Adsorption behavior of nitrogen monoxide on KxGaxSn8-xO16 hollandite

Fine powder of KxGaxSn8-xO16 hollandite was prepared by the sol-gel process using metal alkoxides, and the adsorption behavior of nitrogen monoxide (N O) on it was examined by temperature programmed desorption (TPD) method and in situ diffuse reflectance fourier transform infrared spectroscopy. Any s pecies other than nitrogen monoxide were not detected in the TPD measuremen t, and the profile showed three stages between 420 and 880 K which were reg arded as the desorption of chemically adsorbed NOx species. This desorption behavior seems well consistent with the spectral changes in the FT-IR meas urement. The absorption band at 1270 cm(-1) was decayed in the first stage from 420 to 640 K, and the bands at 1235 and 1570 cm(-1) in the second stag e from 640 and 770 K. In the third stage above 770 K, the strong band at 13 40 cm(-1) disappeared. These NOx species on the hollandite were estimated t o have a form of NO3- in the first and second stages and a form of NO2- in the third stage, considering the data on adsorption of nitrogen oxides on L a2O3 and CaO.