The proposed research project will focus upon utilizing advanced physisorbent materials to efficiently remove trace levels of carbon dioxide (CO2) from methane (CH4). This application is especially relevant to natural gas purification (sweetening) prior to liquefaction, which requires CO2 levels to be less than 50 ppm. Liquid amines are used to capture CO2 in the conventional process for removing CO2 and they require a high-energy cost to be regenerated. Physisorbents are treated as an important alternative because of lower regeneration energy. Whereas existing classes of physisorbent materials, such as MOFs and zeolites, are generally selective towards CO2 over CH4, their selectivity is not high enough to remove trace levels (e.g. 1%) of CO2 from CH4. Whereas selective capture of CO2 from gas mixtures in which CH4 or N2 are the major components has already been demonstrated, selective capture of trace levels of CO2 from CH4 relevant to natural gas sweetening has not yet been achieved by physisorbents. This project will determine the feasibility of using Different solid sorbents such as silicates, activated carbon, metal organic frameworks, and zeolites have been studied for CO2 capture. Zeolites are crystalline, microporous alum inosilicates based upon tetrahedral building units. These frameworks are anions and so they allow for ion exchange and their robust nature enables reversible dehydration with most common zeolites type X and A. Two types of zeolites including ZE1A and ZE1B has been characterized and tested magnetic suspension balance (MSB) equipment for CO2 adsorption at pressure range of 0-10 bar. Thermo-gravimetric analysis (TGA) shows that ZSM-5 material has very strong thermal stability while there is a rapid decrease in ZE1B weight. XRD characteristic patterns were observed for ZE1A and ZE1B peaks at 8.90° and 7.74°, respectively. The CO2 rubotherm balance results indicates that ZE1B has higher CO2 uptake capacity and can capture up to almost 9.6 mmol/g of CO2 due to the larger pore volume.
Acknowledgment: This research was made possible by a grant from the Qatar National Research Fund under its National Priorities Research Program award number NPRP 10-0107-170119. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Qatar National Research Fund.