Zeolite LTA/Carbon membranes for air separation

Zeolite LTA membranes with few defects have been successfully synthesized on a carbon support by the secondary growth method, in which hydrothermal synthesis is preceded by the seeding of the carbon support with colloidal LTA zeolite crystals (about 100 nm) by means of the ElectroPhoretic Deposition (EPD) method. The effect of different synthesis parameters, such as pre-treatments of the carbon support, and different synthesis times and temperatures, on the quality of the zeolite LTA/carbon composite, were analysed by means of XRD, SEM, EDS, and TG–DTA–MS. In addition, in order to analyse the permeation characteristics of the composite materials, they were mounted in a permeation cell, and single gas components or binary mixtures of N2/O2 (in a ratio of 79:21) were fed to the zeolite side. The best zeolite LTA/carbon membrane was obtained using a pre-oxidised and EPD seeded support which then underwent hydrothermal treatment at 373 K for 4.5 h. This final composite, upon reaching the steady state, separates air with a high permeance (about 2.7 x 10-7 mol s-1 Pa-1 m-2) and possesses a good separation factor (about 2.7).Spanish Ministerio de Educación y Ciencia (Project CTQ2006-08958/PPQ) and the EU (FEDER program)