Preparation method of metal cluster in-situ implanted mesoporous silicon oxide catalytic material and application thereof in propane dehydrogenation to propylene

Abstract

The application discloses a preparation method of a metal cluster in-situ implanted mesoporous silica catalytic material and application of the metal cluster in-situ implanted mesoporous silica catalytic material in preparation of propylene from propane dehydrogenation. First, a nanometer colloid with a very small size is prepared in deionized water which is a solvent for synthesizing mesoporous silica through liquid phase pulse laser irradiation technology, and then the nanometer colloid is in-situ synthesized with a silicon source and a surfactant and the like which are precursors for synthesizing mesoporous silica through a one-pot solvothermal method. After the product is subjected to freeze drying and calcination treatment, a composite catalytic material of the metal cluster in-situ implanted mesoporous silica is obtained. The type, loading amount and size of the implanted metal in the silica carrier are controlled by adjusting laser irradiation time, wavelength and energy size, the metal in the obtained composite catalytic material is uniformly dispersed and the loading amount is high, a novel universal strategy is provided for designing and preparing a metal limited mesoporous silica composite catalytic material, and finally, a composite catalytic material with high activity, high propylene selectivity and high stability for preparing propylene from propane dehydrogenation is obtained.

Description

Technical Field

[0001] This invention belongs to the field of thermocatalytic material preparation technology, specifically relating to the preparation method of in-situ implantation of metal clusters into mesoporous silica catalytic materials and their application in propane dehydrogenation to propylene. Background Technology

[0002] Propylene is an indispensable raw material intermediate in the chemical, pharmaceutical, and construction industries, but current propylene production still falls short of demand. Therefore, there is an urgent need to develop industrial technologies for producing propylene with high conversion rates and high selectivity. Due to the abundance of shale gas resources and the availability of large-scale propane extraction, propane dehydrogenation to propylene, with its high propylene selectivity, has become a key technology for meeting global propylene demand. Regarding catalysts, supported Pt-based and Cr-based catalysts are currently two common and highly efficient industrial catalysts for propane dehydrogenation. However, Cr suffers from serious problems of environmental toxicity and low stability, while Pt is expensive and scarce. Therefore, developing inexpensive, environmentally friendly, and highly active alternative catalysts is an important research topic and a significant challenge. Currently, supported non-precious metal nanoparticle / cluster catalysts have been extensively studied due to their abundance, environmental friendliness, tunability, and high activity for propane dehydrogenation. However, structure-sensitive side reactions often occur on the surface of larger clusters and nanoparticles, leading to low propylene selectivity and catalyst deactivation.

[0003] Nanocluster catalysts immobilize isolated active sites on a support, providing a solution for the selective generation of propylene and preventing further C−C(H) breakage during propane dehydrogenation. However, without the constraint of a support, single active sites undergo severe sintering during propane dehydrogenation, transforming into larger clusters or nanoparticles. Therefore, to improve the performance of propane dehydrogenation, it is crucial to find durable and high-surface-area support materials and to confine and stabilize highly catalytically active metal sites within the pores of the support through in-situ implantation. This is also a key technology that those skilled in the art need to address and develop. Summary of the Invention

[0004] To address the issues of high cost, scarcity, and rapid deactivation of precious metals during high-temperature catalysis, this invention proposes a method for preparing a metal cluster in-situ implanted mesoporous silica catalytic material, specifically comprising the following steps:

[0005] Step 1: Prepare a colloidal solution of metal clusters using liquid phase pulsed laser irradiation technology; place the polished metal in deionized water, bombard the metal target with a nanosecond pulsed laser beam under the conditions of condensation temperature of -10-0℃ and continuous ultrasound, and then remove the metal to obtain a colloidal solution of metal clusters.

[0006] Step 2: Dissolve ammonium metavanadate in the metal cluster colloidal solution obtained in Step 1 by ultrasonication, dilute with deionized water, add ammonia water and stir for a period of time until homogeneous, then add hexadecyltrimethylammonium bromide and stir for a certain period of time, then add tetraethyl orthosilicate to carry out hydrolysis reaction to obtain a mixed gel solution.

[0007] Step 3: Heat and stir the mixed gel solution from Step 2 to react, then cool it to room temperature, centrifuge it, wash the precipitate and dry it to obtain the composite powder;

[0008] Step 4: The composite powder obtained in Step 3 is calcined to obtain a composite catalytic material with metal clusters in situ implanted in mesoporous silica.

