Organosilanes functionalization of alumino-silica zeolites for water adsorption applications

Standard zeolites 4A and 13X have been synthesized and modified by reaction with dimethoxydimethyl silane, propyltrimethoxy silane, octyltrimethoxy silane and octadecyltrimethoxy silane, respectively. The modified zeolites were analyzed by X-Ray diffractometry, FTIR spectrometry and water adsorption measurements. Results showed that silane molecules bonded to the external surface of zeolite particles with no chance of entering the zeolite porosity. Only “short-chain” silanes dimethoxydimethyl and propyltrimethoxy grafting demonstrated having an influence on the hydrophilic behavior of the modified zeolites. The main effect was a shift of the adsorption isotherms in the low partial pressure range towards a more hydrophobic trend, which represents an interesting result for adsorption application when low temperature regenerations are required.