Methane adsorbent for wellhead gas and preparation method thereof
By performing nitrogen source impregnation and acrylamide grafting reaction on microporous activated carbon, combined with amide group modification, the problem of insufficient selectivity and efficiency of traditional activated carbon in the wellhead gas methane separation is solved, and efficient methane adsorption and separation is achieved.
Patent Information
- Application Number
- CN202510342687.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-02-27
- Filing Date
- 2025-03-21
- Publication Date
- 2025-05-06
AI Technical Summary
Traditional activated carbon adsorbents are concentrated in the separation of methane at the wellhead gas, which has problems such as insufficient active sites, small specific surface area, many surface impurities, and low selectivity to methane gas, resulting in poor separation effect.
By performing nitrogen source impregnation and acrylamide grafting reaction on microporous activated carbon, the active site and specific surface area are increased, and amide group modification is introduced to enhance adsorption selectivity to methane.
The adsorption rate and selectivity of activated carbon to methane are significantly improved, and the adsorption rate is increased from 30% to 80%, and the adsorption rate is accelerated, the adsorption efficiency is improved, and production costs are reduced.
Smart Images
Figure CN119926360A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of methane separation and adsorption technology for wellhead gas, specifically relating to a methane adsorbent for wellhead gas and its preparation method. Background Technology
[0002] Oilfield extraction processes generate large amounts of associated gas at the wellhead, commonly known as wellhead gas. The main component of wellhead gas is methane, but it varies significantly in different regions, containing varying levels of corrosive and toxic substances such as hydrogen sulfide, carbon dioxide, sulfur dioxide, and carbon monoxide. In the past, due to outdated technology, it was impossible to completely treat the corrosive and toxic components in wellhead gas, resulting in its inability to be recovered and utilized. The vast majority of wellhead gas was vented and burned, causing substantial energy waste and severe environmental pollution. Therefore, the separation and adsorption of wellhead gas plays a crucial role in resource utilization and environmental protection.
[0003] In the separation and adsorption stage of wellhead gas, methane adsorbents play a crucial role. Currently, adsorption separation is the most common method for methane separation and enrichment at wellheads. Common adsorbents include zeolite molecular sieves, metal-organic frameworks (MOFs), and activated carbon. Each of these materials has its advantages in methane separation and enrichment. Zeolite molecular sieves achieve selective adsorption of methane through numerous uniformly sized and regularly shaped pores, reaching an enrichment level of approximately 60%. However, their adsorption capacity is relatively low, limiting the amount of methane they can adsorb, and their adsorption selectivity needs improvement. MOFs, relying on their diverse and tunable pore structure and surface chemistry, achieve methane adsorption, reaching an enrichment level of approximately 80%. However, their stability is poor, their synthesis cost is high, and current laboratory and factory technologies are not yet mature. Therefore, activated carbon, with its wide availability of raw materials, economical price, good stability, large adsorption capacity, and excellent adsorption-desorption performance, has become the preferred method for methane separation and enrichment in deep coalbed methane.
[0004] However, traditional activated carbon adsorbents have some shortcomings in industrial production applications, such as insufficient active sites, small specific surface area, many surface impurities, and low selectivity for methane gas. These problems affect the adsorption and purification of methane.
[0005] Therefore, modifying and optimizing activated carbon has become a key task in industrial production. Summary of the Invention
[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a methane adsorbent for wellhead gas and its preparation method. By modifying activated carbon, its active sites can be increased, its specific surface area can be improved, surface impurities can be reduced, and its selective adsorption capacity for methane gas can be enhanced. This not only improves the methane separation efficiency and reduces production costs, but also improves the resource utilization rate of deep coalbed methane and promotes the sustainable development of the deep coalbed methane industry.
[0007] To achieve the above objectives, the present invention employs the following technical solution:
[0008] This invention provides a method for preparing a methane adsorbent for wellhead gas, comprising the following steps:
[0009] Pretreated microporous activated carbon was impregnated in a solution containing a nitrogen source, and after solid-liquid separation, it was calcined to obtain preliminarily modified activated carbon.
[0010] The preliminarily modified activated carbon was then placed in a solution containing acrylamide, and an initiator was added to carry out a grafting reaction. After the grafting reaction was completed, the modified activated carbon was separated by centrifugation and then washed and dried to obtain a methane adsorbent for wellhead gas.
[0011] In one embodiment, the preparation process of the pretreated microporous activated carbon is as follows:
[0012] S01: Using polystyrene as a carbon precursor, polystyrene is placed in a tube furnace and N2 is introduced at a rate of 300 mL / min. Under N2 protection, the temperature is raised to 750-850℃ at a heating rate of 8-12℃ / min and held for 1-2 hours to obtain activated carbon PSCA.
[0013] S02: Activated carbon PSCA and KOH are mixed and ground to obtain micro powder. Under N2 protection, the micro powder is placed in a tube furnace and N2 is introduced at a rate of 300 mL / min. The temperature is raised to 750-850℃ at a heating rate of 4-6℃ / min and reacted at a constant temperature for 1.5 h. After cooling, pretreated microporous activated carbon is obtained.
[0014] In one embodiment, the mass ratio of activated carbon PSCA to KOH is (0.17-0.5):1; the micro powder passes through an 80-mesh sieve.
[0015] In one embodiment, the ratio of the pretreated microporous activated carbon to the nitrogen-containing solution is 1 g: (6-10) mL.
[0016] In one embodiment, the nitrogen source concentration of the nitrogen source-containing solution is 0.5-1.5 mol / L; the nitrogen source in the nitrogen source-containing solution includes an inorganic nitrogen source and an organic nitrogen source, and the molar ratio of the inorganic nitrogen source to the organic nitrogen source is (0.5-0.6):1.
[0017] In one embodiment, the inorganic nitrogen source is any of ammonium phosphate, diammonium hydrogen phosphate, ammonium carbonate, ammonium bicarbonate, and ammonia water; the organic nitrogen source is any of urea, diphenylamine, pyridine, pyridinediamine, triethylamine, N,N-diisopropylethylamine, and triethylenediamine.
[0018] In one embodiment, the pretreated microporous activated carbon is impregnated in a solution containing a nitrogen source for 8-10 hours.
[0019] The roasting process takes 2 hours and the roasting temperature is 600-700℃.
[0020] In one embodiment, the ratio of the amount of the pre-modified activated carbon to the solution containing acrylamide is 1 g: (5-10) mL;
[0021] The acrylamide monomer content in the solution containing acrylamide is 15%-20%;
[0022] The initiator is azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, or azodimethylpropanesulfonic acid;
[0023] The amount of the initiator is 0.5%-2% of the acrylamide monomer content in the solution containing acrylamide.
[0024] In one embodiment, the grafting reaction temperature is 60-70°C, and the grafting reaction time is 4-7 hours.
[0025] The drying temperature is 50-60℃, and the drying time is 10-12 hours.
[0026] The present invention also provides a methane adsorbent for wellhead gas prepared by the above-described method for preparing methane adsorbent for wellhead gas.
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] This invention provides a method for preparing a methane adsorbent for wellhead gas. First, various nitrogen-containing functional groups, including pyridine nitrogen, pyrrole nitrogen, quaternary ammonium nitrogen, and amide nitrogen, are introduced onto the surface of activated carbon through impregnation with a nitrogen source. This increases the active sites on the activated carbon surface, enhances its alkalinity, and improves the adsorption capacity and selectivity for methane molecules. Second, amide group modification is performed on the activated carbon surface via graft polymerization. The amide group has a unique chemical structure and electron cloud distribution, enabling it to form specific interaction forces with methane molecules, significantly enhancing the adsorption selectivity of the activated carbon for methane. Compared with other gases (such as nitrogen and carbon dioxide), the amide group exhibits stronger adsorption of methane, significantly enhancing the selectivity for methane and facilitating its separation and enrichment. The amide group modification significantly improves the methane adsorption performance; the adsorption rate of methane on the unmodified activated carbon is approximately 30%, while the adsorption rate on the modified activated carbon can reach as high as 80%. In addition, the presence of amide groups can accelerate the adsorption rate of methane by activated carbon, enabling the activated carbon to reach adsorption equilibrium in a shorter time and significantly improving adsorption efficiency.
[0029] Furthermore, the preparation method of activated carbon for methane adsorption of the present invention is simple, has low raw material costs, and is easy to control. The obtained activated carbon for methane adsorption not only has a high specific surface area, micropore volume, and total pore volume, but also has a suitable number of mesopores and macropores, exhibiting excellent physical and chemical adsorption properties. This activated carbon has excellent methane adsorption effect, a long service life, and can effectively reduce the cost of methane purification. It successfully solves the technical problem of poor methane adsorption effect of activated carbon in the prior art, and has strong practicality and broad application prospects.
