Determination of external surface area of ultrahigh silica zeolites by the paramagnetic net methods

We propose a new method for determining the surface area of large-pore adsorbents which do not contain paramagnetic impurities: the paramagnetic net method. The method is based on determining the average distances between paramagnetic centers which are randomly and uniformly distributed over the adsorbent surface. As the paramagnetic probe, we use the stable nitroxide radical 2,2,6,6-tetramethyl-piperidine-1-oxyl. We show that the method is applicable to measurement of the external surface area of crystallites of ultrahigh silica zeolites. Decationation leads to its increase without an increase in the contribution of the amorphous phase. This effect is explained by dispersal of concretions of small crystallites during ion exchange.