Short-contact-time solvent composition

The significance of these calculations is that lower rank coals will require 5% lower conversion than higher rank coals for a given end product. Also, the more severe a coal is to be upgraded, the lower its conversion has to be in the initial phases of liquefaction. One very pertinent question to be addressed is whether or not coals can be converted to the levels shown in Figure 5 in a short contact time process. This paper will deal with that question as well as what compositional features of the coal and the solvent influence short contact time conversions. 

Effect of Solvent Composition of Short Contact Time Conversions ... 

As discussed above, the composition of the solvent used in short contact time conversions can be important. The concentration of H-donors is one factor to be considered. It is known that in long contact time conversions, solvents having high H-donor contents have a better ability to prevent char formation as sulfur is removed from the SRC. Thus, higher yields of upgraded liquids are observed when solvents containing high concentrations of H-donors are used. 

The diene cyclization shown in Eqn. 2, has been reported to take place only over RhCl3 and Wilkinson s catalyst (ref. 6). We have found that it also occurs when run over supported Rh catalysts. The heterogeneously catalyzed reaction is particularly sensitive to the nature of the solvent used. With alcohols or other solvents which can adsorb on the catalyst, there is an apparent competition with the adsorption of the double bonds and the cyclization does not take place. In alkane solvents, which do not interact with the catalyst, the reaction occurs with reasonable facility. This cyclization is run routinely at 145°C in a flow system with a decane solution of 5 passing through a small column containing a Rh/Al2Oj catalyst. The product composition was related to the time 5 was in contact with the catalyst. With fast flow rates (short contact times) 6 was the primary product of the reaction but the isomerized species, 7 and 8, were produced when slower flow rates were used. This indicates that 6 was the primary product of the reaction but that it was isomerized over the catalyst to 7 and 8. 

The overall products of coal conversion can also vary when reacted with solvents of different compositions. A combination of data from our earlier studies using solvents containing 40% tetralin and data from this project shows that in general all of the CO production ceased by about Rs = 50 or in other words, the short contact time regime. 

Relationships between three extraction parameters—solvent composition, temperature, and particle size—can be determined from simple beaker tests. Raw material ground to the desired particle size is contacted with the chosen solvent at the chosen temperature in a beaker and mixed over time. Thief samples are removed at various time intervals and analyzed for the marker. At the completion of the test, the marc is separated from the extract, dried, and analyzed. (In instances when the phytochemical is heat sensitive, the marc can be analyzed wet and the assay calculated on a dry basis). Based on this information, the amount of marker remaining in the dry marc can be determined after correcting for the marker in the absorbed extract in the wet marc. From these data, the equilibrium relationship defined in Equation 11.1 can be determined, as well as the time it takes to reach maximum extraction. Conditions are changed to give a high equilibrium constant and a short extraction time to reach equilibrium. Based on this information, one can select the appropriate extraction equipment as well as the operating conditions to operate the equipment. 

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