CN107469825B - Preparation method and application of oxidation-modified carbon nanotube-loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst - Google Patents
Preparation method and application of oxidation-modified carbon nanotube-loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst Download PDFInfo
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Abstract
The invention discloses a preparation method and application of an oxidation-modified carbon nanotube-loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst. According to the invention, the multi-walled carbon nanotube loaded multi-metal nickel-based catalyst subjected to hydrogen peroxide oxidation treatment is utilized, the reduction energy of a Ni precursor can be effectively reduced by introducing Cu, the dispersion of Ni nanoparticles on the surface of the carbon nanotube is promoted, and more Ni can be promoted by the synergistic effect of Cu and Ni 0+ And (4) forming. The introduction of Mg provides a large number of alkaline sites for the surface of the catalyst, and the formation of NiO-MgO eutectic is beneficial to inhibiting excessive hydrogenation of reactants and avoiding the formation of excessive byproducts. The oxidation treatment of the carbon nano tube can further promote the strong interaction between the carbon tube and the active component, greatly improves the hydrogenation activity of the catalyst, and can obtain higher conversion rate and total product selectivity when being used for the adiponitrile hydrogenation reaction.
Description
Technical Field
The invention relates to the field of material preparation, in particular to a preparation method and application of an oxidation-modified carbon nano tube loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst.
Background
Adiponitrile hydrogenation produces mainly 6-aminocapronitrile and hexamethylenediamine, 6-aminocapronitrile being a very critical step in the new process for the synthesis of caprolactam by the butadiene/adiponitrile process. In the butadiene/adiponitrile process, the first step of the hydrocyanation of butadiene based on a nickel phosphine homogeneous catalyst has been well studied. The yield of adiponitrile can reach 95.6% by the DuPont company through two-step reaction of hydrogenation and then cyanidation of butadiene. Aiming at the research on the process of synthesizing caprolactam by cyclizing 6-aminocapronitrile in the third step, the companies of Basf and Disemann apply relevant patents based on hydrolytic cyclization, and both gas-phase or liquid-phase cyclization processes have considerable yield of caprolactam and selectivity close to 100 percent. Caprolactam is an important chemical basic raw material for producing products such as nylon 6 fibers, nylon 6 resin, films and the like, and is widely applied to other fields such as textiles, automobiles, electronics, machinery and the like. Besides, caprolactam is widely applied to the pharmaceutical industry for producing antiplatelet drugs 6-aminocaproic acid, laurocapram and the like. Meanwhile, hexamethylenediamine is also an intermediate of nylon-66 with economic value. Therefore, the research on the partial hydrogenation of adiponitrile mainly has two routes, namely the development and research of a catalyst for preparing 6-aminocapronitrile with high selectivity, and the research of a process means for coproducing aminocapronitrile and hexamethylene diamine with high selectivity.
At present, partial hydrogenation of adiponitrile is being studied more and more, and the catalysts mainly comprise ruthenium complex homogeneous catalysts and heterogeneous catalysts, wherein the heterogeneous catalysts comprise Raney catalysts, unsupported nickel-based catalysts, supported nickel-based catalysts, amorphous catalysts, noble metal catalysts and the like.
Most of homogeneous catalysts are transition metal complex catalysts, and a U.S. patent (US 5554778 US5559262 US 5599962) invents that a ruthenium complex is used as a catalyst to be applied to adiponitrile hydrogenation reaction, the reaction temperature is 373K, the hydrogen pressure is 7.0MPa, the reaction time is 1h, the conversion rate of adiponitrile can reach 91%, and the selectivity of aminocapronitrile can reach more than 71%. However, although the catalyst has high activity, the catalyst is difficult to separate and is difficult to recycle, so the use cost of the catalyst is high.
Raney-type catalysts for adiponitrile hydrogenation typically employ Raney nickel and Raney cobalt. U.S. Pat. No. 3,3238,3238B 1 U.S. Pat. No. 3262,3262,51543 reports Raney-type catalysts which require very high hydrogen pressure reaction conditions and the coexistence of large amounts of aqueous ammonia or alkali metal hydroxide solutions, with yields of aminocapronitrile of around 70%. The Raney type catalyst has low mechanical strength, easy spontaneous combustion and difficult separation, and has no obvious economic benefit in application due to harsh conditions in use.
In the non-supported Ni-based catalyst, medina and the like research on the application of a pure Ni catalyst to adiponitrile hydrogenation reaction, and on the basis, the modification research of alkali metal or alkaline earth metal oxide is carried out on the pure Ni catalyst, and the research proves that the increase of the surface alkalinity of the catalyst and the larger metal surface area are beneficial to improving the desorption and catalytic performance of aminocapronitrile. At a hydrogen-adiponitrile molar ratio of 1002 and a space velocity of 10242h -1 Under the conditions of normal pressure and 110 ℃, the conversion rate of adiponitrile is 83 percent, and the selectivity of aminocapronitrile reaches 87 percent.
Among the amorphous catalysts, hexing Li, xinbin Yu and the like have studied the application of Ni-P amorphous alloy catalysts and supported Ni-B amorphous alloy catalysts in adiponitrile hydrogenation reaction. Research shows that the amorphous Ni-B/SiO 2 The selectivity of the catalyst aminocapronitrile is 21 percent, the selectivity of the Ni-P amorphous catalyst aminocapronitrile is 20 percent, and the main product of the reaction is hexamethylene diamine under the gas phase condition.
alpha-Al from noble metal catalysts, alini et Al, by ion exchange 2 O 3 The supported noble metal Rh catalyst is applied to liquid-phase hydrogenation of adiponitrile, and when the reaction conditions are 3MPa hydrogen pressure and 373K, the conversion rate of adiponitrile is 60%, and the selectivity of aminocapronitrile reaches 100%. In addition, rh/γ -Al prepared by vapor deposition has also been reported 2 O 3 When the method is applied to adiponitrile hydrogenation reaction, the conversion rate of adiponitrile and the selectivity of aminocapronitrile are respectively 100% and 45% under the conditions of 3MPa and 337K when a certain amount of sodium hydroxide solution is added. However, this catalyst has a low recovery rate and requires a large amount of alkali to suppress the formation of by-products.
In summary, the above catalysts for adiponitrile hydrogenation all have problems to some extent, or are difficult to separate, resulting in difficulty in recycling; or a large amount of noble metals are used as active components, so that resource waste and high cost are caused; or the activity of the catalyst is not very high; or the reaction conditions are very demanding. Noble metal catalysts such as Raney type catalysts, metal rhodium-based catalysts and the like have high cost, low recovery rate and easy inactivation, and simultaneously, a large amount of alkaline water (ammonia water) is used, so that the equipment corrosion is serious, the wastewater treatment capacity is large, the reaction pressure is high, the production cost is further increased, and the economic benefit is not obvious; in the case of amorphous alloy catalysts, the hydrogen consumption in the gas phase process is very high and the reaction temperature is very high, resulting in high production costs and a complicated process. Therefore, the catalyst is suitable for liquid-phase adiponitrile hydrogenation reaction, has low cost and good performance, and has important research value and application prospect.
Disclosure of Invention
The invention aims to provide a preparation method and application of an oxidation-modified carbon nanotube-loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst which is suitable for liquid-phase adiponitrile hydrogenation reaction and has low cost and good performance.
