Catalyst, preparation method thereof and application of catalyst in preparation of benzonitrile from oxidized polystyrene

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a catalyst, a preparation method thereof and application of the catalyst in preparation of benzonitrile from oxidized polystyrene. The catalyst is obtained by carrying out heat treatment on a mixture of urea and TiO2, and the specific preparation method comprises the following steps: firstly, dropwise adding a hydrogen fluoride aqueous solution into tetrabutyl titanate, and uniformly mixing to obtain a milk white gel precursor; then putting the milk white gel precursor into a high-pressure kettle, heating for a period of time, cooling to room temperature to obtain a white solid, washing and drying to obtain TiO2 powder; the preparation method comprises the following steps: adding urea into TiO2 powder, uniformly mixing, and calcining the mixture in air at high temperature to obtain the oxygen vacancy-rich catalyst TiO2-Ov-x (Ov represents oxygen vacancy and x represents the mass of urea added corresponding to every 2 g of TiO2 powder, g). The preparation method of the catalyst is simple, and the catalyst still has good stability after being recycled and calcined for 7 times, and has high catalytic activity for oxidizing polystyrene into benzonitrile.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a catalyst, a preparation method thereof, and an application thereof in the preparation of benzonitrile from oxidized polystyrene. Background Art

[0002] The chemical upgrading and recycling of polystyrene provides a very ideal method for producing value-added small molecule substances, which can reduce plastic pollution and promote the reuse of waste plastics.

[0003] Polystyrene is a plastic widely used in human life and industrial manufacturing due to its low cost, light weight, easy manufacturability, versatility, high thermal efficiency, durability, and strong moisture resistance. However, polystyrene is very stable in nature and extremely difficult to degrade in the environment, which has always been a difficult problem to solve. It is reported that the current recovery rate of polystyrene is less than 1%, and polystyrene accounts for about one-third of the global landfill content. In the past, plastic treatment methods such as incineration and landfilling inevitably caused secondary pollution. Therefore, great attention has been paid to the development of new methods for treating polystyrene products and other plastics. The recycling strategies of polystyrene mainly include two aspects: the closed-loop recycling process (depolymerization of polystyrene into monomers) and the open-loop recycling process (conversion of polystyrene into various chemicals) through pyrolysis, hydrolysis, solvation, etc.

[0004] The C-C bonds and C-H bonds in the polystyrene main chain have high bond energies. Therefore, the chemical conversion of polystyrene requires harsh conditions such as high temperature and / or high pressure, and the degradation products are complex. In this context, the development of economically feasible polystyrene recycling / upgrading recycling methods is of great significance for the practical treatment of polystyrene waste including solids, foams, copolymers, and polymer fillers. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a catalyst (TiO 2 -O v -x), a preparation method thereof, and an application thereof in the preparation of benzonitrile from oxidized polystyrene.

[0006] Surface engineering methods have been proven to be able to effectively regulate the surface properties of photocatalytic materials, thereby improving their photocatalytic performance, such as charge separation / recombination efficiency and surface redox reaction kinetics. In the present invention, by heat-treating the mixture of TiO 2 and urea, a large number of oxygen vacancies (O v ) are generated on the surface of TiO 2 to achieve the purpose of surface modification of the TiO 2 catalyst. The modified catalyst TiO 2 -O v-x has a good effect on the preparation of benzonitrile from oxidized polystyrene.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a catalyst TiO 2 -O v -x, the catalyst TiO 2 -O v -x is rich in oxygen vacancies O v TiO 2 Catalyst, the catalyst TiO 2 -O v -x is the reaction of urea with TiO 2 The mixture is heat treated to obtain, wherein x is 2gTiO 2 The corresponding mass of urea added, the unit of mass is g.

[0009] The present invention also provides the catalyst TiO 2 -O v -x, the preparation method comprising the following steps in sequence:

[0010] (1) adding a hydrogen fluoride aqueous solution dropwise to tetrabutyl titanate and stirring evenly to obtain a milky white gel precursor;

[0011] (2) Add the milky white gel precursor into an autoclave, cool to room temperature after the heating reaction, centrifuge, wash, and dry to obtain TiO 2 powder;

[0012] (3) TiO 2 The powder was fully mixed with urea, placed in a crucible for heating, and cooled to room temperature to obtain the catalyst TiO 2 -O v -x.

