A method for producing methylpentanediamine and methylpiperidine by hydrogenating methylglutaronitrile

Abstract

The present invention provides a method for hydrogenating methylglutaronitrile to produce methylpentanediamine and methylpiperidine, belonging to the field of chemical engineering technology. The method includes: a mixed solution of 2-methylglutaronitrile and a hydrogen-containing solvent enters the lower part of a tubular reactor through a feed pump and a preheater together with a liquid-solid phase material from a high-pressure circulation pump. Hydrogen enters a gas distributor at the bottom of the tubular reactor. The formed gas-liquid-solid three-phase material undergoes a catalytic hydrogenation reaction during the upward movement from the bottom of the tubular reactor, and gas-phase separation is carried out. The unreacted hydrogen is recycled. The liquid-solid material at the bottom of the high-pressure gas-liquid-solid separator is returned to the tubular reactor by a high-pressure circulation pump. The liquid phase extracted from the middle part is sent to a low-pressure liquid-solid separator after pressure reduction. The catalyst separated at the bottom is recovered to a catalyst preparation system. The liquid phase extracted from the middle part enters a hydrogen-containing solvent recovery tower. The hydrogen-containing solvent recovered from the top of the tower is sent back to the raw material tank, and the product is obtained at the bottom of the tower. The method of the present invention is more stable, and the reaction and separation equipment has a small volume and a large production capacity.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering technologies, and particularly relates to a method for producing methylpentanediamine and methylpiperidine by hydrogenating methylglutaronitrile. Background Art

[0002] At present, the industrial production methods of adiponitrile mainly include butadiene hydrocyanation method, adipic acid ammoniation method, caprolactam ammoniation hydrogenation method and acrylonitrile electrolytic dimerization method. The mainstream route is the butadiene hydrocyanation method. However, 15-20% of 2-methylglutaronitrile (MGN) is produced as a by-product during the production process of this route. Therefore, with the continuous expansion of adiponitrile production, a large amount of 2-methylglutaronitrile is brought about. How to improve the economic value of 2-methylglutaronitrile has important industrial significance. Among them, the route of preparing 2-methylpentanediamine (MPMD) and 3-methylpiperidine (MPP) by catalytic hydrogenation of 2-methylglutaronitrile has relatively high economic value. 2-Methylpentanediamine is an important chemical and pharmaceutical intermediate, mainly used for producing polyamide plastics, films and fibers, polyamide adhesives and printing resins, and epoxy resin curing agents. 3-Methylpiperidine is an important organic solvent and can also be used for preparing coatings, dyes, dye auxiliaries and fine chemical products, etc. 2-Methylpentanediamine and 3-methylpiperidine can be hydrogenated to obtain an important organic intermediate β-methylpyridine, which can be used for synthesizing nicotinic acid and nicotinamide, etc. It has a large demand in fine chemical industries such as feed, pesticides, pharmaceuticals and food, and has a good market prospect.

[0003] Generally, a corresponding aliphatic diamine compound is prepared by catalytic hydrogenation of a dinitrile compound. The commonly used catalyst is a Raney nickel catalyst. At the same time, during the hydrogenation process of the dinitrile compound, the intermediate product aminonitrile is prone to side reactions to produce corresponding nitrogen-containing heterocyclic compounds. "Petrochemical Technology" reported in 2010, Volume 39 that amorphous Fe-Mo-Ni-Al catalyst was used to catalyze the hydrogenation of glutaronitrile to prepare pentanediamine. Under the optimized conditions of catalyst dosage of 15%, NaOH cocatalyst dosage of 0.25%, reaction pressure of 3 MPa and reaction temperature of 70 °C, the conversion rate of glutaronitrile was 100%, and the selectivity of pentanediamine reached 66.8%. The literature Appl. Catal. A: Gen. 2009 reported that doping a small amount of Mo, Cr or Fe additives to a Raney nickel catalyst could significantly improve the yield of the aliphatic diamine product.

[0004] U.S. Patent US4885391 discloses a method for hydrogenating MGN to MPMD. Using a chromium-modified Raney cobalt catalyst at 80-150 °C, 2.8-17.2 MPa and in the presence of water, the reaction raw material MGN is basically completely converted, and the selectivities of the products MPMD and MPP are 70.8% and 13.4% respectively, but the heavy by-products are 11.8%.

[0005] Patent CN101990532 / WO2009121704 discloses a preparation method of 2-methylpentanediamine and 3-methylpiperidine. Using a Raney cobalt catalyst doped with nickel and chromium, under the conditions of a reaction pressure less than 5.0 MPa, a temperature of 60 - 160 °C, and the presence of a strong basic inorganic compound, complete conversion of MGN can be achieved, and the selectivities of the products MPMD and MPP are 80% and 20% respectively; for the dinitrile mixture, MGN is completely converted, and the selectivities of the products MPMD and MPP are 64% and 28% respectively. French patents FR2306204 - 2306208 report a method for the hydrogenation conversion of MGN to a mixture of MPMD and MPP based on a nickel or Raney nickel catalyst at a certain temperature and hydrogen pressure. The ratio of the products MPMD and MPP can be adjusted by changing the solvent and catalyst used. The above relevant reports or patent disclosures mainly focus on the high-pressure discontinuous hydrogenation process using a batch reactor, which has problems such as long reaction time, discontinuous production, and safety factors.

