Isothermal oil shale pyrolysis. 1. Oil generation and composition at various pressures

A rich (250 I (59 gal) per ton) Green River oil shale was retorted in a helium atmosphere. Isothermal retort experiments from 375 to 500 °C were carried out at 78 kPa and 765 kPa. Oil was collected as a function of time and a comprehensive analytical procedure was developed and utilized to determine seven oil fractions: straight-chain pentane de-asphaltened dry whole oil (DDWO); solids; saturates (S); aromatics (A); olefins (0); ‘weak’ polars (WP); and polars (P). The objectives of this work were: (a) to develop data to show oil generation and composition at different temperatures and pressures under isothermal, isobaric conditions; (b) to determine the effect of pressure on total oil yield and product-oil composition. Total oil yield was reduced as the pressure was increased. Much of this reduction can be accounted for in the reduced amounts of polar compounds formed at higher pressure because the polar fraction comprises approximately 35–45 wt% of the DDWO. In general, the amounts of aromatics present increase, the amounts of olefins decrease, and the amounts of saturates and ‘weak’ polar compounds remain relatively constant with increased system pressure.