Adsorbent based on benzene cracking deposition porous carbon, preparation method and application

Abstract

The invention provides an adsorbent based on benzene cracking deposition porous carbon, a preparation method and application, aiming at commercially available microporous carbon (the micropore proportion is greater than or equal to 85%), a medium-temperature low-concentration cracking process with the temperature of 720-760 DEG C and the benzene concentration of 15-25 vol% is adopted, and the pore diameter is reduced to 0.35-0.4 nm through small molecule hydrocarbon free radical deposition; the method comprises the following steps: aiming at commercially available mesoporous carbon (the mesopore ratio is greater than or equal to 70%), constructing gradient pores with the surface pore diameter of 0.5-0.6 nm and the interior of 1.0-1.5 nm by adopting a high-temperature high-concentration cracking process with the temperature of 850-900 DEG C and the benzene concentration of 30-40 vol%; the two kinds of adsorbent powder are directly used for an adsorption test, and the test result shows that the purity of C2H4 at an outlet after microporous carbon modification is larger than or equal to 99.5%, and the CO2 adsorption capacity is larger than or equal to 3.5 mmol / g; after mesoporous carbon modification, the purity of C2H4 at an outlet is greater than or equal to 99.1%, and the CO2 adsorption capacity is greater than or equal to 3.4 mmol / g.

Description

Technical Field

[0001] This invention relates to the field of gas adsorption and separation technology, and in particular to an adsorbent based on benzene cracking and deposited porous carbon, its preparation method, and its application. Background Technology

[0002] With rapid industrial development, the environmental problems caused by the large-scale emission of carbon dioxide are becoming increasingly severe. Meanwhile, in many industrial production processes, such as petrochemicals and natural gas purification, it is often necessary to separate CO2 and C2H4 from mixed gases. Currently, common methods for separating CO2 and C2H4 include absorption, membrane separation, and adsorption. Among these, absorption suffers from problems such as equipment corrosion and high energy consumption for absorbent regeneration; membrane separation faces challenges such as high membrane material costs and limited separation selectivity; adsorption, due to its simple operation and low energy consumption, has become a highly promising gas separation technology. However, existing adsorbents still have problems in separating CO2 and C2H4, such as insufficient adsorption capacity, low selectivity, and slow adsorption kinetics, making it difficult to meet the high-efficiency and economical requirements of industrial production. Summary of the Invention

[0003] In view of the above-mentioned problems in the existing technology, the present invention provides an adsorbent based on benzene cracking and deposited porous carbon, its preparation method and application, which improves the adsorption capacity and selectivity of the adsorbent for CO2.

[0004] The specific details of the invention are as follows: In a first aspect, the present invention provides a method for preparing an adsorbent based on benzene pyrolysis deposited porous carbon, the preparation method comprising: The microporous carbon was placed in a quartz tube furnace, purged with nitrogen, and heated to 720-760 ℃. The pressure of the quartz tube furnace is adjusted to 0.3-0.6 MPa, and a benzene vapor-nitrogen mixture is introduced into the quartz tube furnace. The benzene vapor undergoes a mild cracking reaction to generate products mainly composed of small molecule hydrocarbon free radicals. The small molecule hydrocarbon free radicals are deposited on the inner wall of the microporous carbon pores, causing the pore size of the microporous carbon to shrink and form the adsorbent. The small molecule hydrocarbon radicals include: -CH2- and / or -C2H3; In the benzene vapor-nitrogen mixture, the concentration of benzene vapor is 15-25 vol.

[0005] Optionally, the flow rate of the benzene vapor-nitrogen mixture is 3-8 mL / min; The mild pyrolysis reaction takes 3-4 hours.

[0006] Optionally, in the microporous carbon, the micropore content is ≥80%, the micropore diameter is 0.5-0.7 nm, and the specific surface area is 900-1100 m². 2 / g, total pore volume is 0.45-0.55 cm³ 3 / g.

[0007] Optionally, in the adsorbent, the micropore size is reduced to 0.35-0.4 nm.

[0008] In a second aspect, the present invention provides an adsorbent based on benzene pyrolysis deposited porous carbon, wherein the adsorbent is obtained by the preparation method described in the first aspect above.

