Carbon nitride modified halloysite supported nanometal composite catalyst, and preparation method and use thereof

Abstract

The application discloses a carbon nitride modified halloysite supported nanometal composite catalyst and a preparation method and application thereof, and relates to the technical field of nanometer catalyst preparation. The catalyst is prepared by the following steps: etching modification of halloysite nanotubes by means of a eutectic solvent, then forming a graphite phase carbon nitride nanometer thin layer on the surface of the modified halloysite by means of a gas phase deposition-pyrolysis method to obtain a carbon nitride modified halloysite composite; then, depositing Co2(OH)2CO3 precursors on the surface of the carbon nitride modified halloysite by means of a sol-gel method, supporting stannous ions by means of the electrostatic adsorption effect of the hydroxyl groups of the Co2(OH)2CO3 precursors, reducing Pt metal ion precursors into Pt nanoparticles by means of the strong reducing property of the stannous ions and realizing a good anchoring effect, and finally forming a stable CoO / Co-Pt / SnO2 composite by means of inert atmosphere calcination, so as to obtain the catalyst. The catalyst has high catalytic activity, selectivity and stability in a selective catalytic hydrogenation reaction, and thus has a good application prospect in the field of nanometer catalysis.

Description

Technical Field

[0001] This invention relates to the field of nanocatalyst preparation technology, specifically to a carbon nitride-modified halloysite-supported nano-metal composite catalyst, its preparation method, and its applications. Background Technology

[0002] Research on the catalytic application of nano-Pt has always been a hot topic in the field of catalysis. The catalytic performance of Pt nanoparticles is greatly enhanced as their distribution size in catalysts decreases. However, the resulting high surface energy makes Pt nanoparticles prone to sintering and agglomeration during actual preparation or application, which is detrimental to maintaining their original catalytic activity and thus affects their catalytic performance. Moreover, in actual loading processes, due to the lack of an effective anchoring mechanism, the distribution position of Pt nanoparticles on the support surface is not fixed, and the interaction force between them and the support is weak, resulting in low Pt particle dispersion and easy accumulation and agglomeration, which limits the further improvement of the catalytic performance of nano-Pt catalysts. Therefore, exploring methods for anchoring and highly dispersing the spatial distribution of Pt nanoparticles in the support structure from the material preparation level, using chemical additives or surface chemical effects, to enhance their stability and thus improve the catalytic performance of nano-Pt catalysts in complex micro-reaction environments, is a key technical problem that urgently needs to be solved. By designing porous supports with specific structures and chemical properties to encapsulate and immobilize Pt nanoparticles, the special support effect can be used to improve their dispersibility and stability, thereby enabling them to obtain higher reactivity and selectivity.

[0003] In recent years, graphitic carbon nitride (g-C3N4) has been widely used in catalytic fields such as photocatalytic water splitting for hydrogen production, CO2 reduction, pollutant treatment, and organic synthesis due to its stable physicochemical properties, suitable band gap, low cost and availability, good mechanical properties, and environmental friendliness. It is a promising non-metallic semiconductor material. However, bulk g-C3N4 materials prepared by traditional methods suffer from drawbacks such as small specific surface area, severely embedded active sites that are not dispersed and effectively exposed, and low electron separation yield. These drawbacks lead to unsatisfactory catalytic activity in pure g-C3N4 catalysts, greatly limiting their practical applications. Therefore, researchers have improved the chemical properties of g-C3N4 materials and thus enhanced their catalytic activity through doping and compositing with nano-metals and metal oxides. Furthermore, using a large specific surface area support structure to disperse and load g-C3N4 materials, constructing a nanoscale g-C3N4 shell structure, is considered an effective way to improve the catalytic performance and utilization efficiency of g-C3N4 materials.

[0004] HNTs (Al2Si2O5(OH)4·nH2O) is a kind of natural clay nanomaterial, which presents a long-diameter ratio hollow one-dimensional tubular structure characteristics of the outer layer of silicon oxygen tetrahedral and the inner layer of aluminum oxygen octahedral cross-linking each other. It has the characteristics of wide raw material sources, high stability, controllable surface modification, good reusability, excellent adsorption performance and so on. The surface of HNTs has abundant hydroxyl groups, which is easy to be functionalized and modified. The unique double electric property of the inner and outer surface makes it an excellent carrier for constructing high-performance composite materials with specific functional properties by combining with other nanomaterials, thereby expanding the application range of HNTs. In addition, the surface interface electrostatic adsorption effect of HNTs nanotubes has a strong confined adsorption effect on the loaded nanomaterial precursors, which helps to reduce the size of the nanomaterials, so as to realize the construction of nanoscale functional materials with good dispersion and excellent performance on the surface of HNTs. Therefore, as a carrier for surface modification and loading of nanoscale g-C3N4 materials, HNTs can not only improve the specific surface area and utilization efficiency of g-C3N4 materials, fully disperse and expose the active sites, but also provide an important carrier support for the doping and compounding of nanoscale g-C3N4 materials with metal and metal oxide nanoparticles to construct high-performance g-C3N4-based composite materials, ultimately greatly improving the overall catalytic performance of the composite catalyst.

