Comparison of Fe/HBEA catalysts from incipient wetness impregnation with various loading on phenol hydroxylation

Abstract

Iron catalysts on zeolite beta from incipient wetness impregnation, Fe/HBEA with Fe loading 0.5–2.0 wt% were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and temperature-programmed desorption of ammonia (NH3-TPD). Fe in all catalysts was in the form of Fe2O3 and the acidity decreased with an increase of Fe content. From catalytic testing in phenol hydroxylation, the catalysts with lower Fe loading gave higher yields of catechol and hydroquinone and a lower amount of by-products than the catalyst with Fe loading 6.0 wt% in the previous work. The spent catalysts were analyzed by temperature-programmed oxidation using thermogravimetric analysis/mass spectrometry detector (TGA-MS). An amount of carbon deposit from all catalysts was in the range 10–15 wt%. However, carbon on the catalysts with lower Fe loading was removed at higher temperature.