Masahiro Kishino

Effects of organic acid pretreatment on the structure and pyrolysis reactivity of coals

Abstract Mild acid pretreatment was performed using aqueous acetic acid or methoxyethoxy acetic acid to remove bridging cations through oxygen functional groups and to improve the pyrolytic reactivity of three coals (Beulah-Zap, BZ; Wyodak, WY; Illinois #6, IL). The acid pretreatment removed ion-exchangeable cations such as Ca and Mg from lower ranking coals, and enhanced their swelling by pyridine, and increased their volatile yield in the flash pyrolysis. The CO/CO 2 ratio produced in the flash pyrolysis from lower rank coals increased by the acid treatment. The pretreatment liberates the cation-bridging network through the oxygen functional groups of coal. The acid treatment converts the carboxylates into their free carboxylic acids, enhancing the thermal decomposition into smaller hydrocarbons and their devolatilization through the pores. Acid treatment appears to loosen the π–π stacking and intensify the alkyl entanglement. The slow step scan XRD confirms the more influences of such treatments on the lower rank coals.

Hydrogen transferring liquefaction of some bituminous coals with hydrogenated fluoranthene under high temperature-short contact time conditions

Abstract Hydrogen transferring liquefaction using hydrogenated fluoranthene at high temperatures was very effective for three Japanese bituminous coals, with a total yield of oil and asphaltene > 85 wt%. The high temperature-short contact time conditions (480 °C for 10 min or 510 °C for 2.5 min) resulted in a total yield of > 90 wt% from the coal of lowest rank, with low consumption of hydrogenated fluoranthene. The oil yields were as high as 75 and 68 wt% at 480 °C and 510 °C, respectively. In contrast, the lower temperature of 450 °C appeared more effective in diminishing preasphaltene formation with the highest rank coal providing oil and asphaltene yields of 47 and 38 wt%, respectively. Longer times or higher temperature increased the oil yield but without reducing the preasphaltene. Higher temperature was found favourable for the formation of asphaltene of lower molecular weight. The reactivity of butiminous coals of different rank is discussed from the viewpoint of their structure.