Selective production of even-numbered bio-alkanes from fatty acid methyl esters via cascade hydrogenation over Cu-ZnO/γ-Al2O3 catalysts

초록

The selective conversion of fatty acid methyl esters (FAMEs) into even-numbered paraffins remains a fundamental challenge, since conventional deoxygenation catalysts promote hydrodeoxygenation alongside decarbonylation or decarboxylation pathways, thereby producing both even- and odd-numbered hydrocarbons. Here, we demonstrate that a noble-metal-free Cu-Zn/gamma-Al2O3 catalyst, rationally designed to integrate hydrogenation and dehydration functionalities, enables a cascade reaction pathway that selectively produces even-numbered nparaffins from FAMEs. Under high-pressure hydrogen, methyl laurate is sequentially converted through aldehyde and alcohol intermediates, followed by dehydration to alpha-olefins and subsequent hydrogenation to paraffins. Detailed product analysis reveals that Cu-Zn sites catalyze efficient hydrogenation, while moderate Lewis acidity of gamma-Al2O3 promotes alcohol dehydration without inducing excessive cracking, thereby preserving the carbon backbone. As a result, the Cu[1.5]-Zn[3]/gamma-Al2O3 catalyst achieves near-complete conversion with an evenparaffin yield approaching the practical upper limit reported for FAME hydrogenation. Systematic variation of Cu-Zn loading and support textural properties establishes a clear structure-function relationship: increasing surface coverage by Cu-Zn species shifts selectivity toward fatty alcohols, whereas balanced dispersion on alumina favors completion of the dehydration-hydrogenation cascade. The catalyst maintains high performance in shaped form and demonstrates scalability in continuous bench-scale operation using soybean-oil-derived FAMEs. These results identify controlled integration of hydrogenation sites and moderate acidity as a general design principle for producing even-numbered paraffins from renewable lipid feedstocks without noble metals.

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