NIR FT RAMAN-SPECTROSCOPIC STUDIES OF ETA-AL2O3 AND MO ETA-AL2O3 CATALYSTS/

NIR FT Raman spectra excited at 1064 nm have been obtained from sample s of Mo/eta-Al2O3 catalysts after treatment at 773 K in vacuum for 12 h. The samples were heated in quartz tubes which were sealed and trans ferred directly to the spectrometers without exposure to the ambient a tmosphere, The broad background previously observed in the NIR FT Rama n spectra of hydrated Mo/eta-alumina samples disappeared after the deh ydration. Upon exposure to ambient air the broad background signal rea ppeared suggesting that the broad background feature can be attributed to surface hydroxyl groups present in the hydrated samples. Furthermo re, it was observed that upon treating the eta-Al2O3 with water the br oad background signal disappeared and the presence of bayerite (Al(OH) (3)) or boehmite (AlO(OH)) was detected depending on the experimental details. The identification of the various phases is supported by XRPD analysis. The overall conclusion is that the broad NIR FT Raman backg round can be attributed to surface hydroxyl groups in hydrated eta-Al2 O3.