Catalyst applicable to continuous production of methyl cyclohexanediamine by fixed bed and preparation method of catalyst

Abstract

The invention discloses a catalyst applicable to continuous production of methyl cyclohexanediamine by a fixed bed. The catalyst comprises the following components in percentage by mass: 0.5-5.0% of platinum group metal and 95.0-99.5% of modified carrier. The preparation method comprises the following steps: carrying out modification such as additive addition, balling, sieving and vacuum calcination on a carrier, dipping the carrier in a platinum group metal solution, carrying out ultrasonic treatment, drying, reducing, filtering and drying, so that platinum group metal is uniformly and firmly dispersed on the carrier, and the defects of low utilization rate, non-uniform distribution and the like of active components of an existing catalyst are overcome. The catalyst has the advantages of high activity, strong stability and the like. The catalyst is used for synthesizing methyl cyclohexanediamine through diaminotoluene hydrogenation, deamination in the reaction process is inhibited under the action of the catalyst and under the condition of appropriate technological parameters, the conversion rate of diaminotoluene (TDA), the selectivity of methyl cyclohexanediamine (HTDA) and the yield of HTDA are improved, and HTDA is easy to separate and purify and suitable for large-scale continuous production.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and preparation thereof, and particularly relates to a catalyst suitable for continuous production of methylcyclohexanediamine in a fixed bed and a preparation method thereof. Background Art

[0002] Methylcyclohexanediamine (HTDA) is an alicyclic amine curing agent with the advantages of high reactivity, rapid curing at low temperature, insensitivity to humidity, stable color, chemical corrosion resistance and high temperature resistance. Therefore, methylcyclohexanediamine is widely used in leather, accessories, home furnishings and other home furnishing fields, composite materials, coatings, adhesives and flooring and other new building decoration materials, as well as new energy industries such as solar photovoltaic panels and wind turbine blades.

[0003] In the prior art, the main synthesis route of methylcyclohexanediamine is: toluene is nitrated to form dinitrotoluene, then hydrogenated to form diaminotoluene (TDA), and then further hydrogenated to form methylcyclohexanediamine (HTDA). However, the HTDA synthesized by the above synthesis route has low selectivity and many by-products. Therefore, those skilled in the art use catalysts to improve the selectivity of HTDA and reduce by-products in the synthesis process.

[0004] However, existing catalysts are only suitable for batch reactors in laboratories and cannot be applied to industrial-scale continuous production processes. Summary of the invention

[0005] The object of the present invention is to provide a catalyst and a preparation method suitable for the continuous production of methylcyclohexanediamine in a fixed bed, so as to solve the problems raised in the above-mentioned background technology.

[0006] In a first aspect, the present invention provides a catalyst suitable for the continuous production of methylcyclohexanediamine in a fixed bed, the catalyst comprising a modified carrier and an active component; wherein the modified carrier comprises activated alumina and an additive, the additive comprises an alkali metal oxide or an alkaline earth metal oxide, and the activated alumina and the additive are bonded, balled, sieved and calcined to obtain a modified carrier; the active component is any one of the platinum group metals Ru, Rh, Pd, Pt; the active component is supported on the modified carrier.

[0007] As a preferred technical solution of the present invention, the raw material for producing activated alumina includes alumina powder that is rapidly de-powdered; the particle size of the alumina powder that is rapidly de-powdered is 10 μm to 100 μm, and the specific surface area is 220 to 330 m 2 / g; and in the alumina fast de-powdering, the Al2O3 content is ≥98%.

[0008] As a preferred technical solution of the present invention, when the auxiliary agent is an alkali metal oxide, the auxiliary agent includes Na2O; when the auxiliary agent is an alkaline earth metal oxide, the auxiliary agent includes MgO and BaO.

[0009] As a preferred technical solution of the present invention, the particle size of the additive is 20nm to 100nm, and the specific surface area is ≥50m 2 / g, and the purity of the additive is ≥99%.

[0010] As a preferred technical solution of the present invention, the particle size of the modified carrier is 2.0 mm to 3.0 mm, and the specific surface area is 200 to 400 m 2 / g, and the bulk density is 0.40 g / mL~0.80g / mL.

[0011] As a preferred technical solution of the present invention, the catalyst includes 0.5-5.0% of platinum group metals and 95.0-99.5% of modified carriers by mass percentage, and the sum of the mass percentages of the platinum group metals and the modified carrier is 100%.

