A green process for chlorine-free benzaldehyde from the solvent-free oxidation of benzyl alcohol with molecular oxygen over a supported nano-size gold catalyst

Abstract

Benzyl alcohol is oxidized selectively to benzaldehyde with high yield, with a little formation of benzylbenzoate, by molecular oxygen over a reusable nano-size gold catalyst supported on U 3 O 8 , MgO, Al 2 O 3 or ZrO 2 in the absence of any solvent.Liquid phase oxidation of benzyl alcohol is an important preferred reaction practically for the production of chlorine-free benzaldehyde, without loss of carbon in the form of CO 2 (a geenhouse gas). The preparation of benzaldehyde by reacting benzyl alcohol with stoichiometric or excess amounts of potassium or ammonium permanganate in aqueous acidic medium 1 is not environmentally benign at all, because of the formation of a large amount of toxic waste. A few studies on the benzyl alcoholto-benzaldehyde oxidation by H 2 O 2 or O 2 in the presence of organic solvent, using different solid catalysts, such as Pd/C, 2 Pd(II) hydrotalcite, 3 Pd-Ag/pumice, 4 Ru-Co-Al hydrotalcite, 5 Ni-containing hydrotalcite 6,7 and nano-size NiO 2, 8 have been

Supported Nano-Gold Catalysts for Epoxidation of Styrene and Oxidation of Benzyl Alcohol to Benzaldehyde

“…amount of gold deposited), average particle size and distribution of particle size of the gold deposited on support were found to be strongly dependent upon the method of gold deposition (viz. impregnation, co-precipitation, DP and HDP) and metal oxide support used in the supported gold catalysts [37,[45][46][47][48][49][50][51][52][53]. The Au particle size and its distribution in the catalyst were also strongly influenced by the calcination temperature [52,65,66], whereas the presence of different surface Au species depends upon the support used in the gold catalysts [37,46,48,[67][68][69].…”

“…0.1 g catalyst, temperature = 130°C, pressure = 1.5 atm, and reaction time = 5 h) [51]. Among the supported nano-gold catalysts ( .…”

“…IIIA metal oxides [48], rare earth oxides [49], transition metal oxides [46,47] and uranium oxide [49,52] were prepared by depositing gold on these metal oxides using DP and/or HDP methods. These catalysts were characterized for their gold loadings, size and morphology of gold particles and evaluated for their performance in the epoxidation of styrene by TBHP [45][46][47][48][49][50]66] and also in the benzyl alcohol to benzaldehyde oxidation by molecular oxygen [51,52] or TBHP [53,67].…”

“…alkaline earth oxides, Gr. IIIa metal oxides, transition metal oxides, rare earth oxides and U 3 O 8 ), prepared by different methods for the liquid phase epoxidation of styrene by TBHP [45][46][47][48][49][50] and benzyl alcohol to benzaldehyde oxidation by molecular O 2 [51,52] or TBHP [53]. In this article, we have mainly covered the above studies from our group, while citing the important/relevant work from the other groups.…”

Supported Gold Nanoparticles Catalysts for Solvent-free Selective Oxidation of Benzylic Compounds into Ketones at 1 atm O2

“…Among the various reactions, selective oxidation of alcohols with or without solvents with supported gold nanoparticles has grabbed considerable attention due to their higher selectivity and lower susceptibility to leaching [23][24][25][26][27][28]. Moreover, it has been shown that the choice of a suitable metal oxide as support plays a crucial role in determining the catalytic activity and selectivity of the gold catalysts [29].…”