Coal with Tetralin, yields

The classic work of Storch and co-workers showed that essentially all coals below 89% C f can be converted in high yields to acetone soluble materials on extended reaction (12). We have investigated the behavior of coals of varying rank toward short contact time liquefaction. In one series of experiments, coals were admixed with about 5 volumes of a solvent of limited H-donor content (8.5% Tetralin) and heated to 425°C for either 3 or 90 minutes. The solvent also contained 18% p-cresol, 2% y-picolene, and 71.5% 2-methylnaphthalene and represented a synthetic SRC recycle solvent. The conversions of a variety of coals with this... 

Recovery of Coal Material from the Reaction with Tetra in. The yields of the different products from the reactions of the various fractions with tetralin are summarised in Table II. 

Yields of Original Coal Fractions and their Products of Reaction with Tetralin, g/lOOg Original Dry Coal. 

The lower yields of pyridine-solubles obtained with tetralin compared to 9,10-dihydrophenanthrene (Table ni) and even to naphthalene and pyrene for the THF-extracted coal (Table m. Figures 1 and 2) again are probably attributable to tetralin being largely vaporised at liquefaction temperatures. 

The results described above illustrate the problem of separating effects due to catalysis provided by pyrrhotite from those due to the chemistry of the reduction of pyrite. It must also be borne in mind that reduction of pyrite produces a nearly equivalent amount of l S, which remains available to enter subsequent reactions by mechanisms now only poorly understood. In order to remove these complications, pyrrhotite was prepared by the reduction of pyrite with tetralin, isolated from the reaction residue, and then heated with fresh tetralin. Figures 4 and 5 contain the yields of naphthalene and 1-methylindan, and the ratios of trans- to cis-decalin as a function of concentration. In this case, the pyrite was a hand-picked sample of micro-crystals taken from a coal nodule. As may be seen, the yields of naphthalene and 1-methylindan, and the ratio of trans- to cis-decalin all increase with pyrite concentration. The slope of the line for naphthalene yield is 0.91. A slope of 0.53 is calculated for stoichiometric reduction of FeS to FeS by tetralin to yield naphthalene. Thus, roughly half of the naphthalene produced can be accounted for by the demand for hydrogen in the reduction of pyrite. 

Figure 17 shows the product yields of indirect brown coal hydrogenation with tetralin as a function of stratification and texture (lithotype... 

Selection of Solvents. The extraction yield of a low rank coal (Annesley) has been determined after digestion using a selection of solvents (Table II). The results show large variations in solvent power and, in particular, the high extraction yields obtained with hydrogen donor solvents. It is important to differentiate between the ability of a solvent to prevent polymerisation of the dissolved coal by hydrogen transfer, and its ability to retain the dissolved coal in solution. For example, Tetralin is frequently quoted as an... 

Primary Conversions and Influence of Mobile Phase Yields for the various H-donor and non-donor solvent extractions of Linby coal at 400% are summarised in Table III the conversions for the THF-extracted coal include the extracted material. Surprisingly, pre-extraction with THF significantly increases primary conversions in the polynuclear aromatic compounds (PACs) investigated. These findings appear to be contrary to those of other liquefaction (16) and pyrolysis (17) studies where prior removal of chloroform-extractable material significantly reduced conversions. However, Rincon and Cruz (18) have reported recently that pre-swelling coals in THF increases conversions for both anthracene oil and tetralin. The fact that Point of Ayr (87% dmmf C) coal yielded over 80% pyridine-solubles in pyrene (C.E. Snape, unpublished data) without pre-extraction is consistent with the earlier results of Qarke et al (19) for anthracene oil extraction where UK coals... 

Farcasiu (9), with which we have separated the toluene-soluble fractions into subfractions of increasing polarity. The TS fractions for different coals yield different profiles, and yet we find here for the Illinios No. 6 coal that the TS fractions for conversion in water of 29% and 60% are virtually the same. Further, the TS fraction from the tetralin run is also essentially identical in its prof lie. 

