Light olefins are important building blocks for liquid fuels and chemicals such as linear alpha olefins (LAOs) which are produced by coupling light olefins into heavier chained products. To overcome the inherent drawbacks of industrial processes which utilize homogeneous nickel complex, zeolitic solid catalysts containing nickel cations are widely studied. These cation-exchanged zeolites can suffer from catalytic deactivation due to the formation of the bridging metal olefin complex between two neighboring nickel sites.<br/>To address this issue, we will discuss our synthetic strategy to isolate nickel active sites on the lacunary defects of a Wells Dawson polyoxometalate. We utilized defective vacant sites of Wells Dawson polyoxometalates as molecular platforms to isolate a single nickel cation from one another at the Lewis acidic active site. Synthesis of nickel substituted Wells Dawson phosphor-tungstate species was confirmed single crystal x-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The catalytic nature of nickel cations as active sites was evidenced by the comparison between nickel free Wells-Dawson species and blank catalyst support. Upon the dispersion of nickel substituted polyoxometalate species across the surface of mesoporous SBA-15, the ethylene conversions &gt;20% was achieved at the condition of 200°C and 280 psig for 24 hours of time on stream with 75.4% selectivity to C4 and 25.2% selectivity to C6+. After reaction, residual hydrocarbon species were removed via a thermal treatment under inert gas to regenerate the catalyst by removing oligomeric species. This presentation will highlight the synthetic method to effectively isolate single cationic nickel sites and the catalytic properties of these materials for ethylene oligomerization.

Improving Ni stability during ethylene oligomerization through isolation of single site in polyoxometalates

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.