Novel Approach for Enhanced Catalytic Microwave Pyrolysis of Low-Rank Coal

Microwave pyrolysis technology used for the efficient and clean conversion of low-rank coal is of concern in this study. An efficient and cheap Fe2O3/bluecoke (Fe2O3/BC) absorber with a wrapped structure was prepared by the hydrothermal synthesis method using ferric nitrate nonahydrate (iron source), sodium hydroxide (precipitation agent), and CTAB (protective agent), and the effects of BC, Fe2O3, and Fe2O3/BC absorbers on microwave pyrolysis of low-rank coal were investigated through some analytic methods, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). The pyrolysis temperature, yields, and characteristics of pyrolysis products (bluecoke, pyrolysis water, tar, and coal gas) were examined and compared to verify the effect of the Fe2O3/BC absorber. Results showed that the temperature increment rate was improved by these absorbers, and the highest temperature increment rate was obtained with the Fe2O3/BC absorber, followed by Fe2O3 and BC absorbers. The yield of the liquid product (pyrolysis water and tar) obtained with the Fe2O3/BC absorber was the highest, arriving at 14.31 wt %, in which the yield and carbon content of tar were 6.54 and 20.40 wt %, respectively. The characteristics of the products indicated that all of these absorbers enhanced the catalytic cracking reactions of coal, but Fe2O3/BC performed the best among the studied absorbers. A synergistic effect that promoted liquefaction and inhibited coal gasification was exerted by Fe2O3 and BC, and it may have been caused by the composite component and wrapped structure of the Fe2O3/BC absorber.