Synthetic method of antioxidant 618

Abstract

The invention belongs to the technical field of synthesis of antioxidants 618, and discloses a synthesis method of an antioxidant 618. The catalyst comprises an amination carrier and double active components loaded on the carrier, the carrier is an amination ZIF-8 metal organic framework, a first active component is silicotungstic acid H4SiW12O40, a second active component is transition metal ions, and the transition metal ions are selected from one or more of Cu < 2 + >, Mn < 2 + > or Cr < 3 + >; the catalyst can be used for catalyzing two-step ester exchange reaction of triethyl phosphite, pentaerythritol and octadecanol which are used as raw materials to synthesize the antioxidant 618. The catalyst provided by the invention is high in catalytic efficiency, relatively mild in catalytic reaction condition, stable in structure and capable of being efficiently recycled for multiple times; and the obtained product antioxidant 618 is high in selectivity and excellent in quality.

Description

Technical Field

[0001] This invention belongs to the field of antioxidant 618 synthesis technology, and specifically relates to a method for synthesizing antioxidant 618. Background Technology

[0002] Antioxidant 618, also known as AP-618, pentaerythritol diphosphite distearate, or pentaerythritol diphosphite distearate, is a white, waxy, flaky solid. Due to its pentaerythritol structure and high molecular weight, it can be used in combination with hindered phenolic antioxidants in high-temperature processing polymer materials, serving as a high-temperature antioxidant for polyethylene, polypropylene, polyvinyl chloride, and polyesters. As a highly efficient phosphite-based auxiliary antioxidant, Antioxidant 618 is widely used in the processing of polyethylene, polypropylene, ABS resin, polyester, and other polymer materials due to its excellent thermal stability, strong hydrolysis resistance, and significant synergistic effect with primary antioxidants. It effectively inhibits thermo-oxidative aging of materials and extends the service life of products.

[0003] Currently, the industrial synthesis of antioxidant 618 is mainly divided into two routes: the phenol-free route (using phosphorus trichloride as the phosphorus source) and the traditional phenol-containing route (using triphenyl phosphite as the phosphorus source). However, both routes have significant drawbacks: although the phenol-free route leaves no phenol residue, phosphorus trichloride is highly corrosive and generates a large amount of HCl during the reaction, which places stringent requirements on the equipment; the traditional phenol-containing route uses triphenyl phosphite as the phosphorus source, and although the reaction conditions are relatively mild, it is difficult to completely remove phenol from the product, affecting product purity and application safety. In addition, the catalysts are mostly homogeneous systems, which present problems such as difficulty in recovery and environmental pollution.

[0004] In recent years, some researchers have attempted to replace triphenyl phosphite with triethyl phosphite (to avoid phenol formation), but this technology still faces the following core technical challenges:

[0005] (1) Low catalytic efficiency: Triethyl phosphite has lower transesterification activity than triphenyl phosphite. Traditional catalysts (such as anhydrous AlCl3 and p-toluenesulfonic acid) are difficult to activate the PO-C2H5 bond efficiently, resulting in a high activation energy (about 88 kJ / mol in the traditional system). The total time for the two-step transesterification reaction is as long as 12-18 h, the pentaerythritol conversion rate is only 85-90%, and the yield of the target product is generally lower than 82%.

[0006] (2) Poor selectivity: Traditional catalysts cannot precisely control the ester exchange sites, and are prone to side reactions such as monoesterification, multiple substitution and ethanol self-polymerization, generating monooctadecyl pentaerythritol phosphite, trisubstituted impurities, etc., with product purity of only 94-96%, and subsequent purification is energy-intensive and costly.

[0007] (3) The catalyst structure is not stable enough and is difficult to recover: the active components of the catalyst are easily dissolved and lost, the catalyst structure is not stable enough, and the catalytic activity is significantly reduced after several cycles; the homogeneous catalyst cannot be directly separated from the reaction system and requires complex post-treatment such as water washing, neutralization, and liquid separation, which generates a large amount of organic wastewater (COD value ≥3500mg / L), the catalyst cannot be recycled multiple times, and resources are seriously wasted; the ethanol generated in the reaction is miscible with the raw materials and products, which increases the difficulty of separation;

[0008] (4) Harsh catalytic reaction conditions: The synthesis reaction of antioxidant 618 is carried out at a high temperature of 140-160℃, which consumes a lot of energy. Furthermore, the high temperature can easily lead to the oxidation and degradation of octadecyl alcohol and the thermal decomposition of the product, further reducing the product yield and quality.

