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  1. Free, publicly-accessible full text available July 23, 2024
  2. 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 Ni 2+ sites substituted on the lacunary defect of a Wells–Dawson polyoxometalate (K 8 P 2 W 17 O 61 ·Ni 2+ ) 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 Ni 2+ 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. 
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  3. A series of Co–P materials with varying P : Co ratio from 0 to 4 supported on SBA-15 were evaluated for ethane dehydrogenation (EDH) performance. In comparison to monometallic Co, the Co–P materials have improved ethylene selectivity from 41% for Co to 88–90% for Co–P, which was attributed to the segregation of Co atoms and the formation of partial positive Co δ + sites in the Co–P materials due to charge transfer. Among the Co–P materials studied, an optimum in stability was observed in those containing a P : Co ratio in the range 1 to 2. Below this range, limited P is available to adequately separate Co atoms. Above this range, the excess P promotes coke formation through possible acid catalyzed pathways. The stability of two of the Co–P materials containing the Co 2 P and CoP phase, respectively, were further tested for EDH at 700 °C. Under these conditions, the ethylene selectivity was 98%, and both materials remained active with little to no deactivation for over 4 h. In comparison to a Pt–Sn reference, both Co–P materials showed vastly improved stability. Additionally, both Co–P materials showed no signs of sintering after EDH at 700 °C and maintained their respective Co 2 P and CoP phases. These results demonstrate the catalytic improvement with P incorporation and highlights the high stability of Co–P, and possibly other metal phosphides, as high temperature EDH catalysts. 
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  4. Oligomerization of light olefins has become an essential step to convert gaseous olefins to liquid fuels and value-added chemicals. Here, we report the synthesis and application of nickel single sites isolated on Wells Dawson polyoxometalate defects as stable and regenerable catalysts for ethylene oligomerization. 
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