The direct reaction between CO2 and phenol catalyzed by bifunctional catalyst ZrO2

The systematic investigation was carried out to elucidate the direct reaction between CO2 and phenol over multiphase catalyst. Reactions carried out over ZrO2, TiO2, and KF/NaY + Mn2+ gave the high selectivity to 4-[4-hydroxybenzyl] phenol and 2-[2-hydroxybenzyl] phenol (HBP), and the maximum HBP selectivity of 68% was obtained with ZrO2 as catalyst. XRD patterns showed that metastable tetragonal ZrO2 was the active phase for HBP synthesis, and the bidentate carbonate on ZrO2 surface was responsible for high HBP selectivity. If Hbeta, HZSM-5, and Al2O3 were used as catalyst, the main product was diphenyl ether (DPE). But when reactions were catalyzed by KY and KF/NaY, xanthone became the main product; however, xanthone disappeared when KF/NaY coexisted with Mn(OCOCH3)(2) as catalyst. The optimized reaction conditions for HBP synthesis over tetragonal ZrO2 are 350 degrees C, 12 h, and 4.0 MPa CO2 pressure. (C) 2007 Published by Elsevier B.V.