The technical scheme of the invention is as follows:
a preparation method of an oxidation modified carbon nanotube loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst comprises the following steps:
(1) Placing a multi-walled carbon nanotube into a round-bottom flask, adding nitric-sulfuric mixed acid with a corresponding volume according to a liquid-solid ratio of 50-100mL/g, stirring, condensing and refluxing for 8-12 hours in a constant-temperature oil bath kettle at 80-120 ℃, then washing the carbon nanotube to be neutral by deionized water, drying the carbon nanotube, placing the dried carbon nanotube into the round-bottom flask, preparing hydrogen peroxide solution with a series of concentrations of 0.45-2.5mol/L, and adding H with a corresponding volume according to a liquid-solid ratio of 20-30mL/g 2 O 2 Refluxing at 30-50 deg.C for 10-15 hr; washing the treated carbon nanotube (O-MWCNT) with absolute ethyl alcohol, and then drying;
(2) Taking the oxidized multi-wall carbon nano-particles obtained in the step (1)The tube (O-MWCNT) is placed in a round bottom flask, a corresponding volume of deionized water is added according to the liquid-solid ratio of 5-10mL/g, ultrasonic stirring is carried out for 1-2 hours at 30-40 ℃, and then Ni (NO 3 ) 2 . 6H 2 O、Cu(NO 3 ) 2 . 3H 2 O and Mg (NO) 3 ) 2 . 6H 2 Continuously carrying out ultrasonic treatment on the O mixed solution at 30-40 ℃ for 2-6 hours, then heating to 75-95 ℃ to evaporate redundant water at constant temperature, keeping the liquid-solid ratio at 5-10mL/g, then transferring the round-bottom flask to a constant-temperature water bath kettle at 30-50 ℃, ageing at constant temperature for 10-24 hours under the stirring condition, obtaining a paste-like substance after ageing, drying, grinding and sieving the paste-like substance;
(3) Putting the powdery solid obtained in the step (2) into a quartz boat, and heating to 250-550 ℃ under the protection of nitrogen to roast for 4-8 hours;
(4) And (4) putting the powdery substance of the catalyst precursor obtained in the step (3) into a quartz boat, firstly raising the temperature to 250-550 ℃ under the protection of nitrogen, then introducing hydrogen at constant temperature for reduction for 3-8 hours, and then cooling under the protection of nitrogen to obtain the oxidation-modified carbon nano tube-loaded nickel-based multi-metal catalyst, namely MgO-Cu-Ni/O-MWCNT.
Furthermore, in the mixed nitric-sulfuric acid in the step (1), the volume ratio of nitric acid to sulfuric acid is 2-5.
Further, the stirring speed of the step (1) is 750-1000rpm.
Further, the number of deionization washing in step (1) is 10 to 15.
Further, the number of washing times with absolute ethanol in the step (1) is 10 to 15.
Further, the drying in the step (1) is vacuum drying, the temperature is 90-120 ℃, and the time is 3-5 hours.
Further, in the step (2), the stirring speed for aging is 750-1000rpm; the drying is vacuum drying, the temperature is 100-150 ℃, and the time is 10-15 hours; sieving to control the powder size to 100-200 mesh.
Further, in the step (3), the nitrogen is high-purity nitrogen with the purity of more than 99 percent, the flow rate is 30-80mL/min, the temperature is increased by adopting a program, and the temperature increasing speed is 5-10 ℃/min.
Further, in the step (4), the introduced nitrogen is high-purity nitrogen with the purity of more than 99% under the protection of nitrogen, the introduced flow rate is 30-80mL/min, and the programmed heating rate is 5-10 ℃/min; the hydrogen gas introduced by the hydrogen gas reduction is high-purity hydrogen with the purity of more than 99 percent, and the introduction flow rate is 30-80mL/min.
The catalyst obtained by the preparation method is used for adiponitrile hydrogenation reaction and comprises the following steps:
(A) Adding adiponitrile and a quaternary amorphous nickel-based catalyst loaded on a carbon nanotube with the mass of 5-30% into a reaction kettle, and adding a solvent ethanol;
(B) Sealing the reaction kettle, replacing 8978 zxft With nitrogen for 8978 times, vacuumizing the reaction kettle by using a circulating vacuum pump, heating to 40-70 ℃, introducing hydrogen, and starting stirring at the stirring speed of 500-1000rpm;
(C) After the reaction temperature is reached, the pressure is adjusted to 1 to 2.5MPa, and the reaction is carried out for 1 to 10 hours.
