Influence of impregnation parameters on the axial Mo/. gamma. -alumina profiles studied using a novel simple technique

Journal Article · Sat Feb 01 00:00:00 EST 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90256-H· OSTI ID:6977691

Goula, M A; Kordulis, Ch; Lycourghiotis, A ^[1]

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1. Univ. of Patras (Greece)

The effects of pH, temperature, volume, and concentration of the molybdate solutions, as well as the impregnation time, the rate of drying, the modification of {gamma}-alumina with F{sup {minus}}ions, and the nature and concentration of various competitors, have been systematically studied. It was found that decreases in pH as well as increases in the concentration of the molybdate solutions, of the impregnation temperature, and of the rate of drying cause a progressive transformation of the Mo profile from uniform to eggshell type. Doping of {gamma}-alumina with F{sup {minus}} ions and the use of NH{sub 4}F, H{sub 3}PO{sub 4}, and citric acid as competitors transformed the Mo profiles from eggshell to uniform. The change in volume of the impregnating solution had no effect on the Mo profiles. The effect of the impregnation time was found to be complicated. Increases in the impregnation time, until a critical value sufficient for the complete imbibition of the extrudates, allow for the transfer of great amounts of molybdate to the interior of the extrudates, leading to more uniform profiles. Further increases in the impregnation time caused a considerable increase in the sharpness of the Mo profile. Most of the above observations were explained on the basis of derived equations, adopting a very simple macrodistribution model. Finally, it was demonstrated that small chromatographic columns filled with powder supports may be used to study active ion profiles on catalytic supports.

• OSTI ID: 6977691
• Journal Information: Journal of Catalysis; (United States), Vol. 133:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CATALYSTS
CHEMICAL PREPARATION
ALUMINIUM OXIDES
AMMONIUM FLUORIDES
AQUEOUS SOLUTIONS
CATALYST SUPPORTS
CITRIC ACID
DISTRIBUTION
DRYING
FLUORINE
IMPREGNATION
MATHEMATICAL MODELS
MOLYBDATES
MOLYBDENUM
PARAMETRIC ANALYSIS
PH VALUE
PHOSPHORIC ACID
QUANTITY RATIO
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
VOLUME
ALUMINIUM COMPOUNDS
AMMONIUM COMPOUNDS
AMMONIUM HALIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
DISPERSIONS
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
HYDROGEN COMPOUNDS
HYDROXY ACIDS
INORGANIC ACIDS
METALS
MIXTURES
MOLYBDENUM COMPOUNDS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
SOLUTIONS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties