Substituting the solid piston of conventional reciprocating compressors used for the compression of hydrogen with a suitable ionic liquid will solve many practical problems and limitations that conventional reciprocating compressors face. However, because of the large number of cation and anion combinations and many studies on the unique properties of ionic liquids and the role of ionic liquid cations and anions in determining these properties, a systematic review is required to narrow down the choice of ionic liquids. Therefore, in the present review, a comprehensive study to find the most appropriate ionic liquid candidate to replace the solid piston in reciprocating compressors for compressing hydrogen is reported.

Specific criteria concerning the applications of ionic liquids are determined and the roles of the cations and anions, as well as the effect of temperature, are extensively reviewed to identify the most suitable ionic liquid that can fulfill the requirements. As a next step, the options are narrowed down to five ionic liquids with the triflate and bis(trifluoromethylsulfonyl)imide as the anion choices and three different cation types, imidazolium-, phosphonium-, and ammonium-based, as the cation choices. Finally, the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is recommended as the best candidate that can be safely used as a replacement for the solid piston in reciprocating compressors for compressing hydrogen in hydrogen stations.

用合适的离子液体代替用于压缩氢气的常规往复式压缩机的固体活塞将解决常规往复式压缩机面临的许多实际问题和局限性。然而，由于大量的阳离子和阴离子组合以及对离子液体的独特性质以及离子液体阳离子和阴离子在确定这些性质中的作用的许多研究，需要系统地审查以缩小离子液体的选择范围。因此，在本综述中，报告了一项全面的研究，以找到最合适的离子液体候选物来代替往复式压缩机中用于压缩氢的固体活塞。

确定了有关离子液体应用的特定标准，并广泛审查了阳离子和阴离子的作用以及温度的影响，以确定可以满足要求的最合适的离子液体。下一步，选择范围缩小到五种离子液体，其中三氟甲磺酸盐和双（三氟甲基磺酰基）酰亚胺为阴离子选择，而三种不同的阳离子类型为咪唑鎓，phospho和铵基，为阳离子选择。最后，离子液体1-乙基-3-甲基咪唑鎓双（三氟甲基磺酰基）亚胺被推荐为最佳候选物，可以安全地替代往复式压缩机中用于压缩氢气站中氢气的固体活塞。