Catalyst and preparation method therefor, and preparation method for 1,4-cyclohexanedimethanol

Abstract

A catalyst and a preparation method therefor, and a preparation method for 1,4-cyclohexanedimethanol. The catalyst comprises Pd, Co, and a carrier, wherein based on the total mass of the catalyst, the Pd content is 0.2-0.5 wt%, the Co content is 0.12-0.3 wt%, and the carrier content is 99.2-99.68 wt%. The carrier is a mixed oxide of Al, Si, and B, and the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.3. The carbon monoxide poisoning resistance of the catalyst can be significantly improved while reducing the content of Pd and Co elements. In addition, the catalyst has the advantages of high DMT conversion rates and high DMCD selectivity.

Description

Catalyst and preparation method thereof, and preparation method of 1,4-cyclohexanedimethanol

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202311409768.X filed on October 27, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of fine chemicals, and in particular to a catalyst and a preparation method thereof, as well as a preparation method of 1,4-cyclohexanedimethanol. Background Art

[0004] PETG is a transparent, non-crystalline copolyester formed by the transesterification of terephthalic acid (PDA), ethylene glycol (EG), and 1,4-cyclohexanedimethanol (CHDM). Unlike PET and PCT, PETG possesses outstanding toughness and high impact strength, 3-10 times that of modified polyacrylates. It also boasts a wide processing range, high mechanical strength, and excellent flexibility. Compared to PVC, it offers greater transparency, better gloss, easier printing, and environmental advantages.

[0005] At present, the preparation of PETG's important monomer 1,4-cyclohexanedimethanol (CHDM) mainly adopts the two-step hydrogenation route of dimethyl terephthalate (DMT). In the first step, the DMT benzene ring is hydrogenated to become 1,4-cyclohexanedicarboxylic acid dimethyl ester (DMCD), and in the second step, the DMCD ester is hydrogenated to generate CHDM.

[0006] At present, the catalysts used for hydrogenation of DMT benzene ring to produce dimethyl 1,4-cyclohexanedicarboxylate are mainly supported catalysts with precious metals such as Pd, Pd, and Ru as active components. The traditional solution impregnation method is generally used. Due to the solvation effect and the clustering effect of the active components during the impregnation process, the active components cannot be highly dispersed. To achieve catalytic activity that meets the needs of industrial production, it is necessary to increase the active content of precious metals, which cannot fully exert the role of the active catalytic sites of the precious metals and will also increase production costs.

[0007] Furthermore, experiments have revealed that existing catalysts are susceptible to carbon monoxide poisoning, significantly impacting the performance of palladium-based catalysts even at extremely low CO concentrations. Studies have shown that CO poisoning of palladium-based catalysts occurs when CO concentrations in H₂ exceed 10 ppm. Currently, industrial H₂ typically contains hundreds or even thousands of ppm of carbon monoxide, which can adversely affect catalytic activity.

[0008] CN1541762A reports a method for protecting palladium catalysts from carbon monoxide poisoning by adding a ruthenium promoter, with the ruthenium promoter comprising 3-6 wt% of ruthenium. The CO generated during the hydrogenation reaction is absorbed or converted by the ruthenium promoter, reducing the possibility of palladium catalyst poisoning. However, ruthenium is also a precious metal, and while the addition of large amounts of ruthenium can alleviate carbon monoxide poisoning, it also significantly increases catalyst costs, making it unsuitable for industrial production.

[0009] Therefore, there is an urgent need to develop a catalyst with low content of precious metal active components, excellent catalytic activity, strong resistance to carbon monoxide poisoning, and which can be used to catalyze the hydrogenation of dimethyl terephthalate to produce dimethyl 1,4-cyclohexanedicarboxylate.

[0010] Summary of the Invention

[0011] The present invention aims to solve the problems of high content of noble metal active components, poor dispersibility, high production cost and weak resistance to carbon monoxide poisoning in the catalyst used for hydrogenating dimethyl terephthalate to produce dimethyl 1,4-cyclohexanedicarboxylate, and to provide a catalyst and a preparation method thereof, as well as a preparation method of 1,4-cyclohexanedimethanol.

[0012] In order to achieve the above-mentioned object, the first aspect of the present invention provides a catalyst, wherein the catalyst comprises Pd, Co and a carrier; wherein, based on the total mass of the catalyst, the Pd content is 0.2-0.5wt%, the Co content is 0.12-0.3wt%, and the carrier content is 99.2-99.68wt%; the carrier is a mixed oxide of Al, Si and B, and the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.3.

[0013] A second aspect of the present invention provides a method for preparing a catalyst, wherein the method comprises the following steps:

[0014] (P1) preparing an oxide gel mixture;

[0015] (P2) subjecting the oxide gel mixture to a ball rolling process to obtain a spherical precursor;

[0016] (P3) The spherical precursor is first immersed in an impregnation solution containing a palladium source and a cobalt source, and then calcined to obtain the catalyst.

[0017] A third aspect of the present invention provides a method for preparing 1,4-cyclohexanedimethanol, wherein the method comprises:

[0018] T1, in the presence of a first-stage catalyst, dimethyl terephthalate is contacted with hydrogen I to perform a first-stage hydrogenation reaction to obtain an intermediate product; wherein the first-stage catalyst is the catalyst described in the first aspect of the present invention or the catalyst prepared according to the method described in the second aspect of the present invention;

[0019] T2, under the action of a second-stage catalyst, contacting the intermediate product with hydrogen II to perform a second-stage ester hydrogenation reaction to obtain 1,4-cyclohexanedimethanol.

[0020] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0021] 1) The catalyst provided in the present invention uses a composite oxide containing Al, Si, and B as a support, and is loaded with Pd and Co by an impregnation method. This catalyst significantly improves the catalyst's resistance to carbon monoxide poisoning. Using a single oxide support, using only Pd, or replacing Co with other metal elements does not significantly improve the catalyst's resistance to carbon monoxide poisoning.

