Flow MAS NMR for In Situ Monitoring of Carbon Dioxide Capture and Hydrogenation Using Nanoporous Solids

Abstract

The capability of 1 H and 13 C flow magic-angle spinning NMR is demonstrated for monitoring the capture of CO 2 on the surface of mesoporous amine-functionalized silica and the progress of heterogeneously catalyzed CO 2 hydrogenation over the microporous titanosilicate Pt/ETS-10 under in situ conditions. The custom-built gas-handling system allows to maintain a controllable and stable delivery of reaction gases to the sample compartment containing porous material over a period of hours. Using calibration of NMR signals, we obtained the amounts of reactants and products. The presented approach demonstrates a complementary NMR-based in situ method for quantitative investigation of CO 2 capture and conversion over nanoporous solids.

Nuclear Magnetic Resonance Studies of Carbon Dioxide Capture

“…Importantly, in situ measurements are well-suited to gas mixtures, 49 and should also enable kinetic studies, which have been rare to date. 43 We also note that low field NMR methods are being developed for the study of adsorption phenomena. The lower cost of these approaches are particularly attractive, and may be well-suited for industrial applications.…”

“…Here MAS NMR experiments are performed on the solid adsorbent sample with the simultaneous delivery of CO2 gas to the sample via a hole in one of the rotor caps. [43][44][45] This approach has the advantages that the sample is studied directly under operating conditions, and that the gas dosing conditions (sample temperature and partial pressure of CO2) can be varied continuously.…”

“…Kinetic studies should also be accessible with this approach. 43 One potential disadvantage is the potentially high cost of flowing isotopically enriched gases unless a gas recovery system can be employed. The flow of gases also requires more careful planning with regard to safety issues surrounding gas exposure.…”

The Journal of Physical Chemistry C Virtual Special Issue on Advanced Characterization by Solid-State NMR and In Situ Technology and in Recognition of Michael Hunger’s 65th Birthday

“…Hartmann and coworkers combined in situ continuous-flow MAS NMR with in situ powder X-ray diffraction (PXRD) to show two phase transformation mechanisms of the local porous structure and the bulk crystalline in porous materials during adsorption and desorption . The Gläser group used in situ flow 1 H and 13 C MAS NMR to monitor CO 2 capture and hydrogenation on nanoporous solids . The Xu group investigated the relationship between adsorption and mass transport in confined pores of molecular sieves by 129 Xe NMR .…”

“…28 The Glaser group used in situ flow 1 H and 13 C MAS NMR to monitor CO 2 capture and hydrogenation on nanoporous solids. 29 The Xu group investigated the relationship between adsorption and mass transport in confined pores of molecular sieves by 129 Xe NMR. 30 The effect of the Cu state in Cu/zeolite on methane activation at acid sites using the H/ D exchange method was interrogated by the Stepanov group by in situ 1 H MAS NMR monitoring.…”