Modified hydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention provides a modified hydrogenation catalyst as well as a preparation method and application thereof. The modified hydrogenation catalyst comprises a titanium dioxide carrier and palladium and zinc or zinc oxide loaded on the titanium dioxide carrier, and the titanium dioxide carrier comprises anatase type titanium dioxide and rutile type titanium dioxide. The modified hydrogenation catalyst provided by the invention can be used for a terephthalic acid hydrofining reaction, and due to the existence of a mixed phase structure, the hydrogenation efficiency and stability are remarkably improved. Meanwhile, the zinc additive and the anatase / rutile mixed phase structure have a synergistic effect, so that the catalyst shows relatively high selectivity in terephthalic acid hydrofining reaction, and the content of impurities generated in the reaction is reduced. And due to the use of the titanium dioxide carrier, the zinc promotes the effect of palladium in the aspect of reducing the content of 4-CBA or improving the conversion rate of 4-CBA.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and specifically relates to a modified hydrogenation catalyst and a preparation method and application thereof. Background Art

[0002] Terephthalic acid (PTA) is the main raw material for the industrial production of polyester. It is mainly prepared in two steps in industry. First, PX is oxidized to obtain crude terephthalic acid (CTA). The CTA obtained after oxidation contains a small amount of impurity p-carboxybenzaldehyde (4-CBA), which will affect the subsequent esterification performance of PTA and must be removed. CTA is mainly purified in industry through a hydrorefining process. The specific process is to convert 4-CBA into hydroxymethylbenzoic acid and p-toluic acid that are easily soluble in water under the action of a palladium catalyst, and then separate and purify CTA through multiple crystallizations and centrifugation. The most commonly used hydrorefining catalyst in industry is a palladium carbon catalyst. In recent years, the use of titanium dioxide as a carrier for palladium catalysts has attracted widespread attention from researchers at home and abroad. U.S. Patent No. 5,362,908 provides a method for hydrogenating and refining crude terephthalic acid or isophthalic acid using a transition metal catalyst supported by titanium dioxide. Specifically, titanium dioxide is treated at high temperature (400-1000°C) as a carrier, and palladium and rhodium are active components. The evaluation results confirm that under the same evaluation conditions, 0.5% Pd / TiO 2 After the catalyst reacted for 2 hours, the content of 4-CBA was 25ppm, while the content of 4-CBA in the comparative example of 0.5% Pd / C catalyst after 2 hours of reaction was 43ppm. Therefore, compared with the traditional activated carbon-supported palladium catalyst, the titanium dioxide-supported palladium catalyst of the invention achieved a better hydrogenation effect. Chinese patent CN101264444A discloses a method for preparing a titanium dioxide-supported palladium selective hydrogenation catalyst, which mainly uses H 2 PdCl 4 Solution impregnation of TiO 2 The powder is calcined, dechlorinated and reduced at high temperature with hydrogen to obtain a titanium dioxide supported palladium catalyst powder, which is then extruded to obtain a catalyst with a regular shape, and finally dried and calcined under the protection of an inert atmosphere to obtain the catalyst.

[0003] From the perspective of improving the atomic utilization rate of the precious metal palladium, the existing technology still has 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] In view of the problems existing in the prior art, the present invention provides a modified hydrogenation catalyst and a preparation method and application thereof, which improves the hydrogenation efficiency and stability, shows higher selectivity in the hydrogenation refining 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 carrier and a palladium element and a zinc element supported on the titanium dioxide carrier, wherein the titanium dioxide carrier comprises anatase-type and rutile-type titanium dioxide. The palladium element and the zinc element supported on the titanium dioxide carrier may exist in a simple form or in an oxide form.

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

[0007] In some embodiments, the modified hydrogenation catalyst includes, by weight, 0.3-1.0 parts of palladium (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 parts), 0.3-5 parts of 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 90-100 parts of titanium dioxide carrier (e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100 parts).