[0005] Chinese patent CN115931991A discloses a preparation method of a nano gold particle / reduced graphene oxide / graphitic carbon nitride composite material. First, a reduced graphene oxide / graphitic carbon nitride composite is prepared by ultrasonic exfoliation and hydrothermal reaction. Then, Au nanoparticles are dispersed in-situ on the surface and pores of the composite to obtain the material. Chinese patent CN110102326B reports a preparation method of a nano gold loaded porous carbon modified carbon nitride composite photocatalyst. First, yeast bacteria recovering Au ions are calcined in N2 atmosphere to obtain nano gold loaded porous carbon. Then, the catalyst is obtained by doping the carbon nitride through high-temperature co-deposition. However, the composite materials reported in the above two patents have the defects of large Au particle size, uneven distribution, and accumulation and agglomeration of graphitic carbon nitride. Chinese patent CN105344321B discloses a preparation method of a Fe3O4 / halloysite / graphene composite material. The method is to mix halloysite, graphene oxide and Fe metal precursor solution, adjust the alkaline pH with ammonia, and calcine the precursor mixture in N2 atmosphere to obtain the ternary composite material. However, the halloysite and graphene are severely aggregated, the Fe3O4 particle size distribution is uneven and difficult to control. Chinese patent CN112007637B discloses a preparation method of a Au-Pt / halloysite composite catalyst. The catalyst is obtained by adsorbing Au and Pt precursors on amino organosilane modified halloysite and reducing in-situ with sodium borohydride to obtain loaded Au-Pt nanoparticles. Chinese patent CN101879460B discloses a preparation method of a halloysite supported Pt catalyst. First, the halloysite is pretreated with hydrogen peroxide, calcined and ground to obtain purified halloysite. Then, the halloysite is immersed in a Pt metal salt organic solution and reduced with sodium bicarbonate to obtain the catalyst. However, the composite materials reported in the above two patents have the defects of difficult control of metal nanoparticle morphology and size, easy aggregation, deformation and leaching. SUMMARY

[0006] The present application provides a carbon nitride modified halloysite supported nano metal composite catalyst, a preparation method thereof and an application thereof, aiming to solve the problems in the above background art.

[0007] In order to achieve the above technical purposes, the present application mainly adopts the following technical solutions:

[0008] In a first aspect, the present application provides a carbon nitride modified halloysite supported nano metal composite catalyst, comprising:

[0009] Modified halloysite: the modified halloysite is obtained by etching modification of halloysite nanotubes with a eutectic solvent;

[0010] g-C3N4: The g-C3N4 is constructed on the surface of the modified halloysite by a vapor deposition-pyrolysis method to form a nano-thin layer of graphite phase g-C3N4, thereby obtaining a g-C3N4 modified halloysite composite structure; and

[0011] CoO / Co-Pt / SnO2 composite: The CoO / Co-Pt / SnO2 composite is anchored in the g-C3N4 modified halloysite composite structure.

[0012] In some embodiments, the deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor is selected from any one of hydrofluoric acid, triflic acid, trifluoroacetic acid, hexafluorosilicic acid and hexafluorophosphoric acid; and the hydrogen bond acceptor is selected from any one of choline chloride, choline bromide, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride and tetrabutylammonium chloride.

[0013] Further, the g-C3N4 is constructed on the surface of the modified halloysite by a vapor deposition-pyrolysis method using melamine and glucosamine hydrochloride as precursors to form a nano-thin layer of graphite phase g-C3N4; and the CoO / Co-Pt / SnO2 composite is obtained by depositing a Co2(OH)2CO3 precursor on the surface of the g-C3N4 modified halloysite, anchoring stannous ions through electrostatic adsorption of hydroxyl groups, reducing Pt metal ion precursors to Pt nanoparticles using the strong reducing property of the stannous ions, and forming a stable CoO / Co-Pt / SnO2 composite through calcination in an inert atmosphere.

[0014] The outer surface of the modified halloysite after treatment with the deep eutectic solvent is rich in hydroxyl groups and has significant negative charge, which has good electrostatic adsorption effect on the g-C3N4 precursor, and the graphite phase g-C3N4 is stably loaded through in-situ surface grafting method to obtain a graphite phase g-C3N4 modified halloysite composite.

[0015] Glucosamine hydrochloride is a natural marine biological agent with good water solubility extracted from chitin raw materials such as crab shells and shrimp shells, and is widely used in medicine, health products, food, cosmetics and feed additives. Glucosamine hydrochloride has abundant hydroxyl groups and amino groups, which can self-assemble with melamine to form hydrogen bonds and high-temperature triggered supramolecular copolymerization, introduce additional C atoms for g-C3N4 material, provide abundant π electrons, form an enhanced π-electron conjugated system, and help promote the electrostatic adsorption of the derived graphite phase g-C3N4 nano-thin layer to the Co2(OH)2CO3 precursor. The deposition of the Co2(OH)2CO3 precursor provides convenient conditions for the subsequent immobilization of Pt nanoparticles.

[0016] Further, the mass percentage of the carbon nitride is 15-40% of the total mass of the catalyst; the mass percentage of the CoO / Co-Pt / SnO2 composite is 1-20% of the total mass of the catalyst; and the mass percentage of Pt nanoparticles in the CoO / Co-Pt / SnO2 composite is 0.1-8% of the total mass of the catalyst.

