Effect of process variables in catalytic hydropyrolysis on the release of covalently bound aliphatic hydrocarbons from sedimentary organic matter

Hydropyrolysis has considerable promise for application as an analytical tool for release of biomarker hydrocarbons in high yields with minimal structural rearrangements. In this study, the effect of key reactor variables on the product yield and distribution of alkanes obtained from temperature-programmed fixed-bed hydropyrolysis of a Tertiary oil shale (Goynuk, NW Turkey, classified as a type I kerogen) and a Tertiary lignite (Hambach, Lower Rhine Basin, Germany) has been investigated. A combination of slow heating rate (5 °C/min), high hydrogen pressure (15 MPa), and use of a dispersed sulfided molybdenum catalyst represents the best regime for achieving high conversions to dichloromethane-soluble oil while minimizing the structural rearrangement of biomarker species. Staged hydropyrolysis has confirmed that hopanes released at higher temperatures through cleaving relatively strong bonds are quantitatively more significant than those released at lower temperatures. These findings have reinforced the unique ability of hydropyrolysis to maximize the yields of covalently bound alkanes while maintaining the biologically inherited 17β(H),21β(H) stereochemistries of the hopanes, largely intact, even for the lignite investigated.