Porous silicon dioxide, preparation method thereof and hydrogenation catalyst
By preparing a porous silica support with a three-dimensional interconnected channel structure and loading it with cobalt and palladium, the problems of insufficient activity and poor selectivity of traditional hydrogenation catalysts were solved, and a highly efficient hydrogenation reaction was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional hydrogenation catalysts suffer from insufficient activity, poor selectivity, and high cost, especially single palladium-based catalysts. Furthermore, the acidic sites on the alumina support lead to an increase in side reactions, affecting catalytic activity and selectivity.
Porous silica was used as a carrier to prepare a three-dimensional interconnected porous silica structure by controlling the ratio of silicon source, surfactant and concentrated hydrochloric acid. Cobalt and palladium were loaded onto it, and the uniform distribution of cobalt and palladium was achieved by vacuum discharge plasma reduction technology to form a highly efficient hydrogenation catalyst.
It significantly improved the catalytic activity and selectivity of the hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine, with a conversion rate higher than 90.46% and a selectivity higher than 91.85%.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a porous silica, its preparation method, and a hydrogenation catalyst. Background Technology
[0002] Hindered amine light stabilizers are additives used to delay or inhibit the aging of polymeric materials such as rubber, plastics, and films. They play an antioxidant role by interrupting the free radical chain growth reaction of polymeric materials during the aging process. They are obtained by a batch hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine, in which the hydrogenation catalyst plays a key role in the hydrogenation reaction.
[0003] Traditional hydrogenation catalysts include monometallic and bimetallic types. While single cobalt-based catalysts exhibit high activity, they suffer from poor selectivity and are susceptible to poisoning and deactivation. Single palladium-based catalysts offer excellent selectivity but suffer from insufficient hydrogenation activity and high cost. The cobalt-palladium bimetallic combination achieves synergistic optimization of activity, selectivity, and resistance to poisoning, making it one of the optimal catalytic systems for the hydrogenation reaction of this intermediate.
[0004] The structural characteristics of the support used in cobalt-palladium bimetallic catalysts directly regulate the dispersion state, electronic configuration, and active site characteristics of the cobalt-palladium bimetallic particles, thereby affecting the catalytic activity and selectivity of the hydrogenation reaction. Alumina supports are typically porous structures with a certain degree of crystal order (such as the defective spinel structure of γ-Al₂O₃), and their surfaces contain tunable Levi- and Beta-acid sites, which can enhance interfacial interactions and promote Pd oxidation. + While active species are generated, excessive acidic sites can trigger side reactions such as over-hydrogenation of intermediates and carbon deposition, thereby reducing catalytic activity and selectivity. Traditional silica supports are mostly amorphous porous structures with a limited number of surface hydroxyl groups, which makes it difficult for metal precursors to be uniformly adsorbed and prone to aggregation, thus reducing catalytic activity. Summary of the Invention
[0005] The purpose of this invention is to provide porous silica, its preparation method, and a hydrogenation catalyst. The hydrogenation catalyst using porous silica as a support provided by this invention exhibits high catalytic activity and selectivity.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a porous silica having a three-dimensional interconnected pore structure, and the specific surface area of the porous silica is 135.2~143.8 m². 2 / g, the porous silica has a pore volume of 0.35~0.59cm³. 3 / g.
[0007] The present invention also provides a method for preparing the porous silica described in the above technical solution, comprising: A silicon source, surfactant, concentrated hydrochloric acid and water are mixed and then crystallized to obtain a silicon dioxide precursor. The silica precursor is calcined to obtain porous silica.
[0008] Preferably, the molar ratio of the silicon source, surfactant, and hydrogen chloride in concentrated hydrochloric acid is (0.08~0.25):(0.02~0.03):(0.55~0.65).
[0009] Preferably, the crystallization temperature is 90~100℃ and the crystallization time is 12~20h.
[0010] Preferably, the roasting temperature is 500~600℃ and the roasting time is 4~6h.
[0011] The present invention also provides a hydrogenation catalyst, comprising a silica support and cobalt and palladium supported on the silica support; wherein the silica support is the porous silica described in the above technical solution or porous silica prepared according to the preparation method described in the above technical solution.
[0012] Preferably, the cobalt and palladium are distributed on the surface and in the pores of the porous silica.
[0013] Preferably, the hydrogenation catalyst contains 2.0% to 30.0% cobalt by mass and 1.0% to 4.0% palladium by mass.
[0014] The present invention also provides a method for preparing the hydrogenation catalyst described in the above technical solution, comprising: A precursor was obtained by loading a mixture of porous silica, a water-soluble palladium source, a water-soluble cobalt source, and water. The precursor was subjected to vacuum discharge plasma reduction to obtain a hydrogenation catalyst.
[0015] The present invention also provides the application of the hydrogenation catalyst described in the above technical solution or the hydrogenation catalyst prepared according to the preparation method described in the above technical solution in the preparation of hindered amine light stabilizers by hydrogenation of 2,2,6,6-tetramethylpiperidine hexamethylenediamine.