[0009] Thirdly, the present invention provides a method for preparing an adsorbent based on benzene pyrolysis deposited porous carbon, characterized in that the preparation method includes: Mesoporous carbon was placed in a quartz tube furnace, purged with nitrogen, and heated to 850-900 ℃. The pressure of the quartz tube furnace is adjusted to 0.6-0.9 MPa, and a benzene vapor-nitrogen mixture is introduced into the quartz tube furnace. The benzene vapor undergoes a deep cracking reaction to generate a product mainly composed of macromolecular carbon nanoparticles. The macromolecular carbon nanoparticles are deposited on the surface of the mesoporous carbon and at the mesopore inlet, forming a carbon sieve layer. The mesoporous carbon retains mesopore channels inside and obtains the adsorbent. The macromolecular carbon nanoparticles are C n (n=3-5); The concentration of benzene vapor in the benzene vapor-nitrogen mixture is 30-40 vol.

[0010] Optionally, the flow rate of the benzene vapor-nitrogen mixture is 8-15 mL / min; The deep pyrolysis reaction takes 1.5-2.5 hours.

[0011] Optionally, in the mesoporous carbon, the proportion of mesopores is ≥70%, the mesopore diameter is 2.0-3.0 nm, and the specific surface area is 750-900 m². 2 / g, total pore volume is 0.60-0.70 cm³. 3 / g; In the adsorbent, the pore size at the mesopore inlet is reduced to 0.5-0.6 nm.

[0012] Fourthly, the present invention provides an adsorbent based on benzene pyrolysis deposited porous carbon, characterized in that the adsorbent is obtained by the preparation method described in the third aspect above.

[0013] Fifthly, the present invention provides an application of the adsorbent based on benzene cracking deposited porous carbon described in the second and fourth aspects above, wherein the adsorbent is used for the separation of CO2 and C2H4.

[0014] Compared with the prior art, the present invention has the following advantages: This invention provides a method for preparing adsorbents based on benzene pyrolysis deposition of porous carbon. For commercially available microporous carbon (micropore content ≥85%), a medium-temperature, low-concentration pyrolysis process at 720-760 °C and 15-25 vol% benzene concentration is used to reduce the pore size to 0.35-0.4 nm through small molecule hydrocarbon free radical deposition. For commercially available mesoporous carbon (mesopore content ≥70%), a high-temperature, high-concentration pyrolysis process at 850-900 °C and 30-40 vol% benzene concentration is used to construct a gradient pore structure with a surface pore size of 0.5-0.6 nm and an internal pore size of 1.0-1.5 nm. This invention directly uses the above two adsorbent powders for adsorption testing. The test results show that after modification, the purity of C2H4 at the outlet of the microporous carbon is ≥99.5%, and the CO2 adsorption capacity is ≥3.5 mmol / g; after modification, the purity of C2H4 at the outlet of the mesoporous carbon is ≥99.1%, and the CO2 adsorption capacity is ≥3.4 mmol / g. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A flowchart of the adsorbent preparation method based on benzene pyrolysis deposited porous carbon provided in an embodiment of the present invention is shown; Figure 2 This invention provides a flowchart of another method for preparing adsorbents based on benzene pyrolysis deposited porous carbon, according to an embodiment of the invention. Figure 3 A pore size distribution diagram of commercially available microporous carbon provided in an embodiment of the present invention is shown; Figure 4 A pore size distribution diagram of the modified microporous carbon provided in an embodiment of the present invention is shown; Figure 5 A pore size distribution diagram of commercially available mesoporous carbon provided in an embodiment of the present invention is shown; Figure 6 A pore size distribution diagram of the modified mesoporous carbon provided in an embodiment of the present invention is shown. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0018] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0019] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0020] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In the one-step synthesis of olefins from syngas, the product gas often contains CO2 impurities (the volume ratio of CO2 to C2H4 is typically 1:1-3:1), requiring CO2 removal to ensure C2H4 purity (industrial requirements ≥99%). Existing adsorbents (such as traditional porous carbon and molecular sieves) have two major problems: Low adsorption capacity: Poor matching degree between pore size and CO2 molecule diameter (about 0.33 nm), or easy blockage of pore structure, resulting in insufficient adsorption capacity of CO2 per unit mass of adsorbent; Poor selectivity: It cannot effectively distinguish the molecular differences between CO2 (0.33 nm) and C2H4 (approximately 0.39 nm), and the purity of C2H4 after separation is difficult to meet the standard.