[0022] 2) When the catalyst provided by the present invention is used to catalyze the hydrogenation reaction of dimethyl terephthalate, the DMT conversion rate and DMCD selectivity can be ≥99%;

[0023] 3) The catalyst preparation method provided by the present invention, compared with first preparing alumina gel and borosilicate gel separately and then mixing the alumina gel and borosilicate gel, is prepared by mixing the aluminum source, silicon source, and boron source in an alcohol solvent and performing an aging treatment together, that is, using a one-pot method. During the formation process, the alumina gel and borosilicate gel can produce a certain degree of entanglement or other affinity with each other, so that Al2O3, SiO2, and B2O3 are more evenly dispersed with each other, thereby being able to better serve as a catalyst support;

[0024] 4) The preparation method of 1,4-cyclohexanedimethanol provided in the present invention has good stability and high product purity, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is an electron microscope image of the catalyst prepared in Catalyst Preparation Example 1;

[0026] FIG2 is a partial magnified electron microscope image of the catalyst prepared in Catalyst Preparation Example 1. DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0028] A first aspect of the present invention provides a catalyst, wherein the catalyst comprises Pd, Co and a carrier; wherein, based on the total mass of the catalyst, the Pd content is 0.2-0.5wt%, the Co content is 0.12-0.3wt%, and the carrier content is 99.2-99.68wt%; the carrier is a mixed oxide of Al, Si and B, and the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.3.

[0029] The inventors discovered that a mixed oxide of Al, Si, and B, synergistically acting with Pd and Co, can significantly improve the catalyst's resistance to carbon monoxide poisoning while reducing the Pd and Co content. When used in the hydrogenation of dimethyl terephthalate, the catalyst achieved DMT conversion and DMCD selectivity of ≥99%.

[0030] Wherein, in the present invention, the catalyst can be marked as Pd / Co@A x O y The catalyst comprises a mixed oxide of Al, Si, and B, wherein A represents Al, Si, and B, and x and y satisfy oxide valence equilibrium. The catalyst comprises a support composed of a mixed oxide of Al, Si, and B, and supports Pd and Co. The Pd / Co@AxOy catalyst has an Al:Si:B molar ratio of 3.4-4.2:1:0.2-0.3, a Pd content of 0.2-0.5wt%, and a Co content of 0.12-0.3wt%.

[0031] A second aspect of the present invention provides a method for preparing a catalyst, wherein the method comprises the following steps:

[0032] (P1) preparing an oxide gel mixture;

[0033] (P2) subjecting the oxide gel mixture to a ball rolling process to obtain a spherical precursor;

[0034] (P3) The spherical precursor is first immersed in an impregnation solution containing a palladium source and a cobalt source, and then calcined to obtain the catalyst.

[0035] In step (1):

[0036] In one embodiment of the present invention, organic aluminum, tetraalkyl silicate, and trialkyl borate are dispersed in an alcohol solvent, and then carbonate is added to obtain a dispersion; the dispersion is then aged to obtain an oxide gel mixture.

[0037] In one embodiment of the present invention, the organic aluminum is selected from at least one of aluminum isopropoxide and sec-butyl aluminum, the tetraalkyl silicate is selected from at least one of tetraethyl orthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate, and the trialkyl borate is selected from at least one of triisopropyl borate and tributyl borate.

[0038] In one embodiment of the present invention, the alcohol solvent is at least one of ethanol and isopropanol, and the carbonate is selected from at least one of sodium carbonate, potassium carbonate, and ammonium carbonate. The amount of carbonate used is such that the pH of the dispersion is 7.5-8.5. Preferably, after adding the carbonate, stirring is carried out at room temperature for 4-6 hours. Room temperature has a well-known meaning and is not particularly limited in the present invention. For example, room temperature can be 20-35°C.

[0039] In one embodiment of the present invention, the amounts of the organic aluminum, tetraalkyl silicate, and trialkyl borate satisfy a molar ratio of Al:Si:B of 3.4-4.2:1:0.2-0.3.

[0040] In one embodiment of the present invention, the content of the organic aluminum in the dispersion is 0.1-0.6 M, preferably 0.2-0.4 M, where M is mol / L.

[0041] In one embodiment of the present invention, the aging is performed by standing at 20-30° C. for 5-10 hours.

[0042] Among them, in the present invention, the inventors of the present invention have found through research that, compared with preparing alumina gel and borosilicate gel separately and then mixing the alumina gel and borosilicate gel, mixing the aluminum source, silicon source and boron source in an alcohol solvent and performing aging treatment together, the alumina gel and borosilicate gel can produce a certain entanglement or other affinity with each other during the formation process, so that Al2O3, SiO2, and B2O3 are dispersed more evenly with each other, and can thus better serve as catalyst carriers.

[0043] In one embodiment of the present invention, after the aging treatment is completed, solid-liquid separation and washing are performed to obtain an oxide gel mixture.

[0044] In the present invention, the solid-liquid separation is preferably filtration or centrifugation, and the washing preferably includes alkaline water washing and clean water washing. For example, the washing is first washed with an alkaline aqueous solution with a pH of 10-12, and then washed with clean water until neutral, and the alkaline aqueous solution is NaOH and / or KOH solution.

[0045] In step (2):

[0046] In one embodiment of the present invention, the ball rolling treatment is performed in a ball rolling machine with a rotation speed of 20-50 rpm and a running time of 5-10 hours. In the present invention, microspheres with a particle size of 1.5-4 mm can be obtained through the ball rolling treatment.

[0047] In step (3):

[0048] In one embodiment of the present invention, the palladium source is selected from at least one of palladium chloride and palladium chloride; the cobalt source is selected from at least one of cobalt chloride and cobalt nitrate.

[0049] In one embodiment of the present invention, the amounts of the palladium source, cobalt source and microsphere particles are such that the prepared catalyst has a Pd content of 0.2-0.5 wt%, a Co content of 0.12-0.3 wt% and a carrier content of 99.2-99.68 wt%.

[0050] In one embodiment of the present invention, the solvent of the impregnation solution is at least one of water and alcohol solvents, preferably a mixed solvent of water and ethanol; wherein the volume concentration of ethanol in the mixed solvent of water and ethanol is 40-60%.

