A pt-s-1 molecular sieve catalyst, a preparation method thereof and application thereof in preparation of isononyl acid and isononyl isononyl ester by isononyl alcohol oxidation

Abstract

This invention discloses a Pt-S-1 molecular sieve catalyst, its preparation method, and its application in the oxidation of isononanol to prepare isononanoic acid and / or isonononate. The catalyst uses an all-silica S-1 molecular sieve as a support, with Pt as the active component. The support contains both micropores and mesopores, with Pt uniformly dispersed within them. The Pt content in the catalyst is 0.004 wt% to 0.50 wt%, obtained through a secondary crystallization process. The catalyst offers advantages such as high precious metal utilization efficiency, mild reaction conditions, no need for alkali or additives, simple post-treatment, and convenient recycling.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst for the oxidation of isononyl alcohol to prepare isononanoic acid and / or isononyl isononanoate, its preparation method, and its application. Background Technology

[0002] Isonononic acid, also known as 3,5,5-trimethylhexanol, is an important branched carboxylic acid widely used in lubricating oil esters, metalworking fluids, plasticizers, detergents, cosmetics, and resin modification. Therefore, developing efficient and green methods for preparing isonononic acid is of significant application value. Current industrial routes typically involve the further oxidation of isononal or isononol to obtain isonononic acid.

[0003] Existing isononanol oxidation routes still have significant shortcomings. One type of method uses a system of hydrogen peroxide, co-oxidant, and phase transfer catalyst, which suffers from high oxidant cost, process safety issues, and a heavy separation burden (see CN112608227A, A method for green oxidation of isononanol to isononanoic acid). Another type of method uses Pd / C heterogeneous catalysts, which can achieve high selectivity for isononanoic acid, but are usually only applicable to pure oxygen and require the addition of alkaline auxiliaries such as NaOH to the reaction system, which is not conducive to process simplification and greening (see CN112657510A, A catalyst for catalytic oxidation of isononanol to isononanoic acid, its preparation method and application). In addition, nitrogen-doped carbon-supported PtBi catalysts have been disclosed for isononanol oxidation in alkali-free systems, but the Pt content is high (1-7 wt.%), and the method for constructing the all-silicon S-1 confined Pt structure and its crystallization is not involved (see CN118356964A, A catalyst for the oxidation of isononanol to isononanoic acid and isononanoic acid ester, its preparation method and application).

[0004] In addition, metal@molecular sieves, especially confined catalysts such as Pt@MFI or Pt@S-1, have been reported in recent years to be constructed through two-step crystallization, dry gel conversion, recrystallization, or secondary crystallization. Their main purpose is to improve the dispersion, anti-sintering properties, and shape selectivity of Pt species. Published literature indicates that pretreatment with TPAOH followed by recrystallization in a silicon-containing, Na⁺-free crystallization solution can embed Pt into S-1 crystals. Another review points out that controlled recrystallization in a secondary stage can form new microporous / mesoporous shells around the metal, achieving physical embedding and structural protection. These published studies primarily focus on reactions such as hydrogenation, CO oxidation, VOC oxidation, and alkane aromatization, rather than the oxidation of isononanol to isononanoic acid / isononanoate.

[0005] Furthermore, S-1 is an all-silica MFI-type molecular sieve, possessing weak water adsorption, strong hydrophobicity, and a three-dimensional cross-linked 10-membered ring pore structure. This type of all-silica microenvironment is expected to improve the enrichment and diffusion behavior of organic substrates near the catalyst and reduce side reactions that may be caused by traditional molecular sieves containing acidic sites. Based on this, if ultra-low Pt loading is introduced into all-silica S-1 through crystallization and used for the alkali-free oxidation of isononanol, it is expected to simultaneously achieve low Pt loading, structural stability, and selectivity for the target product.

