Catalyst Kinetics and Stability in Homogeneous Alcohol Acceptorless Dehydrogenation

Abstract

The anthropogenic climate changes caused by meeting the energy demands of society by use of fossil fuels render the development of benign alternatives imperative. Probably, the most promising alternative is generating energy by means of power units driven by, e.g., solar, wind, water, etc., and then storing the energy that is not immediately used in battery type devices. Such a device might consist of hydrogen chemically stored as alcohol(s). The advantage of this method is that it allows gaseous hydrogen to be stored much more efficiently when liquefied as an alcohol. Moreover, as will be shown in this review, it is possible to release the hydrogen under mild conditions when employing homogeneous catalysis. This review considers the kinetic aspects of homogeneously catalysed acceptorless alcohol dehydrogenation reactions. For clarity, the sections are divided according to alcohol substrate, and each metal are described and discussed in subsections. Moreover, the kinetic information in the homogeneously catalysed AAD is traditionally provided simply as the turnover frequency, and more in-depth studies on the actual kinetic parameters are to date still largely elusive.

Condensed-Phase Ethanol Conversion to Higher Alcohols over Bimetallic Catalysts

“…From the Arrhenius plot of the rate constant (calculated from the results of each experiment) at each reaction temperature, the overall activation energy for ethanol conversion is E a = 82 kJ/mol. This value is in the range of activation energies (75–100 kJ/mol) for dehydrogenation reactions of short-chain (C1–C3) alcohols over different metals, − supporting ethanol dehydrogenation as the rate-limiting step in the reaction.…”

Heterogenization of Homogeneous Ruthenium(II) Catalysts for Carbon-Neutral Dehydrogenation of Polyalcohols

“…Although the measured activation energies for EG and 1,2-PDO are two to three times greater than those of some alcohol dehydrogenations (e.g., benzyl alcohol) using heterogeneous catalysts, they are closer to other reported E a values, such as those for the dehydrogenation of methanol to methyl formate and the dehydrogenation of cyclohexanol using heterogeneous catalysts (Table S1). − In general, the O–H bonds of polyols are more stable and difficult to activate, making the successful dehydrogenation of EG and 1,2-PDO using our heterogenized molecular catalysts noteworthy.…”

Recent Progress with Pincer Transition Metal Catalysts for Sustainability

“…Research in this area centers on achieving zero-CO 2 emissions and sustainable, eco-friendly chemistry and energy production. Literature is already rich with numerous excellent works reviewing pincer complex chemistry as well as its applications in homogeneous catalysis for sustainable reactions [170][171][172][173][174][175]. As such, in this review we will confine ourselves to discuss the recent progress in the use of pincer complexes as catalysts for sustainable chemistry.…”