采用水热炭化和KOH活化相结合的方法,以生物质莲杆废弃物为碳源,制备了高比表面积多孔炭材料,并探索其CO2吸附性能.分别采用氮气物理吸附、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和元素分析技术(XPS)对这种莲杆基多孔炭材料的孔道结构、形貌和表面化学等特性进行了研究.结果表明,KOH浓度对莲杆基多孔炭材料的孔结构具有较大影响,莲杆基多孔炭材料的比表面积和孔体积分别为2 893 m2/g和1.59 cm3/g,KOH活化处理能在增大多孔炭材料的比表面积和孔体积,同时会在其内部形成部分具有较大尺寸的微孔和较小尺寸的介孔结构.在常压条件下,CO2的吸附测试表明莲杆基多孔炭材料在25℃和0℃时的吸附量分别高达3.85和6.17 mmol/g,这一吸附量在生物质基多孔炭材料中属于较高水平.然而,具有最高比表面积的莲杆基多孔炭材料(AC-4样品)并不具备最高的CO2吸附量,这意味着常压条件下限制CO2吸附量的决定性因素并不是比表面积,而主要由微孔率和孔径分布决定.这一研究结果为设计多孔吸附剂应用于CO2捕集方面提供了重要意义,也为构建低成本且环境友好的具有高吸附量的CO2吸附剂提供思路.%Porous carbons with a large number of micropores were obtained by the hydrothermal carbonization of lotus stems followed by KOH activation,and their CO2 capture performance was evaluated.The influence of KOH/char ratio on the pore texture and surface chemistry of the carbons was investigated by N2 adsorption,SEM,TEM and elemental analysis.Results indicate that asprepared carbons had surface areas up to 2 893 m2/g and pore volumes up to 1.59 cm3/g,and that KOH activation increased their surface areas by forming large micropores and small mesopores.The CO2 uptake in the carbons at ambient pressure was up to 3.85 and 6.17 mmol/g at 25 and 0 ℃,respectively,which are among the highest values for biomass-derived carbons reported in the literature.The porous carbon with the highest surface area did not show the highest CO2 uptake.The decisive factor for their CO2 uptake at ambient pressure is not the surface area but the microporosity and micropore size distribution.This result provides guidance for further searches for porous adsorbents for CO2 capture.The porous carbons from lotus stem waste have the advantages of low cost and high capture ability for CO2.
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