A method for preparing propylene oxide and co-producing δ-valerolactone by biomimetic catalytic oxidation of propylene

Abstract

This invention discloses a biomimetic catalytic oxidation method for preparing propylene oxide and co-producing δ-valerolactone, aiming to provide a highly selective, low-byproduct, simple, safe, and environmentally friendly method for preparing propylene oxide. The technical solution includes: (1) dispersing the catalyst and tetrahydropyran in a solvent in a high-pressure reactor and then sealing the system; (2) introducing propylene, followed by oxygen, and reacting at a pressure of 0.5–2.0 MPa and a temperature of 90–130 °C for 1–10 h to obtain propylene oxide and co-produce δ-valerolactone; this technology belongs to the field of chemical engineering technology.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering technology, specifically to a biomimetic catalytic oxidation method for preparing propylene oxide and co-producing δ-valerolactone. Background Art

[0002] Olefin epoxidation is an important reaction in the chemical industry. The resulting epoxides are important organic synthesis intermediates, widely used in petrochemicals, fine chemicals, and organic synthesis, playing a vital role in the national economy. Propylene oxide (PO), the most representative of these, is a high-value-added commercial chemical with a global annual production exceeding 10 million tons. It is used to manufacture various products, most notably polyurethane foam for the automotive and housing industries, polyester resins for the textile and construction industries, and propylene glycol as an additive in pharmaceuticals, cosmetics, and heat transfer or hydraulic fluids.

[0003] Traditional methods for producing propylene oxide include the chlorohydrin process, indirect oxidation process, and hydrogen peroxide process. However, the chlorohydrin process suffers from environmental pollution, the generation of hypochlorous acid, equipment contamination, and high water and energy consumption, which significantly limit its production. Furthermore, it is gradually being phased out in the context of green development in the new era. Indirect oxidation processes include the isobutane co-oxidation process (PO / TBA process), the ethylbenzene co-oxidation process (PO / SM process), and the cumene peroxide process (CHPPO process). These processes are characterized by long flow rates, high operating pressures, and large co-product volumes. The hydrogen peroxide process produces a single product and has weak resilience. Although the HPPO process has achieved industrial-scale production, the high reactivity of hydrogen peroxide after oxidation unit production presents challenges in transportation safety and storage. Additionally, the process is lengthy and investment costs are relatively high. Currently, the global production capacity for PO using the chlorohydrin process accounts for 40% of total capacity, indirect oxidation accounts for 43%, and other production routes account for 17%. However, these methods have problems such as long process flow, high concentration of oxidants being prone to explosion, low safety, environmental pollution, high energy consumption, and complex processes.

[0004] Oxygen is the most ideal oxidant for the direct epoxidation of propylene due to its wide availability, low cost, high atom utilization, and environmental friendliness. However, the epoxidation of propylene to propylene oxide using oxygen as an oxidant has not yet been industrialized because it faces the challenge of simultaneously achieving a considerable propylene conversion rate and high propylene oxide selectivity. Therefore, there is an urgent need to find a catalyst for the direct gas-phase epoxidation of propylene to produce propylene oxide that can simultaneously improve both propylene conversion rate and propylene oxide selectivity.

[0005] Chinese invention patent CN103012325B discloses a method for preparing propylene oxide using molybdenum acetylacetonate (MoO2(acac)2) as a catalyst, tert-butyl hydrogen peroxide as an oxidant, and propylene as a raw material. While this method overcomes drawbacks such as pollution and high cost, it suffers from problems including numerous co-products and low selectivity for propylene oxide. Chinese invention patent CN104650008A discloses a process for preparing propylene oxide by direct oxidation of propylene with oxygen and hydrogen. Although this method is energy-saving and environmentally friendly, significantly improving the purity and yield of propylene oxide and reducing its loss, it uses a hazardous hydrogen compound as a co-reducing agent, introducing greater safety uncertainties. Compared to the biomimetic catalytic oxidation method for preparing propylene oxide and co-producing δ-valerolactone disclosed in this technology, the propylene oxide prepared by this technology has high selectivity. In this method, the peroxide is generated in situ with a low concentration, ensuring reliable safety. Furthermore, it eliminates the need for separate preparation, purification, and separation of the peroxide. Moreover, the co-product δ-valerolactone is a chemical that can be used as a solvent and extractant, and is also an intermediate in the synthesis of many biomedical products, fibers, and pesticides. Therefore, this technology has advanced features and practical significance. Summary of the Invention

[0006] To address the aforementioned shortcomings, the purpose of this invention is to provide a highly selective, low-byproduct, high-value product, simple process, high safety, and environmentally friendly method for preparing propylene oxide, which overcomes the defects of the epoxidation of propylene to 1,2-propylene oxide described in the background art.

