Quantum dot modified M / SiC-Bx catalyst as well as preparation method and application thereof

Abstract

The invention discloses a quantum dot modified M / SiC-Bx catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation. According to the quantum dot modified M / SiC-Bx catalyst, quantum dot modified SiC-Bx serves as a carrier of the catalyst, transition metal is loaded on the surface of the carrier through an impregnation method, and the quantum dot modified M / SiC-Bx catalyst is obtained. The catalyst can be applied to selective hydrogenation of nitrile compounds, so that imine is prepared through selective hydrogenation of the nitrile compounds, the conversion rate can reach 60-100%, and the selectivity can reach 60-93%.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and specifically relates to a quantum dot (QDs) modified M / SiC-B x The invention relates to a catalyst and a preparation method and application thereof, and more particularly to an application thereof in the selective hydrogenation of nitrile compounds to prepare imines. Background Art

[0002] Imines and their derivatives can be used to synthesize dyes, spices, fungicides, drugs and pesticides. Currently, the commonly used methods for synthesizing imines include the condensation reaction of aldehydes and ketones with amines, the oxidative self-coupling reaction of amines and the oxidative coupling reaction of alcohols and amines. However, amine compounds are expensive and not suitable as raw materials, and these catalytic reactions often generate a large number of by-products. Nitrile compounds can selectively generate imines by hydrogenation. Compared with amine compounds, nitrile compounds are cheaper, and the nitrile hydrogenation reaction is efficient and green, and belongs to an atom-economic reaction. However, nitrile compounds will produce reactants such as primary amines, secondary amines, primary imines, secondary imines, and tertiary amines during the hydrogenation process. Therefore, it is difficult to prepare imines with high selectivity.

[0003] At present, there are few reports on the direct selective hydrogenation of nitrile compounds to form imines, and the reported methods use homogeneous complexes or precious metals as separation and recycling of the products, which has more obvious disadvantages, especially when applied to the pharmaceutical and food industries. Therefore, it is not an environmentally friendly catalyst, and the expensive price of precious metal catalysts limits its application in actual production.

[0004] Li Yingwei from South China University of Technology used Co@NC-900 catalyst to convert nitrile compounds into imines by adjusting the amount of solvent isopropanol added, with a selectivity greater than 90% (ACS Catal. 2017, 7, 275-284). Patent application with publication number CN119080637A discloses a method for preparing imines by selective hydrogenation of nitrile compounds, and prepared M / SiC-B by impregnation method. x The catalyst was prepared and its performance in the selective hydrogenation of nitrile compounds was investigated. The conversion rate of nitrile compounds was 88-100%, and the selectivity of the generated imines was 72-98%. x The catalyst has defects such as low catalytic efficiency, long reaction time, large catalyst usage and high cost. It is not suitable for industrial production and is not suitable for widespread use. Summary of the invention

[0005] In view of the defects existing in the above-mentioned prior art, in order to solve the problems of low imine selectivity, low reaction conditions, long preparation time, large catalyst usage, high cost and low efficiency in the prior art, the present invention provides a method for selectively hydrogenating nitrile compounds using B-doped SiC modified quantum dots loaded with transition metals to generate product imines. The preparation method of the present invention is simple, the obtained catalyst has good performance, and has excellent performance for the catalytic reaction of nitrile compounds.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a quantum dot-modified M / SiC-Bx catalyst, comprising a quantum dot-modified SiC-B x As a catalyst carrier, and M is loaded on the carrier surface;

[0008] SiC-Bx represents B x Doped SiC;

[0009] The quantum dot modified SiC-B x The modification amount of the quantum dots is 0.1 to 20 wt.%;

[0010] The content of M in the quantum dot-modified M / SiC-Bx catalyst is 0.1 to 20 wt.%;

[0011] The M is a transition metal;

[0012] The x is any rational number between 0.1 and 2.

[0013] In the quantum dot-modified M / SiC-Bx catalyst, the transition metal is at least one of Fe, Co, and Ni.

[0014] In a second aspect, the present invention provides a method for preparing a quantum dot-modified M / SiC-Bx catalyst, comprising the following steps:

[0015] (1) Weigh SiC-B x , dispersed in a quantum dot aqueous solution, subjected to hydrothermal reaction after ultrasonic oscillation, cooled to room temperature, centrifuged to remove the supernatant, washed, and dried to obtain quantum dot-modified SiC-B x ;

[0016] (2) Weigh the aqueous solution of transition metal and add the quantum dot-modified SiC-B obtained in step (1) above. x Add water, stir and mix, and dry to obtain quantum dot-modified M / SiC-B x catalyst.

[0017] In the preparation method, the quantum dots in step (1) are at least one of SiC QDs, C QDs or CeO2 QDs.

