Porous hydrous zirconia supported 12-tungstophosphoric acid catalysts for liquid-phase esterification of 2-ethyl-1-hexanol

12-Phosphotungstic acid supported on porous hydrous zirconia was prepared and characterized by N2 adsorption isotherm, powder XRD, FTIR, 31P MAS NMR, H2-TPR, NH3-TPD, SEM and TEM. It is found that the chemical interaction of Keggin anions with hydrous zirconia is different compared to the interaction with ZrO2 and Ce0.5Zr0.5O2 supports. The phosphotungstic acid clusters dispersed on porous hydrous zirconia did not show any split of IR bands at 1080 cm−1 (νP–O) and 983 cm−1 (νWO,ter) while those dispersed on ZrO2 and Ce0.5Zr0.5O2 showed a split in these two bands due to the lowering of symmetry of the central PO4 tetrahedron and direct interaction of WOter with oxide support. The dispersion of phosphotungstic acid on porous hydrous zirconia led to the growth of crystallites which showed catalytic activity for liquid-phase esterification of 2-ethyl-1-hexanol with acetic acid. Both conversion of 2-ethyl-1-hexanol and selectivity for 2-ethyl-1-hexyl acetate can be achieved at 100%.

Porous hydrous zirconia (HZ) supported phosphotungstic acid (PWA) catalysts have been investigated. The interaction of PWA with HZ is mainly though Zr–OH groups while on CexZr1−xO2 the Keggin molecular ions are fixed to M+ ions directly. 35 wt% PWA/HZ catalysts show growth of ∼7 nm size PWA crystallites and give good conversion of 2-ethyl-1-hexanol and selectivity towards 2-ethyl-1-hexyl acetate.Figure optionsDownload as PowerPoint slide