Enhanced catalytic microwave pyrolysis of low-rank coal using Fe2O3@bluecoke absorber prepared by a simple mechanical ball milling

Fe2O3 and bluecoke (BC) powder are used in preparing novel and cheap carbon-based absorbers through simple mechanical ball milling and by enhancing catalytic microwave pyrolysis. The electromagnetic and catalytic properties of the active compositions and matrices are controlled, and the characteristics of the prepared Fe2O3@BC absorbers and pyrolysis products are detected and analyzed in detail through SEM–EDS, XRD, FT-IR, TG-DTG, and GC-MS. Results show that most of the Fe2O3 particles aggregate and uniformly form numerous flower clusters on the surfaces of the BC fragments, developing many edges and interface structures. The presence of iron oxides and iron in BC with Fe2O3 indicates that the catalysis of Fe2O3 on coal is caused by the iron mixture. Enhancement in microwave pyrolysis significantly and rapidly increases temperature and product distribution, and the maximum tar yield of 7.94 wt% is obtained with the Fe2O3@BC absorber. Product analysis shows that the “hot spot” effect of BC and Fe2O3 and the activation of Fe2O3 on free hydrogen result in the complete microwave pyrolysis of low-rank coal and thereby improve the yield and quality of tar and coal gas. Possibly caused by the introduction of magnetic loss and “rim–edge” effect, which enhances catalytic microwave pyrolysis, the synergistic effects of Fe2O3 and BC are confirmed by theoretical calculation and experiment results. The microwave pyrolysis technology of low-rank coal is feasible because of good economic and energy efficient microwave pyrolysis of low-rank coal, and fully utilized pyrolysis products and by-products.