Effect of synthesis media pH and gel separation technique on properties of copper incorporated SBA-15 catalyst

Abstract

Cu-SBA-15 catalysts were synthesized hydrothermally under acidic and slightly higher acidic conditions via solid separation by either gel filtration or evaporation. XRD (X-ray diffraction) patterns and HRTEM (high resolution transmission electron microscopy) images showed that metal loading caused little changes in the ordered structure of SBA-15. Characteristic structural SBA-15's bonds and acid sites were observed in FTIR (Fourier transform infrared) spectrums and synthesis under high pH was created changes in the ranges of silica and silanol groups. Copper incorporation created enhancements more in Lewis acid sites. Metal loading under severe acidic synthesis conditions resulted in improvements in the ordered structure in addition to increases in wall thickness while rise in its concentration caused little structural deterioration. Synthesis with slightly higher acidic conditions although gave a little higher d100 diffraction, caused little broadening of peak. Positive effects in copper incorporation success by separation through evaporation were supported by XRD, HRTEM images, SEM/MAP (scanning electron microscopy/mapping) and ICP-OES (inductively coupled plasma optical emission spectroscopy) analyses results; however its accumulation on pore walls did more worsening of textural properties. Formation of CuO, Cu2O and Cu3Si species after evaporation separation was observed with XRD, XPS (X-ray photoelectron spectroscopy) and UV–Vis DR (UV–visible diffuse reflectance) analyses.