Surface chemistry and catalytic activity of La/sub 1-y/M/sub y/CoO/sub 3/ perovskite (M = Sr or Th). II. Hydrogenation of CO/sub 2/

Journal Article · Fri May 01 04:00:00 EDT 1987 · J. Catal.; (United States)

OSTI ID:5329892

Ulla, M A; Migone, R A; Petunchi, J O; Lombardo, E A

The partial substitution of La/sup III/ by either Sr/sup II/ or Th/sup IV/ in lanthanum cobaltate perovskite affects both the rate of hydrogenation of carbon dioxide and the distribution of products. The active site density was calculated from the measured amount of chemisorbed hydrogen at 25/sup 0/C on the oxides reduced at temperatures between 250 and 500/sup 0/C. The catalytic activity was measured in a standard recirculation system using a H/sub 2/:CO/sub 2/ = 4:1 ratio, total pressure of 160 Torr, and 280/sup 0/C reaction temperature. The total conversion of CO/sub 2/ into products (activity) on LaCoO/sub 3/ is little affected by the extent of reduction of the sample. More sensitive to this parameter are both the rate of methanation and the production of C/sub 2//sup +/ compounds. Reduced La/sub 0.8/Th/sub 0.2/CoO/sub 3/ is very stable giving a constant activity, the highest of all the solids assayed and almost exclusively producing methane. La/sub 0.6/Sr/sub 0.4/CoO/sub 3/ shows a sharp maximum in activity and high selectivity to methane when prereduced at 300/sup 0/C. However, when reduced at increasing temperatures the overall activity sharply drops while the selectivity to higher hydrocarbons increases very rapidly. In runs designed to measure the extent of deactivation due to coke deposition it was found that the degree of activity decay was inversely correlated with the methanation selectivity. To gain further insight into both the matrix and promoter effect a series of catalysts were prepared containing different combinations of Co, Sr, La, and Th supported on either celite or La/sub 2/O/sub 3/. The matrix effect is most important in the Sr-substituted oxide, less so in LaCoO/sub 3/, and unimportant in the Th-containing perovskite. A model was proposed to interpret the effect of lanthanum replacement upon the catalytic activity, selectivity, and stability of these solids.

• Research Organization: Universidad Nacional del Litoral, Sante Fe, Argentina
• OSTI ID: 5329892
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 105:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010408* -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
ACTINIDES
ALKALINE EARTH METALS
ALKANES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CATALYTIC REFORMING
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COBALT COMPOUNDS
COBALT OXIDES
COKE
DEACTIVATION
DEPOSITION
ELEMENTS
FISCHER-TROPSCH SYNTHESIS
HYDROCARBONS
HYDROGEN
HYDROGENATION
ISOMERIZATION
KINETICS
LANTHANUM
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MATHEMATICAL MODELS
METALS
METHANATION
METHANE
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITES
PROMOTERS
RARE EARTH COMPOUNDS
RARE EARTHS
REACTION KINETICS
REDUCTION
REFORMER PROCESSES
SEPARATION PROCESSES
SORPTION
STABILITY
STRONTIUM
THORIUM
TRANSITION ELEMENT COMPOUNDS