PTA hydrogenation catalyst and preparation method thereof

Abstract

The invention belongs to the field of crude terephthalic acid (PTA) hydrofining, and particularly relates to a PTA hydrogenation catalyst and a preparation method thereof. The preparation method comprises the following steps: (1) carrying out parallel flow precipitation on a carbonic acid solution and a nickel nitrate solution into an aluminum sol solution; (2) sequentially carrying out aging, slurrying and water washing treatment on the generated precipitate, and then filtering to obtain a filter cake; (3) sequentially drying, grinding and roasting the filter cake to obtain a catalyst intermediate; and (4) sequentially carrying out reduction and passivation treatment on the catalyst intermediate to obtain the PTA hydrogenation catalyst. The catalyst breaks through the application bottleneck of non-noble metal under the working conditions of high temperature, high pressure, high water content and strong acidity, the 4-CBA removal rate is superior to that of an existing noble metal catalyst, the service life reaches 2-4 years, the cost is reduced by 80%, the problems of carrier breakage and active component loss do not exist, and the catalyst is suitable for PTA hydrofining.

Description

Technical Field

[0001] This invention belongs to the field of crude terephthalic acid (PTA) hydrogenation refining, specifically relating to a PTA hydrogenation catalyst and its preparation method. Background Technology

[0002] Terephthalic acid (PTA) is a core raw material in the polyester industry, widely used in the production of polyester fibers, polyester films, bottled polyester, and other products. Its purity directly determines the performance and quality of downstream polyester products. Currently, in the global PTA refining industry, the hydrogenation refining process uses palladium / activated carbon (Pd / C) catalysts, with palladium as the active component (Pd content approximately 0.5 wt%). The preparation process for this type of catalyst typically involves: first, acid treatment of the coconut shell carbon support, then loading the precious metal Pd through impregnation, and finally reducing the catalyst to obtain the finished product. Because coconut shell carbon, the support for Pd / C catalysts, possesses high strength, high specific surface area, and acid and alkali resistance, and is readily available, it has become the mainstream choice for current industrial production. Currently, my country's PTA plants mainly rely on imports for Pd / C catalysts. Based on an estimated annual PTA production of 70 million tons, approximately 1,800 tons of Pd / C catalyst need to be imported. Only a few domestic companies (such as the Shanghai Petrochemical Research Institute of Sinopec) have achieved industrial-scale production of Pd / C catalysts, indicating a high degree of dependence on imported catalysts in the industry.

[0003] To address the issue of black particles generated by the breakage of Pd / C catalyst supports (coconut shell carbon), which could lead to product damage in downstream polyester plants, the industry began researching non-carbon supported precious metal catalysts in the 1990s. Among these, Pd / TiO2 catalysts using anatase titanium dioxide (TiO2) as a support became a research hotspot. Amoco in the United States developed a Pd / TiO2 catalyst with TiO2 as a support, requiring the support to be calcined at temperatures above 700℃. This catalyst exhibited good 4-CBA removal efficiency in the catalytic purification and recovery of dicarboxylic aromatic acids. Domestically, only the Yangzi Petrochemical Research Institute has developed corresponding TiO2 support molding technology and Pd / TiO2 catalyst preparation technology specifically for the reaction characteristics of the PTA hydrorefining system.

[0004] However, existing PTA hydrorefining catalysts still have technical defects, and related problems have not been effectively resolved for a long time, mainly in the following aspects:

[0005] 1. High cost and reliance on imports: Existing catalysts all use the precious metal Pd as the active component. Pd resources are scarce and expensive, resulting in a unit price of 3 million to 3.8 million yuan / ton for Pd / C catalysts. Moreover, domestic production capacity is insufficient, and there is a long-term reliance on imports, which significantly increases the operating costs of PTA production enterprises.

[0006] 2. Insufficient stability and adaptability: The coconut shell carbon support of Pd / C catalyst is at risk of breakage during use. The resulting fragments entering the downstream polyester unit will cause a decline in product quality. At the same time, Pd / TiO2 catalyst requires high-temperature calcination for preparation, which has stringent process requirements and still does not get rid of its dependence on precious metals, thus failing to reduce costs.