[0012] In a second aspect, the present invention further provides a method for preparing a catalyst suitable for continuous production of methylcyclohexanediamine in a fixed bed, the method for preparing the catalyst for continuous production of methylcyclohexanediamine in a fixed bed in the first aspect, the method comprising the following steps: S1. Preparation of modified carrier: Mix alumina quick-release powder and additives evenly; wherein, the mass ratio of the additive to alumina quick-release powder is (0.1-0.5):1; control the rotation of the ball-forming disk containing the ball seeds, and add the mixture of alumina quick-release powder and additives, as well as a binder, into the ball-forming disk to make the alumina quick-release powder and the additives bond to form spheres; after screening the spheres, calcine them under vacuum conditions at 200°C-600°C for 4h-8h and then cool them to room temperature to obtain a modified carrier.

[0013] S2. Preparation of precursor solution: Add deionized water to any soluble salt of a platinum group metal, add nitric acid solution at 60°C to 100°C and stir until the soluble salt of the platinum group metal is completely dissolved to obtain an active platinum group metal precursor solution.

[0014] S3. Preparation of finished catalyst: Add the modified carrier to the active platinum group metal precursor solution, ultrasonically treat for 0.5h to obtain a semi-finished catalyst; dry the semi-finished catalyst in a drying oven at 60℃~100℃ for 2h~5h, and then cool it to room temperature; add a reducing agent to the semi-finished catalyst to reduce the semi-finished catalyst; filter out the residual liquid in the reduced semi-finished catalyst, wash it with distilled water for 3~5 times, and then dry it in a vacuum drying oven, and obtain the finished catalyst after cooling.

[0015] As a preferred technical solution of the present invention, the binder is any one of pseudo-boehmite, activated clay, kaolin and high-alumina cement, or a mixture of two of them.

[0016] As a preferred technical solution of the present invention, the reducing agent is any one of sodium borohydride, hydrazine hydrate and formic acid.

[0017] As a preferred technical solution of the present invention, the soluble salt of the platinum group metal is any one of RuCl3, K2RuCl6, (NH4)2RuCl6, Ru(OAc)3, Ru(II)(NO)(NO3)3, Rh(NO3)3, PdCl2 and H2PtCl6.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention modifies alumina powder and an alkali metal oxide or alkaline earth metal oxide as an additive to obtain a modified carrier containing an additive. The modified carrier has a particle size of 2.0 to 3.0 mm and a specific surface area of ​​200 to 400 m 2 / g, and the bulk density is 0.40g / mL~0.80g / mL. The modified carrier has developed pores, reasonable pore size distribution, and strong adsorption capacity, which can make the active component platinum group metal more effectively loaded, and has high activity, easy regeneration, and strong thermal stability. When the catalyst loading volume is the same, it can ensure higher production capacity and hydrogenation efficiency, thereby reducing the amount of platinum group metals used and reducing the investment and operating costs of manufacturers.

[0019] 2. In the process of preparing the modified carrier, the present invention performs vacuum calcination on the activated alumina containing the additive to remove the adsorbed water and organic matter on its surface. During the calcination process, the alumina undergoes crystal reconstruction and surface renewal, which enhances the strength of the catalyst, making it less likely to break under the impact and agitation of the gas-liquid flow in the high temperature and high pressure and diaminotoluene (TDA) hydrogenation system, thereby increasing the service life of the catalyst.

[0020] 3. The catalyst prepared by the present invention has been continuously tested in small and medium tests, and the process has been improved, thus avoiding some unfavorable factors that may occur in large-scale production, such as low catalyst activity and selectivity. The expected hydrogenation activity and yield of the target product can be achieved with a single platinum group metal active component, and the generation of deamination side reactions during the hydrogenation process is reduced. The catalyst maintains catalytic activity during continuous hydrogenation reactions in the reaction system, and no intermittent filtration is required, which shortens the reaction time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the principle diagram of the main and side reactions of diaminotoluene (TDA) hydrogenation; Figure 2 This is a flow chart for preparing the catalyst of the present invention; Figure 3 This is a cross-sectional SEM image of the carrier of the present invention; Figure 4 This is a graph showing the thickness of the Ru metal active layer on the surface of the modified carrier of the present invention; Figure 5 This is the energy spectrum diagram of the flat cut center of the catalyst of the present invention; Figure 6 This is the energy spectrum of the flat-cut edge of the catalyst of the present invention; Figure 7 is the original surface energy spectrum of the catalyst of the present invention; Figure 8 This is a distribution diagram of Ru metal active sites in the carrier of Example 1 of the present invention; Fig. 9 This is the distribution diagram of Ru metal active sites of the modified carrier in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Since the alicyclic diamine epoxy resin curing agent containing methylcyclohexanediamine as an adduct has higher carbamate stability than the adduct containing isophoronediamine (IPDA) and meta-phenylenediamine (MXDA), the products cured by the alicyclic diamine epoxy resin curing agent containing methylcyclohexanediamine as an adduct have excellent color and gloss, good transparency and good weather resistance, and can be used in the fields of leather, accessories, home furnishings, new building decoration materials such as composite materials, coatings, adhesives and flooring, as well as new energy industries such as solar photovoltaic panels and wind turbine blades.

