Zirconia-Doped Methylated Silica Membranes via Sol-Gel Process: Microstructure and Hydrogen Permselectivity.

In order to obtain a steam-stable hydrogen permselectivity membrane, with tetraethylorthosilicate (TEOS) as the silicon source, zirconium nitrate pentahydrate (Zr(NO)·5HO) as the zirconium source, and methyltriethoxysilane (MTES) as the hydrophobic modifier, the methyl-modified ZrO-SiO (ZrO-MSiO) membranes were prepared via the sol-gel method. The microstructure and gas permeance of the ZrO-MSiO membranes were studied. The physical-chemical properties of the membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and N adsorption-desorption analysis. The hydrogen permselectivity of ZrO-MSiO membranes was evaluated with Zr content, temperature, pressure difference, drying control chemical additive (glycerol) content, and hydrothermal stability as the inferred factors. XRD and pore structure analysis revealed that, as n increased, the MSiO peak gradually shifted to a higher 2θ value, and the intensity gradually decreased. The study found that the permeation mechanism of H and other gases is mainly based on the activation-diffusion mechanism. The separation of H is facilitated by an increase in temperature. The ZrO-MSiO membrane with n = 0.15 has a better pore structure and a suitable ratio of micropores to mesopores, which improved the gas permselectivities. At 200 °C, the H permeance of MSiO and ZrO-MSiO membranes was 3.66 × 10 and 6.46 × 10 mol·m·s·Pa, respectively. Compared with the MSiO membrane, the H/CO and H/N permselectivities of the ZrO-MSiO membrane were improved by 79.18% and 26.75%, respectively. The added amount of glycerol as the drying control chemical additive increased from 20% to 30%, the permeance of H decreased by 11.55%, and the permselectivities of H/CO and H/N rose by 2.14% and 0.28%, respectively. The final results demonstrate that the ZrO-MSiO membrane possesses excellent hydrothermal stability and regeneration capability.