[0007] 3. Technical bottlenecks exist in the development of non-precious metal catalysts: The industry has attempted to develop non-precious metal hydrogenation refining catalysts, but faces three major challenges: First, the PTA hydrogenation reaction requires harsh conditions of high temperature and high pressure (280℃, nearly 7MPa), and ordinary non-precious metal catalysts are prone to deactivation, making it difficult to meet industrial requirements in terms of stability; Second, the crude PTA solution under high temperature and high pressure is highly acidic due to the presence of two carboxyl groups, requiring extremely high corrosion resistance from the catalyst. Except for Pd / C catalysts, most non-precious metal catalysts are easily corroded and broken; Third, the water content in PTA hydrogenation feedstock exceeds 70%, and the hydrogenation reaction of conventional non-precious metal catalysts (such as nickel-based and copper-based catalysts) must avoid the introduction of free water. Water will cause the active metal particles to grow larger and the redox state to change, making it difficult to maintain hydrogenation activity comparable to that of precious metals in aqueous systems.

[0008] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0009] To address the problems existing in the prior art, the present invention provides a method for preparing a PTA hydrogenation catalyst, the method comprising the following steps: (1) A carbonate solution and a nickel nitrate solution are precipitated together in an aluminum sol solution; wherein the carbonate solution is a sodium bicarbonate solution, an ammonium bicarbonate solution, or an ammonium carbonate solution; (2) The generated precipitate is subjected to aging, pulping and washing in sequence, and then filtered to obtain filter cake; (3) The filter cake is dried, ground and calcined in sequence to obtain a catalyst intermediate; (4) The catalyst intermediate is subjected to reduction and passivation treatment in sequence to obtain the PTA hydrogenation catalyst.

[0010] Preferably, in step (1), the sodium bicarbonate solution is prepared by dissolving 450-500 parts by weight of sodium bicarbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain a sodium bicarbonate solution; the ammonium bicarbonate solution is prepared by dissolving 450-500 parts by weight of ammonium bicarbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain an ammonium bicarbonate solution; the ammonium carbonate solution is prepared by dissolving 450-500 parts by weight of ammonium carbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain an ammonium carbonate solution. And / or, the preparation method of the nickel nitrate solution is as follows: dissolve 250-300 parts by weight of nickel nitrate hexahydrate in 1500 parts by weight of deionized water, and stir evenly to obtain nickel nitrate solution; And / or, the aluminum sol solution is prepared by dissolving 200-250 parts by weight of aluminum sol in 2000 parts by weight of deionized water, stirring evenly to obtain an aluminum sol solution; the concentration of the aluminum sol is 20-25 g / 100 mL, and the specific gravity is 1-1.2 g / mL.

[0011] Preferably, in step (1), during the co-current precipitation process, the temperature is 55-65℃, the pH is 6.5-8.5, and the time is 60-70min.

[0012] Preferably, in step (2), the aging process is as follows: after the precipitation reaction is completed, the reaction system is kept at normal pressure and the temperature is controlled at 65-85℃. The generated precipitation system is aged for 60-120 minutes to allow the precipitate particles to grow and stabilize.

[0013] Preferably, in step (2), the pulping operation is as follows: the aged precipitate is pulped 2-5 times, each time 1000-5500 parts by weight of deionized water is added, the mixture is stirred and dispersed and then allowed to stand, so as to achieve the initial separation of precipitate and impurities.

[0014] Preferably, in step (2), the water washing operation is as follows: after pulping, the precipitate is washed 2-4 times, each time adding 1000-1200 parts by weight of deionized water, stirring and washing, and then filtering to remove impurities.

[0015] Preferably, in step (3), the drying temperature is 110-120℃ and the drying time is 12-14h; And / or, the grinding is performed until it passes through an 180-mesh sieve; And / or, the calcination temperature is 300-600℃, and the calcination time is 2-9h.

[0016] Preferably, in step (4), the reduction operation is as follows: the catalyst intermediate is placed in a reducing atmosphere and reduced at 300-600°C; the reducing atmosphere is hydrogen.

[0017] Preferably, in step (4), the passivation operation is as follows: after the reduction is completed, the catalyst is passivated under normal pressure by "layering and gradually increasing the amount of air" to avoid the catalyst from coming into rapid contact with air and causing a violent reaction.

[0018] Based on the same technical concept, the present invention provides a PTA hydrogenation catalyst obtained by the above preparation method.

