Reaction Mechanisms of 2-Butanol Dehydration over a Phosphorus-Containing Activated Carbon Acid Catalyst

The reaction mechanisms for the carbon-based acid catalytic conversion of 2-butanol into dehydration and dehydrogenation products (alkene derivatives and ketone) have been theoretically studied by assuming that the acid site is a dihydrogen phosphate group bonded to one of the carbon atoms of the central ring of anthracene. The structural model of the active site of the surface of the catalyst reproduces properly the experimental results. Kinetic and thermodynamic magnitudes have been obtained by using standard expressions of Eyring’s transition-state theory and statistical thermodynamics. Interpretation of the calculations (molecular charges, geometries, and energies) demonstrates that the dehydration reaction process is an E 2 mechanism (one-step reaction) with strong character of E 1 mechanism (two-step reaction). The study of the mechanism has been carried out by applying density functional theory with the metaexchange–correlation functional M06-2X. The reactants and products connected by the respective transition states have been unequivocally localized through intrinsic reaction coordinate calculations. Localization of minima and transition states has been performed by using redundant internal coordinates without geometrical constraints.