Nitridation of MoO3/HZSM-5 and Fe-MoO3/HZSM-5

Abstract

Thermal treatment and subsequent ammonolysis of MoO 3 /H-ZSM-5 is shown to be an effective means for the preparation of zeolite dispersed nitrided molybdenum species. However, it is unlikely that these species reflect the bulk structures formed by analogous treatment of bulk MoO 3 precursor. The inclusion of low levels of Fe as a dopant does not produce any apparent effects on the Mo XPS spectra, although the amount of N incorporation is increased, and iron is shown to be reduced to Fe 0 . FTIR studies evidence the migration of molybdenum oxo species into the zeolite at the temperatures employed.

Alternative catalytic materials: carbides, nitrides, phosphides and amorphous boron alloys

“…To some extent, etching procedures can be used to depth profile in these instances revealing lower oxidation state metal features in the sub-near surface region. 36,37 Oxidation states of (IV) and below are commonly reported in XPS studies of nitrides and carbides of Mo or W. It is generally, but not always, the case that high surface areas are desirable for heterogeneous catalysis. In a landmark publication, Volpe and Boudart reported the synthesis of high surface area nitrides (reportedly >200 m 2 g À1 in the case of molybdenum) by the treatment of oxide precursors with high space velocities of ammonia under carefully controlled temperature ramp conditions.…”

Molybdenum imidazole citrate and bipyridine homocitrate in different oxidation states – balance between coordinated α-hydroxy and α-alkoxy groups

“…† The XPS spectrum of bulk MoO 3 in the Mo 3d region showed a single spin-orbit doublet with a Mo 3d 5/2 binding energy of 233.0 eV. 84,85 The widening of the Mo 3d level is associated with the presence of more than one molybdenum states. [86][87][88][89] The Mo 3d…”

Methane dehydroaromatisation and methanol activation over zeolite catalysts: an overview

“…In situ FTIR studies following thermal activation of MoO 3 / H-ZSM-5 evidence loss of OH features at 3733, 3613 and 3440 cm -1 corresponding to terminal OHs, bridging OHs and hydroxyl nests, respectively [13]. Figure 1 presents an in situ FTIR study of the activation of MoO 3 /H-ZSM-5 in vacuo as detailed elsewhere [13]. The insets show the rates of loss of the 3613 and 3440 cm -1 bands as a function of temperature.…”

“…For example, the Mo/Si ratios determined by XPS in elucidating the possible dispersion of molybdenum nitride clusters within H-ZSM-5 from MoO 3 /H-ZSM-5 suggest redistribution of the Mo species upon nitridation [12,13]. In situ FTIR studies following thermal activation of MoO 3 / H-ZSM-5 evidence loss of OH features at 3733, 3613 and 3440 cm -1 corresponding to terminal OHs, bridging OHs and hydroxyl nests, respectively [13]. Figure 1 presents an in situ FTIR study of the activation of MoO 3 /H-ZSM-5 in vacuo as detailed elsewhere [13].…”

“…In the case of the sample generated at 500°C, the carbonaceous residue was harder as evidenced by the temperature programmed oxidation and 13 C MAS NMR studies. In the case of the sample generated at 300°C, there were additional features present in both the temperature programmed oxidation profile and also in the 13 C MAS NMR spectrum (where in addition to the aromatic feature(s) at ca. 130 ppm seen in the 500°C sample, there are also resonances at ca.…”