CN113387908B - Application of magnesium cobaltate catalyst in selective oxidation reaction of styrene - Google Patents

Abstract

The invention discloses an application of magnesium cobaltate in styrene selective oxidation reaction. The specific catalytic reaction process is as follows: styrene, tert-butyl hydroperoxide and solvent are evenly mixed, magnesium cobaltate is added, and the product of styrene oxide is obtained after reaction for a period of time at a certain temperature. The magnesium cobaltate catalytic material is cheap and easy to obtain, the catalytic reaction system is mild in condition, simple and easy to control, good in reaction effect and stable in performance, and is beneficial to large-scale popularization.

Description

Application of Magnesium Cobalt Oxide Catalyst in Selective Oxidation of Styrene

technical field

The invention relates to the application of a magnesium cobaltate catalyst in the selective oxidation reaction of styrene, and belongs to the technical field of catalytic oxidation reaction of olefins.

Background technique

Styrene oxide is an important fine chemical with a wide range of applications. In recent years, the heterogeneous catalytic oxidation process using green oxidants using styrene as the starting material has received extensive attention and research. For example, the literature (ACSCatalysis, 2017, 7, 3483-3488) in situ growth of ultra-small gold nanoparticles on carbon nitride supports for the oxidation of styrene with tert-butyl hydroperoxide as the oxidant, under optimal reaction conditions Under this condition, the conversion rate of styrene is 25.3%, and the selectivity of styrene oxide is 93.2%. Literature (Journal of Energy Chemistry, 2017, 26, 681-687) used Zr-doped CeO ₂ nanoparticles for the oxidation of styrene, using tert-butyl hydroperoxide as the oxidant, after 12 h of reaction, the conversion of styrene was 78.1%, and the selectivity of styrene oxide is 79.3%. The literature (Nanoscale Advances, 2020, 2, 1437) confines Au in mesoporous SiO ₂ as a catalyst for the oxidation of styrene with tert-butyl hydroperoxide as the oxidant, and reacted for 12 h under the optimal reaction conditions Afterwards, the conversion of styrene reached 88.0%, and the selectivity of styrene oxide was 74.0%. Literature (ACS Sustainable Chemistry & Engineering, 2019, 7, 17008−17019) prepared a series of three-dimensional/two-dimensional MnO ₂ /gC ₃ N ₄ composite catalysts for the oxidation of styrene with tert-butyl hydroperoxide as the oxidant Among them, it was found that 8MnO ₂ NP/UCN catalyst had the best catalytic performance, the conversion rate of styrene was 78.3%, and the selectivity of styrene oxide was 77.6%. Although many catalysts have been reported, the current challenge in this field is still to find a catalyst with simple preparation, low cost and excellent reactivity.

Magnesium cobaltate has the advantages of easy preparation and low price, and has been explored as a catalytic material recently, and satisfactory reaction results have been achieved. For example, literature (Chemical Engineering Journal, 2021, 405, 126907) uses magnesium cobaltate for the reaction of carbon dioxide and epoxy to prepare cyclic carbonates; patent (CN 108906063 A) uses magnesium cobaltate to catalyze peroxomonosulfate Used to remove organic pollutants; patent (CN 107335437 A) uses magnesium cobaltate to decompose high-concentration nitrous oxide waste gas. At present, there is no report on the application of magnesium cobaltate in the selective oxidation of styrene.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the defects of the prior art, and to provide an application of a magnesium cobaltate catalyst in the selective oxidation of styrene. The catalytic system is easy to control, the reaction effect is good, and the performance is stable, which is conducive to large-scale promotion .

In order to solve the above technical problems, the present invention provides an application of a magnesium cobaltate catalyst in the selective oxidation of styrene.

Further, the reaction process is: uniformly mixing styrene, tert-butyl hydroperoxide and solvent, adding a magnesium cobaltate catalyst, and reacting to obtain the product styrene oxide.

Further, the solvent is acetonitrile.

Further, the dosage of the magnesium cobaltate catalyst is 3.2-12.8wt.% of styrene.

Further, the mass ratio of styrene, tert-butyl hydroperoxide and solvent is 1:4:18.8.

Further, the reaction temperature is 70 ~ 90 ° C.

Further, the reaction time is 7-10 h.