[0016] This invention provides a porous silica having a three-dimensional interconnected pore structure, and the specific surface area of the porous silica is 135.2~143.8 m². 2 / g, the porous silica has a pore volume of 0.35~0.59cm³. 3 / g. In this invention, porous silica possesses a large specific surface area and pore volume, promoting the dispersion and loading of cobalt and palladium on the porous silica support. This provides more active sites for the hydrogenation catalytic reaction, significantly improving the catalytic activity and selectivity of the hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine. Furthermore, porous silica has a three-dimensional interconnected pore structure, and the hydrogenation catalyst obtained as a support also possesses a three-dimensional interconnected pore structure. When used for catalytic hydrogenation, it can prolong the contact time between the reactants and the catalyst, improve diffusion performance, and synergistically enhance catalytic activity. Experimental results show that the hydrogenation catalyst prepared using porous silica as a support provided in this invention achieves a conversion rate higher than 90.46% and a selectivity higher than 91.85% when used for the hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine. Attached Figure Description
[0017] Figure 1 This is a SEM image of the overall morphology of the hydrogenation catalyst prepared in Example 2 of this invention; Figure 2 This is a magnified SEM image of the hydrogenation catalyst prepared in Example 2 of this invention. Figure 3 This is a magnified EDS image of the hydrogenation catalyst prepared in Example 2 of this invention. Figure 4 This is a diagram showing the total elemental distribution of the hydrogenation catalyst prepared in Example 2 of the present invention; Figure 5 The XRD patterns are of the hydrogenation catalysts prepared in Examples 1-3 of this invention. Figure 6 The following are FT-IR images of the hydrogenation catalysts prepared in Examples 1-3 of this invention; Figure 7 The N2 adsorption-desorption isotherms of the hydrogenation catalysts prepared in Examples 1-3 of this invention; Figure 8 The figures show the catalytic performance of the hydrogenation catalysts prepared in Examples 1-3 and Comparative Examples 1-4 of this invention. Detailed Implementation
[0018] This invention provides a porous silica having a three-dimensional interconnected pore structure, and the specific surface area of the porous silica is 135.2~143.8 m². 2 / g, the porous silica has a pore volume of 0.35~0.59cm³. 3 / g.
[0019] The porous silica provided by this invention has a three-dimensional interconnected channel structure. In this invention, the porous silica has a uniform and ordered mesoporous channel structure, and the channels are interconnected and intersecting in multiple directions. This structure is beneficial for extending the contact time between reactants and catalyst, improving diffusion performance, achieving rapid diffusion (making it easier for reactants to reach active sites and for products to leave), and thus improving the catalytic performance of hydrogenation reactions.
[0020] In this invention, the porous silica is preferably shaped like a lotus root.
[0021] In this invention, the specific surface area of the porous silica is 135.2~143.8 m². 2 / g, preferably 138.5~141.5m 2 / g; the porous silica has a pore volume of 0.35~0.59cm³. 3 / g, preferably 0.48~0.53cm 3 / g. In this invention, the large specific surface area and pore volume of the porous silica promote the dispersion and loading of cobalt and palladium on the porous silica support, which can provide more active sites for the hydrogenation catalytic reaction and significantly improve the catalytic activity and selectivity of the hydrogenation reaction.
[0022] The porous silica in this invention has a three-dimensional interconnected pore structure and a large specific surface area and pore volume, which can prolong the residence time of reactants in the pores, improve diffusion performance, and promote the dispersion and loading of cobalt and palladium on the porous silica support. This provides more active sites for hydrogenation catalytic reactions and can significantly improve the catalytic activity and selectivity of hydrogenation catalysts using the porous silica provided by this invention as a support.
[0023] The present invention also provides a method for preparing the porous silica described in the above technical solution, comprising: A silicon source, surfactant, concentrated hydrochloric acid and water are mixed and then crystallized to obtain a silicon dioxide precursor. The silica precursor is calcined to obtain porous silica.
[0024] This invention involves mixing a silicon source, a surfactant, concentrated hydrochloric acid, and water, followed by crystallization to obtain a silicon dioxide precursor.
[0025] In this invention, the silicon source is preferably tetraethyl orthosilicate and / or silica sol, more preferably tetraethyl orthosilicate.
[0026] In this invention, the surfactant is preferably hexadecyltrimethylammonium bromide and / or polyethylene glycol, more preferably hexadecyltrimethylammonium bromide. The surfactant acts as a template agent, dispersant, and structure-directing agent, controlling the size and morphology of silica particles, preventing particle agglomeration, and improving dispersibility.
[0027] In this invention, the concentrated hydrochloric acid is preferably an aqueous solution with a mass fraction of 36% to 38%. In embodiments of this invention, the concentrated hydrochloric acid used is an aqueous solution with a mass fraction of 30% to 45%. The concentrated hydrochloric acid in this invention acts as a catalyst to accelerate the hydrolysis reaction of the silicon source and, by adjusting the pH of the system, makes the reaction more controllable, avoiding excessive local condensation that could lead to particle agglomeration.
