Preparation method of carbon nanofiber membrane catalyst by using modified kaolin to load palladium

Abstract

The invention discloses a preparation method of a carbon nanofiber membrane catalyst by using modified kaolin to load palladium, and belongs to the technical field of nano material preparation. Active substances are uniformly dispersed in the fibers, so that catalytic reaction can be well carried out even if the fibers are broken in the preparation process. The carbon nanofibers are placed in a porcelain boat for high-temperature calcination, and amorphous carbon and metal catalyst impurities are selectively removed. The catalyst is recycled, washed in absolute ethyl alcohol and dried to be reused. Wherein palladium metal is firstly dissolved in a solution, and then spinning and carbonization are carried out, so that the agglomeration phenomenon is avoided. The palladium-loaded carbon nanofilm catalyst is prepared by using modified kaolin / polyacrylonitrile as a template agent, and the preparation method provided by the invention has the characteristics of simple operation, simple process, efficient performance and the like, and can be widely applied to the field of palladium metal catalysis.

Description

Technical Field

[0001] The present invention relates to a method for preparing a catalyst, in particular to a method for preparing a Pd / APTE-BTMO-KL carbon nanofiber membrane catalyst. Background Art

[0002] In many catalytic reactions, noble metal palladium-based catalysts have attracted much attention due to their excellent catalytic performance. However, traditional palladium-based catalysts have some problems, such as easy aggregation of active components and weak interaction between the support and the active components, which limit their further application. Therefore, developing a new type of palladium-based catalyst has important research significance and application value.

[0003] However, the preparation of carbon nanofiber catalysts by electrospinning still faces many challenges:

[0004] 1. During the carbonization process, the fibers are prone to shrinkage, deformation or even fracture, resulting in a decline in mechanical properties.

[0005] 2. The generated carbon nanofibers may be attached with impurities, such as unreacted catalyst particles, by-products decomposed from the carbon source, etc., and complex post-treatment processes are required for purification.

[0006] 3. The recovery of ordinary powdered heterogeneous catalysts requires steps such as filtration, centrifugation, drying, alkali washing (acid washing), and centrifugation.

[0007] 4. Agglomeration of active substances in the catalyst may occur. Summary of the Invention

[0008] The present invention aims to provide a method for preparing a Pd / APTE-BTMO-KL carbon nanofiber membrane catalyst. The catalyst prepared by this method has good dispersion of active components, strong interaction between the support and the active components, and excellent catalytic performance. In the present invention, the active substances are uniformly dispersed in the fibers, and even if fractures occur during the preparation process, catalytic reactions can still be carried out well. The carbon nanofibers are placed in a porcelain boat and calcined at high temperature to selectively remove amorphous carbon and metal catalyst impurities. For the recovery of this catalyst, it can be washed in absolute ethanol and dried for reuse. Among them, palladium metal is first dissolved in the solution, and then electrospinning and carbonization are carried out to avoid agglomeration.

[0009] The technical solution of the present invention is as follows:

[0010] A method for preparing a Pd / APTE-BTMO-KL carbon nanofiber membrane catalyst, comprising the following steps:

[0011] Take 1 g of Inner Mongolia kaolin (KL) sample and dissolve it in 30 mL of n-heptane solution. Add 1.2 mmol of 3-aminopropyltriethoxysilane (APTE) and 1.2 mmol of phenyltrimethoxysilane (BTMO) to the mixture. Stir the suspension at room temperature for 6 h, place it in the dark for 12 h, centrifuge to remove the solvent, wash the functionalized kaolin with n-heptane, and dry it in vacuum for 12 h to obtain APTE-BTMO-KL.

[0012] Dissolve 0.5 g of polyacrylonitrile (PAN) in 4.5 g of dimethylformamide (DMF). After stirring evenly, add 0.0094 g of palladium chloride (PdCl2) and continue stirring. After stirring evenly, add 0.0709 g of APTE-BTMO-KL and continue stirring until the solution is homogeneous to obtain the precursor solution.

[0013] Pour the precursor solution into a spinning tube and perform electrospinning at a voltage of 18 kV. The distance between the electrode and the aluminum foil is 18 cm to obtain the Pd / APTE-BTMO-KL nanofiber membrane.

[0014] Heat the Pd / APTE-BTMO-KL nanofiber membrane to 250 °C, 300 °C, and 350 °C at a heating rate of 5 °C / min respectively and hold it in air for 2 h to obtain the catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane.

