Abstract
Silver oxide nanoparticles doped manganese carbonates and manganese oxide catalysts were synthesized via a simple co-precipitation approach, which upon calcination at temperatures such as 300 degrees C, 400 degrees C, and 500 degrees C, yields different manganese carbonate such as, [Ag2O(1%)-MnCO3] and manganese oxides [Ag2O(1%)-MnO2] and [Ag2O(1%)-Mn2O3]. Comparative catalytic study investigations were carried out to assess the catalytic efficiency between the carbonates and oxides for the selective oxidation of benzyl alcohol and 1-phenylethanol in presence of molecular oxygen as a green oxidizing agent without using other oxidants additives or bases. Different loadings of Ag2O(0-5% w/w) were doped in MnO2 support, amongst which Ag2O(1%)-MnO2 catalyst showed best catalytic performance. The influence of catalyst loading, reaction time, calcination temperature, catalyst amount employed, and reaction temperature have been entirely examined using oxidation of benzyl alcohol and 1-phenylethanol into benzaldehyde and acetophenone respectively. The Ag2O(1%)-MnO2 calcined at 400 degrees C exhibited the best catalytic activity and possessed highest surface area which suggests that the calcination treatment and surface area play a fundamental role in the oxidation process. A 100% conversion product with selectivity >99% was accomplished within relatively short reaction time 60 mins and 50 mins for benzyl alcohol and 1-phenylethanol oxidation respectively. It was also found that Ag2O nanoparticles perform a significant part in augmenting the catalytic activity for the aerobic oxidation of alcohols. Microscopic techniques such as SEM, EDX, TEM and spectroscopic techniques such as XRD, FT-IR, TGA, and BET were employed to characterize the synthesized catalysts. A variety of benzylic, aliphatic, allylic, heteroaromatic, primary, and secondary alcohols were selectively oxidized into their corresponding aldehydes and ketones with 100% conversion without any over-oxidation i.e., acids formation. The prepared catalyst could be recovered and reused five subsequent reaction cycles without discernible decrease in its catalytic performance and the selectivity remained almost unchanged.