[0006] Chinese invention patent CN11137820.B discloses the use of a Raney nickel composite catalyst doped with Ru and Mo, and a bubble flow reactor for the hydrogenation production of 2-methylpentanediamine from 2-methylglutaronitrile. The reaction temperature is 70 - 100 °C, the reaction pressure is 2.3 - 6.0 MPa, the reaction time is 15 - 50 min, and the hydrogen and liquid phase flow rate ratio is 10 - 20:1. However, this process still has problems such as long reaction time, high reaction pressure, low hydrogen utilization rate, and high selectivity of by-products. The operation stability is not clear, and there is no industrial-related report. Summary of the Invention

[0007] The object of the present invention is to provide a method for the hydrogenation production of methylpentanediamine and methylpiperidine from methylglutaronitrile, which overcomes the serious equipment wear and blockage caused by the current use of high-pressure piston pumps or diaphragm pumps to transport liquid-solid slurries, and solves the problems of frequent equipment shutdown for maintenance and unstable materials in the production system.

[0008] The technical solution of the present invention is realized as follows:

[0009] A method for the hydrogenation production of methylpentanediamine and methylpiperidine from methylglutaronitrile, comprising the following steps:

[0010] (1) The mixed solution of 2-methylglutaronitrile and hydrogen-dissolving solvent in the raw material tank is pressurized by a feed pump and heated by a preheater, and then enters the lower feed pipe of the tubular reactor together with the liquid-solid phase material from the high-pressure circulation pump. The hydrogen from the hydrogen circulator and the fresh supplementary hydrogen converge and enter the gas distributor at the bottom of the tubular reactor. The hydrogen and the liquid-solid phase material form a gas-liquid-solid three-phase material and undergo a hydrogenation reaction during the upward movement from the bottom of the tubular reactor.

[0011] (2) The gas-liquid-solid three-phase material undergoes gas-phase - liquid-solid phase separation in the upper part of the reactor, and the liquid-solid phase material overflows and enters the high-pressure gas-liquid-solid separator for further gas-phase separation; the separated hydrogen gas converges, and after cooling and separation, it returns to the bottom of the tubular reactor by the hydrogen gas recycle compressor; the liquid-solid phase material at the bottom of the high-pressure gas-liquid-solid separator returns to the lower part of the tubular reactor by the high-pressure recycle pump.

[0012] (3) The liquid phase withdrawn from the middle of the high-pressure gas-liquid-solid separator is sent to the low-pressure liquid-solid separator after pressure reduction. The liquid phase withdrawn from the middle of the low-pressure liquid-solid separator enters the hydrogen-dissolving solvent recovery tower. The hydrogen-dissolving solvent recovered from the top of the tower is sent back to the raw material tank, and the bottom of the tower is the mixed liquid of product methylpentanediamine and methylpiperidine, which is sent to the product intermediate tank.

[0013] (4) A small amount of the catalyst separated by the low-pressure liquid-solid separator is recovered to the catalyst preparation system for on-line catalyst regeneration and replenishment.

[0014] As a further improvement of the present invention, the mixed liquid in the raw material tank is prepared according to the mass ratio of 2-methylglutaronitrile to the hydrogen-dissolving solvent of 1.0 - 4.0:1.0, preferably 1.0:1.0; the hydrogen-dissolving solvent is methanol or ethanol, preferably ethanol; it is pressurized to 2.0 - 3.0 MPa by the feed pump, preferably 2.3 - 2.5 MPa; the mixed liquid is preheated to 50 - 90 °C by the preheater, preferably 55 - 65 °C.

[0015] As a further improvement of the present invention, the mixed liquid of methylglutaronitrile and the hydrogen-dissolving solvent is pressurized by the feed pump and preheated by the preheater, and enters the liquid-solid phase material feed pipe at the lower part of the tubular reactor together with the liquid-solid phase material from the high-pressure recycle pump. Among them, the volume flow ratio of the liquid-solid phase material of the high-pressure recycle pump to the mixed liquid of 2-methylglutaronitrile and the hydrogen-dissolving solvent from the feed pump is 300 - 600, preferably 400. The residence time of the mixed liquid phase in the reaction tube is 5 - 15 seconds, preferably 6 seconds.

[0016] As a further improvement of the present invention, the hydrogen gas from the hydrogen gas recycle compressor and the freshly supplemented hydrogen converge and enter the gas distributor at the bottom of the tubular reactor. Among them, the single-hole diameter on the orifice plate of the distributor is 1.0 - 2.0 mm, and it is evenly distributed; the volume flow ratio of the hydrogen gas (standard state) entering the bottom of the tubular reactor to the liquid-solid phase material of the high-pressure recycle pump is 0.3 - 0.5:1.0, preferably 0.4:1.0.

[0017] As a further improvement of the present invention, the tubular reactor is a double-tube empty tube bubbling reactor, with the inner tube being the reaction section and the outer tube being the water-cooling section. The height of the reaction section is the length from the lower liquid-solid material feed pipe orifice to the upper liquid-solid overflow orifice. The diameter-to-height ratio of the reaction section of the tubular reactor is 60–80, preferably 70. A plate-type gas distributor is provided at the bottom, and the lower liquid-solid material feed pipe is arranged above the gas distributor. The reaction pressure in the reaction section of the tubular reactor is 2.0 - 3.0 MPa, preferably 2.3 - 2.5 MPa; the reaction temperature is 50 - 90 °C, preferably 55 - 65 °C. The hydrogenation reaction of 2-methylglutaronitrile is an exothermic reaction, and heat is removed by water cooling in the outer tube cooling section to control the reaction temperature at 50 - 90 °C, preferably 55 - 65 °C.

