Perovskite membrane reactor for continuous and isothermal redox hydrogen production from the dissociation of water (original) (raw)
Related papers
Journal of Membrane Science, 2009
The redox water splitting is one of the most promising routes for sustainable hydrogen production. Towards this goal, serious technological obstacles are set: (i) by the non-isothermal operation of the redox process, that causes serious reactor construction problems, and (ii) by the need for efficient high temperature oxygen/hydrogen separation technology which is a very challenging development. In this paper, perovskite materials having the formula La 0.3 Sr 0.7 FeO 3 were synthesized and subsequently tested for their high temperature oxidation/reduction behavior. The redox activity of the materials in relation to the water splitting reaction has been also investigated. Dense, disc shaped membranes of the materials were synthesized and placed in a membrane reactor. Experiments at 1133 K revealed the possibility of performing the reduction and oxidation steps simultaneously and isothermally on each side of the membrane reactor. A steady-state situation was thereby achieved where hydrogen was continuously produced on one side while the material was simultaneously regenerated on the other side. The created oxygen vacancy gradient formed the driving force for a continuous flux of vacancies from the membrane reduction surface to the membrane oxidation surface. The hydrogen production rate under the particular experimental conditions estimated to be ∼47.5 cm 3 H 2 (STP) m −2 min −1 . It could be increased by a factor of approximately 3, up to ∼145 cm 3 H 2 (STP) m −2 min −1 , if the membrane reduction was enhanced with a reductant such as carbon monoxide. This approach resulted in an efficient execution of the water gas shift reaction towards high purity hydrogen production.
Perovskite Materials for Hydrogen Production
Materials for Hydrogen Production, Conversion, and Storage
The performance of perovskites as redox materials for solar thermochemical hydrogen production and energy storage have been studied theoretically by several authors but there are only a few experimental studies about them. In this work, an evaluation of commercial perovskite materials La 1Àx Sr x MeO 3 (Me ¼ Mn, Co and Fe) for thermochemical water splitting is presented. The studied perovskites showed suitable redox properties for energy storage in thermogravimetric analysis (TGA) in presence of air, although only the Co-perovskite material (LSC) exhibited cyclability capacity. Experiments of thermochemical water splitting revealed hydrogen production, with increasing yields for Mn-, Fe-and Co-substituted perovskites, respectively. La/Sr ratio in the range of x ¼ 0.2 to 0.4 showed only a slight influence on the amount of hydrogen produced and on the temperature required for the processes. On the other hand, metal substitution type seems to be a critical factor for the thermal reduction of these perovskites, taking place at temperatures above 1000 C for the Mn-perovskite, 800 C for Co-material and 900 C for Fe-material. These results experimentally demonstrate the suitability of solar hydrogen production based on La 1Àx Sr x MeO 3 thermochemical cycles. Moreover, the required temperatures for hydrogen production (230 C) are lower than those commonly reported in literature for "pure" Me n O y oxide cycles (500 C), making perovskite-based cycles a promising alternative. The cyclability studies with the LSC showed a slight decrease in the hydrogen production, derived from the segregation of metallic Co during the thermochemical cycle. This study confirmed the LSC perovskite as a promising material for hydrogen production by solar-driven thermochemical water splitting, although a further insight in the optimization of the operation under consecutive cycles is necessary in order to assess the material as alternative as redox material for a full-scale application.
La (1− x) Sr x MnO 3− δ perovskites as redox materials for the production of high purity hydrogen
International Journal of Hydrogen Energy, 2008
Lanthanum strontium manganates Thermochemical water splitting a b s t r a c t Materials of the perovskite structure and of the general formula La 1Àx Sr x MnO 3 (x ¼ 0, 0.3, 0.7) are investigated as redox catalysts for the two-step steam reforming of methane towards the production of high purity hydrogen. During the activation step, methane is oxidized with lattice oxygen to carbon dioxide and carbon monoxide, while oxygen is withdrawn from the material until a maximum deficiency level which depends on the strontium content and the reaction temperature. During the reaction step water is splitted to gaseous hydrogen and lattice oxygen that fills the oxygen vacancies. It appeared that, after the achievement of a characteristic oxygen deficiency level, La 1Àx Sr x MnO 3 materials exhibit good activity for the water-splitting reaction. The activity is further found to be proportional to the oxygen vacancy concentration. At high activity levels, initial water conversions per 15 mmol pulse of up to 70% are achieved at 1000 C. The cumulatively produced hydrogen during the water-splitting step, per injected water, increases with increasing strontium content, reaching a production of 60 mmol H 2 per 500 mmol water passed over 200 mg La 0.3 Sr 0.7 MnO 3 at 1273 K and no coke formation. The materials exhibit stable behavior after eight successive oxidation-reduction cycles. The relations between the redox behavior and the material defect chemistry are discussed. Finally the energy efficiency of the process, future prospects and ways for its optimization are discussed. ª
Investigation on POM reaction in a new perovskite membrane reactor
Catalysis Today, 2001
A perovskite-type oxide of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCFO) shows mixed (electronic/oxygen ionic) conductivity at high temperatures. Membrane made of the oxide has high oxygen permeability under air/helium oxygen partial pressure gradient. At 850 • C, oxygen permeation rate maintained about 1.15 ml/cm 2 min for more than 1000 h under ambient air/helium oxygen gradient. A membrane reactor constructed from the oxide membrane was applied for the partial oxidation of methane (POM) to syngas, LiLaNiO x /␥-Al 2 O 3 with 10 wt.% Ni loading was used as the packed catalyst. At the initial stage, oxygen permeation rate, methane conversion and CO selectivity were closely related with the state of the catalyst. Less than 21 h was needed for the oxygen permeation rate to reach its steady state. A membrane reactor made of BSCFO was successfully operated for POM reaction at 875 • C for about 500 h without failure, with methane conversion of >97%, CO selectivity of >95% and oxygen permeation rate of about 11.5 ml/cm 2 min. Under membrane reaction condition, the POM reaction mechanism was suggested to obey the CRR (complete combustion of CH 4 to CO 2 and H 2 O and a subsequent reforming reaction of the residual CH 4 and with CO 2 and H 2 O to CO and H 2) mechanism.