[0017] In a second aspect, the application provides a preparation method of the carbon nitride modified halloysite supported nanometal composite catalyst according to the first aspect, comprising the following steps:

[0018] Step a): halloysite nanotubes are weighed and dispersed in a eutectic solvent, mixed and stirred for 1-6 h, the solid is recovered by centrifugation, washed with deionized water and anhydrous ethanol until the pH is 5-7, and dried at 40-60°C for 8-12 h to obtain modified halloysite MHNTs material;

[0019] Step b): the MHNTs material, melamine and amino glucose hydrochloride are added to a mixed solution of anhydrous ethanol and deionized water in a set mass ratio, ultrasonically mixed for 2-8 h, heated at 60-95°C until the solution is completely evaporated, the obtained solid is ground and transferred to a tube furnace, calcined at 500-900°C under an inert atmosphere for 1-5 h to obtain a carbon nitride modified halloysite MHNTs / g-C3N4 composite material;

[0020] Step c): the MHNTs / g-C3N4 composite material, a cobalt salt and urea are dispersed in deionized water, heated and refluxed at 60-100°C for 2-6 h under stirring, cooled to room temperature, and subjected to centrifugation, washing and drying to obtain a MHNTs / g-C3N4@Co2(OH)2CO3 composite material;

[0021] Step d): the MHNTs / C3N4@Co2(OH)2CO3 composite material is dispersed in deionized water, stannous salt and an acidic solution are added, mixed and reacted for 7-20 h, centrifuged, washed, redispersed in deionized water, and then a Pt metal anion precursor is added, mixed and reacted for 0.5-3 h, sodium formate is added, mixed and reacted for 8-18 h, and then subjected to centrifugation, washing and drying, and calcined at 500-800°C under an inert atmosphere for 1-3 h to obtain a carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2).

[0022] In a preferred embodiment of the application, in step a), the mass ratio of the halloysite nanotubes to the eutectic solvent is 1:15-60, and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:0.2-1.

[0023] In the preferred embodiment of the present application, in step b), the mass ratio of the MHNTs material, melamine and glucosamine hydrochloride is 1:0.5-2:0.001-0.02; the mass ratio of the anhydrous ethanol and deionized water is 1:0.5-2; and the inert atmosphere is any one of high-purity nitrogen, high-purity helium and high-purity argon.

[0024] In the preferred embodiment of the present application, in step c), the mass ratio of the MHNTs / g-C3N4 composite material, the cobalt salt and urea is 1:1-8:0.5-4; wherein the cobalt salt is any one of cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate.

[0025] In the preferred embodiment of the present application, in step d), the mass ratio of the MHNTs / g-C3N4@Co2(OH)2CO3 composite material, the stannous salt, the acidic solution, the Pt metal anion precursor and sodium formate is 1:0.5-2:2-10:0.001-0.1:0.1-0.8; wherein the stannous salt is any one of stannous sulfate, stannous chloride and stannous acetate; the acidic solution is any one of hydrochloric acid, sulfuric acid and nitric acid; the Pt metal anion precursor is any one of chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, sodium chloroplatous acid, potassium chloroplatous acid and ammonium chloroplatous acid; and the inert atmosphere is any one of high-purity nitrogen, high-purity helium and high-purity argon.

[0026] In a third aspect, the present application also discloses a use of the carbon nitride modified halloysite supported nanometal composite catalyst according to the first aspect or prepared by the method according to the second aspect in a selective catalytic hydrogenation reaction.

[0027] Specifically, the catalyst selectively catalyzes the hydrogenation of cinnamyl aldehyde to prepare cinnamyl alcohol and selectively catalyzes nitrobenzene to prepare amino benzene.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The catalyst provided by the present application has good catalytic activity, selectivity and stability, and shows good application prospects in the field of nanocatalysis, especially in the field of selective catalytic hydrogenation, mainly in the following aspects:

[0030] (1) The halloysite nanotubes are modified by low eutectic solvent etching to remove interface impurities, increase specific surface area, and enrich pore structure. The outer surface of the halloysite nanotubes is rich in hydroxyl groups, and has more Si-OH contact sites, which improves the interface zero potential and micro-reaction environment of the carrier, so that the surface of the halloysite nanotubes has significant electronegativity, which promotes the electrostatic adsorption of the carbon nitride precursor. The graphite phase carbon nitride nanosheet is stably loaded by a surface in-situ grafting method through chemical bonding, to form a core-shell composite carrier, so that the catalyst obtains an optimal carrier effect.

[0031] (2) The glucosamine hydrochloride, as a natural marine biological agent, has rich hydroxyl groups and amino groups, forms hydrogen bonds with melamine, and triggers supramolecular copolymerization at high temperature. The glucosamine hydrochloride introduces additional C atoms into the carbon nitride material, provides rich pi electrons, forms an enhanced pi-electron conjugated system, and promotes the electrostatic adsorption of the graphite phase carbon nitride nanosheet to the Co2(OH)2CO3 precursor.

[0032] (3) The stannous ion is combined with the hydroxyl groups in the Co2(OH)2CO3 precursor through electrostatic adsorption, and has a strong reduction effect. The stannous ion can reduce the Pt metal ion precursor in-situ into Pt nanoparticles to form a Pt / SnO2 composite and construct the Pt / SnO2 composite in the Co2(OH)2CO3 structure. After calcination in an inert atmosphere, a stable CoO / Co-Pt / SnO2 composite is formed, so that the Pt nanoparticles are effectively anchored in the distribution position of the overall structure of the catalyst and effectively combined with the active metal oxide. The catalytic active site is further solidified and reconstructed, and finally the overall catalytic reaction performance of the catalyst is improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 FIG. 4 is a TEM image of the MHNTs / g-C3N4@CoO / Co-Pt / SnO2 composite material prepared in Example 1.