[0018] As a further improvement of the present invention, the gas-liquid-solid three-phase material that undergoes the hydrogenation reaction during the upward movement from the bottom of the reactor is as follows: the gas phase is hydrogen, the solid phase is a catalyst, and the catalyst is a modified nickel catalyst. The liquid phase is a mixed solution composed of 2-methylglutaronitrile, 2-methylpentanediamine, 3-methylpiperidine, hydrogenation by-products, an alkaline auxiliary agent, and a hydrogen-dissolving solvent. During the upward movement of the gas-liquid-solid three-phase material from the bottom of the reactor, the solid-phase catalyst accounts for 10 - 20% of the mass of the three-phase mixed solution, preferably 13%; the alkaline auxiliary agent is sodium hydroxide or potassium hydroxide, and the proportion is 0.01 - 0.5% of the mass of the three-phase mixed solution, preferably 0.3%.

[0019] Preferably, the preparation method of the modified nickel catalyst is as follows:

[0020] S1. Preparation of the composite metal layered oxide: Dissolve an aluminum salt and a magnesium salt in water, add an alkali, heat for crystallization, filter, wash, dry, and calcine to obtain the composite metal layered oxide;

[0021] S2. Magnetic modification: Add the composite metal layered oxide to water, add ferric chloride and ferrous chloride, and under the protection of an inert gas, dropwise add ammonia water, heat and stir for reaction, centrifuge, wash, dry, and calcine to obtain the magnetic composite metal layered oxide;

[0022] S3. Coating with graphene: Disperse graphene oxide in water, add the magnetic composite metal layered oxide, ultrasonically disperse evenly, spray dry, and reduce with hydrazine vapor to obtain the graphene-coated magnetic composite metal layered oxide;

[0023] S4. Preparation of the impregnation solution: Dissolve a nickel salt, a molybdenum salt, and a chromium salt in water to obtain the impregnation solution;

[0024] S5. Preparation of the modified nickel catalyst: Add the graphene-coated magnetic composite metal layered oxide to the impregnation solution, heat to evaporate the solvent, and calcine to obtain the modified nickel catalyst.

[0025] Ordinary Raney nickel catalysts have disadvantages such as poor activity and stability, being prone to fragmentation, and easy loss of Ni and Al during the reaction process, which greatly affects the catalytic activity. The catalyst modified by Mo and Cr can not only improve the catalytic activity but also reduce the loss of Ni and Al. In addition, in the gas-liquid-solid three-phase reaction, changing the stirring speed can change the contact surface and mass transfer surface area of the three-phase reaction. To overcome the influence of external diffusion of the catalyst, a relatively high stirring speed is often used, which also causes serious pulverization of the catalyst. The shear force caused by high-speed stirring will cause wear of the catalyst, thus greatly reducing the catalytic activity. At the same time, due to severe pulverization during the reaction, its separation from the product becomes extremely difficult. The present invention prepares a composite metal layered oxide, loads magnetic iron oxide, and in-situ generates Ni, thereby greatly reducing the inactivation and loss of the catalyst due to pulverization and improving the activity of the catalytic reaction.

[0026] In the present invention, a carbon layer is deposited on the surface of the prepared magnetic composite layered metal oxide by chemical vapor deposition. On the one hand, it greatly increases the specific surface area of the carrier, thereby increasing the loading amount of the metal. On the other hand, it improves the mechanical properties of the carrier and its anti-pulverization ability, so that the prepared catalyst can well resist stirring pulverization and wear, improving the stability of the catalyst and still maintaining a high catalytic activity after multiple recycling.

[0027] Preferably, in step S1, the aluminum salt is aluminum nitrate, the magnesium salt is magnesium chloride, magnesium nitrate or magnesium sulfate, the molar ratio of the aluminum salt to the magnesium salt is 1:1, the base is NaOH or KOH, the temperature of heat crystallization is 85 - 95 °C, the time is 0.5 - 1 h, the temperature of calcination is 400 - 500 °C, and the time is 1 - 2 h.

[0028] Preferably, in step S2, the mass ratio of the composite metal layered oxide, ferric chloride, ferrous chloride and ammonia water is 10:3.24:1.26:3 - 5, the temperature of the heating and stirring reaction is 60 - 70 °C, the time is 2 - 4 h, the temperature of calcination is 400 - 500 °C, and the time is 1 - 2 h.

[0029] Preferably, in step S3, the mass ratio of graphene oxide to the magnetic composite metal layered oxide is 2 - 3:7, and the reduction time is 10 - 12 h.

[0030] Preferably, in step S4, the mass ratio of the nickel salt, molybdenum salt and chromium salt is 15 - 20:2 - 3:1 - 2, the nickel salt is nickel nitrate or nickel chloride, the molybdenum salt is molybdenum nitrate, and the chromium salt is chromium nitrate.

[0031] Preferably, in step S5, the mass ratio of the graphene-coated magnetic composite metal layered oxide to the impregnating solution is 1:3-5, the calcination temperature is 350-450 °C, and the time is 1-2 h.

[0032] As a further improvement of the present invention, the unreacted hydrogen in the gas-liquid-solid three-phase material is separated in the upper part of the reactor and the high-pressure gas-liquid-solid separator, and enters the tube-type water cooler at the top of the tubular reactor. After cooling, the temperature is 30-35 °C. The separated hydrogen-dissolved solvent is refluxed to the tubular reactor, and the unreacted hydrogen is returned to the bottom of the tubular reactor by a hydrogen circulation machine, and fresh hydrogen is supplemented by a hydrogen supply station.

[0033] As a further improvement of the present invention, the liquid-solid phase material in the upper part of the tubular reactor overflows into the high-pressure gas-liquid-solid separator. The high-pressure gas-liquid-solid separator is provided with a lateral cyclone guide tube to promote the sedimentation of the solid phase at the bottom. The bottom is a liquid-solid phase material containing 10-15% catalyst, and then it is returned to the lower feed port of the tubular reactor by a high-pressure circulation pump.