[0051] In one embodiment of the present invention, in the impregnation solution, based on the molar amount of Pd and Co elements, the content of the palladium source is 0.1-0.2M, and the content of the cobalt source is 0.03-0.05M.

[0052] In one embodiment of the present invention, the immersion is performed under ultrasound; wherein the ultrasound frequency is 60-100 kHz, and the ultrasound time is 10-15 h.

[0053] In one embodiment of the present invention, solid-liquid separation and drying are performed after the impregnation is completed. The solid-liquid separation is preferably centrifugation, and the drying can be oven drying or vacuum drying.

[0054] In one embodiment of the present invention, the calcination is performed under a reducing atmosphere; preferably, the calcination is performed under hydrogen.

[0055] In one embodiment of the present invention, the calcination operating conditions include: a calcination temperature of 400-600° C., and a calcination time of 3-5 hours.

[0056] In the present invention, after calcination, the calcined product cooled to room temperature can be sieved, and the spherical particles with a particle size of 1.5-4 mm obtained by separation are the catalyst.

[0057] In one embodiment of the present invention, Pd / Co@A x O y The specific preparation method of the catalyst can be: (P-1) preparing an AxOy oxide gel mixture and obtaining a spherical precursor by a rolling ball machine; (P-2) immersing the spherical precursor in a solution containing a palladium source and a cobalt source under ultrasonic conditions. After the impregnation is completed, centrifugation, drying, calcining under a reducing atmosphere, cooling, and sieving to obtain a modified Pd / Co@Al2O3 / SiO2 / B2O3 catalyst.

[0058] A third aspect of the present invention provides a method for preparing 1,4-cyclohexanedimethanol, wherein the method comprises:

[0059] T1, in the presence of a first-stage catalyst, dimethyl terephthalate is contacted with hydrogen I to perform a first-stage hydrogenation reaction to obtain an intermediate product; wherein the first-stage catalyst is the catalyst described in the first aspect of the present invention or the catalyst prepared according to the method described in the second aspect of the present invention;

[0060] T2, under the action of a second-stage catalyst, contacting the intermediate product with hydrogen II to perform a second-stage ester hydrogenation reaction to obtain 1,4-cyclohexanedimethanol.

[0061] In step T1,

[0062] In one embodiment of the present invention, the dimethyl terephthalate and dimethyl 1,4-cyclohexanedicarboxylate are mixed and dissolved to obtain a mixed solution; the mixed solution is contacted with hydrogen I to perform a first-stage hydrogenation reaction to obtain a first-stage hydrogenation reaction product.

[0063] In one embodiment of the present invention, the mass concentration of dimethyl terephthalate is 10-50%, preferably 20-30%, based on the total mass of the mixed solution.

[0064] In one embodiment of the present invention, the CO concentration in the hydrogen I is lower than 1000 ppm, preferably lower than 500 ppm, and more preferably not more than 100 ppm.

[0065] In one embodiment of the present invention, the one-stage hydrogenation reaction is carried out in a one-stage hydrogenation reactor; wherein the one-stage hydrogenation reactor is a fixed bed reactor, the inlet temperature is 120-140°C, the temperature of the catalyst bed is 150-170°C, the hydrogen pressure is 4-8MPa, and the space velocity (LVSH) of dimethyl terephthalate is 0.4-1h -1 , the raw material hydrogen-oil molar ratio is 30-150.

[0066] In one embodiment of the present invention, the mixed solution and hydrogen I are respectively subjected to heat exchange with the first-stage hydrogenation reaction product. The mixed solution and hydrogen I after heat exchange are mixed, and then preheated and enter from the top of the first-stage hydrogenation reactor. The generated first-stage hydrogenation reaction product flows out from the lower part of the first-stage hydrogenation reactor.

[0067] In one embodiment of the present invention, the first-stage hydrogenation reaction product after heat exchange enters a first-stage gas-liquid separation device, preferably enters a first-stage high-pressure gas-liquid separation tank, for a first-stage gas-liquid separation. The gas phase of the first-stage gas-liquid separation is hydrogen, which is returned to the first-stage hydrogenation reactor for recycling, and the liquid phase of the first-stage gas-liquid separation is a crude DMCD product.

[0068] In one embodiment of the present invention, the crude DMCD product enters a first-stage distillation separation unit for refining to obtain an intermediate product; wherein the intermediate product is dimethyl 1,4-cyclohexanedicarboxylate.

[0069] In one embodiment of the present invention, the intermediate product is divided into at least part A and part B, the part A is returned to the first stage hydrogenation reaction and added to the mixed solution for recycling, and the part B is contacted with hydrogen II for a second stage hydrogenation reaction.

[0070] In one embodiment of the present invention, the portion A accounts for 50-90% of the intermediate product, and the portion B accounts for 10-50% of the intermediate product.

[0071] In one embodiment of the present invention, the first-stage distillation separation unit includes a DMCD light component removal tower and a DMCD distillation tower; wherein, the DMCD light component removal tower is used to remove impurities with a boiling point lower than the boiling point of dimethyl 1,4-cyclohexanedicarboxylate, and the bottom material of the DMCD light component removal tower is fed into the DMCD distillation tower; the DMCD distillation tower is used to separate the intermediate product.

[0072] In step T2,

[0073] In one embodiment of the present invention, the second-stage catalyst is a non-precious metal composite oxide catalyst. The non-precious metal composite oxide catalyst comprises at least two oxides of copper, zinc, and aluminum. Preferably, the non-precious metal composite oxide catalyst is a composite metal oxide of copper oxide and zinc oxide, and optionally further comprises aluminum oxide. For example, the non-precious metal composite oxide catalyst comprises 30-40 wt% copper oxide, 50-60 wt% zinc oxide, and 0-10 wt% aluminum oxide.

[0074] In one embodiment of the present invention, the intermediate product (or part B) is contacted with hydrogen II to carry out a two-stage ester hydrogenation reaction to obtain a two-stage ester hydrogenation reaction product; wherein the two-stage ester hydrogenation reaction is carried out in a two-stage hydrogenation reactor; wherein the catalyst bed temperature of the two-stage hydrogenation reactor is 190-220°C, the hydrogen pressure is 8-10 MPa, and the space velocity (LVSH) of dimethyl 1,4-cyclohexanedicarboxylate is 0.2-0.4h -1 , the raw material hydrogen-oil molar ratio is 80-150.

