Zeolite-Y encapsulated VO[2-(2′-hydroxyphenyl)benzimidazole] complex: investigation of its catalytic activity towards oxidation of organic substrates

Abstract

Zeolite-Y encapsulated VO(IV)2-(2 0 -hydroxyphenyl)benzimidazole (ohpbmzl) was synthesized by flexible ligand approach and characterized using various physico-chemical techniques such as elemental analysis, XRD, inductively coupled plasma-atomic emission, fourier transform infrared spectroscopy, UV-vis-diffuse reflectance and electron paramagnetic resonance spectroscopy, thermogravimetric analysis, BET surface area and cyclic voltammetry (CV). Based on the results a square pyramidal structure was suggested for the encapsulated complex. Shift in UV absorbance to higher wavelength and variations in the redox potential values compared to the nonencapsulated complex in CV confirmed the successful encapsulation of the complex in the zeolite matrix. The catalytic efficacy was investigated towards oxidation of phenol, styrene, cyclohexane and ethyl benzene in acetonitrile using H 2 O 2 as oxidant. Influence of reaction parameters like catalyst and substrate concentration, substrate/H 2 O 2 molar ratio, and temperature were investigated to optimize the reaction conditions for maximum substrate conversion and selectivity towards desired products using the encapsulated complex. The catalytic activity was compared with vanadyl exchanged zeolite-Y (VO-Y) and non-encapsulated complex. The encapsulated complex retained its stability up to 3 runs as confirmed by recycling studies. Mechanistic pathways were proposed for all the probe reactions.

Advanced electron paramagnetic resonance in chemical energy conversion: current status and future potential

“…Other transition metals. Other transition metal catalysts such as Mn, 90,91 Ni, [92][93][94] Ru, 63,95 V, 96,97 and Pt 98 are also accessible using EPR. EPR can probe various oxidation states of Mn ions (Mn 2+ , Mn 3+ , Mn 4+ , and Mn 5+ ) 91 and can be used to detect Ni + which has been found to correlate with the high efficiency of nickel-based catalysts.…”

“…69 EPR can also detect the +3 and +5 oxidation states of Ru, with the latter correlated with higher rates of electrocatalytic hydrogen generation in catalytic materials such as Ru/TiO 2 . 63 EPR has also been used to characterize the metal oxidation state of VO 2+ 96 and BiVO 4 , 97 and for platinum-based catalysts. 98…”