A TGA-MS INVESTIGATION OF THE EFFECT OF HEATING RATE AND MINERAL MATRIX ON THE PYROLYSIS OF KEROGEN IN OIL SHALE; pp. 125–141

A demineralized Dachengzi oil shale sample, p-kerogen, is obtained through hydrochloric and hydrofluoric (HCl and HF) treatment. Themogravimetric analysis combined with on-line mass spectrometry (TGA-MS) tests on original oil shale and p-kerogen were carried out at two heating rates, 5 °C/min and 15 °C/min, to study the effect of heating rate and mineral matrix on the pyrolysis of kerogen in oil shale. In the pyrolysis products, the amounts of both the organic and inorganic gases generated are significant with the evolution of oil in the temperature range of 370–570 °C. Increasing the heating rate from 5 °C/min to 15 °C/min leads to the decrease of most of the small molecule products of interest in this research, which indicates that in the oil shale pyrolysis the secondary cracking reactions may be inhibited by such increase. With increasing heating rate the thermogravimetric (TG) curves shift to a higher temperature region with an increase of about 10 °C due to the temperature difference between the surface and the center of the sample particles. The amount of alkenes generated is higher than that of alkanes and the alkene/alkane ratio increases with heating rate. At the same heating rate, the amounts of both the inorganic and organic compounds generated in the oil shale pyrolysis are higher than those produced in the p-kerogen pyrolysis, suggesting that mineral matrix has an obvious catalytic effect on the pyrolysis of kerogen. Hydrogen release is markedly strengthened in the oil evolution process because of the resultant effect of mineral matter which promotes the cracking reactions in the pyrolysis of kerogen. Compared with oil shale, the TG curves of p-kerogen shift to a lower temperature zone with a decrease of about 10 °C because the pore channels formed in the demineralization treatment intensify the heat and mass transfer in the sample particles.