Distillate cut

This method has a very general application range analysis for metals in crude oils, in their various distillation cuts, and in their residues as well as for metals contained in spent lubricating oils, water, lubricants, etc. 

Because of the differences existing between the quality of different distillation cuts and those resulting from their downstream processing, it is useful to group them according to a major characteristic. That is, they are grouped into the three principal chemical families which constitute them paraffins, naphthenes and aromatics. From a molecular point of view, their chemical reactivities follow this order ... 

Mass spectrometry allows analysis by hydrocarbon family for a variety of petroleum cuts as deep as vacuum distillates since we have seen that the molecules must be vaporized. The study of vacuum residues can be conducted by a method of direct introduction which we will address only briefly because the quantitative aspects are ek r metiy difficult to master. Table 3.6 gives some examples the matrices used differ according to the distillation cut and the chemical content such as the presence or absence of olefins or sulfur. 

As the temperatures of the distillation cuts increase, the problems get more complicated to the point where preliminary separations are required that usually involve liquid phase chromatography (described earlier). This provides, among others, a saturated fraction and an aromatic fraction. Mass spectrometry is then used for each of these fractions. 

Finally, note that hydrocracking is ideal for obtaining middle distillate cuts that can be used in jet fuel formulation. 

Vacuum distillation of the atmospheric residue complements primary distillation, enabli r.ecoyery of heavy distillate cuts from atmospheric residue that will un r o further conversion or will serve as lube oil bases. The vacuum residue containing most of the crude contaminants (metals, salts, sediments, sulfur, nitrogen, asphaltenes, Conradson carbon, etc.) is used in asphalt manufacture, for heavy fuel-oil, or for feed for others conversion processes. 

A light distillate cut (light cycle oil - LCO) similar to gas oil but having high aromaticity and low cetane number. 

Naphthenic acids occur ia a wide boiling range of cmde oil fractions, with acid content increa sing with boiling point to a maximum ia the gas oil fraction (ca 325°C). Jet fuel, kerosene, and diesel fractions are the source of most commercial naphthenic acid. The acid number of the naphthenic acids decreases as heavier petroleum fractions are isolated, ranging from 255 mg KOH/g for acids recovered from kerosene and 170 from diesel, to 108 from heavy fuel oil (19). The amount of unsaturation as indicated by iodine number also increases in the high molecular weight acids recovered from heavier distillation cuts. 

The material obtained in the distillation cut contains both alcoholic and vinylic impurities. The crown may be purified by a second, more careful distillation followed by recrystallization, sublimation or by chromatography in addition to the method described here (see Discussion). 

Two-Stage Crude Distillation (Atmospheric and Vacuum) The vacuum stage can be used alternately to produce heavy gas oil for catalytic cracking feed or raw lube distillate cuts for lubricating oil manufacture. 

Wax Manufacture A waxy distillate cut from crude or the wax byproduct from lube oil dewaxing is first deoiled. Resulting low oil content wax is hydrofmed for color improvement and fractionated into appropriate melting point grades. 

Another important use of correlations is the optimization of existing unit operations. Cat cracking correlations can provide the refiner with valuable information for optimizing reactor temperature level, gasoline/distillate cut point, and feed and recycle rates. The practical application of this information can mean increased profitability for the cat cracking operation. 

Damaged or plugged feed nozzle(s) and/or damaged stripping steam distributor(s) are the common causes of mechanical failures that affect true conversion. Note that the apparent conversion, as discussed in Chapter 5, is affected by the distillation cut point and main column operations. 

Today n-paraffms are exclusively produced from the corresponding distillation cuts of paraffin-rich oils with the use of molecular sieves. Molecular sieves are synthetically manufactured aluminum silicates of the zeolite type, which after dehydration have hollow spaces of specific diameters with openings of specific diameters. The molecules are then able to penetrate the openings in the correct size and form and are held in the hollow spaces by electrostatic or van der Waals forces. The diameter of the zeolite type used for the production of paraffins is 5 A and is refined so that the n-paraffins (C5-C24) can penetrate the hollow spaces while the iso- and cyclic paraffins are unable to pass through [15]. 

Table 1 shows the carbon chain distributions for several typical commercial alkylates. The carbon chain distributions for linear alkylbenzene (LAB) samples A, C, and E are determined by the distillation cut of n-paraffins used to make the LAB. LAB samples B and D represent blended alkylates made by mixing samples such as A and E in different ratios. This provides to the customer LAB products with a wide variety of molecular weights and improves the utilization of the fl-paraffin feedstocks. 