[0015] The inventive method is for catalyst production. For the recovery of powdered heterogeneous catalysts, steps such as water washing and centrifugation are required. The present invention is relatively simple and easy to operate. In terms of the efficiency of catalyst production, compared with powdered catalysts, the number of times the catalyst prepared once can be used is dozens of times that of powdered catalysts. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0017] Figure 1 Scanning electron microscope (SEM) of the carbon nanofiber membrane catalyst synthesized in Example 1 at 50000x.

[0018] Figure 2 Scanning electron microscope (SEM) of the carbon nanofiber membrane catalyst synthesized in Example 1 at 20000x.

[0019] Figure 3 XRD diffraction pattern of the carbon nanofiber membrane catalyst synthesized in Example 1.

[0020] Figure 4 Data graph for the performance test of the catalyst. Detailed implementation mode

[0021] The present invention is further illustrated by the following specific embodiments:

[0022] The technical solution adopted by the present invention is a preparation method of a carbon nanofiber membrane catalyst loaded with palladium using modified kaolin, including the following steps:

[0023] Step (1): Take a kaolin sample and dissolve it in a n-heptane solution to obtain a mixture. Add 3-aminopropyltriethoxysilane (APTE) and phenyltrimethoxysilane (BTMO) to the mixture to obtain a suspension. Stir the suspension at room temperature and place it in the dark. Centrifuge to remove the solvent, wash the functionalized kaolin with n-heptane, and dry it under vacuum. The obtained functionalized kaolin sample is designated as APTE-BTMO-KL.

[0024] Step (2): Add the APTE-BTMO-KL prepared in step (1) to a homogeneous solution of polyacrylonitrile (PAN), dimethylformamide (DMF), and palladium chloride (PdCl2). Thus, a precursor solution is obtained.

[0025] Step (3): Pour the precursor solution prepared in step (2) into a spinning tube and perform electrospinning at a voltage of 18 kV. The distance between the electrode and the aluminum foil is 18 cm. Thus, a Pd / APTE-BTMO-KL nanofiber membrane is obtained.

[0026] Step (4): Heat the Pd / APTE-BTMO-KL nanofiber membrane prepared in step (3) to 250 °C, 300 °C, and 350 °C by programmed heating and keep it in the air for 2 hours. The catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane is obtained.

[0027] Furthermore, in step (1), the kaolin and n-heptane are 1 g and 30 mL respectively; the molar ratio of APTE to BTMO is 1:1, which is 1.2 mmol.

[0028] Furthermore, in step (2), the masses of polyacrylonitrile and DMF are 0.5 g and 4.5 g respectively; PdCl2 and APTE-BTMO-KL are 0.0094 g and 0.0709 g respectively.

[0029] Furthermore, in step (3), electrospinning is performed at a voltage of 18 kV, and the distance between the electrode and the aluminum foil is 18 cm.

[0030] Furthermore, in step (1), the suspension is stirred at room temperature for 6 h, placed in the dark for 12 h, the solvent is removed by centrifugation, the functionalized kaolin is washed with n-heptane, and dried under vacuum for 12 h.

[0031] Parameter Characteristics of Catalyst Pd / APTE-BTMO-KL Carbon Nanofiber Membrane

[0032] 1. Basic Composition

[0033] Precursor materials: Polyacrylonitrile (PAN), 3-aminopropyltriethoxysilane (APTE), phenyltrimethoxysilane (BTMO), kaolin (KL), palladium chloride (PdCl2).

[0034] Support material: Modified kaolin (APTE-BTMO-KL).

[0035] Active component: Palladium nanoparticles (PdNPs).

[0036] Support form: Carbon nanofiber membrane.

[0037] 2. Preparation Process Parameters

[0038] Electrospinning conditions:

[0039] Voltage: 18 kV.

[0040] Collection distance: 18 cm.

[0041] Solution composition: PAN (0.5 g), DMF (4.5 g), PdCl2 (0.0094 g), APTE-BTMO-KL (0.0709 g).

[0042] Carbonization conditions:

[0043] Heating rate: 5 °C / min.

[0044] Carbonization temperature: 250 °C, 300 °C, 350 °C.

[0045] Holding time: 2 hours.

[0046] Atmosphere: Air.