[0075] In one embodiment of the present invention, the intermediate product and hydrogen II are respectively heat exchanged with the second-stage ester hydrogenation reaction product, and the intermediate product and hydrogen II after heat exchange are mixed, and then preheated and enter from the top of the second-stage hydrogenation reactor, and the generated second-stage ester hydrogenation reaction product flows out from the lower part of the second-stage hydrogenation reactor.

[0076] In one embodiment of the present invention, the second-stage ester hydrogenation reaction product after heat exchange enters a second-stage gas-liquid separation device, preferably enters a second-stage high-pressure gas-liquid separation tank for second-stage gas-liquid separation. The gas phase of the second-stage gas-liquid separation is hydrogen and methanol. After low-temperature cooling and separation, most of the hydrogen that does not contain methanol is returned to the compressor for recycling, and the liquid phase of the second-stage gas-liquid separation is a crude CHDM product.

[0077] In one embodiment of the present invention, the crude CHDM product enters a two-stage distillation separation unit for refinement to obtain 1,4-cyclohexanedimethanol.

[0078] In one embodiment of the present invention, the two-stage distillation separation unit includes a methanol removal tower, a CHDM light component removal tower, and a CHDM distillation tower; wherein the methanol removal tower is used to produce methanol at normal pressure, and the bottom material of the methanol removal tower is fed into the CHDM light component removal tower; the CHDM light component removal tower is used to remove impurities having a boiling point lower than the boiling point of 1,4-cyclohexanedimethanol, and the bottom material of the CHDM light component removal tower is fed into the CHDM distillation tower, and the CHDM distillation tower is used to separate 1,4-cyclohexanedimethanol.

[0079] In a preferred embodiment of the present invention, the method for preparing 1,4-cyclohexanedimethanol specifically comprises the following steps:

[0080] (S-1) Dimethyl terephthalate and hydrogen are subjected to a one-stage hydrogenation reaction in the presence of a Pd / Co@AxOy catalyst to prepare dimethyl 1,4-cyclohexanedicarboxylate;

[0081] (S-2) 1,4-cyclohexanedimethanol is prepared by a two-stage hydrogenation reaction of dimethyl 1,4-cyclohexanedicarboxylate and hydrogen in the presence of a non-noble metal composite oxide catalyst;

[0082] In the Pd / Co@AxOy catalyst, A is Al, Si and B, x and y satisfy the oxide valence balance, and the mixed oxide of the catalyst Al, Si and B is used as a carrier to load Pd and Co.

[0083] Furthermore, in the Pd / Co@AxOy catalyst, the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.3, the Pd content is 0.2-0.5wt%, and the Co content is 0.12-0.3wt%.

[0084] Furthermore, in step (S1), the modified Pd / Co@AxOy catalyst is prepared by a preparation method comprising the following steps:

[0085] (P-1) Preparation of AxOy oxide gel mixture and spherical precursors using a rolling ball machine;

[0086] (P-2) Under ultrasonic conditions, the spherical precursor is impregnated in a solution containing a palladium source and a cobalt source. After impregnation, the spherical precursor is centrifuged, dried, calcined under a reducing atmosphere, cooled, and sieved to obtain a modified Pd / Co@Al2O3 / SiO2 / B2O3 catalyst.

[0087] Furthermore, in step (P-1), an organic aluminum, a tetraalkyl silicate, and a trialkyl borate are dispersed in an alcohol solvent, carbonate is added to adjust the pH to 7.5-8.5, stirred for 4-6 hours, aged, and washed to obtain an AxOy oxide gel mixture; preferably, the organic aluminum is selected from at least one of aluminum isopropoxide and sec-butyl aluminum, the tetraalkyl silicate is selected from at least one of tetraethyl orthosilicate, tetrapropyl orthosilicate, and tetrabutyl orthosilicate, and the trialkyl borate is selected from at least one of triisopropyl borate and tributyl borate; the organic aluminum, tetraalkyl silicate, The amount of trialkyl borate is such that the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.3; the alcohol solvent is at least one of ethanol and isopropanol; the carbonate is at least one of sodium carbonate, potassium carbonate, and ammonium carbonate; the aging is performed by standing at 20-30°C for 5-10 hours, and the washing is performed by first washing with an alkaline aqueous solution having a pH of 10-12 and then washing with clean water until neutral, wherein the alkaline aqueous solution is NaOH and / or KOH solution; the ball rolling machine speed is 20-50 rpm, and the ball rolling machine operation time is 5-10 hours, to obtain microspheres with a particle size of 1.5-4 mm.

[0088] The inventors found that when preparing Al2O3 / SiO2 / B2O3 composite carrier materials, it is not possible to prepare alumina gel and borosilicate gel separately and then mix them. The present invention is to produce alumina gel and borosilicate gel at the same time through a one-pot method, which produces certain entanglement or other affinity with each other, so that Al2O3, SiO2, and B2O3 are more evenly dispersed with each other, and thus can better serve as catalyst supports. The inventors unexpectedly found that using the above-mentioned composite oxide containing Al, Si and B as a carrier, a catalyst loaded with Pd and Co was obtained by an impregnation method, which has significantly improved resistance to carbon monoxide poisoning. If a single oxide carrier is used, or a single Pd is used, or Co is replaced by other metal elements, the catalyst's resistance to carbon monoxide poisoning cannot be significantly improved. It is speculated that the composite oxide carrier and the Pd / Co bimetallic active center produce a synergistic effect with each other, which improves the catalyst's resistance to carbon monoxide poisoning under the joint action.

