Hydrothermal synthesis of Mo-V mixed oxides possessing several crystalline phases and their performance in the catalytic oxydehydration of glycerol to acrylic acid

Abstract

The one-step oxydehydration of glycerol to acrylic acid over molybdenum and vanadium mixed oxides was investigated. The Mo-V oxide catalysts were prepared by a simple hydrothermal method under different synthesis and calcination atmospheres and were characterized by in situ XRD, TPD-NH 3 , N 2 adsorption/ desorption, X-ray absorption near vanadium K-edge spectroscopy and thermogravimetry. The catalytic performance of the samples at different temperatures (290, 320 and 350°C) and under different gas flow compositions (20% O 2 in N 2 , 100% O 2 , or 100% N 2) revealed that the arrangement of the crystallographic structures of the active phases directly influenced the catalytic performance. It was found that the catalysts heattreated in oxidizing atmosphere gave superior catalytic results comparing with the catalysts heat-treated in inert atmosphere due to the equilibrium between the crystalline phases MoVO 5 and Mo 4.65 V 0.35 O 14 that contains V +4 and V +5. Catalytic oxydehydration at 320°C under a flow of 100% O 2 gave the best performance, achieving selectivity of 33.5% towards acrylic acid and 100% conversion of glycerol.

Surfactant-assisted synthesis of Mo–V mixed oxide catalysts for upgraded one-step conversion of glycerol to acrylic acid

“…4B) for reference sample, a signicant decrease in the mole percentage of vanadium (from 12.6 to 2.9%), followed by an increase in the amount of molybdenum (from 14.2 to 22.8%) was observed. These observations strongly suggest that MoV 2 O 8 is very unstable in this sample, and the most part of vanadium originally present in this mixed oxide structure is transferred to amorphous phase as shown in eqn (6). Most part of the low amount of vanadium that remained in the crystalline phase is present in the reduced phase MoVO 5 .…”

“…In a previous work, we studied the effect of synthesis and calcination atmospheres in the formation of Mo-V mixed oxides crystalline phases prepared by a hydrothermal method and evaluated their performance in the one-pot glycerol oxydehydration to acrylic acid. 6 We identied the MoV 2 O 8 and Mo 4.65 V 0.35 O 14 as the most active phases in the reaction but with low stability during reaction. Herein, we describe the surfactant-assisted synthesis and structural characterization of Mo x V y O z catalysts and explore how the presence of SDS and CTAB surfactants in the synthesis mixture inuences the composition of phases, porosity, crystal morphology, and catalytic activity of these materials in the one-step oxidative dehydration of glycerol.…”

“…Both mixtures were maintained under stirring for 10 min at 25 C and aer the complete dissolution, they were mixed and stirred for another 10 min at 25 C, resulting in a solution with a pH of 2.8 and a Mo/(Mo + V) mole ratio of 0.60. 6,8 The mole proportion of the reagents was 1 VOSO 4 : 0.2 (NH 4 ) 6 Mo 7 O 24 $4H 2 O : 300 H 2 O. Aerwards, sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) were added to the solution and maintained under stirring for 40 min at 25 C. The mole ratio surfactant/(Mo + V) was 0.10. Later, the solution was transferred to a 50 mL Teon vessel contained in a stainless steel autoclave reactor, occupying approximately 70% of the vessel capacity.…”

“…Due to the increase in biodiesel production and, consequently, the coproduced glycerol, the search for new uses for it becomes indispensable. 1,2 Many studies have been reported for glycerol valorisation in the production of different substances using various processes like dehydration, [3][4][5] oxidative dehydration, [6][7][8] acetalization, 9 acetylation 10 and hydrogenolysis. 11 A high valueadded product that can be obtained from glycerol oxidative dehydration and that has attracted attention because of the increase in its market demand is acrylic acid.…”

Studies on dispersion and reactivity of vanadium oxides deposited on lamellar ferrierite zeolites for condensation of glycerol into bulky products

“…Consequently, the amount of glycerol generated cannot be absorbed by traditional consumer industries, such as the cosmetics, pharmaceutical, and tobacco sectors, hence depressing its price and creating opportunities to find new applications for this compound [3]. Chemical transformations that are being explored in order to add value to glycerol include dehydration [4][5][6][7][8][9], oxidative dehydration [10][11][12], ammoxidation [13,14], hydrogenolysis [15][16][17][18], etherification [19][20][21], esterification [22,23], selective oxidation [24,25], and acetalization [26][27][28][29].…”