摘要
用X射线衍射和程序升温脱附方法研究了八个La-Ce-Co氧化物催化剂的结构及其氧的性能,试验了不同催化剂氨氧化反应前后氧的程脱并比较了其脱出氧的变化。测定了催化剂活性、组成及元素价态。发现催化剂的活性与三价钴离子的浓度成正比。催化剂中晶格氧的再生能力强,即氧化还原性能好,催化活性就高。结果表明,氨在La-Ce-Co氧化物体系催化剂上的氧化可能遵循Redox机理。Co^(3+)是活性中心。在催化剂中以少量Ce^(4+)取代La^(3+),可在催化剂中产生阳离子空位La_(1-x)CoO_(3+λ),有利于Co^(3+)的稳定加速体相中氧和电子的传递,促进催化剂的再氧化速度。从而提高催化剂的活性。
The properties of oxygen and structure of La-Ce-Co oxide catalysts have been studied by means of XRD and TPD. The catalytic activity for ammonia oxidation, the valence states of cobalt arid the difference of oxygen desorption before and after ammoxidation have been also examined. The results show that the ammonia oxidation over La-Ce-Co oxide catalysts may obey the redox mechanism, the active site is Cos + . The substitution of Ce4+ for La3+ can produce cation vacancies and stabilize the higher oxidation state of Co3+ as well as accelerate the transfer rate of oxygen and electron in bulk, therefore the ability of lattice oxygen regeneration is enhanced and the catalytic activity is increased.
