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          Institute: Fritz-Haber-Institut     Collection: Inorganic Chemistry     Display Documents



  history
ID: 256238.2, Fritz-Haber-Institut / Inorganic Chemistry
Surface science meets catalysis research: epitaxial iron oxide films for in-situ model catalysis
Authors:Ranke, Wolfgang
Language:English
Research Context:19: Iron oxide model catalysts: Adsorption and catalysis
Name of Conference/Meeting:International Workshop on Nanostructured Materials, NANOMAT 2006
Place of Conference/Meeting:Antalya, Turkey
(Start) Date of Conference/Meeting
 (YYYY-MM-DD):
2006-06-21
End Date of Conference/Meeting 
 (YYYY-MM-DD):
2006-06-23
 Invitation status:invited
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:I will review a fairly successful attempt to bridge the gaps between surface science studies and real catalysis for the case of ethylbenzene (EB) dehydrogenation to styrene (St) over unpromoted and K-promoted iron oxide catalysts. Epitaxial films of Fe3O4(111), a-Fe2O3(0001), KxFe22O34 and KFeO2 were prepared and characterized using surface science methods. Their catalytic behavior was studied after vacuum-transfer in a micro flow reactor, followed by post-reaction surface analysis. The results are : (i) Defects are necessary for the dehydrogenation step; (ii) most active is Fe3+ in Fe2O3 or KFexOy; (iii) unpromoted catalysts deactivate by reduction to Fe3O4 and by coking; (iv) both can be prevented by some oxygen in the feed; (v) K is catalytically inactive but suppresses reduction and catalyses carbon removal; (vi) K2Fe22O34 and KFeO2 are K-reservoir phases; (vii) “steaming” (reaction in steam without EB) exhausts the K-reservoir phases; (viii) coke has non-zero catalytic activity and contributes to conversion in real catalysis. In cooperation with the ICVT in Stuttgart, microkinetic modelling was performed aiming at a prediction of the behaviour of technical catalysts. Using physically meaningful parameters, mostly determined in surface science experiments, an excellent fit was achieved which could even be extented to porous samples.
Free Keywords:iron oxide, epitaxy, in-situ, catalysis, styrene
Last Change of the Resource (YYYY-MM-DD):2006-03-10
Document Type:Talk at Event
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Inorganic Chemistry/Surface Analysis
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