[0022] Furthermore, existing porous carbon adsorption technologies based on benzene pyrolysis deposition mostly rely on precursors such as lignin and coal-based carbon to produce porous carbon in-house, which is complex and does not take advantage of the standardized pore structure of commercially available porous carbon. Moreover, existing porous carbon adsorption technologies based on benzene pyrolysis deposition mostly adopt a homogenized benzene pyrolysis process within a single temperature range, without designing differentiated control strategies for different pore structures, resulting in low pore size control precision.

[0023] To address the aforementioned problems, this invention develops a simple process and a method for precisely controlling the pore size of an adsorbent for the adsorption and separation of CO2 and C2H4. This invention also proposes a precise modification technology for porous carbon based on benzene pyrolysis deposition, achieving directional control of pore size through differentiated processes for microporous and mesoporous carbon, thus balancing high adsorption capacity and high selectivity. Specific implementation methods are as follows: In a first aspect, the present invention provides a method for preparing an adsorbent based on benzene pyrolysis-deposited porous carbon. Figure 1 A flowchart of the adsorbent preparation method based on benzene pyrolysis deposited porous carbon provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes: S101. Place the microporous carbon in a quartz tube furnace, purge with nitrogen, and heat to 720-760 ℃. In practical implementation, this invention uses commercially available finished microporous carbon, which not only eliminates the steps of carbon precursor pretreatment, carbonization and activation to prepare porous carbon carrier, but also has the advantage of standardized pore structure.

[0024] It should be noted that the nitrogen purging time should be controlled between 10 and 30 minutes to completely purge the air from the quartz tube furnace and remove the moisture and impurities adsorbed on the carbon surface.

[0025] S102. Adjust the pressure of the quartz tube furnace to 0.3-0.6 MPa, and introduce a benzene vapor-nitrogen mixture into the quartz tube furnace. The benzene vapor undergoes a mild cracking reaction to generate products mainly composed of small molecule hydrocarbon free radicals. The small molecule hydrocarbon free radicals are deposited on the inner wall of the pores of the microporous carbon, causing the pore size of the microporous carbon to shrink and forming the adsorbent. In practical implementation, the pore size of commercially available microporous carbon is larger than the molecular diameter of CO2 (0.33 nm) and C2H4 (approximately 0.39 nm). Directly using microporous carbon for adsorption treatment cannot effectively distinguish between CO2 (0.33 nm) and C2H4 (approximately 0.39 nm). This invention controls the mild cracking of benzene molecules to generate products mainly composed of small molecule hydrocarbon radicals (-CH2- and / or -C2H3). These small molecule radicals (-CH2- and / or -C2H3) with diameters of 0.33-0.38 nm are suitable for deposition on the inner wall of the micropores of microporous carbon. The small molecule radicals are uniformly deposited along the inner wall of the micropores through the deposition principle of in-pore diffusion-surface physical adsorption-CC bond combination, reducing the initial micropore size of the microporous carbon to the target range (0.35-0.4 nm), providing structural support for subsequent matching of CO2 molecule diameter and improving adsorption selectivity.

[0026] In specific implementation, this invention controls the degree of benzene cracking by controlling the reaction conditions. When the temperature in the quartz tube furnace is 720-760℃ and the pressure is 0.3-0.6 MPa, under these reaction conditions, benzene molecules undergo a mild cracking reaction, generating more small molecule hydrocarbon free radicals (-CH2- and / or -C2H3). At this temperature, the formation energy barrier of large molecule carbon nanoparticles (approximately 420 kJ / mol) is relatively high, and their proportion is relatively low, thereby avoiding micropore blockage.

[0027] In this embodiment, during the reaction process, the concentration of benzene vapor in the benzene vapor-nitrogen mixture is controlled to be 15-25 vol%. This concentration range ensures that the pyrolysis products are neither excessive (leading to pore blockage) nor insufficient (leading to inadequate pore shrinkage), thereby achieving uniform deposition and precise pore shrinkage.

[0028] In this embodiment, the flow rate of the benzene vapor-nitrogen mixture directly affects the pore-shrinking effect of the microporous carbon. Too high a flow rate leads to insufficient contact time between the mixture and the microporous carbon, resulting in inadequate deposition. Too slow a flow rate leads to the aggregation of localized pyrolysis products and localized micropore blockage. Through extensive experiments, this invention confirms that controlling the flow rate of the benzene vapor-nitrogen mixture at 3-8 mL / min and the reaction time at 3-4 h ensures that all microporous carbon particles exhibit consistent pore-shrinking properties, ultimately reducing the micropore size to 0.35-0.4 nm. This avoids fluctuations in adsorbent performance due to localized deposition differences and improves the stability of mass production.

[0029] In this embodiment of the invention, the preferred microporous carbon has a micropore content ≥80%, a micropore diameter of 0.5-0.7 nm, and a specific surface area of ​​900-1100 m². 2 / g, total pore volume is 0.45-0.55 cm³ 3 / g. The initial micropore size of 0.5-0.7 nm and the target pore size (0.35-0.4 nm) should be reasonably different to avoid the initial pore size being too large, which would prevent CO2 from being matched after pore shrinkage, and too small, which would cause direct blockage after pore shrinkage and render it economically worthless.

[0030] In a second aspect, the present invention provides an adsorbent based on benzene pyrolysis deposited porous carbon, wherein the adsorbent is obtained by the preparation method described in the first aspect above.

[0031] The adsorbent based on benzene pyrolysis deposited porous carbon provided in this invention embodiment has a high specific surface area (900-1100 m²). 2 / g), precise micropores (0.35-0.4 nm), and suitable total pore volume (0.45-0.55 μm). 3 It features three major characteristics: high CO2 adsorption capacity and high C2H4 selectivity.

[0032] Thirdly, the present invention provides a method for preparing an adsorbent based on benzene pyrolysis-deposited porous carbon. Figure 2 The following is a flowchart illustrating another method for preparing an adsorbent based on benzene pyrolysis-deposited porous carbon, as provided in an embodiment of the present invention. Figure 2 As shown, the preparation method includes: S201. Place the mesoporous carbon in a quartz tube furnace, purge with nitrogen, and heat to 850-900 ℃. In practical implementation, this invention uses commercially available finished microporous carbon, which not only eliminates the steps of carbon precursor pretreatment, carbonization and activation to prepare porous carbon carrier, but also has the advantage of standardized pore structure.

[0033] It should be noted that the nitrogen purging time should be controlled between 10 and 30 minutes to completely purge the air from the quartz tube furnace and remove the moisture and impurities adsorbed on the carbon surface.

[0034] S202. Adjust the pressure of the quartz tube furnace to 0.6-0.9 MPa, and introduce a benzene vapor-nitrogen mixture into the quartz tube furnace. The benzene vapor undergoes a deep cracking reaction to generate a product mainly composed of macromolecular carbon nanoparticles. The macromolecular carbon nanoparticles are deposited on the surface of the mesoporous carbon and at the mesopore inlet to form carbon sieve stratification. The mesoporous carbon retains mesopore channels inside and obtains the adsorbent. In practical implementation, the mesoporous pore size of commercially available mesoporous carbon is much larger than the macromolecular diameter of CO2 (0.33 nm) and C2H4 (approximately 0.39 nm). Directly using mesoporous carbon for adsorption treatment also fails to effectively distinguish between CO2 (0.33 nm) and C2H4 (approximately 0.41 nm). This invention controls the deep cleavage of benzene molecules, completely breaking the benzene ring to generate carbon free radicals (C·, C2H3·). The free radicals rapidly polymerize to form macromolecular carbon nanoparticles (C...). n (n=3-5), with molecular diameters of 0.8-1.2 nm. These large molecular carbon nanoparticles are more likely to be deposited on the surface of mesoporous carbon and at the mesopore inlet due to their larger particle size, forming carbon sieve layers. Meanwhile, the mesoporous carbon still retains mesoporous channels, resulting in the adsorbent with excellent mass transfer efficiency.

