A modified hydrogenation catalyst, its preparation method and use

Abstract

This invention provides a modified hydrogenation catalyst, its preparation method, and its application. The modified hydrogenation catalyst comprises a titanium dioxide support and palladium and zinc or zinc oxide supported on the titanium dioxide support, wherein the titanium dioxide support includes anatase-type titanium dioxide and rutile-type titanium dioxide. The modified hydrogenation catalyst provided by this invention can be used in the hydrogenation purification reaction of terephthalic acid. Due to the presence of the mixed-phase structure, the hydrogenation efficiency and stability are significantly improved. Simultaneously, the synergistic effect of the zinc additive and the anatase / rutile mixed-phase structure exhibits high selectivity in the hydrogenation purification reaction of terephthalic acid, reducing the content of impurities generated in the reaction. Furthermore, the use of the titanium dioxide support allows zinc to promote the effect of palladium in reducing 4-CBA content or increasing 4-CBA conversion.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a modified hydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Terephthalic acid (PTA) is a major raw material for the industrial production of polyester. Industrially, it is mainly prepared through a two-step process. First, PX oxidation yields crude terephthalic acid (CTA). The CTA obtained after oxidation contains a small amount of impurity p-carboxybenzaldehyde (4-CBA), which affects the subsequent esterification performance of PTA and must be removed. Industrially, CTA is mainly purified through a hydrorefining process. Specifically, under the action of a palladium catalyst, 4-CBA is hydrogenated to convert it into water-soluble hydroxymethylbenzoic acid and p-methylbenzoic acid, etc., followed by multiple crystallizations and centrifugation to separate and purify the CTA. The most commonly used hydrorefining catalyst in industry is a palladium-on-carbon catalyst. In recent years, the use of titanium dioxide as a support for palladium catalysts has attracted widespread attention from researchers both domestically and internationally. US Patent 5362908 discloses a method for the hydrorefining and purification of crude terephthalic acid or isophthalic acid using a transition metal catalyst supported on titanium dioxide. Specifically, titanium dioxide is treated at high temperature (400-1000℃) and used as a support, with palladium and rhodium as active components. Evaluation results confirmed that, under the same evaluation conditions, the 4-CBA content was 25 ppm after 2 hours of reaction with the 0.5% Pd / TiO2 catalyst, while the 4-CBA content was 43 ppm after 2 hours of reaction with the 0.5% Pd / C catalyst in the comparative example. Therefore, compared with traditional activated carbon-supported palladium catalysts, the titanium dioxide-supported palladium catalyst of this invention achieved better hydrogenation performance. Chinese patent CN101264444A discloses a method for preparing a titanium dioxide-supported palladium selective hydrogenation catalyst. The method mainly involves impregnating TiO2 powder with H2PdCl4 solution, followed by calcination, dechlorination, and high-temperature reduction with hydrogen to obtain titanium dioxide-supported palladium catalyst powder. This powder is then extruded to obtain a catalyst with a regular shape, and finally dried and calcined under an inert atmosphere to obtain the final catalyst.

[0003] From the perspective of improving the atomic utilization rate of the precious metal palladium, the existing technology still suffers from the problem of low catalytic efficiency of palladium catalysts, and the hydrogenation effect of palladium needs to be further improved. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a modified hydrogenation catalyst, its preparation method, and its application. This catalyst improves hydrogenation efficiency and stability, exhibits high selectivity in the hydrogenation purification reaction of terephthalic acid, and reduces the content of impurities (4-CBA) generated in the reaction.

[0005] In a first aspect, the present invention provides a modified hydrogenation catalyst comprising a titanium dioxide support and palladium and zinc elements supported on the titanium dioxide support, wherein the titanium dioxide support comprises anatase or rutile titanium dioxide. The palladium and zinc elements supported on the titanium dioxide support may exist in elemental form or in oxide form.

[0006] In some embodiments, the rutile titanium dioxide accounts for more than 10% by weight of the titanium dioxide carrier, preferably 15% to 70%, and more preferably 45% to 70%. For example, the rutile titanium dioxide accounts for 12%, 15%, 20%, 25%, 30%, 36%, 40%, 45%, 47%, 50%, 53%, 58%, 60%, 68%, and 70% by weight of the titanium dioxide carrier.

