Long time, low temperature pyrolysis of El-Lajjun oil shale

There is continuing interest in in situ production of oil from oil shale, particularly for deep deposits and for environmental reasons. Such production would involve long-time, low temperature pyrolysis. Accordingly, reactions of El-Lajjun oil shale have been carried out under N-2 for 7,14 and 28 days at temperatures in the range 240-320 degrees C. The conversion plateaued at 300 degrees C and above at a value of about 80 wt% dmmf and was the same for 7 and 14 day pyrolysis. The total conversion decreased by 15% as the temperature decreased to 280 degrees C. The lower conversions at 240 and 260 degrees C were the same for 14 and 28 days but oil yield increased at the expense of asphaltene for the longer time. Sulfur content of the oil + asphaltene decreased with increasing reaction temperature (240-300 degrees C) and time (280-300 degrees C) from 13 wt% to a plateau of about 7 wt%. The characteristics of the oil and oil + asphaltene changed steadily with temperature up to 300 degrees C, but increasing the temperature further to 320 degrees C had little effect. The results show that high conversion to products of good characteristics can be obtained for reactions at sufficiently long times at temperatures as low as 300 degrees C.