Investigation of the Pt/MOR–Al2O3 Catalysts by IR Spectroscopy

Different Reaction Mechanisms of Ammonia Oxidation Reaction on Pt/Al2O3 and Pt/CeZrO2 with Various Pt States

“…50,51 Correspondingly, the Brønsted peak was at 1567 and 1401 cm −1 . 31 The area of NH 3 adsorbed decreased with the increase of temperature, which was the same with that of Pt/Al 2 O 3 . It was interesting that the new peak of 1328 cm −1 appeared suddenly at 250 °C and then disappeared with the reaction progress, which must be an intermediate species for ammonia oxidation reaction.…”

“…FTIR spectra of NH 3 adsorbed on Pt/CeZrO 2 are showed in Figure b . In detail, the adsorption peaks of 1300, 1200–1000, and 3500–3000 cm –1 belonged to ammonia bonded on Lewis sites. , Correspondingly, the Brønsted peak was at 1567 and 1401 cm –1 . The area of NH 3 adsorbed decreased with the increase of temperature, which was the same with that of Pt/Al 2 O 3 .…”

“…The bands of 3000−3500 and 1000−1200 cm −1 were ammonia bonded on Lewis sites, whereas ammonia bonded on Brønsted sites was found at 1627 cm −1 . 31,50 The same with Pt/Al 2 O 3 , the ammonia bonded on Lewis sites was a major contributor to NH 3 -SCO activity when the adsorption peak area was decreased significantly. It was very interesting that an adsorbed nitroxyl (HNO) species (1470 cm −1 ) appeared at 5 min, without increasing as the reaction progress, which could be an intermediate species for ammonia oxidation.…”

“…The bands of 2062 cm −1 were CO bonded on metallic Pt states, and the bands of 2097 cm −1 belonged to mild Pt oxidation states. 31 Both metallic Pt and mild Pt oxidation states were observed over Pt/CeZrO 2 and Pt/Al 2 O 3 catalysts. But the Pt species of Pt/CeZrO 2 contained a larger amount of mild Pt oxidation states, whereas more Pt metallic states existed in Pt/ Al 2 O 3 .…”

“…After the samples were pretreated in N 2 , the CO-FTIR result for Pt species was provided in Figure a. The bands of 2062 cm –1 were CO bonded on metallic Pt states, and the bands of 2097 cm –1 belonged to mild Pt oxidation states . Both metallic Pt and mild Pt oxidation states were observed over Pt/CeZrO 2 and Pt/Al 2 O 3 catalysts.…”