Selective Separation of H2 from C2H6 and CO2 through Natural Zeolite

Mixed Matrix Membranes

Afrooz Farjoo, Steven M. Kuznicki

Mixed-­�matrix membranes (MMMs), filled with natural zeolite particles, provide a mean to improve the gas separation performance of inorganic membranes. In this work, MMMs containing the miroporous natural zeolite powders, clinoptilolite, in alumina silicate matrix were characterized in terms of their hydrogen (H2) carbon dioxide (CO2) and ethane (C2H6) separation performance at low and high pressures and different temperatures. Physical properties of natural zeolite, binder and prepared MMMs were analyzed. Scanning electron microscopy (SEM) showed homogeneous distribution of zeolite particles in alumina silicate and water matrix.
Mixed matrix membranes coated on stainless steel substrates were found to
have as much as two times higher ideal selectivity for H2 over CO2 and H2 over
ethane than would be predicted by Knudsen diffusion.
Membrane sections modified by simple hydrothermal treatments and applied to separation of hydrogen from CO2, and C2H6 demonstrated H2 permeance as high as 7.25�10-­�8 the coated membrane on a 0.02 micron stainless steel substrate combined with ideal selectivities of 8 for (H2/CO2) and 7 for (H2/C2H6) at 25°C.
Modified natural zeolite membranes were thermally and chemically stable, and their hydrogen permeance was reproducible after multiple temperature cycles. These unique natural zeolite membranes have the potential to be engineered for high-­�temperature, energy-­�efficient industrial separation and purification applications including hydrogen separation, and to serve as a model for the development of robust synthetic zeolite membranes with superior separation characteristics.