Immobilized n-hydroxysuccinimide catalyst, its preparation method and application

Abstract

The application discloses a kind of immobilized N-hydroxymaleimide catalyst and its preparation method and application, the catalyst is prepared by imidization of styrene-maleic anhydride copolymer, the number average molecular weight of styrene-maleic anhydride copolymer is 20000-35000, preparation method is as follows: (1) preparation styrene-maleic anhydride copolymer;(2) using the reaction liquid containing free hydroxylamine is imidized to styrene-maleic anhydride copolymer, after ending, again by dehydration treatment, filtration, washing and drying, namely the immobilized N-hydroxymaleimide catalyst is obtained.The immobilized N-hydroxymaleimide catalyst prepared by the application can be applied in the oxygen functionalization reaction of cumene as recyclable catalyst, active component does not produce loss in catalytic reaction, stability is good, with high active site density, catalytic effect is good, and can be recycled.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a supported N-hydroxymaleimide catalyst, its preparation method, and its application. Background Technology

[0002] Cumene can be oxidized to oxygen-functionalized products such as cumene hydroperoxide, acetophenone, and 2-phenyl-2-propanol. This reaction can convert inexpensive raw material cumene into oxygen-containing compounds with higher added value. Currently, the industrial method for producing cumene hydroperoxide by oxygen functionalization of cumene involves using air as an oxidant and a small amount of cumene hydroperoxide as an initiator, and carrying out the auto-oxidation reaction of the substrate under high temperature and pressure (operating temperature 353-393K, pressure 100-600kPa) (Chemical Engineering Science, 2018, Vol. 177, pp. 391-398). Besides the drawback of low conversion rate, this method also has some disadvantages, such as poor safety, harsh reaction conditions, and the generation of large amounts of alkaline or sulfur-containing wastewater during the reaction, resulting in expensive wastewater treatment and economic burden (Journal of Molecular Catalysis A: Chemical, 2010, Vol. 331, pp. 40-49). Therefore, exploring novel, environmentally friendly, and green synthetic methods is particularly important. In recent years, the role of N-hydroxyphthalimide (NHPI) in the selective oxidation of hydrocarbons, especially alkylbenzenes, has been emphasized in some studies. Through a combined catalytic system of NHPI and transition metals such as Co(II) or Mn, cumene can be oxidized under mild conditions (Petroleum Chemistry, 2017, Vol. 57, pp. 262-266). N-hydroxymaleimide (NHMI) has a similar NO-H bond structure to NHPI and can be activated to form NO· radicals, i.e., maleimide nitroxide radicals (MINO). However, the separation of cumene oxidation products using NHMI catalysts is currently difficult, and the cost of catalyst recovery and reuse is high, limiting the application of NHMI catalysts in hydrocarbon oxidation reactions. Summary of the Invention

[0003] Objective of the Invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide an immobilized N-hydroxymaleimide catalyst that can exist stably under catalytic reaction conditions, has good catalytic effect, and can be recycled and reused. Another objective of the present invention is to provide a method for preparing the catalyst. Furthermore, the present invention will also provide applications of the catalyst.

[0004] Technical solution: The supported N-hydroxymaleimide catalyst of the present invention is prepared by imidization of styrene-maleic anhydride copolymer.

[0005] Furthermore, the molar ratio of styrene to maleic anhydride is 1:1-3, and the number-average molecular weight of the styrene-maleic anhydride copolymer is 20,000-35,000.

[0006] The preparation method of the supported N-hydroxymaleimide catalyst of the present invention comprises the following steps:

[0007] (1) Preparation of styrene-maleic anhydride copolymer;

[0008] (2) The styrene-maleic anhydride copolymer was subjected to imidization treatment using a reaction solution containing free hydroxylamine. After the treatment, it was dehydrated, filtered, washed and dried to obtain the immobilized N-hydroxymaleimide catalyst.

[0009] Further, in step (1), the preparation method of the styrene-maleic anhydride copolymer is as follows: styrene, maleic anhydride and initiator are added to a solvent to obtain a reaction solution. The reaction solution is subjected to reflux reaction, filtration separation, washing and drying to obtain the styrene-maleic anhydride copolymer. The initiator is AIBN, the solvent is toluene, and the reflux reaction conditions are: reaction temperature 80-85℃, reaction time 1.5-2h. The washing reagent is petroleum ether.

