摘要
以低价元素掺杂SrTiO_3形成的SrTi_(1-x)MxO_(3-δ)(M=Al^(3+),Mg^(2+),Li^+;x=0～0.2)基本保持了SrTiO_3晶格结构。随着掺杂元素价态的降低和掺杂量的增加,p型电导升高,甲烷氧化偶联反应的C_2选择性和C_2收率也增加。在以不同价态元素掺杂的SrTiO_3体系中,发现C_2选择性和C_2收率与催化剂P型电导间有线性关系。认为掺杂SrTiO_3催化剂中的正导电空穴易与晶格氧发生电子交换生成部分还原态的活泼氧物种O^-,它可以使CH_4分子活化生成CH_3,进一步偶联生成C_2产物。掺杂SrTiO_3催化剂在甲烷氧化偶联反应初始阶段可吸收反应中产生的CO_2,使结构发生少许变化,稳定的SrTiO_3结构有利于甲烷氧化偶联活性的稳定。
Acceptor-doped SrTiO3(SrTi1-xMxO3-δ, M = Al3+ , Mg2 + , Li+) has a cubic crystal structure of ABO3. The partial substitution of acceptor impurities (Al3+ , Mg2 + , Li+) for Ti4+ in SrTiO3 could result in a significant improvement of C2 selectivity in the oxidative coupling of methane, while the CH4 conversion appeared to be unchanged. The C2 selectivity was increased with the decrease of the valence of the doped ions or the increase of the doped amount. A good linear relationship between the C2 selectivity and the logarithm of conductivity of the acceptor-doped SrTiO3 was observed. The non-fully-reduced oxygen species O-, O2-, or O22- produced by the interaction between the excess holes in valence band of the p-type semiconductor and the lattice oxygen seems to be responsible for the C2 formation. Acceptor-doped SrTiO3 is a stable catalyst for the oxidative coupling of methane.
基金
国家自然科学基金
