Pemisahan gas alam dengan sistem membran polimer merupakan teknologi terbaru dibandingkan teknologi distilasi kriogenik dan absorpsi. Pemisahan menggunakan membrane mempunyai kelebihan yaitu sederhana, modular, mudah dioperasikan dan biaya rendah dan efisien terhadap pemakaian energi. Pemisahan gas menggunakan membran dengan perpindahan yang terfasilitasi atau facilitated transport membrane mempunyai selektifitas yang tinggi dibandingkan dengan membran polimer yang konvensional karena adanya reaksi bolak balik yang terjadi antara gas yang akan dipisahkan dengan pembawanya (carrier). Proses pembuatan membran dilakukan dengan teknik inversi fasa yaitu presipitasi pencelupan dimana bahan dasar polimer adalah selulosa asetat sedangkan pelarutnya adalah aseton dan formamida. Adapun pembawa (carrier) digunakan natrium karbonat, glycine dan polyetilen glikol (PEG). Komposisi selulosa asetat, aseton, formamida dan pembawa yaitu 1:2,15:1:0,1. Hasil penelitian menunjukkan bahwa membran dengan penambahan pembawa berupa PEG 400 memberikan laju permeasi CO2 sebesar 2.55 x 10^ˉ6 cm³ (STP) cmˉ² ^ˉ1 cmHg dan nilai selektifitas gas CO2 terhadap CH4 yang tinggi yaitu sekitar 178.4 pada tekanan 103.4 cmHg dan suhu 25°C.

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Separation of common gasses (CO2 in natural gas) is commercially accomplished by cryogenic distillation, absorption and more recently by polymeric membrane separation. Membrane separation is promising for CO2 separation process because of its inherent simplicity, ease of control, compact modular nature, lower cost and energy efficiency. Gas separation using facilitated transport membrane has been attracting attention since 'very high selectivity is obtained compared to conventional polymeric membrane include permeability for target species because of reversible reaction between the carriers in membrane and the target species. This research is focus on synthesis of membrane fixed carrier that cellulose acetate is used as based polymer and sodium carbonate, glycine and polyethylene glycol as the carriers. 'The cellulose acetate and the carriers blend that used for this research were prepared by inversion phase method with immersion precipitation The composition of cellulose acetate, icane, formamide and carriers in membrane were 1: 2,15: 1: 0,1 respectively. The results show that the membranes possess better selectivity than that of other fixed carrier membrane reported in the literature (same polymer and carrier). In the measurements with pure gases, at 25 103.4 cmHg of pressure, the membrane with PEG 400 displays a CO2 permeance of 2.55 x 10^ˉ6 cm³ (STP) cmˉ² ^ˉ1 cmHg and highest CO2/CH4 ideal selectivity of 178.4.