[0010] Further, in step (2), the preparation method of the reaction solution containing free hydroxylamine is as follows: hydroxylamine hydrochloride, sodium methoxide and trisodium ethylenediaminetetraacetate are dissolved in an organic solvent to obtain a mixed solution; the mixed solution is reacted at 15-20℃ for 11-12h to obtain the reaction solution containing free hydroxylamine; the molar ratio of hydroxylamine hydrochloride to sodium methoxide is 1.5-2:1, the mass ratio of hydroxylamine hydrochloride to the volume ratio of organic solvent is 5.5-6g:120ml, and the organic solvent is 1,4-dioxane.

[0011] Further, in step (2), the conditions for the imidization treatment are: reaction temperature 40-42℃, reaction time 7-8h.

[0012] Further, in step (2), the dehydration treatment conditions are as follows: in the dehydrating agent, first distill at atmospheric pressure at 80-85℃ and then rapidly dehydrate under reduced pressure using azeotropic distillation, followed by filtration, washing, and drying; the dehydrating agent is toluene.

[0013] Further, in step (2), the washing process is as follows: washing with detergents, deionized water, ether, and acetone in sequence, with each detergent being used to wash 4-5 times.

[0014] The application of the immobilized N-hydroxymaleimide catalyst described in this invention as a recyclable catalyst in the oxygen functionalization reaction of cumene.

[0015] Invention Principle: This invention first polymerizes styrene monomer and maleic anhydride monomer to obtain a styrene-maleic anhydride copolymer (St-MA), which facilitates the subsequent imidization treatment of the copolymer. St-MA is a novel, inexpensive, and high-performance polymer with good heat resistance, dimensional stability, chemical stability, and processability. Its molecular structure contains highly reactive anhydride groups, making it easy to esterify and react with hydroxyl, amino, and other reactive groups to produce a series of novel functional derivatives. The polymerization reaction of styrene monomer and maleic anhydride monomer is shown in the following formula:

[0016]

[0017] In toluene, hydroxylamine hydrochloride is reacted with sodium methoxide to yield free hydroxylamine, which facilitates the subsequent imidization reaction of St-MA. The reaction is shown in the following equation:

[0018] NH2OH·HCl+CH3ONa→NH2OH+NaCl+CH3OH

[0019] Since hydroxylamine is very easy to decompose, the present invention adds the stabilizer trisodium ethylenediaminetetraacetate to stabilize hydroxylamine, ensuring that a higher concentration of hydroxylamine can react with it during the ring-opening reaction with the acid anhydride in the second step, so as to prepare a catalyst with higher activity.

[0020] The free hydroxylamine is then subjected to an imidization reaction with St-MA, followed by ring-closure dehydration to obtain the immobilized N-hydroxymaleimide catalyst, as shown in the following reaction equation:

[0021]

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) The supported N-hydroxymaleimide catalyst does not lose active components during the catalytic reaction and has good stability;

[0024] (2) The supported N-hydroxymaleimide catalyst was made recyclable and used as a recyclable catalyst in the functionalization of cumene phenoxy.

[0025] (3) The supported N-hydroxymaleimide catalyst has a high active site density and good catalytic effect. Attached Figure Description

[0026] Figure 1This is a synthetic route diagram for preparing the immobilized N-hydroxymaleimide catalyst in Example 1 of the present invention;

[0027] Figure 2 The infrared spectra of the styrene-maleic anhydride copolymer and the supported N-hydroxymaleimide catalyst prepared in Example 1 of this invention are shown.

[0028] Figure 3 The styrene-maleic anhydride copolymer prepared in Example 1 of this invention 13 C NMR spectrum;

[0029] Figure 4 The number-average molecular weight and molecular weight distribution of the styrene-maleic anhydride copolymers obtained in Examples 1-4 of this invention are shown in the figure.

[0030] Figure 5 This is a schematic diagram illustrating the application principle of the immobilized N-hydroxymaleimide catalyst of this invention as a recyclable catalyst in the oxygen functionalization reaction of cumene. Detailed Implementation

[0031] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0032] Example 1: As Figure 1 As shown, the supported N-hydroxymaleimide catalyst of the present invention is prepared by imidization of styrene-maleic anhydride copolymer, and the preparation method is carried out according to the following steps:

[0033] (1) Preparation of styrene-maleic anhydride copolymer: 100 ml of toluene and 14.709 g of maleic anhydride were added to a 500 ml four-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel, and nitrogen delivery tube. Before the reaction, the air in the flask was completely replaced with N2 at a flow rate of 100 sccm for 10 min, and the mixture was heated to 75 °C in a water bath. A mixture of 10.4 g of styrene, 0.0202 g of azobisisobutyronitrile, and 40 ml of toluene was added dropwise to the flask through the constant pressure dropping funnel and the addition was completed within 30 min. The temperature was raised to 80℃ and the reaction was allowed to proceed for 2 hours. Observational phenomena were observed: as the mixed droplets were added from the constant-pressure dropping funnel, a white milky suspension gradually appeared in the liquid in the four-necked flask. After the reaction was completed, the mixture was cooled to room temperature, the reflux device was removed, and a white milky substance was obtained. The reaction solution was filtered to obtain a white solid filter cake. The filter cake was washed with 30 ml of petroleum ether, slurried for 10 minutes, and washed 5 times. The resulting white solid powder was dried in a 50℃ oven for 24 hours before use, thus obtaining a styrene-maleic anhydride copolymer, denoted as St-MA-1.5.

[0034] (2) Preparation of immobilized N-hydroxymaleimide catalyst: 5.6 g of hydroxylamine hydrochloride, 4.8 g of sodium methoxide, 0.0098 g of trisodium ethylenediaminetetraacetate and 120 ml of 1,4-dioxane were added to a 250 ml three-necked flask and reacted at 15 °C for 12 h to obtain free hydroxylamine; then 6 g of the St-MA-1.5 powder prepared in the first step was added, and the temperature was raised to 40 °C and reacted for 8 h; after the previous reaction was completed, the solid was obtained by filtration; a distillation apparatus was set up, the solid was added to a 250 ml three-necked flask and a dehydrating agent was added. 80 ml of toluene was distilled at atmospheric pressure at 85 °C for 5 hours, and then immediately distilled under reduced pressure (P = 20-30 kPa) to obtain a yellow solid. The yellow solid was washed by washing with 30 ml of acetone five times, 30 ml of diethyl ether five times, and finally 30 ml of deionized water five times. The resulting beige solid powder was dried in a vacuum drying oven at 40 °C to constant weight (P = 20-30 kPa). The immobilized N-hydroxymaleimide catalyst was prepared and designated as St-NHMI-1.5.

[0035] Infrared characterization was performed on St-MA-1.5 and St-NHMI-1.5, such as... Figure 2 As shown in the infrared spectrum of St-MA-1.5, the values ​​at 3060, 3030, and 3000 cm⁻¹ are... -1 The absorption peak at 2925 cm⁻¹ is a characteristic peak of the unsaturated carbon-hydrogen bonds on the benzene ring. -1 The absorption peaks at 1845 and 1780 cm⁻¹ are the absorption peaks of the saturated carbon-hydrogen bonds on the benzene ring. -1 The absorption peaks at 1490, 1455, and 1400 cm⁻¹ are absorption peaks of the symmetric and asymmetric stretching vibrations of the carbonyl group on the acid anhydride. -1 The peak at 1220 cm⁻¹ represents the absorption peak of the carbon-carbon double bond vibration on the benzene ring. -1 The absorption peak at 710 cm⁻¹ represents the stretching vibration of the carbon-oxygen bond in the acid anhydride. -1 The absorption peak at 3450 cm⁻¹ belongs to the out-of-plane bending vibration of the benzene ring skeleton. In summary, the double bonds in the system underwent a polymerization reaction, forming a polymer. Furthermore, a comparison of the infrared spectra of St-MA-1.5 and St-NHMI-1.5 revealed that St-NHMI-1.5 exhibits a peak at 3450 cm⁻¹. -1 An additional characteristic peak was observed, which is believed to be the absorption peak of the N-OH obtained after dehydration of the acid anhydride following N-imide conversion. Also observed were peaks at 1845 and 1780 cm⁻¹. -1 The absorption peaks belonging to the carbonyl group in acid anhydrides changed to 1780 and 1700 cm⁻¹. -1 The shift in peak position may be due to changes in the surrounding chemical environment.

