Quantitative on-line high-resolution NMR spectroscopy in process engineering applications

Abstract

In many technical processes, complex multicomponent mixtures have to be handled, for example, in reaction or separation equipment. High-resolution NMR spectroscopy is an excellent tool to study these mixtures and gain insight in their behavior in the processes. For on-line studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. A major challenge in engineering applications of NMR spectroscopy is the need for quantitative evaluation. Flow rates, recovery times, and other parameters of the on-line NMR experiments have to be optimized for this purpose. Since it is generally prohibitive to use deuterated solvents in engineering applications, suitable techniques for field homogenization and solvent signal suppression are needed. Two examples for the application of on-line NMR spectroscopic experiments in process engineering are presented, studies on chemical equilibria and reaction kinetics of the technically important system formaldehyde-water-methanol and investigations on reactive gas absorption of CO(2) in aqueous solutions of monoethanolamine.

Online NMR spectroscopic study of species distribution in MEA–H2O–CO2 and DEA–H2O–CO2

“…For the 13 C NMR spectra, this is only the case if certain conditions regarding the relaxation in the experiments are fulfilled, cf. [6][7][8]. This was the case here.…”

“…Recently developed methods for quantitative online NMR spectroscopy allow gaining new insight in reacting multicomponent mixtures [6][7][8]. By NMR spectroscopy, even chemically similar components can be distinguished and their nature and concentration can be determined.…”

Chiral separation of nanomole amounts of alprenolol with cITP/NMR

“…NMR diagnostics NMR is a strong diagnostic tool and especially useful to probe the pH [43,44], temperature [45], and flow dynamics occuring during a separation [46,47] which are not observable with most other detectors. The ability of NMR to study the cITP process has been demonstrated previously [48].…”

Simultaneous 19F–1H medium resolution NMR spectroscopy for online reaction monitoring

“…Thus it is a promising quantitative technique without elaborate calibration. Various theoretical and experimental papers have dealt with quantitative NMR spectroscopy, e.g., with respect to continuous flow [3,4], in agriculture [5], for trace components [6] or process engineering or pharmaceutical chemistry applications [7][8][9][10][11][12].…”