Strong oxide-oxide interactions in silica-supported magnetite catalysts. IV. Catalytic consequences of the interaction in water-gas shift

Journal Article · Thu Jul 01 00:00:00 EDT 1982 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(82)90240-8· OSTI ID:6628914

Lund, C R.F.; Dumesic, J A

Water-gas shift was studied at 663 K and 0.1 MPa over a series of silica-supported magnetite (Fe/sub 3/O/sub 4/) catalysts having magnetite particles from ca. 10 to 160 nm in size. The surface sites on these catalysts were titrated using NO adsorption at 273 K and adsorption from a CO/sub 2//CO gas mixture (CO/sub 2/:CO = 85:15) at 663 K. For these silica-supported catalysts, the water-gas shift turnover frequency, based on NO adsorption for site titration, decreased with decreasing particle size. In contrast, unsupported magnetite did not show this particle size dependence. For the smallest silica-supported magnetite particles, the turnover frequency was three orders of magnitude lower than over unsupported magnetite. The extent of CO and CO/sub 2/ adsorption, per surface site as titrated by NO, was also observed to decrease with decreasing particle size; and, the water-gas shift turnover frequency, based on CO/sub 2//CO adsorption for site titration, is independent of particle size. Thus, while NO adsorption can be used to measure the magnetite surface area of silica-supported samples, the CO/sub 2//CO adsorption uptake is proportional to the number of active sites on the magnetite surface. Compared to unsupported magnetite, the origin of the low catalytic activity of silica-supported magnetite (based on NO adsorption for site titration) is interpreted as being due to the effects of Si/sup 4 +/ substitution into the surface of magnetite, which causes the iron cations at the surface to become electron deficient and coordinatively more saturated with oxygen anions. 2 figures, 1 table.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 6628914
• Journal Information: J. Catal.; (United States), Vol. 76:1
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE
CHEMISORPTION
CARBON MONOXIDE
MAGNETITE
CATALYTIC EFFECTS
SHIFT PROCESSES
CATALYSTS
SILICA
CATALYST SUPPORTS
CHEMICAL REACTION KINETICS
COMPARATIVE EVALUATIONS
EXPERIMENTAL DATA
HIGH TEMPERATURE
LOW TEMPERATURE
MEDIUM PRESSURE
NITRIC OXIDE
PARTICLE SIZE
PRESSURE DEPENDENCE
SURFACE AREA
TEMPERATURE DEPENDENCE
TITRATION
WATER GAS PROCESSES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
INFORMATION
IRON COMPOUNDS
IRON ORES
IRON OXIDES
KINETICS
MINERALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NUMERICAL DATA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)
400201 - Chemical & Physicochemical Properties