Condensed Aromatics, Boiling Points

In processing VGO it has been argued that the heavy poly-aromatic structures characterised by the Ramsbottom Carbon Residue (RCR, Table 1) can be considered as coke precursors [8]. An increase of the boiling point of those structures via condensation reactions or dehydrogenation reactions is responsible for coke deposition onto the catalyst. In order to increase our level of understanding of these processes we consider first the effects of catalyst parameters on the coke formation. 

These alkyl aromatics can then further condense and dimerize to produce products of higher boiling point as discussed above. 

It has been shown that when n-phenylenediamine condenses with aromatic carboxylic acids in a melt at 185-250 °C (or in high boiling point solvents) in the presence of acids such as polyphosphoric... 

The vapor leaving the top of the column is condensed in a water- or air-cooled condenser. The liquid distillate is a heavy naphtha stream, which is used for the production of gasoline. It has ASTM 5% and 95% boiling points of 195 and 375 °F, respectively. In some refineries, it is sent to a reforming unit to produce aromatics (benzene, toluene, and xylenes) and hydrogen. The condensed water is decanted off the reflux drum. Note that this water stream is quite large (17,180 Ib/h) because of all the open stripping steam that is used in the column base and sidestream strippers. 

There is a disadvantage connected with this method. It is difficult to compare the actions of various compounds with each other because the solubility in the coacer-vate plays a great part. If a substance has no influence then this may certainly also be attributed to the insolubility of that substance. Thus the action of aromatic hydrocarbons decreases in a manner parallel to the increase of the boiling point. Does this in fact mean that the condensing action decreases in this direction This seems improbable. The decrease — in the same direction — of the solubility is likely to be the explanation of the observed facts. 

Polybenzimidazoles are a class of thermally stable polymers, typically condensed from aromatic bis-o-diamines and dicarboxylates. The namesake polymer repeat unit, which contains a 1,3-dinitrogen heterocycle, is benzimidazole. As a monomer, benzimidazole, has a melting point of 170°C and a boiling point of >360°C. Benzimidazole s hydrocarbon analog, indene, has a melting point of -2°C and a boiling point of 183°C. With only a molecular weight difference of 2, the differences in thermal behavior between benzimidazole and indene foretells some of the unusual thermal characteristics to be found in benzimidazole polymers. 

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