[0008] In some embodiments, the modified hydrogenation catalyst includes 0.3-1.0 parts of palladium (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 parts), 1-3 parts of zinc (e.g., 1, 1.3, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3 parts), and 90-100 parts of titanium dioxide carrier (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 titanium dioxide and a zinc-containing additive to form a modified titanium dioxide carrier, wherein the modified titanium dioxide carrier comprises anatase titanium dioxide and rutile titanium dioxide; and loading the modified titanium dioxide carrier with active metal palladium. The zinc-containing additive may be solid zinc hydroxide.

[0010] In some embodiments, the step of forming a modified titanium dioxide carrier includes: step S1, mixing an aqueous solution of zinc salt and titanium dioxide, adding alkali to adjust the pH to weak alkalinity, 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 carrier.

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

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

[0013] In some embodiments, in step S1, the weak alkaline has a pH of 8.0 to 9.5; for example, the pH may be 8.0, 8.2, 8.5, 8.8, 9.0, 9.2 or 9.5.

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

[0015] In some embodiments, in step S1, the reaction temperature is 15-40°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 0.3-5% by weight of the titanium dioxide, more preferably 1-3%; 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% by weight of the titanium dioxide.

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

[0018] In some embodiments, the first calcination temperature is 300-450°C, for example, the first calcination temperature 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 metal palladium on a modified titanium dioxide carrier comprises: a. mixing the modified titanium dioxide carrier and an aqueous solution of a palladium salt to obtain a second slurry; b. adjusting the pH of the second slurry to a weak alkaline; c. reacting the second slurry at 50 to 70°C (e.g., 50°C, 53°C, 57°C, 60°C, 62°C, 66°C, or 70°C), preferably for 3 to 6 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours); d. subjecting the second slurry after the reaction in step c to solid-liquid separation and drying. The drying temperature may be 100 to 120°C, e.g., 100°C, 105°C, 110°C, 115°C, or 120°C.

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

[0024] In some embodiments, in step b, the pH of the second slurry is adjusted using sodium formate.

[0025] In some embodiments, in step b, the pH of the second slurry is 8.5 to 9.5, for example, 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 an 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 a terephthalic acid hydrogenation refining reaction.

[0027] The modified hydrogenation catalyst provided by the present invention can be used for terephthalic acid hydrogenation refining reaction, and due to the presence of mixed phase structure, the hydrogenation efficiency and stability are significantly improved. At the same time, the zinc adjuvant and the anatase / rutile mixed phase structure synergistically act to show higher selectivity in the terephthalic acid hydrogenation refining reaction, reducing the content of impurities (4-CBA) produced in the reaction. And the use of titanium dioxide carrier makes zinc promote the effect of palladium in reducing 4-CBA content or improving 4-CBA conversion rate. And the preparation method of the present invention is simple, the preparation process is easy to repeat, the raw materials are cheap and easy to obtain, the production cost is low, and it is conducive to subsequent large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the XRD diagram 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 DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments and drawings. The specific embodiments described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present disclosure. Such structures and technologies are also described in many publications.

[0031] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

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

[0033] In the method of the present invention, the phase composition of the sample is measured by 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 all reacted at room temperature, which refers to 15 to 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 dispersed by ultrasonication; 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 with ammonia water, and the reaction was stirred for 2 h to obtain a mixed slurry;

[0038] (2) centrifuging and drying the mixed slurry, and then treating it at 350° C. for 1 h in a hydrogen atmosphere, and then treating it at 450° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0039] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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 the reaction for 2 h, heat to 60° C. and keep warm for 4 h, then centrifuge, wash, and dry at 100° C. 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. Figure 1 As shown in the figure, it can be seen that the original titanium dioxide is composed of anatase titanium dioxide, while the modified hydrogenation catalyst in Example 1 is composed of a mixture of anatase and rutile phases. The properties of the catalyst are shown in Table 1.

