Numerical modeling of the transport mechanism of NH3/H2 mixtures in nanoporous materials

Abstract

Understanding the nanotransport properties of NH₃ and H₂ is critical for designing adsorption and separation materials. In this work, we develop a novel numerical model at the molecular level by incorporating the M − S approach and effective medium theory, and provide a rigorous and analyzable simulation implementation for a binary transport system of NH₃ and H₂. In addition, the effect of pore length nonuniformity is simultaneously incorporated. The results show that high temperatures and large radii are detrimental to adsorption but favorable for diffusion at the single-pore scale, while the greater conductance increase in large pores dominates the fluid transport property in the pore network. The existence of a pore length distribution can induce greater effective diffusivity and lower apparent tortuosity within the pore network. Moreover, we confirm that at 300 K, the equilibrium selectivity of NH₃ over H₂ reaches approximately 28 in a uniform pore network with a pore radius of 0.25 nm, indicating the feasibility of nanoporous silica materials for use in adsorption separation of NH₃ and H₂ mixtures.