[0030] Furthermore, in the preparation process of this invention, the microporous activated carbon is pretreated with an alkaline substance. This reaction disrupts the pore structure on the activated carbon surface, creating new pores and increasing the specific surface area of the activated carbon. This provides a favorable environment for the subsequent penetration and wetting of the nitrogen source into the activated carbon. After the nitrogen source is impregnated, as the temperature rises, a large number of nitrogen bubbles are generated inside the activated carbon, causing it to expand continuously and form new pores within the activated carbon. At the same time, this expands the existing micropores and promotes the interconnection between micropores, thereby constructing a more developed pore network. This significantly improves the specific surface area and porosity of the activated carbon, providing more diffusion channels and active sites. Attached Figure Description
[0031] Figure 1 This is the adsorption isotherm at 273 K for the methane adsorbent for wellhead gas prepared in Example 3 of the present invention.
[0032] Figure 2 The CH4 / N2 selectivity coefficient of the methane adsorbent for wellhead gas prepared in Example 3 of this invention at 298 K. Detailed Implementation
[0033] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.
[0034] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.
[0035] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values (including integers and fractions) within those ranges.
[0036] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”
[0037] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.
[0038] Activated carbon, due to its wide availability of raw materials, economical price, good stability, large adsorption capacity, and excellent adsorption-desorption performance, has become the preferred adsorbent for the separation and enrichment of methane in deep coalbed methane. However, traditional activated carbon adsorbents suffer from problems such as insufficient active sites, small specific surface area, numerous surface impurities, and low selectivity for methane gas, resulting in poor separation performance. To improve this situation, this invention discloses a method for preparing an adsorbent for the separation and enrichment of methane in wellhead gas. The activated carbon adsorbent prepared by this method has the characteristics of good methane adsorption selectivity, large specific surface area, high methane adsorption rate, good adsorption and separation effect, adjustable pore size, and environmentally friendly preparation process. This invention is expected to further enhance the application value of activated carbon in the separation and purification of methane in wellhead gas.
[0039] Activated carbon, due to its wide availability of raw materials, economical price, good stability, large adsorption capacity, and excellent adsorption-desorption performance, has become the preferred adsorbent for the separation and enrichment of methane in deep coalbed methane. However, traditional activated carbon adsorbents suffer from problems such as insufficient active sites, small specific surface area, numerous surface impurities, and low selectivity for methane gas, resulting in poor separation performance. To improve this situation, this invention provides a method for preparing an adsorbent for the separation and enrichment of methane in wellhead gas. The activated carbon prepared by this method exhibits good methane adsorption selectivity, large specific surface area, high methane adsorption rate, good adsorption and separation effect, adjustable pore size, and an environmentally friendly preparation process. This invention is expected to further enhance the application value of activated carbon in the separation and purification of methane in wellhead gas.
[0040] This invention provides a method for preparing a methane adsorbent for wellhead gas, comprising the following steps:
[0041] Pretreated microporous activated carbon was impregnated in a solution containing a nitrogen source, and after solid-liquid separation, it was calcined to obtain preliminarily modified activated carbon.
[0042] The preliminarily modified activated carbon was then placed in a solution containing acrylamide, and an initiator was added to carry out a grafting reaction. After the grafting reaction was completed, the modified activated carbon was separated by centrifugation and then washed and dried to obtain a methane adsorbent for wellhead gas.
[0043] The specific steps of the above preparation method are as follows:
[0044] (1) Using polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 750-850℃ under N2 protection, and kept at the temperature for 1-2 hours to obtain activated carbon PSCA.
[0045] (2) The activated carbon PSCA is mixed and ground with KOH to obtain micro powder. Under N2 protection, the micro powder is placed in a tube furnace, heated to 750-850℃, and reacted at a constant temperature for 1.5h. After cooling, microporous activated carbon PSCAK is obtained.
[0046] (3) The pretreated microporous activated carbon PSCAK was immersed in a solution containing a nitrogen source, and after solid-liquid separation, it was calcined to obtain pre-modified activated carbon.
[0047] (4) The pre-modified activated carbon is then placed in a solution containing acrylamide, and an appropriate amount of initiator is added. The grafting reaction is carried out by stirring at a certain temperature.
[0048] (5) After the reaction is complete, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is then dried at low temperature to obtain the final product.
