Preparation and genesis of molybdena-alumina and related catalyst systems

Journal Article · Wed Sep 01 04:00:00 EDT 1982 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(82)90163-4· OSTI ID:6593979

Wang, L; Hall, W K

Molybdena-, tungsta-, chromia-, and vanadia-alumina preparations were made using an equilibrium adsorption technique. The Na/sup +/ cation was also tested and other supports (titania, magnesia, and silica gel) were employed. The loading of the support was not very dependent on the solution concentration, but for anions was a strong inverse function of the pH. It is shown that this (and the opposite dependence for cations) reflected the isoelectric point of the support surface. Reflectance spectra of the wet, dried (150/sup 0/C), and calcined (500/sup 0/C) catalysts are reported for molybdena-alumina preparations made at several pH values. In agreement with our previously published Raman data, the catalyst prepared at pH = 8.6 yielded spectra of a monomeric tetrahedral species while those made at lower pH yielded spectra characteristic of octahedral (polymeric) molybdena. Thus, better defined catlaysts could be prepared for further study. The data support a model for the ordinary raw catalyst made by incipient wetness from solutions of ammonium paramolybdate in which the surface of the support becomes populated with randomly distributed small clusters (or islands) of polymolybdate species.

• Research Organization: Univ. of Wisconsin, Milwaukee
• OSTI ID: 6593979
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 77:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
CRYSTAL STRUCTURE
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MINERALS
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RAMAN SPECTRA
REFLECTION
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SPECTRA
STRUCTURAL MODELS
SURFACE PROPERTIES
SYNTHESIS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN OXIDES
VANADIUM COMPOUNDS
VANADIUM OXIDES