Catalytic Hydrodeoxygenation of Methyl-Substituted Phenols:  Correlations of Kinetic Parameters with Molecular Properties

Abstract

The hydrodeoxygenation of methyl-substituted phenols was carried out in a flow microreactor at 300°C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al 2 O 3 catalyst. The primary reaction products were methylsubstituted benzene, cyclohexene, cyclohexane, and H 2 O. Analysis of the results suggests that two independent reaction paths are operative, one leading to aromatics and the other to partially or completely hydrogenated cyclohexanes. The reaction data were analyzed using Langmuir-Hinshelwood kinetics to extract the values of the reactant-to-catalyst adsorption constant and of the rate constants characterizing the two reaction paths. The adsorption constant was found to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions. Ab initio electronic structure calculations were used to evaluate the electrostatic potentials and valence orbital ionization potentials for all of the substituted phenol reactants. Correlations were observed between (a) the adsorption constant and the two reaction rate constants measured for various methyl-substitutions and (b) certain moments of the electrostatic potentials and certain orbitals' ionization potentials of the isolated phenol molecules. On the basis of these correlations to intrinsic reactantmolecule properties, a reaction mechanism is proposed for each pathway, and it is suggested that the dependencies of adsorption and reaction rates upon methyl-group substitution are a result of the substituents' effects on the electrostatic potential and orbitals rather than geometric (steric) effects.

Deactivation of Ni-MoS2 by bio-oil impurities during hydrodeoxygenation of phenol and octanol

“…HDO of phenol can take place by two paths as summarized in Figure 5: a direct deoxygenation of phenol to benzene, followed by hydrogenation to cyclohexane, or an initial hydrogenation of phenol to cyclohexanol followed by dehydration to cyclohexene and then hydrogenation to cyclohexane. The preferred reaction path depends on the catalyst and reaction conditions [45][46][47][48][49][50][51].…”

Hydrodeoxygenation of Phenolic Compounds by Sulfided (Co)Mo/Al2O3Catalysts, a Combined Experimental and Theoretical Study

“…A growing number of experimental studies deals with the HDO of lignocellulosic model compounds in model feeds [10][11][12][13][14][15][16][17][18][19][20][21][22][23] or in coprocessing with petroleum fractions [16,17,24,25]. Phenolic compounds have been proved to be among the most refractory ones to the HDO process [2,7].…”

“…Phenolic compounds have been proved to be among the most refractory ones to the HDO process [2,7]. Hydrodeoxygenation of these molecules proceeds by two pathways: -hydrogenation of the aromatic ring followed by C sp 3-O bond cleavage (HYD pathway); -the direct cleavage of the C sp 2-O bond (DDO pathway) [10][11][12][13][14][15]17]. The Direct DeOxygenation (DDO) reaction pathway is desirable since it limits hydrogen consumption compared to the hydrogenation one.…”

High Selectively Catalytic Conversion of Lignin-Based Phenols into para-/m-Xylene over Pt/HZSM-5

“…By co-feeding methanol, various methylation (1) methylation of cresol into xylenols and met to give toluene [36]; (3) erally, the catalytic HDO of oxygen-containing compounds under different conditions using t catalysts is known to proceed through two reaction pathways [34,35]. The one path is nolysis or direct deoxygenation (DDO) of phenols to produce aromatic hydrocarbons.…”

“…In this study, there is undetectable amount of methylcyclohexanol in the products, implying that the DDO Except alkanes, aromatics, and phenolics, other products such as indane, naphthalene, and their derivatives, also exist in small amounts. Generally, the catalytic HDO of oxygen-containing compounds under different conditions using different catalysts is known to proceed through two reaction pathways [34,35]. The one path is hydrogenolysis or direct deoxygenation (DDO) of phenols to produce aromatic hydrocarbons.…”