Macroporous support coatings for molecular separation membranes having a minimum defect density

Abstract

Bubble number porometry and Hg porosimetry were used to investigate the density and size of percolating channels in gross macroporous support tubes, support tubes coated with one or two macroporous α-alumina layers and the latter coated with a thin mesoporous γ-alumina layer.The key factor in obtaining macroporous thin layers with bulk properties is found in the application of multiple layers rather than the use of a single somewhat thicker layer. The breakthrough pressure of the layered macroporous substrate system drastically increases only when two coatings are applied with sufficient total thickness to shield larger voids. The bubble percolation behaviour of a mesoporous γ-alumina coating is determined by the width of the Hg intrusion curve of the underlying macroporous substrate coating(s). The average size of the macropore distribution is sufficiently low for building up a sol-gel layer, but the large pores cause percolating channels in the mesoporous γ-alumina layer of the same size. This leads to a bubble point size/ mean pore size ratio of the γ-alumina coating >>1. The present results show an increase in the reproducibility of the pore properties up to the γ-alumina layer.

High temperature H2/CO2 separation using cobalt oxide silica membranes

“…Cobalt oxide silica thin film layers were coated on ceramic tubular supports 10 cm in length and 1.4 cm external diameter. The manufacturing of these g-alumina supports provided by the Energy Centre of the Netherlands are described elsewhere [43]. These supports have an intrinsic pore size distribution centered w4 nm, with a very low defect density above 10 nm.…”

The effect of sacrificial templates on the pore characteristics of sintered diatomite membranes

“…32) However, the average pore size and the largest pore size of a metallic membrane with an asymmetrical pore structure 33) are unambiguously different. One important consideration is that these studies 34) focused on the discrepancies among the average pore size, the largest pore size, and pore size distribution as measured by either mercury porosimetry or capillary flow porosimetry. In the present study, we intended to determine experimentally which method is practically more appropriate when designing a membrane with a specific Darcy's permeability constant and a specific pore size, particularly a ceramic membrane prepared by the sacrificial template method.…”

Microporous Silica Based Membranes for Desalination

“…Indeed, supports prepared from α-Al 2 O 3 powders are currently the substrates of choice due to their high porosity and relatively low cost and high mechanical stability. Mesoporous γ-Al 2 O 3 , consisting of much smaller pore sizes of ~4 nm are as used in 2 μm thick intermediate layers, and are able to minimize the defect rate observed [44]. However, γ-Al 2 O 3 exhibits low hydrothermal stability [45], which is of concern if these materials are to be used in applications containing water vapour.…”