High-sulfur petroleum coke-based ordered mesoporous carbon and preparation method thereof

Abstract

The invention discloses high-sulfur petroleum coke-based ordered mesoporous carbon and a preparation method thereof.The preparation method comprises the following steps that smashed high-sulfur petroleum coke particles are subjected to mixed oxidation treatment through concentrated sulfuric acid and concentrated nitric acid, and an amphiphilic carbon material is obtained; uniformly mixing the alkaline silicon dioxide colloidal solution with a cationic surfactant to obtain a template material; the preparation method comprises the following steps: proportionally dispersing an amphiphilic carbon material and a template material in an alkaline solution according to a mass ratio of the amphiphilic carbon material to silicon dioxide of 1: (30-50), and then carrying out a hydrothermal reaction; and carbonizing the hydrothermal product in an inert atmosphere, and etching, washing and drying the carbonized product to obtain the high-sulfur petroleum coke-based ordered mesoporous carbon. The method can effectively solve the problems that a common preparation method in the background art can cause the existence of a large number of micropores in porous carbon, the pore structure is disordered and the energy consumption is high.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy material preparation, and particularly relates to a high-sulfur petroleum coke-based ordered mesoporous carbon and a preparation method thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Ordered mesoporous carbon materials have unique pore size distributions, large specific surface areas, good pore structure stability, and excellent mechanical strength, and are widely used in fields such as electrode materials and catalyst carriers for fuel cells and supercapacitors. High-sulfur petroleum coke has a high carbon content, good thermal stability, low ash content, and low price. Preparing mesoporous carbon from this as a raw material meets China's current energy and environmental protection requirements.

[0004] As a solid carbonaceous material obtained by high-temperature pyrolysis of heavy residues generated during the petroleum refining process, high-sulfur petroleum coke has a high degree of graphitization. Chemical activation methods or physical-chemical combined activation methods are mostly used to prepare high-sulfur petroleum coke-based porous carbon. Although it has a high specific surface area, the prepared porous carbon has a large number of micropores. A large amount of activator and high energy consumption are required for pore expansion, and the degree of pore expansion is still very limited. Excessively large pores will reduce the specific surface area and storage capacity of the material, while excessively small pores will limit the diffusion and adsorption capacity of substances. Moreover, the chemical reaction conditions during the chemical activation process are difficult to precisely control, the pore structure is disordered, and it is easy to cause structural defects in the pore walls, affecting the stability, mechanical strength, conductivity, adsorption capacity, etc. of the pore material, restricting the high-performance application of porous carbon. Therefore, there is an urgent need to develop a method with high precision and low energy consumption to ensure that the porous carbon material has ordered, stable, and controllable rich mesopores. Summary of the Invention

[0005] To solve the problems in the background art that the common preparation methods will cause a large number of micropores in the porous carbon, disordered pore structure, and high energy consumption, the present invention proposes a high-sulfur petroleum coke-based ordered mesoporous carbon and a preparation method thereof.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] In a first aspect, the present invention provides a preparation method of a high-sulfur petroleum coke-based ordered mesoporous carbon, including the following steps:

[0008] Crushed high-sulfur petroleum coke particles are subjected to a mixed oxidation treatment with concentrated sulfuric acid and concentrated nitric acid to obtain an amphiphilic carbon material;

[0009] An alkaline silica sol solution and a cationic surfactant are mixed evenly to obtain a template material;

[0010] Disperse the amphiphilic carbon material and the template material in an alkaline solution in a certain proportion. The mass ratio of the amphiphilic carbon material to silicon dioxide is 1:30 - 50, and then carry out a hydrothermal reaction;

[0011] Carbonize the hydrothermal product in an inert atmosphere. After the carbonized product is etched, washed with water, and dried, highly sulfurous petroleum coke-based ordered mesoporous carbon is obtained.

[0012] In an alkaline environment, the hydroxyl groups (Si-OH) on the silicon surface will react with OH- ions, losing a hydrogen ion to form negatively charged silicate (Si-O-), making the silica colloidal solution carry a negative charge, so that it can undergo electrostatic adsorption with the cationic surfactant carrying a positive charge.

[0013] The main function of the cationic surfactant: The cationic surfactant carries a positive charge and is adsorbed onto the surface of negatively charged silica particles through electrostatic binding, gradually neutralizing and then reversing the surface negative charge to form a template material with an overall positive charge.

[0014] Since the amphiphilic carbon material is soluble in alkali but insoluble in acid, in order to make the amphiphilic carbon material soluble and better combine with the template material, an alkaline environment is adopted during the hydrothermal reaction.

[0015] In an alkaline environment, the amphiphilic carbon material exists in the form of a colloid and carries a negative charge. If no cationic surfactant is added, the amphiphilic carbon material and the silica colloidal particles will repel each other negatively, affecting the combination effect of the two.

[0016] Compared with other methods of changing the charge property, adding a cationic surfactant is simple in operation and can be completely removed during the subsequent calcination process, reducing impurity doping.

[0017] Since the amphiphilic carbon material is soluble in alkali but insoluble in acid, in order to make the amphiphilic carbon material soluble and better combine with the template material, an alkaline environment is adopted during the hydrothermal reaction.

[0018] In some embodiments, the particle size of the crushed highly sulfurous petroleum coke particles is 80 - 140 mesh.

[0019] In some embodiments, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:1 - 3:1.

[0020] Preferably, the time for the mixed oxidation treatment is 2 - 6 h, and the oxidation treatment temperature is 40 - 100 °C.

[0021] In some embodiments, the particle size of silica in the alkaline silica colloidal solution is 10 - 50 nm, and the mass fraction of silica is 20 - 30%.

[0022] Preferably, the mass ratio of the alkaline silica sol to the cationic surfactant is 20 - 50:1.

[0023] More preferably, when mixing the alkaline silica sol with the cationic surfactant, the stirring temperature is 20 - 80 °C and the stirring time is 1 - 4 h.

[0024] In some embodiments, the cationic surfactant is cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, cetyltrimethylammonium chloride, or octadecyltrimethylammonium chloride.

[0025] In some embodiments, the alkaline solution is sodium hydroxide solution, potassium hydroxide solution, or ammonia water solution, and its pH value is 12 - 14.

[0026] In some embodiments, the temperature of the hydrothermal reaction is 100 - 300 °C, and the time of the hydrothermal reaction is 6 - 48 h.

[0027] In some embodiments, the temperature of carbonization is 600 - 1000 °C, and the carbonization time is 1 - 3 h.

[0028] In some embodiments, the etching solution used for etching is hydrofluoric acid, sodium hydroxide solution, or potassium hydroxide solution.

[0029] In a second aspect, the present invention provides a high-sulfur petroleum coke-based ordered mesoporous carbon prepared by the above preparation method.

[0030] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0031] The present invention mixes an amphiphilic carbon material with an alkaline silica sol modified by a cationic surfactant and conducts a hydrothermal reaction in the presence of an alkaline solution. Since the amphiphilic nano-carbon has a negatively charged surface in the alkaline solution and the silica sol particles form a support template after modification and have a positively charged surface, the two are adsorbed by electrostatic force, forming a preliminary stable composite structure during the hydrothermal reaction, and carbonization is carried out at a certain temperature to promote the deposition of the amphiphilic nano-carbon on the template surface, thereby effectively improving the orderliness and performance of the mesoporous carbon.

[0032] Using inexpensive by-products of refineries, high-sulfur petroleum coke, as a carbon source and modified alkaline silica sol as a template, an ordered mesoporous carbon with a high mesopore volume and highly concentrated pore diameters is synthesized, and the carbonization temperature is relatively low, reducing energy consumption. Customizing the reaction conditions according to application requirements can meet the storage and transmission requirements of molecules or ions of different sizes, has good comprehensive performance, realizes the high-value utilization of high-sulfur petroleum coke, and can be used as an adsorbent for macromolecular pollutants, a carrier for catalysts, and an electrode material for supercapacitors, etc.

[0033] The present invention synthesizes ordered mesoporous carbon with high mesopore volume, highly concentrated pore size, and adjustable pore size, realizing the high-value utilization of high-sulfur petroleum coke, which can be used as an adsorbent for macromolecular pollutants, a carrier for catalysts, and an electrode material for supercapacitors, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0035] Figure 1 It is a flow chart of an experiment for preparing high-sulfur petroleum coke-based ordered mesoporous carbon by a hard template method provided for an embodiment of the present invention;

[0036] Figure 2 It is the nitrogen adsorption-desorption isotherm and pore size distribution diagram of the high-sulfur petroleum coke-based ordered mesoporous carbon prepared in Example 1 of the present invention;

[0037] Figure 3 It is the scanning electron microscope image of the high-sulfur petroleum coke-based ordered mesoporous carbon prepared in Example 1 of the present invention;

[0038] Figure 4 It is the pore size distribution diagram of the carbon materials prepared in Example 1 and Comparative Example 1 of the present invention;

[0039] Figure 5 It is the pore size distribution diagram of the carbon materials prepared in Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] This example provides a method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon by a hard template method. The experimental process is shown in Figure 1 and includes the following steps:

[0044] 1) Weigh 2.5 g of 140-mesh high-sulfur petroleum coke and put it into a 500-ml beaker. Add 35 ml of concentrated sulfuric acid and 15 ml of concentrated nitric acid, and oxidize at 80 °C for 3 h to finally obtain an amphiphilic carbon material;

[0045] 2) Weigh 2 g of cetyltrimethylammonium bromide and 60 g of alkaline silica sol (particle size 10 - 15 nm), mix them evenly, and stir for 20 min at 50 °C to obtain a silica template;

[0046] 3) Weigh 1.2 g of the amphiphilic carbon material obtained in step 1), add the silica template obtained in step 2) and 20 ml of 0.01 mol / L sodium hydroxide solution, stir for 2 h, then pour it into a reaction kettle, place it in a forced-air drying oven and keep it at 100 °C for 24 h. The hydrothermal product after suction filtration is dried at 80 °C;

[0047] 4) Put the dried hydrothermal product obtained in step 3) into a tubular furnace for carbonization. Heat it to 800 °C at a rate of 1 °C / min under an argon atmosphere and keep it for 2 h. After the carbonized product is etched with hydrofluoric acid, wash it with deionized water until the pH is neutral, and finally dry the obtained black solid at 80 °C, which is the high-sulfur petroleum coke-based ordered mesoporous carbon. The proportion of different pore sizes is shown in Table 1.

[0048] Table 1 Proportion of different pore sizes of the ordered mesoporous carbon prepared in Example 1

[0049]

[0050] Figure 3 This is the scanning electron microscope image of the high-sulfur petroleum coke-based ordered mesoporous carbon prepared in Example 1 of the present invention, Figure 2 This is the nitrogen adsorption-desorption isotherm and pore size distribution diagram of the carbon material prepared in Example 1 of the present invention. An obvious hysteresis loop is formed between the adsorption and desorption curves in the figure, showing the characteristics of typical mesoporous materials. The pore size of the material is highly concentrated at about 8 - 10 nm, indicating that its pore structure is uniform and ordered. Table 1 also shows that the carbon material prepared in Example 1 of the present invention has a relatively large mesopore proportion, that is, the above method can successfully prepare high-sulfur petroleum coke-based ordered mesoporous carbon.

[0051] Example 2

[0052] The difference between this example and Example 1 is:

[0053] When performing step 2), weigh 2 g of cetyltrimethylammonium bromide and 60 g of alkaline silica sol (particle size 20 - 25 nm), mix them evenly, and stir for 20 min at 50 °C to obtain a silica template. Other conditions are the same as those in Example 1.

[0054] Example 3

[0055] The difference between this example and Example 1 is:

[0056] When performing step 2), weigh 2 g of cetyltrimethylammonium bromide and 60 g of basic silica sol (particle size 30 - 35 nm), mix them evenly, and stir at 50 °C for 20 min to obtain a silica template. All other conditions are the same as in Example 1.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 is that when performing step 2), weigh 0 g of cetyltrimethylammonium bromide and 60 g of basic silica sol (particle size 10 - 15 nm), mix them evenly, and stir at 50 °C for 20 min to obtain a silica template. All other conditions are the same as in Example 1.

[0059] Figure 4 This is the pore size distribution diagram of the carbon materials prepared in Example 1 and Comparative Example 1 of the present invention. As can be seen from the figure, the curve of Comparative Example 1 is flat, the pore size distribution is broader, the pore structure is not uniform enough, the overall pore volume contribution is small, and the degree of pore structure development is lower than that of Example 1.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that when performing step 3), weigh 1.2 g of the amphiphilic carbon material obtained in step 1), add the silica template obtained in step 2) and 20 ml of deionized water, stir for 2 h, then pour it into a reaction kettle, place it in a blast drying oven and keep it at 100 °C for 24 h, and dry the hydrothermal product after filtration at 80 °C. All other conditions are the same as in Example 1.

[0062] Figure 4 and Figure 5 respectively show the comparison of the pore size distributions of Example 1, Comparative Example 1, and Comparative Example 2. It can be seen from the figure that the mesopore distribution in Example 1 is significantly better than that in Comparative Example 1 and Comparative Example 2. In contrast, the curves of Comparative Example 1 and Comparative Example 2 are low and gentle, lacking a significant mesopore structure, indicating that their pore size distributions are broad, the pore structures are disordered, and the degree of pore development is low.

[0063] Table 2 shows the pore structure data of the carbon materials prepared in Example 1 and Comparative Examples 1 - 2

[0064]

[0065] a BET specific surface area, calculated from the N2 adsorption isotherm; b Total pore volume, calculated at a relative pressure (P / Po) of 0.99; c Micropore volume, calculated according to the t-plot method; d Mesopore volume, calculated according to the BJH method; e Average pore size, according to the formula 4Vtotal / S BET Calculated.

[0066] Further analysis in combination with the data in Table 2 shows that Example 1 exhibits the following significant advantages: The specific surface area of Example 1 is as high as 709 m 2 / g, compared with Comparative Example 1 (171 m 2 / g) and Comparative Example 2 (70 m 2 / g), this significant improvement is attributed to the successful use of the template and the optimized preparation process in the present invention, which results in a more developed mesoporous structure in the material; the total pore volume of Example 1 is 1.33 cm 3 / g, compared with Comparative Example 1 (0.33 cm 3 / g) and Comparative Example 2 (0.07 cm 3 / g), the high pore volume indicates that the material of the present invention has a higher porosity and can provide more active sites for adsorption and catalysis; the micropore volume of Example 1 (0.06 cm 3 / g) is slightly higher than that of Comparative Example 1 (0.02 cm 3 / g) and Comparative Example 2 (0.02 cm 3 / g), but the mesopore volume (1.25 cm 3 / g) is much higher than that of Comparative Example 1 (0.22 cm 3 / g) and Comparative Example 2 (0.05 cm 3 / g), indicating that the preparation method of the present invention focuses more on the controllable construction of the mesoporous structure, thus significantly improving the overall performance of the material.

[0067] The above results show that the ordered mesoporous carbon material based on high-sulfur petroleum coke can be successfully prepared by using the method of the embodiment of the present invention, ensuring that the pore structure of the porous carbon is ordered, stable and controllable, and having certain technical advantages.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon, characterized in that: The steps include: The crushed high-sulfur petroleum coke particles are subjected to a mixed oxidation treatment with concentrated sulfuric acid and concentrated nitric acid to obtain an amphiphilic carbon material; The alkaline silica colloidal solution and the cationic surfactant are uniformly mixed to obtain a template material; The amphiphilic carbon material and the template material are dispersed in an alkaline solution in proportion, the mass ratio of the amphiphilic carbon material to silicon dioxide is 1:30-50, and then a hydrothermal reaction is carried out; The hydrothermal product is carbonized in an inert atmosphere, and the carbonized product is etched, washed with water, and dried to obtain high-sulfur petroleum coke-based ordered mesoporous carbon.

2. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The particle size of the crushed high-sulfur petroleum coke particles is 80-140 meshes.

3. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:1 to 3:1; Preferably, the mixed oxidation treatment time is 2 to 6 hours, and the oxidation treatment temperature is 40 to 100°C.

4. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The particle size of silicon dioxide in the alkaline silicon dioxide colloidal solution is 10-50 nm, and the mass fraction of silicon dioxide is 20-30%; Preferably, the mass ratio of the alkaline silica colloidal solution to the cationic surfactant is 20-50:1; Preferably, when the alkaline silica colloidal solution is mixed with the cationic surfactant, the stirring temperature is 20-80° C. and the stirring time is 1-4 h.

5. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The cationic surfactant is hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride or octadecyltrimethylammonium chloride.

6. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The alkaline solution is a sodium hydroxide solution, a potassium hydroxide solution or an ammonia solution, and its pH value is 12-14.

7. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 100-300° C., and the time of the hydrothermal reaction is 6-48 hours.

8. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The carbonization temperature is 600-1000° C., and the carbonization time is 1-3 hours.

9. The method for preparing high-sulfur petroleum coke-based ordered mesoporous carbon according to claim 1, characterized in that: The etching solution used in the etching is HF acid, sodium hydroxide solution or potassium hydroxide solution.

10. A high-sulfur petroleum coke-based ordered mesoporous carbon, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

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