The mechanism and kinetics of oil shale pyrolysis in the presence of water

•Hydrous thermo-simulation experiments on oil shale have been performed.•The formation mechanism of pyrolysates in the presence of water was evaluated.•The consecutive first order reaction model involving bitumen as an intermediate product was developed.•The kinetics parameters were calculated using experimental data. The hydrous thermo-simulation experiments on oil shale sample from Liushuhe basin have been performed using autoclave. The mechanism and kinetics of oil shale pyrolysis were investigated. The formation mechanism of pyrolysates including retorting gas, oil and bitumen, were evaluated in the presence of saturated and unsaturated water, respectively. The results show that the physicochemical properties of water have greatly changed in high temperature and pressure. At the same time, water has three kinds of effect on the oil shale pyrolysis, including the protection of free radical, catalytic action and swelling. The pyrolysis temperature was carried out about 70 °C earlier, and the generated processing of hydrocarbon would be easier under the aqueous. The consecutive first order reaction model involving bitumen as an intermediate product was used in the data analysis in order to determine the pyrolysis kinetic parameters. It was found that the apparent activation energy of kerogen pyrolysis was lower than bitumen pyrolysis.