Hierarchical N‐doped carbons from designed N‐rich polymer: Adsorbents with a record‐high capacity for desulfurization

The removal of 4,6‐dimethyldibenzothiophene is quite challenging in petroleum refining process. Adsorptive desulfurization is an efficient technique but the capacities and/or poor stability of current adsorbents need to be improved. Here, the fabrication of hierarchical N‐doped carbons (NCs) derived from carbonizing the polymerization of 2,4,6‐tris(chloromethyl)mesitylene and p‐phenylenediamine is reported. The results show that the NCs have developed micropores (0.34–0.93 cm³ g^?1) and mesopores (0.15–0.47 cm³ g^?1), and their surfaces have abundant pyrrole‐like/graphitic N and topological defects and vacancies, and high cycle stability (6 cycles). The typical adsorbent NC‐700 shows a record‐high capacity of 2.91 mmol g^?1 under ambient conditions. The computational results show that the doped N is capable of promoting adsorptive strength by 0.055–0.178 eV. In conclusion, the obtained materials exhibit excellent performance for deep desulfurization, and this work may open up new avenues for the development of efficient adsorbents. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3786–3793, 2018     

有机多孔聚合物CO2捕集及分离性能的研究进展

有机多孔聚合物（porous organic polymers,POPs）是一类由有机构建单元连接而形成的新型多孔材料。由于其优异的物理化学稳定性以及CO₂吸附能力,近年来有关POPs在CO₂捕集和分离的研究成为一大研究热点。大量具有优异孔性质（比表面积和孔容）的POPs通过不同有机合成反应被成功地开发出来应用于CO₂吸附分离过程。本文介绍了POPs材料的CO₂捕集与分离性能的研究现状,总结了提高POPs材料CO₂分离性能的合成策略,重点分析了可以通过功能化增强吸附剂与二氧化碳分子之间的相互作用,来提高材料的CO₂分离能力的方法。     

仲胺桥联共价三嗪聚合物对CO2的高选择性吸附

针对有机聚合物材料对CO2的吸附量和吸附选择性不能兼得的问题,由三(4-氰胺基苯基)胺和四(4-氰胺基苯基)甲烷设计合成了仲胺桥联共价三嗪聚合物NB-CTP-1和NB-CTP-2,通过FTIR、TGA、XRD、SEM、TEM和全自动物理吸附分析仪对制备的样品进行了结构和形貌表征.在1.01×105 Pa、273 K条件下,NB-CTP-1和NB-CTP-2的CO2吸附量分别为3.04和3.23 mmol/g.依据亨利定律法和IAST法分别对两种材料在1.01×105 Pa、273 K条件下的吸附选择性进行计算,其中,NB-CTP-1的CO2/N2吸附选择性高达113(亨利定律法)和143(IAST法),而NB-CTP-2也能达到75(亨利定律法)和89(IAST法).此外,通过Clausius-Clapeyron方程计算得出NB-CTP-1和NB-CTP-2的极限吸附热分别为35.3和37.6 kJ/mol,表明其与CO2存在较强的偶极-四极相互作用,有利于提升吸附选择性.     

Adsorption-hydration hybrid process for CO2 capture in a fixed bed of activated carbons

This work reports an investigation of using a fixed bed of activated carbons (ACs) to capture CO₂ at hydrate formation conditions. The experiments were conducted at 277.15 K and 3.5 MPa. The water saturation (WS) of the fixed bed of ACs varies from 0% to 100%. The results indicate that an adsorption-hydration hybrid process occurred in the fixed bed of wet ACs while a single adsorption process occurred in the fixed bed of dry ACs. The adsorption-hydration hybrid process performs better than the single adsorption process for CO₂ capture. Gas consumption at 100% WS is 3.18 times greater than that obtained using dry ACs (single adsorption process). It is found that 40% WS is an optimal value, and the gas consumption obtained at this WS is larger than that obtained at 0%, 70%, and 100% WS. This gas consumption is also greater than that obtained using stirred reactors at the same temperature and pressure conditions, so the adsorption-hydration hybrid process achieved in the fixed bed of wet ACs has a greater potential to capture CO₂ in comparison with the single adsorption or hydrate formation process.     