The invention has the beneficial effects that:
(1) The invention utilizes hydrogen peroxide H 2 O 2 And (3) loading the multi-wall carbon nano tube subjected to oxidation treatment with a multi-metal nickel-based catalyst to obtain the oxidation-modified carbon nano tube loaded double-gold metal copper-magnesium co-doped nickel-based multi-metal catalyst. The introduction of Cu can effectively reduce the reduction energy of the Ni precursor, greatly promote the dispersion of metal Ni nano particles on the surface of the carbon nano tube, and simultaneously promote more Ni through the metal synergistic effect between Cu and Ni 0+ Is performed. The introduction of Mg provides a large number of basic sites for the surface of the catalyst, and the formation of NiO-MgO eutectic is beneficial to inhibiting excessive hydrogenation of reactants and avoiding the formation of excessive byproducts. The unique mesoporous structure of the carrier multi-walled carbon nano-tube and the strong interaction between the carrier multi-walled carbon nano-tube and the active component greatly improve the hydrogenation activity of the catalyst. The oxidation treatment of the carbon nano tube can effectively increase-OH and-COOH functional groups on the surface of the carbon nano tube, thereby effectively promoting the synergistic effect between the carbon tube and the active component and simultaneously increasing the surface of the carbon tubeThe defect position of the surface promotes the adsorption of active components on the surface of the carbon tube, thereby promoting the dispersion of nickel and forming superfine nickel nano particles.
(2) The catalyst obtained by the invention has high activity and low preparation cost, is used for hydrogenation of adiponitrile to co-produce 6-aminocapronitrile and hexamethylene diamine, has high conversion rate of adiponitrile and high total selectivity of products, does not need to add a large amount of ammonia or alkali metal hydroxide to inhibit formation of byproducts, does not cause serious corrosion of equipment, enables the adiponitrile hydrogenation process to be more environment-friendly, has mild reaction conditions, can obviously reduce reaction hydrogen pressure and reaction temperature, and has good industrial application prospect.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the present invention is not limited thereto.
Example 1
Weighing 4g of multi-walled carbon nanotubes, placing the multi-walled carbon nanotubes in a 350mL round-bottom flask, adding nitric-sulfuric mixed acid (V (nitric acid)/V (sulfuric acid) = 3) with a corresponding volume according to the liquid-solid ratio of 50mL/g, and carrying out condensation reflux treatment for 10 hours at the stirring speed of 750rpm in a constant-temperature oil bath kettle at the temperature of 100 ℃. And repeatedly washing the carbon nano tube subjected to the reflux treatment by using deionized water for 10 times until the carbon nano tube is neutral. And (3) putting the washed carbon tube into a vacuum drying oven, and drying for 3 hours at a constant temperature of 110 ℃. 3g of the carbon nano tube treated above is placed in a 150mL round-bottom flask, and hydrogen peroxide H with the concentration of 1.5mol/L is prepared 2 O 2 Adding the solution into the corresponding volume of H according to the liquid-solid ratio of 25 mL/g 2 O 2 Reflux treatment was carried out at 40 ℃ for 12 hours. The carbon nanotubes (O-MWCNT) after the above oxidation treatment were washed with a large amount of anhydrous ethanol 10 times, and then placed in a vacuum drying oven to be vacuum-dried at a constant temperature of 100 ℃ for 3 hours. 2g of the oxidized multi-walled carbon nanotube (O-MWCNT) was placed in a 50mL round-bottomed flask, 10mL of deionized water was added at a liquid-solid ratio of 25 mL/g, and the mixture was ultrasonically stirred at 30 ℃ for 1 hour by an ultrasonic instrument. Dissolve 1.992gNi (NO) in 5mL deionized water 3 ) 2 . 6H 2 O、0.081gCu(NO 3 ) 2 . 3H 2 O and 0.214gMg (NO) 3 ) 2 . 6H 2 After O, the solution was rapidly added to the carbon nanotubes during stirring, sonicated at 30 ℃ for 3 hours using a sonicator, excess water was evaporated at 85 ℃ at constant temperature to maintain the liquid-solid ratio in the round-bottomed flask at 5mL/g, and the round-bottomed flask was transferred to a constant temperature water bath at 30 ℃ and aged at 750rpm for 12 hours at constant temperature. After aging, a paste-like material was obtained, which was placed in a vacuum drying oven and vacuum-dried at 120 ℃ for 12 hours. Grinding into powder with a mortar, and sieving with a 150-mesh sieve to keep the mesh number at not less than 150 meshes. Putting the obtained powdery solid in a quartz boat, putting the quartz boat in a quartz tube in a tube furnace, introducing high-purity nitrogen with the purity of more than 99 percent at the flow rate of 50mL/min, heating the quartz boat from 30 ℃ to 350 ℃ at the speed of 5 ℃/min, and roasting the quartz boat for 4 hours at the constant temperature of 350 ℃; putting the treated powdery catalyst precursor into a quartz boat, putting the quartz boat into a quartz tube in a tube furnace, heating the quartz boat from 30 ℃ to 350 ℃ at the heating rate of 5 ℃/min under the protection of high-purity nitrogen with the flow of 50mL/min being more than 99%, introducing high-purity hydrogen with the flow of 50mL/min being more than 99%, and introducing hydrogen at the constant temperature of 350 ℃ for reduction for 4 hours; after the reduction time, the high-purity nitrogen with the purity of more than 99 percent is introduced at the flow rate of 50mL/min and the temperature is reduced to the room temperature.