[0006] Therefore, developing a Pt-S-1 molecular sieve catalyst that is easy to prepare, requires low Pt dosage, requires no additional reduction or activation, and can be directly reused after water separation after the reaction has significant research value and potential application prospects. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a Pt-S-1 molecular sieve catalyst, its preparation method and its application in the oxidation of isononol to prepare isononanoic acid and / or isononyl isononanoate, so as to improve the utilization efficiency of precious metals, make the reaction conditions mild, require no addition of alkali or auxiliary agents, simplify the post-processing and facilitate recycling.

[0008] To solve the above technical problems, the present invention first discloses a Pt-S-1 molecular sieve catalyst, which uses all-silica S-1 molecular sieve as support and Pt as active component. The support contains both micropores and mesopores, and Pt is uniformly dispersed in the micropores and mesopores of the support. The Pt content in the catalyst is 0.004wt% to 0.50wt%, preferably 0.04wt% to 0.10wt%.

[0009] This invention also discloses a method for preparing the Pt-S-1 molecular sieve catalyst as described above, the method comprising the following steps:

[0010] (1) Add the all-silica S-1 molecular sieve to a mixed solution containing tetrapropylammonium hydroxide and chloroplatinic acid for secondary crystallization treatment; (2) After the secondary crystallization treatment, the obtained solid is subjected to solid-liquid separation and thoroughly washed with a large amount of deionized water; (3) The washed solid was dried and calcined to obtain Pt-S-1 molecular sieve catalyst.

[0011] Further, in step (1), the mixed solution containing tetrapropylammonium hydroxide and chloroplatinic acid is obtained by mixing tetrapropylammonium hydroxide solution with chloroplatinic acid, wherein the concentration of the tetrapropylammonium hydroxide solution is 0.1-0.5 mol / L.

[0012] Furthermore, in step (1), the secondary crystallization treatment temperature is 100-150 °C and the time is 12-48 h.

[0013] Furthermore, in step (3), the roasting temperature is 300–600 °C and the roasting time is 1–10 h.

[0014] This invention further discloses the application of the Pt-S-1 molecular sieve catalyst as described above, or the Pt-S-1 molecular sieve catalyst prepared according to the aforementioned method, in the oxidation of isononanol to prepare isononanoic acid and isonononoate. The catalyst is added to a reaction vessel, using isononanol as a raw material and oxygen or air as an oxidant, in a system with added water or without external solvent to obtain isononanoic acid and / or isonononoate. After the reaction, the catalyst is recovered by adding water for separation, filtration, or centrifugation. The recovered catalyst can be directly reused in the next reaction. No hydrogen reduction treatment is required before use of the catalyst (including the recovered catalyst), and no external alkali is added to the reaction system.

[0015] Furthermore, the mass ratio of isononol to catalyst is 50–200:1, and the mass ratio of deionized water to catalyst in the system is 0–800:1.

[0016] Furthermore, the reaction temperature is 80–150 °C; the reaction time is 2–72 h; the stirring speed is 600–1000 rpm; when the oxidant is oxygen, the reaction pressure is 0.1–1.5 MPa; and the reaction pressure is 0.1–2.0 MPa.

[0017] Furthermore, when the oxidant is air, the reaction pressure is 0.5–2.0 MPa.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] 1. The Pt-S-1 catalyst was constructed using a tetrapropylammonium hydroxide / chloroplatinic acid crystallization system. The preparation process is simple and easy to implement.

[0020] 2. Low Pt usage helps reduce the cost of using precious metals and improves Pt utilization efficiency;

[0021] 3. The catalyst can catalyze the oxidation of isononol without the addition of external alkali, reducing the burden of post-treatment and separation;

[0022] 4. The catalyst can be directly used in the oxidation reaction after calcination, without the need for additional hydrogen reduction and activation, making the process simpler;

[0023] 5. After the reaction is complete, the catalyst can be directly recovered by water separation and can be recycled directly without additional pretreatment, which helps to reduce separation costs and improve the feasibility of industrial applications. Attached Figure Description

[0024] Figure 1This is an electron microscope image of the Pt-S-1 catalyst obtained in Example 1 of the invention. Detailed Implementation

[0025] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, all raw materials used in this invention are commercially available. The S-1 molecular sieve is a commercially available all-silica S-1 molecular sieve (Dalian Evolution Technology Co., Ltd.). The Pt precursor is chloroplatinic acid. The TPAOH is a 0.1–0.5 mol / L tetrapropylammonium hydroxide aqueous solution.