葡萄糖基多孔碳材料对CO2/CH4的分离性能

以淀粉糖（主要成分为葡萄糖）为碳前体,制备了一系列多孔碳材料（C-GLCs-800）,对其进行孔隙结构分析,并应用FT-IR、SEM、TGA对其进行了表征,测定了材料在288、298和308 K下的CO₂和CH₄吸附等温线,根据IAST理论预测了材料对CO₂/CH₄二元体系的吸附选择性。实验结果显示,活化条件对材料的孔隙结构有明显影响,随着KOH/C质量比的增加,所制备的C-GLCs-800比表面积和总孔容先增加后降低。其中C-GLC-800-4的BET比表面积高达3153 m²·g^-1,总孔容为2.056 cm³·g^-1。C-GLC-800-2的窄微孔（V_d<1 nm,孔容0.3538 cm³·g^-1）含量最高,为30.63%。C-GLC-800-2在298 K和10⁵ Pa下对CO₂吸附量高达3.96 mmol·g^-1,明显高于许多传统吸附材料和MOFs材料在相同条件下对CO₂的吸附容量。应用Clausiuse-Clapeyron方程计算了CO₂和CH₄在材料上的吸附热,应用IAST理论计算了CO₂/CH₄的吸附选择性,结果显示C-GLC-800-2对CO₂/CH₄的吸附选择性为8.35。     

Highly efficient and reversible CO2 capture by tunable anion‐functionalized macro‐porous resins

Anion functionalized strategy has been proposed for the synthesis of macro‐porous resins [IRA‐900][An] through the neutral reaction of the basic resin [IRA‐900][OH] with the corresponding donors. Combining CO₂ adsorption results and FT‐IR, solid‐state ¹³C NMR characterization as well as quantum chemical calculations, chemical adsorption mechanism was verified and tunable capture of CO₂ was realized. Among them, the anion functionalized resin [IRA‐900][Triz] exhibits an extremely high adsorption capacity (4.02 mmol g^?1 at 25°C, 0.15 bar), outperforming many other good adsorbents. Finally, we discuss the thermostability and recycling stability of [IRA‐900][Triz], which shows a great potential in the industrial capture of CO₂. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3008–3015, 2017     

Application of polyethylenimine‐impregnated solid adsorbents for direct capture of low‐concentration CO2

A systematic study of CO₂ capture on the amine‐impregnated solid adsorbents is carried out at CO₂ concentrations in the range of 400–5000 ppm, relating to the direct CO₂ capture from atmospheric air. The commercially available polymethacrylate‐based HP2MGL and polyethylenimine are screened to be the suitable support and amine, respectively, for preparation of the adsorbent. The adsorbents exhibit an excellent saturation adsorption capacity of 1.96 mmol/g for 400 ppm CO₂ and 2.13 mmol/g for 5000 ppm CO₂. Moisture plays a promoting effect on CO₂ adsorption but depends on the relative humidity. The presence of O₂ would lead to the decrease of adsorption capacity but do not affect the cyclic performance. The diffusion additive is efficient to improve the adsorption capacity and cyclic performance. Moreover, the adsorbents can be easily regenerated under a mild temperature. This study may have a positive impact on the design of high‐performance adsorbents for CO₂ capture from ambient air. © 2014 American Institute of Chemical Engineers AIChE J, 61: 972–980, 2015     

