Abstract
Recently, in situ studies using nuclear magnetic resonance (NMR) have shown the possibility to monitor local transport phenomena of gas-phase reactions inside opaque structures. Their application to heterogeneously catalyzed reactions remains challenging due to inherent temperature and pressure constraints. In this work, an NMR-compatible reactor was designed, manufactured, and tested, which can endure high temperatures and increased pressure. In temperature and pressure tests, the reactor withstood pressures up to 28 bars at room temperature and temperatures over 400 °C and exhibited only little magnetic shielding. Its applicability was demonstrated by performing the CO2 methanation reaction, which was measured operando for the first time by using a 3D magnetic resonance spectroscopic imaging sequence. The reactor design is described in detail, allowing its easy adaptation for different chemical reactions and other NMR measurements under challenging conditions.
Highlights
Process intensification of chemical reactions is one of the main tasks in chemical engineering aiming to increase the efficiency of production steps.1 In this context, many chemical reactions are optimized toward higher efficiencies driven by economic and ecologic aspects.2 Currently, the optimization of power-to-gas or power-toliquid technologies (PtX) is widely discussed in the literature due to their potential to store excess renewable energy.3–5 A prominent example is the CO2 methanation reaction, where carbon dioxide reacts with hydrogen to give methane and water as follows:6CO2 + 4H2 → CH4 + 2H2O (ΔRH298K = −164 kJmol−1). (1)This gas-phase reaction takes place on the solid surface of a catalyst7 while releasing heat
Its applicability was demonstrated by performing the CO2 methanation reaction, which was measured operando for the first time by using a 3D magnetic resonance spectroscopic imaging sequence
Glass is a suitable material for magnetic resonance imaging (MRI) studies,30 it requires comparably large wall thicknesses in order to withstand elevated pressure. Another application reports an MRI vessel made from polyether ether ketone (PEEK) and brass that is used at 200 bars
Summary
Process intensification of chemical reactions is one of the main tasks in chemical engineering aiming to increase the efficiency of production steps. In this context, many chemical reactions are optimized toward higher efficiencies driven by economic and ecologic aspects. Currently, the optimization of power-to-gas or power-toliquid technologies (PtX) is widely discussed in the literature due to their potential to store excess renewable energy. A prominent example is the CO2 methanation reaction (or the Sabatier process), where carbon dioxide reacts with hydrogen to give methane and water as follows:. A prominent example is the CO2 methanation reaction (or the Sabatier process), where carbon dioxide reacts with hydrogen to give methane and water as follows:6 This gas-phase reaction takes place on the solid surface of a catalyst while releasing heat. Resolved profiles of temperature, gas composition, and velocity are crucial for detailed catalyst studies. Industrially relevant heterogeneous gas-phase reactions usually require elevated temperatures and pressure ranges (e.g., for the CO2 methanation, p = 4–10 bars and T > 250 ○C).. Industrially relevant heterogeneous gas-phase reactions usually require elevated temperatures and pressure ranges (e.g., for the CO2 methanation, p = 4–10 bars and T > 250 ○C).24 These requirements contrast one fundamental constraint of NMR studies: the region of interest (ROI) must be free of electrically conducting bulk material. Its applicability is demonstrated by performing the CO2 methanation in the developed setup
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