Search Results (2)

A series of Fe–Ba mixed oxides, including a pure Fe-containing sample as a reference, have been synthesized via a sol–gel process using Fe³⁺ or Fe²⁺ salts and BaSO₄ as raw materials, with Pluronic P123 serving as a template. These oxides have been thoroughly characterized and subsequently utilized as catalysts for the chlorination of various organic molecules. Commercial hydrochloric acid, known for its relative safety, and environmentally friendly aqueous hydrogen peroxide were employed as the chlorine source and oxidant, respectively. The pure Fe-containing catalyst displays excellent thermal stability between 600 and 800 °C and exhibited moderate to high conversions in the chlorination of toluene, benzene, and tert-butyl hydroperoxide, with remarkable ortho-selectivity in chlorination of toluene. The combination of Fe³⁺ salt with BaSO₄ in the sol–gel process results in a Fe–Ba mixed oxide catalyst composed of BaO₂, BaFe₄O₇, and Fe₂O₃, significantly enhancing the chlorination activity compared to that displayed by the pure Fe catalyst. Notably, the chlorination of tert-butyl hydroperoxide (TBHP) does not require additional oxidants such as H₂O₂, and involves both electrophilic substitution and nucleophilic addition. Notably, the chlorination of bromobenzene yields chlorobenzene as the sole product, a transformation that has not been previously reported. Overall, this catalytic chlorination system holds promise for advancing the chlorination industry and enhancing pharmaceutical production. Full article

Simultaneous generation of plasma by microwave irradiation of perovskite or the spinel type of silica supported porous catalyst oxides and their reduction by nitrogen in the presence of oxygen is demonstrated. As a result of plasma generation in air, NO_x generation is accompanied by the development of highly heterogeneous regions in terms of chemical and morphological variations within the catalyst. Regions of almost completely reduced catalyst are dispersed within the catalyst oxide, across micron-scale domains. The quantification of the catalyst heterogeneity and evaluation of catalyst structure are studied using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and XRD. Plasma generating supported spinel catalysts are synthesized using the technique developed by the author (Catalysts; 2016; 6; 80) and BaTiO₃ is used to exemplify perovskites. Silica supported catalyst systems are represented as M/Si = X (single catalysts) or as M(₁)/M(₂)/Si = X/Y/Z (binary catalysts) where M; M(₁) M(₂) = Cr; Mn; Fe; Co; Cu and X, Y, Z are the molar ratio of the catalysts and SiO₂ support. Composite porous catalysts are synthesized using a mixture of Co and BaTiO₃. In all the catalysts, structural heterogeneity manifests itself through defects, phase separation and increased porosity resulting in the creation of the high activity sites. The chemical heterogeneity results in reduced and oxidized domains and in very large changes in catalyst/support ratio. High electrical potential activity within BaTiO₃ particles is observed through the formation of electrical treeing. Plasma generation starts as soon as the supported catalyst is synthesized. Two conditions for plasma generation are observed: Metal/Silica molar ratio should be > 1/2 and the resulting oxide should be spinel type; represented as M_aO_b (a = 3; b = 4 for single catalyst). Composite catalysts are represented as {M/Si = X}/BaTiO₃ and obtained from the catalyst/silica precursor fluid with BaTiO₃ particles which undergo fragmentation during microwave irradiation. Further irradiation causes plasma generation, NO_x formation and lattice oxygen depletion. Partially reduced spinels are represented as M_aO_b–c. These reactions occur through a chemical looping process in micron-scale domains on the porous catalyst surface. Therefore; it is possible to scale-up this process to obtain NO_x from M_aO_b for nitric acid production and H₂ generation from M_aO_b–c by catalyst re-oxidized by water. Re-oxidation by CO₂ delivers CO as fuel. These findings explain the mechanism of conversion of combustion gases (CO₂ + N₂) to CO and NO_x via a chemical looping process. Mechanism of catalyst generation is proposed and the resulting structural inhomogeneity is characterized. Plasma generating catalysts also represent a new form of Radar Absorbing Material (RAM) for stealth and protection from radiation in which electromagnetic energy is dissipated by plasma generation and catalytic reactions. These catalytic RAMs can be expected to be more efficient in frequency independent microwave absorption. Full article