(653e) Ethylene Oligomerization to Select Oligomers on Ni2+-Containing ETS-10

Converting the abundantly available shorter alkenes, especially ethylene (C₂), to select longer oligomers (C₄-C₁₀) via oligomerization reaction is an industrially important route for the generation of a wide spectrum of commodity chemicals. Oligomerization reaction of ethylene has been studied on various homogenous and heterogeneous catalysts. Heterogeneous catalysts can be utilized in gas-phase continuous reaction conditions without the requirement of a pyrophoric co-catalyst, which is desired for alkene conversion, and are usually dealt with in large scales in industrial processes. Compared to other solid catalysts for ethylene oligomerization reaction, nickel (Ni²⁺) containing ordered microporous materials, due to their well-defined pore structure, well-studied structure and chemical environment of the active sites, offer the opportunity to control and optimize reaction rate and selectivity of these reactions.

ETS-10 (Engelhard Titanosilicate-10) is a thermally stable (up to 650^oC) microporous crystalline titanosilcate (Si/Ti=5) containing corner sharing [TiO₆] and [SiO₄] units. Each [TiO₆] unit generates a -2 charge (due to Ti(IV)), capable of loading divalent ions for ion exchange and water treatment applications. In this work, we present the synthesis and catalytic behaviors of Ni-ETS-10. We introduce a template-free and fluoride-free synthesis method that produces ETS-10 without impurities commonly seen in other systems. Based on these unique structural features of ETS-10, we introduced Ni²⁺ cations into the ETS-10 framework. Ni-ETS-10 is more active for ethylene oligomerization than existing microporous catalysts (such as Ni-CIT-6 and Ni-MOF-74) and has shown higher stability and higher selectivity to C₄ than other microporous catalysts compared in this study.