Working mechanism of oxide catalysts in the partial oxidation of methane to formaldehyde. II. Redox properties and reactivity of SiO{sub 2}, MoO{sub 3}/SiO{sub 2}, V{sub 2}O{sub 5}/SiO{sub 2}, TiO{sub 2}, and V{sub 2}O{sub 5}/TiO{sub 2} systems

Journal Article · Mon Mar 31 23:00:00 EST 1997 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1997.1546· OSTI ID:563500

Arena, F ^[1]; Giordano, N ^[2]; Parmaliana, A ^[1]

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1. Universita degli Studi di Messina (Italy)
2. Istituto CNR-TAE, Messina (Italy)

The redox behavior and the oxygen chemisorption of SiO{sub 2}, MoO{sub 3}/SiO{sub 2}, V{sub 2}O{sub 5}/SiO{sub 2}, TiO{sub 2}, and V{sub 2}O{sub 5}/TiO{sub 2} systems have been systematically evaluated by H{sub 2} and CH{sub 4} temperature programmed reduction (i.e., H{sub 2}-TPR, CH{sub 4}-TPR) and high temperature oxygen chemisorption (HTOC) measurements, respectively. The influence of the oxide loading on the surface structure and dispersity of MoO{sub 3}/SiO{sub 2} and V{sub 2}O{sub 5}/SiO{sub 2} catalysts has been assessed. CH{sub 4}-TPR measurements indicate that the activity-selectivity pattern of oxide catalysts in MPO controlled by their capability to interact with CH{sub 4} undergoing a redox cycle under reaction conditions. The opposite effect of MoO{sub 3} and V{sub 2}O{sub 5} promoters on the catalytic functionality of the {open_quotes}precipitated{close_quotes} silica support has been explained in terms of a different reducibility of MoO{sub 3} and V{sub 2}O{sub 5} {open_quotes}surface species.{close_quotes} The nature of the support as well as the level of the oxide loading affect the {open_quotes}reactivity{close_quotes} of lattice oxygen of supported systems determining their catalytic behavior in MPO. The most effective reaction mechanism leading to the primary formation of HCHO implies the direct participation of gas-phase oxygen, while the involvement of bulk-lattice oxygen ions in the process of product formation mainly leads to CO{sub x}. The interaction occurring between catalyst surface and reaction mixture under steady-state conditions is addressed. 39 refs., 9 figs., 7 tabs.

• OSTI ID: 563500
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 167; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
40 CHEMISTRY
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHEMISORPTION
FORMALDEHYDE
HETEROGENEOUS CATALYSIS
METHANE
MOLYBDENUM OXIDES
PARTIAL OXIDATION PROCESSES
REDUCTION
SILICA
TEMPERATURE DEPENDENCE
TITANIUM OXIDES
VANADIUM OXIDES