Sol-Gel Processed Cobalt-Doped Methylated Silica Membranes Calcined under N(2) Atmosphere: Microstructure and Hydrogen Perm-Selectivity

Methyl-modified, cobalt-doped silica (Co/MSiO(2)) materials were synthesized by sol-gel technique calcined in N(2) atmospheres, and membranes were made thereof by coating method. The effects of Co/Si molar ratio (n(Co)) on the physical-chemical constructions of Co/MSiO(2) materials and microstructures of Co/MSiO(2) membranes were systematically investigated. The gas permeance performance and hydrothermal stability of Co/MSiO(2) membranes were also tested. The results show that the cobalt element in Co/MSiO(2) material calcined at 400 °C exists not only as Si–O–Co bond but also as Co(3)O(4) and CoO crystals. The introduction of metallic cobalt and methyl can enlarge the total pore volume and average pore size of the SiO(2) membrane. The activation energy (E(a)) values of H(2), CO(2), and N(2) for Co/MSiO(2) membranes are less than those for MSiO(2) membranes. When operating at a pressure difference of 0.2 MPa and 200 °C compared with MSiO(2) membrane, the permeances of H(2), CO(2), and N(2) for Co/MSiO(2) membrane with n(Co) = 0.08 increased by 1.17, 0.70, and 0.83 times, respectively, and the perm-selectivities of H(2)/CO(2) and H(2)/N(2) increased by 27.66% and 18.53%, respectively. After being steamed and thermally regenerated, the change of H(2) permeance and H(2) perm-selectivities for Co/MSiO(2) membrane is much smaller than those for MSiO(2) membrane.