High-performance ammonia-selective MFI nanosheet membranes

Abstract

Nanosheet-based MFI membranes, known to be highly selective for hydrocarbon isomer separations, exhibit an NH₃/N₂ mixture separation factor of 2236 with NH₃ permeance of 1.1 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹, and NH₃/H₂ separation factor of 307 with NH₃ permeance of 2.3 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ at room temperature. Consistent with a competitive sorption-based separation, lower operating temperatures and higher pressures result in increased separation factor. At 323 K, with an equimolar mixed feed of NH₃/N₂, the fluxes and separation factors at 3 and 7 bar are 0.13 mol m⁻² s⁻¹ and 191, and 0.26 mol m⁻² s⁻¹ and 220, respectively. This performance compares favorably with that of other membranes and suggests that MFI membranes can be used in separation and purification processes involving mixtures of NH₃/N₂/H₂ encountered in ammonia synthesis and utilization. The membranes also exhibit high performance for the separation of ethane, n-propane and n-butane from H₂.