[0018] In the preparation method, the ultrasonic oscillation time in step (1) is 0.5 to 3 hours;

[0019] The conditions of the hydrothermal reaction are: temperature 150-300° C., time 6-24 h.

[0020] In the preparation method, the drying temperature in step (1) is 30-150°C.

[0021] In the preparation method, the drying method in step (2) is rotary evaporation, and the rotary evaporation temperature is 30-70°C.

[0022] In a third aspect, the present invention provides the use of the quantum dot-modified M / SiC-Bx catalyst in catalyzing the selective hydrogenation of nitrile compounds to prepare imines.

[0023] In a fourth aspect, the present invention provides a method for preparing imines by selective hydrogenation of nitrile compounds, comprising the following steps:

[0024] Weigh a nitrile compound, an organic solvent and the quantum dot-modified M / SiC-Bx catalyst as claimed in claim 1 or 2, mix them evenly, transfer them to a high-temperature and high-pressure reactor, seal them, purge them with hydrogen for 3-6 times, maintain the hydrogen pressure of the reactor at 0.1-2 MPa, react at 30-150° C. under stirring conditions for 0.5-12 h, turn off heating and stirring after the reaction is completed, cool to room temperature, collect the reaction liquid, remove the catalyst particles, and obtain imine.

[0025] The method for preparing imines by selective hydrogenation of nitrile compounds is characterized in that the volume ratio of the nitrile compound to the solvent is 0.01 to 0.6:1;

[0026] The organic solvent is at least one of methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, cyclohexane, N,N-dimethylformamide or 1,4-dioxane.

[0027] The structural formula of the nitrile compound is:

[0028] The structural formula of imine compounds is: In the formula, R represents 1, 2 or 3 substituents connected to the benzene ring, each substituent is independently selected from any one of a hydrogen atom, a halogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, a C6-C20 aryl group, -OR', -OCF3, -NHR', -C(=O)OR', -NHC(=O)R' and -C(=O)R', and R' is H, a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a phenyl group or a benzyl group.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention improves the hydrogen overflow concentration on the SiC surface by modifying quantum dots on the surface of silicon carbide, and at the same time, the oxygen-containing groups such as hydroxyl and carboxyl groups abundant on the surface of the quantum dots can preferentially adsorb and activate C≡N bonds, and B-doped SiC can generate acid sites on the SiC surface, promoting the deamination condensation of imine intermediates and benzylamine in the process of catalyzing the selective hydrogenation of nitrile compounds. The catalyst of the present invention can significantly shorten the reaction time and reduce the amount of catalyst by modifying quantum dots on the carrier, and can ensure both high conversion rate of nitrile compounds and high selectivity of imine products, and no harmful gas is generated during the reaction process, it is green and environmentally friendly, the reaction conditions are mild, the time cycle is short, the operation is simple, the product yield is high, and the cost is low, and it is an efficient and stable catalyst and catalytic reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an electron microscope image of silicon carbide quantum dots modified on the silicon carbide surface. DETAILED DESCRIPTION

[0032] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0033] Embodiment 1:

[0034] (1) Preparation method of SiC quantum dots: SiC QDs were prepared using an etching method. First, 3 g of SiC (40 nm) was dispersed in an aqueous solution containing 22.5 ml of HF (40 wt%) and 7.5 ml of HNO3 (65 wt%) and then heated at 100 ° C for 2 hours. After cooling to room temperature, 50 ml of deionized water was added and the mixture was ultrasonically treated for 30 min. Subsequently, large particles were removed by centrifugation, and residual acid was removed by evaporating the solvent. The liquid was then transferred to a dialysis bag and dialyzed to concentrate the resulting colloid. SiC quantum dots prepared by this method are also used in the following Examples 2-12.

[0035] (2)SiC-B 0.5 Preparation: 14.23g sucrose (sucrose as carbon source, with a C / Si molar ratio of 8:1) was dissolved in 100mL water, ultrasonicated until completely dissolved, 12.47g silica sol (containing 30% Si), boric acid (H3BO3) as boron source, according to the theoretical molar ratio of B / Si of 0.5. All raw materials were mixed evenly, placed in a homogeneous reactor at 180°C, and hydrothermal for 4h. After the hydrothermal treatment, after cooling to room temperature, the solid-liquid separation was carried out by centrifugation to obtain the precursor, and then the dried precursor was placed in a high-temperature tube furnace, Ar protective gas was introduced, the temperature was programmed to 1450°C, and after constant temperature reaction for 8h, it was naturally cooled to room temperature in Ar; the reaction product was calcined at 700°C in a muffle furnace for 3h to remove the unreacted carbon, and then soaked in a mixed acid (HCl, HF) with a volume ratio of 1:3 for 24h to clean the impurities. Finally, SiC-B was obtained through washing, filtering and drying steps. 0.5 In the following Examples 2-12, the SiC-B prepared by this method is also used. 0.5 .

