The distribution of nitrogen between bitumen, water and residue in hydrous pyrolysis of extracted Messel oil shale

Abstract

A series of simulated maturation experiments has been performed on a pre-extracted sample of the Messel oil shale. The nitrogen contents of the generated bitumen, the water phase and the residual organic matter have been determined to establish an overview of the distribution of nitrogen between the phases during the maturation process. Analysis of specific nitrogen species is reported for the aqueous phase. Here the nitrogen is found principally as ammonium ions, and the concentration increases linearly up to the highest temperatures where bitumen cracking processes start to dominate and cause a more rapid increase in the yield. The nitrogen concentration in the bitumen is more or less constant. The proportion of nitrogen to carbon in the residue increases with maturity, indicating that hydrocarbons are released preferentially in the thermal reactions of the kerogen. The mass sums of measured organic nitrogen show that the major contribution comes from the solid residue at all levels of simulated maturation.