Proton-hole mixed conductor, SrCeo.95Yb0.05O3-α(SCYb), has the potential to be used as a membrane for dehydrogenation reactions such as methane coupling due to its high C2-selectivity and its simplicity for fabricating reactor systems. In addition, the mixed conducting membrane in the hollow fibre geometry is capable of providing high surface area per unit volume. In this study, mechanism of methane coupling reaction on the SCYb membrane was proposed and the kinetic parameters were obtained by regression of experimental data. A mathematical model describing the methane coupling in the SCYb hollow fibre membrane reactor was also developed. With this mathematical model, various operating conditions such as the operation mode, operation pressure and feed concentrations affecting performance of the reactor were investigated. The simulation results show that the cocurrent flow in the reactor exhibits higher conversion of methane and higher yield of ethylene compared to the countercurrent flow. In order to achieve the highest C2 yield, especially of ethylene, pure methane should be used as feed and the operating pressure be 300 kPa. Air can be used as the source of oxygen for the reaction and its optimum feed velocity is twice of the methane feed velocity. The air pressure in the lumen side should be kept the same as or slightly lower than the pressure of shell side.
Fluorite-type Y2O2/ZrO2（YSZ） powders with the mean particle size of 1.74 μm were synthesized by the citric acid combustion method.Using the prepared YSZ powders,gas-tight hollow fibre membranes were fabricated by a dry-wet spinning process based on the phase inversion technique,followed by sintering at 1 400 ℃ for（4 h.） The gas tightness,porosity,mechanical strength,microstructure and crystalline phase of the hollow fibre membranes were studied.The results indicate that the prepared YSZ hollow fibre membranes are gas-tight while the porosity remains around 23.04% and the bending strength may be up to 322 MPa.The diameter of the pores in the hollow fibres ranges from 60 to 500 nm.XRD spectra show that the fluorite-type phase is kept unchanged,but the crystal size grows bigger after sintering.SEM micrographs show that the prepared YSZ hollow fibre membranes possess an asymmetric structure that includes a dense layer and porous layers,while the inner and outer surfaces are also dense.
Nanosized SrCe0.95Y0.05O3-δ powders with homogeneous composition were synthesized by the low temperature combustion process based on the Pechini method. A polymeric precursor sol was formed by using citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type SrCe0.95Y0.05O3-δpowders with uniform shape and smaller than 25 nm in size were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found that modulating the quantifies of nitric acid and ammonium hydroxide could control the particle size, and the quantities of residue carbonate ions were also affected by the quantifies of citric acid and ethylene glycol.