[0036] (3) Weigh 167.7 mg of SiC-B 0.5 Dispersed in 40mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 10% SiC QDs-SiC-B 0.5 .

[0037] (4) 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 10% SiC QDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 10 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0038] (5) Take 80 mg of 5wt.%Ni / 10%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 1 hour. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 60.6%, and the selectivity of imine is 86.3%.

[0039] Embodiment 2:

[0040] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0041] Take 80 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 1 hour. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 79.2%, and the selectivity of imine is 87.3%.

[0042] Embodiment 3:

[0043] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 10mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 3% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 3% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 2 4 h. 5 wt. % Ni / 3 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0044] Take 80 mg of 5wt.%Ni / 3%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 1 hour. After the reaction is completed, turn off the heating and stirring. After cooling to room temperature, collect 2 mL of the reaction solution, remove the catalyst particles through a filter, and then perform gas phase analysis. The conversion rate of benzonitrile is 68.3%, and the selectivity of imine is 91.5%.

[0045] Embodiment 4:

[0046] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 3.5 mL of 0.5 mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2 h, transferred to a hydrothermal autoclave, sealed, heated at 200 ° C for 12 h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60 ° C for 12 h to obtain 1% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 1% SiCQDs-SiC-B 0.5and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 1 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0047] Take 80 mg of 5wt.%Ni / 1%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 1 hour. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 65.8%, and the selectivity of imine is 91.5%.

[0048] Embodiment 5:

[0049] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst. Figure 1 5wt.%Ni / 5%SiC QDs-SiC-B 0.5 The electron microscope image of the catalyst, in which the red circle represents nickel and the yellow circle represents quantum dots, indicates that the catalyst of the present invention was successfully prepared.

[0050] Take 80 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 0.5 h. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 49.5%, and the selectivity of imine is 93.1%.

[0051] Embodiment 6:

[0052] SiC Quantum Dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0053] Take 80 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 3 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 98.5%, and the selectivity of imine is 91.1%.

[0054] Embodiment 7:

[0055] SiC Quantum Dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0056] Take 80 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 6 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed by a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 100.0%, and the selectivity of imine is 91.0%.

[0057] Embodiment 8:

[0058] SiC Quantum Dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0059] Take 50 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 6 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed by a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 75.5%, and the selectivity of imine is 92.0%.

[0060] Embodiment 9:

[0061] SiC Quantum Dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0062] Take 60 mg of 5wt.%Ni / 5%SiC QDs-SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 6 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 82.9%, and the selectivity of imine is 93.1%.

[0063] Embodiment 10:

[0064] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0065] Take 100 mg of 5 wt.% Ni / 5% SiC QDs-SiC-B which has been reduced in advance (reduction temperature is 300°C) 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is allowed to react for 12 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 60.5%, and the selectivity of imine is 87.5%.

[0066] Embodiment 11:

[0067] SiC quantum dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0068] Take 100 mg of 5wt.%Ni / 5%SiC QDs-SiC-B which has been reduced in advance (reduction temperature is 400℃) 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 6 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed through a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 99.5%, and the selectivity of imine is 60.3%.

[0069] Embodiment 12:

[0070] SiC Quantum Dots and SiC-B 0.5 The preparation is the same as in the above example. 167.7 mg of SiC-B 0.5 Dispersed in 20mL of 0.5mg / mL SiC quantum dot (SiC QDs) aqueous solution, ultrasonicated for 2h, transferred to a hydrothermal autoclave, sealed, heated at 200℃ for 12h, and then cooled to room temperature. After centrifugation, the supernatant was discarded, washed with water twice, washed with ethanol once, and dried in an oven at 60℃ for 12h to obtain 5% SiC QDs-SiC-B 0.5 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of 5% SiCQDs-SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 2 4 h. 5 wt. % Ni / 5 % SiC QDs-SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0071] Take 100 mg of 5 wt.% Ni / 5% SiC QDs-SiC-B that has been reduced (reduction temperature is 500°C) in advance 0.5The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 12 hours. After the reaction is completed, turn off the heating and stirring. After cooling to room temperature, collect 2 mL of the reaction solution, remove the catalyst particles through a filter, and then perform gas phase analysis. The conversion rate of benzonitrile is 68.9%, and the selectivity of imine is 90.7%.

[0072] Comparative Example 1:

[0073] 1.43 mL of Ni(NO3)2·6H2O aqueous solution (30 mg / mL) and 162 mg of SiC-B 0.5 and 18.57 mL of water were mixed in a 100 mL beaker and stirred for 24 h. 5 wt.% Ni / SiC-B was obtained by rotary evaporation and drying. 0.5 catalyst.

