Hydrogenation of lignite-derived ethanol solubles into potential jet fuels over a novel in-situ reduced NiMo/Al-LDH catalyst

Abstract

The thermal dissolution products of coal, rich in aromatic compounds, can potentially be converted into jet fuels through catalytic hydrogenation, offering an alternative to meet the rising demand for high-quality jet fuels. However, low conversion rates and insufficient cyclane content in the products limited the interest in this approach. Herein, four catalysts—NiMoS/γ-Al₂O₃, NiMoS/CSs, NiMoS/Al₂O₃, and NiMo/Al-LDH (layered double hydroxide) were prepared and tested for hydrogenating an ethanol-soluble portion (ESP) from lignite, with the cyclane content as the key indicator for jet fuel potential. The results show that the pore sizes of NiMo/Al-LDH and NiMoS/Al₂O₃ was larger than those of NiMoS/γ-Al₂O₃ and NiMoS/CSs. NiMo/Al-LDH achieved the highest cyclane content (21.7 %) under optimal conditions, making it the most effective for producing jet fuel-like products. The nickel in NiMo/Al-LDH was mainly in metallic form and NiMoO₄ and obvious electron transfer from Ni to Mo exists in the catalyst, while in NiMoS/γ-Al₂O₃ and NiMoS/Al₂O₃, it existed as sulfides. The use of in-situ reduction with NaBH₄, without calcination, allowed NiMo/Al-LDH to retain its layered structure and larger surface area, leading to superior dispersion of nickel and molybdenum. The unique layered structure and strong interaction between Ni and Mo should be responsible for the superior hydrogenation activity of aromatics in ESP.