Kinetics of aromatic ring hydrogenation in the solvent hydrotreatment of the NEDOL coal liquefaction process

To examine kinetics of aromatic ring hydrogenation in the solvent hydrotreatment of NEDOL coal liquefaction process, hydrotreatment of the solvents recycled in the 150 t/d pilot plant (PP) was carried out over Ni-Mo/γ-Al2O3 catalyst under 8-12 MPa using a fixed bed reactor. Negative influence of thermodynamic equilibrium on the aromatic ring hydrogenation became larger as the hydrotreatment temperature increased. At the temperature of 360-380°C, a temperature dependency of the aromatic ring hydrogenation was restricted by the thermodynamic equilibrium. Kinetics of the aromatic ring hydrogenation involving the thermodynamic equilibrium was a reversible first order reaction. The activation energy was larger for the reverse dehydrogenation reaction (30.5-33.9 kcal/mol) than for the forward hydrogenation reaction (24.1-26.2 kcal/mol). An increase in the hydrogenation pressure reduced the negative influence of the thermodynamic equilibrium. The rate of the aromatic ring hydrogenation was influenced by class of the raw coal and coal concentration in the slurry fed to the liquefaction reactor.