Petroleum solubility classes

Metal Porphyrin and Nonporphyrin Distribution in Petroleum Solubility Classes... 

Fractionation of petroleum in the refinery, to obtain streams with specific boiling ranges for various downstream processes, is performed by distillation in a crude unit. To determine how Ni and V compounds are distributed as a function of boiling point is, therefore, useful for evaluating their impact in the refinery. Petroleum may also be fractionated by solvent separation and chromatography to obtain more detailed information on the distribution of Ni and V compounds. This section will review the available literature on how metals are distributed in petroleum by boiling point and solubility class. It will also include some discussion of the structure of heavy oil in general and asphaltenes in particular. Vercier etal. (1981) have provided an excellent review of methods and procedures involved in petroleum fractionations. 

Asphaltenes are thought to be the most complex, high-molecular-weight, high-boiling components in petroleum. Asphaltenes constitute a solubility class of materials consisting primarily of highly polar and... 

Asphaltenes are, by definition, a solubility class (8, 9, 10) that is precipitated from petroleums and bitumens by the addition of a minimum of forty volumes of the liquid hydrocarbon. In spite of this, there are still reports of asphaltenes being isolated from crude oil by much lower proportions of the precipitating medium (II), which leads to errors not only in the determination of the amount of asphaltenes in the crude oil but also in the determination of the compound type. For example, when insufficient proportions of the precipitating medium are used, resins (a fraction isolated at a later stage of the separation procedure by adsorbtion chromatography) also may appear within the asphaltene fraction by adsorbtion onto the asphaltenes from the supernatant liquid and can be released by reprecipitation in the correct manner (12). Thus, questionable isolation techniques throw serious doubt on any conclusions drawn from subsequent work done on the isolated material. 

Determination of the asphaltene fraction of petroleum has been investigated for most of this century (5-11), and therefore the art is not new. However, it is now generally accepted that asphaltenes are, by definition, a solubility class that is precipitated from petroleum, heavy oil, and bitumen by the addition of an excess of liquid hydrocarbon (11), The procedure not only dictates asphaltene yield but can also dictate the quality of the fraction (12-16), In fact, the very method of asphaltene separation is a prime example of the disturbance of the system by the addition of an external agent. Thus, during deasphalting, the dispersibility (or compatibility) of the asphaltenes in the system is changed. The... 

Taking into account our earlier studies [6,7] on the optimization of the composition of the additives synthesized by us, a batch of petroleum soluble additives was composed on the basis of an oil component and the most effectve of them was found to be the composition containing F SA-SK-N-H PSA-SK-S-U PSA-SK-O-U = 10 50 40 referred to further as batch P-1. The denotations and the most important values for additives preparation have been published earlier [6]. With the selected batch of additives, the possibility to prepare operation-conserving lubricants of transmission and motor type was investigated. For this purpose, basic lubricant mixtures were taken from fractions of the corresponding class of viscosity and the batch P-1 was added to them The standard physicochemical and performance properties of the alloyed lubricants were then determined to estimate their performance quality. The results obtained from the analysis are presented in Table 1. 

Most of the inhibitors in use are organic nitrogen compounds and these have been classified by Bregman as (a) aliphatic fatty acid derivatives, b) imidazolines, (c) quaternaries, (d) rosin derivatives (complex amine mixtures based on abietic acid) all of these will tend to have long-chain hydrocarbons, e.g. CigH, as part of the structure, (e) petroleum sulphonic acid salts of long-chain diamines (preferred to the diamines), (/) other salts of diamines and (g) fatty amides of aliphatic diamines. Actual compounds in use in classes (a) to d) include oleic and naphthenic acid salts of n-tallowpropylenediamine diamines RNH(CH2) NH2 in which R is a carbon chain of 8-22 atoms and x = 2-10 and reaction products of diamines with acids from the partial oxidation of liquid hydrocarbons. Attention has also been drawn to polyethoxylated compounds in which the water solubility can be controlled by the amount of ethylene oxide added to the molecule. 

The final class of water-soluble synthetic detergents derived from petroleum are the cationics. These products, when ionized, have the hydrophobic portion of the molecule in the cation. They are of interest principally because of the bactericidal properties they exhibit. Their performance as detergents is poor. The principal products marketed to date have been derived from normal long-chain amines, but procedures for their preparation from petroleum hydrocarbons (1) have been described as follows ... 

The term oil and grease refers to a broad class of organic substances recovered from the sample matrices by extraction with an appropriate solvent. Such recovery, therefore, is characteristic of certain physical properties of the compounds, primarily the volatility of the compounds and their solubility in the extraction solvent. The solvent must be immiscible in water and volatile, as well as readily distilled on a water bath. Many solvents or mixed-solvent systems should be suitable for the extraction of oil and grease in aqueous and nonaqueous samples. These include petroleum ether, w-hexanc, methylene chloride, methyl ter/-butyl ether, and trichlorotrifhroroethan (freon). These solvents are listed in Table 1. 

In modern terms, asphaltene is conceptually defined as the n-pentane-insoluble and benzene-soluble fraction whether it is derived from coal or from petroleum. There are a number of procedures used to isolate asphaltene (2-7), all of which appear to be reproducible (8) but do not necessarily provide equivalent end-products. The similarity between coal- and petroleum-derived asphaltenes begins and ends at the definition of the separation procedure. Puzinauskas and Corbett s (9) comments on asphalt may be paraphrased and applied to asphaltene. They state that the broad solvent classification is unfortunate it leads to misconceptions that petroleum and coal materials are alike, or at least similar. However, these two classes of materials differ not only in their origin, mode of manufacture and uses, but also in their chemical composition and physical behavior. 

Silicon tetraisocyanate is a stable white crystalline solid which melts at 26.0 0.5° and boils at 185.6 0.3°. It is soluble in benzene, chloroform, carbon tetrachloride, acetone, and petroleum naphtha. On exposure to moist air or water, it is rapidly hydrolyzed to gelatinous silica and cyanic acid. It reacts vigorously with most primary and secondary aliphatic and aromatic amines to produce, respectively, W-mono- or W,W-disubstituted ureas - and thus is useful in the synthesis of these classes of compounds. 

Waxes are one of the two general classes of commercial antiozonants. Waxes are derived from petroleum and are of two common types, paraffin and microcrystalline (20—23). Typical carbon numbers are n = 20-50 for paraffin waxes and n = 30- 70 for microcrystalline materials. If a wax is present in a vulcanizate at a concentration exceeding its solubility, some of it will migrate to the mbber surface where it can form a physical barrier to prevent the penetration of ozone. Waxes, of course, are essentially unreactive towards ozone so that there is no appreciable chemical protection. Commercial waxes are... 

Constituents of Petroleum (New York, 1945). Prepn of high purity cyclohexane Seyer et al., Ind. Eng. Chem. 31, 759 (1939). Cyclohexane can exist in two interconvertible conformations. the boat and the chair. In the chair form its 12 extracyclic bonds fall info two classes six lie parallel to the main axis of symmetry and are designated "axial", while six extend radially outward at 109.5 angles to the axis and are designated as equatorial , Barton et al. Nature 172, 1096 (1954) Science 119, 49 (1954). Solubility F. P. 

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