[0028] In this invention, the preferred molar ratio of the silicon source, surfactant, and hydrogen chloride in concentrated hydrochloric acid is (0.08~0.25):(0.02~0.03):(0.55~0.65). As one embodiment of this invention, the molar ratio of the silicon source, surfactant, and hydrogen chloride in concentrated hydrochloric acid can be (0.08~0.15):(0.02~0.03):(0.55~0.60), or (0.15~0.25):(0.02~0.03):(0.60~0.65). By controlling the molar ratio of the silicon source, surfactant, and hydrogen chloride in concentrated hydrochloric acid within the above range, this invention facilitates the control of the silicon source hydrolysis condensation rate, micelle self-assembly behavior, and the final pore structure and morphology of silica, thereby obtaining porous silica with a specific structure.
[0029] In one embodiment of the present invention, the water may be distilled water.
[0030] In one embodiment of the present invention, the mass-to-volume ratio of the silicon source to water can be (5~15) g:(100~300) mL, or (10~15) g:(100~300) mL. In embodiments of the present invention, the mass-to-volume ratio of the silicon source to water can be 15 g:200 mL, 15 g:150 mL, or 15 g:100 mL. By controlling the ratio of silicon source to water within the above ranges, the present invention facilitates the acquisition of porous silica with a specific structure.
[0031] In one embodiment of the present invention, the mixing temperature of the silicon source, surfactant, concentrated hydrochloric acid, and water can be 30~50°C; in embodiments of the present invention, the mixing temperature can be 30°C, 40°C, or 50°C. In one embodiment of the present invention, the mixing time can be 4~5 hours; the mixing can be carried out under stirring conditions; the stirring speed can be 170~200 rpm / min; in embodiments of the present invention, the stirring speed can be 170 rpm / min, 180 rpm / min, or 200 rpm / min.
[0032] In this invention, the crystallization temperature is preferably 90~100℃, more preferably 95~100℃; the crystallization time is preferably 12~20h, more preferably 15~18h. As one embodiment of this invention, the crystallization can be carried out in a crystallization tank.
[0033] In this invention, when silicon source, surfactant, concentrated hydrochloric acid and water are mixed, silicon source hydrolysis and condensation occur, surfactant self-assembles into micelles, and silicon dioxide is deposited on the surface of micelles. Heating and crystallization form an ordered silicon dioxide structure.
[0034] In one embodiment of the present invention, after crystallization, the obtained product can be dried to obtain a silicon dioxide precursor. In one embodiment of the present invention, the drying temperature can be 90~110℃, and the drying time can be 1.5~2.5h. In an embodiment of the present invention, the drying temperature is 100℃, and the drying time is 2h. In one embodiment of the present invention, the drying can be carried out in an oven.
[0035] After obtaining the silicon dioxide precursor, the present invention calcines the silicon dioxide precursor to obtain porous silicon dioxide.
[0036] In this invention, the calcination temperature is preferably 500~600℃, more preferably 540~560℃; as one embodiment of this invention, the calcination temperature can be 540℃, 550℃, or 560℃. The calcination time is preferably 4~6h, more preferably 5~6h.
[0037] In one embodiment of the present invention, the heating rate of the calcination can be 2~8℃ / min; the cooling rate of the calcination can be 8~20℃ / min. The present invention removes the template formed by the surfactant through the above calcination conditions, and facilitates the obtaining of porous silica with high specific surface area and pore volume, and a uniformly ordered mesoporous three-dimensional interconnected pore structure.
[0038] The method for preparing porous silica of the present invention is advantageous for controlling the pore structure and morphology of silica, thereby obtaining porous silica with a three-dimensional interconnected pore structure and a large specific surface area and pore volume.
[0039] The present invention also provides a hydrogenation catalyst, comprising a silica support and cobalt and palladium supported on the silica support; wherein the silica support is the porous silica described in the above technical solution or porous silica prepared according to the preparation method described in the above technical solution.
[0040] The hydrogenation catalyst provided by this invention includes a silica support. In this invention, the silica support is the porous silica described in the above-described technical solution or the porous silica prepared according to the preparation method described in the above-described technical solution.
[0041] The hydrogenation catalyst provided by this invention comprises cobalt supported on the silica support. In this invention, the cobalt is preferably distributed on the surface and in the channels of the porous silica, more preferably uniformly distributed on the surface and in the channels of the porous silica. The mass content of cobalt in the hydrogenation catalyst is preferably 3.0% to 25.0%, more preferably 4.0% to 20.0%, and even more preferably 5.02% to 15.10%.
[0042] The hydrogenation catalyst provided by this invention comprises palladium supported on the silica support. In this invention, the palladium is preferably distributed uniformly on the surface and in the channels of the porous silica. The mass content of palladium in the hydrogenation catalyst is preferably 2.0% to 3.0%, more preferably 1.03% to 1.98%.
[0043] In this invention, the uniform distribution of cobalt and palladium is beneficial to improving catalytic activity and selectivity; the mass content of cobalt and palladium is controlled within the above-mentioned range, which is beneficial to achieving the synergistic effect between cobalt and palladium.
[0044] In this invention, the specific surface area of the hydrogenation catalyst is preferably 138.2~143.0 m². 2 / g, more preferably 139.4~142.1m 2 / g; the pore size of the hydrogenation catalyst is preferably 6.5~9.0 nm, more preferably 7.1~7.9 nm; the pore volume of the hydrogenation catalyst is preferably 0.45~0.55 cm³. 3 / g, more preferably 0.50~0.53cm 3 / g.