Weighing 0.55 g of the oxidation-modified carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Cu-Ni/O-MWCNT) catalyst, placing the catalyst into a 100mL inner liner of a high-temperature reaction kettle, adding 25mL of absolute ethanol and 2.5 g of adiponitrile, placing magnetons, sealing the high-pressure kettle, replacing air in the kettle for 4 times with nitrogen, vacuumizing the kettle by a vacuum pump, and then placing the reaction kettle into an oil bath. When the reaction temperature is raised to 45 ℃, introducing hydrogen and pressurizing to 2 MPa, starting magnetic stirring at the stirring speed of 750rpm, starting reaction timing, reacting for 6 hours, filtering the reaction mixed liquid, and analyzing the content of each substance in the filtrate by using gas chromatography. The conversion of adiponitrile was 90.65%, the selectivity to 6-aminocapronitrile was 66.32%, the selectivity to hexamethylene diamine was 25.41%, and the overall selectivity was 91.73%.
Example 2
0.55 g of the oxidation-modified carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Cu-Ni/O-MWCNT) obtained in example 1 was weighed and placed in a 100 mL-lined high-temperature reaction vessel, 25mL of absolute ethanol and 2.5 g of adiponitrile were added, magnetons were placed, the autoclave was sealed, the air in the vessel was replaced with nitrogen 4 times, the vessel was evacuated by a vacuum pump, and then the reaction vessel was placed in an oil bath. When the reaction temperature is raised to 55 ℃, introducing hydrogen and pressurizing to 2 MPa, starting magnetic stirring, wherein the stirring speed is 750rpm, starting reaction timing, filtering the reaction mixed liquid after 6 hours of reaction, and analyzing the content of each substance in the filtrate by using gas chromatography. The conversion of adiponitrile was 97.85%, the selectivity to 6-aminocapronitrile was 60.11%, the selectivity to hexamethylene diamine was 32.31%, and the overall selectivity was 92.42%.
Example 3
0.55 g of the oxidation-modified carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Cu-Ni/O-MWCNT) obtained in example 1 is weighed and placed in a 100mL inner liner of a high-temperature reaction kettle, 25mL of absolute ethanol and 2.5 g of adiponitrile are added, magnetons are added, the high-pressure kettle is sealed, air in the kettle is replaced by nitrogen for 4 times, the kettle is vacuumized by a vacuum pump, and then the reaction kettle is placed in an oil bath. When the reaction temperature is increased to 65 ℃, introducing hydrogen and pressurizing to 2 MPa, starting magnetic stirring, wherein the stirring speed is 750rpm, starting reaction timing, filtering the reaction mixed liquid after 6 hours of reaction, and analyzing the content of each substance in the filtrate by using gas chromatography. The conversion of adiponitrile was 100%, the selectivity to 6-aminocapronitrile was 20.31%, the selectivity to hexamethylene diamine was 62.98%, and the overall selectivity was 83.29%.
