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Pokochueva EV, Svyatova AI, Burueva DB, Koptyug IV. Chemistry of nuclear spin isomers of the molecules: from the past of the Universe to emerging technologies. Russ Chem Bull 2023. [DOI: 10.1007/s11172-023-3711-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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Ridder H, Sinn C, Pesch GR, Dreher W, Thöming J. Longitudinal Relaxation ( T 1) of Methane/Hydrogen Mixtures for Operando Characterization of Gas-Phase Reactions. ACS MEASUREMENT SCIENCE AU 2022; 2:449-456. [PMID: 36785657 PMCID: PMC9885991 DOI: 10.1021/acsmeasuresciau.2c00022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 07/11/2022] [Accepted: 07/11/2022] [Indexed: 06/18/2023]
Abstract
Catalytic hydrogenation reactions are important in a modern hydrogen-based society. To optimize these gas-phase reactions, a deep understanding of heat, mass, and momentum transfer inside chemical reactors is required. Nuclear magnetic resonance (NMR) measurements can be used to obtain spatially resolved values of temperature, gas composition, and velocity in the usually opaque catalytic macrostructures. For this, the desired values are calculated from measured NMR parameters like signal amplitude, T 1, or T 2. However, information on how to calculate target values from these NMR parameters in gases is scarce, especially for mixtures of gases. To enable detailed NMR studies of hydrogenation reactions, we investigated the T 1 relaxation of methane and hydrogen, which are two gases commonly present in hydrogenation reactions. To achieve industrially relevant conditions, the temperatures are varied from 290 to 600 K and the pressure from 1 bara to 5 bara, using different mixtures of methane and hydrogen. The results show that hydrogen, which is usually considered to be nondetectable in standard MRI sequences, can be measured at high concentrations, starting at a pressure of 3 bara even at temperatures above 400 K. In the investigated parameter range, the absolute T 1 values of hydrogen show only small dependence on temperature, pressure, and composition, while T 1 of methane is highly dependent on all three parameters. At a pressure of 5 bara, the measured values of T 1 for methane agree very well with theoretical predictions, so that they can also be used for temperature calculations. Further, it can be shown that the same measurement technique can be used to accurately calculate gas ratios inside each voxel. In conclusion, this study covers important aspects of spatially resolved operando NMR measurements of gas-phase properties during hydrogenation reactions at industrially relevant conditions to help improve chemical processes in the gas phase.
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Affiliation(s)
- Harm Ridder
- Chemical
Process Engineering (CVT), Faculty of Production Engineering, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany
- Center
for Environmental Research and Sustainable Technology (UFT), Post box 330 440, 28334 Bremen, Germany
| | - Christoph Sinn
- Chemical
Process Engineering (CVT), Faculty of Production Engineering, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany
- Center
for Environmental Research and Sustainable Technology (UFT), Post box 330 440, 28334 Bremen, Germany
| | - Georg R. Pesch
- Chemical
Process Engineering (CVT), Faculty of Production Engineering, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany
- Center
for Environmental Research and Sustainable Technology (UFT), Post box 330 440, 28334 Bremen, Germany
- MAPEX
Center for Materials and Processes, University
of Bremen, Post box 330 440, 28334 Bremen, Germany
| | - Wolfgang Dreher
- in
vivo MR group, Faculty of Chemistry, University
of Bremen, Leobener Str.
NW2, 28359 Bremen, Germany
| | - Jorg Thöming
- Chemical
Process Engineering (CVT), Faculty of Production Engineering, University of Bremen, Leobener Str. 6, 28359 Bremen, Germany
- Center
for Environmental Research and Sustainable Technology (UFT), Post box 330 440, 28334 Bremen, Germany
- MAPEX
Center for Materials and Processes, University
of Bremen, Post box 330 440, 28334 Bremen, Germany
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