| 1. |
- Ruivo, L. C. M., et al.
(författare)
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Iron-based catalyst (Fe2-xNixTiO5) for tar decomposition in biomass gasification
- 2021
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 300
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a novel Fe2-xNixTiO5 catalyst for potential applications in biomass gasification gas cleaning/ upgrading was investigated. The material was successfully synthesized through combined mechanical activation and microwave firing. Catalytic steam reforming was studied in a fixed bed tubular reactor, using a mixture of toluene and naphthalene as model tar compounds as well as downstream a fluidized bed gasifier. Fe2-xNixTiO5 catalyst showed high activity in converting the model compounds at temperatures higher than 700 degrees C. The catalyst exhibited a tar conversion of 78% at 800 degrees C when exposed to biomass-derived gas from a bubbling fluidized bed gasifier. Nevertheless, the catalytic activity declined with increased time on stream due to structural changes in iron active phases, caused by redox conditions of the producer gas. Furthermore, thermodynamic calculations suggest that sulfur chemisorption on the nickel surface, may also contribute to the catalyst deactivation.
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| 2. |
- Goel, Ashutosh, et al.
(författare)
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Optimization of La2O3-containing diopside based glass-ceramic sealants for fuel cell applications
- 2009
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 189:2, s. 1032-1043
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Tidskriftsartikel (refereegranskat)abstract
- We report on the optimization of La2O3-containing diopside based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC). Seven glass compositions were prepared by modifying the parent glass composition, Ca0.8Ba0.1MgAl0.1La0.1Si1.9O6. First five glasses were prepared by the addition of different amounts of B2O3 in a systematic manner (i.e. 2, 5, 10, 15, 20 wt.%) to the parent glass composition while the remaining two glasses were derived by substituting SrO for BaO in the glasses containing 2 wt.% and 5 wt.% B2O3. Structural and thermal behavior of the glasses was investigated by infrared spectroscopy (FTIR), density measurements, dilatometry and differential thermal analysis (DTA). Liquid-liquid amorphous phase separation was observed in B2O3-containing glasses. Sintering and crystallization behavior, microstructure, and properties of the GCs were investigated under different heat treatment conditions (800 and 850 degrees C: 1-300 h). The GCs with >5 wt.% B2O3 showed an abnormal thermal expansion behavior above 600 degrees C. The chemical interaction behavior of the glasses with SOFC electrolyte and metallic interconnects, has been investigated in air atmosphere at SOFC operating temperature. Thermal shock resistance and gas-tightness of GC sealants in contact with 8YSZ was evaluated in air and water. The total electrical resistance of a model cell comprising Crofer 22 APU and 8YSZ plates joined by a CC sealant has been examined by the impedance spectroscopy. Good matching of thermal expansion coefficients (CTE) and strong, but not reactive, adhesion to electrolyte and interconnect, in conjunction with a low level of electrical conductivity, indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants. (C) 2009 Elsevier B.V. All rights reserved.
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| 3. |
- Kravchenko, Ekaterina, et al.
(författare)
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High-Temperature Structural and Electrical Characterization of Reduced Oxygen-Deficient Ruddlesden-Popper Nickelates
- 2018
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :28, s. 3320-3329
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Tidskriftsartikel (refereegranskat)abstract
- High-temperature characterization of oxygen-deficient Sr-rich (La1-xSrx)(2)NiO4-delta (x = 0.5-0.8) solid solutions under mildly reducing conditions with p(O-2) approximate to 5x10(-5) atm was performed by employing structural and thermal analysis, TEM, and electrical conductivity measurements. Oxygen losses from the crystal lattice on reduction were found to result in a reversible transition from the tetragonal (I4/mmm) to the orthorhombic (Immm) structure and shrinkage of the crystal lattice for the compositions with x > 0.5. TEM and thermogravimetric analysis evidenced slow kinetics of the structural transition. The increase in oxygen deficiency under reducing conditions is accompanied by localization of the electronic charge carriers, a drop of the p-type electronic conductivity, and a transition from metallic-like to semiconducting behavior. The extent of changes in oxygen nonstoichiometry, unit--cell dimensions, average Ni oxidation state, electron-hole concentration, and electronic conductivity on reduction is interrelated with the strontium content. The results suggest that the electrical conductivity of (La1-xSrx)(2)NiO4-delta ceramics depends mainly on the average Ni oxidation state.
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| 4. |
- Ruivo, L., et al.
(författare)
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Catalytic upgrading of biomass-derived raw gas in fluidized bed gasifiers
- 2019
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Ingår i: European Biomass Conference and Exhibition Proceedings. - : ETA-Florence Renewable Energies. ; , s. 551-558
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Konferensbidrag (refereegranskat)abstract
- Natural ilmenite has been proposed as potential low-cost catalyst for biomass gasification due to its mechanical stability and thermochemical properties at high temperature. Previously works demonstrated that ilmenite showed high activity in water-gas shift reactions, but its limited catalytic activity in tar conversion requires improved performance. Therefore, the present work is focused on synthesis of synthetic catalyst based on Fe-Ti-Ni-O system, testing of their catalytic activity, and detailed studies of relevant factors such as structural and microstructural features and redox behavior under gasification conditions. Thermodynamic predictions were performed to assess expected thermochemical conditions required for the synthesis of catalyst, and the corresponding stability windows in prospective catalytic operation. A simple approach based on microwave irradiation was applied in the preparation of the catalyst, revealing a high potential for reducing production costs. Preliminary catalytic testing using model tar compounds demonstrated that the synthesized catalyst shows enhanced performance for conversion of tar impurities through steam reforming reaction.
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