[0019] The beneficial effects of this invention are as follows: This invention not only breaks through the core bottleneck of applying non-precious metal catalysts to PTA hydrorefining, but also surpasses existing precious metal catalysts in terms of cost, performance, and stability, possessing industrial applicability and economic value, specifically as follows: 1. This invention realizes the use of Al2O3 as a support to support non-precious metal Ni as a catalyst for PTA hydrorefining, and successfully solves the technical problems of non-precious metal catalysts under high temperature and high pressure (280-300℃, about 7MPa), high water content (the proportion of raw material water exceeds 70%) and strong acidity conditions in PTA hydrorefining, providing a brand-new non-precious metal solution for PTA hydrorefining technology.

[0020] 2. This invention improves the overall performance of the catalyst through precise loading design of high Ni content on the Al2O3 support: (i) the concentration of p-carboxybenzaldehyde (4-CBA) in the hydrogenation product is less than 1 ppm (almost undetectable), which is far superior to the standard of less than 20 ppm for existing precious metal catalysts, effectively ensuring the stability of downstream polyester polymerization reaction; (ii) it exhibits excellent stability in harsh reaction environments of high temperature, high pressure, and strong acidity, with an expected service life of 2-4 years, which is more than twice that of existing precious metal Pd / C catalysts (1-2 years); (iii) the Al2O3 support has excellent resistance to strong corrosion, effectively solving the problem of easy breakage of coconut shell carbon support and generation of black particulate pollution in downstream polyester units by existing Pd / C catalysts. At the same time, the catalyst has extremely strong resistance to impurities (such as resistance to sulfur poisoning) and no loss of active components, significantly improving the operational stability of PTA production units.

[0021] 3. This invention uses non-precious metal Ni as the active component, and the catalyst unit price is only 500,000-700,000 yuan / ton, which is about 80% lower than the existing precious metal Pd / C catalyst (3 million-3.8 million yuan / ton), significantly reducing the raw material procurement cost of PTA production enterprises. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a photo of a batch reactor. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Example 1 This embodiment provides a method for preparing a PTA hydrogenation catalyst, the method comprising the following steps: (I) Raw material preparation and pretreatment: (I-1) Preparation of aluminum sol solution: Take 246.42g of commercially available aluminum sol (specification 20.54g / 100mL, specific gravity 1.2g / mL), slowly add it to 2000mL of deionized water, stir until completely dissolved to form a homogeneous aluminum sol solution, and set aside. (I-2) Preparation of nickel nitrate solution: Weigh out nickel nitrate hexahydrate (6H2O) 271.23 g of Ni(NO3)2 was added to 1500 mL of deionized water and stirred at room temperature until the solid was completely dissolved to obtain a clear nickel nitrate solution for later use. (I-3) Preparation of precipitant solution: Weigh 490.29g of sodium bicarbonate (NaHCO3), add 4500mL of deionized water, stir until completely dissolved, and prepare a homogeneous sodium bicarbonate precipitant solution for later use.

[0026] (II) Co-current precipitation reaction: The sodium bicarbonate solution and the nickel nitrate solution were simultaneously and continuously injected into a reaction vessel containing the aluminum sol solution in the same direction using a parallel feeding method. During the reaction, the temperature was controlled at 60°C, the pH at 7.0, and the reaction time was 60 minutes. After the reaction was completed, a precipitate was obtained.

[0027] (III) Aging treatment: After the precipitation reaction is completed, the reaction system is kept at normal pressure and the temperature is controlled below 70°C (60°C in this example). The generated precipitation system is then aged for 60 minutes to allow the precipitate particles to grow and stabilize fully, thereby improving the binding strength between the carrier and the active component.

[0028] (IV) Pulping, Washing, and Quality Control: (IV-1) Pulping operation: The aged precipitation system was pulping treated 4 times, with 5000 mL of deionized water added each time. After stirring and dispersing, the mixture was allowed to stand. The pulping process was used to achieve the initial separation of the precipitate and impurities. (IV-2) Water washing operation: After pulping, the system is washed three times with water, each time adding 1000 mL of deionized water, stirring and washing, and then filtering to remove residual soluble impurities in the system. (IV-3) Quality monitoring: During the washing process, the Na2O content (impurity index) and NiO content (active component retention index) in the mother liquor, aged cake, washing filtrate and finished cake are detected to ensure that impurities are thoroughly removed and active components are not lost (the Na2O content in the final three washing filtrates is reduced to 0.00072%, and the NiO loss is only 0.0145%). The specific test results and analysis are shown in Table 1.