[0036] like Figure 3 As shown, this invention has modified St-MA-1.5. 13The sequence structure was determined by comparing the chemical shift changes of the quaternary carbon core on the benzene ring in the maleic anhydride and styrene copolymer using C NMR spectroscopy. 13 In the C1NMR spectrum, the peak at δ = 172.96 ppm represents the characteristic peaks of carbonyl carbons C5 and C6 in maleic anhydride, and the peak at δ = 138.34 ppm represents the characteristic peak of quaternary carbon C7 on the benzene ring. The characteristic peak at δ = 129.62 ppm represents the characteristic peaks of tertiary carbons C8-C12 on the benzene ring, δ = 52.7 ppm represents C3 in maleic anhydride, δ = 42.62 ppm represents C2 and C4 on the main chain, and δ = 20.75 ppm represents C1 on the main chain. The chemical shifts of the MSM, SSM, and / or MSS ternaries can be seen in this spectrum. 13 Analysis using C10 NMR spectroscopy revealed that the polymer possesses blocks with alternating St-MA structures and St-MA random structures.

[0037] St-NHMI-1.5 catalytic oxygen-oxygen functionalization of cumene molecules: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reactor, along with 0.5 g of St-NHMI-1.5 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced 5 times with 2 MPa of high-purity oxygen. After replacement, the reactor was transferred to a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95 °C, and the reaction was carried out for 24 h with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The resulting solid phase was the recovered St-NHMI-1.5 catalyst. The catalytic reaction results are shown in Table 1.

[0038] Recovery of St-NHMI-1.5 catalyst: The recovered catalyst was washed three times with acetone, diethyl ether and deionized water, respectively. The filtered solid sample was dried in a vacuum drying oven at 50°C for 24 hours until constant weight, thus obtaining the recovered immobilized NHMI catalyst St-NHMI-1.5-R1.

[0039] Example 2: The supported N-hydroxymaleimide catalyst of the present invention is prepared by imidization of styrene-maleic anhydride copolymer. The preparation method is as follows:

[0040] (1) Preparation of styrene-maleic anhydride copolymer: 100 ml of toluene and 9.806 g of maleic anhydride were added to a 500 ml four-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel, and nitrogen delivery tube. Before the reaction, the air in the flask was fully replaced with N2 at a flow rate of 100 sccm for 10 min, and the flask was heated to 75 °C in a water bath. A mixture of 10.4 g of styrene, 0.0202 g of azobisisobutyronitrile, and 40 ml of toluene was added dropwise to the flask through the constant pressure dropping funnel and the addition was completed within 30 min. The temperature was raised to 80 °C and the reaction was allowed to proceed for 2 h. The observed phenomenon was that as the mixed liquid droplets were added to the constant pressure dropping funnel, a white milky suspension gradually appeared in the liquid in the four-necked flask. After the reaction was completed, the mixture was cooled to room temperature, the reflux device was removed, and a white milky substance was obtained. The reaction solution was filtered to obtain a white solid filter cake. The filter cake was washed with 30 ml of petroleum ether, pulped for 10 minutes and washed 5 times. The resulting white solid powder was placed in a 50℃ oven and dried for 24 hours before use to obtain St-MA-1.

[0041] (2) Preparation of immobilized N-hydroxymaleimide catalyst: 5.6 g of hydroxylamine hydrochloride, 4.8 g of sodium methoxide, 0.0098 g of trisodium ethylenediaminetetraacetate, and 120 ml of 1,4-dioxane were added to a 250 ml three-necked flask and reacted at 15 °C for 12 h to obtain free hydroxylamine. Then, 6 g of the St-MA copolymer powder prepared in the first step was added, and the temperature was raised to 40 °C and reacted for 8 h. After the reaction in the previous step was completed, the solid was obtained by filtration. A distillation apparatus was set up, and the solid was added to a 250 ml three-necked flask along with 80 ml of toluene as a dehydrating agent. Distillation was carried out at 85 °C under normal pressure for 5 h, and then immediately under reduced pressure (P = 20-30 kPa) was applied until dry to obtain a yellow solid. The solid was washed by washing it five times with 30 ml of acetone, five times with 30 ml of diethyl ether, and five times with 30 ml of deionized water. The resulting light yellow solid powder was dried in a vacuum drying oven at 40 °C to constant weight (P = 20-30 kPa). The target catalyst, styrene-N-hydroxymaleimide St-NHMI-1, was thus prepared.

