Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia

OP-2-20EFFECT OF Ag DOPING IN La-Mn PEROVSKITES FOR THECATALYTIC FLAMELESS COMBUSTION OF METHANEBuchneva O. 1 , Rossetti I. 1 , Kryukov A. 2 , Forni L. 11 Dip. Chimica Fisica ed Elettrochimica, Università di Milano, v. C. Golgi, 19, 20133Milano, Italy. Fax: +39-02-50314300, e-mail: ilenia.rossetti@unimi.it2 D.I. Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9,125047, Moscow, RussiaSamples with nominal composition La 1–x Ag x MnO 3 with x=0, 0.05, 0.1 wereprepared by flame pyrolysis (FP) and by the so-called sol-gel «citrate method» (SG).Lower specific surface area was obtained with the SG-prepared catalysts than withthe FP ones. Silver introduction increased the surface area in all cases. However, noclear relationship between surface area and silver loading was observed. Due to thepoor solubility of silver in the perovskite lattice, reflections of metallic silver weresometimes observed for the doped samples on XRD spectra, with increasingintensity at high Ag loading. Almost all our samples exhibited a very high activity forthe catalytic flameless combustion (CFC) of methane. Indeed, under the adoptedreaction conditions full methane conversion was attained below 600°C. The SGpreparedLaMnO 3 catalyst represented an exception, reaching a maximum 65%methane conversion at 600°C. The activity of FP-prepared catalyst was alwayshigher than that of SG-prepared ones with identical nominal composition. Partialsubstitution of Ag for La led to increasing activity both for SG and FP preparedcatalysts and the catalytic activity increased with increasing the Ag substitution.The resistance to sulphur poisoning was checked for all catalysts, in view of theirapplication for the CFC of biogas. Catalyst poisoning [1,2] was done in operando at450°C by injecting several doses of tetrahydrothiophene. All samples lost part of theirinitial activity after poisoning. Silver substitution did not change the resistance topoisoning for FP prepared samples, whereas a more severe activity loss wasobserved for the poisoned Ag-doped samples than for the unsubstituted one whenprepared by SG. However, due to the great positive effect of Ag on the initial activityinitial activity, the residual conversion after poisoning of all the doped samples wasstill higher than for undoped LaMnO 3 .[1]. I. Rossetti, O. Buchneva, C.Biffi, R. Rizza. Appl. Catal. B: Environmental, 89 (2009) 383.[2]. O. Buchneva, I. Rossetti, C. Biffi, M. Allieta, A. Kruykov, N. Lebedeva. Appl. Catal. A: General 370(2009) 24.64