NMR Characterization of Pore Structure and Connectivity for Nano-self-assembly γ-Al2O3 and Precursor

Abstract

Nano-self-assembly γ-Al₂O₃ (NSAA) is a catalytic material and can be used as a physical model of micro–nano-porous material for understanding shale and tight formations. Herein, we describe the development of an in situ, fast, and quantitative method for the potential nuclear magnetic resonance (NMR) characterization of pore system in a nano-self-assembly precursor (NSAP) for the first time. The surface relaxivity ρ₂ of small pores, which are water saturated is found to be 0.65 and 0.85 μm μs⁻¹, while ρ₂ for large pores, which are hydrocarbon saturated is 0.55 μm μs⁻¹. This points to the interaction of water molecules with inorganic pore surface being stronger than that of hydrocarbon molecules. A new method for reconstructing the capillary pressure curve (Pc) is used to comprehensively reflect the pore structure of NSAA and predict NMR Pc. The pore network model of NSAA is proposed based on NMR quantitative characterization and SEM evaluation, and it has pore channels, which are suitable for macromolecule diffusion. A set of low-field NMR methods for evaluating the pore connectivity of nanomaterials are established. The experiments demonstrate that low-field NMR is a robust tool for characterizing pore channels for macromolecule transport in catalytic materials, with an important application field being shale oil and tight sand oil development and petroleum refining.