Investigation of dissolution mechanism of six Turkish coals in tetralin with microwave energy

Rates of formation of oil, asphaltenes, and preasphaltenes during liquefaction of six Turkish coals in tetralin with microwave heating have been experimentally determined. Five reaction mechanisms have been proposed and tested to estimate the rates of formation of products. Proposed mechanisms are based on assumptions that the reactions are irreversible and pseudo-first order with respect to the reacting species. Pseudo-first order rate constants for each of the indicated mechanistic steps have been calculated by multivariable non-linear regression analysis. The best fit between experimental data and models suggested was obtained from model 3 (this model suggests that oils, asphaltenes and preasphaltenes formed directly from coal) with Tunçbilek and Zonguldak, from model 4 (this model assumes oils to be produced directly from preasphaltenes in addition to being formed from coal according to model 3) with Muğla–Yatağan and Soma–Merkez, and from model 5 (this model describes conversion of coal to solvent fractionation products incorporating both series and parallel reactions) with Bolu–Göynük and Beypazarı coals. The results indicated that the reaction mechanism of coal liquefaction depends on the coal type.