活性炭表面含氧官能团对燃煤烟气氮氧化物脱除的影响

Effect of oxygen-containing functional groups on the removal of nitrogen oxides from coal-fired flue gas on activated carbon

采用HNO3、H2SO4及H2O2对煤基活性炭进行氧化改性处理,研究低温(<250℃)下NH3为还原剂的选择催化还原(SCR)NOx的反应性能.通过元素分析、表面积和孔分布、Boehm滴定、TPD-MS、XPS分析对氧化前后活性炭表面物理化学性质进行分析,对表面含氧基团含量进行了定性定量研究.结果表明,与H2SO4及H2O2处理后相比,活性炭经HNO3氧化处理后表面羧基、酸酐和羟基含量明显增加,在考察温度范围内SCR活性明显提高,HNO3是最佳氧化剂.含氧基团含量与SCR活性的关联结果表明,羧基、酸酐和羟基等3种含氧基团对HNO3改性后活性炭样品的SCR活性提高发挥主要作用.

Coal-based activated carbon was oxidized by HNO3, H2SO4 and H2O2 and applied to the selective catalytic reduction(SCR) of NOx at low temperature(<250 °C) with NH3 as a reducing agent. The physicochemical properties of activated carbon before and after oxidation treatment were characterized by elemental analysis, surface area and pore size distribution, Boehm titration, TPD-MS and XPS analysis, and the content of surface oxygen was studied qualitatively and quantitatively. Results showed that compared with the treatment of H2SO4 and H2O2, the content of carboxyl, anhydride and hydroxyl in the surface of activated carbon was significantly increased after the oxidation treatment of HNO3 and SCR activity was improved obviously in the reaction temperature, thus HNO3 was regarded as the best oxidant reagent. Furthermore, the correlation between the content of oxygen-containing groups and SCR activity indicated that three oxygen-containing groups of carboxyl, anhydride and hydroxyl were found to be mainly responsible for the promoted SCR activity of HNO3 modified AC.