Modified rubbery siloxane membranes for enhanced C3+ hydrocarbon recovery from natural gas: Pure and multicomponent gas permeation evaluation

Abstract

Rubbery siloxane membranes are utilized in industry for the rejection of nitrogen and for the concentration of heavy hydrocarbons in the membrane permeate stream. In this work, modified crosslinked siloxane terpolymer (VinylMeSiO)p(Me2SiO)m(OctMeSiO)n membranes (Ter-PDMS) were fabricated and evaluated for separations of heavy hydrocarbon (C3+) from natural gas. Gas permeation properties were evaluated using pure gas and C3+ hydrocarbon rich multicomponent gas mixtures under varying operating conditions (e.g. feed pressure, temperature, and feed gas composition). Pure gas permeation properties for modified crosslinked siloxane Ter-PDMS membranes displayed enhanced C3+/CH4 ideal selectivity and lessened permeability compared to conventional crosslinked PDMS membrane. Moreover, modified crosslinked siloxane Ter-PDMS membranes also showed enhanced C3+ separation performance under simulated typical field gas testing conditions (i.e. feed pressures up to 800 psi for multicomponent gas mixture consisting C1-C5 hydrocarbons, CO2, N2, and toluene/xylene). At 800 psi, modified crosslinked siloxane Ter-PDMS membrane exhibited C4H10/CH4 mixed gas selectivity and C4H10 permeability of 17.2 and 15,100 Barrer, respectively. These results emphasize the observations that membrane separation performance is strongly related to the testing conditions and feed compositions, highlighting the importance of exploring and designing better modified rubbery siloxane membrane materials for the actual industrial process.