La_0.8Ca_0.2FeO₃Perovskite Monolithic Catalysts For Catalytic Lean Burn Of Methane

Catalytic combustion of methane in air is a highly efficienttechnique with low pollution for purpose of energy ultization and flue gascleaning. LaFeO₃perovskite is a cheap catalyst with medium activity andmodest stability for CH4combustion.In this paper, a series of perovskitecatalysts based on LaFeO₃were washcoated onto α-Al₂O₃honeycombceramic or FeCrAl wire-mesh substrates and used for catalyticcombustion of air diluted methane （0.5vol.%in air）.First,calcium doped La_1-xCa_xFeO₃（x=0～0.4） perovskite catalystswere prepared using co-precipition method. It was found that whendoping ratio is0.2and the calcinations temperature is800℃, theperovskite showed the best catalytic activity. For purpose ofcharacterization of crystalline phase, specific surface area, redoxproperties, XRD, BET N2adorption and H2-temperature programmedreduction were used.ZrO₂、La₂O₃、MgO were introduced as the secondary supports whenpreparing La_0.8Ca_0.2FeO₃/α-Al₂O₃monolithic catalysts. For ZrO₂, twokinds of Zr sources Zr（NO₃）₄and ZrOCl₂were tested which showedsimilar catalytic performance, yet the process of preparing ZrO₂fromZr（NO₃）₄was much easier. The catalyst got the best catalytic activity with ZrO₂washcoated2³times. For La₂O₃and MgO, the calcinationtemperature and washcoating times of secondary support were studied. Itwas found for La₂O₃, the optimized condition was almost the same asZrO₂. For MgO, the optimized washcoating time was1-2times. Traceamount of Pd was introduced to La_0.8Ca_0.2FeO₃/MgO/α-Al₂O₃monolithwhich performance had been improved obviously, especially at the lowertemperature region.Based on our group’s previous work, the method of preparingwire-mesh honeycomb （WMH） was improved and La_0.8Ca_0.2FeO₃wassupported on WMH to test for catalytic combustion of lean methane.Compared with catalyst supported on α-Al₂O₃honeycomb, catalystsupported on WMH demonstrated better catalytic performance due to theenhanced of mass and thermal transfer rates.All work finished above, namely the screening of a propersecondary support, development of Pd-La_0.8Ca_0.2FeO₃monolithic catalyst,and applying of La_0.8Ca_0.2FeO₃to the wire-mesh honeycomb （WMH）substrates, has paved the way for application of LaFeO₃peroskitemonolith in catalytic lean burn of methane in industry.