Gas-phase hydrodeoxygenation of bio-oil model compound over nitrogen-doped carbon-supported palladium catalyst

Abstract

The hydrodeoxygenation (HDO) of bio-oil has attracted considerable attention but is extremely challenging due to low yield and selectivity. In this study, we report the gas-phase hydro-deoxygenation of guaiacol, a typical model compound of lignin-derived bio-oil, into aromatic hydrocarbons with benzene yield up to 85.1% over a nitrogen-doped carbon-supported palladium (Pd/NC) catalyst under atmospheric pressure. The guaiacol HDO products are detected by an on-line VUV photoionization time-of-flight mass spectrometry (TOF-MS) in real-time. Stability evaluation based on time-on-stream profiles of typical markers (benzene and phenol) shows that the benzene selectivity and stability are kept unchanged during 6 h time-on-stream. The mechanism of guaiacol HDO over Pd/NC is also discussed. We infer that the enhanced stability of Pd/NC catalyst is attributed to the prevention of Pd particles' leaching and aggregation by nitrogen-doped carbon materials and the high activity is due to the redistribution of electron density caused by the interaction of nitrogen functionalities and Pd particles. More importantly, efficient deoxygenation of lignin model compound while preserving its aromatic nature is feasible and successfully achieved with Pd/NC catalyst, which is extremely advantageous for the concept of selective conversion of lignin into value-added aromatic chemicals.