Mechanism and Thermodynamics of Hydrogen Sulfide Scavenging by Novel Amine-Functionalised Nanostructured Materials for Nigerian Sour Gas Field Applications

Hydrogen sulphide management in sour gas production from Nigerian deepwater and onshore fields is a critical safety, corrosion, and product quality challenge requiring scavenging materials with superior kinetics, large capacity, structural stability under reservoir conditions, and regenerability, none of which are simultaneously optimised in existing commercial triazine-based or iron sponge scavengers deployed in Nigerian field operations. This study investigates the mechanism and thermodynamics of hydrogen sulphide scavenging by a family of novel amine-functionalised mesoporous silica and carbon nanotube nanostructured materials designed for sour gas field applications. Nanostructured supports are synthesised by template-directed self-assembly and chemical vapour deposition methods and functionalised with primary, secondary, and sterically hindered amine groups by surface grafting and co-condensation protocols. Materials are characterised by Brunauer-Emmett-Teller analysis, transmission electron microscopy, solid-state 29Si and 15N nuclear magnetic resonance spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Hydrogen sulphide scavenging capacity and kinetics are measured in a custom fixed-bed flow system at temperatures and partial pressures representing Nigerian sour gas field conditions. In-situ diffuse reflectance infrared Fourier transform spectroscopy coupled to mass spectrometry characterises surface-bound reaction intermediates and identifies the elementary reaction steps of the scavenging mechanism. Density functional theory calculations using the M06-2X functional evaluate interaction energies and reaction energy profiles for amine-H2S complexation and subsequent thiol or polysulphide formation pathways. Thermodynamic parameters governing scavenging and regeneration cycles are extracted from van't Hoff analysis of temperature-dependent capacity data. An original mechanistic-thermodynamic model predicting scavenging performance as a function of amine site density, pore architecture, and operating conditions is developed. Keywords: hydrogen sulphide scavenging, amine-functionalised nanostructures, sour gas, mechanism, thermodynamics