[0034] Figure 2 FIG. 5 is a SEM image of the MHNTs / g-C3N4@CoO / Co-Pt / SnO2 composite material prepared in Example 1. DETAILED DESCRIPTION

[0035] The present application is further illustrated below in conjunction with specific examples, which should be understood as merely illustrating the present application but not limiting the scope of the present application. After reading the present application, those skilled in the art can make various modifications to the equivalent forms of the present application, which fall within the scope defined by the claims attached hereto.

[0036] The application provides a carbon nitride modified halloysite supported nanometal composite catalyst, a preparation method and use thereof. The catalyst is prepared by the following steps: etching and modifying halloysite by using a eutectic solvent, coating a graphite phase carbon nitride nanometer thin layer on the surface of the modified halloysite by using melamine and glucosamine hydrochloride as precursors through a gas deposition-pyrolysis method to obtain a carbon nitride modified halloysite composite, depositing Co2(OH)2CO3 precursors on the surface of the carbon nitride modified halloysite by using a sol-gel method, immobilizing stannous ions through the electrostatic adsorption of hydroxyl groups, reducing Pt metal ion precursors into Pt nanoparticles by using the strong reducing property of the stannous ions, anchoring the Pt nanoparticles in the Co2(OH)2CO3 precursors, and constructing a stable CoO / Co-Pt / SnO2 composite on the surface of the carbon nitride modified halloysite through an inert atmosphere roasting treatment to obtain the catalyst. The halloysite nanotube is used to disperse and support the graphite phase carbon nitride material, which can improve the utilization efficiency of the carbon nitride material and the specific surface area of the composite carrier, enhance the chemical effect and synergistic catalytic effect between the metal and the carrier, and expose more catalytically active sites. The stannous ions are used to simultaneously play the anchoring and reducing roles of the Pt metal ion precursors, effectively improve the microreaction environment of the supported Pt nanoparticles, and greatly improve the catalytic activity, selectivity and stability of the Pt particles in the selective catalytic hydrogenation reaction.

[0037] The application is described below by means of specific examples.

[0038] Example 1

[0039] At room temperature, 40 g of trifluoroacetic acid and 25 g of choline chloride were mixed to form a eutectic solvent for 6 h, then 3.5 g of halloysite nanotubes were dispersed in the eutectic solvent, mixed and stirred for 4 h, centrifuged, washed with deionized water and anhydrous ethanol until the pH value of the supernatant was 6, and dried at 55 ℃ for 10 h to obtain modified halloysite MHNTs solid.

[0040] At room temperature, 1.5 g of the above MHNTs solid, 2 g of melamine and 0.01 g of glucosamine hydrochloride were dispersed into a mixed solution of 15 mL of anhydrous ethanol and 12 mL of deionized water, ultrasonically mixed for 3 h, heated to 70 ℃ in an oil bath until the solution was completely evaporated, the obtained solid was ground and transferred to a tube furnace, high-purity nitrogen was introduced, and the temperature was raised to 500 ℃ at a rate of 3.5 ℃ / min in the inert atmosphere for 3 h to obtain a carbon nitride modified halloysite MHNTs / g-C3N4 composite material.

[0041] At room temperature, 0.3 g of the above MHNTs / g-C3N4 solid, 1.6 g of cobalt nitrate hexahydrate and 0.8 g of urea were ultrasonically dispersed in 50 mL of deionized water, and the mixture was heated to 90°C in an oil bath for reflux stirring reaction for 4 h. After cooling to room temperature, the solid was recovered by centrifugation, washed with ethanol, and dried at 50°C for 10 h to obtain the MHNTs / g-C3N4@Co2(OH)2CO3 composite material.

[0042] At room temperature, 0.3 g of the above MHNTs / C3N4@Co2(OH)2CO3 solid, 3.5 mL of concentrated hydrochloric acid and 0.4 g of stannous chloride were ultrasonically dispersed in 50 mL of deionized water. After mixing for 12 h, the mixture was centrifuged, washed, and redispersed in 70 mL of deionized water. Then, 0.7 mL of a potassium chloroplatinate solution (15 mg Pt / mL) was added, and the mixture was mixed for 1 h. Then, 6 mL of a sodium formate solution (0.15 mol / L) was added, and the mixture was mixed and stirred for 10 h. The mixture was centrifuged, washed with deionized water, and dried at 50°C for 12 h. Subsequently, under a high-purity nitrogen atmosphere, the temperature was increased to 550°C at a rate of 5°C / min, and the mixture was calcined for 2 h to obtain a carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2).

[0043] The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of Example 1 was as shown in Figs. Figure 1 and Figure 2 The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of Example 1 was as shown in Figs.

[0044] The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of Example 1 was as shown in Figs.

