Monoterpenes oxidation in the presence of Y zeolite-entrapped manganese(III) tetra(4-N-benzylpyridyl)porphyrin

Selective Photooxidation of Valencene and Thymol with Nano-TiO2 and O2 as Oxidant

The selective photocatalytic oxidation with O₂ as oxidant of valencene and thymol was evaluated using nanostructured TiO₂ under UV-Vis radiation at atmospheric conditions. The effect of the morphology and optical properties of TiO₂ nanotubes and aminate nanoparticles was studied. Different scavengers were used to detect the presence of positive holes (h⁺), electrons (e^-), hydroxyl radicals (•OH), and the superoxide radical anion (O₂^-) during the photooxidation reaction. Superoxide anion radical is the main oxidizing specie formed, which is responsible for the selective formation of nootkatone and thymoquinone using aminated TiO₂ nanoparticles under 400 nm radiation.

The polymerization of carvacrol catalyzed by Mn-porphyrins: obtaining the desired product guided by the choice of solvent, oxidant, and catalyst

Less polar solvents could modulate the catalytic activity of Mn(iii)-porphyrins in carvacrol's oxidation leading to polymer/oligomer formation instead of thymoquinone formation.

Development of rapid and selective epoxidation of α-pinene using single-step addition of H2O2 in an organic solvent-free process

This study reports substantial improvement in the process for oxidising α-pinene, using environmentally friendly H₂O₂ at high atom economy (∼93%) and selectivity to α-pinene oxide (100%). The epoxidation of α-pinene with H₂O₂ was catalysed by tungsten-based polyoxometalates without any solvent. The variables in the screening parameters were temperatures (30–70 °C), oxidant amount (100–200 mol%), acid concentrations (0.02–0.09 M) and solvent types (i.e., 1,2-dichloroethane, toluene, p-cymene and acetonitrile). Screening the process parameters revealed that almost 100% selective epoxidation of α-pinene to α-pinene oxide was possible with negligible side product formation within a short reaction time (∼20 min), using process conditions of a 50 °C temperature in the absence of solvent and α-pinene/H₂O₂/catalyst molar ratio of 5 : 1 : 0.01. A kinetic investigation showed that the reaction was first-order for α-pinene and catalyst concentration, and a fractional order (∼0.5) for H₂O₂ concentration. The activation energy (E_a) for the epoxidation of α-pinene was ∼35 kJ mol⁻¹. The advantages of the epoxidation reported here are that the reaction could be performed isothermally in an organic solvent-free environment to enhance the reaction rate, achieving nearly 100% selectivity to α-pinene oxide.

Products obtained from the oxidation of α-pinene with hydrogen peroxide (H₂O₂) in the presence of tungsten-based polyoxometalates (α-pinene 1, α-pinene oxide 2, pinanediol 3, campholenic aldehyde 4, sobrerol 5, verbenol 6 and verbenone 7).

Synthesis, characterization and electrocatalytic properties of bimetallic sulfides CoS/MnS/N-C for oxygen reduction in alkaline media

Synthesis, characterization and oxygen reduction reaction (ORR) catalytic properties of bimetallic sulfides CoS/MnS/N-C catalyst was discussed. The catalyst was derived from a typical Co based zeolitic imidazolate framework (ZIF-67) and manganese aminoporphyrin. 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl) porphyrin manganese oxoacetate loaded with ZIF-67 forms a porphyrin loaded ZIF-67. This product was then calcined at 800ˆ∘C and vulcanized with thioacetamide to obtain the bimetallic sulfide product CoS/MnS/N-C. The structure of CoS/MnS/N-C was further characterized by XRD, XPS, FESEM and HRTEM spectra which indicated a novel porous and hollow sphere structure. The electrocatalytic properties of the bimetallic material as well as its parent porphyrin and ZIF-67 were also compared in alkaline condition (0.1 M KOH) with a rotating disk electrode. The prepared catalyst CoS/MnS/N-C exhibits a higher catalytic performance than its precursors (PorMnOAc, ZIF-67 and PorMnOAc loaded ZIF-67) with almost four electron transfers under this condition.

