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

Abstract

Microwave pyrolysis technology used for the efficient and clean conversion of low-rank coal is of concern in this study. An efficient and cheap Fe 2 O 3 /bluecoke (Fe 2 O 3 /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, Fe 2 O 3 , and Fe 2 O 3 /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 Fe 2 O 3 /BC absorber. Results showed that the temperature increment rate was improved by these absorbers, and the highest temperature increment rate was obtained with the Fe 2 O 3 /BC absorber, followed by Fe 2 O 3 and BC absorbers. The yield of the liquid product (pyrolysis water and tar) obtained with the Fe 2 O 3 /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 Fe 2 O 3 /BC performed the best among the studied absorbers. A synergistic effect that promoted liquefaction and inhibited coal gasification was exerted by Fe 2 O 3 and BC, and it may have been caused by the composite component and wrapped structure of the Fe 2 O 3 /BC absorber.