Facile Synthesis of Titanium-Loaded MCM-48 as an Efficient Heterogeneous Catalyst for Selective Oxidation of Aniline to Azoxybenzene

Abstract

Synthesis of a series of Ti loaded MCM‐48 mesoporous materials have been reported. The formation of these materials with incorporated titanium into the mesoporous framework was confirmed using various characterization techniques. The catalytic activity of the synthesized materials was investigated for the selective oxidation of aniline to azoxybenzene in presence of H2O2 as the oxidant. Variety of substituted anilines gave the corresponding product in good yield under the optimized reaction condition. Reusability of the catalyst was also demonstrated upto 4th run with minimal loss in catalytic activity.

Niobium oxide prepared through a novel supercritical-CO2-assisted method as a highly active heterogeneous catalyst for the synthesis of azoxybenzene from aniline

“…It should be noted that other solvent-related factors might play a role too, including the radical quenching ability of solvents, 59 their interaction with the catalyst surface and their solvating and stabilising effects on reactants, intermediates and products. 25,28,60,61 Finally, the recyclability of the Nb 2 O 5 -scCO 2 catalyst in consecutive runs under the optimum reaction conditions was tested (Fig. S9 †), demonstrating that the catalyst fully retained its activity and selectivity in 4 consecutive runs (aniline conversion or azoxybenzene selectivity ±2%).…”

“…Ti-silicates (TS-1, 26,27 Ti-MCM-48, 28 TAPSO-5, Ti-HMS, and Ti-Beta 29 ) are the most common types of heterogeneous catalysts that have been reported for this reaction. They have been reported to activate H 2 O 2 by forming hydroperoxo species.…”

“…They have been reported to activate H 2 O 2 by forming hydroperoxo species. 23,28 Most of these Ti-based catalysts typically operate in the 50-70°C temperature range, while the TiO 2 pillared montmorillonite clays (∼60 wt% TiO 2 ) allowed the oxidation of aniline at room temperature (RT), reaching 50% aniline conversion with 99% azoxybenzene selectivity after 8 h with a weight ratio between the catalyst and substrate, R c/s = 0.02. 25 Other metal oxide catalysts such as Co-Si-oxide 30 and CuCr 2 O 4 31 were also reported to catalyse the oxidative coupling of aniline.…”

“…The above-mentioned catalytic systems achieve good performance but still have some limitations, which can be related to the synthesis of the catalysts (e.g. synthesis requiring expensive templates [26][27][28][29][30][31][32][33] or dangerous chemicals such as hexafluorosilicic acid 24 ) and/or to the employed conditions in which the oxidation of aniline is carried out (e.g. relatively high reaction temperatures, 23,24,26,28,29,31,33 problematic or hazardous solvents 26,27,[29][30][31][32][33] and/or high loading of the catalyst, e.g.…”

Phosphoric Acid Functionalized Nanostructured Heterogeneous Catalyst for Multicomponent Synthesis of 2‐Amino‐4H‐chromene

“…Among the heterogeneous catalysts, mesoporous materials show much attention to researchers due to their wide applications in catalysis, adsorption and synthesis of fine chemicals as they possesses high surface area, larger pores and narrow pore size distribution . Mobil Oil Corporation in 1992 first synthesized the class of mesoporous materials namely M41S .…”