Synthetic studies of (, Pr, Nd; , Mn; , Pt) perovskites

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

doi:10.1016/j.solidstatesciences.2004.10.002

Cited by 18 publications

(12 citation statements)

References 21 publications

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“…Indeed, it was reported that catalytic activity of perovskites can be increased through the addition of small amounts of noble metals [19,27,28]. This is confirmed by the present data (Table 2 and Fig.5) for Co-based perovskites doped with either Pt or Pd.…”

Section: -Effect Of Noble Metals Additionsupporting

confidence: 91%

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: -Effect Of Noble Metals Additionsupporting

confidence: 91%

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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“…It was reported that catalytic activity of perovskites can be increased through the addition of small amounts of noble metals [23,38,39]. This is confirmed by the present data ( for undoped samples, catalytic activity for Mn-based perovskite was generally a bit higher than for the Co-based ones.…”

Section: Catalytic Activitysupporting

confidence: 91%

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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“…Among the mixed metal oxides, perovskite-type oxides (general formula ABO 3 where A represents a lanthanide and/or alkaline earth metal ion and B a transition metal ion) exhibit a high catalytic activity in the total oxidation of hydrocarbons [5][6][7][8][9][10]. It is predominantly the B-site cations that determine the catalytic activity [4,[9][10][11][12]. A large number of metal ions can be employed in different combinations in the robust perovskite structure [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, noble metals combined with perovskites have investigated to realize a high performance automotive catalyst [10][11][12][14][15][16][17][18]. Such catalysts are termed "intelligent catalysts" since the noble metal regenerates itself during operation as a catalyst, and therefore, the catalytic activity remains constant over longer reaction times [10].…”

Section: Introductionmentioning

confidence: 99%

“…Pd doped perovskites have been studied in the total oxidation of hydrocarbons [3,4,[10][11][12][14][15][16][17][18]. Investigations by Cimino et al [16] of Pd/LaMnO 3 perovskites coated on cordierite monoliths have shown that a high catalytic activity for the total oxidation of methane was reached after thermal activation above the decomposition temperature of PdO to Pd.…”

Section: Introductionmentioning

confidence: 99%

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LaMnO₃ Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane

2007

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Two series of LaMnO 3 supported noble metal (Pt, Pd, Rh) catalysts prepared by the citrate method and calcined in air at 600 and 800°C, respectively, were investigated. The catalysts resulting from method A were prepared by simultaneous incorporation of the noble metals during perovskite preparation and those following method B were generated by impregnation of the calcined perovskites with the noble metal compounds. The noble metals form solid solutions with the perovskite lattice. Reduction of the catalysts with hydrogen prior to the catalytic reaction led to a significant enhancement of the catalytic activity. During the catalytic reaction, the noble metal clusters are partially transformed to highly dispersed noble metal oxides or nonstoichiometric noble metal oxide phases, which are the catalytically active phases for the total oxidation of methane. The best results were obtained with the Pd containing catalysts prepared by method B.

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Synthetic studies of (, Pr, Nd; , Mn; , Pt) perovskites

Cited by 18 publications

References 21 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

LaMnO₃ Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane

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Synthetic studies of (, Pr, Nd; , Mn; , Pt) perovskites

Cited by 18 publications

References 21 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

LaMnO3 Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane

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LaMnO₃ Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane