Oxygen Permeable Ceramic Hollow Fiber Membrane Reactors For Methane Oxidative Coupling

La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF) and SrTi0.9Li0.1O3(STL) powders have been prepared by the ultrasonic spray pyrolysis (S-P) technique and the sol-combustion process based on the Pechini method, respectively. Through XRD, SEM, TEM and laser grain analyzer measurements, the crystalline phase, the microstructure and the size distribution of the prepared powders were investigated. In addition, the catalytic performances to oxidative coupling of methane(OCM) and the conductivity of the resulting powders were also studied. The experimental results indicate that the LSCF powders consist mainly of spherical particles with the mean diameter of 3.3μm. Particle size increases with the increasing of the concentration of precursor solution and conforms to One-Droplet-One-Particle mechanism (ODOP).The prepared powders possess a single perovskite crystalline phase, and the maximum conductivity is 11.59 S cm-1 at 650℃.By the addition of NH4NO3 into the precursor solution, the solid spherical STL particles with a single perovskite structure can be directly synthesized. The powders also possess an even size distribution with the mean diameter of 500nm. The S-P prepared STL ultra-fine powder exhibits much higher C2 selectivity and C2 yield in the methane oxidative coupling reaction than those prepared by the sol-combustion method.La0.6Sr0.4Co0.8Fe0.2O3-δ(LSCF) hollow fiber ceramic membrane was prepared by the phase inversion technique. The ceramic membranes have the asymmetric structure with spongy and dense layers. The dense membranes without defects can be obtained after sintering at 1300℃for 5h. The perovskite crystalline structure of LSCF in the membranes does not change after sintering at high temperatures.Dense ceramic hollow fibre membranes were employed to fabricate hollow fibre membrane reactors for OCM. C2 selectivity attained up to 93.5% at 1198-1248K,but low methane conversion (<20%) was achieved. When no catalyst was used within the membrane reactor, the concentration of oxygen in the hydrocarbon stream is noticeably high. However, if STL was packed inside the fibre lumen as OCM catalysts, the C2 selectivity and oxygen permeation flux would be improved significantly. At 1198K, C2 yield of 14.5% was obtained in the catalytic membrane reactor.Compared to the packed bed reactor, the packed hollow fibre membrane with STL as OCM catalyst could gave higher C2 selectivity (about 10%) at equavalent methane conversions at 1198K.