[0042] St-NHMI-1 catalytic oxygen-oxygen functionalization of cumene molecules: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to the reactor, along with 0.5 g of St-NHMI-1 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced 5 times with 2 MPa of high-purity oxygen. After replacement, the reactor was moved into a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95 °C, and the reaction was carried out for 24 h with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0043] Example 3: The supported N-hydroxymaleimide catalyst of the present invention is prepared by imidization of styrene-maleic anhydride copolymer. The preparation method is as follows:

[0044] (1) Preparation of styrene-maleic anhydride copolymer: Preparation of styrene-maleic anhydride copolymer St-MA-2: 100 ml of toluene and 19.612 g of maleic anhydride were added to a 500 ml four-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel, and nitrogen delivery tube. Before the reaction, the air in the flask was completely replaced with N2 at a flow rate of 100 sccm for 10 min, and the mixture was heated to 75 °C in a water bath. A mixture of 10.4 g of styrene, 0.0202 g of azobisisobutyronitrile, and 40 ml of toluene was added dropwise to the flask through the constant pressure dropping funnel, and the addition was completed within 30 min. The temperature was raised to 80 °C, and the reaction was allowed to proceed for 2 h. The observable phenomenon was that as the mixed liquid droplets were added to the constant pressure dropping funnel, a white milky suspension gradually appeared in the liquid in the four-necked flask. After the reaction was completed, the mixture was cooled to room temperature, the reflux device was removed, and a white milky substance was obtained. The reaction solution was filtered to obtain a white solid filter cake. The filter cake was washed with 30 ml of petroleum ether, pulped for 10 minutes and washed 5 times. The resulting white solid powder was placed in a 50℃ oven and dried for 24 hours before use to obtain St-MA-2.

[0045] (2) Preparation of immobilized N-hydroxymaleimide catalyst: 5.6 g of hydroxylamine hydrochloride, 4.8 g of sodium methoxide, 0.0098 g of trisodium ethylenediaminetetraacetate, and 120 ml of 1,4-dioxane were added to a 250 ml three-necked flask and reacted at 15 °C for 12 h to obtain free hydroxylamine. Then, 6 g of the St-MA copolymer powder prepared in the first step was added, and the temperature was raised to 40 °C and reacted for 8 h. After the reaction in the previous step was completed, the solid was obtained by filtration. A distillation apparatus was set up, and the solid was added to a 250 ml three-necked flask along with 80 ml of toluene as a dehydrating agent. Distillation was carried out at 85 °C under normal pressure for 5 h, and then immediately under reduced pressure (P = 20-30 kPa) was applied until dry to obtain a yellow solid. The solid was washed by washing it five times with 30 ml of acetone, five times with 30 ml of diethyl ether, and five times with 30 ml of deionized water. The resulting light yellow solid powder was dried in a vacuum drying oven at 40 °C to constant weight (P = 20-30 kPa). The target catalyst, styrene-N-hydroxymaleimide St-NHMI-2, was thus prepared.

[0046] St-NHMI-2 catalytic oxygen-oxygen functionalization of cumene molecules: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to the reactor, along with 0.5 g of St-NHMI-2 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced 5 times with 2 MPa of high-purity oxygen. After replacement, the reactor was moved into a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95 °C, and the reaction was carried out for 24 h with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0047] Example 4: The supported N-hydroxymaleimide catalyst of the present invention is prepared by imidization of styrene-maleic anhydride copolymer. The preparation method is as follows:

[0048] (1) Preparation of styrene-maleic anhydride copolymer: 100 ml of toluene and 29.418 g of maleic anhydride were added to a 500 ml four-necked flask equipped with a mechanical stirrer, reflux condenser, constant pressure dropping funnel, and nitrogen delivery tube. Before the reaction, the air in the flask was completely replaced with N2 at a flow rate of 100 sccm for 10 min, and the mixture was heated to 75 °C in a water bath. A mixture of 10.4 g of styrene, 0.0202 g of azobisisobutyronitrile, and 40 ml of toluene was added dropwise to the flask through the constant pressure dropping funnel, and the addition was completed within 30 min. The temperature was raised to 80 °C, and the reaction was allowed to proceed for 2 h. The observed phenomenon was that as the mixed liquid droplets were added to the constant pressure dropping funnel, a white milky suspension gradually appeared in the liquid in the four-necked flask. After the reaction was completed, the mixture was cooled to room temperature, the reflux device was removed, and a white milky substance was obtained. The reaction solution was filtered to obtain a white solid filter cake. The filter cake was washed with 30 ml of petroleum ether, pulped for 10 minutes and washed 5 times. The resulting white solid powder was placed in a 50℃ oven and dried for 24 hours before use to obtain St-MA-3.