[0034] As a further improvement of the present invention, the liquid phase extracted from the middle of the high-pressure gas-liquid-solid separator is sent to the low-pressure liquid-solid separator after decompression. The liquid-solid phase material containing 1-3% catalyst enters the low-pressure liquid-solid separator provided with a lateral cyclone guide tube, and the operating pressure of the low-pressure liquid-solid separator is normal pressure.

[0035] As a further improvement of the present invention, a small amount of catalyst separated by the low-pressure liquid-solid separator is recovered into the catalyst preparation system; the catalyst preparation system is protected by nitrogen. The recovered 1-3% catalyst and the supplemented fresh catalyst are regenerated by 20% sodium hydroxide alkali washing. After regeneration, the catalyst is mixed with an appropriate hydrogen-dissolved solvent, and then sent into the reaction system by high-pressure nitrogen (slightly higher than the reaction system pressure) using the pressure difference.

[0036] Preferably, the pressure of the high-pressure nitrogen is 0.2-0.5 Mpa higher than the reaction system pressure.

[0037] As a further improvement of the present invention, the liquid phase extracted from the middle of the low-pressure liquid-solid separator enters the hydrogen-dissolved solvent recovery tower. The operating pressure of the recovery tower is normal pressure. The cooling reflux temperature at the top of the recovery tower is 30-35 °C, and the reflux ratio is 1-2; the reboiling temperature at the bottom of the recovery tower is 75-80 °C. The material at the bottom outlet of the recovery tower is a mixed solution of 2-methylpentanediamine and 3-methylpiperidine, which is cooled to 30-35 °C and sent to the product intermediate tank.

[0038] The present invention has the following beneficial effects:

[0039] 1. According to the hydrogenation reaction mechanism of dinitrile, reducing the catalyst particle size and adding a hydrogen solvent are beneficial to increasing the hydrogenation sites and the gas-liquid mass transfer rate of hydrogen, and promoting the hydrogenation reaction. Selecting an appropriate amount of hydrogen solvent as the heat transfer carrier at the same time is conducive to removing the reaction heat and stabilizing the reaction section temperature range. Adding an appropriate amount of alkaline auxiliary agent is beneficial to reducing the by-products generated by deamination cyclization and alkylation;

[0040] 2. The pipeline reactor, high-pressure gas-liquid-solid separator and low-pressure liquid-solid separator adopted by the present invention; there are no complex internal parts in the device, the fluid flow is stable and the resistance is small, the relative reaction temperature and pressure are low, and the production operation is simple and safe. The production process adopts three-phase materials to perform multiple rapid circulations and enhanced hydrogenation in the tubular reaction section, with a high hydrogen partial pressure and a high single-pass hydrogen utilization rate in the reaction section. The reaction and separation equipment has a small volume and a large production capacity;

[0041] 3. The present invention uses the principle of pressure difference to recycle and regenerate the catalyst online and supplement it to the reaction system, solving the stability of the mass content and activity of the catalyst in the reaction system. It overcomes the serious equipment wear and blockage caused by using high-pressure piston pumps or diaphragm pumps to transport liquid-solid slurries at present, and solves the problems of frequent equipment shutdown for maintenance and unstable materials in the production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is the process flow diagram of Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] Graphene oxide, with a thickness of <5 nm, an oxygen content of about 35%, and a sheet diameter of about 20 μm, was purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.

[0046] Preparation Example 1 Preparation of the modified nickel catalyst, the method is as follows:

[0047] S1. Preparation of composite metal layered oxide: Dissolve 0.1 mol of aluminum nitrate and 0.1 mol of magnesium nitrate in 200 mL of water, add 0.5 mL of NaOH, heat to 85 °C, crystallize for 0.5 h, filter, wash, dry, and calcine at 400 °C for 1 h to obtain the composite metal layered oxide;

[0048] S2. Magnetic modification: Add 10 g of the composite metal layered oxide to 200 mL of water, add 3.24 g of ferric chloride and 1.26 g of ferrous chloride, under argon protection, dropwise add 3 g of ammonia water, heat to 60 °C, stir and react for 2 h, centrifuge, wash, dry, and calcine at 400 °C for 1 h to obtain the magnetic composite metal layered oxide;

[0049] S3. Graphene coating: Disperse 20 mg of graphene oxide in 200 mL of water, add 70 mg of the magnetic composite metal layered oxide, ultrasonically disperse at 1000 W for 10 min, spray dry, and reduce with hydrazine vapor for 10 h to obtain the graphene-coated magnetic composite metal layered oxide;

[0050] S4. Preparation of impregnation solution: Dissolve 1.5 g of nickel nitrate, 0.2 g of molybdenum nitrate, and 0.1 g of chromium nitrate in 300 mL of water, stir and mix for 15 min to obtain the impregnation solution;

[0051] S5. Preparation of modified nickel catalyst: Add 10 g of the graphene-coated magnetic composite metal layered oxide to 30 g of the impregnation solution, heat to evaporate the solvent, and calcine at 350 °C for 1 h to obtain the modified nickel catalyst.