[0027] In some embodiments of the present invention, the Pt-S-1 molecular sieve catalyst is prepared by the following method: a certain amount of purchased all-silica S-1 molecular sieve is added to a mixed solution containing TPAOH and chloroplatinic acid for secondary crystallization treatment; after crystallization, the sample is filtered or centrifuged, washed with deionized water until neutral or near neutral, dried, and calcined in air atmosphere to obtain the Pt-S-1 molecular sieve catalyst.

[0028] In some embodiments of the present invention, the mass fraction of Pt in the catalyst is 0.004 wt% to 0.50 wt%, preferably 0.04 wt% to 0.10 wt%.

[0029] In some embodiments of the present invention, the application steps of the Pt-S-1 molecular sieve catalyst in the oxidation of isononol are as follows: the catalyst is directly loaded into a 50 mL autoclave reactor, and isononol and deionized water are added, or only isononol is added; the autoclave reactor is pressurized to the set pressure after multiple purgings with oxygen or air, and then heated to the reaction temperature and stirred (800 rpm) to carry out the reaction. After the reaction is completed, the reactor is cooled to room temperature and depressurized, and the catalyst is recovered by adding water and performing layering, filtration, or centrifugation; the recovered catalyst can be directly used in the next reaction without additional reduction and activation.

[0030] In each embodiment, the conversion rate and selectivity are calculated using the following formulas (all units of measurement are molar amounts):

[0031] Isononol conversion rate = (starting material isononol – product isononol) / starting material isononol × 100%

[0032] Isononanoic acid selectivity = (Isononanoic acid in the product) / (converted isononol) × 100%

[0033] Selectivity for isononyl isononanoate = (Isononyl isononanoate in the product x 2) / (converted isononol) × 100%

[0034] The qualitative and quantitative analysis of the raw materials and products before and after the reaction was performed on an Agilent gas chromatograph 7890, and the component analysis was carried out using an FFAP capillary column and an FID detector.

[0035] Example 1: Preparation of Pt-S-1 catalyst

[0036] Two g of purchased all-silica S-1 molecular sieve was added to 10 mL of a mixed solution consisting of 0.3 mol / L TPAOH and 1.71 mg chloroplatinic acid (H₂PtCl₆·6H₂O), and crystallized at 130 °C for 48 h. After crystallization, the resulting solid was filtered and separated, washed with deionized water until neutral, dried at 100 °C for 12 h, and then calcined at 550 °C for 6 h in air to obtain the Pt-S-1 catalyst (electron microscopy image shown). Figure 1 The mass fraction of Pt in the catalyst was measured to be 0.0408 wt%.

[0037] Example 2: Pt-S-1 catalyst for the oxidation of isononanol to isononanoic acid

[0038] 0.05 g of the Pt-S-1 catalyst obtained in Example 1 was added to a high-pressure reactor, along with 5 g of isononol and 5 g of deionized water. The reactor was purged with O2 and pressurized to 0.8 MPa, then stirred at 110 °C for 9 h. After the reaction, the reactor was cooled and depressurized, and water was added for separation. The upper oil phase was then analyzed. The conversion rate of isononol was found to be 95%, the selectivity of isononanoic acid was 90%, and the selectivity of isononyl isononanoate was 8%.

[0039] Example 3: Application of Pt-S-1 catalyst in a system without added solvent

[0040] Except for the absence of deionized water, the operation was the same as in Example 2. The conversion rate of isononol was measured to be 92%, the selectivity of isononanoic acid was 85%, and the selectivity of isononyl isononanoate was 11%.

