Gas Separation Membranes Using Cementitious-Zeolite Composite

Abstract

Natural zeolite-based membranes have recently shown promise in the separation of H2 from CO2 and hydrocarbons. However, these highly dense, naturally monolithic materials can suffer defects which disrupt the continuity of the zeolite micropores and create leak paths through the membrane. Cement materials were explored as a component to generate mixed-matrix zeolite membranes. The ability for cement to intergrow between the zeolite particles promised to, under proper conditions, provide a smooth non-boundary interface with the zeolite particles and eliminate interparticle voids. The influence of zeolite contents in the composite membranes, operating pressures and temperatures on the performance of the membranes were examined. Gas permeation results show a hydrogen permeance of 4.1 × 10-8 mol.m-2.s-1.Pa-1 a CO2 permeance of 1.6 × 10-9 mol.m-2.s-1.Pa-1 and a H2/CO2 single gas selectivity of 25 were obtained at 25oC and 1 atm. The gas permeance through the clinoptilolite cement composite membrane was dependent on operating temperature, indicating that the permeation through the membrane was an activated diffusion process and that the permeation through the zeolite embedded in the composite membrane was predominant. However, the increase of gas permeation and the corresponding decrease of H2/CO2 selectivity with increasing total pressure are an indication of some defects in the composite membranes. Further research to optimize the membrane preparation conditions and to modify the membrane surface to improve hydrogen permeation and H2/CO2 selectivity is needed.