The non-oxidative dehydrogenation of light alkanes offers a promising route for the production of olefins - one of the key reagents in the chemical industry [1]. Our group recently demonstrated that Cu-exchanged zeolites to be effective catalysts for this transformation when operated in a chemical looping mode under significantly milder conditions compared to conventional high-temperature processes [2]. In particular, CuIMOR zeolite has been shown to dehydrogenate alkanes forming π-complexes with olefins, as evidenced by in situ solid-state NMR and FTIR spectroscopies, showing characteristic signals of Cu–olefin intermediates. 

To further elucidate the reaction mechanism, we extended our study to n-butane as a reactant. This system presents greater mechanistic complexity, given the possibility of multiple products. The application of ¹³C-labeled n-butane in combination with in situ solid-state NMR and FTIR spectroscopies, alongside with online gas chromatography detection, allowed us to detect and differentiate between possible products such as 1-butene, iso-butene, and cis-/trans-2-butene. To gain deeper mechanistic insight into the role of Cu-speciation in guiding selectivity and reactivity, we compared reaction rates using a series of alkanes – ethane, propane, n-butane and iso-butane. This comparative kinetic study was further supported by a Hammett plot analysis, which correlates the reaction rates to the electron-donating properties of the reactants. The observed trends provided additional evidence for the proposed mechanism, suggesting that electronic effects play a significant role.

Our findings highlight the potential of Cu-zeolites for low-temperature alkane dehydrogenation and underscore the value of advanced spectroscopic techniques in unveiling reaction mechanisms under realistic operating conditions. This work advances the development of Cu-containing zeolites for energy-efficient catalytic applications. 

[1] Z. Nawaz, Reviews in Chemical Engineering 2015, 31.5, 413-436.

[2] M. Artsiusheuski, et al., J. Am. Chem. Soc. 2025, 147, 18, 15880–15889