Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In...Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.展开更多
In order to comprehend the applicability of microwave irradiation for recovering coalbed methane,it is necessary to evaluate the microwave irradiation-induced alterations in coals with varying levels of metamorphism.I...In order to comprehend the applicability of microwave irradiation for recovering coalbed methane,it is necessary to evaluate the microwave irradiation-induced alterations in coals with varying levels of metamorphism.In this work,the carbon molecular sieve combined with KMnO_(4)oxidation was selected to fabricate carbon molecular sieve with diverse oxidation degrees,which can serve as model substances toward coals.Afterwards,the microwave irradiation dependences of pores,functional groups,and highpressure methane adsorption characteristics of model substances were studied.The results indicated that microwave irradiation causes rearrangement of oxygen-containing functional groups,which could block the micropores with a size of 0.40-0.60 nm in carbon molecular sieve;meanwhile,naphthalene and phenanthrene generated by macro-molecular structure pyrolysis due to microwave irradiation could block the micropores with a size of 0.70-0.90 nm.These alterations in micropore structure weaken the saturated methane adsorption capacity of oxidized carbon molecular sieve by 2.91%-23.28%,suggesting that microwave irradiation could promote methane desorption.Moreover,the increased mesopores found for oxidized carbon molecular sieve after microwave irradiation could benefit CH4 diffusion.In summary,the oxidized carbon molecular sieve can act as model substances toward coals with different ranks.Additionally,microwave irradiation is a promising technology to enhance coalbed methane recovery.展开更多
The activation effect of boric acid as an activator is good,and we investigate the best activation conditions for the boric acid impregnation method.To represent the structural characteristics and adsorption performan...The activation effect of boric acid as an activator is good,and we investigate the best activation conditions for the boric acid impregnation method.To represent the structural characteristics and adsorption performance of the Stellera Chamaejasme based carbon molecular sieves,we use Brunner-Emmet-Teller(BET)measurements,scan-ning electron microscope(SEM),Raman spectra(Raman),X-ray diffraction(XRD),and adsorption property measurement.When the loading ratio was 0.68:1,the specific surface area was 532.21 m^(2)/g,the total pore volume was 0.24 cm 3/g,the average pore size was 1.81 nm,the adsorption value of methylene blue was 145.28 mg/g,and the adsorption value of iodine was 713.33 mg/g,the results showed that boric acid had better activation effect.The carbon molecular sieves made from Stellera Chamaejasme and activated with boric acid produce two peaks on the aperture distribution graph that are densely distributed in the micropore range.This indicates that boric acid’s pore-forming tendency is primarily micropore.展开更多
Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon ...Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon molecular sieve(CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature(700–900 ℃) pyrolysis of polymeric precursor of phenolphthaleinbased cardo poly(arylene ether ketone)(PEK-C). The evolution of the microstructural texture and ultramicroporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes prepared at 700 ℃ exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at900 ℃, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the formation of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.展开更多
Xenon/krypton(Xe/Kr)separation is an important task in industry,yet it remains challenging to develop adsorbents with high Xe/Kr selectivity and adsorption capacity of Xe,especially at low partial pressures.Herein,we ...Xenon/krypton(Xe/Kr)separation is an important task in industry,yet it remains challenging to develop adsorbents with high Xe/Kr selectivity and adsorption capacity of Xe,especially at low partial pressures.Herein,we report a series of microporous carbon molecular sieves(CMSs)for Xe/Kr separation.Those materials have ideal bimodal pore size distributions that not only provide substantial space for the accommodation of gas molecules,but also allow selective diffusion of gas molecules.Additionally,the carbon frameworks decorated with polar oxygen-containing functional groups afford higher affinity for Xe than Kr,which is proven by density functional theory(DFT)calculations and charge density difference analysis.The optimal CPVDC-700 exhibits a high selectivity of Xe/Kr and,more importantly,a record-high uptake of Xe(2.93 mmol g^(-1))at 0.2 bar and298 K,which is the highest among all the reported carbon adsorbents.Breakthrough experiments confirm the excellent performance of such CMSs for Xe/Kr separation,and the dynamic adsorption uptake of Xe and productivity of high-purity Kr are calculated to be 2.91 mmol g^(-1)and 208 m L g^(-1)(9.29 mmol g^(-1)),respectively,which also set up a new benchmark for Xe/Kr separation of carbon adsorbents.展开更多