[0045] Evaluation method: 0.5 mL of cinnamyl aldehyde and 20 mL of ethanol were added to a 50 mL stainless steel high-pressure reactor, 200 mg of the prepared catalyst was dispersed in the above reaction medium, the hydrogen pressure in the reactor was set to 2.0 MPa, the reaction temperature was 100°C, and the reaction time was 2 h. After the reaction was completed, the reactor was quickly cooled to room temperature, the catalyst was separated from the reaction mixture, and a small amount of the reaction liquid was taken for quantitative analysis by gas chromatography to calculate the conversion rate of cinnamyl aldehyde and the selectivity of cinnamyl alcohol.

[0046] The evaluation results show that the conversion rate of cinnamyl aldehyde catalyzed by the catalyst is 97.5%, and the selectivity of cinnamyl alcohol is 82.9%. After centrifugation, washing and drying of the used catalyst, the reaction is carried out again under the same conditions, and after 5 cycles of testing, the conversion rate of cinnamyl aldehyde catalyzed by the catalyst is 91.6%, and the selectivity of cinnamyl alcohol is 75.8%. In order to verify the stability of the active metal components of the catalyst, ICP-AES method is used to detect the reaction clear liquid filtered from the catalyst after the catalytic reaction, and the results show that the leaching amount of Pt and Co metals in the reaction clear liquid is lower than the detection limit of ICP-AES, which indicates that the catalyst has good stability in the process of catalytic hydrogenation reaction.

[0047] Example 2

[0048] At room temperature, 30 g of trifluoromethanesulfonic acid and 18 g of tetramethylammonium chloride were first mixed to react for 3 h to form a eutectic solvent, then 2 g of halloysite nanotubes was dispersed in the above eutectic solvent, mixed and stirred for 3 h, centrifuged, washed with deionized water and anhydrous ethanol until the pH value of the supernatant was 5, and dried at 50°C for 12 h to obtain modified halloysite MHNTs solid.

[0049] At room temperature, 1 g of the above MHNTs solid, 1.5 g of melamine and 0.008 g of glucosamine hydrochloride were dispersed into a mixed solution of 12 mL of anhydrous ethanol and 8 mL of deionized water, and ultrasonic mixing was performed for 4 h, then oil bath heating was performed to 75°C until the solution was completely evaporated, the obtained solid was ground and transferred to a tube furnace, high-purity helium was introduced, and the temperature was increased to 550°C at a rate of 4°C / min under the inert atmosphere and calcined for 2 h to obtain a MHNTs / g-C3N4 composite material modified by carbon nitride.

[0050] At room temperature, 0.2 g of the above MHNTs / g-C3N4 solid, 1.10 g of cobalt sulfate heptahydrate and 0.6 g of urea were dispersed in 50 mL of deionized water, and oil bath heating was performed to 85°C for reflux stirring reaction for 5 h, and after cooling to room temperature, the solid was recovered by centrifugation, washed with ethanol and dried at 45°C for 12 h to obtain a MHNTs / g-C3N4@Co2(OH)2CO3 composite material.

[0051] At room temperature, 0.2 g of the above MHNTs / C3N4@Co2(OH)2CO3 solid, 0.4 mL of concentrated sulfuric acid and 0.2 g of stannous sulfate were dispersed in 50 mL of deionized water, mixed and reacted for 12 h, centrifuged, washed, and redispersed in 70 mL of deionized water, 0.45 mL of chloroplatinic acid ammonium solution (20 mg Pt / mL) was added, mixed and reacted for 2 h, 5 mL of sodium formate solution (0.15 mol / L) was added, mixed and stirred for 8 h, centrifuged, washed with deionized water, and dried at 45°C for 12 h, followed by calcination at 500°C for 3 h at a heating rate of 5°C / min under a high-purity helium atmosphere to obtain a carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2).

[0052] In the carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this Example 2, the characterization results showed that a graphite phase carbon nitride nanosheet was modified on the surface of the halloysite nanotube; and a CoO / Co-Pt / SnO2 composite was anchored in the carbon nitride modified halloysite composite structure.

[0053] The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this Example 2 was subjected to catalytic p-nitrophenol hydrogenation reaction performance evaluation.

[0054] Evaluation method: First, a 45 mL mixed solution containing 25 mg / L p-nitrophenol and 0.8 mol / L sodium borohydride was prepared in a 100 mL reaction vessel, and magnetic stirring was maintained, then 5 mL of the prepared catalyst dispersion solution (6 g / L) was quickly added, and the catalytic hydrogenation reaction was started timing; at a certain reaction time, a small amount of reaction solution was filtered and diluted through a filter head, and the p-nitrophenol hydrogenation conversion rate and p-aminophenol selectivity were analyzed by high performance liquid chromatography.

[0055] Evaluation results: when the reaction was carried out for 8 min, the hydrogenation conversion rate of p-nitrophenol catalyzed by the catalyst was 99%, and the selectivity of p-aminophenol was 100%; the used catalyst was centrifuged, washed and dried, and the reaction was carried out again under the same conditions, and after 3 cycles of testing, the hydrogenation conversion rate of p-nitrophenol catalyzed by the catalyst was 93%, and the selectivity of p-aminophenol was 100%. In order to verify the stability of the active metal components of the catalyst, the reaction clear liquid filtered out after the catalytic reaction was detected by ICP-AES method, and the results showed that the leaching amount of Pt and Co metals in the reaction clear liquid was lower than the detection limit of ICP-AES, which indicated that the catalyst had good stability in the process of catalytic hydrogenation reaction.

