A catalyst and a method for preparing 1,4-cyclohexanedimethanol by one-step hydrogenation of dimethyl terephthalate

Abstract

The application provides a kind of catalyst and the preparation method of 1,4-cyclohexane dimethanol by one-step hydrogenation of dimethyl terephthalate, and the preparation of the catalyst comprises: carbon nanotubes are treated with acid, reacted with Sn salt and citric acid to obtain a carrier, Rh salt is mixed with NH4ReO4 to co-precipitate and react to obtain a metal nanocluster solution, which is added dropwise into the dispersion of the carrier, and then heat-treated to obtain the catalyst. The above-mentioned catalyst catalyzes the one-step hydrogenation of dimethyl terephthalate to prepare 1,4-cyclohexane dimethanol. The metal Re in the catalyst can have a synergistic effect with Rh, promoting the ring hydrogenation catalytic activity of Rh for DMT. During the preparation process, the CNTs modified by nitric acid produce hydrophilic surface functional groups -COOH, -OH and -COR, which improve the dispersion of the metal in the CNTs, the adsorption performance of the raw material dimethyl terephthalate, and the catalytic hydrogenation activity of the catalyst is significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ester hydrogenation, and particularly relates to a catalyst and a method for preparing 1,4-cyclohexanedimethanol by one-step hydrogenation of dimethyl terephthalate. BACKGROUND

[0002] 1,4-cyclohexanedimethanol (CHDM) is one of the key monomers for producing high-end polyesters in industry. Since the melting point (315℃-320℃) of the polyester prepared by using trans-CHDM modification is higher than that (260℃-267℃) of the polyester prepared by using cis-CHDM, it is required that the CHDM used for modifying the polyester contains a higher trans / cis ratio, generally greater than 3:1. The polyester modified by using trans-CHDM has a higher glass transition temperature and softening temperature, good chemical resistance and environmental adaptability, and a wide application range. The addition of CHDM can improve multiple properties of polymeric materials, such as the polyester synthesized by using CHDM as a raw material, PETG, PCTG, PCT, PCTA, etc., which has the advantages of high transparency, good gloss, high strength, high toughness, chemical resistance, recyclability, and excellent processability, and is widely used in medical devices, electrical appliances, baby products, high-end decorative materials, etc., and has strong irreplaceability.

[0003] The existing technology for preparing CHDM is to use dimethyl terephthalate (DMT) as a raw material and to obtain it by two-step hydrogenation reduction. In the first step of hydrogenation reaction, the benzene ring in DMT is selectively hydrogenated and reduced into dimethyl 1,4-cyclohexanedicarboxylate (DMCD), and the catalysts mainly used include rhodium, nickel, palladium, ruthenium, etc., and barium, platinum, calcium, etc. are added as additives, the reaction temperature is 120-250℃, and the reaction pressure is 1-41 MPa. In the second step of reaction, the two carboxyl groups in DMCD are hydrogenated and reduced to prepare 1,4-cyclohexanedimethanol, and the traditional catalyst is a Cu-based catalyst, such as a copper-chromium catalyst or a copper-zinc catalyst, and manganese, barium, etc. are added as additives, the reaction temperature is 230-320℃, the reaction pressure is 9-17 MPa, and a ruthenium, tin, etc. catalyst can also be used, the reaction temperature range is 260-280℃, and the pressure range is 9-10 MPa. However, this process is limited by the catalyst and hydrogenation process, and the hydrogenation conditions are harsh (-30 MPa), and the selectivity of the trans structure is low, which indirectly leads to a decrease in the melting point temperature of the modified polyester.

[0004] CN1291783C discloses a catalyst for producing 1,4-cyclohexane dimethyl acid dimethyl ester, the main active component of which is metal palladium, the carrier is selected from alumina, and the auxiliary agent is composed of two types of auxiliary agents, the first auxiliary agent is silicon oxide, and the second auxiliary agent element is Ru in Group VIII, the metal palladium accounts for 0.5-2% by weight of the total weight of the catalyst, the first auxiliary agent silicon oxide accounts for 0.01-0.5% by weight of the total weight of the catalyst, and the second auxiliary agent element Ru accounts for 0.01-0.5% by weight of the total weight of the catalyst, the catalyst has the characteristics of low hydrogenation reaction pressure and high catalytic activity, the conversion rate of dimethyl phthalate is 95-99%, and the selectivity of 1,4-cyclohexane dimethyl acid dimethyl ester is 94-98%. However, when the catalyst is used for hydrogenation reaction, ethyl acetate is used as a solvent, by-products generated by hydrogenation of ethyl acetate are contained in the product, and the product solvent separation is increased, and the energy consumption is large.

