Coal liquefaction process streams characterization and evaluation. Characterization of coal liquefaction resids employing thermogravimetric analysis and electron spin resonance spectroscopy.

摘要

This study demonstrated the feasibility of using temperature-programmed electron spin resonance (ESR) and thermogravimetric analysis (TGA) for the examination of tetrahydrofuran (THF)-soluble distillation resid materials derived from direct coal liquefaction. TGA is used to quantitate volatile losses in a temperature-programmed experiment. The TGA data are used to correct the free radical densities obtained by ESR as volatile material is evolved from the samples in the temperature-programmed ESR experiment. The techniques, when employed in tandem, can be used to determine the content and nature of the free radicals in the samples at temperatures approximating those used in the liquefaction process. TGA and ESR experiments were performed in flowing nitrogen and hydrogen, at ambient pressure. No significant difference was observed in the ESR spectra in the different atmospheres, except in the case of low-rank coal-derived resids. The TGA results, however, were systematically different; mass loss in an H(sub 2) atmosphere is consistently higher than that observed in an N(sub 2) atmosphere. It was shown that temperature-programmed ESR, which can pinpoint conditions at which the free radical content is the highest, has potential to be a guide for the appropriate choice of conditions for optimum resid upgrading. Further development of these combined analytical methods as process development tools appears justified based on these results.