In-Situ Catalytic Surface Modification of Micro-Structured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF) Oxygen Permeable Membrane Using Vacuum-Assisted technique

Abstract

This paper aims at investigating the means to carry out in-situ surface modification of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) oxygen permeable membrane by using vacuum assisted technique. The unique structure of the LSCF hollow fibre membrane used in this study, which consists of an outer dense oxygen separation layer and conical-shaped microchannels open at the inner surface has allowed the membrane to be used as oxygen separation membrane and as a structured substrate for where catalyst can be deposited. A catalyst solution of similar material, LSCF was prepared using sol-gel technique. Effects of calcination temperature and heating rate were investigated using XRD and TGA to ensure pure perovskites structure of LSCF was obtained. It was found that a lower calcination temperature can be used to obtain pure perovskite phase if slower heating rate is used. The SEM photograph shows that the distribution of catalyst onto the membrane microchannels using in-situ deposition technique was strongly related to the viscosity of LSCF catalytic sol. Interestingly, it was found that the amount of catalyst deposited using viscous solution was slightly higher than the less viscous sol. This might be due to the difficulty of catalyst sol to infiltrate the membrane and as a result, thicker catalyst layer was observed at the lumen rather than onto the conical-shaped microchannels. Therefore, the viscosity of catalyst solution and calcination process should be precisely controlled to ensure homogeneous catalyst layer deposition. Analysis of the elemental composition will be studied in the future using energy dispersive X-ray Spectroscopy (EDX) to determine the elements deposited onto the membranes. Once the elemental analysis is confirmed, oxygen permeation analysis will be carried out.

Fabrication of lanthanum-based perovskites membranes on porous alumina hollow fibre (AHF) substrates for oxygen enrichment

“…In this technique, the membrane substrate was immersed into the coating sol to procure a uniform coating layer on both surface sides of the membrane. Recently, a new coating method where vacuum condition in introduced into the coating system was proposed [33,34]. The use of vacuum allows uniform coating inside the membrane microchannels by removing the air inside the hollow fibre prior to the introduction of coating solution.…”

“…The prepared LSCF perovskite sol-gel was then deposited onto AHF by using vacuumassisted technique to enhance the deposition of perovskite oxides into the pores [35,36]. The AHF was first vacuumed to remove the air inside the hollow fibre and the tube containing the bare fibres was then filled with perovskite sol-gel solution.…”