Magnetic Resonance Imaging

Abstract

The sections in this article are Introduction Basic Principles Magnetic Resonance Imaging Fast Data Acquisition Measurement of Diffusion, Transport and Flow Applications Imaging Individual Catalyst Pellets Hydrodynamics in Reactors Single‐Phase Flow Two‐Phase Flow in Fixed‐Bed Reactors Imaging Reactions In Situ 1 H Imaging 13 C Imaging Conclusion

Diffusion in nanopores: correlating experimental findings with “first-principles” predictions

“…(12)-(15), direct measurement of the distribution of guest concentrations in the interior of the crystals/particles under study and of their variation with time provides the most direct access to the underlying diffusivities. Among the manifold techniques allowing such monitoring, imaging by nuclear magnetic resonance has, most likely, attained largest popularity (Gladden et al 2008;Kahn and Busse 2012;Willis et al 2018), notably due to its unprecedented potentials for application in medical diagnosis. Since the very first applications of "nuclear magnetic imaging" (at this time still under the name "zeugmatography" as coined by its inventor, Paul Lauterbur (P.C.…”

Monitoring Molecular Mass Transfer in Cation-Free Nanoporous Host Crystals of Type AlPO-LTA

“…In contrast to IFM and IRM, measurements by PFG NMR are performed under equilibrium conditions, with the mean-square displacement (eq ) of the guest molecules as the key quantity. PFG NMR measurements are based on the same fundamental law which is also exploited in NMR tomography , (which today, generally referred to as MRT, has become the most powerful imaging technique in medical diagnosis), namely proportionality between the intensity of the magnetic field and the nuclear magnetic resonance frequency. In this way, by superimposing a constant magnetic field an inhomogeneous one (the “field gradient”), the spectrum shows the spin distribution in the gradient direction.…”

“…Operating under equilibrium conditions and with assemblages of crystals, PFG NMR is unable to record mass transfer in the interior of a particular, individual crystal. Although NMR tomography has proved to be useful for recording guest concentrations and fluxes in beds of crystals, despite substantial methodological progress, , spatial and temporal resolutions are not yet high enough to record mass transfer in the interior of the individual crystallites. With the successful application of interference microscopy (IFM) , and infrared microscopy (IRM) , to micro-imaging with individual crystals, , however, this type of information has now become accessible.…”

Transport-Optimized Nanoporous Materials for Mass Separation and Conversion as Designed by Microscopic Diffusion Measurement

“…The value of this type of information is further enhanced if it may be complemented by the microscopic measurement of the evolution of concentration gradients and of molecular fluxes. Though, in principle, this type of information can be made accessible by magnetic resonance imaging (see, e.g., [63][64][65] or, as the probably first application in chemical engineering, [66]), spatial and time resolution are, as a rule, not yet sufficient for a satisfactory recording of the evolution of transient concentration profiles within the individual crystallites. Such a possibility is provided by the techniques of microimaging by interference microscopy (IFM) and IR microscopy (IRM) [25,67,68].…”