Ferrocene addition for suppression of hydrogen sulfide formation during thermal recovery of oil sand bitumen

The occurrence of H2S during thermal recovery production becomes one of the biggest challenges. While various industrial processes can remove H2S at the surface, to prevent the formation of H2S in reservoir is much less successful. Ferrocene was chosen as the likely target reagent after a review of iron compound volatility and environmental considerations. To evaluate this, closed system gold tube pyrolysis experiments were conducted on an Athabasca oil sand at 350–650 °C to examine gas compositions with and without ferrocene addition. Slightly higher hydrocarbon gas yields have been observed from samples with ferrocene addition likely caused by ferrocene decomposition. Yields of carbon dioxide (CO2) are higher in plain oil sand samples before 550 °C but the trend was reversed afterwards with more CO2 being generated from ferrocene addition ones. H2S yields in samples without ferrocene increase from background value at 350 °C to the highest amount at 450 °C then disappear above 625 °C. Thermal decomposition of organosulfur compounds is supposed to be the main route for the occurrence of H2S in the sulfur-rich bitumen pyrolysis. Ferrocene is proved to be powerful H2S removal reagent as no H2S can be detected from ferrocene addition samples. The reactions of ferrocene with H2S may form iron sulfides, cyclopentadiene and hydrogen. Complete, rapid, and predictable reactions and inert reaction products make ferrocene as an ideal in situ H2S scavenger, while the potential for the deposition of metal sulfides may reduce the permeability. Ferrocene is widely available for industry, however, the unit cost has not been assessed in this study.