Hydrogen and carbon nanotubes production by methane decomposition over Ni°/La2 O3 obtained from LaNiO3-δ perovskite

RESUMEN: La perovskita LaNiO3, tanto reducida como no reducida, se evaluó en la reacción de descomposición del metano a 600°C y 700°C. El Ni°/La2 O3 obtenido por este procedimiento mostró la más alta actividad en la descomposición de metano, además la mayor producción de hidrógeno y CNTs: 18 LH2/(gcath) y 2,2 g CNT/(g cat h) respectivamente. Este catalizador presenta la mayor conversión reportada en la literatura (82%) bajo condiciones similares de operación. Cuando se utiliza la perovskita, la conversión de CH4 y la producción de CNTs fue 4 veces menor que la obtenida con el catalizador reducido. Los nanotubos de carbono de pared múltiple (MWCNTs) fueron caracterizados por difracción de rayos X (XRD), área superficial (BET), microscopía electrónica de transmisión (TEM) y de barrido (SEM), análisis termogravimétrico (TGA) y espectroscopia Raman. Las micrografías TEM mostraron que los CNTs poseían diámetros internos entre los 5 a 16 nm, externos hasta los 40 nm, y varias micras de longitud.ABSTRACT: LaNiO3 perovskite, both reduced and non-reduced, was evaluated in the decomposition of methane at 600°C and 700°C. The Ni°/La2 O3 obtained by reduction of LaNiO3 showed the largest methane decomposition activity and also the highest yield of hydrogen and carbon nanotubes (CNTs): 18 LH2/(gcat h) and 2.2 g CNT/(g cat h), respectively. To our knowledge, these figures are among the highest values reported in the scientific literature. When non-reduced perovskite was used, the conversions and yields of CNTs were about 4 times lower than those with reduced catalyst. Multi walled carbon nanotubes were characterized by X-ray diffraction, surface area, transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and Raman spectroscopy. TEM micrographs showed that the CNTs were multi-walled, with inner diameters ranging from 5 to 16 nm, external diameters up to about 40 nm, and several microns in length

Dry reforming of methane with La1-XAXNiO3 and LaNi1-XBXO3 (A: Ce or Pr and B: Co or Mg) perovskites as catalysts precursors

ABSTRACT: Perovskite-type LaNiO3 was synthesized by four different methods: autocombustion, sol-gel, calcination of nitrate and freeze-drying. The catalyst that presented the highest activity in terms of conversion of CH4 and CO2 to H2/CO was obtained from perovskites synthesized by the autocombustion method. The Co-containing catalysts showed less activity than those with only Ni. This decrease in activity was attributed to the formation of Co-Ni alloy. The Mg-substituted catalysts showed a decrease in carbonaceous deposits due probably to increased basicity of the catalysts. The greatest resistance to the accumulation of carbonaceous deposits was observed on the catalysts containing Ce and Pr, which is attributed to the redox properties of oxides (PrYOX and CeYOX) which facilitate the gasification of carbonaceous deposits formed during the reaction.RESUMEN: La perovskita LaNiO3 fue sintetizada por cuatro métodos diferentes: autocombustión, sol-gel, calcinación de nitratos y freeze-drying. El catalizador que presentó la mayor actividad en términos de conversiones de CH4 y CO2 a H2/CO fue el proveniente de la perovskita sintetizada por el método de autocombustión. Los catalizadores sustituidos parcialmente con Co mostraron una actividad inferior que aquellos con sólo Ni. Este decrecimiento en la actividad fue atribuido a la formación de la aleación CoNi. Los catalizadores sustituidos con Mg registraron una disminución de los depósitos carbonosos debido probablemente al aumento de la basicidad de los catalizadores. La mayor resistencia a la acumulación de depósitos carbonosos se observó en los catalizadores que contienen Pr y Ce, lo cual se atribuye a las propiedades redox de los óxidos (PrYOX y CeYOX) facilitando la gasificación de los depósitos carbonosos formados durante la reacción

Non-thermal plasma for catalyst regeneration: A review

International audienceAn alternative technology to the thermal regeneration of coked catalysts is non-thermal plasma (NTP). The main advantage of plasma is that it allows activation of the molecules at low temperature and atmospheric pressure. The species formed under oxygen plasma are able to oxidize coke from various catalysts: zeolite, metal supported over oxide. In the present review catalysts regeneration are discussed with a strong focus on the effect of the nature and location of coke into the porosity of catalyst. Two families of catalysts that differ in pore size have been considered (i) zeolites possessing well-defined, nanometer sized pores (50 nm). Moreover, the interest of NTP assisted by temperature for the regeneration of a coked material is also shown. The review ends with some concluding remarks and outlook in the field of catalyst regeneration

