How important is the (001) plane of M1 for selective oxidation of propane to acrylic acid?

The role of the (001) crystallographic plane of the M1 phase of MoVTeNb mixed oxide catalysts in selective oxidation of propane to acrylic acid has been addressed by investigating a phase-pure M1 material preferentially exposing this surface. A model catalyst has been prepared by com-plete silylation of M1 followed by breakage of the SiO2 covered needles. Using this approach, the reactivity of the M1 (001) surface has been investigated by combining a micro-reactor study of propane oxidation with High-Sensitivity Low Energy Ion Scattering (HS-LEIS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to study shape and microstructure of the model system and to verify the surface exposure of the model catalyst. The specific formation rate of acrylic acid on the model catalyst is similar to that on the phase-pure M1 reference material indicating that the (001) plane of the M1 crystal structure does not possess enhanced catalytic properties com-pared to the lateral surface of M1 needles in propane oxidation

Preparation, characterization and catalytic behavior for propanepartial oxidation of Ga-promoted MoVTeO catalysts

[EN] Two sets of Ga-promoted MoVTeO catalysts were synthesized hydrothermally and heat-treated at 600 degrees C in N-2: (i) materials prepared from gels with Mo/V/Te/Ga atomic ratios of 1/0.60/0.17/x (x=0-0.12) (A-series) and (ii) materials prepared from gels with Mo/V/Te/Ga atomic ratios of 1/0.60-x/0.17/x (x=0.15 or 0.25) (B-series). In addition, a Ga-containing MoVTeO catalyst was also prepared from M1-containing MoVTeO material by impregnation with aqueous solution of gallium and heat-treated at 450 degrees C in N-2. Catalysts were characterized by means of powder XRD, TEM, Raman spectroscopy, NH3-TPD and XPS and tested in the partial oxidation of propane. The results showed that the addition of small amount of gallium significantly increase the selectivity to acrylic acid (AA) at low propane conversion. However, at high propane conversion, the selectivity to AA strongly depends on both the catalyst composition and the gallium incorporation method. The higher selectivity to acrylic acid over Ga-containing MoVTeO catalysts has been related to: (i) structural changes in the M1 phase by the incorporation of Ga3+ into the octahedral structural framework and/or (ii) incorporation of Ga3+ species on the catalyst surface thus modifying catalysts acid properties. (C) 2014 Elsevier B.V. All rights reserved.Financial support from DGICYT in Spain (Project CTQ2012-37925-C03-1 and Program Severo Ochoa SEV-2012-0267) is gratefully acknowledged. EGG acknowledges finantial support through spanish project MAT2010-19837-C06-05 and the ICTS-Microscopia Electronica in Madrid for facilities.Hernández Morejudo, S.; Massó Ramírez, A.; García-González, E.; Concepción Heydorn, P.; López Nieto, JM. (2015). Preparation, characterization and catalytic behavior for propanepartial oxidation of Ga-promoted MoVTeO catalysts. Applied Catalysis A: General. 504:51-61. https://doi.org/10.1016/j.apcata.2014.12.039S516150