[0009] Although researchers have attempted to optimize catalyst types or reaction parameters, none have broken through the technical bottleneck of synergistic improvement in "catalytic efficiency, selectivity, and environmental friendliness," failing to meet the development needs of modern chemical industry for "high efficiency, greenness, and low cost." Therefore, developing a novel catalytic system that is compatible with triethyl phosphite as a phosphorus source and possesses high activity, high selectivity, easy recyclability, and environmental friendliness is of great significance for promoting the green upgrading of the antioxidant 618 industry. Summary of the Invention

[0010] To address the technical problems in the existing antioxidant 618 synthesis process, such as low catalyst efficiency, harsh catalytic reaction conditions, poor product selectivity, unstable catalyst structure, and difficulty in recovery, this invention provides a method for synthesizing antioxidant 618.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0012] On one hand, the present invention provides a method for synthesizing antioxidant 618, comprising the following methods:

[0013] 1.1) Under the action of a catalyst, air is replaced by nitrogen, and pentaerythritol reacts with triethyl phosphite;

[0014] 1.2) After the reaction in step 1.1) is completed, the temperature is increased and octadecyl alcohol is added to the system to continue the reaction. After the reaction is completed, antioxidant 618 is obtained through post-processing steps. The separated catalyst can be recycled.

[0015] The catalyst comprises an amination support and a dual-active component supported on the amination support. The amination support is an amino-modified zeolite-like imidazole ester framework material ZIF-8, and the first active component is silicotungstic acid H4SiW. 12 O 40 The second active component is a transition metal ion, which is selected from Cu.2+ Mn 2+ or Cr 3+ One or more.

[0016] Preferably, based on the mass of the amination carrier, silicotungstic acid H4SiW 12 O 40 The loading rate is 15-25 wt%.

[0017] Preferably, the loading of the transition metal is 3-7 wt% based on the mass of the amination carrier.

[0018] On the other hand, the present invention also provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0019] 4.1) Synthesis of the aminated support: Zinc nitrate and dimethyl 2-aminoimidazolium-4,5-dicarboxylate were dissolved in N,N-dimethylformamide and reacted with stirring at 60-80℃ for 8-12 h to obtain the aminated support NH2-ZIF-8.

[0020] 4.2) The silicotungstic acid loading was carried out by the equal volume impregnation method. The aqueous solution of silicotungstic acid was impregnated in the NH2-ZIF-8 support and the impregnation reaction was stirred at 50-70℃ for 6-10h to obtain the silicotungstic acid / NH2-ZIF-8 composite.

[0021] 4.3) Transition metal supported: The silicotungstic acid / NH2-ZIF-8 composite was impregnated in aqueous solutions of copper nitrate, manganese nitrate or chromium nitrate, dried, calcined under N2 atmosphere, and a binder was added. After pressing and pulverizing, the silicotungstic acid-transition metal ion / NH2-ZIF-8 composite catalyst was obtained.

[0022] Preferably, after stirring and impregnation in step 4.2), the mixture needs to be roasted at a temperature of 250-300℃ for 2-3 hours.

[0023] Preferably, in step 4.3), the material is impregnated at room temperature for 12 hours; the calcination temperature under N2 atmosphere is 350-400℃, and the calcination time is 2-3 hours; the binder is polyethylene glycol.

[0024] Preferably, the molar ratio of triethyl phosphite to pentaerythritol is 2.1-2.4:1, and the amount of catalyst used is 1.5-2.5% of the mass of pentaerythritol.

[0025] Preferably, in a method for synthesizing antioxidant 618, the molar ratio of octadecyl alcohol to pentaerythritol is 2.0-2.3:1.

[0026] Preferably, in step 1.1) of the method for synthesizing antioxidant 618, the reaction temperature is 90-110°C and the reaction time is 2-4 hours.

[0027] The synthesis method of antioxidant 618 of the present invention includes, but is not limited to, the following reaction conditions: Step 1.2) Heating to 120-140°C and continuing the reaction for 4-6 hours, and continuing to recover the ethanol generated in the reaction; Step 1.2) Post-processing includes cooling and filtration, the catalyst is directly separated by filtration and can be recycled, and the filtrate is purified by vacuum distillation to obtain antioxidant 618.

