Competition of chiral modifiers on platinum: A transient catalytic and in situ ATR-IR study in continuous reactors

Fundamental aspects of the competition of chiral modifiers on a metal surface were investigated in a continuous-flow fixed-bed reactor using the enantioselective hydrogenation of ethyl pyruvate on Pt/Al2O3 as an example. The “chiral switch” in the product composition was induced by replacing the modifier (cinchonidine, cinchonine, and quinidine) in the feed. The changes at the catalytic interface were followed by in situ ATR-IR spectroscopy under high-pressure conditions. These studies confirmed the replacement of the chiral modifiers on the metal surface and revealed differences in the adsorption strength and geometry (“flat” and “tilted” species).