[0035] In practical implementation, this invention controls the degree of benzene cracking by controlling the reaction conditions. When the temperature inside the quartz tube furnace is 850-900 ℃ and the pressure is 0.6-0.9 MPa, benzene molecules undergo a deep cracking reaction, causing them to be converted into more large molecular carbon nanoparticles.

[0036] In this embodiment of the invention, mesoporous carbon has a large pore size, and pore-shrinking modification requires a large number of carbon nanoparticles. At the same time, in order to ensure the precise control of the pore size of the carbon sieve layer, and to retain the mesoporous channels inside the internal mesoporous carbon, forming a unique structure of inlet sieving-internal mass transfer, this embodiment controls the concentration of benzene vapor in the benzene vapor-nitrogen mixture to be 30-40 vol%, the flow rate of the benzene vapor-nitrogen mixture to be 8-15 mL / min, and the reaction time to be 1.5-2.5 h, to ensure sufficient supply of benzene vapor and sufficient deep pyrolysis, and to avoid insufficient carbon nanoparticles generated due to insufficient benzene vapor raw material, resulting in incomplete carbon sieve layer deposition.

[0037] In the preferred embodiments of the present invention, the mesoporous carbon has a mesopore content of ≥70%, a mesopore diameter of 2.0-3.0 nm, and a specific surface area of ​​750-900 m². 2 / g, total pore volume is 0.60-0.70 cm³. 3 / g; The initial mesoporous pore size of the mesoporous carbon is 2.0-3.0 nm, which is a reasonable difference from the target shrinkage pore size (0.5-0.6 nm), avoiding the need to consume more benzene vapor due to excessively large initial pore size; In the final adsorbent, the pore size at the mesoporous inlet is reduced to 0.5-0.6 nm, allowing CO2 to enter the internal mesopores rapidly and effectively blocking the entry of C2H4. This achieves a three-way synergy of sieving, adsorption, and mass transfer, solving the problems of slow mass transfer and low selectivity of existing mesoporous adsorbents.

[0038] Fourthly, the present invention provides an adsorbent based on benzene pyrolysis deposited porous carbon, wherein the adsorbent is obtained by the preparation method described in the third aspect above.

[0039] The adsorbent based on benzene pyrolysis deposited porous carbon provided in this invention has a dual structure feature of inlet carbon sieve (0.5-0.6 nm) and internal mesoporous channels. Inlet sieving ensures selectivity, while internal channels improve mass transfer efficiency, breaking through the bottleneck of traditional adsorbents where high selectivity leads to slow mass transfer.

[0040] Fifthly, the present invention provides an application of the adsorbent based on benzene cracking deposited porous carbon described in the second and fourth aspects above, wherein the adsorbent is used for the separation of CO2 and C2H4.

[0041] The adsorbent based on benzene cracking deposited porous carbon provided in this invention is used for the separation of CO2 and C2H4. It can accurately match the composition characteristics of syngas-to-olefins product gas (CO2 to C2H4 = 1:1-3:1)—microporous carbon-based adsorbents are suitable for low CO2 concentration scenarios (1:1), while mesoporous carbon-based adsorbents are suitable for high CO2 concentration scenarios (3:1), covering mainstream industrial operating conditions. Furthermore, under adsorption pressure of 0.1-0.6 MPa, temperature of 25℃, and mixed gas flow rate of 10-20 mL / min, the purity of the outlet C2H4 is ≥99%, meeting the purity requirements of industrial-grade olefin products.

[0042] Furthermore, the adsorbent exhibits good adsorption-desorption cycle stability, with a capacity decay of less than 5% after 50 cycles. Compared to traditional solvent absorption methods (such as the ethanolamine method), this adsorbent does not require high-temperature regeneration, has a desorption temperature of ≤ 80℃, and reduces energy consumption by 30%-40%, which aligns with the trend of green chemical development.

