Methane Catalytic Peroxide Oxidation Over Fe-Containing Zeolite

Abstract

The selectivity of Fe-MFI catalysts to partial peroxide oxidation of methane to methanol and formic acid was studied depending on their topology (Nanocrystals, Microcrystals, and bulk Commercial) and activation with oxalic acid. The catalysts were characterized by XRD, ICP-OES, SEM, UV-vis DR, NH 3-TPD, N 2 adsorption. TOF of methane oxidation increased in the series: Nanocrystals < Microcrystals << Commercial. The selectivity to methanol depended mainly on the crystallite size and increased in the same series. The increase in TOF and selectivity to formic acid, as well as a sharp decrease in the selectivity to CO 2 over all the activated catalysts were accounted for by an increase in the total acidity of the catalysts and the number of oligomeric Fe oxo-clusters. Different pathways to the formation of methanol/CO 2 (via free radical mechanism) and formic acid (via heterogeneous route) over Fe-MFI catalysts were suggested.

Towards Sustainable Production of Formic Acid

“…At least,t hese authorsi ndicated that their zeolites containedi ron (0.02-0.11at%). Boltenkov et al [39] recently reportedaselectivity of 84 %f or the production of formic acid at ac onversion of methane of 1% in experiments with the same typeo fzeolites and conditions close to those used by the Hutchingsg roup.…”

“…It should be noted that the direct conversion of am ixture of CO 2 /H 2 into methanol with Cu/ZnO-based catalysts efficiently takes place at high pressures of 5-10 MPa and temperatures of 523-573 K. [16b] 8. [37][38][39] Hydrolysis or oxidation of biomass cellulose give high yields of formic acid at low temperatures (Schemes 5-7). Some of them used biomass-derived products as chemical intermediates.…”

“…The direct catalytic oxidation of methane to formic acid can be performed at low temperatures (< 373 K), but this reaction does not currently give acceptable yields;moreover,i tr equires the use of hydrogen peroxide. [37][38][39] Hydrolysis or oxidation of biomass cellulose give high yields of formic acid at low temperatures (Schemes 5-7). Catalytic oxidationc an even be achieved at lower temperatures than that of noncatalytic wet oxidation.…”

Formic Acid Production Via Methane Peroxide Oxidation Over Oxalic Acid Activated Fe-MFI Catalysts

“…However, methane molecules are chemically 14 very inert, the dissociation energy of the C-H bond being equal to 440 kJ mol -1 [9]. Thus, the 15 chemical activation of methane is a fundamental problem of vital importance [10] and the 16 development of a direct low temperature process for oxidation of methane to methanol [11, 12] 17 and formic acid [1,[13][14][15] continues to be an urgent problem for modern catalysis. The known 18 methods of methane hydroxylation to methanol by oxidation with O 2 and N 2 O, even when 19 catalytic, still need high temperature and pressure [16][17][18][19][20][21][22].…”

“…Even though Fe-and Cu-11 containing hydroxides and zeolites were shown earlier to catalyze the peroxide oxidation of light 12 paraffins and olefins [43,44], and, recently, of methane to methanol and/or formic acid at a high 13 enough selectivity under mild conditions (323 K) [12,45,46], we failed to find any literature 14 data concerning influence of structural and textural characteristics of the zeolite catalysts on the 15 process selectivity. In our earlier paper [14] we considered the influence of the texture and 16 morphology of Fe-containing zeolites on the selectivity and activity to the peroxide oxidation of 17 methane. We supposed that the large external surface area of the zeolite catalyst characteristic of 18 the nano-and microsize zeolites with the MFI structure decelerates the formation of methanol by 19 the free radical mechanism.…”