Evaluation of oil potential and pyrolysis kinetics of renewable fuel and shale samples by Rock-Eval analyzer

A possibility for preliminary evaluation by Rock-Eval analysis of oil potential and pyrolysis kinetics of six representatives of renewable fuel and two Estonian shales is described. The amount of hydrocarbons volatilised from thermolabile ingredients of the samples at 300 °C (S1) is found to increase from 1.1 to 66.3 mg/g in the row: Dictyonema argillite < Kukersite < peat < pine sawdust < pine bark < willow < reed ≈ spruce needles. The total oil potential by pyrolysis at 300–650 °C (S1 + S2) increases from 47.4 to 367 mg/g in the row: Dictyonema argillite < peat < reed < pine bark < willow < spruce branches < pine sawdust < Kukersite. An increase in oxygen index (OI) decreases the temperature at the pyrolysis maximum rate (Tmax) and S2 but increases S1 of the samples according to relationships approximated to linear regressions. Relationship between hydrogen and oxygen contents expressed by an increase in atomic ratio of (H/C)daf with that of (O/C)daf in Van Krevelen diagram for the initial samples is opposite to a decrease in HI with increase in OI for the volatiles estimated by Rock-Eval analysis.First-order kinetic models are proposed to estimate the values of apparent activation energy (E) and frequency factor (A) for evolution of total hydrocarbons, for release of hydrocarbons from thermolabile ingredients, and for prediction of current yields of hydrocarbons in time and temperature basing on S1, S2, Tmax at one heating rate. A linear relationship is revealed between the pyrolysis kinetic constants, E (kJ/mol) and A (1/min), of the samples studied: ln A = 0.228(±0.010)E − 4.46(±1.61).