[0052] Preparation example 2 Preparation of the modified nickel catalyst, the method is as follows:

[0053] S1. Preparation of composite metal layered oxide: Dissolve 0.1 mol of aluminum nitrate and 0.1 mol of magnesium nitrate in 200 mL of water, add 0.5 mL of NaOH, heat to 95 °C, crystallize for 1 h, filter, wash, dry, and calcine at 500 °C for 2 h to obtain the composite metal layered oxide;

[0054] S2. Magnetic modification: Add 10 g of the composite metal layered oxide to 200 mL of water, add 3.24 g of ferric chloride and 1.26 g of ferrous chloride, under argon protection, dropwise add 5 g of ammonia water, heat to 70 °C, stir and react for 4 h, centrifuge, wash, dry, and calcine at 500 °C for 2 h to obtain the magnetic composite metal layered oxide;

[0055] S3. Graphene coating: Disperse 30 mg of graphene oxide in 200 mL of water, add 70 mg of the magnetic composite metal layered oxide, ultrasonically disperse at 1000 W for 10 min, spray dry, and reduce with hydrazine vapor for 12 h to obtain the graphene-coated magnetic composite metal layered oxide;

[0056] S4. Preparation of impregnation solution: Dissolve 2 g of nickel nitrate, 0.3 g of molybdenum nitrate and 0.2 g of chromium nitrate in 300 mL of water, stir and mix for 15 min to obtain the impregnation solution;

[0057] S5. Preparation of modified nickel catalyst: Add 10 g of graphene-coated magnetic composite metal layered oxide to 50 g of the impregnation solution, heat to evaporate the solvent, and calcine at 450 °C for 2 h to obtain the modified nickel catalyst.

[0058] Preparation of the modified nickel catalyst in Preparation Example 3 is as follows:

[0059] S1. Preparation of composite metal layered oxide: Dissolve 0.1 mol of aluminum nitrate and 0.1 mol of magnesium nitrate in 200 mL of water, add 0.5 mL of NaOH, heat to 90 °C, crystallize for 1 h, filter, wash, dry, and calcine at 450 °C for 1.5 h to obtain the composite metal layered oxide;

[0060] S2. Magnetic modification: Add 10 g of the composite metal layered oxide to 200 mL of water, add 3.24 g of ferric chloride and 1.26 g of ferrous chloride, under argon protection, dropwise add 4 g of ammonia water, heat to 65 °C, stir and react for 3 h, centrifuge, wash, dry, and calcine at 450 °C for 1.5 h to obtain the magnetic composite metal layered oxide;

[0061] S3. Coating with graphene: Disperse 25 mg of graphene oxide in 200 mL of water, add 70 mg of the magnetic composite metal layered oxide, ultrasonically disperse at 1000 W for 10 min, spray dry, and reduce with hydrazine hydrate vapor for 11 h to obtain the graphene-coated magnetic composite metal layered oxide;

[0062] S4. Preparation of impregnation solution: Dissolve 1.7 g of nickel nitrate, 0.25 g of molybdenum nitrate and 0.15 g of chromium nitrate in 300 mL of water, stir and mix for 15 min to obtain the impregnation solution;

[0063] S5. Preparation of modified nickel catalyst: Add 10 g of the graphene-coated magnetic composite metal layered oxide to 40 g of the impregnation solution, heat to evaporate the solvent, and calcine at 400 °C for 1.5 h to obtain the modified nickel catalyst.

[0064] The difference between Comparative Preparation Example 1 and Preparation Example 3 is that step S2 is not carried out, and the details are as follows:

[0065] S1. Preparation of composite metal layered oxide: Dissolve 0.1 mol of aluminum nitrate and 0.1 mol of magnesium nitrate in 200 mL of water, add 0.5 mL of NaOH, heat to 90 °C, crystallize for 1 h, filter, wash, dry, and calcine at 450 °C for 1.5 h to obtain the composite metal layered oxide;

[0066] S2. Coating of graphene: 25 mg of graphene oxide was dispersed in 200 mL of water, 70 mg of composite metal layered oxide was added, ultrasonically dispersed for 10 min at 1000 W, spray-dried, and reduced with hydrazine hydrate vapor for 11 h to obtain graphene-coated composite metal layered oxide;

[0067] S3. Preparation of impregnation solution: 1.7 g of nickel nitrate, 0.25 g of molybdenum nitrate and 0.15 g of chromium nitrate were dissolved in 300 mL of water and stirred and mixed for 15 min to obtain an impregnation solution;

[0068] S4. Preparation of modified nickel catalyst: 10 g of graphene-coated composite metal layered oxide was added to 40 g of the impregnation solution, the solvent was evaporated by heating, and calcined at 400 °C for 1.5 h to obtain a modified nickel catalyst.

[0069] Comparing Preparation Example 2 with Preparation Example 3, the difference is that step S3 was not carried out, as follows:

[0070] S1. Preparation of composite metal layered oxide: 0.1 mol of aluminum nitrate and 0.1 mol of magnesium nitrate were dissolved in 200 mL of water, 0.5 mL of NaOH was added, heated to 90 °C, crystallized for 1 h, filtered, washed, dried, and calcined at 450 °C for 1.5 h to obtain a composite metal layered oxide;

[0071] S2. Magnetic modification: 10 g of the composite metal layered oxide was added to 200 mL of water, 3.24 g of ferric chloride and 1.26 g of ferrous chloride were added, under argon protection, 4 g of ammonia water was added dropwise, heated to 65 °C, stirred and reacted for 3 h, centrifuged, washed, dried, and calcined at 450 °C for 1.5 h to obtain a magnetic composite metal layered oxide;

[0072] S3. Preparation of impregnation solution: 1.7 g of nickel nitrate, 0.25 g of molybdenum nitrate and 0.15 g of chromium nitrate were dissolved in 300 mL of water and stirred and mixed for 15 min to obtain an impregnation solution;

[0073] S4. Preparation of modified nickel catalyst: 10 g of the magnetic composite metal layered oxide was added to 40 g of the impregnation solution, the solvent was evaporated by heating, and calcined at 400 °C for 1.5 h to obtain a modified nickel catalyst.

[0074] Comparing Comparative Preparation Example 3 with Preparation Example 3, the difference is that molybdenum nitrate was not added in step S4, as follows:

[0075] S4. Preparation of impregnation solution: 1.7 g of nickel nitrate and 0.4 g of chromium nitrate were dissolved in 300 mL of water and stirred and mixed for 15 min to obtain an impregnation solution.

