Acceptorless dehydrogenative synthesis of ketones from alcohols using carbon supported ni nano-catalyst

Abstract

Ketones are one of the most indispensable organic moieties found in pharmaceuticals, agrochemicals, and other fine chemical industries. In this study, I have shown the successful example of a reusable catalyst for dehydrogenation of secondary alcohol by Ni/AC (Activated carbon) catalyst. At first nickel sulfate was taken in a beaker and dissolved in distilled water to prepare a nickel sulfate solution. After that, activated carbon was added to the solution, and the mixture was heated for 15 min at 80 ℃ with stirring. This mixture was evaporated with an evaporator and dried in an oven for 6 h at 90 ℃. The solid mixture was then calcined for 2 h at 400 ℃. The supported precursors were reduced in a two-necked reaction flask fitted with a reflux condenser, heated in a sand bath at 80 ℃ with continuous stirring in the presence of N2H4.H2O and NaOH solution to maintain the desired pH of 10-12. The mixture was filtered after reduction and rinsed with distilled water and 99 percent ethanol. To obtain the desired Ni/AC catalyst, then it was dried in an oven at 110°C for 6 hours. Following the previous procedure to prepare Ni/Al2O3, Ni/TiO2, Ni/CeO2, Ni/Nb2O5 &Ni catalyst. Liquid phase chemical reduction method for Catalyst Preparation. In this method activated carbon was impregnated into NiSO4 solution with vigorous stirring at room temperature for 1 h. Then the resulting suspension was heated at 80 ℃ and stirred for 30 min. Then the solution of N2H4. H2O and NaOH were added to the suspension with stirring for 15 min. Then the filtration of the suspension and washed with distilled water with 99% ethanol. Then it was dried in an oven at 110 ℃ for 6 h to get the expected Ni/AC catalyst. Following the previous procedure to prepare Ni/Al2O3, Ni/TiO2, Ni/CeO2, Ni/Nb2O5 &Ni catalyst. Finally, it was characterized by several modern techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). Then the catalytic activity of the Ni/AC catalyst was checked by a model reaction. For the model reaction, 1-phenyl ethanol was mixed in a round bottom flask with the catalyst. Then the solvent was added to the reaction mixtures. Then the reaction mixture was heated in the presence of o-xylene reflux condition for 30 hrs. The progress of the reaction was monitored by thin layer chromatography (TLC) with an appropriate solvent ratio. Finally, completion of the reaction was confirmed by TLC. After completion of the reaction, the catalyst was separated from the reaction mixture by centrifugation, followed by washing with acetone, and dried at 100 ⁰C for 3h. The reusability was checked for the recovered catalyst. The product was purified by column chromatography. The synthesized pure ketone product was characterized by using FT-IR, 1H NMR, 13C NMR, and GC-MS. In conclusion, a novel, versatile and sustainable method was developed for the synthesis of ketones from 1-phenyl ethanol using Ni/AC heterogeneous catalyst. Keywords: ketone, Ni/AC Heterogeneous catalyst.