[0056] Example 3

[0057] At room temperature, 75 g of hydrofluoric acid and 40 g of tetraethylammonium chloride were first mixed to react for 3 h to form a eutectic solvent, then 5 g of halloysite nanotubes were dispersed in the above eutectic solvent, mixed and stirred for 5 h, centrifuged, washed with deionized water and anhydrous ethanol until the pH value of the supernatant was 6, and dried at 55°C for 9 h to obtain modified halloysite MHNTs solid.

[0058] At room temperature, 3 g of the above MHNTs solid, 3.2 g of melamine and 0.02 g of glucosamine hydrochloride were added to a mixed solution of 20 mL of anhydrous ethanol and 15 mL of deionized water, and ultrasonic mixing was carried out for 6 h, then oil bath heating was carried out to 90°C until the solution was completely evaporated, the obtained solid was ground and transferred to a tube furnace, high-purity argon was introduced, and the temperature was raised to 650°C at a rate of 5°C / min under the inert atmosphere and calcined for 1.5 h to obtain a nitrogenated carbon modified halloysite MHNTs / g-C3N4 composite material.

[0059] At room temperature, 1 g of the above MHNTs / g-C3N4, 4 g of cobalt chloride and 2.5 g of urea were dispersed in 80 mL of deionized water, oil bath heating was carried out to 90°C for reflux mixing reaction for 4 h, after cooling to room temperature, the solid was recovered by centrifugation, washed with ethanol, and dried at 50°C for 12 h to obtain a MHNTs / g-C3N4@Co2(OH)2CO3 composite material.

[0060] At room temperature, 1 g of the above MHNTs / C3N4@Co2(OH)2CO3 solid, 3 mL of concentrated nitric acid and 1.5 g of stannous acetate were dispersed in 90 mL of deionized water, mixed and reacted for 16 h, centrifuged, washed, and redispersed in 100 mL of deionized water, 1.8 mL of sodium chloroplatinite solution (30 mg Pt / mL) was added, mixed and reacted for 2 h, 6 mL of sodium formate solution (0.75 mol / L) was added, mixed and stirred for 16 h, centrifuged, washed with deionized water, and dried at 55°C for 10 h, then under the atmosphere of high-purity argon, the temperature was raised to 600°C at a rate of 5°C / min, and calcined for 2 h to obtain a carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2).

[0061] In the carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this embodiment 3, the characterization results show that a graphite phase carbon nitride nanosheet is modified on the surface of the halloysite nanotube; and a CoO / Co-Pt / SnO2 composite is anchored in the carbon nitride modified halloysite composite structure.

[0062] The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this embodiment 3 was subjected to performance evaluation of catalyzing 2-methoxy-4-nitrophenol hydrogenation reaction.

[0063] Evaluation method: first, a 45 mL mixed solution containing 20 mg / L of 2-methoxy-4-nitrophenol and 1 mol / L of sodium borohydride was prepared in a 100 mL reaction container, and magnetic stirring was maintained, then 5 mL of the prepared catalyst dispersion solution (6 g / L) was quickly added, and the catalytic hydrogenation reaction was started and timed; at a certain reaction time, a small amount of reaction solution was filtered and diluted through a filter head, and the conversion rate of 2-methoxy-4-nitrophenol and the selectivity of 2-methoxy-4-aminophenol were analyzed by high performance liquid chromatography.

[0064] Evaluation results: when the reaction was carried out for 25 min, the conversion rate of 2-methoxy-4-nitrobenzene catalyzed by the catalyst was 99%, and the selectivity of 2-methoxy-4-aminobenzene was 100%; the used catalyst was centrifuged, washed and dried, and the reaction was carried out again under the same conditions, and after 3 cycles of testing, the conversion rate of 2-methoxy-4-nitrobenzene catalyzed by the catalyst was 92%, and the selectivity of aminophenol was 100%. In order to verify the stability of the active metal component of the catalyst, ICP-AES method was used to detect the reaction clear liquid filtered after the catalytic reaction, and the results showed that the leaching amount of Pt and Co metals in the reaction clear liquid was lower than the detection limit of ICP-AES, indicating that the catalyst had strong stability in the process of catalytic hydrogenation reaction.

[0065] Example 4

[0066] First, 90 g of hexafluorophosphoric acid and 70 g of choline bromide were mixed to form a eutectic solvent at room temperature, and then 6 g of halloysite nanotubes were dispersed in the eutectic solvent, mixed and stirred for 5 h, centrifuged, washed with deionized water and anhydrous ethanol until the pH value of the supernatant was 5, and dried at 45℃ for 12 h to obtain modified halloysite MHNTs solid.

[0067] At room temperature, 3.5 g of the above MHNTs solid, 5.5 g of melamine and 0.04 g of glucosamine hydrochloride were added to a mixed solution of 40 mL of anhydrous ethanol and 40 mL of deionized water, and ultrasonic mixing was carried out for 5 h, then oil bath heating was carried out to 95℃ until the solution was completely evaporated, the obtained solid was ground and transferred to a tube furnace, high-purity nitrogen was introduced, and the temperature was raised to 700℃ at a heating rate of 5℃ / min under the inert atmosphere, and calcination was carried out for 1.5 h to obtain a nitrogenated carbon modified halloysite MHNTs / g-C3N4 composite material.

