Example 4

[0057] (1) Preparation of metal precursor solution: Measure 510 mL of deionized water into a beaker, add 24 mg of polyvinylpyrrolidone (PVP), and then take 1333.3 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0058] (2) Preparation of reducing agent solution: Measure 510 mL of ice-cold deionized water into a beaker, and then take 66.7 mg of sodium borohydride to prepare an ice-cold sodium borohydride aqueous solution.

[0059] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced, with a flow rate of 10 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (2) with ice water is introduced, with a flow rate of 10 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 51 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0060] (4) Carrier pretreatment: Take 476 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0061] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 20 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded catalyst slurry is collected in a beaker.

[0062] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0063] The catalyst was named 4Cu0.8Pd / C.

[0064] Comparative Example 1-1

[0065] (1) Weigh 1 g of Pd(NO3)2·2H2O and dissolve it in 50 mL of deionized water to prepare a Pd precursor solution (Pd: 7.146 mg / mL) for later use. Weigh 4.065 g of CuCl2·2H2O and dissolve it in 100 mL of deionized water to prepare a Cu precursor solution (Cu: 15 mg / mL) for later use.

[0066] (2) Weigh 481 mg of activated carbon and spread it evenly on a mortar. Take 1000 μL of Cu precursor solution, shake and sonicate it before taking it, then add 559.8 μL of Pd precursor solution and an appropriate amount of deionized water, sonicate for 5 min to mix it evenly, and then drop the mixed solution evenly onto the carrier. Grind until the catalyst is fully impregnated, and put it into an 80 ℃ drying oven to dry for 12 h.

[0067] (3) Take out the impregnated and dried catalyst, grind it into uniform fine particles, and then put it into a vertical tube furnace. The catalyst bed is filled with quartz wool on the top and bottom. The temperature is increased from room temperature to 400℃ at a rate of 5℃ / min. At 400℃, it is reduced with hydrogen at a rate of 50mL / min for 4 hours. After cooling to room temperature, the pipeline is purged with nitrogen and then taken out.

[0068] The catalyst was named 3Cu0.8Pd-impregnation method.

[0069] Comparative Examples 1-2

[0070] (1) Preparation of metal precursor solution: Measure 50 mL of deionized water into a beaker, add 4.2 mg of polyvinylpyrrolidone (PVP), and then take 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 5 min.

[0071] (2) Preparation of reducing agent solution: Measure 50 mL of ice-cold deionized water into a beaker, and then take 10 mg of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1) to prepare an ice-cold sodium borohydride aqueous solution.

[0072] (3) Preparation of Pd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced, with a flow rate of 10 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (2) with ice water is introduced, with a flow rate of 10 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 6 min. The prepared Pd nanoparticles are collected in a beaker and await loading.

[0073] (4) Carrier pretreatment: Take 496 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0074] (5) Nanoparticle loading: Pd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with the Pd nanoparticles prepared in step (3) at a flow rate of 2 mL / min, and the other pipeline is fed with the activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded catalyst slurry is collected in a beaker.

[0075] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0076] The catalyst was named 0.8Pd / C.

[0077] Comparative Examples 1-3

[0078] (1) Preparation of metal precursor solution: Measure 400 mL of deionized water into a beaker, add 19 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio is 1:1), and then take 1000 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0079] (2) Preparation of reducing agent solution: Measure 400 mL of ice-cold deionized water into a beaker, and then take 51.8 mg of sodium borohydride to prepare an ice-cold water solution of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1).

[0080] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) is introduced, with a flow rate of 6 mL / min; another stream of the aqueous solution of sodium borohydride prepared in step (2) with ice water is introduced, with a flow rate of 6 mL / min. The solution is then collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube is 65 min. The prepared CuPd nanoparticles are collected in a beaker and await loading.

[0081] (4) Carrier pretreatment: Take 481 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0082] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 16 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded activated carbon slurry is collected in a beaker.

[0083] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h. After the drying is completed, seal and store it.

[0084] The catalyst was named 3Cu0.8Pd / C-6 mL / min.

[0085] Comparative Examples 1-4

[0086] (1) Preparation of metal precursor solution: Measure 400 mL of deionized water into a beaker, add 19 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio is 1:1), and then take 1000 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0087] (2) Preparation of reducing agent solution: Measure 400 mL of ice-cold deionized water into a beaker, and then take 51.8 mg of sodium borohydride to prepare an ice-cold water solution of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1).

