Fractional refining

Fractions—Refiner s term for the portions of oils containing a number of hydrocarbon compounds but within certain boiling ranges, separated from other portions in fractional distillation. They are distinguished from pure compounds which have specified boiling temperatures, not a range. 

Fig. 5.15 Tensile index of the new composite and reference samples. Commercial copy is a geometric mean value. Abbreviations-. C new composite handsheets. Fibre components euca eucalyptus unrefined, reg. cellulose regenerated cellulose, w fractionated refined softwood...

Sample Impurities. The electron-diffraction experiment itself is a purification process except when the impurity and the compound have similar vapour pressures. However, in unfortunate cases, sample impurities may obviously give serious errors in the results. If the impurity is known, the structure determination may sometimes be carried out as described in p. 30 for mixtures of various conformations. The structural parameters of the impurity (or impurities) may be assumed if they are known with sufficient accuracy, and only the fraction refined together with structural parameters for the main compounds (see, for example, refs. 107 and 108). 

Most petroleum upstream applications for GC-MS are for analyzing whole oils, while most downstream applications are for analyzing distillation fractions, refining streams, and products in the marketplace. In the downstream applications, knowledge of the composition of petroleum and its fractions allows the refiner to optimize conversion of raw petroleum into high-value products. It is important to understand the chemical transformations that occur in a refinery, and the terminology of petroleum products. 

There are little or no olefins in crude oil or straight run (direct from crude distillation) products but they are found in refining products, particularly in the fractions coming from conversion of heavy fractions whether or not these processes are thermal or catalytic. The first few compounds of this family are very important raw materials for the petrochemical Industry e.g., ethylene, propylene, and butenes. 

Generally speaking, these correlations for refined products lead to too-low results for the points at small distilled fractions and to too-high results for those of large distilled fractions. 

The stocks used for jet fuel production come almost essentially from direct distillation of crude oil. They correspond to the fraction distilled between 145 and 240°C, more or less expanded or contracted according to the circumstances. The yield of such a cut depends largely on the nature of the crude but is always larger than the demand for jet fuel which reaches about 6% of the petroleum market in Europe. For the refiner, the tightest specifications are ... 

The potential advantages of LPG concern essentially the environmental aspects. LPG s are simple mixtures of 3- and 4-carbon-atom hydrocarbons with few contaminants (very low sulfur content). LPG s contain no noxious additives such as lead and their exhaust emissions have little or no toxicity because aromatics are absent. This type of fuel also benefits often enough from a lower taxation. In spite of that, the use of LPG motor fuel remains static in France, if not on a slightly downward trend. There are several reasons for this situation little interest from automobile manufacturers, reluctance on the part of automobile customers, competition in the refining industry for other uses of and fractions, (alkylation, etherification, direct addition into the gasoline pool). However, in 1993 this subject seems to have received more interest (Hublin et al., 1993). 

In the manufacture of base oils, one of the refining operations is to extract with the aid of an appropriate solvent (furfural most often) the most aromatic fractions and the polar components. When free of solvent, the extracted aromatic fraction can eventually be refined, particularly to remove color or to thicken it, or still further, to fractionate it. The term, aromatic extract is used in every case. 

Since the discovery of petroleum, the rational utilization of the fractions that compose it has strongly influenced the development of refining processes as well as their arrangement in refining flowsheets. 

In refining, the oligomerization process produces gasoline from C3 fractions containing approximately 75% propylene or fuel-gas containing ethylene and propylene. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Edmister, W.C. and K.K. Okamoto (1959), Applied hydrocarbon thermodynamics. Part 12 equilibrium flash vaporization correlations for petroleum fractions . Petroleum Refiner, Vol. 38, No. 8, p. 117. 

An important industrial example of W/O emulsions arises in water-in-crude-oil emulsions that form during production. These emulsions must be broken to aid transportation and refining [43]. These suspensions have been extensively studied by Sjoblom and co-workers [10, 13, 14] and Wasan and co-workers [44]. Stabilization arises from combinations of surface-active components, asphaltenes, polymers, and particles the composition depends on the source of the crude oil. Certain copolymers can mimic the emulsion stabilizing fractions of crude oil and have been studied in terms of their pressure-area behavior [45]. 

The remarks of this and the last section are only a small fraction of what might be said about these important materials. We have commented on some aspects of the polymerization processes and of the polymers themselves that have a direct bearing on the concepts discussed here and elsewhere in this volume. This material provides an excellent example of the symbiosis between theoretical and application-oriented points of view. Each stimulates and reinforces the other with new challenges, although it must be conceded that many industrial processes reach a fairly high degree of empirical refinement before the conceptual basis is quantitatively developed. 

Wkiterization is a specialized appHcation of fractional crystallization that is utilized to remove saturates or waxes from Hquid oils. Salad oils, which do not cloud at refrigerator temperature, have been produced by winterizing lightly hydrogenated soybean ok. However, many producers now use refined, bleached, deodorized oks for this purpose (24). 

A flow diagram of the solvent-refined coal or SRC process is shown ia Figure 12. Coal is pulverized and mixed with a solvent to form a slurry containing 25—35 wt % coal. The slurry is pressurized to ca 7 MPa (1000 psig), mixed with hydrogen, and heated to ca 425°C. The solution reactions are completed ia ca 20 min and the reaction product flashed to separate gases. The Hquid is filtered to remove the mineral residue (ash and undissolved coal) and fractionated to recover the solvent, which is recycled. 

Ultrahigh Purity Gallium. Many appHcations, particularly those in the electronics industry (see Electronic materials), require high (>99.99999% = 7.N ) purity metallic galHum. This is achieved by a combination of several operations such as filtration, electrochemical refining, heating under vacuum, and/or fractional crystalli2ation (see Ultrapure materials) (14). 

Cationic polymerization of coal-tar fractions has been commercially achieved through the use of strong protic acids, as well as various Lewis acids. Sulfuric acid was the first polymerization catalyst (11). More recent technology has focused on the Friedel-Crafts polymerization of coal fractions to yield resins with higher softening points and better color. Typical Lewis acid catalysts used in these processes are aluminum chloride, boron trifluoride, and various boron trifluoride complexes (12). Cmde feedstocks typically contain 25—75% reactive components and may be refined prior to polymerization (eg, acid or alkali treatment) to remove sulfur and other undesired components. Table 1 illustrates the typical components found in coal-tar fractions and their corresponding properties. 

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