乙二胺不同掺杂模式下多孔有机聚合物对CO2的吸附

利用嫁接法和浸渍法分别在以1,3,5-三苯基苯为单体的有机多孔聚合物（nTPB）上成功掺杂乙二胺,分别研究了乙二胺的不同掺杂模式对多孔聚合物的结构性质以及CO₂吸附性能的影响。结果表明,嫁接法和浸渍法皆可在nTPB上均匀掺杂乙二胺,且nTPB的比表面积和孔容均有所下降。在乙二胺掺杂量相同的前提下,由于浸渍法完全利用nTPB的孔道吸收乙二胺,nTPB的孔道堵塞更明显。两种掺杂乙二胺的模式均可显著提升nTPB对CO₂的吸附选择性,但只有嫁接法对nTPB的CO₂吸附量有明显促进（从4.4 mmol/g升高为5.2 mmol/g;0℃,10⁵ Pa）;浸渍法由于过度堵塞nTPB孔道,且乙二胺的吸附位点被包埋,导致CO₂的吸附量反而下降（仅有3.4 mmol/g;0℃,10⁵ Pa）。此外,嫁接法掺杂乙二胺的nTPB表现出与nTPB基质相同的良好重复利用性。     

基于不同粒径ZIF-8多孔液体的二氧化碳捕集性能

通过粒径调控策略制备了基于不同粒径ZIF-8的多孔液体(PLs),并用于CO₂的捕集。考察了ZIF-8粒径对多孔液体捕集CO₂的吸附容量、吸附速率、CO₂/N₂选择性及循环稳定性的影响,并对不同粒径多孔液体的CO₂吸附动力学进行研究。结果表明,多孔液体中具有永久的孔隙结构,不同多孔液体均具有优异的流动性。3种不同粒径的多孔液体室温下放置60 d或4500 r/min下离心5 min后均未出现聚集、沉积现象,表明不同粒径多孔液体均具有较好的稳定性。由不同粒径ZIF-8合成的多孔液体对CO₂的吸附过程包括物理吸附和化学吸附。其中,ZIF-8粒径为43 nm的多孔液体ZIF-8-PLs(43)对CO₂的饱和吸附容量最大,为63.0 mg/g;ZIF-8-PLs(145)展现了较快的CO₂吸附速率,准二级动力学常数为1.91×10^–3 g/(mg·min);ZIF-8-PLs(1400)具有最高的C...     

Metal-induced polymer framework membrane with high performance for CO2 separation

In this study, a novel porous material, that is, metal-induced polymer framework-1 (MPF-1) was synthesized using Zn(NO₃)₂·6H₂O and a high-molecular weight PVAmacid. MPF-1 has two structural advantages that help to create CO₂ separation membranes with simple fabrication procedure and high performance. First, MPF-1 is a high-molecular weight polymer with certain flexibility, and thus having good membrane-forming ability. Second, MPF-1 has small and uniform distributed pores, and contains amine groups those can react with CO₂ molecules reversibly. Therefore, CO₂ molecules can preferentially adsorb on pore walls of MPF-1 and transport across the pores by monomolecular surface diffusion, while most of N₂, CH₄, or H₂ molecules are excluded out the pores. The MPF-1 was employed to fabricate a microporous membrane by coating the MPF-1 dispersions on a polysulfone ultrafiltration membrane. CO₂ permeance and selectivity of the membrane keep almost unchanged with the feed pressure increasing from 0.11 to 1.0 MPa. © 2018 American Institute of Chemical Engineers AIChE J, 65: 239–249, 2019     

State of the art of ionic liquid-modified adsorbents for CO2 capture and separation

The enormous emission of carbon dioxide (CO₂) from industries has triggered a series of environmental issues. In recent years, ionic liquids (ILs) as novel absorbents are widely used for CO₂ capture owing to their low vapor pressure and tunable structures. IL-modified adsorbents have the advantages of both ILs and porous supports, such as high CO₂ selectivity and high specific surface area, which are novel agents to capture CO₂ with broad application prospects. In this review, more than 140 IL-modified adsorbents for CO₂ capture in recent years were systematically summarized. The types of ILs including conventional ILs and functionalized ILs on CO₂ separation performance of different IL hybrid adsorbents, and their adsorption mechanisms were also discussed. Finally, future perspectives on IL-modified adsorbents for CO₂ separation were further posed.     

