Evolution of Phosphorus-Containing Groups on Activated Carbons during Heat Treatment
Evolution of Phosphorus-Containing Groups on Activated Carbons during Heat Treatment
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DOI：
10.1021/acs.langmuir.7b00095
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发表时间：
2017-03-28
期刊：
影响因子：
3.9
通讯作者：
Yoon, Seong-Ho
中科院分区：
文献类型：
--
作者：
Wang, Yongfang;Zuo, Songlin;Yoon, Seong-Ho
通过H3 PO 4活化木质纤维素和通过H3 PO 4改性活性炭制备了两种类型的活性炭，然后在N2或H2气氛中在400至900 ℃的温度下热处理以研究含磷基团的演变。采用元素分析、X射线光电子能谱、P-31核磁共振、氮吸附和扫描电子显微镜对活性炭的理化性质进行了分析。结果表明，含磷基团的C-O-P键可以逐步演变为C-P-O，C3-P=O，C3-P，并最终作为热处理的结果元素磷。磷酸盐类基团在N2气氛中比在H2气氛中更热稳定。在N-2中，C-O-P键在高达800 ℃时显著地演变成C-P-O和C-3-P=0，而即使在900 ℃时也不形成C-3-P键。在H-2中，在500摄氏度下显著地发生相应的演化，形成C-3-P键并最终形成元素磷。此外，这两种活性炭表现出不同的演变趋势，这表明位于石墨状微晶边缘的含磷基团比晶格中的含磷基团更容易发生演变。最后，我们提出了不同的含磷基团的演化途径后，在N-2和H-2气氛中的热处理。
Two types of activated carbons have been prepared by H3PO4 activation of lignocellulose and by H3PO4 modification of activated carbon, and then heat-treated at temperatures from 400 to 900 degrees C in an atmosphere of N-2 or H-2 to investigate the evolution of phosphorus-containing groups. Elemental analysis, X-ray photoelectron spectroscopy, P-31 nuclear magnetic resonance, nitrogen adsorption, and scanning electron microscopy have been used to analyze the physicochemical properties of the activated carbons. The results show that C-O-P linkages of phosphorus-containing groups can progressively evolve into C-P-O, C-3-P=O, C-3-P, and eventually elemental phosphorus as a result of heat treatment. Phosphate-like groups are much more thermally stable in an N-2 than in an H-2 atmosphere. In N-2, C-O-P linkages significantly evolve into C-P-O and C-3-P=0 at up to 800 degrees C, whereas C-3-P linkages are not formed even at 900 degrees C. In H-2, the corresponding evolution remarkably occurs at 500 degrees C, forming C-3-P linkages and eventually elemental phosphorus. Moreover, the two activated carbons exhibit different evolution trends, suggesting that the evolution happens more easily for phosphorus-containing groups located on the edges of graphite-like crystallites than those in the lattice. Finally, we propose different evolution pathways of phosphorus containing groups upon heat treatment in N-2 and H-2 atmospheres.