[0005] CN108940305B discloses a hydrogenation catalyst and application, a preparation method of cyclohexane dimethyl ester by using the catalyst, and a production method of cyclohexane dimethyl alcohol. The catalyst contains a carrier and active elements and auxiliary elements supported on the carrier, the active elements are one or more than two selected from Rh, Ru and Pd, the auxiliary elements are Cu and / or Ag, and the carrier is active carbon and / or alumina. The hydrogenation catalyst has obviously improved catalytic activity. The ester hydrogenation catalyst is a composite metal oxide, and the metal elements in the composite metal oxide contain Cu, Zn and M, and M is Zr and / or Ti. The ester hydrogenation catalyst has obviously improved catalytic activity, and high raw material conversion rate can be obtained even at a lower temperature, and high product selectivity can also be obtained. However, two different catalysts are needed to carry out two-step hydrogenation in the method, and the target product 1,4-cyclohexane dimethyl alcohol is obtained, the whole process is complex in operation, and the cost is relatively high. SUMMARY

[0006] In order to solve the above problems, the application provides a hydrogenation catalyst and a method for preparing 1,4-cyclohexane dimethyl alcohol by one-step hydrogenation of dimethyl terephthalate. The application provides a noble metal supported composite carrier type catalyst and a preparation method thereof. In particular, when the catalyst is used for hydrogenation reaction of dimethyl terephthalate, the catalyst has high hydrogenation activity, good stability, high selectivity of the catalyst to trans-1,4-cyclohexane dimethyl alcohol, and can improve the trans / cis ratio in the product.

[0007] The technical purposes of the application are achieved by the following technical solutions.

[0008] The technical purpose of the first aspect of the application is to provide a preparation method of a catalyst, comprising the following steps:

[0009] (1) acid treatment of carbon nanotubes, mixing with SnCl4.5H2O aqueous solution, adding citric acid solution to form gel, drying to obtain SnO2-CNTs composite carrier;

[0010] (2) preparing ethylene glycol solution containing RhCl3.3H2O and NH4ReO4, adding alkali solution dropwise until pH>12 to obtain transparent colloidal solution, separating water and alcohol under inert atmosphere to obtain ethylene glycol colloidal solution containing rhodium and rhenium metal nanoclusters;

[0011] (3) dispersing SnO2-CNTs composite carrier obtained in (1) in ethylene glycol, adjusting pH of solution obtained in (2) to 2-7, adding to SnO2-CNTs composite carrier ethylene glycol dispersion, washing and drying after heat treatment to obtain the catalyst.

[0012] Further, the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes, the length of the carbon nanotubes is 80-4000 nm, preferably 100-1000 nm, and the inner diameter of the tube is 0.1-30 nm, preferably 0.5-30 nm.

[0013] Further, the acid treatment in step (1) is first soaking in nitric acid solution, boiling, washing with distilled water and drying. The mass concentration of the nitric acid solution is 30%-50%, preferably 30%-40%, the soaking temperature is 60-100°C, preferably 60-90°C. The boiling temperature is 100-120°C, preferably 100-110°C, in a closed system, and the boiling time is 2-6 h, preferably 2-4 h. The distilled water is washed for 3-7 times, preferably 3-5 times, until the pH is 3-7. The drying temperature is 120-150°C, preferably 120-130°C.

[0014] Further, the molar concentration of SnCl4.5H2O in the aqueous solution of SnCl4.5H2O in step (1) is 0.001-0.005 mol / L, preferably 0.001-0.003 mol / L; and the mass ratio of CNTs to SnCl4.5H2O powder is 1-3:1, preferably 1-2:1.

[0015] Further, the molar concentration of the citric acid solution in step (1) is 0.0001-0.002 mol / L, preferably 0.0001-0.001 mol / L; and the molar ratio of citric acid to SnCl4.5H2O is 1-2:1, preferably 1-1.5:1. After adding citric acid, stirring and reaction, the reaction time is 12-24 h, preferably 12-18 h; and the reaction temperature is 60-100°C, preferably 60-80°C.

[0016] Further, the temperature in step (1) is 110-160°C, preferably 110-140°C, and the time is 6-18h, preferably 6-12h.