[0043] To enable those skilled in the art to better understand the present invention, the following embodiments are provided to illustrate in detail the adsorbent, preparation method, and application of the present invention based on benzene pyrolysis deposited porous carbon.

[0044] The commercially available microporous carbon used in the following examples was purchased from Beihai Xingshi Carbon Materials Technology Co., Ltd., and the commercially available mesoporous carbon was purchased from Shanghai Juna Technology Co., Ltd.

[0045] Example 1 Porous carbon carrier: Commercially available microporous carbon was selected, with the following parameters: micropore content 85%, micropore diameter 0.50-0.70 nm, and specific surface area 980 m². 2 / g.

[0046] Benzene cracking modification: 30 g of microporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 740℃, the benzene vapor concentration was adjusted to 20 vol%, the flow rate of the benzene-nitrogen mixed gas was 5 mL / min, the reaction pressure was maintained at 0.5 MPa, and the reaction was carried out for 3.5 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain the modified microporous carbon adsorbent.

[0047] Figure 3 The diagram shows the pore size distribution of commercially available microporous carbon provided in an embodiment of the present invention. Figure 4 The pore size distribution diagram of the modified microporous carbon provided in the embodiments of the present invention is shown; for comparison Figure 3 and Figure 4 It can be found that after benzene pyrolysis and deposition, the micropore size of microporous carbon can be reduced to about 0.37 nm. This pore size range is exactly between the molecular diameters of CO2 (0.33 nm) and C2H4 (0.41 nm), which can achieve a good molecular sieving effect.

[0048] Adsorption separation test: Take 5 g of modified microporous carbon powder, pass in product gas with CO2 / C2H4=2:1, control the product gas flow rate at 8 mL / min, under the conditions of 0.3 MPa and 25℃, the purity of C2H4 at the outlet is 99.6%, the CO2 adsorption capacity is 3.65 mmol / g, and the C2H4 adsorption capacity is 0.28 mmol / g.

[0049] Example 2 Porous carbon carrier: Commercially available microporous carbon was selected, with a micropore content of 82%, a pore size of 0.6-0.7 nm, and a specific surface area of ​​1050 m². 2 / g).

[0050] Benzene cracking modification: 35 g of microporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 760℃, the benzene vapor concentration was adjusted to 25 vol%, the flow rate of the benzene-nitrogen mixed gas was 8 mL / min, the reaction pressure was maintained at 0.6 MPa, and the reaction was carried out for 4 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain modified microporous carbon (the micropore size was reduced to 0.39 nm).

[0051] Adsorption separation test: 5 g of modified microporous carbon powder was taken and a product gas with CO2 / C2H4 = 3:1 was introduced. The flow rate was 10 mL / min, the pressure was 0.5 MPa, and the temperature was 25℃. The purity of C2H4 at the outlet was 99.5%, the CO2 adsorption capacity was 3.72 mmol / g, and the C2H4 adsorption capacity was 0.31 mmol / g.

[0052] Example 3 Porous carbon carrier: Commercially available microporous carbon was selected, with the following parameters: micropore content 85%, micropore diameter 0.55-0.65 nm, and specific surface area 980 m². 2 / g (same as in Example 1).

[0053] Benzene cracking modification: 32 g of microporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 720℃, the benzene vapor concentration was adjusted to 15 vol%, the flow rate of the benzene-nitrogen mixed gas was 3 mL / min, the reaction pressure was maintained at 0.4 MPa, and the reaction was carried out for 3 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain modified microporous carbon (the micropore size was reduced to 0.36 nm).

[0054] Adsorption separation test: 5 g of modified microporous carbon powder was taken and a product gas of CO2 / C2H4=1:1 was introduced. Under the conditions of flow rate 6 mL / min, 0.2 MPa and 25℃, the purity of C2H4 at the outlet was detected to be 99.7%, the CO2 adsorption capacity was 3.58 mmol / g and the C2H4 adsorption capacity was 0.25 mmol / g.

[0055] Example 4 Porous carbon carrier: Commercially available mesoporous carbon, parameters: mesopore content 75%, mesopore size 2.2-2.8 nm, specific surface area 850 m² 2 / g.

