Palm-polyetheretherketone porous carbons as sorbents for gas adsorption applications

Abstract

Carbon dioxide (CO2) emission is attributed as the major contributing factor for global warming. Absorption with amine solutions is the technology that is currently used for CO2 capture in industries. Adsorption is seen as a viable alternative technology for CO2 capture due to the techno-economic reasons against the amine based technology. In this study, palm shell being one of the abundant biomass in Malaysia, was used together with polyetheretherketone (PEEK) as precursors for the preparation of porous carbons via microwave induced potassium carbonate chemical activation. The porous carbons were investigated as potential sorbents for high temperature CO2 capture and methane storage. Design expert software version 7.1.6. using central composite design coupled with surface response methodology was used in predicting and optimization of the preparation conditions of the porous carbons for CO2 capture. Effects of microwave power, amount of PEEK and irradiation time on the sorbent performance for CO2 adsorption were investigated. The characteristics of the porous carbons were studied by Fourier transform infrared spectroscopy, pH, thermogravimetric and derivative thermogravimetric analysis, scanning electron microscopy, nitrogen adsorption, proximate and ultimate analysis. The ideal CO2 adsorption capacities of porous carbons were determined using volumetric method at temperatures of 30 oC, 70 oC, 105 oC and 170 oC and pressures of 1 - 4 bar, while methane (CH4) adsorption was tested only at 30 oC. Microwave power was found to be the most significant factor influencing the porous carbon for CO2 adsorption. The optimum conditions were microwave power of 500 W, irradiation time of 6.89 min and amount of PEEK 21.91%. Highest CO2 uptake of 2.97 mmol CO2 adsorbed/g adsorbent was achieved by M4P2 (400 W of microwave power, 6 min irradiation time and 20% amount of PEEK) among the sorbents at 30 oC and 1 bar. Highest CH4 uptake of 1.144 mmol CH4 adsorbed/g adsorbent was also recorded by M4P0 (400 W of microwave power, 6 min irradiation time and 0% amount of PEEK) sorbent at 30 oC and 1 bar. The CO2 equilibrium data correlated well with Sips isotherms. In all scenarios studied, increase in temperature led to a decrease in CO2 adsorption while increase in pressure led to an increase in CO2 adsorption. The sorbents remained stable after seven CO2 adsorption/regeneration cycles. As a conclusion, the findings revealed the potential of palm shell-PEEK as CO2 and CH4 sorbents which needs improvement for further gas adsorption applications.