[0047] 3. Physicochemical Characteristics

[0048] Microscopic morphology:

[0049] Fiber diameter: Uniform, no obvious agglomeration.

[0050] Surface characteristics: Smooth, no obvious cracks or protrusions.

[0051] Nanoparticle characteristics:

[0052] Particle size: 3.45 nm (fresh catalyst), 4.85 nm (after one recovery).

[0053] Distribution: Uniformly distributed on the fiber surface.

[0054] Crystal structure:

[0055] XRD characteristic peaks: corresponding to the (002), (101), (110), (112), (211) crystal planes of the PdO cubic structure.

[0056] Interplanar spacing: 0.0246 nm (101 crystal plane).

[0057] Chemical composition:

[0058] Valence state of Pd: Pd 2+ (fresh catalyst), Pd 0 (after recycling).

[0059] Surface functional groups: elements such as C, O, and N are evenly distributed.

[0060] Example

[0061] A preparation method of a carbon nanofiber membrane catalyst using modified kaolin supported palladium, comprising the following steps:

[0062] (1) Take an Inner Mongolia kaolin sample and dissolve it in a n-heptane solution. Add 3-aminopropyltriethoxysilane (APTE) and phenyltrimethoxysilane (BTMO) to this mixture. Stir the suspension at room temperature and place it in the dark. Centrifuge to remove the solvent, wash the functionalized kaolin with n-heptane, and dry it under vacuum. The obtained functionalized kaolin sample is designated as APTE-BTMO-KL.

[0063] (2) Add the APTE-BTMO-KL prepared in step (1) to a homogeneous solution of polyacrylonitrile (PAN), dimethylformamide (DMF), and palladium chloride (PdCl2). Thus, a precursor solution is obtained.

[0064] (3) Pour the precursor solution prepared in step (2) into a spinning tube and perform electrospinning at a voltage of 18 kV. The distance between the electrode and the aluminum foil is 18 cm. Thus, a Pd / APTE-BTMO-KL nanofiber membrane is obtained.;

[0065] (4) Heat the Pd / APTE-BTMO-KL nanofiber membrane prepared in step (3) to 250 °C, 300 °C, and 350 °C by programmed heating and hold it in air for 2 hours. The catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane is obtained.

[0066] In step (1), the kaolin and n-heptane are 1 g and 30 mL respectively; the molar ratio of APTE and BTMO is 1:1, which is 1.2 mmol.

[0067] In step (2), the masses of polyacrylonitrile and DMF are 0.5 g and 4.5 g respectively; the masses of PdCl2 and APTE - BTMO - KL are 0.0094 g and 0.0709 g respectively.

[0068] In step (3), electrospinning is carried out at a voltage of 18 kV, and the distance between the electrode and the aluminum foil is 18 cm.

[0069] In step (1), the suspension is stirred at room temperature for 6 h, placed in the dark for 12 h, the solvent is removed by centrifugation, the functionalized kaolin is washed with n - heptane, and vacuum - dried for 12 h.

[0070] Example 1:

[0071] According to the above step 1, 1 g of Inner Mongolia kaolin (KL) sample is taken and dissolved in a n - heptane solution (30 mL). 1.2 mmol of 3 - aminopropyltriethoxysilane (APTE) and 1.2 mmol of phenyltrimethoxysilane (BTMO) are added to this mixture. The suspension is stirred at room temperature for 6 h, placed in the dark for 12 h, the solvent is removed by centrifugation, the functionalized kaolin is washed with n - heptane, and vacuum - dried for 12 h to obtain APTE - BTMO - KL.

[0072] According to the above step 2, 0.5 g of polyacrylonitrile (PAN) is dissolved in 4.5 g of dimethylformamide (DMF). After stirring evenly, 0.0094 g of palladium chloride (PdCl2) is added and stirring continues. After stirring evenly, 0.0709 g of APTE - BTMO - KL is added and stirring continues until the solution is homogeneous to obtain a precursor solution.

[0073] According to the above step 3, the precursor solution is poured into a spinning tube, and electrospinning is carried out at a voltage of 18 kV, with the distance between the electrode and the aluminum foil being 18 cm, to obtain a Pd / APTE - BTMO - KL nanofiber membrane.

[0074] According to the above step 4, the Pd / APTE - BTMO - KL nanofiber membrane is heated to 250 °C at a heating rate of 5 °C / min and maintained in air for 2 h to obtain a catalyst Pd / APTE - BTMO - KL carbon nanofiber membrane catalyst - 250.

