Monomer acid hydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a monomer acid hydrogenation catalyst (Pd-Co bimetallic supported catalyst) as well as a preparation method and application thereof. The catalyst takes activated carbon and a molecular sieve as a composite carrier, and palladium and cobalt bimetals as active components; wherein the loading capacity of Co is 5%-10%, and the loading capacity of Pd is 0.25%-0.5%. Compared with the prior art, the bimetallic catalyst has the advantages that the catalytic activity can be remarkably improved, the iodine value of a monomer acid hydrogenation product is reduced, and meanwhile, the molecular sieve carrier structure of the bimetallic catalyst can convert and remove stearic acid lactone which is difficult to remove in the monomer acid in the hydrogenation reaction process.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more particularly to a monomeric acid hydrogenation catalyst (Pd-Co bimetallic supported catalyst), its preparation method, and its application. Background Technology

[0002] Monomeric acids are byproducts of the polymerization of oleic acid to produce dimer acids. They are mixtures of various substances, mainly including unreacted oleic acid and its isomers, unreacted stearic acid and other unsaturated fatty acids, and small molecules formed during the high-temperature decomposition of the reactants. Stearic acid and isostearic acid are widely used in the food, cosmetics, pharmaceutical, plastics and rubber industries, as well as candle manufacturing. Currently, major domestic and international isostearic acid industrial production uses monomeric acids as raw materials. Through pretreatment, enrichment, hydrogenation, and separation, isomeric oleic acid in the raw materials is converted into isostearic acid, which is then purified to produce isostearic acid. Furthermore, unreacted oleic acid in the raw materials can also be converted into stearic acid through hydrogenation, creating economic value while reducing waste disposal pressure, achieving a combination of resource utilization and environmental protection.

[0003] Currently, nickel-based catalysts are mainly used in the hydrogenation of unsaturated fatty acids. However, due to the complex composition of monomeric acids and the fact that branched isomers are more difficult to hydrogenate than straight-chain structures, nickel-based catalysts often cannot achieve a deep reaction degree in the hydrogenation of monomeric acids, resulting in low saturation and high iodine values ​​of the reaction products. Furthermore, it has been found that stearyl lactone, an impurity, remains after the hydrogenation reaction of monomeric acids and is difficult to remove using conventional separation methods. Patent CN 116283555 A discloses an isostearic acid composition, its preparation method, and its application, mentioning the use of a cobalt-based catalyst combined with a copper catalyst in the hydrogenation process to complete the hydrogenation reaction and remove stearyl lactone. However, this process has drawbacks such as high hydrogen pressure requirements and long hydrogenation reaction time. Therefore, it is essential to develop a novel catalyst that combines high hydrogenation degree and chemical impurity removal while optimizing the hydrogenation process. Summary of the Invention

[0004] In view of this, the present invention provides a monomeric acid hydrogenation catalyst (Pd-Co bimetallic supported catalyst), its preparation method and application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A monomeric acid hydrogenation catalyst, wherein the catalyst is a composite support of activated carbon and zeolite molecular sieve, and palladium and cobalt bimetallic components are used as active components; wherein the Co loading is 5%~10% and the Pd loading is 0.25~0.5%.

[0006] The composite carrier is formed by mixing activated carbon and molecular sieves at a mass ratio of 2-5:1-2 and then mixing them thoroughly.

[0007] The zeolite molecular sieve is at least one or a combination of Y, LTA, MOR, ETS, ZSM, and SSZ.

[0008] Furthermore, zeolite molecular sieves have a silica-to-alumina ratio of 20-30H and a specific surface area of ​​300-700 m². 2 / g.

[0009] A method for preparing the monomeric acid hydrogenation catalyst described above: 1) Mix activated carbon and molecular sieves at a mass ratio of 2-4:1-2, and mix well to form a composite carrier; 2) The Co and Pd precursor metal salts were dissolved in deionized water and set aside for later use; 3) The solution obtained in step 2) is added dropwise to the composite support obtained in step 1), sealed and left to stand at room temperature to allow the metal ions to fully diffuse and adsorb onto the support for aging for 8-10 hours, and then dried, calcined and reduced with H2 to obtain the catalyst Co-Pd / AC-zeolite.