[0056] Benzene cracking modification: 25 g of mesoporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 880℃, the benzene vapor concentration was adjusted to 35 vol%, the flow rate of the benzene-nitrogen mixed gas was 10 mL / min, the reaction pressure was maintained at 0.8 MPa, and the reaction was carried out for 2 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain modified microporous carbon (the external mesoporous pore size was reduced to 0.56 nm, and the internal pore size was 1.2-1.5 nm).

[0057] Adsorption separation test: 5 g of modified microporous carbon powder was taken and a product gas with CO2 / C2H4 = 2:1 was introduced. Under the conditions of flow rate 15 mL / min, 0.3 MPa and 25℃, the purity of C2H4 at the outlet was 99.2%, the CO2 adsorption capacity was 3.48 mmol / g and the C2H4 adsorption capacity was 0.42 mmol / g.

[0058] Example 5 Porous carbon carrier: Commercially available mesoporous carbon, parameters: mesopore content 72%, mesopore size 2.4-2.8 nm, specific surface area 900 m² 2 / g.

[0059] Benzene cracking modification: 28 g of mesoporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 900℃, the benzene vapor concentration was adjusted to 40 vol%, the flow rate of the benzene-nitrogen mixed gas was 15 mL / min, the reaction pressure was maintained at 0.9 MPa, and the reaction was carried out for 2.5 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain modified microporous carbon (the external mesoporous pore size was reduced to 0.58 nm, and the internal pore size was 1.3-1.6 nm).

[0060] Figure 5 The diagram shows the pore size distribution of commercially available mesoporous carbon provided in an embodiment of the present invention, as shown below. Figure 5 As shown, the mesoporous pore size of commercially available mesoporous carbon is between 2.4 and 2.8 nm; Figure 6 The diagram shows the pore size distribution of the modified mesoporous carbon provided in the embodiments of the present invention; as shown. Figure 6 As shown, a sharp peak forms at approximately 0.58 nm, representing the external pore size formed by benzene cracking deposition, which is crucial for the sieving of gas molecules. A broad secondary peak forms in the 1.3–1.6 nm range, indicating a certain size distribution of the internal cavities. Between the two peaks, there is a distinct valley (at approximately 1 nm), suggesting that there are almost no pore sizes between the external and internal pores in the material.

[0061] Adsorption separation test: 5 g of modified microporous carbon powder was taken and a product gas with CO2 / C2H4 = 3:1 was introduced. Under the conditions of flow rate 20 mL / min, 0.5 MPa and 25℃, the purity of C2H4 at the outlet was 99.1%, the CO2 adsorption capacity was 3.55 mmol / g and the C2H4 adsorption capacity was 0.45 mmol / g.

[0062] Example 6 Porous carbon carrier: Commercially available mesoporous carbon, parameters: mesopore content 75%, mesopore size 2.2-2.8 nm, specific surface area 850 m² 2 / g (same as Example 4).

[0063] Benzene cracking modification: 22 g of mesoporous carbon was placed in a quartz tube furnace and purged with nitrogen for 30 min; the temperature was raised to 850℃, the benzene vapor concentration was adjusted to 30 vol%, the flow rate of the benzene-nitrogen mixed gas was 8 mL / min, the reaction pressure was maintained at 0.6 MPa, and the reaction was carried out for 1.5 h; nitrogen was purged for 10 min, and the mixture was cooled to room temperature to obtain modified microporous carbon (the external mesoporous pore size was reduced to 0.54 nm, and the internal pore size was 1.0-1.3 nm).

[0064] Adsorption separation test: 5 g of modified microporous carbon powder was taken and a product gas with CO2 / C2H4 = 1:1 was introduced. Under the conditions of flow rate 12 mL / min, 0.2 MPa and 25℃, the purity of C2H4 at the outlet was 99.3%, the CO2 adsorption capacity was 3.42 mmol / g and the C2H4 adsorption capacity was 0.39 mmol / g.

