An ¹H NMR Microimaging Visualization of Hexachloroplatinate Dianion Redistribution within a Porous γ-Al₂O₃ Pellet in the Course of Supported Catalyst Preparation

Abstract

The application of the 1H NMR microimaging technique to the indirect mapping of the spatial distribution of hexachloroplatinate dianion within porous alumina pellets is reported. It is demonstrated that the nuclear spin−lattice relaxation times of liquids filling the pores of the pellet increase in the presence of the adsorbed hexachloroplatinate dianion. The microimaging results for the supported catalysts with two types of platinum distribution (egg-shell and egg-white) are shown to be consistent with the results obtained by the staining method and electron probe microanalysis. Finally, the microimaging technique is employed for a nondestructive visualization of the dynamics of the active component redistribution in the course of the supported catalyst preparation by competitive adsorption.

Tailored Microstructured Hyperpolarizing Matrices for Optimal Magnetic Resonance Imaging

“…Magnetic resonance imaging (MRI) is ubiquitous in laboratories and in our daily life,w ith applications ranging from chemical engineering (measurement of molecular diffusion, dispersion, and flow hydrodynamics within reactors [1] or probing of catalysts [2,3] and catalytic processes from the nanometer-to-centimeter scale) to in vivo MRI of tissues or target organs,w ithout the need for damaging radiation. However,N MR (or MRI) suffers from an intrinsically low sensitivity,a rising from the low thermal equilibrium (Boltzmann) polarization of the nuclear spins at room temperature, even with the highest-field instruments.This drawback can be circumvented by dynamic nuclear polarization (DNP), which allows for dramatic NMR signal enhancements well beyond thermal equilibrium at low temperatures by microwaveinduced cross-polarization from highly thermally polarized electron spins to nuclear spins.B ased on this DNP phenomenon, dissolution DNP (d-DNP) setups have been developed since 2003 to polarize as ample at low temperature (1-4 K), astep which is then followed by rapid dissolution to the liquid state;the hyperpolarized solution is then transferred from the polarizer to an NMR spectrometer or MRI scanner.…”

Monitoring the preparation of (Co)Mo/Al2O3 extrudates using spatially resolved spectroscopic techniques

“…Probably, this is partly due to liquid-surface interactions. It is observed that the adsorption of Pt 4+ complexes to the A1 2 O3 surface increases the TI relaxation time of the water inside the pores [18]. Using a special pulse sequence, by which TI weighted images are recorded, it is possible to detect the distribution of these complexes inside the A1 2 O 3 extradâtes.…”

Space-Resolved Profiling Relevant in Heterogeneous Catalysis

“…Furthermore, physicochemical processes during catalyst preparation and resulting distribution of catalytically active metals have been studied, giving rational reasoning for the distribution processes and patterns as shown in Fig. 4 [123][124][125][126].…”