摘要
水热炭化是一种类似煤矿化过程将生物质低能耗转化为炭材料的方法,但这种方法得到的水热炭比表面积较低,限制了其直接作为吸附剂在CO_(2)捕集方面的应用。本文以壳聚糖为前体通过水热炭化联合低浓度KOH活化,制备出高比表面积氮掺杂多孔炭材料,采用氮气物理吸附仪、扫描电镜(SEM)和X-射线衍射仪(XRD)研究水热炭化过程中熔融盐和活化温度对多孔炭材料孔结构及其CO_(2)吸附性能的影响。结果表明升高活化温度能够有效增加孔隙率。水热过程中存在的熔融盐在600和700°C活化时会引起比表面积适度降低,这是由于存在的盐可能在水热炭中引入部分介孔结构。低温活化时水热反应中盐的存在可以增加多孔炭材料CO_(2)吸附量。例如700°C活化水热炭化过程中不含盐样品AC-0-700和含盐样品AC-5-700在常温常压下的CO_(2)吸附量分别为2.97和3.45 mmol/g,这一结论证实比表面积并非影响常压下多孔炭材料中CO_(2)吸附量的唯一因素。水热反应中盐的存在能够有效固定水热炭中的氮元素减少其活化时的挥发程度。另外,虽然600°C活化样品AC-5-600的比表面积仅为1249 m^(2)/g,但其常温常压下的CO_(2)吸附量高达4.41 mmol/g,主要归因于高微孔率和适度氮掺杂的联合效应。
Hydrothermal treatment of biomass is effective in producing hydrochar,but the product usually has a low surface area and is not suitable for direct use as an adsorbent for CO_(2) capture.We report the use of chitosan as a precursor for carbon prepared by a combination of hydrothermal treatment and mild KOH activation.The effect of an additive salt(eutectic salt of KCl/LiCl with a mass ratio of 5.5/4.5)in the hydrothermal treatment and activation temperature on the porosities and surface chemical states of the obtained carbons and their CO_(2) capture were studied by N2 adsorption,XPS,SEM and XRD.Results indicated that the porosities of the carbons were increased by increasing the activation temperature.The salt additive introduced mesopores in the hydrochar and slightly reduced the surface area of the porous carbon after activation,but was useful in increasing the number of N-species during hydrothermal treatment and activation.The carbons produced using the salt additive had much larger CO_(2) uptakes under ambient conditions than those prepared without the salt,suggesting that porosity is not the only factor that determines the CO_(2) uptake.The CO_(2) uptake on the carbon activated by KOH at 600°C produced from the salt-assisted hydrochar was the highest(as high as 4.41 mmol/g)although its surface area was only 1249 m^(2)/g,indicating that CO_(2) uptake was determined by both the microporosity and the active N-species in the carbon.
作者
王静
陈双
徐嘉宇
刘立成
周继承
蔡进军
WANG Jing;CHEN Shuang;XU Jia-yu;LIU Li-cheng;ZHOU Ji-cheng;CAI Jin-jun(Hunan Key Laboratory of Environment Friendly Chemical Process,School of Chemical Engineering,Xiangtan University,Xiangtan 411105,China;CAS Key Laboratory of Bio-based Materials,Qingdao Institute of Bioenergy and Bioprocess Technology,Chinese Academy of Sciences,Qingdao 266101,China)
出处
《新型炭材料》
SCIE
EI
CAS
CSCD
北大核心
2021年第6期1081-1093,共13页
New Carbon Materials
基金
国家自然科学基金(21506184
21676227)
湖南省自然科学基金(2021JJ30665,2019JJ1863)
中科院生物基材料重点实验室基金(BMF-2020-15)
“环境友好与资源高效利用化工新技术”湖南省2011协同创新中心资助项目.
