Ionic Liquid versus Traditional Volatile Organic Solvent in the Natural Gas Dehydration Process: A Comparison from a Life Cycle Perspective

The life cycle environmental sustainability of the natural gas (NG) dehydration process using novel dehydrant [EMIM][Tf2N] ionic liquid (IL) has been evaluated using a cradle to grave life cycle assessment (LCA) methodology, and the results were compared with the traditional dehydrant triethylene glycol (TEG). The LCA results of [EMIM][Tf2N] production indicate that the precursors' production stage is the main hotspot that contributes to most of the environmental burdens. Meanwhile, compared with cation production, the anion production has higher environmental impacts (about 69.8% on average) in most of the categories except human toxicity potential (HTP) and freshwater aquatic ecotoxicity potential (FAETP). The comparative LCA results show that the NG dehydration with [EMIM] [Tf2N] has significantly higher environmental impacts than TEG in all categories, but the TEG-based scenario shows worse impacts than the [EMIM] [Tf2N] in the use stage (about 4.5 times higher). Moreover, the sensitivity analysis proved that the dehydrant recovery ratio is a crucial parameter. When considering the dehydrant recovery, the environmental impacts are comparable for [EMIM] [Tf2N] and TEG-based NG dehydration processes. This study can give guidance on novel material synthesis and process improvement from the life cycle perspective, and encourage further research on the potential of employing novel IL as traditional NG dehydrant alternatives.