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Halogen‐Dependent Surface Confinement Governs Selective Alkane Functionalization to Olefins
Author(s) -
Zichittella Guido,
Scharfe Matthias,
Puértolas Begoña,
Paunović Vladimir,
Hemberger Patrick,
Bodi Andras,
Szentmiklósi László,
López Núria,
PérezRamírez Javier
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201811669
Subject(s) - alkane , surface modification , chemistry , catalysis , selectivity , alkyl , photochemistry , halogen , heterogeneous catalysis , x ray photoelectron spectroscopy , radical , chemical engineering , organic chemistry , engineering
The product distribution in direct alkane functionalization by oxyhalogenation strongly depends on the halogen of choice. We demonstrate that the superior selectivity to olefins over an iron phosphate catalyst in oxychlorination is the consequence of a surface‐confined reaction. By contrast, in oxybromination alkane activation follows a gas‐phase radical‐chain mechanism and yields a mixture of alkyl bromide, cracking, and combustion products. Surface‐coverage analysis of the catalyst and identification of gas‐phase radicals in operando mode are correlated to the catalytic performance by a multi‐technique approach, which combines kinetic studies with advanced characterization techniques such as prompt‐gamma activation analysis and photoelectron photoion coincidence spectroscopy. Rationalization of gas‐phase and surface contributions by density functional theory reveals that the molecular level effects of chlorine are pivotal in determining the stark selectivity differences. These results provide strategies for unraveling detailed mechanisms within complex reaction networks.