Hydrodeoxygenation of Phenolic Model Compounds over MoS 2 Catalysts with Different Structures

Abstract

Several MoS 2 catalysts of different structure, prepared by in situ decomposition of ammonium Keptamolyb-date (AHM) and molybdenum naphthenate (MoNaph), and by MoS 2 exfoliation (TDM), were characterized by BET, X-ray diffraction (XRD), Energy Dispersive X-ray (EDX) and transmission electron microscopy (TEM). The analysis showed that MoS 2 structure was dependant upon the preparation procedure. The activity of the catalysts was determined by measuring the hydrodeoxygenation (HDO) of phenol, 4-methylphenol and 4-methoxyphenol using a batch autoclave reactor operated at 2.8 MPa of hydrogen and temperatures ranging from 320–370qC. By comparing the conversion, the reactivity order of the catalysts was: AHM>TDM-D>MoNaph>thermal>MoS 2 powder> TDM-W. Also, the effect of reaction temperature on the HDO conversion was explained in terms of equilibrium of reversible reaction kinetics. The main products of the HDO for phenolic compounds were identified by gas chromatography/mass spectrometry (GC/MS). The results showed that the product distribution and the HDO selectivity were correlated with the reaction temperature. Two parallel reaction routes, direct hydrogenolysis and combined hydrogenation-hydrogenolysis, were confirmed by the analysis of the product distribution. High temperature favored hydrogenolysis over hydrogenation for HDO of phenol and 4-methoxyphenol, whereas for 4-methylphenol the reverse was true.