ausblenden:
Schlagwörter:
Acetylene; Hydrogenation; Ethene; Sol immobilization; AgPd nanoparticles
Zusammenfassung:
Electric plasma activation of methane opens up the possibility to produce ethene, an important platform chemical in industry, by using sustainable resources like biogas or hydrogenated carbon dioxide and electricity from renewable energies. The ethene stream of such pyrolysis plants contains, however, much higher concentrations of acetylene (≥ 15 vol.%) compared to ethene from conventional steam cracking of naphtha (< 2 vol.%). In this study, silver-palladium catalysts in various compositions supported on alumina were synthesized via a sol-immobilisation technique and investigated in the selective gas-phase hydrogenation of equally concentrated acetylene-ethene mixtures under industrially relevant pressures. A molar Pd concentration of around 10 % in the PdAg alloyed nanoparticles was identified as the optimum composition for simultaneous high activity and ethene selectivity under catalysis conditions. Higher temperatures seem to be crucial for the stability of the catalysts on-stream most likely via increased desorption of active site blocking and high-boiling oligomers from acetylene. The best performing Pd10Ag90 displayed an ethene, ethane and C4+ selectivity of 65, 4 and 14% respectively, at 175 °C while being active for more than 200 minutes. The performance of the catalyst was compared with catalysts synthesized via a mechanochemical and a conventional wet-impregnation procedure.
