FTIR studies of butane, toluene and nitric oxide adsorption on Ag exchanged NaMordenite

Abstract

In this work, we studied the adsorption of butane, toluene and nitric oxide on NaMordenite exchanged with different amounts of silver. The reactions that occurred when the adsorbed hydrocarbons interacted with NO and the effect of water adsorption were also addressed. Different silver species were formed after ion exchange and they were detected by TPR analysis. Highly dispersed Ag 2 O particles were reduced at temperatures lower than 300°C whereas Ag + exchanged ions showed two TPR peaks, which can be ascribed to species exchanged at different mordenite sites. The TPD experiments after adsorption of NO at 25°C showed that the only desorbed species was NO 2 which was formed by the total reduction of Ag 2 O particles. When the adsorbed butane was exposed to NO (1000 ppm), isocyanate species were formed on Ag + ionic sites as well as Ag + -(NOx)-CO species. Toluene adsorption was stronger than butane since adsorbed toluene molecules were held even at 400°C. The characteristic bands of the aromatic ring C=C bond was observed as well as that of methyl groups interacting with Ag + and Na + ions. However, the appearance of carboxylic groups at temperatures above 300°C in inert flow indicated the partial oxidation of toluene due to Ag 2 O species present in the samples. After contacting adsorbed toluene with NO, different FTIR bands correspond to organic nitrocompounds, isocyanate, cyanide and isocyanide species adsorbed on Ag + ions, were detected. The presence of water inhibited the formation of NO 2 species and the hydrocarbon adsorption on Na + sites but did not affect the toluene-Ag + interaction.

Adsorption of iodine on hydrogen‐reduced silver‐exchanged mordenite: Experiments and modeling

“…Previous studies also reported that high temperatures up to 1173 K were required to reduce the Ag in AgZ crystals. The AgZ used in these studies was prepared by ion exchange of commercial NaZ (Si/Al: 6.5:1) in AgNO 3 solution, which had different properties to the commercial AgZ pellets (Si/Al: 5:1) used in this study.…”

Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques

“…This could indicate that a higher fraction of oxide is present in this sample or that the oxide clusters are slightly larger than those in Ag 10 M. The TPR results 26,27 shows that a higher silver content increases the amount of oxide formed in the sample volume. An important advantage of this technique is that it is element specific, thus providing selective information on silver.…”

Influence of the postsynthesis preparation procedure on catalytic behaviour of Ag-loaded BEA zeolites in the hydrodechlorination of 1,2-dichloroethane into value added products

“…The first of them can be attributed to the reduction of Ag2O present in extra-framework positions. Two reduction peaks with the maximum at higher temperature may be assigned to reduction of silver species (Ag + ions) at exchange positions and/or strongly interacting with zeolite support (probably two types of silver species) [45].…”