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Il poster descrive dei risultati dell’attività di sviluppo di membrane di Pd con barriera ceramica, svolta in ambito RdS e in collaborazione con l’Università di Genova, Dip. di Chimica e Chimica Industriale.
Porous stainless steel supports (PSS) are good candidates for the development of inorganic membranes for high temperature applications because of their good mechanical properties, easy assembly into modules, corrosion resistance. Unfortunately, porous stainless steel supports commercially available have a limited variety of porosity and structure and usually pore size distribution is very wide and in the macroporous range. Currently there are some commercial attempts of preparation of asymmetric stainless steel membranes by spraying metal powders, but their quality is not yet satisfactory. Up to now PSS have been widely studied as mechanical supports for the deposition of several ceramic layers as well as zeolite. The presence of a suitable first ceramic layer would lead to the desired morphology by decreasing pore dimensions and leveling of surface roughness. Composite metallic membranes with a mechanically and defect-free stable mesoporous ceramic layer could easily find application in traditional separation fields (e.g. micro and ultrafiltration), but especially in high temperature separation and reactors (catalytic membrane reactors). One advantageous example of high temperature further development could be the synthesis of stable palladium alloy membranes where the ceramic mesoporous layer acts as an interdiffusion barrier. On this basis, our study deals with the chemical formulation and subsequent dip-coating deposition of successive ceramic layers on AISI 316L steel supports for composite membranes. To reach a good quality of the ceramic layer, several sol-gel systems such as Al2O3/PVA/Glycerol, Al2O3/HPC, ZrO2/PVA have been formulated and the role of chemical composition on viscosity and on the resulting morphology of the deposited layer has been investigated. Particular attention has been dedicated to the experimental procedure for preparing the sol-gel and on the stability conditions of the prepared sols, avoiding the formation of networks and gels. To achieve a better leveling effect of the rough surface, we also prepared different aqueous dispersions of α-Al2O3 activated powders, which allow a strict control of particle dimensions. In addition, the effect of time deposition has been considered.Results acquired up to now indicate that a thorough control of viscosity has to be maintained to get a satisfying covering of the support surface avoiding the formation of cracks and/or microscopical defects. Morphological evidences acquired by scanning electron microscopy also demonstrate that the successive depositions of sol-gel systems with decreasing viscosity lead to a good leveling of support surface.
31 Dicembre 2011
Studi sull’utilizzo pulito dei combustibili fossili e cattura e sequestro della CO2 (P08USI)