[0074] Take 100 mg of Ni / SiC-B that has been reduced in advance 0.5 The catalyst is placed in the reactor lining, and 10 mL of methanol solution and 0.1 mL of benzonitrile (1 mmol) are added to the reactor lining. After the drugs are added, the reactor is sealed, and 0.1 MPa of high-purity H2 is filled after ensuring airtightness. The reactor is placed in a heating device, the stirring rate and reaction temperature are set, and the stirring and heating buttons are turned on. When the temperature reaches 100 ° C, the reaction is carried out for 6 hours. After the reaction is completed, the heating and stirring are turned off. After cooling to room temperature, 2 mL of the reaction solution is collected, the catalyst particles are removed by a filter, and then gas phase analysis is performed. The conversion rate of benzonitrile is 96.1%, and the selectivity of imine is 90.2%.

[0075] The catalytic activities of the catalysts prepared in Examples 1 to 6 and Comparative Example 1 in the selective hydrogenation reaction of nitrile compounds are shown in Table 1.

[0076] Table 1 Effect of catalysts in Examples 1 to 6 and Comparative Example 1 on catalytic activity

[0077]

[0078]

[0079] It can be seen from Table 1 that in Examples 1 to 4, SiC-B is modified by quantum dots. 0.5The surface can improve the catalytic activity, and with the increase of SiC QDs content, the catalytic activity continues to increase, but when the mass fraction of SiC QDs is 10%, the conversion rate and selectivity of imine are reduced. At the same time, it can be seen that after modification with quantum dots, the efficiency of the reaction conditions is improved.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A quantum dot modified M / SiC-Bx catalyst, characterized in that: Contains SiC-B modified with quantum dots x As a catalyst carrier, and M is loaded on the carrier surface; The quantum dot modified SiC-B x The modification amount of the quantum dots is 0.1 to 20 wt.%; The content of M in the quantum dot-modified M / SiC-Bx catalyst is 0.1 to 20 wt.%; The M is a transition metal; The x is any rational number between 0.1 and 2.

2. A quantum dot modified M / SiC-Bx catalyst as claimed in claim 1, characterized in that: The transition metal is at least one of Fe, Co and Ni.

3. A method for preparing a quantum dot-modified M / SiC-Bx catalyst according to claim 1 or 2, characterized in that: The following steps are involved: (1) Weigh SiC-B x , dispersed in a quantum dot aqueous solution, subjected to hydrothermal reaction after ultrasonic oscillation, cooled to room temperature, centrifuged to remove the supernatant, washed, and dried to obtain quantum dot-modified SiC-B x ; (2) Weigh the aqueous solution of transition metal and add the quantum dot-modified SiC-B obtained in step (1) above. x Add water, stir and mix, and dry to obtain quantum dot-modified M / SiC-B x catalyst.

4. The preparation method according to claim 3, characterized in that: The quantum dots in step (1) are at least one of SiC QDs, C QDs or CeO2 QDs.

5. The preparation method according to claim 3, characterized in that: The ultrasonic oscillation time in step (1) is 0.5 to 3 hours; The conditions of the hydrothermal reaction are: temperature 150-300° C., time 6-24 h.

6. The preparation method according to claim 3, characterized in that: The drying temperature in step (1) is 30-150°C.

7. The preparation method according to claim 3, characterized in that: The drying method in step (2) is rotary evaporation, and the temperature of rotary evaporation is 30-70°C.

8. Use of the quantum dot-modified M / SiC-Bx catalyst as claimed in claim 1 or 2 in catalyzing the selective hydrogenation of nitrile compounds to prepare imines.

9. A method for preparing imines by selective hydrogenation of nitrile compounds, characterized in that: The following steps are involved: Weigh a nitrile compound, an organic solvent and the quantum dot-modified M / SiC-Bx catalyst as claimed in claim 1 or 2, mix them evenly, transfer them to a high-temperature and high-pressure reactor, seal them, purge them with hydrogen for 3-6 times, maintain the hydrogen pressure of the reactor at 0.1-2 MPa, react at 30-150° C. under stirring conditions for 0.5-12 h, turn off heating and stirring after the reaction is completed, cool to room temperature, collect the reaction liquid, remove the catalyst particles, and obtain imine.

10. The method for preparing imines by selective hydrogenation of nitrile compounds according to claim 9, characterized in that: The volume ratio of the nitrile compound to the solvent is 0.01 to 0.6:1; The organic solvent is at least one of methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, cyclohexane, N,N-dimethylformamide or 1,4-dioxane.

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