Magnetic Resonance Imaging and Velocity Mapping in Chemical Engineering Applications

Abstract

This review aims to illustrate the diversity of measurements that can be made using magnetic resonance techniques, which have the potential to provide insights into chemical engineering systems that cannot readily be achieved using any other method. Perhaps the most notable advantage in using magnetic resonance methods is that both chemistry and transport can be followed in three dimensions, in optically opaque systems, and without the need for tracers to be introduced into the system. Here we focus on hydrodynamics and, in particular, applications to rheology, pipe flow, and fixed-bed and gas-solid fluidized bed reactors. With increasing development of industrially relevant sample environments and undersampling data acquisition strategies that can reduce acquisition times to <1 s, magnetic resonance is finding increasing application in chemical engineering research.

Measuring velocity and turbulent diffusivity in wall-flow filters using compressed sensing magnetic resonance

“…MRI and MR velocity imaging has been used to study a range of flowing systems and interested readers are directed to reviews by Newling [26] and Gladden and Sederman [27,28]. The majority of work in this field has addressed the imaging of liquid flow fields, while the study of gases and their flows are less common.…”

“…The main reasons for this are twofold; gases have a much lower molecular density than liquids, leading to a low signal-tonoise ratio (SNR), and a much larger self-diffusion coefficient, leading to a reduced signal lifetime, image blurring and decreased velocity resolution. However, there is increasing interest in the development and implementation of gas-phase MRI and velocity mapping in engineering systems [26,28].…”

Opportunities for Characterizing Geological Flows Using Magnetic Resonance Imaging

“…The principles of flow measurements can be combined with the principles of MRI spatial distinction and NMR contrast to achieve images of flow and concentration that distinguish between phases and chemical species within a single measurement. A variety of books ( Callaghan, 1991 ; Levitt, 2008 ) and review articles ( Britton, 2017 ; Fukushima, 1999 ; Gladden and Sederman, 2017 , 2013 ; M. Britton, 2010 ; V. Koptyug, 2014 ) provide more information on principles of NMR and MRI, as well as the application of MRI to study chemical reactions and flow.

Figure 2 Schematic of Basic MRI Setup, Concepts and Capabilities (A) Schematic of a sample in an NMR system (left) and pulse sequence to receive NMR signal (center) to achieve contrast and images (right) from NMR.

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Spatially resolved NMR spectroscopy of heterogeneous gas phase hydrogenation of 1,3-butadiene with parahydrogen

“…14 Therefore, MRI of the gas phase products of heterogeneously catalyzed reactions remains a relatively underdeveloped area despite insightful studies, for instance on mapping the spatial distribution of gases and temperature in ethylene hydrogenation in monolith reactors. 12,[15][16][17] A major improvement in gas imaging can be obtained by exploiting hyperpolarized gases which can provide an up to several orders of magnitude increase in signal intensity and hence in the signal-to-noise ratio (SNR) in NMR experiments. The hyperpolarization methods include, for instance, spinexchange optical pumping (SEOP), [18][19][20][21] dynamic nuclear polarization (DNP), 22,23 parahydrogen-induced polarization (PHIP) [24][25][26][27] and signal amplification by reversible exchange (SABRE).…”