The production of 1-butene by ethylene dimerization is an important chemical industrial process currently implemented using homogeneous catalysts. Here, we describe a highly active heterogeneous catalyst (Ni-ZIF-8) for ethylene dimerization, which consists of isolating Ni-active sites selectively located on the crystal surface of a zeolitic imidazolate framework. Ni-ZIF-8 can be easily prepared by a simple one-pot synthesis method in which site-specific anchoring of Ni is achieved spontaneously because of the incompatibility between the d8 electronic configuration of Ni2+ and the three-dimensional framework of ZIF-8. The full exposure and square-planar coordination of the Ni sites accounts for the high catalytic activity of Ni-ZIF-8. It exhibits an average ethylene turnover frequency greater than 1 000 000 h-1 (1-butene selectivity >85%) at 35 °C and 50 bar, far exceeding the activities of previously reported heterogeneous catalysts and many homogeneous catalysts under similar conditions. Moreover, compared to molecular Ni complexes used as homogeneous catalysts for ethylene dimerization, Ni-ZIF-8 has significantly higher stability and shows constant activity during 4 h of continuous reaction. Isotopic labeling experiments indicate that ethylene dimerization over Ni-ZIF-8 follows the Cossee-Arlman mechanism, and detailed characterizations combined with density functional theory calculations rationalize this observed high activity.
KAUST Repository Item: Exported on 2021-05-04
Acknowledged KAUST grant number(s): BAS/1/1372-01
Acknowledgements: The financial support for this work was provided by Baseline Funds (BAS/1/1372-01-01) to Y.H. from King Abdullah University of Science and Technology (KAUST). M.R.A would like to acknowledge Saudi Aramco Advanced Degree Program. This research used resources of the Core Laboratories of KAUST. The computational simulations were performed on the KAUST supercomputers.
- Colloid and Surface Chemistry