Synthesis and modification of Zeolitic Imidazolate Framework (ZIF-8) nanoparticles as highly efficient adsorbent for H2S and CO2 removal from natural gas

Abstract

In this work, synthesis and modification of some ZIF-8 nanoparticles in different functionalization media using ethylenediamine (ED) were investigated for H2S and CO2 efficient removal form synthetic natural gas mixture. Characterization of the prepared ZIF-8 nanoparticles was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and N2 adsorption/desorption analysis. XRD and FTIR analysis of the ZIF-8 nanoparticles before and after H2S adsorption revealed that their structure does not considerably change. CO2 and H2S removal efficiencies of the nanoparticles were evaluated at 25 °C and their Co-adsorption performance was also measured in static and dynamic modes at 25 °C and 0–13 bar. The unmodified ZIF-8 nanoparticles (WS-ZIF-8) adsorption capacities for CH4, CO2 (20 bar and 25 °C) and H2S (10 bar and 25 °C) were found as 4.4, 10.8, 18.8 mmol/g, respectively. Those for modified ZIF-8 nanoparticles (ED-ZIF-8) increased by 15%, 22% and 3 times, respectively. Mixed gas H2S adsorption of ED-ZIF-8 nanoparticles measurements up to 3 mol. % H2S approved their improved acid gases removal efficiencies and also structural stability confirmed by XRD analysis. The unmodified ZIF-8 nanoparticles breakthrough times for H2S and CO2 adsorbed from mixed gas of CH4 / CO2 / H2S /He as 88.8 / 7.3 / 3 / 1 mol. % at 25 °C and 2 bar were found as ˜ 190 and 308 s, respectively, while those for modified ZIF-8 nanoparticles considerably improved ˜ 400 and 531 s, respectively.