Influence of Pressure on Pyrolysis of Coal

The influence of pressure on the gas, liquid and solid products of coal pyrolysis has been investigated. The starting coal was Illinois #6, a high volatile bituminous coal (R o =.5%) obtained from the Argonne premium coal collection. Dry, confined pyrolysis was performed in sealed gold tubes at 300 °C and 340 °C and pressures ranging from 70 to 2000 bars for 72 hours. Results show the rates of gas and liquid product generation and solid maturation are influenced by pressure. At 300 °C and 340 °C, rates of vitrinite maturation and CH 4 and CO 2 gas generation increase with pressure to about 600 bars (R o =1.01% and 1.56%, respectively) and then decrease with further increase in pressure to 2000 bars (R o =.83% and 1.43%, respectively). The opposite trend is observed in the pristane/n-C17 ratio with pristane/n-C17 reaching a minimum at 600 bars. The carbon isotope fractionation observed in methane and CO 2 due to changing pressure is less than .2 ‰. These results suggest that although the effect of pressure on organic maturation is secondary, neglecting it could lead to errors in the interpretation of maturity based on vitrinite reflectance and influence the modeling of hydrocarbon generation in a basin.