The Influence of Physical Interactions on Chemical Reactions in Confinement

Erik E. Santiso1, Keith E. Gubbins1, Aaron M. George2, and Marco Buongiorno-Nardelli2. (1) Center for High Performance Simulation and Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Box 7905, Raleigh, NC 27695, (2) Center for High Performance Simulation and Department of Physics, North Carolina State University, Raleigh, NC 27695

Chemical reactions are often carried out in nano-structured materials due to their large surface area per unit mass and, in some cases, their potential for shape selectivity. It is, however, difficult to understand fully the role of the nano-structure in many chemical reactions due to the superposition of multiple effects. Such effects include: the reduced dimensionality of the system, the chemical heterogeneity of the pore surfaces, the possibility of selective adsorption of reactants/products, catalytic effects, and transport limitations. Experimental studies often show many of these effects at the same time, making the results difficult to interpret.

In this work we present results of density functional theory calculations that illustrate the influence of overlap interactions (i.e. shape-catalytic effects) and electrostatic interactions on several chemical reactions. In particular, we show the effect of confinement in small pores on the rates of rotational isomerizations of small hydrocarbons, and the effect of interactions with carbon walls and nanopores on the unimolecular decomposition of formaldehyde. These results are a first step towards an integrated model for the design of improved catalytic materials.