Methane conversion and SO2 resistance of LaMn1−xFexO3 (x=0.4, 0.5, 0.6, 1) perovskite catalysts promoted with palladium

Koponen, Markus J.; Venäläinen, Tapani; Suvanto, Mika; Kallinen, Kauko; Kinnunen, Toni-J.J.; Härkönen, Matti; Pakkanen, Tapani A.

doi:10.1016/j.molcata.2006.05.045

Cited by 22 publications

(13 citation statements)

References 23 publications

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“…However, any further investigation to discriminate the nature of the sulphur-containing surface or bulk species forming upon poisoning is beyond the scope of the present work. For this point reference has been made to literature data [1,9,10,12,13] …”

Section: -Results and Discussionmentioning

confidence: 99%

“…For Mn-based perovskites the resistance was higher than for Co-based ones, as observed for non-substituted samples (Fig.2). However, the most evident effect has been observed after the first injections, suggesting that noble metals protect the surface sites by reacting more promptly with sulphur [13], Pt doping being more effective than Pd.…”

Section: -Effect Of Noble Metals Additionmentioning

confidence: 99%

“…Depending on the extent of poisoning, the complete destruction of the active phase has been sometimes reached, with formation of segregated B-ion oxide and lanthanum sulphate. The conversion of methane and the resistance of the catalyst to sulphur poisoning have been studied with various combinations of A-and Bsite metals and by adding MgO as promoter [5,10,11,13]. However, though the latter option seems to guarantee a sufficient resistance to poisoning, the promoter essentially acts as a shield, forming stable sulphates and hence competing with the active phase for SO2 adsorption.…”

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Effect of sulphur poisoning on perovskite catalysts prepared by flame-pyrolysis

Rossetti

Buchneva

Biffi

et al. 2009

Applied Catalysis B: Environmental

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ABO3 perovskite-like catalysts are known to be sensitive to sulphur-containing compounds. Possible solutions to increase resistance to sulphur are represented by either catalyst bed protection with basic guards or catalyst doping with different transition or noble metals. In the present work La(1-x)A'xCoO3, La(1-x)A'xMnO3 and La(1-x)A'xFeO3, with A' = Ce, Sr and x=0, 0.1, 0.2, either pure or doped with noble metals (0.5 wt% Pt or Pd), were prepared in nano-powder form by flame pyrolysis. All the catalysts were tested for the catalytic flameless combustion of methane, monitoring the activity by on-line mass spectrometry. The catalysts were then progressively deactivated in operando with a new procedure, consisting of repeated injection of some doses of tetrahydrothiophene (THT), usually employed as odorant in the natural gas grid, with continuous analysis of the transient response of the catalyst. The activity tests were then repeated on the poisoned catalyst. Different regenerative treatments were also tried, either in oxidising or reducing atmosphere.Among the unsubstituted samples, higher activity and better resistance to poisoning have been observed in general with manganites with respect to the corresponding formulations containing Co or Fe at the B-site. The worst catalyst showed LaFeO3, from both the points of view of activity and of resistance to sulphur * Corresponding author: fax +39-02-50314300, e-mail ilenia.rossetti@unimi.it 2 poisoning. La0,9Sr0,1MnO3 showed, the best results, exhibiting very high activity and good resistance even after the addition of up to 8.4 mg of THT per g of catalyst.Interesting results were attained also by adding Sr to Co-based perovskites. Sr showed a first action by forcing Mn or Co in their highest oxidation state, but, in addition, it could also act as a sulphur guard, likely forming stable sulphates due to its basicity. Among noble metals, Pt doping proved beneficial in improving the activity of both the fresh and the poisoned catalyst.Keywords: Methane, catalytic combustion; Sulphur poisoning; Perovskite-like catalysts. -INTRODUCTIONThe catalytic flameless combustion (CFC) of methane outperforms conventional flame combustion because of lower emission of pollutants (HC, CO and NOx) and high thermal efficiency. The catalysts traditionally used for CFC are mainly based on supported noble metals, such as Pd and Pt, which ensure high activity, however accompanied by some drawbacks, due to high cost and poor thermal and chemical stability. La-based catalysts with ABO3 perovskite-like structure [1][2][3][4] have been proposed as a valid alternative for the present application. Indeed, perovskite catalysts combine low cost, thermo-chemical stability at high operating temperature and satisfactory catalytic activity [5][6][7][8]. In spite of this, there are still some open questions, especially regarding their resistance to sulphur poisoning when used for the CFC of methane. Indeed, the poisoning mechanism of perovskite-like catalysts has not been completely understood a...