[0028] This invention provides a composite catalyst based on an aminated ZIF-8 metal-organic framework supported on silicotungstic acid and a transition metal. The catalyst can synthesize antioxidant 618 through a two-step transesterification reaction of triethyl phosphite, pentaerythritol, and octadecyl alcohol. Compared with the prior art, the advantages of this invention are:

[0029] 1. The three-function synergistic catalytic mechanism improves the catalyst's catalytic efficiency:

[0030] Synergistic activation pathway of multiple active sites: In the silicotungstic acid-transition metal ion / NH2-ZIF-8 composite catalyst, silicotungstic acid provides strong Brønsted acidic sites, which precisely activate the PO-C2H5 bond of triethyl phosphite through protonation, significantly reducing the bond breaking activation energy from 88 kJ / mol in the traditional system to 40 kJ / mol; transition metal ions (Cu... 2+ / Mn 2+ / Cr 3+ The amino group forms a stable coordination bond with the hydroxyl group of pentaerythritol, reducing the dissociation energy of the hydroxyl hydrogen and accelerating the transesterification reaction rate. The amino group in the aminated support NH2-ZIF-8 regulates the charge distribution of the intermediate through electron transfer, promoting the rapid desorption of ethanol. Under the synergistic effect of the three centers, the catalytic effect of the catalyst is improved.

[0031] MOF carrier enhances mass transfer and dispersion of active sites: The aminated carrier NH2-ZIF-8 has an ultra-large specific surface area (BET specific surface area ≥1000 m²). 2 The MOF's regular microporous-mesoporous composite structure (pore size 1-3 nm) allows for uniform dispersion of silicotungstic acid and transition metal ions, increasing the exposure rate of active sites and avoiding the decrease in catalytic efficiency caused by the aggregation of active sites. At the same time, the MOF's pore structure constructs efficient mass transfer channels, accelerating the diffusion of feed molecules to active sites and the desorption of product molecules. Compared with similar non-MOF-supported catalytic systems, the reaction time is shortened and the mass transfer resistance is reduced, further enhancing the catalytic effect of the catalyst.

[0032] 2. Targeted catalysis blocks side reaction pathways, allowing for precise control of product selectivity:

[0033] Targeted catalysis blocks side reaction pathways: The transition metal ions in the silicotungstic acid-transition metal ion / NH2-ZIF-8 composite catalyst form specific coordination interactions with the four hydroxyl groups of pentaerythritol, causing a directional twist in the spatial configuration of pentaerythritol. This guides triethyl phosphite to preferentially attack two adjacent hydroxyl groups of pentaerythritol (generating a disubstituted intermediate). Simultaneously, the pore confinement effect of NH2-ZIF-8 (pore size 1-3 nm) effectively blocks the formation of multisubstituted reaction intermediates, thermodynamically blocking the formation of monoesterification, trisubstituted impurities, and ethanol self-polymerization. Therefore, the composite catalyst provided by this invention can block side reaction pathways and improve the selectivity of the target product.

[0034] 3. Simultaneous Improvement in Product Purity and Stability: Through the synergistic effect of selective control and mild reaction conditions, this invention achieves a product purity of over 99.5%, with no phenol residue. It eliminates the need for complex multi-stage distillation purification, requiring only simple vacuum distillation. The antioxidant 618 synthesized in this invention exhibits significantly improved hydrolysis resistance in humid environments due to its high purity and low impurity content. After 6 months of storage at 40℃ and 80% relative humidity, the hydrolysis rate is ≤0.8%, representing a more than 77% improvement in hydrolysis resistance compared to traditional products (hydrolysis rate ≥3.5%), resulting in a substantial improvement in product storage stability.

[0035] 4. The catalyst has a stable structure and can be recycled multiple times.

[0036] The rigid framework of the amination support NH2-ZIF-8 of the composite catalyst of this invention forms a "metal-support strong interaction (SMSI)" with the metal, which can significantly inhibit the dissolution and loss of silicotungstic acid and transition metal ions. The catalyst can still maintain high catalytic activity after multiple cycles. The stability of the composite catalyst provided by this invention is far superior to that of traditional homogeneous catalysts (which cannot be recycled) and ordinary heterogeneous catalysts (activity decay ≥35% after 3 cycles).

[0037] 5. The synthesis reaction conditions for antioxidant 618 are milder.

[0038] The synthesis of antioxidant 618 using the silicotungstic acid-transition metal ion / NH2-ZIF-8 composite catalyst provided by this invention has milder synthesis reaction conditions, significantly reduces energy consumption, and the reaction temperature is lower than that of traditional processes, avoiding the oxidative degradation of octadecyl alcohol and the thermal decomposition of the product, thus improving the quality of antioxidant 618. No special high-temperature and high-pressure equipment is required; ordinary stainless steel reactors can meet the production needs, reducing equipment investment costs.