[0041] The hydrogenation reaction of the 4-CBA is carried out in a stainless steel stirring intermittent high-pressure reactor. The specific reaction conditions are: 2.0 grams of catalyst loading, 30.0 grams of crude terephthalic acid (wherein the 4-CBA content is about 3300ppm), 1000.0mL of aqueous solution, 5.5MPa of reaction pressure, 280°C of reaction temperature, and 1.0h of reaction time. After the reaction, the liquid product is quantitatively analyzed by high performance liquid chromatography equipped with an ultraviolet detector. The activity of the catalyst is evaluated by calculating the content of the remaining 4-CBA. 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 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 with ammonia water, and the reaction was stirred for 2 h to obtain a mixed slurry;

[0045] (2) centrifuging and drying the mixed slurry, and then treating it at 350° C. for 1 h in a hydrogen atmosphere, and then treating it at 450° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0046] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, then centrifuge, wash, and dry at 100° C. 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 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 with ammonia water, and the reaction was stirred for 2 h to obtain a mixed slurry;

[0050] (2) centrifuging and drying the mixed slurry, and then treating it at 350° C. for 1 h in a hydrogen atmosphere, and then treating it at 550° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0051] (3) Weigh 1.0 g of the zinc-modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, then centrifuge, wash, and dry at 100° C. 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 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 dispersed by ultrasonication; 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 reaction was stirred for 2 h to obtain a mixed slurry;

[0055] (2) centrifuging and drying the mixed slurry, and then treating it at 350° C. for 1 h in a hydrogen atmosphere, and then treating it at 650° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0056] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 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 with ammonia water, and the reaction was stirred for 2 h to obtain a mixed slurry;

[0060] (2) centrifuging and drying the mixed slurry, and then treating it at 450° C. for 1 h in a hydrogen atmosphere, and then treating it at 650° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0061] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 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 reaction was stirred for 2 h to obtain a mixed slurry;

[0065] (2) centrifuging and drying the mixed slurry, and then treating it at 450° C. for 1 h in a hydrogen atmosphere, and then treating it at 650° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0066] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 shown in Table 1.

[0068] The phase composition of the modified hydrogenation catalyst was analyzed by XRD powder diffraction. Figure 2 As shown. Figure 2 It can be seen that the modified hydrogenation catalyst is composed of a mixture of anatase and rutile phases, and the content of rutile phase is higher than that of 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 with ammonia water, and the reaction was stirred for 2 h to obtain a mixed slurry;

[0071] (2) centrifuging and drying the mixed slurry, and then treating it at 350° C. for 1 h in a hydrogen atmosphere, and then treating it at 450° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0072] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 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 dispersed by ultrasonication; 0.101 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 reaction was stirred for 2 h to obtain a mixed slurry;

[0076] (2) centrifuging and drying the mixed slurry, and then treating it at 450° C. for 1 h in a hydrogen atmosphere, and then treating it at 550° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0077] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 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 dispersed by ultrasonication; 0.101 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 reaction was stirred for 2 h to obtain a mixed slurry;

[0081] (2) centrifuging and drying the mixed slurry, and then treating it at 450° C. for 1 h in a hydrogen atmosphere, and then treating it at 650° C. for 2 h in a nitrogen atmosphere to obtain a modified titanium dioxide carrier;

[0082] (3) Weigh 1.0 g of the modified titanium dioxide carrier obtained in step (2), 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° C. and keep warm for 4 h, 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 shown in Table 1.

[0084] Example 10

[0085] The process 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 shown in Table 1.

[0087] Embodiment 11

[0088] The method is basically the same as Example 1, except that in step (2), the process is carried out at 450° C. for 1 h under 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 shown in Table 1.

[0090] Comparative Example 1

[0091] Anatase titanium dioxide is used as a carrier, and only metal palladium is loaded, specifically including:

[0092] Weigh 1.0 g of anatase titanium dioxide sample, 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 ° C and keep warm for 4 h, then centrifuge, wash and dry to obtain a pure anatase titanium dioxide supported palladium catalyst.

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

[0094] Comparative Example 2

[0095] 2 grams of rutile titanium dioxide were treated at 450°C for 2 hours in a hydrogen atmosphere, and then treated at 650°C for 2 hours in a nitrogen atmosphere to obtain a titanium dioxide carrier; then 1.0 grams of the titanium dioxide carrier obtained in the above steps was weighed, 0.05 mol / L of chloropalladic acid solution was added, the pH of the solution was adjusted to 9.0 with sodium formate, stirring was continued for 2 hours, the temperature was raised to 60°C and kept warm for 4 hours, and then after centrifugation, washing and drying, a modified titanium dioxide-supported palladium catalyst was obtained.

