Synthesis and characterization of TiO₂ membrane with palladium impregnation for hydrogen separation

• Published in: Journal of membrane science Vol. 366; no. 1-2; pp. 166 - 175
• Main Authors: Ahmad, A.L, Jaya, M.A.T, Derek, C.J.C, Ahmad, M.A
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2011
• Subjects: adsorption; artificial membranes; crossing; crystallization; desorption; hydrogen; nanoparticles; nitrogen; palladium; particle size; pressure; scanning electron microscopes; scanning electron microscopy; separation; surface area; temperature; thermogravimetry; titanium dioxide; transmission electron microscopy; X-ray diffraction
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2010.09.056

This paper reports the synthesis and characterization of TiO₂ membranes impregnated with elemental palladium (Pd–TiO₂) for hydrogen separation at elevated temperatures and pressures. The membranes were prepared by sol–gel method where the elemental Pd was introduced through sol-mixing of titania sol and Pd precursor solution. The Pd–TiO₂ membranes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), thermogravimetric analysis (TG/DTA), N₂ adsorb/desorption analysis, and single permeation test of H₂ and N₂. The XRD analysis revealed that the presence of Pd nanoparticles has retarded the crystallization and anatase-rutile phase transition. The TEM images indicated that the Pd–TiO₂ membranes are composed of non-uniform particle size as compared to that of TiO₂ membranes alone. For four times dip-coating, the membrane thickness was measured to be approximately 634nm. By impregnating small concentration of Pd, it significantly enlarged the pore size of the original TiO₂ membrane structure besides increasing its surface area and pore volume. However, a reverse trend was observed when the Pd concentration was increased further. Single permeance of H₂ and N₂ for both TiO₂ and Pd–TiO₂ membranes showed that the transport mechanism to be dominated by Knudsen diffusion and Poiseuille flow. The ideal selectivity of H₂/N₂ crossing through the Pd–TiO₂ membrane was calculated and found to be less than the theoretical value of Knudsen diffusion based separation. The selectivity of Pd–TiO₂ membrane increased with the temperature increment, whereas the same trend was not observed for TiO₂ membrane. These results show that, there were other transport mechanisms involved apart from Knudsen diffusion and Poiseuille flow.