高温下煤焦表面含氧官能团对NO-煤焦还原反应的影响

Influence of the Oxygen-contained Functional Groups on the Surface of Coal Coke at a High Temperature on the NO-Coal Coke Reduction Reaction

在固定床反应器上考察了高温下不同氧浓度气氛下NO-煤焦还原反应的还原效果,并采用XPS分析了不同氧浓度预处理后的煤焦表面的含氧官能团。研究结果表明,高温下氧气对于NO-煤焦还原反应依然有显著的促进作用,也同样存在临界氧浓度(0.25%)的现象,比低温下临界氧浓度(1%)有所提前。由XPS分析结果发现,高温下氧气对煤焦表面的影响是产生促进NO还原的表面含氧官能团(C(O)),适量的氧气浓度能形成饱和的C(O)活性位,使得还原效果达到最佳。随着温度的升高,C(O)的总量略有减少。有可能是温度过高致使煤焦表面的C(O)极易达到饱和,多余的氧气以O的形式排出。

On a fixed bed reactor,the reduction effectiveness of NO-coal coke at a high temperature in different atmospheres at various oxygen concentrations was investigated and XPS(X-ray photoelectron spectroscopy) was used to analyze the oxygen-contained functional groups on the surface of coal coke after pre-treatment at various oxygten concentrations.The research results show that at a high temperature,oxygen still plays its remarkable role in promoting the NO-coal coke reduction reaction and there exists also a critical oxygen concentration(0.25%) phenomenon,which is somehow less than that(1%) at a low temperature.It can be found from the XPS analytic results that the effect of oxygen on the surface of coal coke is to produce surface oxygen-contained functional groups(C(O)) to promote the NO reduction.A proper oxygen concentration can help form saturated C(O) active sites,making the reduction effectiveness attain its optimum.With a rise in temperature,the total quantity of C(O) will decrease slightly,the possible cause of which is that an excessively high temperature makes the C(O) on the surface of coal coke very easy to attain its saturation and the redundant oxygen will be discharged in the form of O.