The Development of Triphasic Graphene-Based Process for the Effective Sweetening of Sour Natural Gas at Ambient Conditions

Natural gas consumption is steadily increasing locally and globally. Most local natural gas reserves (whether associated or non-associated) contain high levels of H2S and CO2. Thus, the removal of these acid gases from the natural gas (i.e., natural gas sweetening) is an essential process in order to meet the market specifications, in addition to other technical and safety requirements. Processes based on amine absorption, such as methyldiethanolamine (MDEA) and monoethanolamine (MEA), are currently the most widely used methods for the sweetening of sour natural gas. However, these processes are energy intensive, corrosive and hazardous to the environment. Recently, graphene-based materials have emerged as attractive, organic solvent-free, tools for many applications including adsorption processes. Nonetheless, there is a huge lack of information on the utilization of graphene-based materials for the sweetening of sour natural gas, particularly using three-phase (gas-liquid-solid) processes. The published studies so far have focused on the separate adsorption of CO2 or H2S using biphasic (i.e., gas-solid) processes in packed bed columns. Packed columns have several limitations, the most serious one is the gas channeling (i.e., ineffective gas-solid contact). Thus, our key aim in this proposed work is to develop a triphasic (natural gas-water-graphene) process for the effective sweetening of sour natural gas at ambient conditions (i.e., room temperature and atmospheric pressure). The starting material will be graphite that will be oxidized into graphene oxide (GO). This GO will be reduced using different reducing agents and reduction methods to probe their effects on GO performance. Both GO and reduced GO (rGO) will be functionalized with amines, ionic liquids and metals. Such combinations are still lacking in the published literatures. The types of the amines, the ionic liquids (ILs) and the metals as well as their levels in the synthesized graphene-based materials will be tuned in order to optimize the sweetening performance of the developed graphene-based materials (GO, rGO, amine-GO, amine-rGO, IL-GO, IL-rGo, metal-GO, metal-rGO, amine-IL-metal-GO and amine-IL-metal-rGO). To get insights into the effectiveness of the triphasic relative to the biphasic process, sour natural gas will also be sweetened using the biphasic process under the same process conditions.