[0088] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) was introduced, with a flow rate of 14 mL / min; another stream of the sodium borohydride aqueous solution prepared in step (2) with ice water was introduced, with a flow rate of 14 mL / min. The solution was collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube was 29 min. The prepared CuPd nanoparticles were collected in a beaker and awaited loading.

[0089] (4) Carrier pretreatment: Take 481 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0090] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 16 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded activated carbon slurry is collected in a beaker.

[0091] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0092] The catalyst was named 3Cu0.8Pd / C-14 mL / min.

[0093] Comparative Examples 1-5

[0094] (1) Preparation of metal precursor solution: Measure 400 mL of deionized water into a beaker, add 19 mg of polyvinylpyrrolidone (PVP) (PVP to metal ion mass ratio is 1:1), and then take 1000 μL of Cu precursor and 559.8 μL of Pd precursor to prepare an aqueous solution. Stir at 1000 rpm for 10 min.

[0095] (2) Preparation of reducing agent solution: Measure 400 mL of ice-cold deionized water into a beaker, and then take 51.8 mg of sodium borohydride to prepare an ice-cold water solution of sodium borohydride (the molar ratio of sodium borohydride to metal ions is 5:1).

[0096] (3) Preparation of CuPd nanoparticles: One stream of the aqueous solution of the metal precursor prepared in step (1) was introduced, with a flow rate of 18 mL / min; another stream of 400 mL of sodium borohydride aqueous solution prepared in step (2) with ice water was introduced, with a flow rate of 18 mL / min. The solution was collected through a three-way valve and reduced in a Teflon tube. The time taken for the liquid to flow out of the tube was 23 min. The prepared CuPd nanoparticles were collected in a beaker and awaited loading.

[0097] (4) Carrier pretreatment: Take 481 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry.

[0098] (5) Nanoparticle loading: CuPd nanoparticles are loaded onto activated carbon using a continuous flow device. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (3) at a flow rate of 16 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded activated carbon slurry is collected in a beaker.

[0099] (6) Filter the catalyst slurry collected in step (5) and wash it with deionized water until the conductivity is 0. Place the solid obtained after filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After the drying is completed, seal and store it.

[0100] The catalyst was named 3Cu0.8Pd / C-18 mL / min.

[0101] Comparative Examples 1-6

[0102] The difference between this comparative example and Example 1 is that the stabilizer polyvinylpyrrolidone (PVP) is not added (the mass ratio of PVP to metal ions is 0:1).

[0103] Comparative Examples 1-7

[0104] The difference between this comparative example and Example 1 is that 9.5 mg of stabilizer polyvinylpyrrolidone (PVP) was added (the mass ratio of PVP to metal ions was 0.5:1).

[0105] Comparative Examples 1-8

[0106] The difference between this comparative example and Example 1 is that 28.5 mg of stabilizer polyvinylpyrrolidone (PVP) was added (the mass ratio of PVP to metal ions was 1.5:1).

[0107] Comparative Examples 1-9

[0108] The difference between this comparative example and Example 1 is that 38 mg of stabilizer polyvinylpyrrolidone (PVP) was added (the mass ratio of PVP to metal ions was 2:1).

[0109] Comparative Examples 1-10

[0110] The difference between this comparative example and Example 1 is that 10.4 mg of reducing agent sodium borohydride was added (the molar ratio of sodium borohydride to metal ions was 1:1).

[0111] Comparative Examples 1-11

[0112] The difference between this comparative example and Example 1 is that 25.9 mg of reducing agent sodium borohydride was added (the molar ratio of sodium borohydride to metal ions was 2.5:1).

[0113] Comparative Examples 1-12

[0114] The difference between this comparative example and Example 1 is that 77.7 mg of reducing agent sodium borohydride was added (the molar ratio of sodium borohydride to metal ions was 7.5:1).

[0115] Example 5

[0116] Catalyst Application

[0117] (1) The reaction of hydrogenating 5-hydroxymethylfurfural to prepare 2,5-dimethylfuran was carried out in a high-pressure reactor equipped with a thermal conductivity detector. First, 35 mg of the CuPd / C catalyst prepared in Example 1, 1 mmol of 5-hydroxymethylfurfural, and 10 mL of isopropanol were added to the reactor. Before the reaction, the reactor was purged three times with hydrogen at 2 MPa to remove air from the reactor, and then the reactor was charged with hydrogen at 2 MPa. The temperature was maintained at 130 °C, and the reaction time was 90 min.

