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    Abatement of nitrous oxide over natural and iron modified natural zeolites
    (ELSEVIER SCIENCE BV, 2011) Ates, Ayten; Reitzmann, Andreas; Hardacre, Christopher; Yalcin, Huseyin
    The natural zeolite obtained from the Sivas-Yavu region in Turkey and iron modified forms were studied for the decomposition of N(2)O and selective catalytic reduction of N(2)O with NH(3). The natural and iron modified zeolites were characterised by XRD, SEM, H(2)-TPR, NH(3)-TPD and low temperature nitrogen sorption. The effect iron loading, precursor and valency on the catalytic performance of catalysts were studied. The catalytic activity of the zeolites increased up to about 7.0 wt.% Fe. Above this value, the activity decreased as a result of a reduction in the surface area and pore volume of the zeolite. The highest catalytic activity was observed using catalysts prepared with FeCl(2) due to the formation of more reducible iron species in the zeolites. When FeSO(4) was used as the iron precursor, sulphate remained on the surface even after extensive washing resulting in a decrease in the N(2)O decomposition activity and a shift the N(2)O reduction temperature to higher values. Since the natural and iron exchanged natural zeolites prepared using FeCl(2) have comparable activity with synthetic zeolites, the offer a promising alternative catalyst for the abatement of N(2)O, particularly for the selective reduction of N(2)O with NH(3). (C) 2011 Elsevier B.V. All rights reserved.
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    The effect of various treatment conditions on natural zeolites: Ion exchange, acidic, thermal and steam treatments
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2012) Ates, Ayten; Hardacre, Christopher
    Two different natural zeolites having different phase compositions were obtained from different regions of Turkey and modified by ion-exchange (0.5 M NH4NO3) and acid leaching using 1 M HCl. The natural and modified samples were treated at low temperature (LT), high temperature (HT) and steam (ST) conditions and characterised by XRF, XRD, BET, FTIR, DR-UV-Vis, NH3-TPD and TGA. Ion-exchange with NH4+ of natural zeolites results in the exchange of the Na+ and Ca2+ cations and the partial exchange of the Fe3+ and Mg2+ cations. However, steam and acidic treatments cause significant dealumination and decationisation, as well as loss of crystalline, sintering of phases and the formation of amorphous material. The presence of mordenite and quartz phases in the natural zeolites increases the stability towards acid treatment, whereas the structure of clinoptilolite-rich zeolites is mostly maintained after high temperature and steam treatments. The natural and modified zeolites treated at high temperature and in steam were found to be less stable compared with synthetic zeolites, resulting in a loss of crystallinity, a decrease in the surface area and pore volume, a decrease in the surface acidity as well as dealumination, and decationisation. (C) 2012 Elsevier Inc. All rights reserved.
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    Oxidative dehydrogenation of propane with N2O over Fe-ZSM-5 and Fe-SiO2: Influence of the iron species and acid sites
    (ELSEVIER SCIENCE BV, 2012) Ates, Ayten; Hardacre, Christopher; Goguet, Alexandre
    A series of iron containing zeolites with varying Si/Al ratios (11.5-140) and low iron content (similar to 0.9 wt.% Fe) have been synthesised by solid-state ion exchange with commercially available zeolites and tested, for the first time, in the oxidative dehydrogenation of propane (ODHP) with N2O. The samples were characterised by XRD, N-2-Adsorption, NH3-TPD and DR-UV-vis spectroscopy. The acidity of the Fe-ZSM-5 can be controlled by high temperature and steam treatments and Si/Al ratio. The selectivity and yield of propene were found to be the highest over Fe-ZSM-5 with low Al contents and reduced acidity. The initial propene yield over Fe-ZSM-5 was significantly higher than that of Fe-SiO2 since the presence of weak and/or medium acid sites together with oligonuclear iron species and iron oxides on the ZSM-5 are found to enhance the N2O activation. The coking of Fe-ZSM-5 catalysts could also be controlled by reduction of the surface acidity of ZSM-5 and by the use of O-2 in addition to N2O as the oxidant. Fe-ZSM-5 zeolites prepared with solid-state method have been shown to have comparable activity and better stability towards coking compared with Fe-ZSM-5 zeolites prepared by liquid ion exchange and hydrothermal synthesis methods. (C) 2012 Elsevier B.V. All rights reserved.