[0049] (2) Preparation of immobilized N-hydroxymaleimide catalyst: 5.6 g of hydroxylamine hydrochloride, 4.8 g of sodium methoxide, 0.0098 g of trisodium ethylenediaminetetraacetate, and 120 ml of 1,4-dioxane were added to a 250 ml three-necked flask and reacted at 15 °C for 12 h to obtain free hydroxylamine. Then, 6 g of the St-MA copolymer powder prepared in the first step was added, and the temperature was raised to 40 °C and reacted for 8 h. After the reaction in the previous step was completed, the solid was obtained by filtration. A distillation apparatus was set up, and the solid was added to a 250 ml three-necked flask along with 80 ml of toluene as a dehydrating agent. Distillation was carried out at 85 °C under normal pressure for 5 h, and then immediately under reduced pressure (P = 20-30 kPa) was applied until dry to obtain a yellow solid. The solid was washed by washing it five times with 30 ml of acetone, five times with 30 ml of diethyl ether, and five times with 30 ml of deionized water. The resulting light yellow solid powder was dried in a vacuum drying oven at 40 °C to constant weight (P = 20-30 kPa). The target catalyst, styrene-N-hydroxymaleimide St-NHMI-3, was thus prepared.

[0050] St-NHMI-3-catalyzed oxygen-oxygen functionalization of cumene molecules: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reactor, along with 0.5 g of St-NHMI-3 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced 5 times with 2 MPa of high-purity oxygen. After replacement, the reactor was moved into a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95 °C, and the reaction was carried out for 24 h with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0051] Figure 4 Observations on the molecular weight and molecular weight distribution of the styrene-maleic anhydride copolymers obtained in Examples 1-4 revealed that the change in copolymer molecular weight with increasing maleic anhydride concentration in the styrene / maleic anhydride ratio did not exhibit a regular pattern. This is mainly because the monomer was added dropwise during the preparation process, which effectively reduced the monomer concentration during the reaction. Even with a high maleic anhydride concentration, the styrene monomer was added dropwise into the reaction system, resulting in a low concentration of monomer participating in the reaction. Furthermore, the high initiator concentration and temperature in the system led to a faster reaction rate, thus the influence of the maleic anhydride concentration in the feed ratio on the copolymer molecular weight was negligible. The polydispersity index of the copolymer increased with increasing maleic anhydride content in the feed ratio. St-MA-1.5, prepared with a maleic anhydride / styrene feed ratio of 1:1.5, exhibited a lower molecular weight and polydispersity index, making it more advantageous for subsequent processing compared to the other three intermediates.

[0052] Example 5: In this example, the St-NHMI-1.5-R1 catalyst recovered in Example 1 was used to catalyze the oxygen-oxygen functionalization of cumene molecules. 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reactor, along with 0.5 g of St-NHMI-1.5-R1 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced five times with 2 MPa of high-purity oxygen. After replacement, the reactor was transferred to a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95°C, and the reaction was carried out for 24 hours with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1. The obtained solid phase was the recovered St-NHMI-1.5-R1 catalyst. The recovered catalyst was washed three times with acetone, diethyl ether and deionized water, respectively. The filtered solid sample was dried in a vacuum drying oven at 50°C for 24 hours until constant weight, thus obtaining the recovered immobilized NHMI catalyst St-NHMI-1.5-R2.

[0053] Example 6: In this example, the St-NHMI-1.5-R2 catalyst recovered in Example 5 was used to catalyze the oxygen-oxygen functionalization of cumene molecules: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reactor, along with 0.5 g of St-NHMI-1.5-R2 catalyst. The airtightness of the reactor was checked using 2 MPa of high-purity oxygen. If the pressure gauge remained stable and there was no leakage, the air inside the reactor was replaced 5 times with 2 MPa of high-purity oxygen. After replacement, the reactor was transferred to a heater equipped with a magnetic stirrer, and the stirring was turned on. The reactor temperature was raised to 95°C, and the reaction was carried out for 24 h with magnetic stirring at 340 r / min. The reactor was then cooled to room temperature and centrifuged. The resulting liquid phase was the product mixture. The liquid mixture after the reaction was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1. The obtained solid phase was the recovered St-NHMI-1.5-R2 catalyst. The recovered catalyst was washed three times with acetone, diethyl ether and deionized water, respectively. The filtered solid sample was dried in a vacuum drying oven at 50°C for 24 hours until constant weight, thus obtaining the recovered immobilized NHMI catalyst St-NHMI-1.5-R3.