[0010] To elaborate further, 1) Mix activated carbon and molecular sieves at a mass ratio of 2-4:1-2, and then mix them thoroughly in a ball mill or mortar to form a composite carrier; 2) Add the precursor metal salts containing Co and Pd to deionized water to dissolve all the solids, and finally bring the volume to a final level to obtain the metal mother liquor; 3) Add the metal mixed solution obtained in step 2) dropwise slowly to the composite carrier obtained in step 1), stir and mix well so that the metal mixed solution is evenly absorbed by the carrier, and then seal and let stand at room temperature to allow the metal ions to fully diffuse and adsorb onto the carrier for aging for 8-10 hours. 4) Dry the aged wet material at 110-120℃ for 12-24 hours, and then calcine the dried sample in an air atmosphere in a muffle furnace. 5) Place the calcined sample in a tube furnace and reduce it in an atmosphere of H2 / N2 mixed gas (e.g., 10% H2) to obtain the catalyst Co-Pd / AC-zeolite.

[0011] In step 4), the calcination conditions are to raise the temperature to 300-400℃ at a rate of 1-5℃ / min (to avoid excessive temperature causing metal sintering or PdO decomposition) and calcinate for 3-4 hours.

[0012] In step 5), the reduction conditions are to raise the temperature to 350-450°C at a rate of 1-5°C / min, hold the temperature for 2-3 hours, and then cool to room temperature under an inert atmosphere (N2 or Ar).

[0013] In step 2), the precursor metal salts containing Co and Pd are Co(NO3)2·6H2O and Pd(NO3)2·2H2O, which are mixed in a mass ratio of 10:1 to 50:1.

[0014] An application of the aforementioned monomeric acid hydrogenation catalyst, wherein the catalyst is used in the catalytic reaction of monomeric acid hydrogenation.

[0015] Furthermore, the catalyst is added to the raw material monomer acid, and the reaction is carried out at 230~250℃, pressure 2.5~4Mpa, and reaction time 3-4h to achieve catalytic hydrogenation of the raw material; wherein the amount of catalyst added accounts for 1.5-3% of the mass of the raw material.

[0016] The beneficial effects of this invention are as follows: In the method of this invention, the Co-Pd bimetallic active component is more efficient in hydrogenating long-chain unsaturated fatty acids in monomeric acids to saturated fatty acids, and the resulting hydrogenated product has a lower iodine value. Meanwhile, the zeolite molecular sieve, as its support, with its unique structure, converts stearic acid lactone in the system into easily separable stearic acid during the hydrogenation reaction, reducing the difficulty of subsequent separation and purification. Detailed Implementation

[0017] To facilitate understanding of the present invention, the present invention will be further described below with reference to specific embodiments, but there is no way to limit the present invention.

[0018] In this invention, Co-Pd is used as the bimetallic active component in the catalyst to ensure its catalytic activity. Activated carbon AC-zeolite molecular sieve is used as a composite support, which provides a high specific surface area and well-developed pore structure, while also having acidic sites to convert and remove stearic acid lactone in the monomeric acid during the hydrogenation reaction.

[0019] In the examples below, the monomeric acid is a byproduct of the production of dimer acid, wherein the palmitic acid content is about 12%, the C18 saturated fatty acid content is about 10%, the total C18 straight-chain branched unsaturated fatty acid content is about 40%, the stearic acid lactone content is 5%, and the remainder is dimer acid, polyacid, arachidic acid, cyclic acid, etc.

[0020] Example 1 A method for preparing a monomeric acid hydrogenation catalyst includes the following steps: a. Mix 15.4g of activated carbon and 7.8g of Y zeolite molecular sieve in a ball mill or mortar at a certain mass ratio to form a composite carrier.

[0021] Among them, the Y zeolite molecular sieve has a silica-to-alumina ratio of 15 and a specific surface area of ​​680 m². 2 / g.

