Tailoring the Reactive Oxygen Species in Mesoporous NiO for Selectivity-Controlled Aerobic Oxidation of 5-Hydroxymethylfurfural on a Loaded Pt Catalyst
Hao Zhang, Tianyu Gao, Qiue Cao, Wenhao Fang
Abstract
The base-free aerobic oxidation of 5-hydroxymethylfurfural (HMF) in water to 2,5-furandicarboxylic acid (FDCA) is a sustainable upgrading process for cellulosic carbohydrates. A mesoporous NiO-supported Pt nanoparticle (ca. 3 nm) catalyst was reported, which can achieve 100% selectivity to FDCA at a full conversion of HMF without the assistance of any base under mild conditions, that is, 100 °C, 10 bar O2, and 12 h. The catalyst efficiency in terms of productivity reached 22.2 molFDCA molPt–1 h–1, which is the highest value among all the supported Pt catalysts to date in literature. Moreover, the Pt/NiO catalyst showed a remarkably stable and reusable performance during five consecutive cycling. X-ray diffraction, N2 physisorption, transmission electron microscopy, X-ray photoelectron spectroscopy, CO-adsorbed diffuse reflectance Fourier transform infrared spectroscopy, temperature-programed reduction of hydrogen, temperature-programed desorption of oxygen, and electron paramagnetic resonance techniques were used to comprehensively analyze the catalysts. It was disclosed that tailoring the reactive oxygen species in NiO is an effective way to control the initial reaction rate of HMF as well as the derived intermediates (i.e., a reflection of product distribution). This can be manipulated by varying the aging temperature during the preparation of NiO; thus, the role of different oxygen species (i.e., Oads. and Olatt.) in NiO was clarified. The interaction between the metallic Pt active sites and the mobile oxygen species was found to be critical to the excellent catalytic performance.