[0054] Example 7: In this example, the oxy-functionalization of cumene molecules was catalyzed using the St-NHMI-1.5-R3 catalyst recovered in Example 6. 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reaction vessel, along with 0.5 g of the St-NHMI-1.5-R3 catalyst. The resulting liquid mixture was analyzed to obtain the conversion and selectivity of cumene. The catalytic reaction results are shown in Table 1. The obtained solid phase was the recovered St-NHMI-1.5-R3 catalyst. The recovered catalyst was washed three times with acetone, diethyl ether, and deionized water, respectively. The filtered solid sample was dried in a vacuum drying oven at 50°C for 24 h to constant weight, yielding the recovered immobilized NHMI catalyst St-NHMI-1.5-R4.

[0055] Example 8: In this example, the oxy-functionalization of cumene molecules was catalyzed using the St-NHMI-1.5-R4 catalyst recovered in Example 7: 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate initiator were added to a reaction vessel, along with 0.5 g of the St-NHMI-1.5-R4 catalyst. The resulting liquid mixture was analyzed to obtain the conversion and selectivity of cumene. The catalytic reaction results are shown in Table 1. The obtained solid phase was the recovered St-NHMI-1.5-R3 catalyst. The recovered catalyst was washed three times with acetone, diethyl ether, and deionized water, respectively. The filtered solid sample was dried in a vacuum drying oven at 50 °C for 24 h to constant weight, yielding the recovered immobilized NHMI catalyst St-NHMI-1.5-R5.

[0056] Comparative Example 1: 10 ml of acetonitrile and 5 mmol of cumene were added to a 50 ml polytetrafluoroethylene-lined high-pressure reactor. The reaction was carried out at 95 °C and 2.0 MPa oxygen pressure, with magnetic stirring at 340 r / min for 24 h. After cooling the reactor to room temperature, the resulting liquid mixture was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0057] Comparative Example 2: In a 50 ml polytetrafluoroethylene-lined high-pressure reactor, 10 ml of acetonitrile, 5 mmol of cumene, and 0.5 g of St-NHMI-1.5 were added. The reaction was carried out at 95 °C and 2.0 MPa oxygen pressure with magnetic stirring at 340 r / min for 24 h. After cooling the reactor to room temperature, the resulting liquid mixture was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0058] Comparative Example 3: In a 50 ml polytetrafluoroethylene-lined high-pressure reactor, 10 ml of acetonitrile, 5 mmol of cumene, and 0.05 mmol of cobalt acetate were added. The reaction was carried out at 95 °C and 2.0 MPa oxygen pressure with magnetic stirring at 340 r / min for 24 h. After cooling the reactor to room temperature, the resulting liquid mixture was analyzed to obtain the conversion rate and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0059] Comparative Example 4: Catalyst P(HOMI / St) was prepared according to the literature (Chemical Research and Application, 2017, Vol. 29, pp. 344–347) and applied to the molecular oxygen oxidation reaction of cumene. In a 50 mL polytetrafluoroethylene-lined high-pressure reactor, 10 mL of acetonitrile, 5 mmol of cumene, 0.5 g of P(HOMI / St), and 0.05 mmol of cobalt acetate were added. The reaction was carried out at 95 °C and 2.0 MPa oxygen pressure with magnetic stirring at 340 r / min for 24 h. After cooling the reactor to room temperature, the post-reaction liquid mixture was analyzed to obtain the conversion and selectivity of cumene. The catalytic reaction results are shown in Table 1.

[0060] The conversion rates and product selectivity of cumene in Examples 1-8 and Comparative Examples 1-4 are shown in Table 1.

[0061] Table 1 shows that Comparative Example 1, without a catalyst, achieved a conversion rate of 5.9%, with 2-phenyl-2-propanol as the product. Comparative Example 2, with only St-NHMI-1.5 as the catalyst, achieved a cumene conversion rate of 11.2%, a selectivity of cumene hydroperoxide of 18.5%, and a selectivity of 2-phenyl-2-propanol of 81.5%. Comparative Example 3, with only cobalt acetate as the catalyst, achieved a cumene conversion rate of 12.9%, with selectivities of cumene hydroperoxide, acetophenone, and 2-phenyl-2-propanol of 14.2%, 25.8%, and 60.0%, respectively. Since both the catalyst St-NHMI-1.5 and the co-catalyst Co(II) can undergo single-electron transfer upon activation with O2 to generate cumene radicals, although they promote the reaction, they only slightly improve the catalytic efficiency. Comparative Example 4 compares the catalyst with the supported NHMI catalyst reported in the literature, revealing that our synthesized catalyst exhibits higher activity and higher selectivity for the reaction products cumene hydroperoxide and acetophenone. It is noted that when the St-NHMI-1.5 / Co(II) combined catalyst is used for the catalytic oxidation of CM, the conversion rate reaches 73.1%, with selectivities of 74.1%, 10.5%, and 13.9% for AP, PP, and CHP, respectively, and a small amount of AMS (Example 1). This indicates that the catalyst and cobalt ions can synergistically promote the oxidation of CM. Under the same experimental conditions, the catalysts prepared with different styrene / maleic anhydride feed ratios showed different performance in catalytic oxidation of cumene. St-NHMI-1.5 exhibited the best ability to oxidize cumene, achieving a conversion rate of 72.5%. During five cycles of St-NHMI-1.5 recycling, the conversion rate of cumene and the selectivity for cumene hydroperoxide, acetophenone, 2-phenyl-2-propanol, and α-methylstyrene remained stable. This indicates that the catalyst did not cause the loss of active components during use, and that the catalyst has excellent stability under the reaction conditions.

[0062] Table 1. Results of catalytic oxidation of cumene in Examples 1-8 and Comparative Examples 1-4

[0063]

[0064] like Figure 5As shown, the principle of using the immobilized N-hydroxymaleimide catalyst as a recyclable catalyst in the oxygen functionalization reaction of cumene is as follows: An active cobalt complex intermediate is generated through a single-electron transfer between cobalt ions and molecular oxygen, which then abstracts hydrogen from the catalyst to generate the active N-oxygen radical catalyst MINO. The generated MINO radical further abstracts hydrogen atoms from the substrate cumene to produce cumene radicals, which are readily captured by oxygen to form cumene peroxide radicals. The cumene peroxide radicals then abstract hydrogen from the catalyst to obtain the cumene oxidation product; this is the rate-determining step of chain growth.

[0065] There are two possible sources of 2-phenyl-2-propanol in the product. One is direct conversion from the substrate during the oxidation of cumene, resulting from the combination of hydroxyl radicals from the decomposition of cumene hydroperoxide and cumene radicals. Another possibility is the abstraction of hydrogen from cumene oxide radicals generated during the decomposition of cumene hydroperoxide onto cumene and / or the catalyst.

[0066] The formation of dicumyl peroxide may involve the combination of two cumene free radicals, which represents the termination of the chain reaction. There are two pathways for the formation of dicumyl peroxide: one is the combination of two cumeneoxy free radicals, and the other is the combination of one cumene free radical and one cumene peroxy free radical.

Claims

1. A supported N-hydroxymaleimide catalyst for use as a recyclable catalyst in the oxygen functionalization reaction of cumene, characterized in that, The catalyst is prepared by imidization of a styrene-maleic anhydride copolymer; the molar ratio of styrene to maleic anhydride is 1:1.5; the number average molecular weight of the styrene-maleic anhydride copolymer is 20,000-35,000; the preparation method of the supported N-hydroxymaleimide catalyst is as follows: (1) Preparation of styrene-maleic anhydride copolymer; (2) The styrene-maleic anhydride copolymer is subjected to imidization treatment using a reaction solution containing free hydroxylamine. After the treatment, it is dehydrated, filtered, washed and dried to obtain the immobilized N-hydroxymaleimide catalyst. The reaction solution containing free hydroxylamine is prepared by dissolving hydroxylamine hydrochloride, sodium methoxide and trisodium ethylenediaminetetraacetate in an organic solvent to obtain a mixture. The mixture is reacted at 15-20℃ for 11-12h to obtain the reaction solution containing free hydroxylamine. The imidization treatment conditions are: reaction temperature 40-42℃ and reaction time 7-8h.

2. The supported N-hydroxymaleimide catalyst according to claim 1, characterized in that, In step (1), the preparation method of the styrene-maleic anhydride copolymer is as follows: styrene, maleic anhydride and initiator are added to a solvent to obtain a reaction solution. The reaction solution is refluxed, filtered and separated, washed and dried to obtain the styrene-maleic anhydride copolymer.

3. The supported N-hydroxymaleimide catalyst according to claim 2, characterized in that, The reflux reaction conditions are: reaction temperature 80-85℃, reaction time 1.5-2h.

4. The supported N-hydroxymaleimide catalyst according to claim 1, characterized in that, In step (2), the dehydration treatment conditions are: first, distill at atmospheric pressure at 80-85℃ in a dehydrating agent, and then rapidly dehydrate under reduced pressure in an azeotropic manner.

Images