摘要
The reactions of soot with gaseous and adsorbed NO2were tested over the K/MgAlO catalyst.After the reaction intermediates were identified by combination of in situ IR characterization and first-principles calculation,the different mechanisms were elucidated.It was found that the reactivity of adsorbed NO2is lower than that of the gas form.The adsorbed NO2reacts with soot in the form of nitrates,leading to the observation of two IR bands at 2,234and 2,110 cm-1,which are ascribed to the vibration frequencies of cyanates on K sites and cyanides on the MgAlO support,respectively.On the contrary,the isocyanates were confirmed as intermediates in the reaction of soot with gaseous NO2.Because the adsorbed NO2species(i.e.,nitrates)are restricted by the electrostatic field of K+,the cyanates are produced and readily cracked into cyanides,which transfer to the MgAlO support.The gaseous NO2favours the production of isocyanates due to their higher stability.The weaker reactivity of adsorbed NO2at lower temperatures can be attributed to the restriction of the electrostatic field of K+.
The reactions of soot with gaseous and adsor- bed NO2 were tested over the K/MgA1O catalyst. After the reaction intermediates were identified by combination of in situ IR characterization and first-principles calculation, the different mechanisms were elucidated. It was found that the reactivity of adsorbed NOa is lower than that of the gas form. The adsorbed NOe reacts with soot in the form of nitrates, leading to the observation of two IR bands at 2,234 and 2,110 cm-1, which are ascribed to the vibration fre- quencies of cyanates on K sites and cyanides on the MgAlO support, respectively. On the contrary, the isocy- anates were confirmed as intermediates in the reaction of soot with gaseous NO2. Because the adsorbed NOe species （i.e., nitrates） are restricted by the electrostatic field of K＋, the cyanates are produced and readily cracked into cya- nides, which transfer to the MgAlO support. The gaseous NO2 favours the production of isocyanates due to their higher stability. The weaker reactivity of adsorbed NO2 at lower temperatures can be attributed to the restriction of the electrostatic field of K＋.
基金
supported by the National Natural Science Foundation of China (21307142,21077043,21107030 and 21277060)
the China Postdoctoral Science Foundation (2013M531490)
the Foundation for Selected Postdoctoral Project of Zhejiang Province (BSH1302053)
