An oxygen permeable membrane microreactor with an in-situ deposited Bi_1.5Y_0.3Sm_0.2O_3-δ catalyst for oxidative coupling of methane

In this study, a novel catalytic hollow fibre membrane microreactor (CHFMMR) was developed using a micro-structured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) hollow fibre as an oxygen separation membrane as well as a functional substrate for in-situ deposition of a Bi_1.5Y_0.3Sm_0.2O_3-δ (BYS) catalyst using a sol-gel method for oxidative coupling of methane (OCM) reaction. A nano-thickness BYS catalytic layer (300-500nm) was successfully deposited onto the microchannel walls throughout the whole hollow fibre. The differences in the OCM performances between the in-situ sol-gel prepared CHFMMR and a washcoat CHFMMR are highlighted. The performance of such CHFMMR is found to be strongly dependent on the properties of BYS and the reaction conditions. When the particle size of BYS was reduced to nano-sizes and was uniformly dispersed, the performance of such CHFMMRs changes drastically, in which higher oxygen permeation rate and methane conversion were obtained. A decrease in residence time was observed to give a better C₂₊ selectivity and C₂₊ yield, achieving a maximum value of 79% and 39%, respectively at 900°C. To the best of our knowledge, the C₂₊ yield obtained in this study is the highest value reported so far. The C₂₊ productivity rate of the in-situ design CHFMMR was observed to be nearly four times higher than that of the washcoat CHFMMR due to the better accessibility of reactants towards lattice/active site of the uniform BYS catalytic layer.