Study of ethylene/2-butene cross-metathesis over W-H/Al2O3 for propylene production: Effect of the temperature and reactant ratios on the productivity and deactivation

A highly active and selective catalyst based on supported tungsten hydride for the cross-metathesis between ethylene and 2-butenes yielding propylene has been investigated at low pressure with various temperatures and feed ratios. At low temperature (120 °C), the catalyst deactivates notably with time on stream. This phenomenon was extensively examined by DRIFTS, TGA, DSC, and solid-state NMR techniques. It was found that a large amount of carbonaceous species were formed due to a side-reaction such as olefin polymerization which took place simultaneously with the metathesis reaction. However, at 150 °C, the catalyst was stable with time and thereby gave a high productivity in propylene. Importantly, the slight increase in temperature clearly disfavored the side reaction. The ratio of ethylene to trans-2-butene was also studied, and surprisingly, the W-H/Al2O3 catalyst is stable and highly selective to propylene even at substoichiometric ethylene ratios.

Cross-metathesis of ethylene and trans-2-butene is studied at multiple temperatures and reactant ratios. Optimal propylene yield is at 150 °C and 35% C2H4.Figure optionsDownload high-quality image (56 K)Download as PowerPoint slideHighlights
► WH/Al2O3 is highly active and selective for ethylene 2-butene cross-metathesis.
► Temperature significantly affects catalyst deactivation rate and mechanism.
► At low temperature, coking due to olefin polymerization is the dominant deactivation.
► At high temperature, deactivation due to active site changes appear to dominate.
► Substoichiometric ethylene is preferred for optimal yield of propylene.