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New catalytic process to convert algae-derived squalane to high-quality transportation fuels

Researchers at Tohoku University in Japan, with a colleague at the University of Tsukuba, have devised a process to convert squalane, a C30 algae-derived branched hydrocarbon, to smaller hydrocarbons—without skeletal isomerization and aromatization—over ruthenium on ceria (Ru/CeO2). A paper on their work appears in the journal ChemSusChem.

The products were mainly n-alkanes for all of the tested active catalysts, and branched alkanes were hardly observed. This result is in contrast to those achieved over solid-acid catalysts, where branched alkanes are the main products through isomerization.

Liquid alkanes, which are important components of fuels and chemicals, are supplied by petroleum refining. Considering the diminishing reserves of crude oil, biomass, as renewable organic carbon resources, is expected to be a promising substitute. The production of liquid alkanes has been attempted from lignocellulose-derived substrates such as levulinic acid, furanic compounds, and cellulose. Some plants or micro organisms produce pure (bio)hydrocarbons, such as terpenes. One example is squalene (2,6,10,14,18,22-hexaen-2,6,10,15,19,23-hex-amethyltetracosane), high amounts of which have been reported to accumulate in Aurantiochytrium microalgae strains. Typically, biohydrocarbons, in particular algae-derived ones, are large molecules with many branches. While some amount of squalene (derived from sharks) has been used in cosmetics, biohydrocarbons need to be refined into smaller molecules formost other uses such as biofuel.

Conventional methods for refining large hydrocarbons typically use solid acids in combination with noble-metal catalysts, and many side reactions can occur such as isomerization or coke formation. Although isomerization is beneficial for fuel production from linear-alkane-based feedstock such as petroleum, isomerization is undesirable in the case of branched algal hydrocarbons and only complicates the reaction mixture.

Herein, we show that a Ru/CeO2catalyst can produce small alkanes from biohydrocarbons by regio-selective C—C hydrogenolysis, without isomerization and coke formation.

—Oya et al.

The key step in the process is the selective C—C dissociation at internal secondary-secondary bonds over ceria-supported sub-nanometer-sized Ru particles with hydrogen.

Resources

  • Oya, S.-i., Kanno, D., Watanabe, H., Tamura, M., Nakagawa, Y. and Tomishige, K. (2015) “Catalytic Production of Branched Small Alkanes from Biohydrocarbons,” ChemSusChem doi: 10.1002/cssc.201500375

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