Selective Oxidation of Methane to Formaldehyde over a Silica-Supported Cobalt Single-Atom Catalyst

Abstract

Catalytic oxidation of methane to formaldehyde and methanol has attracted attention because of its advantage in energy efficiency over the conventional multistep reaction process involving endothermic steam reforming of CH 4 ; however, it is challenging to selectively obtain the partial oxidation products in the direct oxidation of CH 4 . In the present study, Co/SiO 2 with various Co loadings was tested for the CH 4 /O 2 /H 2 O gas flow reaction. As a result, Co/SiO 2 with a low loading of ≤0.1 wt % showed high selectivity for the partial oxidation reaction and mainly produced HCHO, while Co/SiO 2 with high Co loadings proceeded to complete oxidation. Structural analysis using X-ray absorption finestructure spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning transmission electron microscopy suggested that single Co atoms generated at low Co loadings were effective in the selective oxidation of CH 4 to HCHO, while Co 3 O 4 nanoparticles generated at high Co loadings promoted the complete oxidation.

Elucidation of single atom catalysts for energy and sustainable chemical production: Synthesis, characterization and frontier science

“…• Al 2 O 3 [321] • Carbon/Graphene [59,177,236,353,423] • Carbon nitride [424,425] • MnO 2 [424] • MoS 2 [426] • N 3 P 1 site [427] • SiO 2 [426,428] • TiO 2 [426] • ZnO [361] • ALD [423] • Ball milling [353] • Electrochemical method [425] • Freeze-drying method [59] • Mass-selected soft-landing [236] • Pyrolysis-assisted method [211,426,427,429,430] • Redox-driven hydrolysis [431] • Sol-gel method [361] • Thermal emitting strategy [214] • Thermal polymerization [424] • Wet impregnation [321,426,428] ,…”

“…• Benzene oxidation [321] • CO 2 RR [351,429] • Fenton-like reaction [424] • HER [425] • Hydrogenation [347,353,423,427] • Methane oxidation [428] • Nitrogen reduction [347] • OER [236,426] • ORR [214,236,361] • Toluene oxidation [431] to butadiene as displayed in Fig. 19(c).…”

Non‐Classical Conversion of Methanol to Formaldehyde

“…For the synthesis of CH 2 O, various methods were suggested comprising direct CO and CO 2 hydrogenation [4,5], selective oxidation of methane [6] or higher hydrocarbons such as propane or propene [7]. However, these routes still have not found an industrial application, and on a large scale, CH 2 O is nowadays still manufactured from methanol (CH 3 OH) by selective vapor-phase oxidation (Eq.…”

Single Atom Catalysts: An Overview of the Coordination and Interactions with Metallic Supports

“…[4] Since then, SACs have been utilized to catalyse several reactions such as water oxidation, [5][6][7] CO 2 reduction [8][9][10] and hydrogenation, [11,12] oxygen reduction, [13][14][15] hydrogen evolution, [7,[15][16][17][18] among others. [7,[19][20][21][22][23] Zhang and co-workers also synthesized a mixed gold and palladium SAC, which was supported on ion exchange resins and used to catalyse Ullmann reaction [24] of aryl halides in an aqueous media. [25] The authors reported that the synthesized SAC possessed high yield and selectivity; both can be tuned with the levels of Au and Pd in the SAC.…”

“…The concept of single atom catalysts (SACs) was first introduced by Zhang and co‐workers in 2011, where a single atomic layer of platinum was incorporated into an iron oxide support [4] . Since then, SACs have been utilized to catalyse several reactions such as water oxidation, [5–7] CO 2 reduction [8–10] and hydrogenation, [11,12] oxygen reduction, [13–15] hydrogen evolution, [7,15–18] among others [7,19–23] . Zhang and co‐workers also synthesized a mixed gold and palladium SAC, which was supported on ion exchange resins and used to catalyse Ullmann reaction [24] of aryl halides in an aqueous media [25] .…”