Factors Limiting the Apparent Hydrogen Flux in Asymmetric Tubular Cercer Membranes Based on La27W3.5Mo1.5O55.5-δ and La0.87Sr0.13CrO3-δ.

Zuoan Li,Marie-Laure Fontaine,Wen Xing,Rune Bredesen,Jonathan M Polfus,Christelle Denonville

doi:10.3390/membranes9100126

Abstract

Asymmetric tubular ceramic–ceramic (cercer) membranes based on La27W3.5Mo1.5O55.5−δ-La0.87Sr0.13CrO3−δ were fabricated by a two-step firing method making use of water-based extrusion and dip-coating. The performance of the membranes was characterized by measuring the hydrogen permeation flux and water splitting with dry and wet sweep gases, respectively. To explore the limiting factors for hydrogen and oxygen transport in the asymmetric membrane architecture, the effect of different gas flows and switching the feed and sweep sides of the membrane on the apparent hydrogen permeability was investigated. A dusty gas model was used to simulate the gas gradient inside the porous support, which was combined with Wagner diffusion calculations of the dense membrane layer to assess the overall transport across the asymmetric membrane. In addition, the stability of the membrane was investigated by means of flux measurements over a period of 400 h.

Highlights

Technology that can efficiently separate hydrogen from a mixed gas stream may be integrated in processes that either consume or liberate hydrogen or employed in stand-alone hydrogen production [1,2,3]
Asymmetric tubular membranes were fabricated by extrusion of an La27 W3.5 Mo1.5 O55.5−δ (LWM) porous support Asymmetric tubular membranes were fabricated by extrusion of an LWM porous support and and dip-coating
The permeabilities of the asymmetric membranes were lower than resulting membranes exhibited a dense LWM layer at the membrane/support interface in addition to the dense LWM-La0.87 Sr0.13 CrO3−δ (LSC) top layer

Summary

Introduction

Technology that can efficiently separate hydrogen from a mixed gas stream may be integrated in processes that either consume or liberate hydrogen (e.g., in hydrocarbon upgrading such as non-oxidative methane aromatization) or employed in stand-alone hydrogen production [1,2,3]. Dense metallic membranes based on Pd and its alloys show high solubility and diffusivity of hydrogen and are promising for hydrogen separation at intermediate temperatures (>~300–500 ◦ C) [4,5]. Dense ceramic membranes based on mixed proton and electron conducting materials demonstrate thermal and chemical stability for application in high temperature processes (>700 ◦ C) [6,7], their hydrogen fluxes are much lower than their metallic counterparts. Rare earth tungstates have attracted much attention due to their high chemical stability in CO2 and H2 S containing environments [12,13,14]. Molybdenum substituted rare-earth tungstates, La27 W3.5 Mo1.5 O55.5−δ (LWM), show relatively high hydrogen permeability [15,16]

Methods

Results

Conclusion