[0009] Preferably, the metal nanoclusters in step one include elemental metals (Co, Fe, Ni, Zn, Sn, V, Cr, Ga, Mo, Cu, etc.) and bimetals (FeNi, CoMo, NiZn, etc.).

[0010] Preferably, the laser flux of the nanosecond pulsed laser in step one is 800-1200 mJ. -1 cm -1 The laser beam bombards the metal target for 2-5 minutes.

[0011] Preferably, in step two, the mass ratio of ammonium metavanadate to hexadecyltrimethylammonium bromide is 3:14, and the volume ratio of the metal cluster colloidal solution to untreated deionized water is (3:1) to (1:3), and the ratio of the volume of ammonia water to the total volume of deionized water is 1:35.

[0012] Preferably, the ultrasonic dissolution time in step two is 30 min, the stirring time for adding ammonia is 10-30 min, and the stirring time for adding hexadecyltrimethylammonium bromide is 15-30 min.

[0013] Preferably, in step three, the heating and stirring reaction is carried out in an oil bath, and the hydrolysis time of the tetraethyl orthosilicate is 6-12 h, and the hydrolysis temperature is 40-80℃.

[0014] Preferably, the calcination process of the composite powder in step four specifically includes: calcining the composite powder obtained in step three at 550°C in air for 6 hours with a heating rate of 10°C / min, cooling it down, heating it from room temperature to 400°C in a pure hydrogen atmosphere for 2 hours, and then holding it at that temperature for 2 hours, with a pure hydrogen flow rate of 60 ml / min.

[0015] The present invention also provides a catalytic material in which metal clusters are in situ implanted into mesoporous silica obtained by any of the above preparation methods, wherein the size of the metal clusters is less than 1 nm.

[0016] The present invention also provides the application of in-situ implantation of metal clusters into mesoporous silica catalyst in propane dehydrogenation to propylene. 0.3 g of the composite catalyst is diluted with 0.5 g of 40-60 mesh quartz sand and then loaded into a fixed bed reactor. Under the protection of argon atmosphere, the temperature is raised to the reaction temperature of 550°C for 1 h, and gaseous reactants are introduced. The ratio of propane to argon is 10:50 (ml / min).

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) Based on liquid phase pulsed laser irradiation technology, the present invention successfully implants ultrafine Co clusters and extended non-precious metal clusters into mesoporous silica channels, with uniform loading and a maximum loading amount of up to 9.8 wt%, and the silica channel structure can still be maintained after loading.

[0019] (2) The process of this invention is simple, environmentally friendly and efficient, and does not harm the environment. The obtained Co clusters have no ligands on their surface and have broad application prospects.

[0020] (3) The composite catalytic material prepared by the present invention, such as the Co metal cluster confined in mesoporous silica, is combined with the silica support in a four-coordinate form, which provides a large number of active sites for the catalytic process, so that it has high propane conversion, propylene selectivity and propane conversion when used in the propane dehydrogenation to propylene reaction. Attached Figure Description

[0021] Figure 1 This invention provides a synthetic route for Co NCs@SiO2, a composite catalytic material in which Co metal clusters are implanted into mesoporous silica.

[0022] Figure 2 The images provided by this invention are scanning electron microscope (SEM) images of Co nanocolloids and Co NCs@SiO2 composite catalytic materials, and aberration-corrected high-angle annular dark-field scanning transmission electron microscope (STEM) images. (a) is aberration-corrected high-angle annular dark-field scanning transmission electron microscope image of Co nanocolloids, (b) is a scanning electron microscope image of Co NCs@SiO2 composite catalytic materials, and (ch) is aberration-corrected high-angle annular dark-field scanning transmission electron microscope image.

[0023] Figure 3 The images shown are the powder X-ray diffraction image, X-ray photoelectron spectrum and Fourier transform infrared spectrum of the Co NCs@SiO2 composite catalytic material provided by the present invention, wherein (a) is the X-ray diffraction pattern (XRD), (b) is the X-ray photoelectron spectrum and (c) is the Fourier transform infrared spectrum.

[0024] Figure 4The figures show the nitrogen adsorption-desorption curves and pore size distribution curves of the Co NCs@SiO2 composite catalyst and the SiO2 support provided by this invention, wherein (a) is the nitrogen adsorption-desorption curve of the SiO2 support, (b) is the pore size distribution curve of the SiO2 support, (c) is the nitrogen adsorption-desorption curve of the Co NCs@SiO2 composite catalyst, and (d) is the pore size distribution curve of the Co NCs@SiO2 composite catalyst.

