甲烷在氧化镧上C-H断键活性中心的研究

在不同条件下制备了一系列La~2O~3样品,以CH~4与CD~4间的氢原子交换反应作为测试反应来测量La~2O~3对CH~4分子中C-H键的断键能力.采用NH~3-TPD,CO~2-TPD和NH~3,CO~2对催化剂的中毒反应来研究La~2O~3表面的酸中心和活性中心.La~2O~3的表面组成用XPS测量.实验发现尽管酸中心在活性中心只占较小的部分. 但它与碱中心一样对于CH~4分子的C-H断键是必不可少的.本文提出, 组成活性中心的酸中心各碱中心很可能分别是一部分具有较强酸性的晶格La^3^+和具有较强碱性的晶格O^2^-,而La~2O~3晶体中晶格缺陷的形成能使更多的晶格离子成为活性中心.

Study on active sites for splitting C-H bond of Ch~4 on surface of La~2O~3

A series of La2O3 samples were prepared under different conditions. The hydrogen exchange reaction between CH4 and CD4 was chosen as test reaction to measure the activity of splitting C-H bond on La2O3. The NH3-TPD, CO2-TPD and poisoning experiments were carried out to study the acidic sites and the active sites on La2O3. The surface structure composition (O/La ratio) was measured by XPS. It was found that although being minor component of active sites, the acidic sites are also essential for the cleavage of C-H bond of CH4. The acidic sites and basic sites composing the active sites are probably a part of lattice La3+ and O2- ions, which show enough strength of acidity and basicity, resp. The formation of vacancies in La2O3 crystal can make more lattice ions become active sites.