Abstract

Water is ubiquitous in a broad range of physicochemical phenomena and technological processes. For example, water is a desirable solvent for reasons of cost, safety, and environmental concerns. Solvent effects in chemical reactions are often connected to changes in solubility due to the polarity and other characteristics of the solvent, which can affect transport properties and indirectly overall reaction rates. In addition to the well-known solvation, heat transfer and sink effects, water can also form rich variety of structures at the water/solid interfaces to enhance the reaction performance and even change the kinetics of surface-catalyzed reactions.  This is the main aspect that we want to address in our proposed review.  One of the most common ways in which water can affect the intrinsic rate of reaction is the so-called differential solvation in which the solvent stabilizes the transition state to a greater extent from the initial state.  As a result, a reduction in activation barrier takes place. 

 

Another, just recently recognized, role of water is its mediation in reactions involving H-transfer, thus providing a lower energy path.  Several examples of this phenomenon exist in the literature, including some of our own work, which we would like to analyze.  For example, in Fischer-Tropsch synthesis it has been proposed that water can function as a H-shuttling mediator by transferring a H from the surface onto the CO molecule and thus facilitating the rate-limiting H-assisted CO cleavage.  Similar shuttling mechanism has been proposed for other reactions involving H-transfer, such as hydrogenation of furfural, aldol condensation, and other biomass upgrading reactions.  One aspect that seems to be particularly intriguing is the “remote promotion effect” that only seems to occur in liquid aqueous systems, either involving remote proton hopping or remote bond polarization. Since this water-mediated mechanism seems to be a general phenomenon that can explain water promotion for a number of different reactions, we would like to do a critical analysis of all reactions that have shown to be enhanced by water.  Other mechanisms of water promotion will also be explored.  For instance, the recent analysis of the effect of confinement of hydronium ions in zeolites when reactions are carried out in the aqueous phase will also be reviewed, paying particular attention to the combination of experimental kinetics and theoretical calculations.  

 

Bio

Prof. Daniel E. Resasco (PhD Chemical Engineering, Yale University, Gallogly Chair and GLC Professor at the University of Oklahoma).   Resasco obtained his BS (1975) from Argentina and his PhD (1984) from Yale University. He specializes in heterogeneous catalysis and nanostructured materials for applications in energy, fuels, and chemicals. He has been editor of the Journal of Catalysis and member of editorial boards for several periodicals. He is an industrial consultant in areas related to catalysis, reaction engineering, oil refining, nanotechnology, and carbon nanotubes. Has supervised more 80 graduate students (PhD and MS). 

 

He is the Chair of the Catalysis Division of ACS, a member of the National Academy of Sciences of Argentina, Fellow of the National Academy of Inventors, Distinguished Overseas Professor in Shanghai China, the Inaugural Gallogly Chair of Engineering, George Lynn Cross Research Professor (Highest research honor bestowed by the University of Oklahoma, the Douglas and Hilda Bourne Chair of Chemical.  He has received the Catalysis Club of Philadelphia Award, the Yale Award for Advancement of Basic and Applied Science, the Oklahoma Chemist of the Year award (American Chemical Society), the Regents Award for Superior Research), the Houssay Award for scientific achievement (National Research Council of Argentina). Has received the Sam A. Wilson Professorship, the Janet and Ken Smalley Presidential Professorship. Has been D. B. Robinson Distinguished Speaker (U. Alberta, Edmonton, Canada) and received the N.N. Bakhshi Lectureship Award in Chemical Engineering, (U. Saskatchewan, Canada). Resasco is author of 280 publications and 40+ industrial patents. He has received 24,000+ citations. His h-index is 78.