Molecular-sieve porous graphene as a steady phase of gas chromatography column for dissociation and measurement of nitrous oxide, carbon dioxide and gaseous hydrocarbons

Abstract

A novel gas chromatography stationary phase is introduced for efficient separation of air, nitrous oxide, methane, carbon dioxide, ethane, propane, butane and pentane. Porous graphene was synthesized through a cost-effective approach. The structure and porous texture of the prepared graphene were evaluated by field-emission scanning electron microscopy and nitrogen adsorption/desorption isotherms. The results confirmed the high porosity and surface area of the synthesized porous graphene. Also, the nitrogen adsorption/desorption isotherms showed highly microporous structures with the average pore size being < 2 nm, which has high contribution in gas molecules separation. The prepared structure exhibited an excellent chromatography performance and separation efficiency compared with multi-wall, single-wall carbon nanotube and activated carbon. In addition, common problems in GC packed column by nanomaterials, such as avoiding the use of long column, flow rate reduction, agglomeration, packing compression and high back-pressure, were completely addressed; therefore, in order to overcome these problems and fabricate chromatography column 1.8″, stainless steel tubes were used in three lengths of 10, 20, 30 cm. After testing, the 30 cm column was used for determination and separation of the entered gases in continued work. In this experiment, two types of samples were used. The first sample contains air, methane, carbon dioxide and nitrous oxide gases at 40 °C, and the second sample was compared of methane, ethane, propane, butane and pentane containing hydrocarbons with temperature action of 40–200 °C. The analytical results demonstrated the superior separation efficiency of porous graphene steady phase for some gas dissociation at 40 °C and good preservative for hydrocarbons C1–C5 (while using ramp up rate of 6 °C/min) in temperature range of 40–200 °C. The packed prepared column also showed high resolution, wide linear range and acceptable repeatability in separation of studying gas mixture. The obtained detection limits obtained were lower than 4.2 ppm.