改性活性炭表面羧基的催化动力学分析

Determination of carboxylic group content on modified activated carbon surface by Catalytic kinetic analysis

采用催化动力学分析法测定了浓HNO3或H2O2改性处理的活性炭表面羧基。选择环氧苯乙烷和甲醇在苯甲酸或改性活性炭催化下的加成反应为指示反应，采用固定时间法考察了环氧苯乙烷转化率与催化剂用量关系。结果表明：在反应初始阶段（转化率低于25％），当苯甲酸用量在O．2～0．6mmol、活性炭用量在0．4～0．8g范围内时，环氧苯乙烷的转化率随反应时间的变化为过原点的直线。以苯甲酸羧基量为参照，浓HNO3与H2O2氧化改性活性炭的表面羧基的质量摩尔浓度分别为0．67mmol／g和0．34mmol／g。与经典的Boehm滴定法相比，此法准确地反映了实际液-固反应中活性炭的表面羧基量。

The content of carboxylic groups on activated carbon surface oxidized with concentrated nitric acid or hydrogen peroxide was determined by catalytic kinetic analysis method. Selecting the addition reaction of 1,2-epoxyethy-benzene and methanol catalyzed by benzoic acid or phenol or surface oxidized activated carbons as indication reaction, the content of carboxylic groups on activated carbon surface was determined. At early reaction stage （when conversion is below 25%）, when benzoic acid dosage is 0.2～0.6 mmol or activated carbon 0.4～0.8 g, the variation of the 1,2-epoxyethybenzene conversion efficiency is linear to reaction time. Compared to benzoic acid, the content of carboxylic groups on surface of activated carbon oxidized with concentrated nitric acid or hydrogen peroxide is 0.67, 0.34 mmol/g, respectively. Compared to boehm titration method, catalytic kinetic analysis method is of more simphcity and higher sensitivity.