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The copper-modified ZSM-5 zeolites, prepared by ion-exchange in an aqueous solution of Cu(CH 3 COO) 2 and subjected to different treatments were studied by FTIR spectroscopy using molecular hydrogen adsorbed at 77 K and at room temperature as a probe. For reduced and calcined CuZSM-5 samples broad range IR spectra were measured and discussed in detail. At least two different Cu 1 sites in CuZSM-5 reduced with CO were distinguished using molecular hydrogen as a probe. It was established that the copper adsorption sites which strongly perturb hydrogen molecules are Cu 1 ions that also strongly adsorb dinitrogen molecules. For reduced CuZSM-5 adsorption isoterms of H 2 , N 2 and CO were measured. A comparison of the amounts of strongly adsorbed H 2 , N 2 and CO has also been made. The amounts of adsorbed molecules decreased in the following sequence: CO 4 N 2 4 H 2 . Based both on the results of FTIR studies and measurements of amounts of adsorbed H 2 , N 2 and CO it was concluded that there are different Cu 1 sites which differ in the strength of interaction with adsorbed molecules probably due to different localization in the zeolite framework.

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