An improvement of the hydrogen permeability of C/Al_2O_3 membranes by palladium deposition into the pores

摘要

The development of compact hydrogen separator based on membrane technology is of key importance for hydrogen energy utilization, and the Pd-modified carbon membranes with enhanced hydrogen permeability were investigated in this work. The C/Al_2O_3 membranes were prepared by coating and carbonization of polyfurfuryl alcohol, then the palladium was introduced through impregnation-precipitation and colloid impregnation methods with a PdCl_2HCl solution and a Pd(OH)_2 colloid as the palladium resources, and the reduction was carried out with a N_2H_4 solution. The resulting Pd/C/Al_2O_3 membranes were characterized by means of SEM, EDX, XRD, XPS and TEM, and their permeation performances were tested with H_2, CO_2, N_2 and CH_4 at 25 ℃. Compared with the colloid impregnation method, the impregnation-precipitation is more effective in deposition of palladium clusters inside of the carbon layer, and this kind of Pd/C/Al_2O_3 membranes exhibits excellent hydrogen permeability and permselectivity. Best hydrogen permeance, 1.9 × 10~(-7) mol/m~2 s Pa, is observed at Pd/C = 0.1 wt/wt, and the corresponding H_2N_2 H_2/ CO_2 and H_2CH_4 permselectivities are 275,15 and 317, respectively.