Liquefaction extent

The results are shown in Fig. 2, where the QI yield was adopted as a measure of liquefaction extent. Because the solubility of decacyclene in quinoline was rather limitted, the QI contained a considerable amount of decacyclene. Liquefaction of this coal proceeded scarcely below 420°C of the softening temperature with this solvent as well as pyrene. Above this temperature, the QI yield decreased sharply with the increasing liquefaction temperature until the resolidification temperature of the coal. The maximum LY observed at this temperature was estimated 67%, decacyclene being assumed uncharged under the conditions. Above the resolidification temperature, the QI yield increased sharply. The carbonization may start. Decacyclene was known unreacted at 470°C in its single heat-treatment (10), and in its cocarbonization with some coals(11), although it is fusible. Cocarbonization of fusible... 

Gr. neos, new) Discovered by Ramsay and Travers in 1898. Neon is a rare gaseous element present in the atmosphere to the extent of 1 part in 65,000 of air. It is obtained by liquefaction of air and separated from the other gases by fractional dishhation. 

Carbonaceous solids appear as a result of retrogressive reactions, in which organic thermal fragments recombine to produce insoluble semi-cokes (59,65). Coke formation is observed during liquefaction of all coals and its extent can vary widely according to the coal, the reaction solvent, and reaction conditions. The predominant inorganic species produced during the process of coal... 

The effect of hydrogenation extent on the liquefaction activity was summarized in Table 3. As the... 

The recovery percentages of coal and solvent (BI/ coal fed, BS/solvent fed, respectively) calculated based on the above assumption are summarized in Table 4. They were more than 85% except for the significantly low value for the coal recovery when hydropyrene was used as the solvent. In the latter case, some extent of the coal may be converted into the benzene soluble. Nevertheless, analyses of BS and BI fractions may inform the structural change of coal and solvent after the liquefaction. 

The principal options for hydrogen transport and distribution include pipelines, gaseous and liquid trailers. The choice for the most economic option depends on transport volumes and transport distances. For the transport of liquid hydrogen, additionally the costs of the liquefaction plant need to be taken into account. Another possibility could be to blend hydrogen with natural gas up to a certain extent and either separate the two at the delivery point, or use the mixture, e.g., in... 

Many factors affect the rate and extent of coal liquefaction, including temperature, hydrogen partial pressure, residence time, coal type and analysis, solvent properties, solvent-to-coal ratio, ash composition, and the presence or absence of a catalyst. Many kinetic expressions have appeared in the literature, but since they are generally specific to a particular process, they will not be listed here. In general, liquefaction is... 

There are three possible effects produced in preliquefaction which could lead to improved liquefaction. They are 1) reduced crosslinking 2) increased hydrogenation and 3) increased bond breaking. The experimental results presented above show that effect 1 is the most likely, 2 does not occur and 3 appears to happen to some extent. 

Alkylation Studies. Several preliminary experiments were completed to compare the extent of alkylation obtained with our coal pretreatment method to that obtained with Sternberg and Liotta alkylation. Results for Wyodak coal are summarized in Table III. Clearly, our procedure provides a very mild alkylation treatment compared with the other two methods and does not appear to be sensitive to differences in alkyl chain length (methyl vs. propyl). The increase in THF solubiliw was also small this result again suggests only a small extent of alkylation and in addition, shows that only minimal ion exchange (for example Ca by H ) occurred in the coal mineral matter. The effect of each pretreatment method on low severity liquefaction reactivity is discussed in the next section. 

Figure 4. Liquefaction Reactivity Enhancement as a Function of Alkylation Extent for Three Pretreatment Methods.

Both reactions act to reduce hydrogen bonding within the coal structure which may have a direct positive impact on liquefaction reactivity. More indirectly, these reactions lower the concentration of OH species in coal-derived products and hence, reduce the extent of retrogressive condensation via ether bridge formation. Reducing production of THF-insoluble condensation products increases the net THF-soluble coal conversion observed during the liquefaction experiment. None of the spectra from coals pretreated with alkyl alcohols and HCl showed any significant evidence of alkylation at carbon sites in the coal. 

