吡啶型氮快速热解中HCN和NH_3生成机理研究

Mechanisms of HCN and NH_3 formation during rapid pyrolysis of pyridinic nitrogen containing substances

考虑煤中吡啶六元环与其他杂环的结合形式,对四种典型的吡啶型氮杂环结构及其热解中间产物中各键的Mayer键级进行了计算。通过对比Mayer键级的大小判断热解时最易发生断裂的键,进而对吡啶型氮热解时氮的逸出机理进行了分析。计算结果表明,吡啶型氮热解产生的含氮污染物主要是HCN;由于吡啶环与其他环结合方式的不同,氮的逸出过程也有差异。利用高频炉快速热解装置对吡啶和吖啶两种模型化合物进行了快速热解实验以验证计算结果。结果表明,吡啶和吖啶热解时虽有少量NH3生成,但含氮污染物仍以HCN为主,实验结果可为计算所得的结论提供一定支持。

The Mayer bond orders of 4 typical pyridinic-nitrogen structures in coal and their intermediate products were calculated with considering the combination forms of pyridine cycle with other heterocycles.On the basis of the Mayer bond orders,the bonds apt to crack during pyrolysis were deduced and the mechanisms for the release of nitrogen during pyridinic-N pyrolysis were analyzed.The result showed that pyridinc-N tends to release as HCN during pyrolysis.The diversity of the combination forms of pyridine cycles with other cycles can also lead to a variety of nitrogen release processes.Rapid pyrolysis of pyridine and acridine as pyridinic-N model compounds was conducted experimentally in a high frequency furnace;it suggested that a small quantity of NH3 is formed during pyridine and acridine pyrolysis,but HCN is the dominant nitrogen containing product.Current experimental results provide some evidences to support the calculation results.