Abstrakt

The Keggin-type anion heteropolyacids interaction with significantly different wettability titanium dioxide (TiO2) and boron nitride (BN) supports was discussed based on structural and surface chemistry analysis, as well as catalytic and computational data. The H3PW12O40 (HPW) and H3PMo12O40 (HPMo) heteropolyacids played the role of active phase of supported catalysts in alcohol dehydration in gas-phase in the temperature range from 90 ◦C to 230 ◦C. The impregnation and mechanochemical treatment during catalyst’s synthesis have been implemented. The physicochemical properties of solid catalysts were determined by XRD, FTIR, UV-Vis, SEM/ EDS, N2 adsorption-desorption, XRF, NH3-TPD and GC techniques. The main product of n-butanol dehydration was cis-2-butene. The polyoxotungstate HPW@TiO2 and HPW@BN catalysts exhibited higher catalytic efficiency than the phosphomolybdate counterparts. The theoretical results confirm the structural integrity of HPW and HPMo upon deposition, consistent with experimental observations. Electron density analysis shows that adsorption on BN leads to noticeable charge redistribution, facilitating proton dissociation in HPW, whereas adsorption on TiO₂ involves negligible electron transfer. Calculated Gibbs free energy changes (ΔG) indicate that the formation of the [C₄H₉OH]H⁺ ion is more favourable for supported HPAs, particularly for HPW. NH₃ adsorption/desorption simulations revealed that the orientation of the Keggin anion relative to the surface of supports significantly influences the strength of acid sites, which in turn noticeable affect the catalyst activity.