[0045] The hydrogenation catalyst of this invention enables the dispersion and loading of cobalt and palladium on the surface of a porous silica support, providing more active sites for the hydrogenation catalytic reaction. Furthermore, the special structure of the support can prolong the contact time between the reactants and the catalyst, improve diffusion performance, and give the hydrogenation catalyst high catalytic activity and selectivity.
[0046] The present invention also provides a method for preparing the hydrogenation catalyst described in the above technical solution, comprising: A precursor was obtained by loading a mixture of porous silica, a water-soluble palladium source, a water-soluble cobalt source, and water. The precursor was subjected to vacuum discharge plasma reduction to obtain a hydrogenation catalyst.
[0047] The present invention involves loading a mixture of porous silica, a water-soluble palladium source, a water-soluble cobalt source, and water to obtain a precursor.
[0048] In this invention, the water-soluble palladium source is preferably one or more of palladium chloride, palladium nitrate, and ammonium tetrachloropalladate, more preferably palladium chloride or ammonium tetrachloropalladate; in the embodiments of this invention, the water-soluble palladium source is palladium chloride.
[0049] In this invention, the water-soluble cobalt source is preferably one or more of cobalt nitrate, cobalt chloride, and cobalt sulfate, more preferably cobalt nitrate or cobalt chloride; in the embodiments of this invention, the water-soluble cobalt source is cobalt nitrate.
[0050] In this invention, the preferred molar ratio of the water-soluble palladium source to the water-soluble cobalt source is (0.01~0.02):(0.04~0.09). As one embodiment of this invention, the molar ratio of the water-soluble palladium source to the water-soluble cobalt source can be (0.01~0.02):(0.04~0.045), (0.01~0.02):(0.045~0.09), (0.01~0.015):(0.04~0.09), or (0.015~0.02):(0.04~0.09).
[0051] In this invention, the preferred mass ratio of porous silica to water-soluble palladium source is (31.8~45):(1.77~3.54). In embodiments of this invention, the mass ratio of porous silica to water-soluble palladium source is 33:1.77, 33:2.65, or 39:3.54.
[0052] In this invention, by adjusting the ratio of water-soluble palladium source, water-soluble cobalt source, and porous silica within the above-mentioned range, the mass content of cobalt and palladium in the hydrogenation catalyst can be controlled.
[0053] In one embodiment of the present invention, the water may be distilled water.
[0054] In this invention, the preferred mass-to-volume ratio of porous silica to water is (3~8) g:(100~150) mL. As one embodiment of this invention, the mass-to-volume ratio of porous silica to water can be (5~8) g:(100~150) mL, (5~8) g:(120~150) mL, or (3~5) g:(100~120) mL.
[0055] In this invention, the temperature at which the porous silica, palladium source, cobalt source, and water are mixed is preferably 20-30°C, more preferably 25-30°C. The loading process following the mixing of the silicon source, surfactant, concentrated hydrochloric acid, and water is preferably carried out under stirring conditions. The stirring speed is preferably 170-200 rpm / min, and the loading time is preferably 4-6 hours. By controlling the stirring speed within the above range, this invention facilitates the uniform diffusion and distribution of cobalt and palladium; by controlling the loading time within the above range, it achieves the adsorption of as much cobalt and palladium as possible and avoids agglomeration.
[0056] In one embodiment of the present invention, after the loading is completed, the product obtained from the loading is sequentially centrifuged and dried to obtain the precursor. In another embodiment, the centrifugation speed can be 7000-9000 rpm / min, and the centrifugation time can be 10-15 min; the centrifugation can be performed in a centrifuge. The drying can be performed under vacuum conditions; the drying temperature can be 80-100℃, and the drying time can be 8-12 h. In this invention, vacuum drying avoids the phenomenon of "capillary flow" that occurs during solvent evaporation in ordinary oven drying, which causes the metal precursor to flow and aggregate, allowing the metal precursor to remain more uniformly in situ, which is beneficial for achieving a uniform distribution of cobalt and palladium.
[0057] After obtaining the precursor, the present invention performs vacuum discharge plasma reduction on the precursor to obtain a hydrogenation catalyst.
[0058] In one embodiment of the present invention, the vacuum degree of the reduction can be 50-70 Pa or 55-65 Pa; the discharge power of the reduction can be 220-550 W or 350-400 W; the discharge time of the reduction can be 20-80 min or 30-40 min; and the atmosphere of the reduction can be argon or nitrogen. By using vacuum discharge plasma reduction and controlling the above conditions, the present invention can reduce cobalt and palladium precursors to cobalt and palladium, which is beneficial for achieving uniform distribution of cobalt and palladium on the support and enhancing the interaction between cobalt and palladium and the support.
[0059] The preparation method of the hydrogenation catalyst of the present invention helps to avoid the agglomeration of cobalt and palladium and achieves uniform distribution of cobalt and palladium on the surface and in the pores of the porous silica support.
[0060] The present invention also provides the application of the hydrogenation catalyst described in the above technical solution or the hydrogenation catalyst prepared by the preparation method described in the above technical solution in the hydrogenation of 2,2,6,6-tetramethylpiperidine hexamethylenediamine to prepare hindered amine light stabilizers.
[0061] This invention does not impose any special limitations on the application described herein; any application method known to those skilled in the art can be used.
