Exceptional Selectivity to Olefins in the Deoxygenation of Fatty Acids over an Intermetallic Platinum–Zinc Alloy

Direct deoxygenation of long-chain fatty acids can produce both saturated alkanes (C_n H_2n+2 ) and unsaturated olefins (C_n H_2n ). However, the selectivity for the production of olefins via the decarbonylation route is relatively low because of the more favorable decarboxylation pathway. We present an atomically ordered intermetallic PtZn alloy on carbon catalyst (PtZn/C) with a record-high total selectivity (97 %) for undecane (C₁₁ H₂₄ ) and undecene (C₁₁ H₂₂ ) in the deoxygenation of lauric acid (C₁₂ H₂₄ O₂ ). Interestingly, the selectivity for C₁₁ H₂₂ is as high as 67.0 % on PtZn/C, which is significantly higher than that of 27.5 % obtained on the Pt/C counterpart under the same reaction conditions. Characterization and theoretical calculation results reveal that the intermetallic PtZn alloy not only inhibits the decarboxylation route by increasing the energy barrier of -COO* cleavage, but also facilitates the decarbonylation route by decreasing CO desorption energy, and therefore the major product is switched from alkanes to olefins.