[0007] A biomimetic catalytic oxidation method for preparing propylene oxide and co-producing δ-valerol lactone includes the following steps:

[0008] (1) The system is sealed after the catalyst and reducing agent tetrahydropyran are dispersed in a solvent in a high-pressure reactor;

[0009] (2) Propylene is introduced, followed by oxygen. The reaction is carried out at a pressure of 0.5-2.0 MPa and a temperature of 90-130℃ for 1-10 hours to obtain propylene oxide and δ-valerolactone.

[0010] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerol, the triphenylphosphine metal complex is one or a mixture of bis(triphenylphosphine)palladium(II), bis(triphenylphosphine)cobalt(II), tri(triphenylphosphine)ruthenium(II), bis(triphenylphosphine)platinum(II), bis(triphenylphosphine)nickel(II), and triphenylphosphine)gold(I).

[0011] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerolactone, the solvent is one of acetonitrile, methanol, N,N-dimethylformamide, ethyl acetate, dichloromethane, 1,4-dioxane, and tetrahydrofuran.

[0012] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerolactone, the catalyst in step (1) accounts for 0.001% to 1% of the mass of propylene.

[0013] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerolactone, the volume ratio of tetrahydropyran to solvent is 1 / 1 to 1 / 4.

[0014] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerolactone, the reaction temperature in step (2) is 100-120℃.

[0015] Furthermore, in the above-mentioned biomimetic catalytic oxidation of propylene to prepare propylene oxide and co-produce δ-valerolactone, the reaction time in step (2) is 3-7 h.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages:

[0017] 1. The technical solution provided by this invention uses triphenylphosphine metal as a catalyst. The catalyst has good activity and selectivity, and a stable structure. It directly oxidizes propylene with oxygen as an oxidant to prepare epoxides. The process is simple, the reaction conditions are mild, the catalyst dosage is low, the cost is low, and the process is stable.

[0018] 2. The technical solution provided by this invention uses triphenylphosphine metal as a catalyst. Under the synergistic effect of a reducing agent, oxygen is used as an oxidant to catalyze the oxidation of propylene to 1,2-epoxypropane. The conversion rate of the substrate propylene can reach 27.8%, and the selectivity of 1,2-epoxypropane can reach 96.5%.

[0019] 3. The technical solution provided by this invention has high substrate conversion rate and product selectivity, mild reaction conditions, simple process, lower energy consumption, and is green and safe, and has good prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a thermogravimetric analysis (TGA) diagram of the catalyst provided in Example 1;

[0021] Figure 2 This is a thermogravimetric analysis diagram of the catalyst provided in Example 5;

[0022] Figure 3 This is the thermogravimetric analysis diagram of the catalyst provided in Example 6;

[0023] Figure 4 This is a thermogravimetric analysis diagram of the catalyst provided in Example 7. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of bis(triphenylphosphine)palladium(II) dichloride, 4 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 16 mL of ethyl acetate were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 120 °C and stirred for 6 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 21.4%, and the selectivity for 1,2-epoxypropane was 89.1%. Thermogravimetric analysis of the catalyst was also performed; see [reference needed]. Figure 1 ,pass Figure 1 It can be seen that the structure of bis(triphenylphosphine)palladium(II) dichloride is stable and not destroyed at 120℃, indicating that bis(triphenylphosphine)palladium(II) dichloride has good activity, selectivity and stability.

[0027] Example 2

[0028] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3.5 mg of cobalt bis(triphenylphosphine) chloride, 5 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 16 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 120 °C and stirred for 6 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 27.8%, and the selectivity for 1,2-epoxypropylene was 88.8%.

[0029] Example 3

[0030] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of bis(triphenylphosphine)diplatinum(II) chloride, 5 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 10 mL of 1,4-dioxane were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.8 g of oxygen. The reaction was carried out at 120 °C and stirred for 6 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 20.2%, and the selectivity for 1,2-epoxypropane was 90.2%.

[0031] Example 4

[0032] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of tris(triphenylphosphine) dichloride (II), 4 mL of tetrahydropyran, 50 mg of endophytin (standard), and 16 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 115 °C and stirred for 5 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 33.8%, and the selectivity for 1,2-epoxypropane was 96.5%.

[0033] Example 5

[0034] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 18 mg of bis(triphenylphosphine)nickel(II) chloride, 5 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 15 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.6 g of oxygen. The reaction was carried out at 120 °C and stirred for 7 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 24.8%, and the selectivity for 1,2-epoxypropane was 87.9%. Furthermore, thermogravimetric analysis of the catalyst was performed (see [reference needed]). Figure 2 ,pass Figure 2 It can be seen that the structure of bis(triphenylphosphine)nickel(II) chloride remains stable at 120℃, indicating that bis(triphenylphosphine)nickel(II) chloride has good activity, selectivity and stability.