[0089] Furthermore, in step (P-2), the ultrasonic conditions are not particularly limited, for example, the impregnation is carried out at an ultrasonic frequency of 60-100kHz; the palladium source is selected from at least one of palladium chloride and palladium chloride; the cobalt source is selected from at least one of cobalt chloride and cobalt nitrate. In the solution of the palladium source and the cobalt source, the solvent is at least one of water and ethanol, preferably a mixed solvent of water and ethanol with an alcohol volume concentration of 40-60%; in the solution, the molar concentration of Pd is 0.1-0.2M, and the concentration of Co is 0.03-0.05M; the impregnation time is 10-15h. There is no particular limitation on drying, and both oven drying and vacuum drying are acceptable. The reducing atmosphere is calcination under hydrogen, the calcination temperature is 400-600°C, and the calcination time is 3-5h. Spherical particles with a particle size of 1.5-4mm are obtained by sieving.

[0090] Furthermore, in step (S-2), the non-precious metal composite oxide catalyst is at least two oxides of copper, zinc, and aluminum; preferably, the non-precious metal composite oxide catalyst is a composite metal oxide of copper oxide and zinc oxide, and optionally further comprises aluminum oxide. For example, in one embodiment of the present invention, in step (S2), the non-precious metal composite oxide comprises 30-40 wt% copper oxide, 50-60 wt% zinc oxide, and the remainder aluminum oxide.

[0091] Furthermore, the preparation method of 1,4-cyclohexanedimethanol further specifically comprises the following steps:

[0092] (T-1) Dimethyl terephthalate and dimethyl 1,4-cyclohexanedicarboxylate are added to a dissolving tank to obtain a mixed solution. The mixed solution enters a first-stage hydrogenation reaction unit, where hydrogen is introduced for first-stage hydrogenation to produce dimethyl 1,4-cyclohexanedicarboxylate. The crude product is subjected to gas-liquid separation, and the liquid phase enters a DMCD crude product tank, which is then sent to a first-stage distillation separation unit for refining. A portion of the refined dimethyl 1,4-cyclohexanedicarboxylate is recycled back to the dissolving tank as a solvent for the mixed solution, and the remaining portion is sent to an intermediate product tank as a raw material for a second-stage hydrogenation reaction.

[0093] (T-2) The 1,4-cyclohexanedicarboxylic acid dimethyl ester in the intermediate product tank enters the second-stage hydrogenation reaction unit, where hydrogen is introduced for the second-stage ester hydrogenation reaction. The crude product is separated into gas and liquid, and the liquid phase enters the CHDM crude product tank and is then sent to the second-stage distillation separation unit for refining to obtain the product 1,4-cyclohexanedimethanol.

[0094] Furthermore, in step (T-1), the mass concentration of dimethyl terephthalate in the mixed solution is 10-50wt%, preferably 20-30wt%; the one-stage hydrogenation reaction unit is a fixed reaction bed, and the reaction conditions of the one-stage hydrogenation reaction unit are: reactor inlet 120-140°C, catalyst bed temperature 150-170°C, hydrogen pressure 4-8MPa, dimethyl terephthalate space velocity (LVSH) 0.4-1.0h-1, and raw material hydrogen-to-oil molar ratio 30-150; CO concentration is lower than 1000ppm, preferably lower than 500ppm, and more preferably not more than 100ppm.

[0095] Furthermore, in step (T-1), a portion of the refined 1,4-cyclohexanedicarboxylic acid dimethyl ester, preferably 50-70 wt%, is recycled back to the dissolution tank as a mixed solution solvent; the remaining portion is sent to an intermediate product tank as a second-stage hydrogenation reaction raw material.

[0096] Furthermore, in step (T-1), the mixed solution and the reaction product from the first-stage hydrogenation reaction unit are heat exchanged, and the hydrogen passes through a circulation compressor to exchange heat with the reaction product of the first-stage hydrogenation reaction unit. The mixed solution and hydrogen after heat exchange enter the first-stage hydrogenation reactor from the top, and the product flows out from the bottom of the first-stage hydrogenation reactor; the gas-liquid separation device is a high-pressure gas-liquid separation tank; after gas-liquid separation, the gas phase is hydrogen, which returns to the compressor for recycling; the first-stage distillation separation unit includes a DMCD light component removal tower and a DMCD distillation tower. The pressure of the DMCD light component removal tower and the DMCD distillation tower is 1-3 kPa; the tower top temperature is controlled at 120-150°C.

[0097] Furthermore, in step (T-2), the catalyst bed temperature is 190-220°C, the hydrogen pressure is 8-10 MPa, the space velocity of 1,4-cyclohexanedicarboxylic acid dimethyl ester (LVSH) is 0.2-0.4h-1, and the raw material hydrogen-to-oil molar ratio is 80-150; 1,4-cyclohexanedicarboxylic acid dimethyl ester is heat exchanged with the product of the second-stage hydrogenation reaction unit, and the hydrogen is heat exchanged with the reaction product of the second-stage hydrogenation reaction unit through a circulation compressor, and the heat exchanged 1,4-cyclohexanedicarboxylic acid dimethyl ester and hydrogen are mixed, preheated, and then heated from the second stage hydrogenation reaction unit. The first-stage hydrogenation reactor is fed at the top, with the product flowing out from the bottom. The gas-liquid separation device is a high-pressure gas-liquid separator. After gas-liquid separation, the gas phase consists of hydrogen and methanol. After low-temperature cooling and separation, the majority of the hydrogen without methanol is returned to the compressor for recycling. The second-stage distillation separation unit includes a methanol removal tower, a CHDM light component removal tower, and a CHDM distillation tower. Methanol is produced from the methanol removal tower under normal pressure, and the bottom liquid is fed into the CHDM light component removal tower. The bottom material is then fed into the CHDM distillation tower, and the product 1,4-cyclohexanedimethanol is produced from the top of the tower. The pressure of the CHDM light component removal tower and CHDM distillation tower is 1-3 kPa, and the tower top temperature is controlled at 150-170°C.

[0098] The present invention will be described in detail below through examples.

[0099] Catalyst Preparation Example 1

[0100] (P1) Aluminum isopropoxide, tetraethyl orthosilicate, and triisopropyl borate were added to a reactor at a molar ratio of Al:Si:B = 3.4:1:0.2, and ethanol was added to fully disperse the mixture to obtain a dispersion, wherein the molar concentration of aluminum isopropoxide in the dispersion was 0.2 M. Ammonium carbonate was added to adjust the pH to 8.5, and the mixture was stirred for 5 hours. The mixture was then aged at 25° C. for 8 hours, centrifuged, washed with a NaOH aqueous solution having a pH of 12, and then washed with deionized water until the effluent was neutral to obtain a mixed oxygen compound gel;

[0101] (P2) The ball mill was used to produce a spherical precursor with an average particle size of 1.9 mm. The speed was adjusted to 50 rpm and the ball mill was operated for 6 h.

