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Journal of Chemistry
Volume 2017, Article ID 2937108, 17 pages
https://doi.org/10.1155/2017/2937108
Research Article

Synthesis, Characterization, and Relative Study on the Catalytic Activity of Zinc Oxide Nanoparticles Doped MnCO3, –MnO2, and –Mn2O3 Nanocomposites for Aerial Oxidation of Alcohols

Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia

Correspondence should be addressed to Syed Farooq Adil; as.ude.usk@lidafs

Received 27 March 2017; Revised 22 May 2017; Accepted 6 June 2017; Published 12 July 2017

Academic Editor: Mohamed Afzal Pasha

Copyright © 2017 Mohamed E. Assal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Zinc oxide nanoparticles doped manganese carbonate catalysts [% ZnOx–MnCO3] (where = 0–7) were prepared via a facile and straightforward coprecipitation procedure, which upon different calcination treatments yields different manganese oxides, that is, [% ZnOx–MnO2] and [% ZnOx–Mn2O3]. A comparative catalytic study was conducted to evaluate the catalytic efficiency between carbonates and oxides for the selective oxidation of secondary alcohols to corresponding ketones using molecular oxygen as a green oxidizing agent without using any additives or bases. The prepared catalysts were characterized by different techniques such as SEM, EDX, XRD, TEM, TGA, BET, and FTIR spectroscopy. The 1% ZnOx–MnCO3 calcined at 300°C exhibited the best catalytic performance and possessed highest surface area, suggesting that the calcination temperature and surface area play a significant role in the alcohol oxidation. The 1% ZnOx–MnCO3 catalyst exhibited superior catalytic performance and selectivity in the aerial oxidation of 1-phenylethanol, where 100% alcohol conversion and more than 99% product selectivity were obtained in only 5 min with superior specific activity (48 mmol·g−1·h−1) and 390.6 turnover frequency (TOF). The specific activity obtained is the highest so far (to the best of our knowledge) compared to the catalysts already reported in the literatures used for the oxidation of 1-phenylethanol. It was found that ZnOx nanoparticles play an essential role in enhancing the catalytic efficiency for the selective oxidation of alcohols. The scope of the oxidation process is extended to different types of alcohols. A variety of primary, benzylic, aliphatic, allylic, and heteroaromatic alcohols were selectively oxidized into their corresponding carbonyls with 100% convertibility without overoxidation to the carboxylic acids under base-free conditions.