Structure–Activity Relationships in Lewis Acid–Base Heterogeneous Catalysis

Abstract

Heterogeneous catalysts are the key components in industrial chemical transformations. Metal oxides are particularly appealing as catalysts owing to their inherent Lewis acid–base properties that facilitate the activation of chemically inert paraffinic C–H bonds. Computational chemistry provides a rich mechanistic understanding of catalyst functionality through the calculation of accurate thermodynamic and kinetic data that cannot be experimentally accessible. Using these data, one can relate the energy needed for elementary reaction steps with properties of the catalyst, paving the way for computational catalyst discovery. At the heart of this process is the development of structure–activity relationships (SARs) that facilitate the rapid prediction of promising catalytic materials for energy intense industrial transformations, guiding experimentation. In this review article, we highlight SARs on oxides for chemical reactions of high industrial relevance including (i) methane activation and conversion, (ii) alkane dehydrogenation, and (iii) alcohol dehydration. We also discuss current limitations and challenges on SARs and propose future steps to advance catalyst discovery.

Toward Understanding and Controlling Organic Reactions on Metal Oxide Catalysts

“…Thus, from a conceptual point of view, an experimentalist can consider Δ E rxn to be similar to Δ H rxn °. Various electronic-structure-based chemical descriptors and linear relations have been shown to be successful for reactions over metal oxides, ,− including oxygen vacancy formation energies (Δ E vac ) and hydrogen adsorption energies (Δ E H,ads ). Δ E vac refers to the energy of removing a lattice oxygen (which is related to the energy required for refilling oxygen vacancies (−Δ E vac = Δ E refill ), and Δ E H,ads refers to the energy for creating a hydrogen atom on the surface by adsorption from the gas phase (typically using H 2 gas as a reference state).…”

Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst

“…Negative segregation energy indicates that segregation to the surface is thermodynamically favored. The binding energy of dissociated hydrogen (H 2 BE) 10,23,52,53 on metal-nitrogen surface site pairs is calculated as follows:…”

“…Negative segregation energy indicates that segregation to the surface is thermodynamically favored. The binding energy of dissociated hydrogen (H 2 BE) 10,23,52,53 on metal–nitrogen surface site pairs is calculated as follows:H 2 BE = E surface/H 2 − ( E H 2 + E clean surface )where E surface/H 2 and E clean surface are the total electronic energy of a heterolytically dissociated H 2 on metal–nitrogen site pair and clean (112̄0) AlN surface, respectively. E H 2 is the total electronic energy of an isolated H 2 molecule in the gas phase.…”

Understanding and Optimizing the Behavior of Al- and Ru-Based Catalysts for the Synthesis of Polyisobutenyl Succinic Anhydrides

“…Aluminum-based Lewis acid catalysts have been shown to be active for a variety of reactions of industrial importance. For example, alumina has been shown to selectively activate C–H bonds of alkanes due to its inherent Lewis acidity (metal centers) and basicity (oxygen centers) . This nonoxidative alkane dehydrogenation has been shown to be a promising route to produce olefins that are commonly used as building blocks in the chemical industry to produce commodity chemicals such as polymers, plastics, and petrochemicals .…”