Lower-Boiling Constituents

Many of the gaseous and liquid constituents of the lower-boiling fractions of petroleum and also those in petroleum products fall into the class of chemicals that have one or more of the following characteristics, considered to be hazardous by the EPA. 

Ignitability-flammability. A liquid that has a flash point of less than 60°C (140°F) is considered ignitable. Some examples are benzene, hexane, heptane, benzene, pentane, petroleum ether (low boiling), toluene, and xylene(s). 

Corrosivity. An aqueous solution that has a pH less than or equal to 2, or greater than or equal to 12.5, is considered corrosive. Most petroleum constituents and petroleum products are not corrosive, but many of the chemicals used in refineries are corrosive. Corrosive materials also include substances such as sodium hydroxide and some other acids or bases. 

Reactivity. Chemicals that react violently with air or water are considered hazardous examples are sodium metal, potassium metal, and phosphorus. Reactive materials also include strong oxidizers such as perchloric acid, and chemicals capable of detonation when subjected to an initiating source, such as solid, dry 10% H2O picric acid, benzoyl peroxide, or sodium borohydride. Solutions of certain cyanide or sulfides that could generate toxic gases are also classified as reactive. The potential for finding such chemicals in a refinery is 

For the analysts, laboratories wishing to dispose of materials containing dilute concentrations of these constituents should contact the Department of Environmental Health and Safety for advice regarding the proper disposition of the materials. In addition, the list of such materials is not included here, as it is subject to periodic updates. Furthermore, the list is not meant to be complete and may not include substances that have the hazardous characteristics as defined above. Omission of a chemical from this list does not mean that it is without toxic properties or any other hazard. 

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DEPHLEGMATION. Partial condensation of vapor from a distillation operation to produce a liquid richer in higher-boiling constituents than the original vapor. The residual vapor is richer in the lower boiling constituents. 

It is clear from these FID traces that significant differences exist between all of the samples analysed. Not only do the different macerals from the same coal exhibit differences, but so do similar macerals from different coals. Thus, not all vitrinites are the same, not all sporinites are the same and not all inertinites are the same. This is especially clear when we compare the two inertinite FID traces. The Indiana No. 5 inertinite contains significant amounts of both low and high retention time products which are absent in the Herrin No. 6 inertinite. Although the absence of the lower boiling constituents may be due to their evaporation in the work-up procedures, we believe this not to be the case since an identical work-up procedure was used for all samples. 

From the above it is evident that the larger portion of the lower boiling constituents of the oil of this tree is dextro-rotatory limonene. Dipentene does not occur. From the slightly lower rotation and boiling-point of the first fraction, it is probable that a small amount of pinene was present, but it can only occur in traces. A trace of the sesquiterpene... 

Transfer the sample to a clean hydrometer cylinder without splashing, to avoid the formation of air bubbles, and to reduce to a minimum evaporation of the lower boiling constituents of more volatile samples. Transfer highly volatile samples to the cylinder by water displacement or by siphoning (Note 3). Remove any air bubbles formed, after they have collected on the surface of the sample, by touching them with a piece of clean filter paper before inserting the hydrometer. 

The primary fractions from a distUlation unit are equUibrium mixtures and contain some proportion of the lighter constituents characteristic of a lower boiling fraction. The primary fractions are stripped of these constituents (stabUized) before storage or further processing. 

In conventional vapor phase molecular sieve operations, the operating temperature must be even higher and the operating pressure must be even lower than that required by the dew point curve for the high boiling constituents. These extra requirements are needed to prevent capillary condensation. Condensa-... 

In order to understand the composition of heavy oils and residua, it is necessary to present a very brief description of the constituents of the lower boiling fractions of petroleum. Acceptance that petroleum is a continuum of molecular types that continues from the low-boiling fractions to the nonvolatile fractions (Speight, 1999 and references cited therein) is an aid to understanding the chemical nature of the heavy feedstocks. 

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