碱金属离子对吡咯热解生成NO_x前驱物HCN机理的影响

为了解碱金属离子对煤热利用过程中NO_x污染物形成的影响,针对煤中含氮模型化合物吡咯,在吡咯常规非催化热解机理的研究基础上,采用密度泛函理论B3LYP/6-31+G(d,p)方法,研究了碱金属离子(Na~+,K~+)对吡咯催化热解反应机理和路径的影响。结果表明,碱金属离子能显著促进吡咯热解生成HCN路径中的内部氢转移反应、协同开环反应和协同裂解反应的发生,但对分子异构化反应的影响较小。Na~+和K~+均能降低吡咯热解生成HCN决速步的活化能,从而可促进HCN的形成,且两种碱金属离子的催化作用能力为Na~+K~+。

Effect of alkali metal ions on the formation mechanism of HCN as NOx precursor during pyrrole pyrolysis

Pyrrole is selected as the N containing model compound for the investigation of the effect of alkali metal ions(Na+,K+) on NOx formation during coal thermal utilization process.Based on conventional non catalytic mechanism studies,the density functional theory(DFT) method and B3LYP/6 31+G(d,p) basis set are adopted to elucidate the pyrolysis mechanism and pathways of pyrrole.The calculation results indicate that both Na+ and K+ show significant effects on the internal hydrogen transfer,ring opening and concerted decomposition reactions,while rarely influence the internal hydrogen isomerization reaction.It is found that the alkali metal ions(Na+ and K+) can promote the formation of HCN from pyrrole through decreasing the activation energy of the rate determining step.In addition,Na+ exhibits a better catalytic activity than K+.