[0068] At room temperature, 3 g of the above MHNTs / g-C3N4 solid, 15 g of cobalt acetate and 9 g of urea were dispersed in 100 mL of deionized water, and reflux reaction was carried out at 95℃ for 3 h, and then the solid was recovered by centrifugation after cooling to room temperature, washed with ethanol and dried at 50℃ for 12 h to obtain a MHNTs / g-C3N4@Co2(OH)2CO3 composite material.

[0069] At room temperature, 3 g of MHNTs / C3N4@Co2(OH)2CO3 solid, 20 mL of concentrated hydrochloric acid, and 5 g of stannous chloride were ultrasonically dispersed in 150 mL of deionized water, mixed and reacted for 18 h, centrifuged, washed, and redispersed in 100 mL of deionized water, 5 mL of potassium chloroplatinite solution (35 mg Pt / mL) was added, mixed and reacted for 2 h, 15 mL of sodium formate solution (0.75 mol / L) was added, mixed and stirred for 12 h, centrifuged, washed with deionized water, and dried at 50°C for 12 h, then heated to 650°C at a heating rate of 5°C / min under a high-purity nitrogen atmosphere, and calcined for 2 h to obtain a carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2).

[0070] In the carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this embodiment 4, the characterization results show that a graphite phase carbon nitride nanosheet is modified on the surface of the halloysite nanotube, and a CoO / Co-Pt / SnO2 composite is anchored in the carbon nitride modified halloysite composite structure.

[0071] The carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst (MHNTs / g-C3N4@CoO / Co-Pt / SnO2) prepared by the method of this embodiment 4 was subjected to catalytic 2-chloro-4-nitrophenol hydrogenation reaction performance evaluation.

[0072] Evaluation method: First, a 45 mL mixed solution containing 20 mg / L of 2-chloro-4-nitrophenol and 0.8 mol / L of sodium borohydride was prepared in a 100 mL reaction container, and magnetic stirring was maintained, then 5 mL of prepared catalyst dispersion liquid (5 g / L) was quickly added, and the catalytic hydrogenation reaction was started timing; a small amount of reaction solution was taken at different reaction times, filtered through a filter head and diluted, and then the 2-chloro-4-nitrophenol conversion rate and 2-chloro-4-aminophenol selectivity were analyzed by high performance liquid chromatography.

[0073] The evaluation results are as follows: when the reaction is carried out for 16 min, the hydrogenation conversion rate of 2-chloro-4-nitrophenol catalyzed by the catalyst is 98%, and the selectivity of 2-chloro-4-aminophenol is 100%; after the used catalyst is centrifuged, washed and dried, the reaction is carried out again under the same conditions, and after three cycles of testing, the hydrogenation conversion rate of 2-chloro-4-nitrophenol catalyzed by the catalyst is 93%, and the selectivity of 2-chloro-4-aminophenol is 99%. In order to verify the stability of the active metal components of the catalyst, the reaction clear liquid filtered from the catalyst after the catalytic reaction is detected by ICP-AES method, and the results show that the leaching amount of Pt and Co metals in the reaction clear liquid is lower than the detection limit of ICP-AES, which indicates that the catalyst has strong stability in the process of catalytic hydrogenation reaction.

[0074] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the essence of the present application should be covered within the protection scope of the present application.

Claims

1. A carbon nitride-modified halloysite-supported nano-metal composite catalyst, characterized in that, include: Modified halloysite: The modified halloysite is etched and modified by a eutectic solvent to form halloysite nanotubes; Carbon nitride: The carbon nitride was constructed on the surface of modified halloysite via vapor deposition-pyrolysis to form a graphitic carbon nitride nanofilm, resulting in a carbon nitride-modified halloysite composite structure; and, CoO / Co-Pt / SnO2 composite: The CoO / Co-Pt / SnO2 composite is anchored in a carbon nitride-modified halloysite composite structure; The eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor is selected from any one of hydrofluoric acid, trifluoromethanesulfonic acid, trifluoroacetic acid, hexafluorosilicic acid, and hexafluorophosphoric acid; the hydrogen bond acceptor is selected from any one of choline chloride, choline bromide, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, and tetrabutylammonium chloride. The preparation method of carbon nitride modified halloysite supported nano-metal composite catalyst is as follows: Step a): Weigh halloysite nanotubes and disperse them in a eutectic solvent composed of hydrogen bond donors and hydrogen bond acceptors. Mix and stir for 1-6 h, centrifuge to recover the solid, wash with deionized water and anhydrous ethanol until the pH is 5-7, and dry at 40-60℃ for 8-12 h to obtain modified halloysite MHNTs material. Step b): The MHNTs material is added to a mixed solution of anhydrous ethanol and deionized water at a set mass ratio with melamine and glucosamine hydrochloride. After ultrasonic mixing for 2-8 h, the mixture is heated at 60-95℃ until the solution is completely evaporated. The obtained solid is ground and transferred to a tube furnace and calcined at 500-900℃ for 1-5 h under an inert atmosphere to obtain carbon nitride modified halloysite MHNTs / g-C3N4 composite material. Step c): Disperse the MHNTs / g-C3N4 composite material, cobalt salt and urea in deionized water, and heat and reflux at 60~100℃ for 2~6 h under stirring and mixing. After cooling to room temperature, centrifuge, wash and dry to obtain the MHNTs / g-C3N4@Co2(OH)2CO3 composite material. Step d): The MHNTs / C3N4@Co2(OH)2CO3 composite material was dispersed in deionized water, stannous salt and acidic solution were added, and the mixture was reacted for 7-20 h. After centrifugation, washing, and redispersing in deionized water, Pt metal anion precursor was added, and the mixture was reacted for 0.5-3 h. Sodium formate was added, and the mixture was reacted for 8-18 h. After centrifugation, washing, and drying, the mixture was calcined at 500-800℃ for 1-3 h under an inert atmosphere to obtain the carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst MHNTs / g-C3N4@CoO / Co-Pt / SnO2.