Effect of porphyrin metal center on synthesis, structure, morphology and oxygen reduction properties of porphyrin encapsulated metal organic frameworks

A series of different metal centered 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl)porphyrins (PorM) where M = H2, MnOAc, FeCl, Co or Zn were synthesized, and then encapsulated in zeolite imidazole framework-8 (ZIF-8) by typical template directed strategy to generate PorM@ZIF-8 metal organic frameworks (MOFs). These composites were characterized by UV-vis, FTIR, XRD, FESEM and HRTEM methods. Each prepared PorM@ZIF-8 MOF retained the molecular structure of porphyrin and crystal structure of ZIF-8. It is clearly shown that porphyrin centered metal ions will affect MOFs morphology. Both PorH2@ZIF-8 and PorZn@ZIF-8 gave a rhombic dodecahedron, PorMnOAc@ZIF-8 gave a truncated hexagonal prism-like structure, while no specific structures were obtained for PorFeCl@ZIF-8 and PorCo@ZIF-8 due to aggregation as characterized by FESEM spectrum. Oxygen reduction catalytic ability of ZIF-8, PorM and PorM@ZIF-8 were measured in alkaline condition (0.1 M KOH) with the number of electrons transferred being [Formula: see text] = 2.20–2.60 and generating HO[Formula: see text] as the oxygen reduction product. The catalytic property slightly increased after the porphyrin was encapsulated, due possibly to the capacity limit, inappropriate molecular distance or the direction of encapsulated porphyrin molecular.

Abatement of formaldehyde with photocatalytic and catalytic oxidation: a review

Formaldehyde is one of the vital chemicals produced by industries, transports, and domestic products. Formaldehyde emissions adversely affect human health and it is well known for causing irritation and nasal tumors. The major aim of the modern indoor formaldehyde control study is in view of energy capacity, product selectivity, security, and durability for efficient removal of formaldehyde. The two important methods to control this harmful chemical in the indoor environments are photocatalytic oxidation and catalytic oxidation with noble metals and transition metal oxides. By harmonizing different traditional photocatalytic and catalytic oxidation technologies that have been evolved already, here we give a review of previously developed efforts to degrade indoor formaldehyde. The major concern in this article is based on getting the degradation of formaldehyde at ambient temperature. In this article, different aspects of these two methods with their merits and demerits are discussed. The possible effects of operating parameters like preparation methods, support, the effect of light intensity in photocatalytic oxidation, relative humidity, etc. have been discussed comprehensively.

An ionic liquid immobilized copper complex for catalytic epoxidation

A catalytic system consisting of copper complex and hydrogen peroxide in Emim ionic liquid medium was effective in the epoxidation of olefins and terpenes. The catalyst and the ionic liquid mixture was recycled and reused consistently.

Characterization of electrodes chemically modified with Mn(III) porphyrin/polypyrrole films as catalytic surfaces for an azo dye

In this study we describe the electrochemical behavior of 5,10,15,20-tetrakis(2'-aminophenylporphyrin)manganese(III) chloride supported on a glassy carbon electrode, as well as the electrochemical preparation and characterization of thin films based on pyrrole-3-carboxylic acid. The electrocatalytic action of the electrode modified with the Mn(III) porphyrin toward an azo dye was tested, and the characteristic strong interaction between the incorporated metalloporphyrin and RR120 dye was verified.

Metalloporphyrins in the biomimetic oxidative valorization of natural and other organic substrates

Cheap and abundant natural products can be transformed into products of higher commercial value. One of the approaches for the functionalization of organic compounds is their oxidation in the presence of an oxygen atom donor, under the influence of a suitable catalyst. Metalloporphyrins, with structures based on the well known meso-tetraphenylporphyrin (TPPH2), are amongst the catalysts commonly studied and have demonstrated to be efficient in the oxygenation of organic compounds. These transformations have been studied in the presence of different oxygen atom donors. However, our biomimetic oxidative approach is based on the use of clean and environmentally benign hydrogen peroxide in the presence of metalloporphyrins. This approach will be outlined in this review.