[0076] Comparative Preparation Example 4 is different from Preparation Example 3 in that chromium nitrate was not added in step S4, specifically as follows:

[0077] S4. Preparation of the impregnation solution: Dissolve 1.7 g of nickel nitrate and 0.4 g of molybdenum nitrate in 300 mL of water, stir and mix for 15 min to obtain the impregnation solution.

[0078] Comparative Preparation Example 5 is different from Preparation Example 3 in that molybdenum nitrate and chromium nitrate were not added in step S4, specifically as follows:

[0079] S4. Preparation of the impregnation solution: Dissolve 2.1 g of nickel nitrate in 300 mL of water, stir and mix for 15 min to obtain the impregnation solution.

[0080] Test Example 1

[0081] The specific surface area of the modified nickel catalysts prepared in Preparation Examples 1-3 and Comparative Preparation Examples 1-5 was measured using an ASAP2460 fully automatic specific surface area and porosity analyzer produced by Micromeritics Instrument Corporation, USA. The results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from the above table, the modified nickel catalysts prepared in Preparation Examples 1-3 of the present invention have a relatively high specific surface area.

[0085] Example 1

[0086] The process flow of this example is as Figure 1 shown, and specifically includes the following steps:

[0087] (1) Prepare a mixed solution in the raw material tank according to a mass ratio of 2-methylglutaronitrile to ethanol of 1.0 ± 0.2; the mixed solution is pressurized to 2.3 ± 0.1 MPa (gauge pressure) by a feed pump, heated to 55 ± 5 °C by an electric heating preheater, and merged with the liquid-solid phase material from the high-pressure circulation pump into the lower feed pipe of the pipe reactor. The volume flow rate of the liquid-solid phase material of the high-pressure circulation pump is 400 ± 50 times that of the mixed solution from the feed pump. The hydrogen from the hydrogen circulator and the freshly supplemented hydrogen converge and enter the gas distributor at the bottom of the pipe reactor. The hydrogen flow rate (standard state) is controlled to be 0.4 ± 0.1 times the volume flow rate of the liquid-solid phase material of the high-pressure circulation pump.

[0088] (2) The hydrogen and the liquid-solid phase material at the bottom of the pipe reactor form a gas-liquid-solid three-phase material, and a hydrogenation reaction occurs during the upward movement from the bottom of the pipe reactor.

[0089] Specifically, the tubular reactor used is a double-tube empty-tube bubbling reactor. The inner tube is the reaction section, the outer tube is the water-cooling section, and the top is a shell-and-tube water-cooling separator for the gas phase. The diameter-to-height ratio of the reaction section of the tubular reactor is selected to be 70. The reaction pressure in the inner tube of the tubular reactor is controlled at 2.3 ± 0.1 MPa (gauge pressure); the reaction temperature is controlled at 60 ± 5 °C, and the water-cooling heat transfer in the outer tube cooling section is used to assist in controlling the reaction temperature. Three temperature points are set in the vertical direction of the reaction section, and the middle point is used as the control point.

[0090] Specifically, the gas-liquid-solid three-phase materials in the tubular reactor are as follows: the gas phase is hydrogen, the solid phase is the catalyst prepared in Preparation Example 1, and the liquid phase is a mixed solution composed of 2-methylglutaronitrile, 2-methylpentanediamine, 3-methylpiperidine, hydrogenation by-products, sodium hydroxide additive, and ethanol. The catalyst accounts for 13 ± 5% of the mass content of the three-phase mixed solution; the basic additive is sodium hydroxide, and the proportion is 0.3 ± 0.1% of the mass content of the three-phase mixed solution.

[0091] (3) The gas-liquid-solid three-phase materials are separated into gas-liquid-solid phases at the upper part of the reactor. The liquid-solid phase materials enter the high-pressure gas-liquid-solid separator laterally through the overflow port to further separate the unreacted hydrogen. The two streams of unreacted hydrogen enter the shell-and-tube water-cooler at the top of the tubular reactor, and the temperature after cooling is controlled at 32 ± 2 °C. The separated ethanol flows back to the tubular reactor, and the unreacted hydrogen returns to the bottom of the tubular reactor by the hydrogen circulation machine, and fresh hydrogen is supplemented by the hydrogen supply station to maintain the hydrogen addition amount.

[0092] (4) The liquid-solid phase materials at the upper part of the reactor overflow into the high-pressure gas-liquid-solid separator provided with a lateral cyclone guide tube to promote the sedimentation of the solid-phase catalyst at the bottom to form a more viscous mixed solution with a higher solid content, and then return to the lower feed port of the tubular reactor by the high-pressure circulation pump. The liquid phase containing 2% catalyst is taken out from the middle of the high-pressure gas-liquid-solid separator and enters the low-pressure liquid-solid separator provided with a lateral cyclone guide tube after depressurization. The operating pressure of the low-pressure liquid-solid separator is atmospheric pressure, and the catalyst separated at the bottom is recovered to the catalyst preparation system.

[0093] (5) The liquid phase taken out from the middle of the low-pressure liquid-solid separator enters the hydrogen-dissolving solvent recovery tower. The operating pressure of the recovery tower is atmospheric pressure. The cooling reflux temperature at the top of the recovery tower is 32 ± 2 °C, and the reflux ratio is 1.5; the reboiling temperature at the bottom of the recovery tower is 77 ± 2 °C. The material at the bottom outlet of the recovery tower is a mixed solution of 2-methylpentanediamine and 3-methylpiperidine, which is cooled to 32 ± 2 °C and sent to the product intermediate tank for further dehydration, dealkalization, removal of by-products, and separation and purification.