[0102] (P3) Under 100kHz ultrasonic conditions, the spherical precursor obtained in step (P1) was immersed in an ethanol aqueous solution containing 0.2M H2PdCl4 and 0.05M CoCl2 (ethanol volume concentration 60%) for 10 hours. The product was centrifuged, dried, and calcined at 500°C for 5 hours under H2 atmosphere. The product was cooled and sieved to obtain spherical particles with an average particle size of 1.9 mm, which is the catalyst.

[0103] After testing, the Pd content in the catalyst is 0.42wt%, the Co content is 0.19wt%, the content of the carrier is 99.39wt%, and the molar ratio of Al, Si and B elements in the carrier is 3.4:1:0.2.

[0104] FIG1 is an electron microscope photograph of the catalyst obtained in Preparation Example 1, and FIG2 is a partially enlarged view of the electron microscope photograph of the catalyst obtained in Preparation Example 1.

[0105] Preparation Example 2

[0106] Other conditions were the same as those in Preparation Example 1, except that in step (P1), aluminum isopropoxide, tetraethyl orthosilicate, and triisopropyl borate were added to the reactor at a molar ratio of Al:Si:B = 4.2:1:0.3. Testing revealed that the spherical particle catalyst obtained in this Preparation Example had a Pd content of 0.41 wt%, a Co content of 0.19 wt%, and a carrier content of 99.40 wt%. The molar ratio of Al, Si, and B in the carrier was 4.2:1:0.3.

[0107] Preparation Example 3

[0108] Other conditions were the same as those in Preparation Example 1, except that in step (P2), the concentration of H2PdCl4 was 0.1 M and the concentration of CoCl2 was 0.03 M. Testing revealed that the spherical particle catalyst obtained in this Preparation Example had a Pd content of 0.21 wt%, a Co content of 0.12 wt%, a carrier content of 99.67 wt%, and a molar ratio of Al, Si, and B elements in the carrier of 3.4:1:0.2.

[0109] Comparative Preparation Example 1

[0110] Other conditions were the same as those in Preparation Example 1, except that tetraethyl orthosilicate was not added in step (P1).

[0111] Comparative Preparation Example 2

[0112] Other conditions were the same as those in Preparation Example 1, except that triisopropyl borate was not added in step (P1).

[0113] Comparative Preparation Example 3

[0114] Other conditions were the same as those in Preparation Example 1, except that in step (P3), 0.02 M CoCl2 was replaced by 0.02 M RuCl3.

[0115] Comparative Preparation Example 4

[0116] Other conditions were the same as those in Preparation Example 1, except that in step (P3), 0.02 M CoCl2 was replaced by 0.02 M ZnCl2.

[0117] Comparative Preparation Example 5

[0118] Other conditions were the same as those in Preparation Example 1, except that in step (P3), 0.02 M CoCl2 was replaced by 0.02 M NiCl2.

[0119] Example 1

[0120] (T1) dimethyl terephthalate (DMT) is added to a dissolution tank, and dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is added to the dissolution tank via a first-stage distillation separation unit via a flow controller to obtain a mixed solution, wherein the mass concentration of DMT in the mixed solution is 25%;

[0121] The mixed solution is heat exchanged with the first-stage hydrogenation reaction product flowing out of the lower part of the first-stage hydrogenation reactor, and hydrogen I (carbon monoxide content <5 ppm) is heat exchanged with the first-stage hydrogenation reaction product flowing out of the lower part of the first-stage hydrogenation reactor through a compressor. The two heat-exchanged materials are mixed, preheated, and then pressurized by a feed pump and enter the first-stage hydrogenation reactor from the top to carry out a first-stage hydrogenation reaction to obtain a first-stage hydrogenation reaction product; wherein the first-stage hydrogenation reactor is a fixed bed reactor, the inlet temperature is 130° C., the first-stage catalyst in the catalyst bed is obtained in Preparation Example 1, the catalyst bed temperature is 160° C., the H2 pressure is 5 MPa, and the dimethyl terephthalate space velocity (LVSH) is 0.5 h -1 , the raw material hydrogen-oil molar ratio is 100;

[0122] The first-stage hydrogenation reaction product flows out from the lower part of the first-stage hydrogenation reactor, exchanges heat with the mixed solution and hydrogen I, and is cooled before entering a first-stage high-pressure gas-liquid separation tank for a first-stage gas-liquid separation. The gas phase of the first-stage gas-liquid separation is mainly hydrogen, which is returned to the first-stage hydrogenation reactor for recycling. The liquid phase of the first-stage gas-liquid separation is the crude DMCD product.

[0123] The crude DMCD product is fed into a crude product tank and then into a first-stage distillation separation unit for refining. The crude DMCD product is first fed into a DMCD light component removal tower (top pressure 3 kPa, top temperature 120°C) to remove impurities with a boiling point lower than that of dimethyl 1,4-cyclohexanedicarboxylate. The bottoms of the DMCD light component removal tower are then fed into a DMCD distillation tower (top pressure 3 kPa, top temperature 150°C). An intermediate product (DMCD purity >99.9%) is extracted from the top of the DMCD distillation tower.

[0124] The intermediate product is divided into part A and part B, with part A accounting for 75% of the intermediate product mass and part B accounting for 25% of the intermediate product mass. Part A is recycled back to the dissolution tank as the mixed solution solvent, and part B is sent to the intermediate product tank as the feedstock for the second-stage hydrogenation reaction. The DMT conversion rate is 99.9%, and the DMCD selectivity is 99.5%.

