Selective oxidation of C*4* hydrocarbons over (VO)*2*P*2*O*7 catalyst: Nature of the redox mechanism

Technical Report · Wed Sep 09 00:00:00 EDT 1992

OSTI ID:6827027

Kamat, S N

For selective oxidation of n-butane to maleic anhydride, (VO)[sub 2]P[sub 2]O[sub 7] has been identified as the most active and selective V-P-0 phase. A three stage solid state procedure was used to synthesize a (VO)[sub 2]P[sub 2]O[sub 7] catalyst labeled with [sup 18]O. Spectroscopy, etc. pointed to a highly site-specific [sup 18]O labeling. Anaerobic pulse micro-reactor studies using C[sub 4] hydrocarbons (n-butane, 1-butene) as reactants were conducted with this labeled catalyst. [sup 18]O incorporation into oxygenated products was determined by mass spectrometry. A comparison between the [sup 18]O content of products to those in various catalyst lattice sites allowed to associate specific surface layer reactive sites with the different mechanistic steps in the selective and nonselective pathways. These studies further revealed that n-butane is irreversibly chemisorbed and activated at the vanadyl dimer sites in a highly specific manner. Oxygen insertion at nearby V-O/[sup P]-V sites leads to form a furan-like surface species, which undergoes additional oxygen addition at P-O-V sites forming maleic anhydride. More than one nonselective pathways were evident: either by the direct combustion of n-butane, involving its cracking at V=O sites; or by the consecutive oxidation of the reaction intermediates and maleic anhydride. Reactivity of a site was found to be dependent on the nature of the hydrocarbon feed. Thus, the initial interaction of n-butane was found to be fundamentally different from 1-butene. Quantitative measurements showed that participation of the bulk oxygen is limited, and the redox mechanism is thus limited to a few near surface monolayers.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6827027
• Report Number(s): IS-T-1548; ON: DE93004799
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BUTANE
OXIDATION
BUTENES
PHOSPHORUS OXIDES
CATALYTIC EFFECTS
VANADIUM OXIDES
CATALYSTS
LABELLED COMPOUNDS
LAYERS
OXYGEN
OXYGEN 18
ALKANES
ALKENES
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
EVEN-EVEN NUCLEI
HYDROCARBONS
ISOTOPES
LIGHT NUCLEI
NONMETALS
NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PHOSPHORUS COMPOUNDS
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties