A pitch-based hierarchical porous carbon material, and a preparation method and use thereof

Abstract

The present application relates to a kind of asphalt-based hierarchical porous carbon materials and its preparation method and purposes, the preparation method includes the following steps: (1) the asphalt raw material is obtained by being successively broken and sieved to the asphalt with softening point ≥110 ℃;(2) the asphalt raw material obtained in step (1) is mixed with magnesium carbonate and potassium carbonate, then ball milling is carried out, to obtain mixed raw material;(3) the mixed raw material obtained in step (2) is heated to the end point temperature 750-900 ℃ and is calcined under the condition of heat preservation, the product after calcination is successively washed and dried, to obtain asphalt-based hierarchical porous carbon material.The preparation method of asphalt-based hierarchical porous carbon material provided by the present application is simple, the chemical reagent used is mild, the equipment corrosion is less, and the adsorption of various VOCs shows excellent adsorption performance, and has good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorbents, in particular to a pitch-based hierarchical porous carbon material and a preparation method and use thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) are one of the main pollutants in the atmospheric environment, mainly including alkanes, aromatic hydrocarbons, alkenes, halogenated hydrocarbons, alcohols, esters, aldehydes, ketones and S / N-containing compounds, etc. VOCs can react with nitrogen oxides and sulfur oxides in the atmosphere to generate ozone and secondary organic aerosols (SOA), thereby causing haze and photochemical smog. Some VOCs can enter the human body through the skin and respiratory system, inducing various chronic diseases and malignant tumors, and seriously endangering human health. Therefore, VOCs treatment technology is a current research hotspot.

[0003] VOCs treatment technologies include thermal incineration, catalytic incineration, biodegradation, adsorption, condensation and membrane separation, etc. Among them, the adsorption technology has the characteristics of simple operation, mature process, low energy consumption, high efficiency and recyclability, and has been widely used in practical engineering. Adsorbent is the core of adsorption technology, and the structure and performance of adsorbent greatly affect the adsorption effect.

[0004] Hierarchical porous carbon is a kind of carbon material with hierarchical pore structure of micropore, mesopore and macropore. The microporous channels have excellent adsorption performance for small molecule VOCs; the large / mesoporous pores provide transmission channels and storage space for VOC molecules, improve the adsorption rate of VOCs, effectively increase the adsorption capacity, and also meet the adsorption of macromolecular VOCs. Therefore, hierarchical porous carbon has a significant development prospect in efficient removal of VOCs.

[0005] Asphalt is a common by-product in the process of coal tar processing and petroleum refining. At present, asphalt is mainly used in road and bridge construction and building waterproofing, and a small part is used for fuel combustion, which greatly reduces the economic value of asphalt. From the composition, asphalt is mainly composed of polycyclic, condensed ring aromatic hydrocarbons, with high carbon content and low ash content, which is an excellent precursor for preparing high-value-added porous carbon materials. The preparation methods of asphalt-based porous carbon materials usually include physical activation, template method and chemical activation method. Due to the low oxygen content in asphalt, the lack of active sites required for activation, it is difficult to prepare activated carbon with high specific surface area and rich pore structure by physical activation; the template method usually uses zeolite and mesoporous silica as a template agent, and the pore structure of the prepared porous carbon is single, and a large amount of strong acid such as hydrochloric acid and hydrofluoric acid needs to be added to remove the template agent during the preparation process, which does not meet the green and environmental protection development concept, and the price of the template agent is expensive, and the production cost is high; the chemical activation method usually uses strong alkali such as potassium hydroxide or sodium hydroxide to activate asphalt, which has high requirements for the corrosion resistance of equipment, and the product is mainly microporous with single pore structure.

[0006] Therefore, it is a problem to be solved at present to provide an asphalt-based hierarchical porous carbon material and a preparation method thereof and use it in the field of VOCs treatment. SUMMARY

[0007] In view of the above problems, the purpose of the present application is to provide an asphalt-based hierarchical porous carbon material and a preparation method and use thereof. Compared with the prior art, the preparation method of the asphalt-based hierarchical porous carbon material provided by the present application is simple, the chemical reagents used are mild, the corrosion to the equipment is small, and the adsorption performance of the asphalt-based hierarchical porous carbon material to various VOCs is excellent, which has good industrial application prospect.

[0008] In order to achieve the purpose of the present application, the following technical solutions are adopted:

[0009] In the first aspect, the present application provides a preparation method of an asphalt-based hierarchical porous carbon material, which comprises the following steps:

[0010] (1) crushing and sieving asphalt with a softening point of ≥110℃ in sequence to obtain asphalt raw materials;

[0011] (2) mixing the asphalt raw materials obtained in step (1), magnesium carbonate and potassium carbonate, and then ball milling to obtain a mixed raw material;

[0012] (3) heating the mixed raw material obtained in step (2) to a final temperature of 750-900℃ and calcining under the condition of heat preservation, and then washing and drying the calcined product in sequence to obtain an asphalt-based hierarchical porous carbon material.

[0013] In the present application, on the one hand, high softening point asphalt with a softening point ≥ 110°C is used as raw material, which has the following advantages: (1) good thermal stability, not easy to soften at high temperature, better thermal stability; (2) stronger oxidation resistance than low softening point asphalt, can resist the action of oxygen in the air and ultraviolet light, thereby having a longer service life; (3) strong adhesion, can firmly bond activated carbon particles together to form carbon blocks with higher strength; (4) lower impurity content, can reduce the impurity content in activated carbon and improve the purity and adsorption performance of activated carbon; (5) low price and wide source. On the other hand, potassium carbonate and magnesium carbonate are used as template agent and activator, which is mild and less corrosive to equipment. The produced magnesium oxide, potassium oxide and unreacted potassium carbonate can be recovered by washing, reducing production cost and meeting the development concept of green environmental protection.

[0014] The softening point is ≥ 110°C, for example, it can be 110°C, 112°C, 114°C, 116°C, 118°C or 120°C, but is not limited to the listed values, other unlisted values within the value range are also applicable.

[0015] The end point temperature is 750-900°C, for example, it can be 750°C, 780°C, 800°C, 820°C, 850°C, 880°C or 900°C, but is not limited to the listed values, other unlisted values within the value range are also applicable.

[0016] In the present application, by controlling the end point temperature of calcination within a specific range, the activation and pore forming effect can be improved, and the collapse of three-dimensional pore structure caused by excessive temperature can be avoided.

[0017] Preferably, the asphalt in step (1) includes any one or a combination of at least two of natural asphalt, coal tar pitch or petroleum pitch.

[0018] Preferably, the initial weight loss temperature of the asphalt is ≥ 300°C, for example, it can be 300°C, 320°C, 340°C, 360°C or 380°C, but is not limited to the listed values, other unlisted values within the value range are also applicable.

[0019] Preferably, the carbon residue rate of the asphalt is ≥ 35%, for example, it can be 35%, 36%, 38%, 40%, 42%, 44%, 46% or 48%, but is not limited to the listed values, other unlisted values within the value range are also applicable.

[0020] In the present application, the carbon residue rate of the asphalt is preferably controlled within a certain range, which can improve the yield of the asphalt-based hierarchical porous carbon material.

[0021] Preferably, the particle size of the asphalt raw material in step (1) is ≤40 mesh, for example, it can be 40-60 mesh, 60-100 mesh, 100-200 mesh or 200-400 mesh, but is not limited to the listed values, and other values not listed in the value range are also applicable, and preferably <200 mesh.

[0022] Preferably, the mass ratio of the asphalt raw material, magnesium carbonate and potassium carbonate in step (2) is 1:(0.5-6):(0.5-6), for example, it can be 1:0.5:0.5, 1:0.5:1, 1:0.5:2, 1:0.5:4, 1:0.5:6, 1:1:0.5, 1:2:0.5, 1:4:0.5 or 1:6:0.5, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] In the present application, by using magnesium carbonate and potassium carbonate as the template agent, accumulation during carbonization of the asphalt can be prevented, and primary pores can be formed by occupying space, and then new pores can be generated by etching and pore-forming of the carbon material under high temperature as the activator.

[0024] Preferably, the grinding balls used in the ball milling in step (2) include corundum balls.

[0025] Preferably, the ball milling time is 2-6 h, for example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0026] Preferably, the rotation speed of the ball milling is 250-350 r / min, for example, it can be 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min or 350 r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] Preferably, the ball milling is carried out in a ball milling tank with a polytetrafluoroethylene inner lining.

[0028] Preferably, the calcination in step (3) is carried out under a protective atmosphere.

[0029] Preferably, the protective atmosphere includes nitrogen and / or argon.

[0030] Preferably, the rate of temperature increase is 3-10℃ / min, for example, it can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] In the present application, the rate of temperature increase is preferably controlled, which can avoid the situation that the calcination efficiency is too low due to too long temperature increase time and is not conducive to controlling the decomposition rate of magnesium carbonate and potassium carbonate, affecting the generation of three-dimensional pore structure; at the same time, it can also avoid the situation that the pitch is not completely carbonized due to too short temperature increase time, reducing the yield of porous carbon.

[0032] Preferably, the calcination time is 30-120min, for example, it can be 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min or 120min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] In the present application, the calcination time is preferably controlled in a specific range, which can make the pore of the porous carbon material fully developed, increase the total pore volume and specific surface area, and realize the preparation of hierarchical porous carbon material, while avoiding the situation that the three-dimensional pore collapses seriously due to too long calcination time.

[0034] Preferably, the washing liquid used in step (3) includes water or acid solution.

[0035] Preferably, the washing is performed 1-2 times.

[0036] Preferably, the washing liquid includes hydrochloric acid solution.

[0037] Preferably, the concentration of the hydrochloric acid solution is 0.1-1mol / L, for example, it can be 0.1mol / L, 0.2mol / L, 0.4mol / L, 0.6mol / L, 0.8mol / L or 1mol / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0038] In the present application, the use of acid solution for washing can remove magnesium oxide, potassium oxide and unreacted potassium carbonate generated after calcination.

[0039] As a preferred technical solution of the first aspect of the present application, the preparation method comprises the following steps:

[0040] (1) crushing and screening bitumen with a softening point ≥110℃ in sequence to obtain bitumen raw material;

[0041] The asphalt includes any one or a combination of natural asphalt, coal pitch or petroleum pitch, the initial weight loss temperature of the asphalt is greater than or equal to 300 DEG C, the carbon residue rate of the asphalt is greater than or equal to 35%, and the particle size of the asphalt raw material is less than or equal to 40 mesh;

[0042] (2) mixing the asphalt raw material, magnesium carbonate and potassium carbonate obtained in step (1) in a mass ratio of 1:(0.5-6):(0.5-6), and then performing ball milling for 2-6 hours to obtain a mixed raw material;

[0043] (3) heating the mixed raw material obtained in step (2) to a final temperature of 750-900 DEG C at a rate of 3-10 DEG C / min under a protective atmosphere, and performing calcination under the condition of heat preservation for 30-120 minutes, washing the calcined product with water or a hydrochloric acid solution with a concentration of 0.1-1 mol / L, and then drying to obtain an asphalt-based hierarchical porous carbon material.

[0044] In a second aspect, the present application provides an asphalt-based hierarchical porous carbon material, which is obtained by the preparation method of the asphalt-based hierarchical porous carbon material according to the first aspect of the present application.

[0045] In a third aspect, the present application provides a use of the asphalt-based hierarchical porous carbon material according to the second aspect of the present application, which is used for adsorption or separation of VOCs gas.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] (1) The present application uses high softening point asphalt as raw material, which has the characteristics of wide source and low price, has better thermal stability and oxidation resistance than low softening point asphalt, and has higher adhesion and strength and lower impurity content, which can improve the purity and adsorption performance of the hierarchical porous carbon material.

[0048] (2) The present application uses potassium carbonate and magnesium carbonate as a template agent and an activator, which has mild properties and less corrosion to the equipment, and the produced magnesium oxide, potassium oxide and unreacted potassium carbonate can be recovered by washing, which reduces the production cost and meets the development concept of green environmental protection.

[0049] (3) The preparation method of the asphalt-based hierarchical porous carbon material provided by the present application is simple and easy to control, the specific surface area of the obtained asphalt-based hierarchical porous carbon material can reach 1026 m 2 / g or more, and has a hierarchical structure, and under the more optimal conditions, the specific surface area can reach 1268 m 2 / g or more.

[0050] (4) The asphalt-based hierarchical porous carbon material provided by the present application has excellent adsorption performance for various VOCs. For example, for adsorbing mixed VOCs steam containing formaldehyde, dichloromethane, toluene and ethyl acetate, the saturated adsorption capacity of formaldehyde can reach 60 mg / g or more, the saturated adsorption capacity of dichloromethane can reach 112 mg / g or more, the saturated adsorption capacity of toluene can reach 218 mg / g or more, and the saturated adsorption capacity of ethyl acetate can reach 368 mg / g or more; under more optimal conditions, the saturated adsorption capacity of formaldehyde can reach 119 mg / g or more, the saturated adsorption capacity of dichloromethane can reach 234 mg / g or more, the saturated adsorption capacity of toluene can reach 345 mg / g or more, and the saturated adsorption capacity of ethyl acetate can reach 851 mg / g or more. BRIEF DESCRIPTION OF DRAWINGS

[0051] Wax content, wt% is the N2sorption-desorption curve of the asphalt-based hierarchical porous carbon material obtained in Example 1-3 of the present application;

[0052] Penetration (25°C, 100 g, 5 s), (1 / 10 mm) is the DFT pore size distribution graph of the asphalt-based hierarchical porous carbon material obtained in Example 1-3 of the present application;

[0053] Softening point, °C is the N2sorption-desorption curve of the asphalt-based hierarchical porous carbon material obtained in Comparative Example 1-3 of the present application;

[0054] Extensibility is the DFT pore size distribution graph of the asphalt-based hierarchical porous carbon material obtained in Comparative Example 1-3 of the present application;

[0055] Solubility, wt% is the SEM graph of the asphalt-based hierarchical porous carbon material obtained in Example 1 of the present application;

[0056] Carbon residue, wt% is the XRD graph of the asphalt-based hierarchical porous carbon material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0057] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0058] Example 1

[0059] The present embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, which comprises the following steps:

[0060] (1) The asphalt raw material is obtained by crushing and sieving the asphalt with a softening point of 123℃ in sequence;

[0061] The particle size of the asphalt raw material is 200-400 mesh;

[0062] The asphalt is selected from deoiled asphalt of a refinery in North China, and the specific properties are shown in Table 1:

[0063] Table 1

[0064] Saturates, wt% 4.5 Aromatics, wt% 0 Gel, wt% 123 Asphaltene, wt% 0 Density (20°C), g / cm 3 ]] 1.065 Figure 1 99.82 Figure 1 38.59 Figure 2 2.7 Figure 2 13.7 Figure 3 47.2 Figure 3 36.4

[0065] (2) 1 g of the asphalt raw material obtained in step (1), 2.5 g of magnesium carbonate and 0.5 g of potassium carbonate were mixed in a ball mill tank lined with polytetrafluoroethylene at a mass ratio of 1:2.5:0.5, and then ball milling was performed at a rotation speed of 300 r / min for 4 h to obtain a mixed raw material;

[0066] (3) The mixed raw material obtained in step (2) was transferred to a corundum boat and placed in a horizontal tube furnace, and the temperature was raised to a final temperature of 800 ℃ at a rate of 5 ℃ / min under a nitrogen atmosphere, and then calcination was performed under the condition of heat preservation for 60 min. After the calcined product was cooled, it was washed with 50 mL of a hydrochloric acid solution with a concentration of 0.05 mol / L, and then vacuum filtration and drying at 80 ℃ for 12 h were performed to obtain an asphalt-based hierarchical porous carbon material.

[0067] Example 2

[0068] The present embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, which comprises the following steps:

[0069] (1) An asphalt with a softening point of 123 ℃ was crushed and sieved in sequence to obtain an asphalt raw material;

[0070] The particle size of the asphalt and the asphalt raw material is the same as that in Example 1;

[0071] (2) 1 g of the asphalt raw material obtained in step (1), 2.0 g of magnesium carbonate and 1.0 g of potassium carbonate were mixed in a ball mill tank lined with polytetrafluoroethylene at a mass ratio of 1:2.0:1.0, and then ball milling was performed at a rotation speed of 250 r / min for 2 h to obtain a mixed raw material;

[0072] (3) The mixed raw material obtained in step (2) was transferred to a corundum boat and placed in a horizontal tube furnace, and the temperature was raised to a final temperature of 600 ℃ at a rate of 3 ℃ / min under a nitrogen atmosphere, and then calcination was performed under the condition of heat preservation for 120 min. After the calcined product was cooled, it was washed with 50 mL of a hydrochloric acid solution with a concentration of 0.1 mol / L, and then vacuum filtration and drying at 80 ℃ for 12 h were performed to obtain an asphalt-based hierarchical porous carbon material.

[0073] Example 3

[0074] The embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, and the preparation method comprises the following steps:

[0075] (1) crushing and screening asphalt with a softening point of 123 DEG C in sequence to obtain asphalt raw materials;

[0076] The particle sizes of the asphalt and the asphalt raw materials are the same as those in Embodiment 1;

[0077] (2) mixing 1g of the asphalt raw materials obtained in step (1), 1.5g of magnesium carbonate and 1.5g of potassium carbonate in a mass ratio of 1:1.5:1.5 in a ball mill tank with a polytetrafluoroethylene lining, and then performing ball milling under the condition that the rotating speed is 350r / min for 6h to obtain mixed raw materials;

[0078] (3) transferring the mixed raw materials obtained in step (2) into a corundum boat and placing the corundum boat in a horizontal tube furnace, heating to a terminal temperature of 1000 DEG C at a rate of 10 DEG C / min under a nitrogen atmosphere, and performing calcination under the condition of heat preservation for 30min, washing the calcined product with 50mL of a hydrochloric acid solution with a concentration of 1mol / L after cooling, and then performing vacuum filtration and drying at 80 DEG C for 12h to obtain the asphalt-based hierarchical porous carbon material.

[0079] Embodiment 4

[0080] The embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, and the preparation method is different from that in Embodiment 1 only in that the addition amount of magnesium carbonate is 1.0g and the addition amount of potassium carbonate is 2.0g in step (2).

[0081] Embodiment 5

[0082] The embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, and the preparation method is different from that in Embodiment 1 only in that the addition amount of magnesium carbonate is 0.5g and the addition amount of potassium carbonate is 2.5g in step (2).

[0083] Embodiment 6

[0084] The embodiment provides a preparation method of an asphalt-based hierarchical porous carbon material, and the preparation method is different from that in Embodiment 1 only in that the total mass of magnesium carbonate and potassium carbonate is kept unchanged in step (2), the addition amount of magnesium carbonate is adjusted, and the mass ratio of magnesium carbonate to potassium carbonate is 0.3:7, that is, the mass ratio of asphalt raw materials, magnesium carbonate and potassium carbonate is 1:0.3:7.

[0085] Embodiment 7

[0086] The embodiment provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the total mass of the magnesium carbonate and the potassium carbonate is ensured unchanged in the step (2), the adding amount of the magnesium carbonate is adjusted, and the mass ratio of the magnesium carbonate and the potassium carbonate is 7:0.3, that is, the mass ratio of the asphalt raw material, the magnesium carbonate and the potassium carbonate is 1:7:0.3.

[0087] Embodiment 8

[0088] The embodiment provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the ball milling time is 1h in the step (2).

[0089] Embodiment 9

[0090] The embodiment provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the calcination time is 20min in the step (3).

[0091] Comparative example 1

[0092] The comparative example provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the magnesium carbonate is not added in the step (2), and the adding amount of the potassium carbonate is adjusted to 3g.

[0093] Comparative example 2

[0094] The comparative example provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the potassium carbonate is not added in the step (2), and the adding amount of the magnesium carbonate is adjusted to 3g.

[0095] Comparative example 3

[0096] The comparative example provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the petroleum-based asphalt with a softening point temperature of 85 DEG C is selected in the step (1).

[0097] Comparative example 4

[0098] The comparative example provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the calcination temperature is 700 DEG C in the step (3).

[0099] Comparative example 5

[0100] The comparative example provides a preparation method of the asphalt-based hierarchical porous carbon material, and the preparation method is only different from the embodiment 1 in that the calcination temperature is 950 DEG C in the step (3).

[0101] Taking the pitch-based graded porous carbon materials obtained in Examples 1-3 as an example, their N2 adsorption-desorption isotherms are as follows: Figure 4 As shown, from Figure 4 It can be seen that the adsorption isotherm conforms to the combination of IUPAC type I and type IV isotherms. The sharp rise of the adsorption isotherm in the low relative pressure range (p / p0<0.1) indicates that the sample contains a large number of micropores. Subsequently, the adsorption isotherm gradually increases with the increase of p / p0. At a relative pressure of 0.45, the adsorption-desorption isotherm shows an obvious hysteresis loop, which belongs to the H3 loop (IUPAC classification). The results show that the porous carbon material has a hierarchical structure, containing micropores, mesopores and macropores.

[0102] Taking the pitch-based graded porous carbon materials obtained in Examples 1-3 as examples, their DFT pore size distribution diagrams are as follows: Figure 5 As shown, from Figure 5 It can be seen that the product obtained by this invention has a wide pore size distribution, mainly consisting of micropores and mesopores, with some macropores also present, further confirming that the obtained pitch-based hierarchical porous carbon material has a hierarchical structure.

[0103] Taking the pitch-based porous carbon material obtained in Comparative Examples 1-3 as an example, its N2 adsorption-desorption isotherm curve is as follows: Figure 6 As shown, from Figure 6 As can be seen, Comparative Example 1 exhibits typical Type I adsorption isotherm characteristics. At low relative pressure (p / p0<0.1), the adsorption amount increases sharply with increasing relative pressure, then the increase slows down, and an adsorption plateau appears, indicating that the sample is mainly microporous. Comparative Example 2 exhibits typical Type IV adsorption isotherm characteristics. At low relative pressure (p / p0<0.1), the adsorption amount increases with increasing relative pressure, but the nitrogen adsorption amount is relatively small, indicating that its microporous content is low. It shows obvious hysteresis loops at relative pressures of 0.45-1.0, and the hysteresis loop belongs to the H3 loop (IUPAC classification), indicating that the sample is mainly mesoporous and macroporous. Comparative Example 3 conforms to the combination of IUPAC type I and type IV isotherms, and the hysteresis loop belongs to the H3 loop (IUPAC classification), indicating that the porous carbon material has a hierarchical structure, containing micropores, mesopores, and macropores.

[0104] Taking the pitch-based porous carbon materials obtained in Comparative Examples 1-3 as an example, their DFT pore size distribution diagrams are as follows: ​ As shown, from ​ It can be seen that Comparative Example 1 is mainly composed of micropores; Comparative Example 2 is mainly composed of mesopores and macropores; Comparative Example 3 contains both micropores and mesopores and macropores.

[0105] Taking Example 1 as an example, the SEM image of the pitch-based graded porous carbon material obtained in Example 1 is as follows: ​ As shown, from ​It can be seen that the obtained asphalt-based hierarchical porous carbon material presents a lamellar structure, and the surface of the material presents abundant pores, which is beneficial to the transmission of VOCs molecules in the adsorption process.

[0106] The XRD pattern of the asphalt-based hierarchical porous carbon material obtained in Example 1 is shown in FIG. 1. ​ ​ It can be seen that two relatively wide diffraction peaks are shown in the figure, indicating that the obtained asphalt-based hierarchical porous carbon material is amorphous carbon, and the positions of the diffraction peaks are 21° and 43°, respectively, corresponding to the (002) and (100) crystal planes in hexagonal graphite. The absence of other diffraction peaks in the figure indicates that the washing process can sufficiently remove the residual metal compounds after calcination.

[0107] Application Example 1

[0108] The application example provides a use of an asphalt-based hierarchical porous carbon material, which is prepared in Example 1, and a method for adsorbing VOCs mixed gas, which is as follows:

[0109] A dynamic adsorption method is used, and synthetic air is used as a carrier gas. VOCs vapors (formaldehyde, dichloromethane, toluene and ethyl acetate) with different kinetic diameters are generated by a bubbling method. The adsorption process of the porous carbon material obtained in Example 1 is carried out in a quartz tube with an inner diameter of 8 mm. The bubbling flow rate and the carrier gas flow rate are adjusted to keep the VOCs vapor concentration at 500 (±10) ppm, the total flow rate is 100 mL / min, the adsorption temperature is controlled at 25°C, the adsorbent dosage is 50 mg per adsorption test, an Agilent 7980A gas chromatograph is used to measure the outlet concentration of VOCs, a hydrogen flame ionization detector (FID) is used to measure the outlet concentration of VOCs, until the adsorption process reaches equilibrium, and the adsorption capacity is calculated according to the following formula:

[0110]

[0111] wherein q (mg / g) is the saturated adsorption capacity, Q (mL / min) is the total gas flow rate, C0 (mg / m 3 ) is the inlet concentration of VOCs vapor, C t (mg / m 3 ) is the outlet concentration of VOCs vapor at t, M (g) is the adsorbent dosage, and T e is the adsorption equilibrium time.

[0112] Application Example 2

[0113] The application example provides a use of an asphalt-based hierarchical porous carbon material, which is used for adsorbing VOCs mixed gas, and the difference between the method and Example 1 is only that the porous carbon material used is prepared in Example 2.​

[0114] Application Example 3

[0115] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 3.

[0116] Application Example 4

[0117] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 4.

[0118] Application Example 5

[0119] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 5.

[0120] Application Example 6

[0121] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 6.

[0122] Application Example 7

[0123] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 7.

[0124] Application Example 8

[0125] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 8.

[0126] Application Example 9

[0127] This application example provides a use of a pitch-based hierarchical porous carbon material for VOCs mixed gas adsorption, which is different from example 1 only in that the used porous carbon material is prepared by example 9.

[0128] Application Comparative Example 1

[0129] The present application comparative example provides a use of a pitch-based porous carbon material for VOCs mixed gas adsorption, the difference between the method and example 1 is only that the porous carbon material used is prepared by comparative example 1.

[0130] Application Comparative Example 2

[0131] The present application comparative example provides a use of a pitch-based porous carbon material for VOCs mixed gas adsorption, the difference between the method and example 1 is only that the porous carbon material used is prepared by comparative example 2.

[0132] Application Comparative Example 3

[0133] The present application comparative example provides a use of a pitch-based porous carbon material for VOCs mixed gas adsorption, the difference between the method and example 1 is only that the porous carbon material used is prepared by comparative example 3.

[0134] Application Comparative Example 4

[0135] The present application comparative example provides a use of a pitch-based porous carbon material for VOCs mixed gas adsorption, the difference between the method and example 1 is only that the porous carbon material used is prepared by comparative example 4.

[0136] Application Comparative Example 5

[0137] The present application comparative example provides a use of a pitch-based porous carbon material for VOCs mixed gas adsorption, the difference between the method and example 1 is only that the porous carbon material used is prepared by comparative example 5.

