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Carbon Dynamics on the Molybdenum Carbide Surface during Catalytic Propane Dehydrogenation
Author(s) -
Frank Benjamin,
Cotter Thomas P.,
Schuster Manfred E.,
Schlögl Robert,
Trunschke Annette
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201302420
Subject(s) - dehydrogenation , catalysis , hydrogenolysis , chemistry , propane , inorganic chemistry , methanation , oxidizing agent , molybdenum , carbide , carbon fibers , hydrogen , reactivity (psychology) , water gas shift reaction , oxidation state , materials science , organic chemistry , composite number , medicine , alternative medicine , pathology , composite material
The effect of the gas‐phase chemical potential on surface chemistry and reactivity of molybdenum carbide has been investigated in catalytic reactions of propane in oxidizing and reducing reactant mixtures by adding H 2 , O 2 , H 2 O, and CO 2 to a C 3 H 8 /N 2 feed. The balance between surface oxidation state, phase stability, carbon deposition, and the complex reaction network involving dehydrogenation reactions, hydrogenolysis, metathesis, water‐gas shift reaction, hydrogenation, and steam reforming is discussed. Raman spectroscopy and a surface‐sensitive study by means of in situ X‐ray photoelectron spectroscopy evidence that the dynamic formation of surface carbon species under a reducing atmosphere strongly shifts the product spectrum to the C 3 ‐alkene at the expense of hydrogenolysis products. A similar response of selectivity, which is accompanied by a boost of activity, is observed by tuning the oxidation state of Mo in the presence of mild oxidants, such as H 2 O and CO 2 , in the feed as well as by V doping. The results obtained allow us to draw a picture of the active catalyst surface and to propose a structure–activity correlation as a map for catalyst optimization.