[0062] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0063] Example 1 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 141.8 cm². 2 / g, pore volume 0.56cm 3 / g.
[0064] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 200mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.09:0.02:0.55, the silicon source is tetraethyl orthosilicate, the surfactant is hexadecyltrimethylammonium bromide, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 30℃ with a stirring speed of 170r / min for 4h. Then, the mixture is crystallized in a crystallization tank at 90℃ for 12h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 500℃ at a heating rate of 5℃ / min and calcined for 4h. Then, it is cooled to room temperature at a cooling rate of 10℃ / min to obtain porous silica.
[0065] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the cobalt loading in the hydrogenation catalyst is 15.10% and the palladium loading in the hydrogenation catalyst is 1.03%.
[0066] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 100mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.01:0.045, the mass ratio of porous silica to water-soluble palladium source is 33:1.77, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 4h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 10min to separate the precursor. The precursor was then vacuum dried at 80℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 60Pa, atmosphere argon, discharge power 250W, discharge time 30min) to obtain the hydrogenation catalyst.
[0067] Example 2 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 140.1 cm². 2 / g, pore volume 0.53cm 3 / g.
[0068] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 150mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.15:0.02:0.60, the silicon source is tetraethyl orthosilicate, the surfactant is hexadecyltrimethylammonium bromide, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 40℃ with a stirring speed of 200r / min for 5h. Then, the mixture is crystallized in a crystallization tank at 95℃ for 15h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 550℃ at a heating rate of 5℃ / min and held at that temperature for 5h for calcination. Then, it is cooled to room temperature at a cooling rate of 10℃ / min to obtain porous silica.
[0069] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the cobalt loading in the hydrogenation catalyst is 10.04% and the palladium loading in the hydrogenation catalyst is 1.51%.
[0070] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.015:0.045, the mass ratio of porous silica to water-soluble palladium source is 33:2.65, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor and vacuum dried at 80℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 60Pa, atmosphere argon, discharge power 350W, discharge time 40min) to obtain the hydrogenation catalyst.
[0071] Example 3 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 138.9 cm². 2 / g, pore volume 0.53cm 3 / g.
[0072] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 150mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.25:0.03:0.60, the silicon source is tetraethyl orthosilicate, the surfactant is hexadecyltrimethylammonium bromide, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 50℃ with a stirring speed of 200r / min for 5h. Then, the mixture is crystallized in a crystallization tank at 100℃ for 18h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 600℃ at a heating rate of 6℃ / min and calcined for 6h. Then, it is cooled to room temperature at a cooling rate of 20℃ / min to obtain porous silica.
[0073] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the loading of cobalt in the hydrogenation catalyst is 5.02% and the loading of palladium in the hydrogenation catalyst is 1.98%.
[0074] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.02:0.045, the mass ratio of porous silica to water-soluble palladium source is 39:3.54, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 6h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor and vacuum dried at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 70Pa, atmosphere argon, discharge power 500W, discharge time 30min) to obtain the hydrogenation catalyst.
[0075] Example 4 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 137.6 m². 2 / g, pore volume 0.48cm 3 / g.
[0076] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 200mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.08:0.02:0.55, the silicon source is silica sol, the surfactant is polyethylene glycol, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 40℃ with a stirring speed of 180r / min for 4h. Then, the mixture is crystallized in a crystallization tank at 90℃ for 12h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 500℃ at a heating rate of 5℃ / min and calcined for 5h. Then, it is cooled to room temperature at a cooling rate of 10℃ / min to obtain porous silica.
[0077] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the cobalt loading in the hydrogenation catalyst is 21.3% and the palladium loading in the hydrogenation catalyst is 1.2%.
[0078] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 150mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.01:0.04, the mass ratio of porous silica to water-soluble palladium source is 33:1.77, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 10min to separate the precursor and vacuum dried at 80℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 60Pa, atmosphere argon, discharge power 250W, discharge time 30min) to obtain the hydrogenation catalyst.
[0079] Example 5 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 139.1 m². 2 / g, pore volume 0.51cm 3 / g.
[0080] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 150mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.15:0.025:0.60, the silicon source is silica sol, the surfactant is polyethylene glycol, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 40℃ with a stirring speed of 200r / min for 4h. Then, the mixture is crystallized in a crystallization tank at 90℃ for 15h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 550℃ at a heating rate of 5℃ / min and held at that temperature for 5h for calcination. Then, it is cooled to room temperature at a cooling rate of 10℃ / min to obtain porous silica.
[0081] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the cobalt loading in the hydrogenation catalyst is 18.7% and the palladium loading in the hydrogenation catalyst is 2.4%.
[0082] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.015:0.045, the mass ratio of porous silica to water-soluble palladium source is 33:2.655, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor. The precursor was then vacuum dried at 80℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 60Pa, atmosphere argon, discharge power 350W, discharge time 40min) to obtain the hydrogenation catalyst.
[0083] Example 6 Porous silica: possesses a three-dimensional interconnected pore structure with a specific surface area of 135.8 m². 2 / g, pore volume is 0.43cm 3 / g.
