The interaction of molecular hydrogen with the surface of MoO3-ZrO2 was observed using infrared IR and electron spin resonance (ESR) spectroscopy, and the hydrogen adsorption was quantitatively evaluated in the temperature range of 323-573 K. The hydrogen adsorbed IR results confirmed the formation of a new broad band in the range of 3700-3400 cm(-1). which corresponds to hydrogen-bonded OH groups. A decrease in the ESR signals indicated the formation of electrons that have been trapped by the electron-deficient metal cations and/or oxygen radicals. The hydrogen adsorbed IR and ESR results suggested that the protons and electrons were formed on the surface of MoO3-ZrO2 from molecular hydrogen enhancing the isomerization of n-heptane. A quantitative study of the hydrogen adsorption showed that the rate of hydrogen uptake was high for the first few minutes at 473 K and above, and the rate reached an equilibrium value within 10 h. At 423K. different features of the hydrogen adsorption were observed on MoO3-ZrO2, where the hydrogen uptake increased slowly with time and did not reach equilibrium after 10 h. The rate of hydrogen adsorption increased slightly at 373 K and below. Hydrogen adsorption on MoO3-ZrO2 involves two successive steps. The first step involves hydrogen dissociation on a specific site on the MoO3-ZrO2 catalyst to form hydrogen atoms, and the second step involves the surface diffusion of the hydrogen atoms on the MoO3-ZrO2 surface. Then the hydrogen atom becomes a proton by donating an electron to an adjacent Lewis acid site. The rate-controlling step involves the surface diffusion of hydrogen atoms and has an activation energy of 62.8 kJ/mol. A comparison of the hydrogen adsorption on SO42--ZrO2, WO3-ZrO2 and MoO3-ZrO2 catalysts is discussed. (C) 2011 Elsevier B.V. All rights reserved.