[0024] The main and side reaction principle of diaminotoluene (TDA) hydrogenation, such as Figure 1 As shown in the figure, the main synthesis route of methylcyclohexanediamine is: toluene is nitrated to form dinitrotoluene, then hydrogenated to form diaminotoluene (TDA), and then further hydrogenated to form methylcyclohexanediamine (HTDA). In the process of synthesizing methylcyclohexanediamine, since toluene usually produces a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene after nitration and hydrogenation, and diaminotoluene (TDA) has two amino groups and one methyl group in the molecule, it is easy to undergo deamination and produce side reactions during the hydrogenation reaction, resulting in the production of by-products such as o-methylaniline, p-methylaniline, o-methylcyclohexylamine and p-methylcyclohexylamine. The presence of by-products affects the activity of the catalyst and easily leads to a decrease in the selectivity of HTDA. Therefore, the development of the catalyst and the selection of process conditions are particularly important for TDA to selectively hydrogenate the target product under high requirements such as temperature, pressure, and solvent.

[0025] In order to solve the problem of low selectivity and many by-products in the synthesis of HTDA by hydrogenation of TDA, those skilled in the art use hydrogenation catalysts in the synthesis process to obtain the target product with high selectivity and no by-products. Specifically, in the preparation process of the catalyst used, the active components are selected from Ru, Rh, Pd and Pt, etc. under laboratory conditions, and are prepared by direct impregnation method, precipitation method or blending method. However, when the catalyst prepared under laboratory conditions is used for industrial continuous production, there are many problems.

[0026] For example, a method for preparing methylcyclohexanediamine comprises dissolving RuCl3 and RhCl3 in a polyethylene glycol aqueous solution and stirring; adding hydrazine hydrate for reduction; adding carrier Al2O3 after reduction and stirring and filtering; eluting the final catalyst with tetrahydrofuran (THF); and then stirring and reacting under a certain range of hydrogen pressure and temperature conditions in the presence of an inorganic salt auxiliary to obtain the methylcyclohexanediamine. The yield of methylcyclohexanediamine obtained by this method is as high as 97%, but the activity of the catalyst is significantly reduced after being used three times.

[0027] Another example is the method and catalyst for selective hydrogenation of toluene diamine to produce methylcyclohexane diamine. The active component is Ru, the auxiliary agent is one or more of Ce, Mn, and La, the carrier is one or more of TiO2, Al2O3, SiO2, and AC (activated carbon), and the dispersant is polyethylene glycol and sodium dodecylbenzene sulfonate. The catalyst is obtained by preparing an impregnation solution containing the active component, auxiliary agent, and dispersant; then immersing the carrier; and finally drying and calcining the carrier. The catalyst prepared by this method is used for TDA hydrogenation in a high-pressure reactor, using tetrahydrofuran as a solvent, adding LiOH auxiliary agent to the reaction system, and replacing the air in the reactor with nitrogen. The catalyst is used in 20 batches, with a conversion rate of up to 99% and a selectivity of up to 95%, but each filtration requires the addition of new catalysts and auxiliary agents, a long reaction time, and low production efficiency.