[0039] Experimental data demonstrates that the total time for the two-step transesterification reaction in the antioxidant 618 synthesis method provided by this invention is shortened from 12-18 hours in the traditional process to 6-10 hours, with a reaction efficiency increase of over 50%. The pentaerythritol conversion rate exceeds 99%, and the yield and selectivity of the target product antioxidant 618 reach over 95%. The total content of by-products is ≤0.5%, an improvement of more than 10 percentage points compared to the traditional process. The product purity directly reaches over 99.5%, with a maximum of 99.9%. After the composite catalyst is recycled 12 times, the raw material conversion rate still remains ≥97%, the selectivity ≥96%, and the activity decay rate ≤3%. The synthesis conditions for antioxidant 618 are milder, with the two reaction temperatures controlled at 90-110℃ and 120-140℃ respectively, significantly lower than the traditional process (140-160℃). The synthesis process of antioxidant 618 completely eliminates the generation of large amounts of organic wastewater (COD value ≥ 3500 mg / L) in traditional homogeneous catalytic processes. The COD value of the mother liquor after the reaction is ≤ 120 mg / L, which can be directly recycled for the next batch of reaction or simply treated to meet the discharge standards. The wastewater discharge is reduced by more than 95% compared with traditional processes. Detailed Implementation

[0040] This invention discloses a method for synthesizing antioxidant 618. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0041] Unless otherwise specified, the pentaerythritol conversion rate, antioxidant 618 selectivity, and antioxidant 618 yield of the present invention are calculated according to the following formulas:

[0042] Pentaerythritol conversion rate = {n(initial pentaerythritol) - n(remaining pentaerythritol)} / n(initial pentaerythritol) 1-1

[0043] Antioxidant 618 selectivity = n(antioxidant 618) / {n(initial pentaerythritol) - n(remaining pentaerythritol)} 1-2

[0044] Antioxidant 618 yield = Pentaerythritol conversion rate × Antioxidant 618 selectivity 1-3

[0045] In the above formula, n refers to the amount of substance.

[0046] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments.

[0047] Example 1 Catalyst Silicotungstic Acid-Cu 2+ Preparation and catalytic reaction of / NH2-ZIF-8

[0048] Catalyst preparation: (1) Take 10g of zinc nitrate and 15g of dimethyl 2-aminoimidazole-4,5-dicarboxylate and dissolve them in 100ml of DMF. Stir and react at 70℃ for 10h. After centrifugation, wash with DMF and ethanol three times alternately and dry under vacuum at 80℃ for 12h to obtain NH2-ZIF-8 support. (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 1.25g of silicotungstic acid, stir and immerse at 60°C for 8h, filter and dry, and calcine at 280°C for 2.5h to obtain 25wt% silicotungstic acid / NH2-ZIF-8 complex; (3) The composite was impregnated in an aqueous solution containing 0.25 g of copper nitrate for 12 h at room temperature; dried at 60 °C for 12 h; calcined at 380 °C under N2 atmosphere for 2.5 h; 0.2 g of polyethylene glycol was added; and the mixture was compressed into tablets and pulverized to 30 mesh to obtain silicotungstic acid-Cu. 2+ / NH2-ZIF-8 composite catalyst, Cu 2+ Loading capacity: 5 wt%.

[0049] Catalytic reaction:

[0050] (1) Add 20g pentaerythritol and 0.4g of the catalyst silicotungstic acid-Cu prepared in Example 1 to a 500mL reactor. 2+ / NH2-ZIF-8, purged with nitrogen 3 times, added 48g of triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.2:1), heated to 100℃, stirred at 400rpm, reacted for 3h, and ethanol was recovered.

[0051] (2) Heat to 130℃, add 75g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.1:1), stir at 500rpm, react for 5h, and continue to recover ethanol;

[0052] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0053] Results: Pentaerythritol conversion rate was 99.7%, antioxidant 618 selectivity was 98.9%, antioxidant 618 yield was 98.6%, product antioxidant 618 purity was 99.8%, and after 12 catalyst cycles, pentaerythritol conversion rate was 97.8% and antioxidant 618 selectivity was 96.9%.

[0054] Example 2 Catalyst Silicotungstic Acid-Mn 2+ Preparation and catalytic reaction of / NH2-ZIF-8

[0055] Catalyst preparation:

[0056] (1) Weigh 10g of zinc nitrate and 15g of dimethyl 2-aminoimidazole-4,5-dicarboxylate and dissolve them in 100mL of DMF. Stir and react at 60℃ for 12h. After centrifugation, wash with DMF and ethanol three times alternately and dry under vacuum at 80℃ for 12h to obtain NH2-ZIF-8 carrier.

