Influence of Phase Composition of Bulk Tungsten Vanadium Oxides on the Aerobic Transformation of Methanol and Glycerol

• Published in: European journal of inorganic chemistry Vol. 2018; no. 10; pp. 1204 - 1211
• Main Authors: Delgado, Daniel, Chieregato, Alessandro, Soriano, M. Dolores, Rodríguez‐Aguado, Elena, Ruiz‐Rodríguez, Lidia, Rodríguez‐Castellón, Enrique, López Nieto, José M.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 14.03.2018
• Subjects: Acids; Acrylic acid; Ammonia; Carbon oxides; Catalysis; Fourier transforms; Glycerol; Heterogeneous catalysis; Hydrothermal synthesis; Inorganic chemistry; Methanol; Oxidation; Oxydehydration; Phase composition; Properties (attributes); Selectivity; Spectrum analysis; Thermogravimetric analysis; Tungsten; Tungsten bronze; Tungsten oxides; Vanadium; Vanadium oxides
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201800059

A series of W–V–O catalysts with different m‐WO3 and h‐WO3 phase contents were hydrothermally synthesized by employing different tungsten, vanadium, and ammonium precursors and characterized by powder XRD, N2 adsorption, SEM, X‐ray energy‐dispersive spectroscopy, thermogravimetric analysis, Raman and FTIR spectroscopy, NH3 temperature programmed desorption, H2 temperature‐programmed reduction, and XPS. Finally, the acid/redox properties were analyzed by using aerobic transformation of methanol as a characterization reaction. A correlation between phase composition as well as acid and redox properties was observed, which were correlated to the catalytic performance of the title materials in a one‐pot oxydehydration reaction of glycerol. The hexagonal tungsten bronze (h‐WO3) phase shows a significantly higher concentration of acid sites than monoclinic m‐WO3, so that the acid properties of W–V–O oxides are directly related to the presence of h‐WO3 crystals. The presence of a higher concentration of acid sites in V‐containing h‐WO3 crystals is a key factor to achieve high selectivity to both acrolein and acrylic acid during one‐pot glycerol oxydehydration. Also, V sites in h‐WO3 show higher selectivity in the consecutive reaction (partial oxidation of acrolein to acrylic acid), while V sites in the m‐WO3 phase fundamentally lead to the formation of carbon oxides. The acid/redox properties of the W–V–O system were tuned by means of the W, V, and NH4+ precursors. These properties depend on the content of h‐WO3 (acid/redox sites) and/or m‐WO3 (redox sites) phases in the catalysts. The presence of V‐containing h‐WO3 crystals is pivotal to achieve good yields of acrolein and acrylic acid in the gas‐phase oxydehydration of glycerol.