State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China.
Sci Total Environ. 2020 Oct 20;740:140158. doi: 10.1016/j.scitotenv.2020.140158. Epub 2020 Jun 12.
A series of N-doped carbons were prepared to investigate the effect of different N-containing groups on selective catalytic reduction (SCR) of NOx with NH. Combined the SCR activity with the results of porosity analysis and X-ray photoelectron spectroscopy, it's deduced that the pyridinic N (N-6) rather than the surface area or doped total N was mainly responsible for the promoted SCR activity. The electron paramagnetic resonance and O-temperature programmed desorption (O-TPD) experiments indicated that N-6 created numerous of oxygen vacancy. The NO+O-TPD and transient response of NH further demonstrated that the increased oxygen vacancy enhanced the absorbability and reactivity of NOx, therefore the SCR reaction was elevated by accelerating the reaction in the Langmuir-Hinshelwood (L-H) mechanism. Furthermore, the NH-TPD suggested that N-6 was conductive to the NH adsorption. In situ DRIFTs of NH adsorption and reaction illustrated that the increased NH mainly existed as NH species, which were quickly consumed by NO+O, further elevated the reaction between gaseous NO and adsorbed NH in the Eley-Rideal (E-R) mechanism. The N-6 groups doped in the activated carbons facilitated the L-H and E-R reactions and thus promoted the SCR activity.
一系列氮掺杂碳被制备出来，以研究不同含氮基团对 NH3 选择性催化还原（SCR）NOx 的影响。结合 SCR 活性、孔隙率分析和 X 射线光电子能谱的结果表明，吡啶氮（N-6）而不是比表面积或掺杂总氮是主要负责促进 SCR 活性的物质。电子顺磁共振和 O-程序升温脱附（O-TPD）实验表明，N-6 产生了大量的氧空位。NO+O-TPD 和 NH 的瞬态响应进一步表明，增加的氧空位增强了 NOx 的吸收和反应性，因此通过加速 Langmuir-Hinshelwood（L-H）机制中的反应来提高 SCR 反应。此外，NH-TPD 表明 N-6 有利于 NH 的吸附。原位 DRIFTs 吸附和反应表明，增加的 NH 主要以 NH 物种存在，它们很快被 NO+O 消耗，进一步提高了 Eley-Rideal（E-R）机制中气相 NO 和吸附 NH 之间的反应。在活性炭中掺杂的 N-6 基团促进了 L-H 和 E-R 反应，从而促进了 SCR 活性。