[0049] In the specific implementation process, in step (1), the rate at which N2 is introduced into the tube furnace is 300 mL / min; the heating rate is 8-12℃ / min; in step (2), the mass ratio of PSCA to KOH is (0.17-0.5):1; the micro powder passes through an 80-mesh sieve; in step (2), the rate at which N2 is introduced into the tube furnace is 300 mL / min; the heating rate is 4-6℃ / min.
[0050] In the specific implementation process, in step (3), the mass-to-volume ratio of PSCAK to the nitrogen-containing solution is 1:(6-10)(g / mL), that is, 1g of activated carbon corresponds to 6-10mL of solution. The nitrogen source concentration in the nitrogen-containing solution is 0.5-1.5mol / L, and the nitrogen source in the nitrogen-containing solution includes inorganic nitrogen source and organic nitrogen source, with a molar ratio of inorganic nitrogen source to organic nitrogen source of (0.5-0.6):1;
[0051] The inorganic nitrogen source is any of the following: ammonium phosphate, diammonium hydrogen phosphate, ammonium carbonate, ammonium bicarbonate, and ammonia water; the organic nitrogen source is any of the following: urea, diphenylamine, pyridine, pyridine diamine, triethylamine, N,N-diisopropylethylamine, and triethylenediamine.
[0052] The pretreated microporous activated carbon was impregnated in a solution containing a nitrogen source for 8-10 hours; the calcination time was 2 hours and the calcination temperature was 600-700℃.
[0053] In step (4), the ratio of the amount of pre-modified activated carbon to the solution containing acrylamide is 1g:(5-10)mL; the acrylamide monomer content in the solution containing acrylamide is 15%-20%; and the amount of initiator in step (4) is 0.5%-2% of the acrylamide monomer content.
[0054] In step (4), the initiator is azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, or azobismethylpropanesulfonic acid.
[0055] In step (4), the grafting reaction temperature is 60-70℃ and the reaction time is 4-7h.
[0056] In step (5), the drying temperature is 50-60℃ and the drying time is 10-12h.
[0057] The chain segment structure formed by the activated carbon surface linking unit synthesized in step 4 above is shown in the following formula.
[0058]
[0059] In this reaction, "-C-" represents the carbon free radical site on the activated carbon surface, followed by the basic unit formed by the polymerization of acrylamide monomers. The amide group (-CONH2) is retained and attached to the carbon chain. As the reaction proceeds, the chain segments continuously grow, forming polymer chains of a certain length and structure attached to the activated carbon surface. At a suitable temperature, the free radical initiator releases free radicals, which interact with the active functional groups such as carboxyl and hydroxyl groups on the activated carbon surface, abstracting hydrogen atoms to generate carbon free radicals. These carbon free radicals then undergo addition reactions with the acrylamide double bonds to form new units.
[0060] This invention provides a methane adsorbent for wellhead gas prepared using the aforementioned method. After impregnation with an alkaline solution and a nitrogen source, the nitrogen source releases nitrogen gas, causing continuous expansion and thus expanding and connecting the micropores to form a high specific surface area. Nitrogen-containing functional groups are introduced to achieve nitrogen doping, further increasing the specific surface area and micropore volume. Functional monomers are introduced to improve stability and selectivity; amide group modification enhances the selectivity and rate of methane adsorption, increasing the adsorption rate from 30% to 80%. This method is simple, low-cost, and produces activated carbon with a large specific surface area, combining the advantages of physical and chemical adsorption. It exhibits good adsorption performance and a long lifespan, solving the problem of poor adsorption performance in existing methods and showing broad application prospects.
[0061] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0062] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.
[0063] Example 1
[0064] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 2h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 8℃ / min.
[0065] (2) 15g of activated carbon PSCA was mixed and ground with 60g of KOH to obtain micro powder. After passing the micro powder through an 80-mesh sieve, it was placed in a tube furnace under N2 protection, heated to 750℃, and reacted at a constant temperature for 1.5h. After cooling, microporous activated carbon PSCAK was obtained. The rate of N2 being introduced into the tube furnace was 300mL / min, and the heating rate was 6℃ / min.
[0066] (3) 20g PSCAK was immersed in 120mL of a solution containing 1.5mol / L nitrogen source for 10h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonium phosphate, ammonium bicarbonate and ammonium carbonate, and the organic nitrogen source was urea, diphenylamine and triethylamine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.6:1.