Carbon molecular sieve membrane(CMSM)/paper-like stainless steel fibers(PSSF)has been manufactured by pyrolyzing poly(fiirfuryl alcohol)(PFA)coated on the metal fibers.PFA was synthesized using oxalic acid dihydrate a...Carbon molecular sieve membrane(CMSM)/paper-like stainless steel fibers(PSSF)has been manufactured by pyrolyzing poly(fiirfuryl alcohol)(PFA)coated on the metal fibers.PFA was synthesized using oxalic acid dihydrate as a catalyst and coated on microfibers by dip coating method.For the purpose of investigating the effects of final carbonization temperature,the composites were carbonized between 400℃ and 800℃ under flowing nitrogen.The morphology and microstructure were examined by X-ray diffraction,Fourier transforms infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,N2 adsorption and desorption,Raman spectra and X-ray photoelectron spectra.The consequences of characterization showed that the CMSM containing mesopores o f 3.9 nm were manufactured.The specific surface area of the CMSM/PSSF fabricated in different pyrolysis temperature varies from 26.5 to 169.1 m^2·g^-1 and pore volume varies from 0.06 to 0.23 cm^3·g^-1.When pyrolysis temperature exceeds 600℃,the specific surface,pore diameter and pore volume decreased as carbonization temperature increased.Besides,the degree of graphitization in carbon matrix increased with rising pyrolysis temperature.Toluene adsorption experiments on different structured fixed bed that was padded by CMSM/PSSF and granular activated carbon(GAC)were conducted.For the sake of comparison,adsorption test was also performed on fixed bed packed with GAC.The experimental results indicated that the rate constant κ′ was dramatically increased as the proportion of CMCM/PSSF composites increased on the basis of Yoon-Nelson model,which suggested that structured fixed bed padded with CMSM/PSSF composite offered higher adsorption rate and mass transfer efficiency.展开更多
A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue ...A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas(85%N_(2)/15%CO_(2)).In the first enriching stage,carbon molecular sieve(CMS),which shows kinetic selectivity for CO_(2)/N_(2),is adopted as the adsorbent to remove most N_(2)in feed gas,thereby upgrading CO_(2)and significantly reducing the amount for further refinement.The second stage loads zeolite 13X as adsorbent to purify the CO_(2)-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory.Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis.The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here.The optimal results achieved 95.1%purity and 92.9%recovery with a high CO_(2)productivity(1.89 mol CO_(2)·h^(-1)·kg^(-1))and an appropriate energy consumption of 1.07 MJ·(kg CO_(2))^(-1).Further analysis has been carried out by simulation for explicating the temperature,pressure,and concentration distribution at cyclic steady state.展开更多
Anthracite coal was used as raw material to prepare activated carbons as the carbon support in the carbonization-activation process. Modification of the pore size of the activated carbon by chemical vapor deposition o...Anthracite coal was used as raw material to prepare activated carbons as the carbon support in the carbonization-activation process. Modification of the pore size of the activated carbon by chemical vapor deposition of carbon from benzene was examined. These samples were characterized by adsorption of N2 at 77 K and CH4 and N2 at 303 K. The microporosity of these samples was evaluated by the Dubinin-Astakhov Equation. The pore size distribution was obtained by the DFT method applied to the N2 adsorption data at 77 K. The separation selectivity was obtained by the Langmuir Equation. The surface morphology was characterized by an environmental scanning electron microscope. It was observed that all samples of carbon molecular sieves studied were microporous carbonaceous materials. CMS-2 prepared in the present study has a better N2/CH4 separation performance; it can satisfy the requirements of the pressure swing adsorption for concentrating CH4 from the N2/CH4 mixture gas.展开更多
基金supported by the renewable energy and hydrogen projects in National Key Research and Development Plan of China(2019YFB1505000).
文摘Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.
基金supported by the National Natural Science Foundation of China(42272202 and 52264001)the Yunnan Fundamental Research Projects(202201AT070144)+1 种基金the Yunnan Ten Thousand Talents Plan Young&Elite Talents Project(YNWRQNBJ-2019-164)Training Programmes of Innovation and Entrepreneurship for Undergraduates of Yunnan Province(S202210674128).