[0084] Preparation method of porous silica: 15g of silicon source, surfactant, concentrated hydrochloric acid and 200mL of water (where the molar ratio of silicon source, surfactant and concentrated hydrochloric acid is 0.09:0.02:0.55, the silicon source is silica sol, the surfactant is polyethylene glycol, the mass fraction of concentrated hydrochloric acid is 38%, and the water is distilled water) are stirred and mixed at 50℃ with a stirring speed of 200r / min for 5h. Then, the mixture is crystallized in a crystallization tank at 95℃ for 18h and dried at 100℃ for 2h to obtain a silica precursor. The silica precursor is heated to 550℃ at a heating rate of 6℃ / min and calcined for 6h. Then, it is cooled to room temperature at a cooling rate of 10℃ / min to obtain porous silica.
[0085] Hydrogenation catalyst: composed of a silica support and cobalt and palladium supported on the silica support, wherein the loading of cobalt in the hydrogenation catalyst is 8.5% and the loading of palladium in the hydrogenation catalyst is 3.7%.
[0086] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.02:0.045, the mass ratio of porous silica to water-soluble palladium source is 39:3.54, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor and vacuum dried at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 70Pa, atmosphere argon, discharge power 450W, discharge time 30min) to obtain the hydrogenation catalyst.
[0087] Comparative Example 1 Porous silica: Porous silica prepared in Example 2.
[0088] Hydrogenation catalyst: composed of a silica support and cobalt supported on the silica support, wherein the cobalt loading in the hydrogenation catalyst is 9.7%.
[0089] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble cobalt source and 120mL of water (mass ratio of porous silica to water-soluble cobalt source is 33:8.23, water-soluble cobalt source is cobalt nitrate, water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. After separation, the mixture was centrifuged at 8000rpm / min for 15min and dried under vacuum at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree is 70Pa, atmosphere is argon, discharge power is 450W, discharge time is 30min) to obtain the hydrogenation catalyst.
[0090] Comparative Example 2 Porous silica: Porous silica prepared in Example 2.
[0091] Hydrogenation catalyst: composed of a silica support and palladium supported on the silica support, wherein the palladium loading in the hydrogenation catalyst is 1.89%.
[0092] Preparation method of hydrogenation catalyst: 5g of porous silica, water-soluble palladium source and 120mL of water (the mass ratio of porous silica to water-soluble cobalt source is 33:3.54, the water-soluble palladium source is palladium chloride, and the water is distilled water) were mixed at 25℃ and loaded for 6h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor. The precursor was then vacuum dried at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 70Pa, atmosphere argon, discharge power 450W, discharge time 30min) to obtain the hydrogenation catalyst.
[0093] Comparative Example 3 Hydrogenation catalyst: Mesoporous silica support (commercial SBA-15, purchased from Shanghai Latin Biochemical Technology Co., Ltd., specific surface area 600~800 m²) 2 The catalyst consists of cobalt and palladium supported on the mesoporous silica support (with a pore size of 6-11 nm and a pore size of 6-11 nm), with the cobalt loading in the hydrogenation catalyst being 10.1% and the palladium loading in the hydrogenation catalyst being 1.4%.
[0094] Preparation method of hydrogenation catalyst: 5g of mesoporous silica, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.015:0.045, the mass ratio of mesoporous silica to water-soluble palladium source is 39:2.65, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 5h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor. The precursor was then vacuum dried at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 70Pa, atmosphere argon, discharge power 450W, discharge time 30min) to obtain the hydrogenation catalyst.
[0095] Comparative Example 4 Hydrogenation catalyst: It consists of an alumina support (commercial neutral spherical alumina powder, purchased from Sinopharm Chemical Reagent Co., Ltd., with a particle size of 200~400nm) and cobalt and palladium supported on the alumina support. The loading of cobalt in the hydrogenation catalyst is 9.8%, and the loading of palladium in the hydrogenation catalyst is 1.5%.
[0096] Preparation method of hydrogenation catalyst: 5g of alumina, water-soluble palladium source, water-soluble cobalt source and 120mL of water (the molar ratio of water-soluble palladium source to water-soluble cobalt source is 0.015:0.045, the mass ratio of porous silica to water-soluble palladium source is 39:2.65, the water-soluble palladium source is palladium chloride, the water-soluble cobalt source is cobalt nitrate, and the water is distilled water) were mixed at 25℃ and loaded for 6h under stirring at 180r / min. The mixture was then centrifuged at 8000rpm / min for 15min to separate the precursor and vacuum dried at 100℃ for 10h to obtain the precursor. The precursor was then subjected to vacuum discharge plasma reduction (vacuum degree 70Pa, atmosphere argon, discharge power 450W, discharge time 30min) to obtain the hydrogenation catalyst.
[0097] The specific surface area, average pore size, and pore volume of the silica supports and hydrogenation catalysts prepared in Examples 1-3 were determined using a TriStar II 3020 3.02 nitrogen adsorber. The specific surface area of the hydrogenation catalysts prepared in Examples 1-3 was calculated based on the adsorption-desorption isotherms using the Brunauer-Emmett-Teller (BET) method. The silica supports and hydrogenation catalysts prepared in Examples 1-3 were characterized by ICP to obtain the mass fraction of cobalt and palladium (i.e., loading) in the hydrogenation catalysts.