[0094] (6) Samples are taken from the outlet of the high-pressure circulation pump every 8 hours to test the content of the catalyst in the material, and part of the catalyst configuration system is discharged regularly. The catalyst configuration system is protected by nitrogen. The recycled and regularly discharged catalyst, as well as the supplemented fresh catalyst, are regenerated and activated by alkali washing with 20% sodium hydroxide. The prepared catalyst is then sent into the reaction system by using high-pressure nitrogen (0.3 Mpa higher than the reaction system pressure) through the pressure difference to ensure that the mass content of the catalyst in the three-phase mixture in the reaction tube is 13 ± 5%.

[0095] In this example, the tubular reaction tube has a diameter of 50 mm, a reaction section height of 3500 mm, a raw material feed pump flow rate of 8.75 L / h, and a high-pressure circulation pump flow rate of 3.5 m 3 / h, and the hydrogen flow rate at the reactor inlet is 1.5 m 3 / h.

[0096] Compared with Example 1, the difference in Example 2 is that the catalyst is prepared from Preparation Example 2.

[0097] Compared with Example 1, the difference in Example 3 is that the catalyst is prepared from Preparation Example 3.

[0098] Compared with Example 1, the difference in Comparative Example 1 is that the catalyst is prepared from Comparative Preparation Example 1.

[0099] Compared with Example 1, the difference in Comparative Example 2 is that the catalyst is prepared from Comparative Preparation Example 2.

[0100] Compared with Example 1, the difference in Comparative Example 3 is that the catalyst is prepared from Comparative Preparation Example 3.

[0101] Compared with Example 1, the difference in Comparative Example 4 is that the catalyst is prepared from Comparative Preparation Example 4.

[0102] Compared with Example 1, the difference in Comparative Example 5 is that the catalyst is prepared from Comparative Preparation Example 5.

[0103] In Test Example 2, the methods in Examples 1-3 and Comparative Examples 1-5 of the present invention were evaluated, and the results are shown in Table 2.

[0104] Table 2

[0105]

[0106] As can be seen from the above table, in the methods of Examples 1-3 of the present invention, the conversion rate of 2-methylglutaronitrile is high, and the selectivity of 2-methylglutaronitrile and the selectivity of 3-methylpiperidine are even higher.

[0107] Test Example 3

[0108] After the catalysts prepared in Examples 1-3 or Comparative Examples 1-5 of the present invention were subjected to continuous catalytic reaction for 200 h, the specific surface areas of the catalysts before and after were measured. The results are shown in Table 3.

[0109] Table 3

[0110]

[0111] As can be seen from the above table, after the catalysts in Examples 1-3 of the present invention were subjected to continuous catalytic reaction for 200 h, the specific surface areas were not much different, indicating that their physicochemical properties changed little.

[0112] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing methylpentanediamine and methylpiperidine by hydrogenating methylglutaronitrile, characterized in that: The steps include: (1) In the raw material tank, the mixed liquid of 2-methylglutaronitrile and hydrogen-soluble solvent is pressurized by a feed pump and heated by a preheater, and enters the lower feed pipe of the pipeline reactor together with the liquid and solid phase materials from the high-pressure circulation pump. The hydrogen from the hydrogen circulation machine and the fresh supplementary hydrogen are combined and enter the gas distributor at the bottom of the pipeline reactor. The hydrogen and the liquid and solid phase materials form a gas-liquid-solid three-phase material and undergo a catalytic hydrogenation reaction during the process of rising from the bottom of the pipeline reactor; (2) The gas-liquid-solid three-phase materials are separated into gas phase-liquid-solid phase at the upper part of the reactor, and the liquid-solid phase materials overflow into the high-pressure gas-liquid-solid phase separator for further gas phase separation; the separated hydrogen is combined and cooled and separated; and then returned to the bottom of the pipeline reactor by the hydrogen circulation machine; the liquid-solid phase materials at the bottom of the high-pressure gas-liquid-solid phase separator are returned to the lower part of the pipeline reactor by the high-pressure circulation pump; (3) The liquid phase produced in the middle of the high-pressure gas-liquid-solid phase separator is sent to the low-pressure liquid-solid phase separator after decompression. The liquid phase produced in the middle of the low-pressure liquid-solid phase separator enters the hydrogen-soluble solvent recovery tower. The hydrogen-soluble solvent recovered at the top of the tower is sent back to the raw material tank. The product methylpentanediamine and methylpiperidine mixed liquid at the bottom of the tower is sent to the product intermediate tank. (4) The catalyst separated by the low-pressure liquid-solid phase separator is recovered to the catalyst configuration system for online catalyst regeneration and replenishment; The gas-liquid-solid three-phase material for catalytic hydrogenation reaction during the process of rising from the bottom of the reactor is: the gas phase is hydrogen, the solid phase is a catalyst, and the liquid phase is a mixed liquid composed of 2-methylglutaronitrile, 2-methylpentanediamine, 3-methylpiperidine, hydrogenation by-products, alkaline auxiliary agents and hydrogen-soluble solvents. During the process of the gas-liquid-solid three-phase material rising from the bottom of the reactor, the solid phase catalyst accounts for 10-20% of the mass content of the three-phase mixed liquid; the alkaline auxiliary agent is sodium hydroxide or potassium hydroxide, and the proportion is 0.01-0.5% of the mass content of the three-phase mixed liquid; The catalyst is a modified nickel catalyst, and the preparation method of the modified nickel catalyst is as follows: S1. Preparation of composite metal layered oxide: dissolving aluminum salt and magnesium salt in water, adding alkali, heating for crystallization, filtering, washing, drying, and calcining to obtain a composite metal layered oxide; S2. Magnetic modification: adding a composite metal layered oxide to water, adding ferric chloride and ferrous chloride, adding ammonia water dropwise under inert gas protection, heating and stirring to react, centrifuging, washing, drying, and calcining to obtain a magnetic composite metal layered oxide; S3. Graphene coating: dispersing graphene oxide in water, adding a magnetic composite metal layered oxide, uniformly dispersing by ultrasonication, spray drying, and reducing with hydrazine hydrate vapor to obtain a graphene-coated magnetic composite metal layered oxide; S4. Preparation of an impregnation solution: dissolving a nickel salt, a molybdenum salt and a chromium salt in water to obtain an impregnation solution; S5. Preparation of modified nickel catalyst: adding graphene-coated magnetic composite metal layered oxide to the impregnation solution, heating to evaporate the solvent, and calcining to obtain a modified nickel catalyst.