[0041] Example 4: Recycling Experiment

[0042] After completing one reaction according to Example 2, water was added to the reaction system to recover the catalyst. The resulting catalyst was used directly in the next reaction without hydrogen reduction or other activation treatment. After four cycles, the isononol conversion rate (93-96%) and the selectivity of isononanoic acid / isonononyl isononanoate remained basically stable in each cycle, and the Pt content of the catalyst remained basically unchanged after recycling (0.0405 wt%), indicating that the catalyst has good recycling performance.

[0043] Example 5:

[0044] The Pt-S-1 catalyst was synthesized according to Example 1, with the TPAOH concentration changed to 0.1 mol / L, the H2PtCl6·6H2O mass changed to 0.17 mg, the crystallization temperature changed to 120℃, the crystallization time changed to 12 h, and the calcination temperature changed to 450℃. The mass fraction of Pt in the catalyst was measured to be 0.004 wt%. All other synthesis conditions remained unchanged.

[0045] The isononol oxidation reaction was carried out under the conditions in Example 2, and its activity and selectivity were compared.

[0046] Example 6:

[0047] The Pt-S-1 catalyst was synthesized according to Example 1, with the TPAOH concentration changed to 0.5 mol / L, the H2PtCl6·6H2O mass changed to 17.1 mg, the crystallization temperature changed to 150℃, and the crystallization time changed to 24 h. The mass fraction of Pt in the catalyst was measured to be 0.50 wt%. All other synthesis conditions remained unchanged.

[0048] The isononol oxidation reaction was carried out under the conditions in Example 2, and its activity and selectivity were compared.

[0049] Example 7:

[0050] The Pt-S-1 catalyst was synthesized according to Example 1, with the TPAOH concentration changed to 0.5 mol / L, the H2PtCl6·6H2O mass changed to 3.5 mg, the crystallization temperature changed to 150℃, and the crystallization time changed to 24 h. The mass fraction of Pt in the catalyst was measured to be 0.1 wt%. All other synthesis conditions remained unchanged.

[0051] The isononol oxidation reaction was carried out under the conditions in Example 2, and its activity and selectivity were compared.

[0052] Example 8:

[0053] In Example 2, O2 was replaced with air, the pressure was changed to 1 MPa, and all other conditions remained the same. The isononol oxidation reaction was carried out, and its activity and selectivity were compared.

[0054] Comparative Example 1: Pt / S-1 catalyst (impregnation method)

[0055] Two g of purchased all-silica S-1 molecular sieve was added to 3 mL of an aqueous solution containing 20.92 mg of chloroplatinic acid (H₂PtCl₆·6H₂O). The mixture was impregnated at room temperature for 12 h, then dried at 100 ℃ for 12 h, and finally calcined at 550 ℃ in air for 6 h to obtain the Pt / S-1 catalyst. The mass fraction of Pt in the catalyst was determined to be 0.5 wt%.

[0056] The Pt / S-1 catalyst was reduced at 450℃ for 3 hours under a hydrogen atmosphere to obtain the Pt / S-1-H catalyst.

[0057] Isononol oxidation was performed under the conditions described in Example 2, and its activity and selectivity cycling performance were compared.

[0058] Comparative Example 2: Pt catalyst supported on a non-molecular sieve support (impregnation method)

[0059] Supported Pt catalysts were prepared using the same method as in Comparative Example 1 (metal loading maintained at 0.5 wt%), but with SiO2 used instead of S-1 molecular sieve, resulting in comparative catalysts Pt / SiO2 and Pt / SiO2-H. Pt / SiO2-H represents the reduction of Pt / SiO2 catalyst at 450 °C for 3 h under a hydrogen atmosphere.

[0060] The isononol oxidation reaction was carried out under the conditions in Example 2, and its activity and selectivity were compared.