[0022] b. Weigh 5.8g Co(NO3)2·6H2O and 0.46g Pd(NO3)2·2H2O into a beaker, add deionized water to dissolve all the solids, and finally bring the volume to 34.8mL.

[0023] c. Place 23.2g of AC-Zeo composite carrier powder in a large evaporating dish. Using a dropper or pipette, slowly add the prepared metal mixture solution drop by drop onto the carrier, stirring constantly and gently with a glass rod to ensure the solution is evenly absorbed by the carrier without clumping. After the addition is complete, seal the container with sealing film and allow it to age at room temperature for 8 hours.

[0024] d. Dry the aged wet material at 120°C for 12 hours, then calcine the dried sample in a muffle furnace at a rate of 2°C / min to 400°C in air atmosphere for 4 hours.

[0025] e. The calcined sample was placed in a tube furnace and reduced in an H2 / N2 mixed gas (10% H2) atmosphere. The temperature was increased to 350℃ at a rate of 5℃ / min and held for 3 hours. The sample was then cooled to room temperature in an inert atmosphere (N2 or Ar) to obtain the final catalyst Co-Pd / AC-Zeo.

[0026] Example 2 A method for preparing a monomeric acid hydrogenation catalyst includes the following steps: a. Mix 15.4g of activated carbon and 7.8g of ZSM-35 in a ball mill or mortar at a certain mass ratio to form a composite carrier.

[0027] Among them, ZSM-35 molecular sieve has a silica-to-alumina ratio of 25 and a specific surface area of ​​550 m². 2 / g b. Weigh 11.64g of Co(NO3)2·6H2O and 0.46g of Pd(NO3)2·2H2O into a beaker, add deionized water to dissolve all the solids, and finally bring the volume to 34.8mL.

[0028] c. Place 23.2g of AC-Zeo composite carrier powder in a large evaporating dish. Using a dropper or pipette, slowly add the prepared metal mixture solution drop by drop onto the carrier, stirring constantly and gently with a glass rod to ensure the solution is evenly absorbed by the carrier without clumping. After the addition is complete, seal the container with sealing film and allow it to age at room temperature for 8 hours.

[0029] Dry at 110-120℃ for 12 hours, then heat to 300-400℃ in a muffle furnace at a rate of 1-5℃ / min and calcine for 4 hours.

[0030] e. The calcined sample was placed in a tube furnace and reduced in an H2 / N2 mixed gas (10% H2) atmosphere. The temperature was increased to 400℃ at a rate of 5℃ / min and held for 3 hours. The sample was then cooled to room temperature in an inert atmosphere (N2 or Ar).

[0031] Example 3 A method for preparing a monomeric acid hydrogenation catalyst includes the following steps: a. Mix 15.4g of activated carbon and 7.8g of MOR molecular sieve in a ball mill or mortar at a certain mass ratio to form a composite carrier.

[0032] Among them, the MOR molecular sieve has a silica-to-alumina ratio of 10-12 and a specific surface area of ​​600 m². 2 / g.

[0033] b. Weigh 11.64g of Co(NO3)2·6H2O and 0.23g of Pd(NO3)2·2H2O into a beaker, add deionized water to dissolve all the solids, and finally bring the volume to 34.8mL.

[0034] c. Place 23.2g of AC-Zeo composite carrier powder in a large evaporating dish. Using a dropper or pipette, slowly add the prepared metal mixture solution drop by drop onto the carrier, stirring constantly and gently with a glass rod to ensure the solution is evenly absorbed by the carrier without clumping. After the addition is complete, seal the container with sealing film and allow it to age at room temperature for 8 hours.

[0035] Dry at 110-120℃ for 12 hours, then heat to 300-400℃ in a muffle furnace at a rate of 1-5℃ / min and calcine for 4 hours.

[0036] e. The calcined sample was placed in a tube furnace and reduced in an H2 / N2 mixed gas (10% H2) atmosphere. The temperature was increased to 350°C at a rate of 5°C / min and held for 3 hours. The sample was then cooled to room temperature in an inert atmosphere (N2 or Ar).

