Before catalyst characterization, the slurry catalysts were centrifuged,
extracted with petroleum ether for 2 d, and dried at room
temperature, and then the solid samples were obtained.
Powder X-ray diffraction (XRD) patterns were recorded on a
Rigaku D/M AX-2500 diffractometer.
The H2 temperature-programmed reduction (TPR) tests were
performed in TP-5000, using 5% H2/N2 gaseous mixture.
The surface areas of samples were carried out by N2 adsorption
at liquid nitrogen temperature 77K, using a Micromeritics Quanta
chrome instrument.
X-ray photoelectron spectroscopy (XPS) measurements were
conducted using an ESCALAB 250 spectrometer (VG Scientific Ltd,
UK) equipped with monochromated Al K (h = 1486.6 eV, 150W)
under ultrahigh vacuum (7 × 10−8 Pa).
The NH3 temperature-programmed desorption (NH3-TPD) was
carried out in a tubular reactor. The samples were saturated with
pure NH3 for 30 min and then flushed with He to remove all
physically adsorbed molecules. Afterward, the desorbed NH3 was
detected by an AMETEK mass spectrometer.