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Section: -Results and Discussionmentioning

confidence: 99%

Section: -Effect Of Noble Metals Additionmentioning

confidence: 99%

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confidence: 99%

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Effect of sulphur poisoning on perovskite catalysts prepared by flame-pyrolysis

Rossetti

Buchneva

Biffi

et al. 2009

Applied Catalysis B: Environmental

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“…For Mn-based perovskites the resistance was higher than for the Co-based one, as observed for the non-substituted samples (Table 1). However, the most evident effect has been observed after the first poisoning injections, suggesting that noble metals protect the surface sites by reacting more promptly with sulphur [22], Pt doping being more effective than Pd.…”

Section: Resistance To Sulphur Poisoningmentioning

confidence: 99%

Perovskite-like catalysts for the catalytic flameless combustion of methane

2012

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QUESTIONNAIREThe catalytic flameless combustion (CFC) of methane outperforms conventional flame combustion because of lower emission of pollutants (HC, CO and NO x ) and high thermal efficiency. The catalysts traditionally used for CFC are mainly based on supported noble metals, such as Pd and Pt, which ensure high activity, however accompanied by some drawbacks, due to high cost and poor thermal and chemical stability. La-based catalysts with ABO 3 perovskite-like structure have been proposed as a valid alternative for the present application. Indeed, perovskite catalysts combine low cost, thermochemical stability at high operating temperature and satisfactory catalytic activity. In spite of this, there are still some open questions, especially regarding their resistance to sulphur poisoning when used for the CFC of methane. Indeed, the poisoning mechanism of perovskite-like catalysts has not been completely understood and only a few papers deal with this very important topic.In general, the partial substitution of the perovskitic lattice metal ions is one of the important means to modulate catalytic activity. In LaBO 3 perovskites, the influence of dopants such as A' 2+ and A' 4+ has been widely investigated in the literature.* Corresponding author: fax +39-02-50314300; e-mail ilenia.rossetti@unimi.it 2In the recent past, attention has been devoted to catalyst nanostructuring, aiming at obtaining high surface area and defectivity, which should enhance oxygen mobility through the lattice and ensure good catalytic activity. To this purpose, we set up and optimised a flame-pyrolysis (FP) apparatus for the onestep synthesis of perovskitic mixed oxides. It is based on a specially designed burner fed with oxygen and an organic solution of the precursors, the solvent acting as fuel for the flame. FP-synthesized perovskites, showed good phase purity, along with nanometer-size particles and hence very high surface area (sometimes in excess of 100 m 2 /g). In addition, the high temperature of the flame in principle should also ensure thermal stability.In the present work we prepared a set of samples by FP, namely La 1-x A x MeO 3 , with A' = Ce, Sr, Ag Me=Mn, Co, x=0, 0.1, 0.2, either pure or doped with noble metals (Pt, Pd or Ag). In addition silver containing samples were synthesized by a traditional sol-gel (SG) method. The catalysts were tested for the CFC of methane, monitoring the activity by online mass spectrometry. Also the resistance to sulphur poisoning was investigated, using tetrahydrothiophene as poisoning agent.

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“…Lanthanum oxide, due to its basicity, has a tendency to form sulfate, sulfite and chloride. These unstable surface species, which probably lead to deactivation, have already been investigated [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Study on the poisoning tolerance and stability of perovskite catalysts for catalytic combustion of volatile organic compounds

Huang

Sun

et al. 2010

Reac Kinet Mech Cat

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La 0.8 Cu 0.2 MnO 3 and La 0.8 Sr 0.2 MnO 3 perovskite catalysts were prepared by the co-precipitation method. The resistance of these catalysts to sulfur poisoning was tested via catalytic combustion of toluene. The results show that the perovskite catalysts were poisoned in the presence of SO 2 . In the presence of dodecyl mercaptan (C 12 H 25 SH), La 0.8 Sr 0.2 MnO 3 exhibits better resistance to sulfur poisoning than La 0.8 Cu 0.2 MnO 3 . It was determined that the SO 2 deactivation is due to the formation of CuSO 4 on the catalyst surface.

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Methane conversion and SO2 resistance of LaMn1−xFexO3 (x=0.4, 0.5, 0.6, 1) perovskite catalysts promoted with palladium

Cited by 22 publications

References 23 publications

Effect of sulphur poisoning on perovskite catalysts prepared by flame-pyrolysis

Effect of sulphur poisoning on perovskite catalysts prepared by flame-pyrolysis

Perovskite-like catalysts for the catalytic flameless combustion of methane

Study on the poisoning tolerance and stability of perovskite catalysts for catalytic combustion of volatile organic compounds

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