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The sections in this article are Introduction Importance of Light Alkenes Historical Developments Conceptual Approach Influence of Temperature on the Equilibrium Influence of Partial Pressure on the Equilibrium Energy of Alkane Dehydrogenation Formation of By‐Products Removal of Hydrogen to Shift the Equilibrium Spatial Separation of Dehydrogenation and Hydrogen Combustion Dehydrogenation and Hydrogen Combustion in a Catalyst Bed Oxidative Dehydrogenation ( ODH ) Catalytic Systems Supported Chromia Catalysts Chromia on Al 2 O 3 Supports A Structure and Reactivity B Oxidized State C Reduced State D Regeneration Chromia on Si O 2 / Zr O 2 Supports Supported Platinum/Tin Catalysts Platinum as Active Component Tin as Modifier State and Mode of Operation of Platinum and Tin A State of Pt and Sn B Mode of Operation of Pt and Sn C Ensemble Effect D Ligand Effect Role of the Support Regeneration of Supported Platinum/Tin Catalysts A Treatment with Molecular Oxygen B Treatment with Chlorine C Treatment with Hydrogen Kinetics and Mechanism Kinetics of Dehydrogenation Chromia/Alumina Catalysts A Mechanism 1 B Mechanism 2 Platinum and Platinum/Tin Catalysts Kinetics of Deactivation Reactor Concepts Endothermic Character Preheating the Feed and Carrying out the Reaction in an Adiabatic Reaction System Carrying Out the Reaction in a Heated Reactor Preheating the Catalyst and Carrying Out the Reaction in an Adiabatic Reactor Regeneration Continuous Systems Discontinuous Systems Commercial Processes UOP Oleflex Process U hde STAR Process ABB Lummus CATOFIN Process Linde PDH Process S namprogetti‐ Y arsintez FBD Process Dehydrogenation of Other Alkanes Dehydrogenation of Heavy n ‐Alkanes Dehydrogenation of Cyclohexane Future Developments Membrane Technology CO 2 as a Diluent Conclusions and Future Prospects

In THF solution the dirhenium complex Re 2 (µ-H)(µ-PCy 2 )(CO) 8 (1) reacts with an equimolar amount of LiPh at -100°C to afford after warming up to room temperature within 1 h the salt Li[Re 2 (µ-H)(µ-PCy 2 )(C(Ph)O)-(CO) 7 ] (Li[2]). Through cation exchange of Li + against PPh 4 + , Li[2] gives the airstable solid PPh 4 [2] in 86% yield. The selectivity of the LiPh attack at one of the four axial carbonyls in 1 was proved by the chiral shift reagent Eu(hfac) 3 which was dissolved in a CDCl 3 solution of PPh 4 [2]. The 1 H and 31 P NMR spectra show the diastereomeric resolution of the respective peaks in an integral ratio of 1:1 e.g. ∆δ(µ-P) 0.43. The anion [2 -] generates with 2 equiv of XAuPPh 3 (X ) Cl, Br, I) in THF at room temperature within 15 min under release of the leaving group PhCHO the yellow cluster complexes Re 2 (AuPPh 3 ) 2 (µ-PCy 2 )(CO) 7 X (4a-c). Their precursor complex anions [Re 2 (µ-AuPPh 3 )(µ-PCy 2 )(CO) 7 X] -(3a-c) are obtained from 1 and an equimolar amount of XAuPPh 3 or from the deauration by treatment of 4a (X ) Cl) with 1 equiv of LiPh via a transmetalation reaction. Such anions are isolable as salts, N(PPh 3 ) 2 [3a-c]. All new cluster complexes are identified by means of 1 H NMR, 31 P NMR and ν(CO) IR spectroscopic measurements, Li[2] and 4a (X ) Cl) additionally by means of X-ray single-crystal structure analyses. Li[2] crystallizes triclinic, space group P1 h, Z ) 2, a ) 10.536(2) Å, b ) 11.433(2) Å, c ) 19.125(3) Å, R ) 98.01(1)°, ) 89.94(1)°, and γ ) 112.22(1)°; 4a crystallizes monoclinic, space group P2 1 /c, with Z ) 4, a ) 18.615(5) Å, b ) 13.606 (2) Å, c ) 24.223(6) Å, and ) 105.14(2)°. The molecular structure of Li[2] shows a µ-H-, µ-P-bridged Re-Re bond of 3.1667(7) Å, the one of 4a a tetrahedrally shaped Re 2 Au 2 core with a µ-P-bridged Re-Re edge of 3.2680(10) Å.

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An improved understanding of the nature and distribution of boron and cesium species in BCsX zeolites is a prerequisite to guide future developments in the environmentally attractive, yet challenging, production of styrene through the side-chain alkylation of toluene with methanol. Herein, standard characterization and catalytic tests are complemented by integrated visualization through time-of-flight secondary-ion mass spectrometry and energy-dispersive X-ray spectroscopy and detailed assessment by Cs and B NMR spectroscopy, to correlate the properties and performance during successive ion-exchange and impregnation steps in the preparation of both powders and millimeter-sized granules. The results highlight a significant impact of catalyst scaleup on the effective introduction of boron species, which originates chemical heterogeneity that is linked to selectivity losses. They also illustrate the complexity of elucidating the role of this promotor, which interacts with cesium cations and exhibits different coordination states and chemical environments, depending on the pretreatment.