Study of improving carbon dioxide adsorption capacity using adsorbents impregnated with piperazine

Abstract

The adsorption of carbon dioxide (CO2) for the natural gas processing application was performed with adsorbents modified with piperazine (PZ). To optimize CO2 adsorption capacity, the effects of adsorption pressure, PZ loading, and types of adsorbents (activated carbon, or AC, and silica gel, or SG) were studied. Piperazine was impregnated onto the surface of AC and SG adsorbents by the wet impregnation method. The surface morphology of the unimpregnated and impregnated adsorbents was characterized using a surface area analyzer. The PZ loading was detected by a gas chromatography-flame ionization detector. It was found that the maximum PZ loading on the AC and SG were 3.45 wt% and 8.33 wt%, respectively. In the CO2 adsorption and regeneration experiments, the adsorbents were tested in a stainless steel reactor. The breakthrough curves obtained from the feed gas containing 15% CO2/N2 with a flow rate of 15 mL/min were determined by using a gas chromatography-thermal conductivity detector. The effects of adsorption pressure were carried out at 298 K at various pressures, i.e. 14.7, 30, 50, and 70 psi. The results showed that PZ impregnated on AC and SG at pressure 70 psi showed the highest CO2 adsorption capacity of 6.7 mmol/g and 7.7 mmol/g, respectively. The efficiency of regeneration of the impregnated adsorbents was more than 85 % during three consecutive test cycles.