Photooxidation of Methane over TiO₂

Abstract

Fourier‐transform infrared spectroscopy has been employed to investigate the adsorption and photo‐oxidation of CH4 over powdered TiO2. The interaction between the CH4 and TiO2 surface is weak. It is found that no CH4 molecules are adsorbed on the surface at 35 °C in a vacuum. Under UV irradiation, CH4 decomposes to form CO(a), CO2(g), H20(a), and HCOO(a) in the presence of O2. The photoreaction rate is retarded and only small amounts of CO(a) and HCOO(a) are formed in the absence of O2. It is observed that the oxygen atoms of O2 are incorporated into these photoproducts as 18O2 is used. The major 18O‐containing products are C18O(a), C18O2(g), H2 18O(a), HC16O18O(a), and HC18O18O(a) after 180 min UV irradiation. However, the extent of 18O incorporating into the adsorbed formate is dependent on UV irradiation time. In the early stage of UV irradiation HC16O16O(a) is the major formate form indicating the involvement of TiO2 lattice oxygens for its formation, but HC18O18O(a) becomes the major one after 180 min indicating the involvement of 18O2. Formate on TiO2 further photodecomposes to CO2(g), but not to CO(a). CO(a) formation is directly from CH4 photodecomposition with the participation of TiO2 lattice oxygens and O2.

Reprocessing effect on the quality of domestically cooked (boiled/stir-fried) frozen vegetables

“…For best nutrient retention during cooking, the authors concluded that methods involving short cooking times and minimal water should be used. Similarly, more folate was retained in stirfried than in boiled vegetables [8]. Our results show that ascorbic acid retention in the studied vegetables is greater with stir-frying than with boiling.…”

“…Folate contents in fresh, boiled and stir-fried vegetables were compared, although cooking methods were not examined as a factor in the frozen product [8]. The effects of domestic cooking methods (including boiling, steaming, microwaving, baking and stir-frying) on different nutrients in a range of vegetables have also been studied [9].…”

Photocatalytic oxidation of methane over silver decorated zinc oxide nanocatalysts

“…Semiconductor photocatalysis, as a technology utilizing sunlight, has been shown to be promising in both water splitting and environmental remediation 15 16 17 18 19 . Earlier reports have also shown that by using the approach of photocatalysis, activation and oxidation of methane can take place even at room temperature at atmospheric pressure 20 21 22 23 . The efficiency of photocatalytic oxidation of methane, however, remains notoriously low even under light irradiation using ultraviolet sources.…”

Photocatalytic and Thermocatalytic Conversion of Methane

“…[ 94 ] Recently, the complete photocatalytic oxidation of methane has attracted increasing attention. [ 78,95–103 ] The Yi group reported that Ag‐modified ZnO (Ag/ZnO) nanostructures showed very high photocatalytic activity for CH 4 oxidation under simulated‐sunlight illumination. [ 78 ] It was found that the built‐in electric field of a ZnO polar semiconductor promotes the separation of photogenerated electrons and holes.…”