[0065] The adsorption test results shown in the above embodiments indicate that the purity of C2H4 at the outlet after microporous carbon modification is ≥99.5%, and the CO2 adsorption capacity is ≥3.5 mmol / g; the purity of C2H4 at the outlet after mesoporous carbon modification is ≥99.1%, and the CO2 adsorption capacity is ≥3.4 mmol / g.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0067] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0068] The above provides a detailed description of an adsorbent based on benzene pyrolysis deposited porous carbon, its preparation method, and its application. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing an adsorbent based on benzene pyrolysis-deposited porous carbon, characterized in that, The preparation method includes: The microporous carbon was placed in a quartz tube furnace, purged with nitrogen, and heated to 720-760 ℃. The pressure of the quartz tube furnace is adjusted to 0.3-0.6 MPa, and a benzene vapor-nitrogen mixture is introduced into the quartz tube furnace. The benzene vapor undergoes a mild cracking reaction to generate products mainly composed of small molecule hydrocarbon free radicals. The small molecule hydrocarbon free radicals are deposited on the inner wall of the microporous carbon pores, causing the pore size of the microporous carbon to shrink and form the adsorbent. The small molecule hydrocarbon radicals include: -CH2- and / or -C2H3; In the benzene vapor-nitrogen mixture, the concentration of benzene vapor is 15-25 vol.

2. The method for preparing adsorbents based on benzene pyrolysis deposited porous carbon according to claim 1, characterized in that, The flow rate of the benzene vapor-nitrogen mixture is 3-8 mL / min; The mild pyrolysis reaction takes 3-4 hours.

3. The method for preparing adsorbents based on benzene pyrolysis deposited porous carbon according to claim 1, characterized in that, The microporous carbon contains ≥80% micropores with a pore size of 0.5-0.7 nm and a specific surface area of ​​900-1100 m². 2 / g, total pore volume is 0.45-0.55 cm³ 3 / g.

4. The method for preparing adsorbents based on benzene pyrolysis deposited porous carbon according to claim 1 or 3, characterized in that, In the adsorbent, the micropore size is reduced to 0.35-0.4 nm.

5. An adsorbent based on benzene pyrolysis deposited porous carbon, characterized in that, The adsorbent is obtained by any of the preparation methods described in claims 1-4.

6. A method for preparing an adsorbent based on benzene pyrolysis-deposited porous carbon, characterized in that, The preparation method includes: Mesoporous carbon was placed in a quartz tube furnace, purged with nitrogen, and heated to 850-900 ℃. The pressure of the quartz tube furnace is adjusted to 0.6-0.9 MPa, and a benzene vapor-nitrogen mixture is introduced into the quartz tube furnace. The benzene vapor undergoes a deep cracking reaction to generate a product mainly composed of macromolecular carbon nanoparticles. The macromolecular carbon nanoparticles are deposited on the surface of the mesoporous carbon and at the mesopore inlet, forming a carbon sieve layer. The mesoporous carbon retains mesopore channels inside and obtains the adsorbent. The macromolecular carbon nanoparticles are C n (n=3-5); The concentration of benzene vapor in the benzene vapor-nitrogen mixture is 30-40 vol.

7. The method for preparing adsorbents based on benzene pyrolysis deposited porous carbon according to claim 6, characterized in that, The flow rate of the benzene vapor-nitrogen mixture is 8-15 mL / min; The deep pyrolysis reaction takes 1.5-2.5 hours.

8. The method for preparing adsorbents based on benzene pyrolysis deposited porous carbon according to claim 6, characterized in that, The mesoporous carbon contains ≥70% mesopores with a pore size of 2.0-3.0 nm and a specific surface area of ​​750-900 m². 2 / g, total pore volume is 0.60-0.70 cm³. 3 / g; In the adsorbent, the pore size at the mesopore inlet is reduced to 0.5-0.6 nm.

9. An adsorbent based on benzene pyrolysis deposited porous carbon, characterized in that, The adsorbent is obtained by any of the preparation methods described in claims 6-8.

10. The application of an adsorbent based on benzene pyrolysis deposited porous carbon as described in claim 5 or 9, characterized in that, The adsorbent is used for the adsorption and separation of CO2 and C2H4 in the one-step synthesis of olefins from syngas.

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