[0138] The specific surface area and pore structure of the porous carbon materials obtained in examples 1-9 and comparative examples 1-5 were tested on a specific surface area and pore size tester (ASAP2020plus, Micrometer), and the pretreatment condition was vacuum degassing at 200°C for 8h. The nitrogen adsorption-desorption isotherm of the obtained porous carbon material was determined at 77K, the specific surface area was calculated using the multipoint BET method, the micropore volume was calculated using the t-plot method, and the pore size distribution was calculated using the density functional theory (DFT) model, and the equation Dpore=4V T / S BET The average pore size was calculated. The obtained test analysis results are shown in Table 2.

[0139] The VOCs adsorption performance test results of application examples 1-9 and application comparative examples 1-5 are shown in Table 3.

[0140] Table 2

[0141]

[0142]

[0143] Table 3

[0144]

[0145] From the data of Table 2 and Table 3, the following points can be seen:

[0146] (1) From the data of Examples 1-9, it can be seen that the specific surface area of the asphalt-based hierarchical porous carbon material provided by the present application can reach 1026 m2 / g or more, and has a hierarchical structure, and under more optimal conditions, the specific surface area can reach 1268 m2 / g or more. Taking the example of being used for adsorbing mixed VOCs steam containing formaldehyde, dichloromethane, toluene and ethyl acetate, the saturated adsorption capacity of formaldehyde can reach 60 mg / g or more, the saturated adsorption capacity of dichloromethane can reach 112 mg / g or more, the saturated adsorption capacity of toluene can reach 218 mg / g or more, and the saturated adsorption capacity of ethyl acetate can reach 368 mg / g or more; under more optimal conditions, the saturated adsorption capacity of formaldehyde can reach 119 mg / g or more, the saturated adsorption capacity of dichloromethane can reach 234 mg / g or more, the saturated adsorption capacity of toluene can reach 345 mg / g or more, and the saturated adsorption capacity of ethyl acetate can reach 851 mg / g or more. 2 2 (2) From the data of Examples 1, 6-7 and Comparative Examples 1-2, Application Examples 1, 6-7 and Application Comparative Examples 1-2, it can be seen that the difference between Comparative Examples 1-2 and Example 1 is only that only any one of magnesium carbonate or potassium carbonate is used, the difference between Examples 6-7 and Example 1 is only that the ratio of asphalt raw material, magnesium carbonate and potassium carbonate is not within the preferred range of the present application, and the specific surface area of Example 1 is obviously superior to Examples 6-7 and Comparative Examples 1-2, and the saturated adsorption capacity of Application Example 1 is obviously superior to Application Examples 6-7 and Application Comparative Examples 1-2, thus it can be seen that by using magnesium carbonate and potassium carbonate together as an activator and a template, and preferably controlling the ratio of asphalt raw material, magnesium carbonate and potassium carbonate, the pore structure of the porous carbon material can be further controlled, thereby improving the adsorption performance.

[0147] (2) From the data of Examples 1, 6-7 and Comparative Examples 1-2, Application Examples 1, 6-7 and Application Comparative Examples 1-2, it can be seen that the difference between Comparative Examples 1-2 and Example 1 is only that only any one of magnesium carbonate or potassium carbonate is used, the difference between Examples 6-7 and Example 1 is only that the ratio of asphalt raw material, magnesium carbonate and potassium carbonate is not within the preferred range of the present application, and the specific surface area of Example 1 is obviously superior to Examples 6-7 and Comparative Examples 1-2, and the saturated adsorption capacity of Application Example 1 is obviously superior to Application Examples 6-7 and Application Comparative Examples 1-2, thus it can be seen that by using magnesium carbonate and potassium carbonate together as an activator and a template, and preferably controlling the ratio of asphalt raw material, magnesium carbonate and potassium carbonate, the pore structure of the porous carbon material can be further controlled, thereby improving the adsorption performance.

[0148] ​(3) From the data of Example 1, 8-9 and Application Example 1, 8-9, it can be seen that the difference between Example 8 and Example 1 is only that the ball milling time is not within the preferred range of the present application, the difference between Example 9 and Example 1 is only that the calcination time is not within the preferred range of the present application, the specific surface area of Example 1 is significantly better than that of Examples 8-9, and the saturated adsorption capacity of Application Example 1 is significantly better than that of Application Examples 8-9, thus it can be seen that the present application can promote the mixing of raw materials by preferably controlling the ball milling time to improve the pore forming effect, and can improve the activation and pore forming effect by preferably controlling the calcination time, so that the asphalt is fully carbonized, thereby greatly improving the adsorption performance.

