Temperature-programmed desorption of organic bases on NaY zeolite under chromatographic conditions

Temperature programmed desorption (TPD) of pyridine, 2,6-dimethylpyridine, piperidine, quinoline and n-butylamine on NaY zeolite has been studied under chromatographic conditions at temperatures ranging from 353 to 623°K using gas chromatography. The shape and width of the TPD chromatograms and the dependence of the initial temperature of desorption on the initial concentration of adsorbed base indicate a broad site energy distribution on the zeolite. The extent of irreversible adsorption of these bases in NaY at 623°K follows the order: pyridine < 2,6-dimethylpyridine < n-butylamine < piperidine < quinoline Pyridine is not adsorbed irreversibly ta 623°K on NaY but it is adsorbed strongly at lower temperatures. All the other bases are adsorbed strongly at or below 623°K. Since NaY has neither Lewis not protonic acid centres, the results indicate that these bases (except pyridine at > 623°K) are adsorbed strongly on the non-acidic sites at or below 623°K