低阶煤中含氧官能团分布的研究

采用化学法测定了四种典型中国低阶煤中羧基、醇羟基、酚羟基、甲氧基和羰基含氧官能团。其中,羧基的定量分析采用醋酸钙溶液和pH值为8.3的缓冲溶液进行,分析了测定条件对羧基和酸性含氧官能团测定结果的影响。结果表明,在N₂气氛下比空气条件下测定羧基含量准确,褐煤中羧酸根的主要存在形式为羧酸盐,酸洗后煤样中酚羟基的测定值随着离子交换溶液pH值的增加而增大;褐煤中的含氧官能团主要是羧基和羟基,分别占总氧量的34.49%和34.79%;在不同低阶煤中存在不同含量的羰基,甲氧基含量较小。

Determination of O-containing functional groups distribution in low-rank coals by chemical titration

Distribution of oxygen-functional groups (carboxyl, alcohol-hydroxyl, phenol-hydroxyl, methoxyl and carbonyl) in 4 Chinese low-rank coals was evaluated based on chemical analysis. Concentration of carboxyl was quantitated by acetic acid calcium ion exchange method and the buffer (pH=8.3). The effect of analysis condition on the concentration of carboxyl and total acidity was studied. The results show that the reliable results are obtained in N₂ atmosphere other than in air. The occurrence of carboxyl in coal is carboxylate. When quantitating the concentration of phenol-hydroxyl in the acid-washing brown coal with ion exchanged method, its concentration increases with increasing pH value. Concentration of carboxyl and hydroxyl account for 34.49% and 34.79%, respectively, in the total oxygen for the dry ash free basis brown coal. Different concentrations of carbonyl exist in the low-rank coals, but that of methoxyl is little.