Thermolysis of crude oil sludge using CO₂ as reactive gas medium

Up to date, despite the massive generation of crude oil sludge (COS), the technical completeness for disposing COS has not been fully achieved. Considering its harmfulness and the high content of hydrocarbon species, establishing an environmentally benign platform for the simultaneous waste disposal and energy recovery will be greatly important. To this end, this study mainly focuses on pyrolysis of COS. To develop the more sustainable pyrolytic platform for COS, this study particularly employed carbon dioxide (CO₂) as reactive gas medium. To chase the thermolytic behaviors of COS in the presence of CO₂, a series of the TGA tests of COS was conducted, and the TGA tests confirmed that CO₂ did not change the thermolytic behaviors, such as onset and end temperature for the thermolysis of COS. Nevertheless, CO₂ greatly influenced the pyrogenic products via the heterogeneous reactions (i.e., volatilized hydrocarbons and CO₂). In detail, CO₂ expedited the thermal cracking and dehydrogenation of volatilized hydrocarbons evolved from COS, thereby resulting in the enhanced generation of H₂, CH₄, C₂H₆, C₂H₄, and C₂H₂. Despite the fact that the enhanced thermal cracking and dehydrogenation generally enhances the aromaticity in pyrolytic oil, the enhanced generation of CO was observed only from pyrolysis of COS in CO₂, of which enhanced generation of CO effectively decreased the aromaticity by restricting the formation of benzene derivatives.