[0029] Table 1

[0030] (V) Drying, shaping and firing: (V-1) Drying treatment: Place the washed filter cake into the drying equipment, control the drying temperature at 110℃, and continue drying for 12 hours to completely remove the free moisture in the filter cake; (V-2) Grinding and molding: The dried filter cake is taken out and ground until it passes through a 180-mesh sieve. Then, it is pressed into tablets to form a tablet catalyst precursor. (V-3) Calcination treatment: The sheet-like catalyst precursor is placed in a calcination furnace, the calcination temperature is controlled at 340℃, and the calcination time is 8h. After the calcination is completed, the catalyst intermediate is obtained.

[0031] (VI) Reduction and passivation treatment: (VI-1) Reduction reaction: The calcined catalyst intermediate is placed in a reduction reactor and reduced under normal pressure and hydrogen atmosphere at a reduction temperature of 340℃, so that the Ni in the catalyst... + It is fully reduced to metallic Ni, which is active for hydrogenation; (VI-2) Passivation treatment: After reduction, the catalyst is passivated under normal pressure by "layering and gradually increasing the amount of air" to avoid the catalyst from coming into rapid contact with air and causing a violent reaction. (VI-3) Finishing: The passivated catalyst is discharged from the reactor and ground again into powder with a particle size ≥180 mesh, which is the PTA hydrogenation catalyst (40~60 (weight)% Ni / Al2O3).

[0032] Example 2 This embodiment provides a method for preparing a PTA hydrogenation catalyst. The operation of the preparation method is basically the same as that in Example 1, except for the change of parameters. The preparation method briefly includes the following steps: (1) Dissolve 246.42g of aluminum sol (20.54g / 100mL, specific gravity 1.2g / mL) in 2000mL of deionized water to obtain an aluminum sol solution; dissolve 271.23g of 6H2O Ni(NO3)2 was dissolved in 1500 mL of deionized water to obtain a nickel nitrate solution; 490.29 g of NaHCO3 was dissolved in 4500 mL of deionized water to obtain a sodium bicarbonate solution; (2) Under the conditions of 55℃ and pH=6.5, the sodium bicarbonate solution and the nickel nitrate solution are precipitated in the aluminum sol solution in a co-current manner. The entire precipitation process takes about 70 minutes. (3) The generated precipitate was subjected to aging (atmospheric pressure, temperature of 85℃, time of 70min), pulping (5 pulpings, 5500mL of water added each time) and washing (4 washings, 1000mL of water added each time) in sequence, and then filtered to obtain filter cake. (4) The filter cake was subjected to drying (120°C, 14h), grinding (passing through a 180-mesh sieve) and calcination (550°C, 6h) in sequence to obtain a catalyst intermediate; (5) The catalyst intermediate is subjected to reduction (hydrogen atmosphere, 400°C) and passivation (layering, gradually increasing the amount of air) in sequence to obtain the PTA hydrogenation catalyst (40~60 (wt)%Ni / Al2O3).

[0033] Example 3 This embodiment provides a method for preparing a PTA hydrogenation catalyst. The operation of the preparation method is basically the same as that in Example 1, except for the change of parameters. The preparation method briefly includes the following steps: (1) Dissolve 246.42g of aluminum sol (20.54g / 100mL, specific gravity 1.2g / mL) in 2000mL of deionized water to obtain an aluminum sol solution; dissolve 271.23g of 6H2O Ni(NO3)2 was dissolved in 1500 mL of deionized water to obtain a nickel nitrate solution; 490.29 g of NaHCO3 was dissolved in 4500 mL of deionized water to obtain a sodium bicarbonate solution; (2) Under the conditions of 65°C and pH=7.5, the sodium bicarbonate solution and the nickel nitrate solution are precipitated in the aluminum sol solution in a co-current manner. The entire precipitation process takes about 65 minutes. (3) The generated precipitate was subjected to aging (atmospheric pressure, temperature of 65℃, time of 65min), pulping (5 pulpings, 5200mL of water added each time) and washing (4 washings, 1200mL of water added each time) in sequence, and then filtered to obtain filter cake. (4) The filter cake was subjected to drying (115°C, 13h), grinding (passing through a 180-mesh sieve) and calcination (450°C, 7h) in sequence to obtain a catalyst intermediate; (5) The catalyst intermediate is subjected to reduction (hydrogen atmosphere, 360°C) and passivation (layering, gradually increasing the amount of air) in sequence to obtain the PTA hydrogenation catalyst (40~60 (wt)%Ni / Al2O3).

