Hydrogenative Liquefaction and Solvent Extraction of Illinois No. 6 Coal up to 60 MPa Pressure -Study on Coal Liquefaction. VIII.-

Abstract

Noncatalytic liquefactions of Illinois No.6 coal in tetralin and toluene-tetralin mixture were studied at residence time of 4 to 20 min by continuous flow method. Liquefied products were fractionated into unreacted coal, preasphaltene, asphaltene and oil in order to obtain the yield-time profiles. Chemical reaction engineering analysis was performed for those profiles using the model involving all possible pathways for the formation of preasphaltene, asphaltene and oil from coal. Pseudo-first-order rate constants for each of these mechanistic steps were estimated by nonlinear regression and were compared with those of Wandoan and Morwell coals described previously. In hydrogenative liquefaction at 450°C and 20 MPa, tetralin was unusually converted to isomer 1-methylindan which causes to lose the hydrogen-donor ability as shown in Fig.4. Therefore, noncatalytic reactions with tetralin (hydrogenative liquefaction)were mainly carried out at a temperature of 400°C and pressures of 20 to 60 MPa. The rate constant estimation shown in Table 3 indicated that Illinois No.6 coal liquefaction fairly proceeds via direct formation of asphaltene from parent coal. The largest pressure acceleration for the initial stage of dissolution of Illinois No.6 coal was observed as shown in Fig.8. Comparing with the results of solvent extraction by using toluene-tetralin mixture under the same experimental conditions, the reason for this is that Illinois No.6 coal contains characteristically a fairly large amount of the weak-linked macromolecule as asphaltene, this weakbonded fraction can be easily liquefied by extraction and such a physical process is also accelerated by pressure.