[0028] For another example, a method for synthesizing methylcyclohexanediamine by hydrogenation of diaminotoluene is to add water to Al2O3 powder with different particle size distributions, and then stir and mix with a certain amount of Zr salt solution, and then add preferred LiOH·H2O and Na2CO3 alkaline solutions to adjust the pH to 7-9, and obtain Al2O3-ZrO2 carrier by stirring, filtering, drying and roasting. Ru soluble salt (preferably RuCl3), leaching agent (preferably formic acid, salicylic acid), water and the prepared composite carrier are mixed, stirred and heated, and then a certain concentration of alkaline solution and Rh soluble salt aqueous solution (preferably RhCl3) are added dropwise to the system, and the pH is adjusted, stirred, filtered, dried, roasted, and hydrogen reduction activation is performed to obtain the finished catalyst. Although the catalyst prepared by this method has high hydrogenation activity and selectivity, the catalyst is in powder form, has not been subjected to large-scale production tests, is not easy to filter in the reactor system liquid, and is easy to agglomerate into slurry as the reaction time increases, which is not good for the reaction system, and the price of the precious metal Rh is relatively expensive, and the production cost is high.

[0029] Based on this, the inventors have conducted in-depth research and provided a catalyst suitable for the continuous production of methylcyclohexanediamine in a fixed bed and a preparation method thereof, so as to obtain a catalyst with high activity, good selectivity, excellent stability, and adaptability to the continuous production of methylcyclohexanediamine in a fixed bed.

[0030] The invention mixes and modifies alumina powder and an auxiliary alkali metal oxide or alkaline earth metal oxide (at least one of Na2O, MgO and BaO) to obtain an activated alumina modified carrier containing an auxiliary. In the preparation process of the modified carrier, the activated alumina balls containing the auxiliary are vacuum calcined. During the calcination process, the alumina undergoes crystal reconstruction and surface renewal, thereby enhancing the strength of the catalyst, making it difficult to break under the impact and agitation of the gas-liquid flow in the high temperature and high pressure and diaminotoluene (TDA) hydrogenation system, thereby increasing the service life of the catalyst. The modified carrier has developed pores, reasonable pore size distribution, and strong adsorption capacity, and can load the active component platinum group metal more effectively, and has high activity, easy regeneration, and strong thermal stability. When the catalyst loading volume is the same, higher production capacity and hydrogenation efficiency can be guaranteed, thereby reducing the amount of platinum group metals used and reducing the investment and operating costs of manufacturers.

[0031] During the large-scale production of fixed-bed continuous production of methylcyclohexanediamine, adverse factors such as changes in reaction temperature and pressure, impure materials, and irregular production operations may occur, resulting in rapid reduction in catalyst activity and easy agglomeration, thereby causing problems such as low catalyst activity and selectivity. In the process of preparing the catalyst, the present invention modifies alumina with alkali metal oxides or alkaline earth metal oxides to obtain an active alumina modified carrier. The modified carrier has developed pores, reasonable pore size distribution, and strong adsorption capacity, which can make the active component platinum group metal more effectively loaded, and has high activity, easy regeneration, and strong thermal stability. It is not easy to break under the impact and stirring of high temperature, high pressure and gas-liquid flow in the diaminotoluene (TDA) hydrogenation system, ensuring the activity of the catalyst and increasing the service life of the catalyst. Therefore, in the production of diaminotoluene (TDA) continuous hydrogenation to synthesize methylcyclohexanediamine (HTDA), the generation of deamination side reactions during the hydrogenation process is reduced, and the catalyst maintains catalytic activity in the continuous hydrogenation reaction in the reaction system, thereby improving the conversion rate of TDA, the selectivity and yield of HTDA, and no intermittent filtration is required during the production process, shortening the reaction time.

[0032] like Figure 2 As shown, the preparation method of the catalyst for the continuous production of methylcyclohexanediamine in a fixed bed provided in the embodiment of the present application comprises the following steps: S1. Preparation of modified carrier: uniformly mix the alumina powder and the additive, add the mixture of the alumina powder and the additive while the balling disk containing the ball seeds rotates, spray the binder, spheronize, sieve, vacuum calcine, and cool to room temperature to obtain the modified carrier. S2. Preparation of precursor solution: place a soluble salt of a platinum group metal in a beaker, add deionized water, add nitric acid solution under heating at 60 to 100°C and stir until the platinum group metal salt is completely dissolved to obtain an active platinum group metal precursor solution. S3. Preparation of finished catalyst: add the modified carrier to the active platinum group metal precursor solution and perform ultrasonic treatment for 0.5h to obtain a semi-finished catalyst; treat the semi-finished catalyst in a drying oven at 60 to 100°C for 2 to 5h, add a reducing agent to reduce it after cooling to room temperature, filter, wash with distilled water, place it in a vacuum drying oven for drying, and cool it to obtain a finished catalyst.