[0013] Furthermore, in step (1), the mass concentration of the aqueous hydrogen fluoride solution is 40%, the volume ratio of the aqueous hydrogen fluoride solution to tetrabutyl titanate is (1-6): (20-30), preferably 3:25; the stirring speed is 30-70 rpm, preferably 50 rpm; and the stirring time is 1-4 h, preferably 2 h.

[0014] Furthermore, the heating condition in step (2) is heating at 160-200°C for 24-28h, preferably heating at 180°C for 26h; washing is washing with distilled water and ethanol 3-4 times each, preferably washing with distilled water and anhydrous ethanol 3 times each; the drying condition is drying in a vacuum oven at 40-80°C for 10-14h, preferably drying in a vacuum oven at 60°C for 12h.

[0015] Further, in the step (3), the mass ratio of TiO 2 powder to urea is (0.5 - 2):(1 - 16), preferably 2:4, and the condition for sufficient mixing is to mix evenly by using ball milling technology; the heating condition is to heat the mixture to 550 °C at a rate of 1 - 3 °C / min (preferably 2.3 °C / min) and hold for 4 h.

[0016] The brief flow chart for forming the above catalyst TiO 2 -O v -x structure is as shown in the attached Figure 5 description.

[0017] The present invention also provides an application of the above catalyst TiO 2 -O v -x in the preparation of benzonitrile from oxidized polystyrene.

[0018] Further, the steps of the application are as follows: Disperse the catalyst TiO 2 -O v -x described in claim 1 or the catalyst TiO 2 -O v -x obtained by the preparation method described in any one of claims 2 - 5 and polystyrene in a mass ratio of (1 - 4):(1 - 8) (preferably 2:4) into solvent A, add it to a reactor, seal it and fill it with reaction gas, heat it to the reaction temperature under stirring, and then keep it under light irradiation for reaction. After the reaction is completed, the product benzonitrile is obtained.

[0019] Further, in the application, the number average molecular weight M n of the polystyrene is ~70 kDa.

[0020] Further, in the application, solvent A is acetonitrile; the gas in the reactor is 1 MPa O 2 .

[0021] Further, the heating condition is: the heating rate is 10 - 15 °C / min, the reaction temperature is 80 - 180 °C, and the reaction time is 3 - 30 h (preferably the heating rate is 10 °C / min, the reaction temperature is 130 °C, and the reaction time is 24 h); the light irradiation condition uses a 3W LED lamp with a wavelength of 420 nm; the stirring rate is 600 rpm.

[0022] Compared with the prior art, the advantages and beneficial effects of the catalyst and its application of the present invention are as follows:

[0023] By performing heat treatment on TiO 2 in the presence of urea, abundant oxygen vacancies (O v ) are generated, and urea has an effect on TiO2 The surface of the catalyst was modified, and the prepared TiO rich in oxygen vacancies by modification 2 -O v -x catalyst has strong stability in the oxidation conversion of polystyrene to benzonitrile under light at a wavelength of 420 nm and a temperature of 130 °C. In addition, the method of the present application can also effectively oxidize and convert plastics containing polystyrene into benzonitrile in practical applications, showing great application potential.

[0024] The present invention precisely constructs active sites through a simple calcination method, which can not only promote the O 2 activation process to generate ·O 2- , but also obtain Lewis acid centers to promote the hydrolysis of acetonitrile. ·O 2- is formed directionally and participates in the deep oxidation of polystyrene. This work reveals the relationship between the precise regulation of active sites and the directional generation of active species, and also inspires new ideas for the rational design of excellent photothermal catalysts for various environmental remediation and energy fields.

[0025] The catalyst prepared by the present invention is a non-noble metal photothermal catalyst with low cost and simple preparation process.

[0026] The catalyst preparation process of the present invention is simple, has good stability, and can be recycled more than 7 times. Description of the Drawings

[0027] Figure 1 In (a) is the transmission electron microscope image and high-resolution transmission electron microscope image (inset) of the TiO 2 -O v -4 catalyst prepared in Example 1; Figure 1 In (b) is the XRD spectrum of the catalyst prepared in Example 2; Figure 1 In (c) is the EPR spectrum of the catalyst prepared in Example 2;

[0028] Figure 2 In (a) are the product selectivity results of TiO 2 , TiO 2 -O v -1, TiO 2 -O v -2, TiO 2 -O v -4, TiO 2 -O v -8 catalysts after the reaction, and also include the comparison results with TiO 2 -O v -4 as the catalyst using acetonitrile as the solvent; Figure 2 In (b) shows TiO prepared in Example 2 at different temperatures2 -O v -x light absorption ability of the catalyst;