[0017] Further, in step (2), an ethylene glycol solution of RhCl3·3H2O and an ethylene glycol solution of NH4ReO4 are prepared respectively, the two solutions are mixed, and then a lye is added dropwise. The molar concentration of RhCl3·3H2O in the ethylene glycol solution of RhCl3·3H2O is 0.1-0.8mmol / L, preferably 0.2-0.6mmol / L; the molar concentration of NH4ReO4 in the ethylene glycol solution of NH4ReO4 is 0.1-0.5mmol / L, preferably 0.2-0.4mmol / L.

[0018] Further, in step (2), the lye is an aqueous NaOH solution, and the molar concentration is 0.5-0.8mol / L, preferably 0.5-0.6mol / L.

[0019] Further, in step (2), the temperature is raised to 150-180°C, preferably 150-160°C, at which the colloidal system is in a boiling state, and the time is maintained for 3-12h, preferably 3-8h.

[0020] Further, in step (3), the mass ratio of SnO2-CNTs composite carrier to ethylene glycol is 0.3:1-1:1, preferably 0.5:1-1:1.

[0021] Further, in step (3), the pH is adjusted to 2-7 by dilute hydrochloric acid, and the mass concentration of the dilute hydrochloric acid is 10%-20%, preferably 10%-15%.

[0022] Further, in step (3), the temperature of the heat treatment is 40-120°C, preferably 50-100°C, and the time is 12-60h, preferably 12-48h.

[0023] Further, in step (3), the drying is vacuum drying and / or air blowing drying, preferably vacuum drying first, and then air blowing drying; the temperature of the vacuum drying is 60-90°C, preferably 60-80°C, and the time is 12-72h, preferably 12-48h; the temperature of the air blowing drying is 110-170°C, preferably 120-160°C, and the time is 3-12h, preferably 3-8h.

[0024] Further, in the above preparation method, the addition amount of each raw material is such that the mass percentage of the metal Rh in the prepared catalyst is 0.3wt%-1.5wt%, preferably 0.5wt%-1.5wt%, and the mass percentage of the metal Re in the catalyst is 0.1wt%-0.8wt%, preferably 0.3wt%-0.8wt%.

[0025] Further, the catalyst further comprises a reduction process before catalyzing the reaction, specifically, hydrogen is used as the reducing agent, the reduction temperature is 400-600℃, preferably 450-500℃, and the reduction time is 3-12h, preferably 4-8h.

[0026] The technical purpose of the second aspect of the present application is to provide the catalyst prepared by the above method.

[0027] The technical purpose of the third aspect of the present application is to provide a method for preparing 1,4-cyclohexanedimethanol by one-step hydrogenation of dimethyl terephthalate, using the above catalyst to catalyze the reaction process.

[0028] Further, the catalyst is reduced by hydrogen before catalyzing the above reaction.

[0029] Further, the specific conditions of the hydrogenation reaction are as follows: the catalyst is loaded into a fixed-bed reactor, and the reaction process is as follows: the catalyst is loaded into a fixed-bed reactor, and the reaction is catalyzed under the conditions that the reaction temperature is 100-260℃, preferably 120-250℃, the reaction pressure is 2-9MPa, preferably 3-8MPa, the liquid feed space velocity is 0.05-10h -1 , preferably 0.1-5h -1 , and the hydrogen liquid molar ratio is 100:1-800:1, preferably 100:1-500:1.

[0030] Further, the raw material of the above reaction is dimethyl terephthalate, and the reaction is carried out after dilution with a solvent, and the solvent is selected from at least one of methanol, ethanol, butanol, n-propanol, isopropanol, and 1,4-cyclohexanedimethanol; the mass fraction of the raw material is 1.5%-25%, preferably 5%-15%, based on the total weight of the raw material and the solvent.

[0031] More specifically, the fixed-bed reactor, pump, pipeline, etc. used in the above reaction are all provided with heat preservation equipment, and the heat preservation of the pipelines, pumps, tanks, etc. of the fixed-bed is turned on first during the reaction, the system temperature and pressure are adjusted to the reaction temperature and pressure, then the H2 flow is adjusted to the reaction conditions, and then a certain hydrogen liquid molar ratio is ensured, the pump feeding of the raw material tank is turned on to ensure a certain liquid space velocity feeding, and the device starts one-step hydrogenation reaction. In the product receiving tank at the tail of the reaction, samples are taken every certain time, and product analysis is carried out.