Development and application of perovskite‐based catalytic membrane reactors
Catalysis Letters, 1998
The preparation and characterization of catalytic membranes containing La‐based perovskites are reported. The membranes were prepared by in situ crystallization of different perovskites inside a porous α‐alumina matrix. Preponderance of the Knudsen‐diffusion regime during membrane operation was obtained with perovskite loads of 2 wt% and higher. The catalytic membranes obtained were used as combustors of VOCs (toluene and methyl ethyl
Hydrogen separation through LSF-perovskite membrane prepared by chelating method
Journal of Natural Gas Science and Engineering, 2015
La 0.3 Sr 0.7 FeO 3Àd (LSF) perovskite was prepared according to two methods: (1) applying new phenolic derivative of serine amino acid (L) as chelating agent, and (2) in absence of L as ligand-free perovskite (LFP). The newly prepared aminophenolic ligand L was fully characterized by 1 H and 13 C NMR, IR as well as elemental analysis while the LSF perovskite samples were characterized using the IR spectra, powder x-ray diffraction (PXRD) patterns, and SEM micrographs. The PXRD pattern obtained for the perovskite prepared by L (PPP) indicated on the presence of pure perovskite phase. The hydrogen permeation through PPP and LFP membranes with thickness of 1.0 mm were measured as a function of temperature within 973e1223 K while hydrogen partial pressure was constantly kept at 0.5 bar. The hydrogen flux of PPP and LFP membranes were measured as 0.043 and 0.033 mL/min cm 2 at the operating temperature of 950 C. The effect of grain size distribution on hydrogen permeation through PPP and LFP perovskites was investigated. To the best of our knowledge, this is the first report on hydrogen permeation through LSF dense membranes. Experimentally, the hydrogen flux rate through PPP represented a sharper increase in comparison with LFP.
Performance of functional perovskite membranes for oxygen production
Journal of Membrane Science, 2006
In this paper, the influence of composition, thickness, porous activation layers, and measurement conditions on the oxygen permeation rates of mixed ion electron conducting membranes is discussed. To this end, functional membranes, rather than pressed pellets, with an effective surface area of ∼18cm2 and a thickness of ∼200μm with the compositions SrCo0.8Fe0.2O3−δ, Sr0.5Ba0.5Co0.8Fe0.2O3−δ, Sr0.8La0.2Co0.8Fe0.2O3−δ, Ba0.8La0.2Co0.8Fe0.2O3−δ, and Sr0.4La0.6Co0.2Fe0.8O3−δ, have been prepared
Journal of Membrane Science, 1998
La 1Àx Sr x Co 1Ày Fe y O 3À perovskite-type oxides are typical of mixed-conducting ceramic membrane materials with very high oxygen semipermeability. In this study, several different synthesis methods were compared for the preparation of La 0.8 Sr 0.2 Co 0.6 Fe 0.4 O 3À (LSCF) powders. The coprecipitation method was found most suitable for preparation of the LSCF powder in terms of processibility into dense ceramic membranes. The oxygen permeation¯ux through 1.85 mm LSCF membrane exposed to O 2 /N 2 mixture and helium is about 1Â10 À7 mol/cm 2 s at 9508C. The oxygen permeation¯ux increases sharply around 8258C due to an order±disorder transition of the oxygen vacancies in the membrane. Oxidative coupling of methane (OCM) was performed in the LSCF membrane reactor with one membrane surface exposed to O 2 /N 2 mixture stream and other to CH 4 /He mixture stream. At temperatures higher than 8508C, high C 2 selectivity (70±90%) and yield (10±18%) were achieved with a feed ratio (He/CH 4 ) of 40±90. The C 2 selectivity dropped dramatically to less than 40% as the He/CH 4 ratio decreased to 20. The surface catalytic properties for OCM of LSCF membranes strongly depend on the oxygen activity of the membrane surface exposed to methane stream. #
Planar and tubular perovskite-type membrane reactors for the partial oxidation of methane to syngas
Journal of Solid State Electrochemistry, 2004
Dense planar and tubular oxygen separation membranes of La0.6Ca0.4Fe0.75Co0.25O3−δ were investigated as reactors for the partial oxidation (POX) of methane to syngas. Their permeation properties were measured in an air/argon pO2 gradient as a function of temperature. At 900 °C, the oxygen flux through a 1.26-mm-thick membrane was 0.075 μmol/cm2·s and through a 0.25-mm-thick tube, 0.24 μmol/cm2·s. For the POX measurements, a catalyst was added to the membrane and methane was introduced on the argon side. This resulted in a gradual increase of the oxygen flux with increasing concentration of methane, reaching 2 μmol/cm2·s at 900 °C with pure methane. For the planar reactor, the CO selectivity reached 99% and the CH4 conversion 75% at 918 °C with pure methane. For the tubular reactor, the CO selectivity and CH4 conversion were 83 and 99%, respectively, under the same conditions. After 1,400 h of operation in a tubular POX reactor, the membrane was examined revealing phase demixing and local decomposition.