Development of a Novel Low-Cost Carbon Nanotube Membrane Technology for Gas Separation Applications in Nigerian Gas Processing

Membrane-based gas separation technologies offer energy-efficient alternatives to conventional absorption-based acid gas removal processes, but their adoption in Nigerian gas processing has been limited by high membrane material costs and inadequate performance data for Nigerian gas stream conditions. This study develops and characterises a novel low-cost carbon nanotube (CNT) composite membrane for CO2 and H2S removal from natural gas, targeting Nigerian gas processing plant applications. The research employs a materials synthesis and characterisation methodology, developing CNT composite membranes through a scalable chemical vapour deposition and polymer matrix impregnation process using locally sourced precursors where feasible. Membrane structural characterisation employs transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS). Gas permeation testing is conducted at a purpose-built membrane testing rig at the University of Lagos chemical engineering laboratory, measuring CO2, H2S, CH4, and N2 single-component and mixed gas permeabilities and selectivities across the pressure and temperature ranges relevant to Nigerian gas processing applications. The study systematically investigates the role of CNT functionalisation with amine and hydroxyl groups in enhancing CO2 and H2S selectivity, and evaluates membrane stability under extended exposure to wet gas containing trace heavy hydrocarbons and mercury vapour at concentrations representative of Niger Delta gas compositions. The study's original contributions include: a scalable synthesis protocol for functionalised CNT composite membranes achieving CO2/CH4 selectivity of 48 and H2S/CH4 selectivity of 35, a membrane module design optimised for modular application in existing Nigerian gas plant configurations, and a techno-economic comparison with amine absorption demonstrating cost parity at CO2 concentrations above 5 percent. Recommendations include pilot plant installation at a Nigerian gas processing facility and collaboration with local chemical manufacturers for membrane material scale-up. Keywords: carbon nanotube membrane, gas separation, CO2 removal, Nigeria, membrane technology.