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.