[0067] (4) Then place 20g of pre-modified activated carbon into 100mL of a solution containing 20% acrylamide monomer, and add 2% azobisisobutyramidine hydrochloride as an initiator. Stir at 70℃ for 4h to carry out the grafting reaction.
[0068] (5) After the reaction is completed, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is dried at 60°C for 10 hours to obtain the final product.
[0069] Example 2
[0070] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 2h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 8℃ / min.
[0071] (2) 15g of activated carbon PSCA was mixed and ground with 45g of KOH to obtain micro powder. After passing the micro powder through an 80-mesh sieve, it was placed in a tube furnace under N2 protection, heated to 750℃, and reacted at a constant temperature for 1.5h. After cooling, microporous activated carbon PSCAK was obtained. The rate of N2 being introduced into the tube furnace was 300mL / min, and the heating rate was 6℃ / min.
[0072] (3) 20g PSCAK was immersed in 200mL of a solution containing 1.5mol / L nitrogen source for 8h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonium phosphate, diammonium hydrogen phosphate, and ammonium carbonate, and the organic nitrogen source was urea, diphenylamine, and pyridine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.5:1.
[0073] (4) Place 20g of modified activated carbon in 100mL of a solution containing 15% acrylamide, and add 2% of azobisisobutyramidine hydrochloride as an initiator. Stir at 65℃ for 7h to carry out the grafting reaction.
[0074] (5) After the reaction is completed, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is dried at 50°C for 12 hours to obtain the final product.
[0075] Example 3
[0076] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 2h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 10℃ / min.
[0077] (2) 20g of activated carbon PSCA was mixed and ground with 40g of KOH to obtain micro powder. After passing the micro powder through an 80-mesh sieve, it was placed in a tube furnace under N2 protection, heated to 850℃, and reacted at a constant temperature for 1.5h. After cooling, microporous activated carbon PSCAK was obtained. The rate of N2 being introduced into the tube furnace was 300mL / min, and the heating rate was 4℃ / min.
[0078] (3) 20g PSCAK was immersed in 180mL of a solution containing 1.5mol / L nitrogen source for 8h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonium phosphate, diammonium hydrogen phosphate, and ammonium carbonate, and the organic nitrogen source was urea, diphenylamine, and pyridinediamine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.6:1.
[0079] (4) Place 20g of modified activated carbon in 200mL of a solution containing 20% acrylamide, and add 1% of azobisisopropylimidazoline hydrochloride as an initiator. Stir at 70℃ for 6h to carry out the grafting reaction.
[0080] (5) After the reaction is complete, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is then dried at 60°C for 12 hours to obtain the final product.
[0081] Example 4
[0082] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 1h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 10℃ / min.
[0083] (2) Mix 10g of activated carbon PSCA with 40g of KOH and grind to obtain micro powder. After passing the micro powder through an 80-mesh sieve, place it in a tube furnace under N2 protection, heat it to 850℃, and react at a constant temperature for 1.5h. After cooling, obtain microporous activated carbon PSCAK. The rate of N2 introduced into the tube furnace is 300mL / min; the heating rate is 4℃ / min.
[0084] (3) 15g PSCAK was immersed in 90mL of a solution containing 1mol / L nitrogen source for 10h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonium phosphate, diammonium hydrogen phosphate, and ammonium carbonate, and the organic nitrogen source was urea, N,N-diisopropylethylamine, and pyridinediamine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.6:1.
[0085] (4) Place 20g of modified activated carbon in 200mL of a solution containing 20% acrylamide, and add 1.5% of azobisisopropylimidazoline hydrochloride as an initiator. Stir at 70℃ for 7h to carry out the grafting reaction.
[0086] (5) After the reaction is completed, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is dried at 60°C for 10 hours to obtain the final product.
[0087] Example 5
[0088] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 1h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 12℃ / min.
[0089] (2) Mix 10g of activated carbon PSCA with 30g of KOH and grind to obtain micro powder. After passing the micro powder through an 80-mesh sieve, place it in a tube furnace under N2 protection, heat it to 800℃, and react at a constant temperature for 1.5h. After cooling, obtain microporous activated carbon PSCAK. The rate of N2 introduced into the tube furnace is 300mL / min; the heating rate is 6℃ / min.
[0090] (3) 25g PSCAK was immersed in 200mL of a solution containing 1.5mol / L nitrogen source for 10h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonia, triethylamine, and ammonium carbonate, and the organic nitrogen source was diphenylamine, N,N-diisopropylethylamine, and pyridinediamine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.5:1.
