2.3. Catalyst characterization
Small-angle X-ray powder diffraction (XRD) patterns were acquired on a Rigaku D/MAX-3B powder X-ray diffractometer with the Cu Ka radiation source of wavelength 0.154 nm. Fourier transform infrared spectra (FTIR) were recorded with a Shimadzu
IR-Prestige-21 spectrometer using KBr pressed powder discs. Scan- ning electron microscope (SEM) measurements were conducted with a field-emission microscope (JEOL, JSM-6390LV) using an accelerating voltage of 15 kV. Transmission electronic microscopy (TEM) images were recorded on a JSM-6390LV transmission electronic microscope.
The nitrogen porosimetry measurements were carried out on a Quantachrome NOVA 1000e instrument at liquid nitrogen temperature (-196 oC). The specific surface area was calculated following the Brunauer–Emmett–Teller (BET) method. The pore volume and pore size distribution were obtained by using the Bar rett–Joyner–Halenda (BJH) method applied to the adsorption branch of the nitrogen adsorption–desorption isotherm. Elemental analyses for C, H, and N were performed by Carlo-Erba 1106 elemental analyzer. The extent of biguanides loaded on the SBA-15 silica was measured by the elemental analysis.