The product workup consisted of continuously extracting the filter cake with tetrahydrofuran (THF) and combining the THF and filtrate to make up a sample for distillation. In some experiments the THF extracted filter cake was extracted with pyridine and the pyridine extract was included in the liquid products. Extraction with pyridine increased coal conversion to soluble products by an average of 1.6 weight percent. The hot filtrate-THF-pyridine extract was distilled. Distillation cuts were made to give the following fractions, THF (b.p. <100 C), light oil (b.p. 100-232 C), solvent (b.p. 232-482), and SRC (distillation residue, b.p. >482 C). 

Figure 15. Relative removal of dibenzothiophenes and benzothiophenes from the middle-distillate cut of OB oil in the presence (left frame) and absence (right frame) of sulfate. Compounds are ranked in order of their relative depletion. Bars with solid and hatched lines represent the sum of the results for alkylated compounds with n pendant carbons, with CO indicating the unalkylated parent open bars in the left frame represent individual dibenzothiophenes. In the right frame, the bars represent sum of alkylated analogs for each carbon number. Figure reproduced from Ref. [86],...

To better understand these high-volume materials, we divided all those substances reported as produced in quantities of one million pounds per year or more into several categories such as organics, inorganics, polymers, etc. This exercise was most revealing. We found that those materials which can be classified as petroleum derivatives (gasoline, kerosine, distillation cuts,... 

Dispersants are being increasingly used to combat oil spills in the marine environment. The new generation of dispersants are commonly fatty acid-polyethoxylate esters (25) and are relatively non toxic. The specific compounds in petroleum responsible for MFO induction in fish have not been defined. Dispersed oil could increase the availability of inducing components, either the particulates or solubles, but alternatively, soluble compounds may be rapidly lost from dispersed oil (26). Preliminary experiments have been carried out to assess the effectiveness of dispersed oil in AHH induction. Venezuelan crude and bunker (distillation cut above 300-400°C).and two polyethoxylate oil spill dispersants,... 

Petroleum crude and its refinery products have two major component based on distillation. The portion that can be distilled under refinery conditions can be called volatiles and the nondistillables are the nonvolatiles. The volatiles can be analyzed by GC or GC-MS. The crude has both components. The distillate as the names applied, such as naphtha and kerosene contain only volatiles. When GPC is used for analyzing various distillates, the fractions separated by GPC can be characterized by GC or GC-MS. These data can be used to verify the nature of components present in various distillation cuts as a function of GPC elution volume. If the samples such as crude contains both volatiles as well as nonvolatiles, the samples should be separated into volatiles and nonvolatiles. The GPC of both components should be used to calibrate the GPC of the total crude. The parameter that can be obtained from GPC is effective molecular length. It can be used to relate other molecular parameters of interest after calibration. 

Sidestream distillate cuts of kerosene, heating oil, and gas oil can be separated in a single tower or in a series of topping towers, each tower yielding a successively heavier product stream. 

Coal liquids, petroleum crudes, and their distillation cuts have been separated into four or five fractions by SEC (5 15). The SEC fractions were analyzed by use of GC. The procedure was performed manually. It was inefficient, and susceptible to human error. The automated fraction collection followed by injection of the fraction into the GC reduces analysis time, and offers an option for collection of the desired number of fractions at predetermined time intervals. The manual collection of up to 10 one-ml fractions is also used in order to study the effectiveness of the automated method. 

The chemical lumping pattern shown in Figure 4 is very similar to the plotting of distillation temperatures vs. composition, a technique commonly used in petroleum refining to simulate the composition of distillate as a function of temperature. Since SEC includes nonvolatiles, information on their size distribution is also shown. In each chemical lump the molecular weight decreases as SEC retention volume increases. The individual chemical lump has a SEC separation pattern similar to a distillation temperature vs. molecular weight plot, a technique used in petroleum refining to illustrate the composition of various distillation cuts. 

The current RP-1 hydrocarbon fuel used in high thrust boosters is an example of a special kind of tailoring. This hydrocarbon blend or distillation cut was selected to meet a series of special property and combustion requirements for liquid oxygen-oxidized high thrust systems. 

A sample of raw bitumen recovered from Athabasca tar sands and provided by Sun Oil Co. was analyzed without further upgrading. Three distillate cuts of shale oil obtained from The Oil Shale Corp. were also analyzed without further upgrading. 

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