Ru/HY and Ru/NaY catalysts were prepared by ion-exchange from an aqueous solution of [Ru(NH3)(6)]Cl-3 The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR). The results showed that Si/AI ratio of the zeolite framework after use depends on the catalyst preparation procedure. Upon activation in He, Si/A1 ratio in Ru/NaY is similar to that of initial zeolite NaY. After exposure to reaction conditions, NMR data show dealumination, whose extent increases with Ru loading. Samples activated in He followed by ion exchange with NaNO3 (neutralization) and reactivated in CH4/CO2/N-2 undergo only slight dealumination. The results suggest that during reaction the charge compensating protons, generated during Ru reduction, cause dealumination, accompanied by local destruction of the zeolite structure. The structure of zeolite and Ru dispersion was therefore, stabilized and the catalyst specific activity increased by neutralizing the protons prior to use in CO2 reforming.