点击次数：

论文类型：期刊论文

发表时间：2010-11-01

发表刊物：ENVIRONMENTAL SCIENCE & TECHNOLOGY

收录刊物：EI、PKU、ISTIC、SCIE、Scopus

卷号：44

期号：21

页面范围：8254-8258

ISSN号：0013-936X

摘要：The soot combustion with NOx and/or O-2 on potassium-supported Mg-Al hydrotalcite mixed oxides under tight contact condition was studied using temperature-programmed oxidation (TPO), isothermal reaction and in situ FTIR techniques. The presence of NOx in O-2 favors the soot combustion at lower temperatures (<300 degrees C). However, a little suppression was observed at higher temperatures (>300 degrees C), which was accompanied by a substantial NO,reduction. The ketene (C=C=O) and isocyanate (NCO-) species were determined as the reaction intermediates. In NOx + O-2, NO2 directly interacts with the free carbon sites (C=C*) through two parallel reactions: (1) NO2 + C=C* -> C=C=O + NO; (2) NO2 + C=C* -> NCO- + CO2. The two reactions can proceed easily, which accounts for the promotion effect of NOx on soot combustion at lower temperatures. The further oxidation of NCO- by NO2 or O-2 is responsible for the simultaneous reduction of NOx. However, the reactions between NO2 and C=C* are limited by the amount of free carbon sites, which can be provided by the oxidation of soot by O-2 at higher temperatures. The interaction of NOx and catalyst results in the formation of nitrates and nitrites, which poisoned the active K sites.