Cheng Kai, Song Weiyu, Cheng Ying, Zheng Huiling, Wang Lu, Liu Jian, Zhao Zhen, Wei Yuechang
State Key Laboratory of Heavy Oil Processing, China University of Petroleum 18# Fuxue Road, Chang Ping District Beijing 102249 China
Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong New Territories, Hong Kong SAR Shatin China.
RSC Adv. 2018 May 24;8(34):19301-19309. doi: 10.1039/c8ra02931h. eCollection 2018 May 22.
A series of Fe Cu TiO catalysts with variable Cu doping amounts was directly synthesized by the sol-gel method and their catalytic performances were tested for the selective catalytic reduction of NO with ammonia. The highest activity was achieved on FeCuTi catalyst. NO conversion was above 80% and N selectivity exceeded 90% on this catalyst in the temperature range of 200-375 °C. High NO and NH oxidation activities facilitated the high NH-SCR activities of the catalysts in the low temperature range, while too strong NH oxidation ability resulted in the decline of NH-SCR activity. DFT calculations based on the Fe and Cu co-doping TiO model showed that the barrier of NH activation is dramatically reduced as compared to pure Fe doping. This is due to the lowered p-band of lattice O. However, such activated O will also strongly decrease the barrier for the dissociation of NH to NH species, which will lead to the formation of NO. Both Brønsted and Lewis acid sites over FeCuTi catalyst are involved in the NH-SCR reaction. The adsorption of NO is strong in the low temperature range, and large amounts of nitrates were decomposed on the catalyst surface in the high temperature range.
通过溶胶-凝胶法直接合成了一系列具有不同铜掺杂量的铁-铜-钛氧化物催化剂，并测试了它们在氨选择性催化还原一氧化氮反应中的催化性能。铁铜钛催化剂表现出最高的活性。在200-375℃的温度范围内，该催化剂上的一氧化氮转化率高于80%，氮气选择性超过90%。较高的一氧化氮和氨氧化活性促进了催化剂在低温范围内的高氨选择性催化还原活性，而太强的氨氧化能力则导致氨选择性催化还原活性下降。基于铁和铜共掺杂二氧化钛模型的密度泛函理论计算表明，与纯铁掺杂相比，氨活化的能垒显著降低。这是由于晶格氧的p带降低。然而，这种活化的氧也会强烈降低氨分解为亚氨物种的能垒，这将导致一氧化氮的形成。铁铜钛催化剂上的布朗斯特酸位和路易斯酸位都参与了氨选择性催化还原反应。一氧化氮在低温范围内的吸附很强，大量硝酸盐在高温范围内在催化剂表面分解。