Example 4
The catalyst of examples 1, 2 and 3 was separated from the reaction mixture, washed with absolute ethanol several times, vacuum-dried at 100 ℃ and collected for further use. Weighing 0.55 g of the above-mentioned circulating oxidation-modified carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Cu-Ni/O-MWCNT-R1) catalyst, placing it into a 100mL liner of a high-temperature reaction kettle, adding 25mL of absolute ethanol, 2.5 g of adiponitrile, placing in magnetons, sealing the autoclave, replacing the air in the kettle with nitrogen for 4 times, vacuumizing the kettle by a vacuum pump, and then placing the reaction kettle into an oil bath. When the temperature is raised to 55 ℃, hydrogen is introduced and the pressure is increased to 2 MPa, magnetic stirring is started, the stirring speed is 750rpm, the reaction timing is started, after 6 hours of reaction, the reaction mixed liquid is filtered, and the content of each substance in the filtrate is analyzed by gas chromatography. The conversion of adiponitrile was 96.98%, the selectivity to 6-aminocapronitrile was 61.22%, the selectivity to hexamethylene diamine was 31.93%, and the overall selectivity was 93.15%.
In the same step, the catalyst of the reaction is recycled for the second time, 0.55 g of the recycled MgO-Cu-Ni/O-MWCNT-R2 catalyst is weighed and placed in a 100mL liner of a high-temperature reaction kettle, 25mL of absolute ethyl alcohol and 2.5 g of adiponitrile are added, magnetons are placed, the autoclave is sealed, air in the autoclave is replaced by nitrogen for 4 times, the autoclave is vacuumized by a vacuum pump, and then the reaction kettle is placed in an oil bath. When the temperature is raised to 55 ℃, hydrogen is introduced and the pressure is increased to 2 MPa, magnetic stirring is started, the stirring speed is 750rpm, the reaction timing is started, after 6 hours of reaction, the reaction mixed liquid is filtered, and the content of each substance in the filtrate is analyzed by gas chromatography. The conversion of adiponitrile was 94.34%, the selectivity to 6-aminocapronitrile was 60.79%, the selectivity to hexamethylene diamine was 31.88%, and the overall selectivity was 92.67%.
Comparative example 1
Weighing 4g of multi-walled carbon nanotubes, placing the multi-walled carbon nanotubes in a 350mL round-bottom flask, adding nitric-sulfuric mixed acid (V (nitric acid)/V (sulfuric acid) = 3) with the corresponding volume according to the liquid-solid ratio of 50mL/g, and carrying out condensation reflux treatment for 10 hours at the stirring speed of 750rpm in a constant-temperature oil bath kettle at the temperature of 100 ℃. And repeatedly washing the carbon nano tube subjected to the reflux treatment by using deionized water for 10 times until the carbon nano tube is neutral. The carbon tube after washing was dried in a vacuum drying oven at a constant temperature of 110 ℃ for 3 hours. 3g of the carbon nano tube treated above is placed in a 150mL round-bottom flask, and hydrogen peroxide H with the concentration of 1.5mol/L is prepared 2 O 2 Adding the solution into the corresponding volume of H according to the liquid-solid ratio of 25 mL/g 2 O 2 The mixture was refluxed at a constant temperature of 40 ℃ for 12 hours. The carbon nanotubes (O-MWCNT) after the above oxidation treatment were washed with a large amount of anhydrous ethanol 10 times, and then placed in a vacuum drying oven to be vacuum-dried at a constant temperature of 100 ℃ for 3 hours. Placing 2g of the above oxidized multi-walled carbon nanotubes (O-MWCNT) in a 50mL round-bottom flask, adding 10mL deionized water at a liquid-solid ratio of 25 mL/g, and ultrasonically stirring with an ultrasonic instrument at 30 ℃ for 1 hourWhen the user wants to use the device. Dissolve 1.992gNi (NO) in 5mL deionized water 3 ) 2 . 6H 2 O and 0.214gMg (NO) 3 ) 2 . 6H 2 After O, the solution is quickly added into the carbon nano tube in the stirring process, ultrasonic treatment is carried out for 3 hours by using an ultrasonic instrument at the temperature of 30 ℃, and redundant water is evaporated at the constant temperature of 85 ℃, so that the liquid-solid ratio in the round-bottom flask is kept at 5mLg -1 Then, the round-bottom flask was transferred to a constant temperature water bath at 30 ℃ and aged at 750rpm for 12 hours. After aging, a paste-like material was obtained, which was placed in a vacuum drying oven and vacuum-dried at 120 ℃ for 12 hours. Grinding into powder with mortar, sieving with 150 mesh sieve, and keeping mesh number at 150 mesh or more. Putting the obtained powdery solid in a quartz boat, putting the quartz boat in a quartz tube in a tube furnace, introducing high-purity nitrogen with the purity of more than 99 percent at the flow rate of 50mL/min, heating from 30 ℃ to 350 ℃ at the speed of 5 ℃/min, and roasting for 4 hours at the constant temperature of 350 ℃; putting the treated catalyst precursor powdery substance into a quartz boat, putting the quartz boat into a quartz tube in a tube furnace, heating the quartz boat from 30 ℃ to 350 ℃ at the heating rate of 5 ℃/min under the protection of high-purity nitrogen with the flow rate of 50mL/min and the temperature of more than 99%, introducing high-purity hydrogen with the flow rate of 50mL/min and the temperature of more than 99%, and introducing hydrogen to reduce the quartz boat for 4 hours at the constant temperature of 350 ℃; after the reduction time, the high-purity nitrogen with the purity of more than 99 percent is introduced at the flow rate of 50mL/min and is cooled to the room temperature.
