Cashew nut shell liquid conversion into renewable marine-range cycloalkanes: In situ activation of Ru/NbOPO4 catalysts for efficient hydrodeoxygenation

The continued reliance on conventional marine fuels significantly contributes to sulfur oxide (SO x ) emissions, creating persistent challenges for environmental and regulatory initiatives aimed at combating climate change. Despite increasing pressure to reduce these emissions, viable alternatives to fossil marine fuels remain limited. In this context, the use of renewable hydrocarbons derived from waste feedstocks offers a promising opportunity to advance the decarbonization of the maritime transport sector. This study explored solvent-free hydrodeoxygenation (HDO) of cashew nut shell liquid (CNSL) to produce marine-range cycloalkanes over Ru/NbOPO 4 catalysts, with varying Ru loadings. The findings demonstrated complete CNSL HDO, achieving 100% hydrocarbons selectivity with yields exceeding 89 wt%, independent of Ru loading. The in situ activation of RuO 2 nanocrystals generated larger metallic Ru 0 nanocrystals, which facilitated both aromatic ring hydrogenation and C–O bond hydrogenolysis, resulting in high yields of long-chain cycloalkanes. The heavier cycloalkane fractions (C 21 –C 23 ) possess properties suitable for marine fuel applications, such as high cetane index and flash point, highlighting their potential as renewable bunker fuels. Collectively, these results support a promising strategy for producing marine-range hydrocarbons from waste phenolic feedstocks. This process may contribute to decarbonizing the maritime sector and address environmental challenges posed by the improper disposal of cashew industry waste.