[0034] Verification example: Evaluation of catalysts Using the PTA hydrogenation catalyst obtained in Example 1 as the test object, in a batch reactor (1L reactor, such as...) Figure 1 As shown), PTA is purified by hydrogenation. The reaction conditions are: 2.5g catalyst, 7.5g terephthalic acid, 0.5g p-carboxybenzaldehyde, 300g water, reaction temperature 280℃, hydrogen pressure 7MPa (6-8MPa is acceptable), and reaction time 2h.

[0035] After the reaction was completed, the product analysis results are shown in Table 2.

[0036] Table 2

[0037] As shown in Table 2, the Ni-based non-precious metal catalyst with high metal content can efficiently hydrogenate p-carboxybenzaldehyde (whose content is less than 1 ppm and was not detected) in saturated terephthalic acid; after hydrogenation, this impurity mainly produces benzoic acid and methylbenzoic acid.

[0038] The comparison results of the catalyst of the present invention with existing noble metal catalysts are shown in Table 3.

[0039] Table 3

[0040] As shown in Table 3, using non-precious metal hydrorefining catalysts to replace the current PTA precious metal hydrorefining catalysts (mainly Pd / C palladium on carbon catalysts) has advantages in hydrogenation activity, stability, and cost, and also has the ability to resist loss of active components and strong resistance to impurities.

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a PTA hydrogenation catalyst, characterized in that, The preparation method includes the following steps: (1) A carbonate solution and a nickel nitrate solution are precipitated together in an aluminum sol solution; wherein the carbonate solution is a sodium bicarbonate solution, an ammonium bicarbonate solution, or an ammonium carbonate solution; (2) The generated precipitate is subjected to aging, pulping and washing in sequence, and then filtered to obtain filter cake; (3) The filter cake is dried, ground and calcined in sequence to obtain a catalyst intermediate; (4) The catalyst intermediate is subjected to reduction and passivation treatment in sequence to obtain the PTA hydrogenation catalyst.

2. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (1), the sodium bicarbonate solution is prepared by dissolving 450-500 parts by weight of sodium bicarbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain a sodium bicarbonate solution; the ammonium bicarbonate solution is prepared by dissolving 450-500 parts by weight of ammonium bicarbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain an ammonium bicarbonate solution; the ammonium carbonate solution is prepared by dissolving 450-500 parts by weight of ammonium carbonate in 4500 parts by weight of deionized water and stirring until homogeneous to obtain an ammonium carbonate solution. And / or, the preparation method of the nickel nitrate solution is as follows: dissolve 250-300 parts by weight of nickel nitrate hexahydrate in 1500 parts by weight of deionized water, and stir evenly to obtain nickel nitrate solution; And / or, the aluminum sol solution is prepared by dissolving 200-250 parts by weight of aluminum sol in 2000 parts by weight of deionized water, stirring evenly to obtain an aluminum sol solution; the concentration of the aluminum sol is 20-25 g / 100 mL, and the specific gravity is 1-1.2 g / mL.

3. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (1), during the co-current precipitation process: the temperature is 55-65℃, the pH is 6.5-8.5, and the time is 60-70min.

4. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (2), the aging process is as follows: after the precipitation reaction is completed, the reaction system is kept at normal pressure and the temperature is controlled at 65-85℃. The generated precipitation system is aged for 60-120 minutes to allow the precipitate particles to grow and stabilize.

5. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (2), the pulping operation is as follows: the aged precipitate is pulped 2-5 times, each time 1000-5500 parts by weight of deionized water is added, the mixture is stirred and dispersed and then allowed to stand, so as to achieve the initial separation of precipitate and impurities.

6. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (2), the water washing operation is as follows: after pulping, the precipitate is washed 2-4 times, each time with 1000-1200 parts by weight of deionized water, stirred and washed, and then filtered to remove impurities.

7. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (3), the drying temperature is 110-120℃ and the drying time is 12-14h; And / or, the grinding is performed until it passes through an 180-mesh sieve; And / or, the calcination temperature is 300-600℃, and the calcination time is 2-9h.

8. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (4), the reduction operation is as follows: the catalyst intermediate is placed in a reducing atmosphere and reduced at 300-600°C; The reducing atmosphere is hydrogen.

9. The method for preparing the PTA hydrogenation catalyst according to claim 1, characterized in that, In step (4), the passivation operation is as follows: after the reduction is completed, the catalyst is passivated under normal pressure by "layering and gradually increasing the amount of air" to avoid the catalyst from coming into rapid contact with air and causing a violent reaction.

10. The PTA hydrogenation catalyst obtained by the preparation method according to any one of claims 1-9.

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