[0025] Figure 5 The propane conversion rate and propylene selectivity of the Co NCs@SiO2 and Co NPs@SiO2 composite catalytic materials provided in the embodiments of the present invention are shown in the embodiments. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0027] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein.

[0028] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] To address the issues of high cost, scarcity, and rapid deactivation of precious metals during high-temperature catalysis, this invention first utilizes liquid-phase pulsed irradiation technology to prepare a series of non-precious metal nanocolloids in deionized water, such as elemental metals (Co, Fe, Ni, V, etc.) and bimetallic (FeNi, CoMo, NiZn, etc.) liquid-phase laser nanocolloids. Then, a non-precious metal catalyst is successfully implanted into mesoporous silica using a liquid-phase laser in-situ implantation method. The soft template is then removed through a two-step calcination process in air and hydrogen. Furthermore, this invention allows for the control of the Co mass fraction within the range of 0.7-9.8% by adjusting the laser irradiation time, wavelength, and energy, ultimately enabling its application in the propane dehydrogenation catalysis process.

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments: Example 1

[0031] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -5℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 1000 mJ was used. -1 cm -2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 2 min.

[0032] (2) Dissolve 30 mg of ammonium metavanadate in 105 ml of deionized water, sonicate for half an hour until completely dissolved, then add 35 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0033] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0034] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Keep the temperature at 60℃ and stir for 8 h.

[0035] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0036] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 2

[0037] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -5℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 1000 mJ was used. -1 cm -2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 5 min.

[0038] (2) Dissolve 30 mg of ammonium metavanadate in 140 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0039] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0040] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Keep the temperature at 60℃ and stir for 8 h.

[0041] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0042] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 3

[0043] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -10℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 1200 mJ was used. -1 cm-2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 1 min.

[0044] (2) Dissolve 30 mg of ammonium metavanadate in 70 ml of deionized water, sonicate for half an hour until completely dissolved, then add 70 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0045] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0046] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Keep the temperature at 60℃ and stir for 8 h.

[0047] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0048] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 4

[0049] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -5℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 1000 mJ was used. -1 cm -2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 2 min.

[0050] (2) Dissolve 30 mg of ammonium metavanadate in 105 ml of deionized water, sonicate for half an hour until completely dissolved, then add 35 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0051] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0052] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Control the temperature at 80℃ and stir for 12 h.

[0053] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0054] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 5

[0055] (1) The polished metal Co foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water and the glass bottle was fixed in an ultrasonic machine with water circulation at -5℃. Under continuous ultrasonic conditions, the metal Co foil was bombarded for 2 min with a nanosecond pulse laser beam (Nd:YAG) with a laser flux of 1000 mJ pulse-1 cm-2 to prepare a Co cluster colloidal solution.

[0056] (2) Dissolve 30 mg of ammonium metavanadate in 105 ml of deionized water, sonicate for half an hour until completely dissolved, then add 35 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0057] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0058] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Keep the temperature at 40℃ and stir for 10 h.

[0059] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0060] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 550°C for 2 h in a pure hydrogen atmosphere (flow rate of 40 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 6

[0061] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -3℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 800 mJ was used. -1 cm -2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 5 min.

[0062] (2) Dissolve 30 mg of ammonium metavanadate in 35 ml of deionized water, sonicate for half an hour until completely dissolved, then add 105 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0063] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0064] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Control the temperature at 80℃ and stir for 12 h.

[0065] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0066] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support. Example 7

[0067] (1) The polished Co metal foil (2 cm × 2 cm, 1 mm thick) was placed in a glass bottle containing 10 ml of deionized water, and the glass bottle was fixed in an ultrasonic machine with water circulation at -10℃. Under continuous ultrasonic conditions, a laser pulse with a flux of 1200 mJ was used. -1 cm -2 A Co cluster colloidal solution was prepared by bombarding a metallic Co foil with a nanosecond pulsed laser beam (Nd:YAG) for 3 min.

[0068] (2) Dissolve 30 mg of ammonium metavanadate in 70 ml of deionized water, sonicate for half an hour until completely dissolved, then add 70 ml of the Co cluster colloidal solution prepared in step (1), add 4 ml of ammonia water and stir for 10 min until uniform, then place in an oil bath at 40°C and stir.