[0118] (2) After the reaction is complete, the reaction vessel is placed in ice water and rapidly cooled to room temperature. The catalyst and reaction solution are then separated by centrifugation. The filtered catalyst powder is washed with ethanol multiple times and then recycled. The filtrate is analyzed using a gas chromatograph (GC) equipped with an HP-5 capillary column and a flame ionization detector (FID).

[0119] (3) The CuPd / C catalyst was used to catalyze the preparation of 2,5-dimethylfuran from 5-hydroxymethylfurfural. The conversion rate of 5-hydroxymethylfurfural reached 100%, and the selectivity of 2,5-dimethylfuran reached 97.5%.

[0120] Example 6

[0121] The difference between this embodiment and embodiment 5 is that the reaction temperature is 100 ℃, while the rest is the same as in embodiment 2.

[0122] Example 7

[0123] The difference between this embodiment and embodiment 5 is that the reaction temperature is 110 ℃, while the rest is the same as in embodiment 2.

[0124] Example 8

[0125] The difference between this embodiment and embodiment 5 is that the reaction temperature is 120 °C, while the rest is the same as in embodiment 2.

[0126] Example 9

[0127] The difference between this embodiment and Example 5 is that the reaction temperature is 130 °C, while the rest is the same as in Example 2.

[0128] Example 10

[0129] The difference between this embodiment and Example 5 is that the reaction temperature is 140 °C, while the rest is the same as in Example 2.

[0130] Example 11

[0131] The difference between this embodiment and Example 5 is that the reaction temperature is 150 °C, while the rest is the same as in Example 2.

[0132] Example 12

[0133] The difference between this embodiment and Example 5 is that the reaction temperature is 160 ℃, while the rest is the same as Example 2.

[0134] Example 13

[0135] The difference between this example and Example 5 is that the reaction temperature is 170 °C, while everything else is the same as in Example 2. For the catalysts prepared in the other examples and comparative examples, the conversion rate and selectivity of the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran were tested using the method described in Example 5.

[0136] Table 1 Actual metal loading of CuPd / C catalysts with different metal ratios

[0137]

[0138] Table 2. Effects of different catalysts on the hydrogenation reaction of 5-hydroxymethylfurfural

[0139]

[0140] According to the experimental results in Table 1, the catalysts with different Cu and Pd doping ratios in Examples 1-4 significantly affected the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran. The selectivity of the target product 2,5-dimethylfuran showed a volcano-like trend as the Cu doping ratio increased. When the Cu:Pd doping ratio was 3:0.8, 5-hydroxymethylfurfural was completely converted, and the selectivity of the target product 2,5-dimethylfuran reached its highest level of 97.5%. Comparative Example 1-1 was a CuPd / C catalyst prepared by the impregnation method, with a 5-hydroxymethylfurfural conversion rate of 78% and a 2,5-dimethylfuran selectivity of 80.8%. Comparative Example 1-2 was a Pd / C catalyst prepared by the continuous flow method, with a 5-hydroxymethylfurfural conversion rate of 100% and a 2,5-dimethylfuran selectivity of 31.9%.

[0141] In Example 1, the CuPd / C catalyst (3Cu0.8Pd) prepared by the continuous flow method achieved 100% conversion of 5-hydroxymethylfurfural and a selectivity of 97.5% for 2,5-dimethylfuran, representing the optimal catalyst preparation conditions. Compared to the CuPd / C catalyst (3Cu0.8Pd) prepared by the impregnation method, the yield of 2,5-dimethylfuran was increased by more than 34.5%; and compared to the Pd / C catalyst (0.8Pd) prepared by the continuous flow method, the yield of 2,5-dimethylfuran was increased by more than 65%.

