The thermal decomposition of CO2 to CO and O2 is a potential route for the consumption and utilization of CO2. However, this reaction is limited by both the thermodynamic equilibrium and the kinetic barrier. In this study, we reported an innovative catalytic process to decompose CO2 in an oxygen-permeation membrane reactor packed with a mixed-conducting oxide supported noble metal catalyst, or Pd/SrCo0.4Fe0.5Zr0.1O3-delta (Pd/ SCFZ), which is of high activity in the decomposition of CO2 into CO and O2. Pd/SCFZ catalyst was prepared by incipient wetness impregnation of the SCFZ powders with an aqueous solution of PdCl2, and the CO2 sorption/desorption property was examined by in situ Fourier transform infrared spectroscopy and temperature-programmed desorption-mass spectrometry technologies. It was shown that there appeared a typical of bridged carbonyls (Pd-CO) on the surface of the Pd/SCFZ catalyst formed after CO2 decomposition. Both CO2 and CO could be detected in the species desorbed from Pd/SCFZ catalyst, which implied that the Pd/SCFZ catalyst could effectively activate the CO2 molecule. During the catalytic process, furthermore, the activity of the Pd/SCFZ catalyst can self-regenerate by removing the produced lattice oxygen through the dense oxygen-permeable ceramic membrane. At 900 degrees C, this catalytic process attains 100% of CO formation selectivity at 15.8% of CO2 conversions.
[Show abstract][Hide abstract] ABSTRACT: A triple-layer composite membrane with porous-dense-porous structure was proposed to develop a high performance membrane reactor. The triple-layer composite membrane consists of a porous Sr0.7Ba0.3Fe0.9Mo0.1O3−δ (SBFM) layer, a dense 0.5 wt% Nb2O5-doped SrCo0.8Fe0.2O3−δ (SCFNb) layer and a porous La0.8Sr0.2MnO3−δ–yttria stabilized zirconia (LSM/YSZ) layer. The porous layers can effectively reduce the corrosion of the reactive atmosphere to the membrane, while the dense layer permeated oxygen effectively. Compared with single layer dense SCFNb membrane reactor, the triple-layer composite membrane reactor can be operated for more than 500 h. At the temperature of 900 °C, the CO2 conversion can reach 20.58% with the CH4 conversion, CO selectivity and O2 flux being about 84%, 97% and 2.13 mL (STP) cm−2 min−1, respectively. The porous-dense-porous structure can successfully combine the high oxygen permeation and stability of the membrane reactor.
[Show abstract][Hide abstract] ABSTRACT: To decompose carbon dioxide, which is a representative greenhouse gas, a plasma torch was designed and manufactured. To examine the characteristics of carbon dioxide decomposition via plasma discharge, a case wherein pure carbon dioxide was supplied and a case wherein methane and/or were injected as additives were investigated and compared. The carbon dioxide and methane conversion rate, energy decomposition efficiency, produced gas concentration, carbon monoxide and hydrogen selectivity, carbon-black and were also investigated. The maximum carbon dioxide conversion rate was 28.9% when pure carbon dioxide was supplied; 44.6% when was injected as am additive; and 100% percent when methane was injected as an additive. Therefore, this could be explained that the methane injection showed the highest carbon dioxide decomposition. Furthermore, the carbon-black and were compared with each commercial materials through XRD and SEM. It was found that the carbon-black that was produced in this study is similar for commercial materials. It was found that the that was produced in this study is suitable for photocatalyst and pigment because it has mixed anataze and rutile.
[Show abstract][Hide abstract] ABSTRACT: A new series of Nb2O5-doped (0.5, 1, 3, 5, 10 and 15 wt.%) SrCo0.8Fe0.2O3−δ (SCF) mixed conducting materials have been synthesized by the solid-state reaction method. The crystal structure, phase stability, oxygen desorption behavior, thermal expansion behavior, electrical conductivity and oxygen permeability of the prepared materials were systematically investigated. Doped Nb2O5 was completely incorporated into the SCF structure and effectively suppressed the coexisting orthorhombic phase in bulk cubic SCF and the perovskite–brownmillerite transition under low oxygen partial pressure. In situ high-temperature X-ray diffraction (HTXRD) also indicated good chemical and structure stability of the slightly doped Nb2O5 (0.5 wt.%) at both 0.21 × 105 and 1 × 10−2 Pa oxygen partial pressures at high temperatures. Nb2O5 dissolved into the SCF lattice served to some extent to decrease the electrical conductivity and oxygen flux, and increase the thermal expansion. The grain size of the membranes were significantly suppressed by the doping of Nb2O5. In particular, SCFNb0.5 with the cubic perovskite structure has the smallest cell parameters, the lowest thermal expansion and the highest oxygen flux.
Journal of Membrane Science 07/2012; s 405–406:300–309. DOI:10.1016/j.memsci.2012.03.026 · 5.06 Impact Factor
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