[0029] Figure 3 For the TiO prepared in Example 1 at different reaction temperatures in Example 3 2 -O v -4 product distribution map of polystyrene degradation by the catalyst;

[0030] Figure 4 For the TiO prepared in Example 1 at different reaction times in Example 4 2 -O v -4 product distribution map of polystyrene degradation by the catalyst;

[0031] Figure 5 For the catalyst TiO of the present invention 2 -O v -x brief process of structure formation;

[0032] Figure 6 In (a) is the TiO prepared in Example 1 2 -O v -4 action spectrum between the light absorption performance at different wavelengths and the production of benzonitrile; Figure 6 In (b) is the TiO prepared in Example 1 2 -O v -4 fluorescence quantum yield under different wavelength excitations; Figure 6 In (c) is the use of TiO prepared in Example 1 2 -O v -4 product distribution map of polystyrene (PS) degradation at different light intensities by the catalyst.

[0033] Figure 7 For the TiO prepared in Example 1 in Example 6 2 -O v -4 catalyst cycle experiment data.

[0034] Figure 8 For the TiO prepared in Example 1 in Example 7 2 -O v -4 catalyst degradation experiment on 4 kinds of plastics containing polystyrene.

[0035] Figures 2 to 4 、 Figures 6 to 7 In which CN represents carbon nitride (g-C 3 N 4 ), AP represents acetophenone, BAD represents benzoic acid, PH represents benzaldehyde, BA represents benzamide, BT represents benzonitrile. Detailed implementation method

[0036] The following are some specific embodiments to further illustrate the present invention, but not to limit the scope of protection claimed by the present invention.

[0037] Example 1:

[0038] A preparation method of an oxygen vacancy-rich TiO 2 photothermal catalyst (TiO 2 -O v -4) comprises the following steps:

[0039] 3.0 mL of hydrofluoric acid aqueous solution (40 wt%, the same below) was dropped into 25.0 mL of tetrabutyl titanate, and stirred at a speed of 50 rpm for 2 h to obtain a uniform milky white gel precursor. The obtained milky white gel precursor was transferred to an autoclave and heated at 180 °C for 26 h. After cooling to room temperature (25 °C, the same below) with the autoclave, the obtained white solid was collected by centrifugation and washed 3 times with distilled water and anhydrous ethanol respectively. Finally, the sample was vacuum dried at 60 °C for 12 h to obtain TiO 2 powder.

[0040] 2.0 g of TiO 2 powder was fully mixed with 4.0 g of urea by using ball milling technology. Then the mixture was transferred to a crucible and heated to 550 °C at a rate of 2.3 °C / min in air and held at 550 °C for 4 h. After cooling to room temperature, TiO 2 -O v -4 catalyst was obtained and ground for further use and characterization. Figure 1 In (a) is the transmission electron microscopy image and high-resolution transmission electron microscopy image (inset) of the TiO 2 -O v -4 catalyst prepared in this example. The crystal plane spacing of 0.35 nm in the high-resolution transmission electron microscopy represents the (101) crystal plane of TiO 2 of.

[0041] Example 2:

[0042] 3.0 mL of hydrofluoric acid aqueous solution was dropped into 25.0 mL of tetrabutyl titanate, and stirred at a speed of 50 rpm for 2 h to obtain a uniform milky white gel precursor. The obtained milky white gel precursor was transferred to an autoclave and heated at 180 °C for 26 h. After cooling to room temperature with the autoclave, the obtained white solid was collected by centrifugation and washed 3 times with distilled water and anhydrous ethanol respectively. Finally, the sample was vacuum dried at 60 °C for 12 h to obtain TiO 2 powder.

[0043] 2.0 g of TiO 2The powder was thoroughly mixed with 0.0 g, 1.0 g, 2.0 g, 4.0 g, and 8.0 g of urea. Then the mixture was transferred to a crucible and heated in air to 550 °C at a rate of 2.3 °C / min and held at 550 °C for 4 h. After cooling to room temperature, TiO 2 , TiO 2 -O v -1, TiO 2 -O v -2, TiO 2 -O v -4, TiO 2 -O v -8 catalysts were obtained and ground for later use. The XRD patterns of the catalysts are shown in Figure 1 (b), and the EPR patterns are shown in Figure 1 (c). Figure 1 (b) in shows characteristic diffraction peaks at 25.3°, 37.9°, 48.2°, 54.1°, and 55.3°, which belong to the (101), (004), (200), (105), and (211) planes of anatase TiO 2 , and the XRD patterns of the TiO 2 -O v -x samples are similar to those of the precursor TiO 2 , indicating that the co-calcination process with urea did not change the crystal structure of TiO 2 . In addition, no diffraction peaks related to graphitic carbon nitride (g-C 3 N 4 , Figure 1 (b) CN) were found, suggesting that the nitrogen element of urea was not doped into TiO 2 . Figure 1 The height of the peak amplitude in (c) in is positively correlated with the oxygen vacancy content.

[0044] 20 mg of each of the above 5 catalysts and 40 mg of polystyrene (number-average molecular weight M n ~ 70 kDa, the same below) were added to the reactor, and 10 mL of acetonitrile (analytical grade, the same below) was added. After flushing with O 2 for 10 min to remove the air in the reactor, 1 MPa of O 2 was filled. It was heated to the designed temperature (130 °C) at a rate of 10 °C / min (the same below), and then under the light irradiation of a 3 W LED lamp (wavelength 420 nm), it was magnetically stirred at a speed of 600 rpm and maintained for 24 h. After the reaction, the catalyst was centrifuged and recovered, and the remaining liquid mixture was analyzed.

[0045] Meanwhile, g-C 3 N 4 was used to replace TiO​2 -O v Using -4 as the catalyst, the remaining reaction conditions were the same as those in the above reaction process for the control reaction.

[0046] Quantitative detection was carried out using an Agilent 7890A gas chromatography system equipped with an HP-5MS UI chromatographic column. The specific operation was to determine the contents of benzonitrile and other substances using nitrobenzene as the internal standard (the same below).

[0047] The experimental results are as shown in Figure 2 (a). When photothermal degradation of polystyrene was carried out on pure titanium dioxide, only a small amount of benzonitrile and benzoic acid were produced. By comparison, it can be seen that the introduction of O in TiO 2 greatly improved the catalytic activity of TiO v -O 2 -x catalyst (x = 1 - 4) for oxidizing polystyrene to benzonitrile. However, the further increase in the O content in the TiO v -O 2 -x catalyst (x = 4 - 8) led to a decrease in catalytic activity. TiO with an appropriate O content v -O v -4 had the best catalytic performance and the highest yield of benzonitrile. v The light absorption ability of different catalysts at the same temperature in 2 -O v (b) also confirmed that TiO Figure 2 -O 2 -4 had the best light absorption ability. v -4 had the best light absorption ability.

[0048] Example 3: Activity of the TiO 2 -O v -4 catalyst prepared in Example 1 at different reaction temperatures

[0049] 20 mg of the TiO 2 -O v -4 catalyst and 40 mg of polystyrene were added to the reactor, and 10 mL of acetonitrile was added. After flushing with O 2 for 10 min to remove the air in the reactor, 1 MPa of O 2 was filled. The mixture was heated to the designed temperature (80 - 180 °C) respectively, and under the light irradiation of a 3 W LED lamp (wavelength 420 nm), it was magnetically stirred at a speed of 600 rpm and maintained for 24 h. After the reaction, the catalyst was centrifugally recovered, and the remaining liquid mixture was analyzed. The experimental results are as shown in Figure 3As shown in the figure. The reaction temperature shows a significant effect on the preparation of benzonitrile by the oxidation of polystyrene. The temperature not only affects the oxidation degradation efficiency of polystyrene, but also has a great impact on the distribution of aromatic products. The total yield of aromatic products increases from 0.9 mmol / g at 80 °C ps (mmol / g ps (representing the total number of moles of aromatic products formed from 1 g of polystyrene, the same below) to 7.3 mmol / g at 130 °C ps . At 80 °C, benzoic acid is the main product with a selectivity of 93%, and there are almost no acetophenone and benzaldehyde intermediates. When the reaction temperature is raised to 110 °C and 130 °C, the C-C bond of polystyrene breaks to form benzaldehyde, and ammonia is produced by the hydrolysis of acetonitrile and combines with benzaldehyde to convert benzaldehyde into benzylamine. Benzylamine is unstable and is easily oxidized and dehydrogenated by O 2 to form benzonitrile, which becomes the main product. At the reaction temperatures of 110 °C and 130 °C, benzamide and benzoic acid are detected by GC-MS and are by-products in the main reaction process. As can be seen from Figure 3 , the reaction is significantly affected by temperature. As the reaction temperature increases from 80 °C to 130 °C, the conversion rate of polystyrene and the yield of benzonitrile gradually increase; after the temperature is raised to 150 °C, the conversion rate of polystyrene in this process slightly decreases, and the yield of benzonitrile significantly decreases. Therefore, 130 °C is selected as the reaction temperature for the practicality test.