[0057] (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 0.75g of silicotungstic acid, stir and immerse at 50℃ for 10h, filter and dry, then calcine at 250℃ for 3h to obtain a 15wt% silicotungstic acid / NH2-ZIF-8 composite; (3) Immerse the composite in an aqueous solution containing 0.15g of manganese nitrate, immerse at room temperature for 12h, dry at 60℃ for 12h, calcine at 350℃ in N2 atmosphere for 3h, add 0.15g of polyethylene glycol, compress and pulverize to 20 mesh to obtain silicotungstic acid-Mn 2+ / NH2-ZIF-8 composite catalyst (Mn 2+ (Loading capacity 3wt%)

[0058] Catalytic reaction:

[0059] (1) Add 18g pentaerythritol and 0.27g of the catalyst silicotungstic acid-Mn prepared in this example to a 500mL reactor. 2 + / NH2-ZIF-8, purged with nitrogen three times, added 41g of triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.1:1), heated to 90℃, stirred at 300rpm, reacted for 4h, and ethanol was recovered.

[0060] (2) Heat to 120℃, add 68g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol 2.0:1), stir at 400rpm, react for 6h, and continue to recover ethanol;

[0061] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0062] Results: Pentaerythritol conversion rate was 99.2%, antioxidant 618 selectivity was 98.4%, antioxidant 618 yield was 97.6%, product purity was 99.6%, and after 12 catalyst cycles, pentaerythritol conversion rate was 97.2% and antioxidant 618 selectivity was 96.3%.

[0063] Example 3 Catalyst Silicotungstic Acid-Cr 3+ Preparation and catalytic reaction of / NH2-ZIF-8

[0064] Catalyst preparation:

[0065] (1) Weigh 10g of zinc nitrate and 15g of dimethyl 2-aminoimidazole-4,5-dicarboxylate and dissolve them in 100ml of DMF. Stir and react at 80℃ for 8h. After centrifugation, wash with DMF and ethanol three times alternately and dry under vacuum at 80℃ for 12h to obtain NH2-ZIF-8 support.

[0066] (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 1.0g of silicotungstic acid, stir and immerse at 70°C for 6h, filter and dry, and calcine at 300°C for 2h to obtain 20wt% silicotungstic acid / NH2-ZIF-8 complex;

[0067] (3) The composite was impregnated in an aqueous solution containing 0.3 g of chromium nitrate for 12 h at room temperature; dried at 60 °C for 12 h; calcined at 400 °C under N2 atmosphere for 2 h; 0.25 g of polyethylene glycol was added; and the mixture was compressed into tablets and pulverized to 40 mesh to obtain silicotungstic acid-Cr 3+ / NH2-ZIF-8 composite catalyst (Cr 3+ (Loading capacity 6wt%).

[0068] Catalytic reaction:

[0069] (1) Add 22g pentaerythritol and 0.55g of the above catalyst silicotungstic acid-Cr to a 500mL reactor. 3+ / NH2-ZIF-8, purged with nitrogen 3 times, added 55g of triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.4:1), heated to 110℃, stirred at 500rpm, reacted for 2h, and ethanol was recovered.

[0070] (2) Heat to 140℃, add 82g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.3:1), stir at 600rpm, react for 4h, and continue to recover ethanol;

[0071] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0072] Results: Pentaerythritol conversion rate was 99.8%, antioxidant 618 selectivity was 98.7%, antioxidant 618 yield was 98.5%, product purity was 99.7%, and after 12 catalyst cycles, pentaerythritol conversion rate was 97.9% and antioxidant 618 selectivity was 97.1%.

[0073] Example 4: Low-Silicotungstic Acid Loading Catalyst Cu 2+ Preparation and catalytic reaction of / NH2-ZIF-8

[0074] Catalyst preparation:

[0075] (1) Prepare the NH2-ZIF-8 support in the same manner as in Example 1, step (1);

[0076] (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 0.9g of silicotungstic acid, stir and immerse at 60°C for 8h, filter and dry, and calcine at 280°C for 2.5h to obtain 18wt% silicotungstic acid / NH2-ZIF-8 complex;

[0077] (3) The composite was impregnated in an aqueous solution containing 0.2 g of copper nitrate for 12 h at room temperature; dried at 60 °C for 12 h; calcined at 380 °C under N2 atmosphere for 2.5 h; 0.2 g of polyethylene glycol was added; and the mixture was compressed into tablets and pulverized to 30 mesh to obtain silicotungstic acid-Cu. 2+ / NH2-ZIF-8 composite catalyst (Cu 2+ (Loading capacity 4wt%).

