Optimization of key parameters for effective vanadium substitution into cubic SBA-16 in the presence of co-surfactant at low acidity: Application in the selective oxidation of ethylbenzene

摘要

Highly ordered three-dimensional V-SBA-16 materials were prepared at mild acidic condition by tuning the key parameters for metal substitution such as molar ratio of silica to 1-butanol (TEOS/BuOH), water to hydrochloric acid (H2O/HCl ratio) and hydrothermal aging time in the initial gel containing 0.0035 F127/0.01 V/0.91-2.00 TEOS/2.08-0.76 BuOH/0.70-1.16 HCl/118.6-120.1 H2O. The extent of mesopore structural ordering was confirmed by small-angle X-ray scattering and nitrogen adsorption isotherms. The presence of incorporated vanadium in a highly dispersed tetrahedral state was confirmed by electron spin resonance (ESR) and Drs-UV spectroscopy. The NH3-TPD profile showed that the materials tend to posses medium-acidic V-OH sites; strong-acidic sites increased with decreasing Si/V ratios. TEM analysis shows that the cubic phase was stable up to 3.6 wt.% vanadium loading. The activity of V-SBA-16 was tested for the selective oxidation of ethylbenzene to acetophenone by studying the effect of temperatures, time on stream, and the mole ratio of ethylbenzene to TBHP.