[0069] (3) The mixed solution obtained in step (2) is placed in an oil bath and heated and stirred. After the oil bath temperature is controlled at 40°C, 140 mg of cetyltrimethylammonium bromide is added.

[0070] (4) After stirring the solution obtained in step (3) for 15 min, add 0.18 ml of tetraethyl orthosilicate to allow it to undergo hydrolysis. Keep the temperature at 60℃ and stir for 12 h.

[0071] (5) After cooling the product obtained in step (4) to room temperature, centrifuge at 7000 rpm, wash three times with deionized water, and freeze dry for 12 h.

[0072] (6) The powder obtained in step (5) was calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it was heated from room temperature to 400°C for 2 h in a pure hydrogen atmosphere (flow rate of 60 ml / min) and then kept at that temperature for 2 h. After cooling, a light gray powder was obtained, which is the composite catalytic material with Co clusters encapsulated in a mesoporous silica support.

[0073] Examples 1-7 prepared Co NCs@SiO2 composite catalytic materials with Co metal clusters encapsulated in mesoporous silica. The catalyst prepared in Example 1 is characterized and propane dehydrogenation catalytic tests are performed using the sample from Example 1 as an example.

[0074] Figure 1 Synthetic route for composite catalytic materials in which Co clusters are confined to mesoporous silica.

[0075] Figure 2Image a is a high-angle annular dark-field scanning transmission electron microscope image of Co nanocolloids prepared by liquid-phase laser pulse technology with spherical aberration correction. Uniform atomic clusters (~0.7 nm) can be observed. Since the colloids were individually dropped onto the ultrathin carbon film without any support, this led to the aggregation and growth of Co clusters. In reality, the clusters in the colloids are even smaller. Figure 2 b is a scanning electron microscope image of the Co NCs@SiO2 composite catalyst, which shows a plate-like structure. This structure is conducive to the rapid adsorption and desorption of propane and propylene at the Co reactive sites. Figure 2 High-angle annular dark-field scanning transmission electron microscopy (STEM) images corrected for spherical aberration show that Co is highly uniformly dispersed in the Co NCs@SiO2 composite material, with Co cluster size of approximately 0.5 nm. Figure 2 The selected area electron diffraction pattern in inset c shows that SiO2 is an amorphous material and Co exhibits amorphous characteristics. Figure 2 The energy-dispersive X-ray spectra obtained from the Eh further confirmed the uniform dispersion of Si, O, and Co throughout the composite material.

[0076] Figure 3 The powder X-ray diffraction (XRD) pattern of the Co NCs@SiO2 composite material showed that SiO2 is amorphous. The XRD curve of the Co NCs@SiO2 composite material obtained by in-situ implantation with liquid phase laser did not show obvious metal peaks, indicating that no large nanoparticles were present. This further proves that Co is implanted in mesoporous silica in a highly dispersed Co cluster state. Figure 3 The surface chemical state of the catalyst was studied by X-ray photoelectron spectroscopy. XPS spectra of Co 2p showed that all samples had two broad and asymmetric main peaks at 775–790 eV and 790–810 eV, corresponding to Co 2p3 / 2 and Co 2p1 / 2, respectively. This showed the spin-orbit doublets of Co(II) (Co 2p3 / 2 at 781.8 eV and Co 2p1 / 2 at 797.7 eV) and their broad satellite peaks, indicating that no Co nanoparticles were present on the catalyst and that it was not oxidized to Co3O4. Figure 3 The Fourier transform infrared spectrum of c shows that after Co is implanted into the mesoporous silica, the 1060 cm⁻¹... -1 and 801 cm -1 The characteristic peak at 960 cm⁻¹ has undergone a redshift, and at 960 cm⁻¹... -1 The peaks at the point also became more pronounced, which indicates that Co was successfully incorporated into the framework of mesoporous silica.

[0077] Figure 4The nitrogen adsorption-desorption curves and pore size distribution curves of the SiO2 support and the Co NCs@SiO2 composite material are shown. The calculated specific surface areas of Brunauer-Emmett-Teller (BET) are 737.69 and 663.82 m², respectively. 2 g -1 The specific surface area of ​​the CoNCs@SiO2 composite material decreased after Co implantation, but the mesoporous structure did not change significantly.

