Chemical modification of petroleum coke and applications of derived materials
Date
2021-05-07
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Abstract
Petroleum coke (petcoke) is a by-product from the oil industry and is a solid product mainly composed of carbon (> 80 wt%) with some impurities. These impurities, in particular sulfur, limit petcoke as feedstock for the application-like fuel. The aim of this thesis was to explore the possible application of petcoke without activation procedure, which took advantage of the highly aromatic structure and high sulfur content (6.5 wt%) of petcoke. Petcoke was used as a precursor for preparing solid acid catalysts through direct functionalization (i.e., without an activation step) with nitric acid to access the inherent sulfur. For comparison, catalysts were also prepared using sulfuric acid and a mixture of nitric and sulfuric acid (1:3 vol ratio). Although compared to the sulfonated petcoke, nitric acid-treated petcoke showed higher strong acidity, the ester yield was lower than that of sulfonated petcoke. The effect of acid treatment conditions and ball milling pretreatment on the nitric acid-treated solid acid catalysts were investigated. Higher treatment temperature resulted in higher total acidity but did not increase the amount of sulfonic acid groups. The acidity increased with the increase of the treatment time and remained stable after 6 hours. However, the yield of the product is not only related to the number of sulfonic groups but shows a negative correlation with total acidity/oxygen-containing functional groups implying the adsorption effect of oxygen-containing functional groups might hinder the esterification reaction. With ball milling pretreatment, the defects and aromatic hydrogen of petcoke increased, which promoted the subsequent acid treatment to obtain more sulfonic acid groups. DFT calculations were used to analyze the pathways of sulfonic acid group formation, and the reaction pathway with NO2• was the most thermodynamically and kinetically preferable. The side product from the nitric acid treatment of petcoke was collected and it showed fluorescence characteristics and therefore was used to synthesis carbon dots-TiO2 photocatalysts, which improved the hydrogen production in the photocatalytic hydrogen generation reaction. The results in this thesis helped to explore the possible modifications and applications for using petcoke and taking advantage of its highly aromatic structure and high sulfur content.
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Huang, Q. (2021). Chemical modification of petroleum coke and applications of derived materials (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.