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.

In this study, a SrCo 0.4 Fe 0.5 Zr 0.1 O 3-δ (SCFZ) dense mixed-conducting membrane was applied to a membrane reactor for the thermal decomposition of carbon dioxide (TDCD) (CO 2 T CO + 1 / 2 O 2 ). The SCFZ membrane broke after the membrane reactor ran for about 36 h, because the eroding gases, such as CO 2 and CO, corroded the membrane material. To improve the stability of the membrane reactor, the surface modification of the SCFZ membrane was applied by coating a porous layer. After surface modification on the membrane surface, the porous layer can reduce effectively the corrosion of gases for the membrane material. The effect of coating a porous layer on the membrane surface exposed to the feed side (CO 2 ) on improving the performance of the membrane was more remarkable than that on the membrane surface exposed to the permeate side. This phenomenon can be elucidated by the reaction pathway of TDCD in the membrane reactor.

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Oxygen permeation through a mixed conducting membrane is essentially controlled by both the bulk diffusion and the surface reactions on the both sides of the membrane; therefore, it is important to know the proportion of surface reactions in the overall oxygen permeation to improve the oxygen permeability of membranes effectively. In this study, the contribution of surface reactions to the overall oxygen permeation was investigated in detail through the calculation and the oxygen permeation measurement of the noncoated or coated SrCo0.4Fe0.5Zr0.1O3 - δ (SCFZ) mixed conducting membranes. The contribution of the surface reactions to the overall oxygen permeation was observed to increase with decreases in the membrane thickness for both the noncoated and coated membranes, and that the contribution of the surface reactions was significantly reduced by coating a porous layer. The effect of applying a porous layer on the permeate side (low oxygen partial pressure) on the decrease of the contribution of the surface reactions was more remarkable than that on the feed side (high oxygen partial pressure).

A one-step process for the synthesis of La2NiO4+ δ (LNO) mixed-conductive oxide was reported. During the process, LNO powders were synthesized via the combustion of mixtures with the desired metal ions as cation precursors and glycine as fuel. X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometry, and specific surface area analysis were used to characterize the crystal structures, morphologies, sintering behavior, and surface area of the LNO powders. The effect of the fuel ratio (Φ) on the crystal structures of LNO oxide was studied to reveal the optimal synthesis conditions. It was determined that almost-pure LNO oxide with a K2NiF4-type phase could be achieved when Φ = 1.2 without calcination steps. The synthesized LNO powders had good sintering properties, and the membranes derived from the powders could become dense after sintering in air at 1423 K for 5 h. The LNO powders possessed more interstitial oxygen ions in the rock-salt layers of LNO lattice than those derived from the traditional solid-state reaction (SSR) method. The oxygen permeability of the LNO membrane was examined by a high-temperature oxygen permeation measurement. The oxygen permeation flux (at 1173 K and the oxygen partial pressure gradient is 0.21 × 105/1 × 102 Pa) of the LNO membrane originated from combustion process was 1.5 × 10-7 mol cm-2 s-1, which was 1.5 times greater than that of the SSR-derived membrane.