[0007] In some embodiments, the modified hydrogenation catalyst comprises, by weight, 0.3 to 1.0 parts palladium (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts), 0.3 to 5 parts zinc (e.g., 0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.3, 3.8, 4.3, 4.8, or 5 parts), and 90 to 100 parts titanium dioxide support (e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 parts).

[0008] In some embodiments, the modified hydrogenation catalyst comprises 0.3 to 1.0 parts palladium (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts), 1 to 3 parts zinc (e.g., 1, 1.3, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, or 3 parts), and 90 to 100 parts titanium dioxide support (e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 parts).

[0009] In a second aspect, the present invention provides a method for preparing a modified hydrogenation catalyst, comprising: calcining a mixture containing titanium dioxide and a zinc-containing additive to form a modified titanium dioxide support, wherein the modified titanium dioxide support comprises anatase titanium dioxide and rutile titanium dioxide; and loading the modified titanium dioxide support with an active metal palladium. The zinc-containing additive may be solid zinc hydroxide.

[0010] In some embodiments, the step of forming the modified titanium dioxide support includes: step S1, mixing an aqueous solution of zinc salt and titanium dioxide, adjusting the pH to weakly alkaline by adding alkali, and reacting to obtain a mixed slurry; step S2, performing solid-liquid separation on the mixed slurry, and calcining the obtained solid to obtain the modified titanium dioxide support.

[0011] In some embodiments, the titanium dioxide used in step S1 may be anatase titanium dioxide.

[0012] In some embodiments, the alkali in step S1 is ammonia.

[0013] In some embodiments, in step S1, the weakly alkaline pH is 8.0 to 9.5; for example, it can be pH 8.0, 8.2, 8.5, 8.8, 9.0, 9.2 or 9.5.

[0014] In some preferred embodiments, the reaction time in step S1 is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0015] In some embodiments, in step S1, the reaction temperature is 15 to 40°C, for example, the reaction temperature is 15°C, 17°C, 20°C, 25°C, 30°C, 35°C or 40°C.

[0016] In some embodiments, in step S1, the zinc salt is selected from zinc nitrate and / or zinc chloride, preferably zinc nitrate; preferably, the zinc in the zinc salt accounts for 0.3% to 5% of the weight of the titanium dioxide, more preferably 1% to 3%; for example, the zinc in the zinc salt accounts for 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5% of the weight of the titanium dioxide.

[0017] In some embodiments, the calcination includes a first calcination under a hydrogen atmosphere and a second calcination under a nitrogen atmosphere.

[0018] In some embodiments, the temperature of the first roasting is 300 to 450°C, for example, the temperature of the first roasting is 300°C, 320°C, 350°C, 380°C, 400°C, 420°C or 450°C.

[0019] In some embodiments, the first calcination time is 0.5 to 2 hours, for example, 0.5 hours, 0.7 hours, 1 hour, 1.3 hours, 1.5 hours, 1.8 hours or 2 hours.

[0020] In some embodiments, the second calcination temperature is 450–650°C. For example, the second calcination temperature is 450°C, 480°C, 500°C, 520°C, 550°C, 570°C, 600°C, 630°C, or 650°C.

[0021] In some embodiments, the second calcination time is 0.5 to 4 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0022] In some embodiments, the step of loading active palladium onto a modified titanium dioxide support includes: a. mixing the modified titanium dioxide support and an aqueous solution of palladium salt to obtain a second slurry; b. adjusting the pH of the second slurry to weakly alkaline; c. reacting the second slurry at 50–70°C (e.g., 50°C, 53°C, 57°C, 60°C, 62°C, 66°C, or 70°C), preferably for 3–6 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours); d. performing solid-liquid separation and drying on the second slurry after the reaction in step c. The drying temperature can be 100–120°C, for example, 100°C, 105°C, 110°C, 115°C, or 120°C.

[0023] In some embodiments, in step a, the palladium salt is selected from chloropalladium acid and / or palladium nitrate.

[0024] In some embodiments, in step b, sodium formate is used to adjust the pH of the second slurry.

[0025] In some embodiments, in step b, the pH of the second slurry is 8.5 to 9.5, for example, it can be 8.5, 8.6, 8.7, 8.8, 9.0, 9.1, 9.2, 9.3, 9.4 or 9.5.

[0026] In a third aspect, the present invention provides the application of the modified hydrogenation catalyst described in the first aspect of the present invention or the modified hydrogenation catalyst prepared by the preparation method described in the second aspect of the present invention in the hydrogenation purification reaction of terephthalic acid.

[0027] The modified hydrogenation catalyst provided by this invention can be used in the hydrogenation purification reaction of terephthalic acid. Due to the presence of the mixed-phase structure, the hydrogenation efficiency and stability are significantly improved. Simultaneously, the synergistic effect of the zinc additive and the anatase / rutile mixed-phase structure exhibits high selectivity in the terephthalic acid hydrogenation purification reaction, reducing the content of impurities (4-CBA) generated during the reaction. Furthermore, the use of titanium dioxide support allows zinc to enhance the effect of palladium in reducing 4-CBA content or increasing 4-CBA conversion. Moreover, the preparation method of this invention is simple, the preparation process is easily repeatable, the raw materials are inexpensive and readily available, and the production cost is low, which is beneficial for subsequent large-scale preparation. Attached Figure Description

[0028] Figure 1 These are the XRD patterns of the raw material titanium dioxide and the modified hydrogenation catalyst prepared in Example 1;

[0029] Figure 2 This is the XRD pattern of the modified hydrogenation catalyst prepared in Example 6. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0031] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] The present invention will be described in detail below through embodiments.

[0033] In the method of this invention, the phase composition of the sample is determined by a D8 ADVANCE diffractometer.

[0034] The reagents used in the following examples are commercially available and of analytical grade.

[0035] Unless otherwise specified, the following examples and comparative examples were carried out at room temperature, which refers to 15–30°C.

[0036] Example 1

[0037] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.037 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 by ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0038] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under hydrogen atmosphere, and then treated at 450°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0039] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry at 100℃ to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0040] The phase composition of the modified hydrogenation catalyst was analyzed by XRD powder diffraction, see [link to XRD analysis]. Figure 1 As shown in the figure, the original titanium dioxide is composed of anatase titanium dioxide, while the modified hydrogenation catalyst in Example 1 is composed of a mixed two-phase structure of anatase and rutile. The properties of the catalyst are shown in Table 1.

[0041] The hydrogenation reaction of 4-CBA was carried out in a stainless steel stirred batch high-pressure reactor. The specific reaction conditions were: 2.0 g catalyst, 30.0 g crude terephthalic acid (containing approximately 3300 ppm 4-CBA), 1000.0 mL aqueous solution, reaction pressure 5.5 MPa, reaction temperature 280 °C, and reaction time 1.0 h. The liquid product after the reaction was quantitatively analyzed by high-performance liquid chromatography with a UV detector. The catalyst activity was evaluated by calculating the remaining 4-CBA content; the lower the remaining 4-CBA content, the higher the hydrogenation efficiency of the catalyst.

[0042] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0043] Example 2

[0044] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.073 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 by ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0045] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under hydrogen atmosphere, and then treated at 450°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0046] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry at 100℃ to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0047] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0048] Example 3

[0049] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.146 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 by ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0050] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under hydrogen atmosphere, and then treated at 550°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0051] (3) Weigh 1.0 g of the zinc-modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep warm for 4 h, and then centrifuge, wash and dry at 100℃ to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0052] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0053] Example 4

[0054] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.219 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 with ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0055] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under hydrogen atmosphere, and then treated at 650°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0056] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at that temperature for 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0057] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0058] Example 5

[0059] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.146 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 by ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0060] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 1 hour under hydrogen atmosphere, and then treated at 650°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0061] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0062] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0063] Example 6

[0064] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.366 g of zinc nitrate hexahydrate was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 with ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0065] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 1 hour under hydrogen atmosphere, and then treated at 650°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0066] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0067] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0068] The phase composition of the modified hydrogenation catalyst was analyzed by XRD powder diffraction, see [link to XRD analysis]. Figure 2 As shown. By Figure 2As can be seen from the table, the modified hydrogenation catalyst is composed of a mixture of anatase and rutile phases, with the rutile phase content being higher than that of the anatase phase. The properties of the catalyst are shown in Table 1.