[0032] The above catalyst is used to catalyze the one-step hydrogenation of dimethyl terephthalate to prepare 1,4-cyclohexanedimethanol, the conversion rate of dimethyl terephthalate is ≥80%, the cis-trans ratio of the prepared 1,4-cyclohexanedimethanol is ≥3.35:1, and the selectivity of 1,4-cyclohexanedimethanol is 70%-85%.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] (1) In the preparation process of the catalyst, Re is introduced to promote the catalytic activity of Rh for the ring hydrogenation of DMT. At the same time, the electron-deficient environment in the carbon nanotube CNTs carrier can limit the aggregation and growth of metal nanoparticles in the lumen. The strong interaction between the metal and the CNTs carrier makes the Rh(0) on the smaller Rh-Re / SnO2-CNTs more stable, ensuring the stability of the DMT hydrogenation catalytic reaction.

[0035] (2) In the preparation process of the catalyst, the CNTs modified by nitric acid produce hydrophilic surface functional groups -COOH, -OH and -COR, which can greatly improve the dispersion of SnO2 in CNTs. In addition, SnO2 changes the adsorption properties of the SnO2-CNTs composite carrier for the raw material dimethyl terephthalate, causing changes in the local concentration of the raw material on the surface of the carrier, changing the reaction control step and thus speeding up the reaction process. Therefore, CNTs and SnO2 have a synergistic catalytic effect, which significantly improves the catalytic hydrogenation activity of the catalyst.

[0036] (3) In the preparation process of the catalyst, SnO2 is easily reduced in the presence of Rh, forming Rh-Sn alloy on the Rh metal particles, thereby having high ester hydrogenation catalytic activity and 1,4-cyclohexane dimethanol selectivity. In addition, the lumen size effect of the catalyst carrier CNTs changes the diffusion kinetics of trans-1,4-cyclohexane dimethanol in the lumen, making the catalyst have high selectivity for trans-1,4-cyclohexane dimethanol and improving the trans / cis ratio in the product.

[0037] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0038] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but in no way limit the present application.

[0039] The method and effects of the present application will be further described in detail below in conjunction with specific examples. The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0040] In the following examples, the experimental methods are conventional methods in the art unless otherwise specified. The experimental materials used in the following examples can be purchased from biochemical reagent stores unless otherwise specified.

[0041] The conversion of dimethyl terephthalate, the selectivity of 1,4-cyclohexanedimethanol and the trans / cis ratio of 1,4-cyclohexanedimethanol were determined by gas chromatography. The gas chromatography conditions were as follows: SHIMADZU GC-2030 gas chromatograph with FID detector; SE-54 capillary column, 30 m x 0.25 mm x 0.25 μm; injection port temperature 280 °C; injection volume 1 μL; split injection, split ratio 50:1; column initial temperature 160 °C, temperature rising rate 8 °C / min to 270 °C, holding for 5 min; then temperature rising rate 15 °C / min to 300 °C, holding for 5 min; detector temperature 280 °C.

[0042] (1) Conversion of dimethyl terephthalate:

[0043] X = (A0 - A1) / A0 x 100%

[0044] In the formula, X is the conversion of dimethyl terephthalate; A0 is the area percentage content of dimethyl terephthalate in the raw material, %; and A1 is the area percentage content of dimethyl terephthalate in the product, %.

[0045] (2) Selectivity of 1,4-cyclohexanedimethanol:

[0046] Y = (B CHDM / 144) / (B CHDM / 144 + C 杂质 / 153) x 100%

[0047] In the formula, Y is the selectivity of 1,4-cyclohexanedimethanol; B CHDM is the area percentage content of 1,4-cyclohexanedimethanol in the product, %; and C 杂质 is the total area percentage content of impurities in the product, %.

[0048] (3) Trans / cis ratio of 1,4-cyclohexanedimethanol:

[0049] Trans / cis ratio = B 反 / B 顺

[0050] In the formula, B 反 is the area percentage content of trans-1,4-cyclohexanedimethanol in the product, %; and B 顺 is the area percentage content of cis-1,4-cyclohexanedimethanol in the product, %.

