Abstract
Mixed-matrix membranes (MMMs) are promising candidates to improve the competitiveness of membrane technology against energy-intensive conventional technologies. In this work, MMM composed of poly(octylmethylsiloxane) (POMS) and activated carbon (AC) were investigated with respect to separation of higher hydrocarbons (C3+) from permanent gas streams. Membranes were prepared as thin film composite membranes on a technical scale and characterized via scanning electron microscopy (SEM) and permeation measurements with binary mixtures of n-C4H10/CH4 under varying operating conditions (feed and permeate pressure, temperature, feed gas composition) to study the influence on separation performance. SEM showed good contact and absence of defects. Lower permeances but higher selectivities were found for MMM compared to pure POMS membrane. Best results were obtained at high average fugacity and activity of n-C4H10 with the highest selectivity estimated to be 36.4 at n-C4H10 permeance of 12 mN3/(m2·h·bar). Results were complemented by permeation of a multi-component mixture resembling a natural gas application, demonstrating the superior performance of MMM.
Highlights
IntroductionNatural gas is the fastest growing energy source and with a worldwide production of 3.5 billion mN 3 per year making it a highly promising market for separation processes [1]
Today, natural gas is the fastest growing energy source and with a worldwide production of 3.5 billion mN 3 per year making it a highly promising market for separation processes [1].Around 95% of all industrial separations are covered by the refinery and processing of fossil fuels like crude oil or natural gas or the treatment of associated effluent gas [2]
By comparing the two membrane types, In order to increase the driving force for permeation and the pressure-ratio influencing the effect is more pronounced for POMS as indicated by the higher slope of trend curve (0.36 for the separation performance, membrane-based separations are often performed with vacuum on the POMS and 0.29 for matrix membranes (MMMs))
Summary
Natural gas is the fastest growing energy source and with a worldwide production of 3.5 billion mN 3 per year making it a highly promising market for separation processes [1]. State-of-the art materials for the separation of condensable hydrocarbons (C3+ ) are siloxane based polymers such as poly(dimethylsiloxane) (PDMS) or poly(octylmethylsiloxane) (POMS) with a highly rubbery character and a solubility controlled permeation in favour of higher hydrocarbons They have achieved commercial significance in some areas of application today but their performance requires further improvement to ensure competitiveness. The concept of hybrid mixed-matrix materials (MMMs) based on inorganic filler particles dispersed in a polymeric matrix has attracted much interest and research in recent years Advantages of both materials are exploited resulting in improved separation performance, mechanical, thermal or chemical stability or specific properties such as conductivity [9].
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