Brønsted acid-promoted ethylene dimerization to 1-butene over Ni-containing zeolite catalysts

Abstract

Ethylene dimerization is a critical industrial process traditionally catalyzed by homogeneous systems employing cocatalysts or solvents. Although heterogeneous catalysts show potential to circumvent these limitations, they often exhibit low activity and limited selectivity toward 1-butene. In this work, a transition-metal-confined FAU zeolite catalyst featuring precisely defined, coordinatively unsaturated Ni sites and abundant acidic functionalities, is explored for the reaction. This unique catalyst, denoted as H-Ni@Y, demonstrates remarkable ethylene dimerization performance without the need for cocatalysts or additive activators. In a fixed-bed reactor, an exceptional 1-butene formation rate of 4.28 × 10⁵ h^-1 and high 1-butene selectivity of 83.6% can be achieved with H-Ni@Y catalyst. Comprehensive characterization results and DFT calculations elucidate the significant influence of Brønsted acidity on the catalytic performance, revealing the in situ-generated Ni-alkyl species as the active sites. The reaction proceeds via the Cossee-Arlman mechanism, facilitated by dynamic proton transfer processes. These findings provide valuable insights into the rational design of heterogeneous catalysts for industrially relevant ethylene dimerization.