Properties and catalytic performance in phenol hydroxylation of iron on zeolite beta prepared by different methods

Abstract

Iron (Fe) was loaded on zeolite beta (BEA) in ammonium (NH4BEA) or proton (HBEA) forms by various methods. Fe/HBEA-LSIE and Fe/NH4BEA-LSIE were prepared by liquid state ion exchange (LSIE). This method resulted in low Fe loading and a good dispersion. The form of Fe was Fe2O3 mainly located at the ion exchange position in the zeolite channels. Fe/HBEA-IWI and Fe/HBEA-PM were prepared by incipient wetness impregnation (IWI) and physical mixing (PM), respectively. Both catalysts had higher Fe loading and larger Fe2O3 particles located on both external surface and in the zeolite channels. Despite the different loadings, all samples gave similar phenol conversion in phenol hydroxylation, around 60 % and yielded products catechol (CAT) and hydroquinone (HQ) with the CAT/HQ mole ratio 2:1. After the catalytic testing, all catalysts had a dark color from coking. A further investigation revealed a formation of coke and organic acids. According to temperature programmed oxidation (TPO), heavy coke was produced from Fe/HBEA-LSIE and Fe/NH4BEA-LSIE. The coke from Fe/HBEA-LSIE was heavier than that from Fe/NH4BEA-LSIE. Only light coke was produced from Fe/HBEA-IWI and Fe/HBEA-PM.