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

[0097] Comparative Example 3

[0098] Coconut shell-based activated carbon (20-40 mesh, specific surface area 997m 2 / g, pore volume 0.46cm 3 / g) as a carrier, weigh 1.0 g of the coconut shell-based activated carbon, add 0.05 mol / L chloropalladic acid solution, adjust the pH of the solution to 9.0 with sodium formate, continue stirring for 2 hours, heat to 60°C and keep warm for 4 hours, then centrifuge, wash and dry to obtain an activated carbon-supported palladium catalyst.

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

[0100] Comparative Example 4

[0101] Coconut shell-based activated carbon (20-40 mesh, specific surface area 997m 2 / g, pore volume 0.46cm 3 / g) is a carrier, specifically comprising:

[0102] (1) dispersing 2 g of coconut shell-based activated carbon into 20 mL of aqueous solution by ultrasonic dispersion; weighing 0.146 g of zinc nitrate hexahydrate and adding it to the above solution, adjusting the pH of the solution to 9.0 with ammonia water to obtain a mixed slurry;

[0103] (2) the mixed slurry was centrifuged and dried, and then treated at 450° C. for 2 h in a hydrogen atmosphere, and then treated at 650° C. for 2 h in a nitrogen atmosphere to obtain a modified coconut shell carbon support;

[0104] (3) Weigh 1.0 g of the modified coconut shell carbon carrier 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 ° C and keep warm for 4 h, then centrifuge, wash and dry to obtain a modified coconut shell carbon-supported palladium catalyst.

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

[0106] Comparative Example 5

[0107] (1) dispersing 2 g of anatase titanium dioxide powder into 20 mL of aqueous solution by ultrasonic dispersion; weighing 0.146 g of zinc nitrate hexahydrate and adding it to the above solution, adjusting the pH of the solution to 9.0 with ammonia water to obtain a mixed slurry;

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

[0109] (3) Weigh 1 g of the acid-washed titanium dioxide carrier 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 ° C and keep warm for 4 h, then centrifuge, wash and dry to obtain a modified titanium dioxide supported palladium catalyst.

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

[0111] Comparative Example 6

[0112] (1) 2 g of anatase titanium dioxide powder was dispersed in 20 mL of aqueous solution and ultrasonically dispersed; 0.05 mol / L of chloropalladic acid solution was added to obtain a second slurry; the pH of the second slurry was adjusted to 9.0 with sodium formate, and the stirring was continued for 2 h, the temperature was raised to 60° C. and kept warm for 4 h, 0.037 g of zinc nitrate hexahydrate was weighed and added to the solution, and the pH of the solution was adjusted to 9.0 with ammonia water to obtain a mixed slurry;

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

[0114] Comparative Example 7

[0115] Weigh 2 grams of rutile titanium dioxide powder, use 0.02 grams of methyl cellulose as a binder, 15 grams of lactic acid as a plasticizer, add 0.072 grams of water to extrude, then dry at 120°C for 5 hours, and roast at 550°C for 4 hours to make a cylindrical carrier of ∮3 mm × 5 mm. Weigh 1 gram of the above carrier, weigh 0.0025 grams of chloropalladic acid solution containing 20% ​​palladium, add 0.00686 grams of zinc nitrate hexahydrate, add an appropriate amount of surfactant and sodium carbonate, and finally add deionized water to dilute the solution to the amount of solution just enough to immerse the titanium dioxide carrier. That is, the catalyst active component solution is impregnated into the carrier, and after aging for 24 hours, it is reduced with hydrogen, and then washed with pure water to neutrality and dried to obtain the catalyst product.

[0116] The properties of the catalysts obtained in the above examples and comparative examples and the evaluation results of their hydrogenation performance 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 a zinc additive and controlling the calcination treatment conditions in different atmospheres, a titanium dioxide-supported palladium catalyst with a mixed phase composition of different proportions can be obtained.