[0051] Example 1

[0052] The multi-walled carbon nanotubes with a length of 500 nm and an inner diameter of 10 nm were immersed in a 35% nitric acid solution at 90°C, boiled at 110°C for 4h in a closed system, washed with distilled water for 6 times until the pH was 6.5, and dried at 130°C. The dried carbon nanotubes were mixed with a 0.003 mol / L SnCl4·5H2O aqueous solution, and the mass ratio of CNTs to SnCl4·5H2O powder was 1.5:1. A 0.001 mol / L citric acid solution was added, and the molar ratio of citric acid to SnCl4·5H2O was 1.5:1. The mixture was stirred at 80°C for 18h to form a gel, and dried at 140°C for 12h to obtain a SnO2-CNTs composite carrier. Meanwhile, a 0.6 mmol / L RhCl3·3H2O ethylene glycol solution and a 0.4 mmol / L NH4ReO4 ethylene glycol solution were prepared, respectively. The two solutions were mixed, and a 0.6 mol / L NaOH aqueous solution was added dropwise until the pH value was greater than 12 to obtain a transparent colloidal solution. The solution was boiled in a closed system to 160°C for 8h, and the water and excess alcohol were separated in an inert atmosphere to obtain an ethylene glycol colloidal solution containing rhodium and rhenium metal nanoclusters. The pH was adjusted to 6.5 by adding 15% dilute hydrochloric acid. The SnO2-CNTs composite carrier prepared above was dispersed in ethylene glycol, and the mass ratio of the SnO2-CNTs composite carrier to ethylene glycol was 0.5:1. The pH-adjusted ethylene glycol colloidal solution containing rhodium and rhenium metal nanoclusters was added to the SnO2-CNTs composite carrier dispersion in ethylene glycol, and was heat-treated at 100°C for 48h. After washing, the catalyst A was obtained by vacuum drying at 80°C for 48h and air drying at 160°C for 8h. The mass fraction of metal Rh was 1.3 wt%, and the mass fraction of metal Re was 0.7 wt%.

[0053] Operation reaction conditions: Catalyst A was loaded on a fixed bed reactor, and was reduced by H2 at a temperature of 500°C for 8h. Isopropyl alcohol was used as a solvent and mixed with the raw material at 80°C. The mass fraction of the raw material was 10%, and at the same time, the pipelines, pumps, tanks, etc. of the fixed bed were opened for heat preservation. The reaction temperature was adjusted to 220°C, the pressure was 6 MPa, the liquid feed space velocity was 2h -1 , the hydrogen liquid molar ratio was 400:1, and the catalytic terephthalic acid dimethyl ester reaction was carried out. The product in the tail of the reaction was sampled at certain time intervals, and product analysis was carried out. The conversion rate of terephthalic acid dimethyl ester in the product was 89.1%, the selectivity of 1,4-cyclohexane dimethanol was 78.2%, and the cis-trans ratio of 1,4-cyclohexane dimethanol was 3.46:1.

[0054] Example 2

[0055] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that single-walled carbon nanotubes with a length of 1500 nm and an inner diameter of 0.5 nm were used, and catalyst B was prepared, in which the mass ratio of metal Rh was 0.9 wt%, and the mass ratio of metal Re was 0.6 wt%.

[0056] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 81.3%, the selectivity of 1,4-cyclohexane dimethanol was 73.3%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.40:1.

[0057] Example 3

[0058] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that the catalyst C was prepared by soaking in a 45% mass concentration nitric acid solution at 95°C, boiling in a closed system at 120°C for 5h, in which the mass ratio of metal Rh was 1.5 wt%, and the mass ratio of metal Re was 0.8 wt%.

[0059] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 88.7%, the selectivity of 1,4-cyclohexane dimethanol was 76.4%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.47:1.

[0060] Example 4

[0061] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that the catalyst D was prepared by washing with distilled water for 3 times until the pH was 4.4, and drying at 140°C, in which the mass ratio of metal Rh was 0.8 wt%, and the mass ratio of metal Re was 0.5 wt%.

[0062] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 80.4%, the selectivity of 1,4-cyclohexane dimethanol was 71.2%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.38:1.

[0063] Example 5

[0064] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that an aqueous solution of SnCl4.5H2O with a molar concentration of 0.004 mol / L was used to mix with the dried carbon nanotubes, and the CNTs and SnCl4.5H2O powder were fed in a mass ratio of 2.5:1. Catalyst E was prepared, in which the mass ratio of metal Rh was 0.9 wt%, and the mass ratio of metal Re was 0.5 wt%.

[0065] The other operations were the same as in Example 1, and samples were taken at intervals in the product receiving tank at the tail of the reaction, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 81.5%, the selectivity of 1,4-cyclohexane dimethanol was 72.3%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.41:1.

