Aerobic oxidation of primary amines into corresponding nitriles over MnxCe1-xOs catalysts prepared by co-impregnation method
Graphical abstract
Mn-Ce mixed oxides catalysts with different Mn/Ce molar ratio were prepared and used in the oxidation of primary amines to corresponding nitriles. The formation of Mn0.67Ce0.33Os solid solution between CeO2 and MnOx can greatly reduce the formation energy of oxygen defects and facilitate the mobility of oxygen species from the bulk to the surface, this leads to the Mn0.67Ce0.33Os sample showing the best catalytic performance.
Introduction
Nitriles are important industrial intermediates, used to produce various polymers [1]. Nitriles are generally prepared by either nucleophilic substitution of halogenated hydrocarbon with cyanide ions, ammonia oxidation, or the Sandmeyer reaction [2]. These traditional methods usually require dangerous chemical reagents and stringent reaction conditions. This has motivated the exploration of new strategies to produce these commodities. Various methods have been developed for the synthesis of nitrile derivatives, the most direct of which is aerobic oxidation of amines [3]. Recently, the conversion of amines to nitriles has attracted the attention of researchers, several favorable results have been obtained. Metal-based oxidants [4] and noble metal catalysts such as Ru [5], [6] and Au [7] have been reported, these processes often lead to the production of wastes. Although the addition of noble metal can improve the reaction activity, their high costs may limit their application. It is more reasonable to use molecular oxygen as sole oxidant from the consideration of green and sustainable chemistry [8].
A redox transformation between Ce3+ and Ce4+ in ceria and the high mobility of absorbed oxygen enables the formation of oxygen vacancies [9]. This promotes the activation and transportation of oxygen species, and leads to the high oxygen storage capacity of ceria [10]. Many reports have shown that adding a second metal to the ceria can effectively improve its activity in oxidation reactions [11], [12]. The incorporation of manganese has been shown to improve the thermal stability as well as redox properties due to the formation of an efficient redox couple [13]. Synergistic interactions between MnOx and CeO2 can supply more active oxygen species [14], making Mn-Ce mixed oxides very attractive in various catalytic applications, such as hydrocarbons oxidation, combustion of volatile organic compounds and CO oxidation [14], [15], [16].
Herein, we have synthesized Mn-Ce mixed oxides catalysts, as well as the singular oxides via a co-impregnation method. We have investigated their catalytic performances for the oxidation of benzylamine, and obtained the most active catalyst Mn0.67Ce0.33Ox. This catalyst has achieved excellent catalytic results in the oxidation of several kinds of amines to corresponding nitriles. As far as we all know, it is the first time to report the aerobic oxidation of primary amines into corresponding nitriles over Mn-Ce mixed oxides.
Section snippets
Materials and methods
Ce (NO3)3·6H2O, Mn (CH3COO)2·4H2O, and Na2CO3, were purchased from Aladdin Industrial Corporation. Mn-Ce mixed oxides with different Mn/Ce mole ratios were prepared (respectively as 1:2, 1:1 and 2:1) through a modified co-impregnation method [11], [17]. In a typical procedure, a certain amount of Ce(NO3)3·6H2O and Mn(CH3COO)2·4H2O was dissolved in 20 ml H2O and titrated to pH 10 with 1 M Na2CO3, and the solution was stirred at room temperature for 40 min. The resulting solids were filtered, washed
Optimization of reaction conditions
The oxidation of benzylamine was chosen as a model reaction to determine the optimal reaction conditions (Table 1). Firstly, the reactions were performed over various catalysts in acetonitrile solvent (Table 1, entries 1–5). Mn0.67Ce0.33Os gave the highest conversion and 100% benzonitrile selectivity with 0.5 h (Table 1, entry 5). In addition, both the MnOx and CeO2 exhibited poor activity on benzylamine even with 1 h (Table 1, entries 1 and 2). Higher conversion was observed using oxygen as
Conclusions
A series of Mn-Ce mixed oxides, pure MnOx, and CeO2 were prepared by a co-impregnation method and used in the aerobic oxidation of primary amines to the corresponding nitriles, which has achieved favorable conversion and selectivity. Mn-Ce mixed oxides exhibited better catalytic activity than MnOx or CeO2. When the mole ratio of Mn/Ce was 2:1, the catalytic activity of Mn-Ce mixed oxides showed the best catalytic performance, this catalyst can be used for five times without any loss of
Acknowledgements
This work is financially supported by the National Natural Science Foundation of China (21303085), the Natural Science Foundation of Jiangsu Province (BK20130901, BK20130930), the Program to Cultivate Outstanding Young Key Teachers of Nanjing Normal University, Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX17-1087) and the Priority Academic Program Development of Jiangsu Higher Education Institutions.
References (58)
- et al.
Tetrahedron Lett.
(1968) - et al.
Catal. Today
(2000) - et al.
J. Catal.
(1998) - et al.
Catal. Today
(2013) - et al.
J. Rare Earths
(2009) - et al.