[0091] (4) Place 20g of modified activated carbon in 200mL of a solution containing 20% acrylamide, and add 0.5% of azodimethylpropanesulfonic acid as an initiator. Stir at 60℃ for 5h to carry out the grafting reaction.
[0092] (5) After the reaction is completed, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is dried at 60°C for 10 hours to obtain the final product.
[0093] Example 6
[0094] (1) Using 50g of polystyrene as a carbon precursor, it was placed in a tube furnace and heated to 800℃ under N2 protection and kept at that temperature for 2h to obtain activated carbon PSCA; the rate of N2 being introduced into the tube furnace was 300mL / min; the heating rate was 12℃ / min.
[0095] (2) 15g of activated carbon PSCA was mixed and ground with 30g of KOH to obtain micro powder. After passing the micro powder through an 80-mesh sieve, it was placed in a tube furnace under N2 protection, heated to 800℃, and reacted at a constant temperature for 1.5h. After cooling, microporous activated carbon PSCAK was obtained. The rate of N2 being introduced into the tube furnace was 300mL / min, and the heating rate was 6℃ / min.
[0096] (3) 20g PSCAK was immersed in 140mL of a solution containing 1.5mol / L nitrogen source for 10h. After solid-liquid separation, it was calcined at 700℃ for 2h to obtain preliminarily modified activated carbon. The inorganic nitrogen source was ammonia, triethylamine, and ammonium carbonate, and the organic nitrogen source was diphenylamine, N,N-diisopropylethylamine, and pyridine. The molar ratio of inorganic nitrogen source to organic nitrogen source was 0.6:1.
[0097] (4) Place 20g of modified activated carbon in 200mL of a solution containing 15% acrylamide, and add 1.5% of azodimethylpropanesulfonic acid as an initiator. Stir at 70°C for 7h to carry out the grafting reaction.
[0098] (5) After the reaction is completed, the modified activated carbon is separated from the reaction solution by centrifugation and washed with deionized water. The washed activated carbon is dried at 60°C for 10 hours to obtain the final product.
[0099] To characterize the effects of different synthesis conditions on the dynamic adsorption capacity, specific surface area, and adsorption performance of the methane adsorbent, the dynamic adsorption capacity, specific surface area, desorption rate, adsorption rate, and micropore volume of the adsorbents synthesized in Examples 1-6 were tested, and the results are shown in Table 1.
[0100] Table 1 Performance Tests of Methane Adsorbent
[0101]
[0102] The research results show that this activated carbon methane adsorbent exhibits extremely high adsorption capacity. Under standard temperature and pressure conditions, the dynamic adsorption capacity of the methane adsorbent prepared by this product can reach a maximum of 32.9 mL / g, higher than the average level of similar activated carbon adsorbents on the market. This means that under the same usage and operating conditions, it can adsorb more methane, making it effective for applications requiring efficient methane enrichment or removal, such as coal mine gas control and natural gas purification. It also demonstrates excellent selectivity for methane in complex gas mixtures. The adsorbent exhibits superior adsorption performance, with a methane adsorption rate reaching up to 29.7%. Furthermore, the adsorbent demonstrates excellent desorption performance, with a desorption rate reaching up to 81% under conventional desorption conditions. This allows the adsorbent to quickly and effectively release the adsorbed methane after completing its adsorption task, facilitating methane recovery and providing favorable conditions for the recycling of the adsorbent. It also possesses a large specific surface area, reaching up to 807.8 m². 2 This activated carbon methane adsorbent, with a density of / g, possesses abundant microporous and mesoporous structures. The micropores provide numerous adsorption sites, facilitating the adsorption of methane molecules, while the mesopores promote rapid diffusion and transport of methane molecules within the adsorbent. The synergistic effect of these two structures results in excellent methane adsorption performance. Furthermore, this activated carbon methane adsorbent is environmentally friendly during production and use, containing no harmful substances and causing no pollution. After disposal, it is easy to handle and can be recycled through simple regeneration or recovery processes, meeting modern green and environmentally friendly development requirements.
[0103] like Figure 1 As shown, the methane adsorbent prepared in Example 3 exhibits a continuously increasing adsorption capacity for methane at 273 K with increasing absolute pressure. Within a lower pressure range, the adsorption capacity increases rapidly with increasing pressure; however, as the pressure further increases, the rate of increase gradually slows down. This is because the adsorption sites on the adsorbent surface are gradually occupied, reaching near saturation, and further increases in pressure no longer significantly improve the adsorption capacity.
