Gas permeation and isobutane dehydrogenation over very thin Pd/ceramic membranes

An attempt was made in this study to prepare very thin palladium membranes. Pd was electrolessly deposited an the inner side surface of a mesoporous ceramic tube using a persitaltic pump to circulate the electroless solution through the tube. To obtain defect-free Pd membranes, a two-step deposition procedure from a dilute Pd2+ bath and a concentrated Pd2+ bath was practised with great care to avoid the difficulties associated with the mismatch of thermal expansion coefficients between Pd and the ceramic substrate. The various membranes produced were characterized through a study of their permeation behaviors. A dense Pd membrane about 2 mu m thick was permselective to hydrogen, It was found that in this very thin Pd membrane case, the hydrogen permeation flux was better correlated to hydrogen pressure using a power higher than 0.5, showing deviation from Sieverts' law. To evaluate the efficiency of the prepared thin Pd/ceramic membranes, iso-butane dehydrogenation was used as a model reaction, Enhanced dehydrogenation yields were obtained in the membrane reactor due to the separation of hydrogen from the reaction medium.