Further, the preparation method of the magnesium cobaltate catalyst is as follows: weigh magnesium nitrate hexahydrate and cobalt nitrate hexahydrate and dissolve them in deionized water, then add urea to the above solution, after stirring, move the above solution into a hydrothermal kettle , keep the temperature at 120-200 °C for 6-18 h, cool to room temperature, filter, wash with deionized water and ethanol, dry and calcinate to obtain the magnesium cobaltate catalyst.

Further, the mass ratio of magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, and urea is 1:2.23:2.34.

Further, the drying temperature is 50-120 °C, and the drying time is 6-18 h; the calcination temperature is 400-600 °C, and the calcination time is 1-4 h.

The beneficial effect that the present invention reaches:

(1) The magnesium cobaltate catalyst of the present invention is easy to prepare, and is cheap and easy to obtain;

(2) The catalytic system is easy to control, the reaction effect is good, and the performance is stable, which is conducive to large-scale promotion.

Description of drawings

Figure 1 is the XRD pattern of the magnesium cobaltate catalyst (MgCo ₂ O ₄ ) prepared in Example 1 of the invention, MgO in Comparative Example 1 and Co ₃ O ₄ in Comparative Example 2.

Fig. 2 is an SEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1 of the invention.

Figure 3 is an SEM image of the MgO catalyst prepared in Comparative Example 1 of the invention.

Fig. 4 is an SEM image of the Co ₃ O ₄ catalyst prepared in Comparative Example 2 of the invention.

Fig. 5 is a TEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1 of the invention.

Fig. 6 is the HRTEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1 of the invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

Example 1

Weigh 2 mmol of magnesium nitrate hexahydrate and 4 mmol of cobalt nitrate hexahydrate and dissolve them in 50 mL of deionized water, then add 1.2 g of urea to the above solution, stir for half an hour, then transfer the above solution into a hydrothermal kettle, and heat at 180 ° C for 12 h at a constant temperature, cooled to room temperature, filtered, washed with deionized water and ethanol, and then dried at 60 °C for 12 h; the above-mentioned sample was calcined at 500 °C for 2 h to obtain the magnesium cobaltate catalyst . FIG. 1 contains the XRD pattern of the MgCo ₂ O ₄ catalyst prepared in Example 1. FIG. 2 is an SEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1. FIG. 5 is a TEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1. FIG. 6 is an HRTEM image of the MgCo ₂ O ₄ catalyst prepared in Example 1.

The prepared catalyst was used in the selective oxidation of styrene. First, 15 mmol styrene, 45 mmol tert-butyl hydroperoxide and 16 mL acetonitrile were mixed, then 0.1 g catalyst was added, and reacted at 80 °C for 10 h. The product was analyzed by gas chromatography, and it was found that the conversion of styrene The yield reached 99.5% at the 10th hour, and the selectivity of styrene oxide reached 83.4%. In addition, in order to test the recycling performance of the catalyst, the reacted catalyst was filtered out, washed fully with hot water and acetone, and then vacuum-dried at 120 °C for 24 h, and then used for cycle testing. It was found that within five cycles, the catalyst There was no significant decrease in activity and selectivity.

Comparative example 1

Weigh 6 mmol of magnesium nitrate hexahydrate and dissolve it in 50 ml of deionized water, and prepare magnesium oxide as a catalyst under the same conditions as in Example 1 under other reaction conditions. Figure 1 contains the XRD spectrum of the MgO catalyst prepared in Comparative Example 1 of the invention. Figure 3 is an SEM image of the MgO catalyst prepared in Comparative Example 1 of the invention.

When other reaction conditions were the same as in Example 1, the catalytic performance test was carried out, and the results showed that the conversion rate of styrene was 27.4%, and the selectivity of styrene oxide was 69.2%.

Comparative example 2

Weigh 6 mmol of cobalt nitrate hexahydrate and dissolve it in 50 ml of deionized water, and prepare cobalt tetroxide as a catalyst under the same conditions as in Example 1. Fig. 1 contains the XRD spectrum of the Co ₃ O ₄ catalyst prepared in Comparative Example 2 of the invention . Fig. 4 is an SEM image of the Co ₃ O ₄ catalyst prepared in Comparative Example 2 of the invention.

When other reaction conditions were the same as in Example 1, the catalytic performance test was carried out, and the results showed that the conversion rate of styrene was 61.3%, and the selectivity of styrene oxide was 55.6%.