文摘In order to comprehend the applicability of microwave irradiation for recovering coalbed methane,it is necessary to evaluate the microwave irradiation-induced alterations in coals with varying levels of metamorphism.In this work,the carbon molecular sieve combined with KMnO_(4)oxidation was selected to fabricate carbon molecular sieve with diverse oxidation degrees,which can serve as model substances toward coals.Afterwards,the microwave irradiation dependences of pores,functional groups,and highpressure methane adsorption characteristics of model substances were studied.The results indicated that microwave irradiation causes rearrangement of oxygen-containing functional groups,which could block the micropores with a size of 0.40-0.60 nm in carbon molecular sieve;meanwhile,naphthalene and phenanthrene generated by macro-molecular structure pyrolysis due to microwave irradiation could block the micropores with a size of 0.70-0.90 nm.These alterations in micropore structure weaken the saturated methane adsorption capacity of oxidized carbon molecular sieve by 2.91%-23.28%,suggesting that microwave irradiation could promote methane desorption.Moreover,the increased mesopores found for oxidized carbon molecular sieve after microwave irradiation could benefit CH4 diffusion.In summary,the oxidized carbon molecular sieve can act as model substances toward coals with different ranks.Additionally,microwave irradiation is a promising technology to enhance coalbed methane recovery.
基金Graduate Innovation Project of Qinghai University for Nationalities(2021XJXS12)Graduate Innovation Project of Qinghai University for Nationalities(12M2021018).
文摘The activation effect of boric acid as an activator is good,and we investigate the best activation conditions for the boric acid impregnation method.To represent the structural characteristics and adsorption performance of the Stellera Chamaejasme based carbon molecular sieves,we use Brunner-Emmet-Teller(BET)measurements,scan-ning electron microscope(SEM),Raman spectra(Raman),X-ray diffraction(XRD),and adsorption property measurement.When the loading ratio was 0.68:1,the specific surface area was 532.21 m^(2)/g,the total pore volume was 0.24 cm 3/g,the average pore size was 1.81 nm,the adsorption value of methylene blue was 145.28 mg/g,and the adsorption value of iodine was 713.33 mg/g,the results showed that boric acid had better activation effect.The carbon molecular sieves made from Stellera Chamaejasme and activated with boric acid produce two peaks on the aperture distribution graph that are densely distributed in the micropore range.This indicates that boric acid’s pore-forming tendency is primarily micropore.
基金the National Key R&D Program of China(2017YFB0603403)National Natural Science Foundation of China(21676044,21878033,21978034)+1 种基金High Level Innovation Team of Liaoning Province(XLYC1908033)Fundamental Research Funds for the Central Universities(DUT19ZD211,DUT 2018TB02)for the financial support。
文摘Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon molecular sieve(CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature(700–900 ℃) pyrolysis of polymeric precursor of phenolphthaleinbased cardo poly(arylene ether ketone)(PEK-C). The evolution of the microstructural texture and ultramicroporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes prepared at 700 ℃ exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at900 ℃, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the formation of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.
基金supported by the National Natural Science Foundation of China(21878260,21978254,22141001)the Ministry of Education-Singapore(MOE2018-T2-2-148,MOE2019-T2-1-093)+4 种基金the Energy Market Authority of Singapore(EMA-EP009-SEGC-020)the Agency for ScienceTechnology and Research(U2102d2004,U2102d2012)the National Research Foundation(NRF-CRP26-2021RS-0002)the China Scholarship Council(CSC,202106310172)for a fellowship to support his study at National University of Singapore。
文摘Xenon/krypton(Xe/Kr)separation is an important task in industry,yet it remains challenging to develop adsorbents with high Xe/Kr selectivity and adsorption capacity of Xe,especially at low partial pressures.Herein,we report a series of microporous carbon molecular sieves(CMSs)for Xe/Kr separation.Those materials have ideal bimodal pore size distributions that not only provide substantial space for the accommodation of gas molecules,but also allow selective diffusion of gas molecules.Additionally,the carbon frameworks decorated with polar oxygen-containing functional groups afford higher affinity for Xe than Kr,which is proven by density functional theory(DFT)calculations and charge density difference analysis.The optimal CPVDC-700 exhibits a high selectivity of Xe/Kr and,more importantly,a record-high uptake of Xe(2.93 mmol g^(-1))at 0.2 bar and298 K,which is the highest among all the reported carbon adsorbents.Breakthrough experiments confirm the excellent performance of such CMSs for Xe/Kr separation,and the dynamic adsorption uptake of Xe and productivity of high-purity Kr are calculated to be 2.91 mmol g^(-1)and 208 m L g^(-1)(9.29 mmol g^(-1)),respectively,which also set up a new benchmark for Xe/Kr separation of carbon adsorbents.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.21776106)Pearl River S&T Nova Program of Guangzhou(Grant No.201610010171)for this work.