2. The carbon nitride-modified halloysite-supported nano-metal composite catalyst according to claim 1, characterized in that, The mass percentage of carbon nitride is 15-40% of the total mass of the catalyst; the mass percentage of the CoO / Co-Pt / SnO2 composite is 1-20% of the total mass of the catalyst; and in the CoO / Co-Pt / SnO2 composite, the mass percentage of Pt nanoparticles is 0.1-8% of the total mass of the catalyst.

3. A method for preparing a carbon nitride-modified halloysite-supported nano-metal composite catalyst as described in any one of claims 1 or 2, characterized in that, Includes the following steps: Step a): Weigh halloysite nanotubes and disperse them in a eutectic solvent composed of hydrogen bond donors and hydrogen bond acceptors. Mix and stir for 1-6 h, centrifuge to recover the solid, wash with deionized water and anhydrous ethanol until the pH is 5-7, and dry at 40-60℃ for 8-12 h to obtain modified halloysite MHNTs material. Step b): The MHNTs material is added to a mixed solution of anhydrous ethanol and deionized water at a set mass ratio with melamine and glucosamine hydrochloride. After ultrasonic mixing for 2-8 h, the mixture is heated at 60-95℃ until the solution is completely evaporated. The obtained solid is ground and transferred to a tube furnace and calcined at 500-900℃ for 1-5 h under an inert atmosphere to obtain carbon nitride modified halloysite MHNTs / g-C3N4 composite material. Step c): Disperse the MHNTs / g-C3N4 composite material, cobalt salt and urea in deionized water, and heat and reflux at 60~100℃ for 2~6 h under stirring and mixing. After cooling to room temperature, centrifuge, wash and dry to obtain the MHNTs / g-C3N4@Co2(OH)2CO3 composite material. Step d): The MHNTs / C3N4@Co2(OH)2CO3 composite material was dispersed in deionized water, stannous salt and acidic solution were added, and the mixture was reacted for 7-20 h. After centrifugation, washing, and redispersing in deionized water, Pt metal anion precursor was added, and the mixture was reacted for 0.5-3 h. Sodium formate was added, and the mixture was reacted for 8-18 h. After centrifugation, washing, and drying, the mixture was calcined at 500-800℃ for 1-3 h under an inert atmosphere to obtain the carbon nitride modified halloysite supported CoO / Co-Pt / SnO2 composite catalyst MHNTs / g-C3N4@CoO / Co-Pt / SnO2.

4. The method for preparing the carbon nitride-modified halloysite-supported nano-metal composite catalyst according to claim 3, characterized in that, In step a), the mass ratio of halloysite nanotubes to eutectic solvent is 1:(15~60), and the molar ratio of hydrogen bond donor to hydrogen bond acceptor is 1:(0.2~1).

5. The method for preparing the carbon nitride-modified halloysite-supported nano-metal composite catalyst according to claim 3, characterized in that, In step b), the mass ratio of the MHNTs material to melamine and glucosamine hydrochloride is 1:(0.5~2):(0.001~0.02), the mass ratio of anhydrous ethanol to deionized water is 1:(0.5~2), and the inert atmosphere is any one of high-purity nitrogen, high-purity helium, and high-purity argon.

6. The method for preparing the carbon nitride-modified halloysite-supported nano-metal composite catalyst according to claim 3, characterized in that, In step c), the mass ratio of the MHNTs / g-C3N4 composite material, cobalt salt, and urea is 1:(1~8):(0.5~4), wherein the cobalt salt is any one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

7. The method for preparing the carbon nitride-modified halloysite-supported nano-metal composite catalyst according to claim 3, characterized in that, In step d), the mass ratio of Pt element to sodium formate in the MHNTs / g-C3N4@Co2(OH)2CO3 composite material, stannous salt, acidic solution, and Pt metal anion precursor is 1:(0.5~2):(2~10):(0.001~0.1):(0.1~0.8). The stannous salt is any one of stannous sulfate, stannous chloride, and stannous acetate. The acidic solution is any one of hydrochloric acid, sulfuric acid, and nitric acid. The Pt metal anion precursor is selected from any one of chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, sodium chloroplatinate, potassium chloroplatinate, and ammonium chloroplatinate. The inert atmosphere is any one of high-purity nitrogen, high-purity helium, and high-purity argon.

8. The application of the carbon nitride-modified halloysite supported nano-metal composite catalyst as described in any one of claims 1 or 2, or the carbon nitride-modified halloysite supported nano-metal composite catalyst prepared by the method described in any one of claims 3-7, in the selective catalytic hydrogenation of cinnamaldehyde to cinnamyl alcohol or the catalytic hydrogenation of nitrobenzene compounds to aminobenzene compounds.

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