Chromic acid dealumination of zeolites

Commercial zeolites with CHA, MFI, and LTL framework topology are subjected to acid treatment chromic (H2CrO4) solutions concentrations ranging between 0.1 10 w/%. As forms polymeric species as a function of concentration, specific effects obtained these three zeolites, differing by their topology, pore size, Si/Al ratios crystal size. The etched characterized X-ray diffraction, SEM, TEM, N2 physisorption, ICP-AES, 27Al 29Si MAS NMR, 29Si{1H} cross-polarization spectra, EDX. Their acidic properties probed pyridine d3-acetonitrile in situ FTIR. Results indicate that the 8 MR (CHA) (MFI) more resistant than 12 (LTL) zeolite. This paves way for rational control zeolite dealumination since adjusting concentration will generate anions appropriate treating particular