2. The method according to claim 1, characterized in that: The mixed liquid in the raw material tank is prepared according to the mass ratio of 2-methylglutaronitrile to hydrogen-soluble solvent of 1.0-4.0:1.0; the hydrogen-soluble solvent is methanol or ethanol; the pressure is increased to 2.0-3.0 MPa by a feed pump; and the mixed liquid is preheated to 50-90° C. by a preheater.

3. The method according to claim 1, characterized in that: The mixed liquid of methylglutaronitrile and hydrogen-soluble solvent is pressurized by a feed pump and preheated by a preheater, and enters a liquid-solid material feed pipe at the bottom of a pipeline reactor together with liquid-solid materials from a high-pressure circulation pump, wherein the volume flow ratio of the liquid-solid materials from the high-pressure circulation pump to the mixed liquid of 2-methylglutaronitrile and hydrogen-soluble solvent from the feed pump is 300-600, and the residence time of the mixed liquid phase in the reaction tube is 5-15 seconds.

4. The method according to claim 1, characterized in that: The hydrogen from the hydrogen circulation machine and the fresh supplementary hydrogen merge into the gas distributor at the bottom of the pipeline reactor, wherein the diameter of a single hole on the distributor orifice plate is 1.0-2.0 mm and is evenly distributed; the volume flow ratio of the hydrogen in the standard state entering the bottom of the pipeline reactor to the liquid-solid phase material of the high-pressure circulation pump is 0.3-0.5:1.

0.

5. The method according to claim 1, characterized in that: The pipeline reactor is a sleeve-type empty tube bubbling reactor, wherein the inner tube is a reaction section, the outer tube is a water cooling section, the height of the reaction section is the length from the lower liquid-solid phase material feed pipe port to the upper liquid-solid phase overflow port, the diameter-to-height ratio of the pipeline reactor reaction section is 60-80, a gas distributor is arranged at the bottom and is a perforated plate type, the lower liquid-solid phase material feed pipe is arranged above the gas distributor, the reaction pressure of the pipeline reactor reaction section is 2.0-3.0 MPa; the reaction temperature is 50-90° C., the hydrogenation reaction of 2-methylglutaronitrile is an exothermic reaction, and the outer tube cooling section is used for water cooling to transfer heat, and the reaction temperature is controlled to be 50-90° C.

6. The method according to claim 1, characterized in that: The gas-liquid-solid three-phase material is separated from the unreacted hydrogen at the top of the reactor and the high-pressure gas-liquid-solid phase separator, and enters the tube-type water cooler at the top of the pipeline reactor. After cooling, the temperature is 30-35°C, and the separated hydrogen-dissolving solvent is refluxed to the pipeline reactor. The unreacted hydrogen is returned to the bottom of the pipeline reactor by the hydrogen circulation machine and is supplemented with fresh hydrogen from the hydrogen supply station.

7. The method according to claim 1, characterized in that: The liquid-solid materials at the top of the pipeline reactor overflow into the high-pressure gas-liquid-solid phase separator, and the high-pressure gas-liquid-solid phase separator is provided with a lateral cyclone guide pipe to promote the solid phase to settle at the bottom. The bottom is the liquid-solid materials containing 10-15% catalyst, which are then returned to the lower feed port of the pipeline reactor by the high-pressure circulation pump.

8. The method according to claim 1, characterized in that: The liquid phase extracted from the middle of the high-pressure gas-liquid-solid phase separator is sent to the low-pressure liquid-solid phase separator after decompression, and the liquid-solid phase materials containing 1-3% catalyst enter the low-pressure liquid-solid phase separator provided with a lateral cyclone guide pipe. The operating pressure of the low-pressure liquid-solid phase separator is atmospheric pressure.

9. The method according to claim 1, characterized in that: The catalyst separated by the low-pressure liquid-solid phase separator is recovered to the catalyst configuration system; the catalyst configuration system is protected by nitrogen, and the recovered 1-3% catalyst and the supplemented fresh catalyst are regenerated by 20% sodium hydroxide alkaline washing. After regeneration, the catalyst is mixed with an appropriate hydrogen-soluble solvent and then fed into the reaction system by high-pressure nitrogen using the pressure difference. The pressure of the high-pressure nitrogen is 0.2-0.5Mpa higher than the pressure of the reaction system.

10. The method according to claim 1, characterized in that: The liquid phase extracted from the middle of the low-pressure liquid-solid phase separator enters the hydrogen-dissolving solvent recovery tower. The operating pressure of the recovery tower is atmospheric pressure. The cooling reflux temperature at the top of the recovery tower is 30-35° C., and the reflux ratio is 1-2. The reboiling temperature at the bottom of the recovery tower is 75-80° C., and the outlet material at the bottom of the recovery tower is a mixed liquid of 2-methylpentanediamine and 3-methylpiperidine, which is cooled to 30-35° C. and sent to the product intermediate tank.

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