[0125] (T2) DMCD in the intermediate product tank is heat exchanged with the second-stage ester hydrogenation reaction product flowing out of the lower part of the second-stage hydrogenation reactor, hydrogen II is heat exchanged with the second-stage ester hydrogenation reaction product flowing out of the lower part of the second-stage hydrogenation reactor through a compressor, and the two materials after heat exchange are mixed and preheated and then enter the second-stage hydrogenation reactor from the top to carry out the second-stage ester hydrogenation reaction to obtain the second-stage ester hydrogenation reaction product; wherein, the inlet temperature of the second-stage hydrogenation reactor is 150°C, the second-stage catalyst in the catalyst bed is a composite metal oxide, wherein copper oxide 34wt%, zinc oxide 57wt%, and aluminum oxide 9wt%; the catalyst bed temperature is 210°C, the H2 pressure is 8MPa, and the dimethyl 1,4-cyclohexanedicarboxylate space velocity (LVSH) is 0.3h -1 , the raw material hydrogen-to-oil molar ratio is 80;

[0126] The second-stage ester hydrogenation reaction product flows out from the lower part of the second-stage hydrogenation reactor, exchanges heat with DMCD and hydrogen II entering the second-stage hydrogenation reactor for cooling, and then enters the second-stage high-pressure gas-liquid separation tank for second-stage gas-liquid separation. The gas phase of the second-stage gas-liquid separation is mainly hydrogen and methanol. After low-temperature cooling and separation, the hydrogen without methanol returns to the second-stage hydrogenation reactor for recycling. The liquid phase of the second-stage gas-liquid separation is the crude CHDM product.

[0127] The crude CHDM product is fed into a CHDM crude product tank and then into a two-stage distillation separation unit for refining. The crude CHDM product is fed into a methanol removal tower, where methanol is extracted from the top of the tower under normal pressure. The bottom material of the methanol removal tower is fed into a CHDM light component removal tower (top pressure 3 kPa, top temperature 150°C) to remove impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol. The bottom material of the CHDM light component removal tower is fed into a CHDM distillation tower (top pressure 3 kPa, top temperature 170°C), where CHDM product is extracted from the top of the tower after distillation. The DMCD conversion rate is 99.4%, and the CHDM selectivity is 98.5%.

[0128] Examples 2-3, and Comparative Preparation Examples 1-5

[0129] Other conditions and operations were the same as in Example 1, except that in step (T1), the catalyst bed of the first-stage hydrogenation reactor used the first-stage catalysts prepared in Preparation Examples 2-3 and Comparative Preparation Examples 1-5, respectively. The properties of the first-stage catalysts are shown in Table 1:

[0130] The carbon monoxide poisoning test involves running the system continuously for one month at a carbon monoxide concentration of 100 ppm in hydrogen to determine whether it can maintain a DMT conversion rate greater than 99% and a DMCD selectivity greater than 97%. If these conditions are met, the system passes the test; if either the DMT conversion rate or the DMCD selectivity fails to meet the requirements, the system fails the test.

[0131] Table 1

[0132] As shown in Table 1, the present invention utilizes a mixture of oxides containing Al, Si, and B as a support, loaded with a bimetallic catalyst of Pd and Co, to hydrogenate dimethyl terephthalate (DMT) to produce dimethyl 1,4-cyclohexanedicarboxylate (DMCD). The catalyst exhibits excellent DMT conversion and DMCD selectivity, meeting industrial requirements. Importantly, the catalyst prepared in this example exhibits unexpectedly good resistance to carbon monoxide poisoning.

[0133] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A catalyst, characterized in that The catalyst comprises Pd, Co and a carrier; wherein, based on the total mass of the catalyst, the Pd content is 0.2-0.5wt%, the Co content is 0.12-0.3wt%, and the carrier content is 99.2-99.68wt%; the carrier is a mixed oxide of Al, Si and B, and the molar ratio of Al:Si:B is 3.4-4.2:1:0.2-0.

3.

2. A method for preparing a catalyst, characterized in that: The method comprises the following steps: (P1) preparing an oxide gel mixture; (P2) subjecting the oxide gel mixture to a ball rolling process to obtain a spherical precursor; (P3) The spherical precursor is first impregnated in an impregnation solution containing a palladium source and a cobalt source, and then calcined to obtain the catalyst.

3. The preparation method according to claim 2, wherein Organic aluminum, tetraalkyl silicate and trialkyl borate are dispersed in an alcohol solvent, and then carbonate is added to obtain a dispersion; then the dispersion is subjected to an aging treatment to obtain an oxide gel mixture.

4. The preparation method according to claim 3, wherein The organic aluminum is selected from at least one of aluminum isopropoxide and sec-butyl aluminum, the tetraalkyl silicate is selected from at least one of tetraethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate, and the trialkyl borate is selected from at least one of triisopropyl borate and tributyl borate; And / or, the alcohol solvent is at least one of ethanol and isopropanol, and the carbonate is at least one of sodium carbonate, potassium carbonate and ammonium carbonate; And / or, the amounts of the organic aluminum, tetraalkyl silicate and trialkyl borate satisfy the molar ratio of Al:Si:B of 3.4-4.2:1:0.2-0.3; and / or, the carbonate is used in an amount such that the pH value of the dispersion is 7.5-8.5, and the carbonate is added and stirred for 4-6 hours; And / or, the aging is standing at 20-30° C. for 5-10 hours; And / or, washing is performed after the aging treatment is completed, first with an alkaline aqueous solution with a pH of 10-12, and then with clean water until neutral, the alkaline aqueous solution being a NaOH and / or KOH solution; And / or, the ball rolling treatment is carried out in a ball rolling machine, wherein the speed of the ball rolling machine is 20-50 rpm, the running time of the ball rolling machine is 5-10 hours, and microspheres with a particle size of 1.5-4 mm are obtained.

