Polyaromatic distillate

Historically aromatic compounds were produced from hard coal by coking. The polyaromatics present in coal are released under the pyrolytic conditions and are absorbed in oil or on activated charcoal to separate them from the other coal gases. The components are freed by codistillation with steam or by simple distillation. The contaminant nitrogen- and sulfur-containing compounds are removed by washing with sulfuric acid or by hydrogenation. 

The first polyaromatic polar fraction from the Athabasca oil was similar to the largest fraction in this class from the Lloydminster oil. All the simulated distillation chromatograms of the first polyaromatic polar fractions in the C region of the liquid chromatograms are shown in Figures 14-17. Sulfur peaks from the three oils are fairly well resolved,... 

Separation, Characterization and Analysis of the Distillate Fractions. Results from the analyses of the <200° C coal-liquid distillates (after removal of trace quantities of acids and bases) are summarized in Table IV. Results from the dual silica-gel/alu-mina-gel adsorption chromatography separations of the 200° to 325° C, 325° to 425° C, and 425° to 540° C coal-liquid distillates are summarized in Table V. Data for the acid and base extracts of the polyaromatic-polar adsorption fractions are also included in Table V. Summary data on analysis of the saturate fractions are listed in Table VI. Data in Table VI show a trend toward higher percentages of zero- and one-ring saturates in lower-rank coals. 

Adsorption Chromatographic Fractions. Examination of the data of Table V shows a tendency for distillates of lower-rank-coal liquids to contain more saturate material and less polyaromatic-... 

Figure 4. Polyaromatic-polar vs. nitrogen content, 325°—425° C distillate...

While originally designed for cracking the overhead stream from vacuum distillation units, known as vacuum gas oil (4), most FCC units currently operate with some higher boiling vacuum distillation bottoms (Resid) in the feed. Table 5.1 illustrates the difficult challenges faced by refiners, process licensors and FCC catalysts producers the resid feeds are heavier (lower API gravity), contain many more metals like Ni and V as well as more polyaromatic hydrocarbons prone to form coke on the catalysts (Conradson Carbon Residue, or CCR). 

Table I summarizes the analytical results for deasphaltened Athabasca bitumen (without prior distillation) on a series of columns used in the USBM-API 60 procedure, and those obtained by the simplified silica and alumina class separation scheme. As seen, the results are comparable provided that the polyaromatic and polar fractions are combined. The total analyses of the separated fractions obtained by the two methods listed in Table II are also in good agreement, with the exception that sulfur values from the simplified procedure are somewhat higher in all aromatic fractions except the polyaromatic/polar fraction.

The separation scheme for deasphaltened bitumen on silica [WOELM, activated at 140°C (4 hr)] is shown in Figure 1. The fractions obtained were loosely termed hydrocarbons. Polar I, II, and III. The IR spectra of these fractions, as shown in Figure 2, suggested that Polar I was very similar to the polyaromatic/neutral polar fraction from the API 60-based separation after removal of additional material from alumina with pure benzene. Also, simulated distillation curves for this fraction from either procedure are very similar (Figure 3). The IR spectra of the Polar II and III fractions show the presence of all the functional groups which can be distinguished in these complex mixtures and which... 

Figure 3. Simulated distillation of polyaromatic/ polar fraction from APF60 (O) and of Polar I fraction (%)...

The nature of crude oils depends on their source. Initial separation into components is carried out by atmospheric and vacuum distillation. Heavy ends are particular boiling point cuts, which can include atmospheric gas oil (250-350°C), atmospheric residues (350°C+) vacuum gas oil (350-5S0°C) and vacuum residues (5S0°C+). The descriptions are based on boiling points and, within a particular distillation cut, various chemical species can be identified. These include saturated and unsaturated hydrocarbons, aromatic and polyaromatic hydrocarbons and inorganic atoms such as V, Ni, and S, which are associated with large organic molecules [5]. As a result of this complexity, the composition of the boiling cuts is often described in terms of their content of oils, resins and asphaltenes [6,7,8], the relative amounts of which vary depending on the cut and the source of the crude [6] Of these species, asphaltenes are particularly important in the present context since they are known to be associated with heavy coke formation [7,8]. 

However, separation and characterization of the constituents of coal liquids can be performed by compound type (Figure 18.14). This involves utilization of a separation scheme whereupon the entire sample or individual distillation cuts are separated into seven major classes of compounds acids, bases, neutral nitrogen compounds, saturates, monoaromatics, diaromatics, and polyaromatics plus polar compounds. To avoid excessive dilution and use of solvents, a recycle column (Figure 18.15) may be anployed that enables recycling of carrier solvent and accumulation of product in a flask from which fresh solvent is distilled. 

Petroleum, or crude oil, is an extremely complex mixture derived like coal from prehistoric vegetation. The components range from gaseous to semi-solid or solid hydrocarbons, with compounds of sulphur, nitrogen, oxygen and various metals as impurities. Distillation gives roughly the fractions shown in Table 12.1. The hydrocarbons are almost entirely saturated paraffins, cycloparaffins (naphthenes) and aromatics/polyaromatics the proportions vary enormously from one source to another. 

One such application is the fabrication of carbon electrodes for the electrolytic production of ferrous and nonferrous metals. Coal pitches are used as binders. Pitches are the concentrate left after the destructive distillation of coal tar. They are complex mixtures of polyaromatic compounds of a wide range of molecular weights. Dhamelincourt et al. [118]... 

---