ZIF-8的合成、 表征及正己烷吸附性能

doi:10.7503/cjcu20160263

摘要/Abstract

摘要：

以甲醇为溶剂, 硝酸锌六水合物为锌源, 2-甲基咪唑为有机配体, 通过溶剂热法合成了金属有机骨架材料ZIF-8; 采用X射线衍射(XRD)、氮气吸附、热重-差热分析(TG-DSC)和扫描电子显微镜(SEM)等方法对ZIF-8样品进行了表征; 研究了正己烷在ZIF-8上的液相吸附动力学和动态选择性吸附性能. 结果表明, 合成的ZIF-8晶体具有方钠石结构, 结晶度较高, 孔结构主要为0.37~1.10 nm的微孔, BET比表面积为1836 m²/g, 孔体积为0.65 cm³/g. TG-DSC和高温原位XRD分析结果表明, 合成的ZIF-8具有良好的热稳定性能. 283~313 K时, 正己烷在ZIF-8上液相吸附的扩散系数为(2.53~8.88)×10^-12 cm²/s, 扩散活化能为31.11 kJ/mol; 308 K时, ZIF-8对正己烷的动态饱和吸附量为187.3 mg/g, 由吸附穿透曲线计算得出Thomas速率常数为2.17×10^-3 mL·min^-1·mg^-1. 与5A分子筛相比, ZIF-8对正己烷的吸附容量高出约1倍, 液相吸附表观扩散时间常数高出约70%.

关键词: ZIF-8, 正己烷, 吸附动力学, 吸附容量, 动态吸附

Abstract:

The zeolitic imidazolate framework ZIF-8 was synthesized through a solvothermal process employing methanol as the solvent, zinc nitrate hexahydrate and 2-methylimidazole as zinc source and organic ligand, respectively. The products were characterized by means of XRD, N₂ adsorption, TG-DSC and SEM. In addition, selective adsorption performance for n-hexane on ZIF-8 was investigated. It is indicated that synthesized ZIF-8 has the sodalite crystal structure and a high crystallinity. From the N₂ adsorption results, ZIF-8 product has a pore size range of 0.4—1.1 nm, BET specific surface area of 1836 m²/g and pore volume of 0.65 cm³/g. Both TG-DSC and high-temperature in situ XRD analyses suggest its excellent thermal stability. As the temperature increases from 283 to 313 K, the diffusion coefficient for n-hexane adsorption on ZIF-8 varies from 2.53×10^-12 to 8.88×10^-12 cm²/s and diffusion activation energy is evaluated to be 31.11 kJ/mol. At 308 K, the dynamic adsorption capacity and Thomas adsorption rate constant for n-hexane on ZIF-8 are 187.3 mg/g and 2.17×10^-3 mL·min^-1·mg^-1, respectively. As compared to 5A molecule sieve, ZIF-8 displays around 100% higher adsorption capacity and almost 70% faster diffusion rate.

Key words: ZIF-8, n-Hexane, Adsorption kinetics, Adsorption capacity, Dynamic adsorption

中图分类号:

O647

TrendMD:

刘克峰, 任丹妮, 孙辉, 沈本贤, 刘纪昌. ZIF-8的合成、表征及正己烷吸附性能. 高等学校化学学报, 2016, 37(10): 1856.

LIU Kefeng, REN Danni, SUN Hui, SHEN Benxian, LIU Jichang. Synthesis, Characterization and n-Hexane Adsorption Performance of ZIF-8^†. Chem. J. Chinese Universities, 2016, 37(10): 1856.

图/表 7

Fig.1 Experimental and simulated XRD patterns of ZIF-8a. Simulated pattern; b. experimental pattern;c. high-temperature in situ sample.

Fig.2 N2 adsorption-desorption isotherms(A) and micropore size distribution(B) of ZIF-8

Fig.3 SEM images of ZIF-8 with different magnifications

Fig.4 TG-DSC curves of ZIF-8

Fig.5 Adsorption rate curves of n-hexane on ZIF-8Qt/Qm: adsorption equilibrium approaching degree. The solid lines represent fitting results.

Table 1 Kinetics parameters for adsorption of n-hexane on ZIF-8

Temperature/K	10⁴D· $r - 2$ /s^-1	10¹²D/(cm²·s^-1)
283	1.12	2.53
298	2.91	6.55
313	3.95	8.88

Table 1 Kinetics parameters for adsorption of n-hexane on ZIF-8

Temperature/K	10⁴D· $r - 2$ /s^-1	10¹²D/(cm²·s^-1)
283	1.12	2.53
298	2.91	6.55
313	3.95	8.88

Fig.6 Adsorption breakthrough curve of n-hexane on a fixed bed filled with ZIF-8The solid line represents fitting breakthrough curve.

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