Adsorption properties of gases on mesoporous chromium silicate.

The properties of nitrogen, carbon dioxide, and nitrogen dioxide adsorption onto mesoporous chromium silicates were studied by measurements of both the adsorption isotherms and the IR spectra. The pore sizes of two types of chromium silicates, Cr-FSM-16 (Si/Cr=170 (Cr-FSM-16 [170]) and 390 (Cr-FSM-16 [390])), which contain different amount of Cr, were 2.75 nm. BET surface areas of Cr-FSM-16 were 590 m2/g and they were smaller than that onto FSM-16. The initial heat of adsorption of nitrogen onto Cr-FSM-16 was higher than that onto FSM-16. But the initial heat of adsorption of carbon dioxide onto Cr-FSM-16 was smaller than that onto FSM-16. These results indicated that Cr in Cr-FSM-16 decreased adsorption interaction with carbon dioxide. When nitrogen dioxide was adsorbed on FSM-16 and Cr-FSM-16 at 303 K under no light, an absorption band of nitrogen monoxide adsorbed was measured by IR spectroscopy. This decomposition of nitrogen dioxide by FSM-16 and Cr-FSM-16 was caused by SiOH and Cr, respectively.