Catalytic studies on the dehydration of cyclohexanol by crystalline titanium phosphate and mixed titanium-zirconium phosphates: I. Effect of thermal phase changes on catalytic activity

Abstract

Crystalline α-titanium phosphates, Ti(HPO 4) 2 · H 2O, and solid solutions of titanium-zirconium phosphates were prepared and their activity in the dehydration of cyclohexanol examined. The α-phases were found to lose 1 mol of water at slightly above 100 °C and convert to the ζ-phase. A second, reversible phase change, to form η-phases, occurs at about 250 °C while condensation of the monohydrogen phosphate groups takes place from 300 to 400 °C. When sufficient—OH groups are lost, the η-phases do not revert to the ζ-phases on cooling. However, the alcohol dehydration reaction catalyzed by the η-phases apparently restores sufficient hydroxyl groups to allow the catalysts to reform the low temperature ζ-phases. There seems to be no correlation of catalytic activity with either the Ti content of the catalysts or their surface areas. However, all of them were found to be more active than α-zirconium phosphate.