A new oxygen-free HTC pyrolysis reactor – first insights and results

Numerous compound-specific isotope analyses (CSIA) methods have been developed and applied in various scientific fields during the last decades. Many of them focus on the carbon and hydrogen isotopic composition of lipid biomarkers. By contrast, albeit commercially available for about 20 years (e.g. Hener et al., 1998), compound-specific δ¹⁸O analyses are hitherto hardly applied and thereby almost exclusively focus on sugar biomarkers (Bittner et al., 2022; Zech & Glaser, 2009). This can be explained with analytical challenges associated also with the commercially available δ¹⁸O HTC pyrolysis reactor (Hitzfeld et al., 2017). Still, the oxygen isotopic composition of e.g. oxygenated lipids has large potential to improve our scientific knowledge in various fields (palaeo-environmental science, forensics, biogeochemical cycles). The current δ¹⁸O HTC reactor is build up by an aluminium oxide ceramic tube containing a Pt tube fitted with several Ni wires. However, at high temperatures, oxygen diffuses through the Pt (Velho & Bartlett, 1972) and the oxygen-aluminium ceramic is a potential source of oxygen contamination. Additionally, neither the life-time nor the performance of these reactors is convincing and therefore alternatives are eagerly awaited.
Here we present a new oxygen-free ceramic HTC pyrolysis reactor design without Pt tube, Ni wires, shielding gas, reactor conditioning or tricky balance of hydrogen and graphite. We present first results of the application of various compounds.