[0078] Catalytic reaction:

[0079] (1) Add 19g pentaerythritol and 0.38g of the above catalyst to a 500mL reactor, purge with nitrogen three times, add 45g triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.2:1), heat to 95℃, stir at 450rpm, react for 3.5h, and recover ethanol.

[0080] (2) Heat to 125℃, add 71g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.05:1), stir at 550rpm, react for 5.5h, and continue to recover ethanol;

[0081] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0082] Results: Pentaerythritol conversion rate was 99.0%, antioxidant 618 selectivity was 98.2%, antioxidant 618 yield was 97.2%, product purity was 99.5%, and after 12 catalyst cycles, pentaerythritol conversion rate was 96.9% and antioxidant 618 selectivity was 96.1%.

[0083] Example 5: Preparation and catalytic reaction of composite transition metal supported catalyst

[0084] Catalyst preparation:

[0085] (1) Prepare the NH2-ZIF-8 support in the same manner as in Example 1, step (1);

[0086] (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 1.25g of silicotungstic acid, stir and immerse at 60°C for 8h, filter and dry, and calcine at 280°C for 2.5h to obtain 25wt% silicotungstic acid / NH2-ZIF-8 complex;

[0087] (3) The composite was impregnated in a mixed aqueous solution containing 0.125 g copper nitrate and 0.125 g manganese nitrate for 12 h at room temperature; dried at 60 °C for 12 h; calcined at 380 °C for 2.5 h in a N2 atmosphere; 0.2 g polyethylene glycol was added; and the mixture was compressed into tablets and pulverized to 30 mesh to obtain silicotungstic acid-Cu. 2+ -Mn 2+ / NH2-ZIF-8 composite catalyst (Cu 2+ and Mn 2+ (Total load is 5wt%).

[0088] Catalytic reaction:

[0089] (1) Add 20g pentaerythritol and 0.4g of the above catalyst silicotungstic acid-Cu to a 500mL reactor. 2+ -Mn 2+ / NH2-ZIF-8, purged with nitrogen 3 times, added 48g of triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.2:1), heated to 100℃, stirred at 400rpm, reacted for 3h, and ethanol was recovered.

[0090] (2) Heat to 130℃, add 75g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.1:1), stir at 500rpm, react for 5h, and continue to recover ethanol;

[0091] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0092] Results: Pentaerythritol conversion rate was 99.6%, antioxidant 618 selectivity was 99.1%, antioxidant 618 yield was 98.7%, product purity was 99.9%, and after 12 catalyst cycles, pentaerythritol conversion rate was 98.1% and antioxidant 618 selectivity was 97.5%.

[0093] Example 6 Catalyst Silicotungstic Acid-Cr 3+ Preparation and catalytic reaction of / NH2-ZIF-8

[0094] Catalyst preparation:

[0095] (1) Prepare the NH2-ZIF-8 support in the same manner as in Example 3 (1);

[0096] (2) Take 5g of the above carrier, immerse it in an aqueous solution containing 1.0g of silicotungstic acid, stir and immerse at 70°C for 6h, filter and dry, and calcine at 300°C for 2h to obtain 20wt% silicotungstic acid / NH2-ZIF-8 complex;

[0097] (3) The composite was impregnated in an aqueous solution containing 0.35 g of chromium nitrate for 12 h at room temperature; dried at 60 °C for 12 h; calcined at 400 °C under N2 atmosphere for 2 h; 0.25 g of polyethylene glycol was added; and the mixture was compressed into tablets and pulverized to 40 mesh to obtain silicotungstic acid-Cr 3+ / NH2-ZIF-8 composite catalyst (Cr 3+ (Loading capacity 7wt%).

[0098] Catalytic reaction:

[0099] (1) Add 22g pentaerythritol and 0.55g of the above catalyst to a 500mL reactor, purge with nitrogen three times, add 55g triethyl phosphite (2.4:1 ratio of triethyl phosphite to pentaerythritol), heat to 110℃, stir at 500rpm, react for 2h, and recover ethanol.

[0100] (2) Heat to 140℃, add 82g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.3:1), stir at 600rpm, react for 4h, and continue to recover ethanol;

[0101] (3) The catalyst was separated by filtration, and the filtrate was purified by vacuum distillation to obtain antioxidant 618. The COD value of the mother liquor after the reaction was ≤120mg / L.