[0104] like Figure 2As shown, in the initial stage, the dimensionless concentration of methane is almost 0, while the dimensionless concentration of nitrogen rapidly rises to approximately 1.3. This indicates that in this stage, the adsorbent has a strong adsorption capacity for methane, adsorbing almost all the methane entering the system, resulting in an extremely low methane concentration at the outlet; while nitrogen is hardly adsorbed or adsorbed in very small amounts, passing through the system in large quantities, causing a significant increase in the nitrogen concentration at the outlet relative to the initial concentration. In the intermediate stage, the dimensionless concentration of methane begins to gradually increase, and the rate of increase gradually accelerates. This indicates that as time progresses, the adsorption sites on the adsorbent gradually approach saturation, and the adsorption capacity for methane begins to decrease, allowing more methane to pass through the system to the outlet, thus increasing the outlet methane concentration. This demonstrates that the adsorbent has excellent adsorption, separation, and purification capabilities for methane in wellhead gas.
[0105] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for preparing a methane adsorbent for wellhead gas, characterized in that: The following steps are involved: The pretreated microporous activated carbon is immersed in a solution containing a nitrogen source, and then subjected to solid-liquid separation and then subjected to roasting treatment to obtain a preliminarily modified activated carbon; The preliminarily modified activated carbon is then placed in a solution containing acrylamide, and an initiator is added to carry out a grafting reaction. After the grafting reaction is completed, the modified activated carbon is separated by centrifugation, and is washed and dried in sequence to obtain a methane adsorbent for wellhead gas.
2. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The preparation process of the pretreated microporous activated carbon is as follows: Using polystyrene as a carbon precursor, placing polystyrene in a tube furnace and filling it with N2 at a rate of 300 mL / min, heating it to 750-850°C at a heating rate of 8-12°C / min under N2 protection, and keeping it warm for 1-2 hours to obtain activated carbon PSCA; The activated carbon PSCA was mixed with KOH and ground into fine powder. Under the protection of N2, the fine powder was placed in a tubular furnace and filled with N2 at a rate of 300 mL / min. The temperature was increased to 750-850°C at a heating rate of 4-6°C / min, and the reaction was carried out at a constant temperature for 1.5 hours. The pretreated microporous activated carbon was obtained by cooling.
3. The method for preparing a methane adsorbent for wellhead gas according to claim 2, characterized in that: The mass ratio of the activated carbon PSCA to KOH is (0.17-0.5):1; the micro powder is passed through an 80-mesh sieve.
4. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The dosage ratio of the pretreated microporous activated carbon to the solution containing the nitrogen source is 1 g: (6-10) mL.
5. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The nitrogen source concentration of the solution containing the nitrogen source is 0.5-1.5 mol / L; the nitrogen source in the solution containing the nitrogen source includes an inorganic nitrogen source and an organic nitrogen source, and the molar ratio of the inorganic nitrogen source to the organic nitrogen source is (0.5-0.6):
1.
6. The method for preparing a methane adsorbent for wellhead gas according to claim 5, characterized in that: The inorganic nitrogen source is any one of ammonium phosphate, diammonium hydrogen phosphate, ammonium carbonate, ammonium bicarbonate and ammonia water; the organic nitrogen source is any one of urea, diphenylamine, pyridine, pyridinediamine, triethylamine, N,N-diisopropylethylamine and triethylenediamine.
7. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The pretreated microporous activated carbon is immersed in the solution containing the nitrogen source for 8-10 hours; The calcination time is 2 hours, and the calcination temperature is 600-700°C.
8. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The ratio of the primary modified activated carbon to the solution containing acrylamide is 1 g: (5-10) mL; The acrylamide monomer content in the acrylamide-containing solution is 15%-20%; The initiator is azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride or azodimethylpropanesulfonic acid; The amount of the initiator used is 0.5%-2% of the acrylamide monomer content in the solution containing acrylamide.
9. The method for preparing a methane adsorbent for wellhead gas according to claim 1, characterized in that: The reaction temperature of the grafting reaction is 60-70°C, and the reaction time of the grafting reaction is 4-7h; The drying temperature is 50-60° C. and the drying time is 10-12 hours.
10. A methane adsorbent for wellhead gas prepared by the method for preparing a methane adsorbent for wellhead gas as claimed in any one of claims 1 to 9.