论文部分内容阅读
本文采用了ＣＯ２程序升温脱附（ＣＯ２－ＴＰＤ）、ＣＯ２分步热脱附（ＣＯ２－ＳＴＤ）、ＣＯ２气氛中电导测量和ＣＯ２作为甲烷氧化偶联反应（ＯＣＭ）稀释气等方法，研究了在受主掺杂ＣａＴｉＯ３体系的ＯＣＭ反应中ＣＯ２的作用．受主杂质Ｌｉ＋、Ｍｇ２＋、Ａｌ３＋掺杂的ＣａＴｉＯ３系列催化剂在制备过程或ＯＣＭ反应过程中能吸附大量ＣＯ２，ＣＯ２吸附量与气氛中ＣＯ２的分压及吸附温度等因素有关．大部分吸附的ＣＯ２与催化剂中的Ｃａ（ＯＨ）２作用形成了ＣＯ３－，少部分与催化剂晶格中的活泼氧物种Ｏδ－结合形成了．在Ｈｅ气氛中６００℃时开始分解释放出ＣＯ２，７５０℃以上开始分解同时使活泼氧物种Ｏδ－裸露出来．ＣＯ２吸脱附过程是可逆的．在ＣＯ２中测量样品电导的结果表明，吸附的ＣＯ２还可能捕获价带中的正导电空穴ｈ＇，使样品的Ｐ型电导下降，从而减少了催化剂中活泼氧物种Ｏδ－的浓度，加之ＣＯ２可使Ｏδ－形成不活泼的因此ＣＯ２的存在降低了ＯＣＭ反应中Ｃ２烃的选择性．
In this paper, CO2-TPD, CO2-STD, conductivity measurement in CO2 atmosphere and CO2 as diluent gas for methane oxidative coupling reaction (OCM) The role of CO2 in the OCM reaction of CaTiO3 system doped with acceptor. CaTiO3 series catalysts doped with Li +, Mg2 + and Al3 + as acceptor impurities can adsorb a large amount of CO2 during the preparation process or OCM reaction. The amount of CO2 adsorbed depends on the partial pressure of CO2 and adsorption temperature in the atmosphere. Most of the adsorbed CO2 interacted with Ca (OH) 2 in the catalyst to form CO3-, and a small part of it formed with the active oxygen species Oδ- in the catalyst lattice. In He atmosphere begins to decompose at 600 ℃, releases CO2, starts to decompose above 750 ℃ and exposes the active oxygen species Oδ-. CO2 adsorption and desorption process is reversible. The results of measuring the conductivity of the sample in CO2 show that the adsorbed CO2 may also capture the positive conductive hole h ’in the valence band and decrease the P conductivity of the sample, thereby reducing the concentration of active oxygen species Oδ- in the catalyst. In addition, Oδ- can be made inactive so the presence of CO2 reduces the selectivity of C2 hydrocarbons in the OCM reaction.