Abstract: Differential heats of adsorption for pyridine on NaY, CaY, R_EY and HY zeoli- tes in the temperature range from ambient temperature to 620 K have been measu- red by a micro-calorimeter. Experimental results show that there are two types of different acidic site in these four Y-zeolites. One type is B-acid site and the other one is non-active L-acid site. Acid strength of B-acid site would increase and non-active L-acid site would decrease as the temperature is raising. Only Na~+ ions act as the non-active L-acid sites on NaY surface and H~+ as the B-acid sites on HY surface for pyridine adsorption, but both B-sites and L-sites present on the surface of R_EY and CaY simultaneously. At higher temperatures the adsorption of pyridine prefers to occur on the strong B-acid sites.
At room temperature the amounts of adsorption for pyridine on these all samples are around 3.0—3.2 mmol g~(-1) which are in accordance with the numbers of the total adsorption sites in super-cages and β-cages.