Effect of oxygen on composition of light hydrocarbons evolved in oil shale pyrolysis

The changes in the absolute and relative levels of light alkane and alkene hydrocarbons evolved during the thermal degradation of oil shale have been studied with respect to pyrolysis atmosphere for milligram samples. Programmed temperature gas--solid chromatography on Spherocarb carbon molecular sieve gives effective resolution of alkane--alkene pairs up to the C/sub 5/ compounds. n-Alkane formation is favored over that of 1-alkenes under inert pyrolysis, but the alkane/alkene ratios decrease as the atmospheric oxygen content is raised to the 10% level. Thereafter they change relatively little up to 20% oxygen atmosphere. Absolute amounts of alkanes evolved increase up to a 5% oxygen level as do those of alkenes, which however exhibit the effect to a considerably greater degree. Absolute amounts of all the light hydrocarbon gases evolved decrease markedly above the 5% oxygen level. 7 figures, 1 table.