NANOSIZED GOLD/PEROVSKITE COMPOSITES AS POTENTIAL CATALYSTS FOR PROPANE REFORMING (Abstract/Comunicazione in atti di convegno)

Type
Label
  • NANOSIZED GOLD/PEROVSKITE COMPOSITES AS POTENTIAL CATALYSTS FOR PROPANE REFORMING (Abstract/Comunicazione in atti di convegno) (literal)
Anno
  • 2005-01-01T00:00:00+01:00 (literal)
Alternative label
  • S. Barison, M. Battagliarin, S. Daolio, M. Fabrizio, E. Miorin, P.L. Antonucci, S. Candamano, V. Modafferi, E. M. Bauer, C. Bellitto, G. Righini (2005)
    NANOSIZED GOLD/PEROVSKITE COMPOSITES AS POTENTIAL CATALYSTS FOR PROPANE REFORMING
    in Meeting on Syntheses and Methodologies in Inorganic Chemistry SAMIC 2005 - Trends in Nanoscience, Bressanone (BZ), Italy, 4-7 December 2005
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • S. Barison, M. Battagliarin, S. Daolio, M. Fabrizio, E. Miorin, P.L. Antonucci, S. Candamano, V. Modafferi, E. M. Bauer, C. Bellitto, G. Righini (literal)
Note
  • Comunicazione (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • 1. CNR - Institute for Energetics and Interphases - Corso Stati Uniti, 4 - 35127 Padova - Italy, 2. Department of Mechanics and Materials - University of Reggio Calabria - Località Feo di Vito - 89100 Reggio Calabria - Italy, 3. CNR - Institute of Structure of Matter - Area della Ricerca di Roma 1 - Via Salaria km 29,300 - 00016 Monterotondo Scalo (Roma) - Italy (literal)
Titolo
  • NANOSIZED GOLD/PEROVSKITE COMPOSITES AS POTENTIAL CATALYSTS FOR PROPANE REFORMING (literal)
Abstract
  • Direct hydrocarbon fuel cells have been developed using Solid Oxide Fuel Cells (SOFCs) working at intermediates temperatures (i.e. 500÷800°C). This eliminates the need for fuel processing reactions before the introduction on the stacks. Usually, the anodic catalysts used in SOFCs are based on nickel. However, hydrocarbon fuels (e.g. propane) cause severe carbon deposition and hence rapid deactivation of the catalyst.[1] Therefore, the search for new anodic materials in order to avoid the carbon deposition is one of the key issues in this field. The interest in perovskite-based materials lies in their good mixed ionic and electronic conduction properties. Thus, mixed oxides such as Strontium-doped Lanthanum Manganite and Chromite have been investigated as anodes for IT-SOFCs, due to their electrocatalytic performances and fairly good thermo-chemical properties. La1-xSrxMnO3 (x?0.4) perovskite is characterized by high electrical conductivity and low interface resistance and demonstrated to be a good active catalyst for hydrocarbon oxidation at low temperatures,[2] while La1-xSrxCrO3 (x?0.15) showed higher stability at high temperatures. Therefore, this work deals with the synthesis of high surface area La0.59Sr0.41MnO3 (LSM) and La0.85Sr0.15CrO3 (LSC) powders obtained by a modified nitrate-citrate Pechini process [3] using low calcination temperatures. Three different types of hydrocarbon reforming processes were investigated, e.g. steam reforming (SR), partial oxidation (POX) and autothermal reforming (ATR). Moreover, considering that several noble metals show excellent catalytic activity for hydrocarbon reforming, nanosized gold has been tested as a promoter of the catalytic performance of the perovskite anodic material. In fact, it has been observed that the use of gold promoted CH4 oxidation and reforming over Au/MnOx/Al2O3 [4] catalysts and that the catalytic performance of gold is significantly adjustable by control of the particle size.[5] For this purpose, the syntheses of nanosized 1 and 5 wt% Au/ perovskite composites have been carried out in this work. The coating of perovskite powders with nanosized gold particles was carried out by an ultrasound-driven synthesis.[6] Pure single phase perovskite powders were obtained by this synthetic procedure at lower calcination temperatures respect to usual solid state synthesis (as an example LSM has been isolated as a single-phase in the trigonal R-3c space group). SEM and TEM observations assured that the Pechini process favored the formation of ultra-fine particles. In fact, calculating the particles diameters from TEM micrographs of powders thermal treated at 1000°C, a size distribution centered around 40÷60 nm was estimated for LSM samples, while a distribution around 200÷300 nm was calculated for LSC ones. TEM investigations of the Au/perovskite composites revealed a homogeneous distribution of metallic gold nanoparticles on the powders surface, having dimensions <= 5 nm in the case of 1 wt% Au addition and around 20÷25 nm in the case of 5 wt% Au one. As an example, a TEM micrograph for the Au/La0.59Sr0.41MnO3 composite, with a gold amount around 0.7 wt%, is reported in Figure. The catalytic tests in the propane partial oxidation conditions showed that LSM and Au/LSM catalysts attained nearly 100% conversion already at 600 °C and a nearly equimolar syngas composition (H2:CO?1) was obtained in the whole temperature range (600÷800 °C). Nevertheless, when the steam was introduced in the gas stream, a significant drop in propane conversions was observed. In fact, in ATR conditions an almost complete propane conversion was attained only at 800 °C and in the SR tests only 76% conversion was reached at 800 °C. However, the introduction of gold in the composite improved the catalytic performances in all reaction conditions. Moreover, a further gain on catalytical activity was due to the rising of the gold amount. The characterization after catalytic tests revealed low single phase LSM stability, especially in the steam presence, and showed some particle aggregation phenomena. However, the addition of gold to the perovskite seems to increase the stability of the powders during catalytic reactions. The role of gold regarding the composites stability is still an open question. Therefore further investigations were carried out on Au/La0.85Sr0.15CrO3 composites and on the influence of gold on their catalytic behavior. In the case of LSC and Au/LSC powders, slightly lower conversions respect to LSM were obtained for LSC powders and no influence on gold presence was observed. The aged catalysts characterization is in progress. Moreover, the synthesis of nanosized composites with the La1-xSrxCr1-yMnyO3 perovskite, which already demonstrated good performances and stability as anodic catalysts for methane reforming,[7] is in progress. (literal)
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