Multicomponent hydrogen/hydrocarbon separation by MFI‐type zeolite membranes

Separation of an eight‐component simulated refinery gas mixture including hydrogen (∼84 mol %) and light hydrocarbons (C1–C4, 7.5∼0.3 mol %) by α‐alumina‐supported polycrystalline MFI zeolite membranes was studied at 25–500°C and feed pressures of 0.1–0.4 MPa. The zeolite membrane showed excellent separation properties for rejection of hydrogen from the hydrogen/hydrocarbon mixture at <100°C. At room temperature and atmospheric pressure on both feed and permeate sides, hydrogen permeation rate is almost zero, while the hydrocarbon permeation rate is 2–4×10−4 mol·m−2·s−1. The zeolite membrane outperforms the microporous carbon membrane in terms of both selectivity and permeance for hydrocarbons over hydrogen. At 500°C the zeolite membrane becomes permselective for hydrogen over hydrogen (C1–C4). In the whole temperature range iso‐butane is nonpermeable (with a permeance below the GC analysis limit) through the zeolite membrane. Separation results of the zeolite membrane can be characterized by a solution‐diffusion model considering competitive adsorption of hydrocarbons over hydrogen and configurational diffusion in the zeolite pores. The MFI‐type zeolite membranes showed promise for applications in separation processes for hydrogen concentration/purification from various hydrogen/hydrocarbon mixtures (at lower temperatures) and in membrane reactors for dehydrogenation reactions (at high temperatures).