Influence of Metal Doping on the Lewis Acid Catalyzed Production of Butadiene from Ethanol Studied by using Modulated Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Mass Spectrometry

Due to an increasing gap between the demand and supply, the catalytic coupling of ethanol has regained the attention of the scientific and industrial community as an "on-purpose" production route to butadiene. The most promising systems are based on bifunctional catalysts, comprising of metal sites that can dehydrogenate ethanol to acetaldehyde, and Lewis acid sites that catalyze the aldol condensation between two aldehyde molecules, as well as the Meerwein-Ponndorf-Verley (MPV) reduction of the intermediate crotonaldehyde. Here, we investigate the role of Ag in an established Ag-Zr-BEA catalyst using modulated operando DRIFTS-MS experiments. We obtain insights into the complex reaction network that involves several consecutive and parallel reactions. Based on our investigations, we formulate suggestions for catalyst optimization.