Decarboxylation of Oleic Acid Using Pt@SAPO-11 Catalysts Fabricated by In Situ Encapsulation

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.