The effect of acid treatment on pyrolysis of Longkou oil shale

The effect of acid treatment on mineral removal and pyrolysis of Longkou oil shale were investigated. X-ray diffraction (XRD) and X-ray fluorescence (XRF) indicated that the HCl treatment can remove the calcite, the H2SO4 treatment can convert the calcite to CaSO4, and the HF treatment can remove the quartz and convert the calcite to CaF2; moreover, all three treatments cannot remove the pyrite in the oil shale. Oil shale was individually treated with HCl, H2SO4, and HF before conducted the pyrolysis experiment. The pyrolysis results showed that oil shale treated with H2SO4 or HF almost equally enhanced the oil yield, while HCl treatment had a negative effect on the oil yield. Thermogravimetry (TG) analysis indicated that the carbonates had a catalytic effect, sulfates may also had a catalytic effect and the silicates had an inhibitive effect on the decomposition of kerogen. Combining the TG analysis, oil yield and the price of every acid, the H2SO4 treatment was considered to be the best method to treat oil shale.Moreover, the carbonate minerals can be removed after H2SO4 treatment, so it would reduce the amount of pyrolysis feed to increase production efficiency.