Metal‐organic framework membrane process for high purity CO2 production

Gas separation by metal‐organic framework (MOF) membranes is an emerging research field. Their commercial application potential is, however, still rarely explored due in part to unsatisfied separation characteristics and difficulty in finding suitable applications. Herein, we report “sharp molecular sieving” properties of high quality isoreticular MOF‐1 (IRMOF‐1) membrane for CO₂ separation from dry, CO₂ enriched CO₂/CH₄, and CO₂/N₂ mixtures. The IRMOF‐1 membranes exhibit CO₂/CH₄ and CO₂/N₂ separation factors of 328 and 410 with CO₂ permeance of 2.55 × 10^?7 and 2.06 × 10^?7 mol m^?2 s^?1 Pa^?1 at feed pressure of 505 kPa and 298 K, respectively. High grade CO₂ is efficiently produced from the industrial or lower grade CO₂ feed gas by this MOF membrane separation process. The demonstrated “sharp molecular sieving” properties of the MOF membranes and their potential application in production of value‐added high purity CO₂ should bring new research and development interest in this field. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3836–3841, 2016     

碱式碳酸镁催化酚醛聚合制备多孔炭及其CO2吸附性能

利用碱式碳酸镁的催化功能及易分解特性,实现间苯二酚、甲醛的快速凝胶,炭化得到孔隙发达的整体式多孔炭(MCM-Mg),其轴向抗压强度达9.4 MPa。与普通碳酸盐催化的样品相比,MCM-Mg孔隙更为发达。273 K下该系列样品的静态CO₂吸附量可达3.49~4.50 mmol·g^-1 (0.1 MPa),0.015 MPa最高可达1.87 mmol·g^-1。研究发现,微孔对材料吸附性能起主导作用;MCM-Mg的单位微孔比表面积可吸附7.15 μmol CO₂,超过了大部分活化法制备的炭材料。多组分动态穿透实验表明,该系列材料可实现CO₂/N₂的完全分离;材料具有良好的耐水汽性能和循环吸附-脱附性能,室温下经惰性气体吹扫即可实现再生。     

Technico‐economical assessment of MFI‐type zeolite membranes for CO2 capture from postcombustion flue gases

A detailed survey of the effect of moisture on the CO₂/N₂ permeation and separation performance of Mobile Five (MFI) zeolite membranes in view of downstream postcombustion CO₂ capture applications in power plants and incinerators is presented. The membranes, displaying a nanocomposite architecture, have been prepared on α‐alumina tubes by pore‐plugging hydrothermal synthesis at 443 K for 89 h using a precursor clear solution with molar composition 1 SiO₂:0.45 tetrapropylammonium hydroxide:27.8 H₂O. The synthesized membranes present reasonable permeation and CO₂/N₂ separation properties even in the presence of high water concentrations in the gas stream. A critical discussion is also provided on the technico‐economical feasibility (i.e., CO₂ recovery, CO₂ purity in the permeate, module volume, and energy consumption) of a membrane cascade unit for CO₂ capture and liquefaction/supercritical storage from standard flue gases emitted from an incinerator. Our results suggest that the permeate pressure should be kept under primary vacuum to promote the CO₂ driving force within the membrane. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3183–3194, 2012     

Fabrication of mixed‐matrix membranes with MOF‐derived porous carbon for CO2 separation

