Abstract
In this paper, we explore the use of high resolution transmission electron microscopy (HRTEM) in the degradation of the poly aromatic hydrocarbon (PAH) in coals of different ranks subjected to chemical plus heat treatment. The crystallite diameter on peak (10) approximations, La (10), of 37.6 Å for the high rank coal char at 700 oC fell within the HRTEM’s range of minimum-maximum length boundary of 11 x 11 aromatic aromatic fringes (28 – 44 Å). The La (10), 30.5 Å for the low rank lignite chars fell nearly on the minimum-maximum length range of 7 x 7 aromatic fringes (17 – 28 Å).The HRTEM results showed that the high rank anthracite chars at 700 oC comprised a higher distribution of larger distribution of larger aromatic fringes (11 x 11 parallelogram catenations). The mechanism for the similarity between coal chars of different ranks was the greater transition occurring in the low rank coals (lignite and sub-bituminous) to match the more resistant medium and high rank coals (bituminous – anthracite). This emphasized that the transitions in the properties of the low rank coals were more thermally accelerated than those of the high rank coals. The total PAHs detected in the coals of different ranks during pyrolysis are dominated by two- and three- ring PAHs. The amount of PAHs increase and then decrease with increase in pyrolysis temperature.
Highlights
The increased focus on renewable sources of energy has made current research efforts on coal geared towards clean coal technology
Benzene that have one aromatic ring is not considered as a PAH but compounds such as naphthalene; anthracene and phenanthrene and other multiple aromatic rings are poly aromatic hydrocarbons with no appendages of halogens or other substituent compounds (Hsu, Liu, Hung, Chang, & Chang, 2016).They are lipophilic in nature and insoluble in water (Wang, Yousaf, Sun, Zhang, Zhang, & Liu, 2016)
The results revealed that napthalene and anthracene were more predominant in the coal and coal char material than the other numerous PAHs (Bartonova, 2015).These aromatics belongs to the group that classified as “small” (PAHs containing two to four fused aromatic ring) molecular weight poly aromatic hydrocarbons (PAHs) (Ravindra, Sokhi, & Grieken, 2008; Bartonova, 2015)
Summary
The increased focus on renewable sources of energy has made current research efforts on coal geared towards clean coal technology. Benzene that have one aromatic ring is not considered as a PAH but compounds such as naphthalene (two aromatic rings); anthracene and phenanthrene (three aromatic rings) and other multiple aromatic rings are poly aromatic hydrocarbons with no appendages of halogens or other substituent compounds (Hsu, Liu, Hung, Chang, & Chang, 2016).They are lipophilic in nature and insoluble in water (Wang, Yousaf, Sun, Zhang, Zhang, & Liu, 2016) The emmission of these polycyclic aromatic matter into the atmosphere has its environmental (Alves, Vincente, Gomes, Nunes, Duarte, & Bandowe, 2016) and health effects (Abdel-Shafy, & Mansour, 2016). All the coal samples used were demineralized to account for only the organic component of coal
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