Selective oxidation of methane to formaldehyde by oxygen over silica-supported iron catalysts

Influence of Adding Molybdenum on Structure and Performance of FexOy/SBA‐15 Catalysts in Selective Oxidation of Propene

“…The broad diffraction peak at 23°2θ corresponded to the amorphous SBA-15 support material. [13] Small-angle diffraction patterns of all samples exhibited characteristic diffraction peaks (10 l), (11 l), and (20 l) of SBA-15 ( Figure 1, right). [14,15] Hence, two-dimensional hexagonal symmetry of the support material SBA-15 was retained after supporting iron and molybdenum oxides.…”

“…Analogous to the model of the particle in the box, decreasing DR-UV-Vis edge energy is reported to correlate with an increasing size of transition metal oxide domain. [13,26,27] DR-UV-Vis edge energies of Mo x O y _Fe x O y /SBA-15 samples, 1.3 wt% Mo_SBA-15, and iron oxide references were determined according to Weber, [27] and depicted as function of Mo/Fe atomic ratio ( Figure 5 [27,28] The smallest species size together with the presence of mainly isolated, mononuclear species was in accordance with the low metal oxide loading and the results from N 2 physisorption measurements. All Mo x O y _Fe x O y /SBA-15 A dispersion effect of molybdenum on iron oxidic species was also reported for MoÀ Fe catalysts supported on activated carbon [29] and FeÀ Mo catalysts supported on Al 2 O 3 .…”

Catalytic selective oxidation or oxidative functionalization of methane and ethane to organic oxygenates

“…The dispersion of FePO 4 species might be beneficial to the improvement of HCHO selectivity. The modification of FeO x species introduced into SBA-15 or SiO 2 by phosphorus also led to the formation of FePO 4 nanoclusters and significantly enhanced HCHO selectivity [68,70]. In a communication, Groothaert et al [77] reported that the chemisorbed oxygen on Cu-ZSM-5, which had been pretreated in O 2 at ≥ 623 K, oxidized methane to CH 3 OH at ≥ 398 K. Spectroscopic characterizations suggested the formation of the bis(μ-oxo)dicopper core, [Cu 2 -(μ-O) 2 ] 2+ , and this species was proposed as being responsible for the oxidation of methane to CH 3 OH at low temperatures.…”

“…Because the sol-gel method is known to be capable of producing supported catalysts with homogeneously distributed active sites, we studied the catalytic performances of the FeO x -SiO 2 catalysts prepared by the sol-gel method for methane selective oxidation [68]. We found that the 0.5 wt% FeO x -SiO 2 catalyst prepared by the sol-gel method showed significantly higher methane conversion than the 0.5 wt% FeO x /SiO 2 prepared by an impregnation method, while HCHO selectivities over the two catalysts were almost the same under the same reaction conditions (Figure 7).…”

Critical review and exergy analysis of formaldehyde production processes

“…Among the catalysts that have been used for partial oxidation of methane to formaldehyde, iron oxide, molybdenum oxide, and vanadium oxide are the most common catalysts (Zhang et al 2003, Launay et al 2007, He et al 2009). It is difficult to activate the relatively inert methane on the surface of a catalyst to make formaldehyde, considering the weak chemisorption of methane on the catalyst surface (Michalkiewicz et al 2008).…”