Dehydration of 1,5-Pentanediol over CeO₂-MeOx Catalysts

The dehydration reaction of 1,5-pentanediol was performed over CeO₂ and modified CeO₂ (CeO₂−MnO_x, CeO₂−ZnO, CeO₂−MgO, CeO₂−CaO, CeO₂−Na₂O) catalysts in a fixed-bed tubular reactor at 350 °C and an atmospheric pressure. The undoped CeO₂ produced a mixture of the products containing mainly 4-penten-1-ol, 1-pentanol, cyclopentanol, cyclopentanone and tetrahydropyran-2-one from 1,5-pentanediol, while additions of MgO, MnO_x, or ZnO to CeO₂ was found to enhance the overall production rate of unsaturated alcohol. On the other hand, more basic metals like CaO or Na₂O tend to decline the dehydration activity of CeO₂. The porous structure of CeO₂ did not change appreciably with the addition of metal oxides. Temperature programmed desorption of adsorbed CO₂ on an activated catalyst suggest more CO₂ remain on the catalyst surface, particularly CeO₂−CaO and CeO₂−Na₂O indicating that fewer defect sites are only available for reaction. The defect sites or oxygen vacancy on CeO₂ controls both activity and selectivity for the dehydration of 1,5-pentanediol.