[0069] Example 7

[0070] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.034 g of zinc chloride was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 by ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0071] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under hydrogen atmosphere, and then treated at 450°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0072] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0073] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0074] Example 8

[0075] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.101 g of zinc chloride was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 with ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0076] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 1 hour under hydrogen atmosphere, and then treated at 550°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0077] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0078] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0079] Example 9

[0080] (1) At room temperature, 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.101 g of zinc chloride was weighed and added to the above solution, the pH of the solution was adjusted to 9.0 with ammonia water, and the mixture was stirred for 2 h to obtain a mixed slurry.

[0081] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 1 hour under hydrogen atmosphere, and then treated at 650°C for 2 hours under nitrogen atmosphere to obtain modified titanium dioxide carrier.

[0082] (3) Weigh 1.0 g of the modified titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution to obtain the second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, raise the temperature to 60℃ and keep it at 4 h, and then centrifuge, wash and dry to obtain a modified hydrogenation catalyst with a palladium loading of 0.4%.

[0083] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0084] Example 10

[0085] It is basically the same as Example 1, except that in step (1), 0.45 g of zinc nitrate hexahydrate is added.

[0086] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0087] Example 11

[0088] It is basically the same as Example 1, except that in step (2), it is treated at 450°C for 1 hour in a hydrogen atmosphere.

[0089] The modified hydrogenation catalyst prepared in this example was used for the hydrogenation reaction of 4-CBA, and the conversion rate of 4-CBA was measured and is shown in Table 1.

[0090] Comparative Example 1

[0091] Using anatase titanium dioxide as a carrier, only palladium metal is loaded, specifically including:

[0092] Weigh 1.0 g of anatase titanium dioxide sample, add 0.05 mol / L chloropalladium acid solution, adjust the pH of the solution to 9.0 with sodium formate, continue stirring for 2 h, heat to 60℃ and keep warm for 4 h, and then obtain pure anatase titanium dioxide palladium-supported catalyst after centrifugation, washing and drying.

[0093] The catalyst prepared in Comparative Example 1 was used for the hydrogenation reaction of 4-CBA under the same reaction conditions as in Example 1. The conversion rate of 4-CBA was measured and is shown in Table 1.

[0094] Comparative Example 2

[0095] Two grams of anatase titanium dioxide were treated at 450°C for 2 hours under a hydrogen atmosphere, and then at 650°C for 2 hours under a nitrogen atmosphere to obtain a titanium dioxide support. Then, 1.0 gram of the titanium dioxide support obtained in the above steps was weighed and added to a 0.05 mol / L chloropalladium acid solution. The pH of the solution was adjusted to 9.0 with sodium formate, and the mixture was stirred for 2 hours. The temperature was raised to 60°C and held for 4 hours. After centrifugation, washing, and drying, the modified titanium dioxide palladium catalyst was obtained.

[0096] The catalyst prepared in Comparative Example 2 was used for the hydrogenation reaction of 4-CBA under the same reaction conditions as in Example 1. The conversion rate of 4-CBA was measured and is shown in Table 1.

[0097] Comparative Example 3

[0098] Coconut shell-based activated carbon (20-40 mesh, specific surface area 997 m²) was used. 2 / g, pore volume 0.46cm³ 3 Using / g) as a carrier, 1.0 g of the above coconut shell-based activated carbon was weighed and added to a 0.05 mol / L chloropalladic acid solution. The pH of the solution was adjusted to 9.0 with sodium formate. The mixture was stirred for 2 h, heated to 60 °C and kept at that temperature for 4 h. After centrifugation, washing and drying, the palladium catalyst supported on activated carbon was obtained.

