Insights into the deactivation mechanism of supported tungsten hydride on alumina (W-H/Al2O3) catalyst for the direct conversion of ethylene to propylene

• WH3/γ-Al2O3 shows a high initial activity in direct conversion of ethylene to propylene.
• Extensive contact time study revealed that the dimerization of ethylene to 1-butene is the primary and also the rate limiting step.
• The deactivation mechanism of this reaction has been examined by DRIFTS, solid-state NMR, EPR, UV–Vis, TGA and DSC techniques.
• The deactivation mechanism is related to ethylene polymerization through insertion on the active sites.

Tungsten hydride supported on alumina prepared by the surface organometallic chemistry method is an active precursor for the direct conversion of ethylene to propylene at low temperature and pressure. An extensive contact time study revealed that the dimerization of ethylene to 1-butene is the primary and also the rate limiting step. The catalytic cycle further involves isomerization of 1-butene to 2-butene, followed by cross-metathesis of ethylene and 2-butene to yield propylene with high selectivity. The deactivation mechanism of this reaction has been investigated. The used catalyst was extensively examined by DRIFTS, solid-state NMR, EPR, UV–Vis, TGA and DSC techniques. It was found that a large amount of carbonaceous species, which were due to side reaction like olefin polymerization took place with time on stream, significantly hindering the dimerization of ethylene to 1-butene and therefore the production of propylene.

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