Preparation and characterization of mesoporous Cs2HPW12O40 salt, active in transformation of m-xylene

The samples of Cs2HPW12O40 salt were precipitated with CsCl, CsBr or CsI reagent as well as with commonly used Cs2CO3. The use of cesium halides resulted in the Cs2HPW12O40 samples of mesoporous structure composed of relatively loosely aggregated primary particles. It was observed that the type of halogen ion influenced textural properties of the Cs2HPW12O40 samples. As the atomic size of halogen ion increased (from Cl to I), the specific surface area and microporosity decreased. The so-obtained samples exhibited textural and morphological features similar to those of Cs2.5H0.5PW12O40 salt. In the transformation of m-xylene, the pore-size sensitive reaction, the catalytic activity of the Cs2HPW12O40 samples prepared with CsBr and CsI reagents was about two-fold higher than that of Cs2.5H0.5PW12O40 salt. All these samples exhibited similar strength of acid sites. Therefore, high catalytic activity of the samples prepared with CsBr and CsI could be ascribed to their open pore structure, which allowed the accessibility of almost all active sites for m-xylene molecules.

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► Reagent used for Cs2HPW12O40 precipitation influences its textural properties.
► Strong increase of specific surface area of Cs2HPW12O40 salt after HBr addition.
► Higher activity of Cs2HPW12O40 prepared with CsBr and CsI than Cs2.5H0.5PW12O40 salt.