[0066] Example 6

[0067] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that a citric acid solution with a molar concentration of 0.002 mol / L was used, and the molar ratio of citric acid to SnCl4.5H2O was 2:1. The gel was formed by stirring at 90°C for 24 h, and dried at 150°C for 18 h. Catalyst F was prepared, in which the mass ratio of metal Rh was 1.4 wt%, and the mass ratio of metal Re was 0.5 wt%.

[0068] The other operations were the same as in Example 1, and samples were taken at intervals in the product receiving tank at the tail of the reaction, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 87.8%, the selectivity of 1,4-cyclohexane dimethanol was 75.1%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.42:1.

[0069] Example 7

[0070] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that a RhCl3.3H2O ethylene glycol solution with a molar concentration of 0.7 mmol / L and a NH4ReO4 ethylene glycol solution with a molar concentration of 0.1 mmol / L were used. Catalyst G was prepared, in which the mass ratio of metal Rh was 1.3 wt%, and the mass ratio of metal Re was 0.3 wt%.

[0071] The other operations were the same as in Example 1, and samples were taken at intervals in the product receiving tank at the tail of the reaction, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 88.4%, the selectivity of 1,4-cyclohexane dimethanol was 77.3%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 3.44:1.

[0072] Example 8

[0073] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that the pH was adjusted to more than 12 by adding a 0.8 mol / L aqueous NaOH solution dropwise until a transparent colloidal solution was obtained, and the system was boiled to 170°C for 12 h in a closed system, and water and excess alcohol were separated under an inert atmosphere. Catalyst H was prepared, in which the mass fraction of Rh was 0.8 wt%, and the mass fraction of Re was 0.7 wt%.

[0074] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 80.5%, the selectivity of 1,4-cyclohexanedimethanol was 71.3%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.37:1.

[0075] Example 9

[0076] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that 20% dilute hydrochloric acid was added to the ethylene glycol colloidal solution containing rhodium and rhenium metal nanoclusters to adjust the pH to 4.5. Catalyst I was prepared, in which the mass fraction of Rh was 0.7 wt%, and the mass fraction of Re was 0.5 wt%.

[0077] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 80.3%, the selectivity of 1,4-cyclohexanedimethanol was 71.0%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.36:1.

[0078] Example 10

[0079] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that the SnO2-CNTs composite carrier was dispersed in ethylene glycol at a mass ratio of 0.3:1. Catalyst J was prepared, in which the mass fraction of Rh was 0.6 wt%, and the mass fraction of Re was 0.4 wt%.

[0080] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 80.1%, the selectivity of 1,4-cyclohexanedimethanol was 70.8%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.35:1.

[0081] Example 11

[0082] The catalyst was prepared and the reaction conditions were the same as in Example 1, except that the ethylene glycol colloidal solution containing the metal nanoclusters of rhodium and rhenium after pH adjustment was added dropwise into the ethylene glycol dispersion of the SnO2-CNTs composite carrier, and after heat treatment at 110°C for 60h, the catalyst was washed, vacuum dried at 90°C for 60h, and then air-dried at 110°C for 12h. Catalyst K was prepared, in which the mass fraction of metal Rh was 0.5wt%, and the mass fraction of metal Re was 0.4wt%.

[0083] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 80.0%, the selectivity of 1,4-cyclohexanedimethanol was 70.7%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.37:1.

[0084] Example 12

[0085] The catalyst was the same as in Example 1, and catalyst A was prepared. The difference was that methanol was used as the solvent, and the feedstock was mixed with the raw material at 60°C. The mass fraction of the feedstock was 4.5%.

[0086] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 85.3%, the selectivity of 1,4-cyclohexanedimethanol was 79.9%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.44:1.

[0087] Example 13

[0088] The catalyst was the same as in Example 1, and catalyst A was prepared. The difference was that the reaction temperature was 260°C.

[0089] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 89.9%, the selectivity of 1,4-cyclohexanedimethanol was 75.1%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.43:1.

[0090] Example 14

[0091] The catalyst was the same as in Example 1, and catalyst A was prepared. The difference was that the reaction pressure was 9MPa.

[0092] The other operations were the same as in Example 1, and samples were taken from the product receiving tank at the tail end of the reaction at certain time intervals, and product analysis was performed. The conversion rate of dimethyl terephthalate in the product was 88.0%, the selectivity of 1,4-cyclohexanedimethanol was 75.3%, and the cis / trans ratio of 1,4-cyclohexanedimethanol was 3.45:1.

