Zeolite Membranes Supported On Thin Porous Metal Sheet for Water/Ethanol Separation

This paper investigates the feasibility of hydrophilic and hydrophobic zeolite membranes growth on a unique porous metal sheet of 50um thickness in order to develop low-cost inorganic membrane module of high surface area packing density such as >1000m2/m3. The porous Ni alloy sheet of micrometer or sub-micrometer pore size was prepared by a proprietary process recently developed at PNNL at a controllable thickness over a range of 20 to 1000µm. The hydrophilic and hydrophobic zeolites are NaA zeolite and silicalite zeolite respectively. The membranes were deposited on the porous metal substrate by secondary hydrothermal growth. Effects of seed coating, precursor growth solution, growth conditions, and post-synthesis treatment on the membrane performance were studied. The membranes were characterized by SEM, XRD and water/ethanol separation at various conditions. The hydrophilic membrane, which is water-selective, exhibited a high water/ethanol selectivity of >15,000 and a permeation flux of ~4 kg/m2•h at 75ºC with a feed of 10wt% water in ethanol. The membrane also exhibited good stability in 70-h continuous testing at 75ºC and 90 ºC. The hydrophobic membrane, which is ethanol-selective, exhibited an ethanol/water selectivity of 23 and a permeation flux of 1.7 kg/m2•h at 75ºC with a feed of 90wt% water in ethanol.