[0033] The raw materials used in the present invention are all commercially available raw materials.

[0034] The preparation method of a catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine comprises the following preparation steps: Embodiment 1:

[0035] S1. Carrier preparation: While the ball-forming plate containing the ball seeds is rotating, alumina powder is added and the binder pseudo-boehmite is sprayed. The ball is formed, sieved (the material on the 8-mesh sieve and the material under the 6-mesh sieve is taken), and then calcined at 400℃ under vacuum for 6 hours and cooled to room temperature to obtain the carrier. The alumina powder has a particle size of 10μm, an Al2O3 content of 98%, and a specific surface area of ​​220m2 / g.

[0036] S2. Preparation of precursor solution: Place a soluble platinum group metal salt Ru(II)(NO)(NO3)3 in a beaker, add deionized water, add nitric acid solution while heating at 80°C and stir until the platinum group metal salt Ru(II)(NO)(NO3)3 is completely dissolved to obtain a ruthenium-based precursor solution.

[0037] S3. Preparation of finished catalyst: Add the carrier to the ruthenium-based precursor solution and carry out ultrasonic treatment for 0.5h to obtain a semi-finished catalyst; treat the semi-finished catalyst in an 80°C drying oven for 3h, cool to room temperature, add reducing agent sodium borohydride (NaBH4) for reduction, filter out the residual liquid, wash with distilled water 3 times, and place in a vacuum drying oven at 120°C for 6h, take out and cool to obtain a finished catalyst.

[0038] Embodiment 2:

[0039] S1. Preparation of modified carrier: Mix the auxiliary agent MgO and alumina powder at a mass ratio of 0.1:1, add the mixture of auxiliary agent MgO and alumina powder while the ball-forming plate containing the ball seeds rotates, and spray the binder pseudo-boehmite, form balls, sieve (take the 8-mesh sieve and the 6-mesh sieve), calcine at 400℃ under vacuum for 6h, and cool to room temperature to obtain the modified carrier. The alumina powder has a particle size of 10μm, an Al2O3 content of 98%, and a specific surface area of ​​220m 2 / g; the particle size of the modified carrier is 2.0 mm and the specific surface area is 200 m 2 / g, bulk density is 0.40g / mL; the particle size of the auxiliary agent MgO is 20nm, the purity is 99%, and the specific surface area is 50m 2 / g.

[0040] S2. Preparation of precursor solution: Place a soluble platinum group metal salt Ru(II)(NO)(NO3)3 in a beaker, add deionized water, add nitric acid solution while heating at 80°C and stir until the platinum group metal salt Ru(II)(NO)(NO3)3 is completely dissolved to obtain a ruthenium-based precursor solution.

[0041] S3. Preparation of finished catalyst product: add the modified carrier to the ruthenium-based precursor solution and carry out ultrasonic treatment for 0.5h to obtain a semi-finished catalyst product; treat the semi-finished catalyst product in a drying oven at 80°C for 3h, cool to room temperature, add reducing agent sodium borohydride (NaBH4) for reduction, filter out the residual liquid, wash with distilled water for 3 times, and place in a vacuum drying oven at 120°C for 6h, take out and cool to obtain a finished catalyst product, in which the content of platinum group metal Ru is 5.0% and the content of modified carrier is 95.0% by mass.

[0042] Embodiment three:

[0043] The difference from the second embodiment is that the auxiliary agent is BaO, the auxiliary agent BaO and the alumina quick powder are mixed uniformly at a mass ratio of 0.1:1, the alumina quick powder has a particle size of 100 μm, an Al2O3 content of 99%, and a specific surface area of ​​330 m 2 / g; the particle size of the modified carrier is 3.0 mm and the specific surface area is 400 m 2 / g, bulk density is 0.80g / mL; the particle size of the additive BaO is 100nm, the purity is 99.5%, and the specific surface area is 50m 2 / g. The catalyst has a platinum group metal Ru content of 0.5% and a modified carrier content of 99.5% by mass.

[0044] Embodiment 4:

[0045] The difference from Example 2 is that the auxiliary agent is Na2O, and the auxiliary agent Na2O and alumina powder are mixed uniformly at a mass ratio of 0.1:1. The particle size of alumina powder is 50 μm, the Al2O3 content is 98.5%, and the specific surface area is 300 m 2 / g; the particle size of the modified carrier is 2.5 mm and the specific surface area is 300 m 2 / g, bulk density is 0.50g / mL; the particle size of the auxiliary agent Na2O is 50nm, the purity is 100%, and the specific surface area is 60m 2 / g. The catalyst has a platinum group metal Ru content of 2.0% and a modified carrier content of 98.0% by mass.