Appl. Catal. B: Environ.
(2008) - et al.
Catal. B: Environ.
(2015) - et al.
J. Catal.
(2007) - et al.
Appl. Catal. B: Environ.
(2016) - et al.
Appl. Catal. B: Environ.
(2013)
Mater. Chem. Phys.
Appl. Surf. Sci.
Appl. Catal. A: Gen.
Colloids Surf. A: Physicochem. Eng. Asp.
Catal. Today
Spectrochim. Acta Part A: Mol. Biomol. Spectrosc.
J. Catal.
J. Rare Earth
J. Catal.
Chem. Eng. J.
Catal. Today
Appl. Catal. A: Gen.
Catal. Commun.
Microporous Mesoporous Mater.
J. Alloys Compd.
Catal. Today
Chem. Eng. J.
J. Catal.
ACS Catal.
Cited by (16)
Solvent-free toluene aerobic selective oxidation over Co(OH)<inf>2</inf>/Cr<inf>2</inf>O<inf>3</inf>:The effect of calcination temperature on product selectivity
2022, Applied Catalysis A: GeneralCitation Excerpt :We can clearly see the change of crystal plane before and after calcination. As shown in Fig. 5a, uncalcined catalyst shows only one lattice fringe with a lattice spacing of 0.25 nm, corresponding to the crystal plane of Cr2O3 [34,35]. The catalyst calcined at 500 °C showed a lattice with a lattice spacing of 0.43 nm, which is determined to be the crystal plane [36] of Co3O4, thus further confirms that Co(OH)2 after calcination at 500 °C is transformed into Co3O4 completely.
Highly selective oxidation of amines to imines by Mn<inf>2</inf>O<inf>3</inf> catalyst under eco-friendly conditions
2019, Chinese Chemical LettersControllable synthesis of novel nanoporous manganese oxide catalysts for the direct synthesis of imines from alcohols and amines
2019, Chinese Journal of Chemical EngineeringCitation Excerpt :The peak at 529.8 eV corresponded to the lattice oxygen atoms (O2−, denoted as Olatt); the peak at 531.3 eV was attributed to the surface adsorbed oxygen species (O2−, O22−, O−, denoted as Oads); the small peak at 533.0 eV was attributed to the adsorbed OH groups, molecular water and carbonate species (denoted as Osuf) [25,34]. M-350 and M-400 had the more adsorbed oxygen species (Table 2), implying the better catalytic activity for the organic oxidative reactions due to the mobility and availability of the surface adsorbed oxygen species [35]. By comparing Table 2, it was found that the higher the (Mn3+ + Mn4+)/Mn2+ ratio, the higher the content of surface adsorbed oxygen species was.
Rational design of CrO<inf>x</inf>/LaSrMnCoO<inf>6</inf> composite catalysts with superior chlorine tolerance and stability for 1,2-dichloroethane deep destruction
2019, Applied Catalysis A: GeneralCitation Excerpt :The appearance of Mn3O4 peaks in the LSMC samples can be contributed to the interaction between CrOx and LSMC, which results in the exposure of the Mn3O4 crystal phase. FTIR was also used to prove the formation of doped oxides as the vibration frequencies of metal-oxygen bonds are sensitive to be detected [36]. As displayed in Fig. S1, the broad band at around 600 cm–1 is assigned to the stretching vibration of O CO functional group in plane and out of plane bending modes [37].
Melamine-Schiff base/manganese complex with denritic structure: An efficient catalyst for oxidation of alcohols and one-pot synthesis of nitriles
2018, Journal of Colloid and Interface ScienceCitation Excerpt :Some methods have been reported for the one-pot conversion of alcohols to nitriles including the treatment of H5IO6/KI [16], NaIO4/KI [17], Ni2+/S2O82–/OH– [18], MnO2/MgSO4 [19], 1,3-diiodo-5,5-dimethylhydantoin or I2 [20], KI or I2/tert-butyl hydroperoxide (TBHP) [21], Ru(OH)x/Al2O3/air [22], trichloroisocyanuric acid [23], copper salts/(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)/O2 [15], I2 or t-BuOCl/TEMPO [24] with ammonia as a nitrogen source. Oxidative conversion of primary amines into the corresponding nitriles has also been studied well using MnxCe1−xOs [25], Pb(OAc)4 [26], AgO [27], cobalt peroxide [28], Co3O4-based catalysts [29], Cu/ N,N′-dimethylethylendiamine (DMEDA)/TEMPO [30], Cu(I) or Cu(II) with oxygen [31], RuCl3 and related Ru reagents [32], Ru/activated carbon [33] and trichloroisocyanuric acid with TEMPO [7]. However, most of applied catalysts for the oxidation of benzylamines to benzonitriles suffer from lack of selectivity due to various oxidation products (Scheme 1a).
Shape-Controlled MoO<inf>3</inf>/MnO<inf>x</inf> Nanocatalyst for the Selective Synthesis of 2-Phenylquinoxaline Drug Motifs
2023, ACS Applied Nano Materials