[0098] Table 1. Results of the determination of specific surface area, average pore size and pore volume, and mass fraction of cobalt and palladium for silica support and its hydrogenation catalyst.
[0099] As can be seen from the table above, the hydrogenation catalyst prepared by this invention has an average pore size of 7.1~7.9 nm, all belonging to mesoporous structures; and a specific surface area of 139.4~142.1 m². 2 / g, with a relatively large specific surface area; pore volume of 0.50~0.53m³. 3 / g. As can be seen from the ICP characterization results in the table above, the Pd / Co mass ratio in the hydrogenation catalyst can be controlled using the preparation method of this invention.
[0100] The hydrogenation catalyst prepared in Example 2 was analyzed by SEM, and the SEM image of the overall morphology of the hydrogenation catalyst is shown below. Figure 1 As shown, Figure 1 A magnified view of the part is as follows Figure 2 As shown.
[0101] Depend on Figure 1 and Figure 2 It can be seen that the present invention has prepared a hydrogenation catalyst with a lotus root-like three-dimensional interconnected cross-channel structure.
[0102] Select Figure 2 EDS analysis was performed on the area within the middle frame, resulting in a magnified EDS image of the hydrogenation catalyst, as shown below. Figure 3 As shown, the distribution chart of the total number of elements is as follows: Figure 4 As shown.
[0103] Depend on Figure 3 It can be seen that Si, O, Co, and Pd elements are uniformly distributed in the catalyst. The simultaneous and uniform presence of Co and Pd metals leads to coordination and stress effects between them, which can effectively improve the catalytic hydrogenation performance of the catalyst. Figure 4 The percentage content of each element in the hydrogenation catalyst prepared by this invention can be clearly determined.
[0104] XRD analysis was performed on the hydrogenation catalysts prepared in Examples 1-3, and the XRD patterns of the obtained hydrogenation catalysts are shown below. Figure 5 As shown.
[0105] Comparison with the standard cards shows that the diffraction peaks at 40.3° and 46.7° in the XRD patterns of the catalysts prepared in Examples 1-3 belong to the (111) and (200) crystal planes of Pd (JCPDS NO. 46-1043); the diffraction peaks at 44.5° and 51.5° correspond to the reflections from the (110) and (200) planes of Co (JCPDS NO. 15-0806), respectively. Figure 5 It can be seen that the diffraction peaks of cobalt and palladium in the XRD patterns of the hydrogenation catalysts prepared in Examples 1-3 are relatively weak, indicating that the cobalt and palladium prepared in this invention do not aggregate on the surface of the porous silica support and have good dispersion. The high dispersion is one of the reasons for the high activity of the catalyst.
[0106] The hydrogenation catalysts prepared in Examples 1-3 were characterized by FT-IR, and the FT-IR spectra of the hydrogenation catalysts are shown below. Figure 6 As shown.
[0107] Figure 6 All hydrogenation catalysts exhibit Si-O-Si bond bending vibrations and symmetric and asymmetric stretching vibration peaks, with a peak at 1485 cm⁻¹. -1 The absorption peak corresponds to the vibration of Si-OH on the surface of the porous silica support. After modification, Si-OH can act as a support to stabilize the metal. The absorption peak intensity of Si-OH on the hydrogenation catalysts prepared in Examples 1 to 3 is slightly reduced. This may be because Pd and Co coordinate with O to form Si-O-Pd and Si-O-Co structures, respectively. These functional groups can improve the reaction kinetics in the hydrogenation reaction.
[0108] The hydrogenation catalysts prepared in Examples 1-3 of this invention were subjected to nitrogen adsorption-desorption tests, and the obtained N2 adsorption-desorption isotherms are as follows: Figure 7 As shown.
[0109] Depend on Figure 7 It can be seen that the N2 adsorption and desorption curves of the three hydrogenation catalysts are quite similar. When the relative pressure is around 0.5~1.0 (P / P0), the isotherm shows a hysteresis phenomenon. In particular, the curves of Example 2 and Example 3 have obvious H2-type hysteresis loops, indicating that the hydrogenation catalysts prepared in Examples 1~3 have a uniform and ordered mesoporous structure. This structure can effectively improve the mass and heat transfer rate during the hydrogenation catalytic reaction.
[0110] The reaction equation for the hydrogenation of 2,2,6,6-tetramethylpiperidine hexamethylenediamine to prepare hindered amine light stabilizers is as follows: The specific operating procedure is as follows: 40g of 2,2,6,6-tetramethylpiperidine hexamethylenediamine and 2g of hydrogenation catalyst are simultaneously placed in a hydrogenation reactor. The reactor is then purged with nitrogen and hydrogen three times each. The temperature inside the reactor is increased at a rate of 3℃ / min until it reaches 75℃. The hydrogen valve is then opened to introduce hydrogen into the reactor and maintain the pressure at 2.5MPa. The temperature inside the reactor is controlled at 120℃ using an electric heating system. After the hydrogenation reaction has been going on for 8 hours, the temperature inside the hydrogenation reactor is reduced to room temperature at a rate of 10℃ / min. The reaction solution is then passed through a precision filter to separate the hydrogenation catalyst and the hydrogenation reaction solution. The filtered hydrogenation reaction solution is then transferred to a distillation vessel for distillation purification to obtain the hindered amine light stabilizer.
