Steering linear 1-alkene, propene or gasoline yields in ethene oligomerization via the interplay between nickel and acid sites

- The acid and nickel sites interplay during ethene oligomerization was quantified.
- 2 catalyst descriptors suffice to adequately reproduce data on different catalysts.
- Reaction pathway analyses provided guidelines for in-silico catalyst design.
- In-silico tuning of product yields via the interplay between acid and nickel sites.
- Product inhibition occurred by alkylates, resulting in a lower catalyst activity.

The ethene oligomerization performance of heterogeneous, Ni-based acid catalysts has been assessed by combining experimental measurements and Single-Event MicroKinetic (SEMK) modelling. In addition to the independently determined physisorption parameters, two catalyst descriptors, i.e., the ethene coordination enthalpy on the Ni-ion sites and the alkene protonation enthalpy on the acid sites, sufficed to adequately describe experimental data acquired on 1.8 wt% Ni-SiO2-Al2O3 and 4.9 wt% Ni-Beta zeolite.While Ni-sites ensure ethene dimerization, further alkylation, isomerization and cracking reactions occur on the acid sites. Unavoidably, alkylated species lead to product inhibition by hindering the accessibility of active Ni-ion sites for ethene. Very pronounced product physical adsorption was demonstrated to even result in reduced ethene conversion and, hence, catalyst activity.Through extensive reaction pathway analyses, guidelines for rational catalyst design for heterogeneous, Ni-based acid catalysts were proposed which are simulated to lead to selectivities of 60% towards 1-alkenes, 50% towards gasoline and 25% towards propene.

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