Contribution of the Surface Reactions to the Overall Oxygen Permeation of the Mixed Conducting Membranes

Abstract

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).

One-Step Synthesis and Characterization of La2NiO4+δ Mixed-Conductive Oxide for Oxygen Permeation

“…To further ascertain the rate-limiting step in the oxygen permeation, the characteristic thickness of the LNO-CS membrane is calculated as follows. Fitting the experimental data to eq 4 yields a characteristic membrane thickness of L c ≈ 97 μm, which indicates that the oxygen permeation is controlled by the surface reactions for a membrane thickness of <97 μm. Therefore, for the membranes used in the experiment, the oxygen permeation is governed by both the bulk diffusion and surface reactions: where the parameter λ is a constant, L the thickness of the membrane, and L c the characteristic membrane thickness.…”

Experimental and modeling study of oxygen permeation modes for asymmetric mixed-conducting membranes

“…Fig. 9 shows the oxygen flux of a 4.8 × 10 −4 m thickness symmetric membrane as a function of oxygen partial pressures at the air and He sides at 1223 K. According to our previous work [20], it was calculated that the surface reactions on two sides of this membrane accounted for 61.12% of its overall oxygen permeation resistance at the oxygen partial pressure gradient of 2.1 × 10 4 /1 × 10 2 Pa, meaning that in Table 2 Oxygen permeation resistances in the thin dense layer (R D ) and the support (R S ) of asymmetric membranes (200 m thick membrane layer and 1.3 mm thick support) at 1223 K and oxygen partial pressure gradient of 2.1 × 10 4 /1 × 10 2 Pa…”

“…When a porous layer with a good oxygen exchange property is coated on a surface of membrane, the oxygen surface exchanges rate on the sides of membrane can be significantly improved, and then the oxygen permeation flux through the membrane is enhanced [18][19][20]. At this time, the oxygen permeation flux through a dense membrane can be derived as [17,20] Air side :…”

“…k a and k d are from the literature reported by Zeng and Lin [25]. L c is from our previous study [20]. s is chosen from the literature reported by Lee et al [22].…”

Improving Performance of a Dense Membrane Reactor for Thermal Decomposition of CO2 via Surface Modification

“…The reactor module for membrane reaction experiments is illustrated in Figure 1a, which is similar to those previously reported by our laboratory. 9 A prepared membrane disc was mounted on a quartz tube (6 mm i.d., 12 mm o.d.) using a gold ring seal, and the gold rings were the same dimensions as the quartz tubes, which left an effective area of about 0.283 cm 2 for oxygen permeation.…”