Oxidative Dehydration of Glycerol over Molybdenum- and Vanadium-Based Catalysts

Abstract

Surplus of glycerol production from the biodiesel industry has led to the search for glycerol conversion routes, the most common of which are dehydration and oxidative dehydration. Vanadium and molybdenum oxides were supported on γ-Al 2 O 3 and their properties were analyzed through several characterization techniques, showing that the acidity increases after addition of oxides and that in the catalyst with vanadium and molybdenum there is decrease in the band referring to V 5+ , responsible for sequential oxidation to CO 2 . The effect of the metal oxides on catalytic activity and stability during oxidative dehydration of glycerol to acrolein was investigated and correlated with chemical composition, acidity, and textural properties. Moreover, the global reaction, turnover frequency (TOF), and activation energy were determined. Catalyst performance and stability were found to depend on acidity and the supported metal with larger residence times (W/F) favored acrolein formation over CO x . In addition, metal oxides decreased catalyst deactivation via coke oxidation.

Supported MoOx and WOx Solid Acids for Biomass Valorization: Interplay of Coordination Chemistry, Acidity, and Catalysis

“…Exciting results were found in pure and mixed MoV oxide catalyzed oxidative dehydration of glycerol. 157 Catalyst deactivation was noticed over the MoO x /Al 2 O 3 catalyst, which showed a higher selectivity to acrolein. The addition of vanadium oxide prevents the deactivation of MoO x /Al 2 O 3 solid acid by promoting coke oxidation with its labile lattice oxygen via the Mars-van Krevelen mechanism.…”

“…The optimization of metal loading or the addition of appropriate amounts of another metal oxide can improve the metal−support interaction that will inhibit the leaching of acid sites as noticed in aqueous-phase HMF synthesis over SnO 2supported MoO x and WO x solid acids. 243 For the inhibition of coke formation, several strategies are reported: (i) the addition of another metal oxide, like vanadium oxide to a MoO x /Al 2 O 3 solid acid, 157 which can promote coke oxidation with its labile lattice oxygen via the Mars-van Krevelen mechanism; (ii) using the porous supporting materials like mesoporous silica, which can enhance the diffusion of the coke precursors through the pores; (iii) partial oxidation of coke using oxygen during the reaction, for instance, in the case of oxidative dehydration of glycerol; (iv) the presence of atmospheric pressure H 2 in the reactor, which was also found to minimize the production of char and coke. 186 The aforesaid challenges and prospects indicate the urgency of performing more studies for biomass valorization using different types of supported MoO x and WO x solid acids at various atmospheres as well as exploring the effect of various factors (redox metal, reaction medium, byproducts, gases, etc.)…”

Synthesis of MoO 3 by pilot‐scale combustion reaction and evaluation in biodiesel production from residual oil

“…10,12,17,18 Also, their selectivity and high catalytic activity are primarily related to Lewis and Brønsted-Lowry acidity. [19][20][21] In biodiesel production, heterogeneous catalysts based on molybdenum trioxide are expected to meet the premises of economics and environmental benefits, as already mentioned. 10,17 Studies reporting MoO 3 -or Mobased compounds as catalysts in the production of biodiesel are scarce in the literature; in general, they are used as active phase supported in other materials, for example, W x -Mo y /CaO, CaO-MoO 3 /SBA-15, 16 MoO 3 /B-ZSM-5, 18 and MoPO/Y-Al 2 O 3.…”

“…Among the solid catalysts studied, molybdenum trioxide and materials based on the transition metal Mo, have been the focus of several technological applications, mainly due to their structural characteristics, as photocatalysts, 9,13 gas sensors, 14 battery applications, 5,15,16 and for biodiesel production 10,12,17,18 . Also, their selectivity and high catalytic activity are primarily related to Lewis and Brønsted‐Lowry acidity 19‐21 …”

The Use of Laser Induced Breakdown Spectroscopy (LIBS) to Study Catalyst Deactivation of V2O5/γ‐Al2O3 as Compared to Inductively Coupled Plasma Optical Emission Spectrometry

“…Lehr et al used supercritical water condition for liquid dehydration of glycerol, which was derived from sugar with ZnSO 4 catalyst. Bezerra et al described oxidative dehydration of glycerol over γ‐Al 2 O 3 supported V 2 O 5 (V 2 O 5 /γ‐Al 2 O 3 ) and MoO 3 /γAl 2 O 3 catalysts. Kim et al performed a comparison of zeolites with γ‐Al 2 O 3 as support for glycerol dehydration that showed catalysts with lower conversion and selectivity had better stability.…”