Development of Metal-doped Silica Membranes for Increased Hydrothermal Stability and Their Applications to Membrane Reactors for Steam Reforming of Methane

Abstract

Hydrothermal stability is one of the most important technical challenges for hydrogen separation silica membranes. Metal doping into silica matrix was proposed, and it was found that Ni and Co were effective to improve the hydrothermal stability. Co-doped silica membranes showed a high permeance of 1.8 10 -7 mol/(m 2 ・s・Pa) and H2/N2 permeance ratio of 730 with hydrothermal stability (500 , steam partial pressure 300 kPa). Using hydrothermally stable silica membranes, permeation properties of helium, hydrogen and water vapor were examined based on the activation energy of permeation. The activation energy of H2 permeation correlated well with the permeance ratio of He/H2. The permeance ratios of H2/H2O of silica membranes are always larger than unity, although the kinetic diameter of hydrogen (0.289 nm) is larger than that of water (0.265 nm). Silica membranes were applied to bimodal catalytic membranes, which consisted of microporous silica top layer for selective permeation of hydrogen and a bimodal catalytic support layer where catalysts such as Ni were impregnated inside a bimodal support consisting of mesopores (γ-alumina) and macropores (α-alumina). Increased performance for production of hydrogen was confirmed by catalytic membranes for steam reforming of methane.

Pervaporation of acetic acid aqueous solutions by organosilica membranes

“…Even water vapor at room temperature affects the permeation properties of silica membranes. A great improvement in hydrothermal stability has been reported by doping metal ions such as Ni, Co, and Zr [16,17]. Successful improvement of stability was reported in the pervaporation dehydration of aqueous alcohol solutions with 94 wt% alcohol concentration [16].…”

Silica-Based Membranes with Molecular-Net-Sieving Properties: Development and Applications

“…Separation of molecules typically requires a size that is less than 1 nm, and this has been accomplished using zeolite, carbon, and silica-based materials. Silicon oxide (silica, SiO 2 ) membranes have been most extensively reported due to a variety of advantages (Tsuru, 2001(Tsuru, , 2008(Tsuru, , 2011. Silica confers great advantages with its thermal stability, and in the controllability of pore sizes that range from subnano to several nanometers.…”

Methylcyclohexane dehydrogenation for hydrogen production via a bimodal catalytic membrane reactor

“…In addition, the available membranes must provide sufficient permeability and/or permselectivity and always provide long‐term stability in both mechanical and chemical properties under technical conditions . Considerable research effort has been devoted to the utilization of CMRs for hydrogen production from hydrogen carriers, including methane steam reforming, NH 3 decomposition, and the dehydrogenation of CH 29–31 and MCH . Table summarizes the typical reactions used for hydrogen production in membrane reactors.…”