The preparation effect on activity and thermal stability of La0.8Ca0.2FeO3 perovskite honeycombs dispersed by MgAl2O4 spinel washcoat for catalytic combustion of dilute methane. Issue 2 (June 2016)

• Record Type: Journal Article
• Authors: Li, Huaiyou; Fu, Ruifeng; Duan, Weijie; Jiang, Zhidong
• Is Part Of: Journal of environmental chemical engineering. Volume 4:Issue 2(2016:Jun.)
• Page Start: 2187
• Page End: 2195
• Publication Date: 2016-06
• Subjects: Catalytic combustion of methane -- Honeycomb -- Thermal stability -- Calcium-doped LaFeO3 perovskite -- MgAl2O4 spinel washcoat; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2015.11.039
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: La0.8 Ca0.2 FeO3 perovskite (LCF) honeycombs stabilized by MgAl2 O4 spinel (MgAl) washcoat have been developed for the first time and applied in catalytic combustion of air diluted CH4 (0.5 vol.%). The honeycombs were prepared by washcoating the α-Al2 O3 monoliths in sequence with the slurries of MgAl and LCF precursors, intermediated by calcination at corresponding temperatures. The effects of LCF powder preparation method, the calcination temperature and thickness of MgAl washcoat, and the loading of LCF were investigated. Meanwhile, the first order reaction rate constants ( k ) were calculated and activation energy ( E a ) regressed for powder and honeycomb LCF catalysts. The LCF prepared by a modified co-precipitation method was found more active and stable than that made by citrate method in literature. Calcination of bulk LCF powder at 700–800 °C led to a linear deactivation proportional to S BET . For LCF honeycombs immediately washcoated on α-Al2 O3 substrates, k and E a values are comparable to that measured with LCF powder, which is almost inert upon calcination at 1000 °C. When supported on MgAl washcoat, activity of LCF honeycombs is enhanced by folds, and the effect is more pronounced at higher calcination or reaction temperatures. Meanwhile, performance of the honeycombs is very sensitive to the washcoat preparation, with the optimum calcination temperature and proper thickness of the MgAl washcoat identified as 850 °C and 40 μm, respectively. Conversion of CH4 goes up with LCF loading of honeycombs, but the values of k and E a vary in different way. When LCF loading is low, k is the highest, accompanied by a lowest E a ∼99 kJ/mol; for intermediate loadings, k and E a are both medium and constant; in cases of overloaded LCF, k reduces and E a rises to 132 kJ/mol, approaching to that measured with bulk LCF (135 kJ/mol). The change of E a with LCF loadings reflects the modification of active sites due to the interaction of LCF with MgAl, and the proper mass ratio of LCF/MgAl is at the range of 0.8–0.9. Finally, thermal resistance of LCF honeycombs supported by MgAl or MgO were compared after thermal aging at 1000 °C for 4 h. The MgAl supported LCF is about 200 °C more stable than MgO supported, indicating a much improved thermal resistance.