The in situ interaction of nitric oxide (NO) gas on the cerium framework-substituted ZSM-5 and mordenite zeolites was studied by FT-IR spectroscopy. Samples of ZSM-5 and mordnite-containing cerium (7.5 wt.% expressed as CeO2) have been hydrothermally synthesized from starting gel upon which the introduction of cerium is being made during synthesis of zeolites. The morphological and textural characteristics of cerium-free and cerium-containing zeolites were studied using XRD, FT-IR in the T-O range, and N-2 adsorption at -196 degrees C. The results revealed that the insertion of cerium in both zeolites led to a decrease in their degree of crystallinity. Such a decrease was 36% for Ce-ZSM-5 while it was 18% for Ce-mordenite. The results indicated a significant decrease in nitrogen sorption capacity (BET) by 31% from 624 to 431 m(2)/g and also a decrease of the micropore volume by 27.8% from 0.579 to 0.418 cm(3)/g for Ce-ZSM-5. These results were found on the other extreme in case of Ce-mordenite. The presence of Cc did not affect the cell volume of ZSM-5 much, while it increased that of mordenite. Most of Ce-IV ions were embedded in the framework of mordenite, where they exposed as extra-framework CeO2 and cerium silicate in ZSM-5. The in situ interaction of NO on Ce-zeolites was studied using an FT-IR quartz cell. The adsorption of NO gas led to the formation of a series of nitrosyl species: N2O (2245 cm(-1)), NO+ (2160 cm(-1)), NO (1910 cm(-1)), N2O3 (1880, 1580 cm(-1)), (NO)(2s,as) (1844, 1734-1720 cm(-1)), NO2 (1630 cm(-1)) and ionic compounds were stable upon evacuation, i.e. nitrato and nitrito NOx- (x = 2-3) (1300-1500 cm(-1)). Such nitrosyl complexes were favorably formed on Ce-ZSM-5 than on Ce-mordenite due to facilitated intervention of the cerium couple (Ce-III/Ce-IV) on the former than on the latter. (c) 2005 Elsevier B.V. All rights reserved.