As part of the consortium for Computational Physics and Chemistry we have conducted a collaboration with PNNL and ORNL scientists who are independently developing catalysts to produce butenes from ethanol derived from renewable sources. We will present the highlights of our mechanistic studies on both supported nanoparticle and single atom catalysts. Using a combination of ab initio molecular dynamics (AIMD) and global optimization techniques, we explore the complex energy landscape associated with the conversion pathway on nanoparticles of silver and other metals. Here, we find that the critical ingredients for controlling the conversion pathway are: (i) intermediate Lewis acidity for promoters to balance C-C coupling vs dehydration; (ii) a balance of both cationic and fully reduced metals to control dehydrogenation and hydrogenation reactions; and (iii) the proximity of the functional groups at the perimeter sites. Conversely, the zeolite-based catalysts have all reactive sites geometrically separated, but confinement contributes to enhanced conversions. AIMD combined with in situ XAS confirms the presence of CuH in silanol nests which is active towards hydrogenation and dehydrogenation reactions. AIMD also shows that sintering of mobile CuH into nanoparticles is facile and strongly dependent upon the acidity of the zeolite and the presence of water. Although sintering reduces the catalytic activity, it is fully reversible upon re-oxidation.

Theoretical mechanistic studies of conversion of alcohols to butenes over catalysts composed of silica supported nanoparticles and isolated metal atoms confined in zeolites

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.