Spatially resolved insights from operando FT-IR on integrated CO2 capture and hydrogenation in the presence of NOx

In this work we develop and exploit a simple and effective spatially resolved operando FT-IR particularly suited for the analysis of catalytic processes where a strong concentration gradient develops along the catalytic bed. As probe system, we have investigated the competition between NOx and CO2 during integrated CO2 capture and hydrogenation, envisioning the use of Dual Function Materials (DFMs) to capture and convert CO2 contained in combustion flue gases. In fact, CO2 is adsorbed as carbonates and NOx is adsorbed as nitrates on the DFM basic sites. When both CO2 and NOx are present in the flue gas, we show direct evidence of carbonates displacement by nitrates at the DFM basic sites following an adsorption front moving along the DFM. By calibrating the intensity of the spectral features, we also provide a fully quantitative analysis of the concentration of adsorbed species with time and space resolution, exploiting the potential of the employed experimental technique. Starting from those results, we demonstrate that, by tuning the adsorption time based on the relative amount of CO2 and NOx in feed, it is possible to operate DFMs even in the presence of NOx without significantly affecting their performance in terms of CO2 capture and hydrogenation.