[0142] Table 3 Catalytic activity of 3Cu0.8Pd / C catalysts prepared at different flow rates

[0143]

[0144] Based on the experimental results in Table 3, Examples 1 and Comparative Examples 1-3, 1-4, and 1-5 demonstrate the effect of different flow rates within the continuous flow apparatus on the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran. For the 3Cu0.8Pd / C catalyst at 6 mL / min, 5-hydroxymethylfurfural was completely converted, but the selectivity for the target product, 2,5-dimethylfuran, was only 69%. As the flow rate within the continuous flow apparatus increased to 10 mL / min, the prepared 3Cu0.8Pd / C catalyst not only achieved complete conversion of 5-hydroxymethylfurfural in this reaction but also achieved a high selectivity of 97.5% for 2,5-dimethylfuran. However, as the flow rate further increased, the conversion rate of 5-hydroxymethylfurfural gradually decreased; for the 3Cu0.8Pd catalyst at 18 mL / min, the conversion rate was only 70.6%. The flow rate within the apparatus significantly affects the mixing mode of CuPd atoms. When the liquid flow rate in the tube is slow (6 mL / min), CuPd atoms are uniformly mixed, and more Pd atoms are exposed on the surface of the metal nanoparticles, resulting in a high HMF conversion rate, but low selectivity for 2,5-dimethylfuran. When the liquid flow rate in the tube is fast (18 mL / min), more Pd atoms aggregate inside the bimetallic nanoparticles, resulting in less exposed surface Pd atoms, a decrease in HMF conversion rate, and an increase in the accumulation of byproducts during HMF hydrogenation. By precisely controlling the hydrodynamic conditions through a continuous flow method, the atomic arrangement on the surface of CuPd bimetallic nanoparticles can be determined, thereby controlling the hydrogenation selectivity between C=O and C=C in the HMF hydrogenation reaction. The catalyst prepared under optimal conditions exhibits the best activity-selectivity balance, providing a new strategy for designing highly efficient hydrodeoxygenation catalysts.

[0145] Table 4. Catalyst parameters prepared with different PVP dosages

[0146]

[0147] Table 4, in conjunction with Example 1 and Comparative Examples 1-6, 1-7, 1-8, and 1-9, shows the effects of different PVP dosages on the particle size and catalytic performance of the 3Cu0.8Pd / C catalyst. At low dosages, PVP only partially covers the particle surface, leaving uncovered areas still capable of reacting with metal ions in the solution. Insufficient surface adsorption leads to particle agglomeration due to van der Waals forces, resulting in larger and unevenly distributed nanoparticles. When the dosage is moderate (Cu+Pd:PVP=1:1 (g:g)), PVP forms a complete adsorption layer, maximizing steric hindrance and resulting in uniform particle size. However, when the dosage exceeds a critical value, excessive PVP molecules form micelles in the solution, potentially encapsulating multiple particles or hindering metal ion diffusion, thus broadening the particle size distribution.

[0148] Table 5. Catalyst parameters prepared with different amounts of sodium borohydride

[0149]

[0150] Table 5, in conjunction with Example 1 and Comparative Examples 1-10, 1-11, and 1-12, shows the effect of different sodium borohydride dosages on the particle size and catalytic performance of the 3Cu0.8Pd / C catalyst. When the sodium borohydride dosage is low, the metal ions (Cu²⁺) increase significantly. + / Pd² + Incomplete reduction leaves residual oxidized species (such as CuO and PdO), leading to a reduction in active sites. Simultaneously, the slow reduction rate prolongs the diffusion time of metal atoms, making it easier to form larger particles (e.g., particle size > 5 nm). With increasing sodium borohydride dosage (NaBH4:Cu+Pd(mol:mol) = 5:1), the particle size of the metal nanoparticles gradually decreases to 3.41 ± 0.38 nm; however, when the molar ratio of NaBH4 to metal ions exceeds 5:1, excess reducing agent induces local supersaturation, making the metal nanoparticles more prone to aggregation.

[0151] Application: According to Figure 6 The effect of reaction temperature on product distribution was demonstrated. The yield of 2,5-dimethylfuran increased with increasing temperature, reaching a maximum at 130 °C. As the temperature increased from 100 °C to 130 °C, the HMF conversion increased from 53% to 100%. At 100 °C, the DMF yield was low (40.4%). With gradually increasing reaction temperature, the DMF yield increased rapidly, reaching a maximum of 97.5% at 130 °C. Further increasing the temperature to 170 °C maintained a 100% HMF conversion, but the DMF selectivity decreased from 97.5% to 43.9%, indicating that excessively high temperatures are detrimental to DMF formation.

