Single-site, Ni-modified Wells–Dawson-type polyoxometalate for propylene dimerization?

Catalysis Science & Technology Pub Date: 2022-08-25 DOI: 10.1039/D2CY01065H

Abstract

Olefin oligomerization is an essential step in the production of liquid fuels, chemicals, and chemical precursors. Here, we report gas phase propylene oligomerization catalyzed by isolated Ni2+ sites substituted on the lacunary defect of a Wells–Dawson polyoxometalate (K8P2W17O61·Ni2+) supported on SBA-15 (Ni-POM-WD/SBA-15). The Ni-POM-WD/SBA-15 catalyst exhibited high product selectivity for linear propylene dimers (>76%) relative to branched propylene dimers (<24%). The linear dimer selectivity was independent of the overall propylene conversion between 0.6–5% but was dependent on reaction temperature. The propylene dimerization activation energy was measured as 44.5 kJ mol?1, which is consistent with the reported values for Ni2+ exchanged-zeolites for propylene oligomerization. Further, the measured dimerization reaction rate order was a strong function of the initial propylene partial pressure and transitioned from second order to first order at higher propylene partial pressures. The catalyst was fully regenerated after reaction by applying a thermal regeneration step in helium. Transient, time-on-stream catalyst performance measurements showed the catalyst had a mean life of ～0.6–1.15 h during three reaction cycles and had a slightly increased initial propylene consumption rate with each cycle.

Graphical abstract: Single-site, Ni-modified Wells–Dawson-type polyoxometalate for propylene dimerization
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