Effects of phenolic hydroxyl and carboxyl groups on the concentration of different forms of water in brown coal and their dewatering energy
Effects of phenolic hydroxyl and carboxyl groups on the concentration of different forms of water in brown coal and their dewatering energy
复制标题
酚羟基和羧基对褐煤中不同形态水浓度及其脱水能的影响
DOI：
10.1016/j.fuproc.2016.08.006
复制
发表时间：
2016-12-15
影响因子：
7.5
通讯作者：
Li, Wen
中科院分区：
文献类型：
--
作者：
Han, Yan-Na;Bai, Zong-Qing;Li, Wen
含氧官能团作为水的主要吸附位，是控制褐煤水分再吸附和干燥行为的关键因素之一。褐煤因含氧官能团不同而产生的脱水能尚不清楚。因此，选择了两种孔结构相似、酚羟基和羧基含量较高的氧化褐煤样品。根据恒温恒湿条件下的持水量和热重-差示扫描量热法分析的脱水实验结果，确定了不同水形态的样品浓度。结果表明，自由水、毛细水和分子水的浓度与羧基浓度有较好的相关性。对比干燥和增湿样品的H-1 NMR分析表明，含氧官能团的类型主要影响煤中的水环境。干燥和吸附后的D2 O样品的红外光谱表明，羧基比酚羟基更容易破坏OH-pi氢键。羧基含量高的样品的初生位水脱附能和脱水能均低于酚羟基含量高的样品，这是因为水与羧基羟基氧的氢键结合能低于水与酚羟基羟基氧的氢键结合能。(C)2016爱思唯尔B. V.保留所有权利。
Oxygen functional groups as primary adsorption site of water are one of key factors controlling water re-adsorption and drying behaviors of brown coal. The dewatering energy of brown coal because of different oxygen functional groups is still unclear. Thus, two kinds of oxidized brown coal samples carrying more phenolic hydroxyl or carboxyl groups with similar pore structures were chosen. The concentrations of different water forms of the samples were determined from the moisture holding capacity at constant humidity and temperature and from the results of dewatering experiments analyzed by thermogravimetry coupled with differential scanning calorimetry. The results showed that the concentrations of three forms of water, i.e. free water, capillary water, and molecular water, showed good correlations with concentration of carboxyl groups. Comparison of H-1 NMR analysis of dried and moisturized samples showed that the types of oxygen functional groups predominantly affected the water environment in coal. IR spectra of dried and adsorbed D2O samples showed that OH-pi hydrogen bond due to carboxyl groups was easier broken than that due to phenolic hydroxyl groups. The water desorption energy of primary site and dewatering energy of samples with more carboxyl groups were lower than that of samples with more phenolic hydroxyl groups, because hydrogen bonding energy of water bonded to hydroxyl oxygen of carboxyl groups was lower than that of water bonded to hydroxyl oxygen of phenolic hydroxyl groups. (C) 2016 Elsevier B.V. All rights reserved.