Unsteady-state operation of trickle-bed reactors

• Published in: Chemical engineering science Vol. 59; no. 22; pp. 5355 - 5361
• Main Authors: Lange, Rüdiger, Schubert, Markus, Dietrich, Wulf, Grünewald, Marcus
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2004; Elsevier
• Subjects: Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Dynamic simulation; Exact sciences and technology; General and physical chemistry; Heat and mass transfer. Packings, plates; Hydrodynamics of contact apparatus; Mathematical modelling; Multiphase reactions; Packed bed; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Trickle-bed reactor; Unsteady-state operation; Trickle-bed reactor; Dynamic simulation; Packed bed; Mathematical modelling; Multiphase reactions; Unsteady-state operation; Trickle bed reactor; Wetting; Liquid holdup; Unsteady state; Laboratory scale; Hydrodynamics; Reaction rate; Hydrogenation; Modeling; Steady state; Mass transfer; Gas solid; Liquid flow; Kinetics; Catalyst
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2004.09.007

An experimental and theoretical study of forced unsteady-state operation of trickle-bed reactors in comparison to the steady-state operation is the subject of this paper. It is well known that changes in the control variables influence the regime and the performance of trickle-bed reactors. In this study as one example for a forced periodic operation of a trickle-bed reactor an unsteady-state technique was used in which the catalyst bed is contacted periodically with different liquid flow rates. The unsteady-state operation was considered as square-waves cycling liquid flow rate at the reactor inlet. The hydrogenation of alpha-methylstyrene to cumene: C 6 H 5 (CH 3 )=CH 2 ( L ) + H 2 ( G ) → C 6 H 5 CH(CH 3 ) 2 ( L ) over a Palladium-catalyst (0.7% Pd/ γ -Al 2 O 3 ) was selected as a model reaction. The experimental results of the alpha-methylstyrene hydrogenation in a laboratory-scale trickle-bed reactor showed, that the reactor performance can be significantly improved by feed liquid flow modulation. The simulation studies demonstrate that the liquid flow variation has a strong influence on the liquid hold-up oscillation and on the catalyst wetting efficiency. Consequently the time average alpha-methylstyrene conversion will be increased, because the mass transfer resistance between the phases (gas–liquid, gas–solid and liquid–solid) affect the overall reaction rate and consequently the conversion will be improved.