New mechanistic insight into the aerobic oxidation of methylaromatic compounds catalyzed by Co–Mn–Br and its applications

Oxidation of NMST to NMSBA catalyzed by Co/Mn/Br together with porous carbon made from coconut shell with acetic acid as an activator

In this paper, a heterogeneous catalytic system consisting of Co/Mn/Br/activated carbon is used to catalyze 2-nitro-4-methylsulfonyl benzoic acid (NMSBA) production from the oxidation of 2-nitro-4-methylsulfonyltoluene (NMST) by oxygen. The activated carbon (AC) is made from coconut shell with acetic acid as an activator. The experiments indicate that the best AC is made by immersing coconut shell in 12 mol L−1 HAc solution at 50 °C for 32 h with a liquid/solid ratio (mL/g) of 5:1 and then being heated in nitrogen at 800 °C for 6 h. Compared with the Co/Mn/Br/H3PMo12O40@CAC (CAC, commercial activated carbon originated from coconut shell) catalytic system, the Co/Mn/Br/AC catalytic system is able to gain much higher NMSBA selectivity. In spite of holding smaller surface and less acidic groups, the AC owns much more carboxyl than CAC, which is the main reason for its better performance in the preparation of NMSBA.

Manganese and Cobalt Doped Hierarchical Mesoporous Halloysite-Based Catalysts for Selective Oxidation of p-Xylene to Terephthalic Acid

Bimetallic MnCo catalyst, supported on the mesoporous hierarchical MCM-41/halloysite nanotube composite, was synthesized for the first time and proved its efficacy in the selective oxidation of p-xylene to terephthalic acid under conditions of the AMOCO process. Quantitative yields of terephthalic acid were achieved within 3 h at 200–250 °C, 20 atm. of O2 and at a substrate to the Mn + Co ratio of 4–4.5 times higher than for traditional homogeneous system. The influence of temperature, oxygen, pressure and KBr addition on the catalyst activity was investigated, and the mechanism for the oxidation of p-toluic acid to terephthalic acid, excluding undesirable 4-carboxybenzaldehyde, was proposed.

Efficient catalytic oxidation of methyl aromatic hydrocarbon with N-alkyl pyridinium salts

A series of N-alkyl pyridinium salts were synthesized and employed as metal-free catalyst for the selective oxidation of methyl aromatic hydrocarbon with molecular oxygen. The electronic effect of the substitutes was found to be an important factor for the catalytic performance. With the introduction of electron-donating substitute –N(CH₃)₂, the conversion of p-xylene and selectivity of p-toluic acid could be simultaneously increased. 1-Benzyl-4-N,N-dimethylaminopyridinium salt showed the highest catalytic activity, and 95% conversion with 84% of selectivity to p-toluic acid could be obtained for the selective oxidation of p-xylene. Several methyl aromatic hydrocarbons could all be efficiently oxidized with the reported catalyst at the absence of any metal species.

A series of N-alkyl pyridinium salts were synthesized and employed as metal-free catalyst for the selective oxidation of methyl aromatic hydrocarbon with molecular oxygen.

Synergistic effect between Cu–Cr bimetallic oxides supported on g-C3N4 for the selective oxidation of toluene to benzaldehyde

Supported Cu–Cr/g-C₃N₄ catalysts were prepared via an in situ heating treatment method for the selective oxidation of toluene to benzaldehyde.