[0046] Embodiment five:

[0047] The difference from Example 2 is that the auxiliary agent MgO and the alumina quick-release powder are evenly mixed in a mass ratio of 0.5:1, the alumina quick-release powder has a particle size of 80 μm, an Al2O3 content of 99%, and a specific surface area of ​​260 m 2 / g; the particle size of the modified carrier is 2.5 mm and the specific surface area is 260 m 2 / g, bulk density is 0.60g / mL; the particle size of the auxiliary agent MgO is 20nm, the purity is 99%, and the specific surface area is 50m 2 / g. The catalyst has a platinum group metal Ru content of 2.8% and a modified carrier content of 97.2% by mass.

[0048] Embodiment six:

[0049] The difference from Example 2 is that the soluble salt of platinum group metal is a mixed solution of Ru(II)(NO)(NO3)3 and Rh(NO3)3, the mass ratio of Ru(II)(NO)(NO3)3 and Rh(NO3)3 is 1:0.3, the particle size of alumina powder is 60 μm, the Al2O3 content is 98%, and the specific surface area is 300 m 2 / g; the particle size of the modified carrier is 2.0 mm and the specific surface area is 350 m 2 / g, bulk density is 0.60g / mL; the particle size of the auxiliary agent MgO is 60nm, the purity is 99.5%, and the specific surface area is 55m 2 / g. The catalyst has a platinum group metal content of 1.5% and a modified carrier content of 98.5% by mass.

[0050] The catalysts prepared in Examples 1, 2, 3, 4, 5 and 6 were evaluated for hydrogenation performance using a fixed bed continuous hydrogenation reactor. Diaminotoluene (TDA) was used as a reactant raw material to prepare a raw material liquid with a mass ratio of TDA to solvent ethyl acetate of 1:20. During the feeding process, the raw material tank was protected by nitrogen. The TDA hydrogenation reaction evaluation conditions were as follows: the pressure was 6 MPa, the temperature was 100°C, and the liquid product was collected after 720 hours of reaction to analyze the conversion rate of diaminotoluene (TDA), the selectivity of methylcyclohexanediamine (HTDA) and the yield of methylcyclohexanediamine (HTDA).

[0051] Table 1: Catalyst performance evaluation table

[0052] ‌‌‌TDA conversion rate refers to the percentage of TDA participating in the reaction and converted to the target product in a statistical period, and the calculation formula is: TDA conversion rate = (amount of TDA participating in the reaction / amount of TDA passing through the reactor) × 100%‌. ‌‌HTDA selectivity‌ refers to the ratio of the amount of TDA converted to the target product to the total amount of TDA converted by participating in all reactions in the reaction system, and the calculation formula is: HTDA selectivity = (number of moles of TDA converted to the target product / number of moles of TDA reacted) × 100%‌. ‌HTDA yield‌ describes the efficiency of the reaction process from the perspective of the product, that is, the percentage of the number of moles of TDA converted to the target product to the number of moles of TDA passing through the reactor, and the calculation formula is: HTDA yield = (number of moles of TDA converted to the target product / number of moles of TDA passing through the reactor) × 100%‌.

[0053] As shown in Table 1, the TDA conversion rate, HTDA selectivity and HTDA yield in Example 1 are 90.5%, 92.6% and 91.5%, respectively; the TDA conversion rate, HTDA selectivity and HTDA yield in Example 2 are 99.9%, 99.9% and 99.8%, respectively; the Al2O3 carrier for preparing the catalyst in Example 1 is not modified; in Example 2, the additive MgO is added to modify Al2O3 under certain conditions to obtain a spherical activated alumina modified carrier containing the additive MgO; the catalytic performance of the prepared catalyst is significantly higher than that of the catalyst prepared by the carrier without additive addition; the modified carrier has developed pores, reasonable pore size distribution and strong adsorption capacity, which can make the active component platinum group metal more effectively loaded, and has high activity, easy regeneration and strong thermal stability; when the catalyst loading volume is the same, higher production capacity and hydrogenation efficiency can be guaranteed, the generation of deamination side reactants during hydrogenation is reduced, and the TDA conversion rate, HTDA selectivity and HTDA yield are improved.