Hydroamination of ethylene with NH 3 induced by non-thermal atmospheric plasma

International audienceWe show here that non-thermal atmospheric plasma induces the cleavage of the N–H bond of NH 3 to form aminium radicals, which then add onto ethylene to form ethylamine in 17% yield. This technology can be also extended to n-octene, leading to the formation of 1-octylamine, i.e. with anti-Markovnikov addition of NH3

Metane partial oxidation bythe lattice oxygen of the lanio 3d perovskite. A pulse study

LaNiO3 perovskite was prepared by the selfcombustion method and tested as catalyst for CH4 activation using the oxygen lattice at 700°C and 800°C. Based on the nonstoichiometryexperiments, the perovskite formula is written as La 3+ Ni 3+ 0.37Ni 2+ 0.63O2.68. When unreduced LaNiO3dperovskite is used, only type oxygen species were responsible for the partial CH4 oxidation. Over non reduced perovskite high CH4 conversions to H2 and CO were obtained. CH4 conversion and H2, CO and CO2, selectivities under quasistationary conditions were 100%,80%, 98% and 2 % respectively at 800°C. At the beginning of the reaction, a complete oxidation of methane to CO2 and H2O took place, whereas a partial oxidation to CO and H2 was observed after that period. In such conditions the H2/CO molar ratio obtained was 1.7, indicating a contribution of the parallel reverse water gas shift reactionLa Perovskita LaNiO3 fue preparada por el método de auto-combustión y probada como catalizador en la activación del CH4 utilizando el oxígeno de la red a 700°C y 800°C. Basados en experimentos de no estequiometria se encontró que la fórmula de la perovskita es La 3+ Ni 3+ 0.37Ni 2+ 0.63O2.68.Cuando se usó la perovskita no reducida, solo las especies oxigeno b fueron las responsables de la oxidación parcial del CH4. En este caso la conversión de CH4 y las selectividades hacia H2, CO y CO2 en estado cuasi estacionario fueron 100%, 80%, 98% y 2% respectivamentea800°C. Al principio de la reacción, la completa oxidación del metano hacia CO2 y H2O fue observada, mientras que la oxidación parcial hacia CO y H2 fue la reacción predominante el resto de la reacción. La relación molar H2/CO obtenida fue de 1.7, indicando la contribución de la reacción inversa de gas a agua en forma paralel

Selective conversion of glycerol to hydroxyacetone in gas phase over La2CuO4 catalyst

International audienceThe gas phase dehydration of glycerol to hydroxyacetone was investigated over La2CuO4 catalyst under inert conditions. The reaction was performed in the temperature range of 260-400 degrees C. At low temperature (260 and 280 degrees C) high yields of hydroxyacetone can be achieved: 76% while at higher temperatures carbon deposition occurred. We showed that the structure of the La2CuO4 catalyst was modified during time on stream: Cu2+ was partially reduced into Cu1+ even at 260 degrees C. The formation of Cu2O was revealed by XRD and XPS analysis confirmed that both Cu2+ and Cu1+ are present at the surface of the catalyst. After reduction of La2CuO4 into Cu-0/La2O3, low catalytic activity was observed proving that metallic copper is not the required species to perform the dehydration of glycerol into hydroxyacetone under our experimental conditions. TGA analysis revealed that only small amount of carbon deposition occurred during time on stream at 260 degrees C, no catalytic deactivation being observed during 20 h of reaction

Methane partial oxidation by the lattice oxygen of the lanio₃δ perovskite. a pulse study

LaNiO₃ perovskite was prepared by the selfcombustion method and tested as catalyst for CH4 activation using the oxygen lattice at 700°C and 800°C. Based on the non-stoichiometry experiments, the perovskite formula is written as La³⁺+ Ni³⁺ 0.37Ni²⁺ 0.63O2.68. When unreduced LaNiO3d perovskite is used, only type oxygen species were responsible for the partial CH₄ oxidation. Over non reduced perovskite high CH4 conversions to H₂ and CO were obtained. CH4 conversion and H₂, CO and CO₂, selectivities under quasistationary conditions were 100%, 80%, 98% and 2 % respectively at 800°C. At the beginning of the reaction, a complete oxidation of methane to CO₂ and H₂O took place, whereas a partial oxidation to CO and H₂ was observed after that period. In such conditions the H₂/CO molar ratio obtained was 1.7, indicating a contribution of the parallel reverse water gas shift reactio

Long Distance Charge Redistribution Upon Cu,Zn-Superoxide Dismutase Reduction

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Electrochemically induced FTIR difference spectroscopy in the mid- to far infrared (200 μm) domain: A new setup for the analysis of metal–ligand interactions in redox proteins

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Catalyst assisted by non-thermal plasma in dry reforming of methane at low temperature

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