Methanol interaction with NO 2: An attempt to identify intermediate compounds in CH 4-SCR of NO with Co/Pd-HFER catalyst

Abstract

The objective of this work is the study of fundamental common aspects of NO x catalytic reduction over a Co/Pd-HFER zeolite catalyst, using methanol or methane as reducing agent. Temperature Programmed Surface Reaction (TPSR) studies were performed with reactant mixtures comprising NO 2 and one of the reducing agents. The formation of formaldehyde was detected in both studied reactions (NO 2–CH 4 and NO 2–CH 3OH) in the temperature range between 100 and 220 °C. At higher temperature, when the NO x reduction process effectively begins, formaldehyde starts to be consumed. Using methanol as reducing agent, nitromethane and nitrosomethane, are detected. At 300 °C these species are consumed and cyanides and iso-cyanides formation occurs. On the contrary, with methane, these last species were not detected; however, there are strong evidences for CH 3NO and CH 3NO 2 formation. Thus, using methanol or methane, similar phenomena were detected. In both cases, common intermediary species seem to play an important role in the NO x reduction process to N 2. These results suggest that methanol can be considered as a reaction intermediate species in the mechanism of the reduction of NO 2 with methane, over cobalt/palladium-based ferrierite catalysts.