Abstract
Objectives: Alcohols oxidation is one of the important organic transformation in fine chemical industries. Prevailing processes are hazardous due to involvement of stoichiometric oxidants and homogeneous catalysts. In the present work, oxidation of cinnamyl alcohol was carried out using unconventional, affordable, and feasible heterogeneous catalysts.
Method: Copper-titania (Cu-Ti) nanoparticles were prepared and supported on functionalized multi walled carbon nanotubes (F-CNTs). Various instrumental techniques such as X-ray Diffractometery (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) Analysis and Brunauer Emmett Teller (BET) surface area analyzer were used to characterize the synthesized catalysts. Both catalysts; Cu-Ti and Cu-Ti/F-CNTs were evaluated for their potencies in conversion of cinnamyl alcohol (CnOH) to cinnamaldehyde (CnHO). Different derivatives of CnOH (with attached electron withdrawing and donating groups) were also oxidized in presence of prepared catalysts to determine the substituents effect and get maximum yield. The prepared catalyst was used five times to determine its reuseablity.
Results: The presence of copper and titania in the synthesized catalyst structure was confirmed through XRD and EDX analysis. The agglomeration level was confirmed from SEM analysis. Little reduction in surface area on parental carbon nanotubes was observed due to deposited metals. Appreciable yield of CnHO were obtained at the optimal reaction conditions: temperature = 70 degrees C, catalyst amount = 0.1 g, pO2 = 760 Torr, substrate solution concentration and volume = 1 mmol CnOH/10 mL ethanol, stirring speed = 900 rpm, and time interval = 60 min. The conversion rate was improved to 100% through attachment of electron donating groups at ortho and para position of parental compound benzene ring. No appreciable decrease in activity of catalyst were observed after 4th cycle.
Conclusion: Cu-Ti/F-CNTs showed excellent catalytic activity, selectivity, true heterogeneous nature, low cost, and recyclability, hence it could be used as a potent catalyst for CnOH to CnHO conversion. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license.