[0111] The hydrogenation catalytic conversion and selectivity of the hydrogenation catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were calculated. The catalytic performance of the hydrogenation catalysts prepared in Examples 1-3 and Comparative Examples 1-4 was calculated using the formulas: Conversion CA% = (Amount of reactant consumed / Total initial amount of reactant) × 100% and Selectivity S% = (Yield of target product / Conversion) × 100%. Figure 8 As shown.
[0112] Depend on Figure 8It can be seen that the hydrogenation catalysts prepared in Examples 1-3 exhibit significantly better conversion and selectivity for 2,2,6,6-tetramethylpiperidine hexamethylenediamine than the hydrogenation catalysts prepared in Comparative Examples 1-4. The superior performance of the bimetallic hydrogenation catalysts prepared in Examples 1-3 compared to the monometallic hydrogenation catalysts prepared in Comparative Examples 1-2 is mainly due to the fact that when Co containing d-band holes and Pd without d-band holes hybridize, each atom in the 4d orbital of Pd provides 0.36 holes to accept d electrons from Co. The electron transfer between Co and Pd produces a significant ligand effect, causing a shift in the d-band centers of Pd and Co, thereby significantly improving the conversion and selectivity of 2,2,6,6-tetramethylpiperidine hexamethylenediamine. The catalytic performance of the hydrogenation catalysts prepared in Examples 1-3 is clearly related to the Co / Pd ratio. With the increase of Pd content, the catalytic activity of 2,2,6,6-tetramethylpiperidine hexamethylenediamine increases significantly. The conversion rate of Example 1 is only 90.46%, and the selectivity is 91.85%. After increasing the mass fraction of Pd to 1.51, the conversion rate of Example 2 is 99.36%, and the selectivity is 95.62%. With further increasing the amount of Pd, the conversion rate of the sample in Example 3 decreases, and the selectivity also shows a decreasing trend. Comparative Examples 3 and 4 were prepared using different supports for hydrogenation catalysts. The hydrogenation catalyst prepared in Example 2 showed significantly higher conversion and selectivity than that in Comparative Examples 3 and 4. This indicates that the three-dimensional interconnected cross-channel structure formed by the porous silica support used in the hydrogenation catalyst prepared by this invention can prolong the residence time of reactants in the channels, improve diffusion, and enhance hydrogenation catalytic performance. At the same time, the large specific surface area and pore volume of this structure promote the dispersion of cobalt and palladium on the porous silica support, providing more active sites for the hydrogenation catalytic reaction, which can significantly improve the catalytic activity and selectivity of the hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine.
[0113] As can be seen from the above embodiments, the hydrogenation catalyst prepared using the porous silica provided by the present invention as a support has a three-dimensional interconnected pore structure; cobalt and palladium do not aggregate and have good dispersion, and are uniformly distributed on the surface and in the pores of the porous silica support; the average pore size belongs to the mesoporous structure, and the specific surface area and pore volume are relatively large; it can significantly improve the catalytic activity and selectivity of the hydrogenation reaction of 2,2,6,6-tetramethylpiperidine hexamethylenediamine.
[0114] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A porous silica, characterized in that, The porous silica has a three-dimensional interconnected pore structure, and its specific surface area is 135.2~143.8 m². 2 / g, the porous silica has a pore volume of 0.35~0.59cm³. 3 / g.
2. The method for preparing porous silica according to claim 1, characterized in that, include: A silicon source, surfactant, concentrated hydrochloric acid and water are mixed and then crystallized to obtain a silicon dioxide precursor. The silica precursor is calcined to obtain porous silica.
3. The preparation method according to claim 2, characterized in that, The molar ratio of the silicon source, surfactant, and hydrogen chloride in concentrated hydrochloric acid is (0.08~0.25):(0.02~0.03):(0.55~0.65).
4. The preparation method according to claim 2, characterized in that, The crystallization temperature is 90~100℃, and the crystallization time is 12~20h.
5. The preparation method according to claim 2, characterized in that, The roasting temperature is 500~600℃, and the roasting time is 4~6h.
6. A hydrogenation catalyst, characterized in that, It includes a silica support and cobalt and palladium loaded on the silica support; the silica support is the porous silica as described in claim 1 or the porous silica prepared according to any one of claims 2 to 5.
7. The hydrogenation catalyst according to claim 6, characterized in that, The cobalt and palladium are distributed on the surface and in the pores of the porous silica.
8. The hydrogenation catalyst according to claim 6 or 7, characterized in that, The hydrogenation catalyst contains 2.0% to 30.0% cobalt by mass and 1.0% to 4.0% palladium by mass.
9. The method for preparing the hydrogenation catalyst according to any one of claims 6 to 8, characterized in that, include: A precursor was obtained by loading a mixture of porous silica, a water-soluble palladium source, a water-soluble cobalt source, and water. The precursor was subjected to vacuum discharge plasma reduction to obtain a hydrogenation catalyst.
10. The application of the hydrogenation catalyst according to any one of claims 6 to 8 or the hydrogenation catalyst prepared by the preparation method according to claim 9 in the hydrogenation of 2,2,6,6-tetramethylpiperidine hexamethylenediamine to prepare hindered amine light stabilizers.