Kinetics of kukersite low-temperature pyrolysis in autoclaves

A systematic experimental study of the effect of reaction time on the low-temperature pyrolysis of Baltic oil shale (kukersite) in autoclaves at nominal temperatures 340–380 °C was carried out. The results show an increase in the yields of gas and coke in time, whereas the yield of the target product, soluble in benzene fraction, has a maximum value (ca. 90%) and the yield of solid residue has a minimum value at a reaction time depending on the nominal temperature and heating rate. The process kinetics is described approximately by the first order parallel-consequent decomposition of initial kerogen and thermobitumen formed. A mathematical model is deduced for estimation of the rate coefficients and apparent kinetic constants for formation of gas, soluble in benzene phase, and coke at the low-temperature pyrolysis and for prediction of the current yields of the products. The experimental and calculated yields of gas, soluble in benzene phase (thermobitumen and oil) and solid residue (coke and not decomposed kerogen) obtained under non-linear increase of temperature agree satisfactorily.