[0102] Results: Pentaerythritol conversion was 99.7%, antioxidant 618 selectivity was 98.8%, and yield was 98.5%; product purity was 99.8%; after 12 catalyst cycles, conversion was 98.0% and selectivity was 97.3%. This example of Cr... 3+ A slightly higher loading (7wt%) will cause the active sites to aggregate, resulting in a slightly lower product purity and yield than in Example 1. Considering the requirements of cost and catalytic activity, the content of transition metal ions should not be increased further.

[0103] Hydrolysis resistance testing showed that the antioxidant 618 synthesized in Examples 1-6 of this invention has high purity and low impurity content, resulting in significantly improved hydrolysis resistance in humid environments. Tests showed that the composite catalyst can be stored for 6 months at 40°C and 80% relative humidity with a hydrolysis rate ≤0.8%, which is more than 77% higher than the hydrolysis resistance of traditional products (hydrolysis rate ≥3.5%), and the product storage stability is greatly improved.

[0104] Comparative Example 1: Catalyst supported on unaminated ZIF-8 support and catalytic reaction

[0105] Catalyst preparation: Except for replacing 2-aminoimidazolium-4,5-dicarboxylate with imidazole to prepare pure ZIF-8 support, the other steps were the same as in Example 1; the catalyst silicotungstic acid-Cu was obtained. 2+ / ZIF-8;

[0106] Catalytic reaction: using silicotungstic acid-Cu as the catalyst 2+ Antioxidant 618 was prepared using ZIF-8, with the same catalytic reaction conditions as in Example 1;

[0107] Results: Pentaerythritol conversion was 91.5%, antioxidant 618 selectivity was 90.2%, and yield was 82.5%; product purity was 96.1%. After three cycles of catalyst recycling, pentaerythritol conversion decreased to 84.3%, and antioxidant 618 selectivity was 86.9%. The unaminated support lacked electron transfer regulation, had poor dispersion of active sites, low mass transfer efficiency, and weak catalyst stability, resulting in significant activity degradation after three cycles.

[0108] Comparative Example 2: Catalyst Cu 2+ Preparation and catalytic reaction of / NH2-ZIF-8

[0109] Catalyst preparation: Except for the absence of silicotungstic acid, the reaction conditions and steps were the same as in Example 1, yielding the catalyst Cu. 2 + / NH2-ZIF-8;

[0110] Catalytic reaction: using Cu as a catalyst 2+ Antioxidant 618 was prepared by catalysis with NH2-ZIF-8, and the reaction conditions were the same as in Example 1;

[0111] Results: Pentaerythritol conversion was 90.8%, antioxidant 618 selectivity was 88.4%, and antioxidant 618 yield was 80.3%; product purity was 92.6%, and monoesterification impurities content reached 6.2%. Without silicotungstic acid to provide Brønsted acidic sites, the catalyst could not efficiently activate the PO-C2H5 bond, resulting in low catalyst efficiency, reduced feed conversion, high levels of monoesterification impurities, and a significant decrease in product purity and yield.

[0112] Comparative Example 3: Preparation and catalytic reaction of catalyst silicotungstic acid-NH2-ZIF-8

[0113] Catalyst preparation: except for the absence of transition metal Cu 2+ Except for the reaction conditions and steps, the rest of the reaction was the same as in Example 1, and the catalyst silicotungstic acid / NH2-ZIF-8 was obtained.

[0114] Catalytic reaction: Antioxidant 618 was prepared using silicotungstic acid / NH2-ZIF-8 catalyst under the same reaction conditions as in Example 1;

[0115] Results: Pentaerythritol conversion was 89.5%, antioxidant 618 selectivity was 82.3%, and antioxidant 618 yield was 73.7%; product purity was 89.8%, with polyesterification and isomerization impurities reaching 8.5%. This comparative catalyst lacks transition metal ions to coordinate with the pentaerythritol hydroxyl group, making it difficult to directionally control the reaction site, leading to increased side reactions and significantly insufficient catalytic efficiency and product selectivity.

[0116] Comparative Example 4: Homogeneous Catalytic Reaction of Traditional Anhydrous AlCl3

[0117] Catalytic reaction:

[0118] (1) Add 20g pentaerythritol to a 500mL reactor, replace with nitrogen three times, add 48g triethyl phosphite (molar ratio of triethyl phosphite to pentaerythritol 2.2:1), add 1.2g commercially available anhydrous AlCl3, heat to 150℃, stir at 500rpm, and react for 6h.

