Oleic acid decarboxylation to produce C8-C17 alkanes catalyzed by Pt and Ni on a MOF-derived zirconia

Abstract

UiO-66 specimens having different acetic acid/ZrCl₄ molar ratios were prepared and pyrolyzed to ZrO₂ as supports for Pt and Ni, intended to catalyze the decarboxylation of oleic acid. Brunauer-Emmett-Teller surface area analyses, NH₃ temperature-programmed desorption and pyridine adsorption infrared spectroscopy showed that the material made using an acetic acid/ZrCl₄ molar ratio of 100 (ZrO₂-100) had the largest specific surface area, acid amount and acid strength values. The yield of C₈-C₁₇ alkanes obtained from Ni/ZrO₂-100 exceeded that provided by Pt/ZrO₂-100 because the latter possessed more acidic sites than the former, which excessively cracked long-chain hydrocarbons. The 1 wt% Ni/ZrO₂-100 catalyst showed the best catalytic performance, with 96.4% conversion of oleic acid and an 80.6% yield of C₈-C₁₇ alkanes after 4 h at 340 °C under a CO₂ atmosphere at a pressure of 18 bar. The conversion of oleic acid remained almost unchanged after 4 reuses of this catalyst whereas the yield of C₈-C₁₇ alkanes decreased to 66.7%. This result is attributed to a loss of acidic sites and an increase in carbon build-up.