Platinum catalyzed hydrodeoxygenation of guaiacol in illumination of cresol production: a density functional theory study

Abstract

The unprocessed bio-oil obtained by the pyrolysis of lignocellulosic biomass comprises hundreds of oxy-components which vitiate its quality in terms of low heating value, low stability, low pH, etc. Therefore, it has to be upgraded prior to its use as transportation fuel. In this work, guaiacol, a promising compound of the phenolic fraction of unprocessed bio-oil, is considered as a model component for studying its hydrodeoxygenation over a Pt3 catalyst cluster. The production of catechol, 3-methylcatechol, m-cresol and o-cresol from guaiacol over a Pt3 cluster is numerically investigated using density functional theory. Further, the kinetic parameters are obtained over a wide range of temperature, i.e. 473–673 K at an interval of 50 K. Briefly, results indicate that O─H and C─H bond scissions determine the reaction rates of ‘guaiacol to catechol’ and ‘catechol to 3-methylcatechol’ reactions with activation energies of 30.32 and 41.3 kcal mol−1, respectively. On the other hand, C─O bond scissions determine the rates of 3-methylcatechol to m- and o-cresol production reactions, respectively. The kinetics of all reactions indicate that ln k versus 1/T plots are linear over the entire range of temperature considered herein.

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

“…Once formed, the desorption of phenol from the surface is kinetically slow (3.49×10 1 s -1 at 500 K) and energy demanding (Edes = 4.45 eV), which means it would be likely to accumulate on the surface. The adsorption energy, which can be calculated as the negative of the desorption energy, suggests that the adsorption of phenol on the surface is at least 2 eV stronger than that observed over transition metals 54,55,[61][62][63] . Thus, the accumulated phenol could convert further to benzene, which is considered further herein via two mechanisms.…”

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

“…Once formed, the desorption of phenol from the surface is kinetically slow (3.49×10 1 s -1 at 500 K) and energy demanding (Edes = 4.45 eV), which means it would be likely to accumulate on the surface. The adsorption energy, which can be calculated as the negative of the desorption energy, suggests that the adsorption of phenol on the surface is at least 2 eV stronger than that observed over transition metals 56,57,[65][66][67] . Thus, the accumulated phenol could convert further to benzene, which is considered further herein via two mechanisms.…”

Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

“…R9 is kinetically very favorable, with a rate constant of 3.68×10 12 s -1 is calculated for 500 K; however, structure 2 can also convert to Once formed, the desorption of phenol from the surface is kinetically slow (3.49×10 1 s -1 at 500 K) and energy demanding (Edes = 4.45 eV), which means it would be likely to accumulate on the surface. The adsorption energy, which can be calculated as the negative of the desorption energy, suggests that the adsorption of phenol on the surface is at least 2 eV stronger than that observed over transition metals 58,59,[67][68][69] . Thus, the accumulated phenol could convert further to benzene, which is considered further herein via two mechanisms.…”