Coal-derived products solvent

With the demonstration of supercritical fluid extraction, an obvious extension would be to extract or dissolve the compounds of interest into the supercritical fluid before analysis with SFC.(6) This would be analogous to the case in HPLC, where the mobile phase solvent is commonly used for dissolving the sample. The work described here will employ a system capable of extracting materials with a supercritical fluid and introducing a known volume of this extract onto the column for analysis via SFC. Detection of the separated materials will be by on-line UV spectroscopy and infrared spectrometry. The optimized SFE/SFC system has been used to study selected nonvolatile coal-derived products. The work reported here involved the aliphatic and aromatic hydrocarbon fractions from this residuum material. Residua at several times were taken from the reactor and examined which provided some insight into the effects of catalyst decay on the products produced in a pilot plant operation. 

Work to present has demonstrated both the existence of organically bound metals in coal derived products as well as the feasibility for direct detection and quantitation in organic solvents by ICP-AES. Before reliable speciation can be accomplished, better chromatographic separations need to be developed. These include preliminary separation into various fractions by polarity followed by subsequent analysis by HPLC. 

Solvent Analysis of Coal>Derived Products Using Pressure Filtration... 

Solvent solubility is widely used to classify coal-derived products (1.,2). The most popular methods are based on some form of Soxhlet extraction. Methods involving Soxhlet extraction are normally time consuming thus complete solvent solubility classification is laborious. An alternate method, used initially by Bertolacini et al. (3.) and modified for our use, employs pressure filtration. Pressure filtrations carried out at room temperature have been used to classify a number of coal-derived products obtained under a variety of liquefaction conditions. 

In summary, the pressure-filtration technique is a useful and precise analytical tool in performing the solvent classification of certain coal-derived products. The method will not only give meaningful results comparable to continuous, room-temperature Soxhlet extractions but, most importantly, save many hours in the laboratory. We have found it rapid enough to monitor continuous operations. With coal-oil slurry reaction mixtures obtained from high-temperature coal-liquefaction reactions, the solvent classification can be completed in 1 1/2 to 2 hours. 

Montan Wax. Montan wax [8002-53-7] is derived by solvent extraction of lignite (qv). The earliest production on a commercial scale was in Germany during the latter half of the nineteenth century, and Germany continues to supply the majority of the world s production of montan wax. Montan wax production at Amsdorf is part of a massive coal-mining operation from a continuous vein and raw material is expected to last for decades. Montan wax is also produced in the United States. Imports of montan wax into the United States for the years 1990—1995 are Hsted in Table 1. Germany suppHes over 80% of the montan wax imported into the United States (3). 

The Pott-Broche process (101) was best known as an early industrial use of solvent extraction of coal but was ended owing to war damage. The coal was extracted at about 400°C for 1—1.5 h under a hydrogen pressure of 10—15 MPa (100—150 atm) using a coal-derived solvent. Plant capacity was only 5 t/h with an 80% yield of extract. The product contained less than 0.05% mineral matter and had limited use, mainly in electrodes. 

A schematic diagram of the liquid solvent extraction process is illustrated in Figure 1. Where the production of liquid hydrocarbons is the main objective an hydrogenated donor process solvent is used, whereas in the production of needle coke this is not necessary and a coal derived high boiling aromatic solvent may be used (e.g. anthracene oil). An essential economic requirement of the process is that a high extraction yield of the coal is obtained and this will depend upon the coal used and the digestion conditions. 

In step one, conversion of coal to a THF soluble product is rapid. The THF solubles are unstable in the presence of a coal derived solvent, but in the absence of hydrogen. In step two, the addition of molecular hydrogen to the system or of Tetralin to the solvent to increase hydrogen transfer to the coal increases the THF soluble conversion but does not lower the sulfur... 

Proposed methods for predicting heats of formation and absolute entropies are tested on two fractions of synthetic crude oil obtained by the EDS process, one sample of H-Coal, one sample of Synthoil, two samples of Solvent Refined Coal, and five pure compounds found in coal liquefaction products. For these samples, the heats of combustion are calculated using predicted values of AHf° and compared in Table IV with observed values. Note that Equations 8 and 9 were used to predict AHf° and S° of the EDS heavy naphtha. Equations 6 and 7 are applied to other samples of coal-derived liquids, and Equations 3 and 4 to the pure compounds. 

One phase of the Exxon Donor Solvent (EDS) coal liquefaction research and development program addresses the quality of liquid products. The broad objectives of EDS product quality studies are to identify potential end-uses for coal-derived liquids and to evaluate the properties of these liquids to allow meaningful assessment in these end-uses. 

Acid catalyzed depolymerization of coal with phenol affords a means for dissolution of coal under relatively mild conditions (185°C, ambient pressure). Once dissolved, separation of ash constituents and unreacted char is accomplished by filtration or centrifugation (also under mild conditions). Depolymerized coal recovered as a low ash product from excess phenol could be dissolved in a coal derived solvent and hydrogenated to stable liquids. It might be anticipated that access to hydrogen and contact with the catalyst would be more efficient in the case of the solubilized coal substance than for coal particle slurries. Hydrogenation might proceed more efficiently and with less... 

A Co-Mo-AlgOs catalyst (Harshaw CoMo 0402T, 3% CoO - 15% M0O3) was used In some experiments either with or without potassium carbonate. Pyrlte Isolated from coal was also used as a catalyst with potassium carbonate In some experiments. Anthracene oil obtained from Crowley Tar Products Company was used as the start-up solvent. In the recycle runs with Sheridan Field Coal (W-74-45), 80% of the anthracene oil was gradually replaced by coal-derived oil after nine recycles. The benzene and pentane used for separation of oil, and asphaltene were Fisher solvent grade. 

By conducting the liquefaction In the presence of potassium carbonate, pyrlte or cobalt molybdate a remarkable Increase In the overall conversion and selectivity to oil was achieved while the viscosity of product oil was considerably lowered. The recycle characteristics of liquefied coal after nine recycles, when 80% of the start-up solvent was replaced with coal-derived oil, were quite acceptable. The viscosity of the recycled product oil remained remarkably low, and the sulfur level was reduced from 3.4 maf% In the starting coal to 0.22 wt7.. 

Asphaltene content bears directly on the physical properties of the liquid product. Viscosity is of particular interest because of the importance of this parameter to operation of liquefaction plants and as a measure of the extent of liquefaction. The correlation between asphaltene content and the viscosity of the liquid has been a subject of a number of investigations (23-27). The logarithm of the viscosity ratio, In 7j/rj0 (where i and y0 are the viscosities of the solution and solvent, respectively) was found to be a linear function of concentration when asphaltene was redissolved in the pentane-soluble oil isolated from a coal-derived liquid (24). The slopes of these lines, termed the logarithmic viscosity numbers, are a measure of the contribution to the viscosity of a solution attributable to asphaltene. By comparison of logarithmic viscosity numbers of asphaltenes and their acidic and basic subfractions, it was determined that intermolecular association, which is especially strong between the acid and base subfractions, is responsible for a significant portion of the viscosity of these solutions. 

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