THE SELECTIVITY OF SODIUM CARBONATE-DOPED ZINC PHOSPHATE IN THE GAS-PHASE DEHYDROGENATION-DEHYDRATION OF CYCLOHEXANOL

In this work, Zn-3(PO4)(2) (solid ZnP) was synthesized by precipitation from an aqueous solution containing ZnCl2 and Na2HPO4. A zinc oxide was also synthesized under the same conditions by precipitation from aqueous ZnCl2. Addition of Na2CO3 to the medium and heating at 323-343 K for 6 h gave rise to NaZnPO4 (solid NaZnP) and ZnO, respectively, both of which were found to exhibit excellent activity in the dehydrogenation of cyclohexanol. XRD and IR analyses revealed amorphous Na2CO3 to be deposited on the solid surface, as well as the potential presence of residual zinc oxides resulting from decomposition of the ZnCO3 formed. The presence of Na2CO3 on the solid surface increases its basicity and inhibits dehydration of cyclohexanol. At 773 K, Zn-3(PO4)(2) yields cyclohexene and cyclohexanone, whereas, under the same reaction conditions, NaZnPO4 produces the ketone selectively. (C) 1995 Academic Press, Inc.