Sulfur Migration and Transformation Mechanisms during Catalytic Pyrolysis of Oil-based drilling cuttings with Metal Oxides.

Authors

Xiangle Chen, Quanwei Lv, Wenrou Yu, Li'ao Wang

Published in

Environmental research. Pages 125572. Aug 28, 2026. Epub Aug 28, 2026.

Abstract

Oil-based drilling cuttings (OBDC) is a hazardous waste with significant resource potential; however, its high sulfur content poses serious environmental risks and compromises product quality during pyrolysis. This study investigated the migration and transformation mechanisms of sulfur compounds in the catalytic pyrolysis of OBDC using CaO, MgO, and Fe₂O₃, with particular attention to the effects of pyrolysis temperature (400-600 °C) and catalyst loading (2-10 wt%). Results found that sulfur in the raw OBDC was predominantly organic (84.32%), with thiophenic sulfur accounting for the largest fraction (40.14%). Increasing pyrolysis temperature enhanced sulfur release into gas and liquid phases, and H₂S and SO₂ emissions increased markedly at 600 °C. The three metal oxides exhibited distinct regulatory effects on sulfur distribution: Fe₂O₃ and CaO promoted sulfur retention in solid residues by capturing sulfur-containing intermediates to form stable metal sulfides, thereby reducing sulfur in the oil and gas fractions; MgO, in contrast, facilitated sulfur migration into the liquid phase while suppressing SO₂ emissions. Higher Fe₂O₃ and CaO loadings effectively reduced H₂S release, with Fe₂O₃ demonstrating greater desulfurization activity than CaO. At 10 wt% loading, Fe₂O₃ reduced H₂S emissions by 82.48% and achieved 81.12% solid-phase sulfur retention, outperforming CaO (89.4% H₂S reduction and 80.38% solid-phase sulfur retention at the same loading). XPS and XRD analyses confirmed that metal oxides accelerated thiophene ring decomposition and promoted the conversion of organic sulfur to inorganic sulfides and sulfates. A horizontal comparison revealed that the sulfur-fixation capacity follows the order Fe₂O₃ > CaO > MgO for solid-phase retention, while MgO is the most effective for SO₂ suppression. These findings clarify the sulfur evolution pathways during OBDC catalytic pyrolysis and provide a theoretical basis for the clean and high-value utilization of OBDC using low-cost metal oxide catalysts.

PMID:
42665247
Bibliographic data and abstract were imported from PubMed on 29 Aug 2026.

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