阅读说明：本技术 纳米金刚石的改性方法以及改性纳米金刚石及其应用和乙苯脱氢制备苯乙烯的方法 (Modification method of nano-diamond, modified nano-diamond and application thereof, and method for preparing styrene by ethylbenzene dehydrogenation ) 是由 缪长喜 危春玲 陈铜 刘岳峰 冯璐 于 2019-10-14 设计创作，主要内容包括：本发明涉及催化剂制备领域,公开了纳米金刚石的改性方法以及改性纳米金刚石及其应用和乙苯脱氢制备苯乙烯的方法,所述改性纳米金刚石包括：纳米金刚石、硼元素以及氮元素,其中,硼元素的含量为1-10重量％,硼元素和氮元素的质量比为1：(1-35)。纳米金刚石的改性方法包括：(1)将氮源、硼源、纳米金刚石和溶剂以及任选地分散剂混合,得到悬浊液；(2)将步骤(1)得到的悬浊液依次进行干燥、预煅烧和煅烧。本发明提供的改性纳米金刚石用于乙苯氧化脱氢反应时,具有较高的选择性。(The invention relates to the field of catalyst preparation, and discloses a method for modifying nano-diamond, modified nano-diamond and application thereof, and a method for preparing styrene by ethylbenzene dehydrogenation, wherein the modified nano-diamond comprises the following steps: the nano-diamond comprises nano-diamond, boron and nitrogen, wherein the content of the boron is 1-10 wt%, and the mass ratio of the boron to the nitrogen is 1: (1-35). The method for modifying the nano-diamond comprises the following steps: (1) mixing a nitrogen source, a boron source, nano-diamond, a solvent and an optional dispersing agent to obtain a suspension; (2) and (2) drying, pre-calcining and calcining the suspension obtained in the step (1) in sequence. The modified nano-diamond provided by the invention has higher selectivity when used in ethylbenzene oxidative dehydrogenation reaction.)

1. A modified nanodiamond, wherein the modified nanodiamond comprises: the nano-diamond comprises nano-diamond, boron and nitrogen, wherein the content of the boron is 1-10 wt%, and the mass ratio of the boron to the nitrogen is 1: (1-35).

2. The modified nanodiamond according to claim 1, wherein the content of the boron element is 2 to 6.5 wt%.

3. The modified nanodiamond according to claim 1 or 2, wherein the mass ratio of the boron element to the nitrogen element is 1: (2-20), preferably 1: (4-15).

4. The modified nanodiamond according to any one of claims 1-3, wherein the modified nanodiamond further comprises elemental phosphorus;

preferably, the mass ratio of the phosphorus element to the boron element is 1: (1-12), more preferably 1: (4-8).

5. The modified nanodiamond according to any one of claims 1-4, wherein the specific surface area of the modified nanodiamond is 250-350m²Per g, pore volume of 1-1.5cm³(ii)/g, the average pore diameter is 9-15 nm;

preferably, the specific surface area of the modified nano-diamond is 280-330m²Per g, pore volume of 1.15-1.35cm³(ii)/g, the average pore diameter is 10.4-13.6 nm.

6. A method of modifying nanodiamond, the method comprising:

(1) mixing a nitrogen source, a boron source, nano-diamond, a solvent and an optional dispersing agent to obtain a suspension;

(2) sequentially drying, pre-calcining and calcining the suspension obtained in the step (1);

wherein the nitrogen source, the boron source and the nano-diamond are used in such amounts that the prepared modified nano-diamond contains 1-10 wt% of boron, and the mass ratio of boron to nitrogen is 1: (1-35).

7. The modification method according to claim 6, wherein the dispersant is selected from at least one of citric acid, ammonium citrate and polyethylene glycol, preferably citric acid;

preferably, the mass ratio of the dispersing agent to the nano-diamond is 0.5-2: 1, preferably 1 to 1.5: 1.

8. the modification method according to claim 6, wherein the nitrogen source is at least one selected from ammonium carbonate, ammonium sulfate, urea and aqueous ammonia, preferably ammonium carbonate;

the boron source is selected from boric acid and/or sodium tetraborate, preferably boric acid;

the solvent is water;

preferably, the mixing in step (1) is carried out under ultrasonic conditions, and the ultrasonic time is 10-200min, preferably 50-80 min;

preferably, the content of the boron element in the suspension is 0.1 to 10 wt%, more preferably 0.5 to 5 wt%, based on the weight percentage of the boron element in the solvent.

9. The modification method according to any one of claims 6 to 8, wherein the nitrogen source, the boron source and the nanodiamond are used in amounts such that the modified nanodiamond is produced with a boron element content of 2 to 6.5 wt%, and a mass ratio of boron element to nitrogen element of 1: (2-20), preferably 1: (4-15).

10. The modification method according to any one of claims 6 to 9, wherein the suspension further contains a phosphorus source in an amount such that the modified nanodiamond produced contains phosphorus and boron in a mass ratio of 1: (1-12), more preferably 1: (4-8);

preferably, the source of phosphorus is selected from at least one of monoammonium phosphate, diammonium phosphate and ammonium phosphate.

11. The modification method according to any one of claims 6 to 10, wherein the drying conditions of step (2) include: the temperature is 100-150 ℃, and the time is 5-12 hours;

preferably, the pre-calcining conditions of step (2) include: under the oxygen-containing atmosphere, the temperature is 350-550 ℃, and preferably 400-500 ℃; the time is 1 to 8 hours, preferably 2 to 6 hours;

preferably, the calcining conditions of step (2) include: under inert atmosphere, the temperature is 600-900 ℃, and preferably 700-900 ℃; the time is 1 to 12 hours, preferably 2 to 8 hours;

preferably, the oxygen-containing atmosphere is air;

preferably, the inert atmosphere is neon and/or argon.

12. Modified nanodiamonds obtained by the modification method according to any one of claims 6 to 11.

13. Use of a modified nanodiamond according to any one of claims 1-5 and 12 in ethylbenzene dehydrogenation reactions.

14. A process for the dehydrogenation of ethylbenzene to styrene, which process comprises:

contacting a mixed gas containing ethylbenzene, a diluent and an oxidant with a catalyst under ethylbenzene dehydrogenation reaction conditions, wherein the catalyst is the modified nano-diamond of any one of claims 1-5 and 12;

preferably, the diluent is selected from at least one of inert gases, preferably from at least one of nitrogen, helium and argon;

preferably, the oxidant is an oxygen-containing gas, further preferably air and/or oxygen, more preferably oxygen;

preferably, the volume ratio of ethylbenzene to oxidant in terms of oxygen is 1: (0.1-2), preferably 1: (0.6-1.2);

preferably, the ethylbenzene dehydrogenation reaction conditions comprise: the temperature is 350-580 ℃, and the space velocity of the mixed gas is 1000-18000 mL/g-h.

Technical Field

The invention relates to the field of catalyst preparation, in particular to a method for modifying nano-diamond, modified nano-diamond and application thereof, and a method for preparing styrene by ethylbenzene dehydrogenation.

Background

Styrene is a very important basic organic monomer and plays an important role in national economy. Can be used for producing products such as polystyrene resin, ABS resin, synthetic rubber and the like, and has wide application. In 2018, the global styrene capacity has exceeded 3300 ten thousand tons per year. The predominant process for the commercial acquisition of styrene is the catalytic dehydrogenation of ethylbenzene to styrene. The process is carried out in the presence of Fe₂O₃-K₂Under the action of O-series metal oxide catalyst, it is implemented under the condition of high temp. (over 600 deg.C), and in the course of reaction a large quantity of water vapour is consumed. High energy consumption is a significant problem with this process.

Compared with direct catalytic dehydrogenation, the oxidative dehydrogenation reaction is a strong exothermic reaction, and is characterized by no limitation of equilibrium conversion rate, and the exothermic reaction at lower temperature is used to replace the endothermic reaction at high temperature, so that the energy consumption can be greatly reduced, and the efficiency can be improved. For the oxidative dehydrogenation of ethylbenzene, the major side reactions are favored by the elevated reaction temperature by thermodynamic analysis, and therefore, it is critical to find a catalyst with high catalytic activity and styrene selectivity.

In recent years, non-metallic catalysts, such as nanocarbon materials, boron carbide, carbon nitride, and the like, have been receiving attention because of their stability and excellent catalytic activity. For example, CN109126843A discloses the use of a boron carbide material as a catalyst for preparing styrene by ethylbenzene dehydrogenation, wherein when boron carbide is used as a catalyst in ethylbenzene dehydrogenation, the conversion rate of ethylbenzene is 15% to 60%, and the selectivity of styrene is 85% to 95%. In the reported literature, a nanocarbon material is used to catalyze the oxidative dehydrogenation reaction of ethylbenzene (Supported Carbon fibers for the fixed-bed synthesis of styrene, Carbon, vol 799 and 823 page 44 in 2006), and at 550 ℃, the conversion rate of the oxidative dehydrogenation of ethylbenzene can reach 65% and the selectivity of styrene can reach 80% by using the nanocarbon fiber as a catalyst.

However, due to the complicated surface structure of the carbon material, when the carbon material is used as a catalyst for oxidative dehydrogenation, a large amount of byproducts are produced, and thus the competitiveness of the catalyst for dehydrogenation needs to be further improved.

Disclosure of Invention

The invention aims to overcome the problem of poor selectivity of a catalyst for ethylbenzene oxidative dehydrogenation in the prior art, and provides a method for modifying nano-diamond, the modified nano-diamond, application of the modified nano-diamond and a method for preparing styrene by ethylbenzene dehydrogenation. The modified nano-diamond provided by the invention has higher selectivity when used in ethylbenzene oxidative dehydrogenation reaction.

In order to achieve the above object, a first aspect of the present invention provides a modified nanodiamond, comprising: the nano-diamond comprises nano-diamond, boron and nitrogen, wherein the content of the boron is 1-10 wt%, and the mass ratio of the boron to the nitrogen is 1: (1-35).

Preferably, the modified nanodiamond further comprises a phosphorus element.

Preferably, the mass ratio of the phosphorus element to the boron element is 1: (1-12), more preferably 1: (4-8).

In a second aspect, the present invention provides a method for modifying nanodiamond, comprising:

(1) mixing a nitrogen source, a boron source, nano-diamond, a solvent and an optional dispersing agent to obtain a suspension;

(2) sequentially drying, pre-calcining and calcining the suspension obtained in the step (1);

wherein the nitrogen source, the boron source and the nano-diamond are used in such amounts that the prepared modified nano-diamond contains 1-10 wt% of boron, and the mass ratio of boron to nitrogen is 1: (1-35).

The third aspect of the present invention provides a modified nanodiamond obtained by the above modification method.

The fourth aspect of the invention provides an application of the modified nano-diamond in ethylbenzene dehydrogenation reaction.

In a fifth aspect, the present invention provides a method for preparing styrene by ethylbenzene dehydrogenation, the method comprising:

under the condition of ethylbenzene dehydrogenation reaction, the mixed gas containing ethylbenzene, diluent and oxidant is contacted with a catalyst, wherein the catalyst is the modified nano-diamond provided by the invention.

The modified nano-diamond provided by the invention is used as a catalyst, the reaction temperature is 450 ℃, the dosage of the catalyst is 150mg, the total flow of reaction gas is 30ml/min, and the molar ratio of ethylbenzene to oxygen is 1: 1 hour, after stable operation for 16 hours, the conversion rate can reach more than 48.9 percent, the selectivity can reach more than 89.4 percent, and better technical effects are achieved.

Drawings

Fig. 1 is an SEM image of the modified nanodiamond obtained in example 1 of the present invention at different magnifications.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The present invention provides, in a first aspect, a modified nanodiamond, including: the nano-diamond comprises nano-diamond, boron and nitrogen, wherein the content of the boron is 1-10 wt%, and the mass ratio of the boron to the nitrogen is 1: (1-35).

According to a preferred embodiment of the present invention, the content of the boron element is 2 to 6.5% by weight, for example, 2% by weight, 2.5% by weight, 3% by weight, 3.5% by weight, 4% by weight, 4.5% by weight, 5% by weight, 5.5% by weight, 6% by weight, 6.5% by weight, and any value in the range of any two of these values. The adoption of the preferred embodiment is more beneficial to further improving the selectivity of the modified nano-diamond as the catalyst.

According to the present invention, preferably, the mass ratio of the boron element to the nitrogen element is 1: (2-20), preferably 1: (4-15).

According to the present invention, preferably, the modified nanodiamond further includes a phosphorus element; further preferably, the mass ratio of the phosphorus element to the boron element is 1: (1-12), more preferably 1: (4-8). The adoption of the preferred embodiment is more beneficial to further improving the selectivity of the modified nano-diamond as the catalyst.

According to the present invention, preferably, the specific surface area of the modified nanodiamond is 250-350m²Per g, pore volume of 1-1.5cm³(ii)/g, the average pore diameter is 9-15 nm; further preferably, the specific surface area of the modified nano-diamond is 280-330m²Per g, pore volume of 1.15-1.35cm³(ii)/g, the average pore diameter is 10.4-13.6 nm.

In the present invention, the specific surface area, pore volume and average pore diameter of the modified nanodiamond may be measured by a Tristar 3000 type physical adsorption apparatus of Micromeritics, USA for testing catalyst N₂Adsorption-desorption isotherm and specific surface area, with N₂As adsorbates, the samples were subjected to vacuum pretreatment at 300 ℃ and the specific surface area, pore volume and pore diameter of the catalyst samples were calculated by the BET method and the BJH method.

In a second aspect, the present invention provides a method for modifying nanodiamond, comprising:

(1) mixing a nitrogen source, a boron source, nano-diamond, a solvent and an optional dispersing agent to obtain a suspension;

(2) sequentially drying, pre-calcining and calcining the suspension obtained in the step (1);

wherein the nitrogen source, the boron source and the nano-diamond are used in such amounts that the prepared modified nano-diamond contains 1-10 wt% of boron, and the mass ratio of boron to nitrogen is 1: (1-35).

In the mixing process of the nitrogen source, the boron source, the nanodiamond and the solvent and optionally the dispersant in the step (1), the adding sequence of the materials is not particularly limited, and the dispersant, the nitrogen source, the boron source, the nanodiamond and the solvent can be added together, or after mixing some two of the components, the other rest components can be added in sequence. To enhance the mixing uniformity, it may be preferred to first dissolve the boron source in the solvent, then add the nitrogen source and optionally the dispersant, and finally add the nanodiamond.

According to the invention, preferably, the mixing in step (1) is carried out under ultrasonic conditions for 10-200min, preferably 50-80 min.

In the present invention, the mixing temperature is not particularly limited, and may be, for example, from room temperature to 80 ℃ and, for energy saving and ease of operation, it is preferable that the mixing is carried out at room temperature (20 to 30 ℃).

According to the present invention, preferably, the solvent is water, such as distilled water, deionized water or ultrapure water, more preferably ultrapure water.

In the invention, a dispersing agent can be added or not added in the mixing process, and preferably, the dispersing agent is added in the mixing process.

The invention has wide selection range of the dispersant as long as the aim of dispersing powder can be achieved. Preferably, the dispersant is selected from at least one of citric acid, ammonium citrate and polyethylene glycol, and further preferably citric acid. It is further advantageous to obtain suitable particles with this preferred embodiment.

According to the modification method provided by the invention, preferably, the mass ratio of the dispersing agent to the nano-diamond is 0.5-2: 1, preferably 1 to 1.5: 1.

according to the present invention, the nitrogen source may be a nitrogen-containing compound soluble in the solvent or soluble in the solvent under the action of a dispersant, and preferably, the nitrogen source is at least one selected from ammonium carbonate, ammonium sulfate, urea and aqueous ammonia, and more preferably ammonium carbonate.

According to the invention, the boron source may be a boron-containing compound soluble in the solvent or soluble in the solvent under the action of a dispersant, preferably the boron source is selected from boric acid and/or sodium tetraborate, more preferably boric acid.

In the present invention, the content of the boron source in the suspension is selected in a wide range, and in principle, the more the amount of the solvent in the suspension is, the more the boron source and the nitrogen source are uniformly dispersed, but the energy consumption for the subsequent drying is large, and both aspects are considered together, and the content of the boron element in the suspension is preferably 0.1 to 10 wt%, and more preferably 0.5 to 5 wt%, based on the weight percentage of the boron element in the solvent.

According to the modification method provided by the invention, preferably, the nitrogen source, the boron source and the nano-diamond are used in amounts such that the content of boron in the prepared modified nano-diamond is 2-6.5 wt%, and the mass ratio of boron to nitrogen is 1: (2-20), preferably 1: (4-15). The amount of nitrogen source and boron source added to the nanodiamond can be determined by those skilled in the art based on the above disclosure.

In order to further improve the selectivity of the modified nano-diamond prepared by the modification method as a catalyst, a phosphorus source is preferably introduced in the mixing process. In the present invention, the introduction of the phosphorus source is not particularly limited as long as the suspension further contains a phosphorus source. Preferably, the suspension further contains a phosphorus source, and the amount of the phosphorus source is such that the mass ratio of phosphorus element to boron element in the prepared modified nano-diamond is 1: (1-12), more preferably 1: (4-8).

According to the present invention, the phosphorus source may be a phosphorus-containing compound soluble in the solvent or soluble in the solvent under the action of a dispersant, preferably, the phosphorus source is selected from at least one of monoammonium phosphate, diammonium phosphate, and ammonium phosphate, and more preferably, monoammonium phosphate.

According to the present invention, preferably, the drying conditions of step (2) include: the temperature is 100 ℃ and 150 ℃, and the time is 5-12 hours.

According to a preferred embodiment of the present invention, the conditions of the pre-calcination in step (2) include: under the oxygen-containing atmosphere, the temperature is 350-550 ℃, and preferably 400-500 ℃; the time is 1 to 8 hours, preferably 2 to 6 hours. The oxygen-containing atmosphere may be pure oxygen or may contain an inert gas (non-reactive gas) in addition to oxygen; the oxygen-containing atmosphere preferably contains oxygen in an amount of 10 vol% or more, and preferably contains air for the purpose of reducing the production cost.

According to a preferred embodiment of the present invention, the calcination conditions of step (2) include: under inert atmosphere, the temperature is 600-900 ℃, and preferably 700-900 ℃; the time is 1-12h, preferably 2-8 h. The inert atmosphere is preferably neon and/or argon. The present invention is illustrated, in part, by the example of argon.

The third aspect of the present invention provides a modified nanodiamond obtained by the above modification method. The modified nano-diamond doped with boron, nitrogen and optionally phosphorus is obtained by the modification method, and the inventor of the invention finds that the modified nano-diamond is used as a catalyst to catalyze ethylbenzene dehydrogenation reaction, so that the styrene selectivity is higher.

Accordingly, a fourth aspect of the present invention provides the use of the modified nanodiamond as described above in ethylbenzene dehydrogenation reactions.

In a fifth aspect, the present invention provides a method for preparing styrene by ethylbenzene dehydrogenation, the method comprising:

under the condition of ethylbenzene dehydrogenation reaction, the mixed gas containing ethylbenzene, a diluent and an oxidant is contacted with a catalyst, wherein the catalyst is the modified nano-diamond provided by the invention. The method provided by the invention is used for carrying out surface modification on the nano-diamond, and the obtained modified nano-diamond is used as a catalyst for oxidative dehydrogenation reaction, so that fewer byproducts are generated, and the selectivity of the product is improved, thereby improving the competitiveness of the catalyst for dehydrogenation reaction process.

According to the present invention, the diluent may be a gas inert to the reaction, preferably at least one selected from the group consisting of nitrogen, helium and argon.

According to the present invention, the oxidizing agent is preferably an oxygen-containing gas, and more preferably a gas having an oxygen content of 10 vol% or more. Further preferably, the oxidant is air and/or oxygen, more preferably oxygen.

According to the method for preparing styrene by ethylbenzene dehydrogenation provided by the invention, the amount of the oxidant is related to the addition amount of ethylbenzene, so that the oxidative dehydrogenation of ethylbenzene can be realized, and preferably, the volume ratio of the ethylbenzene to the oxidant calculated by oxygen is 1: (0.1-2), preferably 1: (0.6-1.2).

According to the method for preparing styrene by ethylbenzene dehydrogenation provided by the invention, the total volume content of ethylbenzene and oxidant in the mixed gas is preferably 3.5-35%, and preferably 5.5-10%.

According to a preferred embodiment of the present invention, the ethylbenzene dehydrogenation reaction conditions comprise: the temperature is 350-580 ℃, and the space velocity of the mixed gas is 1000-18000 mL/g.h; preferably, the temperature is 450-550 ℃, and the space velocity of the mixed gas is 6000-12000 mL/g-h.

The present invention will be described in detail below by way of examples. In the following examples, the contents of boron, nitrogen and phosphorus in the modified nanodiamond were determined by the amounts of the charged materials; specific surface area, pore volume and average pore diameter of the modified nanodiamond catalyst N was tested by a Tristar 3000 type physical adsorber from Micromeritics, usa₂Adsorption-desorption isotherm and specific surface area, with N₂As adsorbates, the samples were subjected to vacuum pretreatment at 300 ℃ and the specific surface area, pore volume and pore diameter of the catalyst samples were calculated by the BET method and the BJH method.

The raw materials used in the examples are all commercially available products. Wherein the nano-diamond is commercially available from Reliter technology Limited of Beijing, and has a specification of 4-6 nm.

Example 1

(1) At room temperature (25 ℃, the same below), adding boric acid equivalent to 0.031 g boron into 3ml water, stirring to dissolve, after dissolving, dissolving ammonium carbonate equivalent to 0.248 g nitrogen into the solution (a large amount of bubbles are generated in the process), after forming a uniform and stable solution, adding 0.721g nano diamond powder, and carrying out ultrasonic treatment for 60min to form a suspension;

(2) drying the suspension obtained in the step (1) in an oven at 130 ℃ for 5 h; then carrying out precalcination for 2h at 400 ℃ in air atmosphere; and finally, calcining at 700 ℃ in an argon atmosphere for 7 hours to prepare the modified nano-diamond S-1, wherein the composition and parameters of the modified nano-diamond S-1 are shown in Table 1. SEM images of the modified nano-diamond S-1 under different magnifications are shown in figure 1, and as can be seen from figure 1, macropores are hardly seen on the surface of the boron-nitrogen modified nano-diamond and are all fine micropores.

Comparative example 1

Following the procedure of example 1, except that ammonium carbonate was not added in step (1), i.e. no nitrogen source was introduced, the specific step (1) included:

boric acid equivalent to 0.031 g boron is added into 3ml water to be stirred and dissolved at room temperature, then 0.969g nano diamond powder is added, and ultrasonic treatment is carried out for 60min to form suspension.

The modified nanodiamond prepared in this comparative example was denoted as modified nanodiamond D-1, and the composition and parameters of modified nanodiamond D-1 are shown in table 1.

Comparative example 2

The process of example 1 is followed except that no boric acid is added in step (1), i.e. no boron source is introduced, and a specific step (1) comprises:

ammonium carbonate equivalent to 0.248 g of nitrogen was added to 3ml of water at room temperature, stirred and dissolved (a large amount of bubbles were generated in the process), and then 0.752g of nano-diamond powder was added, and subjected to ultrasonic treatment for 60min to form a suspension.

The modified nanodiamond prepared in this comparative example was denoted as modified nanodiamond D-2, and the composition and parameters of modified nanodiamond D-2 are shown in table 1.

Example 2

(1) Adding boric acid equivalent to 0.02 g of boron into 3ml of water at room temperature, stirring and dissolving, dissolving ammonium carbonate equivalent to 0.30 g of nitrogen into the solution after dissolving (a large amount of bubbles are generated in the process), adding 0.68g of nano diamond powder after forming uniform and stable solution, and carrying out ultrasonic treatment for 60min to form suspension;

(2) drying the suspension obtained in the step (1) in an oven at 130 ℃ for 5 h; then carrying out precalcination for 2h at 400 ℃ in air atmosphere; and finally, calcining at 800 ℃ in argon atmosphere for 6 hours to prepare the modified nano-diamond S-2, wherein the composition and parameters of the modified nano-diamond S-2 are shown in Table 1.

Example 3

(1) At room temperature, adding boric acid equivalent to 0.065 g of boron into 3ml of water, stirring and dissolving, after dissolving, dissolving ammonium carbonate equivalent to 0.26 g of nitrogen into the solution (a large amount of bubbles are generated in the process), after forming uniform and stable solution, adding 0.675g of nano-diamond powder, and carrying out ultrasonic treatment for 60min to form suspension;

(2) drying the suspension obtained in the step (1) in an oven at 130 ℃ for 5 h; then carrying out precalcination for 2h at 500 ℃ in air atmosphere; and finally, calcining at 900 ℃ in an argon atmosphere for 5 hours to prepare the modified nano-diamond S-3, wherein the composition and parameters of the modified nano-diamond S-3 are shown in Table 1.

Example 4

(1) At room temperature, adding boric acid equivalent to 0.10 g of boron into 3ml of water, stirring and dissolving, after dissolving, dissolving ammonium carbonate equivalent to 0.10 g of nitrogen into the solution (a large amount of bubbles are generated in the process), after forming uniform and stable solution, adding 0.80g of nano diamond powder, and carrying out ultrasonic treatment for 60min to form suspension;

(2) drying the suspension obtained in the step (1) in an oven at 130 ℃ for 5 h; then carrying out precalcination for 2h at 500 ℃ in air atmosphere; and finally, calcining at 900 ℃ in an argon atmosphere for 5 hours to prepare the modified nano-diamond S-4, wherein the composition and parameters of the modified nano-diamond S-4 are shown in Table 1.

Example 5

According to the method of example 1, except that the suspension obtained in step (1) further contains citric acid, the specific step (1) comprises:

(1) adding 0.36 g of citric acid into 3ml of water at room temperature, stirring and dissolving, dissolving boric acid equivalent to 0.031 g of boron into the solution after dissolution, dissolving ammonium carbonate equivalent to 0.248 g of nitrogen into the solution (a large amount of bubbles are generated in the process), adding 0.721g of nano diamond powder after uniform and stable solution is formed, and performing ultrasonic treatment for 60min to form suspension.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-5, and the composition and parameters of modified nanodiamond S-5 are shown in table 1.

Example 6

According to the method of example 1, except that the suspension obtained in step (1) further contains citric acid, the specific step (1) comprises:

(1) at room temperature, adding 1.442 g of citric acid into 3ml of water, stirring and dissolving, after dissolving, dissolving boric acid equivalent to 0.031 g of boron into the solution, dissolving ammonium carbonate equivalent to 0.248 g of nitrogen into the solution (a large amount of bubbles are generated in the process), after forming a uniform and stable solution, adding 0.721g of nano diamond powder, and carrying out ultrasonic treatment for 60min to form a suspension.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-6, and the composition and parameters of modified nanodiamond S-6 are shown in table 1.

Example 7

According to the method of example 1, except that the suspension obtained in step (1) further contains citric acid, the specific step (1) comprises:

(1) adding 0.721g of citric acid into 3ml of water at room temperature, stirring and dissolving, dissolving boric acid equivalent to 0.031 g of boron into the solution after dissolution, dissolving ammonium carbonate equivalent to 0.248 g of nitrogen into the solution (a large amount of bubbles are generated in the process), adding 0.721g of nano diamond powder after uniform and stable solution is formed, and performing ultrasonic treatment for 60min to form suspension.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-7, and the composition and parameters of modified nanodiamond S-7 are shown in table 1.

Example 8

The method of example 1 was followed, except that the suspension obtained in step (1) further contained ammonium dihydrogen phosphate, and the specific step (1) included:

(1) at room temperature, boric acid equivalent to 0.031 g boron is dissolved in 3ml water, and stirred to dissolve, after dissolution, ammonium carbonate equivalent to 0.248 g nitrogen is dissolved in the solution (a large amount of bubbles are generated in the process), then ammonium dihydrogen phosphate equivalent to 0.0026 g phosphorus is added into the solution, after a uniform and stable solution is formed, 0.721g nano diamond powder is added, and after ultrasonic treatment is carried out for 60min, a suspension is formed.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-8, and the composition and parameters of modified nanodiamond S-8 are shown in table 1.

Example 9

The method of example 1 was followed, except that the suspension obtained in step (1) further contained ammonium dihydrogen phosphate, and the specific step (1) included:

(1) at room temperature, boric acid equivalent to 0.031 g boron is dissolved in 3ml water, stirred and dissolved, ammonium carbonate equivalent to 0.248 g nitrogen is dissolved in the solution after dissolution (a large amount of bubbles are generated in the process), ammonium dihydrogen phosphate equivalent to 0.031 g phosphorus is added into the solution, 0.69g nano diamond powder is added after uniform and stable solution is formed, and ultrasonic treatment is carried out for 60min to form suspension.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-9, and the composition and parameters of modified nanodiamond S-9 are shown in Table 1.

Example 10

The method of example 1 was followed, except that the suspension obtained in step (1) further contained ammonium dihydrogen phosphate, and the specific step (1) included:

(1) at room temperature, boric acid equivalent to 0.05 g of boron is dissolved in 3ml of water and stirred for dissolution, ammonium carbonate equivalent to 0.248 g of nitrogen is dissolved in the solution (a large amount of bubbles are generated in the process), ammonium dihydrogen phosphate equivalent to 0.012 g of phosphorus is added into the solution, 0.69g of nano diamond powder is added after uniform and stable solution is formed, and ultrasonic treatment is carried out for 60min to form suspension.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-10, and the composition and parameters of modified nanodiamond S-10 are shown in Table 1.

Example 11

The process of example 1 is followed except that step (2) precalcination and calcination are both in an air atmosphere and at a temperature of 700 ℃, with the specific step (2) comprising:

(2) drying the suspension obtained in the step (1) in an oven at 130 ℃ for 5 h; and calcining at 700 ℃ for 9 hours in air atmosphere to prepare the modified nano-diamond S-11, wherein the composition and parameters of the modified nano-diamond S-11 are shown in Table 1.

Example 12

The process of example 1 was followed except that ammonium carbonate was added in step (1) at a different amount, and the specific step (1) included:

(1) at room temperature, boric acid equivalent to 0.031 g boron is added into 3ml water to be stirred and dissolved, ammonium carbonate equivalent to 0.031 g nitrogen is dissolved in the solution after the boric acid is dissolved (a large amount of bubbles are generated in the process), 0.938g nano diamond powder is added after the uniform and stable solution is formed, and the suspension is formed after ultrasonic treatment is carried out for 60 min.

The modified nanodiamond prepared in this example was designated as modified nanodiamond S-12, and the composition and parameters of modified nanodiamond S-12 are shown in Table 1.

TABLE 1

Test example 1

The test example is used for illustrating the catalytic performance of the modified nano-diamond provided by the invention in the process of ethylbenzene oxidative dehydrogenation.

The ethylbenzene oxidative dehydrogenation reaction is carried out in an isothermal fixed bed reactor, the modified nano-diamond prepared in the above examples and comparative examples and the commercially available nano-diamond are respectively used as catalysts, the loading amount of the catalysts is 150mg, the reaction temperature is 450 ℃, the flow rate of the reaction gas is 30mL/min, and the ethylbenzene content is 2.9 vol%, the oxygen content is 2.9 vol%, and the balance is helium in the reaction gas. The ethylbenzene conversion and styrene selectivity at 16 hours after the reaction are shown in Table 2.

TABLE 2

As can be seen from the results in table 2, when the modified nanodiamond provided by the present invention is used as a catalyst, the reaction temperature is 450 ℃, the amount of the catalyst is 150mg, the total flow of the reaction gas is 30ml/min, and the molar ratio of ethylbenzene to oxygen is 1: 1 hour, after stable operation for 16 hours, the conversion rate can reach more than 48.9 percent, the selectivity can reach more than 89.4 percent, and better technical effects are achieved.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.