Probing the Transport of Paramagnetic Complexes inside Catalyst Bodies in a Quantitative Manner by Magnetic Resonance Imaging

Magnetic resonance microscopy of iron transport in methanogenic granules

“…A pioneering study was presented by Nestle and Kimmich [25], measuring metal sorption in well defined, highly homogeneous alginate gels and immobilized cells. Similar studies were performed in sandy aquifers [12] and catalyst bodies [13]. Most recently, Phoenix and Holmes [24] presented a MRI study on copper immobilization in phototrophic biofilm.…”

“…In situ metal concentrations can be measured by microelectrodes, but these microelectrodes are poorly developed [7]. Magnetic Resonance Imaging (MRI) can measure metal transport in porous matrixes non-destructively and non-invasively based on changes in spin-lattice (T 1 ) or spin-spin (T 2 ) relaxation times due to the presence of paramagnetic metal ions [8][9][10][11][12][13]. Although MRI measurements have often been applied to reveal structural and diffusional properties of microbial biofilms [14][15][16][17][18][19], only a few studies have focused on metal-biofilm interactions [20][21][22][23][24].…”

Chemical Imaging of Spatial Heterogeneities in Catalytic Solids at Different Length and Time Scales

“…In other words, the proportion of paramagnetic nuclei can be monitored in space and time within a catalyst body by monitoring the quenching of the 1 H MRI signal. [35][36][37] The proof of principle is illustrated in Figure 14 Lighter shades of gray correspond to higher signal intensity. Reproduced from reference [18], copyright Elsevier, 2007. catalyst body at different times after impregnation, while Figure 14 b shows a quantitative Co 2+ -ion distribution plot derived from the 2D images.…”

Recent Trends in Operando and In Situ Characterization: Techniques for Rational Design of Catalysts

“…It has already been used to study several catalysts, such as Ni/Al 2 O 3 [59] and Co/Al 2 O 3 during impregnation [60]. For Co/Al 2 O 3 , it was shown that the distribution of Co 2+ over an extrudate can be quantified with an empirical correlation between the 1 H NMR signal intensity and the Co 2+ concentration [60]. In a later study, experimental parameters were varied to check their effect on the macrodistribution.…”

“…The pH of the impregnation solution also influenced the distribution of Co over the support. This means that by controlling the concentration of citrate and solution pH, it is possible to tune the macrodistribution of Co over the Al 2 O 3 extrudate to achieve the desired spatial distribution [61].…”