[0050] Example 4: Activity of the TiO 2 -O v -4 catalyst prepared in Example 1 at different reaction times

[0051] 20 mg of TiO 2 -O v -4 catalyst and 40 mg of polystyrene were added to the reactor and 10 mL of acetonitrile was added. After flushing with O 2 for 10 min to remove the air in the reactor, 1 MPa of O 2 was filled. It was heated to the designed temperature (130 °C), and under the light irradiation of a 3 W LED lamp (wavelength 420 nm), it was magnetically stirred and maintained at a rotation speed of 600 rpm. The reaction times were 3, 4, 5, 6, 12, 18, 24, 30 h respectively. After the reaction, the catalyst was centrifugally recovered, and the remaining liquid mixture was analyzed. The results of the product distribution are shown in Figure 4 . During the process of increasing the reaction time from 3 h to 24 h, the conversion rate of polystyrene and the yield of benzonitrile gradually increase, and the selectivity of benzonitrile at 24 h is also the best. When the reaction time is 30 h, the substrate conversion rate significantly decreases. Therefore, 24 h is selected as the reaction time for the subsequent comparative experiment.

[0052] Example 5: Influence of Light Wavelength on the Activity of the TiO 2 -O v -4 Catalyst

[0053] Add 20 mg of the TiO 2 -O v -4 catalyst and 40 mg of polystyrene into the reactor and add 10 mL of acetonitrile. Flush with O 2 for 10 min to remove the air in the reactor, and then fill it with 1 MPa of O 2 . Heat to the designed temperature (130 °C), and under the light irradiation of a 3 W LED lamp (wavelength 365 - 530 nm), stir magnetically at a speed of 600 rpm and maintain it. The reaction time is 24 h. After the reaction, the catalyst is recovered by centrifugation, and the remaining liquid mixture is analyzed.

[0054] At the same time, detect the light absorption performance of the TiO 2 -O v -4 catalyst at different wavelengths and its relationship with the production of benzonitrile (see Figure 6 (a) in). Figure 6 (b) in is the fluorescence quantum yield of the TiO 2 -O v -4 catalyst under various wavelength excitations. Use the TiO 2 -O v -4 catalyst to degrade the product distribution of polystyrene at different light intensities (the light intensities corresponding to each wavelength in Figure 6 (b)) (see Figure 6 (c) in).

[0055] Although the light absorption intensity at 365 nm in the ultraviolet region is stronger than that at 420 nm, under the irradiation of 420 nm LED light, the photothermal conversion of polystyrene shows the highest benzonitrile yield ( Figure 6 (a) in). The highest photothermal efficiency at 420 nm should be due to the highest fluorescence quantum yield (FQE) at 420 nm and the relatively high incident photon - electron conversion efficiency ( Figure 6 (b) in). It can be seen from Figure 6 (c) in that the yield of benzonitrile is positively correlated with the irradiation intensity at 420 nm.

[0056] Example 6: Explore the Stability of the TiO 2 -O v -4 Catalyst Prepared in Example 1

[0057] Add 20 mg of the TiO 2 -O v-4 catalyst and 40 mg of polystyrene were added to the reactor, and 10 mL of acetonitrile was added. After flushing with O 2 for 10 min to remove the air in the reactor, 1 MPa of O 2 was filled in. It was heated to the designed temperature (130 °C), and under the light irradiation of a 3 W LED lamp (wavelength 420 nm), it was magnetically stirred at a speed of 600 rpm and maintained for 24 h. After the reaction, the catalyst was centrifugally recovered, and the remaining liquid mixture was analyzed. The centrifugally collected catalyst was washed 3 times each with water and absolute ethanol in sequence; after drying, it was directly used for the second experiment. The catalyst used in the 3rd - 7th cycles was the catalyst recovered from the previous experiment after being calcined at high temperature (heated to 550 °C at a rate of 2.3 °C / min in air and maintained at 550 °C for 4 h) and then reused. The results are as Figure 7 shown. The disappearance of the activity in the second time was due to the adsorption of oxygen-containing groups in the aromatic compounds in the previous reaction on the O v sites. Each time after being calcined and recycled, the catalyst still had good catalytic activity after being recycled 7 times.