[0075] Example 2:

[0076] According to steps 1 and 2 of Example 1, a precursor solution is prepared.

[0077] According to the above step 3, the precursor solution is poured into a spinning tube, and electrospinning is carried out at a voltage of 18 kV, with the distance between the electrode and the aluminum foil being 18 cm, to obtain a Pd / APTE - BTMO - KL nanofiber membrane.

[0078] According to Step 4 above, heat the Pd / APTE-BTMO-KL nanofiber membrane to 300 °C at a heating rate of 5 °C / min and hold it in air for 2 h to obtain the catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane-300.

[0079] Example 3:

[0080] Prepare the precursor solution according to Steps 1 and 2 of Example 1.

[0081] According to Step 3 above, pour the precursor solution into the spinning tube and perform electrospinning at a voltage of 18 kV. The distance between the electrode and the aluminum foil is 18 cm to obtain the Pd / APTE-BTMO-KL nanofiber membrane.

[0082] According to Step 4 above, heat the Pd / APTE-BTMO-KL nanofiber membrane to 350 °C at a heating rate of 5 °C / min and hold it in air for 2 h to obtain the catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane-350.

[0083] Performance test:

[0084] Perform performance tests on the catalysts prepared in Examples 1-3 above. As Figure 4 shown, the results indicate that the catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane has good dispersion of active components, strong interaction between the support and the active components, and excellent catalytic performance. Among them, the catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane-300 has the best catalytic performance.

[0085]

[0086] The present invention provides a preparation method of a Pd / APTE-BTMO-KL carbon nanofiber membrane catalyst. The catalyst prepared by this method has good dispersion of active components, strong interaction between the support and the active components, and excellent catalytic performance, and has broad application prospects.

Claims

1. A method for preparing a carbon nanofiber membrane catalyst using modified kaolin loaded with palladium, characterized in that: The following steps are involved: Step (1), taking a sample of Inner Mongolia kaolin and dissolving it in an n-heptane solution; 3-aminopropyltriethoxysilane APTE and phenyltrimethoxysilane BTMO were added to the n-heptane solution; the suspension was stirred at room temperature and placed away from light; the solvent was removed by centrifugation, the functionalized kaolin was washed with n-heptane, and the functionalized kaolin sample obtained by vacuum drying was designated as APTE-BTMO-KL; Step (2), adding the APTE-BTMO-KL prepared in step (1) to a uniform solution of polyacrylonitrile PAN, dimethylformamide DMF, and palladium chloride PdCl2 to obtain a precursor solution; Step (3), pouring the precursor solution prepared in step (2) into a spinning tube, performing electrospinning and obtaining a Pd / APTE-BTMO-KL nanofiber membrane; Step (4), heating the Pd / APTE-BTMO-KL nanofiber membrane prepared in step (3) to 250°C, 300°C, and 350°C by programmed temperature increase, and keeping it in air for 2 hours to obtain a catalyst Pd / APTE-BTMO-KL carbon nanofiber membrane.

2. The method for preparing a carbon nanofiber membrane using modified kaolin loaded with palladium according to claim 1, characterized in that: In the step (1), kaolin and n-heptane are 1 g and 30 mL respectively; the molar ratio of APTE to BTMO is 1:1, which is 1.2 mmol.

3. The method for preparing a carbon nanofiber membrane using modified kaolin loaded with palladium according to claim 1, characterized in that: The masses of polyacrylonitrile and DMF in step (2) are 0.5 g and 4.5 g respectively; the masses of PdCl2 and APTE-BTMO-KL are 0.0094 g and 0.0709 g respectively.

4. The method for preparing a carbon nanofiber membrane using modified kaolin loaded with palladium according to claim 1, characterized in that: The electrospinning in step (3) was carried out at a voltage of 18 kV, and the distance between the electrode and the aluminum foil was 18 cm.

5. The method for preparing a carbon nanofiber membrane using modified kaolin loaded with palladium according to any one of claims 1 to 4, characterized in that: In step (1), the suspension is stirred at room temperature for 6 hours, placed in the dark for 12 hours, centrifuged to remove the solvent, and the functionalized kaolin is washed with n-heptane and vacuum dried for 12 hours.

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