| Coal-liquefaction catalysts suffer from massive deactivation resulting from coke and metal deposits. Problems associated with catalytic coal liquefaction on an experimental scale include non-uniform catalyst deactivation, gradients in temperature and concentration, line plugging and difficulty conducting long-term experimental runs. The catalytic coal liquefaction microreactor solved these problems. It was designed, built, and successfully used to hydrotreat raw creosote oil, to screen new catalysts, and to liquefy both untreated and acid-washed coal. This reactor employs an ebullated catalyst bed and has high internal recycle rates. Uniform catalyst deactivation and gradientless operation resulted.; A catalyst specifically designed to liquefy coal, Amocat 1A, was promoted with calcium, lithium, sodium and potassium. These metals, especially potassium, lowered surface acidity. Liquefaction conversions increased for all metals excluding the cyclohexane conversion of the calcium promoted Amocat 1A run. The potassium promoted Amocat 1A significantly outperformed the base-line run for toluene and pyridine conversions. Coke contents varied randomly with promoter.; Preliminary liquefaction runs showed that a shell of calcite grew on the catalyst periphery with time. To reduce shell formation, calcium was leached from the coal with a dilute solution of nitric acid. Several acids were tested and nitric acid gave the highest and most reproducible calcium reductions, although the oxygen content of the coal increased. The acid-washed coal was liquefied to determine thermal activity and catalyst longevity. The spent catalyst from the acid-treated coal-liquefaction run had a lower shell thickness, 13 {dollar}pm{dollar} 5 {dollar}mu{dollar}m, as compared to the shell on the catalyst used while processing untreated coal, 44 {dollar}pm{dollar} 5 {dollar}mu{dollar}m. In addition, the new shell consisted mostly of iron and appeared porous when viewed through an electron microscope. Overall liquefaction activity increased mainly from higher thermal activity. Although the formation of the shell was inhibited, the other major deactivation mechanism, coking, still reduced liquefaction activity to thermal levels after twenty days of service. |