[0058] Example 7: Exploring the actual application ability of the TiO 2 -O v -4 catalyst

[0059] 20 mg of TiO 2 -O v -4 catalyst and 40 mg of plastics containing polystyrene (plastic foam, yogurt can, bottle cap, plastic cup) were added to the reactor, and 10 mL of acetonitrile was added. After flushing with O 2 for 10 min to remove the air in the reactor, 1 MPa of O 2 was filled in. It was heated to the designed temperature (130 °C), and under the light irradiation of a 3 W LED lamp (wavelength 420 nm), it was magnetically stirred at a speed of 600 rpm and maintained for 48 h. After the reaction, the catalyst was centrifugally recovered, and the remaining liquid mixture was analyzed. The experimental results are as Figure 8 shown. After the catalytic reaction, the total mass of the reaction system decreased significantly, indicating that the catalyst also had a certain degradation ability for plastics containing polystyrene. The yields of benzonitrile were 0.73 g / g plastic foam , 0.43 g / g yogurt po , 0.58 g / g bottle cap and 0.63 g / g plastic cup respectively, where g / g plastic foamMass of benzonitrile produced from 1 g of plastic foam, g / g yogurt po Mass of benzonitrile produced from 1 g of yogurt pot, g / g bottle cap Mass of benzonitrile produced from 1 g of bottle cap, g / g plastic cup Mass of benzonitrile produced from 1 g of plastic cup.

Claims

1. A catalyst TiO2-O v -x, characterized by: The catalyst TiO2-O v -x is rich in oxygen vacancies O v TiO2 catalyst; the catalyst TiO2-O v -x is obtained by heat treating a mixture of urea and TiO2, wherein x is the mass of urea added per 2 g of TiO2, and the unit of mass is g.

2. A catalyst TiO2-O according to claim 1 v -x preparation method, characterized in that, The preparation method comprises the following steps in sequence: (1) Add hydrogen fluoride aqueous solution dropwise into tetrabutyl titanate and stir evenly to obtain a milky white gel precursor; (2) Add the milky white gel precursor into an autoclave, cool to room temperature after the heating reaction is completed, centrifuge, wash, and dry to obtain TiO2 powder; (3) TiO2 powder and urea are fully mixed, placed in a crucible for heating, and cooled to room temperature to obtain the catalyst TiO2-O v -x.

3. The preparation method according to claim 2, characterized in that: In the step (1), the mass concentration of the hydrogen fluoride aqueous solution is 40%; the volume ratio of the hydrogen fluoride aqueous solution to tetrabutyl titanate is (1-6): (20-30); the stirring speed is 30-70 rpm, and the stirring time is 1-4 h.

4. The preparation method according to claim 2, characterized in that: The heating condition in step (2) is heating at 160-200°C for 24-28 h; the washing is washing with distilled water and anhydrous ethanol for 3-4 times respectively; the drying condition is drying in a vacuum oven at 40-80°C for 10-14 h.

5. The preparation method according to claim 2, characterized in that: In step (3), the mass ratio of TiO2 powder to urea is (0.5-2):(1-16); the condition for sufficient mixing is to mix evenly using ball milling technology; the heating condition is to heat the mixture to 550°C at 1-3°C / min and maintain it for 4 hours.

6. A catalyst TiO2-O according to claim 1 v -x or the catalyst TiO2-O obtained by the preparation method according to any one of claims 2 to 5 v Application of -x in the preparation of benzonitrile by oxidation of polystyrene.

7. The use according to claim 6, characterized in that: The application steps are as follows: the catalyst TiO2-O v -x or the catalyst TiO2-O obtained by the preparation method according to any one of claims 2 to 5 v -x and polystyrene are dispersed in solvent A in a mass ratio of (1-4):(1-8), added into a reactor, sealed, filled with reaction gas, heated to the reaction temperature under stirring, maintained and reacted under light, and after the reaction is completed, the product benzonitrile is obtained.

8. The use according to claim 7, characterized in that: In the application, the number average molecular weight M of the polystyrene n ~ 70 kDa; solvent A is acetonitrile; the reaction gas in the reactor is 1 MPa O2.

9. The use according to claim 7, characterized in that: In the application, the heating conditions are: a heating rate of 10-15°C / min, a reaction temperature of 80-180°C, and a reaction time of 3-30 h; the lighting conditions use a 3 W LED lamp with a wavelength of 420 nm; and the stirring rate is 600 rpm.

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