Nitric oxide adsorption and desorption on alumina supported palladium

The adsorption properties of nitric oxide (NO) on alumina supported palladium were studied by a simultaneous thermogravimetric-analysis and differential-scanning-calorimetry (TGA-DSC) in a temperature ranges between 220 and 470 K. Upon adsorption, NO molecules on both Pd/Al2O3 and Pd/NaOH-Al2O3 samples were molecularly adsorbed between 220 and 300 K. Some NO molecules were strongly adsorbed on Pd/NaOH-Al2O3 and possessed a higher enthalpy of adsorption [approximately 140 kJ (mol NO)(-1)] than Pd/Al2O3 [approximately 114 kJ (mol NO)(-1)]. Upon heating above 320 K, the adsorbed NO molecule on these palladium surface was dissociated. In addition, a temperature programmed desorption and mass spectrometer (TPD-MS) study in a temperature range between 300 and 1100 K further indicated that some strongly adsorbed NO molecules may stay on basic sites (*b) and Pd-NaOH interface sites (*i) to enhance the decomposition of NO.