5. The preparation method according to claim 2, wherein: The palladium source is selected from at least one of palladium chloride and palladium chloride; the cobalt source is selected from at least one of cobalt chloride and cobalt nitrate; And / or, the amount of the palladium source, the cobalt source and the microsphere particles is such that the prepared catalyst has a Pd content of 0.2-0.5wt%, a Co content of 0.12-0.3wt%, and a carrier content of 99.2-99.68wt%; And / or, the solvent of the impregnation solution is at least one of water and an alcohol solvent, preferably a mixed solvent of water and ethanol; wherein the volume concentration of ethanol in the mixed solvent of water and ethanol is 40-60%; And / or, in the impregnation solution, based on the molar amount of Pd and Co elements, the content of the palladium source is 0.1-0.2M, and the content of the cobalt source is 0.03-0.05M; And / or, the immersion is carried out under ultrasound; wherein the ultrasound frequency is 60-100 kHz and the ultrasound time is 10-15 h; And / or, the calcination is carried out under a reducing atmosphere; preferably, the calcination is carried out under hydrogen; And / or, the calcination operating conditions include: calcination temperature of 400-600°C, calcination time of 3-5h; And / or, the calcination is followed by cooling and sieving to obtain spherical particles with a particle size of 1.5-4 mm.

6. A method for preparing 1,4-cyclohexanedimethanol, characterized in that: The method The following steps are involved: T1, under the action of a first-stage catalyst, dimethyl terephthalate is contacted with hydrogen I to carry out a first-stage hydrogenation reaction to obtain an intermediate product; wherein the first-stage catalyst is the catalyst according to claim 1 or a catalyst prepared by the method according to any one of claims 2 to 5; T2, under the action of a second-stage catalyst, the intermediate product is contacted with hydrogen II to carry out a second-stage ester hydrogenation reaction to obtain 1,4-cyclohexanedimethanol.

7. The preparation method according to claim 6, wherein: Mixing and dissolving the dimethyl terephthalate and dimethyl 1,4-cyclohexanedicarboxylate to obtain a mixed solution; contacting the mixed solution with hydrogen I to perform a first-stage hydrogenation reaction to obtain a first-stage hydrogenation reaction product; and / or, based on the total mass of the mixed solution, the mass concentration of dimethyl terephthalate is 10-50%; and / or, the CO concentration in the hydrogen I is lower than 1000 ppm; And / or, the one-stage hydrogenation reaction is carried out in a one-stage hydrogenation reactor; wherein the one-stage hydrogenation reactor is a fixed bed reactor, the inlet temperature is 120-140°C, the temperature of the catalyst bed is 150-170°C, the hydrogen pressure is 4-8MPa, and the space velocity (LVSH) of dimethyl terephthalate is 0.4-1h -1 , the raw material hydrogen-to-oil molar ratio is 30-150; And / or, the mixed solution and hydrogen I are respectively heat exchanged with the first-stage hydrogenation reaction product, the mixed solution and hydrogen I after heat exchange are mixed, and then preheated and enter from the top of the first-stage hydrogenation reactor, and the generated first-stage hydrogenation reaction product flows out from the lower part of the first-stage hydrogenation reactor; And / or, the first stage hydrogenation reaction product after heat exchange enters a first stage gas-liquid separation device for first stage gas-liquid separation, wherein the first stage gas-liquid separation gas phase is hydrogen, which is returned to the first stage hydrogenation reactor for recycling, and the first stage gas-liquid separation liquid phase is a DMCD crude product; And / or, the crude DMCD product enters a distillation separation unit for a stage of refining to obtain an intermediate product; wherein the intermediate product is dimethyl 1,4-cyclohexanedicarboxylate; And / or, the intermediate product is divided into at least part A and part B, the part A is returned to the first stage hydrogenation reaction and added to the mixed solution for recycling, and the part B is contacted with hydrogen II for a second stage hydrogenation reaction; And / or, the A part accounts for 50-90% of the intermediate product, and the B part accounts for 10-50% of the intermediate product.

8. The preparation method according to claim 7, wherein: The first stage distillation separation unit includes a DMCD light component removal tower and a DMCD distillation tower; wherein the DMCD light component removal tower is used to remove impurities with a boiling point lower than that of dimethyl 1,4-cyclohexanedicarboxylate, and the bottom material of the DMCD light component removal tower is fed into the DMCD distillation tower; the DMCD distillation tower is used to separate the intermediate product.

9. The preparation method according to claim 6, wherein: The second stage catalyst is a non-precious metal composite oxide type catalyst; wherein the non-precious metal composite oxide type catalyst is at least two of the oxides of copper, zinc and aluminum; and / or, contacting the intermediate product with hydrogen II to carry out a two-stage ester hydrogenation reaction to obtain a two-stage ester hydrogenation reaction product; wherein the two-stage ester hydrogenation reaction is carried out in a two-stage hydrogenation reactor; the catalyst bed temperature of the two-stage hydrogenation reactor is 190-220° C., the hydrogen pressure is 8-10 MPa, and the space velocity (LVSH) of 1,4-cyclohexanedicarboxylic acid dimethyl ester is 0.2-0.4 h -1 , the raw material hydrogen-to-oil molar ratio is 80-150; And / or, the intermediate product and hydrogen II are respectively heat exchanged with the second-stage ester hydrogenation reaction product, the intermediate product and hydrogen II after heat exchange are mixed, and then preheated and enter from the top of the second-stage hydrogenation reactor, and the generated second-stage ester hydrogenation reaction product flows out from the lower part of the second-stage hydrogenation reactor; And / or, the second-stage ester hydrogenation reaction product after heat exchange enters the second-stage gas-liquid separation device for second-stage gas-liquid separation, the gas phase of the second-stage gas-liquid separation is hydrogen and methanol, after low-temperature cooling and separation, the hydrogen part without methanol is returned to the compressor for recycling, and the liquid phase of the second-stage gas-liquid separation is the CHDM crude product; And / or, the CHDM crude product enters a two-stage distillation separation unit for refining to obtain 1,4-cyclohexanedimethanol.

10. The preparation method according to claim 9, wherein: The two-stage distillation separation unit includes a methanol removal tower, a CHDM light component removal tower and a CHDM distillation tower; The methanol removal tower is used to produce methanol under normal pressure, and the bottom materials of the methanol removal tower are sent to the CHDM light component removal tower; The CHDM light component removal tower is used to remove impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol, and the bottom materials of the CHDM light component removal tower are fed into the CHDM distillation tower; The CHDM distillation tower is used to separate 1,4-cyclohexanedimethanol.

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