[0037] Example 4 A method for preparing a monomeric acid hydrogenation catalyst includes the following steps: a. Mix 15.4g of activated carbon and 7.8g of SSZ-13 in a ball mill or mortar at a certain mass ratio to form a composite carrier.

[0038] The SSZ-13 molecular sieve has a silica-to-alumina ratio of 45 and a specific surface area of ​​600 m². 2 / g.

[0039] b. Weigh 5.8g of Co(NO3)2·6H2O and 0.23g of Pd(NO3)2·2H2O into a beaker, add deionized water to dissolve all the solids, and finally bring the volume to 34.8mL.

[0040] c. Place 23.2g of AC-Zeo composite carrier powder in a large evaporating dish. Using a dropper or pipette, slowly add the prepared metal mixture solution drop by drop onto the carrier, stirring constantly and gently with a glass rod to ensure the solution is evenly absorbed by the carrier without clumping. After the addition is complete, seal the container with sealing film and allow it to age at room temperature for 8 hours.

[0041] Dry at 110-120℃ for 12 hours, then heat to 300-400℃ in a muffle furnace at a rate of 1-5℃ / min and calcine for 4 hours.

[0042] e. The calcined sample was placed in a tube furnace and reduced in an H2 / N2 mixed gas (10% H2) atmosphere. The temperature was increased to 350℃ at a rate of 5℃ / min and held for 2 hours. The sample was then cooled to room temperature in an inert atmosphere (N2 or Ar).

[0043] Example 5 Take 4g of the catalyst prepared in Example 1 and place it in a 500ml high-pressure reactor. Add 200g of monomeric acid raw material, seal the reactor, purge with nitrogen three times and hydrogen three times, control the hydrogen pressure at 4MPa, start stirring at 1000rpm, heat to 240℃, react for 3h, cool to 70℃, filter the product, titrate to analyze the iodine value of the product, and analyze the lactone content by gas phase analysis.

[0044] Example 6 Take 4g of the catalyst prepared in Example 2 and place it in a 500ml high-pressure reactor. Add 200g of monomeric acid raw material, seal the reactor, purge with nitrogen three times and hydrogen three times, control the hydrogen pressure at 3MPa, start stirring at 1000rpm, heat to 250℃, react for 3h, cool to 70℃, filter the product, titrate to analyze the iodine value of the product, and analyze the lactone content by gas phase analysis.

[0045] Example 7 Take 4g of the catalyst prepared in Example 3 and place it in a 500ml high-pressure reactor. Add 200g of monomeric acid raw material, seal the reactor, purge with nitrogen three times and hydrogen three times, control the hydrogen pressure at 2.5MPa, start stirring at 1000rpm, heat to 230℃, react for 3h, cool to 70℃, filter the product, titrate to analyze the iodine value of the product, and analyze the lactone content by gas phase analysis.

[0046] Example 8 Take 4g of the catalyst prepared in Example 4 and place it in a 500ml high-pressure reactor. Add 200g of monomeric acid raw material, seal the reactor, purge with nitrogen three times and hydrogen three times, control the hydrogen pressure at 3MPa, start stirring at 1000rpm, heat to 230℃, react for 3h, cool to 70℃, discharge and filter, titrate to analyze the iodine value of the product, and analyze the lactone content by gas phase analysis.

[0047] Comparative Example 1 Take 4g of Ni-based catalyst and place it in a 500ml high-pressure reactor. Add 200g of monomeric acid raw material, seal the reactor, purge with nitrogen three times and hydrogen three times, control the hydrogen pressure at 4MPa, start stirring at 1000rpm, heat to 250℃, react for 3h, cool to 70℃, discharge and filter, titrate to analyze the iodine value of the product, and analyze the lactone content by gas phase analysis.

[0048] The iodine value of the hydrogenation product was determined according to GB-T 9104-2008, the test method for industrial stearic acid. Gas chromatography analysis was used to determine its component content, referring to AOCS Official Method Ce 1b-89.

[0049] The iodine value and lactone content of the products in the above embodiments are shown in Table 1.

