Catalytic properties and acidity of ZSM-12 zeolite with different textures

Three MTW (H-ZSM-12) zeolite samples were synthesized by (i) direct hydrothermal method, (ii) desilication of the hydrothermal obtained product and (iii) mesostructuration of zeolite ZSM-12 seeds in the presence of hexadecyltrimethylammonium bromide. The samples were characterized by XRD, nitrogen adsorption isotherms, SEM, 27Al-MAS NMR and FTIR spectroscopy. Their acidity was evaluated by FTIR spectroscopy of CO probe molecule adsorbed at 100 K. The IR results were correlated with the fraction of aluminum in tetrahedral positions found by 27Al-MAS NMR as well as with the catalytic behavior toward the transformation of the test molecule of 1,2,4-trimethylbenzene. It was concluded that the density of the strong Brønsted acid sites, rather than the textural properties, are the dominating factor governing the catalytic performance of the samples in the target reaction.

The density of the bridging hydroxyls, rather than the textural properties, are the dominating factor governing the catalytic performance of ZSM-12 samples in the 1,2,4-trimetylbenzene transformation.Figure optionsDownload as PowerPoint slideHighlights
► Zeolite ZSM-12 samples with different texture.
► Direct hydrothermal synthesis, alkali desilication and seed mesostructuration.
► Acidity evaluation by FTIR spectra of low temperature CO probe molecule adsorption.
► Acidity controls catalytic transformations of 1,2,4-trimethylbenzene.