Characterisation and long-term usage catalytic properties of (VO) 2P 2O 7/γ-Al 2O 3 stainless steel coated catalyst in p-cymene oxidation

Abstract

(VO) 2P 2O 7/γ-Al 2O 3 catalyst was coated onto a stainless steel plate in order to evaluate the long-term catalytic performance and the (VO) 2P 2O 7 catalyst structure behaviour in liquid phase oxidation of p-cymene in a continuous simulated on-stream test. The stainless steel coated catalyst (containing 11 wt% loading) displayed a slow, yet significant deactivation over an extended reaction period of up to 250 h on-stream testing. Comparable results to the pure (VO) 2P 2O 7 and (VO) 2P 2O 7/γ-Al 2O 3 supported catalysts with the stainless steel coated catalyst was obtained with tertiary cymene hydroperoxide (TCHP) selectivity in a range of 75–85% giving 20–30% yield at conversions between 25 and 40%. The activity of the stainless steel coated catalyst was only partially regenerated by calcination at 550 °C for 4 h, thereafter it showed a rapid activity drop in further catalytic testing. Powder XRD structural analysis of the used (VO) 2P 2O 7 catalyst after continuous 75 h showed that the catalyst converted back to its precursor, VOHPO 4·0.5H 2O phase during oxidation reaction. The TGA–MS of the same used catalyst sample showed the loss of higher mass fragments ( m/ z) at decomposition temperatures of 350–800 °C indicating that considerable poisoning of the catalyst surface occurred during its continuous use.