Novel consecutive 11C- and 12C-methanol adsorption technique for the catalytic active sites characterization of vanadium modified MCM-41

The development of 11C-carbonylation chemistry: A systematic view

The prospects for using carbon-11 labelled compounds in molecular imaging has improved with the development of diverse synthesis methods, including 11C-carbonylations and refined techniques to handle [11C]carbon monoxide at a nanomole scale. Facilitating biological research and molecular imaging was the driving force when [11C]carbon monoxide was used in the first in vivo application with carbon-11 in human (1945) and when [11C]carbon monoxide was used for the first time as a chemical reagent in the synthesis of [11C]phosgene (1978). This review examines a rich plethora of labelled compounds synthesized from [11C]carbon monoxide, their chemistry and use in molecular imaging. While the strong development of the 11C-carbonylation chemistry has expanded the carbon-11 domain considerably, it could be argued that the number of 11C-carbonyl compounds entering biological investigations should be higher. The reason for this may partly be the lack of commercially available synthesis instruments designed for 11C-carbonylations. But as this review shows, novel and greatly simplified methods to handle [11C]carbon monoxide have been developed. The next important challenge is to make full use of these technologies and synthesis methods in PET research. When there is a PET-tracer that meets a more general need, the incentive to implement 11C-carbonylation protocols will increase.

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

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 ¹¹ C 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 [¹¹ C]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.