[0050] Table 1

[0051] As can be seen from the data in Table 1, the Pd-Co bimetallic active components of the catalyst prepared in this invention synergistically promote catalytic activity, while the AC-Zeo support ensures full contact between the active components and the materials. At the same time, the special structure of the zeolite molecular sieve removes impurities through isomerization during the catalytic reaction, which improves product quality and reduces process complexity.

Claims

1. A catalyst for the hydrogenation of a monomeric acid, characterized in that: The catalyst uses activated carbon and molecular sieve as a composite support, and palladium and cobalt bimetals as active components; wherein the Co loading is 5%~10% and the Pd loading is 0.25~0.5%.

2. The monomeric acid hydrogenation catalyst according to claim 1, characterized in that: The composite carrier is formed by mixing activated carbon and molecular sieves at a mass ratio of 2-5:1-2 and mixing them thoroughly.

3. The monomeric acid hydrogenation catalyst according to claim 1 or 2, characterized in that: The molecular sieve is a zeolite molecular sieve with a silica-to-alumina ratio of 15-50 and a specific surface area of ​​300-700 m². 2 / g.

4. A method for preparing the monomeric acid hydrogenation catalyst according to claim 1, characterized in that: 1) Mix activated carbon and molecular sieves at a mass ratio of 2-5:1-2, and mix well to form a composite carrier; 2) The Co and Pd precursor metal salts were dissolved in deionized water and set aside for later use; 3) The solution obtained in step 2) is added dropwise to the composite support obtained in step 1), sealed and left to stand at room temperature to allow the metal ions to fully diffuse and adsorb onto the support for aging for 8-10 hours, and then dried and calcined to obtain the catalyst Co-Pd / AC-zeolite.

5. The method for preparing the monomeric acid hydrogenation catalyst according to claim 4, characterized in that: 1) Mix activated carbon and molecular sieves at a mass ratio of 2-5:1-2, and then mix them thoroughly in a ball mill or mortar to form a composite carrier; 2) Add the precursor metal salts containing Co and Pd to deionized water to dissolve all the solids, and finally bring the volume to a final level to obtain the metal mother liquor; 3) Add the metal mixed solution obtained in step 2) dropwise slowly to the composite carrier obtained in step 1), stir and mix well so that the metal mixed solution is evenly absorbed by the carrier, and then seal and let stand at room temperature to allow the metal ions to fully diffuse and adsorb onto the carrier for aging for 8-10 hours. 4) Dry the aged wet material at 110-120℃ for 12-24 hours, and then calcine the dried sample in an air atmosphere in a muffle furnace. 5) The calcined sample is placed in a tube furnace and reduced in a mixed H2 / N2 atmosphere to obtain the catalyst Co-Pd / AC-zeolite.

6. The method for preparing the monomeric acid hydrogenation catalyst according to claim 5, characterized in that: In step 4), the calcination conditions are to raise the temperature to 300-400℃ at a rate of 1-5℃ / min and calcin for 3-4 hours.

7. The method for preparing the monomeric acid hydrogenation catalyst according to claim 5, characterized in that: In step 5), the reduction conditions are to raise the temperature to 350-450°C at a rate of 1-5°C / min, hold the temperature for 2-3 hours, and then cool to room temperature under an inert atmosphere.

8. The method for preparing the monomeric acid hydrogenation catalyst according to claim 5, characterized in that: In step 2), the precursor metal salts containing Co and Pd are Co(NO3)2·6H2O and Pd(NO3)2·2H2O, which are mixed in a mass ratio of 10:1 to 50:

1.

9. The application of the monomeric acid hydrogenation catalyst according to claim 1, characterized in that: Application of the catalyst in the hydrogenation catalytic reaction of monomeric acids.

10. The application of the monomeric acid hydrogenation catalyst according to claim 9, characterized in that: The catalyst described in claim 1 is added to the raw material monomer acid, and the reaction is carried out at 230~250℃, pressure 2.5~4MPa, and reaction time 3-4h to achieve catalytic hydrogenation of the raw material; wherein the amount of catalyst added accounts for 1.5-3% of the mass of the raw material.

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