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Single-event microkinetics of aromatics hydrogenation on Pt/H-ZSM22

Tapan Bera (UGent) , Joris Thybaut (UGent) and Guy Marin (UGent)
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Abstract
A fundamental Single-Event Micro Kinetic (SEMK) model for the hydrogenation of aromatic components on a Pt catalyst has been developed. It is based on the Horiuti-Polanyi mechanism considering atomic hydrogen addition steps to the (partially hydrogenated) aromatic species on the catalyst surface. The reaction network used accounts for the position at which the hydrogen atoms are added to the ring. In accordance with a quantum chemical assessment of the reaction pathway it was assumed that the kinetic parameters only depend on the saturation degree of the nearest neighbor carbon atoms and the branching degree of the carbon atom involved in the hydrogen atom addition. Six reactions families, of which three occur in the reaction network for benzene, are considered. The total number of 18 model parameters was reduced to 7 by calculation of the pre-exponential factors and by accounting for thermodynamic constraints. Experimental benzene hydrogenation data measured at temperatures in the range from 423 to 498 K, benzene inlet partial pressures in the range from 10 to 60 kPa, and hydrogen inlet partial pressures from 100 to 600 kPa on Pt catalyst have been regressed. In accordance with quantum chemical, statistical, and thermodynamic calculations, the selected version of the model gives the best description of the data with an F value of 4150. According to this selected SEMK model, the activation energies for the hydrogen addition to a carbon atom between two unsaturated or two saturated carbon atoms are identical and lower than the activation energy for hydrogen addition to a carbon atom between an unsaturated and saturated hydrogen atom. The estimated chemisorption enthalpy of hydrogen amounts to -59.4 kJ mol(-1) and corresponds with an average surface coverage of 30%. A value of -56.0 kJ mol(-1) for the chemisorption enthalpy of benzene is obtained. The total surface coverage by hydrocarbon species amounts to 60% under typical reaction conditions, without a pronounced Most Abundant Surface Intermediate (MASI).
Keywords
PT/US-Y ZEOLITES, GAS-PHASE HYDROGENATION, BENZENE HYDROGENATION, KINETIC-BEHAVIOR, P-XYLENE, UNSUPPORTED PALLADIUM, CATALYTIC CRACKING, 1ST PRINCIPLES, REACTION MODEL, RATE-EQUATIONS

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Chicago
Bera, Tapan, Joris Thybaut, and Guy Marin. 2011. “Single-event Microkinetics of Aromatics Hydrogenation on Pt/H-ZSM22.” Industrial & Engineering Chemistry Research 50 (23): 12933–12945.
APA
Bera, T., Thybaut, J., & Marin, G. (2011). Single-event microkinetics of aromatics hydrogenation on Pt/H-ZSM22. INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 50(23), 12933–12945.
Vancouver
1.
Bera T, Thybaut J, Marin G. Single-event microkinetics of aromatics hydrogenation on Pt/H-ZSM22. INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH. 2011;50(23):12933–45.
MLA
Bera, Tapan, Joris Thybaut, and Guy Marin. “Single-event Microkinetics of Aromatics Hydrogenation on Pt/H-ZSM22.” INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 50.23 (2011): 12933–12945. Print.
@article{1960771,
  abstract     = {A fundamental Single-Event Micro Kinetic (SEMK) model for the hydrogenation of aromatic components on a Pt catalyst has been developed. It is based on the Horiuti-Polanyi mechanism considering atomic hydrogen addition steps to the (partially hydrogenated) aromatic species on the catalyst surface. The reaction network used accounts for the position at which the hydrogen atoms are added to the ring. In accordance with a quantum chemical assessment of the reaction pathway it was assumed that the kinetic parameters only depend on the saturation degree of the nearest neighbor carbon atoms and the branching degree of the carbon atom involved in the hydrogen atom addition. Six reactions families, of which three occur in the reaction network for benzene, are considered. The total number of 18 model parameters was reduced to 7 by calculation of the pre-exponential factors and by accounting for thermodynamic constraints. Experimental benzene hydrogenation data measured at temperatures in the range from 423 to 498 K, benzene inlet partial pressures in the range from 10 to 60 kPa, and hydrogen inlet partial pressures from 100 to 600 kPa on Pt catalyst have been regressed. In accordance with quantum chemical, statistical, and thermodynamic calculations, the selected version of the model gives the best description of the data with an F value of 4150. According to this selected SEMK model, the activation energies for the hydrogen addition to a carbon atom between two unsaturated or two saturated carbon atoms are identical and lower than the activation energy for hydrogen addition to a carbon atom between an unsaturated and saturated hydrogen atom. The estimated chemisorption enthalpy of hydrogen amounts to -59.4 kJ mol(-1) and corresponds with an average surface coverage of 30\%. A value of -56.0 kJ mol(-1) for the chemisorption enthalpy of benzene is obtained. The total surface coverage by hydrocarbon species amounts to 60\% under typical reaction conditions, without a pronounced Most Abundant Surface Intermediate (MASI).},
  author       = {Bera, Tapan and Thybaut, Joris and Marin, Guy},
  issn         = {0888-5885},
  journal      = {INDUSTRIAL \& ENGINEERING CHEMISTRY RESEARCH},
  keyword      = {PT/US-Y ZEOLITES,GAS-PHASE HYDROGENATION,BENZENE HYDROGENATION,KINETIC-BEHAVIOR,P-XYLENE,UNSUPPORTED PALLADIUM,CATALYTIC CRACKING,1ST PRINCIPLES,REACTION MODEL,RATE-EQUATIONS},
  language     = {eng},
  number       = {23},
  pages        = {12933--12945},
  title        = {Single-event microkinetics of aromatics hydrogenation on Pt/H-ZSM22},
  url          = {http://dx.doi.org/10.1021/ie200541q},
  volume       = {50},
  year         = {2011},
}

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