Frontiers of Chemical Science and Engineering ( IF 4.5 ) Pub Date : 2020-09-21 , DOI: 10.1007/s11705-020-1967-0 Yanxia Wang , Xiude Hu , Tuo Guo , Jian Hao , Chongdian Si , Qingjie Guo
In this work, nitrogen-doped porous carbons (NACs) were fabricated as an adsorbent by urea modification and KOH activation. The CO2 adsorption mechanism for the NACs was then explored. The NACs are found to present a large specific surface area (1920.72–3078.99 m2·g−1) and high micropore percentage (61.60%–76.23%). Under a pressure of 1 bar, sample NAC-650-650 shows the highest CO2 adsorption capacity up to 5.96 and 3.92 mmol·g−1 at 0 and 25 °C, respectively. In addition, the CO2/N2 selectivity of NAC-650-650 is 79.93, much higher than the value of 49.77 obtained for the nonnitrogen-doped carbon AC-650-650. The CO2 adsorption capacity of the NAC-650-650 sample maintains over 97% after ten cycles. Analysis of the results show that the CO2 capacity of the NACs has a linear correlation (R2 = 0.9633) with the cumulative pore volume for a pore size less than 1.02 nm. The presence of nitrogen and oxygen enhances the CO2/N2 selectivity, and pyrrole-N and hydroxy groups contribute more to the CO2 adsorption. In situ Fourier transform infrared spectra analysis indicates that CO2 is adsorbed onto the NACs as a gas. Furthermore, the physical adsorption mechanism is confirmed by adsorption kinetic models and the isosteric heat, and it is found to be controlled by CO2 diffusion. The CO2 adsorption kinetics for NACs at room temperature and in pure CO2 is in accordance with the pseudo-first-order model and Avramís fractional-order kinetic model.
中文翻译:
氮掺杂多孔碳对CO 2的高效吸附及其机理
在这项工作中,通过尿素改性和KOH活化制备了氮掺杂多孔碳(NAC)作为吸附剂。然后探讨了NAC的CO 2吸附机理。发现NAC具有较大的比表面积(1920.72–3078.99 m 2 ·g -1)和高微孔百分比(61.60%–76.23%)。在1 bar的压力下,样品NAC-650-650在0和25°C下分别显示最高的CO 2吸附能力,分别高达5.96和3.92 mmol·g -1。另外,NAC-650-650的CO 2 / N 2选择性为79.93,远高于非氮掺杂碳AC-650-650的49.77。一氧化碳2十个循环后,NAC-650-650样品的吸附容量保持97%以上。结果分析表明,NAC的CO 2容量与孔径小于1.02 nm的累积孔体积具有线性相关性(R 2 = 0.9633)。氮和氧的存在增强了CO 2 / N 2的选择性,并且吡咯-N和羟基对CO 2的吸附贡献更大。在原位傅立叶变换红外光谱的分析表明,CO 2被吸附到顾问委员会作为气体。此外,通过吸附动力学模型和等渗热证实了物理吸附机理,并且发现其受CO控制。2扩散。NAC在室温和纯CO 2中的CO 2吸附动力学符合拟一阶模型和Avramís分数阶动力学模型。