A newly developed nuclear magnetic resonance (NMR) probe enhances the real-time investigation of catalytic reactions by offering high sensitivity and resolution. This large-volume, continuous-flow magic angle spinning (CF-MAS) technology allows in situ analysis of reaction dynamics, intermediates, and mechanisms, providing valuable insights for industrial catalysis development and optimization.

In the field of heterogeneous catalysis, understanding the mechanisms of reactions on catalysts is crucial. Often, current in situ techniques like ultraviolet-visible and infrared spectroscopies fall short, especially for complex reactions such as selective oxidation of organics. These limitations can lead to insufficient data on reaction intermediates and dynamics, affecting industrial efficiency and innovation.

Traditional magic angle spinning NMR techniques, particularly those for larger sample volumes, have struggled with sensitivity and practicality issues. This can result in shallow bed reactions and inadequate data collection from thick catalyst beds. These shortcomings are a significant barrier, limiting advancements in catalysis research and commercial applications.

Developed at Pacific Northwest National Laboratory, this new CF-MAS NMR rotor and probe system overcomes these barriers by allowing high-resolution NMR investigations in situ. Utilizing a large-sample-volume design, it significantly enhances sensitivity, permitting comprehensive in situ natural abundance ¹³C CF-MAS studies. The rotor’s design includes a specialized sample chamber that facilitates efficient diffusion of reactants and products through the catalyst. This results in improved sensitivity and clear detection of reaction intermediates and mechanisms.

Scientists at Pacific Northwest National Laboratory engineered this CF-MAS technology to handle a sample chamber volume greater than 0.01 cm³, which is a major improvement over previous designs. The result is superior signal-to-noise ratios, enabling real-time, high-resolution data acquisition even for reactions involving complex species. This innovation addresses the problem of insufficient catalyst interaction data by allowing detailed, quantitative analysis, which is crucial for industrial applications.

APPLICABILITY
This technology can be leveraged by industries involved in catalysis for chemical manufacturing, pharmaceuticals, and materials science. Potential users include research and development departments, industrial chemists, and those engaged in the study of catalytic processes.

DESIGN
The development of a large-sample-volume CF-MAS NMR probe is reported for in situ investigation of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. The reactants are flowed into the catalyst bed by a fixed tube at one end of the rotor while a second fixed tube linked to a vacuum pump is attached at the other end of the magic angle spinning rotor to form a flow inside the catalyst bed by utilizing the pressure difference at both ends of the catalyst bed inside the sample cell space. The formation of the flow through the catalyst bed improves the diffusion of the reactants and products, allowing the use of a large sample volume for enhanced sensitivity and thus permitting in situ ¹³C CF-MAS studies at natural abundance.