Takemoto Masanori, Fujinuma Haruko, Sugawara Yoshihiro, Sasaki Yukichi, Iyoki Kenta, Okubo Tatsuya, Yamaguchi Kazuya, Wakihara Toru
Department of Chemical System Engineering, School of Engineering, The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan
Nanostructures Research Laboratory, Japan Fine Ceramics Center 2-4-1 Mutsuno, Atsuta-ku Nagoya 456-8587 Japan.
RSC Adv. 2024 Nov 6;14(48):35498-35504. doi: 10.1039/d4ra05934d. eCollection 2024 Nov 4.
Manganese octahedral molecular sieves with an α-MnO crystal structure (OMS-2) and their related materials have attracted significant attention for the selective catalytic reduction of NO using NH (NH-SCR) at low temperatures. Further lowering their operating temperature should be an effective method to develop an environmentally friendly de-NO system; however, their catalytic activity at low temperatures, especially below 100 °C, remains poor. This study describes a post-synthetic approach to develop Mn-based catalysts superior to those in the literature that operate at ultralow temperatures. Post-synthetic planetary ball milling for OMS-2 caused the partial conversion of OMS-2 into β-MnOOH. The obtained nanocomposite catalysts possessed abundant surface oxygen vacancies and strong surface acidity, allowing the milled catalyst to exhibit higher NO conversion at 90 °C (91%) than that in freshly prepared OMS-2 without planetary ball milling (29%). Lowering the operation temperature of OMS-2 catalysts contributed to the suppression of NO evolution during NH-SCR over manganese-based catalysts, resulting in high N selectivity over the milled OMS-2 catalyst (93%).
