Promotional Effects on NH 3 -SCR Performance of CeO 2 –SnO 2 Catalysts Doped by TiO 2 : A Mechanism Study,Catalysis Surveys from Asia

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Promotional Effects on NH 3 -SCR Performance of CeO 2 –SnO 2 Catalysts Doped by TiO 2 : A Mechanism Study
Catalysis Surveys from Asia ( IF 3 ) Pub Date : 2021-01-02 , DOI: 10.1007/s10563-020-09318-0
Caixia Liu , Yalian Bi , Huijun Wang , Ziyin Zhang , Jian Wang , Mingyu Guo , Qingling Liu

Abstract

A novel Ti-doped Ce– Sn mixed oxide (Ce–Sn–Ti) catalysts were developed for the selective catalytic reduction (SCR) of NOx with NH₃. The addition of titanium could improve SCR activity at a low-temperature window. By optimizing the element proportions, the NOx conversion of Ce_0.6Sn_2.4Ti₂ catalysts could reach more than 90% in a wide-operating temperature window (200 –450 °C). The appropriate doping Ti formed Sn–O-Ti, Sn–O-Ce and Ti–O-Ce structures, which could increase the content of Ce³⁺ through electrons transfer from Sn or Ti to Ce (Ce³⁺ + Ti⁴⁺ ↔ Ce⁴⁺ + Ti³⁺ and 2Ce⁴⁺ + Sn²⁺ ↔ 2Ce³⁺ + Sn⁴⁺). The solid solution structure increased specific surface areas, active sites (Ce³⁺), and Lewis acid sites over the Ce_0.6Sn_2.4Ti₂ catalysts. According to DRIFTS results, only bidentate nitrate could react with adsorbed NH₃ species. However, adsorbed NH₃ species could quickly react with the gaseous NO. The NH₃-SCR reaction mechanism over Ce_0.6Sn_2.4Ti₂ catalysts mainly followed the Eley –Rideal mechanism.

Graphic Abstract

The electron transfer between tin, cerium, and titanium elements led to generate more active sites (Ce³⁺) used for NH₃ and NO_x activation/oxidation, which improved SCR activity. The NH3-SCR reaction mechanism over Ce_0.6Sn_2.4Ti₂ catalyst mainly followed the Eley−Rideal mechanism, in which adsorbed NH₃ species could quickly react with the gaseous NO to generate N₂ and H₂O.

中文翻译：

TiO 2掺杂对CeO 2 -SnO 2催化剂NH 3 -SCR性能的促进作用机理研究

摘要

开发了一种新型的Ti掺杂的Ce-Sn混合氧化物（Ce-Sn-Ti）催化剂，用于用NH ₃选择性还原NOx 。钛的添加可以改善低温窗口下的SCR活性。通过优化元素比例，Ce _0.6 Sn _2.4 Ti ₂催化剂的NOx转化率可在宽工作温度范围（200 –450°C）中达到90％以上。合适的掺杂的Ti形成的Sn-O-Ti系，Sn-O的铈和Ti-O-Ce的结构，这可能会增加Ce的含量³⁺通过电子选自Sn或Ti转移到的Ce（铈³⁺ +的Ti ⁴⁺ ↔Ce ⁴⁺ + Ti ³⁺和2Ce ⁴⁺ + Sn²⁺ ↔2Ce ³⁺ + Sn ⁴⁺）。固溶体结构增加了Ce _0.6 Sn _2.4 Ti ₂催化剂的比表面积，活性位点（Ce ³⁺）和路易斯酸位点。根据DRIFTS结果，只有硝酸双齿可以与吸附的NH ₃发生反应。但是，吸附的NH ₃物质可以与气态NO快速反应。Ce _0.6 Sn _2.4 Ti ₂催化剂上的NH ₃ -SCR反应机理主要遵循Eley-Rideal机理。