Weighing 0.55 g of the carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Ni/O-MWCNT) catalyst, placing the catalyst into a 100mL inner liner of a high-temperature reaction kettle, adding 25mL of absolute ethyl alcohol and 2.5 g of adiponitrile, placing magnetons, sealing the high-pressure kettle, replacing air in the kettle with nitrogen for 4 times, vacuumizing the kettle by a vacuum pump, and then placing the reaction kettle into an oil bath. When the reaction temperature is raised to 45 ℃, introducing hydrogen and pressurizing to 2 MPa, starting magnetic stirring at the stirring speed of 750rpm, starting reaction timing, reacting for 6 hours, filtering the reaction mixed liquid, and analyzing the content of each substance in the filtrate by using gas chromatography. The conversion of adiponitrile was 75.12%, the selectivity to 6-aminocapronitrile was 71.13%, the selectivity to hexamethylene diamine was 9.67%, and the overall selectivity was 80.8%.
Comparative example 2
Weighing 0.55 g of the carbon nanotube-supported nickel-based polymetallic catalyst (MgO-Ni/O-MWCNT) catalyst, placing the catalyst into a 100mL inner liner of a high-temperature reaction kettle, adding 25mL of absolute ethyl alcohol and 2.5 g of adiponitrile, placing magnetons, sealing the high-pressure kettle, replacing air in the kettle with nitrogen for 4 times, vacuumizing the kettle by a vacuum pump, and then placing the reaction kettle into an oil bath. When the reaction temperature is raised to 55 ℃, introducing hydrogen and pressurizing to 2 MPa, starting magnetic stirring, wherein the stirring speed is 750rpm, starting reaction timing, filtering the reaction mixed liquid after 6 hours of reaction, and analyzing the content of each substance in the filtrate by using gas chromatography. The conversion of adiponitrile was 80.63%, the selectivity to 6-aminocapronitrile was 62.58%, the selectivity to hexamethylene diamine was 20.96%, and the overall selectivity was 83.54%.
