Fe/Fe₃C Boosts H₂O₂ Utilization for Methane Conversion Overwhelming O₂ Generation

Abstract

H 2 O 2 as aw ell-known efficient oxidant is widely used in the chemical industry mainly because of its homolytic cleavage into COH (stronger oxidant), but this reaction always competes with O 2 generation resulting in H 2 O 2 waste.Here,we fabricate heterogeneous Fenton-type Fe-based catalysts containing Fe-N x sites and Fe/Fe 3 Cn anoparticles as am odel to study this competition. Fe-N x in the low spin state provides the active site for COH generation. Fe/Fe 3 C, in particular Fe 3 C, promotes Fe-N x sites for the homolytic cleavages of H 2 O 2 into COH, but Fe/Fe 3 Cn anoparticles (Fe 0 as the main component) with more electrons are prone to the undesired O 2 generation. With ac atalyst benefiting from finely tuned active sites,1 8% conversion rate for the selective oxidation of methane was achieved with about 96 %s electivity for liquid oxygenates (formic acid selectivity over 90 %). Importantly,O 2 generation was suppressed 68 %. This work provides guidance for the efficient utilization of H 2 O 2 in the chemical industry.

Molecular oxygen enhances H2O2 utilization for the photocatalytic conversion of methane to liquid-phase oxygenates

“…The concentration of H 2 O 2 in the aqueous solution was quantified by the colorimetric method 13 , 21 . Typically, a reagent aqueous solution was prepared by dissolving 0.636 g K 2 TiO(C 2 O 4 ) 2 and 20 μL concentrated H 2 SO 4 (98%) in 100 mL deionized water.…”

“…However, photocatalytic activation of H 2 O 2 by photo-generated holes into O 2 usually occurs facilely 25 , which strongly competes and decreases the utilization efficiency of H 2 O 2 for the methane conversion, defined as the ratio of the H 2 O 2 amount consumed for methane conversion against the total consumed H 2 O 2 amount. So far, the highest utilization efficiency of H 2 O 2 , in the means of ·OH radicals, was reported as 72.3% in photocatalytic CH 4 conversion over a Fenton-type Fe-based catalyst 21 . Adsorption of H 2 O 2 molecules on photocatalyst surfaces is a prerequisite for occurrences of photocatalytic reactions.…”

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

“…Based on the reaction mechanism study, the superior catalytic activity of FeO x /TiO 2 is ascribed to the efficient electron transfer from TiO 2 to iron species. [389] As the important point to selectively generate CH 3 OH is hydrogen detachment from CH 4 , •OH radical is impressively accountable for the dehydrogenation of CH 4 to make •CH 3 radical, [394][395][396] as shown in step 2 of the reaction mechanism in Figure 19c. Thereby, cocatalyst-H 2 O 2 oxidant system plays an essential role in determining CH 3 OH generation.…”

“…As the important point to selectively generate CH 3 OH is hydrogen detachment from CH 4 , •OH radical is impressively accountable for the dehydrogenation of CH 4 to make •CH 3 radical, [ 394 , 395 , 396 ] as shown in step 2 of the reaction mechanism in Figure 19c . Thereby, cocatalyst‐H 2 O 2 oxidant system plays an essential role in determining CH 3 OH generation.…”

Homogeneous Carbon Dot-Anchored Fe(III) Catalysts with Self-Regulated Proton Transfer for Recyclable Fenton Chemistry

“…Fenton and Fenton-like reactions have been widely studied in a variety of fields, including geochemistry, 1 , 2 chemical oxidation, 3 , 4 in situchemical oxidation for environmental remediation, 5 methane oxidation, 3 , 6 fuel cell-related Nafion membrane degradation, 7 , 8 and tumor chemodynamic therapy 9 , 10 since Fenton reagents were found in 1894. Reactive oxygen species ( • OH, • O 2 – , 1 O 2 , etc.)…”