Ce掺杂增强粉煤灰基Cu-SSZ-13分子筛催化剂的NH_(3)-SCR脱硝性能和水热稳定性

A study of Ce doping of the coal fly ash-derived Cu-SSZ-13 molecular sieve catalysts and their enhancement on NH_(3)-selective catalytic reduction and hydrothermal

以煤粉煤基霞石为原料,通过原位转晶法制备Cu-SSZ-13分子筛催化剂,采用离子交换法负载一定量的Ce离子,研究其NH_(3)选择性催化还原(SCR)氮氧化物的性能.Cu-SSZ-13在200~700℃内的NO转化率均超过90%.Ce改性显著提高了Cu-SSZ-13在低温范围内的NO转化率,水热老化后,NO转化率超过90%的温度窗口由220~515℃拓宽至180~560℃,Ce^(3+)的引入提高了水热过程中的抗老化性能.采用X射线衍射分析(XRD)、扫描电子显微镜分析(SEM)、H_(2)程序升温还原(TPR)和NH_(3)程序升温脱附(TPD)等手段对样品进行了表征.结果表明,Ce^(3+)与分子筛脱硝性能和水热稳定性密切相关.水热老化后,酸性位点和活性组分Cu2+得以大部分保存.

Molecular sieve catalyst Cu-SSZ-13 was prepared from coal fly ash(CFA)-derived cancrinite by in-situ interzeolite transformation,and the Ce^(3+)-doped catalyst CeCu-SSZ-13 was further made by ion-exchange method.The catalysts were used to study the ammonia selective catalytic reduction(NH_(3)-SCR)of NO_(x).The NO conversion of catalyst Cu-SSZ-13 was over 90%in 200~700℃.The Ce^(3+)doping broadened the temperature window for NO_(x) conversion to be 90%or higher from 220~515℃to 180~560℃.The addition of Ce^(3+)also improved the aging resistance during hydrothermal treatment.The catalysts were characterized by X-ray diffraction(XRD)analysis,scanning electron microscopy(SEM)analysis,H_(2) temperature-programmed reduction(TPR)and NH_(3) temperature-programmed desorption(TPD).The doping of Ce^(3+)not only enhanced the denitrification performance but also preserved the acidic sites and active component Cu^(2+)of the catalysts.