摘要
采用共沉淀法制备了系列锰掺杂六铝酸镧LaMnxAl12-xO19催化剂。XRD表征发现,只有在锰掺杂量为2.0～2.5时,经1 200℃焙烧处理得到的催化剂中才有完整的六铝酸盐晶相。由UV-vis漫反射、H2-TPR和BET比表面积分析表明,掺杂的锰离子主要以Mn3+形式取代六铝酸盐八面体位置的Al;同时随锰掺杂量增多,催化剂中Mn3+/Mn2+比例变大,而比表面积却相应减小。O2-TPD表征也进一步发现,随锰掺杂量增多,催化剂上化学吸附晶格氧量增加,而物理吸附氧分子量减少。在甲苯催化燃烧净化反应中,锰掺杂六铝酸镧催化剂表现出良好的低温催化活性,且锰掺杂量为2.0～2.5时活性最优。推测该反应是遵循Mars-van Krevelen机理,由Mn3+和Mn2+的协同作用共同促进晶格氧的流动性。
Manganese-substituted hexaaluminate catalysts（LaMnxAl12-xO19） were prepared by coprecipitation method.X-ray diffraction（XRD） characterization indicated that the LaMnxAl12-xO19 catalysts calcined at 1 200 ℃ has only hexaaluminate phase,while no inactive LaAlO3 or LaMnO3 perovskite phase,when the amount of manganese substituted（x） is 2.0~2.5.The UV-vsible diffuse reflection spectra,H2-TPR profiles and BET specific surface area measurements showed that Al sites substituted by Mn3＋ are mainly the octahedral ones in hexaaluminate crystal at x ≥ 1.5.With the increase of the amount of manganese substituted,the Mn3＋/Mn2＋ ratio in the catalyst is increased and the specific surface area is decreased instead.O2-TPD profiles showed that the amount of lattice oxygen by chemisorption is increased and the amount of molecular oxygen by physisorption is decreased instead,with the increase of the value x.The catalytic tests for toluene combustion showed that the manganese-substituted hexaaluminate catalysts exhibits excellent low temperature activity and the preferable x value is 2.0~2.5.The catalytic combustion of toluene over LaMnxAl12-xO19 may follow the Mars-van Krevelen mechanism,in which Mn3＋ and Mn2＋ cooperate to promote the mobility of lattice oxygen.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2012年第1期100-104,共5页
Journal of Fuel Chemistry and Technology
基金
广州市科技计划项目(2010Z1-E061)
关键词
六铝酸盐
锰
甲苯
催化燃烧
hexaaluminate
manganese
toluene
catalytic combustion