[0093] Example 15

[0094] The catalyst is the same as Example 1, Catalyst A is prepared. The difference is that the liquid hourly space velocity is 6 h -1 .

[0095] The other operations are the same as Example 1. The product in the product receiving tank at the end of the reaction is sampled at regular intervals and analyzed. The conversion of dimethyl terephthalate in the product is 86.4%, the selectivity of 1,4-cyclohexanedimethanol is 74.4%, and the cis / trans ratio of 1,4-cyclohexanedimethanol is 3.40:1.

[0096] Example 16

[0097] The catalyst is the same as Example 1, Catalyst A is prepared. The difference is that the hydrogen liquid molar ratio is 600:1.

[0098] The other operations are the same as Example 1. The product in the product receiving tank at the end of the reaction is sampled at regular intervals and analyzed. The conversion of dimethyl terephthalate in the product is 83.4%, the selectivity of 1,4-cyclohexanedimethanol is 72.1%, and the cis / trans ratio of 1,4-cyclohexanedimethanol is 3.37:1.

[0099] Comparative Example 1

[0100] The difference from Example 1 is that the carrier is prepared separately using an acid-treated CNT carrier during catalyst preparation. Catalyst L is prepared, in which the mass ratio of metal Rh is 1.2wt%, and the mass ratio of metal Re is 0.6wt%.

[0101] The other operations are the same as Example 1. The product in the product receiving tank at the end of the reaction is sampled at regular intervals and analyzed. The conversion of dimethyl terephthalate in the product is 73.0%, the selectivity of 1,4-cyclohexanedimethanol is 62.1%, and the cis / trans ratio of 1,4-cyclohexanedimethanol is 3.08:1.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that the carrier is prepared separately using a SnO2 carrier prepared from a single Sn salt during catalyst preparation. Catalyst M is prepared, in which the mass ratio of metal Rh is 1.1wt%, and the mass ratio of metal Re is 0.4wt%.

[0104] The other operations are the same as Example 1. The product in the product receiving tank at the end of the reaction is sampled at regular intervals and analyzed. The conversion of dimethyl terephthalate in the product is 72.4%, the selectivity of 1,4-cyclohexanedimethanol is 61.7%, and the cis / trans ratio of 1,4-cyclohexanedimethanol is 3.13:1.

[0105] Comparative Example 3

[0106] The difference from Example 1 is that the carrier used in the preparation of the catalyst is ordinary activated carbon instead of CNTs. Catalyst N is prepared, in which the mass percentage of metal Rh is 1.2wt%, and the mass percentage of metal Re is 0.6wt%.

[0107] Other operations are the same as Example 1. In the product receiving tank at the tail of the reaction, samples are taken at certain time intervals, and product analysis is performed. The conversion rate of dimethyl terephthalate in the product is 73.4%, the selectivity of 1,4-cyclohexane dimethanol is 62.6%, and the cis-trans ratio of 1,4-cyclohexane dimethanol is 3.21:1.

[0108] Comparative Example 4

[0109] The difference from Example 1 is that only metal Rh salt is used to prepare RhCl3·3H2O ethylene glycol solution, and no metal Re salt is contained. Catalyst O is prepared, in which the mass percentage of metal Rh is 1.4wt%.

[0110] Other operations are the same as Example 1. In the product receiving tank at the tail of the reaction, samples are taken at certain time intervals, and product analysis is performed. The conversion rate of dimethyl terephthalate in the product is 74.2%, the selectivity of 1,4-cyclohexane dimethanol is 62.3%, and the cis-trans ratio of 1,4-cyclohexane dimethanol is 3.24:1.

[0111] Comparative Example 5

[0112] The difference from Example 1 is that only metal Re salt is used to prepare NH4ReO4 ethylene glycol solution, and no metal Rh salt is contained. Catalyst P is prepared, in which the mass percentage of metal Re is 0.8wt%.

[0113] Other operations are the same as Example 1. In the product receiving tank at the tail of the reaction, samples are taken at certain time intervals, and product analysis is performed. The conversion rate of dimethyl terephthalate in the product is 70.2%, the selectivity of 1,4-cyclohexane dimethanol is 61.0%, and the cis-trans ratio of 1,4-cyclohexane dimethanol is 2.81:1.

