Operando Spectroscopic Monitoring of Active Species in CO2 Hydrogenation at Elevated Pressure and Temperature: Steady-State versus Transient Analysis
journal contributionposted on 2021-09-07, 15:36 authored by Alina Gau, Jannis Hack, Nobutaka Maeda, Daniel M. Meier
Operando infrared spectroscopy is an invaluable tool to provide a deep insight into underlying mechanisms in heterogeneous catalysis. Recent advances in spectroscopic techniques enabled operando analysis under elevated pressure and temperature. In this study we compared a conventional steady-state IR analysis with a transient IR analysis by modulation excitation spectroscopy (MES) using a model reaction, CO2 hydrogenation to methanol at 30 bar and 250 °C. The steady-state IR spectra provide information about surface properties of catalysts while the transient IR spectra are a powerful tool to unveil the kinetics of surface species involved in catalytic cycles and therefore to determine rate-limiting step. Operando MES-IR spectroscopy evidenced that under the reaction conditions (30 bar, 250 °C) hydrogenation of surface methoxy species (CH3O−) is the rate-limiting step for the Cu–Zn based catalyst. We herein demonstrate that comparative analysis of both steady-state and transient spectra at elevated pressure provides a solid understanding of surface processes, allowing a rational catalyst design.
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rational catalyst designmodulation excitation spectroscopyir spectroscopy evidenced250 ° coperando spectroscopic monitoring3 </ sub2 </ subtransient ir analysistransient ir spectrasurface species involvedsurface methoxy specieselevated pressure providesstate ir analysistransient spectraelevated pressurecomparative analysisactive speciessurface propertiessurface processesunderlying mechanismssolid understandingrecent advancesreaction conditionspowerful tooloperando mesmodel reactionlimiting stepinvaluable toolheterogeneous catalysisherein demonstratedeep insightcatalytic cycles30 bar