Adsorption/Desorption Studies on Solid Acid Alkylation Catalysts S.V. Nayak, M.P. Dudukovic, and P. A. Ramachandran Chemical Reaction Engineering Laboratory, Washington University in St.Louis

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Adsorption/Desorption Studies on Solid Acid
Alkylation CatalystsS.V. Nayak, M.P. Dudukovic,
and P. A. Ramachandran Chemical Reaction
Engineering Laboratory, Washington University in
St.Louis
Results and Discussion
Introduction

• Problem Safety, environmental and reliability
  issues associated with current liquid acid
  alkylation technologies
• Challenge Develop and demonstrate an
  environmentally friendly and competitive Solid
  Acid Catalyst (SAC) technology to replace HF and
  H2SO4 technologies
• Different solid acid catalysts are tested for
  alkylation of isobutane and n-butene to form
  2,2,4 trimethylpentane (gasoline)
• Zeolites
• Supported Nafion
• Hetropoly acids
• Ion exchange resins
• Zeolites
• High product selectivity ( 85 95 )
• Rapid decrease in activity

Modified residence time vs. inverse square root
temperature for isobutane and argon over
beta-zeolities
Modified residence time vs. inverse square root
temperature for isobutane and argon over inert
quartz particles
Residence time divided by the square root
molecular weight vs. inverse square root of
temperature (Nayak et al., 2007)
The catalytic cycle in alkylation reaction
catalyzed by zeolites
TAP experimental responses of argon and isobutane
over beta-zeolites
Single Pulse TAP Experiments
Mean Adsorption Capacity Spread Diffusivity,
Adsorption/ Desorption Constants
Important questions How do organic molecules
diffuse inside a nanoporous zeolite? How does the
intra-crystalline channel network of a zeolite
influence diffusion, adsorption/ desorption and
reaction pathway of organic molecules?
vant Hoff plot for equilibrium constant (Nayak
et al., 2007)
Theoretical Representation of TAP
Inert Zone II
Inert Zone I
Zeolite Zone
Table1 Heat of Adsorption and pre-exponential
factor (Nayak et al., 2007)
Sub-Project Goal
To understand and quantify the overall adsorption
kinetics and transport processes of the reactant
and products involved in Solid Acid Alkylation
Processes
Narrow Inlet BC
Vacuum BC at outlet
Observed Exit Flow
Methodology
Adsorption-Desorption and Intraparticle Diffusion
model for Zeolite Zone Using LDF approximation
(Nayak et al., 2008)
TAP Reactor Model Accumulation - Transport Term
Reaction Rate

• Conclusions
• TAP approach can be effectively used for
  transport studies
• Experimental procedure and method for
  quantifying TAP results are presented
• The understanding gained with TAP results should
  help in quantifying the frequency for periodic
  regeneration and the key features needed for the
  optimal catalysts design and regeneration
  techniques for solid acid alkylation processes

Diffusion
Knudsen Diffusion

• References
• Nayak S. V., Ramachandran P. A., Dudukovic M. P.,
  2007 Transport in nanoporous Beta and
  ultrastable Y zeolite, AIChE,fall meeting
• Nayak S. V., Ramachandran P. A., Dudukovic M.
  P., 2008 Adsorption-desorption and intraparticle
  diffusion model using LDF approximation, in
  preparation
• Acknowledgement NSF Grant, EEC-0310689

Temporal Analysis of Products (TAP) Pulse
Response Experiment