Comparative example 3

Repeat Example 1, except that the calcination temperature used for catalyst preparation is 600 °C. Under the same condition of other reaction conditions, the conversion rate of styrene is 53.2%, and the selectivity of styrene oxide is 84.2%.

Example 2

Repeat Example 1, except that 0.05 g of MgCo ₂ O ₄ catalyst is added to the catalytic reaction system. Under the same other reaction conditions, the conversion rate of styrene was 78.1%, and the selectivity of styrene oxide was 86.8%.

Example 3

Repeat Example 1, except that 0.15 g of MgCo ₂ O ₄ catalyst is added to the catalytic reaction system. Under the same other reaction conditions, the conversion rate of styrene is 99.5%, and the selectivity of styrene oxide is 80.5%.

Example 4

Repeat Example 1, except that 0.20 g of MgCo ₂ O ₄ catalyst is added to the catalytic reaction system. Under the same other reaction conditions, the conversion rate of styrene was 97.3%, and the selectivity of styrene oxide was 78.2%.

Comparative example 4

Repeat Example 1, except that 0.02 g of MgCo ₂ O ₄ catalyst is added to the catalytic reaction system. Under the same other reaction conditions, the conversion rate of styrene was 34.8%, and the selectivity of styrene oxide was 80.3%.

Example 5

Repeat Example 1, except that the catalytic reaction temperature is 70 °C. Under the same other reaction conditions, the conversion rate of styrene was 43.6%, and the selectivity of styrene oxide was 66.9%.

Example 6

Repeat Example 1, except that the catalytic reaction temperature is 90 °C. Under the same other reaction conditions, the conversion rate of styrene was 99.7%, and the selectivity of styrene oxide was 78.1%.

Comparative example 5

Repeat Example 1, except that the catalytic reaction temperature is 60 °C. Under the same condition of other reaction conditions, the conversion rate of styrene is 24.2%, and the selectivity of styrene oxide is 43.0%.

Example 7

Repeat Example 1, except that the catalytic reaction time is 7 h. Under the same other reaction conditions, the conversion rate of styrene was 68.0%, and the selectivity of styrene oxide was 83.8%.

Example 8

Repeat Example 1, except that the catalytic reaction time is 8 h. Under the same other reaction conditions, the conversion rate of styrene was 79.9%, and the selectivity of styrene oxide was 83.7%.

Example 9

Repeat Example 1, except that the catalytic reaction time is 9 h. Under the same conditions, the conversion rate of styrene was 91.8%, and the selectivity of styrene oxide was 83.5%.

Comparative example 6

Repeat Example 1, except that the catalytic reaction time is 6 h. Under the same other reaction conditions, the conversion rate of styrene was 59.0%, and the selectivity of styrene oxide was 83.9%.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (8)

1. the application of magnesium cobaltate catalyst in styrene selective oxidation reaction, the preparation method of described magnesium cobaltate catalyst is: take by weighing magnesium nitrate hexahydrate and cobalt nitrate hexahydrate and be dissolved in deionized water, add urea again in After stirring the above solution, move the above solution into a hydrothermal kettle, keep the temperature at 120-200°C for 6-18 h, cool to room temperature, filter, wash with deionized water and ethanol, dry and calcinate to obtain cobalt Magnesium acid catalyst; the drying temperature is 50-120 °C, and the drying time is 6-18 h; the calcination temperature is 400-600 °C, and the calcination time is 1-4 h. 2. application according to claim 1, is characterized in that, its reaction process is: styrene, tert-butyl hydroperoxide and solvent are uniformly mixed, add magnesium cobaltate catalyst, make product styrene oxide after reaction alkyl. 3. application according to claim 2, is characterized in that, described solvent is acetonitrile. 4. application according to claim 2, is characterized in that, the consumption of described magnesium cobaltate catalyst is 3.2～12.8wt.% of styrene. 5. application according to claim 2, is characterized in that, the mass ratio of described styrene, tert-butyl hydroperoxide and solvent is 1:4:18.8. 6. application according to claim 2, is characterized in that, temperature of reaction is 70～90 ℃. 7. application according to claim 2, is characterized in that, reaction time is 7～10 h. 8. application according to claim 1, is characterized in that, the mass ratio of described magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, urea is 1:2.23:2.34.

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