Revealing the formation mechanism of trapped and deactivating species in oligomerization of 1-butene by using FT-ICR mass spectrometry

The transformation of 1-butene into valuable fuels using HZSM-5 zeolite catalysts is significantly hindered by deactivation caused by trapped species and coke formation. This comprehensive study delves into the formation and growth of these deactivating species under a range of conditions, including temperatures from 275 to 325 °C, pressures ranging from 1.5 to 40 bar, and space-times between 2 and 6 gcatalyst h/molC. We have employed an extensive characterization of the used catalysts, integrating conventional techniques with advanced methodologies. Notably, we utilized Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), which allows for the isolation and detailed molecular-level analysis of these species within the soluble coke. This advanced technique provides a deeper understanding of the molecular composition and structural characteristics of the deactivating species. Our findings reveal that higher pressures promote oligomerization, resulting in an increased accumulation of trapped species. Conversely, higher temperatures facilitate the cracking of these oligomers into lighter fractions or their further conversion into coke molecules through condensation reactions. This dual behavior underscores the complex interplay between temperature and pressure in influencing the deactivation pathways. The insights gained from this study are invaluable for optimizing reaction conditions. By understanding the overall reaction mechanism and the specific formation and growth patterns of trapped and deactivating species, we can develop strategies to mitigate catalyst deactivation. This optimization is crucial for enhancing both the longevity and efficiency of catalysts in hydrocarbon transformation processes, ultimately leading to more sustainable and efficient industrial applications.