文摘Carbon molecular sieve membrane(CMSM)/paper-like stainless steel fibers(PSSF)has been manufactured by pyrolyzing poly(fiirfuryl alcohol)(PFA)coated on the metal fibers.PFA was synthesized using oxalic acid dihydrate as a catalyst and coated on microfibers by dip coating method.For the purpose of investigating the effects of final carbonization temperature,the composites were carbonized between 400℃ and 800℃ under flowing nitrogen.The morphology and microstructure were examined by X-ray diffraction,Fourier transforms infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,N2 adsorption and desorption,Raman spectra and X-ray photoelectron spectra.The consequences of characterization showed that the CMSM containing mesopores o f 3.9 nm were manufactured.The specific surface area of the CMSM/PSSF fabricated in different pyrolysis temperature varies from 26.5 to 169.1 m^2·g^-1 and pore volume varies from 0.06 to 0.23 cm^3·g^-1.When pyrolysis temperature exceeds 600℃,the specific surface,pore diameter and pore volume decreased as carbonization temperature increased.Besides,the degree of graphitization in carbon matrix increased with rising pyrolysis temperature.Toluene adsorption experiments on different structured fixed bed that was padded by CMSM/PSSF and granular activated carbon(GAC)were conducted.For the sake of comparison,adsorption test was also performed on fixed bed packed with GAC.The experimental results indicated that the rate constant κ′ was dramatically increased as the proportion of CMCM/PSSF composites increased on the basis of Yoon-Nelson model,which suggested that structured fixed bed padded with CMSM/PSSF composite offered higher adsorption rate and mass transfer efficiency.
基金financially supported by the Renewable Energy and Hydrogen Projects National Key Research&Development Program of China(2019YFB1505000)。
文摘A two-stage vacuum pressure swing adsorption(VPSA)process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas(85%N_(2)/15%CO_(2)).In the first enriching stage,carbon molecular sieve(CMS),which shows kinetic selectivity for CO_(2)/N_(2),is adopted as the adsorbent to remove most N_(2)in feed gas,thereby upgrading CO_(2)and significantly reducing the amount for further refinement.The second stage loads zeolite 13X as adsorbent to purify the CO_(2)-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory.Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis.The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here.The optimal results achieved 95.1%purity and 92.9%recovery with a high CO_(2)productivity(1.89 mol CO_(2)·h^(-1)·kg^(-1))and an appropriate energy consumption of 1.07 MJ·(kg CO_(2))^(-1).Further analysis has been carried out by simulation for explicating the temperature,pressure,and concentration distribution at cyclic steady state.
文摘Anthracite coal was used as raw material to prepare activated carbons as the carbon support in the carbonization-activation process. Modification of the pore size of the activated carbon by chemical vapor deposition of carbon from benzene was examined. These samples were characterized by adsorption of N2 at 77 K and CH4 and N2 at 303 K. The microporosity of these samples was evaluated by the Dubinin-Astakhov Equation. The pore size distribution was obtained by the DFT method applied to the N2 adsorption data at 77 K. The separation selectivity was obtained by the Langmuir Equation. The surface morphology was characterized by an environmental scanning electron microscope. It was observed that all samples of carbon molecular sieves studied were microporous carbonaceous materials. CMS-2 prepared in the present study has a better N2/CH4 separation performance; it can satisfy the requirements of the pressure swing adsorption for concentrating CH4 from the N2/CH4 mixture gas.