[0119] (2) Add 75g of octadecyl alcohol (molar ratio of octadecyl alcohol to pentaerythritol is 2.1:1) and continue the reaction for 8 hours;

[0120] (3) After the reaction is complete, neutralize with 10% sodium hydroxide aqueous solution, wash with water 3 times, separate the liquid and purify by distillation to obtain product antioxidant 618.

[0121] Results: Pentaerythritol conversion rate was 88.7%, antioxidant 618 selectivity was 86.8%, and antioxidant 618 yield was 77.0%; product purity was 95.3%; 120 mL of organic wastewater (COD=3800 mg / L) was generated; the catalyst could not be recovered and required a one-time addition. Traditional homogeneous catalysts, such as anhydrous AlCl3, exhibit low catalytic activity, require high reaction temperatures (150℃), result in numerous side reactions, low product yield and purity, and the catalyst is not recyclable, generating large amounts of high-COD organic wastewater, leading to poor environmental performance.

[0122] Table 1. Data on the catalytic synthesis of antioxidant 618 using various catalysts.

[0123]

[0124] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing antioxidant 618, characterized in that, Including the following methods: 1.1) Under the action of a catalyst, air is replaced by nitrogen, and pentaerythritol reacts with triethyl phosphite; 1.2) After the reaction in step 1.1) is completed, the temperature is increased and octadecyl alcohol is added to the system to continue the reaction. After the reaction is completed, antioxidant 618 is obtained through post-processing steps. The separated catalyst can be recycled. The catalyst comprises an amination support and a dual-active component supported on the amination support. The amination support is an amino-modified zeolite-like imidazole ester framework material ZIF-8, and the first active component is silicotungstic acid H4SiW. 12 O 40 The second active component is a transition metal ion, which is selected from Cu. 2+ Mn 2+ or Cr 3+ One or more.

2. The synthesis method according to claim 1, characterized in that, In the catalyst, based on the mass of the amination support, silicotungstic acid H4SiW 12 O 40 The load is 15-25wt%.

3. The synthesis method according to claim 1 or 2, characterized in that, In the catalyst, the loading of the transition metal is 3-7 wt% based on the mass of the amination support.

4. The synthesis method according to claim 1, 2, or 3, characterized in that, The catalyst preparation method includes the following steps: 4.1) Synthesis of the aminated support: Zinc nitrate and dimethyl 2-aminoimidazolium-4,5-dicarboxylate were dissolved in N,N-dimethylformamide and reacted with stirring at 60-80℃ for 8-12 h to obtain the aminated support NH2-ZIF-8. 4.2) The silicotungstic acid was loaded using an equal-volume impregnation method. The aqueous solution of silicotungstic acid was impregnated in the NH2-ZIF-8 support and stirred at 50-70°C for 6-10 h to obtain the silicotungstic acid / NH2-ZIF-8 composite. 4.3) Loading of transition metals: The silicotungstic acid / NH2-ZIF-8 composite was impregnated in aqueous solutions of copper nitrate, manganese nitrate, or chromium nitrate, dried, calcined under N2 atmosphere, and a binder was added. After pressing and pulverizing, the silicotungstic acid-transition metal ion / NH2-ZIF-8 composite catalyst was obtained.

5. The synthesis method as described in claim 4, characterized in that, Step 4.2) After stirring and impregnation, it needs to be roasted at a temperature of 250-300℃ for 2-3 hours.

6. The synthesis method according to claim 4, characterized in that, Step 4.3) Impregnate at room temperature for 12 hours; calcinate at 350-400℃ in N2 atmosphere for 2-3 hours; the binder is polyethylene glycol.

7. The synthesis method according to claim 1, characterized in that, The molar ratio of triethyl phosphite to pentaerythritol is 2.1-2.4:1, and the amount of catalyst used is 1.5-2.5% of the mass of pentaerythritol.

8. The synthesis method according to claim 1, characterized in that, The molar ratio of octadecyl alcohol to pentaerythritol is 2.0-2.3:

1.

9. The synthesis method according to claim 1, characterized in that, Step 1.1) The reaction temperature is 90-110℃ and the reaction time is 2-4h.

10. The synthesis method according to claim 1 or 9, characterized in that, The reaction conditions include, but are not limited to, the following: Step 1.2) Heating to 120-140℃ and continuing the reaction for 4-6 hours to recover the ethanol generated in the reaction; Step 1.2) Post-processing includes cooling and filtration. The catalyst is directly separated by filtration and can be recycled. The filtrate is purified by vacuum distillation to obtain antioxidant 618.

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