[0099] The catalyst prepared in Comparative Example 3 was used for the hydrogenation reaction of 4-CBA under the same reaction conditions as in Example 1. The conversion rate of 4-CBA was measured and is shown in Table 1.

[0100] Comparative Example 4

[0101] Coconut shell-based activated carbon (20-40 mesh, specific surface area 997 m²) was used. 2 / g, pore volume 0.46cm³ 3 / g) is used as a carrier, specifically including:

[0102] (1) Disperse 2 g of coconut shell-based activated carbon into 20 mL of aqueous solution and ultrasonically disperse it; weigh 0.146 g of zinc nitrate hexahydrate and add it to the above solution, and adjust the pH of the solution to 9.0 with ammonia water to obtain a mixed slurry;

[0103] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 2 hours under hydrogen atmosphere, and then treated at 650°C for 2 hours under nitrogen atmosphere to obtain modified coconut shell carbon carrier.

[0104] (3) Weigh 1.0 g of the modified coconut shell carbon support obtained in step (2), add 0.05 mol / L chloropalladium acid solution, adjust the pH of the solution to 9.0 with sodium formate, continue stirring for 2 h, heat to 60℃ and keep warm for 4 h, and then centrifuge, wash and dry to obtain the modified coconut shell carbon supported palladium catalyst.

[0105] The catalyst prepared in Comparative Example 4 was used for the hydrogenation reaction of 4-CBA under the same reaction conditions as in Example 1. The conversion rate of 4-CBA was measured and is shown in Table 1.

[0106] Comparative Example 5

[0107] (1) Disperse 2 g of anatase titanium dioxide powder into 20 mL of aqueous solution and ultrasonically disperse; weigh 0.146 g of zinc nitrate hexahydrate and add it to the above solution, and adjust the pH of the solution to 9.0 with ammonia water to obtain a mixed slurry;

[0108] (2) The above mixed slurry was centrifuged and dried, and then treated at 450°C for 2 hours under a hydrogen atmosphere, and then treated at 650°C for 2 hours under a nitrogen atmosphere to obtain a modified titanium dioxide support; it was repeatedly washed with 12% dilute hydrochloric acid to obtain an acid-washed titanium dioxide support.

[0109] (3) Weigh 1 gram of the acid-washed titanium dioxide support obtained in step (2), add 0.05 mol / L chloropalladic acid solution, adjust the pH of the solution to 9.0 with sodium formate, continue stirring for 2 h, heat to 60℃ and keep warm for 4 h, and then centrifuge, wash and dry to obtain the modified titanium dioxide palladium catalyst.

[0110] The catalyst prepared in Comparative Example 5 was used for the hydrogenation reaction of 4-CBA under the same reaction conditions as in Example 1. The conversion rate of 4-CBA was measured and is shown in Table 1.

[0111] Comparative Example 6

[0112] (1) Disperse 2 g of anatase titanium dioxide powder into 20 mL of aqueous solution and ultrasonically disperse; add 0.05 mol / L chloropalladic acid solution to obtain a second slurry; adjust the pH of the second slurry to 9.0 with sodium formate, continue stirring for 2 h, heat to 60℃ and keep warm for 4 h, weigh 0.037 g of zinc nitrate hexahydrate and add it to the above solution, adjust the pH of the solution to 9.0 with ammonia water to obtain a mixed slurry;

[0113] (2) The above mixed slurry was centrifuged and dried, and then treated at 350°C for 1 hour under a hydrogen atmosphere, and then treated at 450°C for 2 hours under a nitrogen atmosphere to obtain the modified hydrogenation catalyst.

[0114] Comparative Example 7

[0115] Weigh 2 grams of anatase titanium dioxide powder, use 0.02 grams of methylcellulose as a binder and 15 grams of lactic acid as a plasticizer, add 0.072 grams of water, extrude into strips, dry at 120°C for 5 hours, and calcine at 550°C for 4 hours to prepare a cylindrical support of ∮3 mm × 5 mm. Weigh 1 gram of the above support, weigh 0.0025 grams of chloropalladium acid solution containing 20% ​​palladium, add 0.00686 grams of zinc nitrate hexahydrate, add appropriate amounts of surfactant and sodium carbonate, and finally add deionized water to dilute until the solution just submerges the titanium dioxide support. Impregnate the support with the catalyst active component solution, age for 24 hours, reduce with hydrogen, wash with pure water until neutral, and dry to obtain the catalyst product.