[0054] The TDA conversion, HTDA selectivity and HTDA yield in Example 3 were 94.2%, 95.1% and 94.5% respectively. Compared with Example 2, the auxiliary agent MgO was replaced with BaO, and the catalytic performance of the catalyst obtained by replacing the auxiliary agent was reduced.

[0055] In Example 4, the TDA conversion rate, HTDA selectivity and HTDA yield were 96.1%, 97.5% and 96.9% respectively. Compared with Example 2, the auxiliary agent MgO was replaced with Na2O, and the catalytic performance of the catalyst obtained by replacing the auxiliary agent was reduced.

[0056] In Example 5, the TDA conversion rate, HTDA selectivity and HTDA yield were 95.8%, 96.2% and 95.3% respectively. Compared with Example 2, the mass ratio of the auxiliary agent MgO and the alumina powder removal was changed. As the auxiliary agent ratio increased, the TDA conversion rate, HTDA selectivity and HTDA yield decreased instead.

[0057] In Example 6, the TDA conversion rate, HTDA selectivity and HTDA yield are 99.9%, 99.9% and 99.6%, respectively. Compared with Example 2, the soluble salt of the platinum group metal is a mixed solution of Ru(II)(NO)(NO3)3 and Rh(NO3)3. The catalysts prepared in Example 2 and Example 6 both make the TDA conversion rate as high as 99.9% and the HTDA selectivity as high as 99.9%, but the market price of Rh metal is more than three times more expensive than that of Ru, and the doping of the platinum group metal Rh increases the preparation steps of the catalyst, which significantly increases the cost.

[0058] Under the preparation process of the catalyst of the present invention, only a single platinum group metal-loaded modified carrier is required to achieve a high catalytic effect, thereby improving the TDA conversion rate, HTDA selectivity and HTDA yield.

[0059] The structure of the carrier was determined by scanning electron microscopy (SEM). Figure 3 Figure a is a SEM image of the unmodified carrier of Example 1. Figure 3 Figure b is a SEM image of the modified carrier of Example 2. The modified carrier has abundant pores, developed porosity, reasonable pore size distribution, and strong adsorption capacity, so that the platinum group metal Ru can be evenly and firmly adsorbed on the carrier surface.

[0060] Figure 4 This is the thickness diagram of the Ru metal active layer on the surface of the modified carrier in Example 2. Figure 4 Figure A is a graph of the thickness of the Ru metal active layer observed at the first position of the catalyst. Figure 4 Figure B is a diagram of the thickness of the Ru metal active layer observed at the second position of the catalyst. Figure 4 Figure A and Figure 4 In Figure B, the black part represents the Ru metal active layer, and the white part is the modified support. Figure 4 It can be clearly observed that the thickness of the Ru metal active layer is not only controllable, but also very uniformly distributed, which indicates that the Ru metal is uniformly loaded on the surface of the modified support. It should be noted that the thickness of the Ru metal active layer is crucial. If the Ru metal thickness is too deep, the reactants cannot contact the active components, wasting the Ru metal. If the Ru metal layer is too shallow, there are few active components, the reaction is incomplete, and by-products are easily produced.

[0061] Figure 5 , Figure 6 and Figure 7 They are respectively the cut core energy spectrum, cut edge energy spectrum and original surface energy spectrum of the catalyst prepared in Example 2, Figure 5 , Figure 6 and Figure 7 This indicates that the components of the modified support and the Ru metal are loaded on the support surface, which is beneficial to the catalyst-catalyzed hydrogenation reaction of diaminotoluene (TDA) to produce methylcyclohexanediamine (HTDA), thereby improving the TDA conversion rate, HTDA selectivity and HTDA yield.

[0062] Figure 8 This is the distribution diagram of Ru metal active sites in the carrier of Example 1. Fig. 9 This is the distribution diagram of Ru metal active sites in the modified carrier of Example 2. Figure 8 The Ru metal active sites are unevenly distributed. Fig. 9 This indicates that the modified carrier has abundant and evenly distributed Ru metal active sites, thereby improving the activity of the catalyst and reducing the production of deamination side reactants during the hydrogenation process.

