Facile method for synthesis of nanosized β –MoO ₃ and their catalytic behavior for selective oxidation of methanol to formaldehyde

Abstract

β-MoO 3 was successfully synthesized from all commercial materials using a fast, effective and simple method and characterized by differential scanning calorimetry, x-ray powder diffraction, field emission scanning electron microscopy, infrared and Raman spectroscopy. The prepared sample was highly active and selective to formaldehyde formation from methanol over a wide range of reaction temperatures. β-MoO 3 catalyst also exhibited stable methanol conversion and formaldehyde selectivity at around 84% and over 95% respectively for over 15 operating hours at 320 °C. However, it may be deactivated at elevated reaction temperature due to transformation of metastable to stable phase. It was revealed that the prepared catalyst maintains its high selectivity to formaldehyde during deactivation. This can be considered as an advantage of the prepared MoO 3 catalyst in comparison with the industrial one.

Deactivation behavior of an iron-molybdate catalyst during selective oxidation of methanol to formaldehyde

“…This is below the catalyst temperature in the present study, which means that the β-MoO3 observed in this study should have quickly transformed to α-MoO3. However, in the experiment reported by Pham et al [39] methanol is fully converted and due to the exothermic reaction the catalyst bed might be subject to a hot spot and the actual temperature where β-MoO3 transformed could thus be higher. Furthermore, the prepared β-MoO3 was calcined at 350 °C as part of the synthesis procedure without transforming to the α-MoO3.…”

“…Pham et al [39] synthesized β-MoO3 and studied its catalytic performance compared to the thermodynamically stable α-MoO3 under reaction conditions (6.2 % MeOH in air, W/F = 15 gcat h mol -1 MeOH) in an fixed bed reactor. They concluded that the synthesized β-MoO3 transforms to α-MoO3 at 350 °C.…”

Nanostructured MoO3 for Efficient Energy and Environmental Catalysis

“…A transformation from the β to α phase took place spontaneously at the temperature ranging from 387 to 450 °C, according to the reported result. Moreover, β-MoO3 exhibited higher catalytic properties than α-MoO3 in some catalysis reactions [32][33][34].…”

“…The monoclinic structure of β-MoO 3 is a monoclinic ReO 3 -related structure, in which each MoO 6 octahedral shares all the corners with adjacent MoO 6 octahedral. Breaking the Mo-O bonds can produce more unsaturated Mo atoms on the surface compared with α-MoO 3 , which would behave as active centers for oxidation of small organic molecules, such as partial oxidation of methanol [34]. Unlike α-MoO 3 , metastable h-MoO 3 easily permits the ready intercalation and migration of some monovalent cations because of the open structure tunnels.…”

Tweaking the Electronic and Optical Properties of α-MoO3 by Sulphur and Selenium Doping – a Density Functional Theory Study

“…Molybdenum trioxide (MoO 3 ) has garnered much research attention recently due to this material offering promising applications, coupled with its non-toxic nature, low cost and outstanding catalytic properties 1 – 7 . Further, MoO 3 is found to be one of the most important metal oxides used as the electron-injection layers and the electrode material in the fast-growing field of photovoltaics and solar-cell devices.…”