Polyaromatic coronene

FIGURE 8.11 Polyaromatic coronene derivatives found or suspected to be in fuels hydrocracker bottoms streams. 

Figure 5.12 Polyaromatic hydrocarbon species (1) phenanthrene, (2) anthracene, (3) pyrene, (4) benz[o]anthracene, (5) chrysene, (6) naphthacene, (7) benzo[c]phenanthrene, (8) benzo[ghi] fluoranthene, (9) dibenzo[c,g]phenanthrene, (10) benzo[g/ ]perylene, (11) triphenylene, (12) o-terphenyl, (13) m-terphenyl, (14) p-terphenyl, (15) benzo[o]pyrene, (16) tetrabenzonaphthalene, (17) phenanthro[3,4-c]phenanthrene, (18) coronene...

In [m] circulenes, a family of polyaromatic hydrocarbons so named in 1975 by Wynsberg, in which m refers to the number of aromatic rings arranged in a circle, the total number of n electrons does not indicate aromaticity or anti-aromaticity according to the Hiickel rule. This rule is strictly only applicable to monocyclic systems. It is adequate, however, to consider the inner and the outer n electrons separately whose numbers obey the An + 2 Hiickel criterion for aromaticity, since both these circuits are monocyclic [49]. Coronene, a flat graphite frag-... 

Downstream of the probe the sampling line is electrically heated to avoid undesirable condensation of organic compounds. Gas temperature is kept at temperatures around 300-400°C. Thus, line blocking is minimised. Heavy polyaromatic compounds (heavy tars, from pyrene to coronene) are condensed at a controlled temperature (in the range from 130-260"C) in a filter trap housed in a forced air circulation oven. The lower the temperature in the filter is, the faster the plugging of the filter is due to a higher deposition of tars. Therefore, the selection of an appropriate temperature in the filter is of paramount importance. It must be chosen as high as... 

Other Reactions on Zeolites. - Coke deposits on USHY, H-OFF, and HZSM-5 zeolites were characterized by EELS. The EELS spectra were taken on small areas during a short period of time to minimize specimen drift and electron beam-induced damages. Because of this, the spectra were too noisy to proceed with a data reduction, and therefore no quantitative treatment of the EELS spectra was attempted. A qualitative analysis was carried out, comparing the spectra taken on the coked zeolite (or on the insoluble coke) with the EELS spectra taken on reference carbon compounds of known structure. Figure 5 shows the results. It was found that in HZSM-5 and H-OFF the coke forms an external envelope around the zeolite crystal and stands as an empty mold after zeolite extraction. Its structure is similar to that of coronene (polyaromatic-pregraphitic). In USHY zeolite, the coke has a structure more like pentacene (linear polyaromatic). 

The formation of both p-SiC and carbon is evidenced by transmission electron microscopy (TEM) [1] [16]. The p-SiC phase appears as tiny crystals with a mean size of 2 nm. The carbon phase appears as randomly oriented 0.7 to 0.8 nm BSUs, which consist of polyaromatic species associated face to face and which could be related to coronene, C24H12 [16]. PCS pyrolytic residues contain 20 at.% residual hydrogen after pyrolysis at 850°C and 4... 

Structure-directing elements. The size of the cages was varied by changing the diboronic acid building block. The authors used these complex structures to encapsulate polyaromatic molecules such as triphenylene or coronene. 

Polyaromatic hydrocarbons, the group of polycyclic hydrocarbons from naphthalene to and beyond coronene. 

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