[0116] The properties of the catalysts obtained in the above embodiments and comparative examples and their hydrogenation performance evaluation results are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] As can be seen from Table 1, the hydrogenation catalyst provided by the present invention is composed of a mixed phase of anatase and rutile. By adding zinc additives and controlling the roasting conditions under different atmospheres, titanium dioxide palladium-supported catalysts with different proportions of mixed phases can be obtained.

[0121] As shown in Table 1, the hydrogenation catalyst developed in this invention exhibits significantly better hydrogenation performance than the pure anatase phase titanium dioxide-supported palladium catalyst, achieving superior technical results in the hydrogenation refining reaction of crude terephthalic acid. A comparison of Example 5 with Comparative Examples 1-4 reveals that the synergistic effect caused by the zinc additive and the anatase / rutile mixed phase is a crucial reason for the improved performance of the modified palladium catalyst. This effect occurs on the titanium dioxide support but has no significant effect on the activated carbon support. This invention provides new insights for developing novel titanium dioxide-supported metal catalysts and their hydrogenation applications.

[0122] Zinc acts as an additive, primarily assisting in the diffusion and distribution of the active component palladium, thereby achieving efficient dispersion of the formed palladium on the TiO2 surface. Zn alone, as an active component, has no hydrogenation effect; therefore, Comparative Example 6 exhibits a higher content of the remaining 4-CBA.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a modified hydrogenation catalyst for the hydrogenation purification reaction of terephthalic acid, comprising: A modified titanium dioxide carrier is formed by calcining titanium dioxide and zinc-containing additives, wherein the modified titanium dioxide carrier includes anatase titanium dioxide and rutile titanium dioxide. The calcination includes a first calcination under a hydrogen atmosphere and a second calcination under a nitrogen atmosphere. The temperature of the first calcination is 300-450°C and the temperature of the second calcination is 450-650°C. The modified titanium dioxide support is loaded with active metal palladium; The step of forming the modified titanium dioxide support includes: Step S1: Mix the aqueous solution of zinc salt and titanium dioxide, add alkali to adjust the pH to weakly alkaline, and react to obtain a mixed slurry; The zinc in the zinc salt accounts for 1 to 3% of the weight of the titanium dioxide; Step S2 involves solid-liquid separation of the mixed slurry and calcination of the resulting solid to obtain the modified titanium dioxide carrier.

2. The preparation method according to claim 1, characterized in that, In step S1, the alkali is ammonia; and / or In step S1, the weakly alkaline pH is 8.0–9.5; and / or In step S1, the reaction time is 1 to 3 hours, and the reaction temperature is 15 to 40°C.

3. The preparation method according to claim 1, characterized in that, The zinc salt is selected from zinc nitrate and / or zinc chloride.

4. The preparation method according to claim 3, characterized in that, The zinc salt is zinc nitrate.

5. The preparation method according to claim 1, characterized in that, The first calcination time is 0.5–2 hours; and / or The second roasting time is 0.5 to 4 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The steps for loading active palladium onto a modified titanium dioxide support include: a. Mix the modified titanium dioxide support and an aqueous solution of palladium salt to obtain a second slurry; b. Adjust the pH of the second slurry to a slightly alkaline state; c. React the second slurry at 50–70°C; d. Perform solid-liquid separation and drying on the second slurry after the reaction in step c.

7. The preparation method according to claim 6, characterized in that, The second slurry is reacted at 50–70°C for 3–6 hours.

8. The preparation method according to claim 6, characterized in that, The palladium salt is selected from chloropalladium acid and / or palladium nitrate; and / or The pH of the second slurry was adjusted using sodium formate; and / or The pH of the second slurry is 8.5 to 9.

5.

9. The application of a modified hydrogenation catalyst prepared by any one of claims 1 to 8 in the hydrogenation purification reaction of terephthalic acid.

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