Experimental investigation of adsorbed natural Gas (mainly CH4) storage

Abstract

With the increasing concern of global warming, natural gas presents to be a promising alternative source of fuel. Due to the workplace and environmental hazards of CNG, ANG was found as a sustainable method to substitute CNG. To commercialize ANG technology, this method of storage required to fulfill two desired targets adsorption uptake set by the US Department of Energy to achieve similar storage capacity as CNG. The gravimetric and volumetric targets are 0.5g/g and 350cm3(STP)/cm3 respectively. Till date, research emphasis is placed on MOFs, namely PCN-14, HKUST-1 and MIL-101, with the displayed adsorption characteristic to storage methane gas. However, these adsorbents are unable to meet the targeted uptake requirements in ambient temperature with a pressure up to 35bar. In this study, two MOFs, namely MIL-101 and 10% Sodium doped MIL-101, were analyzed using SEM, XRD and TGA to study the material characteristics and investigate for any modification or enhancement to the parent MOF structural. Subsequently, experimental investigation was done with a volumetric adsorption apparatus, cryogenic setup, with a pressure ranging up to 10 bar at temperature between from 125K to 298K. This investigation aims to simulate the coupling of LNG with ANG which is scarcely reported on past research. With the collated experimental data from the cryogenic setup, experimental uptakes, in both gravimetric and volumetric, were evaluated on the adsorption capacity. Successively, adsorption isotherm fittings were done on three equations, namely (i) Chakraborty-Sun, (ii) Langmuir, (iii) Toth. In comparison of experimental uptakes and equation fittings, RMSE and RSQ percentages were used to discuss on the presented errors. In addition, comparisons were made with past research results for better interpretation with other adsorbents. From the experimental findings, 10% Sodium doped MIL-101 does not enhance the adsorption capacity in sub- and supercritical temperature environment. Hence, on-going studies have proceeded with these collected findings for further evaluation on new doping percentages and elements. This aims to enhance the adsorption capacity and achieve US Department of Energy adsorption uptake targets.