Ni-H-Beta Catalysts for Ethylene Oligomerization: Impact of Parent Cation on Ni Loading, Speciation, and Siting

Ni-H-Beta catalysts for ethylene oligomerization (EO) were prepared by ion exchange of NH4-Beta and H-Beta zeolites with aqueous Ni(NO3)2 characterized H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS). Quadruple at 70 °C resulted in 2.5 wt.% Ni loading corresponding to a Ni2+/framework aluminum (FAl) molar ratio 0.52. [NiOH]+ H+ are the primary charge-compensating cations uncalcined catalyst, as evidenced TPR DRIFTS. Subsequent calcination 550 air yielded catalyst containing primarily bare Ni2+ ions bonded framework oxygens. gave 2.0 (Ni2+/FAl = 0.41). After °C, resulting comprises mixture ions: NiO species. The relative abundance increases number exchanges. In situ pretreatment 500 flowing He converted species via dehydration. interact strongly Beta perturbed antisymmetric T-O-T vibration 945 cm−1. DRIFT spectra CO adsorbed 20 indicate that occupy two distinct positions. results EO testing 225 11 bar (ethylene) suggested specific initially presented (e.g., Ni2+, [NiOH]+) did not significantly affect catalytic performance.