UiO-66 specimens having different acetic acid/ZrCl 4 molar ratios were prepared and pyrolyzed to ZrO 2 as supports for Pt and Ni, intended to catalyze the decarboxylation of oleic acid. Brunauer-Emmett-Teller surface area analyses, NH 3 temperature-programmed desorption and pyridine adsorption infrared spectroscopy showed that the material made using an acetic acid/ZrCl 4 molar ratio of 100 (ZrO 2 -100) had the largest specific surface area, acid amount and acid strength values. The yield of C 8 -C 17 alkanes obtained from Ni/ZrO 2 -100 exceeded that provided by Pt/ZrO 2 -100 because the latter possessed more acidic sites than the former, which excessively cracked long-chain hydrocarbons. The 1 wt% Ni/ZrO 2 -100 catalyst showed the best catalytic performance, with 96.4% conversion of oleic acid and an 80.6% yield of C 8 -C 17 alkanes after 4 h at 340 °C under a CO 2 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 C 8 -C 17 alkanes decreased to 66.7%. This result is attributed to a loss of acidic sites and an increase in carbon build-up.
An in situ encapsulation process was used to prepare ordered worm-like mesoporous Pt@SAPO-11 catalysts with different Pt loadings. Transmission electron microscopy images showed that Pt nanoparticles encapsulated within the SAPO-11 support mesopores were uniformly distributed and highly dispersed and had a narrow particle size distribution of 2–7 nm. Scanning electron microscopy indicated that increasing the Pt loading from 0.6 to 1.6 wt % did not significantly change the crystalline morphology of the catalyst, although the crystallinity decreased slightly. The specific surface area and average pore diameter of the Pt@SAPO-11 were in the ranges of 72–116 m2/g and 8.1–9.5 nm, respectively, which are determined by the Brunauer–Emmett–Teller method and Barrett–Joyner–Halenda method, respectively. The NH3 thermal-programmed desorption established that increasing the Pt loading gradually decreased the total NH3 desorption and that a loading of 1.2 wt % produced the highest concentration of medium-strong acid sites (6.2 cm3/g STP). X-ray photoelectron spectroscopy and H2 temperature-programmed reduction showed that a Pt loading of 1.2 wt % gave the strongest interaction between Pt nanoparticles and the SAPO-11 support. The Pt@SAPO-11 catalysts were used for the preparation of C8–C17 alkanes by decarboxylation of oleic acid. Employing a reaction temperature of 340 °C, a CO2 atmosphere, a Pt loading on the catalyst of 1.2 wt %, and a reaction time of 4 h, 100% oleic acid conversion was obtained together with an 80% yield of C8–C17 alkanes.
A series of mesoporous Pt@SAPO-11 catalysts with different Pt loadings were prepared using an in situ encapsulation process. These materials exhibited good topological structures and high Brunauer–Emmett–Teller (BET) surface areas (132–166 m2 g−1). Transmission electron microscopy images showed that the Pt nanoparticles in this material were in the 5–8 nm size range and were highly dispersed on the inner surfaces of the SAPO-11 support. N2-BET analyses demonstrated that the samples had mesoporous structures with average pore sizes of 7.3–8.5 nm. Characterization of the 1.0 wt% Pt@SAPO-11 catalyst by X-ray photoelectron spectroscopy and H2-temperature programmed reduction indicated strong interactions between the Pt nanoparticles and the carrier. This material was used to promote oleic acid decarboxylation under CO2 and gave a C8–C17 alkane yield of 80.8% after 4 h at 340 °C. After five repeated uses, the catalyst still gave a yield of 77.6%.
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