[0061] Comparative Example 3: Pt catalyst supported on a non-molecular sieve support (impregnation method)

[0062] Supported Pt catalysts (metal loading maintained at 0.5 wt%) were prepared using the same method as Comparative Example 1, but activated carbon (AC) was used instead of S-1 molecular sieve to obtain comparative catalysts Pt / AC and Pt / AC-H. Pt / AC-H represents the reduction of Pt / AC catalyst at 450 °C for 3 h under a hydrogen atmosphere.

[0063] Isononol oxidation was performed under the conditions described in Example 2, and its activity, selectivity, and cyclicity were compared.

[0064] Comparative Example 4: Pt-S-1 catalyst after hydrogen reduction

[0065] The Pt-S-1 catalyst from Example 1 was reduced at 450°C for 3 hours under a hydrogen atmosphere to obtain the Pt-S-1-H catalyst.

[0066] The isononol oxidation reaction was carried out under the conditions in Example 2, and its activity and selectivity were compared.

[0067] Table 1. Results of catalyst performance in the isononanol oxidation reaction in each example and comparative example.

[0068] Examples and Comparative Examples Catalyst code Isononol conversion rate % Isonononanoic acid selectivity % Selectivity of isononyl isononanoate % Remark Example 2 Pt-S-1 95 90 8 Example 3 Pt-S-1 92 85 11 Example 4 Pt-S-1 93 89 8 First application Example 4 Pt-S-1 94 88 9 Second application Example 4 Pt-S-1 96 91 6 Third application Example 4 Pt-S-1 93 89 9 Fourth application Example 5 Pt-S-1 38 57 4 Example 6 Pt-S-1 99 91 7 Example 7 Pt-S-1 96 90 7 Example 8 Pt-S-1 94 89 9 Comparative Example 1 Pt / S-1 20 35 0 Comparative Example 1 Pt / S-1-H 82 85 12 Comparative Example 1 Pt / S-1-H 76 83 15 First application Comparative Example 1 Pt / S-1-H 65 80 17 Second application Comparative Example 2 <![CDATA[Pt / SiO2]]> 15 25 0 Comparative Example 2 <![CDATA[Pt / SiO2-H]]> 62 59 13 Comparative Example 3 Pt / AC 33 42 2 Comparative Example 3 Pt / AC-H 90 90 8 Comparative Example 3 Pt / AC-H 76 82 6 First application Comparative Example 3 Pt / AC-H 57 78 5 Second application Comparative Example 4 Pt-S-1-H 93 88 9

[0069] As can be seen from the electron micrograph of the Pt-S-1 catalyst given in Example 1, Pt is highly dispersed on the S-1 support, and no Pt agglomeration occurs.

[0070] As can be seen from Examples 1-4, the Pt-S-1 catalyst prepared by the crystallization method can achieve efficient conversion of isononol to isononanoic acid and isononanoic acid ester in the high-pressure autoclave process of isononol oxidation reaction under mild reaction conditions without alkali, and has excellent cycle stability performance.

[0071] Examples 2 and 3 demonstrate that the oxidation of isononol on the Pt / S-1 catalyst can proceed in solvent-free conditions or with water as the solvent. Using water as the solvent increases the conversion rate of isononol and the selectivity of isononanoic acid.

[0072] Examples 2, 5, 6, and 7 show that the Pt loading has a significant impact on catalytic performance. When the Pt loading is between 0.0408 wt% and 0.1 wt%, the conversion rate and acid / ester selectivity of isononanol have reached a high level. Further increasing the Pt loading does not significantly increase the catalyst activity and target product selectivity. However, when the Pt loading is very low, both the catalyst activity and target product selectivity are low.

[0073] As can be seen from Example 8, the isononol oxidation reaction on the Pt-S-1 catalyst can also use air as an oxidant instead of oxygen and achieve a similar catalytic effect.

