RESUMEN

Electric plasma assisted pyrolysis of methane represents a highly promising greener alternative to produce ethylene from biogas and renewable energies compared to  conventional steam cracking of naphtha. The mediocre performance of typical Pd-Ag catalysts for the downstream purification of the substantially higher concentrated acetylene impurities (≥ 15 vol.-%) in those ethylene streams via selective hydrogenation is yet limiting economic interest. Following the concept of solid catalysts with ionic liquid layer  (SCILL), we have modified an intrinsically non-selective palladium catalyst with imidazolium based ionic liquids varying among 10 different anions and investigated them in this  reaction. The best performing [C4C1IM][MeSO4]-SCILL reaches an outstanding average ethylene selectivity over 20 h on-stream of 82% at full acetylene conversion without any sign of deactivation, clearly outperforming conventional Pd-Ag catalysts. By varying parameters like ionic liquid (IL) loading, temperature, feed gas composition, cations, and by using XPS for surface analysis we could gain a very comprehensive understanding of the underlying mechanisms that reduce the competing over-hydrogenation and oligomerisation side-reactions.