Three‐Dimensional Imaging of Surface Chemical Processes in Catalysis Using High‐Resolution Positron Emission Tomography

Abstract

The positron emission tomography (PET) technique is a well‐known method in nuclear medicine for molecular imaging of biochemical functions in the human body, but it can also be applied to molecular imaging of the chemical processes on the surfaces of heterogeneous catalysts. Dynamic studies of adsorption, desorption, and realignment of 11C positron‐emitter‐labeled compounds can be performed. In the work reported herein, a small PET scanner with approximately 1.3 mm spatial resolution, originally dedicated for small‐animal studies, is applied to image the location and quantitative distribution of [11C]methanol in a catalyst bed of approximately 8 cm3 volume in three dimensions. The PET imaging technique in combination with radio‐gas chromatographic analysis was also used to study different strengths of chemical bonds during catalytic processes on fresh and used Linde A‐type zeolites as catalysts. The PET technique has been highly developed in the last few years with higher resolution and sensitivity and improved image reconstruction algorithms. The commercial human and small‐animal PET scanners have great potential for imaging of well‐functioning, poorly functioning, or partially covered catalyst surfaces in academic and industrial research for the development of catalysts. High‐resolution PET scanning is a great catalysis imaging technique because of both axial and radial imaging of the catalyst bed; therefore, the distribution of radioactive compounds is analyzable in the total catalyst volume.

Probing the Influence of SSZ‐13 Zeolite Pore Hierarchy in Methanol‐to‐Olefins Catalysis by Using Nanometer Accuracy by Stochastic Chemical Reactions Fluorescence Microscopy and Positron Emission Profiling

“…The spatial resolution of this technique is limited to approximately 1 mm, the distance the positron can travel before annihilation. The use of PET imaging using 11 C‐labeled methanol allows us to monitor the build‐up of hydrocarbon pool species, which cannot leave the CHA pores and coke in the catalyst bed . As catalysts we used SSZ‐13‐R and SSZ‐13‐F‐M25 zeolites placed in a fixed‐bed reactor.…”

Compound‐Specific Imaging of Methanol Fuel Cell for Performance and Degradation Studies Using a Mini Positron Emission Tomograph

“…The small detector ring (MiniPET) camera (also known as small animal PET camera) is applied for imaging of the positron‐emitter labeled compounds with high ∼1.2 mm spatial resolution compared to bigger, human PET camera with 4–5 mm resolution [35] . In the previous works the PET imaging was already effectively used in molecular imaging of liquid chromatography and heterogeneous catalysis processes [36–38] . In the present work the 11 C‐radiolabeled methanol as a tracing fuel compound (labeled by 11 C‐positron‐emitter isotope) and its 11 C‐derivatives (their collective name 11 C‐adsorbates) were determined in terms of chemical property on the reactive surface area along the layers of the fuel cell.…”

“…[35] In the previous works the PET imaging was already effectively used in molecular imaging of liquid chromatography and heterogeneous catalysis processes. [36][37][38] In the present work the 11 C-radiolabeled methanol as a tracing fuel compound (labeled by 11 C-positronemitter isotope) and its 11 C-derivatives (their collective name 11 C-adsorbates) were determined in terms of chemical property on the reactive surface area along the layers of the fuel cell. Primarily the well-functioning and the gradually degraded anode catalyst was monitored.…”

Three‐Dimensional Imaging of High Performance Liquid Chromatography Processes Using a Mini Positron Emission Tomograph

“…Small animal PET (or MiniPET) cameras have higher spatial resolution than conventional human PET cameras (∼1.3 mm compared to 4–6 mm, average distances) due to their smaller diameter and smaller scintillation crystals, therefore finer structures of an object can be studied. The authors have already adapted the MiniPET imaging for studying surface chemical processes (adsorption, desorption, distribution and coke formation) in heterogeneous catalysts ,. In the present work, the MiniPET technique has been extended in order to study and visualize compound bands in high‐performance liquid chromatography.…”

“…The authors have already adapted the MiniPET imaging for studying surface chemical processes (adsorption, desorption, distribution and coke formation) in heterogeneous catalysts. [8,9] In the present work, the MiniPET technique has been extended in order to study and visualize compound bands in high-performance liquid chromatography. The PET provides real-time information and in situ monitoring about the compound bands by isotope labeling of the analytes.…”