Development of Nanostructured Membranes from Nigerian Zeolite Resources for Natural Gas Dehydration and Sweetening Applications

Nigeria's natural gas sector is expanding significantly under the Decade of Gas initiative, and the dehydration and sweetening of associated gas before pipeline injection represents a major processing cost centre that could be substantially reduced through membrane-based separation using materials synthesised from domestic mineral resources. This study develops nanostructured zeolite membranes fabricated from natural clinoptilolite zeolite deposits in Ogun State and Sodalite synthesised from Osun State kaolin, and evaluates their performance for simultaneous water vapour and hydrogen sulphide removal from natural gas streams. An original membrane fabrication protocol is developed for growing well-intergrown, defect-minimised zeolite films on alpha-alumina tubular supports using a two-stage crystal seeding and hydrothermal synthesis approach, optimised through an experimental design covering crystallisation temperature, duration, synthesis solution composition, and seed crystal loading. Membrane quality was characterised by X-ray diffraction, scanning electron microscopy, gas permeation testing, and molecular simulation validation using Grand Canonical Monte Carlo methods. Original contributions include a novel quantitative relationship between clinoptilolite synthesis composition parameters and resulting membrane H2S/CH4 selectivity, and an empirical-theoretical hybrid model for permeance prediction incorporating both activated diffusion and configurational diffusion mechanisms. The clinoptilolite membrane achieved water vapour to methane selectivity greater than 3,000 and H2S to methane selectivity of 28 at 100 degrees Celsius and 20 bar, satisfying pipeline injection specifications in simulated field gas compositions. Keywords: zeolite membrane, natural gas sweetening, dehydration, clinoptilolite, Nigerian mineral resources