Study of the Ferzeolite-L system Part II: CO and H chemisorption behavior

The chemisorption properties of two solids, called FerZLK and FerZLH were studied. The samples were obtained by dry impregnation of potassic and acidic forms of zeolite-L with a ferric salt, as described in Part I. The adsorption isotherms of CO at 193 K and H2 at 673 K were measured. ‘‘In situ’’ Mo¨ssbauer spectroscopy MS.at 298 and 193 K of the reduced solids with chemisorbed CO allowed to confirm the preferential location of the Fe2q exchanged with the support in both samples, in agreement with that obtained in Part I: sites D for FerZLK and sites A for FerZLH. The CO chemisorption resulted in an inappropriate method to obtain the metallic area of reduced FerZLK, since Fe2q ions in sites D also chemisorb CO with a 1:2sFe2q:CO stoichiometry. In order to obtain the amount of Fe0 surface atoms, H2 chemisorption at 673 K in 10–80 Torr pressure range was successfully used. Combining this technique with MS, it was possible to determine the values of the Fe0 crystal diameters. q2000 Elsevier Science B.V. All rights reserved.