The chemistry of coat liquefaction Is less well understood and how studies of this matter are Interpreted depends to some extent on how the "molecular" structure of coal Is perceived. 

One of the major results of SEC-GC-MS studies is the discovery of an orderly pattern, by which various isomers and homologs of similar chemical species exist in coal liquids. For example almost any direct coal liquefaction process produces very similar species, which differ from each other by size and extent of isomerization but with an orderly distribution pattern. Alkanes... 

Hydrogen sulfide in the reaction atmosphere has been reported to accelerate liquefaction directly, in addition to controlling the extent of sulfiding of iron, Ni-Mo, and Co-Mo catalysts (39, 40). 

Liquefaction catalysts, such as sulfides, lose their catalytic activity, especially hydrogenation activity when they are transformed into sulfate or oxide. Even reduction of the extent of sulfiding leads to a significant loss in catalyst activity. The crystalline form of the catalyst may also influence the catalytic activity. Thus, the level of sulfur during coal liquefaction is critical. This can be controlled by the addition of sulfur additives. 

The theoretical formulation of the collapse of a polymer chain [4,6] and the volume phase transition of gels [1-3] has been developed by utilizing an analogy between the liquefaction of a real gas and the condensation of polymer segments. In fact, this analogy is quite helpful to understand the phenomenological aspect of the collapse of a polymer chain and of a polymer network. However, we do not know to what extent this analogy is valid in reed cases. Because a gel is a solid, the elastic deformation of the network may play an important role in real phase transition processes. 

Xenon occurs in the atmosphere to the extent of approximately 0.00087%, making it the least abundant of the rare of noble gases in the atmosphere. In terms of abundance, xenon does not appear on lists of elements in the earth s crust because it does not exist in stable compounds under normal conditions. However, xenon because of its limited solubility in HjO. is found in seawater to the extent of approximately 950 pounds per cubic mile (103 kilograms per cubic kilometer). Commercial xenon is derived from air by liquefaction and fractional distillation. There are nine... 

Amestica and Wolf (12) in a study closely related to the one described herein, measured the conversion of Illinois No. 6 coal in toluene and ethanol. Their results clearly showed that conversions increased with temperature and solvent density but were not detailed enough to show the time dependence of the conversion. However, a result important to this study was that toluene converts coal to liquids without significantly reacting itself. After reaction, 98% of the toluene used was recovered versus only 73 -85% of the ethanol in runs using it. Ethanol is a hydrogen donor and reacts extensively with the coal. While toluene probably reacts with coal to a small extent, its effect was primarily physical in nature. As such, it is a good candidate for studying the effects of a supercritical solvent on coal liquefaction kinetics since the enhancement effect of supercritical conditions is physical in nature. 

Coal liquefaction processes are designed to clean coal chemically by removing ash, sulfur and to a lesser extent, nitrogen from a feed coal. The principal differences between the fuels tested at Plant Sweatt and their petroleum counterparts are that synthetic fuels have a higher carbon/hydrogen molar ratio (C/H,... 

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. 

Starch conversion refers to the process of converting starch into other products. It involves gelatinization, liquefaction, and saccharification. Liquefaction refers to the acid-or enzyme-catalyzed conversion of starch into maltodextrin. Starch, usually from wet milling of com, is pumped in a slurry to the conversion plant, where it undergoes one or more hydrolytic processes to yield mixtures of various carbohydrates in the form of syrups. The kind and amount of the various carbohydrates obtained depend upon the type of hydrolysis system used (acid, acid-enzyme, or enzyme-enzyme), the extent to which the hydrolytic reaction is allowed to proceed, and the type of enzyme(s) used. The fact that most starches consist of two different kinds of polymers... 

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