[0035] Example 6

[0036] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 8 mg of triphenylphosphine gold(I) chloride, 4 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 16 mL of dichloromethane were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 120 °C and stirred for 6 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 25.8%, and the selectivity for 1,2-epoxypropane was 91.1%. Thermogravimetric analysis of the catalyst was also performed (see [reference needed]). Figure 3 ,pass Figure 3 It can be seen that the structure of (triphenylphosphine) gold chloride (I) remains stable at 120℃, indicating that (triphenylphosphine) gold chloride (I) has good activity, selectivity and stability.

[0037] Example 7

[0038] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of tris(triphenylphosphine) dichloride (II), 2 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 20 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.6 g of oxygen. The reaction was carried out at 110 °C and stirred for 5 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 30.8%, and the selectivity for 1,2-epoxypropane was 93.5%. Thermogravimetric analysis of the catalyst was also performed; see [reference needed]. Figure 4 ,pass Figure 4 It can be seen that the structure of tris(triphenylphosphine)ruthenium dichloride remains stable and intact at 120℃, indicating that tris(triphenylphosphine)ruthenium dichloride has good activity, selectivity and stability.

[0039] Comparative Example 1

[0040] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 4 mL of tetrahydropyran, 50 mg of biphenyl internal standard, and 16 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 115 °C under stirring at 0.8–1.5 MPa for 5 h. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 2.8%, and the selectivity for 1,2-epoxypropane was 28.5%. This indicates that the catalyst, triphenylphosphine metal, played a key synergistic role.

[0041] Comparative Example 2

[0042] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of tris(triphenylphosphine) dichloride (II), 50 mg of biphenyl internal standard, and 20 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 115 °C and stirred for 5 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 4.3%, and the selectivity for 1,2-epoxypropylene was 6.5%, indicating that tetrahydropyran produced a synergistic effect.

[0043] Comparative Example 3

[0044] In a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, 3 mg of tris(triphenylphosphine) dichloride (II), 6 mL of tetrahydrofuran, 50 mg of biphenyl internal standard, and 20 mL of acetonitrile were added sequentially. After sealing the autoclave, 0.6 g of propylene was introduced by bubbling, followed by the introduction of 0.9 g of oxygen. The reaction was carried out at 115 °C and stirred for 5 h at 0.8–1.5 MPa. After the reaction was completed, the mixture was cooled to room temperature with ice water, and samples were taken for gas chromatography analysis. The propylene conversion rate was found to be 18.3%, and the selectivity for 1,2-epoxypropylene was 68%, indicating that tetrahydropyran has superior performance compared to other reducing agents.

[0045] It should be noted that the analytical method for the reaction results in this invention is as follows: After the reaction is completed, an appropriate amount of the reaction solution is taken for analysis. Using biphenyl as an internal standard, gas chromatography analysis is performed to calculate the conversion rate of propylene and the selectivity of 1,2-epoxypropane.

[0046] The reaction result analysis method states that since propylene is a gas under normal temperature and pressure conditions and is not uniformly distributed in the gas and liquid phases in the reaction system, it cannot be accurately quantified directly by the peak area of ​​GC. Therefore, the amount of propylene oxidation products generated is calculated and then the amount of propylene consumed is deduced, thereby obtaining the conversion rate of propylene.

Claims

1. A method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene, characterized in that, Including the following steps: (1) The system is sealed after the catalyst and tetrahydropyran are dispersed in a solvent in a high-pressure reactor; (2) Propylene is introduced, followed by oxygen, and the reaction is carried out at a pressure of 0.5~2.0 MPa and a temperature of 90~130 °C for 1~10 h to obtain propylene oxide and δ-valerolactone. The catalyst is a triphenylphosphine metal complex; the triphenylphosphine metal complex is one or a mixture of bis(triphenylphosphine)palladium(II), bis(triphenylphosphine)cobalt(II), tri(triphenylphosphine)ruthenium(II), bis(triphenylphosphine)platinum(II), bis(triphenylphosphine)nickel(II), and triphenylphosphine)gold(I).

2. The method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene according to claim 1, characterized in that, The solvent is acetonitrile, methanol, N,N - One of dimethylformamide, ethyl acetate, dichloromethane, 1,4-dioxane, and tetrahydrofuran.

3. The method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene according to claim 1, characterized in that, The catalyst in step (1) accounts for 0.001% to 1% of the mass of propylene.

4. The method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene according to claim 1, characterized in that, The volume ratio of the tetrahydropyran to the solvent is 1 / 1 to 1 / 4.

5. The method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene according to claim 1, characterized in that, The reaction temperature in step (2) is 100~120 °C.

6. The method for preparing propylene oxide and co-producing δ-valerol by biomimetic catalytic oxidation of propylene according to claim 1, characterized in that, The reaction time in step (2) is 3 to 7 hours.

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