[0074] As can be seen from Example 2 and Comparative Example 1, although the metal Pt content on Pt / S-1 obtained by impregnation is much greater than that on Pt-S-1 obtained by secondary crystallization, the conversion rate of isononanol and the selectivity of the target product on Pt / S-1 before and after hydrogen reduction are both lower than those on Pt-S-1, and the activity of catalysts decreases significantly during catalyst reuse.

[0075] As can be seen from Example 2 and Comparative Examples 2 and 3, the conversion rate of isononol and the selectivity of the target product on Pt catalysts prepared by other support impregnation methods are lower than those of Pt-S-1, and the activity decreases significantly during catalyst reuse.

[0076] Examples 2 and 4 show that hydrogen reduction has little effect on the oxidation performance of isononanol on Pt-S-1 catalysts, and the catalysts exhibit excellent performance without hydrogen reduction treatment. However, Comparative Examples 1-3 show that the catalysts obtained by the impregnation method require hydrogen reduction treatment to achieve better oxidation performance.

Claims

1. A Pt-S-1 molecular sieve catalyst characterized by: The catalyst uses all-silica S-1 molecular sieve as support and Pt as active component. The support contains both micropores and mesopores, and Pt is uniformly dispersed in the micropores and mesopores of the support. The Pt content in the catalyst is 0.004 wt% to 0.50 wt%.

2. The Pt-S-1 molecular sieve catalyst according to claim 1, characterized in that: The Pt content in the catalyst is 0.04 wt% to 0.1 wt%.

3. A method for preparing a Pt-S-1 molecular sieve catalyst as described in claim 1 or 2, characterized in that: The method includes the following steps: (1) Add the all-silica S-1 molecular sieve to a mixed solution containing tetrapropylammonium hydroxide and chloroplatinic acid for secondary crystallization treatment; (2) After the secondary crystallization treatment, the obtained solid is subjected to solid-liquid separation and washing; (3) The washed solid was dried and calcined to obtain Pt-S-1 molecular sieve catalyst.

4. The preparation method according to claim 3, characterized in that: In step (1), the mixed solution containing tetrapropylammonium hydroxide and chloroplatinic acid is obtained by mixing tetrapropylammonium hydroxide solution with chloroplatinic acid, wherein the concentration of the tetrapropylammonium hydroxide solution is 0.1-0.5 mol / L.

5. The preparation method according to claim 3, characterized in that: In step (1), the secondary crystallization treatment temperature is 100-150 °C and the time is 12-48 h.

6. The preparation method according to claim 3, characterized in that: In step (3), the roasting temperature is 300-600 ℃ and the roasting time is 1-10 h.

7. The application of a Pt-S-1 molecular sieve catalyst as described in claim 1 or 2, or a Pt-S-1 molecular sieve catalyst prepared according to the preparation method of any one of claims 3-6, in the oxidation of isononanol to prepare isononanoic acid and isonononyl isononanoate, characterized in that: The catalyst is added to a reaction vessel, and isononol is used as a raw material. Oxygen or air is used as an oxidant. The reaction is carried out in a system with added water or a system without added solvent to obtain isonononic acid and / or isononyl isononanoate. After the reaction is completed, the catalyst is recovered by adding water to separate the layers, filtration or centrifugation. The recovered catalyst can be directly reused in the next reaction.

8. The application according to claim 7, characterized in that: The mass ratio of isononol to catalyst is 50–200:1, and the mass ratio of deionized water to catalyst in the system is 0–800:

1.

9. The application according to claim 7, characterized in that: The reaction temperature is 80–150 °C; the reaction time is 2–72 h; the stirring speed is 600–1000 rpm; and the reaction pressure is 0.1–2.0 MPa.

10. The application according to claim 9, characterized in that: When the oxidant is oxygen, the reaction pressure is 0.1–1.5 MPa; when the oxidant is air, the reaction pressure is 0.5–2.0 MPa.

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