NO and C 3H 6 adsorption and coadsorption in oxygen excess—A comparative study of different type zeolites modified with gold

Abstract

Non-acidic NaY, and acidic H-Beta and H-ZSM-5 with various Si/Al ratios were used as supports for gold loaded by deposition-precipitation method. Acidity of the pristine supports and Au/zeolites was estimated from adsorption of pyridine followed by FTIR spectroscopy measurements. NO selective reduction with propene (SCR-HC) was studied by the use of FTIR technique. Adsorption and co-adsorption of the reagents of NO SCR-HC (NO, C 3H 6 and O 2) allowed a discussion of the reaction pathways. The catalytic behaviour of NaY referring to the intermediate formed was not significantly changed by gold modification and Au/NaY did not activate the partial oxidation of propene in the absence of NO. Au particles in Au/Na-Y play an important role in the total oxidation to CO 2. The role of Brønsted acidity in Au/H-Beta and Au/H-ZSM-5 is on the oxidation of NO towards various intermediates (NO 2 −/NO 3 −, N 2O 4, NO +) and their further interaction with propene, whereas gold species enhance this process by inducing formation of additional active complex (Au n+ -NO). Moreover, gold species are responsible for the second reaction pathway via primary partial oxidation of propene to oxygenates and further reaction with NO and R-CN and R-NCO active intermediates as observed on Au/H-Beta and Au/H-ZSM-5.