[0121] As can be seen from Table 1, the hydrogenation effect of the hydrogenation catalyst developed by the present invention is significantly better than that of the pure anatase phase titanium dioxide supported palladium catalyst, and a good technical effect has been achieved in the crude terephthalic acid hydrogenation refining reaction. By comparing Example 5 with Comparative Examples 1-4, it can be seen that the synergistic effect caused by the zinc adjuvant and the anatase / rutile mixed phase in the present invention is an important reason for the improved performance of the modified palladium catalyst. This effect occurs on the titanium dioxide carrier and has no obvious effect on the activated carbon carrier. The invention provides a new idea for the development of a new type of metal catalyst with titanium dioxide as a carrier and its hydrogenation application.

[0122] Since zinc is an additive, it is mainly used to assist the diffusion and distribution of the active component palladium, and then realize the formation of palladium on TiO 2 The surface is efficiently dispersed. Zn alone as an active component has no hydrogenation effect, so the content of residual 4-CBA in Comparative Example 6 is relatively high.

[0123] 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, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A modified hydrogenation catalyst, comprising a titanium dioxide carrier and palladium and zinc elements loaded on the titanium dioxide carrier, wherein the titanium dioxide carrier comprises anatase titanium dioxide and rutile titanium dioxide.

2. The modified hydrogenation catalyst according to claim 1, characterized in that The weight percentage of the rutile titanium dioxide in the titanium dioxide carrier is greater than 10%, preferably 15% to 70%, and more preferably 45% to 70%.

3. The modified hydrogenation catalyst according to claim 1, characterized in that The modified hydrogenation catalyst comprises, by weight, 0.3 to 1.0 parts of palladium, 0.3 to 5 parts of zinc, and 90 to 100 parts of a titanium dioxide carrier; Preferably, the modified hydrogenation catalyst comprises 0.3 to 1.0 parts of palladium, 1 to 3 parts of zinc, and 90 to 100 parts of a titanium dioxide carrier.

4. A method for preparing a modified hydrogenation catalyst, comprising: calcining titanium dioxide and a zinc-containing additive to form a modified titanium dioxide carrier, wherein the modified titanium dioxide carrier comprises anatase titanium dioxide and rutile titanium dioxide; The modified titanium dioxide carrier is loaded with active metal palladium.

5. The preparation method according to claim 4, characterized in that: The step of forming the modified titanium dioxide support comprises: Step S1, mixing an aqueous solution of zinc salt and titanium dioxide, adding alkali to adjust the pH to weak alkalinity, 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 carrier; Preferably, in step S1, the base is aqueous ammonia; and / or In step S1, the pH of the weak alkaline solution is 8.0 to 9.5; and / or In the step S1, the reaction time is 1 to 3 hours, and the reaction temperature is 15 to 40°C.

6. The preparation method according to claim 5, characterized in that: The zinc salt is selected from zinc nitrate and / or zinc chloride, preferably zinc nitrate; Preferably, the zinc in the zinc salt accounts for 0.3-5% by weight of the titanium dioxide, more preferably 1-3% by weight.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The calcination includes a first calcination in a hydrogen atmosphere and a second calcination in a nitrogen atmosphere; Preferably, the temperature of the first calcination is 300-450° C., and the time of the first calcination is 0.5-2 h; and / or The temperature of the second calcination is 450-650° C., and the time of the second calcination is 0.5-4 hours.

8. The preparation method according to any one of claims 4 to 6, characterized in that: The steps of modifying the titanium dioxide carrier to load active metal palladium include: a. mixing the modified titanium dioxide support and an aqueous solution of a palladium salt to obtain a second slurry; b. adjusting the pH of the second slurry to be weakly alkaline; c. reacting the second slurry at 50 to 70 ° C, preferably for 3 to 6 hours; d. subjecting the second slurry after the reaction in step c to solid-liquid separation and drying.

9. The preparation method according to claim 8, characterized in that: The palladium salt is selected from chloropalladic acid and / or palladium nitrate; and / or adjusting the pH of the second slurry with sodium formate; and / or The pH of the second slurry is 8.5-9.

5.

10. Use of the modified hydrogenation catalyst according to any one of claims 1 to 3 or the modified hydrogenation catalyst prepared by the preparation method according to any one of claims 4 to 9 in a hydrogenation refining reaction of terephthalic acid.

Images