Zirconia catalysts (ZrO2 and Na-ZrO2) for the conversion of phenethyl phenyl ether (PPE) in supercritical water

• Na-ZrO2 was active for ether bond cleavage of PPE under supercritical water.
• Na-ZrO2 was comparable to homogenous catalysis (Na2CO3) in activity.
• Na-ZrO2 was enhanced in BET area and base site concentration.
• Na-ZrO2 was more active than ZrO2 in terms of PPE conversion and product yields.
• The acid–base concentration governed the reaction pathway and product distribution.

In this study, the mesoporous ZrO2 and Na-ZrO2 were examined as heterogeneous solid catalysts under supercritical water for the β-ether bond scission of phenethyl phenyl ether (PPE). Na-ZrO2 was more efficient than ZrO2 in the dissociation of PPE. Yields of phenol and styrene were 39% and 16%, respectively, under 97% PPE conversion when 2.5 wt.% of Na-ZrO2 catalyst was applied to a batch reactor filled with supercritical water (400 °C, 20 bar H2 (initial pressure)) containing 2.5 wt.% PPE. The characterization revealed that the activities of ZrO2 and Na-ZrO2 were closely associated with the textural and acid/base properties of the catalysts. Notably, the reaction pathway and product distribution were determined by the concentration of acid and base sites on the catalyst's surface.

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