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Structural Characteristics, Stability, and Activity of (VO) 2 P 2 O 7 and VO(PO 3 ) 2 Catalysts in p ‐Cymene Liquid‐Phase Oxidation
Author(s) -
Makgwane Peter R.,
Ferg Ernst E.,
Zeelie Ben
Publication year - 2011
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201000241
Subject(s) - catalysis , calcination , chemistry , phase (matter) , adsorption , redox , heterogeneous catalysis , crystallography , inorganic chemistry , organic chemistry
The post‐reaction structural characteristics of VO(PO 3 ) 2 and (VO) 2 P 2 O 7 catalysts and their reusability in liquid‐phase oxidation of p ‐cymene to tertiary cymene hydroperoxide (TCHP) are investigated and characterized. The VO(PO 3 ) 2 structure remains unchanged after being used for extended reaction times, whereas (VO) 2 P 2 O 7 undergoes structural changes back to its precursor phase, VOHPO 4 ⋅0.5 H 2 O, that affect its catalytic properties. The structure of the (VO) 2 P 2 O 7 that has undergone phase changes is successfully restored by calcination under N 2 flow at 750 °C for 2 h. Fresh and used catalysts show different particle morphologies, indicating that the reaction medium influences the microstructure. Both catalysts show considerable reusability with (VO) 2 P 2 O 7 showing slight gradual deactivation. Taking into account the characterization and catalytic results obtained, the slight (VO) 2 P 2 O 7 deactivation can probably be ascribed to the adsorption of organic compounds on the catalyst surface, which appears to initiate structural transformation of the (VO) 2 P 2 O 7 catalyst under oxidation reaction conditions for extended reaction times. The VO(PO 3 ) 2 and (VO) 2 P 2 O 7 catalysts showed to be effective for synthesis of the industrially important intermediate TCHP, a precursor to p ‐cresol in liquid‐phase oxidation reactions.