[0149] (4) From the data of Example 1 and Comparative Examples 3-5, Application Example 1 and Application Comparative Examples 3-5, it can be seen that the difference between Comparative Example 3 and Example 1 is only that a low softening point asphalt is used, the difference between Comparative Examples 4-5 and Example 1 is only that the calcination temperature is not within the preferred range of the present application, the specific surface area of Example 1 is significantly better than that of Comparative Examples 3-5, and the saturated adsorption capacity of Application Example 1 is significantly better than that of Application Comparative Examples 3-5, thus it can be seen that the present application can improve the pore structure and adsorption performance of the porous carbon material by selecting a high softening point asphalt and controlling the calcination temperature.

[0150] In summary, the preparation method of the asphalt-based hierarchical porous carbon material provided by the present application is simple, the chemical reagents used are mild in nature and less corrosive to equipment, and the adsorption performance of the material for various VOCs is excellent, thus having good industrial application prospects.

[0151] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a pitch-based hierarchical porous carbon material, characterized by, The preparation method comprises the following steps: (1) crushing and screening bitumen with a softening point of ≥ 110℃ in sequence to obtain bitumen raw material; (2) mixing the bitumen raw material obtained in step (1), magnesium carbonate and potassium carbonate, and then ball milling to obtain mixed raw material; (3) heating the mixed raw material obtained in step (2) to a final temperature of 750-900℃ and calcining under the condition of heat preservation, and then washing and drying the calcined product in sequence to obtain bitumen-based hierarchical porous carbon material; The mass ratio of the bitumen raw material, magnesium carbonate and potassium carbonate in step (2) is 1:(0.5-2.5):(0.5-2.5).

2. The production method according to claim 1, characterized by, The bitumen in step (1) comprises any one or a combination of at least two of natural bitumen, coal tar pitch or petroleum pitch.

3. The preparation method according to claim 1, characterized in that, The bitumen has an initial weight loss temperature of ≥ 300℃.

4. The method of claim 1, wherein, The bitumen has a carbon residue rate of ≥ 35%.

5. The preparation method according to claim 1, characterized in that, The particle size of the bitumen raw material in step (1) is ≤ 40 mesh.

6. The production method according to claim 5, wherein The particle size of the bitumen raw material in step (1) is < 200 mesh.

7. The preparation method according to claim 1, characterized in that, The grinding ball used in the ball milling in step (2) comprises corundum ball.

8. The method of claim 1, wherein, The ball milling is performed for 2-6 h.

9. The method of claim 1, wherein, The rotation speed of the ball milling is 250-350 r / min.

10. The method of claim 1, wherein, The ball milling is performed in a ball mill tank with a polytetrafluoroethylene lining.

11. The method of claim 1, wherein, The calcining in step (3) is performed under a protective atmosphere.

12. The method of claim 11, wherein, The protective atmosphere comprises nitrogen and / or argon.

13. The method of claim 1, wherein, The heating rate is 3-10℃ / min.

14. The method of claim 1, wherein, The calcining is performed for 30-120 min.

15. The method of claim 1, wherein, The washing liquid used in the washing in step (3) comprises water or acid solution.

16. The method of claim 1, wherein, The washing is performed for 1-2 times.

17. The method of claim 15, wherein, The washing liquid comprises hydrochloric acid solution.

18. The method of claim 17, wherein, The concentration of the hydrochloric acid solution is 0.1-1 mol / L.

19. The method of claim 1, wherein, The preparation method comprises the following steps: (1) crushing and screening bitumen with a softening point of ≥ 110℃ in sequence to obtain bitumen raw material; The bitumen comprises any one or a combination of at least two of natural bitumen, coal tar pitch or petroleum pitch, the bitumen has an initial weight loss temperature of ≥ 300℃, the bitumen has a carbon residue rate of ≥ 35%, and the particle size of the bitumen raw material is ≤ 40 mesh; (2) mixing the bitumen raw material obtained in step (1), magnesium carbonate and potassium carbonate in a mass ratio of 1:(0.5-2.5):(0.5-2.5), and then ball milling for 2-6 h at a rotation speed of 250-350 r / min to obtain mixed raw material; (3) heating the mixed raw material obtained in step (2) to a final temperature of 750-900℃ at a rate of 3-10℃ / min under a protective atmosphere, and calcining under the condition of heat preservation for 30-120 min, and then washing the calcined product with water or hydrochloric acid solution with a concentration of 0.1-1 mol / L, and drying to obtain bitumen-based hierarchical porous carbon material.

20. A pitch-based hierarchically porous carbon material, characterized in that, The bitumen-based hierarchical porous carbon material is obtained by the preparation method of the bitumen-based hierarchical porous carbon material according to any one of claims 1-19.

21. Use of the pitch-based hierarchically porous carbon material according to claim 20, characterized in that, The bitumen-based hierarchical porous carbon material is used for adsorption or separation of VOCs gas.

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