[0114] Comparative Example 6

[0115] The difference from Example 1 is that the catalyst of Example 2 described in CN201210007690.4 is used. The active components of the prepared catalyst, ruthenium, tin and platinum, are supported on the carrier Al2O3, in which the mass percentage of ruthenium is 5%, the mass percentage of platinum is 11.7%, and the mass percentage of tin is 11.7%. The particle size of the catalyst is 40-60 mesh.

[0116] Other operations were the same as in Example 1, and samples were taken from the product receiving tank at the end of the reaction at intervals and subjected to product analysis. The conversion rate of dimethyl terephthalate in the product was 86.2%, the selectivity of 1,4-cyclohexane dimethanol was 60.2%, and the cis / trans ratio of 1,4-cyclohexane dimethanol was 2.64:1.

Claims

1. A method for preparing a catalyst, comprising the following steps: (1) acid treating carbon nanotubes, mixing with an aqueous solution of SnCl4·5H2O, and feeding the carbon nanotubes and SnCl4·5H2O powder at a mass ratio of 1-3:1, adding a citric acid solution, and adding the citric acid at a molar ratio of 1-2:1 of citric acid to SnCl4·5H2O; after adding the citric acid, the reaction time is 12-24 h, and the reaction temperature is 60-100℃, and a gel is formed by the reaction, dried, and a SnO2-CNTs composite carrier is obtained; (2) preparing an ethylene glycol solution of solutes including RhCl3·3H2O and NH4ReO4, adding an alkali solution dropwise until the pH value is greater than 12 to obtain a transparent colloidal solution, heating to 150-180℃ in a sealed state, and maintaining for 3-12 h, and separating water and alcohol under an inert atmosphere to obtain an ethylene glycol colloidal solution containing rhodium and rhenium metal nanoclusters; (3) dispersing the SnO2-CNTs composite carrier obtained in (1) in ethylene glycol, adjusting the pH of the solution obtained in (2) to 2-7, and adding it to the ethylene glycol dispersion of the SnO2-CNTs composite carrier, and washing and drying after heat treatment to obtain the catalyst; the heat treatment temperature is 40-120℃, and the time is 12-60 h; The amount of each raw material is such that the mass ratio of the metal Rh in the catalyst prepared is 0.3wt%-1.5wt%, and the mass ratio of the metal Re in the catalyst is 0.1wt%-0.8wt%.

2. The production method according to claim 1, characterized by, The carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

3. The preparation method according to claim 2, characterized in that, The length of the carbon nanotubes is 80-4000 nm, and the inner diameter of the tube is 0.1-30 nm.

4. The method of claim 1, wherein, In step (1), the acid treatment is first immersion in a nitric acid solution, boiling, washing with distilled water, and drying.

5. The preparation method according to claim 4, characterized in that, The mass concentration of the nitric acid solution is 30%-50%, and the immersion temperature is 60-100℃; the boiling temperature is controlled by pressure to be 100-120℃, and the boiling time is 2-6 h.

6. The method of claim 1, wherein, In step (2), the ethylene glycol solutions of RhCl3·3H2O and NH4ReO4 are prepared separately, the two solutions are mixed, and then an alkali solution is added dropwise; the molar concentration of RhCl3·3H2O in the ethylene glycol solution of RhCl3·3H2O is 0.1-0.8 mmol / L, and the molar concentration of NH4ReO4 in the ethylene glycol solution of NH4ReO4 is 0.1-0.5 mmol / L.

7. The preparation method according to claim 1, characterized in that, In step (2), the alkali is an aqueous NaOH solution with a molar concentration of 0.5-0.8 mol / L.

8. The method of claim 1, wherein, In step (3), the mass ratio of the SnO2-CNTs composite carrier to ethylene glycol is 0.3:1-1:

1.

9. The method of claim 1, wherein, The catalyst further comprises a reduction process before the catalytic reaction, with hydrogen as the reducing agent, a reduction temperature of 400-600℃, and a reduction time of 3-12 h.

10. The catalyst prepared by the method of any one of claims 1-9.

11. A process for the one-step hydrogenation of dimethyl terephthalate to 1,4-cyclohexanedimethanol, characterized in that, The catalyst of claim 10 is used in a catalytic reaction process.

12. The method of claim 11, wherein, The reaction process is as follows: the catalyst is loaded into a fixed bed reactor, and dimethyl terephthalate is catalytically reacted under the conditions that the temperature is 100-260℃, the pressure is 2-9 MPa, the liquid feed space velocity is 0.05-10 h -1 -1, and the hydrogen liquid molar ratio is 100:1-800:1.