Mixed‐matrix membranes (MMMs) have shown great advantages but still face some challenges, such as the trade‐off between permeability and selectivity, stability, and the lack of efficient ways to enhance them simultaneously. Here, the fabrication of MMMs with metal‐organic frameworks derived porous carbons (MOF‐PCs) as fillers which exhibit selective‐facilitating CO₂ transport passage originating from interactions between fillers and CO₂ is showed. With the aid of the developed multicalcination method, MOF‐PCs with variable N‐contents were prepared and incorporated into PPO‐PEG matrix for the first time to prepare MMMs, which show excellent separation performance for CO₂/CH₄ mixture with a tunable separation performance by combining different N‐contents and surface areas of MOF‐PCs. Moreover, the developed MMMs have hydrothermal and chemical stability. This work not only presents a series of MMMs with both good separation properties and stability, it also provides useful information for guiding the fabrication of high performance MMMs for practical application. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3400–3409, 2018     

A Study on CO2 Absorption Kinetics by Aqueous Solutions of N,N‐Diethylethanolamine and N‐Ethylethanolamine

N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising candidate alkanolamines for CO₂ removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO₂ and EEA was determined from the absorption rate measurements of CO₂ in a blend comprising DEEA, EEA and H₂O. A stirred‐cell reactor with a plane, horizontal gas‐liquid interface was used for the absorption studies. While the DEEA concentration in the formulated solution was varied in the range of 1.5–2.5 kmol/m³, the initial EEA concentration was 0.1 kmol/m³. A zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics. At 303 K, the second‐order reaction rate constant for the CO₂ reaction with EEA was found to be 8041 m³/(kmol s). The liquid‐side mass transfer coefficient was also estimated, and its value (0.004 cm/s) is in line with those typical of stirred‐cell reactors.     

CO2 Adsorption capacity of activated N‐doping porous carbons prepared from graphite nanofibers/polypyrrole

In this study, N‐doping porous carbons (NPCs) with a 3D aperiodic hierarchical and layered structure were prepared by the sodium hydride (NaOH) activation of graphite nanofibers (GNFs)/polypyrrole (PPY) composites. The effects of the N groups and structural features on the CO₂ adsorption capacity of NPCs were investigated by N₂ full isotherms, XRD, SEM, and TEM. The CO₂ adsorption capacity was measured by the CO₂ isothermal adsorption at 25°C and 1 atm. It was found that GNFs served as a substrate and layered graphitic carbons were formed by the thermal annealing of PPY. The content of N groups and textural properties of NPCs were enhanced with increasing activation temperature, resulting in improved CO₂ adsorption capacity. The CO₂ adsorption isotherms showed that GPK‐600 exhibited the best CO₂ adsorption capacity of 88.8 mg/g when the activation temperature was 600°C. The result indicates that the pore size and its distribution of NPCs lead to feasible contact CO₂, and the presence of high N groups on the NPCs could have resulted in further stabilization of the surface effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40517.     

Preparation and characterization of a novel activated carbon‐supported N‐doped visible light response photocatalyst (TiO2−xNy/AC)

A photocatalyst, TiO_2?xN_y/AC (activated carbon (AC) supported N‐doped TiO₂), highly active in both the Vis and UV range, was prepared by calcination of the TiO₂ precursor prepared by acid‐catalyzed hydrolysis in an ammonia atmosphere. The powders were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, X‐ray diffraction, N₂ adsorption, Fourier transform infrared spectroscopy and phenol degradation. The doped N in the TiO₂ crystal lattice creates an electron‐occupied intra‐band gap allowing electron‐hole pair generation under Vis irradiation (500–560 nm). The TiO_2?xN_y/AC exhibited high levels of activity and the same activity trends for phenol degradation under both Vis and UV irradiation: TiO_2?xN_y/AC calcined at 500 °C for 4 h exhibited the highest activity. The band‐gap level newly formed by doped N can act as a center for the photo‐generated holes and is beneficial for the UV activity enhancement. The performance of the prepared TiO_2?xN_y/AC photocatalyst revealed its practical potential in the field of solar photocatalytic degradation of aqueous contaminants. Copyright © 2007 Society of Chemical Industry