In-situ catalytic pyrolysis of heavy oil residue with steel waste to upgrade product quality

Abstract

Heavy oil residue (HOR) as a kind of oil-containing wastes (OW) is suitable to be treated by pyrolysis to obtain valuable products. However, the recovered products remain poor quality due to much heavy fractions in feedstock. This paper employed two typical steel wastes, i.e. iron-rich rolling sludge (FOS) and steel slags (SS), for catalytic pyrolysis of HOR to upgrade pyrolytic products. FOS and SS additions both effectively decreased the temperature of HOR pyrolysis stage and the activation energy. Compared with SS, FOS addition enhanced the yield of CH4 and H2, leading to higher heating values for pyrolytic gases. However, insufficient FOS couldn’t provide enough energy to trigger the conversion of macromolecules as well as the cracking of short-chain alkanes and alkenes. In terms of pyrolytic oil, SS addition greatly improved the content of light fractions and exhibited stronger selectivity in reforming of alkanes into alkenes, while FOS addition promoted aromatization. Furthermore, Fe-doping carbon materials with different valent Fe and abundant defects were obtained through pyrolysis of HOR/FOS and HOR/SS. Combined with their magnetic properties, the separation of materials from contaminants and subsequent cycle utilization could be achieved. Subsequently, the addition of different Fe compounds validated the promotion of zero-valent Fe on aromatization while Fe2O3 on alkenes production as well as Fe oxides would offer active oxygen species to participate in the pyrolysis reaction. However, model Fe compounds were hard to simulate catalytic behaviors of FOS and SS in gas production due to the complex components of steel wastes. This paper provides a novel perspective for upgrading all products from HOR pyrolysis and opens a path for simultaneous disposal of multiple solid wastes.