H 2-SCR of NO on Pt–MnO x catalysts: Reaction path via NH 3 formation

• Published in: Applied catalysis. A, General Vol. 395; no. 1; pp. 120 - 128
• Main Authors: Park, Se Min, Kim, Mi-Young, Kim, Eun Seok, Han, Hyun-Sik, Seo, Gon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2011
• Subjects: H 2-SCR; Manganese oxide; NH 3 formation; Platinum impregnation; NO; NH 3 formation; Platinum impregnation; H 2-SCR; Manganese oxide
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2011.01.033

[Display omitted] ► Prepared Pt–MnO x catalysts are active in the formation of NH 3 from NO x and H 2. ► They effectively reduce NO x by using supplied H 2 or produced NH 3. ► Manganese oxide and platinum show a synergistic effect in H 2-SCR of NO x . Pt–MnO x catalysts without any alkali or transition metals were prepared and their performance in the selective catalytic reduction (SCR) of NO by H 2 was examined. Their physicochemical properties were investigated using X-ray diffraction (XRD), extended X-ray adsorption fine structure (EXAFS), and X-ray photoelectron spectroscopy (XPS). The adsorption and removal of NO during H 2-SCR were monitored by an in situ FT-IR spectrophotometer. The co-presence of MnO and MnO 2 on Pt–MnO x was confirmed by EXAFS and XPS. NO was adsorbed on them as nitrate and nitrite, which were subsequently transformed to NH x species by the introduction of H 2. The NH x species adsorbed on the acid sites of manganese oxide were active in the reduction of NO, although a direct reduction by H 2 was also possible. The conversion of NO over the Pt(2.0)–MnO x catalyst was maximized to 64% at around 100 °C and fell with further increases in temperature. The N 2 yield over the Pt(2.0)–MnO x catalyst was 30% at the same condition, indicating that about a half of NO was converted to N 2. On the contrary, the Pt(2.0)/SiO 2 catalyst exhibited very low N 2 yield, 10%, because N 2O was highly produced. The reaction between the hydrogen atoms activated on the platinum and the activated NO on the manganese oxide was considered essential for H 2-SCR, and NH 3 that formed as an intermediate effectively participated to the selective reduction.