Coal liquefaction process streams characterization and evaluation: The application of (sup 252)Cf-plasma desorption mass spectrometry to analysis of direct coal liquefaction heavy products

摘要

This study demonstrated the feasibility of using (sup 252)Cf PDMS, GPC, and MPLC for the examination of the tetrahydrofuran (THF)-soluble portion of distillation resid materials derived from direct coal liquefaction. The (sup 252)Cf-PDMS technique was used to determine molecular weight distributions of twenty-five THF-soluble resids. In order to detemine if (sup 252)Cf-PDMS responds differently to different chemical classes of compounds, Lehigh separated five of the samples into chemically distinct fractions by MPLC, then analyzed the parent samples, their fractions, and the re-mixed fractions by (sup 252)Cf-PDMS and GPC. Irreversible alteration of the samples upon separation was noted by Lehigh. This was confirmed by use of gas chromatographic (GC) analyses. The noted irreversible alterations prevented a direct comparison of the remixed materials and the original samples. Thus, the selective response of (sup 252)Cf-PDMS to different chemical classes of compounds could not be confirmed or ruled out. The number average molecular weights (M(sub n)) obtained by (sup 252)Cf-PDMS and GPC agreed well. However, the weight average molecular weights (M(sub w)) obtained by GPC are always higher than the corresponding (sup 252)Cf-PDMS results. Number average molecular weights and weight average molecular weights obtained with (sup 252)Cf-PDMS and GPC were compared with those obtained by field ionization mass spectrometry (FIMS), previously reported by SRI International for the parent resid samples from which the Lehigh THF-soluble samples were derived.