Available rate and thermochemical data allow estimates to be made for bond homolysis rate constants for virtually all covalent bonds presumed or found to be present in coal and model compound reactions. In Table III is compiled a list of coal-related homolysis rate constants, k, and bond homolysis half lives at 400°C, T1/2 (ti/2 = In 2/k is equal to the time required to break one-half of the bonds if homolysis were the only mode of reaction). Most of these values are estimated relative to measured rate constants for bibenzyl dissociation in tetralin, and relative values are expected to be only weakly dependent on solvent. It is evident from Table III, with few exceptions, that only bonds that yield two resonance stabilized radicals upon breaking are likely to undergo significant homolysis under coal liquefaction conditions. 

The reactions of tetralin in the presence of coal were investigated to determine the extent of conversion along various pathways in the absence of further added catalysts. As may be seen from Figure 1, the yield of products generated under typical liquefaction conditions (450°C, 30 minutes) increases with the amount of coal added. Three products arise from tetralin naphthalene, n-butylbenzene, and 1-methylindan. Positive identification of the latter isomer was made by comparison of gas chromatographic retention times with those of authentic samples of 1- and 2-methylindan prepared by independent synthesis. 

Figures 2 and 3 contain yield curves for naphthalene and 1-methylindan as a function of reaction time for tetralin and tetralin plus coal, pyrite, or asphaltene. The asphaltene was a homogenized mixture of several samples isolated from coal liquefaction products during other work in our laboratory (9). This asphaltene sample contained essentially a negligible ash content (<0.1%). Therefore, it contains many organic structures similiar to those found in coal, but unlike coal, its reactions will be free of any complicating factors due to mineral matter. The yields of naphthalene and 1-methylindan are greater in the presence of asphaltene than in its absence, although not quite as high as in the presence of coal. This is additional evidence that these two products arise mainly from reactions associated with the presence of the organic portion of coaly matter. These reactions are quite likely free radical in nature.

The maximum conversion obtained was 21.7% with 5 mol% tetralin, and 6.0% liquid yield with pure toluene at 10.9 MPa and 623 K. These figures are rather small when compared to literature data, being necessary to investigate different levels of thermal depolymerization and different solvents to optimize the conversion of the high-ash sub-bituminous Butia-coal. High levels of sulfur reduction were observed - up to 44%, and it has been also shown that the dessulfurization of the coal under study is selective with regard to the solvent mixture. 

In addition, since this coal crude was distilled from a coal hydrogenation mixture leaving pitch, coke, and other residue behind, it is unnaturally deficient in residue compared with petroleum-based crude oil. The distillation yields show that the coal crude is especially rich in the medium naphtha-kerosene fraction boiling up to 250°C (480°F) and can be attributed to the presence of benzene (bp 80°C [176°F]), toluene (bp 111°C [232°F]), o-xylene (bp 144°C [291 ]), m-xylene (bp 139°C [282°F]), p-xylene (bp 138°C [280°F]), naphthalene (bp 218 C [424 F]), and tetralin (bp 207°C [405°F]), as well as various alkyl (methyl) derivatives of the aforanentioned compounds, hydroaromatic analogs, and alkanes. 

In the Pott-Broche process, tetralin was used as a solvent for coal extraction in a mixture with cresols (80/20). This method was used to produce 30,000 tpa of coal extract in a plant operated by Ruhrol in Welheim (Bottrop), Germany between 1938 and 1944. Extraction was carried out under a pressure of around 100 bar at a temperature of 415 to 435 °C. The coal extract was used as a low-sulfur fuel, for the production of electrode coke, or refined by hydrogenation to yield benzole, middle oil and heavy oil. The solvent had to be regenerated, i.e. hydrogenated, before each extraction. 

The NiMo catalyst supported on nanoporous CB was compared with the commercial NiMo/Al203 catalyst and synthetic pyrite during the two-stage liquefaction of several coals.In this study the eifect of the tetralin/coal ratio on the yield of oil was the focus of attention. As expected, the yield of oil decreased with the decreasing tetralin/coal ratio. However, in every case, the NiMo/CB catalyst was the most active. Thus, even in the absence of tetralin, the yield of oil reached 52 and 64% after the first and second stage, respectively. Moreover, the 373 to 573 K fraction was the largest in the oil product obtained using the NiMo/CB catalyst. 

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