Claims (9)
1. The application of the oxidation-modified carbon nanotube-loaded bimetallic copper-magnesium co-doped nickel-based multi-metal catalyst in the hydrogenation reaction of adiponitrile is characterized by comprising the following steps of:
(1) Putting multi-wall carbon nano-tubes into a round bottom flask, adding nitric-sulfuric mixed acid with corresponding volume according to liquid-solid ratio of 50-100mL/g, stirring, condensing and refluxing for 8-12 hours in a constant-temperature oil bath kettle at 80-120 ℃, then washing the carbon nano-tubes to be neutral by deionized water, drying the carbon nano-tubes, putting the dried carbon nano-tubes into the round bottom flask, preparing hydrogen peroxide solution with 0.45-2.5mol/L series concentration, adding H with corresponding volume according to liquid-solid ratio of 20-30mL/g 2 O 2 Refluxing at 30-50 deg.C for 10-15 hr; washing the treated carbon nano tube (O-MWCNT) by using absolute ethyl alcohol, and then drying;
(2) Placing the oxidized multi-walled carbon nanotube (O-MWCNT) obtained in the step (1) into a round-bottom flask, adding deionized water with a corresponding volume according to a liquid-solid ratio of 5-10mL/g, ultrasonically stirring for 1-2 hours at 30-40 ℃, and then adding Ni (NO) 3 ) 2 ·6H 2 O、Cu(NO 3 ) 2 ·3H 2 O and Mg (NO) 3 ) 2 ·6H 2 Mixing with O, and continuously performing ultrasonic treatment at 30-40 deg.CTreating for 2-6 hr, heating to 75-95 deg.C, evaporating excessive water at constant temperature to keep liquid-solid ratio at 5-10mL/g, transferring round bottom flask to 30-50 deg.C constant temperature water bath, stirring, aging at constant temperature for 10-24 hr to obtain paste-like substance, drying, grinding, and sieving;
(3) Putting the powdery solid obtained in the step (2) into a quartz boat, and heating to 250-550 ℃ under the protection of nitrogen to roast for 4-8 hours;
(4) And (4) putting the powdery substance of the catalyst precursor obtained in the step (3) into a quartz boat, firstly heating to 250-550 ℃ under the protection of nitrogen, then introducing hydrogen at constant temperature for reduction for 3-8 hours, and then cooling under the protection of nitrogen to obtain the oxidation-modified carbon nano tube-loaded nickel-based multi-metal catalyst, namely MgO-Cu-Ni/O-MWCNT.
2. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based multimetal catalyst in the adiponitrile hydrogenation reaction of claim 1, wherein the volume ratio of nitric acid to sulfuric acid in the nitric-sulfuric mixed acid in the step (1) is 2-5.
3. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based polymetallic catalyst in the adiponitrile hydrogenation reaction is characterized in that the stirring speed in the step (1) is 750-1000rpm.
4. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based multimetal catalyst in the adiponitrile hydrogenation reaction of claim 1, wherein in the step (1), the number of deionization washing times is 10-15; the washing times with anhydrous ethanol are 10-15 times.
5. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based polymetallic catalyst in the adiponitrile hydrogenation reaction is characterized in that the drying in the step (1) is vacuum drying at the temperature of 90-120 ℃ for 3-5 hours.
6. The application of the oxidation modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based multimetal catalyst in the adiponitrile hydrogenation reaction of claim 1, wherein in the step (2), the stirring speed for aging is 750-1000rpm; the drying is vacuum drying, the temperature is 100-150 ℃, and the time is 10-15 hours; sieving to control the powder size to 100-200 mesh.
7. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based polymetallic catalyst in the adiponitrile hydrogenation reaction is characterized in that in the step (3), nitrogen is high-purity nitrogen with the purity of more than 99%, the flow rate is 30-80mL/min, the temperature is increased by adopting a temperature programming method, and the temperature increasing rate is 5-10 ℃/min.
8. The application of the oxidation-modified carbon nanotube-supported bimetallic copper-magnesium co-doped nickel-based polymetallic catalyst in the adiponitrile hydrogenation reaction is characterized in that in the step (4), introduced nitrogen is protected by nitrogen and is high-purity nitrogen with the purity of more than 99%, the introduced flow rate is 30-80mL/min, and the programmed temperature rise rate is 5-10 ℃/min; the hydrogen introduced by the hydrogen reduction is high-purity hydrogen with the purity of more than 99 percent, and the introduction flow is 30-80mL/min.
9. The application of the oxidation modified carbon nanotube supported bimetallic copper-magnesium co-doped nickel-based multimetallic catalyst in adiponitrile hydrogenation reaction according to claim 1, which comprises the following steps:
(A) Adding adiponitrile and a quaternary amorphous nickel-based catalyst loaded by carbon nano tubes with the mass of 5-30% into a reaction kettle, and adding a solvent ethanol;
(B) Sealing the reaction kettle, replacing the reaction kettle with nitrogen for 1-6 times, vacuumizing the reaction kettle by using a circulating vacuum pump, heating to 40-70 ℃, introducing hydrogen and starting stirring, wherein the stirring speed is 500-1000rpm;
(C) After the reaction temperature is reached, the pressure is adjusted to 1-2.5 MPa, and the reaction lasts for 1-10 hours.
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