Competitive adsorption of NO, SO 2 and H 2O onto mordenite synthesized from perlite

Abstract

A new material, mordenite synthesized from volcanic ash (perlite) in the presence of sodium salts, has been shown to be a weak sorbent for NO and a strong and reversible sorbent for SO 2. The mordenite's capacity to adsorb SO 2 was found to be related to the amount of sodium present in the material. Capacities as high as 8 wt% were achieved at 1250 ppm of SO 2 in helium at 25°C. In multicycle tests the mordenite maintained its capacity after more than 40 cycles when desorbing the SO 2 at 300°C. The adsorption rate of SO 2 in the absence of water was modelled and the adsorption activation energy was found to be 3.2 kcal mol −1. Water significantly decreased the mordenite's capacity to adsorb SO 2 and also caused the SO 2 to be chromatographically desorbed in a roll-up peak. In these water-SO 2 adsorption experiments a peculiar breakthrough was observed for water, where the water concentration exiting the bed first decreased and then increased. This peculiar water breakthrough could not be explained by assuming independent adsorption of the two species, but was qualitatively predicted by assuming that water adsorption is enhanced by the presence of adsorbed SO 2.