DEVELOPMENT OF CERAMIC MIEC MEMBRANES FOR OXYGEN SEPARATION: APPLICATION IN CATALYTIC INDUSTRIAL PROCESSES
- Autores: Julio García Fayos
- Directores de la Tesis: José Manuel Serra Alfaro (dir. tes.), María José Climent Olmedo (tut. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Antonio Chica Lara (presid.), Glenn Christhofer Mather (secret.), Wolff-Ragnar Kiebach (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
The present Thesis is focused on the development of ceramic membranes for the production of O2, as well as their use in several industrial applications (e.g. power generation, chemical industry). Different materials such as perovskites (BSCF and LSCF), fluorites (CGO) and composites, different membrane architectures have been considered. Catalytic activation was considered for the optimization of permeation, and for improving the selectivity/yield of chemical reactions.
In the chapter dedicated to BSCF, the influence of thickness and the use of porous supports in the permeation was studied. An improvement in the permeation was observed for the thinner membranes. With respect to the porous supports, it was found that they contribute with an additional resistance within the permeation process, reducing the potential improvement when reducing thickness. The conducted tests also allowed to study more in deep the different processes affecting oxygen membranes, as well as defining a permeation model for monolithic and asymmetric membranes. Aiming to improve the surface reactions involved in the oxygen permeation the use of catalytic layers was considered, by means the addition of porous BSCF backbones. The best results were obtained when coating both sides of membranes with catalytic layers. The concept of BSCF activated membranes was also considered for the production of C2H4 by means of the oxidative de-hydrogenation of C2H6, obtaining high C2H4 yields. BSCF membranes presenting tubular geometry were characterized for application such as production of O2 and production of C2H4 by means of oxidative coupling of CH4.
LSCF was considered for conducting studies under CO2-containing atmospheres. For both systems it was conducted a complete permeation study with a focus on permeation performance under CO2 environments. Furthermore a study focused on the different substrates was carried out for determining the structure presenting the lower gas diffusion resistance. Despite very good results were obtained for both membrane types, even under CO2 conditions, freeze casted membranes reached higher oxygen fluxes, being optimized with the catalytic activation of membranes.
Materials presenting fluorite structure stand out for their stability under reaction conditions or when exposed to CO2 environments. Nevertheless, delivered oxygen fluxes are typically low. Hence, a thin 40 micron-thick CGO-Co membrane activated with Pd nanoparticles was considered for conducting a study on O2 permeation performance, and its behaviour when exposed to CO2 and CH4-containing atmospheres. A good stability was demonstrated, as well as a significant improvement in oxygen permeation when exposed to CH4 environments. Thus, CGO membranes present promising properties for their application in oxyfuel and for the conduction of chemical reactions.
Composite materials based on NFO-CTO was carried out. An evaluation of the CTO content and its relation with permeation was conducted, determining that a higher ionic phase ratio in the membrane results in a higher permeation. A composite consisting of 50NFO-50CTO was considered for performing a permeation study under harsh application conditions, with presence of SO2. Despite the significant loss in permeation, the composite material resulted to be stable after a long exposure to SO2. A broad study about the effect of CO2 and SO2 on the oxygen surface reactions was conducted by means of EIS measurements on 60NFO-40CTO electrodes. It was observed a significant effect of SO2 on the surface exchange reactions by promoting the deactivation of the O2 active sites, due to a SO2 adsorption on them. This effect was minimized by activating 60NFO-40CTO backbones with different catalysts, being characterized by EIS under CO2&SO2 conditions. This improvement was later confirmed when performing permeation tests. Permeation was improved notably by reducing membrane thickness, depositing composite membranes on LSCF porous substrates.
