The separation of
CO2/CH4 using porous carbon
can be increased by the presence of a functional group of nitrogen
on the carbon surface. This study explores the potential of porous
carbon derived from the palm kernel shell (C-PKS) impregnated with
a deep eutectic solvent (DES), which is one of the chemicals containing
a nitrogen element. The DES was composed of a quaternary ammonium
salt of choline chloride (ChCl) and a hydrogen bond donor of alcohol.
Three alcohols of 1-butanol (-ol), ethylene glycol (-diol), and glycerol
(-triol) were employed to study the effects of a number of hydroxyl
groups in the separation performance. The research steps included
(i) the preparation of DES-impregnated porous carbon synthesized from
the palm kernel shell (DES/C-PKS), (ii) characterization of the material,
and (ii) a separation test of CO2/CH4 with a
breakthrough system. Materials were characterized using scanning electron
microscopy (SEM) combined with energy-dispersive X-ray spectroscopy
(EDX), N2-sorption analysis, and Fourier transform infrared
(FTIR) spectroscopy. SEM images showed a significant morphological
difference of pristine carbon and DES/C-PKS. There was a significant
decrease in the range of 67–73% of a specific surface area
with respect to pristine carbon, having initially 800 m2/g. However, the N element on the carbon surface increased after
impregnation treatment, which was shown from the intensity of the
FTIR graphs and EDX analysis. Adsorption isotherm revealed that DES/C-PKS
could enhance up to 1.6 times the adsorption capacity of CO2 at 1 atm and 30 °C while increasing the selectivity of CO2/CH4 up to 125%. The breakthrough experiment showed
that all DES/C-PKS materials displayed a better performance for the
separation of CO2/CH4, indicated by a longer
breakthrough time and enhancement of CO2 uptake. The best
separation performance was achieved by DES/C-PKS using glycerol as
a hydrogen bond donor with 15.4 mg/g of CO2 uptake or equivalent
to 95% enhancement of the uptake capacity compared to pristine porous
carbon. Also, the cycling test revealed that DES/C-PKS can be used
repetitively, which further highlights the efficiency of the material
for the separation of CO2/CH4.
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