Intensifying strategy of ionic liquids for Pd-based catalysts in anthraquinone hydrogenation

Abstract

A novel strategy was employed to prepare Pd–IL complex catalysts for the anthraquinone hydrogenation reaction, taking advantage of the ionic liquid (IL). The IL microphase provides an excellent environment for augmenting the content of Pd⁰ active species, since the tunable surface acidic sites by altering the IL amount can offer more metallic activity sites and change the electron density of Pd nanoparticles. With a low Pd loading amount of 0.3%(wt), the optimal Pd–4%IL catalyst exhibits a stable hydrogenation efficiency of 7.7 g L⁻¹ and the selectivity of 99.9%, obviously superior to those of the traditional catalyst of Pd/Al₂O₃ (4.9 g L⁻¹ and 96.9%). DFT calculations indicate that the addition of IL would significantly enhance the activation degree of the reactant EAQ, reduce the energy barriers of the desirable hydrogenation reaction and consequently increase the selectivity. This work offers a new perspective for the highly-efficient fabrication of IL-intensified Pd-based catalysts as well as their utilization for anthraquinone hydrogenation.