[0063] In summary, the present invention adds auxiliary agents to the carrier, screens the spheres, and performs vacuum calcination and other modifications, and then immerses the carrier in a platinum group metal solution and then performs ultrasonic treatment, drying, reduction, and filtration and drying, so that the platinum group metal is evenly and firmly dispersed on the carrier, thereby solving the defects of low utilization rate and uneven distribution of active components of existing catalysts. The catalyst has the advantages of high activity and strong stability. The catalyst of the present invention is used in the synthesis of methylcyclohexanediamine by hydrogenation of diaminotoluene, and under the conditions of catalyst action and suitable process parameters, the occurrence of deamination in the reaction process is suppressed, the TDA conversion rate, HTDA selectivity and HTDA yield are improved, and HTDA is easy to separate and purify, and is suitable for large-scale continuous production.

[0064] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A catalyst suitable for the continuous production of methylcyclohexanediamine in a fixed bed, characterized in that: The catalyst comprises a modified carrier and an active component; wherein, The modified carrier comprises activated alumina and an auxiliary agent, wherein the auxiliary agent comprises an alkali metal oxide or an alkaline earth metal oxide, and the activated alumina and the auxiliary agent are bonded, balled, sieved and calcined to obtain the modified carrier; The active component is any one of the platinum group metals Ru, Rh, Pd, and Pt; the active component is supported on the modified carrier; The preparation method of the catalyst for continuously producing methylcyclohexanediamine using a fixed bed comprises the following steps: S1. Preparation of modified carrier: uniformly mix alumina quick-release powder and an auxiliary agent; wherein the mass ratio of the auxiliary agent to the alumina quick-release powder is (0.1-0.5):1; control the rotation of a ball-forming disk containing ball seeds, and add a mixture of the alumina quick-release powder and the auxiliary agent, as well as a binder, to the ball-forming disk, so that the alumina quick-release powder and the auxiliary agent are bonded to form a sphere; sieve the sphere, calcine it under vacuum conditions at 200°C-600°C for 4h-8h, and then cool it to room temperature to obtain a modified carrier; S2. Preparation of precursor solution: Add deionized water to a soluble salt of any platinum group metal, add nitric acid solution at 60°C to 100°C and stir until the soluble salt of the platinum group metal is completely dissolved to obtain an active platinum group metal precursor solution; S3. Preparation of finished catalyst: adding the modified carrier to the active platinum group metal precursor solution, ultrasonically treating for 0.5h to obtain a semi-finished catalyst; drying the semi-finished catalyst in a drying oven at 60℃~100℃ for 2h~5h, and then cooling to room temperature; adding a reducing agent to the semi-finished catalyst to reduce the semi-finished catalyst; filtering out the residual liquid in the reduced semi-finished catalyst, washing with distilled water for 3~5 times, and then drying in a vacuum drying oven, and cooling to obtain a finished catalyst.

2. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, characterized in that: The raw material for producing the activated alumina includes alumina powder which is quick-released; the particle size of the alumina powder is 10 μm to 100 μm, and the specific surface area is 220 to 330 m 2 / g; and the Al2O3 content in the alumina quick-de-powdering is ≥98%.

3. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, characterized in that: When the auxiliary agent is an alkali metal oxide, the auxiliary agent includes Na2O; When the auxiliary agent is an alkaline earth metal oxide, the auxiliary agent includes any one of MgO and BaO.

4. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1 or 3, characterized in that: The particle size of the additive is 20nm to 100nm, and the specific surface area is ≥50m 2 / g, and the purity of the auxiliary agent is ≥99%.

5. The catalyst for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, 2 or 3, wherein the particle size of the modified carrier is 2.0 mm to 3.0 mm, and the specific surface area is 200 m 2 / g~400m 2 / g, and the bulk density is 0.40g / mL~0.80g / mL.

6. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, 2 or 3, characterized in that: The catalyst comprises 0.5-5.0% of the platinum group metal and 95.0-99.5% of the modified carrier in terms of mass percentage, and the sum of the mass percentages of the platinum group metal and the modified carrier is 100%.

7. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, characterized in that: The binder is any one of pseudo-boehmite, activated clay, kaolin and high-alumina cement, or a mixture of two of them.

8. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, characterized in that: The reducing agent is any one of sodium borohydride, hydrazine hydrate and formic acid.

9. The catalyst suitable for the fixed bed continuous production of methylcyclohexanediamine according to claim 1, characterized in that: The soluble salt of the platinum group metal is any one of RuCl3, K2RuCl6, (NH4)2RuCl6, Ru(OAc)3, Ru(II)(NO)(NO3)3, Rh(NO3)3, PdCl2 and H2PtCl6.

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