Effect of coal rank on hydrocracking reactivities of primary coal extracts prepared in a flowing-solvent reactor - The Argonne premium coal sample set

Catalytic hydrocracking experiments were performed using 'primary' coal extracts, to establish correlations between coal rank and extract reactivities, in isolation from secondary effects associated with the coal dissolution step. A strong correlation was obtained between liquefaction conversion and carbon content of the original coals: R(2)=0.96. Strong correlations were also found between hydrocracking conversions of material boiling >450 degrees C in the extracts and carbon content: for 30 and 60 min hydrocracking reaction times, R(2)=0.92 and 0.93 respectively. The data indicate that the 450 degrees C b.p. material taken into solution during extraction of higher-rank coals is more difficult to hydrocrack. Large shifts were observed between s.e.c. profiles of liquefaction extracts and their corresponding hydrocracked (30 min) products, including the apparent disappearance of most material appearing under the excluded peaks. The extension of reaction time from 30 to 60 min gave rise to much less significant changes. U.v. fluorescence (u.v.-f.) spectra also showed that the first 30 min of hydrocracking gave rise to more significant structural changes than subsequent reaction did. The use of reaction times <30 min might allow more detailed information to be gleaned about the relative rates of coal extract hydrocracking as a function of coal rank. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-m.s.) was used to confirm (1) the presence of very large molecular mass materials in the extracts and (2) the very significant reduction in molecular masses achieved by the hydrocracking process. The results clearly show that in two-stage liquefaction processes, the overall yield of distillates (b.p. <450 degrees C) is strongly influenced by coal rank. Copyright (C) 1996 Elsevier Science Ltd.