Clay-induced oil loss and alkene isomerization during oil shale retorting

Sunnyside (Utah) tar sand was subjected to programmed temperature pyrolysis and the volatile products were detected by tandem on-line mass spectrometry (MS/MS) in real time analyses- A heating rate of 4°C/min from room temperature to 900°C was employed. Evolution of hydrogen, light hydrocarbons, nitrogen-, sulfur- and oxygen-containing compounds was monitored by MS or MS/MS detection. Evolution of volatile organic compounds occurred in two regimes: 1) low temperature (maximum evolution at 150 to 175°C) , corresponding to entrained organics, and 2) high temperature (maximum evolution at 440 to 460°C) , corresponding to cracking of large organic components. The pyrolysis yields were dominated by the evolution of light hydrocarbons. Alkanes and alkenes of two carbons and higher had temperatures of maximum evolution at approximately 440°C, and methane at approximately 474°C. Aromatic hydrocarbons had temperatures of maximum evolution slightly higher, at approximately 450°C. Comparing the Sunnyside pyrolysis to the pyrolysis of other domestic tar sands indicated the following for hydrocarbon evolution: 1) the evolution of entrained organics relative to the total evolution was much less for Sunnyside tar sand, 2) the temperatures of maximum evolution of hydrocarbons due to cracking reactions were at slightly lower, and 3) the temperatures of maximum evolution for benzene and toluene are slightly higher than observed for other tar sands. In general, the noncondensible gases, H2, CO, and CO2, exhibited evolution associated with hydrocarbon cracking reactions, and high temperature evolution associated with mineral decomposition, the water-gas shift reaction, and gasification reactions. Compared to other domestic tar sands, the gas evolution reflected more mineral decomposition character for Sunnyside tar sand.