[0152] Based on the reaction results, this invention utilizes a continuous flow method to prepare a CuPd bimetallic catalyst. By optimizing the Cu and Pd doping ratio, the flow rate within the continuous flow tube, the amount of stabilizer, and the amount of reducing agent, the optimal catalyst was obtained for the hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran, resulting in a significant improvement in yield. The prepared particles are uniformly distributed and have a small particle size. Compared to previous production routes, the process of this invention is simpler, and mechanized operation effectively avoids human error, allowing for the production of the desired catalyst in one step, greatly reducing production time. The raw materials are renewable, the catalyst has high activity, and the reaction conditions are mild, reducing energy consumption to some extent and making it environmentally friendly, effectively alleviating the current global energy problem. Therefore, this invention has broad application potential in industrial production.

Claims

1. A method for preparing CuPd / C catalyst by continuous flow, characterized in that... Includes the following steps: (1) Weigh 1 g of palladium nitrate dihydrate Pd(NO3)2·2H2O and dissolve it in 50 mL of deionized water to prepare a Pd precursor solution with a Pd concentration of 7.146 mg / mL for later use. Weigh 4.065 g of copper chloride dihydrate CuCl2·2H2O and dissolve it in 100 mL of deionized water to prepare a Cu precursor solution with a Cu concentration of 15 mg / mL for later use. (2) Preparation of metal ion solution: Weigh 19 mg of polyvinylpyrrolidone (PVP, PVP:metal mass ratio = 1:1) and dissolve it in 400 mL of deionized water. Add 1000 μL of Cu precursor solution and 559.8 μL of Pd precursor solution in sequence, and continue stirring for 10 min. Prepare reducing agent solution by weighing 51.8 mg of sodium borohydride (NaBH2O). 4， NaBH4:metal molar ratio = 5:1) was dissolved in 400 mL of ice-cold deionized water and magnetically stirred for 10 min; (3) CuPd nanoparticles were prepared using a continuous flow apparatus; liquid was introduced into two pipelines, one of which was the metal ion solution prepared in step (2), and the other was the reducing agent solution prepared in step (2). The peristaltic pumps of both pipelines were at a speed of 10 mL / min. The liquid was then collected through a three-way valve and CuPd nanoparticles were synthesized in the Teflon pipeline. The time taken for the liquid to flow out of the pipeline was 40 min. The prepared CuPd nanoparticles could be stored in a refrigerator at 4 °C. (4) Take 481 mg of activated carbon in a beaker, add 200 mL of deionized water, stir at 1000 rpm for 10 min, and then sonicate for 10 min to obtain activated carbon slurry; (5) Using a continuous flow device, CuPd nanoparticles are loaded onto activated carbon. Two pipelines are fed simultaneously. One pipeline is fed with CuPd nanoparticles prepared in step (2) at a flow rate of 16 mL / min, and the other pipeline is fed with activated carbon slurry prepared in step (4) at a flow rate of 4 mL / min. The slurry is collected by a three-way valve and the loaded activated carbon slurry is collected in a beaker.

2. The method for preparing CuPd / C catalyst by continuous flow according to claim 1, characterized in that... The process also includes step (6): the collected effluent activated carbon slurry after loading is washed with deionized water until the conductivity is 0 μs / cm, the filter cake is placed in a petri dish and dried in a vacuum drying oven at 80 ℃ for 12 h, and then sealed and stored.

3. The method for preparing CuPd / C catalyst by continuous flow according to claim 1, characterized in that... The continuous flow device consists of a raw material unit, a feed conveying unit, a reactor unit, and a collection unit; the feed conveying unit is a peristaltic pump; the reactor unit consists of a temperature control device and a spiral reaction pipeline.

4. The CuPd / C catalyst prepared according to any one of claims 1-3.

5. The application of the CuPd / C catalyst according to claim 4, characterized in that... The prepared CuPd / C-based catalyst, 35 mg of catalyst, 1 mmol / L 5-hydroxymethylfurfural, and 10 mL of isopropanol were added to the reactor. Before the reaction, the reactor was purged three times with 2 MPa of hydrogen to remove air. Then, 2 MPa of hydrogen was introduced. The reaction temperature was 130 °C, and the reaction time was 1.5 h. After the reaction, the reactor was placed in ice water and rapidly cooled to room temperature. The catalyst and reaction solution were then separated, and the composition of the reaction solution was analyzed by gas chromatography to obtain the reaction results.

6. The application of the CuPd / C catalyst according to claim 5, characterized in that... The CuPd / C catalyst was used to catalyze the preparation of 2,5-dimethylfuran from 5-hydroxymethylfurfural, achieving a 100% conversion rate of 5-hydroxymethylfurfural and a 97.5% selectivity for 2,5-dimethylfuran.

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