Ethylene oligomerisation over Co/SiO2 in the presence of trace carbon monoxide: The Eidus reaction revisited

• Trace CO increases C3+ selectivity during the C2H4 + H2 reaction over Co/SiO2.
• The predominant primary products are ethane and cis-2-butene.
• C4 isomerisation and other secondary reactions are prominent at high conversion.
• CO inhibits very strongly, by more than two orders of magnitude at 60 ̊C.
• The catalyst deactivates with and without CO but the C3+ selectivity is unchanged.

The oligomerisation of ethylene in excess hydrogen and trace CO over a Co/SiO2 catalyst has been investigated. Higher hydrocarbons were produced with yields up to 50%. The catalyst deactivated continuously but the selectivity to C3+ hydrocarbons was largely independent of conversion. cis-2-Butene dominated amongst the oligomers formed initially. It reacted further to other butenes, n-butane, C3, C5, C6, etc. when the ethylene conversion was near complete. Trace CO greatly inhibited the reaction at temperatures below 120 ̊C but increased the selectivity to higher hydrocarbons. The latter behaviour can be interpreted on the basis that CO competes with hydrogen thus disfavouring hydrogenation to ethane, which requires surface hydrogen, over dimerisation, which does not. The catalyst could be regenerated repeatedly through burn-off of carbonaceous material, which occurred near 180 ̊C with simultaneous oxidation of cobalt, necessitating a subsequent re-reduction.

Traces of CO slow the C2H4 + H2 reaction over Co/SiO2 but increase selectivity to C3+.Figure optionsDownload high-quality image (189 K)Download as PowerPoint slide