[0078] Figure 5 The propane conversion rate and propylene selectivity of the composite catalytic materials prepared in Examples 1 and 2 of this invention during the propane catalytic reaction are shown. In Example 1, the initial propane conversion rate of the Co NCs@SiO2 composite material was ~36%, and the propylene selectivity was ~95%, with the conversion rate remaining at ~24% after nearly 33 hours of reaction. However, when the Co implantation amount was too high, such as in Example 2, the initial conversion rate of the Co NPs@SiO2 composite catalyst was ~30%, and the propylene selectivity was ~90%, and rapid deactivation occurred during the long reaction period. Obviously, the extremely small Co clusters in the Co NCs@SiO2 composite material can be confined within the pores of silica, increasing the contact area of ​​active sites and inhibiting the aggregation and deactivation of active sites during the high-temperature propane dehydrogenation process to a certain extent.

Claims

1. A method for preparing a metal cluster in situ implanted mesoporous silica catalytic material, characterized in that, Includes the following steps: Step 1: Preparation of metal cluster colloidal solution by liquid phase pulsed laser irradiation technology: The polished metal is placed in deionized water, and the metal target is bombarded with a nanosecond pulsed laser beam under the conditions of condensation temperature of -10-0℃ and continuous ultrasound. Then the metal is taken out to obtain a metal cluster colloidal solution; the metal cluster is Co cluster. Step 2: Dissolve ammonium metavanadate in the metal cluster colloidal solution obtained in Step 1 by ultrasonication, dilute with deionized water, add ammonia water and stir for a period of time until homogeneous, then add hexadecyltrimethylammonium bromide and stir for a certain period of time, then add tetraethyl orthosilicate to carry out hydrolysis reaction to obtain a mixed gel solution. Step 3: Heat and stir the mixed gel solution from Step 2 to react, then cool it to room temperature, centrifuge it, wash the precipitate and freeze-dry it to obtain the composite powder; Step 4: The composite powder obtained in Step 3 is calcined to obtain a composite catalytic material with metal clusters in situ implanted in mesoporous silica. The calcination process of the composite powder is as follows: the composite powder obtained in Step 3 is calcined in air at 550°C for 6 h with a heating rate of 10°C / min. After cooling, it is heated from room temperature to 400°C in a pure hydrogen atmosphere for 2 h, and then held at that temperature for 2 h. The flow rate of pure hydrogen is 60 ml / min.

2. The method for preparing a metal cluster in-situ implanted mesoporous silica catalytic material according to claim 1, characterized in that, In step one, the laser flux of the nanosecond pulsed laser is 800-1200 mJ. -1 cm -1 The laser beam bombards the metal target for 2-5 minutes.

3. The method for preparing a metal cluster in-situ implanted mesoporous silica catalytic material according to claim 1, characterized in that, In step two, the mass ratio of ammonium metavanadate to hexadecyltrimethylammonium bromide is 3:14, and the volume ratio of the metal cluster colloidal solution to untreated deionized water is (3:1) to (1:3), and the ratio of the volume of ammonia water to the total volume of deionized water is 1:

35.

4. The method for preparing a metal cluster in-situ implanted mesoporous silica catalytic material according to claim 1, characterized in that, The ultrasonic dissolution time in step two is 30-60 min, the stirring time for adding ammonia is 10-30 min, and the stirring time for adding hexadecyltrimethylammonium bromide is 15-30 min.

5. The method for preparing a metal cluster in-situ implanted mesoporous silica catalytic material according to claim 1, characterized in that, In step three, the reaction is carried out by heating and stirring in an oil bath. The hydrolysis time of the tetraethyl orthosilicate is 6-12 h, and the hydrolysis temperature is 40-80℃.

6. The catalytic material with in-situ implantation of metal clusters into mesoporous silica obtained by the preparation method according to any one of claims 1-5, characterized in that, The size of the metal clusters is less than 1 nm.

7. The application of the metal cluster in-situ implanted mesoporous silica catalyst material according to claim 6 in the propane dehydrogenation to propylene.

8. The application of the metal cluster in-situ implanted mesoporous silica catalyst material according to claim 7 in the propane dehydrogenation to propylene production, characterized in that, 0.3 g of the composite catalyst was diluted with 0.5 g of 40-60 mesh quartz sand and then loaded into a fixed-bed reactor. Under argon atmosphere protection, the temperature was raised to the reaction temperature of 550°C in 1 h. The gaseous reactants were introduced, and the ratio of propane to argon was 10:50 ml / min.

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