Abstract
Deactivation of heterogeneous catalysts is an issue of high importance and extensive study. However, under normal isothermal plug flow operation the experimental conditions within the catalyst bed can change dramatically with time as the catalyst deactivates and the concentrations of reactants and products respond. Changes of reaction conditions can have diverse simultaneous effects on the rates of catalytic and homogeneous reactions, leading to a discrepancy between the real rate and the measured rate of catalyst deactivation, and/or can directly affect the rates of individual mechanisms for catalyst deactivation. Here we present a simple approach to investigating long-term changes in catalyst activity, whereby the total flow rate of all feed components is varied in response to changes in activity to maintain a targeted overall conversion. This allows experimental measurements to focus in on quantifiable changes in the catalytically active sites directly without a priori knowledge of the reaction kinetics. The dry reforming of methane reaction with a Ni/Al 2 O 3 catalyst is used here as a case study. Using kinetic isoconversion loop catalysis to deconvolute simultaneous deactivation processes, we show that CO disproportionation is the cause of carbon deposition at 550 °C and estimate an apparent activation energy of 160 kJ mol -1 for a second deactivation mechanism attributed to Ni sintering.
Original language | English (US) |
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Pages (from-to) | 2481-2491 |
Number of pages | 11 |
Journal | Industrial and Engineering Chemistry Research |
Volume | 58 |
Issue number | 7 |
DOIs | |
State | Published - Feb 20 2019 |
Funding
This work was made possible by a NPRP exceptional grant award [NPRP-EP X-100-2-024] from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. Patrick Littlewood would like to thank Prof. Reinhard Schomäcker for many informative discussions regarding catalyst kinetics and deactivation.
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering
- Industrial and Manufacturing Engineering