CO2 adsorption and desorption procedure

“The adsorption of CO2 was carried out at 25°C and atmospheric pressure using 15/85 vol% CO2/N2 as a feed gas representing the concentration of CO2 in the flue gas from the coal-fired power plant. In a typical run, 0.5 g of adsorbent was packed into a stainless-steel tube reactor (12 mm id) supported by glass wool. Before measurement, the adsorbent was pre-treated at 100°C using heating tape (±2°C) under an N2 flow rate of 20 mL/minute for 1 hour to remove physically adsorbed moisture and remaining CO2 in the adsorbent and then it was cooled to room temperature (25°C), which was measured using a thermometer (±2°C). CO2 adsorption was begun by switching to the 15% CO2 at 20 mL/minute. The flow rate of the feed gas was controlled using a mass flow controller (AALBORG, GFC-17 with a range of 0–200 mL/minute) and accurately measured using a volumetric (bubble) flowmeter (Agilent Optiflow Digital Flowmeter) with an accuracy of within ±3%. When 15% CO2 was purged to the reactor, the CO2 concentration at the outlet of the reactor was continuously detected using a gas chromatograph equipped with a thermal conductivity detector (GC-TCD, Agilent, model 7280A, USA) fitted with Porapak-Q column (0.32 mm id × 60 m l dimension) until saturation (i.e. the CO2 concentration in the effluent gas was equal to the feed concentration).

The desorption experiment was further carried out after the adsorption was complete by switching the CO2 feed gas to the N2 gas at the same flow rate and applying heat at 100°C. It was performed by continuously detecting the CO2 concentration until no more CO2 peak was observed in the gas chromatogram. The experimental set-up for the CO2 adsorption–desorption is shown in Fig. 2.”


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