Abstract
Coking leads to the deactivation of solid acid catalyst. This phenomenon is a ubiquitous problem in the modern petrochemical and energy transformation industries. Here, we show a method based on microwave cavity perturbation analysis for an effective examination of both the amount and the chemical composition of cokes formed over acid zeolite catalysts. The employed microwave cavity can rapidly and non-intrusively measure the catalytically coked zeolites with sample full body penetration. The overall coke amount is reflected by the obtained dielectric loss (ε″) value, where different coke compositions lead to dramatically different absorption efficiencies (ε″/cokes’ wt%). The deeper-dehydrogenated coke compounds (e.g., polyaromatics) lead to an apparently higher ε″/wt% value thus can be effectively separated from lightly coked compounds. The measurement is based on the nature of coke formation during catalytic reactions, from saturated status (e.g., aliphatic) to graphitized status (e.g., polyaromatics), with more delocalized electrons obtained for enhanced Maxwell–Wagner polarization.
Highlights
Coking leads to the deactivation of solid acid catalyst
Zeolite catalysts, such as acid zeolite H-Y, H-ZSM-5, and HSAPO-34 are widely employed across the modern petrochemical and fine chemical industries, for their excellent catalytic performance in hydrocarbon conversions and related chemistries[1, 2]
Nuclear magnetic resonance (NMR) spectroscopy works in a sample inside EM field mode, where the sample is instead bathed in the EM field for measurement with the entire sample body volumetrically interrogated
Summary
Coking leads to the deactivation of solid acid catalyst. This phenomenon is a ubiquitous problem in the modern petrochemical and energy transformation industries. We show a microwave cavity perturbation based method to effectively measure the coke accumulation in the whole structure of an acid zeolite catalyst (volumetrically), and separate different coke compositions.
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