Description:

Sol Ahn, Notestein/Farha Groups:

Title
Solid Acid Catalyzed C-C Bond Isomerization and Disproportionation over Tungstated NU-1000

Abstract
Acid-catalyzed skeletal C-C bond isomerizations are important reactions for the petrochemical industries. Hydrocarbons such as hexane and xylene are crucial reactants in the production of fuels and basic petrochemicals, and these have been model reactions that provide structural information on solid acid catalysts. Among those, o-xylene isomerization/disproportionation is a probe reaction for strong Brønsted acid catalysis, and it is also sensitive to the local acid site density and pore structure.

I will discuss the use of phosphotungstic acid (PTA) encapsulated within a Zr-based metal–organic framework (MOF), NU-1000, as a catalyst for o-xylene isomerization and disproportionation. Extended X-ray absorption fine structure (EXAFS), 31P NMR, N2 physisorption, and powder x-ray diffraction (PXRD) show that the catalyst is stable after the reaction condition. Initial rates over the NU-1000-supported catalyst were comparable to a control WOx-ZrO2, however the NU-1000 supported catalyst was unusually active toward the transmethylation pathway that requires two adjacent active sites in a confined pore, as created when PTA is confined in NU-1000. This work shows the promise of metal–organic framework topologies in giving access to unique activity, even for aggressive reactions such as hydrocarbon isomerization.

Anyang Peng, Kung Group:

Title
Low temperature selective oxidation of ethylbenzene by catalyzed co-oxidation using Co-ZSM-5 and solubilized Au clusters catalysts: extend the reach of heterogeneous catalysis

Abstract
Selective oxidation of hydrocarbon using of the ubiquitous molecular O2 as the terminal oxidant is economically attractive but challenging due to the kinetic constraint imposed by the triplet ground state of dioxygen and the inherently inertness of the C-H bonds. One such oxygen driven strategy is co-oxidizing two or more substrates through one-pot cascade reactions in which a kinetically or thermodynamically limited partial oxidation reaction is facilitated by another partial oxidation reaction occurring simultaneously, with the help of multiple heterogeneous catalysts or multi-functional heterogeneous catalysts.
Throughout its history, heterogeneous catalysis process has been considered to occur by kinetic coupling of elementary steps including adsorption, surface reactions and desorption; nevertheless, this process is often accompanied by formation of reactive intermediates, which can diffuse through the surrounding fluid media and lead to cascade reactions that are beyond the reach of heterogeneous catalysis. Herein we report the Au & Co co-catalyzed co-oxidation of cyclooctene (COE) and ethylbenzene (EB) with molecular O2 to form the useful products of cyclooctene epoxide and acetophenone under mild temperature and ambient pressure. To the best of our knowledge, this is the first example of a unique cascade reaction, in which a sequential reaction was catalyzed by the active intermediate generated from a previous reaction. A better understanding of properties of
energetic reactive intermediates and their contributions to multi-reaction networks would ultimately lead to more efficient use of atoms and energy in chemical transformations