Preparation and Characterization of Nb2O5/C-CNT Catalysts for the Selective Oxidation of Cyclopentene to Glutaraldehyde

A series of niobium-based catalysts with carboxylated multi-walled carbon nanotube (C-CNT) as support were prepared by modified wet-chemical technique under ultrasonication. Three types of catalysts with active component niobium attached only on the inner or outer walls respectively, or mainly on the outer walls were obtained by adjusting the impregnation strategies. The catalysts were characterized systematically by SEM, TEM, XRD, Raman, FT-IR, XPS, and N-2 adsorption-desorption. It was found that niobia species was highly dispersed on the outer wall or the channels of C-CNT. There are abundant oxygen-containing groups on the catalysts. Strong chemical interactions between the support and Nb2O5 are evident. The catalytic performances of the C-CNT-supported catalysts were evaluated for the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA) with 30 wt% aqueous H2O2 as oxidant. The conversion of CPE and the selectivity to GA reached 98.3% and 59.3% respectively under the optimized conditions. No significant deterioration of the catalytic performance was found in the catalyst-cycling experiments, indicating the stability of the catalyst. Hot filtration experiments revealed that the catalytic reaction was heterogeneous. The good performance of the catalyst in ethanol makes the catalytic system of an excellent application prospect. [GRAPHICS]