Bitumen definition

This measurement provides a definition of the bitumen content in bitumen materials as the portion soluble in carbon disulfide (in France, in trichloroethylene, carbon tetrachloride or tetrachloroethylene). The method is defined by AFNOR NF T 66-012 or IP 47, or ASTM D 4 (the latter is not equivalent to the others). 

The classic definition of asphaltenes is based on the solution properties of petroleum residua in various solvents. The word asphaltene was coined in France by J.B. Boussingault in 1837. Boussingault described the constituents of some bitumens (asphalts) found at that time in eastern France and in Peru. He named the alcohol insoluble, essence of turpentine soluble solid obtained from the distillation residue "asphaltene", since it resembled the original asphalt. 

Table 3.2 shows the remaining potential (the sum of reserves and resources) of conventional oil at the end of 2005, which amounts to around 1800 Gb, made up of 1200 Gb reserves and 600 Gb resources. In line with the definition in Section 3.3.1, these figures do not include unconventional oil, such as crude bitumen from oil sands production in Canada or extra heavy oil from Venezuela.11 Almost three-quarters of... 

However, to define conventional petroleum, heavy oil, and bitumen, the use of a single physical parameter such as API gravity or viscosity is not sufficient and is only a general indicator of the nature of the material. Other properties, such as the method of recovery, composition, and most of all, the properties of the bnlk deposit, must also be included in any definition of these materials. Only then will it be possible to classify petroleum and its derivatives (Speight, 1999). 

It is possible that a pretreatment step is required for organic ion-exchange materials before immobilization, although it is not definitely the case. The immobilization matrices currently used are cement, bitumen, and some polymers. 

Asphaltenes are dark brown to black friable solids that have no definite melting point, and when heated, usually intumesce, then decompose leaving a carbonaceous residue. They are obtained from petroleums and bitumens by addition of a nonpolar solvent (such as a hydrocarbon) with a surface tension lower than 25 dynes cm-1 at 25°C (such as liquefied petroleum gases, the low-boiling petroleum naphthas, petroleum ether, pentane, isopentane, and hexane) but are soluble in liquids having a surface tension above 25 dynes cm-1 (such as pyridine, carbon disulfide, carbon tetrachloride, and benzene) (6, 7). 

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. 

The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. This generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale. With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. This effort is summarized by Speight and Moschope-dis (i) in their chapter in this volume along with a good summary of the current thinking. Thus, there are petroleum asphaltenes, coal tar asphaltenes, shale oil asphaltenes, tar sands bitumen asphaltenes, and so on. In this chapter I will attempt to show how these materials are special cases of an overall concept based directly on the physical chemistry of solutions and that the idea that they have a specific chemical composition and molecular weight is incorrect even for different crude oil sources. 

The precise chemical composition of bitumen is, despite the large volume of work performed in this area, largely speculative. In very general terms (and as observed from elemental analyses), tar sand bitumen is an extremely complex mixture of 1) hydrocarbons 2) nitrogen compoimds 3) oxygen compounds 4) sulfur compounds and 5) metallic constituents. However, this general definition is not adequate to describe the composition of petroleum as it relates to the behavior of the feedstocks. 

In all of these attempts at a definition or classification of petroleum, it must be remembered that petroleum exhibits wide variations in composition and properties, and these variations not only occur in petroleum from different fields but may also be manifested in petroleum taken from different production depths in the same well. The mixture of hydrocarbons is highly complex. Paraffinic, naphthenic, and aromatic structures can occur in the same molecule, and the complexity increases with boiling range of the petroleum fraction. In addition, petroleum varies in physical appearance from a light-colored liquid to the more viscous heavy oil. The near-solid or solid bitumen that occurs in tar sand deposits is different from petroleum and heavy oil, as evidenced by the respective methods of recovery (Speight, 1999,2000). 

On the basis of the definition of tar sand (above), bitumen is a naturally occurring hydrocarbonaceous material that has little or no mobility under reservoir conditions and which cannot be recovered through a well by conventional oil well production methods including currently used enhanced recovery techniques current methods for bitumen recovery involve mining (Speight, 1990). 

Oil sands are essentially beds of sand containing a heavy hydrocarbon bitumen. Bitumen is chemically similar to conventional oil but has comparatively high density (low API gravity) and high viscosity. Although a number of definitions for bitumen have been used by various authors, a reasonable set of definitions is given in Table I, based on the United Nations Institute for Training and Research (UNITAR)-sponsored attempts to establish definitions (1—3). 

Table L Table of UNITAR-Sponsored Established Definitions for Bitumen...

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... 

In summary, the definition of the asphaltenes, the resins, and the nonvolatile oil fraction that occur in heavy oil and bitumen is an operational aid. Such separations cannot be based on any chemical or structural features of the constituent molecules (II, 13, IS, 19). 

As the intermediates and products were not physically or chemically characterized, their precise definitions are omitted to avoid introducing arbitrary terms. The reaction scheme reveals a similarity between intermediate and the bitumen in oil shale (B). Intermediate 2 could be associated with bitumen generated by the thermal treatment of oil shale, which pyrolyses at lower temperatures in the same way as the bitumen originally present in oil shale. This is indicated by the almost identical activation energies obtained by TGA analysis. 

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