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

Abstract

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.

Heterogeneous Dendrimer-Based Catalysts

“…In particular, larger sized nanoclusters (>30 atoms) promoted the cleavage of the O–O bond of the adsorbed O 2 or tert -butylhydroperoxide molecule, thus providing the charge transfer to the adsorbed substrate molecule [ 180 , 245 ]. At the same time, electron-deficient subnanoclusters (12–19 atoms) of less oxophilic metals, such as Pt, tended to one-end coordination of O–O bond, thus providing the formation of peroxide radicals on the surface with the subsequent one-electron transfer followed by C–H bond cleavage, hence initiating toluene radical oxidation processes similar to homogeneous or nanoheterogeneous molecular oxidation catalysts [ 180 , 324 , 325 ]. More oxophilic metals, such as Ru or Cu, and vice versa, were prone to form partial surface oxides, resulting in a drastic decrease in the catalyst activity, with TOF values not exceeding 100 h −1 [ 180 ].…”

Chromogenic detection of xylene isomers and luminogenic chemosensing of o-xylene employing a new macrocyclic cobalt complex: synthesis, and X-ray crystallographic, spectroscopic and computational studies

“…Karakhanov's group synthesized a mesoporous hierarchical MCM-41/halloysite nanotube composite as the supported bimetallic MnCo catalyst for the selective oxidation of p -xylene to terephthalic acid. 41 Dang-Bao and coworkers synthesized a family of cobalt-doped ceria nanorods, whereby the catalytic activity of the as-prepared sample was studied in deep oxidation of p -xylene at 225–300 °C, representing the most efficient deep oxidation of p -xylene as >95% conversion of p -xylene to CO 2 at 275 °C. 42 Lyu and coworkers employed a Co-Mn-Br ternary catalyst for p -xylene or m -xylene oxidation in the liquid phase and investigated the effects of the Co/Mn ratio and water content in HOAc/H 2 O on the side reaction rate for the p -xylene and m -xylene oxidation.…”

Fe3O4@MCM‐41@ZrCl2: A novel magnetic mesoporous nanocomposite catalyst including zirconium nanoparticles for the synthesis of 1‐(benzothiazolylamino)phenylmethyl‐2‐naphthols

“…[33,34] In order to obtain interesting and remarkable catalytic capabilities from these magnetic mesoporous nanocomposites, modification of their surface by stabilization of metal nanoparticles on their structure is one of the best selections. [14,32,[35][36][37][38][39] This method is also a useful way of preventing the accumulation of metal nanoparticles. In this field, zirconium (IV)-based nanoparticles are one of the most useful cases because of their commercial availability, low price, and low toxicity.…”